Chapter 6 Chip Seals From… Maintenance Technical Advisory Guide (MTAG)

transcript

Chapter 6Chip Seals

From… Maintenance Technical

Advisory Guide (MTAG)

Manager’s Overview

Introduction to Chip Seal

What is Chip Seal?Why use Chip Seal?When to use Chip Seal? Where to use Chip Seal?Chip Seal Variations

What Is Chip Seal

Description

Application of asphalt binder on existing pavement followed by a layer of aggregate chips. The treatment is then rolled to embed the aggregate into the binder.

Performance and Cost-Why to Use

Performance• Proper application of binder and aggregate

• Proper embedment

• Typical treatment life: 4 to 7 years

Average cost• $0.96/m2 to $1.32/m2 ($0.80 to $1.10/yd2)

Surface for light to medium traffic Waterproof layer Skid resistant surface Restore weathered surface Address bleeding Temporary base course cover Define shoulders

Where and When to Use

When NOT to Use!

Structurally deficient pavements Cracks >6 mm (0.25 in) wide Medium- to high-severity alligator

cracking Large number of potholes Rutting >25 mm (1 in) Very rough surface

Keys for Success

Proper surface preparation Use the right emulsion and clean aggregates Determine the appropriate spread rates for the

emulsion and the aggregate Follow the construction specs, including the

need for traffic control Chip seal in good weather conditions

CHIP SEALSCHIP SEALS

Sweeping (before and after)Sweeping (before and after)

RollingRollingAggregate Aggregate ApplicationApplication

Binder Binder ApplicationApplication

Proper Application

Loose Chips

Bleeding Streaking

Chip Seal Variations

Single chip seals Double or triple chip seals Cape Seals Sand seals Fabric and chip seals

Chip Seal VariationsSingle Chip Seals

Existing Pavement Binder

Chip Seal VariationsDouble Chip Seals

Second BinderApplication

Chip Seal VariationsCape Seals

Slurry Seal

Chip Seal VariationsSand Seals

Chip Seal VariationsFabric and Chip Seals

Existing PavementTackCoat

Paving Fabric

BinderApplication

Chip Seal VariationsFabric and Chip Seals

Chip Seal CourseTraining Modules Available

1. Design, Materials & Specifications

2. Construction, QC & Trouble Shootings

End Overview

Begin Project Design, Materials & Specifications

Design, Materials & Specifications

Module 6-1

Topics to be covered

Chip Seal Design Process Design Considerations -Quantity

Selection Chip Seal Design Methods Material Selection – Binder and

Aggregate

Chip Seal Design Process

Assess existing pavement Select chip seal variation Select compatible binder and aggregate Quantity selection

Design ConsiderationsQuantity Selection

Residual asphalt content• Asphalt cement factor = 1.0

• Emulsion factors range = 0.55 to 0.65

Aggregate application rate• Single chip layer

• No more than 10% excess chips

• 70% embedment recommended

Chip Seal Design Methods

McLeod procedure Asphalt Institute method

Asphalt Institute Method

1. Determine aggregate size and specific gravity

2. Aggregate and asphalt emulsion quantities from table

3. Adjust aggregate (if necessary)

4. Adjust asphalt content based on condition of road (if necessary)

WorkshopChip Seal Design Problem

Break into groups Work design problem in Participant’s

Workbook Present findings to class

Material SelectionBinder

2-4.28

Material SelectionBinder

Rapid setting emulsions Polymer-modified emulsions Asphalt cement Rubberized asphalt

Asphalt Water Emulsifying agent (surfactant)

Material SelectionEmulsion Ingredients

Material SelectionEmulsion Classification

Electrical charge (+ or –) Speed of break: slow (SS), medium (MS),

and rapid set (RS) Asphalt relative viscosity: hard (h) or soft

(s) Polymer-modified asphalt (P or L) High float (HF)

EmulsionType

SlowSetting

MediumSetting

RapidSetting

Anionic SS-1SS-1h

MS-1MS-2

MS-2hHFMS-1HFMS-2

HFMS-2hHFMS-2s

RS-1RS-2

HFRS-2

Cationic CSS-1CSS-1h

CMS-2CMS-2h

CRS-1CRS-2

Material SelectionEmulsion Classification

Material SelectionRubberized Asphalt Chip Seal

2-4.33

Binder MaterialField Blended using hot asphalt, extender oil and crumb rubber.

Oil application is usually .60 gal / square yard through an agitated distributor truck attached with a vapor recovery system.

Aggregate ChipChips are always hot pre-coated, and applied at 35-40 lbs. per square yard

Hot Rubber Chip Seals

Asphalt Rubber Chip Seal

BinderTerminal Blended using hot asphalt, polymer and can use crumb rubber.

Application rate is 0.35 - 0.50 gals/sy depending on size of chip

ChipsChips can be 3/8” up to 1/2” (25-35 lbs. / sy)

Chips can also be pre-coated but not required

Polymer Modified Chip Seals

PolymerModified EmulsionChip Seals

Crack Seal before PM Emulsion Seal

BinderPolymer modified emulsion with a solvent free rejuvenating agent additive

Application rate is 0.25 - 0.40 gals/sy depending on size of chip and degree of cracking.

ChipsChips can be 1/4” up to 1/2” (18-35 lbs. / sy)

Can be applied at temperatures down to 40o F

Crack filling is not required

PM Emulsion Rejuvenating Chip Seals

Material SelectionAggregates

Clean and durable One size: 6 to 16 mm (0.25 to 0.6 in) Cubical shape Flat and elongated particles limited to 25

to 30 percent Fines limited to 1 to 2 percent

Material SelectionProblem With Flat Aggregates

End Project Design, Materials & Specifications

Begin Construction, QC, and Trouble Shooting

Construction and Inspection

Module 6-2

Construction & Inspection 45

Construction Procedures

Quality Control

Inspection

Troubleshooting

Topics to be covered

ConstructionConstruction

2-4.46

ConstructionConventional Chip Seal Procedure

1. Clean existing pavement

2. Apply binder

3. Spread aggregate

4. Roll

5. Allow binder to cure

6. Broom loose aggregate

ConstructionCleaning Existing Pavement

ConstructionStart and Stop Application on Mat

ConstructionBinder Application

Spray Bar and Nozzles

Single Overlap

ConstructionBinder Overlap

Roadway SurfaceDouble Overlap

Roadway SurfaceTriple Overlap

Roadway Surface

ConstructionBinder Application Overlap

Triple OverlapTriple Overlap

ConstructionBinder Application

ConstructionAggregate Application

Immediate rolling of aggregate Pneumatic-tired rollers No fewer than three passes Full coverage necessary before asphalt

hardening

ConstructionRolling

Time depends on temperature and relative humidity

Emulsion break should begin just after first roller pass

Open to traffic in about 2 hours

ConstructionCuring of Binder

ConstructionBrooming Loose Aggregate

Project review Document review Material checks

Quality ControlPreliminary Responsibilities

Surface preparation Equipment inspection

• Asphalt distributor

• Chip spreader

• Haul trucks

• Rollers

• Brooms

Quality ControlPre-Application Inspection

Weather requirements Determining application rates Checking application rates Traffic control plan and setup

Quality ControlPre-Application Inspection (continued)

Asphalt application Aggregate application Truck operation Rolling Longitudinal joints Transverse joints Brooming

Quality ControlProject Inspection

Cleanup Opening to traffic

Quality ControlPost-Application Inspection

• Chip spreader

• Haul trucks

• Rollers

• Brooms

• Chip spreader

• Haul trucks

• Rollers

• Brooms

TroubleshootingTroubleshooting

2-4.76

TroubleshootingWhat is wrong here?

StreakingStreaking

Poor Longitudinal JointPoor Longitudinal Joint

BleedingBleeding

Loss of Cover AggregateLoss of Cover Aggregate

Inadequate Aggregate CoverageInadequate Aggregate Coverage

Problem:

TroubleshootingPossible Construction Problems

Aggregate embedment > 80 percent

Potential causes?

Problem:

TroubleshootingPossible Construction Problems

Aggregate embedment < 50 percent

Potential causes?

Loss of aggregate due to inadequate curingLoss of aggregate due to inadequate curing

Single OverlapSingle Overlap

TroubleshootingWhat happened here?

Questions?

Chapter 6 Chip Seals From… Maintenance Technical Advisory Guide (MTAG)

Documents