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The precipitation rate and cementation strength of calcium carbonate crystals during the process of microorganism-induced calcium carbonate precipitation (MICP) are key factors that affect the application effect of this technology. In order to improve the quality of calcium carbonate formation in the MICP process, egg white protein with a volume fraction of 20%, bovine serum albumin with a mass fraction of 0.3%, sucrose with a mass fraction of 5%, bamboo leaves with a mass concentration of 25 g/L, and bamboo leaf-magnesium chloride (M g 2 + / C a 2 + = 4 : 1) were added during the experiment of different groups of MICP solutions. The results of the solution test study showed that there was no obvious lag period for bacterial growth under the action of organic matrix. The concentration of bacteria in the reaction solution was higher under the action of sucrose and egg white. The conversion rate of Ca2+ under the action of egg white was the fastest, which was about 2.5 times higher than that of the control group. After 14 days of grouting reaction, it was found that the proportion of calcite-type calcium carbonate produced under the action of egg white was the highest, and the Ca element accounted for 66.24% in the solidified material. Sucrose was second; bovine serum albumin was the lowest. The calcium carbonate crystals generated by the control of each organic matrix had a high degree of pore size matching with the tailings under a dry-wet cycle. The structural characteristics of the calcium carbonate crystals, such as crystal form, morphology, and particle size, were mainly due to the interaction between the organic matrix and the calcium carbonate crystals. This study proves that the addition of the organic matrix can improve the formation rate and crystal structure of calcium carbonate during MICP, thus providing a new reference for the development of MICP technology. [ABSTRACT FROM AUTHOR]

Microbial Induced Calcium Carbonate Precipitation (MICP) has some disadvantages, such as low crystallization conversion rate of calcium carbonate and insufficient strength properties of tailings. In this paper, a modified method combining soft template calcium carbonate mineralization technology with microbial grouting reinforcement technology was proposed. The tailings solidification was studied with the control of nine different concentrations of egg white (0%, 5%, 10%, 15%, 20%, 30%, 40%, 60% and 80%). After 14 days of grouting reinforcement experiment, the results are as follows. ① The shear strength of tailings was improved remarkably, and the best reinforcement effect was at 5% egg white. Compared with the control group, the effective cohesion of tailings increased by 437.61%. ② The fitting curve between the content of calcium carbonate in tailings and its cohesion shows that there is an exponential relationship between them. ③ The results of microscopic examination showed that the proportion of columbite-type calcium carbonate increased with the increase of egg white concentration. The corresponding egg white concentration of calcite-type calcium carbonate was 5%. At this time, the maximum particle size could reach 100 µm. ④ The infrared absorption characteristic curves of the interporous cements of tailings indicate that the changes of crystal form, crystal morphology and particle size of calcium carbonate may be due to the strong interaction between polar groups such as N H, C H and C O in the composition of egg white and calcium carbonate crystal. ⑤ The bonding, connecting and packaging of fibers in egg white will cause fundamental changes in the bonding mode of tailings. The test results showed that the combination of mineralization regulation of egg white and MICP technology can achieve complementary advantages, which is of great engineering significance for improving the stability and safety of tailings dam. [ABSTRACT FROM AUTHOR]