Microbially induced carbonate precipitation (MICP), an emerging technique recently, has been investigated in extensive studies for its ability to improve or enhance the properties of materials. This paper mainly explored the effect of MICP on the early strength and hydration products in fly ash blended cement paste (FABC) under different MICP treatment measures. Firstly, the influence of different environment on the growth of microorganism and three calcium source (CaCl, Ca(CHCOO) and Ca(NO)) on the production of calcium carbonate precipitation were investigated. The experimental results presented that the efficiency of CaCO precipitation in the Ca(NO) sample by adding bacterial solution is higher than other groups. Compared to untreated specimens, the mechanical properties of FABC paste are adversely affected by direct mixing with bacterial solution (MICP1) due to the fact that the hydration reactions of CS and Ca(OH)(CH) in FABC system were negatively affected as indicated by the hydration heat measurement. In contrast, the early performance of drying-immersing sample in bacterial solution (MICP2) was improved, with a maximum efficacy of 52.03%. The hydration process was facilitated in FABC paste treated with MICP2 treatment, further leading to increased formation of CH, C-S-H and AFt. Furthermore, Nanoindentation showed the HD C-S-H gel and CH were the dominant phases in MICP2 samples, and the matrix became denser with more hydration products, which also confirmed the increase in macroscopic compressive strength. The findings of this work can provide a guidance for the application of FA based on MICP method for enhancing the early strength in cementitious materials.

中文翻译：

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微生物诱导碳酸盐沉淀（MICP）对粉煤灰掺合水泥早期强度增强和微观力学性能的影响

微生物诱导碳酸盐沉淀（MICP）是最近一项新兴技术，因其改善或增强材料性能的能力而受到广泛研究。主要探讨了不同MICP处理措施下MICP对粉煤灰掺合水泥浆体(FABC)早期强度和水化产物的影响。首先考察了不同环境对微生物生长的影响以及三种钙源(CaCl、Ca(CH3COO)和Ca(NO))对碳酸钙沉淀生成的影响。实验结果表明，添加菌液在Ca(NO)样品中沉淀CaCO的效率高于其他组。与未经处理的样品相比，直接与细菌溶液 (MICP1) 混合，FABC 糊剂的机械性能受到不利影响，因为 FABC 系统中 CS 和 Ca(OH)(CH) 的水合反应受到负面影响，如下所示：水化热测量。相比之下，菌液干燥浸泡样品（MICP2）的早期性能有所改善，最大功效为52.03%。经过 MICP2 处理的 FABC 糊剂促进了水合过程，进一步导致 CH、CSH 和 AFt 的形成增加。此外，纳米压痕显示HD CSH凝胶和CH是MICP2样品中的主要相，并且基质变得更致密，水化产物更多，这也证实了宏观抗压强度的增加。这项工作的结果可以为基于MICP方法的FA用于提高胶凝材料早期强度的应用提供指导。