Abstract

One of the most important material used in the construction industry is concrete. Adaptability with steel also provides the necessary tensile strength for constructing towering structures. However, concrete is susceptible to shrinkage during the curing process which produces micro cracks. These tiny fissures provide gateways to fluids for entering into concrete. The fluids undergo various reactions under favorable conditions inside concrete reducing the pH of concrete core, making the reinforcing bars vulnerable to corrosion. This presents serious durability issues for the whole structure and bio-concrete is a solution for the same. Various studies have dealt with usages of bacillus bacteria and metakaolin to improve some parameters in concrete. Bacteria produces calcium carbonate (calcite) by urea–calcium chloride reactions inside concrete thereby reducing the threat of fluid penetration. Previous works that metakaolin reacts with calcium hydroxide (responsible for durability issues) produces secondary cementitious products, increasing the density of concrete. This study examines the usage of Bacillus megaterium MTCC 3353 in concrete with metakaolin as partial substitution for cement. It was found that the strength and durability properties exhibited by bio-concrete were overall satisfactory compared to ordinary concrete. The calcite precipitation due to the bacterial action was studied through microstructure analysis by SEM and XRD.

摘要

建筑业中使用的最重要的材料之一是混凝土。与钢的适应性也为建造高耸的结构提供了必要的抗拉强度。然而，混凝土在养护过程中容易收缩，从而产生微裂缝。这些微小的裂缝为流体进入混凝土提供了通道。流体在混凝土内部的有利条件下发生各种反应，降低了混凝土芯的 pH 值，使钢筋容易受到腐蚀。这对整个结构提出了严重的耐久性问题，而生物混凝土是解决这一问题的方法。各种研究都涉及使用芽孢杆菌和偏高岭土来改善混凝土中的某些参数。细菌通过尿素-氯化钙在混凝土内的反应产生碳酸钙（方解石），从而减少流体渗透的威胁。偏高岭土与氢氧化钙反应（负责耐久性问题）的先前工作会产生二次胶凝产品，从而增加混凝土的密度。本研究探讨了使用用偏高岭土部分替代水泥的混凝土中的巨大芽孢杆菌MTCC 3353。结果表明，与普通混凝土相比，生物混凝土的强度和耐久性能总体上令人满意。通过SEM和XRD的微观结构分析研究了由于细菌作用引起的方解石沉淀。