Post on 15-Jan-2016
PAVEMENT MAINTENANCE IIPart 1b: Chip Seal Construction
IdahoRoads Scholar Program
Objectives Review how to set up a good chip
seal, Investigate equipment operation, and
field checks, Identify common problems and
possible solutions.
Field Checks
Weather/Surface Condition Traffic Control Aggregate Asphalt Asphalt and Chip Distributor Rollers Sweeping
Weather/Surface Condition
Dry or Damp Surface
Temperature Rain/Humidity
Wind
Surface Temperature
Proper Traffic Control is Essential!
Aggregate Requirements for Successful Seal Coat
Must be clean. Less then 1% passing #200 sieve.
Cubical chips are better then flat chips.
Must be crushed. At least 2 crushed faces.
More single sized the better.
Dirty Chips
> 1% passing the #200 sieve Impedes the ability of binder to
bond chip to roadway. Limits amount of binder that can
be applied. Creates dust after sweeping.
Aggregate Condition
Emulsions => Damp Surface
Asphalt Cement => Dry Surface
Can only glue down a single layer of chips.
Must have chips at least 60 to 70% embedded to withstand traffic and snow plow damage.
Should see emulsion at top of chips before emulsion breaks.
Chip Considerations
Which are the better chips?
Distributors
Asphalt Distributor Components
Nozzles
Spray Bar Height
Application Rate
Product Temperature
Nozzle Angle
Spray Bar Height
Triple Coverage
Test Shot
Apply Asphalt Product for Known Distance & Width
Calculate Amount of Applied Asphalt Product
Calculate Spread Rate
Product Temperature
Typically 140 to 185oF
Check At Distributor
Common Emulsion: CRS-2P
Develops strength in hours that normally take days.
Sweep same day. Requires clean chips. Must place chips within one minute
of placement of binder. Eliminates bleeding
Higher softening point
Sample Asphalt Product
Sample Location Truck or Trailer Nozzle
Sample Container 1 Gallon Plastic w/Lined
Screw Cap, Wide Mouth
Chip Spreaders
Chip Spreader Issues
Correct Application Rate
Uniform Application Rate
Test Shot to Insure Correct Application Rate
Apply aggregate for known distance and width
Calculate Amount of Aggregate
Calculate Spread Rate
Check Rollers
Type
Weight
Speed
Rolling
Best Pneumatic-Tire Roller
Buns Up: Check Embedment
Factors Affecting Breaking and Curing Weather Conditions:
temperature, humidity, wind Water Absorption Aggregate moisture content:
although wet aggregate may facilitate coating, it tends to slow the curing process
Mechanical forces: roller pressure forces water from mix
Surface area: excessive fines or dirty aggregate accelerate breaking
Surface chemistry
Broom
Safety
Approved Vests
Communication
Eye Contact
Typical Problems
Streaked Appearance Bleeding/Flushing Loss of Cover Aggregate Bad Centerline Joint Utilities/New Patches Tight Alignment or Steep Grades Heavy Tree Canopy Fall Weather
Common Chip Seal Problems
Rules of Thumb for Seal Coats• Make sure pavement is clean• Use high quality materials• Proper application rate for binder• Proper application rate for aggregates.
Extra aggregates only cause failure.• Keep distance between the distributor
and the chipper to minimum. Aggregate must be placed before emulsion starts to break.
Rules of Thumb for Seal Coats, cont.
Minimum of three rollers. Keep speed under 5 mph. Compaction must be completed before emulsion is broken.
Final sweeping of roadway as soon as possible. No later then the next morning.
Remember that Details count.
Questions?
Chip Seals