科氏芽孢杆菌对再生粗骨料混凝土抗压强度的影响

将实验室废弃的强度等级为C30混凝土试块经人工破碎后通过筛选得到粒径为20～50 mm的再生粗骨料。为探究科氏芽孢杆菌矿化沉积对再生粗骨料的影响,研制了不同pH条件科氏芽孢杆菌菌液浸泡处理的再生粗骨料。利用科氏芽孢杆菌菌液浸泡处理后的再生粗骨料(取代率选用20%)制备再生骨料混凝土,开展了再生骨料混凝土试件的单轴抗压强度和声发射损伤特征试验,分析了不同pH条件的科氏芽孢杆菌矿化沉积再生粗骨料对浸泡液残余Ca²⁺浓度、混凝土峰值抗压强度和损伤演化的影响。试验结果表明:科氏芽孢杆菌菌液浸泡处理再生粗骨料后,残余Ca²⁺浓度随浸泡液pH值的减小而减少,科氏芽孢杆菌菌液浸泡能有效改善再生粗骨料的密实性,且酸性条件下效果最好;再生粗骨料经酸性环境的科氏芽孢杆菌菌液浸泡处理后制备的再生骨料混凝土的峰值强度有明显的提高;在抗压过程中,损伤演化减缓,损伤劣化程度降低,当浸泡液从pH=8到pH=5时,再生骨料混凝土损伤变量逐渐减小且累积损伤明显降低。研究成果可为微生物改良再生骨料的实际应用提供参考。

Effect of Recycled Coarse Aggregate Soaked in Bacillus Cohnii Solution on Compressive Strength of Concrete

The compressive strength and damage evolution of recycled coarse aggregate concrete under the influence of mineralization and precipitation of Bacillus Cohnii were examined via uniaxial compression test and acoustic emission test. The recycled coarse aggregates used in the present test were prepared from waste C30 concrete blocks through crushing and screening (particle size in the range of 20-50 mm), and then soaked in Bacillus Cohnii solutions of different pH values. In subsequence, the recycled coarse aggregates were used for preparing recycled concrete specimens with a replacement ratio of 20%. Test results demonstrated that the residual Ca²⁺ concentration in the used solution declined with the reduction of pH value, which implied that Bacillus Cohnii solution enhanced the compactness of recycled coarse aggregates, especially under acidic environment. Concrete made of the treated recycled aggregates witnessed a notable increment in peak strength. During compression, damage evolution alleviated and damage deterioration attenuated. The damage variable and cumulative damage of concrete specimens made of recycled aggregates soaked in solution of pH=8 were evidently smaller than those in solution of pH=8.