Experimental investigation on mode II fracture toughness KIIC of concrete and fracture behavior

Using the double-edge notched geometry proposed by Xu and Reinhardt recently, the dimension of 200 mm x 200 mm x 100mm concrete cube specimens, of which the crack length are 10 mm, 20 mm, 30mm, 40mm, 50mm respectively, are designed to experimentally measure mode II fracture toughness K-IIC of concrete. For almost all specimens, typical shear fracture features i.e. approximately 0 degrees initial cracking angle as well the following crack forwards propagation along the direction of ligament is phenomenally observed. This fact strongly confirms that this double-edge notched geometry is validly and capable of being utilized as a mode II fracture geometry to evaluate mode II fracture behavior. Then, from the discontinuity point of the measured load-displacement plot, the critical shear fracture load P-c is determined and the corresponding mode II fracture toughness K-IIC is also calculated using the formula developed by Xu and Reinhardt. The computed results show that K-IIC has no dependency on initial crack length, about 3.36MPa(.)m(1/2) for the tested specimens.