Enhancement of Mechanical Properties and Freeze–Thaw Durability of Recycled Aggregate Concrete using Aggregate Pretreatment

Recycling construction demolition waste as aggregates for concrete production is a sustainable solution to reduce its environmental impact and challenges. However, recycled concrete aggregate (RCA) possesses inferior physical properties as compared to natural coarse aggregate. Thus, concrete prepared with recycled aggregate has poor mechanical and durability performance, which limits the wider application of recycled aggregate. In this study, surface treatment methods, silane modification and water-soaking methods were employed to pretreat RCA, which enhanced the mechanical and durability properties of concrete prepared with RAC. Concrete with various w/c ratios (0.35, 0.45, and 0.55) and RCA replacement ratios (50%, 70%, and 100%) were prepared. The properties assessment included compressive strength, tensile strength, water permeability, and freeze–thaw resistance. Besides, a pavement model of concrete incorporating the modified RAC was developed based on ATENA software. The results showed that the silane-surface modification for RCA can efficiently improve mechanical strength and water impermeability as compared to water-soaked RCA mixes. Similarly, the freeze–thaw resistance was improved for silane surface-treated RCA mixes as compared to the control mix having RCA without any treatment and silane in the cement base mix. From the numerical analysis results, RAC pavement using 50% silane-modified recycled aggregate can achieve the same peak load-carrying performance as concrete pavement using 100% natural aggregate, proving the effectiveness of silane modification. The findings in the study can provide a wider application of RCA in transportation infrastructure.