Study on the effect of cementation solution concentration on sand fixation by fiber reinforced MICP

This study systematically investigates the influence of cementation solution concentration on the sand fixation effect induced by palm fiber-enhanced microorganisms through microbial induced calcium carbonate precipitation (MICP), aiming to optimize its application in ecological restoration and engineering reinforcement. A series of experiments including unconfined compressive strength tests, direct shear tests, permeability tests, nuclear magnetic resonance analysis, calcium carbonate content determination, scanning electron microscopy (SEM), and X-ray diffraction (XRD) evaluates the mechanical properties, permeability, and microstructural characteristics of MICP-treated sand under varying cementation concentrations ranging from 0.2 to 0.7 mol/L. Results show that a concentration of 0.5 mol/L yields the best mechanical performance, with significantly higher unconfined compressive strength (666.65 kPa) and shear strength compared to other concentrations. At lower concentrations from 0.2 to 0.4 mol/L, increasing the concentration enhances calcium carbonate deposition, which improves mechanical properties and reduces both permeability coefficient and porosity. In contrast, higher concentrations above 0.5 mol/L inhibit microbial enzymatic activity, leading to reduced calcium carbonate content and mechanical strength, along with increased permeability and porosity. Microscopic analysis reveals that at 0.5 mol/L, calcium carbonate crystals form densely and uniformly, effectively filling pore spaces and strengthening inter-particle bonding. Therefore, 0.5 mol/L represents an optimal balance between performance and cost, reducing resource waste while ensuring mechanical enhancement and supporting applications in sand dune stabilization, windbreaks, sand fixation, and ecological vegetation restoration.