Adhesion between asphalt layers through the leutner shear test

Abstract

Reflective cracking is a common issue present in recently rehabilitated pavements, especially when hot mix asphalt overlay is applied over the cracked pavement. It can cause the cracks to propagate to the new asphalt layer in a short period of time, wasting most of the resources spent in the rehabilitation project. Among many existing techniques to control reflective cracking, there is the application of an asphalt interlayer capable of relieving the stresses that reach the overlay, also known as Stress Absorbing Membrane Interlayer (SAMI). This solution can be highly efficient but it is essential to ensure adequate adhesion at the interface between layers, otherwise movement at the interface will eventually cause cracking at the pavement surface. The described rehabilitation solution was applied in a test site at BR-116 highway. As for the SAMI, an asphalt mixture produced with fine granite aggregates and Highly Modified Asphalt (HiMA) binder was used. The hot mix asphalt (HMA) overlay was produced using SBS-modified asphalt binder and the same aggregates source. Tack coat was applied between the asphaltic layers to ensure proper bonding. In this study, field samples were taken and the Leutner Shear Test was used to assess the bond strength at the interlayer-overlay interface. Results have shown that the bond strength was adequate in the test section. Therefore, the efficiency of the solution can be studied without influence of any debonding effects. The values obtained for the shear strength were higher than recommended, so lower rates of tack coat could still be effective.