Influence of Microcrack Healing on Interface Bond Shear Strength of Asphalt Concrete

Saad Issa Sarsam; Samah Abdulrazzaq AL Nuaimi

Abstract

The flexible pavement layers are susceptible to cracks throughout its service life under the repeated loading and environmental impact. However, microcracks can heal itself through rest period and variation in temperature. In this investigation, the influence of microcrack healing on the interface shear strength of asphalt concrete was assessed. Two types of tack coat (rapid curing cutback RC-70 and cationic medium setting emulsion CMS) and three application rates have been implemented in the preparation of two layers slab samples (base overlaid by binder, and binder overlaid by wearing). Asphalt concrete core specimens were obtained from the roller compacted slab samples and subjected to 1200 cycles of shear stresses, and the permanent deformation was monitored. Half of the specimens were tested for interface bond shear strength at 20 °C, while the other half was subjected to microcracks healing under external heating, then tested for interface bond shear strength. It was concluded that the healing process decline the permanent deformation by (2.6, 27.6, 6.7) % for (binder-base) interface and (18.6, 7.1, 26.3)% for (wearing-binder) interface at CMS application rate of (0.1, 0.23 , 0.35) l/m2 respectively. However, it declines the permanent deformation by (34.9, 23.1, 23.6) % for (binder-base) interface and (47.8, 48.6, 16.1)% for (wearing-binder) interface at RC-70 application rate of (0.1,0.23 , 0.35) l/m2 respectively. The (binder-base) interface exhibits higher interface bond shear strength than (wearing-binder) interface for RC-70 tack coat, while the (wearing-binder) interface shows higher interface bond shear strength than that of (binder-base) interface when CMS tack coat. CMS tack coat exhibit the best healing efficiency at (wearing-binder) interface as compared to other interfaces or tack coat type.