Process
Crack sealing involves the placement of an adhesive material into and/or over working cracks (i.e., those that open and close with temperature changes, such as transverse, thermal and reflective cracks, diagonal cracks, and certain longitudinal reflective cracks) at the pavement surface in order to prevent the infiltration of moisture into the pavement structure.
Reference - NCHRP Report 784 - Best Practices for Crack Treatments
Crack sealing operations typically require good crack preparation (i.e. routing or sawing a reservoir over the crack and power cleaning the reservoir) and the placement of high-quality flexible materials (i.e. thermosetting or thermoplastic bituminous materials that soften upon heating and harden upon cooling) into and possibly over the reservoir.
Variations
Equipment Variations
There are 2 variations on equipment that prepares the crack for sealant.
- The "Rout and Seal" method utilizes a router. This method is utilized where transverse cracks are < 3/4" wide and will be widened to create a proper reservoir.
- The "Clean and Seal" method utilizes a hot air lancer to clean and dry out the crack. This method should be utilized when the cracks are non-working.
A crack must be free of dust and/or moisture to have a high percentage of success.
Material Variations
ASTM D6690-12 identifies four different types of sealants as follows:
- Type I: Sealant for moderate climates, with low-temperature performance tested at -18°C with 50% extension.
- Type II: Sealant for most climates, with low-temperature performance tested at -29°C with 50% extension.
- Type III: Sealant for most climates, with low-temperature performance tested at -29°C with 50% extension—special tests are also included (ASTM notes that these specification requirements were formerly Federal Specification SS-S-1401C).
- Type IV: Sealant for very cold climates, with low-temperature performance tested at -29°C with 200% extension.
Common Combinations
CRACK SEAL + HMA OVERLAY - one would want to use this combination since a HMA overlay will not seal cracks
CRACK SEAL + CHIP SEAL: When cracks in the existing surface exceed 1/8” in width, crack sealing them in advance of chip sealing will help keep water from intruding deeper into the pavement structure after the cracks reflect through the new wearing surface.
CRACK SEAL + MICRO SURFACING: When cracks in the existing surface exceed 1/8” in width, crack sealing them in advance of micro surfacing will help keep water from intruding deeper into the pavement structure after the cracks reflect through the new wearing surface.
CRACK SEAL + SLURRY SEAL: When cracks in the existing surface exceed 1/8” in width, crack sealing them in advance of slurry will help keep water from intruding deeper into the pavement structure after the cracks reflect through the new wearing surface.
For best results when using a combination treatment with crack seal, let the crack seal cure for a minimum of 2 weeks before placing the next treatment over the top. If overband is present, a longer cure time will be needed.
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