Influences of Surface Characteristics and Modified Asphalt Binders on Interface Shear Strength

Weak bonding between layers of pavement leads to damages on the composite pavement. Bonding plays an important role in the durability and maintenance of composite pavement layers. The present study evaluates the factors effective in bond strength of the interface between concrete and asphalt pavements. The factors considered for this purpose include steel slag percentage in the concrete pavement, different types of modified bitumen, and rates of tack-coat. To measure the bond properties, direct shear and shear fatigue tests were carried out. In addition, texture depth and abrasion resistance were used in accordance with EN 1338 standard to measure the roughness properties of concrete pavement. The test results showed that 50% replacement of  steel slag with aggregate resulted in an increase in physical properties and texture depth of concrete pavement. Moreover, the results of the shear strength test of composite pavement revealed that the optimal rate of using tack-coat varies between 0.6 and 0.9 l/m2 and depends on the type of tack-coat. Finally, a higher shear strength was obtained for crumb rubber bitumen containing hydrated lime compared to crumb rubber modified bitumen and control bitumen.