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.