Experimental determination of the tension-softening relations for cementitious composites

Abstract

A novel experimental technique based on the J-integral is employed to experimentally determine the tension-softening (σ-δ) relations in cementitious composites. The σ-δ relation provides information on fracture resistance and could be used for numerical simulations of crack formation and propagation in structures constructed from materials which exhibit “tension-softening” behavior. With this method, no complicated modifications to testing machines are required. In the experiment, two pre-cracked specimens with slightly different notch lengths are used. The corresponding values of load, load point displacement and crack tip separation are simultaneously recorded. From this experimental data, the J-integral as a function of crack tip separation as well as the tension-softening curve can be deduced. These curves also provide a measure of the critical energy release rate. The experimental technique has been applied to mortar. It is suggested that the relatively simple technique can provide reliable material parameters for characterization of fracture resistance in plain and fiber reinforced cementitious composites independent of specimen geometry, size and loading configurations.