Failure criterion and compressive constitutive model of seawater concrete incorporating coral aggregate subjected to biaxial loading

Abstract

To overcome the lower bearing strength of coral concrete and the high cost of conveying raw materials from the mainland to the island, a new method was presented. This method suggested to apply the coral aggregate instead of the natural coarse aggregate (NCA) in seawater concrete, which was denoted as CAC. In this paper, 18 axial loading prism specimens and 90 cubic lateral loading specimens were cast. Two concrete strengths, three replacement ratios of coral coarse aggregate (CCA) (50%, 75% and 100%) and five biaxial stress ratios (0, 0.15, 0.3, 0.45 and 0.75) were designed. A Digital Image Correlation (DIC) system was used to investigate all the failure patterns and stress–strain curves, which were used to analyze the influence of the above parameters on the peak stress and the peak strain. In addition, the lateral–axial strain relationship and biaxial failure criterion were also established. After determining the biaxial failure surface, a hardening law and a softening law were proposed to describe the uniaxial stress–strain curves based on the Weibull distribution and Guo’s model, respectively. Finally, a new constitutive model for CAC under biaxial stress was developed using the two-dimensional incremental constitutive model. The results indicated that the crack development of CAC was similar to that of natural coarse aggregate concrete (NAC), and the failure patterns of biaxial specimens were related to the biaxial stress ratio. Furthermore, the biaxial stress showed an increase in the peak stress and the peak strain. The increase in CCA replacement weakened the enhancement effect on the peak stress, while it slightly influenced the peak strain. Additionally, the proposed lateral–axial strain model and biaxial failure criterion were in good agreement with the measured results. Through comparison, the proposed biaxial incremental constitutive model was verified using the tested curves.