Evaluation of bond strength between hot mix asphalt surfacing layers

Abstract

This paper investigates the effect of tack coat types, application rates, and layer thickness on HMA interface shear strength. The performance of tack coat materials on AC 10 was evaluated. Three emulsions were selected as tack coat material which are RS-1K, RS-2K, and RS-2KL.These tack coat materials were applied at three application rates, namely 0.25 l/m², 0.40 l/m², and 0.55 l/m². The selected application rates are in accordance with the JKR specification and represents low, medium and high rates respectively Three different surface thickness were considered namely 35 mm, 50 mm and 65 mm. Only laboratory scale specimens at three replicates for each test configuration were used throughout the study. Direct shear test were carried out shearing rate of 1 mm/min. Results show modified emulsion can provide better shear strength than conventional emulsion where RS-2KL performs better than RS-1K and RS-2K due to the present of latex in RS-2KL which relate to the viscosity that can improve shear strength. On the other hand, higher thickness of wearing course and application rate can provide higher interfaces shear strength. However, their relationships were not strong due to inconsistency of R2 values