Experimental study on performance of MICP solidified sand enhanced by alkali modified fly ash

The application of alkali modified fly ash in MICP technology can fully utilize its adsorption performance, reduce the ammonia nitrogen generated during the MICP process, and open up new avenues for environmentally friendly soil solidification technology. This article conducts macroscopic and microscopic experimental research on alkali modified fly ash as a reinforcing agent to enhance MICP solidified sand. The research contents cover the determination of bacterial fixation rate, ammonia removal rate, calcium carbonate content, uniaxial compressive strength, permeability, and scanning electron microscopy (SEM) observation. The results show that: (1) The alkali modified fly ash significantly improves the removal efficiency of ammonia nitrogen, reaching 62.6%. Compared with unmodified fly ash, its ability to adsorb ammonia nitrogen increases by 42.2%. (2) During the process of microbial induced calcium carbonate precipitation (MICP) reinforcement of sandy soil, alkali modified fly ash can significantly improve the bacterial fixation rate and cement production. The bacterial fixation rate almost doubles, and when the dosage is 7%, the proportion of cement generation reaches 17.3%. (3) The addition of alkali modified fly ash helps to enhance the compressive strength and impermeability of the solidified body. When the dosage is 7%, the compressive strength of MICP solidified sand is increased by 2.6 times, and the permeability coefficient is reduced by two orders of magnitude.