The following are some issues that could occur during construction of a scrub seal:
LARGE AMOUNT OF SCRUB SEAL EMULSION WHEN STOPPING BROOM:
This happens when the operator does not pull out the excess emulsion at the end of a pull.
Operator should shut off nozzles about 50 feet before the end point and pull out the remaining emulsion that has accumlated in the broom sled.
SCRUB SEAL EMULSION IS BEING PUSHED OUTSIDE THE FRONT ROW OF BROOM HEADS:
Too much emulsion is being sprayed or
Too much downward pressure on the front broom heads
Correct Emulsion Wave
THERE IS NO EMULSION WAVE AHEAD OF THE FRONT ROW OF BROOM HEADS:
The front row of broom heads are not touching the surface
Not enough emulsion is being applied
Reduce aggregate spreader speed. If the spreader’s forward travel speed is too fast, the spreader will begin to bounce or jump and the aggregate will fall out of the hopper. When this happens, the aggregate will be heavy for a few inches and then light for a few inches then heavy again. This cycle will continue repeating itself until the spreader speed is adjusted.
Follow correct patching procedures. Poor patching can also cause this problem.
The following are the most common post-construction problems with potential solutions. It may take an investigative approach to determine the actual problem.
LOSS OF AGGREGATE:
Increase the emulsion application rate
Removing the dust off the aggregate or switching to a cleaner aggregate
Verifying that the aggregate gradation meets specification and is consistent with the mix design results
Decrease the aggregate application rate to ensure it is not too heavy
Pre-treat all patches with a fog seal prior to scrub seal emulsion application
Applying the treatment only when weather conditions are suitable
Ensure that the aggregate spreaders and rollers were operating closely behind the asphalt distributor
Control traffic speeds until emulsion is properly set
Ensure that brooming does not occur before the emulsion is properly set
BLEEDING OR FLUSHING:
Use a cubical shaped aggregate instead of a flat and elongated aggregate
Reduce the emulsion application rate
Increase the aggregate application rate
Verify that the distributor and aggregate spreader calibrations are correct