Department of Civil and Environmental Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-hiroshima, Hiroshima, 739-8527, Japan.
School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, USA.
Sci Rep. 2022 Jul 26;12(1):12754. doi: 10.1038/s41598-022-16879-9.
As a soil biomineralization process, casein-assisted enzyme-induced carbonate precipitation (EICP) yielded biocemented specimens with significantly higher compressive strength than specimens cemented by regular or skim-milk-assisted EICP treatments. The compound concentration and curing strategy of casein-assisted EICP were experimentally optimized to maximize the compressive strength of precipitates with low calcium carbonate content. Under the optimized EICP conditions (0.893 M urea, 0.581 M CaCl, 2.6 g/L urease enzyme, and 38.87 g/L casein), the unconfined compressive strengths reached 2 MPa. The scanning electron micrographs of selected samples provided microscopic evidence that EICP treatments assisted using skim milk and casein impart distinctive strength-enhancement mechanisms. The ammonium ions released from urea hydrolysis created an alkaline environment that makes casein dissociated into the pore water. As the casein-containing pore water became more viscous, the increased contact area with particles facilitated the precipitation of co-bound CaCO minerals and casein in the pore water. Casein was identified as a more efficient assisting agent than skim milk for low-level CaCO precipitation by EICP treatment.
作为一种土壤生物矿化过程，酪蛋白辅助酶诱导碳酸盐水（EICP）沉淀生成的生物固结标本的抗压强度明显高于常规或脱脂奶辅助 EICP 处理固结的标本。通过实验优化了酪蛋白辅助 EICP 的复合浓度和养护策略，以最大限度地提高低碳酸钙含量沉淀物的抗压强度。在优化的 EICP 条件下（0.893 M 尿素、0.581 M CaCl、2.6 g/L 脲酶和 38.87 g/L 酪蛋白），无侧限抗压强度达到 2 MPa。选定样品的扫描电子显微镜照片提供了微观证据，表明使用脱脂奶和酪蛋白辅助的 EICP 处理具有独特的增强强度机制。尿素水解释放的铵离子会产生碱性环境，使酪蛋白解离到孔隙水中。随着含有酪蛋白的孔隙水变得更加粘稠，与颗粒的接触面积增加，促进了共结合 CaCO 矿物和孔隙水中的酪蛋白沉淀。酪蛋白被确定为比脱脂奶更有效的 EICP 处理低水平 CaCO 沉淀的辅助剂。
