Gu Zhaorui, Chen Qing, Wang Lishuang, Niu Shuang, Zheng Junjie, Yang Min, Yan Yunjun
Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China.
Institute of Geotechnical and Underground Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
Materials (Basel). 2022 Nov 3;15(21):7754. doi: 10.3390/ma15217754.
Recently, microbially induced carbonate precipitation (MICP) has shown potent potential in the field of civil engineering. The calcium carbonate crystals produced by bacteria during the MICP process play a central role in sticking the soil. However, the morphological changes of calcium carbonate crystals in this process and the mechanical performance of soil in the corresponding stages have not been clearly explored. In this paper, the alterations in the morphology of calcium carbonate crystals were continuously observed via scanning electron microscopy during the MICP process in one week, and the mechanical changes of the samples were monitored every day, so as to reveal the relationship between the morphology of calcium carbonate crystals and the mechanical performance of the samples. The results show that the calcium carbonate crystals undergo a gradual change from ellipsoid to rhombic at the 72nd hour. The mechanical properties of both were greatly improved, among which the compressive strength was increased by 2.78 times compared with the previous time point, and the flexure strength was increased by 2.57 times; this time point was also the time when calcite appears. In addition, we found direct evidence on the first day that bacteria act as the nucleation site of calcium carbonate formation. The above findings have certain guiding significance for the in-depth understanding of the internal microscopic changes of MICP and the influence of calcium carbonate morphology on sample mechanics.
最近，微生物诱导碳酸钙沉淀（MICP）在土木工程领域展现出巨大潜力。在MICP过程中，细菌产生的碳酸钙晶体在加固土壤方面起着核心作用。然而，这一过程中碳酸钙晶体的形态变化以及相应阶段土壤的力学性能尚未得到清晰探究。本文通过扫描电子显微镜在一周的MICP过程中持续观察碳酸钙晶体的形态变化，并每天监测样品的力学变化，以揭示碳酸钙晶体形态与样品力学性能之间的关系。结果表明，在第72小时，碳酸钙晶体从椭球形逐渐变为菱形。两者的力学性能均得到显著改善，其中抗压强度较上一个时间点提高了2.78倍，抗弯强度提高了2.57倍；这个时间点也是方解石出现的时间。此外，我们在第一天就找到了细菌作为碳酸钙形成的成核位点的直接证据。上述发现对于深入理解MICP的内部微观变化以及碳酸钙形态对样品力学的影响具有一定的指导意义。
