Mechanism of bacterial control of mineralisation gradient at the surface layer of cement-based materials

Abstract

As the primary material for the structure of infrastructures, the steel bar reinforced cement-based composite's durability in the service environment is a crucial topic. The application of bio-mineralization technology shows great prospects in improving the properties of the cement-based materials. Therefore, in this study, we excavate the underlying mechanism by investigating the effects of factors on the gradient mineralization at the surface layer of cement-based materials. The following four parts were studied to conform with the process of bacterial action: the absorption of CO₂ from air, transformation of CO₂ to HCO₃^-, adsorption of Ca^- from the pore solution of cement-based materials and formation of CaCO₃ in pores, which results in the decrease of porosity. The content of CaCO₃ and porosity indicated that bacteria could regulate the gradient mineralization at the surface of cement-based materials. For further prediction, numerical calculations and experimental measurements were conducted.