Surface scaling of CO2-cured concrete exposed to freeze-thaw cycles

Surface scaling of concrete is one of the major durability issues for cold-region concrete materials. This study presents a solution of using CO2 curing to mitigate the concrete surface salt scaling induced by the freeze-thaw exposure. A laboratory freeze-thaw cyclic test was performed on the concrete made with Portland cement and fly ash. To understand the underlying mechanism, the pore structure of cement paste was evaluated by mercury intrusion porosimetry (MIP) and nitrogen adsorption/desorption (NAD). It was found that the total pore volume and pore size were noticeably reduced in the CO2-cured samples. CO2 curing leads to a dramatic refinement of the capillary pores, hence lessening the available microporous space for the ice formation. The densified concrete surface accounts for the enhanced resistance to the surface scaling.