Interface shear strength of composite concrete-to-concrete bond

Abstract

Interface shear strength between two concrete layers cast at different times plays an important role to develop composite action of the floor slabs. Most previous studies when quantifying interface shear strength for interface concrete with projecting steel did not take concrete cohesion into consideration. In contrast, interface concrete without projecting steel depended solely on concrete cohesion in quantifying the interface shear strength. Although there are studies conducted on the action of interface shear strength under variable normal stresses, the findings only considered smooth or left “as-cast” surface. Furthermore, Finite Element Modeling (FEM) of the interface shear behavior for concrete-to-concrete bond is also limited in research. In this study, a total of 72 “push-off” tests were carried out to study the interface shear strength of composite slab with six different surface textures. This included smooth or left “as-cast”, roughened by wire-brushing in the longitudinal and transverse direction, groove, indented and projecting steel crossing the interface. Loading was then applied horizontally on the concrete topping until failure was observed under various normal stresses; ?n = 0 N/mm2, 0.5 N/mm2, 1.0 N/mm2 and 1.5 N/mm2. The relationship between surface texture, interface shear strength and normal stress was then proposed in this study. The roughness profile of the concrete base was measured using a portable stylus roughness instrument.