As an environmentally friendly biotechnology, the microbial induced calcium carbonate precipitation (MICP) provides a new approach to repair concrete cracks. Most existing studies focused on finding a suitable environment for bacteria to induce as much calcium carbonate as possible, but the effect of actual concrete service environment on the repair of concrete cracks was usually ignored. This work compared the repair quality of cracked specimens via MICP with the original strain and salt-tolerant strain in the deionized water and simulated seawater. Then the adverse effects of seawater ions on the MICP process was investigated. The results showed that the permeability coefficient of repaired specimens was 175.7 % higher, and the bond strength between the calcium carbonate and concrete surface was lower in the simulated seawater as compared with the deionized water environment. The high concentration of sodium, chloride, magnesium, and sulfate ions in the seawater led to the decrease of the urea decomposition rate and calcium carbonate yield rate, which further induced the decreased super-saturation of calcium carbonate and the conversion of the calcium carbonate crystal form from calcite to vaterite. Besides, the salt-tolerant strain with a high salt adaptability showed a higher repair ability in the simulated seawater as compared with the original strain.

中文翻译：

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MICP过程中海水离子对尿素分解和碳酸钙沉淀的影响


微生物诱导碳酸钙沉淀（MICP）作为一种环境友好的生物技术，为修复混凝土裂缝提供了新的途径。现有的研究大多集中于寻找一个适合细菌诱导尽可能多的碳酸钙的环境，但实际混凝土使用环境对混凝土裂缝修复的影响通常被忽视。这项工作将通过 MICP 修复裂纹样本的质量与去离子水和模拟海水中的原始应变和耐盐应变进行了比较。然后研究了海水离子对MICP过程的不利影响。结果表明，与去离子水环境相比，修复试件在模拟海水中的渗透系数提高了175.7%，碳酸钙与混凝土表面的粘结强度较低。海水中钠、氯、镁、硫酸根离子浓度较高，导致尿素分解率和碳酸钙产率下降，进一步诱发碳酸钙过饱和度降低和碳酸钙晶体转化。形成从方解石到球霰石。此外，具有高盐适应性的耐盐菌株在模拟海水中表现出比原始菌株更高的修复能力。