Mesoscopic study of concrete with random aggregate model using phase field method

Abstract In the present work, the phase field method implemented by the user-defined element (UEL) subroutine of commercial finite element software ABAQUS is adopted to investigate the failure pattern and mechanical responses of meso-scale concrete specimens. To build the structure model of meso-scale concrete specimens, the recently proposed random sequential addition (RSA) method is used. With the proposed numerical model, the uniaxial tensile test was carried out as a benchmark test to investigate the influence of several parameters, such as the volume fraction, size, and major axis direction of aggregates on the mechanical responses and failure mode of concrete specimens. Then, two classic examples, namely, a three-point bending (TPB) test and a four-point bending (FPB) test, are investigated with the proposed numerical model. The numerical results from the proposed numerical model indicate that: A higher interfacial transition zone (ITZ) content has an adverse effect on the peak strength of concrete; A negative correlation is shown between major axis direction of aggregates and peak strength of concrete; Intergranular fracture mode is observed, in which the damage areas of concrete are mainly distributed around the ITZ; The linear elastic stiffness and peak strength are almost independent of the aggregate distribution, but the fracture propagation patterns are sensitive to meso-structures of concrete; and numerical results of TPB and FPB tests also indicate that the notch of concrete has non-negligible influences on fracture propagation path, as well as linear elastic stiffness and peak load of concrete specimens.