Investigation of the interface bonding between concrete slab and asphalt overlay

Interface bonding between the cement slab and asphalt overlay is a significant point affecting mechanical behaviour and service life of the pavement. Many factors may influence the interfacial adhesive capacity, including asphalt mixture type, tack coat type and dosage, surface texture on layer below, temperature and moisture conditions. The aim of this study is to determine the most influential factors at the interlayer and evaluate their significant levels. An apparatus is designed to apply the direct shear test with normal load. Specimen is prepared by drilling cores from asphalt overlay over cement concrete pavement, which is constructed in laboratory. Six parameters with three values are examined by orthogonal test. Effects of these factors on interlayer performance are validated by boxplot. The test results conclude that surface texture on cement slab has the most significant influence on interlayer shear strength, and tack coat type, moisture and temperature come next. Rough surface texture like tining helps increase layers’ bonding. Cutback asphalt is not suitable as tack coat binder compared to emulsified asphalt. In addition, low temperature and dry condition can also improve interlayer shear performance.