Recent studies in the field of concrete materials show that the early cracking criteria in micro-size can occur as soon as the cement matrix becomes hardened. In many ways, these cracks can become macro-size and opened cracks resulting in significant issues for the durability and appearance of concrete structures as water leakage and corrosion. The technique of self-healing using bacteria has recently received attention for its potential applications. However, the effectiveness and the repeatability of this method over a long period have not been clarified. The information on both the survival and the number of bacteria after healing is limited. This paper aims to improve the self-healing ability and repeatability of concrete when using Bacillus subtilis natto. The experimental studies evaluate the effect of biomineralization with lightweight aggregate as the protecting-carrying vehicle, which can control the release of healing fluid through four cracking-healing cycles. The urease activity and the biomineralization of the bacteria with urea as the main carbon source were assessed and the effect of cracking age on the self-healing capacity, associated with the compressive strength improvement was studied. The results obtained from the optical microscope and SEM/EDS analysis indicated the existence of bacteria CaCO3 forming in concrete after four healing cycles. During long duration, bacterial concentration in concrete was determined by microscopic counting method. Based on experimental results, the restoration of the compressive strength confirmed the high self-healing ability of concrete when using bacteria in lightweight aggregate.

中文翻译：

---

纳豆枯草芽孢杆菌生物矿化对自愈混凝土重复性及强度提高的研究

混凝土材料领域的最新研究表明，一旦水泥基体硬化，就会出现微观尺寸的早期开裂标准。在许多方面，这些裂缝可以变成宏观尺寸和开放裂缝，导致混凝土结构的耐久性和外观出现重大问题，如漏水和腐蚀。利用细菌进行自我修复的技术最近因其潜在的应用而受到关注。然而，这种方法在很长一段时间内的有效性和可重复性尚未阐明。关于愈合后细菌的存活率和数量的信息是有限的。本文旨在提高使用纳豆枯草芽孢杆菌时混凝土的自愈能力和重复性。实验研究评估了以轻质骨料作为保护载体的生物矿化效果，该载体可以通过四个裂化-愈合循环控制愈合液的释放。评估了以尿素为主要碳源的细菌的尿素酶活性和生物矿化，并研究了开裂年龄对自愈能力的影响，与抗压强度的提高有关。从光学显微镜和 SEM/EDS 分析获得的结果表明，在四个愈合周期后，混凝土中存在形成 CaCO3 的细菌。长时间使用显微计数法测定混凝土中细菌浓度。根据实验结果，