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

In construction engineering and mining engineering, CaCl 2 is the most commonly used calcium source in microbial-induced carbonate precipitation (MICP) technology because it can generate CaCO 3 , 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, NH 3 emission, and other effects of CaCl 2 , Ca(CH 3 COO) 2 , and Ca(NO 3 ) 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(CH 3 COO) 2 as its calcium source is higher than that with CaCl 2 and Ca(NO 3 ) 2 as calcium sources. After adding cement to three calcium sources (CaCl 2 , Ca(CH 3 COO) 2 , and Ca(NO 3 ) 2 ), the CH 3 COO − sample is more stable and has higher biomass and urease activity than the Cl − and NO 3 − samples. Since CH 3 COO − is a weak acid, CH 3 COOH generated by CH 3 COO − can easily react with NH 3 under the alkaline condition provided by cement, reducing NH 3 emissions. When Ca(CH 3 COO) 2 was used as a calcium source, the NH 3 emission of its sample decreased by 54.2% and 51.4% compared with CaCl 2 and Ca(NO 3 ) 2 . Therefore, CH 3 COO − , as an anionic calcium source, will have more application prospects than CaCl 2 and Ca(NO 3 ) in bio-cement production. • Ca(CH 3 COO) 2 used as the calcium source is more suitable than others for biocement. • Part of CH 3 COO − reacts with NH 3 to generate CH 3 COONH 4 , reducing NH 3 emissions. • CH 3 COO − improves the mineralization rate of MICP because of its large relative molar mass. • Ca(CH 3 COO) 2 helps to generate more CaCO 3 to improve the compactness of biocement. • The stability of Ca(CH 3 COO) 2 in biocement is higher than that of CaCl 2 and Ca(NO 3 ) 2 .