Another option for contractors is hot pour mastic crack filler, a bendable crack filler containing fine aggregate. "The fine aggregate gives the crack filler strength," Curtis says. If using mastic, consult with the manufacturer on how to apply it. The aggregate in the material might not flow through all application tools and might call for special application requirements.
Rubber- and fiber-modified asphalt materials are another option. These materials must be heated and mixed using indirect-heating equipment. Indirect heating can be safer and provide a more controlled and uniform heating. Like mastic material, fiber-modified asphalt materials also require specific equipment for application. Fiber-modified materials create a thicker consistency requiring the need for kettles with heavy-duty application pumps, large hoses, and full-sweep agitation equipment.
Other materials and methods of application some contractors prefer to use include applying a tack coat, filling the crack with cold asphalt material, and then tamping the asphalt into the crack. Some cracks can be repaired using partial depth mill and adding fabric to the crack. Although this won't solve a cracking issue 100%, the fabric will help make future cracks more manageable, Curtis says.
The Manual of Practice suggests four guidelines contractors should follow:
- Apply the material with the nozzle in the crack channel, so that the channel is filled from the bottom up and air is not trapped beneath the material.
- Apply the material in a continuous motion, being sure to fill the channel to the proper level for recessed configurations or provide a sufficient amount of material for flush, capped, or overbanded configurations
- Reapply material to crack segments where material has sunk into the crack or an insufficient amount was furnished in the previous pass
- Recirculate material through the wand into the melting vat during idle periods.
Sometimes a bond-breaker material, such as backer rod, is placed at the bottom of a crack prior to filling or sealing. The backer rod prevents the filling or sealing material from going down into the crack during application and prevents the material from forming a three-sided bond with the crack's reservoir perimeter. Often, a bond-breaker is only used if it the crack is relatively straight with very little edge deterioration, the Manual of Practice says.
The final step in cracksealing or filling is to finish and shape. To ensure the best finish possible, keep the squeegee close behind the application equipment. Keep the application equipment and the finishing squeegee centered over the crack channel. Periodically remove any material buildup from the squeegee.
Some jobs may require a blotting material after the finish to prevent the uncured cracksealer or filler from tracking. Common materials used with rubber-modified asphalt materials include toilet paper, talcum powder, and limestone dust. Sand is often used with emulsion materials and should be applied in a thin layer. A variety of spray-on blotting materials are also available. These materials are applied immediately after finishing.
Repairing Filled CracksCrack filler should bond to the pavement keeping water out of the crack. But some cracks might reopen or widen even after repair. If this is the case be prepared to do a little extra prep work. "New crack filler won't easily stick to old crack filler," Curtis says. The old crack filler will need to be reheated before applying new crack filler over the top of it.
Educating customers on how and why cracks occur is essential. "Even after crack filling or sealing, pavement still wants to relieve pressure and will probably crack in other places," Curtis says. Make sure a customer understands this. Let the customer know his or her options for repairing the asphalt. But don't oversell your product or service.
Summary of Asphalt Pavement Crack Treatment Materials
Material type and recommended application. From Table 4 from Materials and Procedures for Sealing and Filling Cracks in Asphalt-Surfaced Pavements Manual of Practice