Properties of concretes bearing mixed recycled aggregate with polymer-modified surfaces

Abstract The growing socio-economic interest in conserving the environment constitutes a challenge for businesses with a heavy environmental impact. In the construction industry, the efficient use of recycled construction and demolition waste (CDW) as aggregates in structural concrete and the implications of that practice for a sustainable flow of materials are contributing to the establishment of a circular economy. Mixed recycled aggregates (MRA) account for a substantial fraction of the total. The main hurdle to MRA valorisation is its non-uniformity and certain intrinsic properties that have a direct effect on the performance of recycled concretes. In light of those drawbacks, this study assessed a surface treatment consisting in soaking these mixed materials in polymers to improve their physical and mechanical properties with a view to their use, determining the optimal treatment conditions (concentration, soaking time and drying method). The study also addressed the effect of using the treated MRA to replace 100% of the natural gravel (~40% of the total aggregate) on the fresh state consistency and hardened state compressive and tensile strength and water permeability of the new material. The findings showed that the treatment induced a reduction in mixed recycled aggregate water absorption and a rise in its abrasion resistance. Although treating the MRA as described had no significant effect on concrete mechanical properties, it improved durability significantly.