i Preface - APAI€¦ · Asphalt Paving Materials 2-1 Chapter 2 Asphalt and Asphalt Paving...

Prefacei

ASPHALT PAVING DESIGN GUIDEPublished by the

Asphalt Paving Association of Iowa

The Asphalt Paving Association of Iowa (APAI) is an organization of asphalt concreteproducers and their associate members from the paving industry around the state. APAIwas formed in 1955 for the purpose of advancing knowledge in the use of this pavingmaterial and to provide a service to the public and to the users of asphalt.

The APAI is constantly seeking new techniques, product improvements, and designmethods, all of which are made available for the benefit of pavement users. Design andconstruction seminars and educational reports and brochures are developed anddisseminated to ensure a high-quality product. A wide variety of technical literature andaudio-visual presentations are available by calling the APAI office.

The ultimate quality of your asphalt paving project is directly related to the experience,skill, and equipment of the contractor doing the work. Behind each contractor is atremendous investment in equipment, highly skilled manpower, and a pride ofworkmanship in building asphalt pavement of the highest quality. Whatever the project,APAI members are your assurance of quality.

APAIÕs professional staff and member firms are qualified and eager to serve you. Theywelcome inquiries about design procedures and cost estimates at any time.

Partners in QualityExecutive Offices

3408 Woodland Ave.Suite 209

West Des Moines, IA 50266-6506

Table of Contents ii

Table of ContentsPreface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i

Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . ii

Forward . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

Chapter 1 — The Asphalt Advantage . . . . . . . . . . 1-1

Chapter 2 — Asphalt and Asphalt Paving Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

Asphalt Defined . . . . . . . . . . . . . . . . . . . . . . . . 2-1Aggregates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1Asphalt Cement . . . . . . . . . . . . . . . . . . . . . . . . . 2-4Asphalt Concrete . . . . . . . . . . . . . . . . . . . . . . . . 2-5Cold Mix Asphalt Concrete . . . . . . . . . . . . . . . 2-6

Chapter 3 — Design Considerations . . . . . . . . . . 3-1Fundamentals of Design . . . . . . . . . . . . . . . . . . 3-1Traffic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

Traffic Classifications . . . . . . . . . . . . . . . . . 3-2Soil Support Capability . . . . . . . . . . . . . . . . . . . 3-4

Subgrade Classes . . . . . . . . . . . . . . . . . . . . 3-8Drainage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-9Design Types . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11Asphalt Concrete Specifications . . . . . . . . . . . . 3-12Construction of Asphalt Pavements . . . . . . . . 3-15

Construction Equipment . . . . . . . . . . . . . . 3-15Construction Practices . . . . . . . . . . . . . . . . 3-17Pavement Markings . . . . . . . . . . . . . . . . . . 3-18Traffic Control Through Work Areas . . . . 3-19

Testing and Inspection . . . . . . . . . . . . . . . . . . . 3-21

Chapter 4 — Thickness Design . . . . . . . . . . . . . . . 4-1General Considerations . . . . . . . . . . . . . . . . . . 4-1Pavement Thickness Design Tables . . . . . . . . . 4-2

Residential Streets . . . . . . . . . . . . . . . . . . . 4-3Collector Streets . . . . . . . . . . . . . . . . . . . . . 4-4Arterial Streets . . . . . . . . . . . . . . . . . . . . . . 4-5Low-Volume Secondary and

Rural Roads . . . . . . . . . . . . . . . . . . . . . 4-6High-Volume Secondary and

Rural Roads . . . . . . . . . . . . . . . . . . . . . 4-7

Chapter 5 — Parking Lot Design . . . . . . . . . . . . . 5-1General Considerations . . . . . . . . . . . . . . . . . . 5-1

General Planning . . . . . . . . . . . . . . . . . . . . 5-2Thickness Design for Parking Lots . . . . . . . . . 5-7

Heavy Loaded Areas . . . . . . . . . . . . . . . . . 5-10Industrial Parking Lots . . . . . . . . . . . . . . . 5-10

Asphalt Concrete Curb . . . . . . . . . . . . . . . . . . . 5-11Asphalt Mat-Platform for Building

Construction and Site Paving . . . . . . . . . . 5-13

Chapter 6 — Designs for Recreational Uses . . . . 6-1Asphalt Pavements For

Non-Vehicular Use . . . . . . . . . . . . . . . . . . . . 6-1Bikeways, Golf Cart Paths, Recreational

Trails, and Walkways . . . . . . . . . . . . . . . . . 6-2Pavement Thickness . . . . . . . . . . . . . . 6-4

Recreational Areas . . . . . . . . . . . . . . . . . . . . . . 6-5Basketball Courts . . . . . . . . . . . . . . . . . . . . 6-5Pavement Thickness . . . . . . . . . . . . . . . . . . 6-7

Tennis Courts . . . . . . . . . . . . . . . . . . . . . . . . . . 6-8Pavement Thickness . . . . . . . . . . . . . . . . . . 6-10

Asphalt-Rubber Running Tracks . . . . . . . . . . . 6-11

Chapter 7 — Pavement Management . . . . . . . . . . 7-1Pavement Management Concepts . . . . . . . . . . 7-1

Rating a Road . . . . . . . . . . . . . . . . . . . . . . . 7-2Interpretation of a Condition Rating . . . . 7-2

Pavement Maintainance . . . . . . . . . . . . . . . . . . 7-4Full-depth Asphalt Patching . . . . . . . . . . . 7-5Thin Surface Treatments . . . . . . . . . . . . . . 7-8

Asphalt Concrete Overlays . . . . . . . . . . . . . . . . 7-10Overlay Thickness Calculations . . . . . . . . 7-11

Chapter 8 — Rehabilitation . . . . . . . . . . . . . . . . . 8-1Recycling Asphalt Pavements . . . . . . . . . . . . . 8-1Breaking and Seating . . . . . . . . . . . . . . . . . . . . 8-3Rubblizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-4Paving Fabrics . . . . . . . . . . . . . . . . . . . . . . . . . . 8-5Sawcut and Sealing Joints . . . . . . . . . . . . . . . . . 8-5

Appendix A — Pavement Failure Indentification A-1Identifying and Correcting Pavement

FailuresTypes of Pavement Failures

Appendix B — Glossary . . . . . . . . . . . . . . . . . . . . . B-1

Appendix C — Conversion Tables . . . . . . . . . . . . . . C-1Table C-1. Approximate Quantities of

Asphalt Concrete perSquare Yard

Table C-2. Gallons of Emulsified AsphaltRequired Per 100 Linear Feet:Various Widths and Rates

Table C-3. Tons of Material Required Per100 Linear Feet for VariousWidths and Pounds PerSquare Yard

Table C-4. Cubic Yards of Material Per100 Linear Feet: VariousWidths and Depths

Appendix D — Publications . . . . . . . . . . . . . . . . . D-1National Asphalt Pavement Association

PublicationsThe Asphalt Institute PublicationsGovernment Publications

Appendix E — Credits and References . . . . . . . . E-1CreditsReferences

Forwardiii

FORWARD

This Asphalt Paving & Design Guide has been prepared by the members and staff of theAsphalt Paving Association of Iowa to assist you in understanding Asphalt Concretepavement design and construction.

This Design Guide is not intended to circumvent asphalt pavement designs bycompetent design engineers using actual project traffic loading data and known subgradesoil characteristics. However, it will provide the owner, architect, engineer, developer, andgovernment official with basic guidelines to be used in the absence of professionalservices. Readers are cautioned that the information contained in this Design Guide maybe insufficient when used alone, and other resource materials and authorities should beconsulted for specific site design.

The criteria for specific pavement design applications are unpredictably varied. Theexamples contained in the Design Guide are composites of those designs, procedures, andapplications that have proven successful in the state of Iowa. References to authorities andagencies do not constitute their endorsement of this Design Guide. Suggested referencesand authorities should be used by the reader if further clarification is required.

All Asphalt mixes referred to in this Design Guide comply with the Iowa Departmentof TransportationÕs specifications for Asphalt Concrete mixes. These are proven mixes,readily available throughout the state of Iowa from companies experienced in producingand constructing quality hot mixed Asphalt Concrete pavements.

DESIGN GUIDE FORMAT

The purpose of this Design Guide is to present materials that provide a basic knowledgeof asphalt pavement design without being too technical. Understanding some of the basicproperties of asphalt and aggregates is essential when relating pavement designs tospecific conditions and needs. Thickness design tables and construction details areincluded for various roadway and recreational uses. Pavement management andrehabilitation options are also important considerations.

The Design Guide is presented in a logical format for asphalt paving design,construction, and maintenance processes.

I.

THE

ASPHALT

ADVANTAGE

Chapter 1The Asphalt Advantage

Paving with asphalt concrete allows you to pave faster, more efficiently, more economically, andwith greater serviceability than with any other paving material in the world. That may seem like apretty bold claim, but those who work in paving know itÕs true. Asphalt Concrete has an absoluteadvantage in every paving application. This Design Guide will tell you about those advantages.

SMOOTHNESS

Asphalt will consistently give the drivingpublic the smooth, quiet ride they have cometo expect from this product. Asphalt Concreteis machine-placed, so it has a uniform surfaceunsurpassed by other pavements. Repetitivejoints, noisy surface texture, and blowups areeliminated by this method of construction.These features benefit airport users, too.Asphalt Concrete runways and taxiways meansafer landings and takeoffs, because suchsurfaces are smoother and easier to maintain.

STAGED CONSTRUCTION

A major advantage for Asphalt Concrete isthe potential for staged construction. Theasphalt base course can be placed and usedunder traffic during initial construction. Thispavement can then be overlaid with finalsurface courses. Staged construction improveson-site conditions, removes the aspect ofmuddy soils, and provides a place to storeconstruction materials and equipment. Thismethod also provides an opportunity todiscover and correct unanticipated problemareas, such as a weak subgrade, poor drainage,or poorly compacted trenches, which can berepaired at minimal cost.

The Asphalt Advantage 1-1

EASE OF CONSTRUCTION

Asphalt Concrete is machine-placed, remov-ing the need for time-consuming form workand steel reinforcement. Traffic can use thepavement almost immediately Ð no delay isrequired to allow the pavement to cure. Thelack of pavement joints reduces maintenancerequirements. Repair of an asphalt surface isquick and easy, because there is little down-time waiting for a patch to cure.

DURABILITY

Asphalt Concrete is a flexible pavement, withsame bridging action, which allows it to with-stand occasional overloads without seriousdamage. Its resistance to freeze-thaw anddeicing salts allows it to wear better duringwinter. Its lack of repetitive joints removes thepossibility of blowups that plague PortlandCement Concrete during summer. Inch forinch, asphalt cement concrete performs betterthan Portland Cement Concrete.

ECONOMICAL

The Federal Highway Administration hasshown that a dollar spent on asphalt pave-ments goes 26.9 percent farther than a dollarspent on concrete pavements. ThatÕs becauseasphalt is cost-effective. It has a lower first costthan concrete and it lasts longer. Stagedconstruction helps spread out the cost ofplacement. Because asphalt pavement has nojoints to repair and is not affected by freeze-thaw actions, it is much less expensive tomaintain.

The Asphalt Advantage1-2

SAFETY

Asphalt pavements offer high skid resist-ance values. The dark color of asphalt reducesglare, helps melt ice and snow, and provides ahigh contrast for lane markings.

The Asphalt Advantage 1-3

RECYCLABLE

Another major advantage of AsphaltConcrete is its ability to be completelyrecycled. Not only can the aggregates bereused, but the asphalt cement binder alsoretains its cementing properties and can be re-used in a new mix. Pavements can be recycledboth on site using cold mix or via a hot mixplant. Recycled pavements have been testedand proven in both the laboratory and the fieldto perform at least as well as virgin aggregatemixes. Over 90% of the hot mix asphalt plantsin Iowa are capable of using reclaimed asphaltpavement (RAP). Asphalt pavements are 100percent recyclable.

VERSATILITY

The versatility and popularity of asphalt isevident across the state of Iowa and allAmerica Ð factories and schools, office parksand playgrounds, and the overwhelmingmajority of our streets and roads stand as cleartestimony that the advantages of asphalt makeit AmericaÕs first choice for paving andrehabilitation.

II.

ASPHALT

and

ASPHALT PAVING

MATERIALS

Asphalt Paving Materials 2-1Asphalt Paving Materials 2-1

Chapter 2Asphalt and Asphalt Paving Materials

ASPHALT DEFINED

The black cementing agent known as asphalthas been used for road construction forcenturies. Although there are natural depositsof asphalt, or rock asphalt, most used today isproduced by the oil refining industry. Asphaltis a constituent of most petroleums and isisolated through the refining process ofdistillation. (See Figure 2-1.)

Figure 2-1. Petroleum Asphalt Flow Chart forEmulsified and Cutback Asphalts.

Asphalt is called a bituminous materialbecause it contains bitumen, a hydrocarbonmaterial soluble in carbon disulfate. The tarobtained from the destructive distillation ofsoft coal also contains bitumen. Both petrol-eum asphalt and coal tar are referred to asbituminous materials. However, because theirproperties differ greatly, petroleum asphaltshould not be confused with coal tar. Whereaspetroleum asphalt is composed almost entirelyof bitumen, the bitumen content in coal tar isrelatively low. The two materials should betreated as separate entities.

One of the characteristics and advantages ofasphalt as an engineering construction andmaintenance material is its great versatility.Although a semi-solid at ordinary tempera-tures, asphalt may be liquified by applyingheat, dissolving it in solvents, or emulsifyingit. Asphalt is a strong cement that is readilyadhesive and highly waterproof and durable,making it particularly useful in road building.It is also highly resistive to the actions of mostacids, alkalis, and salts.

Covering more than 90 percent of thenationÕs paved highways, Asphalt Concrete isthe most widely used paving material in theUnited States. For versatility, durability, andease of construction, it has no equal.

AGGREGATES

Aggregates (or mineral aggregates) are hard,inert materials such as sand, gravel, crushedstone, slag, or rock dust. Properly selected andgraded aggregates are mixed with the cement-ing medium asphalt to form pavements.Aggregates are the principal load-supportingcomponents of an Asphalt Concrete pavement.They total 90 to 95 percent of the mixture byweight and 75 to 85 percent by volume.

Asphalt Paving Materials2-2

ClassificationsAsphalt Concrete paving aggregates are

classified according to source or means ofpreparation. A brief description of the classifi-cations follows.

Pit or Bank-Run AggregatesBoth gravel and sand are typically pit or

bank-run natural aggregates. They usually arescreened to proper size and washed to removedirt before being used for Asphalt Concretepaving purposes.

Processed AggregatesWhen natural pit or bank-run aggregate has

been crushed and screened to make it suitablefor Asphalt Concrete pavements, it is consider-ed a processed aggregate. Crushing typicallyimproves the particle shape by making the

rounded particles more angular. Crushingalso improves the size distribution and range.

Crushed stone is also a processed aggregate.It is created when the fragments of bedrockand large stones are crushed so that all particlefaces are fractured. Variation in size of particlesis achieved by screening. Aggregates that havereceived little or no screening are known ascrusher run. These aggregates are generallymore economical than screened aggregatesand can be used in Asphalt Concrete pave-ments in many instances.

In the processing of crushed limestone, therock dust produced is separated from the othercrushed aggregate and may be used as crushedsand or as a mineral filler in Asphalt Concretepavements.

Asphalt Paving Materials 2-3

2. Cleanliness. Foreign or deleterious sub-stances make some materials unsuitable forpaving mixtures.

3. Toughness. Toughness or hardness is theability of the aggregate to resist crushing ordisintegration during mixing, placing, andcompacting; or under traffic loading.

4. Soundness. Although similar to toughness,soundness is the aggregateÕs ability to resistdeterioration caused by natural elementssuch as the weather.

5. Particle shape. The shapes of aggregateparticles influence the asphalt mixtureÕsoverall strength and workability as well asthe density achieved during compaction.When compacted, irregular particles suchas crushed stone tend to ÒlockÓ togetherand resist displacement.

6. Surface texture. Workability and pavementstrength are influenced by surface texture. Arough, sandpapery texture results in ahigher strength than a smooth texture.Although smooth-faced aggregates are easyto coat with an asphalt film, they aregenerally not as good as rough surfaces. It isharder for the asphalt to ÒgripÓ the smoothsurface.

7. Absorption. The porosity of an aggregatepermits the aggregate to absorb asphalt andform a bond between the particle and theasphalt. A degree of porosity is desired, butaggregates that are highly absorbant aregenerally not used.

8. Stripping. When the asphalt film separatesfrom the aggregate because of the action ofwater, it is called stripping. Aggregatescoated with too much dust also can causepoor bonding which results in stripping.Aggregates readily susceptible to strippingaction usually are not suitable for asphaltpaving mixes unless an anti-stripping agentis used.

Synthetic AggregatesAggregates produced by altering both

physical and chemical properties of a parentmaterial are called synthetic or artificialaggregates. Some are produced and processedspecifically for use as aggregates; others arethe byproduct of manufacturing and a finalburning process. Blast furnace slag is anexample of a synthetic aggregate.

Desirable Properties of AggregatesSelection of an aggregate material for use in

an Asphalt Concrete pavement depends on theavailability, cost, and quality of the material, as well as the type of construction for which it is intended. To determine if an aggregatematerial is suitable for use in asphalt construc-tion, evaluate it in terms of the followingproperties:

1. Size and grading. The maximum size of anaggregate is the smallest sieve throughwhich 100 percent of the material will pass.How the Asphalt Concrete is to be useddetermines not only the maximum aggre-gate size, but also the desired gradation(distribution of sizes smaller than themaximum).


ASPHALT CEMENTAsphalt is produced in a variety of types

and grades ranging from hard-brittle solids tonear water-thin liquids. The semi-solid formknown as asphalt cement is the basic materialused in Asphalt Concrete pavements. Liquidasphalt is produced when asphalt cement is

blended or Òcut backÓ with petroleum distillatesor emulsified with water and an emulsifyingagent. Liquid asphalt products may be pro-duced for various uses and applications.

Some of the types and characteristics ofasphalt are noted in the following table.

ASPHALT BINDER TYPE OF CORRIDOR LOCATION TYPE OF MIX

PG 70-22 Heavy Duty Full Depth Asphalt Surface Mixture (sp125 or SMA) andClass V-VI first underlying lifts

PG 64-22 Remaining lifts

PG 70-22 Asphalt Overlays All Mixtures

PG 64-22 Medium Duty Full Depth All MixturesClass III-IV and Overlays

PG 64-22 Light Duty Full Depth All MixturesClass I-II and Overlays

Table 2-1. Asphalt Types, Characteristics and General Uses

Percent FlashAsphalt Types-Percent Penetration Point Applic.

Type/Grade* (Min) Cutback (Min-Max) (Min) Temp. General Uses

SS- 1 57 Water 43 100-200 70- 160 Tack

SS-1 H 57 Water 43 40-90 70- 160 Tack, Slurry Surface Treatment

CSS- 1 57 Water 43 100-250 70- 160 Tack

CSS-1 H 57 Water 43 40-90 Boils 70-160 Tack, Slurry Surface Treatment

RS-1 55 Water 45 100-200 Over 70-140 Bituminous Seal Coat

RS-2 63 Water 37 100-200at

125-185 Bituminous Seal Coat

CRS-1 60 Water 40 100-250180°F

125-170 Bituminous Seal Coat

CRS-2 65 Water 35 100-250 125-170 Bituminous Seal Coat

viscosity

RC-70 55 Naphtha 45 70-140 80°F Tack

MC-30 55 Kerosene 45 120-250 100°F 70-150 Prime

MC-70 55 Kerosene 45 70-140 100°F 145-165 Bit. Seal Coat, Tack, Cold Mix, Patch Mix



MC-3000 80 Kerosene 20 3000-6000 150°F 215-290 Bituminous Seal Coat

Note: Flashpoint does not necessarily indicate burning or explosive point. However, care should be exercised whenheating all RC and MC asphalts because the cutback used reacts the same as gasoline. All material used as cold patchshould be mixed at the lowest temperature possible to prevent loss of cutback causing the mixture to harden before use.


ASPHALT CONCRETE

Asphalt Concrete is known by many differ-ent names: hot mix asphalt, plant mix,bituminous mix, bituminous concrete, andmany others. It is a combination of twoprimary ingredients - aggregates and asphalt

cement. The aggregates total 90 to 95 percent ofthe total mixture by weight. They are mixedwith 5 to 10 percent asphalt cement to formAsphalt Concrete.

The aggregates and asphalt are combined inan efficient manufacturing plant capable of


producing specified materials. Plant equip-ment includes: cold bins for storage of gradedaggregate; a dryer for drying and heatingaggregates to the required mixing tempera-ture; a pug mill for combining the graded,heated aggregate and liquid asphalt cementaccording to specified mix formulas; and tanksfor storing the liquid asphalt.

Asphalt Concrete is transported by truck tothe paving site where it is spread to a uniformthickness with a mechanical paving or finish-ing machine. Then the material is compactedto the required degree by heavy, self-propelledrollers, producing a smooth, well-compactedpavement course.

The paving or finishing machine places theAsphalt Concrete at temperatures above 225¡F. The material should be compacted before themix temperature falls below 175¡ F to achieveadequate density.

COLD MIX ASPHALT CONCRETE

Cold mix Asphalt Concrete, or cold placedmixture, is generally a mix made with emulsi-fied or cutback asphalt. Emulsified asphaltsmay be anionic or cationic MS or SS grades.Aggregate material may be anything from adense-graded crushed aggregate to a granularsoil having a relatively high percentage ofdust. At the time of mixing, the aggregate may

either be damp, air-dried, or artificially heatedand dried.

Mixing methods may be performed either inthe roadway, on the side of the roadway, or ina stationary mixing facility. The resultantmixtures usually are spread and compacted atatmospheric temperatures.

Cold mix asphalt may be used for surface,base, or subbase courses if the pavement isproperly designed. Cold mix surface coursesare suitable for light and medium traffic;however, they normally require a seal coat orhot Asphalt Concrete overlay as surface pro-tection. When used in the base or subbase, theymay be suitable for all types of traffic.

Bituminous Treated Aggregate BaseBituminous treated aggregate base is one

type of cold mix Asphalt Concrete. It canconsist of processing gravels; crushed stones;or blends of gravel, sand, and crushed stonematerials Ð each stabilized with a specifiedpercentage of asphalt. Job mix formulas(mentioned in Chapter 3) are not required.These mixtures are placed as a base course andstabilized-shoulder surfacing, although otheruses may be assigned by special design. Alldesigns should provide for a seal coat or sur-face course to provide protection from trafficabrasion and weathering.


A Grade of emulsion other than FHMS-2h may be used where experience has shown that they give satisfactory performanceB Diluted with water by the manufacturer.C Diluted with waterD Mixed in prime only.

Table 2-2 acts as a guide to uses of asphalt in cold mixes.

For additional information on asphalt and asphalt paving materials, refer to The AsphaltHandbook. Other references are listed in Appendix D.

Table 2.2. General Uses of Emulsified Asphalt

Type of Construction

Asphalt-aggregate mixtures:

For pavement bases and surfaces: .... .... .... .... XA .... .... .... .... .... .... .... .... ....Plant mix (hot)

Plant mix (cold) .... .... .... X X .... .... .... .... .... X X .... ....Open-graded aggregate .... .... .... .... .... X X X .... .... .... .... X XDense-graded aggregate .... .... .... .... .... X X X .... .... .... .... X XSand

Mixed-in-place:

Open-graded aggregate .... .... .... X X .... .... .... .... .... X X .... ....Dense-graded aggregate .... .... .... .... .... X X X .... .... .... .... X XSand .... .... .... .... .... X X X .... .... .... .... X XSandy soil .... .... .... .... .... X X X .... .... .... .... X XSlurry seal .... .... .... .... .... X X X .... .... .... .... X X

Asphalt-aggregate applications:

Treatment and seals:

Single surface treatment (Chip Seal) X X .... .... .... .... .... .... X X .... .... .... ....Multiple surface treatment X X .... .... .... .... .... .... X X .... .... .... ....Sand seal X X X .... .... .... .... .... X X .... .... .... ....

Asphalt applications:

Fog seal .... .... XA .... .... .... XB XB .... .... .... .... XB XB

Prime coat-penetrable surface .... .... .... XC .... .... XC XC .... .... .... .... XC XC

Tack coat .... .... XA .... .... .... XB XB .... .... .... .... XB XB

Dust binder .... .... .... .... .... .... XB XB .... .... .... .... XB XB

Mulch treatment .... .... .... .... .... .... XB XB .... .... .... .... XB XB

Crack filler .... .... .... .... .... .... X X .... .... .... .... X XMaintenance mix:

Immediate use .... .... .... .... .... X X X .... .... .... .... X X

RS

-1

RS

-2

MS

-1, H

FM

S-1

MS

-2, H

FM

S-2

MS

-2h

, HF

MS

-2h

HF

MS

-2s

SS

-1

SS

-1h

CR

S-1

CR

S-2

CM

S-2

CM

S-2

h

CS

S-1

CS

S-1

h

ASTM D2397AASHTO M140

ASTM D2397AASHTO M140

III.

DESIGN

CONSIDERATIONS

Design Considerations 3-1

Chapter 3Design Considerations

FUNDAMENTALS OF DESIGN

Many types of asphalt pavement structuresexist, along with a number of differentmethods for designing the thickness of eachelement in any pavement. Fundamental toeach design are the following:

1. Traffic loading (volume and weight)2. Soil-support capability (including drainage

considerations)3. Material specifications (aggregate and

asphalt)

Each element is an important variable in thestructural design process. The economic life ofthe final product could depend on the closeattention given to detail when analyzing trafficloadings, soil-support capability, and materialspecifications.

The degree of detail needed in a specificdesign situation is related to the type of useintended for the pavement and the sensitivityof each variable. For example, a freewaydesign with large traffic volumes and heavily-loaded trucks requires a careful estimate oftraffic; however, the number of bicycles andthe loading on a bicycle path would not besignificant factors in the pathÕs structuraldesign.

An obviously unstable soil condition (noted,perhaps, from previous experiences) indicatesthe need for a soil analysis during thethickness design process of almost any type ofpavement. Because drainage and soil-supportvalues are major factors in pavement life, it isimportant to know the quality of the support-ing soil. This is especially true for a facility thatwill require a large construction investment.

On the other hand, a specific traffic study orsoil analysis for a residential street or parking

lot may not be deemed necessary in a certainlocation. For example, a location having a longand successful record of asphalt pavementsconstructed for a specific use (e.g., drivewaysand residential streets) provides the designerwith a background for selecting acceptablevalues.

For the users of this Design Guide, much ofthe design work has been done Ð design chartsare presented for selecting pavement thick-ness. Traditionally, many designers grouppavements according to use and Òuse tablesÓare commonly applied throughout the UnitedStates. Chapter 4 provides design tables byspecific type of facility use.

TRAFFIC

Because the primary function of a pavementis to transmit and distribute wheel loads ofvehicles to the supporting subgrade, informa-tion about the traffic stream is required.Pavement must be designed to serve trafficneeds over a period of years. Therefore, thevolume of traffic and the various types ofvehicles using the facility must be estimatedfor the pavementÕs anticipated life.

A traffic assignment is made based on: (1)historic records of traffic volumes on com-parable types of highways and the anticipatedfunction of the highway under consideration,and (2) the percentage of trucks. The trafficanalysis procedure determines the repetitionsof an equivalent single axle load (ESAL). Thisparameter is defined as the equivalent numberof applications of an 18,000-pound, single-axleload during the pavementÕs design life.

The effects of truck traffic on a pavement canbe dramatic. Tests have shown that a single-unit, fully loaded, 80,000-pound truck cancause pavement damage equivalent to thatcaused by 6,000 automobiles. This illustrateswhy carefully made estimates of expectedtraffic are critical to proper pavement design.

Design Considerations3-2

In The Asphalt InstituteÕs Asphalt PavementThickness Design (IS-181), traffic is separatedinto classes. This Design Guide follows theInstituteÕs traffic class style by breaking trafficinto six classes, I through VI. Each class isdefined by an average daily traffic range, theaverage number of heavy trucks expected onthe pavement during the design period, andthe appropriate type of street or highway.

TRAFFIC CLASSIFICATIONS

Class I(Very Light) Less than 50 autos per day, lessthan 7,000 heavy trucks expected duringdesign period.

Parking lots, drivewaysLight traffic farm roadsSchool areas and playgroundsSeasonal recreational roadsSidewalks and bicycle pathsGolf cart pathsTennis courts

Class II(Light) Up to 200 autos per day, 7,000 to 15,000trucks expected during the design period.

Residential streetsRural farm roadsParking lots of less than 500 stallsAirports - 7,500 pound maximum gross

weight

Class III(Medium) Up to 700 autos per day, 70,000 to150,000 trucks expected during design period.

Urban minor collector streetsRural minor collector streetsParking lots - more than 500 stallsAirports - 15,000 pound maximum gross

weight.


Class IV(Medium) Up to 4,500 autos per day, 700,000 to1,500,000 trucks expected during designperiod.

Urban minor arterial and light industrialstreets

Rural major collector and minor arterialhighways

Industrial lots, truck stallsBus driveways and loading zonesAirports - 30,000 pound maximum gross

weight.

Class V(Heavy) Up to 9,500 autos per day, 2,000,000 to4,500,000 trucks expected during designperiod.

Urban freeways, expressways and otherprincipal arterial highwaysRural interstate and other principal arterialhighwaysLocal industrial streetsMajor service drives or entrancesAirports - 60,000 pound maximum gross

weight

Class VI(Very Heavy) Unlimited autos, 7,000,000 to15,000,000 trucks expected during designperiod.

Urban interstate highwaysSome industrial roadsAirports - over 60,000 pounds maximum

gross weight

For more information on this subject refer tothe Asphalt InstituteÕs publications ThicknessDesign-Asphalt Pavements for Highways and Streets (MS-1) and Asphalt PavementThickness Design (IS-181).


SOIL SUPPORT CAPABILITY

The ability of the subgrade to support loadstransmitted from the pavement is one of themost important factors in determining pave-ment thickness. The subgrade must serve as aworking platform to support construction

different abilities to provide support. A sandysoil, for example, will support greater loadswithout deformation than a silty clay soil.Thus, for any given traffic volume and weightof vehicles using the roadway, a greaterpavement thickness must be provided on claysoils than on sandy soils.

Figure 3-1. Spread of wheel-load through pavement structure.

equipment and as a foundation for the pave-ment structure that supports and distributestraffic loads. Thus, it is essential to evaluate thestrength of the subgrade before beginning thestructural design of the pavement. Figure 3-1shows the spread of wheel load through thepavement structure and on to the subgrade.

If sufficient pavement thickness is not pro-vided, the applied loads could cause greaterstresses on the subgrade than it can resist. Thismay result in deflection of the pavement andultimately in its failure.

In street and highway construction, thesubgrade provides the foundation for thepavement. Different types of soils have

Soil ClassificationsSoil is classified for road and street construc-

tion in order to predict subgrade performanceon the basis of a few simple tests. The AmericanAssociation of State and Highway Transporta-tion Officials (AASHTO) classification systemfor soils is commonly used as a test forsubgrade-support value.

According to the AASHTO system, soils thathave approximately the same general load-carrying capabilities are grouped in classifica-tions of A-1 through A-7. (See Table 3-1.) Ingeneral the best highway subgrade soils are A-1, and the worst are A-7. The classification isbased on the sieve analysis, plasticity index,and liquid limit of the soil being tested.


Table 3-1. Classification of Soils and Soil-Aggregate Mixtures (With Suggested Subgroups)

Silt-Clay Materials

General Granular Materials (More than 35% of Total Sample

Classification (35% or Less of Total Sample Passing No. 200) Passing No. 200)

A-7

A-1 A-3 A-2 A-4 A-5 A-6 A-7-5

Group A-7-6

Classification A-1-a A-1-b A-2-4 A-2-5 A-2-6 A-2-7

Sieve Analysis,

percent passing:

No. 10 50 max

No. 40 30 max 50 max 51 min

No. 200 15 max 25 max 10 max 35 max 35 max 35 max 35 max 36 min 36 min 36 min 36 min

Characteristics of

fraction passing

No. 40:

Liquid Limit 40 max 41 min 40 max 41 min 40 max 41 min 40 max 41 min

Plasticity Index 6 max NP 10 max 10 max 11 min 11 min 10 max 10 max 11 min 11 min

Usual Types of

Significant

Constituent Stone Fragments, Fine

Materials Gravel & Sand Sand Silty or Clayey Gravel and Sand Silty Soils Clayey Soils

General Rating

As Subgrade Excellent to Good Fair to Poor

The state of Iowa has been subdivided intosurface soil areas that reflect their engineeringsoil classification. The accompanying figureprovides a general soil classification map ofIowa. In addition, soil bulletins with morecomplete and detailed descriptions of soiltypes are available for each Iowa county. Notethat these maps provide only a generalgrouping of a range of soils. Local spots mayvary considerably.


Subgrade StrengthBecause thickness calculations depend on

the strength of the finished subgrade, the soilmust be tested for this information. Tests arebased on bearing capacity related to themoisture and density of the soil. The CaliforniaBearing Ratio (CBR) is one of the most widelyused methods of designing pavementstructure. Once the CBR value is determined,the soil classification can be identified. Or,when the soil classification is known, a relativeCBR value can also be identified.

The lower the CBR value of a particular soil,the less strength it has to support thepavement. This means that a thicker pavementstructure is needed on a soil with a low CBRrating than on a soil with a high CBR rating.Generally, clays have a CBR classification of 6.Silty loam and sandy loam soils are next withCBR values of 6 to 8. The best soils for roadbuilding purposes are sands and gravelswhose CBR ratings normally exceed 10.

The change in pavement thickness needed tocarry a given traffic load is not directlyproportional to the change in CBR value of thesubgrade soil. For example, a one-unit changein CBR from 5 to 4 requires a greater increasein pavement thickness than does a one-unitCBR change from 10 to 9.

A number of soil classification-strengthsystems are currently in use for roads and air-ports. A correlation chart follows for a generalsoil overview.



ModerateModerate subgrade soils are those that

retain a moderate degree of firmness underadverse moisture conditions. Included aresuch soils as loams, silty sands, and sandgravels containing moderate amounts of claysand fine silts. When this soil becomes acohesive material, it should have a minimumproctor density of 110 pounds per square inch.A soil classified as moderate will have a CBRvalue of 6 to 8.

PoorPoor subgrade soils are those that become

quite soft and plastic when wet. Included arethose soils having appreciable amounts of clayand fine silt (50 percent or more) passing a No. 200 sieve. The coarse silts and sandy loamsmay also exhibit poor bearing properties inareas where deep-frost penetration into thesubgrade is encountered for any appreciableperiods of time. This also is true where thewater table rises close to the surface duringcertain periods of the year. A soil classified aspoor will have a CBR value of 3 to 5.

Very poor soils (those with a CBR of 3 orlower) often perform poorly as pavementsubgrades. However, to improve their per-formance, these soils can be stabilized withgranular material or a geotextile. Lime, fly-ash,asphalt cement, portland cement, and combi-nations of cement stabilizers also can be addedto improve the subgrade support. Theselection of a stabilizing agent, the amount touse, and the application procedure depend onthe soil classification and the subgrade-support value desired. These should bedetermined through appropriate laboratorytesting.

Soil TestingA qualified laboratory can conduct tests to

provide soil classification and subgradestrength information (such as the CBR). Suchtesting is necessary to ensure a properstructural design and is part of all majorprojects. However, such soil testing isrelatively expensive, especially for smallprojects, and may not be available for allprojects.

Subgrade ClassesFor the designs recommended in this

manual, all soils have been divided into threeclasses: good (G), Moderate (M), and poor (P),CBR design values are assigned to thesedifferent subgrade classes.

GoodGood subgrade soils retain a substantial

amount of their load-supporting capacitywhen wet. Included are the clean sands, sand-gravels, and those free of detrimental amountsof plastic materials. Excellent subgrade soilsare relatively unaffected by moisture or frostand contain less than 15 percent passing a No. 200 mesh sieve. A soil classified as goodwill have a CBR value of 9 or greater.


DRAINAGE

General ConsiderationsHighway engineers recognize the impor-

tance of good drainage in the design, construc-tion, and maintenance of any pavement.Probably no other single factor plays such animportant role in determining the ability of apavement to provide trouble-free servicethroughout long periods of time.

The accumulation of water in the subgrade,or in an untreated aggregate base course,usually creates problems. When the soil issaturated, application of dynamic wheel loadsinduces pore pressures and lowers the resist-ance to shear. Some soils have a high volumechange (when water is added), which causesdifferential heaving. The subsequent weaken-ing of the pavement structure causes it to losestability and its capability to support trafficloads.

The combination of water in the pavementÕsasphalt layers and dynamic, repeated trafficloading can strip or separate the asphalt filmfrom the aggregate. This reduces the load-carrying capacity of the mixture.

When developing the features of a highwaydrainage system, it is important to consider thesystemÕs principal purposes: (1) to collect anddrain away both surface water and subsurfacewater; (2) to lower the groundwater table, ifnecessary; (3) to intercept water from sur-rounding areas and carry it away from theroadway; and (4) to prevent or retard erosion.

There are two basic categories of drainage Ðsurface and subsurface. Surface drainageincludes the disposal of all water present onthe pavement surface, shoulder surface, andthe adjacent ground when sloped toward thepavement. Subsurface drainage deals withwater in the subbase, the surrounding soil, and

in the several pavement courses. Inadequateattention to either of these two drainage condi-tions can lead to premature pavement failure.

Surface DrainageIn surface drainage conditions, the

pavement and shoulders must be crowned orcross-sloped to facilitate the flow of water offof the roadway. Normally, the cross-slopemoves the water to a curbed or inverted-shaped gutter and then off of the pavementinto a storm sewer or flume to a ditch.

On parking areas or playgrounds, the cross-slope or crown may be inverted toward acenter swale with a grated inlet for drainageinterception.

Shoulders can best be drained if the entireshoulder width has an asphalt-paved surface.If the shoulder is not asphalt, its cross-slopeshould be steeper in order to minimize seepagethrough the aggregate or grass shoulder.

Surface drainage from the pavement andfrom the adjacent land areas must be inter-cepted and disposed of. If a curbed section isprovided, drainage is accumulated in thegutter area and periodically discharged intoeither a pavement inlet or a ditch through aflume. The determination of inlet locationsrequires technical calculations and studies tomaintain a tolerable spread of water on thepavement.

Drainage ditches are constructed along theedges of non-curbed roadway sections. Waterflowing from the pavement and shouldersurfaces moves down the roadway foreslopeinto a rounded ditch area. A backslope leadsfrom the bottom of the ditch up to intercept theadjacent land. The adjacent land is frequentlysloped toward the ditch and can contribute toa sizable portion of the drainage flow.


Good design practices will provide cross-slopes both on the surface and in theunderlying pavement courses and subgrade.In this way, water will not accumulate but willflow laterally to the sides.

Subsurface DrainageSubsurface water is free water that

percolates through, or is contained in, the soilbeneath the surface. When it emerges orescapes from the soil, it is referred to asseepage water. The point of emergence iscalled a seepage area or a spring.

Pavement subsurface water usually ispresent as free water that flows under the forceof gravity or as capillary water that movesunder capillary action in the soil.

Water will rise from the underlying soilthrough the subgrade and into an untreatedaggregate pavement course. This free waterwill move readily into an untreated aggregatebase to a low point on the profile. If steepgrades are present, and the subsurface waterflowing in an untreated aggregate base to thelow spot is not intercepted, a hydrostatic headmay result. This lifting force will cause afailure of the pavement structure. Water in thepavement courses also may contribute to thestripping of asphalt films from the aggregateparticles.

SubdrainsWhen water collects in the structural

elements of the pavement, subdrains are

required. Identification of these areas anddetermination of drain locations require thetechnical expertise and insight of an engineer.The choice of drain filter material and thedesign of the drainage system must be givencareful attention by experts. Perforated andslotted pipe usually serve to move the freewater from the trouble spot to a drainage area.

Check Drainage During ConstructionRegardless of the care used in the pre-

liminary investigation, the soil survey, and inthe pavement structureÕs design, it is usuallynot possible to determine from borings theexact elevation of water-bearing strata or therate of flow that will develop. For this reason,it is essential that the engineer reevaluate theconditions and check the need for, and theadequacy of, any subsurface drainage indicat-ed on the plans.

Soil conditions should be observed duringthe grading and subgrade preparation work.Any wet, soft, or spongy areas encountered atgrade should be investigated and provisionsmade for their proper drainage. Even a minorrate of seepage may build up to a largequantity of water over a period of time if ameans of escape is not provided. Such a softspot usually forewarns of a structural failure ata later date-even shortly after traffic has usedthe new facility. After the pavement is in place,corrective measures are costly, create trafficproblems, and can cause poor public relations.


Figure 3-4 Figure 3-5

DESIGN TYPES

In general, the design of a new asphaltpavement structure involves two basicpavement types: (1) full-depth pavements, and(2) pavements with an untreated aggregatebase course.

Full-depth, Asphalt Concrete paving is onein which asphalt mixtures are used for allcourses above the subgrade. Such pavementsare less affected by subgrade moisture and aremore conducive to staged construction. Full-depth asphalt pavement is used in all types ofhighway construction and where highvolumes of traffic and trucks are anticipated.

Untreated aggregate base pavements may beused where local aggregates and subsurfacedrainage conditions are suitable and wheretraffic loadings are minimal. The untreatedaggregate base is placed and compacted on the prepared subgrade. In general, an asphaltbinder and surface course are used to completethe pavement structure. Although the initialcost for untreated aggregate base asphaltpavements may be lower than the cost for full-depth, hot mix types, the former type shouldbe used with caution. Moisture in the base maycause pavement failure.

Table 3-2 Gradation of sample RAP material

Sieve %Passing %PassingSize Rang AVERAGE

3/4" 98-100 1001/2" 94-100 983/8" 84-98 93

No. 4 65-88 77No. 8 51-74 62

No. 16 36-57 49No. 30 28-42 36No. 50 17-30 24No. 100 11-26 18No. 200 9-22 14


ASPHALT CONCRETESPECIFICATIONS

It is recommended that specifications forAsphalt Concrete follow Iowa Department ofTransportation Standard Specifications for theparticular class and mixture size required. Thiswill result in uniformity and economy becausemost APAI-member contractors may have jobmixes on several mixtures already preparedfor state and local agency use. In the absence ofa previously prepared job mix, the contractoror private testing should develop a job mixformula for the desired project, and intendeduse.

The following gradations are suggestedguidelines for the class and mixture sizespecified. The asphalt cement content is aguide only and may need to be adjusted tomeet local aggregate conditions and intendeduse.

Quality of aggregates (according to factorssuch as freeze and thaw, abrasion, plasticityindex, etc.) for the various mixes can beobtained from the Iowa DOT StandardSpecifications in the 3 sections listed in thefollowing tables.

Salvaged and Reclaimed MaterialRecycling of reclaimed asphalt pavement

(RAP) material into new asphalt concrete hasbecome a routine and accepted process for useof the salvaged product. The contractorsubstitutes reclaimed aggregate and binder for

virgin materials at varying ratios from 10-50%by weight. The salvaged material may be takenfrom the project or a stockpile provided by thecontractor. Control of the use and quality of therecycled mix shall be through the job mixformula process. Salvaged material may beused in the base, binder, and surface courses oftype A or B mixes for which it qualifies.Historical test reults from milled materialtaken from Iowa DOT projects indicate thatmillings are falling within the following limits.

Salvaged materials, whether previouslyprocesses or not, shall be sized for the intendedmix use. Final gradation of the recycled mixshall meet the requirements for the specifiedmix size and type.

Aggregate for Type B. Asphalt Concrete

Aggregate for Type B asphalt concrete shallmeet the requirements as specified in Section4126, lowa DOT Standard Specifications.

Gradation: The job mix formula for the mix-ture size specified, when tested by means oflaboratory sieves, shall meet the followingrequirements:

Table 3-3. Gradation of Job Mix: Type BAsphalt Concrete

Percent PassingClass 1 and 2*Mixture Size

SieveSize 1 inch 3/4 inch 1/2 inch 3/8 inch

1-1/2 inch 100

1 inch 92-100 100

3/4 inch 77-92 98-100 100

1/2 inch 60-80 76-95 92-100 100

3/8 inch — 60-88 70-94 98-100

No. 4 34-55 42-70 50-75 63-89

No. 8 20-38 30-56 36-60 44-68

No. 30 7-20 14-32 16-34 20-37

No. 200 2-7 3-7 3-7 3-7

Asphalt Cement Content: 5-7%

AC-5 grade recommended for Type B BaseAC-10 grade recommended for Type B Surface*Class 1 - 30 percent crushed particles (minimum)*Class 2 - no minimum percentage of crushed particles50 - Blow Marshall mix criteria normally specified


Aggregate for Type A Asphalt Concrete

Aggregate for Type A asphalt concrete shallmeet the requirements as specified in Section4127, lowa DOT Standard Specifications.

Gradation: The job mix formula for themixture size specified, when tested by meansof laboratory sieves, shall meet the followingrequirements:

Table 3-4. Gradation of Job Mix: Type AAsphalt Concrete

Percent PassingMixture Size

Sieve Size 1 inch 3/4 inch 1/2 inch 3/8 inch

1 -1/2 inch 100

1 inch 92-100 100

3/4 inch 77-92 98-100 100

1/2 inch 60-80 76-95 92-100 100

3/8 inch — 60-88 70-94 98-100

No. 4 37-58 42-70 50-75 63-89

No. 8 28-44 30-56 36-60 44-68

No. 30 13-27 14-32 16-34 20-37

No. 200 3-7 3-7 3-7 3-7

Asphalt Cement Content: 5-7%

AC-10 grade recommended for Type A Concrete*60 percent crushed particles (minimum)50 - Blow Marshall mix criteria normally specified


Standard Mix DescriptionsIt is recommended that designs and

specifications for Asphalt Concrete follows the Iowa Department of Transportation stand-ards for the specific type and mix designrequired. Instructional Memorandum on FieldInspection manuals published by the CentralOffice of Materials, are available from the DOTstoreroom. Designated mix descriptionsfollow.

Recycled Asphalt ConcreteRecycled asphalt concrete mixtures are

composed of a combination of virgin gravel,crushed stone, sand and salvaged/reclaimedasphalt paving (RAP) materials. The combinedaggregates are mixed with asphalt cementthrough a hot mix plant mix process toproduce a recycled mix.

Job mix formulas are required by thespecifications to determine the target percentasphalt binder for a specified mix type andgradation. Recycled materials are routinelyused in base, binder, and surface courses.These mixtures may be designed as type A or Basphalt concrete with the same qualityrequirements, therefore requiring no namechange or designation.

Type B Asphalt ConcreteType B Asphalt Concrete base, binder,

leveling, strengthening, and surface coursemixtures are composed of gravel; crushedstone; or combinations of gravel, stone, andsand, produced from approved sources andformulated to provide service for roadscarrying low to moderate traffic. Theformulation procedure results in a job mixformula for each aggregate combination alongwith a recommended percentage of asphaltcement.

Type B Asphalt Concrete may be placed as abase, binder, or surface course dependingupon mix class and size. Type B specificationsare used in secondary road systems, municipalstreets, parking lots, and other areas. To meetall appropriate requirements, and becauseseveral options are available, care must beexercised in selecting the mix class, liftthickness, and mix size during the variousstages of design and construction.

Job mix formulas are required by thespecifications for all aggregate combinations.The formulas are comprised of the aggregatepercentages, percent asphalt, and gradation aslimited by the specification requirements.

Type A Asphalt ConcreteType A Asphalt Concrete binder, leveling,

strengthening, and surface course mixtures arecomposed of combinations of high-qualitygravel, crushed stone, and sand producedfrom approved sources and formulated forservice on road surfaces carrying a highvolume of traffic; and as surface courses withlower-quality base courses for other uses.Because four mix sizes are available, care mustbe exercised in selecting the lift thickness and mix sizes during the various stages ofdesign and construction so that appropriaterequirements are met.

Job mix formulas are required by thespecifications for all aggregate combinations.The formulas are comprised of the aggregatepercentages, percent asphalt, and gradation aslimited by specified tolerances for eachcontrolling sieve size.


CONSTRUCTION OF ASPHALT PAVEMENTS

Construction EquipmentIt is the responsibility of the contractor to

provide equipment that will produce results incompliance with the plans and specificationsof the contract. The following section containsinformation on the basic equipment used toproduce and construct Asphalt Concretepavements.

Asphalt Mixing FacilitiesThe mixing facility produces the Asphalt

Concrete mixture placed as pavement. Thefacility should be designed and coordinated toproduce mixtures within specified job mixtolerances.

Asphalt storage tanks must have a device forthe controlled heating of material to tempera-ture requirements as specified. Heating shouldbe accomplished so that no flame will come incontact with the tank. The circulating systemshould be large enough to ensure proper andcontinuous circulation of asphalt betweenstorage tank and mixer during the entireoperating period. While the pump is inoperation, the discharge end of the circulatingpipeline should be kept below the surface ofthe asphalt in the tank.

The facility should have an accurate meansfor feeding the aggregate into the dryer toensure uniform production and a constanttemperature. The facility should contain arotary drum dryer that will continuouslyagitate the aggregates during the heating,drying, and mixing processes.

For batch mixing processes, screens may bepositioned over the hot aggregate storage binsto separate all aggregates to sizes required forproportioning to meet the job mix formulae.Where no such screens are used, proportioningmust be handled as part of the cold-feedsystem.

If drum mixers or continuous mixing plantsare used in the production of mixes, approvedmaterials must be fed into the cold-feed systemin the proper proportions to meet the job mixformulae.

The facility must have the means to obtainthe required percentage of asphalt in the mixwithin the tolerance specified. This can beaccomplished by weighing, metering, ormeasuring volumetrically. Steam jacketing orother insulation should maintain the specifiedtemperature of asphalt in pipelines, meters,buckets, spray bars, flow lines, and othercontainers.

A thermometer ranging from 200¡F to 400¡Fshould be placed in the asphalt feed line ortank.

The facility should have a dust collector, amixer cover, and whatever additional housingnecessary to ensure proper dust control.

Adequate and safe stairways to the mixerplatform and guarded ladders to other units ofthe facility should be provided. All gears,pulleys, chains, sprockets, and other danger-ous moving parts should be well guarded andprotected. A platform for sampling andinspection of the mix should be located nearthe facility.


The use of surge or storage bins is permittedfor storing asphalt pavement materials.

Hauling EquipmentHaul trucks are used to bring the Asphalt

Concrete from the asphalt mixing facility to thepaving site. Equipment used in haulingbituminous mixtures should be clean and havetight bodies to prevent material loss. Theseunits can be equipped with suitable covers toprotect the mixture in transit duringunfavorable weather conditions.

the depth and crown section specified withoutthe aid of manual adjustment during opera-tion. Pavers should be capable of spreadingmixes without segregation or tearing andproducing a finished surface of even anduniform texture.

Compaction EquipmentCompaction equipment is used to compact

the Asphalt Concrete to attain density afterplacement. The compaction equipment shouldbe of the type or types that will produce therequired density and pavement smoothness.Steel-wheeled rollers are of four types Ð three-wheeled, two-axle tandem, three-axle tandem,and vibratory. These rollers should beequipped with power units. Rollers should bein good working condition and equipped witha reversing clutch. Rollers should haveadjustable scrapers to keep the wheel surfacesclean and an efficient means of keeping themwet to prevent mixes from sticking. Thesesurfaces should have no flat areas, openings,or projections that will mar the surface of thepavement.Spreading Equipment

Spreading equipment is used to place theAsphalt Concrete as pavement. Where feasible,the Asphalt Concrete should be placed andspread by a mechanical spreader. Mechanical,self-powered pavers should be capable ofspreading the mix within the specifiedtolerances and true to the line, grade, andcrown indicated on the plans. A motor patrolmay be used for the leveling course.

Pavers should be equipped with efficientsteering devices and should be capable oftraveling both forward and in reverse. Theyshould be equipped with hoppers anddistributing screws that place the mix in frontof screeds. The screed unit should be adjust-able in height and crown and equipped with acontrolled heating device for use whenrequired. The screed must strike off the mix to

Pneumatic-tired rollers should be self-pro-pelled. The rollers should be equipped withpneumatic tires of equal size and diameter that are capable of exerting average contactpressure.


The wheels of the roller should be spaced sothat one pass will accomplish one completecoverage equal to the rolling width of themachine. There should be a minimum of 1/4inch-overlap of the tracking wheels. The rollershould be constructed so that the contactpressure will be uniform for all wheels and thetire pressure of the tires will not vary morethan 5 pounds per square inch. The rollersshould be constructed with enough ballastspace to provide uniform wheel loading asmay be required. The operating weight andtire pressure of the roller may be varied toobtain contact pressures that will result in thedensity.

Cold MillingCold milling is the most common pavement

scarification method for salvaging material.This method uses a self-propelled millingmachine with a rotating drum containingspecial teeth that cut the pavement to apredetermined depth and reduce the size ofthe salvaged material. Single-pass cuttingwidths of up to 12 feet and depths of 4 incheshave been attained with this type of machine.The drums are hydraulically controlled andare capable of maintaining road profile anddepth of cut to 1/8 inch. Milled material isusually suitable for hot or cold recycling withlittle additional breakdown.

Construction PracticesPreparation of Subgrade

Remove all large rock, debris, and topsoilfrom the area to be paved. All vegetation,including root systems, should be removed. Toprevent future growth, the subgrade should betreated with an approved herbicide. Install alldrainage and utility facilities and thenproperly backfill and compact.

The subgrade must be properly shaped tomeet true lines and elevations and compactedto not less than 95 percent of maximumlaboratory density. The surface of the com-pacted subgrade should not vary more than3/4 inch from the established grade.

Areas showing pronounced deflectionunder construction traffic indicate instabilityin the subgrade. If the situation is not correctedby reworking and additional rolling, the areasmust be removed and replaced with suitablematerial and compacted or stablized using ageotextile. The use of Asphalt Concrete base orcourse granular material is recommended.

Constructing Asphalt Concrete BaseThe Asphalt Concrete base may consist of

one or more courses placed on a prepared sub-grade. It must have a total compactedthickness as indicated on the plans or as speci-fied. In general, a base with total thickness of 4inches or less should be placed in one lift. Abase with a total thickness of more than 4inches may be placed in two or more lifts withthe bottom lift having a minimum of 3 inches.

Untreated Aggregate BaseThe crushed aggregate base course may

consist of one or more layers placed directly onthe prepared subgrade. The material must bespread and compacted to the requiredthickness, grades, and dimensions indicated inthe plans or as specified. The minimumcompacted thickness of each lift should be noless than two times the size of the largestaggregate particle, or 4 inches, whichever isgreater. The maximum compacted lift thick-ness should be 6 inches.

Binder and Surface CoursesThe upper lifts of the pavement may consist

of one or more courses of Asphalt Concreteplaced on the previously constructed AsphaltConcrete base. In general, the top or wearingcourse must not be constructed to a depthgreater than 3 inches. Where a thicknessgreater than 3 inches is indicated, it should beplaced in two courses consisting of a binderand a surface or wearing course. The mini-mum lift thickness must be 1 inch, but thisthickness should never be less than two timesthe maximum particle size.


Figure 3-6

Tack CoatA tack or bond coat of CSS-1, SS-1, MC-70 or

an approved alternate should be appliedbetween each course at an undiluted rate of0.02 to 0.05 gallons per square yard. Thesurface must be cleaned of all dust, dirt, orother loose material before the bond coat isapplied. If emulsion is used, it should bediluted with equal parts of water or asspecified in the proposal.

All pavement markings on public highwaysmust comply with the Manual on UniformTraffic Control Devices (MUTCD). Standardsfor color, materials, width, shape, and conceptare set forth in the MUTCD.

The most frequently used pavement mark-ings are longitudinal markings. The basicconcept is to use yellow lines to delineate theseparation of traffic flows in opposing direc-tions or to mark the left edge of pavement ofdivided highways and one-way roads. Solidyellow lines are also used to mark no passingzones. White lines are used to separate trafficlanes flowing in the same direction or to markthe outside edge of pavements.

Minimum GradeIt is recommended that the minimum

pavement grade be not less than 2 percent(approximately 1/4 inch per foot) to ensureproper surface drainage.

Pavement MarkingsPavement markings have an important

function in traffic control. They convey certainregulations and warnings in a clearly under-standable manner without diverting thedriverÕs attention from the roadway. Anasphalt pavement clearly has an advantage inproviding highly visible, attention-attractingmarkings Ð even under adverse weatherconditions. White- and yellow-painted mark-ings or thermo markings stand out on theblack background.

The patterns and width of longitudinal linesvary with use. A broken line is formed bysegments and gaps, usually in the ratio of 1:3.On rural highways, a recommended standardis 10-foot segments and 30-foot gaps. A normalline is 4 to 6 inches wide.

Flaggers may be neededfor safety. It is importantthat they be properlydressed and instructed inflagging standards.Flagging procedures areset forth in Part Xl of theMUTCD, and the lowaDOT providessupplemental informationand training booklets.

Figure 3-7. Use of handdevices by flagger.


It is beyond the scope of this Design Guideto present these standards in more detail. Theuser should refer to these standards whenplacing pavement markings. All city andcounty engineering offices and most othertransportation engineering organizations havea copy of the MUTCD.

Traffic Control Through Work AreasThe control of traffic through work areas in a

safe and expeditious manner, while maintain-ing good public relations, is an essential part ofhighway construction and maintenanceoperations. In todayÕs litigious society, efficient

traffic control may mean the differencebetween no liability and a large financialaward should an accident occur. No agency,owner, or construction company is immunefrom alleged responsibility for an accident.

Because of the multitude of construction andmaintenance applications, it is impossible tolist the standards for signs, barricades, andmarkings in this publication. For more detailedinformation on a specific application, refer toPart VI in the MUTCD and to the Iowa DOT.

Barricades are portabledevices used to controltraffic by closing,restricting, or delineatingconstruction areas. TheMUTCD specifies the typeof barricade to use for aspecific situation anddescribes barricadecharacteristics. Thediagonal stripes slopedownward either left orright from the upper tolower panel and should“slope downward in thedirection toward whichtraffic must turn indetouring.”

When a road or a site normally used by traffic is closed, it should be barricaded and signed inaccordance with the MUTCD.

Figure 3-8. Channelizing devices.


Aggregate Weighing-Job Mix Formulas Compaction Testing-Nuclear Gauge


TESTING AND INSPECTION

Inspection and testing of the production andplacement of Asphalt Concrete Ð or of anymaterial Ð is necessary to ensure a qualityproduct. Plant and field inspections include:(1) the preparation of the aggregate; (2) theAsphalt Concrete plant setup and operation;(3) the control of the Asphalt Concrete mixture;(4) the delivery and placement; and (5) thefinal finishing and compaction.

It is beyond the scope of this Design Guideto do more than emphasize the importance ofa quality testing and inspection program. TheIowa DOT publishes manuals on asphalt plantinspection and field testing that are availablethrough the DOT Storeroom. Training courseson this subject are offered by APAI and otheragencies.

Hot Box Sample Smoothness Testing-California Profilograph

III.

DESIGN

CONSIDERATIONS

Thickness Design 4-1

Chapter 4

Thickness Design

GENERAL CONSIDERATIONS

Several procedures can be used to calculatethe thickness of the proposed asphaltpavement. All are based on the volume andweight of the traffic that will use the facilityand on the load-supporting capability of theunderlying soil.

The AASHTO Road Test and other studieshave indicated that heavy-vehicle wheel loadscause much greater damage to roads than dolight loads. Thus, where large volumes oftraffic with heavily loaded trucks are antici-pated, an in-depth analysis of the pavementthickness is important. Because all of thehigher functional classifications have thepotential for heavy loadings, a traffic analysisis an important part of the preparation forthickness computations. Similarly, a know-ledge of the load-bearing capability of the soilis an important aspect of the structural design

process. The lack of a soil study with appro-priate corrective action could significantlyshorten the life of a poorly drained pavement.

All of the design procedures available for astructural thickness analysis cannot beincluded here. Additional information isincluded in The Asphalt InstituteÕs ThicknessDesign Manual (MS 1) and their Simplifiedand Abridged Version published in Informa-tion Series No. 18 (IS-181). Another reference isThe AASHTO Guide for Design of PavementStructures, 1986. These guides are based onmechanistic/empirical design models, andthey use Nomographs to attain pavementthickness. Several computer programs fordesigning pavements (including AsphaltInstitute and AASHTO programs) are alsoavailable. The APAI or your contractor canhelp you with design questions.

Thickness Design4-2

PAVEMENT THICKNESS DESIGNTABLES

Future traffic assignments can be rathernebulous and are subject to many externalinfluences. Some areas see no growth over adesign period. Therefore, common practice isto group categories of traffic into classes.Similarly, it has been found that, based on alocal knowledge, soil-supporting values can begrouped into classifications of poor, moderate,and good. These classifications (see Chapter 3)provide an opportunity to use pavementthickness design tables rather than moredetailed formula procedures. These tableshave been prepared by experts in the industryto simplify the process for engineers, tech-nicians, and architects who prepare apavement design.

Design Procedure

Tables 4-1 through 4-5 can be used directly toselect design thicknesses from the design inputfactors. In order to use the tables, appropriatetraffic and subgrade classes must be selected asfollows.

TrafficThe design procedure separates traffic into

six classes (I through VI). Each class is definedby the number of autos per day, the averagedaily number of heavy trucks expected on thefacility during the design period, and the typeof street or highway. Traffic classifications arepresented in Chapter 3. The pavementthicknesses given in the tables of this and thefollowing chapter are based on the averagedaily traffic (ADT) values over a 20-yeardesign period. Heavy trucks are described astwo-axle, six-tire vehicles or larger.

SoilsIt is desirable to have laboratory tests on the

subgrade soil. However, if tests are not

available, a design may be based on carefulfield examinations by an engineer. Soils maybe classified as good, moderate, or poor or bya CBR value. Soil classifications are presentedin Chapter 3. If a soil CBR value lies betweenthose given in the classifications, the lowerclassification is used.

Design StepsThe following steps can be used to deter-

mine a pavement thickness.

1. From the known average daily traffic,determine the total number of trucksover the design period. Using thisinformation, select the trafficclassifications (Class I through VI) fromChapter 3.

2. Select a subgrade class (good, moderate,or poor) from Chapter 3 using soil datafrom the project. If no soil information isknown, use the poor classification for thesubgrade.

3. Select a design thickness from Tables 4-1through 4-5 using the selected trafficclass and subgrade class.

Design Example¥ A collector street is estimated to carry 500

vehicles and 20 trucks a day. Traffic classIII is selected using Chapter 3.

¥ No soil data is known, so the engineerselects the poor soil classification.

¥ The total design thickness selected fromTable 4-2 is 7-1/2 inches. The base courseis 6 inches, and the surface course is 1-1/2 inches.


Table 4-1. Thickness Design: Residential Streets

A. For Asphalt Concrete Base Pavements

Thickness in InchesDesign Criteria* Asphalt Concrete

Traffic Class Subgrade(ADT) Class CBR Base Surface Total

II Good 9 4.0 1.0 5.0(50-200 ADT) Moderate 6 5.0 1.0 6.0

Poor 3 5.5 1.5 7.0

III Good 9 4.0 1.5 5.5(201-700 ADT) Moderate 6 5.0 1.5 6.5

Poor 3 6.0 1.5 7.5

B. For Untreated Aggregate Base Pavements

Design Criteria* Thickness in Inches

Untreated Asphalt AsphaltTraffic Class Subgrade Aggregate Concrete Concrete

(ADT) Class CBR Base Base Surface Total

II Good 9 5.0 .0 3.0 8.0(50-200 ADT) Moderate 6 8.0 .0 3.0 11.0

Poor 3 8.0 2.0 2.0 12.0

III Good 9 7.0 .0 3.0 10.0(201-700 ADT) Moderate 6 8.0 2.0 2.0 12.0

Poor 3 8.0 3.0 2.0 13.0

*See chapter 3 for traffic and soil class details

Residential StreetsThe primary function of residential streets is

to provide access to abutting property. Thisclassification consists of the largest portion ofthe street and road network and provides thelinkage to connect to higher types of facilities.MotoristsÕ speeds may be low, or higher,depending on the standards to which thespecific facility is designed.

Most trips on residential streets are short,and traffic volumes are low. Truck traffic isusually limited to vehicles that provideresidential services such as trash pickup,moving vans, heating oil delivery, etc.

Thickness Design4-4

Collector StreetsCollector or feeder streets connect the

residential street system with arterial routes.This classification of street serves dualfunctions of both land access and through-traffic movement. The mileage of collectors inany one jurisdiction may be very small.Generally, collectors have moderate amountsof low-to-intermediate-speed traffic, includingsome bus traffic, and heavy trucks.

Table 4-2. Thickness Design: Collector Streets





Poor 3 5.5 1.5 7.0


Poor 3 6.0 1.5 7.5

IV Good 9 5.5 2.0 7.5(1,501-4,500 ADT) Moderate 6 6.5 2.0 8.5

Poor 3 7.5 2.0 9.5






Poor 3 8.0 2.0 2.0 12.0


Poor 3 8.0 3.0 2.0 13.0

IV Good 9 8.0 3.0 2.0 13.0(1,500-4,500 ADT) Moderate 6 8.0 3.5 2.0 13.5

Poor 3 8.0 4.5 2.0 14.5



Table 4-3. Thickness Design: Arterial Streets



IV Good 9 5.5 2.0 7.5

(1,501-4,500 ADT) Moderate 6 6.5 2.0 8.5

Poor 3 7.5 2.0 9.5

V Good 9 7.5 2.5 10.0

(6,001-9,500 ADT) Moderate 6 8.0 3.0 11.0

Poor 3 9.0 3.0 12.0

VI Good 9

(9,501 & Above ADT) Moderate 6

Poor 3


Special design considerationneeded. Refer to a morecomplete design procedure.

Arterial StreetsArterial streets provide the highest operat-

ing speeds and the highest levels of trafficservice. They serve the major corridors oftraffic and are usually multiple lane in urbanareas. They are typically high-volume facilitiesthat connect major activity centers.

As with the design of residential and collect-or facilities, many localities have adoptedstandards for the design and construction ofarterials. All applicable local and state codes,standards, and specifications should becomplied with when designing and construct-ing these facilities. The information containedin this Design Guide should augment localguidelines in assuring the proper planning anddesign of arterials.

Although arterials frequently carry verylarge traffic volumes and heavy truck traffic,

pavement designs recommended herein areapplicable only to facilities having a lowpercentage of truck traffic. Design of AsphaltConcrete pavements for trucking highwaysrequires considerable expertise and detailedanalysis.

Thickness Design4-6

Low-Volume Secondary and Rural RoadsLow-volume rural roads consist of local

roads and collectors whose primary function isto provide access to abutting property andfrom there to arterial routes. MotoristsÕ speedsmay be low, or higher depending on the stand-ards to which the specific facility is designed.

Truck traffic is usually low, consisting ofsome bus traffic and heavy trucks. Most trafficconsists of vehicles providing local servicesuch as heating oil and gasoline, local farmtraffic, and farm vehicles.

Table 4-4. Thickness Design: Low Volume Secondary and Rural Roads





Poor 3 5.5 1.5 7.0


Poor 3 6.0 1.5 7.5

IV Good 9 5.5 2.0 7.5(1,501-4,500 ADT) Moderate 6 6.5 2.0 8.5

Poor 3 7.5 2.0 9.5






Poor 3 8.0 2.0 2.0 12.0


Poor 3 8.0 3.0 2.0 13.0

IV Good 9 8.0 3.0 2.0 13.0(1,500-4,500 ADT) Moderate 6 8.0 3.5 2.0 13.5

Poor 3 8.0 4.5 2.0 14.5



High-Volume Secondary and Rural RoadsHigh-volume rural roads consist of arterial

roads and the highway system. They providethe highest operation speeds and highest levelof traffic service. These roads serve as themajor corridors of traffic and frequently havemultiple lanes.

These roads frequently carry large trafficvolumes and heavy truck traffic. The informa-tion contained within this guide shouldaugment local guidelines in assuring properplanning and design of high-volume roads. Thevalues found here are only applicable to lowtruck volumes. Design of Asphalt Concretepavements for trucking highways requiresconsiderable expertise and detailed analysis.Table 4-5. Thickness Design: High Volume Secondary and Rural Roads



III Good 9 4.0 1.5 5.5

(201-700 ADT) Moderate 6 5.0 1.5 6.5

Poor 3 6.0 1.5 7.5

IV Good 9 5.5 2.0 7.5

(1,501-4,500 ADT) Moderate 6 6.5 2.0 8.5

Poor 3 7.5 2.0 9.5

V Good 9 7.5 2.5 10.0

(6,001-9,500 ADT) Moderate 6 8.0 3.0 11.0

Poor 3 9.0 3.0 12.0

VI Good 9

(9,501 & Above ADT) Moderate 6

Poor 3


Special design considerationneeded. Refer to a morecomplete design procedure.

V.

PARKING LOT

DESIGN

Parking Lot Design 5-1

Chapter 5

Parking Lot Design

GENERAL CONSIDERATIONS

The parking lot is the first - and the last -part of a building complex to be viewed by theuser. It is the gateway through which allcustomers, visitors, and employees pass. Thisfirst impression is very important to theoverall feeling and atmosphere conveyed tothe user.

Developers want their new facilities to beattractive, well designed, and functional.Though many hours are spent on producingaesthetically pleasing building designs, thesame design consideration for the parking area

is often overlooked. Pavements in parkingareas that are initially under-designed canexperience excessive maintenance problemsand a shortened service life.

When properly designed and constructed,parking areas can be an attractive part of thefacility that is also safe, and most important,usable to the maximum degree. In addition,parking areas should be designed for lowmaintenance costs and easy modification forchanges in use patterns.

Parking Lot Design5-2

Rules have been developed for optimizingparking area space. Among them are thefollowing:

1. Use rectangular areas where possible.2. Make the long sides of the parking areas

parallel.3. Design so that parking stalls are located

along the lotÕs perimeter.4. Use traffic lanes that serve two rows of

stalls.

Table 5-1. Recommended Parking Requirements

Land Use Spaces/Unit

Residential

Single-Family 2.0/Dwelling

Multifamily

Efficiency 1.0/Dwelling

1 -2 Bedroom 1.5/Dwelling

Larger 2.0/Dwelling

Hospital 1.2/Bed

Auditorium/Theater/Stadium 0.3/Seat

Restaurant 0.3/Seat

Industrial 0.6/Employee

Church 0.3/Seat

College/University 0.5/Student

Retail 4.0/1000 GFA

Office 3.3/1000 GFA

Shopping Center 5.5/1000 GLA

Hotels/Motel 1.0/Room

0.5/Employee

Senior High Schools 0.2/Student

1.0/Staff

Other Schools 1.0/Classroom

GFA, sq. ft. of gross floor areaGLA, sq. ft. of gross leasable area

The information in this chapter will providea general guide to proper parking area design,construction, and facility layout. Minimumpavement thickness designs are given forvarious size parking lots, heavily-loaded areas,and industrial parking lots. In addition, thischapter gives comparable designs for both fulldepth asphalt pavements and asphalt overuntreated aggregate base.

General PlanningIn developing the parking area plan, several

important details should be considered. Firstand foremost in the mind of the developer maybe providing the maximum parking capacityin the available space while ensuring conveni-ence and safety.

If the locality does not have a zoningordinance identifying specific requirements foroff-street parking, the general recommenda-tions in Table 5-1 may be useful.


Figure 5-1. Parking lot angles

Special attention should be given to the flowof traffic in and out of the lot as well as circu-lating routes inside the lot. Keep entrances faraway from busy street intersections and fromlines of vehicles stopped at a signal or stopsign. Be sure that the entering vehicles canmove into the lot on an internal aisle, therebyavoiding entering congestion caused by in-volvement with turning vehicles. A pedestriantraffic-flow study is important to provide in-formation about both safety and convenience.

spaces for a given area but is the onlyacceptable angle for a herringbone parking lotpattern.

The 90¡ parking angle provides the mostparking spaces for a given area. The highdegree of difficulty for entering and leavingthese parking stalls makes this type of parkingmore suited to all-day parking, such asemployee parking. This angle is generally notpreferred for Òin and outÓ lots such as those offast food restaurants and banks.

Parking AngleThe most popular angles for parking stalls

are 60¡, 45¡, and 90¡ . The most common anglefor parking is the 60¡ angle because of the easeof operation it provides. This angle permitsreasonable traffic lane widths and eases entryand exit of the parking stall.

Where lot size restricts the dimensionsavailable for aisles and stalls, a 45¡ angle maybe used. The smaller change of directionrequired to enter and back-out of the stallspace permits use of narrower aisles. The 45¡angle reduces the total number of parking

Parking Space DimensionsTypical parking stall dimensions vary with

the angle at which the stall is arranged inrelation to the aisle. Stall widths (measuredperpendicular to the vehicle when parked)range from 8-1/2 to 9-1/2 feet. The minimumwidth for public use parking spaces is 9 feet by19 feet. Recommended stall dimensions forcompacts and similar-sized vehicles are 7-1/2feet by 15 feet. If a number of such spaces areto be provided, they should be groupedtogether in a prime area to promote their use.Stall widths for parking lots where shoppersgenerally have large packages, such assupermarkets and other similar parkingfacilities, should be 9-1/2 feet or even 10 feetwide.


Figure 5-2.

Table 5-2. Parking layout dimensions (ft) for 9 ft stalls at various angles.

STALL LAYOUT ELEMENTS

OnDimension diagram 45° 60° 75° 90°

Stall width parallel to aisle A 12.7 10.4 9.3 9.0Stall length of line B 25.0 22.0 20.0 18.5Stall depth to wall C 17.5 19.0 19.5 18.5Aisle width between stall lines D 12.0 16.0 23.0 26.0Stall depth, interlock E 15.3 17.5 18.8 18.5Module, wall to interlock F 44.8 52.5 61.3 63.0Module, interlocking G 42.6 51.0 61.0 63.0Module, interlock to curb face H 42.8 50.2 58.8 60.5Bumper overhang (typical) I 2.0 2.3 2.5 2.5Offset J 6.3 2.7 0.5 0.0Setback K 11.0 8.3 5.0 0.0Cross aisle, one-way L 14.0 14.0 14.0 14.0Cross aisle, two-way M 24.0 24.0 24.0 24.0

Parking Lot MarkingsMarkings are a very important element of a

good parking lot. The parking area should beclearly marked to designate parking spacesand to direct traffic flow. As specified in theManual on Uniform Traffic Control Devices(MUTCD), parking on public streets should bemarked out by using white traffic paint, exceptfor dangerous areas, which should be markedin yellow.

However, yellow lines are commonly usedin off-street parking lots. All pavement stripingshould be 4 inches in width.

New asphalt surfaces can be marked witheither traffic paint or cold-applied markingtape. For best results with paint application,allow the Asphalt Concrete to cure for severaldays.

Construction PracticesDrainage Provisions

Drainage problems are frequently a majorcause of parking area pavement failures. It iscritical to keep water away from the subgradesoil. If the subgrade becomes saturated, it willlose strength and stability, making theoverlying pavement structure susceptible tobreakup under imposed loads.

Drainage provisions must be carefullydesigned and should be installed early in theconstruction process. Parking area surfacesshould have a minimum slope of 2 percent or1/4 inch per foot. They should be constructedso water does not accumulate at the pavementedge. Areas of high natural permeability mayrequire an underdrain system to carry wateraway from the pavement substructure. Anysoft or spongy area encountered duringconstruction should be immediately evaluatedfor underdrain installation or for removal andreplacement with suitable materials.


The use of Asphalt Concrete base (comparedto use of untreated aggregate base) will greatlyreduce the potential for problems related towater strength and stability.

Subgrade PreparationsAll underground utilities should be protect-

ed or relocated before grading. All topsoilshould be removed. Low-quality soil may beimproved by adding granular materials, lime,asphalt, or other mixtures. Laboratory tests arerecommended to evaluate the load-supportingcharacteristics of the subgrade soil. However,designs are frequently selected after carefulfield evaluations based on experience andknowledge of local soil conditions.

The area to be paved should have all rock,debris, and vegetation removed. The areashould be treated with a soil sterilant to inhibitfuture flora growth. Grading and compaction

of the area should be completed so as toeliminate yielding or pumping of the soil.

The subgrade should be compacted to auniform density of 95 percent of the maximumdensity. This should be determined inaccordance with Standard Proctor density(Test Method 103). The compaction require-ment may substitute a specified number ofdiskings and roller coverages of each lift.When finished, the graded subgrade shouldnot deviate from the required grade and crosssection by more than 1/2 inch in 10 feet.

Prime CoatAn application of a low-viscosity liquid

asphalt may be required over untreatedaggregate base before placing the AsphaltConcrete surface course. A prime coat and itsbenefits differ with each application, and itsuse often can be eliminated. Discussrequirements with the paving contractor.


Asphalt Base ConstructionThe asphalt base course material should be

placed directly on the prepared subgrade inone or more lifts. It should be spread andcompacted to the thickness indicated on theplans. Compaction of this asphalt base is oneof the most important construction operationscontributing to the proper performance of thecompleted pavement. This is why it is soimportant to have a properly prepared andunyielding subgrade against which tocompact. The asphalt base material shouldmeet the specifications for the mix typespecified.

Untreated Aggregate Base ConstructionThe untreated aggregate base course should

consist of one or more layers placed directly onthe prepared subgrade. It should be spreadand compacted to the uniform thickness anddensity as required on the plans. The minimumthickness of untreated aggregate is 4 inches. Theaggregate material should be of a type approv-ed and suitable for this kind of application.

It should be noted that an untreatedaggregate base is sensitive to water in thesubgrade. The pavement failures associatedwith water in the subgrade are accelerated ifan untreated base allows water to enter thepavement structure.

Tack CoatBefore placing successive pavement layers,

the previous course should be cleaned and atack coat of diluted emulsified asphalt shouldbe applied if needed. The tack coat may beeliminated if the previous course is freshlyplaced and thoroughly clean.

Asphalt Concrete Surface CourseMaterial for the surface course should be an

Asphalt Concrete mix placed in one or morelifts to the true lines and grade as shown on theplans. The plant mix material should conformto specifications for Asphalt Concrete.

The asphalt surface should not vary fromestablished grade by more than 1/4 inch in 10feet when measured in any direction. Anyirregularities in the surface of the pavementcourse should be corrected directly behind thepaver. As soon as the material can becompacted without displacement, rolling andcompaction should start and should continueuntil the surface is thoroughly compacted andall roller marks disappear.


THICKNESS DESIGN FOR PARKING LOTS

Design thicknesses given in this section areminimum values calculated on the volume andtype of traffic that will use the facility and onthe load-supporting capability of theunderlying soils. For additional soil classinformation, refer to Chapter 3.

Special truck lanes are sometimes requiredto expedite traffic to loading areas, trashdumpster sites, and equipment areas. Designthicknesses for these lanes or pavement areasshould be increased. Drainage problems arealso a major cause of pavement failures. Theirsignificance warrants a special section ondrainage that should be reviewed beforeselecting a pavement design either from thisguide or from any other source.

Design ProcedureTables 5-3 through 5-6 can be used directly to

select design thicknesses for a number ofdesign input factors. To use the tables,appropriate traffic and subgrade classes mustbe selected as follows.

Design StepsThe following steps can be used to

determine a pavement thickness.

1. Using the number of parking spaces tobe marked, select the traffic class (lessthan 50 spaces, 50 to 500, more than 500,or industrial) to be used. Determine ifany areas will receive heavy truck traffic.

2. Using soil data from the project, select asubgrade class (good, moderate, or poor)from Chapter 3. If no soil information isknown, use the poor classification for thesubgrade. (If the CBR value for the soillies between the values given, use thelower classification. )

3. Using the selected traffic class andsubgrade class, select a design thicknessfrom Tables 5-3, 5-4, or 5-6. Use Table 5-5to design heavily-loaded areas.

Design Example

¥ A new department store wishes to placea 350-car parking lot in front. A truckloading zone and dumpster site will beplaced in back. From Chapter 3, trafficclass II is selected.

¥ No soil data are known, so the engineerselects the poor soil classification.

¥ The total full-depth asphalt designthickness selected from Table 5-4 for theparking lot is 6-1/2 inches; the basecourse is 5 inches, and the surface courseis 1-1/2 inch. The total full-depth asphaltdesign thickness selected from Table 5-5for the truck loading zone andapproaches is 8 inches; the base course is6 inches and the surface course is 2inches.


Table 5-3. Thickness Chart: Parking Lots with Less Than 50 Spaces



Traffic Class Subgrade(Spaces) Class CBR Base Surface Total

I Good 9 3.0 1.0 4.0

(<50 spaces) Moderate 6 3.5 1.0 4.5

Poor 3 4.0 1.0 5.0



Untreated AsphaltTraffic Class Subgrade Aggregate Concrete

(Spaces) Class CBR Base Surface Total

I Good 9 4.0 3.0 7.0

(<50 spaces) Moderate 6 4.0 3.0 7.0

Poor 3 6.0 3.0 9.0


Pavement Thickness TablesThe pavement thickness for parking lots

should be in accordance with the followingtables:


Table 5-4. Thickness Chart: Parking Lots with More Than 50 Spaces


Thickness in InchesDesign Criteria* Hot Mix Asphalt

Traffic Class Subgrade(Spaces) Class CBR Base Surface Total

II Good 9 3.0 1.0 4.0

(50-500 spaces) Moderate 6 3.5 1.5 5.0

Poor 3 4.5 1.5 6.0

III Good 9 3.5 1.5 5.0

(500 & Above spaces) Moderate 6 4.5 1.5 6.0

Poor 3 5.5 1.5 7.0




(Spaces) Class CBR Base Surface Total

II Good 9 4.0 3.0 7.0

(50-500 spaces) Moderate 6 6.0 3.5 9.5

Poor 3 8.0 3.5 11.5

III Good 9 6.0 3.0 9.0

(500 & Above spaces) Moderate 6 8.0 3.5 11.5

Poor 3 8.0. 4.0 12.0



Note: Untreated aggregate base courses are not recommended for industrial parking lots or forparking areas for heavy trucks.

Table 5.5. Thickness Chart: Heavily-Loaded Areas in Parking Lots


SubgradeTraffic Class Class CBR Base Surface Total

I-III Good 9 4.0 2.0 6.0

(Up to 20 heavy Moderate 6 5.0 2.0 7.0

trucks per day) Poor 3 6.0 2.0 8.0


Table 5.6. Thickness Chart: Heavily-Loaded Areas in Parking Lots


Traffic Class Subgrade(ADT Class CBR Base Surface Total

IV Good 9 5.5 2.0 7.5

(20 to 200 trucks Moderate 6 6.5 2.0 8.5

per day) Poor 3 6.5 3.0 9.5


Heavily-Loaded AreasThe pavement for entrances, frontage roads,

trash dumpster sites, and delivery truckparking, as well as the approach areas to thesespaces, must be increased in thickness toprevent pavement failure caused by the weightand dynamic loading. These areas should be

constructed with full-depth asphalt in athickness that will support this special type ofpavement loading. Failure to provide thisstrengthening can result in severe pavementfailure. The pavement thickness for these areasshould be in accordance with the followingtable:

Industrial Parking LotsIndustrial parking lots and those designed

primarily for trucks require a thicker designthan the other lots described in this chapter.Because of heavy loads associated with trucks,

it is not recommended that untreated aggregatebase courses be used. The pavement thicknessfor truck lots should be in accordance with thefollowing table:


PLANNED STAGE CONSTRUCTION

Planned stage construction is a means ofproviding fully adequate pavements with theeffective use of funds, materials, and energy.As defined, it is the construction of an AsphaltConcrete parking lot or roadway in two ormore stages, separated by a predeterminedinterval of time. In many situations, buildingpavements by stages makes good economicalsense. It is a technique long used by city andhighway engineers.

Stage Construction is not maintenance. It isthe placement of a minimum depth ofpavement during initial construction, and afinal surface course placed at a planned futuredate. Asphalt Concrete lends itself to this kindof construction.

As an example, the owner of a newdepartment store with a 350-car parking lot,for financial reasons, decides to stage constructthe 6-1/2Ó full-depth asphalt parking lot. Stage1 is constructed at the time the store is built. Atotal depth of 5Ó of asphalt concrete is placed.Stage 2, consisting of the final surface course of1-1/2Ó, will be placed at a set time in thefuture. The truck loading zone and dumpstersite are paved the full depth during initialconstruction.

Stage construction has the advantage ofproviding a thoroughly adequate, all-weatherpavement for the initial development of anarea. Any damage to the Stage 1 pavementcaused by traffic, settlements, or utility tearupscan be repaired prior to placement of the finalsurface. With a proper asphalt tack coat, whereneeded, the Stage 2 pavement bonds to the oldsurface and becomes an integral part of theentire pavement structure.

ASPHALT CONCRETE CURB

Asphalt curbs have become increasinglypopular as accessories to paving because theyare: (1) economical and easy to construct; (2)can be built much faster than other types; (3)are not affected by ice- and snow-meltingchemicals; and (4) can be laid on an existingpavement using a slip form paver.

Many parking facilities have some form ofcurbing around the perimeter for bothfunctional and aesthetic reasons. The curbscontrol drainage, delineate the pavement edge,prevent vehicular encroachment on adjacentareas, and enhance the parking lot.

Curb MixtureThe method of mixing the Asphalt Concrete

and the composition of the mixture mustconform with IDOT Specification 2303, 2304,or an approved commercial mix. The bitumencontent should be modified as necessary toproduce a suitable mixture for AsphaltConcrete curb construction. Curb mixes thatare proportioned using the mixture sizes of3/8- or 1/2-inch have proven to be mostsatisfactory and are recommended for curbconstruction in Iowa.


Figure 5-3. Figure 5-4. Typical curb sections

The addition of 10 to 25 pounds ofpowdered asphalt per ton of mix will producean exceptionally tough and durable curb. Theasphalt cement used in the mix should bereduced on a pound-for-pound basis whenpowdered asphalt is added to the mixture.The temperature of the mixture at the time ofmixing and laying should range from 250¡ Fto a maximum of 300¡ F.

Curb ConstructionBefore curb construction begins, the place-

ment area must be cleaned thoroughly. A tackcoat must be applied to the pavement surfaceat a maximum rate of 0.10 gallons per squareyard.

The Asphalt Concrete curb must be laid trueto the specified line, profile, and cross sectionwith an approved self-propelled curb-layingmachine. The mixture must be fed to thehopper of the machine directly from the truckwith a chute or conveyor, or it should beshoveled by hand into the hopper.

Asphalt Concrete curbs should be backedwith earth fill or by constructing a double lineof curb and filling the median with compactedasphalt mix.

The following illustrates two basic types ofsystems Ð Asphalt Concrete curbs andPortland Cement Concrete curb and gutter.


ASPHALT MAT-PLATFORM FOR BUILDING CONSTRUCTION AND SITE PAVING

Site paving is the recommended first step inmany types of building construction projects.It offers several advantages as a working mator platform before building construction beginsfor shopping centers, schools, manufacturingconcerns, warehouses, and similar facilities.

In this technique, an Asphalt Concrete basecourse is constructed on a prepared subgradeover the entire area that will become parkingareas, service roadways, and buildings. Whenbuilding construction is completed, a finalAsphalt Concrete surface course is placed onthe asphalt base.

AdvantagesPaving a building site before construction is

completed has several benefits. These includethe following:

1. It ensures constant accessibility andprovides a firm platform upon whichpeople and machines can operate efficiently,speeding construction.

2. It provides a dry, mud-free area forconstruction offices, materials storage, andworker parking, eliminating dust controlexpenditures.

3. It eliminates the need for costly selectmaterialÑthe asphalt subfloor ensures afloor slab that is dry and waterproof.

4. Steel-erection costs can be reduced becausea smooth, unyielding surface results ingreater mobility for cranes and hoists.


5. The engineer can set nails in the asphaltpavement as vertical- and horizontal-controlpoints, effectively avoiding the risk of lossor disturbance of this necessary survey work.

6. Excavation for footings and foundationsand trenching for grade beams can beaccomplished without regard for theasphalt base.

Construction PracticesSubgrade Preparation

All vegetation (including root systems),rocks, debris, and topsoil should be removedfrom the area to be paved. To prevent futuregrowth, the subgrade should be treated withan approved soil sterilant. Install drainage andutility facilities; backfill and compact. Adjust-ments in utilities or underground facilities canbe readily accomplished through the asphaltbase should changes occur.

The subgrade must be properly shaped tomeet true lines and elevations. It must becompacted to not less than 95 percent ofmaximum laboratory density. The surface ofthe compacted subgrade must not deviate bymore than 3/4 inch from the established grade.A minimum slope of about 2 percent or 1/4inch per foot should be maintained to provideadequate drainage of surface water from thefinished pavement.

Areas that show pronounced deflection underconstruction traffic indicate instability in thesubgrade. If reworking and additional rollingdo not correct the situation, the area soil must beremoved, replaced with suitable material, andcompacted. The use of asphalt-treated base orcoarse granular material is recommended.

Base-Platform ConstructionAsphalt Concrete Base Material must be

placed on the prepared subgrade. A base of 4inches or less in depth should be placed in onelift. A base of a total thickness of more than 4inches may be placed in two or more lifts with

the bottom lift being a minimum of 3 inches.The material must be spread and compacted tothe required thickness and density as specifiedand in the grades and dimensions shown onthe plans.

The surface of the base must not deviatemore than 1/2 inch when measured with a 10-foot straight edge.

Surface Course ConstructionAfter building construction is essentially

completed, and all building materials andoffices have been removed from the previouslypaved base, preparation for placement of thefinal surface course of Asphalt Concrete canbegin. Should building operations or winterweather delay placement of the final surface,the Asphalt Concrete base will adequatelyserve traffic needs during the interim.

Preparation for the surface course requiresthorough cleaning and sometimes washing ofthe asphalt base to remove tracked-on dirt andforeign particles. After cleaning, any crackedor broken areas in the base should be removed,replaced with bituminous mix, and thoroughlycompacted. All manholes, valve boxes, andother pavement fixtures should be brought tofinished grade.

The hot mix asphalt surface course consistsof one or more layers placed on the previouslyconstructed Asphalt Concrete base course. Thematerial must be spread and compacted to therequired thickness and in the grades anddimensions shown on the plans.

The finished surface must not deviate morethan 1/4 inch when measured with a 10-footstraight edge.

Tack CoatBefore placing the surface course, the base

course should be cleaned thoroughly. Ifneeded, a tack coat of diluted emulsifiedasphalt may be applied for bonding.

VI.

DESIGNS FOR

RECREATIONAL

USES

Designs for Recreational Use 6-1

Chapter 6

Designs for RecreationalUses

ASPHALT PAVEMENTS FOR NON-VEHICULAR USE

In addition to highways, streets, andparking lots that carry autos and trucks, manyother applications for asphalt pavements exist.Sidewalks, bicycle and golf cart paths, play-ground areas, tennis courts, and site paving aresome common applications.

Because of the unique nature of theseasphalt pavement applications, a more detail-

ed approach to their design is presented here. Inmany cases, the primary design consideration is a pavement structure capable of supportingoccasional maintenance and emergencyvehicles and resisting freeze/thaw cycles.Therefore, a minimum thickness to accom-modate these loads may be the basis of thethickness design.

Designs for Recreational Use6-2

BIKEWAYS, GOLF CART PATHS,RECREATIONAL TRAILS, ANDWALKWAYS

It is desirable to blend this type of pathwayinto the contours of the existing ground topreserve aesthetics and to reduce the impacton the natural environment. Surface drainageshould flow away from these pathways wher-ever possible.

Because of the variety of designs and appli-cations, individual pathway widths are notlisted here. For bikeway and golf cart paths inparticular, the size and availability of conven-tional road construction and maintenanceequipment may determine width. Generally, aminimum width of 8 feet is recommended; a12-foot width may be more cost effective. As a

safety measure, additional widening on sharpcurves is recommended.

Recreation trails and walkways are usuallypaved to an 8-foot width to accommodateconstruction and maintenance operations andto provide access for emergency vehicles. Itmay be desirable to pave a walkway in anurban environment only 4-feet wide (or widerif significant numbers of pedestrians arepresent). These pavements usually are notdesigned to withstand repeated loads frommaintenance or emergency vehicles, but anoccasional heavy-load application can be madewithout damage.


Construction PracticesDrainage

It is very important to keep water away fromthe subgrade soil. If the soil becomes saturated,it will lose strength and stability, making theoverlying pavement structure susceptible tobreakup under imposed loads. Both surfaceand subsurface drainage must be considered.All drainage must be carefully designed andshould be installed as early in the constructionprocess as practical.

Bicycle and golf cart paths should have aminimum slope of 2 percent or 1/4 inch perfoot. They should be constructed in such a waythat water will not collect at the pavementedge. Areas of very high natural permeabilitymay require an underdrain system to carrywater away from the pavement structure.

Subgrade PreparationBecause the subgrade must serve both as the

working platform to support constructionequipment and as the foundation for thepavement structure, it is vital to ensure that thesubgrade is properly compacted and graded.All underground utilities should be protectedor relocated before grading. All drainagestructures should be completed with thegrading. Remove all topsoil, debris, and rocksfrom the areas to be paved and treat with a soilsterilant to inhibit future flora growth. Thesubgrade should be shaped properly to meettrue alignment and elevation. It should becompacted to not less than 95 percent ofmaximum laboratory density. The surfaceshould not vary more than 3/4 inch from theestablished grade.

Areas that show a pronounced deflectionunder heavy construction traffic indicate insta-bility in the subgrade. Such areas probably

require removal of the material and replace-ment with suitable subgrade soil material suchas compacted, crushed stone or compacted,bituminous-concrete base. If a water seepagearea is encountered, the subgrade should bedrained.

Asphalt Concrete PavementsBicycle, golf cart paths, recreational trails,

and sidewalks may be constructed in onecourse or with a separate base and surfacecourse.

The Asphalt Concrete base course should beplaced directly on the prepared subgrade inone lift in a thickness of 4 inches or less, andspread and compacted. Compaction is one ofthe most important construction operations interms of its contribution to the performance ofthe completed pavement.

If a compacted aggregate base is proposed,place it on the prepared subgrade and compactit to ensure a hard, uniform, well-compactedsurface.

The surface course, or the full-depth AsphaltConcrete base course, should be placed to thetrue line and grade. Any irregularities in thesurface of this course should be correcteddirectly behind the paver. As soon as thematerial can be compacted without displace-ment, rolling and compaction should bestarted and should continue until the surface isthoroughly compacted and all roller markshave disappeared.

Before placing successive layers, theprevious course should be clean. If necessary, atack coat of diluted emulsified asphalt may beapplied.


Table 6-1. Thickness Chart: Bikeways, Paths, Trails, and Walkways



Traffic Class Subgrade(ADT) Class CBR Surface Total

Good 9 3.0 3.0I Moderate 6 3.5 3.5

Poor 3 4.0 4.0



Untreated Hot MixTraffic Class Subgrade Aggregate Asphalt

(ADT) Class CBR Base Surface Total

Good 9 4.0 2.5 6.5I Moderate 6 4.0 3.0 7.0

Poor 3 6.0 3.0 9.0

*See chapter 3 for soil class details

Figure 6-1.

Pavement MarkingsPavement markings for bicycle paths are covered in the MUTCD under Part XI. Markings are

especially important when the designated bicycle lane is to be accommodated on the roadway andshared with motorists.

Pavement ThicknessThe pavement thickness for bikeways, golf cart paths, recreational trails, and walkways should

be in accordance with the following table:


RECREATIONAL AREAS

The following information and designguidance cover the basic components of build-ing durable, economical asphalt playgrounds.

Basketball CourtsA common section of the playground or

recreational area is the basketball court. Thefollowing information and design guidancecover the basic components of buildingbasketball courts. General guidelines for courtlayout and dimensions are included.

Court LayoutThe basic layout and dimensions of a

basketball court and backboard are illustratedin the following figure (6-2).

Court dimensions are:

¥ Professional: 94 feet long by 50 feet wide.¥ High school: 84 feet long by 50 feet wide.

Because individual designs are based onintended uses and available funds, dimensionsand suggested layouts are not included here.

Backboard dimensions are:

¥ Rectangular backboard: 74 inches wide by48 inches high.

¥ Fan backboard: 54 inches wide by 35 incheshigh.

An unobstructed space of at least 3 feetoutside the end lines and sidelines is required.This space would preferably be 10 feet wide.All end lines, sidelines, and other court linemarkings, except neutral zone markers, mustbe a minimum of 2 inches wide.

These pavements usually are not designed towithstand repeated loads from heavy mainte-nance or emergency vehicles, but an occasionalload application can be made without damage.


Figure 6-2

Construction PracticesDrainage

Both surface and subsurface drainageshould be investigated. If excessive moisture isallowed to accumulate under the pavement,the life of the playground surface may beshortened. If necessary, a system of subsurfacedrainage must be constructed.

Surface drainage on the playground shouldbe directed to the pavement edges and carriedaway in suitable channels or drainagefacilities. It is recommended that the minimumpavement cross-slope be 2 percent or 1/4 inchper foot to preclude standing water and ensurerapid drainage.

Subgrade PreparationBecause the subgrade must serve as both the

working platform to support constructionequipment and as the foundation for the pave-

ment structure, it is critical that the subgradebe properly compacted and graded. All drain-age structures should be completed with thegrading.

Remove all topsoil, debris, and rocks fromthe areas to be paved and treat with a soilsterilant to inhibit future flora growth. Thesubgrade should be properly shaped to meettrue alignment and elevation. It should becompacted to not less than 95 percent ofmaximum laboratory density. The surfaceshould not vary more than 3/4 inch from theestablished grade.

Areas that show a pronounced deflectionunder heavy construction traffic indicate insta-bility in the subgrade. Such areas probablyrequire removal of the material and replace-ment with suitable subgrade soil material suchas compacted, crushed stone or compacted,bituminous-concrete base.


Table 6-2. Thickness Chart: Playgrounds




Good 9 3.0 1.0 4.0

I Moderate 6 3.5 1.0 4.5

Poor 3 4.0 1.0 5.0





Good 9 4.0 2.5 6.5

I Moderate 6 4.0 3.0 7.0

Poor 3 6.0 3.0 9.0


Base ConstructionAsphalt Concrete base material should be

placed on the prepared subgrade in one lift ina thickness of 4 inches or less. The materialmust be spread and compacted to the requiredthickness and density as specified and in thegrades and dimensions shown on the plans.

The surface of the completed base must notdeviate more than 1/2 inch when measuredwith a 10-foot straight edge.

Tack CoatBefore placing successive courses, the

previous course should be clean. If needed, atack coat of diluted emulsified asphalt may beapplied as a bond coat.

Surface Course ConstructionA surface course of Asphalt Concrete may be

placed on the previously constructed AsphaltConcrete base. It must be spread and com-pacted to the required thickness and density asspecified and in the grades and dimensionsshown on the plans.


Pavement ThicknessThe pavement thickness for playgrounds

should be in accordance with the followingtable:


Figure 6-3

TENNIS COURTS

The following information and designguidance cover the basic components ofbuilding durable, economical asphaltpavements for tennis courts. General guide-lines for the layout and dimensions areincluded. These pavements usually are notdesigned to withstand repeated loads fromheavy maintenance or emergency vehicles, butan occasional load application can be madewithout damage.

Court LayoutThe basic layout and dimensions of a tennis

court are illustrated in the following figure.

Post foundations should be:¥ 24 inches in diameter at the top,¥ 30 inches in diameter at the bottom, and¥ not less than 36 inches in depth.

The dimension between posts is:¥ 33 feet on single courts and¥ 42 feet on double courts.

New posts are galvanized, 2-7/8 inches indiameter, and equipped with a net-tighteningdevice.

The standard net is:¥ 42 feet in length and¥ 3 feet-3 inches wide.

An edging of brick, concrete, steel, or treatedwood should be installed around the entireperimeter of the court area. Top elevation of theedging should be 1/2 inch below the finishedgrade level, and the courtÕs surface should betapered from 6 inches from the edge to meet it.


Construction PracticesDrainage and Surface Slope

Both surface and subsurface drainage mustbe thoroughly investigated. Proper drainage isvital to ensure a non-cracked, smooth playingsurface for many years. If subsurface drainageconditions are not satisfactory, a perimeterdrain is recommended. An Asphalt Concretebase on a suitable type of subgrade soil maynot require underdrainage.

In order to drain properly, the finished courtsurfaces should have a minimum slope of 1inch per 10 feet on a true plane from side toside, end to end, or corner to corner. Thesurface should not slope away in twodirections from the net.

Subgrade PreparationRemove all rock, vegetation (including root

systems), debris, and unsuitable topsoil fromthe area to be paved. To prevent future growth,treat the subgrade with an approved soilsterilant. Install all drainage facilities andadjust or relocate utilities.

The subgrade must be shaped to meet truelines and elevations and compacted to not lessthan 95 percent of maximum laboratorydensity. The surface of the compactedsubgrade must not vary more than 3/4 inchfrom the established grade. Good compactionis particularly important in tennis courtconstruction, because subsequent settlement ofthe subgrade may cause cracking in the courtsurface. In some cases this can render the courtunusable.

Base ConstructionAsphalt Concrete base material must be

placed on the prepared subgrade in one lift ina thickness of 4 inches or less. The materialmust be spread and compacted to the requiredthickness and density as specified and in thegrades and dimensions shown on the plans.

The surface of the completed base must notdeviate more than 3/8 inch when measuredwith a 10-foot straight edge but must slope 1inch per each 10 feet on a true plane from sideto side, end to end, or corner to corner asindicated on the plans.

Tack CoatBefore placing successive courses, the

previous course should be clean. If needed, atack coat of diluted emulsified asphalt may beapplied for bonding.

Surface Course ConstructionA surface course of Asphalt Concrete must

be placed on the previously constructedAsphalt Concrete base, spread and compactedto the required thickness and density asspecified and in the grades and dimensionsshown on the plans.

The finished surface shall not deviate morethan 1/8 inch when measured with a 10-footstraight edge but must slope 1 inch per each 10feet on a true plane from side to side, end toend, or corner to corner as indicated on theplans.

Color Finish Course (If Specified)Before applying the color finish course, the

court should be given a water check to deter-mine if there are any depressions (birdbaths).This is done by flooding the surface with waterand allowing it to drain. Depressions of sizabledimensions Ð greater than 1/8 inch Ð should bepatched and leveled with the material recom-mended by the color finish manufacturer.

The color finish material may be one ofseveral proprietary products and must beapplied according to manufacturerÕs directions.

Playing LinesFollowing construction, it is recommended

that a minimum of 15 days elapse beforeapplying the playing lines. A latex striping-paint should be used. It should be placed no


Table 6-3. Thickness Chart: Tennis Courts




Good 9 3.0 1.0 4.0

I Moderate 6 3.5 1.0 4.5

Poor 3 4.0 1.0 5.0





Good 9 4.0 2.5 6.5

I Moderate 6 4.0 3.0 7.0

Poor 3 6.0 3.0 9.0


thicker than necessary for delineation. Baselines should not be more than 4 inches wide,and playing lines should not be more than 2inches wide. Base and playing lines must beaccurately located and marked in accordancewith the rules of the United States Lawn TennisAssociation.

If a color finish has been applied, the strip-ing paint should be from a manufacturer andof a type recommended by the surface coatingmanufacturer. It should be painted in accor-dance with the paint manufacturerÕs standardspecifications. Traffic, oil, alkyd, or solventvehicle-type paints should not be used.

Tennis Court OverlaysThere are many reasons for overlaying an

existing tennis court. For example, it may havea badly oxidized or aged surface, poor drain-age, or a poorly constructed base. Each of theseconditions and their severity should beconsidered in determining the requiredoverlay pavement thickness.

Many items should be considered whendetermining the most sound and economicalprocedures to follow in resurfacing a tenniscourt. Therefore, it is strongly recommendedthat a qualified asphalt paving contractor, oneexperienced in tennis court construction, beconsulted.

Pavement ThicknessThe pavement thickness for tennis courts

should be in accordance with the following table:


ASPHALT-RUBBER RUNNINGTRACKS

High schools and colleges are increasing thedemand for outdoor and indoor asphalt-rubber running tracks and runways for longjump, high jump, and pole vault. Forinformation on track size, number of lanes,and other features, refer to the AmateurAthletic Union or other official specifications.

Construction PracticesSubgrade Preparation

Remove all large rocks, debris, and topsoilfrom the area to be paved. All vegetation,including root systems, should be removed. Toprevent future growth, treat the subgrade withan approved herbicide. Install all drainage andutility facilities, and properly backfill andcompact the subgrade.

The subgrade must be properly shaped tomeet true lines and elevations. It must becompacted to not less than 95 percent ofmaximum laboratory density. The surface ofthe compacted subgrade must not vary morethan 3/4 inch from the established grade.

Areas that show pronounced deflectionunder construction traffic indicate instabilityin the subgrade. If reworking and additionalrolling do not correct the situation, the areasmust be removed, replaced with suitablematerial, and compacted. The use of AsphaltConcrete base or coarse granular material isrecommended.

Base ConstructionAsphalt Concrete base material must be

placed on the prepared subgrade. The materialmust be spread and compacted to the required


thickness and density as specified and in thegrades and dimensions shown on the plans.

A minimum thickness of 4 inches is recom-mended. In general, a total base thickness of 4inches or less should be placed in one lift.

The surface of the completed base must notdeviate more than 1/2 inch when measuredwith a 10-foot straight edge.

Asphalt-Rubber Surface ConstructionSeveral manufacturers supply rubber mater-

ial for use in asphalt-rubber surface mixes.Obtaining advice from these companies is sug-gested. Because many members of the APAIare familiar with various mixes, informationmay also be obtained by contacting membersin your area.

If an asphalt-rubber mix proves to beuneconomical or impractical, an alternativerecommendation would be to specify anasphalt sand mix.

The surface course material must be placedon the previously constructed AsphaltConcrete base, spread, and compacted to therequired thickness and density as specifiedand in the grades and dimensions shown onthe plans. A minimum thickness of 1 inch isrecommended.


Tack CoatA tack or bond coat of CSS-1, SS-1, MC-70, or

an approved alternative must be applied at therate of 0.02 to 0.05 gallons per square yardbetween each course. The surface must becleaned of all dust, dirt, or other loose materialbefore the bond coat is applied. If emulsion isused, it must be diluted with equal parts ofwater or as specified in the proposal.

VII.

PAVEMENT

MANAGEMENT

Pavement Management 7-1

Figure 7-1.

Chapter 7

Pavement Management

PAVEMENT MANAGEMENTCONCEPTS

Historically, small agencies have developedan informal process for managing pavement.Pavements are examined periodically and theworst ones are repaired, rehabilitated, orreconstructed. At times, individuals with cloutbring pressure to bear to repair a particularstreet or road. Through the years, this informalprocess has worked because the knowledge,experience, and common sense of those indecision making positions led to logical streetand highway programs.

Today, however, as traffic volumes andvehicle loadings increasingly burden pave-ments, local governmentsÕ maintenancebudgets have not kept pace with the risingcosts of labor, materials, and equipment.Because local agencies today are faced withincreasing economic demands, a more system-atic process is needed to justify and account forpavement maintenance expenditures.

More and more agencies are adopting apavement management program that willanswer the following questions:

1. How does one determine what pavementis ÒworstÓ?

2. When is the best time to schedule repair,resealing, or resurfacing?

3. What is the savings or cost of deferringrepairs?

4. What is the most cost-effective action totake in repair or restoration?

Pavement management can be defined as anorderly process for providing, operating,maintaining, repairing, and restoring a network ofpavements.

Carrying out a pavement managementprogram involves the development of arecordkeeping strategy with the appropriateforms. The procedures can be relatively simpleor very complex depending on the size of theagency. Complex and costly computeroperations are used in large jurisdictions. Inthe case of a smaller street or road network,there are a number of microcomputer pro-grams available from consultants, or throughpublic agencies. Iowa State UniversityExtensionÕs Local Transportation InformationCenter offers workshops on the subject.

The decision to repair or rehabilitate iscomplicated because of the variety of types ofpavement distress Ð some serious and othersrelatively minor. If pavements with someserious levels of distress are not rehabilitatedin an expedient manner, their ultimate repairmay be significantly more expensive. Anoverlay made at the proper time in the life of apavement, for example, may extend the life formany years. If not overlayed, the same pave-ment may require complete reconstruction.

Pavement Management7-2

Figure 7-2.

Figure 7-3

The Asphalt Institute has developed A Pave-ment Rating System for Low-Volume AsphaltRoads. Information about its system is con-tained in Information Series No. 169 (IS-169).The subject also is covered in some detail inThe Asphalt Handbook manual series No. 4(MS-4).

Rating a RoadThe Asphalt InstituteÕs publication provides

a system for any individual or agency to inspecta road, rate it, and interpret the results. All thatis needed is an individual or individuals withmaintenance knowledge - such as a super-intendent or foreman - to walk the road andassign a numerical value to each type of pave-

ment defect. The type of distress, the extentof the distress, and its relative seriousnessmust be recorded.

In this procedure, lower values are assignedto less serious problems and higher values tomore serious problems. A rating of zeroindicates that the pavement is relatively free ofdefects. A rating of 5 or 10 would indicateserious distress. After each defect has beenrated, the individual ratings are added. Thesum is then subtracted from 100 and the resultis a condition rating for that particular piece ofroad.

It is important that pavements are evaluatedin a consistent manner. Those conducting acondition rating survey must have knowledgeof the various types of defects, their cause, andthe remedial action required. A guide foridentifying and correcting pavement failures isincluded in Appendix A of this Design Guide.Additional detailed information on this subjectis available in The Asphalt InstituteÕspublications (MS-16), (MS-17), (MS-4), andothers.

Interpretation of a Condition RatingThe absolute value assigned by the con-

dition rating provides an indicator of the typeand degree of repair work necessary. As ageneral rule, if the condition rating is between80 and 100, normal maintenance operations(crackfilling, pothole repair, or seal coat) are allthat are required. If the condition falls below80, it is likely that an overlay will be necessary.If the condition rating is below 30, majorreconstruction may be necessary.


Another valuable use for the condition rating is to provide a rational method for ranking roadsand streets according to their condition. A priority ranking should be the basis for programmingand budgeting maintenance, rehabilitation, and reconstruction.

Figure 7-4. Asphalt pavement rating form

ASPHALT PAVEMENT RATING FORM

STREET OR ROUTE ___________________________ CITY OR COUNTY _______________

LENGTH OF PROJECT ________________________ WIDTH _________________________

PAVEMENT TYPE ____________________________ DATE ___________________________

(Note: A rating of Ò0Ó indicates defect does not occur)

DEFECTS RATING

Transverse Cracks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0-5 _______

Longitudinal Cracks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0-5 _______

Alligator Cracks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0-10 _______

Shrinkage Cracks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0-5 _______

Rutting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0-10 _______

Corrugations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0-5 _______

Raveling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0-5 _______

Shoving or Pushing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0-10 _______

Pot Holes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0-10 _______

Excess Asphalt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0-10 _______

Polished Aggregate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0-5 _______

Deficient Drainage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0-10 _______

Overall Riding Quality (0 is excellent;

10 is very poor) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0-10 _______

Sum of Defects _______

Condition Rating = 100 - Sum of Defects

= 100 - ______________

Condition Rating =


PAVEMENT MAINTAINENCE

Pavement maintenance is the routine workperformed to keep a pavement, which is ex-posed to normal conditions of traffic andnature, as near to its original condition aspossible. Because destructive environmentaland traffic forces are constantly at work, allpavements require maintenance. Cracks, holes,depressions, and other types of distress are thevisible evidence of pavement wear. In urbanareas, utility cuts and repairs are major contri-butors to the need for pavement maintenance.

Taking care of pavement deterioration at theproper time and in the proper manner cansignificantly increase the life of the pavement.Early detection and repair of minor defects areamong the most important activities of roadmaintenance crews. In their first stages, cracksand other surface breaks are almost unnotic-

eable, but they may develop into seriousdefects if not soon repaired. Open joints andcracks allow water to enter the subgrade andlead to pumping and faulting with resultantstructural failure. It has been estimated that onrural pavements in Iowa, 70 percent of the

Figure 7-5.


subgrade moisture originates at the edge of thepavements.

Pavement maintenance involves theidentification of pavement distress types andthe determination of appropriate maintenanceactivities. The following sections provideinformation on full-depth patching, thinoverlays, and overlays. In addition, a sectionon identifying and correcting pavementfailures is included in Appendix A.

Full-Depth Asphalt PatchingThe full-depth asphalt patch is an important

maintenance technique for protecting andpreserving the sizable investment in roads. It isused to repair all types of localized pavementdistress that extend below the roadway sur-face. Examples include potholes, alligatorcracking, upheaval, and shoving.

The following illustration outlines thecorrect procedure for constructing a full-depthpatch:

1. Untreated pothole.2. Surface and base removed to firm support.3. Tack coat applied.4. Full-depth asphalt mixture placed and

being compacted.5. Finished patch compacted to level of

surrounding pavement.

Simply stated, the procedure is to removethe failed area and replace it with fresh asphaltmix. Although the operation is not difficult,some of the necessary fine points are frequent-ly not given sufficient attention. Yet thesedetails often determine whether the completedpatch will be a temporary expedient or anintegral part of a functional pavement system.

Removing Surface & Base

Applying Tack Coat

Backfilling Holes with Plant Mix


Constructing the Patch

• With a pavement saw or pneumatic hammer, cut the outline of thepatch, extending at least 1 foot outside of the distressed area. Theoutline should be square or rectangular with two of the sides at rightangles to the direction of traffic.

• Excavate as much pavement as necessary to reach firm support. If apatch is to be an integral part of the pavement, its foundation must beas strong or stronger than that of the original roadway. This may meanthat some of the subgrade will also have to be removed. The faces ofthe excavation should be straight and vertical.

• Trim and compact the subgrade.

• Apply a tack coat to the vertical faces of the excavation. Emulsifiedasphalts or liquid asphalt are all suitable.

• Backfill with the asphalt mixture. Shovel the mixture directly from thetruck into the prepared excavation. Place the mixture against the edgesof the hole first (rather than in the center and then raking to the edges).The maximum lift thickness largely depends upon the type of asphaltmixture and the available compaction equipment. Hot mix asphalt canand should be placed in deep lifts, because the greater heat retentionof the thicker layers facilitates compaction. From a compactionstandpoint, patches using hot mix asphalt can be backfilled in one lift.However, when placing a patch that is deeper than 5 inches, it is oftenuseful to leave the first lift 1 to 2 inches below the finished grade,making it easier to judge the total quantity of mixture required for thepatch.

Spreading the Mix

Compacting the Mix

Straightedging the Patch


• Spread carefully to avoid segregation of the mixture. Avoid pulling thematerial from the center of the patch to the edges. If more material isneeded at the edge, it should be deposited there and the excess rakedaway. The amount of mixture used should be sufficient to ensure thatafter compaction, the patch surface will not be below that of theadjacent pavement. On the other hand, if too much material is used, ahump will result.

• Compact each lift of the patch thoroughly. Use equipment that is suitedfor the size of the job. A vibratory plate compactor is excellent for smalljobs, while a vibratory roller is likely to be more effective for larger areas.

• When compacting the final lift (which may be the only lift), overlap thefirst pass and return of the vibratory roller or plate compactor no morethan 6 inches on the patch on one side. Then move to the opposite sideand repeat the process. Once this is accomplished, proceed at rightangles to the compacted edges with each pass and return, overlappinga few inches on the uncompacted mix. If there is a grade, compactionshould proceed from the low side to the high side to minimize possibleshoving of the mix.

• When adequate compaction equipment is used, the surface of the patchshould be at the same elevation as the surrounding pavement.However, if hand tamping or other light compaction methods are used,the surface of the completed patch should be slightly higher than theadjacent pavement because the patch is likely to be further compressedby traffic.

• Check the vertical alignment and smoothness of the patch with astraight edge or stringline.


surface treatments is essential to ensure bestresults. It is vital to make a careful study oftraffic requirements and an evaluation of thecondition of existing materials and pavementlayers.

Single Surface TreatmentA single surface treatment, often called a

Òseal coat,Ó involves spraying asphalt emulsionfollowed at once by a thin aggregate cover. Thiscover is rolled as soon as possible after laying.

When the aggregate is compacted to itsdensest position, the voids between aggregatesare filled about two-thirds to three-fourths fullwith asphalt. A typical design will call for 70percent of the voids to be filled. A full outlineof materials and procedures can be found inSection 2307 of the IHD Standard Specifica-tions. Application rates are given in Table 7-1.

Table 7-1. Surface Treatment ApplicationRates

Asphalt EmulsionAggregate

Spreading SpreadingAggregate Rate Basic Rate Rate

Size Gallons/Sq. Yd. Gallons/Sq. Yd. Pounds/Sq. Yd.

Sand 0.15-0.20 0.15 10-15

3/8 inch 0.25-0.35 0.30 20-25

1/2 inch 0.35-0.45 0.40 25-30

A single surface treatment or seal coat maybe used for one of several reasons:

1. As an interim measure pending applica-tion of a higher pavement type.

2. To correct surface raveling and oxidationof old pavements.

3. To provide a waterproof cover over anexisting pavement structure.

4. To correct excessive traffic wear beyondthat presumed in the original design.

Thin Surface TreatmentsAsphalt surface treatment is a broad term

embracing several types of asphalt and asphaltaggregate applications, which are usually lessthan 1 inch thick and can be applied to anykind of road surface. The road surface may bea primed granular base or similar surface, or itmay be an existing pavement. Surface treat-ments applied to an existing pavement surfaceoften are called seal coats.

This chapter covers surface treatments cons-isting of asphalt emulsion-aggregate applica-tions only. Because surface treatments and sealcoats differ in name only for this type of con-struction, they are treated as a single subject.

A single surface treatment involves sprayingasphalt emulsion, which is immediatelyfollowed by application of a thin aggregatecover that is rolled as soon as possible. Formultiple surface treatments, the aggregatecover process is repeated two or even threetimes, with the aggregate size becomingsmaller with each application. The maximumsize aggregate for each successive applicationis about one-half that of the previous one. Thetotal thickness of the treatment is about thesame as the maximum size aggregate particlesof the first course.

Properly constructed, asphalt surface treat-ments are economical, easy to place, andeffective. They seal and add life to road sur-faces. However, each type has one or morespecial purposes. A surface treatment is notactually pavement. Rather, it resists trafficabrasion and provides a waterproof cover overthe underlying structure. It adds little load-carrying strength and therefore is not normallytaken into account when computing the loadlimit of a pavement. While a surface treatmentcan provide an excellent surface if used for thecorrect purpose, it is not a cure-all for allpaving problems. A clear understanding of theadvantage and limitations of asphalt-emulsion


The single treatment approach is especiallywell-suited for light-duty traffic and as aninterim maintenance procedure. It also may beused following crack sealing operations. Thesurface treatment is applied to resist theabrasive forces of the traffic.

Problems that can be associated with atreatment of this type include:

1. Construction during cool weather. Itusually requires about one month ofwarm weather following construction forthe aggregate particles to becomereoriented and properly embedded inthe asphalt membrane.

2. Possible loss of cover aggregate mayoccur because of the relatively thin layerand the time required for embedding andbonding to develop. In single treatmentsthe larger aggregate particles are moreprone to be lost.

Multiple Surface TreatmentA multiple surface treatment can produce a

pavement thickness in the range of 1/2 to 3/4inch. Some extra reinforcement may be addedwith this type of treatment. If properlydesigned and constructed, double surfacetreatments give about three times the servicelife of a single surface treatment for about oneand one-half times the construction cost.Because the cover stone for the second layer issmaller, loss of particles from a graded coveraggregate is greatly minimized.

In a double surface treatment, the largestsize of stone in the first course determines thesurface layer thickness. The second courseserves to fill the voids in the mat of the firstcourse aggregate. The extent to which thesevoids are filled determines the texture andriding quality of the surface treatment.

Sand SealSand seal is defined as a spray application of

asphalt emulsion followed by a light coveringof fine aggregate, such as clean sand orscreenings. Although this is a rather simpleoperation, it can be useful in correcting anumber of pavement flaws. The procedureinvolves an emulsion spray application.Usually emulsion grades RS-1, CRS-1, orHFMS-1 are used at a rate of about 0.15 to 0.20gallons per square yard. This is followed byabout 10 to 15 gallons per square yard of sandor screenings cover.

The sand seal is used primarily for thefollowing purposes:

¥ To enrich a dry, weathered, or oxidizedsurface. The sand seal will help prevent lossof material from the old surface by trafficabrasion.

¥ To prevent the intrusion of moisture and air.When an existing pavement surface beginsto crack, moisture and air pass into theunderlying pavement structure, reducing itsload-carrying ability. A sand seal canprovide a barrier to prevent this intrusion.

¥ To develop a skid-resistant surface texture.By selecting a sharp, angular, fine aggregate,a highly skid-resistant surface can beprovided. The sand may also be used toÒsoak upÓ spots of asphalt that haveappeared on the surface because of an overlyrich condition.

Slurry SealA slurry seal is a mixture of well-graded fine

aggregate, mineral filler (if needed), emulsifiedasphalt, and water applied to a pavement as asurface treatment. It is used in both thepreventive and corrective maintenance ofasphalt pavement surfaces. It does not, nor isit intended to, increase the structural strengthof a pavement section. Any pavement that is


structurally weak in localized areas should berepaired before applying the slurry seal. Allruts, humps, low pavement edges, crown defi-ciencies, waves, or other surface irregularitiesthat diminish the riding quality should becorrected before placing the slurry seal.

When applied to the surface of an olderpavement, slurry seal can be used quiteeffectively. It will seal the surface cracks, stopraveling and loss of matrix, make opensurfaces impermeable to air and water, andimprove skid resistance. Its timely applicationwill help reduce surface distress caused byoxidation of the asphalt and embrittlement ofthe paving mixture.

Slurry seal offers the following advantages:

¥ Rapid application.¥ No loose cover aggregate.¥ Excellent surface texture for paint striping.¥ Ability to correct minor surface irregularities.¥ Minimum loss of curb height.¥ No need for manhole and other structural

adjustments.¥ In many cases, the relatively low cost of the

treatment makes it practical to importaggregates for special effects, such as high-skid resistance, color contrast, andnoise reduction.

¥ Resists degrading effect of oil and gasolinedripped from cars.

ASPHALT CONCRETE OVERLAYS

Asphalt Concrete is an excellent resurfacingmaterial that is equally effective for overlayingasphalt/aggregate surfaces, existing AsphaltConcrete pavements, or Portland cement pave-ments. Asphalt overlays add strength to an oldpavement structure, extend service life, andprovide a smooth, skid-resistant pavement.They improve riding quality and the crosssection, and they increase a pavementÕsresistance to water intrusion and deicingchemicals. The result is a better riding surfaceand stronger pavement than the original.

AdvantagesA Asphalt Concrete overlay offers the

following advantages:

1. Convenience. The pavement mayremain in use while it is being upgraded.

2. Economy. An old pavement frequentlymay be improved and returned to servicemore quickly and for less cost than a newroad can be constructed.

3. Durability. Well-designed, well-construct-ed improvements provide a pavementthat is stronger than new, which reducesmaintenance requirements.


Design ConsiderationsBefore constructing a Asphalt Concrete over-

lay, careful and correct preparation of theexisting pavement is essential for maximumpavement performance. Each resurfacing pro-ject must be designed on an individual basis.

Local RepairsAll weak areas should be repaired.

Structural patches should be designed andconstructed with full-depth Asphalt Concreteto ensure strength equal to or exceeding that ofthe surrounding pavement. Carefully placedand adequately compacted patches willproduce uniform support for the overlay andensure good performance.

Structural DeficienciesPavement deficiencies that do not affect

structural adequacy are usually corrected bythin resurfacings using thicknesses selectedfrom experience.

Weakened pavement structures call foroverlays of designed thicknesses that willsufficiently strengthen the pavement structureto accommodate the traffic expected to use it.

DrainageOlder pavements may show signs of fatigue

because of intrusion of groundwater frombelow or from surface water entering along theedge between pavement and shoulder. Thiswater should be removed by underdrains orby other means several weeks before con-structing the asphalt overlay.

LevelingWhen the surface is distorted, the

construction of leveling courses or wedges isrequired to restore proper line and crosssection.

Overlay ThicknessAsphalt Concrete overlays may be used to

correct both surface and structural defici-encies. Present pavement condition andestimates of future traffic influence appropri-ate thicknesses of these overlays. A 1-inchaverage depth of Asphalt Concrete surfaceshould be the minimum thickness. As astandard rule, the lift thickness should be atleast twice the maximum aggregate size in themixture.

Overlay Thickness CalculationsHow thick should the overlay be? Two

publications available from The AsphaltInstitute can aid in the calculations. The first,for roads and streets carrying up to 100 heavytrucks per day, is A Simplified Method for TheDesign of Asphalt Overlays for Light toMedium Traffic Pavements (IS-139).

The second procedure, for overlays on roadsand streets carrying more than 100 heavytrucks per day, is detailed in The AsphaltInstituteÕs manual, Asphalt Overlays forHighway and Street Rehabilitation (MS17).

When the majority of the heavy trucks havea gross weight of more than 60,000 pounds,these simplified overlay design methodsshould not be used.

The following steps and tables may be usedto determine overlay thickness needs.

¥ Using the estimated average number ofheavy trucks per day, and the assignedsubgrade category, determine the requiredthickness of full-depth asphalt pavementrequired using the appropriate table.

¥ Also, determine the effective thickness of theexisting pavement as if it were converted tofull-depth Asphalt Concrete. Each individual


ASPHALTCONCRETE

EMULSIFIEDOR CUTBACK

ASPHALTMIXTURES

PORTLANDCEMENT

CONCRETE

AGGREGATE

SOIL

Subgrade Class(CBR)

Traffic Poor Moderate GoodClass (3) (6) (9)

I 6.0 4.5 4.0II 7.0 6.0 5.0III 7.5 6.5 5.5IV 9.5 8.5 7.5V 12.0 11.0 10.0

Table 7-3. Typical Thickness of Full-DepthAsphalt Concrete For Light to Moderate TrafficRoads

course of the existing pavement is evaluated,using the appropriate table, to determine itsequivalent thickness of Asphalt Concretepavement; the sum is the effective thickness.

¥ The thickness of the Asphalt Concrete over-lay required is equal to the requiredthickness determined in Step 1 minus theeffective thickness of the existing pavementdetermined in Step 2.

Table 7-2FACTORS EMPLOYED TO CONVERT

EXISTING COURSES TO EQUIVALENT THICKNESSOF FULL-DEPTH ASPHALT CONCRETE

PavementCourse Minimum Requirements Factor

Stable, generally uncrackedwith little or no deformation in the wheel paths 0.9- 1.0

Stable, some fine cracking or slight deformation in the wheel paths 0.7 - 0.9

Appreciable cracking and crack patterns, or appreciable deformation in the wheel paths 0.5 - 0.7

Stable, generally uncracked and exhibiting little deformationin the wheel paths 0.7 - 0.9

Stable, some fine cracking, some raveling or aggregatedegradation, and slight deformation in the wheel paths 0.5 - 0.7

Extensive cracking, considerableraveling or aggregate degradation, appreciable deformation in the wheel paths and lack of stability 0.3 - 0.5

PavementCourse Minimum Requirements Factor

Stable, undersealed and generally uncracked 0.9 -1.0

Stable, undersealed, some cracks but no pieces smaller than about one square metre (yard) 0.7 - 0.9

Appreciably cracked and faulted,cannot be undersealed. Slabfragments, ranging in size from approximately one to four squaremetres (yards) have been well-seated on the subgrade by heavy pneumatic rolling 0.5 - 0.7

Pavement broken into small pieces, 0.6m (2 ft) or less inmaximum dimension. Use upper part of range when subbase ispresent; lower part of range when slab is on subgrade 0.3 - 0.5

Granular subbase or base –reasonably well-graded, hardaggregates with some plastic fines and CBR not less than 20. Use upper part of range if P.l. is 6 or less; lower part of range if P.l. is more than 6 0.1 - 0.2

Improved subgrade or nativesubgrade, in all cases 0


Figure 7-7.

Table 7-4. Typical Overlay Thickness (Inches) For Local Roads, ResidentialStreets, and Collectors

Condition RatingSubgrade Type Local and Residential Streets

<25 25-50 <25 25-50Local Roads and Residential Streets

<200 ADT >200 ADTGood 1 - 1.5 1

Medium 1.5 1 2 1.5Poor 2 1 2.5 2

Collector Roads and Streets<1,500 ADT >1,500 ADT

Good 2 1.5 2.5 2Medium 2.5 2 3 2.5

Poor 3 2.5 3.5 3

For a discussion on the condition rating procedure for this particular tablesee the Pavement Management section.

Adequate preparation of the existing pave-ment prior to an asphalt overlay is important.When repairs are completed, the surface to beoverlaid must be thoroughly cleaned. Then a tack coat of asphalt must be applied to ensure uniform and complete adherence of theoverlay.

As discussed earlier under pavement man-agement concepts, the condition ratingprovides a rational method for evaluating theneed for an overlay. If the condition rating fallsbelow 80, it probably calls for an overlay.Deferring the overlay allows further deteriora-tion of the pavement. At some point in time,the life of the pavement is severely affected,which will increase costs significantly.

The predictive capabilities of a pavementmanagement system allow an agency toanalyze alternative programs and select a

maintenance strategy that is cost effective.Deferred maintenance is more costly in thelong run as illustrated by the quality ofdeterioration over time example.

VIII.

REHABILITATION

Rehabilitation 8-1

Removal by Cold Milling

Salvaged Material (RAP) Stockpile

Chapter 8

Rehabilitation

RECYCLING ASPHALT PAVEMENTS

As natural resources become more scarceand more costly to obtain, their rehabilitationand re-use, or recycling, becomes more impor-tant. Asphalt cement and aggregates used inroadway construction constitute a sizablepublic investment. They are two very impor-tant natural resources whose value as con-struction materials are recoverable. This abilityto recycle has enormous implications not onlyfor the conservation of valuable resources butalso for energy savings and total economicbenefits.

Recycling asphalt concrete pavements canbe accomplished through: removal andtransport to another location for crushing andreprocessing with transport to the new site forlaydown and rolling; or through cold milling

Reprocessing the salvaged materials, plusthe addition of virgin asphalt and newaggregates, can be accomplished through threedifferent processes. In a hot mix process, aspecial drum for mixing is used to complywith environmental pollution requirementsand the mixture produced is a fully recycledproduct containing 15-50% RAP. A cold, in-place recycling process normally involvesprocessing a 2Ó- 4Ó depth followed by anAsphalt Concrete overlay. A third process,termed surface recycling involves heaterscarification of the top 1Ó of pavementfollowed by an asphalt concrete overlay.

the surface; and/or conventional removal,with crushing, reprocessing, laydown, androlling accomplished on the site.

Rehabilitation8-2

Hot Mix Recycling Advantages

1. Significant structural improvements canbe obtained with little or no change inthickness.

2. Additional right-of-way is not needed.3. Frost susceptibility may be reduced.4. Surface and base distortion problems

may be corrected.5. Base preparation and shoulder work are

reduced.

Cold Mix Recycling Advantages

1. Can correct many types of pavementdistress that involve both surface andbase courses.

2. Reduces the need for new materials andoverall cost.

3. Hauling costs may be decreased if in-place method is used.

4. Increases structural strength withoutadding to pavement thickness.

5. Drainage problems are avoided.6. Adding asphalt waterproofs the base and

renders it less susceptible to frost actionand moisture change.

Surface Recycling Advantages

1. Provides a very low-cost maintenancestrategy.

2. Restores flexibility of aged and brittleasphalt.

3. Cracks are interrupted and filled.4. Surface distortion, removed and leveled,

drainage and crowns are re-established.5. Improves skid resistance.6. Eliminates the need for surface repairs.

Rehabilitation 8-3

BREAKING AND SEATING

A Portland Cement Concrete (PCC) pave-ment that has good drainage and is stillrelatively sound can be salvaged throughbreaking and seating and a hot mix AsphaltConcrete overlay. This option for rehabilitationis designed to reduce the opportunity forreflective cracking by decreasing the slab sizeof the PCC. Proper breaking and seating willvirtually eliminate reflective cracking. Ifreflective cracks should appear, they usuallywill be small, tight cracks that can bemaintained easily.

With this method of rehabilitation, the PCCis cracked at 24- to 30-inch intervals withheavy drop hammer equipment to create amore uniform pattern of cracking. Next, thecracked PCC pavement is seated with arubber-tired roller of at least 35 tons. Thisseating action by the roller pushes down anypieces of PCC that might be over a void in thesubbase. After the breaking and seating stepsare completed, a 3-to 5-inch asphalt overlay isplaced directly on the prepared old pavement.

This method offers the following benefits:

1. Prevents/delays reflective cracking.2. Extends pavement service life.3. Reduces maintenance costs.4. Improves riding smoothness.

The procedural steps of the breaking andseating process are:

1. Crack the PCC slabs.2. Seat cracked pieces.3. Remove and patch soft areas.4. Sweep clean.5. Apply tack coat.6. Place asphalt leveling course/overlay.

This method of recycling has been used formore than 30 years in many states.

Rehabilitation8-4

RUBBLIZING

The rubblizing of Portland Cement Concretepavements before an Asphalt Concrete overlaymeans the complete destruction of the concreteslab and of all concrete slab action. With thistechnique, the concrete-to-steel bond is brokenon jointed-reinforced concrete pavements andon continously-reinforced concrete pavements.The rubblizing process effectively reduces theexisting slab to an in-place crushed aggregatebase.

The benefits of this method are:

1. Prevents reflective cracking.2. Provides a sound base for the overlay.3. Extends service of the pavement.4. Provides a maintainable surface.

The procedural steps in the rubblizingprocess are:

1. Install necessary drainage.2. Remove any existing overlay.3. Sawcut the full thickness of the

pavement adjacent to remaining sections.4. Pulverize the PCC pavement.5. Cut off the exposed steel reinforcement.6. Compact the pulverized PCC pavement.7. Apply a prime coat.8. Place the Asphalt Concrete leveling

course and overlay.

Rehabilitation 8-5

PAVING FABRICS

In recent years, paving fabrics, or geomem-branes, have been used to reduce reflectivecracking from the underlying pavement jointsor cracks. A membrane is established throughthe application of liquid asphalt cement, fabric,and an Asphalt Concrete overlay. Fabric hasbeen shown to be effective in developing awaterproof layer to minimize surface waterintrusion .

An example of a possible use would be as aspot application on asphalt pavement sectionsthat show signs of alligator cracking related toa weakened subgrade condition. Fabric wouldbe placed just before the asphalt concrete

Experimental studies of fabric applicationsin Iowa have not been conclusive. Earlyreflective cracking may be delayed through theuse of fabric in many cases, especially over anonworking joint. Also, where water in thepavement structure is a potential problem,fabric can aid in the development of awaterproof membrane.

For additional assistance on specific applica-tions of paving fabrics, contact the APAI.

overlay. Strip application of fabrics will bemore effective if the crack or joint is a non-working joint, such as a longitudinal joint in aPCC pavement.

Rehabilitation8-6

SAWCUT AND SEALING JOINTS

On PCC rehabilitation projects, sawing andsealing the Asphalt Concrete overlay over theunderlying PCC joints may extend the over-layÕs service life. Unless special procedures,such as crack and seat, are used to prepare theexisting PCC pavement, the joints mayeventually reflect through the asphalt overlay.These cracks can occur within a short time,depending on factors such as the thickness ofthe overlay, traffic, and environmentalconditions. Reflective cracking is caused by theunderlying joints moving because of tempera-ture and moisture changes, warping of theslab, and loading conditions that result intensile, shear, and flexural forces greater thanthe strength of the pavement. This results in acrack in the overlay approximately above theunderlying joint.

Primary candidates for sawing and sealingof overlays over joints in the underlying PCCpavements are those overlays that have notlost structural integrity at the joints. Examplesare overlays that are intended to increasestructural capacity, correct skid resistance,prevent further scaling, or reduce noise.

To be effective, the sawcut in the overlayshould be directly over the underlying joint. A maximum tolerance of 1 inch is required.

Reference marks, which will not be obliter-ated during the overlay operation, must beestablished at the underlying joint. Theunderlying joint must also be thoroughlycleaned and sealed with an approved sealerbefore overlaying.

BenefitsSawcut and sealing of the asphalt overlay is

an effective technique to reduce the detrimen-tal effect of uncontrolled reflective crackingover the underlying PCC joints. The sawcutand seal technique establishes a weakenedplane joint in the overlay directly above thejoint, and it can then be effectively sealed andmaintained.

The technique of sawcut and sealing jointsoffers the following benefits:

1. Controls reflective cracking.2. Provides maintainable joints.3. Extends service life.4. Controls maintenance costs.5. Adjoining surface will be stronger than

at the natural crack.6. Better appearance.7. Smoother riding pavement.

The procedural steps in the process are:

1. Locate and reference existing joints in theunderlying slab.

2. Thoroughly clean and seal joints.3. Place overlay.4. Sawcut directly over the referenced joint.5. Clean and dry the sawcut.6. Seal the sawcut.

After placement of a backer rope or tape, thewidth-to-depth ratio on saw and seal jointsshould be 1:1. The initial cut should benarrower than the final width and almosttwice the depth. This is with the use of hot-type sealers.

APPENDICES

Appendix A – Pavement Failure Identification

Appendix B – Glossary

Appendix C – Conversion Tables

Appendix D – Publications

Appendix E – Credits and References

Appendix F – Member Firms

APPENDIX A

PAVEMENT

FAILURE

IDENTIFICATION

Pavement Failure Identification A-1

Appendix A

Pavement FailureIdentification

IDENTIFYING AND CORRECTINGPAVEMENT FAILURES

The key to proper maintenance of asphaltpavements is to understand the causes offailures and the action(s) needed for correctionbefore any repair work is done. To make themost of maintenance budgets, proven methodsmust be used to correct failures and to preventtheir recurrence.

The following section provides basic infor-mation on the most common types of pave-ment failures, including their probable causeand the measures recommended for theircorrection. Personnel involved in asphaltmaintenance operations must be well advised,trained, and properly equipped. With diligentapplication, the following section can assist inhelping them achieve an efficient, effective,and consistent asphalt pavement maintenancesystem.

Types of Pavement FailuresThe following photographs illustrate the

types of pavement failures most commonlyencountered in asphalt pavements. Next toeach photograph is a description of the failuretype, probable cause of the failure, andrecommended correction.

Bleeding or FlushingThis distress is caused by excess asphalt in

the surface layer. Contributing factors includeinsufficient or excess covering stone, lack ofproper rolling during placement, or failure toprotect a newly constructed surface fromtraffic until the asphalt has cured sufficiently.

Minor bleeding can often be corrected byapplying coarse sand or stone screenings toblot up excess asphalt.

Major bleeding can be corrected by cuttingoff excess asphalt with a motor grader orremoving it with a Òheater planer.Ó If theresulting surface is excessively rough, resur-facing may be necessary.

Corrugations and ShovingCorrugations and shoving are caused by

instability in the asphalt layers caused by amixture that is too rich in asphalt, has too highof a proportion of fine aggregate, has coarse orfine aggregate that is too rounded or toosmooth-textured, or has asphalt cement that istoo soft. Corrugations and shoving may also becaused by excessive moisture, contaminationcaused by oil spillage, or lack of curing timebetween placing seal treatments. This type ofdistress frequently occurs at grade inter-sections as a result of braking forces imposedby stopping vehicles.

Pavement Failure IdentificationA-2

To repair corrugations in an aggregate baseoverlain with a thin surface treatment, scarifythe pavement, add aggregate as needed, mixwell, re-compact, prime, and then resurface.Where the surface has 2 inches or more ofasphalt plant mix, corrugations can beremoved with a ÔÕheater planer.ÕÕ After removalof corrugations, cover with a new surfacetreatment or new asphalt overlay. To repairshoved areas, remove surface and base asnecessary and replace with a more stablematerial to prevent a recurrence. For out-of-season inclement weather repairs, smoothshoved areas with patching if the surfaceunevenness is hazardous to traffic.

Cracking, AlligatorInterconnected cracks forming a series of

small polygons resembling an alligatorÕs skinare called alligator cracks. There are numerouskinds of alligator cracks, some of which areillustrated and discussed below.

In situ investigations must be performed todetermine the most probable of several causesof alligator cracking. If poor drainage isimplicated, corrections should be made asquickly as possible. Should the pavement beproperly drained, then the base is probablyinadequate, and the pavement will requirereconstruction or a heavy resurfacing. Majorresurfacing will also be required if crackingresults from the fatigue effect of repetitiveheavy truck loads. If the cause of distress

cannot be corrected soon (rebuilding of thepavement may be several years in the future),temporary repairs may be required.

Alligator Cracking without Surface Distortion

Skin patching should be applied whenweather permits. This is often a temporarymeasure and should not be considered apermanent correction of a major problem.Alligator cracking generally requires removalof the cracked pavement and an asphalt patchof at least 4 inches in depth.

Alligator Cracking with Distortion of IntactSurfaces

Where distortion is 1 inch or less and theexisting surface is intact, a skin patch shouldbe applied. Where distortion is more than 1inch and the existing surface is intact, a tackcoat should be applied followed by an AsphaltConcrete overlay.


Alligator Cracking with Broken Surfaces

Where the existing surface is badly crackedand loose (regardless of amount of distortion),remove old surface, tack area, and repair usingAsphalt Concrete. Sound judgment should beused to determine when the existing surface isconsidered firm and should remain in place orwhen it is considered loose and should beremoved before placing the Asphalt Concreteoverlay.

Alligator Cracking with Surface Distortionand Pumping

There are several causes of this type ofdistress. Often poor drainage resulting in a wetbase and/or subgrade is responsible. If thepavement is properly drained, then water isgetting to the base and/or subgrade fromcracks or holes in the surface or from moisturecoming up through the subgrade.

This distress should be repaired as follows:

1. Cut out pavement and wet material.2. If the base or surface is wet from

underneath, install necessary underdrainsto prevent future saturation.

3. Prime area.4. Replace with a minimum of 4 inches of

Asphalt Concrete.5. Compact Asphalt Concrete.

For out-of-season inclement weather repair,keep the area filled with either cold patchmaterial or treated aggregate base.

Note: If you follow the photographs onrandom surface cracks and alligator cracking,you can see how surface distress can progressfrom undesirable to intolerable because of lackof proper drainage. This is not to imply thatpoor drainage is the only cause of surface crack-ing. However, it is often a major contributor.

Cracking, EdgeThe following items discussing edge cracks

concern those pavement surfaces underlain bybase material and not areas where the surfacehas been gradually widened over the yearsuntil its edge is inadequately supported by abase layer.

Cracking without surface distortion isusually caused by lack of shoulder (lateral)support. When the surface is distorted,possible causes are more diverse. In somecases, the base layer may be of insufficientquality or thickness to support the trafficloads. Poor drainage is also a frequent cause. Iswater getting in from the top, sides, or bottom?Is base failure causing distortion and allowingwater to wet the base and/or subgrade? Is aclogged ditch line causing water to seepthrough porous shoulder material and saturatethe base and subgrade? Corrective measuresshould be undertaken as soon as possible.


Edge Cracks without Surface Distortion Edge Cracks with Broken Surfaces

The first step is to correct the problem of lackof lateral support if necessary. For cracks lessthan 1/4 inch in width, no maintenance isrequired. A skin patch is sufficient for largercracks.

Edge Cracks with Distortion of IntactSurfaces

Where distortion is 1 inch or less and theexisting surface is intact, a skin patch shouldbe applied. Where distortion is more than 1inch and existing surface is intact, tack areaand build up with Asphalt Concrete.

Where the existing surface is badly crackedand loose, regardless of distortion, the oldsurface must be removed. Prior to replacingthe surface, consideration should be given tothe necessity of first replacing the basematerial if it has been pushed up and out intothe shoulder. This action will have reduced theamount of base material that remains in placeand thus will have reduced the strength of thepavement. If this condition exists, it should becorrected by either replacing the base materialor by building up the depressed area withAsphalt Concrete.

Sound judgment should be used todetermine whether the existing surface isconsidered firm and should remain in place orif it is considered loose and should be removedand replaced. When Asphalt Concrete is usedto replace the base material, it should be ofequal or greater strength than the material itreplaces.


Edge Cracks with Surface Distortion andPumping

This distress is caused by wetting or dryingaction beneath the shoulder surface caused byconditions that trap water and allow it to standalong and seep through the joint between theshoulder and the mainline surface.

If the cracking is less than 1/4 inch in width,no maintenance is required. Otherwise, a crackshould be filled with a cutback or emulsifiedasphalt.

Joint Crack at Lane Joints

To repair such distress, take the followingsteps:

1. Remove unsuitable material. 2. Install any necessary underdrains. 3. Replace base with a well-graded aggregate. 4. Compact aggregate. 5. Prime area. 6. Replace surface using Asphalt Concrete.

When inclement weather prohibits properrepair, try to keep the distressed area filledwith cold patch material.

Cracking, JointJoint cracks occur where the shoulder or

paved wedge separates from the mainlinepavement or along weak seams of adjoiningpavement spreads in the surface layers.

Joint Crack at Pavement Edge

Distress is caused by a weak seam betweenadjoining spreads in the courses of thepavement.

If the cracking is less than 1/4 inch in width,no maintenance is required. Otherwise, thecrack should be filled with a cutback oremulsified asphalt.

Cracking, RandomThe causes of random cracking are

numerous and, in its early stages, difficult todetermine. Consequences range from severe,such as deep foundation settlement, to slight,such as a construction error or mishap.


Narrow Cracks Note: Both methods are acceptable, andgood judgment should be used to determinewhich method is best according to theparticular distress, materials available, andprevious experience.

Cracking, ReflectionReflection cracking is caused by vertical and

horizontal movements in the pavementbeneath overlays that result from expansionand contraction with temperature or moisturechanges. Reflection cracking is very apparentwhere plant mix has been placed over PortlandCement Concrete pavement or where oldalligator cracks have propagated up throughan overlay or patch.

For cracking less than 1/4 inch in width,take no action. If associated distress of anothertype exists, the cracking will progress, andremedial action will ultimately be required.

Wide Cracks

When random cracks reach 1/4 inch or morein width, remedial action is often required.However, the appropriate action may bedifficult to determine. On some pavements,cracking will not progress significantly fromyear to year. Previous experience and/or thetraffic volume and type of pavement mayindicate that it is not necessary to takeimmediate action. Sound judgment should beused when deciding if action should be takenin this case. In most cases, the crack shouldeither be covered with a skin patch or be filledwith a cutback or emulsified asphalt andcovered with sand.

If reflection cracks are no more than 1/4 inchin width, no maintenance is required. Largercracks should be filled with a cutback or anemulsified asphalt and covered with sand.

Such treatment is seldom permanent whenapplied to overlays over old Portland CementConcrete pavement. Continual expansion andcontraction of the concrete causes convention-ally repaired cracks to reappear quickly. Asingle course surface treatment over theexisting pavement immediately preceding theoverlay is a good crack relief measure thatminimizes reflective cracking.


Cracking, ShrinkageShrinkage cracking appears on the pave-

ment surface as interconnected cracks forminga series of polygons, usually having sharpangles at the corners. Unlike alligator cracking,which is associated primarily with trafficloading, shrinkage cracking is caused byvolume change within the Asphalt Concrete,the aggregate base, and/or the subgradelayers.

If the shrinkage cracking is severe and hasseriously weakened the pavement structure, astructural overlay will be necessary to restoreit. Most likely, however, the cracking will notbe progressive, and a surface treatment Ðpreceded by filling the larger cracks with acutback or emulsified asphalt Ð will suffice forsurface restoration.

Cracking, SlippageSlippage cracks are crescent-shaped cracks

that usually point in the direction of trafficmovement. They result from insufficient bondbetween the surface and underlaying courses,caused by dust, oil, rubber, dirt, water, or notack coat between the two courses.

To repair slippage cracks, neatly remove theunbonded section of the surface, apply a suit-able tack, and replace the surface with a highquality Asphalt Concrete. During inclementweather, keep the exposed area filled with coldmix material if it is likely to be a traffic hazard.

Cracking, TransverseA transverse crack follows a course approxi-

mately at right angles to the pavement centerline, usually extending across the full pave-ment width. In Iowa, transverse cracks aremost often the result of reflection cracking.However, they can also result from stressesinduced by low-temperature contraction of thepavement, especially if the asphalt is hard andbrittle.

Repair procedures for transverse crackingare similar to those for reflection cracking.

Polished AggregateAlthough uncrushed gravels often have

surfaces that are initially smooth andpotentially hazardous, crushed rock initiallyhas a rough, skid-resistant texture. Under theaction of traffic, however, some aggregates Ðincluding many limestones Ð become polishedand slick, especially when wet. The likelihoodof aggregate becoming polished increases withthe volume of traffic. Because polishedaggregate results in a loss of skid resistance, itis potentially hazardous. The most economicalrepair is to apply a skid-resistant surfacetreatment.

PotholesPotholes occur most frequently during the

winter months when it is difficult to make themost desirable repairs. Consequently, it isoften necessary to repair potholes in ways thatare less than permanent. General patchingshould not be done during inclement weatherexcept to correct hazardous conditions. Soundjudgment must be exercised when makingrepairs during poor weather conditions.

Potholes are caused by water penetrat-ing the surface and causing the base and/or subgrade to become wet and unstable. They also may be caused by a surface that is too thin or that lacks


sufficient asphalt content, lacks sufficient base, or has too many or too few fines. Did youand/or your personnel fail to performmaintenance that would have preventedpothole formation? If water is the culprit, it iscaused by a cracked surface, high shoulders orpavement depressions ponding water on thepavement, porous or open surface, or cloggedside ditches? Correct the cause of the problemas soon as possible.

Potholes in Surface Treatments overAggregate Base

To repair potholes in Asphalt Concrete, takethe following actions:

1. Clean out hole.2. Remove any wet base.3. Square up pothole so that it has neat lines

both perpendicular and parallel to thecenter line and has vertical sides.

4. Prime the pothole.5. Fill the pothole with Asphalt Concrete.

RavelingRaveling is caused by a dry brittle surface;

dirty, dusty, or soft aggregate; patching beyondbase material; lack of compaction of surfaceduring construction; too little asphalt in mix;or excessive heating during mixing.

To repair potholes in surface treatments,take the following actions:

1. Clean out hole. 2. Remove any wet base. 3. Shape hole so that it has vertical sides. 4. Prime hole. 5. Fill hole with Asphalt Concrete.

Potholes in Asphalt Concrete

When a small percentage of the pavement israveling, repair with a skin patch (this includesedge raveling). When a large percentage of thepavement shows raveling, the pavementshould be resurfaced.

Note: If the raveling is not a part of thepaved surface, no action should be taken. Inother words, donÕt patch beyond the edge ofthe pavement.

Channels or RuttingChannels are caused by heavy loads and high

tire pressures, subgrade settlement caused bysaturation, poor construction methods, orasphalt mixtures of inadequate strength.


Intact Surface

Where the depression is 1 inch or less andthe surface is cracked but still largely intact,skin patch the area. Where the depression ismore than 1 inch and the surface is cracked butstill largely intact, repair with asphalt concrete.

Disintegrated Surface

Where the surface is badly cracked and loose(regardless of amount of depression), removethe old surface. If the area shows signs of mudbeing pumped to the surface, remove all wetmaterial, replace base material, compact,prime, and build up with Asphalt Concrete.

Upheaval or Frost BoilUpheaval is caused by expansion of freezing

moisture in the lower courses of the pavementor subgrade or by the swelling effect ofmoisture in expansive soils.

When this distress occurs, repair byinstalling combination drains as necessary andreplacing base and surface.

APPENDIX B

GLOSSARY

Glossary B-1

Appendix B Glossary

A

AASHTO – The American Association of StateHighway and Transportation Officials. Anorganization of highway engineers from the 50states that develops guides and standards.

AGGREGATE – Any hard, inert, mineralmaterial used for mixing in graduated frag-ments. It includes sand, gravel, crushed stone,or slag.

ASPHALT – A dark brown to black cementi-tious material that can be solid, semi-solid, orliquid in consistency, in which the predominantconstituents are bitumens that occur in natureas such or are obtained as residue in refiningpetroleum. Asphalt is a constituent in varyingproportions of most crude petroleums.

ASPHALT BASE COURSE – A foundationcourse consisting of mineral aggregate, boundtogether with asphaltic material.

ASPHALT BINDER COURSE – An inter-mediate course between a base course and anasphalt surface course. The binder course isusually a coarse-graded aggregate AsphaltConcrete containing little or no mineral matterpassing through a No. 200 sieve.

ASPHALT CEMENT (AC) – Asphalt that isrefined to meet specifications for paving,industrial, and special purposes. Its penetra-tion is usually between 40 and 300.

ASPHALT CONCRETE – High quality,thoroughly controlled hot mixture of asphaltcement and well-graded, high qualityaggregate, thoroughly compacted into auniform dense mass typified by the MissouriDepartment of Transportaion Type B and Cand Superpave mixes.

ASPHALT INTERMEDIATE COURSE – Acourse between a base course and asphaltsurface course. Sometimes called bindercourse.

ASPHALT JOINT FILLER – An asphalticproduct used for filling cracks and joints inpavement and other structures.

ASPHALT OVERLAY – One or more coursesof asphalt construction on an existingpavement. The overlay generally includes aleveling course to correct the contour of the oldpavement, followed by a uniform course orcourses to provide needed thickness.

ASPHALT PAVEMENTS – Pavements con-sisting of a surface course of mineral aggregatecoated and cemented together with asphaltcement on supporting courses such as asphaltbases; crushed stone, slag, or gravel.

ASTM – The American Society for Testing andMaterials. A national organization of users andproducers of materials that establishesstandards.

ASPHALT SOIL STABILIZATION (Soil treat-ment) – Treatment of naturally occurringnonplastic or moderately plastic soils withliquid asphalt at normal temperatures. Aftermixing, aeration and compaction providewater resistant base and subbase courses withimproved load-bearing qualities.

ASPHALT SURFACE TREATMENTS –Applications of asphaltic materials to any typeof road or pavement surface, with or without acover of mineral aggregate that produces anincrease in thickness of less than 1 inch.

GlossaryB-2

B

BASE COURSE – The layer of materialimmediately beneath the surface orintermediate course. It may be composed ofcrushed stone; crushed slag; crushed oruncrushed gravel and sand; or combinations ofthese materials. It also may be bound withasphalt (asphalt base course).

BINDER COURSE – A transitional layer ofbituminous paving between the base and thesurface course.

BORROW – Suitable material from sourcesoutside the roadway prism used primarily forembankments.

BITUMINOUS CONCRETE – A designedcombination of graded crushed stone, filler,and bituminous cement mixed in a centralplant, laid and compacted while hot.

C

CBR (California Bearing Ratio) – A measure-ment of the strength and support value of acrushed stone base or subgrade soil.

CAPILLARY ACTION – The rise or move-ment of water in the voids of a soil caused bycapillary forces.

CEMENT-TREATED BASE – Cement-treatedbase consists of specified soil aggregates andPortland Cement Concrete mixed in a pug milland deposited on the subgrade to the specifiedthickness.

COARSE AGGREGATE – Aggregate particlesretained on a No. 8 sieve.

COARSE GRADED AGGREGATE – Anaggregate having a continuous grading in sizeof particles from coarse through fine with apredominance of coarse sizes.

COMPACTION – The densification ofcrushed stone base, subgrade soil, orbituminous material by means of vibration orrolling.

CONTRACT – The written agreement ex-ecuted between the contractor and otherparties, setting forth the obligations of theparties thereunder; including, but not limitedto the performance of the work, the furnishingof labor and materials, and a basis of payment.

CONTRACTOR – The individual, partner-ship, corporation, or joint venture contractingfor performance of prescribed work.

CRUSHED STONE – The product resultingfrom the artificial crushing of rocks, boulders,or large cobblestones with the particlesresulting from the crushing operation havingall faces fractured.

CRUSHER RUN – Aggregates that havereceived little or no screening after initialcrushing operations. Crusher run aggregatesare generally more economical than screenedaggregates.

CUL-DE-SAC – An area at the terminus of adead-end street or road constructed for thepurpose of allowing a vehicle to turn around.

CULVERT – Any structure that is not classifiedas a bridge and that provides an openingunder any roadway.

CUT – The portion of the roadway formed byexcavation below the surface of the earth.

Glossary B-3

CUTBACK ASPHALT – Asphalt cement thathas been liquified by blending with petroleumsolvents. Upon exposure to atmosphericconditions, the solvents evaporate, leaving theasphalt cement to perform its function.

D

DEEP LIFT ASPHALT PAVEMENT – A pave-ment in which the asphalt base course isplaced in one or more lifts of 4 or more inchescompacted thickness.

DESIGN THICKNESS – The total pavementstructure thickness above the subgrade.

DENSE GRADED AGGREGATE – A mineralaggregate uniformly graded from the maxi-mum size down to and including sufficientmineral dust to reduce the void space in thecompacted aggregate to exceedingly smalldimensions approximating the size of voids inthe dust itself.

DRAINAGE – Structures and facilities forcollecting and carrying away water.

E

EARTHWORK – The work consisting of theconstruction of the roadway, excludingbridges, pavement structure, and selected orcapping material.

EMBANKMENT – A structure of soil, soilaggregate, or broken rock between theembankment foundation and the subgrade.

EMULSIFIED ASPHALT – An emulsion ofasphalt cement and water that contains a smallamount of an emulsifying agent, a hetero-geneous system containing two normallyimmiscible phases (asphalt and water), inwhich the water forms the continuous phase ofthe emulsion and minute globules of asphaltform the discontinuous phase. Emulsifiedasphalts may be either anionic, electro-negatively-charged asphalt globules orcationic, electro-positively-charged asphaltglobules, depending upon the emulsifyingagent.

EQUIPMENT – All machinery, tools, andother apparatus, together with the necessarysupplies for upkeep and maintenance, neededfor the proper construction and acceptablecompletion of the work.

EROSION – Removal and transportation ofsoil by the action of water or wind.

F

FINE AGGREGATE – Aggregate particlespassing a No. 8 sieve.

FINE GRADED AGGREGATE – An aggre-gate having a continuous grading in sizes ofparticles from coarse through fine withpredominance of fine sizes.

FLEXIBLE PAVEMENT – A pavementstructure that maintains intimate contact withand distributes loads to the subgrade anddepends on aggregate interlock, particlefriction, and cohesion for stability. Asphalt orbituminous concrete pavements are flexiblepavements; concrete is not.

GlossaryB-4

FOG SEAL – A light application of liquidasphalt without mineral aggregate cover.Slow-setting asphalt emulsion diluted withwater is the preferred type.

FREE WATER (GROUNDWATER) – Waterthat is free to move through a soil mass underthe influence of gravity.

FRENCH DRAIN – A trench loosely backfilledwith stones, the largest being placed on thebottom with the size decreasing toward thetop.

FULL-DEPTH ASPHALT PAVEMENT – Anasphalt pavement in which asphalt mixturesare employed for all courses above thesubgrade or improved subgrade. A full-depthasphalt pavement is laid directly on theprepared subgrade.

G

GRAVEL – A coarse granular material (usuallylarger than 1/4 inch in diameter) resultingfrom the natural erosion and disintegration ofrock. Crushed gravel is the result of artificialcrushing with most fragments having at leastone face resulting from fracture.

H

HYDROSTATIC PRESSURE – The pressurein a liquid under static conditions; the productof the unit weight of the liquid and thedifference in elevation between the givenpoints and the free water elevation.

l

IMPROVED SUBGRADE – Any course orcourses of select or improved material betweenthe foundation soil and the subbase is usuallyreferred to as the improved subgrade. Theimproved subgrade can be made up of two ormore courses of different quality materials.

L

LEVELING COURSE – An asphalt/aggregatemixture of variable thickness used to eliminateirregularities in the contour of an existingsurface before superimposed treatment orconstruction.

LIQUID ASPHALT – An asphalt materialhaving a soft or fluid consistency that isbeyond the range of measurement by thenormal penetration test, the limit of which is300 maximum. Liquid asphalts includecutback asphalt and emulsified asphalts.

M

MATERIALS – Any substances specified foruse in the construction of the project and itsappurtenances.

MEDIUM CURING ASPHALT (MC) – Liquidasphalt composed of asphalt cement and akerosene-type diluent of medium volatility.

MINERAL DUST – The portion of the fineaggregate passing a No. 200 sieve.

MINERAL FILLER – A finely divided mineralproduct at least 65 percent of which will pass aNo. 200 sieve. Pulverized limestone is the mostcommon manufactured filler, although otherstone dust, hydrated lime, Portland cement,and certain natural deposits of finely dividedmineral matter are also used.

Glossary B-5

N

NATURAL ASPHALT – Asphalt occurring innature that has been derived from petroleumby natural processes of evaporation of volatilefractions leaving the asphalt fractions. Thenative asphalts of most importance are foundin the Trinidad and Bermudez Lake deposits.Asphalt from these sources is called LakeAsphalt.

O

OPEN GRADED AGGREGATE – An aggre-gate containing little or no mineral filler or inwhich the void spaces in the compactedaggregate are relatively large.

P

PAVEMENT STRUCTURE (COMBINATIONOR COMPOSITE) – All courses of selectedmaterial placed on the foundation or subgradesoil, other than any layers or coursesconstructed in grading operations. When theasphalt pavement is on an old PortlandCement Concrete base or other rigid-type base,the pavement structure is referred to as acombination or composite-type pavementstructure.

PERCOLATION – The movement of freewater through soil.

PERMEABILITY – A measure of the rate orvolume of flow of water through a soil.

PETROLEUM ASPHALT – Asphalt refinedfrom crude petroleum.

PLANS – The standard drawings current onthe date bids are received; and the officialapproved plans, profiles, typical cross sections,

electronic computer output listings, workingdrawings and supplemental drawings, orexact reproductions thereof, current on thedate bids are received; and all subsequentapproved revisions thereto, which show thelocation character, dimensions, and details ofthe work to be done.

PLANT MIX – A mixture produced in anasphalt mixing plant, that consists of mineralaggregate uniformly coated with asphaltcement or liquid asphalt.

PORTLAND CEMENT CONCRETE (PCC) –A composite material that consists essentiallyof Portland cement and water as a bindingmedium in which is mixed coarse and fineparticles of crushed stone.

PRIME COAT – An application of low-viscosity liquid asphalt to an absorbentsurface. It is used to prepare an untreated basefor an asphalt surface.

PROPOSAL – The offer of a bidder, submittedon the approved official form, to perform thework and to furnish the labor and material atprices set forth therein, valid only whenproperly signed and guaranteed.

R

RAPID CURING ASPHALT (RC) – Liquidasphalt composed of asphalt cement and anaphtha- or gasoline-type diluent of highvolatility.

REHABILITATION – The renewal of an exist-ing surface or pavement structure by repair,recycling, or overlay techniques.

RECLAIMED ASPHALT PAVEMENT (RAP) –Removed and/or reprocessed pavementmaterials containing asphalt and aggregates.

GlossaryB-6

RESURFACING – Existing surfaces may beimproved by resurfacing (or overlaying) with aplant mix asphalt mat of varying thicknesses.It may be considered in two categories: (1)overlays to provide smooth, skid- and water-resistant surfaces or to make improvements ingrade and/or cross section; and (2) overlays tostrengthen existing pavements to handleheavier loads or increased traffic. Sometimescalled overlays.

RIGID PAVEMENT – A pavement structurethat distributes loads to the subgrade, havingas one course a Portland Cement Concrete slabof relatively high bending resistance.

ROAD – A general term denoting a public wayfor purpose of vehicular travel, including theentire area within the right-of-way.

ROADBED – The graded portion of ahighway within the top and side slopes,prepared as a foundation for the pavementstructure and shoulders.

ROCK – From which crushed stone, sand, andgravel are made; the rock most suitable formaking good aggregates.

S

SEAL COAT – A thin asphalt surface treat-ment used to waterproof and improve thetexture of an asphalt wearing surface.Depending on the purpose, seal coats may ormay not be covered with aggregate. The maintypes of seal coats are aggregate seals, fogseals, emulsion slurry seals, and sand seals.

SELECT MATERIAL – Suitable materialobtained from roadway cuts, borrow areas, orcommercial sources and designated orreserved for use as foundation for the subbase,for subbase material, shoulder surfacing, orother specific purposes.

SHOULDER – The portion of the roadwaycontiguous with the traveled way foraccommodation of stopped vehicles, foremergency use, and for lateral support of baseand surface courses.

SLOW CURING ASPHALT (SC) – Liquidasphalt composed of asphalt cement and oilsof low volatility.

SLAG – The air-cooled, non-metallic by-product of a blast furnace operation consistingessentially of silicates and alumino-silicates oflime and other bases that is developedsimultaneously with iron in a blast furnace.Naturally it is only available in those localitieswhere pig iron is produced. Crushed slagweighs about 80 pounds per cubic foot.

SLURRY SEAL – A mixture of slow-settingemulsified asphalt, fine aggregate, and mineralfiller with water added to produce slurryconsistency.

SOIL AGGREGATE – Natural or preparedmixtures consisting predominantly of hard,durable particles or fragments of stone, slag,gravel, or sand, that contain some soil-clay orstone dust conforming to specifiedrequirements.

SOIL CEMENT BASE – Consists of a mixtureof the natural subgrade material and Portlandcement in the proper amounts. After thoroughmixing, the proper amount of water is added,and the material is compacted to the requiredthickness.

SOIL SUPPORT – A term expressing theability of the roadbed material, or subgradesoil, to support the traffic loads transmittedthrough a flexible pavement structure.

Glossary B-7

SPECIAL PROVISIONS – Special directions,provisions, or requirements peculiar to theproject under consideration and not otherwisethoroughly or satisfactorily detailed or setforth in the specifications. Special provisionsset forth the final contractual intent in thematter involved.

STAGE CONSTRUCTION – The constructionof roads and streets by applying successivelayers of Asphalt Concrete according to designand a predetermined time schedule.

STREET – A general term denoting a publicway for purpose of vehicular travel, includingthe entire area within the right-of-way.

SUBBASE – The course in the asphaltpavement structure immediately below thebase course is the subbase. If the subgrade soilis of adequate quality, it may serve as thesubbase.

SUBCONTRACTOR – Any individual, part-nership, or corporation to whom the contractorsublets part of the contract.

SUBDRAIN – A structure placed beneath theground surface to collect and carry awayunderground water.

SUBGRADE – The uppermost material placedin embankments or unmoved from cuts in thenormal grading of the roadbed. It is thefoundation for the asphalt pavement structure.The subgrade soil sometimes is called base-ment soil or foundation soil.

SUBGRADE STABILIZATION – Modifica-tion of roadbed soils by admixing withstabilizing or chemical agents that will increaseload-bearing capacity, firmness, and resistanceto weathering or displacement.

SURFACE COURSE – One or more layers of apavement structure designed to accommodatethe traffic load, the top layer of which resistsskidding, traffic abrasion, and the disintegrat-ing effects of climate. The top layer is some-times called the Ôwearing course.Õ

SUBSURFACE DRAINAGE – Removal of freewater from various structural components ofthe pavement or the surrounding soil.

U

UNDERDRAIN – A perforated or porous-walled pipe placed with suitable perviousbackfill beneath the ground surface to collectand carry away underground water.

V

VISCOSITY – This is a measure of theresistance to flow. The term is used as ÒhighviscosityÓ or Òlow viscosity.Ó A high viscositymaterial refers to a heavy or still material thatwill not flow easily. A low viscosity material isthe opposite. Viscosity is measured in absoluteunits called poises. It was formerly measuredin empirical values of time, distance, andtemperature. This method was called SayboltFurol Viscosity.

W

WEARING COURSE – The top course ofasphalt pavements, also called the surfacecourse.

APPENDIX C

CONVERSION

TABLES

Galsper WIDTH - FEETSq.Yd. 1 2 6 7 8 9 10 11 12 14 16 18 20 22 24

0.10 1.1 2.2 6.7 7.8 8.9 10.0 11.1 12.2 13.3 15.6 17.8 20.0 22.2 24.4 26.70.15 1.7 3.3 10.0 11.7 13.3 15.0 16.7 18.3 20.0 23.3 16.7 10.0 33.3 36.7 40.00.20 2.2 4.4 13.3 15.6 17.8 20.0 22.2 24.4 26.7 31.1 35.6 40.0 44.4 48.9 53.30.25 2.8 5.6 16.7 19.4 22.2 25.0 27.8 30.6 33.3 38.9 44.4 50.0 55.6 61.1 66.70.30 3.3 6.7 20.0 23.3 26.7 30.0 33.3 36.7 40.0 46.7 53.3 60.0 66.7 73.3 80.00.35 3.9 7.8 23.3 27.2 31.1 35.0 38.9 42.8 46.7 54.4 62.2 70.0 77.8 85.5 93.30.40 4.4 8.9 26.7 31.1 35.6 40.0 44.4 48.9 53.3 62.2 71.1 80.0 88.9 97.8 107.0.45 5.0 10.0 30.0 35.0 40.0 45.0 50.0 55.0 60.0 70.0 80.0 90.0 100. 110. 120.0.50 5.6 11.1 33.3 38.9 44.4 50.0 55.5 61.1 66.7 77.8 88.9 100. 111. 122. 133.0.55 6.1 12.2 36.7 42.8 48.9 55.0 61.1 67.2 73.3 85.5 97.8 110. 122. 134. 147.0.60 6.7 13.3 40.0 46.7 53.3 60.0 66.7 73.3 80.0 93.3 107. 120. 133. 147. 160.0.65 7.2 14.4 43.3 50.6 57.8 65.0 72.2 79.4 86.7 101. 115. 130. 144. 159. 173.0.70 7.8 15.6 46.7 54.4 62.2 70.0 77.8 85.5 93.3 109. 124. 140. 156. 171. 187.0.75 8.3 16.7 50.0 58.3 66.7 75.0 83.3 91.7 100. 117. 133. 150. 167. 183. 200.0.80 8.9 17.8 53.3 62.2 71.1 80.0 88.9 97.8 107. 124. 142. 160. 178. 196. 213.0.85 9.4 18.9 56.7 66.1 75.5 85.0 94.4 104. 113. 132. 151. 170. 189. 208. 227.0.90 10.0 20.0 60.0 70.0 80.0 90.0 100. 110. 120. 140. 160. 180. 200. 220. 240.0.95 10.6 21.1 63.3 73.9 84.4 95.0 106. 116. 127. 148. 169. 190. 211. 232. 253.1.00 11.1 22.2 66.7 77.8 88.9 100. 111. 122. 133. 156. 178. 200. 222. 244. 267.1.10 12.2 24.4 73.3 85.5 97.8 110. 122. 134. 147. 171. 196. 220. 244. 269. 293.1.20 13.3 26.7 80.0 93.3 107. 120. 133. 147. 160. 187. 213. 240. 267. 293. 320.1.25 13.9 27.8 83.3 97.2 111. 125. 139. 153. 167. 194. 222. 250. 278. 306. 333.1.30 14.4 28.9 86.7 101. 116. 130. 144. 159. 173. 202. 230. 260. 288. 318. 347.1.40 15.6 31.1 93.3 109. 124. 140. 156. 171. 187. 218. 249. 280. 311. 342. 373.1.50 16.7 33.3 100. 117. 133. 150. 167. 183. 200. 233. 267. 300. 333. 367. 400.1.75 19.4 38.9 117. 136. 156. 175. 194. 214. 230. 272. 311. 350. 389. 427. 467.2.00 22.2 44.4 133. 156. 178. 200. 222. 244. 267. 311. 356. 400. 444. 499. 533.2.25 25.0 50.0 150. 175. 200. 225. 250. 275. 300. 350. 400. 450. 500. 550. 600.2.50 27.8 55.6 167. 194. 222. 250. 278. 306. 333. 389. 444. 500. 556. 611. 667.2.75 30.6 61.1 183. 214. 244. 275. 306. 336. 367. 428. 489. 550. 611. 672. 733.3.00 33.3 66.7 200. 233. 267. 300. 333. 367. 400. 467. 533. 600. 667. 733. 800.

Conversion Tables C-1

Appendix CConversion TablesTABLE C-1. Approximate Quantities of Asphalt Concrete per Square Yard

Approximate Thickness Weight Per Square Yard - PoundsGravel or Granite Limestone or Trap Rock

BinderTotal Surface or Total Surface Binder or Total Surface Binder orDepth Base Weight Weight Base Weight Weight Weight Base Weight1” 1” — 110 110 — 115 115 —1 1/2” 1 1/2” — 165 165 — 173 173 —2” 2” — 220 220 — 230 230 —2 1/2” 1” 1 1/2” 275 110 165 288 115 1733” 1” 2” 335 115 220 350 120 2303 1/2” 1” 2 1/2” 390 115 275 408 120 2884” 1” 3” 454 115 339 474 120 3545” 1” 4” 577 115 462 592 120 4726” 1” 5” 680 115 565 710 120 5907” 1” 6” 793 115 678 828 120 7088 1/2” 1” 7 1/2” 960 115 845 1004 120 8849” 1 1/2” 7 1/2” 1018 173 845 1064 180 884

TABLE C-2. Gallons of Emulsified Asphalt Required Per 100 Linear Feet: Various Widths and Rates

100WNote.- Formula used for calculation: Q = ––––– R = 11.11WR

9

Where: Q = Quantity of asphalt required, in gallons per 100 ft. R = Rate of application in gallons per sq. yd. W= Width of application, in feet

Conversion TablesC-2

WIDTH - FEETlb/yd2

1 2 6 7 8 9 10 11 12 14 16 18 20 22 24

10 0.06 0.11 0.17 0.22 0.28 0.33 0.39 0.44 0.50 0.56 1.11 1.67 2.22 2.78 3.3320 0.11 0.22 0.33 0.44 0.56 0.67 0.78 0.89 1.00 1.11 2.22 3.33 4.44 5.56 6.6730 0.17 0.33 0.50 0.67 0.83 1.00 1.17 1.33 1.50 1.67 3.33 5.00 6.67 8.33 10.0040 0.22 0.44 0.67 0.89 1.11 1.33 1.56 1.78 2.00 2.22 4.44 6.67 8.89 11.11 13.3350 0.28 0.56 0.83 1.11 1.39 1.67 1.94 2.22 2.50 2.78 5.56 8.33 11.11 13.89 16.6760 0.33 0.67 1.00 1.33 1.67 2.00 2.33 2.67 3.00 3.33 6.67 10.00 13.33 16.67 20.0070 0.39 0.78 1.17 1.56 1.94 2.33 2.72 3.11 3.50 3.89 7.78 11.67 15.56 19.44 23.3380 0.44 0.89 1.33 1.78 2.22 2.67 3.11 5.56 4.00 4.44 8.89 13.33 17.78 22.22 26.6790 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00 10.00 15.00 20.00 25.00 30.00

100 0.56 1.11 1.67 2.22 2.78 3.33 3.89 4.44 5.00 5.56 11.11 16.67 22.22 27.78 33.33200 1.11 2.22 3.33 4.44 5.56 6.67 7.78 8.89 10.00 11.11 22.22 33.33 44.44 55.56 66.67300 1.67 3.33 5.00 6.67 8.33 10.00 11.67 13.33 l 5.00 16.67 33.33 50.00 66.67 83.33 100.00400 2.22 4.44 6.67 8.89 11.11 13.33 15.56 17.78 20.00 22.22 44.44 66.67 88.89 111.11 133.33500 2.78 5.56 8.33 11.11 13.89 16.67 19.44 22.22 25.00 27.78 55.56 83.33 111.11 136.89 166.67600 3.33 6.67 10.00 13.33 16.67 20.00 23.33 26.67 30.00 33.33 66.67 100.00 133.33 166.67 200.00700 3.89 7.78 11.67 15 .56 19.44 23.33 27.22 31.11 35.00 38.89 77.78 116.69 155.56 194.44 233.33800 4.44 8.89 13.33 17.78 22.22 26.67 31.11 35.56 40.00 44.44 88.89 133.33 177.78 222.22 266.67900 5.00 10.00 l 5.00 20.00 25.00 30.00 35.00 40.00 45.00 50.00 100.00 l50.00 200.00 250.00 300.00

1,000 5.56 11.11 16.67 22.22 27.78 33.33 38.89 44.44 50.00 55.56 111.11 166.67 222.22 277.78 333.33

TABLE C-3. Tons of Material Required Per 100 Linear Feet for Various Widths and Pounds PerSquare Yard

W 100 RNOTE: Formula used for calculation w = —— —— —— = 0.005556 RW3 3 2000

Where: w = Weight of material in tons per 100 feet R = Rate of application, lb/yd2

W = Width of application, feet[ ] [ ] [ ]

NOTE: Formula used for calculation:

D W 100Per 100 Lin. Ft.: q = —— —— —— = 0.3086 DW36 3 3

D W 5,280Per Mile: q = —— —— ——– = 16.2963 DW36 3 3

Where: q = Quality of material, cubic yards D = Depth, inchesW = Width, feetL = Length

[ ] [ ] [ ][ ] [ ] [ ]

TABLE C-4. Cubic Yards of Material per 100 Linear Feet: Various Widths and Depths

Wldth, Depth - InchesFeet

1 2 3 4 5 6 7 8 9 10 11 12

1 0.31 0.62 0.93 1.23 1 .54 1.85 2.16 2.47 2.78 3.09 3.40 3.702 0.62 1.23 1.85 2.47 3.09 3.70 4.32 4.94 5.56 6.17 6.79 7.413 0.93 1.85 2.78 3.70 4.63 5.56 6.48 7.41 8.33 9.26 10.2 11.14 1.23 2.47 3.70 4.94 6.17 7.41 8.64 9.88 11. 1 12.3 13.6 14.85 1.54 3.09 4.63 6.17 7.72 9.26 10.8 12.3 13.9 15.4 17.0 18.5

6 1.85 3.70 5.56 7.4 l 9.26 11.1 13.0 14.8 16.7 18.5 20.4 22.27 2.16 4.32 6.48 8.64 10.8 13.0 15.1 17.3 19.4 21.6 23.8 25.98 2 47 4.94 7.41 9.88 12.3 14.8 17.3 19.8 22.2 24.7 27.2 29.69 2 78 5.56 8.33 11.1 13.9 16.7 19.4 22.2 25.0 27.8 30.6 33.3

10 3.09 6.17 9.26 12.3 15.4 18.5 21.6 24.7 27.8 30.9 34.0 37.0

20 6.17 12.3 18.5 24.7 30.9 37.0 43.2 49.4 55.6 61.7 67.9 74.130 9.26 18.5 27.8 37.0 46.3 55.6 64.8 74.1 83.3 92.6 102 11140 12.3 24.7 37.0 49.4 61.7 74.1 86.4 98.8 111 123 136 14850 15.4 30.9 46.3 61.7 77.2 92.6 108 123 139 154 170 185

60 18.5 37.0 55.6 74.1 92.6 111 130 148 167 185 204 22270 21.6 43.2 64.8 86.4 108 130 151 173 194 216 238 25980 24.7 49.4 74.1 98.8 123 148 173 198 222 247 272 29690 27 8 55.6 83.3 111 139 167 194 222 250 278 306 333

100 30.9 61.7 92.6 123 154 185 216 247 278 309 340 370

Per

100

Lin

ear

Fee

t

Conversion Tables C-3

TABLE C-5. TABLE C-6.

APPENDIX D

PUBLICATIONS

Publications D-1

Appendix D

Publications

NATIONAL ASPHALT PAVEMENT

ASSOCIATION (NAPA)

The following publications are availablefrom the National Asphalt PavementAssociation (NAPA). A more complete listingof available publications and other materialcan be obtained by contacting either the APAIoffice or NAPA.

QIP-97 Quality Control for Hot MixAsphalt Manufacturing Facilitiesand Paving Operations

QIP-108 Tender Mixes Ð Probable Causes,Possible Remedies

QIP-109 Asphalt Cement Content Diag-nostic Approach for Hot MixAsphalt (HMA) Facilities

QIP-110 Hot Mix Asphalt Segregation:Causes and Cures

QIP-111 The Design of Hot Mix Asphaltfor Heavy Duty Pavements

QIP-112 Constructing Quality Hot MixAsphalt Pavements Ð TroubleShooting Guide

QIP-113 Improving Performance ofLongitudinal Construction Jointsin Hot Mix Asphalt Pavements

QIP-114A Using Additives and Modifiersin Hot Mix Asphalt - Part A

QIP-114B-E Using Additives and Modifiersin Hot Mix Asphalt Ð Parts B, C,D, & E

IS-69 Stockpiling and Cold Feed forQuality

IS-71 Hot Recycling in Hot Mix BatchPlants

IS-77 Are Hot Mix Tarps Effective?

IS-84 Development of Marshall Proce-dures for Designing AsphaltPaving Mixtures

IS-85 Selecting Proper Marshall Proce-dures for Optimum Asphalt Con-tent of Dense Graded PavingMixtures

IS-97 Blistering in Asphalt PavementsÐ Causes and Cures

IS-98 Cracking and Seating of PCCPavements Prior to Overlayingwith Hot Mix Asphalt

IS-101 Guidelines on the Use of Bag-house Fines

IS-107 Estimating User Costs of Asphaltand Concrete Pavement Rehabil-itation

IS-109 Design of HMA Pavements forCommercial, Industrial & Resi-dential Applications

IS-111 Pavement SmoothnessIS117 Guidelines For Use of HMA

Overlay to Rehabilitate PCCPavement

IS-119 Hot Mix Asphalt for High StressApplications

PS-12 Recreation AsphaltPS-14 For Your Parking Area Asphalt is

Just BetterPS-20 Pavement Life Cycle CostingPS-21 Which of These Claims Being

Made for Concrete Pavement DoYou Find Believable?

PublicationsD-2

THE ASPHALT INSTITUTE

The following publications are availablefrom the Asphalt Institute (AI). A morecomplete listing of publications and othermaterial can be obtained by contacting eitherthe APAI office or the Asphalt Institute.

ES-2 Vibratory Compaction of AsphaltPaving Mixtures

ES-3 Design of Hot Asphalt MixturesES-8 Paving AsphaltES-9 Factors Affecting CompactionES-10 Cause and Prevention of Strip-

ping in Asphalt PavementsES-12 Asphalt Surface Treatments Ð

Construction TechniquesIS-91 Full-Depth Asphalt Pavements

for Parking Lots, Service Stationsand Driveways

IS-96 How to Design Full-DepthAsphalt Pavements for Streets

IS-139 A Simplified Method for theDesign of Asphalt Overlays forLight to Medium Traffic Pave-ments

IS-147 Athletics and Recreation onAsphalt

IS-154 Thickness Design Ð AsphaltPavements for General Aviation

IS-168 Tender Mixes Ð The Causes andthe Cures

IS-169 A Pavement Rating System forLow-Volume Asphalt Roads

IS-173 Energy Requirements for Road-way Pavements

IS-178 Alternatives in Pavement Main-tenance, Rehabilitation, andRestoration

IS-180 Safe Storage and Handling ofHot Asphalt

IS-181 Asphalt Pavement ThicknessDesign

MS-1 Thickness Design Ð AsphaltPavements For Highways andStreets

MS-2 Mix Design Methods for AsphaltConcrete Ð And Other Hot-mixTypes

MS-4 The Asphalt HandbookMS-8 Asphalt Paving HandbookMS-10 Soils Manual Ð For the Design of

Asphalt Pavement StructuresMS-14 Asphalt Cold Mix ManualMS-15 Drainage of Asphalt Pavement

StructuresMS-16 Asphalt in Pavement Main-

tenanceMS-17 Asphalt Overlays for Highway

and Street RehabilitationMS-19 A Basic Asphalt Emulsion

ManualMS-20 Asphalt Hot-Mix RecylingMS-21 Asphalt Cold-Mix RecyclingMS-22 Principles of Construction of

Hot-Mix Asphalt PavementsSP-1 Superpave PG Asphalt Binder

Specification & TestingSP-2 Superpave Level I Mix Design

Publications D-3

AMERICAN ASSOCIATION OF STATEHIGHWAY AND TRANSPORTATION

OFFICIALS (AASHTO)

The following publications are availablefrom the American Association of State High-way and Transportation Officials (AASHTO).A more complete listing of publications andother material can be attained by contactingAASHTO.

AASHTO Guide for Design of PavementStructures 1993

AASHTO Guide for Design of PavementStructuresVolume 2, 1986

ORDERING INSTRUCTIONS

Call or write the appropriate organizationfor purchase or rental instructions.

Asphalt Paving Association of Iowa3408 Woodland AvenueSuite 209West Des Moines, Iowa 50266-6506Phone: (515) 222-0015Fax: (515) 222-1238

National Asphalt Pavement Association(NAPA)Publications Department5100 Forbes Blvd.Lanham, Maryland 20706-4413Phone: (301) 731-4748Fax: (301) 731-4621

The Asphalt Institute (AI)Research Park DriveBox 14052Lexington, Kentucky 40512-4052Phone: (606) 288-4960Fax: (606) 288-4999

American Association of State Highway andTransportation Officials (AASHTO)444 N. Capitol Street, N.W., Suite 249Washington, D.C. 20001800-231-3475FAX: 800-525-5562

Iowa Department of TransportationOffice Supply800 Lincoln WayAmes, Iowa 50010(515) 239-1324

GOVERNMENT PUBLICATIONS

The following publications are available fromthe Government Printing Office, Superinten-dent of Documents, Washington, D.C. 20402;phone 202/783-3238. Make checks or moneyorders payable to Superintendent of Documents.

Manual on Uniform Traffic Control Devicesfor Streets and Highways (MUTCD, 1988Edition), Stock No. 050-001-00308-02. Price is$22 (domestic) and $27.50 (foreign). This newedition incorporates revisions one throughfive. A list of all official rulings withappropriate effective dates and compliancedates is also contained in this bound edition ofthe MUTCD. Because incremental revisionswill not be made to this edition, subscriptionservice is not necessary.

Standard Highway Signs Book, Stock No. 950-044-00000-4. Price is $30 (domestic) and$37.50 (foreign) and includes subscriptionservice for revisions. There are currently tworevisions available.

Traffic Control Device Handbook, Stock No.050-001-00270-1. Price is $20 per copy or $1,500for 100 copies to a single address.

APPENDIX E

CREDITS

AND

REFERENCES

Credits and References E-1

Appendix E

Credits and References

CREDITS

Special recognition is given to the followingagencies or associations for their help inproviding information and resources whichcontributed to the writing of this DesignGuide.

The Asphalt InstituteThe Iowa Department of TransportationThe Plantmix Asphalt Industry of

Kentucky, Inc.The Virginia Asphalt Associates, Inc.The National Asphalt Pavement Association

Also, special recognition is given to Dr. Stanley L. Ring, PE, PhD., Professor Emeritus,Civil Engineering Dept., Iowa State Universityfor his work in assisting APAI Engineering staffin development of the Iowa Design Guide for Asphalt Paving.

REFERENCES

The Asphalt Institute. A Pavement RatingSystem for Low-Volume Asphalt Roads,Information Series No. 169 (IS-169). CollegePark, Maryland, 1981.

The Asphalt Institute. Asphalt PavementThickness Design, Information Series No.181 (IS-181). College Park, Maryland, 1983.

The Asphalt Institute. Thickness Design ÐAsphalt Pavements for Highways andStreets, Manual Series No. 1 (MS-1). CollegePark, Maryland, 1984.

The Asphalt Institute. The Asphalt Handbook,Manual Series No. 4 (MS-4). College Park,Maryland, 1989.

The Asphalt Institute. Asphalt Overlays forHighway and Street Rehabilitation, ManualSeries No. 17 (MS-17). College Park,Maryland, 1983.

The Asphalt Institute. A Basic AsphaltEmulsion Manual, Manual Series No. 19(MS-19). College Park, Maryland, 1987.

Institute of Transportation Engineers. Trans-portation and Traffic Engineering Handbook(2nd Ed.). Arlington, Virginia, 1982.

Iowa Department of Transportation. StandardSpecifications for Highway and BridgeConstruction, 1984.

Iowa State Highway Commission. Iowa SoilsResearch Report. Ames, Iowa, 1960.

Transportation Research Board, NationalResearch Council. Highway CapacityManual. Washington, D.C., 1985.

APPENDIX F

MEMBER

FIRMS

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