Study on Fracture Behavior of Concrete by means of Fracture Mechanics Approach

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We studied the testing methods to determine the fracture energy (energy required for unit crack area) and the tension softening curves (relations between tensile stress and crack opening at cracked region) of concrete. We also investigated the numerical methods to simulate fracture behavior of concrete using these fracture mechanics parameters and the evaluation methods of concrete properties. Following results were obtained.(1) Tension softening curves of concrete were measured from the newly proposed tube tension tests, where specimens with two cylindrical slits were subjected to compression load.(2) The crack propagation process was detected by means of AE (acoustic emission) source location tests. It was observed that the distribution of damages was not uniform.(3) The new testing method based on J-integral concept to determine tension softening curves from bending tests was proposed. The tension softening curves of steel fiber reinforced concrete were obtained by this new testing method. They were quite similar to those obtained from direst tension tests. The testing conditions to obtain stable results were presented by numerical analysis.(4) Concrete cracks due to alkali-aggregate reaction were numerically simulated by FEM, where tension softening of concrete was considered.(6) Tension softening curves and the fracture energy of various kinds of concrete, including resin concrete, light weight concrete, concrete in early ages, damaged concrete due to AAR, etc. were measured. It was observed that these fracture mechanics parameters were suitable for evaluation of concrete tension properties.(7) The beak-off tests, one of local destructive tests, were improved to measure tension softening curves of concrete.