Abstract:

The development of green and low-carbon chemical solidification technology is crucial for rapid solidification of soft ground under the “Dual Carbon” context. This study introduces an innovative synergistic technology that combines active nano-SiO₂with microbial induced carbonate precipitation (MICP) for sludge solidification. Through unconfined compressive strength tests, pH monitoring, Ca²⁺ utilization rate analysis, and scanning electron microscopy, the reinforcement efficiency and micromechanisms of this technology are examined. Key findings include: 1) An increase in compressive strength of nano-SiO₂-MICP solidified sludge is observed with increasing nano-SiO₂ content up to 0.1%. 2) Samples treated with 0.1% nano-SiO₂at Ca²⁺ concentrations of 0.5, 1, and 2 mol/L exhibit compressive strength enhancements of 64.21%, 10.28%, and 75.98%, respectively, compared to those without nano-SiO₂. 3) Nano-SiO₂ provides new nucleation sites for MICP, fills pores, induces aragonite-to-calcite transformation, and forms cementitious gels, thereby boosting sample strength. 4) The presence of nano-SiO₂enhances Ca²⁺ utilization and pH regulation within the pore solution. Together, microbial-induced bio-CaCO₃ processes (cementation, filling, bridging) and nano-SiO₂-induced physicochemical effects (new nucleation sites, micro aggregate filling, and gelling products) synergistically improve the mechanical properties of solidified sludge and optimize the microscopic structural construction.

Key words: Nano-SiO₂, microbial induced carbonate precipitation, unconfined compressive strength, Ca²⁺ utilization, scanning electron microscopy, solidified sludge