| Abstract: |
The rapid increase in the construction and demolition (C&D) waste around the world is forcing us to find alternative sustainable options of natural aggregate (NA) from other resources to make concrete. This experimental study examines the mechanical and durability behavior of concrete designed with different replacement percentage of recycled coarse aggregate (RA) as partial and full replacement of natural coarse aggregate. The eight mixes were 0%, 10%, 20%, 30%, 40%, 50%, 75%, and 100% of the replacement of RA with a water-to-cement (w/c) ratio of 0.45 and a cement content of 380 kg/m³. Compressive strength at 7, 14, 28, 56 and 90 days; split tensile and flexural strengths at 28 days; durability indices such as water permeability, chloride ion penetration, and carbonation depth as well as drying shrinkage at 28 days were determined. Statistical analyses consisting of one-way ANOVA, Pearson correlation and regression modeling were performed to quantify relationships between RA content and properties of concrete. The results shown that 10% RA replacement reduced the compressive strength by 3.7% and 100% replacement reduced the compressive strength by 52.3% when compared to the control. A strong inverse relationship (r: ≥ −0.979) was confirmed between RA content and all mechanical strength metrics, with all durability indices degrading significantly after 30% replacement. This research confirms that for structural concrete there is a realistic technical upper bound for RA replacement at 30%, exploiting the trade-off between structural viability and sustainability. When substitution rate becomes greater than 50%, the mechanical qualities of concrete drop below acceptable structural thresholds; therefore, their use should be limited to nonstructural applications. These results provide a data-driven framework to guide the implementation of recycled aggregates in sustainable construction practice. |
