Experimental investigation on the triaxial behavior of lightweight concrete

In this research, active true triaxial tests with different stress ratios were conducted on cubic specimens made from structural lightweight aggregate concrete (LWAC) to study their mechanical behavior. Different combinations of normal stresses were applied to the specimens to obtain various load paths and load angles. Force and displacement values were recorded during the tests, and stress-strain curves were plotted at each principal direction. Furthermore, the obtained peak stresses at failure points were used to draw the compressive and tensile meridians and failure surfaces in the deviatoric plane. Results show that different combinations of lateral confining stresses have a remarkable effect on the strength and deformation of LWAC under triaxial stresses. Results of the tests intended to capture the compressive meridian show that the variation of lateral confining stresses in a range of (0 - 0.98)f(cu) yields in peak axial stresses, which vary in a range of (1.00-4.38)f(cu) In contrast, for the tests aimed to obtain the tensile meridian, the change in the lateral confining stress in a range of (0-0.25)f(cu) leads to the peak axial stress variations in the range of (1.14-1.92)f(cu) Comparison of different types of LWAC shows that increasing the uniaxial strength of LWAC leads to improvement in their triaxial compressive characteristics. Finally, the model parameters of the well-known Willam-Warnke five-parameter failure criterion for normal concrete were modified for LWAC based on the test results. The experimental test data of the current study can be used for the development of other constitutive models for LWAC.