Current recommendations for Crack Sealing Machine both direct and bond breaker applications are to give rubber modified asphalt sealants a shape factor and silicone sealants a shape factor. Generally, seals with smaller shape factors risk adhesion loss, while those with larger shape factors have increased resistance to adhesion loss.
Bond-breaker application should only be considered when the following two factors apply, which also can be used for Crack Sealing Machine:
The costs of installing backer rod are anticipated to be lower than the cost benefits of improved Crack Sealing Machine performance.
Working cracks are relatively straight ( as with joint reflection cracks) and are accompanied by very little edge deterioration.
Most hot-applied rubber-modified sealants are recommended for direct application; the increased costs of using backer rod with these materials is not justified. Silicone is perhaps the only material recommended for placement with backer rod.
