Cement-based materials are subject to degradation during their service life. Most of the structural failures have been associated with corrosion of the rebar due to chloride ingress, alkali aggregate reaction, and/or sulfate attack. Microbial activities, especially in waste water collection points such as sewer lines, may compromise the integrity of concrete structures. This study reports an experimental work carried out to determine the effect of Starkeya novella bacteria species on mechanical and microstructural properties of cement mortars. Mortar prisms were prepared from selected ordinary Portland cement (OPC) and Portland pozzolana cement (PPC) in Kenyan markets. Bacterial solution of 1.0 × 107 cell/mL concentration was used as either mix water, curing media, or both. Distilled water was used to prepare mortar prisms for control samples. Compressive strength was determined after the 7th, 28th, 56th, and 90th day of curing. Scanning electron microscopy (SEM) was tested on both bacterial and control mortar prisms after the 28th day of curing. Both PPC and OPC exhibited significant decrease in compressive strength for bacterial-prepared mortars as compared to controls. SEM analysis showed extreme erosion on the microstructure of the microbial mortars. This was denoted by massive formation of ettringite and gypsum which are injurious to mortar/concrete.

中文翻译：

---

Starkeya中篇小说对水泥砂浆力学和微观结构性能的影响

水泥基材料在其使用寿命期间会发生降解。大多数结构故障与由于氯化物进入、碱骨料反应和/或硫酸盐侵蚀导致的钢筋腐蚀有关。微生物活动，尤其是在污水收集点（例如下水道）中的微生物活动，可能会损害混凝土结构的完整性。本研究报告了一项实验工作，以确定 Starkeya 中型细菌对水泥砂浆机械和微观结构性能的影响。砂浆棱柱由肯尼亚市场上选定的普通波特兰水泥 (OPC) 和波特兰火山灰水泥 (PPC) 制成。1.0 × 107 细胞/mL 浓度的细菌溶液用作混合水、固化介质或两者。蒸馏水用于制备对照样品的砂浆棱柱。在固化第 7、28、56 和 90 天后测定抗压强度。在固化第 28 天后，对细菌和对照砂浆棱镜进行了扫描电子显微镜 (SEM) 测试。与对照相比，PPC 和 OPC 均表现出细菌制备砂浆的抗压强度显着降低。SEM 分析表明微生物砂浆的微观结构受到极大侵蚀。这由对砂浆/混凝土有害的钙矾石和石膏的大量形成表示。SEM 分析表明微生物砂浆的微观结构受到极大侵蚀。这由对砂浆/混凝土有害的钙矾石和石膏的大量形成表示。SEM 分析表明微生物砂浆的微观结构受到极大侵蚀。这由对砂浆/混凝土有害的钙矾石和石膏的大量形成表示。