Influence of the effect of recycled fine aggregate and powder on the frost resistance of recycled concrete

Abstract The study of frost resistance of recycled concrete (RC) can provide a theoretical reference for assessing its safety and durability for service in cold environments, thereby facilitating the engineering application of sustainable construction materials. To verify the feasibility of replacing cementitious materials with recycled fine powder (RFP), cement paste was prepared by substituting RFP for cementitious materials by mass fraction at 0, 10%, 20%, and 30%. The microstructures were characterized by X-ray diffraction (XRD), thermogravimetry (TG), and scanning electron microscope (SEM). And the results presented that the incorporation of 10% RFP promoted the hydration of cementitious materials. Subsequently, the effect of the addition of recycled fine aggregate (RFA) and RFP on the frost resistance of RC was investigated. River sand and cementitious materials were separately replaced by RFA and RFP at a mass fraction of 0–30%, and various properties of the RC were tested after different numbers of freeze–thaw cycles (FTCs), including the relative dynamic elastic modulus (RDEM), mass loss rate, compressive strength, and microstructural morphology. The results revealed that RFP was highly sensitive to low-temperature environments, with specimens containing only RFP failing under fewer than 100 FTCs. However, the addition of RFA helped improve the frost resistance of RC by filling microcracks and reducing water infiltration. Optimal frost resistance of the RC was achieved when the mass fractions of RFP and RFA reached 10% and 30%, respectively, with an RDEM value of 69.65%, a mass loss rate of 1.32%, and a compressive strength of 15.7 MPa after 200 FTCs.