Experimental study on solidification of bauxite tailing clay with quicklime and microorganism

Because the pores of bauxite tailing clay are small, the microbial induced calcite precipitation (MICP) is rarely used in this research area at present. Based on the reclamation requirements of tailings pond, the quicklime and microbial co-curing technology (biochemical curing technology) is given to treat the super-wet bauxite tailing soil, and the results are compared with those by the lime curing treatment. Through SEM scanning, mercury injection tests, shear tests and compressibility tests, the change rules of element composition and microstructure and strength are revealed. The results show that numerous large pores are formatted by the hydration reaction between the quicklime and the water, which provides space for the survival of microorganisms. Ca(OH)₂ is generated by the reaction of quicklime and water in the bauxite tailings soil so as to increase the pH value and temperature. The soil temperature rise caused by the addition of quicklime is within the allowable range of the test strains. The sporosarcina pasteurii used in the experiment is alkali-resistant and can mineralize with Ca⁺ produced by the hydrolysis of quicklime. However, high alkalinity will affect the metabolism, and the content of quicklime should be controlled. The shear strength of the soil is improved and the compressibility is reduced after treated by the quicklime. The soil can be filled and bonded effectively by the biochemical curing, and the effect is better than that by the quicklime. The optimal amount of the quicklime in biochemical curing is 23.33 kg/m³.