In microbially induced calcium carbonate precipitation (MICP) process, it is the precipitated calcium carbonate that cements loose sand particles together to improve their mechanical properties. Seashell nacre composed of calcium carbonate is a natural product, which is worth researching for its remarkable hardness, strength and toughness. However, there has been no study that bridges this natural nacre mineralisation with MICP. Therefore, a precedent herein is established to modify the MICP process by way of the water-soluble matrix (WSM) extracted from nacre, where WSM contributes to the great mechanical properties of nacre. This study examines the effects of WSM with different concentrations on urease activity of bacteria and strength as well as the microstructure of bio-cemented sand samples. The results show that a small number of WSM (50 mg/l) can improve the average strength of bio-cemented sand samples by 1·5 times. This is because 50 mg/l WSM can significantly improve the urease activity. Thus, more calcium carbonate crystals are precipitated, and the higher unconfined compressive strength of bio-cemented sand samples is achieved. The microstructures are investigated by x-ray diffraction and scanning electron microscopy. Overall, this study is an unprecedented exploration imitating nacre that hopefully paves way for future studies.

中文翻译：

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通过珍珠层提取物改善微生物诱导的碳酸钙沉淀效果

在微生物诱导的碳酸钙沉淀 (MICP) 过程中，沉淀的碳酸钙将松散的沙粒粘合在一起以改善其机械性能。由碳酸钙组成的贝壳珍珠层是一种天然产物，其卓越的硬度、强度和韧性值得研究。然而，还没有研究将这种天然珍珠层矿化与 MICP 联系起来。因此，本文建立了一个先例，通过从珍珠层中提取的水溶性基质 (WSM) 来改进 MICP 工艺，其中 WSM 有助于珍珠层的出色机械性能。本研究考察了不同浓度的 WSM 对细菌脲酶活性和强度以及生物胶结砂样品微观结构的影响。结果表明，少量的WSM（50 mg/l）可使生物胶结砂样品的平均强度提高1·5倍。这是因为 50 mg/l WSM 可以显着提高脲酶活性。因此，更多的碳酸钙晶体析出，生物胶结砂样品的无侧限抗压强度更高。通过X射线衍射和扫描电子显微镜研究微观结构。总体而言，这项研究是一项前所未有的模仿珍珠层的探索，有望为未来的研究铺平道路。通过X射线衍射和扫描电子显微镜研究微观结构。总体而言，这项研究是一项前所未有的模仿珍珠层的探索，有望为未来的研究铺平道路。通过X射线衍射和扫描电子显微镜研究微观结构。总体而言，这项研究是一项前所未有的模仿珍珠层的探索，有望为未来的研究铺平道路。