Experimental study on the fluidity and strength of enzyme-assisted MgO fluidized solidified soil

Enzyme-assisted MgO carbonation (EMC) is a novel, environmentally friendly curing method that combines the advantages of various materials. It has been successfully applied in sand curing and cultural relic restoration. In the Loess Plateau region, check dams, which serve as crucial soil and water conservation structures, have long been susceptible to severe erosion and dam failure risks. This study explores an innovative curing method by integrating the EMC technique with fluidized solidified technology. The fluidity and strength of the enzyme-assisted MgO carbonation fluidized solidified (EMCF) soil were examined via fluidity tests, rheological analyses, and unconfined compressive strength assessments. Additionally, the mineral composition and structure of the EMCF soil were investigated via X-ray diffraction, thermogravimetric analysis, and scanning electron microscope. Results showed that the EMCF mud could be molded within 24 hours. The initial fluidity of the mud decreased with increasing MgO content but increased with higher liquid-solid ratios or urea concentrations. Conversely, the unconfined compressive strength of the coagulated mud exhibited the opposite trend. Carbonate ions, produced by soybean enzyme-catalyzed urea decomposition, combined with MgO to generate various biocarbonated minerals, identified as hydrated magnesium carbonates and nesquehonite. The reticulation of hydrated magnesium carbonate significantly enhances soil properties through multiple mechanisms. It increases interfacial friction between soil particles, fills interstitial voids, and encapsulates adjacent fine particles. These processes collectively improve soil cohesion and structure, resulting in a substantial increase in strength, with maximum values reaching approximately 1.2 MPa. While enzymes catalyzed urea decomposition to produce carbonate ions, thereby accelerating MgO hydration and carbonation, the rate of the carbonation reaction had less impact on strength compared to the liquid-solid ratio. In conclusion, EMCF shows promise as a potential method for soil solidification and void filling. • Novel integration of enzyme-assisted MgO carbonation with fluidized solidified soil technology. • Systematic study of curing mechanisms and influential factors in combined approach. • Evaluates fluidity and strength properties of various mixing ratios.