Workability and flexural strength of binary blended concrete made with recycled aggregates and marble dust under two-point loading

The growing need for sustainable construction materials has encouraged the use of industrial waste in concrete. This study investigates the combined effect of recycled coarse aggregates (RCA) from demolished concrete and marble dust (MD), a fine waste powder from marble processing, on the workability and flexural behavior of concrete. Unlike earlier studies that examined RCA or MD separately, this work evaluates their binary interaction and measures performance under two-point loading, a more realistic bending condition for structural elements. This study evaluates the combined use of 50% recycled coarse aggregates (RCA) and 1–10% marble dust (MD) as cement replacement on the workability and flexural behavior of concrete. The constant water-binder proportion of 0.55 was used to prepare 11 mixes with proportions of 1:2:4. Slump testing indicated that the decrease in workability was gradual, with a variation that was between 14 and 89% as the MD content dose. The flexural tests of 100 mm × 100 mm × 500 mm prisms that were placed at two points load test showed that MD reduced the strength by 0.6% to 34% of the mixes. The sustainable alternative concrete mix performance was at 7% MD + 50% RCA which resulted in a 15% decrease in flexural strength than the control mix and had an 11% increase in the central deflection. The findings uphold the fact that when proportioned correctly, an RCA -MD binary mixture can be used to form a structure-wise acceptable and environmentally efficient concrete. A binary blend of recycled coarse aggregates (RCA) and marble dust (MD) was evaluated for flexural behavior under two-point loading. Eleven concrete mixes were prepared using 1–10% MD with a fixed 50% RCA replacement. Moderate MD content (7%) improved ductility by 11% while maintaining acceptable flexural performance. Higher MD contents led to strength reduction due to increased water demand and cement dilution. The optimized mix (7% MD + 50% RCA) demonstrated a balanced combination of sustainability and structural performance. Findings confirm that RCA–MD concrete can serve as an eco-efficient alternative for non-critical structural applications.