Effect of carbonic anhydrase bacteria on the carbonation process of γ-C₂S

Carbonation has been proven to be a promising way to improve the mechanism properties and durability of steel slag products. Carbonic anhydrase (CA) bacteria can promote the early-age carbonation process of γ-dicalcium silicate (γ-C₂S), which is one of the main mineral phases of steel slag. In this study, one kind of alkali-resistant CA bacteria was chosen to investigate its effects on the carbonation process of γ-C₂S. Results showed that the bacteria could increase the compressive strength of carbonated γ-C₂S by 19.0% when compared with carbonated samples without bacteria. The main products of carbonated γ-C₂S were vaterite, calcite and silicon dioxide gel. The addition of bacteria could only accelerate the deposition of calcium carbonate, while hardly changing the types and properties of the carbonation products. The accelerated carbonation was found to reduce the inward diffusion of carbon dioxide. In addition, reasons for the decline of the accelerating carbonation effect were explained by X-ray computed tomography testing results. However, CA bacteria could change the morphology of calcium carbonated during the carbonation process of β-C₂S and further accelerate the hydration process of β-C₂S. The pore structure could also be refined with the incorporation of bacteria.