Investigation of interlayer bonding performance between asphalt concrete overlay and Portland cement concrete using inclined shear fatigue test

The interlayer bonding between the asphalt concrete (AC) overlay and the Portland cement concrete (PCC) layer has an essential influence on the composite asphalt pavement performance. However, there is still little work on the interlayer bonding performance of composite pavement by inclined shear fatigue test. The purpose of this study is to investigate the interlayer bonding performance with four tack coat types and three PCC surfaces under the effect of repeated loading and water erosion. The optimal tack coat application rates were first determined by shear strength and applied in the following study. The shear fatigue performance of interlayer bonding with different tack coats and PCC surfaces was analyzed based on the conventional S-N fatigue model. Then, the effect of freeze-thaw cycles on the interlayer bonding was investigated according to fatigue lives and fatigue life ratios. Furthermore, the axle load conversion factor was calculated based on the shear fatigue life used for the composite pavement design. The analysis results indicate that the interlayer applied modified asphalt as the tack coat realizes higher strength and more extended shear fatigue life, which means better loading and moisture resistance. The calculated conversion factor shows a higher value compared to the specification stipulation. This research contributes to the interlayer design and construction of composite pavement, including tack coat selection, PCC surface treatment, interlayer fatigue life prediction, and axle load conversion.