Experimental Study on Mechanical Properties and Failure Criteria of Self-Compacting Concrete under Biaxial Tension-Compression

In order to explore the basic mechanical properties of self-compacting concrete, ordinary concrete, lightweight aggregate concrete, self-compacting ordinary concrete, and self-compacting lightweight aggregate concrete were tested under biaxial tension-compression using a large true triaxial test machine. The failure modes and principal tensile stress-strain curves under different lateral pressures were obtained. By comparing the characteristic values of principal tensile stress and analysis of failure mechanisms, the mechanical characteristics of self-compacting concrete under biaxial tension-compression were studied. The results show that these four types of concrete are subject to the tensile failure model under different lateral compressive stresses. The splitting lines of ordinary concrete and self-compacting ordinary concrete are relatively straight considering less influence of lateral compressive stress, whereas those of lightweight aggregate concrete and self-compacting lightweight aggregate concrete exhibit an irregular bending radian. With the increase of lateral compressive stress, the principal tensile stress of these four concrete materials reduces gradually, and the effect of ratio of pressure and concrete strength becomes more significant. Based on biaxial tension-compression failure criteria and octahedral stress space failure criteria from the literature, two different failure criteria were proposed. Analysis of the failure mechanism indicated that the water:cement ratio (w/c) and material compactness have a greater effect on the change trend of principal tensile stress influenced by lateral compressive stress. Results drawn from this study can serve as an essential reference on the engineering applications of self-compacting concrete.