PAVEMENT MAINTENANCE II Part 1b: Chip Seal Construction Idaho Roads Scholar Program

Objectives n Review how to set up a good chip seal, n Investigate equipment operation, and field checks, n Identify common problems and possible solutions.

Field Checks n Weather/Surface Condition n Traffic Control n Aggregate n Asphalt n Asphalt and Chip Distributor n Rollers n Sweeping

Weather/Surface Condition n Dry or Damp Surface n Temperature n Rain/Humidity n Wind

Surface Temperature

Proper Traffic Control is Essential!

Aggregate Requirements for Successful Seal Coat n Must be clean. u Less then 1% passing #200 sieve. n Cubical chips are better then flat chips. n Must be crushed. u At least 2 crushed faces. n More single sized the better.

Dirty Chips n > 1% passing the #200 sieve u Impedes the ability of binder to bond chip to roadway. u Limits amount of binder that can be applied. u Creates dust after sweeping.

Aggregate Condition n Emulsions => Damp Surface n Asphalt Cement => Dry Surface

n Can only glue down a single layer of chips. n Must have chips at least 60 to 70% embedded to withstand traffic and snow plow damage. n Should see emulsion at top of chips before emulsion breaks. Chip Considerations

Which are the better chips?

Distributors

Asphalt Distributor Components n Nozzles n Spray Bar Height n Application Rate n Product Temperature

Nozzle Angle

Spray Bar Height

Triple Coverage

Test Shot n Apply Asphalt Product for Known Distance & Width n Calculate Amount of Applied Asphalt Product n Calculate Spread Rate

Product Temperature n Typically 140 to 185 o F n Check At Distributor

Common Emulsion: CRS-2P n Develops strength in hours that normally take days. n Sweep same day. n Requires clean chips. n Must place chips within one minute of placement of binder. n Eliminates bleeding u Higher softening point

Sample Asphalt Product n Sample Location u Truck or Trailer u Nozzle n Sample Container u 1 Gallon Plastic w/Lined Screw Cap,Wide Mouth

Chip Spreaders

Chip Spreader Issues n Correct Application Rate n Uniform Application Rate

Test Shot to Insure Correct Application Rate n Apply aggregate for known distance and width n Calculate Amount of Aggregate n Calculate Spread Rate

Check Rollers n Type n Weight n Speed

Rolling

Best Pneumatic-Tire Roller

Buns Up: Check Embedment

Factors Affecting Breaking and Curing n Weather Conditions: temperature, humidity, wind n Water Absorption n Aggregate moisture content: although wet aggregate may facilitate coating, it tends to slow the curing process n Mechanical forces: roller pressure forces water from mix n Surface area: excessive fines or dirty aggregate accelerate breaking n Surface chemistry

Broom

Safety n Approved Vests n Communication n Eye Contact

Typical Problems n Streaked Appearance n Bleeding/Flushing n Loss of Cover Aggregate n Bad Centerline Joint n Utilities/New Patches n Tight Alignment or Steep Grades n Heavy Tree Canopy n Fall Weather

Common Chip Seal Problems

Rules of Thumb for Seal Coat s 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 Coat s, cont. n Minimum of three rollers. Keep speed under 5 mph. Compaction must be completed before emulsion is broken. n Final sweeping of roadway as soon as possible. No later then the next morning. n Remember that Details count.

Questions? Chip Seals