Effect of MICP-recycled shredded coconut coir (RSC) reinforcement on the mechanical behavior of calcareous sand for coastal engineering

Abstract

The combination of fiber reinforcement method with microbially induced carbonate precipitation (MICP) for calcareous sand treatment has been widely concerned. In this study, the effects of initial relative density (Dr=30%, 50%, 70%) and MICP treatment (N = 2, 4) on calcareous sand samples with different recycled shredded coconut coir (RSC) content (C = 0.00%, 0.20%, 0.40%, 0.60%) were investigated through a series of comparative tests. The results showed that the calcium carbonate content of the cemented samples was not significantly related to the RSC content, but was related to the relative density of the sand itself. The larger the relative density of the sand, the smaller the porosity, which is not conducive to the generation of calcium carbonate. The maximum shear modulus and permeability coefficient of the samples were positively related to the N and Dr, and exponentially related to the calcium carbonate content. The treated calcareous sand samples after N = 4 showed brittle failure characteristics, and the addition of RSC improved this result. For the peak stress of samples, the optimum amount of RSC was about 0.4% under different conditions. Scanning electron microscopy of shear-failure samples showed that calcium carbonate crystals could bind the sand and RSC and increase the contact area between them.