Slurry Seal

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Application Sequence

  1. Calibrate and set the paver for the Job Mix Formula as determined by the Mix Design process.
  2. If required, a test strip should be placed in conditions similar to those that are expected to occur during the project.
  3. Prepare the surfacing using surface preparation guidelines.
  4. If required, apply the tack coat.
  5. Apply slurry seal, closely adhering to guidelines.
  6. Open the pavement back to traffic when the slurry seal has sufficiently cured.

Application Guidelines

Typical Slurry Seal application


  • If required, a test strip should be placed in conditions similar to those that are expected to occur during the project.


  • When the asphalt pavement is hot and dry, the surface should be fogged with water ahead of the spreader box.
  • The rate of fog spray application is adjusted as the temperature, surface texture, humidity, and dryness of the pavement change.
  • Avoid pooling of water ahead of the spreader box.


  • The slurry seal needs to have an appropriate consistency to meet the pavement owner’s requirements of texture and application rate.
  • Application rates are affected by the gradation of the aggregate and the demand of the pavement surface. (For example, a very rough surface texture will require a certain amount of material to fill the voids, unlike a smooth, polished surface.)
  • Ensure that the asphalt pavement is completely covered. No lumps or unmixed aggregate can be deposited on the asphalt pavement.
  • Drag marks are not acceptable.


  • Areas which cannot be accessed by the paver will need to be surfaced using hand squeegees. This will provide complete and uniform coverage (If necessary, the area to be hand worked should be lightly fogged with water prior to mix placement).
  • As much as possible, handwork should exhibit the same finish as that applied by the spreader box, and should be completed prior to final surfacing.
  • Spray the surface to be hand-worked lightly with water before applying the material.
  • Perform handwork first, so as to have as much area as possible applied by the spreader box.
  • Tar paper can be used at the beginning and end of a pull to provide a straight edge.
Longitudinal joint


  • Joints must be clean, without excess buildup, uncovered areas, or unsightly appearance.
  • Longitudinal joints should be placed on lane lines.
  • Partial width passes should only be used when necessary and should not be the last pass of any paved area.
  • Overlaps must be kept to a minimum, as they will be noticeable upon completion of the project.
  • Transverse joints are to be butt joints (not overlapped) to avoid creating a bump in the surface. The end of the first pass will be cut clean with a flat shovel, and the second pass will start with the primary strikeoff at this same point.
  • Using tar paper (roofing felt) to end the first pass will provide a straight edge and eliminate handwork.
  • Pulling a spreader box until empty will cause problem in the slurry seal in the future.
Proper slurry seal edge line
  • The aesthetics of the project will improve greatly when lines at curbs, shoulders and intersections are kept straight.
  • Longitudinal edge lines should not vary by more than ± 2 in (± 51 mm) horizontal variance in any 96 ft (29 m) of length.
Slurry Seal consistency



  • The slurry seal should be sufficiently stable, so that the mixture doesn’t prematurely break in the spreader box.
  • The mixture should be homogeneous during and following mixing and spreading.
  • It should be free of excess liquids, which create segregation of the aggregate.
  • Do not spray additional water into the spreader box.
  • The mixture of the mat must be consistent, and not too wet.
  • The texture should reveal larger stones in the mix.
  • The surface produced by a finish course slurry seal will reflect the surface it is being applied to. For further information, please review ISSA’s web-based courses on slurry seal .