Chapter 6 Chip Seals

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Chapter 6Chip Seals

• From Maintenance Technical
• Advisory Guide (MTAG)

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Managers Overview

• From Maintenance Technical
• Advisory Guide (MTAG)

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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

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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.
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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)

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Where and When to Use

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

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When NOT to Use!

• Structurally deficient pavements
• Cracks gt6 mm (0.25 in) wide
• Medium- to high-severity alligator cracking
• Large number of potholes
• Rutting gt25 mm (1 in)
• Very rough surface

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Keys for Success
CHIP SEALS

• 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

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Binder Application
Sweeping (before and after)
Aggregate Application
Rolling
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Proper Application
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Loose Chips
Bleeding
Streaking
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Chip Seal Variations

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

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Chip Seal VariationsSingle Chip Seals
Existing Pavement
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Chip Seal VariationsDouble Chip Seals
Existing Pavement
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Chip Seal VariationsCape Seals
Brooming
Existing Pavement
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Chip Seal VariationsSand Seals
Existing Pavement
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Chip Seal VariationsFabric and Chip Seals
Existing Pavement
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Chip Seal VariationsFabric and Chip Seals
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Chip Seal CourseTraining Modules Available

• Design, Materials Specifications
• Construction, QC Trouble Shootings

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End OverviewBegin Project Design, Materials
Specifications
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Design, Materials Specifications
Module 6-1

• From Maintenance Technical
• Advisory Guide (MTAG)

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Topics to be covered

• Chip Seal Design Process
• Design Considerations -Quantity Selection
• Chip Seal Design Methods
• Material Selection Binder and Aggregate

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Chip Seal Design Process

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

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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

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Chip Seal Design Methods

• McLeod procedure
• Asphalt Institute method

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Asphalt Institute Method

• Determine aggregate size and specific gravity
• Aggregate and asphalt emulsion quantities from
  table
• Adjust aggregate (if necessary)
• Adjust asphalt content based on condition of road
  (if necessary)

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WorkshopChip Seal Design Problem

• Break into groups
• Work design problem in Participants Workbook
• Present findings to class

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Material SelectionBinder
2-4.28
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Material SelectionBinder

• Rapid setting emulsions
• Polymer-modified emulsions
• Asphalt cement
• Rubberized asphalt

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Material SelectionEmulsion Ingredients

• Asphalt
• Water
• Emulsifying agent (surfactant)

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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)

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Material SelectionEmulsion Classification
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Material SelectionRubberized Asphalt Chip Seal
2-4.33
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Hot Rubber Chip Seals

• Binder Material
• Field 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 Chip
• Chips are always hot pre-coated, and applied at
  35-40 lbs. per square yard

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Asphalt Rubber Chip Seal
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Polymer Modified Chip Seals

• Binder
• Terminal Blended using hot asphalt, polymer and
  can use crumb rubber.
• Application rate is 0.35 - 0.50 gals/sy
  depending on size of chip
• Chips
• Chips can be 3/8 up to 1/2 (25-35 lbs. / sy)
• Chips can also be pre-coated but not required

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Polymer Modified Emulsion Chip Seals
Crack Seal before PM Emulsion Seal
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PM Emulsion Rejuvenating Chip Seals

• Binder
• Polymer 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.
• Chips
• Chips 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

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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

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Material SelectionProblem With Flat Aggregates
Existing Pavement
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End Project Design, Materials
SpecificationsBegin Construction, QC, and
Trouble Shooting
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Construction and Inspection
Module 6-2

• From Maintenance Technical
• Advisory Guide (MTAG)

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Topics to be covered

• Construction Procedures
• Quality Control
• Inspection
• Troubleshooting

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Construction
2-4.46
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ConstructionConventional Chip Seal Procedure

• Clean existing pavement
• Apply binder
• Spread aggregate
• Roll
• Allow binder to cure
• Broom loose aggregate

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ConstructionCleaning Existing Pavement
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ConstructionStart and Stop Application on Mat
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ConstructionBinder Application
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ConstructionBinder Overlap
Spray Bar and Nozzles
Single Overlap
Roadway Surface
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ConstructionBinder Application Overlap
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ConstructionBinder Application
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ConstructionAggregate Application
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ConstructionAggregate Application
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ConstructionRolling

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

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ConstructionRolling
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ConstructionRolling
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ConstructionCuring of Binder

• Time depends on temperature and relative humidity
• Emulsion break should begin just after first
  roller pass
• Open to traffic in about 2 hours

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ConstructionBrooming Loose Aggregate
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Quality ControlPreliminary Responsibilities

• Project review
• Document review
• Material checks

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Quality ControlPre-Application Inspection

• Surface preparation
• Equipment inspection
• Asphalt distributor
• Chip spreader
• Haul trucks
• Rollers
• Brooms

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Quality ControlPre-Application Inspection
(continued)

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

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Quality ControlProject Inspection

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

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Quality ControlPost-Application Inspection

• Cleanup
• Opening to traffic

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Quality ControlPreliminary Responsibilities

• Project review
• Document review
• Material checks

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Quality ControlPre-Application Inspection

• Surface preparation
• Equipment inspection
• Asphalt distributor
• Chip spreader
• Haul trucks
• Rollers
• Brooms

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Quality ControlPre-Application Inspection
(continued)

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

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Quality ControlProject Inspection

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

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Quality ControlPost-Application Inspection

• Cleanup
• Opening to traffic

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Quality ControlPreliminary Responsibilities

• Project review
• Document review
• Material checks

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Quality ControlPre-Application Inspection

• Surface preparation
• Equipment inspection
• Asphalt distributor
• Chip spreader
• Haul trucks
• Rollers
• Brooms

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Quality ControlPre-Application Inspection
(continued)

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

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Quality ControlProject Inspection

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

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Quality ControlPost-Application Inspection

• Cleanup
• Opening to traffic

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Troubleshooting
2-4.76
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TroubleshootingWhat is wrong here?
Streaking
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TroubleshootingWhat is wrong here?
Poor Longitudinal Joint
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TroubleshootingWhat is wrong here?
Bleeding
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TroubleshootingWhat is wrong here?
Loss of Cover Aggregate
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TroubleshootingWhat is wrong here?
Inadequate Aggregate Coverage
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TroubleshootingPossible Construction Problems

• Problem

Aggregate embedment gt 80 percent

• Potential causes?

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TroubleshootingPossible Construction Problems

• Problem

Aggregate embedment lt 50 percent

• Potential causes?

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TroubleshootingWhat is wrong here?
Loss of aggregate due to inadequate curing
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TroubleshootingWhat is wrong here?
Single Overlap
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TroubleshootingWhat happened here?
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Questions?