Mixed mode I/II and I/III fracture toughness investigation for preplaced aggregate concrete mixtures: Experimental study and theoretical prediction

In this paper, mixed mode I/II and I/III fracture toughness of preplaced aggregate concrete was studied using an edge-notched disc bend specimen. The results showed the dependency of the fracture toughness value on the mode mixity. The values of modes I, II, and III fracture toughness were obtained to be equal to 0.67MPam$$ 0.67 MPa\sqrt{m} $$, 0.72MPam$$ 0.72 MPa\sqrt{m} $$, and 0.42MPam$$ 0.42 MPa\sqrt{m} $$, respectively. Several theoretical fracture criteria were examined for predicting the trends of experimental data in the tested preplaced aggregate concrete material. The 3D averaged strain energy density criteria provided the best predictions for the KIIIc/KIc ratio. Mixed mode I/III fracture toughness data were between the predicted envelopes of the maximum tensile stress and 3D maximum tangential strain theories. The generalized maximum tangential stress criterion provided accurate predictions for pure mode II and mixed mode I/II fracture data among the investigated mixed mode fracture criteria. By comparing the preplaced aggregate concrete fracture results with those of other types of concrete, it is observed that preplaced aggregate concrete has acceptable and in-the-range fracture resistance. The compressive and tensile strengths of preplaced aggregate concrete were obtained. Pure mode I, II, and III and mixed mode I/II and I/III fracture toughness of preplaced aggregate concrete mixtures were obtained using ENDB specimen. The accuracy of the data relevant to the experimental results was examined by standard prediction criteria. The fracture parameters (equivalent fracture toughness and work of fracture trend) for mode mixities I/II and I/III were investigated.