Department of Metallurgical Engineering, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Ganesha 10, Bandung, 40132, Indonesia.
Geomicrobiology-Biomining & Biocorrosion Laboratory, Microbial Culture Collection Laboratory, Biosciences and Biotechnology Research Center (BBRC), Institut Teknologi Bandung, Ganesha 10, Bandung, 40132, Indonesia.
Sci Rep. 2020 Oct 21;10(1):17873. doi: 10.1038/s41598-020-74127-4.
Concrete can be harmful to the environment due to its high energy consumption and CO emission and also has a potential crack formation, which can promote a drop in its strength. Therefore, concrete is considered as a non-sustainable material. The mechanisms by which bacterial oxidation of organic carbon can precipitate calcite that may fill the voids and cracks on cement-based materials have been extensively investigated to prevent and heal the micro-cracks formation. Hence, this study focused on utilizing a new alkaliphilic bacterial strain indigenous to an Indonesian site, Lysinibacillus sphaericus strain SKC/VA-1, incorporated with calcium lactate pentahydrate, as a low-cost calcium source, with various bacterial inoculum concentrations. The bacterium was employed in this study due to its ability to adapt to basic pH, thus improving the physical properties and rejuvenating the micro-cracks. Experimentally, the addition of calcium lactate pentahydrate slightly affected the mortar properties. Likewise, bacteria-incorporated mortar exhibited an enhancement in the physical properties of mortar. The highest improvement of mechanical properties (an increase of 45% and 36% for compressive and indirect tensile strength, respectively) was achieved by the addition of calcium lactate pentahydrate incorporated with 10% v/v bacterial inoculum [about 7 × 10 CFU/ml (colony-forming unit/ml)]. The self-healing took place more rapidly on bacterial mortar supplemented with calcium lactate pentahydrate than on the control specimen. XRD analysis demonstrated that the mineralogical composition of self-healing precipitates was primarily dominated by calcite (CaCO), indicating the capacity of L. sphaericus strain SKC/VA-1 to precipitate calcite through organic carbon oxidation for self-healing the artificial crack on the mortar. To our knowledge, this is the first report on the potential utilization of the bacterium L. sphaericus incorporated with calcium lactate pentahydrate to increase the mortar properties, including its self-healing ability. However, further study with the water-cement ratio variation is required to investigate the possibility of using L. sphaericus and calcium lactate pentahydrate as an alternative method rather than reducing the water-cement ratio to enhance the mortar properties.
由于其高能耗和 CO 排放，混凝土对环境有害，而且还有潜在的裂缝形成，这可能会导致其强度下降。因此，混凝土被认为是一种不可持续的材料。细菌氧化有机碳沉淀方解石的机制已经被广泛研究，以防止和修复水泥基材料中的微裂缝形成。因此，本研究侧重于利用一种源自印度尼西亚的新的嗜碱性细菌菌株，即球形芽孢杆菌 SKC/VA-1 菌株，与乳酸钙五水合物结合，作为一种低成本的钙源，同时使用不同的细菌接种浓度。由于该细菌能够适应碱性 pH 值，从而改善物理性能并恢复微裂缝，因此在本研究中使用了该细菌。实验中，乳酸钙五水合物的添加略微影响了砂浆性能。同样，掺入细菌的砂浆表现出了更好的砂浆物理性能。添加乳酸钙五水合物并添加 10% v/v 细菌接种物（约 7×10 CFU/ml（菌落形成单位/ml））可使力学性能提高最高（抗压强度和间接拉伸强度分别提高 45%和 36%）。在补充了乳酸钙五水合物的细菌砂浆中，自修复过程比对照样发生得更快。XRD 分析表明，自修复沉淀物的主要矿物组成是方解石（CaCO3），这表明 L. sphaericus strain SKC/VA-1 菌株能够通过有机碳氧化沉淀方解石，从而自我修复砂浆上的人工裂缝。据我们所知，这是首次报道利用球形芽孢杆菌菌株 L. sphaericus 与乳酸钙五水合物结合来提高砂浆性能，包括其自修复能力。然而，需要进一步研究水灰比的变化，以研究利用 L. sphaericus 和乳酸钙五水合物作为替代方法而不是降低水灰比来提高砂浆性能的可能性。
