Evaluating Tack Coat Applications and the Bond Strength between Pavement Layers

摘要

Poor bond between two layers of hot mix asphalt (HMA) is the cause of many highway and airfield pavement problems. Slippage cracks which often occur at locations where vehicles turn, accelerate, or decelerate, are the most commonly observed problem related to poor bond between layers. Other pavement problems may also be attributed to insufficient bond between layers of HMA. Compaction difficulty, premature fatigue, top down cracking, and surface layer delamination have also been linked to poor bond between HMA layers. This study included the evaluation of test conditions for measuring the bond strength between pavement layers. Bond strengths between HMA layers bonded with different tack coat materials and application rates were investigated. The laboratory experiment evaluated effects of tack coat type, application rate, mixture type, testing temperature and normal pressure on the bond strength. It was found that all of the main factors affected bond strength. Testing temperature had the greatest effect on bond strength. As the temperature increases, bond strength decreases significantly. Normal pressure affected bond strength more at the high test temperature. The effects of tack coat type and application rates on bond strengths are different for the fine-graded and coarse-graded mixtures. Based on the laboratory study, the best conditions for the method for determining the bond strength between pavement layers were selected.