A 3D plastic-damage constitutive model for concrete failure

A coupled plastic-damage mathematical and numerical model to investigate the mechanical behaviour of concrete at the scale of its constituents is presented herein. The plastic-damage model combines a pressure-dependent plastic model with a damage model able to combine compressive and tensile mechanisms to describe concrete failure. Specifically, the damage model includes a stiffness recovery function for a more realistic description of the transition from tensile to compressive failure of the composite. The plastic potential is defined based on the mechanical behaviour of concrete under triaxial stress states. Along this line the model is expected to simulate the local confinement effects that involve the cement paste when surrounded by the aggregates. A new cohesive contact law has been used to characterize the Interfacial Transition Zone (ITZ) between the two, so accounting for the control of the shear stresses developed during the slipping of the two phases during failure. After calibrating the model, a uniaxial compression test has been reproduced numerically. The experimental stress-strain curve is found to be in good agreement with the model prediction. Moreover, a comparison with experimental results prove that the specific cohesion contact law formulation is able to efficiently describe the behaviour of ITZ, as well as the gradual decohesion process around aggregates.