Analyzing the effects of recycled aggregates on the workability and mechanical characteristics of concrete through mixture design and optimization techniques

Purpose This paper aims to report the results of an experimental program using a statistical modeling technique to enhance the formulation of ordinary concrete with recycled concrete aggregates (RCA) derived from demolition trash in the Biskra region, Algeria. Design/methodology/approach The valorized materials consist of coarse recycled aggregates from dry concrete (RCA) and presaturated concrete (SRCA), available in two granular fractions (3 / 8 mm and 8 / 16 mm), obtained through crushing and screening operations. These recycled aggregates partially substitute natural coarse aggregates (NCA). A three-factor experimental design was used to evaluate the effects of RCA, SRCA and NCA on the fresh and hardened properties of conventional concrete. The research effectively created and recognized mathematical models that most accurately describe the experimental findings. Findings The results demonstrate that SRCA notably improves the workability of fresh concrete due to its presaturation, which reduces water absorption and elevates the availability of free water. In contrast, mechanical strength (compressive strength at 14 and 28 days) is highest when NCA content is maximal (100%), but an increasing proportion of RCA and SRCA leads to a progressive reduction in strength. Furthermore, flexural strength at 14 days increases with a higher proportion of NCA and RCA aggregates; but, at 28 days, deflection is notably more pronounced when using combinations with a high concentration of NCA. Originality/value The experimental optimization and validation confirmed the predicted values with an error margin under 8%, emphasizing the feasibility of RCA as a sustainable construction material. These findings offer significant insights into the effective utilization of recycled aggregates in concrete design, enabling their incorporation into practical applications while maintaining structural performance and sustainability.