Experimental Assessment of the Tensile Bond Strength of Mortar-Mortar Interfaces: Effects of Interface Roughness and Mortar Strength

Abstract

Abstract Concrete gravity dams are subject to external forces that can lead to sliding at the base and overturning about the toe. The latter may result in mobilization of the tensile bond strength of the concrete-rock interface at the dam heel. This article attempts to address this issue by experimentally characterizing the bond strength according to the “concrete” material strength and the interface surface roughness. Experimentation was conducted in a laboratory environment using mortar interface replicas to simulate concrete dams and medium-strength bedrock foundations. Two different mortar strengths and five different roughness profiles were assessed. The surface roughness was characterized using the slope root mean square “Z2” roughness parameter. The bond strength was determined by a direct tensile method. The analysis of variance method was used to assess parameter significance. Results showed meaningful tensile bond strength variation with respect to the interface roughness, but no variation was caused by different material strengths. Reported bond strengths may contribute to increase the accuracy in predicting the tensile bond of a concrete-rock interface. It may help engineers in the field of dam stability make more accurate predictions regarding dam overturning safety factors.