CO₂Pretreatment to Aerated Concrete with High-Volume Industry Wastes Enables a Sustainable Precast Concrete Industry

Carbon dioxide (CO2) pretreatment to concrete at the early curing ages is a feasible technique towards achieving a greener and more sustainable concrete industry. However, the carbonation efficiency of ordinary concrete blocks is greatly limited due to their dense compactness. Here we proposed that the aeration of concrete blended with high-volume industry wastes may bring about improved sustainability of the precast concrete industry by enhancing the carbonation efficiency. We designed two different CO2 pretreatment courses: that is, the gas pressure of CO2 = 0.1 atm (0.01 MPa) for 8 h and 1 atm (0.1 MPa) for 4 h. The strength and microstructure of the aerated concrete with and without the CO2 pretreatments were investigated by macro- and microscopic tests. Results showed that the CO2 pretreatments greatly altered the minerals and pore structure of the aerated concrete blocks. The higher CO2 pressure with less curing time raised the carbonation extent, crystal size, and compressive strength at 3 days. Compared with ordinary solid concrete, the aerated concrete showed a higher CO2 sinking efficiency by more than one order of magnitude. This technique would potentially sink millions of tons of CO2 from the precast aerated concrete industry.