Triaxial Compressive Strength of Concrete Subjected to High Temperatures

An experimental study was undertaken to develop an extension of Mohr-Coulomb and Newman models to predict the failure of concrete subjected to elevated temperatures. Concrete specimens of 83x166-mm dimensions were prepared and subjected to various temperature levels of 300, 500, and 700 degrees C. The tests were carried out in triaxial cell using various confining stress levels. The applied confining pressures varied between 1.4 and 24MPa, corresponding to 3 and 54% of the uniaxial compressive strength. Test results indicated that the increase in temperature and/or confining pressure lead to a significant change in the mechanical properties of concrete. Furthermore, the Mohr-Coloumb and Newman models did not provide good fitting of the experimental data obtained on concrete subjected to high temperature of up to 700 degrees C. A dehydrate index is introduced and used to define new variables in the existing models. The modified models are shown to adequately predict the residual strength of concrete that has been subjected to high temperatures.