Study of the Improved Behavior of Portland Cement Mortar Based on Adsorption and Deposition of Microbial Cement

Abstract

Microbial cement (MC) can generate biocalcium carbonate on the surface of mortar in the liquid environment, which shows potential advantages to enhance the surface property of prefabricated components. This paper is aimed to investigate the cementation solution (CS) concentrations (0.5, 1.0, 1.5 M) and treatment times (3, 6, 9, 12 time) on capillary water absorption coefficient (coefficient k) and compressive strength of MC treated mortar, and attempted to point out the macroproperties and microstructure evolution mechanism of mortars based on adsorption and deposition of MC. The results indicated that when CS concentration was 0.5 M, the reduction rate of coefficient k increased from 29% to 76% with increasing treatment times from 3 to 12, and the growth rate of compressive strength also increased from 7.4% to 27.5%. For a CS concentration of 1.5 M, shorter less treatment times resulted in a significant reduction in coefficient k, whereas it had little effect on compressive strength. The adsorption and deposition of MC treated mortar surface led to an increase in the pore volume fraction of less harmful and harmless pore (<50 nm) in the near-surface layer by filling the pores with calcite and altering the content of hydration products. This process decreased the content of portlandite and increased that of calcite. Increasing the content of surface deposition was beneficial for reducing coefficient k, whereas improving the inner pore structure was beneficial for increasing compressive strength.