Investigating Crack Sealant Performance and Causes of Bumps in New Hot Mix Asphalt Overlays Over Crack Sealants

摘要

This final report is intended to provide information regarding the performance of crack sealants supplied and installed by three manufacturers for experimental use in a three-year evaluation of in-service pavements on three Colorado highways. In addition, preliminary conclusions have been developed regarding the propensity of three of these sealants to contribute to bumps in new overlay hot mix asphalt. Results of performance evaluations made, to date, indicate that the crack sealants failed at a surprising rate after only one winter. However, subsequent performance surveys after an additional twenty-four months indicate a tendency for the sealants to heal. Routing the cracks prior to filling appears to provide the best performance when the filler is overbanded, and filling the cracks to within 14 inch of the surface instead of flush with the surface or overbanding produced the poorest performance. Bumps accompanied by transverse cracking occurred over the crack sealants when a new hot mix overlay was placed after the crack sealants had been in service for two years in one of the test pavements. The bumps and transverse cracks were exacerbated by utilizing steel rollers with vibration on breakdown of the hot mix asphalt overlay. The number of passes of the vibrating steel rollers further exacerbated the presence of the bumps and cracks. The same rollers used in static mode reduced the effect, and pneumatic rollers used for breakdown eliminated the effect. The ambient temperature and temperature of the substrate pavement during construction appears to have had little effect, as the same bumps and cracking occurred during vibratory breakdown after a small rain shower moistened and cooled down the substrate pavement surface prior to the overlay hot mix asphalt placement.