Enhanced Compressive Strength of the Bentonite-Amended Cement via Bio-Mineralization

Abstract

Bentonite, a supplementary cementitious material for Portland cement, has greatly contributed to environmental sustainability. However, few studies have investigated mortar samples produced by substituting bentonite for cement, and cement strength may be adversely affected when cement is replaced with bentonite in larger proportions. Therefore, this paper investigates and discusses the effect of microbially induced calcium carbonate precipitation (MICP) on improving the strength of bentonite-amended cement. The bio-mineralization process of MICP was characterized by SEM-EDS, while the biominerals formed in bentonite-amended mortar were identified by FIIR and XRD analysis. The results showed that: at bentonite concentrations of 0%, 10%, 20%, 30%, and 40% in cement, the bacterial suspension and reaction solution enhanced the compressive strength of bentonite-amended cement by 17%, 20%, 79%, 78%, and 38%, respectively, after 28 days, compared to control specimens; With the increased bacterial concentration in the presence of the reaction solution, the strength of the bentonite-amended cement (20% bentonite) increased remarkably compared to the control specimen (without bacteria). When the bacterial concentration was OD600 2.0, the compressive strength of bentonite-amended cement (20% bentonite) increased by 80% after 28 days; MICP process has a great effect on improving the strength of bentonite-amended cement. It is a green and economical choice to use MICP to improve the strength of bentonite-amended cement.