Enhancing Shear Strength of Bonding Materials Used for Asphalt Concrete and Composite Pavement Layers

Abstract

A tack coat is a thin cut-back cement or asphalt emulsion coating applied on an existing non-absorbent pavement. A good bonding between the asphalt and concrete is necessary to provide sufficient structural strength. Poor adhesion will result in shear failure. The shear test is one of the basic tests to determine bond strength. This study aims to quantify the best shear resistance obtained using three types of cut-back asphalts (RC70, RC800 modified with polymer 4.5% and MC70), PG (76-10) modified asphalt cement with polymer 4.5%, Sikadur®-31 CF usage at elevated temperatures between +25°C and +45°C and Nitomortar TC2000 epoxy from Fosrok company. All are applied on concrete surfaces with an application rate of 0.5kg/m2 except for Nitomortar, which depends on layer thickness ranges between (1-2.5) mm instead of the application rate. A special attachment and loading mechanism were designed to facilitate the measurement of the asphalt-to-concrete contact shear strength in Al-Ahmad Lab-Baghdad. Vertical shear force is applied to a multiple-layer sample with a 0.25 kN/sec rate until the failure occurs at the interface. The final result of this test is stated in terms of the maximal force or power needed to break the bond. The average shear strength of tack coat materials is (0.049, 0.0455, 0.0085, 0.677, 1.088, 1.361) MPa Respectively. It concluded that Fosrok epoxy has the maximum shear strength. Also, adding polymer to asphalt increased the viscosity. All materials used enhanced the shear strength of bonding materials used for asphalt concrete and composite pavement layers

Keywords

• direct shear test
• tack coat
• bonding strength
• shear strength