A study of the performance of six crack seal installation procedures

The most common method of preventing moisture and debris infiltration into cracked pavement structures is by filling the cracks with asphalt sealers. Maintenance personnel responsible for this activity often have different opinions regarding the most effective method to use to seal these cracks and little objective evidence exists in the literature regarding the best techniques. Often, expedience and safety lead workers to fill the cracks as rapidly as possible without significant initial preparation. Mechanical routing of the crack to form a geometrically defined reservoir for the sealant requires more effort and time. This research was conducted to measure differences in performance between minimal crack preparation and significant preparation. Preparation techniques included routing cracks and air blowing to remove debris, blowing out debris while simultaneously heating the crack to remove any moisture, and simply blowing out debris with compressed air. After crack preparation each crack was filled using two techniques. These techniques included filling to the surface and overfilling and spreading the excess sealant over the edges of the crack. Three sealant suppliers provided five different products at three separate sites. Each combination of product and application technique was placed in six transverse cracks. This resulted in an experiment with a total of 420 filled cracks on approximately 16 km (10 miles) of pavement at three sites. Results after twelve months service indicate a significant difference in performance depending on the preparation method and filling technique. The best results were obtained when cracks were filled using the overbanding technique regardless of whether routed, hot air lanced or air blown. In addition, performance improved between the five month survey and the twelve month survey for some treatments indicating that some healing of the crack sealants may be occurring.