Alkali-silica reaction(ASR)is a reaction between alkaline pore solutions in concrete and reactive non-crystalline SiO2 in aggregates,which leads to expansion and cracking of the concrete,and degradation of mechani-cal properties.In this study,based on the microbial induced calcium carbonate precipitation(MICP)technique of Bacillus pasteurus,various treatment frequencies and methods,including surface treatments of potentially active aggregates and mortar bars made by them,to comprehensively evaluate the inhibition law and mechanism of MICP on ASR.The results showed that the MICP treatment could form a dense CaCO3 layer with adhesive effect on the surface of aggregates and mortar bars,thus preventing the intrusion of alkaline ions and water,and the inhibiting effect became stronger with the treatment numbers.Compared with the control group,the maximum increase in mechanical properties of 13.8%,and the decrease in expansion rate of 35%were observed when the mortar bars were treated.When treating the aggregate,the mechanical properties were improved by 25.3%and the expansion rate was reduced by 59.6%with a better inhibition effect,as the surface CaCO3 layer could simultaneously block the alkaline ions and water existing in the pore solution and invading from outside.Microstructural and compositional analyses showed that the proportion of Si and Na atoms on the aggregate surface decreased by 69.6%and 88.9%,respectively,after treatment,indicating a significant reduction in the ASR gel.
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