Experimental study and application of mechanical properties for the interface between cobblestone aggregate and mortar in concrete

Abstract

The failure mechanism under the combined state of normal and shear stresses for the interface between cobblestone aggregate and mortar was investigated by testing the interfacial bond strength. It was revealed that the tensile bond strength of the interface between cobblestone aggregate and mortar was about half the tensile strength of the mortar, but the shear bond strength of the interface was close to the shear strength of the mortar. Moreover, the shear bond strength increased with increases in the normal stress when the normal stress was smaller than 60% of the compressive strength of the mortar, but it can be assumed that the shear bond strength decreases with increases in the normal stress if it was larger than 60% of the compressive strength of the mortar. The failure criterion for the interface under combined normal and shear stresses was established by regressing the experimental data. Finally, a two-dimensional mesoscopic mechanical model, in which the mechanical properties of the interface were described by the obtained bond strength and failure criterion, was used to simulate the fracture process of concrete. Verification of the simulation was performed by comparing the simulated results with those obtained from the tests, in which the aggregate roughness was similar to that in the interfacial experiment. It was found that, by using the mechanical properties of the interface in the numerical model, the behavior of concrete could be predicted to a reasonable degree of accuracy. The propagation of cracks and the failure modes of concrete can also be determined using the proposed numerical model.