LAUSR

The stacking of steel slag has detrimental effects mainly for the waste of resources and the pollution of environment. In this study, a novel method based on microbially induced calcium precipitation (MICP) was proposed by utilizing a type of microorganism named Bacillus mucilaginosus, which could secrete carbonic anhydrase (CA) through the metabolism process, accelerating the hydration of carbon dioxide (CO2) and thus facilitating the formation of carbonate ions (CO32-). First, comparing the biologically deposited calcium carbonate with the chemically deposited one, it was found that the crystallinity and crystal size of the biological deposition was lower, leading to its cementitious properties. Under the condition of 1 wt. (weight) % dosage, the carbonation degree increased from 66.34 to 86.25% and the compressive strength improved greatly from 7.4 to 11.2 MPa as well. The weight gain rate of biologically carbonated specimens was also twice as much as the directly carbonated ones. This work strongly demonstrated that biological carbonation technology could not only improve the CO2 sequestration potential of steel slag but also enhance the mechanical properties and durability of steel slag products. KEY POINTS: • Bacillus mucilaginosus could resuscitate and proliferate in the steel slag environment. • B. mucilaginosus secreted carbon anhydrase, which could accelerate the hydration of CO2 and facilitate the precipitation of calcium carbonate. • Biologically carbonated steel slag had greater mechanical performance than directly carbonated one.