Recycled concrete aggregate (RCA) has been used as an alternative sustainable material in the construction industry, but RCA long-term environmental impacts are unknown. In this study, the bacterial enrichment potential to reduce the alkalinity of two different types of RCA was examined, from laboratory-produced concrete and from a stockpile of demolished concrete that had been in service in transportation applications. Washed and un-washed lab and field RCA were biostimulated by being exposed to ATCC® Medium 661 in batch experiments. pH, metal composition and microbial community changes in the leachates were monitored over time. Results show that initial pH of field RCA leachate could be decreased to less concerning values, as low as 8, but concentrations of some metals in the leachate exceeded groundwater quality standards. However, the biostimulated RCA released lower metal concentration and was more resistant to pH increases than non-biostimulated RCA during a long-term leaching experiment with DI water. The microbial community was enriched on anaerobic, halotolerant and alkaliphile microorganisms, resistant to extreme environmental conditions. The outcome of this research suggests a baseline for field RCA pretreatment before field application, using a biostimulation method that would generate a less environmentally detrimental runoff.

再生混凝土骨料 (RCA) 已被用作建筑行业的替代可持续材料，但 RCA 对环境的长期影响尚不清楚。在这项研究中，研究了降低两种不同类型 RCA 碱度的细菌富集潜力，这些 RCA 来自实验室生产的混凝土和已在运输应用中使用的拆除混凝土堆。洗涤和未洗涤的实验室和现场 RCA 通过暴露于ATCC® 培养基 661进行生物刺激在批量实验中。随着时间的推移监测渗滤液中的 pH 值、金属成分和微生物群落变化。结果表明，现场 RCA 渗滤液的初始 pH 值可以降低到不太重要的值，低至 8，但渗滤液中某些金属的浓度超过了地下水质量标准。然而，在使用 DI 水的长期浸出实验中，生物刺激的 RCA 释放的金属浓度较低，并且比非生物刺激的 RCA 更能抵抗 pH 值升高。微生物群落富含厌氧、耐盐和嗜碱微生物，能够抵抗极端环境条件。这项研究的结果提出了在现场应用前使用生物刺激方法进行现场 RCA 预处理的基线，该方法将产生对环境危害较小的径流。