Mechanical properties of microorganism solidified red clay immobilized by activated carbon in Guiyang

Although microorganisms can solidify soil, its consolidation strength needs to be enhanced further. This work proposed a combination of immobilized microbial technology and microbial induced calcium carbonate precipitation technology (MICP). In this method, about 0, 4%, 7%, 10%, 15% of activated carbon is uniformly mixed with the remolded red clay, and the soil is solidified by MICP, then conventional triaxial compression tests are performed on soil samples. At the same time, comparison tests of generating calcium carbonate in the liquid bottle with or without the cement solution under the same conditions are carried out. By means of scanning electron microscopy analysis, the mechanical properties of the sample, the role of activated carbon in the MICP process, and the microstructure are obtained. The test results show that in the process of microbial solidification of soil, activated carbon acts as a carrier for immobilized microorganisms, which plays a role of the “enhancing effect” on microorganisms during the MICP process, and increases calcium carbonate production during microbial induced calcium carbonate precipitation. The presence or absence and content of the soil have an important influence on the microbial solidified soil. Combined with the change of water film thickness, filling of pores and cementation by calcium carbonate, the effective C value of the shear strength of red clay is greatly increased, the effective φ value is reduced, and the peak shear stress is increased. These changes demonstrate that adding activated carbon can optimize the biomineralization environment, and pose a certain control effect on the crystal structure and morphology during crystallization. Consequently, a block with a certain structure with activated carbon as the "core" is formed, and the mechanical properties of the soil are enhanced. This research would be valuable for future microbial geotechnical technology and engineering applications.