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Tenth Edition 2008
HOT MIX ASPHALT
PAVEMENT DESIGN
GUIDE
Th e Maryland Asp h alt Association , Inc .
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Requirements
for Successful Asphalt
Pavement Construction1 GOOD PLANNING
2 GOOD DESIGN
3 GOOD CONSTRUCTIONA) Materials
B) Subgrade
C) Workmanship
4 GOOD MAINTENANCE
published for
Maryland Asp ha lt Associa tion, Inc .
2408-G Pepp er Mill Drive, Glen Burn ie, MD 2106 1
410-761-2160 Fax 410-761-0339
Editor: Brian Dolan
Auth or: Brian Dolan
pub lishe d by
P/ T Enterp r ises , Inc.
Fallston , MD 210 47
410-879-7606 Fax 410 -893-5721
p r in te d b y
E. John Schmit z & Sons , Inc.
Sparks, MD 21152
410-329 -300 0 Fax 410-771-4342
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INTRODUCTION
This guide is pro vided by the Maryland Asph alt Association as a tool for ow ner s, architects, enginee rs and develop ers wh en
preparing plans and specifications for pavements to be constructed in Maryland.
The guide is not intend ed to be used as a substitute for p rofessional asph alt p avement design by co mp etent e ngineers using
spec ific traffic and soils information. By nece ssity this manual uses generalizations and simp lifications; ho we ver, the u se of these
designs and sp ecifications,together with p roper construction co ntrols, will provide users with econo mic and satisfactory
pavements that will provide good performance with relatively little maintenance.
The tenth edition of this guide has been prep ared in order to bring designers information on the c urrent Maryland State Highway
Administration Specifications and to incorp orate the latest know ledge, techniques and technology that h ave been
developed in asph alt p avemen t construction over th e p ast several years. This pub lication is not intended to set standards or
regulations. The roadway typical sections are Perpetual Pavements and have been verified using the Per Road
Flex ib le Pe rp et ua l Des ig n & Ana lys is Sof tw are.
HOT MIX ASPHALT
WHAT IS HOT MIX ASPHALT?
Hot mix asphalt may be referred to by several names. In
differen t sections of the state it may also b e referred to as
bituminous concrete, hot plant mix, asphalt concrete,
blacktop or Superpave.
Hot mix asphalt is comp osed of aggregate boun d together
into a solid mass by asph alt ceme nt. The aggregates total
ninety-three (93) to ninety-seven (97) percent by weight of
the total mixture and are mixed w ith three (3) to seven (7)
percen t asph alt cement. It is manufactured in a central
mixing plant whe re the asphalt and aggregates are heated,
properly proport ioned, and mixed. The completed paving
mixture is hauled by trucks to th e mech anical spreader w here
it is placed in a smooth layer and compacted by rollers while
stil l hot. (Hot mix asphalt may be placed by h and w hen it is
impractical to use a paver.)
Asphalt pavemen ts are con structed of one or more co urses
of hot m ix asph alt placed directly on th e subgrade or on
a subbase.
HOT MIX ASPHALT SPECIFICATIONS
All wo rk involving hot mix asph alt p avemen ts and resurfacing
can be covered by using the Maryland State HighwayAdm inistration July 200 8 Stand ard Spe cifications for
Construction and Materials in conjunction with the typical
sections th at follow.
HOT MIX ASPHALT RESURFACING
Resurfacing is the placing of one or more courses of hot mix
asphalt over an existing hard surface p avemen t. This is the
most often used means for salvaging and extending the
service life of older d eteriorating p avemen ts.
ADVANTAGES OF HOT MIX ASPHALT
1. Versatility
Hot mix asphalt pavements can be designed to
hand le virtually any traffic loading, soils and
materials, and can be used to salvage old p avemen ts
as well as to build new ones.
Phased construction can easily be incorporated.
2 . Ec on o my
Hot Mix Asph alt Pavemen ts are:
economical to construct may be con structed rapidly and are immediately
ready for use
may be recycled
require minimal maintenance
provide outstanding performance
3. HMA pavements are not affected b y ice controlchemicals.
4. Building and site esthetics are enhanced.
5. Traffic no ise is minimized w hen HMA pavement
is u se d .
6. Pavement striping is highly visible on th e dark
colored surface.
7. HMA is a flexible-type pavem ent.
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SUPERPAVE
Superpave is a state of the art paving system which our industry and the state of Maryland embraced in
the late 1990s. Marshall mixes are no longer readily available and should b e rep laced w ith the appro pri-
ate Sup erp ave specifications.
There are four imp ortant Sup erpave parameters w hich the ow ner m ust specify in order to insure theprop er design. These parameters include the type of liquid asph alt wh ich, in all but the m ost unusual
circum stances sho uld be PG 64-22; the com pac tion level shou ld be N Design 50 or Level 1 for all
applications excep t minor or p rincipal arterial streets. The next tw o parameters go hand in hand and
shou ld always be co nsidered togeth er. Aggregate size and lift thickn ess are insep arable. All mix selections
shou ld allow for at least 4 times the n om inal max imum aggregate size for th e desired lift thickness. This
means 9.5mm aggregate surfaces should be a m inimum of 1-1/2 thick.
Please con sult with the Maryland Asph alt Association for guidanc e in sp ecifying the pr op er sup erp ave
spec ification for your individual p roject.
SPECIFICATIONS FORHOT MIX ASPHALT
There are a wide variety of hot mix asphalt compositions used
in Maryland th at vary from fine to c oarse in size and
gradation. Furtherm ore, Maryland hot mix asphalt mixtures
utilize differen t aggregates or comb inations of aggregates, the
principal types being crushed stone, sand, gravel, bank run
gravel, roofing shingles and recycled asph alt pavem ent.
Econ omics req uire th e u se of locally available aggregates.
The most widely used hot mix asphalt specifications in
Maryland are those contained in the State HighwayAdministration Standard Spe cifications for Con struction
and Materials dated July 2008 including re visions
and additions.
The Maryland Asph alt Association reco mm end s the use of
these specifications.
BASE DESIGNATIONS
19 MM Sup erp ave
Gene rally a minimum lift thickness of 3" is recomm end ed.
Aggregate sizes of the mix design should be checked prior
to u se in thinn er lifts.
12.5 MM Sup erp ave
Gene rally a minimum lift thickness of 2" is recomm end ed.
Aggregate sizes of the mix design should be checked prior
to u se in thinn er lifts.
SURFACE DESIGNATIONS
9.5 MM Sup erp ave
This surface mix is recommended for most surface
applications.
Recommen ded minimum lift thickness 11/2".
4.75 MM Sup erp ave
This mix is designed pr imarily for thin lift leveling o r
correcting minor deviations. It is a fine mix that can be
placed in lifts as thin as 1/2". It should not be placed in
lifts exceeding 1" and sho uld no t no rmally be sp ecified
as a final wearing cou rse for structu ral repairs or
resurfacings.
SMA (Ston e Matrix Asph alt)
This is a high stability mix d esigned for spe cific con ditions
such as high volume Interstate Highways.
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A m odern ho t m ix asphalt facilit y prov ides h igh
produ ction , good qu ality m ixes ( in cluding recy cled
asphalt pavem ent if desired) w hile meeting stringent
air qu ality stan dards.
ASPHALT PAVING MIXTURES
The pavement design requires the p roper h ot mix asphalt
paving mixtures for the base and surface pavements.
It is impor tant th at a Job Mix Formu la for th e p aving
mixture be established for and approved b y the en gineer.A reputable h ot m ix asphalt producer, providing standard
mixes, can readily furnish the engineer w ith a w ritten Job
Mix Formula.
The asphalt mixtures referred to in this manual are Maryland
State Highw ay Adm inistration Job Mix Designs w hich are
readily available throu ghou t Maryland an d h ave proven
through extensive use to have all of the desirable
characteristics of good asphalt pavements.
SPECIFICATIONSMaryland State Highway Administration Standard
Spe cifications for Constru ction an d Materials, dated
July 2008, including revision s and additions,
con tain the following section s for Hot Mix Asph alt Pavemen t
and Asph alt Cemen ts and Hot Mix Asph alt:
Section 504 Hot Mix Asph alt Pavem ent
Section 505 Ho t Mix Asp halt Patch es
Sect ion 508 Milling Existing Hot Mix Asph alt
Pavement
Section 901 Aggregates
Section 904 Performanc e graded asphalt bin &
HMA
Section 915 Produ ction Plants
Se c tio n 9 15 .0 2 Ho t Mix Asp h a lt Pla nt s
TACK COATA tack coat of asph alt (usually em ulsified asphalt) is app lied
to ensure bo nd b etween the existing surface and the asphalt
overlay. It should be ap plied in an even, thin coat at a rate ofapplication of .05 gallons per square yard with a tolerance of
.01 gallons per square yard. Excessive tack coat can cause
slipp age or can flush to the surface. All longitudinal and
transverse joints shall be properly tacked.
SUBGRADE SPECIFICATIONS
Top soil, large rocks and oth er types of low q uality, unsu itable
soil shall be remo ved and replaced. The subgrade must be
prop erly shaped to the d esired sections and elevation and
shall be comp acted so that i t is firm, hard and un yielding. A
firm an d un yielding subgrade is essential for good p avemen t
construction. The Subgrade shall be comp acted to 95% of
dry w eight d ensity as deter mined by AASHTO Designation
T-18O, Method C or D as applicable. (Note:There are areas in
Maryland w here, due to the type of soil ,i t is not po ssible to
attain 95% of dry w eight den sity using the T-180 Metho d. In
these areas the co mp action requirements shall be 95% of the
dry w eight d ensity as deter mined by AASHTO Designation
T-99 Method.) To prevent grow th of weed s, the subgrade
should be treated with an app roved herbicide. (See NAPA
Pub lication IS-51)
ENGINEERING SERVICESThe Maryland Asph alt Association w elcome s the o pp ortu nity
to work w ith architects,co nsulting engineers, pub lic agency
officials, own ers, and industry engineers in the p reparation ofpavement specifications,co nstruction d etails and co nstruction
controls toward the end of quality asph alt pavemen t
installation s. The Association h as professional engine ering
services available for th is purp ose. The Associations add ress
and te lephone n umber appear on the back cover. Other
sources where information and guidance on asphalt pavement
construction may be ob tained are:
Nat ion al Asph alt Pavem ent Association
5100 Forbes Boulevard
Lanha m , Maryland 20706-4413
(301 ) 731-4748 FAX(30 1) 731 -4621
The Asphalt In stituteCarlos Rosen berger
PO Box 337
2 E.Ha rrisburg St.
Dillsbu rg, PA. 17019
717-432-5965
The Asphalt In stitute
P.O. Box 140 52
Lexin gton , Kentu cky 40512-4052
859-288-4960
ESTIMATING QUANTITIESFor a cursory estimate of the quantity of material required,
use1 ton of hot mix asph alt covers 17 square yards, l" thick.
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Chart 1: Recomme nded Mixes for Normal HMA Applications ( Propose d compact ion le vels based on NCHRP 9-9 levels @ 4% Per Voids)
Low Volume Design Level
Recommen d ed
Aggre gate Siz e Binde r Type Co m pactio n Le ve l Co m pacte d Thickn e s s
Surface 9.5m m PG64-22 50 gyrations 1.5
Base 12.5m m PG64-22 50 gyrations 219m m PG64-22 50 gyrations 3
Minor Arterial Design Level
Aggre gate Siz e Binde r Type Co m pactio n Le ve l
Surface 9.5m m PG64-22 50 gyrations 1.5
Base 12.5m m PG64-22 50 gyrations 2
19m m PG64-22 50 gyrations 3
High Volume Design Level
Aggre gate Siz e Binde r Type Co m pactio n Le ve l
Surface 9.5m m PG64-22 65 gyrations 1.5
9.5m m PG76-22 65 gyrations 1.5
9.5m m SMA PG76-22 80 gyrations 1.5
12.5m m SMA PG76-22 80 gyrations 2
Base 12.5m m PG64-22 65 gyrations 2
19m m PG64-22 65 gyrations 3
Reco m m en ded Mix Designs
MAA Chart 1
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Traffic
Des ignation Typical Roadway ApplicationsEquivalent Single
Axle Loadings
Low
Moderate
High
< 300,000 ESALs
300,000 to < 10,000,000
ESALs
> 10,000,000 ESALs
Roadways with very light traffic volumes such as local roads, coun ty
roads, and city streets wh ere truck traffic is prohibited or at minimum.
Traffic considered local in nature, not regional, or interstate.
Special purp ose roadw ays serving recreational sites or areas.
Most local roadways.
Two-lane, multilane, divided, and p artially or c omp letely controlled
access roadw ays.
Medium to h ighly trafficked city streets, state routes, U.S. highways,
and some rural interstates.
Two-lane, multilane, divided, and p artially or c omp letely controlled
access roadw ays.
Medium to h ighly trafficked city streets, state routes, U.S. highways,
and some rural interstates.
Truck -we ighing stations or tru ck-climbing lanes on tw o-lane roadw ays.
Chart 2: Traffic Volum es
PAVEMENT DESIGNThe design of a hot m ix asph alt pavement requires some
knowledge of the following:
TRAFFIC
DRAINAGE
SUBGRADE SOILS SUPPORT
TRAFFIC
Asphalt pavements must be designed using the prop er
num ber and weight of axle loads expected during a given
period of time to insure adequate pavement p erformance.
Of primary conce rn is heavy truck traffic. Pavement life can
be significantly affected b y truck traffic, there fore, the w eight
and volum e of th e h eaviest traffic is a princ ipal factor in
pavement design. The following traffic assumptions h ave
been made for the p urpo ses of providing typical pavement
sections for the follow ing:
TYPICAL PAVEMENT SECTION 2Residential Drive
Essentially limited to passenger cars.
TYPICAL PAVEMENT SECTION 3 Park ing Lot s & Reside nt ial
or Light Du ty Streets p resent and futu re traffic limited to
passenger cars plus normal service trucks.
TYPICAL PAVEMENT SECTION 4Minor Arterial & Light
Industrial Streets p resent an d future traffic limited to a
medium duty classification which includes some heavy
truck and bus traffic.
TYPICAL PAVEMENT SECTION 5Principal Arterial,
Comm ercial or Ind ustrial Roads presen t and futu re traffic
is a heavy duty classification.
DRAINAGEProper drainage is imperative in the design and construction
of hot m ix asph alt pavements.
Where high w ater tables occur or w here w ater may
accumulate in low areas, consideration must b e given to
subsurface drainage. The installation of unde rdrains and/ or
interceptor drains may be requ ired to prevent the
accumulation of water ben eath the p avemen t structure.
Good surface drainage is also essential. A minimu m slope or
crown o f 1.5% per foot is recom mend ed. The roadway
shoulder or adjacent ground sho uld be graded so th at surface
drainage runs away from th e p avemen t and doe s not stand on
the p avement's edge.
On large parking lots,sloped sections, catch basins, and storm
drains may be necessary for proper drainage.
TABLE ISoil Classification Strengths:
MAA Chart 2
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Chart 3: Gene ral Ratings of Soil Quality
6
SUBGRADE SOILSA FIR M AND UNYIELDING SUBGR ADE IS
ESSEN TI AL TO GOOD PAVEMENT CONS TR UCTION.
For th e designs reco mm end ed in th is manual all soils are
divided into th ree classes: Good (G), Medium (M) and
Poor (P).
California Bearing Ratio (CBR) design values are assigned for
each class.
It is desirable to u se laboratory tests to e valuate th e load-
suppo rting characteristics of subgrade soils. However, if
laboratory test equip men t is not available, designs may be
made on the basis of a careful field evaluation b y an enginee r
who can assign the subgrade soils to one of the following
categories:
(G) GO OD SUBGRADE SOILSGo od sub grade soils retain
a substantial amount of their load bearing capacity when
wet. Included are the clean sands and sandy gravels and
soils free of detrimen tal amou nts of plastic materials. Agood subgrade will have a CBR value of 20 o r highe r.
(M) MEDIUM SUBGRADE SOILSThese retain a moderate
degree of firmness under adverse m oisture co nditions.
Included are such so ils as loams, silty sands and sandy
gravels containing m ode rate amo unt s of clay and fine silt.
A medium classification will have a CBR value of 6
through 20.
(P) POO R SUBGRADE SOILSThe se so ils bec om e q uite
soft and plastic when wet. Included are those soils having
app reciable amoun ts of clay and fine silt. The co arser silts
and sandy loams also may exhibit poo r bearing p roperties
in areas where frost pen etration into the subgrade is afactor. A poor classification w ill have a CBR value of 5 o r
less. Soils with a CBR value of less than 5 sho uld b e
stabilized or removed and replaced using suitable material.
A stable subgrade is always requ ired.
The add ition of soil stabilizers such as Portland Cemen t or
lime to th e p aving sub -grade alters the soil in several ways.
1. Reduction of p lasticity of the soil
2. Promotes imme diate structural changes in the soil
3. Adjusts the moisture - den sity relationsh ip
4. Promo tes sub-grade soil strength and incre ased CBR values
The end result is a sub-grade soil that provides an enhancedplatform for placing new paving.
California Bearing Ratio (CBR) is a test used for evaluating
bases, subgrades and subbases for p avemen t thickness design.
The correlation chart above may be used w hen o ne of the
system values indicated is known.
The Asph alt Institut e's "Soil Manual for Design of Asph alt
Pavemen t Struct ures" Series No. 10 (MS 10), describe s in detail
the commonly used soil evaluation systems and test proce-
dures. Field evaluation o f the soil involves visual insp ection
and simp le field tests.
California
Bearin g RatioR Valu e
Highw ay Soil
Classification
Unified Soil
ClassificationRelative Q uality
High Q uality
Good
Weak
Ver y Poor
Greater th an 80 Greater th an 70
55 to 80 20 to 70
5 to 20
Less than 5
A-1
A-4,A-5
A-6,A-7
GW, SW, GP, GM
OH,CH,CL
ML, OL, MH
SW, SP, SM, SCA-2,A-3
25 to 55
Less than 25
MAA Chart 3
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Hot mix asph alt recycling is a proven tec hn ology. It is cost
effective, mee ts all specifications and th e qu ality of the
recycled asphalt pavement has been proven to b e equal to
conventional mixes. When u sing reclaimed asphalt pavement
(RAP) in HMA, the virgin aggregate and asphalt are redu ced,
therefore a savings can be realized. In addition the u se of rap
or reclaimed asphalt materials aids the environment.
Recycling may include the use of glass,p lastic, asphalt, asphalt
shingles, and p aper.
The use of reclaim ed m aterial is less expensive than usin g all virgin aggregate and asphalt. Cold m illing
existing asphalt pavem ents allow desired section a nd grade to be established. It can also be used to ma in tain a
desired height of curbs and bridge clearan ces when overlaying existing roadways. Existing pavem ents m ay be
removed by the cold milling process.
Removal of badly deter iorated pavemen ts, surface
irregularities and maintaining curb reveal, etc. can b e
economically accomplished with minimal disruption to traffic
using the cold milling or carbide grinding p roce ss. The RAP
obtained through these proc esses can be recycled in a cost
effective rehab ilitation pro cess. (Maryland State Highw ay
Administration Standard Spe cifications for Co nstruc tion an d
MaterialsSect ion 508 Milling Existing Hot Mix Asph alt
Pavement)
HOT MIX ASPHALT RECYCLING
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SIDEWALKS, GOLF CART PATHS,
BIKE PATHS
SUBGRADE
Subgrade soils must be evaluated to determine theload-supp orting character istics. Refer to page 6.
The subgrade must be p roperly shaped to the desired
section and elevation and shall be co mp acted. Refer to p age 6.
DRAINAGEGood subsurface and surface d rainage is essential to
quality hot mix asphalt pavements. Refer to page 5.
HOT MIX ASPHALT CONSTRUCTION
A single course of 9.5 mm m ixture is recommen ded d ue to
the confined areas generally involved where constructing
Sidewalk, Golf Cart Paths or Bike Paths excep t wh ere p oorsubgrade is encountered. Hot mix asphalt shall be designed
mixed and constructed in accordance with Maryland State
Highway Administration Standard Specifications for
Constru ction an d Materials, July 2008 including revisions and
additions.
CONSTRUCTION DETAILS
Subgrade
Class
Good
Medium
Poor
Surface Cou rse
CompactedThickness
DesignLevel
SuperpaveMix
3
4
Low Volum e
50 Gyrations
Low Volum e
50 Gyration s
9.5 MM
9.5 MMSurface Cou rse
8
9.5 mm Surface should be placed by a paver.
Hand w ork should b e restricted wh ere feasible.
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RESIDENTIAL DRIVES,
PLAY AREAS
PAVEMENT WIDTHResiden tial driveways for a single automo bile, the
pavement should be a m inimum 10' in w idth.
The minimum radius for a right angle whe re the driveway
meets the street is 10'.
SUBGRADESubgrade soils must be evaluated to determine the
load-supp orting character istics. Refer to page 6.
Top soil must be rem oved and subgrade p roperly shaped to
the d esired section and e levation and shall be c omp acted.
Refer to page 5. Treat the subgrade w ith an approved
herbicide to inhibit future weed growth.
AGGREGATE BASE CONSTRUCTIONIn certain situations graded aggregate base construction may
be d esirable. See "Pavemen t Base Course Equivalency" page
16 for recomm ended thickness.
DRAINAGEGood subsurface and surface drainage is essential to qu ality
hot m ix asphalt pavements. Refer to p age 5.
TACK COATRefer to page 3.
HOT MIX ASPHALT CONSTRUCTION
Hot mix asphalt shall be designed, mixed and
constructed in accordance with Maryland State Highway
Adm inistration Standard Spe cifications for Constru ction
and Materials, July 2008 including revision s and
additions.
The hot mix asphalt base may be placed in a single course to
the req uired thickness. Small mechanical pavers are
available for this type o f construction. When ever possible,
hand placement should be avoided. However, where access
to the work area is l imited, hand p lacemen t may be the only
feasible method.
SUGGESTIONS FOR OBTAINING A QUALITY RESIDENTIAL DRIVEWAY PAVEMENTSelect con tractors know n for quality work and established rep utations in the com mu nity. Ask for local references.
Insist on a written con tract or agreemen t. Spe cify mater ials and w orkm anship in accordan ce w ith Maryland State Highw ay
Administration Spe cifications. Spe cify a minimum c om pacte d thickne ss.
CONSTRUCTION DETAILS
Subgrade
Class
Good
Medium
Poor
Base Cou rse
Subgrade CBR or Greater than 20
Surface Co ur se
Compacted
Thickness
1 12
2 12
1 12
Base Cou rse
Sub grade CBR 5
Surface Cou rse
3 12
Low Volum e
Low Volum e
Low Volum e
Low Volum e
9.5 MM
12.5 MM
9.5 MM
12.5 MM
Superpave
Mix
Design
Level
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PARKING LOTS, RESIDENTIAL
OR LIGHT DUTY STREETS,
STORAGE AREAS
DESIGN CRITERIA < 1 0 0 0 ADT 1 % TRUCKS
SUBGRADE
Subgrade soils must be evaluated to determine the
load-supp orting character istics. Refer to page 6.
The subgrade must be p roperly shaped to the desired
section and elevation and shall be co mp acted. Refer to p age 6.
DRAINAGE
Good subsurface and surface d rainage is essential toquality hot mix asphalt pavements. Refer to page 5.
TACK COAT
Refer to p age 3.
HOT MIX ASPHALT CONSTRUCTIONHot mix asphalt shall be designed, mixed and
constructed in accordance with Maryland State Highway
Administration Standard Spe cifications for Co nstruc tion an d
Materials, July 2008 including revisions and add itions.
The hot m ix asph alt base may be p laced in a single course. A
total thickness of up to 4.5" of base mix may be placed in one
lift. If several cou rses are desired or if job spec ifications
require several courses,it is recommen ded that the first base
course be 3" minimum depth.
An intermediate course of 9.5mm should be added to red uce
permeability and increase durability during construction if thefinal surface is not sch edu led un til subdivision build out.
CONSTRUCTION DETAILS
Subgrade
Class
Medium
Poor
Base Cou rse
Subgrade CBR 20 or Greater
Surface Co ur se
Compacted
Thickness
Superpave
Mix
1 12
3 12
1 12
Base Cou rse
Sub grade CBR 5
Surface Cou rse 1 12
5 12
Base Cou rse
Subgrade CBR 6-20
Surface Cou rse
4 12
Good9.5 MM
12.5 MM
9.5 MM
12.5 MM
9.5 MM
19 MM
0
Low Volum e
Low Volum e
Low Volum e
Low Volum e
Low Volum e
Low Volum e
Design
Level
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Subgrade CBR 20 or Greater
MINOR ARTERIAL AND LIGHT
INDUSTRIAL STREETS
DESIGN CRITERIA < 2 5 0 0 ADT 3 % TRUCKS
SUBGRADE
Subgrade soils must be evaluated to determine the
load-supp orting character istics. Refer to page 6.
The subgrade must be p roperly shaped to the desired section
and elevation and shall be co mp acted. Refer to p age 6.
DRAINAGE
Good subsurface and surface d rainage is essential to quality
hot m ix asph alt pavements. Refer to p age 5.
TACK COAT
Refer to p age 3.
HOT MIX ASPHALT CONSTRUCTION
Hot mix asphalt shall be de signed, mixed and c onstructed in
accord ance w ith Maryland State Highw ay Adm inistration
Standard Spe cifications for Constru ction and Materials,
July 2008 includ ing revisions an d add itions.
The ho t mix asphalt base may be placed in a single cou rse.A
total thickness of up to 4.5" of base mix may be placed in one
lift. If several cou rses are desired or if job spec ificationsrequire several courses,it is recommen ded that the first base
course be 3" minimum dep th.
CONSTRUCTION DETAILS
Subgrade
Class
Medium
Poor
Base Cou rse
Surface Cou rse
Compacted
Thickness
Superpave
2
4
2
Base Cou rse
Sub grade CBR 5
Surface Co ur se 2
6 12
Base Cou rse
Subgrade CBR 6-20
Surface Co ur se
5
Good9.5 MM
12.5 MM
9.5 MM
12.5 MM
9.5 MM
19 MM
Minor
ArterialMinor
Arterial
Minor
ArterialMinor
Arterial
Minor
ArterialMinor
Arterial
Design
Level
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PRINCIPAL ARTERIAL,
COMMERCIAL OR
INDUSTRIAL ROADSDESIGN CRITERIA < 4 LANES,1 0 ,0 0 0 ADT,
6% TRUCKS
SUBGRADE
Subgrade soils must be evaluated to determine the
load-supp orting character istics. Refer to page 6.
The subgrade must be p roperly shaped to the desired section
and elevation and shall be co mp acted. Refer to p age 6.
DRAINAGE
Good subsurface and surface d rainage is essential to
quality hot mix asphalt pavements. Refer to page 5.
TACK COAT
Refer to p age 3.
HOT MIX ASPHALT CONSTRUCTION
Hot mix asphalt shall be designed, mixed and
constructed in accordance with Maryland State Highway
Administration Standard Spe cifications for Con struction
and Materials, July 2008 includ ing revisions an d
additions.
The hot m ix asph alt base may be p laced in a single course. A
total thickness of up to 4.5" of base mix may be placed in one
lift. If several cou rses are desired or if job spec ifications
require several courses,it is recommen ded that the first
course be 3" minimum dep th.
CONSTRUCTION DETAILS
Subgrade
Class
Medium
Poor
Base Cou rse
Subgrade CBR 20 or Greater
Surface Cou rse
Compacted
Thickness
Superpave
2
7
2
Base Cou rse
Sub grade CBR 5
Surface Co urse 2
9
Base Cou rse
Subgrade CBR 6-20
Surface Co ur se
8
Good12.5 MM
19 MM
12.5 MM
19 MM
12.5 MM
19 MM
2
High Volum e
High Volum e
High Volum e
High Volum e
High Volum e
High Volum e
Design
Level
* Mix Selection: Please re fer to NAPA pub lication IS 128 for furthe r d esign assistance.
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TENNIS & MULTI-USE COURTS,
RUNNING TRACKS
SUBGRADE
Subgrade soils must be evaluated to determine the
load-supp orting character istics. Refer to page 6.
The subgrade must be p roperly shaped to the desired section
and elevation and shall be co mp acted. Refer to p age 6.
TACK COAT
Refer to p age 3.
HOT MIX ASPHALT CONSTRUCTION
Hot mix asphalt shall be de signed, mixed and c onstructed inaccord ance w ith Maryland State Highw ay Adm inistration
Standard Spe cifications for Constru ction and Materials,
July 2008 includ ing revisions an d add itions.
A specia l m ix other than 9.5 m m m ay be used for the su rface course for ru nnin g t rack s.There are sev eral
resilient hot m ixes available which com bine rubber aggregate w ith regular aggregate plus a high asphalt con-
tent. Specifications an d technical assistance are available from the firm s that fu rnish the special aggregate.
The ho t mix asphalt may be p laced w ith a mechanical paver
or by hand, if the contractor elects. In either case, for tennis
court con struction, the finished course must not vary from
line, grade or cross-section mo re than l/8" in 10' whe n
measured in any direction. For runn ing tracks,the finished
course m ust not vary more than 1/ 4" in 10'.
Proprietary surfacing is available for tennis courtsand running tracks . Most mem ber s of The Maryland
Asph alt Association are familiar w ith th e various mater ials and
can p rovide information on them or it may be ne cessary to
contact the manufacturer directly.
DRAINAGE
The finished tenn is cou rt surface should slope l" in 10', 0.83%,
on a true plane from end to end, corner to corne r, or side to
side. Side to side is pre ferable for a p laying surface and for
construction. The surface should not slope to th e net or away
from th e net in more th an one direction.
CONSTRUCTION DETAILS
Subgrade
Class
Good
Medium Leveling Cour se
Base Cou rse
Surface Cou rse
Subgrade CBR 6 or Greater
Compacted
Thickness
1.5
1.5
2
Super Pave
9.5 MM
9.5 MM
12.5 MM
Poor Leveling
Base Cou rse
Surface Cou rse
Subgrade CBR 3-5
1.5
1.5
2
9.5 MM
9.5 MM
12.5 MM
Low Volum e
Low Volum e
Low Volum e
Low Volum e
Low Volum e
Low Volum e
Design
Level
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Asph alt overlays are the mo st comm on , practical and
econo mical way to salvage, strengthen and mode rnize
old pavements.
Properly designed, constructed and m aintained h ot
mix asphalt pavement resurfacings offer the following
advantages:
1. Strengthen existing p avement structurally
2. Reduce maintenance app reciably
3. Exten d service life app reciably
4.Allows use of roadway while improvements are in progress
5. Provides safer p avemen ts
6. Improve ride quality and appe arance
7. Reduced energy costs
8. 100% Recyclable
9. Provides noise reduction
RESURFACING CONSID ERATIONS
The ke y to suc cessful resurfacing is careful evaluation of theexisting pavement and the selection of an adeq uate
pavement de sign. The following information shou ld be
considered: 1. Physical con dition including surface condition
and structu ral adequ acy. 2.Type of con struction of existing
pavem ent 3. Drainage of existing pavement 4. Load and traffic
use (weight and volume of heaviest traffic) of present and
future traffic.
The thickness of the overlay is designed to improve a lower-
than-average pavemen t cond ition, but n ot to p rovide the extra
strength ne eded for localized, structu rally we ak areas. Sho uld
the overlay thickness be based on the w eakest condition in
the section, it would be overdesigned for the rest of the
section, and more costly. The proper pro cedure is to correct
the w eaker areas. Removal of structurally weak areas and
patching w ith full-dep th h ot m ix asphalt to ensure strength
equal to or exceeding the surrounding pavement is an eco-
nomical means of preparing for overlays.
A minimum thickness of 4 12" of hot m ix asphalt is
recomm ended for rigid pavement overlays.
PAVING FABRICPaving fabrics are available for use w ith HMAo verlays. When
placed between the original pavement and the HMA overlay
or betw een tw o cou rses of an HMA overlay it becomes an
integral part of the roadway section. When p roperly used, fab-
rics reduce w ater infiltration and reflective c racking. Thereare several pro pr ietary fabrics available w hich sh ould b e
installed in accordance with the manufacturers instructions.
The addition of the correct fabric into a pavement overlay
reduces the effect of mech anisms w hich deteriorate pave-
ments and increases the life of the overlay pavement section.
Paving Fabrics Shou ld:
Meet AASHTO M288 guidelines for paving fabrics
Provide a w aterproof barrier for subgrade protection
Improve the fatigue resistance of the new overlay by
pro viding a stress relieving interface
Retard the propagation of an existing crack through
the new overlay (reflective cracking)
Exten d th e useful life of the o verlay
Be able to w ithstand the high temp erature of asph alt
Strengthen the en tire p avemen t section
Can be used o ver milled surfaces and are m illable &
recyclable onc e installed
A Certificate of Com pliance for the paving fabric used on anyproject should be furnished by the manufacturer to the engi-
neer. The p aving fabric shall be sup plied in a p rotective cover
that is capable of p rotec ting the fabric from u ltraviolet rays,
abrasion and water. Paving fabric should meet or exceed
AASHTO M288 guide line s.
Asphalt Sealant: The en gineer shall app rove theasphalt cemen t. A grade of asphalt of the same type u sed in
the manufacture of the hot mix asphalt for the overlay should
be acceptable.
EQUIPMENT:
Asph alt Dis tributor: The distributor must be suitablymetered and capable of spraying the asphalt cement uniform-
ly and at the prescribed application rate.
Fabric Handling Equipm en t: A tractor or similarmech anical device w ith m ounted laydown e quipmen t that is
capab le of handling full rolls of fabric shall be u sed. The
equipment shall be capable of laying the paving fabric
smoothly without excessive wrinkles and/or folds.
Miscel laneous Equipment: Stiff bristle broomsused to smoo th, and scissors (or blades used to cut th e paving
fabric shall be pro vided b y the installer.
INSTALLATION PROCEDURE:
Surface Preparation: The surface on w hich thepaving fabric is to be p laced shall be free of dirt, wate r,vegeta-
tion and other foreign materials. Open cracks 3/8 inch or
larger shall be filled w ith sand m ixed asph alt as directed b y
the en gineer. Cracks larger than 3/ 8 inch or h oles shall be
filled w ith cold or ho t mix asphalt . The use of a leveling
course may be required prior to placing the paving fabric in
severe cases.
Application o f Seal ant: The asphalt cemen t andbinder must be uniformly spray-applied at the specified rate.
The qu antity required may vary with the surface con dition of
the existing p avemen t (e.g. degree of porosity), but shall be
applied at a nominal rate of 0.25 gallons per square yard of
residual asphalt.
App lication of asphalt cem ent w ill be p erformed by truck-
moun ted distribution equipm ent wh enever possible, with
hand spraying kept to a minimum.
Paving Fabric Placem en t: The p aving fabric shall beplaced onto the asphalt cemen t with a minimum of wrinkles
before the asphalt can cool or lose its tackiness.
4
HOT MIXASPHALT RESURFACING
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HOT MIX ASPHALT CONSTRUCTION
Hot mix asph alt shall be de signed , mixed and co nstruc ted in accord ance w ith Maryland State Highway Adm inistration Standard
Spe cifications for Construction and Materials, July 2008 includ ing revisions and additions.
The paving fabric shall be placed so that the non-heat treated
(bearded or fuzzy) side is placed downward into the sealant,
thus providing optimum b ond b etween fabric and p avement
during the construction process. As directed by the engineer,
wr inkles severe eno ugh to cau se foldssh all be slit and laid
flat in the direction o f paving op erations. Brooming the
paving fabric will assist in m aking intimate con tact w ith the
pavement surface.
Any overlap of the paving fabric should be minimized,
although an overlap of 1 to 3 inches is recommen ded to
insure full closure of overlapp ing layers. Transverse joints
should be shingled (overlapp ed) in th e direction of paving
operations to prevent edge pick-up by the paver.
NOTE: In the event th at asph alt cemen t should bleedthrough the p aving fabric be fore the hot m ix asph alt is
placed, it may be n ecessary to absorb any visible sealant by
spreading sand or h ot mix asphalt over those areas. This
should minimize the tendenc y for construction equipm ent
tires to lift the paving fabric wh en dr iving over it. Turn ing of
paving equ ipment and oth er vehicles on th e p aving fabric
must be kep t to a minimum to avoid movemen t or damage to
the fabric.
CONSTRUCTION DETAILS
HIGH VOLUME SINGLE LIFT RESURFACING
Old Pavemen t
Surface Co ur se
Average
Compacted
Thickness
Superpave
2
1 12
12.5 MM
9.5MM
Old Pavemen t
Surface Cou rse
Refer to MAA Char t 1
Refer to MAA Char t 1
Design
Level
TACK COAT
Refer to page 3
A tack coat of asphalt (usually emulsified asphalt) is applied
to ensure bo nd b etween the existing surface and the asphaltoverlay. It should be applied in an e ven, thin coat at a rate
of application .05 gallons per squ are yard. Exce ssive tack coat
can cause slipp age or can flush to the surface.
All longitudn al and transverse co nstruc tion joints shall be
prop erly tacked.
CONSTRUCTION DETAILS
MULTIPLE LIFT RESURFACING
Base Cou rse
Leveling (wh en required)
Surface Cou rse
Old Pavement
Average
CompactedThickness
1 12
Design Thickness
1= (variable)
Superpave
9.5 MM
19.5MM
9.5 MM*
Leveling Co ur se
Surface Cou rse
Old Pavement
1 12
1= (variable)
9.5 MM
9.5 MM
* If Wedge and Level course exce eds 3 you may con sider going to 12.5 mm W/ C course.
Refer to MAA Char t 1
Refer to MAA Char t 1
Refer to MAA Char t 1
Refer to MAA Char t 1
Refer to MAA Char t 1
DesignLevel
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EQUIVALENCES
Consideration may be given to a pavement section using a
graded aggregate base cou rse with a h ot mix asph alt binder
and surface course. Maryland h as several excellent aggregate
sources that may m ake locally available aggregate an
econo mic alternative. All graded aggregate base should mee t
Maryland State Highway Administration Specifications for
Construction and Maintenance, July 2008 including
revisions an d add ition s.
Paving mater ials have differen t ab ilities to sustain the loads to
wh ich they are subjected. Relative strength values of the
various materials used in asphalt pavements have been
evaluated so that it is possible to d evelop d esigns with
different com pon ents to give com parable pavemen t
performance. The AASHTO Design Committee from road test
findings e stablished a list of coe fficients of pavem ent
comp onen ts for surface, base and subbase courses. The use of
these coefficients permits equating materials into inches of
one com pon ent to inches of another in the asphalt pavement
structures.
The criteria established in th e AASHTO Guide for Design of
Pavemen t Structu res,The Asph alt Institute's "Thickness DesignManual" MS-1, The Nation al Asph alt Paving Association 's
IS-129 and IS-132 , and The Maryland Asph alt Association 's
experience with millions of square yards of pavements con-
structed in Maryland were considered and utilized in part to
develop the pavement designs and material equivalences
used in this manual.
Asphalt pavements must retain a minimum thickness of hot
mix asphalt surfacing (including b inder cou rses) whe n used
on granular bases. Minimum surface thicknesses should be
increased with increased weight and volume of traffic and
when used on poor subgrades.
PAVEMENT BASE COURSE EQUIVALENCYONE INCH HOT MIX ASPHALT BASE COURSE EQUALS 2 12''
CRUSHER RUN O R GRADED AGGREGATE BASE. RCR-6
(CRUSHED CONCRETE OR RCR-6 (MILLED HMA).
OTHER USES FOR
HOT MIX ASPHALT
There are a wide variety of uses for hot mix asphalt mixes
and/or p avemen ts that are not l isted or shown elsewh ere inthis guide. The same basic pr inciples used for con structing
successful pavements would apply to installing pavements for
other uses. Some p avement or mix modifications might be
required, but are generally, minor in nature. Some of the other
uses for th e p roduct follow:
AIRFIELDSRunways
Taxiways
6
NAPA and The Asphalt Institute publications are available for specialized mix design and placement techniques.
MOTOR SPORTS RACE TRACKSSpecialty mixes not included in MAAs
Recommended mixes for normal HMA applica-
tions(Chart 1) may be requ ired. NAPA,The
Asphalt Institute and automotive sanctioning bod-
ies shou ld be con sulted du ring the de sign p rocess.
DRAINAGE FACILITIESDitches & Gutter s
CurbsBerms
Slope Protection
Porous Pavements
EROSION CONTROLJetties & Groins
Grout for Jetties
Storm water management ponds
FARM
BarnyardsFeed lots
Stable Floors
Silage Storage
HYDRAULICSReservoir Linings
Pond Linings
Dam Faces
Canal Linin gs
Sewage Lagoons
Leach ate facilities
INDUSTRIAL-COMMERCIALDock Surfaces
Building Floors
Material Storage Areas
PATCHINGMaintenance For All Types of Pavements
RAILROADSHMA Ballast Un de rlaymen t
Full Dep th Hot Mix Asph alt
RECREATIONBoat Ramp s
Ath letic Fields
Skate b oard and roller blade facilities
Holding Areas
Helioports
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Ad van ce d Asp halt Te ch no lo gie s, L.P. Ste rlin g, VA 703-4 44-420 0 703-44 4-4368
Alban Tractor Com p any, Inc. Baltimore, MD 410-686-7777 410-686-3729
Am erican Paving Fabrics, Inc. Hanover, MD 410-379-2209 410-796-0272Associated Asp halt Greensboro , NC 336-294-0025 336-297-3316
Astec, Inc . Ch attanooga,TN 423-867-4210 423-867-3570
Bitumar USA, Inc. Baltimore, MD 410-370-0360 410-757-1471
BP Lubrican ts USA, Inc. Baltimore, MD 800-777-1466 410-682-9485
Carroll Indep enden t Fuel Co. Baltimore, MD 410-235-1066 410-235-1941
C he sa p ea ke Fo rd & St e rlin g Tr u ck Sa le s Ba lt im o re ,M D 4 10 -6 8 2-4 00 0 4 1 0-3 91 -4 3 57
C on st e lla tio n N ew En e rg y-G as D iv is io n Ba lt im o re ,M D 4 10 -2 3 0-4 78 3 4 1 0-2 30 -4 6 79
CreaFill Fibers Corp oration Ch estertow n, MD 800-832-4662 410-810-0793
Financial Benefit Services Kensington , MD 301-949-1000 301-949-7038
Fleet Transit, Inc. Baltimore, MD 410-355-7910 410-355-2372
George Associates, Inc. Silver Sp ring, MD 301-589-9490 310-588-6605
Hi Tech Asp halt Solutions Mech an icsville ,VA 804-730-4871 804-730-7789
HMS In su ran ce Asso ciat es, I nc . Bro ok lan dville , MD 4 10 -3 37 -9 75 5 4 10 -3 37 -0 55 1
Humbolt Manufactu ring Co. Raleigh , NC 919-833-3190 919-833-5283
L&J Construction Service, Inc. Baltimore, MD 410-243-3844 410-243-2309
Luck Stone Corp oration Leesburg,VA 703-777-3177 703-779-4774Martin Marietta Aggregates Boonsboro, MD 301-739-0846 301-739-4718
Maryland Materials, Inc. North East, MD 410-287-8177 410-287-3654
Meeker Equip m ent Co., Inc. Lansdale, PA 215-361-2900 215-361-1725
E. Stew art Mitchell, Inc. Baltimore, MD 410-354-0600 410-354-3029
Nustar Energy LC West Dep tford, NJ 856-224-7200 856--224-7201
Patuxen t Materials, Inc. Crofton , MD 410-793-0181 410-793-0741
QPR a div. of Lafarge Ch ester, CT 800-388-4338 678-746-2238
Recon Construction Services, Inc. York, PA 717-779-0663 717-779-0724
Rifk in ,Liv in gs to n ,Le vit an & Silve r,LLC G re e n be lt ,M D 3 01 -3 4 5-7 70 0 3 0 1-3 45 -1 2 94
Roadtec, Inc. Ch attanooga,TN 423-265-0600 423-265-7521
Seaboard Asp halt Products Co. Baltimore, MD 410-355-0330 410-355-5864
Sie man s, WT-Hyd ro car bo n Se rvic es Alex an dr ia, VA 7 03 -3 70 -7 30 6 7 03 -3 70 -8 06 7
Stonetech , LLC Salisbury, MD 410-742-2851 410-749-7411
Valero Services Lafayette Hill, PA 888-207-3727 610-567-3291
Volvo Construction Equip ment Elkridge, MD 410-796-3200 410-796-3350
Vulcan Materials Comp any Manassas,VA 703-631-9690 703-368-2139York Building Products Co ., Inc . York, PA 717-848-2831 717-854-9156
ASSOCIATE MEMBERS
Company Location Phone No. Fax No.
HOT MIX ASPHALT
SAFE, SMO OT H, QUIET, D URABLE AND 1 0 0 % RECYCLABLE
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MARYLAND ASP HALT A SSOCIATION, IN C.
24 0 8 -G Pep p er Mi l l Dr i ve
G len B u r n i e , M a r y l a n d 2 1 0 6 1
4 1 0 -7 6 1-2 1 6 0 Fax 4 1 0 -7 6 1-0 3 3 9
E-ma i l : off i ce@m d a sp ha lt .o r g
MARYLAND ASPHALT ASSOCIATION, INC.
PRODUCERS
Company Location Phone No. Fax No.
Aggre gate In du strie s Mid -Atlan tic Gre en be lt, MD 30 1-982-1 400 30 1-513 -0 016
American Infrastructure Malvern , PA 610-560-7913 610-560-7955
American Paving C orp oration Salisbury, MD 410-742-8484 410-742-0504
David A. Bram ble, Inc . Chester tow n, MD 410-778-3023 410-778-3427
Francis O. Day Com p any, Inc. Rockville , MD 301-652-2400 301-424-4443
Ed ge m oo r Ma te rials o f Mar ylan d , In c . N or th Ea st , MD 4 10 -2 87 -5 55 5 4 10 -2 87 -3 48 1
P. Flan igan & Sons, Inc. Baltim ore, MD 410-467-5900 410-467-3127
C.William Hetzer, Inc . Hagerstow n, MD 301-733-7300 301-733-0812
IA Construction Corp . Cum berland, MD 301-724-1760 301-724-0864
Keystone Lime Co . Sp rings, PA 814-662-2711 814-662-4421
Richard F. Kline, Inc. Frederick, MD 301-662-8211 301-662-2083
Lafarge North America Tow son , MD 410-847-3300 410-847-3308
Laurel Sand & Gravel, Inc. Laurel, MD 301-953-7650 301-470-4075
Maryland Paving, Inc. Aberdeen , MD 410-879-6970 410-879-5478
C J Miller, LLC Hamp stead, MD 410-239-8006 410-239-4204
Fo rt Mye r Co n st ru c tio n Co rp o rat io n Wash in gt on , D C 2 02 -6 36 -9 53 5 2 02 -6 35 -0 57 5
Pen nsy Sup ply In c./ Tilcon Delaw are Dover, DE 302-735-9950 302-678-3379
Re lia ble Co n tr ac tin g Co m p an y, I n c. Mille rsville , MD 4 10 -9 87 -0 31 3 4 10 -9 87 -8 02 0
River Asp halt, LLC Dover, DE 302-342-3137 302-342-3160
Valley Q uarries Chambersburg, PA 717-267-2244 717-267-2521
LW Wolfe En terp rises, Inc. Myersville , MD 301-293-2351 301-293-3578
Asp halt General Beltsville , MD 301-937-3900 301-937-3893
Asp halt & Co nc re te Se rvic es, In c. Fre de ric k, MD 301 -682-56 90 30 1-682 -5 695
Melvin Benhoff Sons, Inc. Baltim ore, MD 410-477-5650 410-477-5091
Central Main tenance Corp . Baltim ore, MD 410-355-8800 410-355-4847
College Park Paving Co., Inc. Beltsville , MD 301-937-1447 301-937-6971
Comer Construction Co. Forest Hill, MD 410-879-6094 410-638-0289
Dix ie Construction Co ., Inc . Churchville , MD 410-879-8055 410-836-2029
Fran k J.Go ett ne r Co nst ru ctio n Co ., In c. Kin gsville , MD 4 10 -5 92 -7 70 0 4 10 -5 92 -5 96 8
Gray & Son , Inc. Butler, MD 410-771-4311 410-771-8125
Iacoboni Site Sp ecialists Baltim ore, MD 410-686-2100 410-686-8559
Kinsley Construction , Inc. Timonium , MD 410-453-6707 410-453-6709
M.T. Laney Co., Inc. Eldersburg, MD 410-795-1761 410-795-9546
Pleasan ts Construction , Inc. Clarksburg, MD 301-428-0800 301-428-3922
Priceless Industries, Inc. Baltimore, MD 410-285-1900 410-282-8347
Quarry Ridge Asp halt Co. Cum berland, MD 301-777-8825 301-777-8274Ross Contracting, Inc. Mt.Airy, MD 301-831-5500 301-831-5900
CONTRACTORS
Avalon Consulting Services Baltim ore, MD 410-945-9553 410-945-9554
The Rober t B. Balter Com p any Ow ings Mills, MD 410-363-1555 410-363-8073
CNA, Inc. Forest Hill, MD 410-879-7200 410-838-1811
Co n st ellat io n D esig n Gr ou p , In c . Tim o niu m , MD 4 10 -2 52 -1 88 4 4 10 -5 60 -3 63 2
De ve lo p me nt Fac ilit at or s, I nc . Mille rsville , MD 4 43 -3 08 -2 10 0 4 43 -3 08 -2 10 8
EBA Engineering, Inc. Baltim ore, MD 410-358-7171 410-358-7213
Greenhorne & OMara, Inc. Baltim ore, MD 410-583-6700 410-583-6704
Greenman-Pedersen , Inc. Jessup , MD 410-880-3055 301-490-2649
Indam Engineers, Inc. Ellicott City, MD 410-461-0001 410-461-0006
Joh nson , Mirm iran & Thom p son Sp arks, MD 410-329-3100 410-472-2200
KCI Technologies, Inc. Hunt Valley, MD 410-316-7970 410-316-7972
PB Americas, Inc. Gaitherburg,MD 703-742-5833 703-742-5789
Progressive Engineering Consultants,Inc Columbia, MD 410-715-0390 410-715-1745
URS Corp oration Hunt Valley, MD 410-785-7220 410-785-6818
Rum mel, Klep p er & Kahl Baltim ore, MD 410-728-2900 410-728-2834
Sp ec ialized Engineering Hanover, MD 410-768-4800 410-768-4803
Wallace Mon tgom er y & Associates Tow son , MD 410-494-9093 410-825-5714
CONSULTING ENGINEERS