Shear behaviour and constitutive model of old-to-new concrete interface with single roughness tooth: Experimental and numerical investigation

Abstract

The shear behaviour of the interface between an old and new concrete can be improved by adjusting the size and shape of the surface roughness teeth. Existing studies on concrete-to-concrete interfaces highlight the significant effect of the surface roughness texture. However, information on the influence of the geometrical parameters of the surface roughness tooth on the shear behavior of concrete interfaces are few. In an effort to bridge this gap, this work examines the shear behaviour of twelve (12) double shear test specimens with single roughness tooth and varying roughness tooth angles and tooth depths at the interface between an old and new concrete. Following the test, a 3D Finite Element model was developed and validated to simulate the experimental testing and for numerical parametric studies. The test results showed that the complete failure of the test specimens included the adhesive and cohesive failure of the interface and the roughness tooth, respectively. The numerical results highlighted that by increasing the roughness tooth angle, the interface shear strength increased by up to 146%, with the maximum interface shear strength achieved at a roughness tooth angle of about 35°. By increasing the roughness tooth depth from 5 mm to 35 mm, the interface shear capacity increased by about 87%. However, further increase beyond the 35 mm tooth depth showed no effect on the shear capacity. An analytical model was proposed to predict the shear capacity of the single tooth specimens considering the roughness tooth angle and tooth depth. Finally, a shear constitutive model was proposed which describes the mechanical behavior of the interface under combined normal pressure and shear stress.