Cape Seal Roadway Surfacing Treatments

Chip Seal Portion

The following are the most common construction problems.  Included with these problems are potential solutions. It may take an investigative approach to determine the actual problem.

STREAKING OR DRILLING OF EMULSION:

Potential Solutions

• Verify that the binder is at the correct application temperature
• Ensure that the correct nozzle size is installed
• Verify the nozzle angle is correct
• Make sure all nozzles are clear
• Verify triple overlap coverage

WASHBOARDING:

Potential Solutions

• 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.

Slurry Seal/Micro Surfacing Portion

The following are the most common problems with slurry seal/micro surfacing and potential solutions. It may take an investigative approach to determine the actual problem. If you are experiencing a problem not addressed here, consult the ISSA Inspector’s Manual.

IF FINISH TEXTURE IS TOO ROUGH:

• Discuss with the contractor to modify secondary strike off/drag setting.
• Application rate may be too low for the aggregate gradation.
• Mix may be placed too dry or is breaking too quickly.
• If using Type III aggregate, it may not be possible to decrease the roughness.

IF FINISH TEXTURE IS TOO SMOOTH:

• Discuss with the contractor to modify secondary strikeoff/drag setting.
• Application rate may be too high for gradation.
• Excess liquids may be floating emulsion to the top.

IF DRAG MARKS APPEAR IN FINISH MAT:

• Aggregate may be oversized, improve stockpile quality control and screen aggregate if you are not already doing so.
• Material may be built up, scrape pugmill and spreader box more often. Clean pugmill and spreader box daily at a minimum, and more often as needed to provide a proper application.
• Mix may be breaking too quickly, use additive to slow down the break and set of the material.
• Clean the secondary strikeoff or replace the drag.

IF EXCESS LIQUID IS COMING OUT OF THE SPREADER BOX:

• If a test strip was placed successfully, determine what condition changed since then.
• Decrease water content added to the mix.
• Verify paver is set to the proper ratios as specified in the Job Mix Formula (Mix Design).
• Decrease the amount of water used to fog the pavement.

IF MIX IS BREAKING TOO FAST, INCLUDING SETTING UP IN THE CORNERS OF THE SPREADER BOX:

• Verify paver is set to the proper ratios as specified in the Job Mix Formula, especially Mineral Filler.
• Determine if aggregate has been contaminated, particularly with soil.
• Verify the spreader box augers (if present, not all slurry seal spreader boxes use augers) are not worn excessively, and turning the right direction.
• Verify the asphalt emulsion strainer is clean, to ensure sufficient flow to the pugmill.
• Water fog the pavement ahead of the spreader box.
• Ensure that the asphalt emulsion is formulated for current temperatures.
• Check the asphalt emulsion temperature to determine if it is too hot.
• Check the gradation and sand equivalence of the aggregate.
• Add retarder (additive) to the mix.
• Verify the pugmill water delivery system is not clogged in the strainer or pugmill spray hood.
• Add water to the mix.
• Verify the pugmill is running at the proper speed, excessive speed can cause early breaking.
• Verify the surface is clean, as dust and dirt on the street can cause the emulsion to break.

IF MIX IS BREAKING TOO SLOW:

• Verify paver is set to the proper ratios as specified in the Job Mix Formula, especially mineral filler.
• Reduce the retarder (additive) being added to the mix.
• Reduce the water being added to the mix.
• Ensure that asphalt emulsion is formulated for current temperatures.

IF DRY AGGREGATE ON PAVEMENT:

• On a continuous paver, check the nurse truck/paver interface, ensure all aggregate is deposited in the front hopper.
• Check conveyor(s) seals, repair if necessary.
• Check pugmill/conveyor belt interface, ensure all aggregate is being deposited in pugmill.

Chip Seal Portion

The following are the most common post-construction problems.  Included with these problems are potential solutions. It may take an investigative approach to determine the actual problem.

LOSS OF AGGREGATE:

Potential Solutions

• Increase the binder 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 before binder 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:

Potential Solutions

• Use a cubical shaped aggregate instead of a flat and elongated aggregate
• Reduce the binder application rate
• Increase the aggregate application rate
• Verify that the distributor and aggregate spreader calibrations are correct

For potential remedies on bleeding and flushing chip seals, please refer to Chip Seal Maintenance - Bleeding and Flushed Surfaces.pdf

STREAKED APPEARANCE:

Potential Solutions

• Verifying that the spray bar height is set at 12 inches
• Verifying that all nozzles are set at a 30 degree angle
• Making sure that all nozzles on the spray bar are clean and operating properly

Slurry seal/Micro Surfacing Portion

IF THERE IS EXCESSIVE RAVELING:

• The aggregate may lack sufficient embedment in the matrix caused from insufficient asphalt quantity to hold the larger aggregate.
• Poor quality aggregates may de-bond from the matrix.
• The application rate may have been too thin to hold larger aggregates.
• The matrix may have a lack of fines to fill voids between larger aggregates.
• Cooler temperature may result in slowing of the cure necessary for traffic.
• The project may have been prematurely opened to traffic.
• The project may have been exposed to rain before final cure was achieved.

IF THERE ARE EXCESSIVE TIRE MARKS AND SURFACE ABRASION:

• The base asphalt may have been too soft.
• Rolling of low traffic areas will properly set the aggregate in the matrix.
• For subsequent projects, the slurry seal/micro surfacing could be placed during cooler weather, to allow a full cure before being exposed to traffic at elevated temperatures.
• Broadcast sand to help break the bond and friction between the slurry seal/micro surfacing and vehicle tires.