Assessment of the freeze–thaw resistance of concrete incorporating carbonated coarse recycled concrete aggregates

This study aims to characterise the freeze–thaw resistance of concrete incorporating carbonated coarse recycled concrete aggregate (C-CRCA) at partial or full replacement rates of coarse natural aggregate (CNA). Experimental work is conducted for C-CRCA with varying CO2 curing time (0 day, 3 day, 7 day) and C-CRCA weight replacement percentages (0, 20, 50, 100%) for concrete production. Weight loss, relative dynamic modulus of elasticity (RDME) and residual compressive strength were monitored after 300 freeze–thaw cycles. Pore size distribution and crack volume variation were also measured via nuclear magnetic resonance to investigate changes in the microstructure of the concrete interior. The compressive strength of concrete decreases with the replacement percentage of CNA by the C-CRCA. The internal freeze–thaw resistance of concrete with C-CRCA was higher or equal to those of concrete with CRCA and CNA. The total replacement of CNA by C-CRCA led to the highest RDME, and 50% replacement of CNA by C-CRCA led to the highest residual compressive strengths after the freeze–thaw cycles. However, the weight loss was more severe with the increasing replacement of CNA by C-CRCA. Increasing CO2 curing time improved the frost resistance of C-CRCA concrete. The analyses of concrete mesostructure based on pore size distribution and crack volume variation agreed with the results of RDME and the compressive strength of concrete.