Numerical modelling crack propagation under Mode II fracture in plain concretes containing siliceous fly-ash additive using XFEM method

Many types of defects occurs in complex concrete materials. Therefore one can use various theoretical micro-crack models to simulate real behaviour of such materials. In order to apply any model it is necessary to carry out proper experiments to estimate fracture toughness for Modes I and II, to be able to perform simulation of the material response.For experiments we used structural concretes containing siliceous fly-ash additives. Mode II fracture toughness for fictitious cracks and their development was carried out using specimens for two concrete mixtures: (a) concrete without siliceous fly-ash (FA), (b) concrete with 20% FA additive. Compact Shear Specimens (CSSs) – 150 × 150 × 150 concrete cube with two fictitious cracks were used for tests under quasi-static loading.A new 3-D numerical model for CSS used for experimental testing of the Mode II fracture was created using XFEM. In calculations we used peak principal stress criterion for description of the crack grow, taking into account own experimental data concerning strength and fracture mechanics parameters. The calculated results with the newly formulated 3-D CSS numerical model coincide with experimental tests very well. There was a convergence of: cracks shapes, FQ, critical force values that enabled initial crack development and force–displacement graphs.

► A new 3-D numerical model of the specimens for Mode II fracture was created.
► 3-D fracture process was investigated with application XFEM.
► Fracture toughness of concrete containing silica fly-ash additive was assessed.
► Numerical results coincide with experimental tests very well.