Crack propagation in concrete under compression

Mixed-mode crack initiation and propagation starting from the aggregate- matrix interface in concrete under uniaxial compression was investigated using fracture mechanics approach, finite element modeling, and holographic interferometry techniques. Experiments were conducted with specimens containing stone-matrix interface oriented at four different angles. During loading, interface debonding, initiation of matrix cracking (kink cracks), and propagation of matrix cracks were observed using laser holographic interferometry. The crack initiation and propagation were simulated by using both the analytical approach and finite element method with quarter-tip singular elements. With an increasing kink length, the finite element solution differed from the infinite plate analytical solution. To obtain an essentially constant value of the apparent critical stress-intensity factor for different orientation angles of the interfacial crack and for different kink extensions, a cohesive crack model was used. The magnitude of the normal and the shear tractions for the theoretical model was obtained by matching the FEM-calculated crack-opening and sliding displacements with the experimentally measured values.