Calcium acetate as calcium source used to biocement for improving performance and reducing ammonia emission

Abstract

In construction engineering and mining engineering, CaCl2 is the most commonly used calcium source in microbial-induced carbonate precipitation (MICP) technology because it can generate CaCO3, which has a high degree of crystallization and is thermodynamically stable, in tailings or soil. However, this calcium source is not the best choice for biocement. This study aims to compare the stability, strength, NH3 emission, and other effects of CaCl2, Ca(CH3COO)2, and Ca(NO3)2 in bio-cement to determine the best calcium source for bio-cement. The results indicate that after curing for 28 days, the strength of bio-cement with Ca(CH3COO)2 as its calcium source is higher than that with CaCl2 and Ca(NO3)2 as calcium sources. After adding cement to three calcium sources (CaCl2, Ca(CH3COO)2, and Ca(NO3)2), the CH3COO− sample is more stable and has higher biomass and urease activity than the Cl− and NO3− samples. Since CH3COO− is a weak acid, CH3COOH generated by CH3COO− can easily react with NH3 under the alkaline condition provided by cement, reducing NH3 emissions. When Ca(CH3COO)2 was used as a calcium source, the NH3 emission of its sample decreased by 54.2% and 51.4% compared with CaCl2 and Ca(NO3)2. Therefore, CH3COO−, as an anionic calcium source, will have more application prospects than CaCl2 and Ca(NO3) in bio-cement production.