The disposal and recycling of industrial by-products such as marble and limestone powders pose pressing environmental challenges due to the substantial amounts of waste generated annually by marble processing plants and limestone quarries. The integration of these by-products into concrete production is justified by their widespread availability and the potential to alleviate the environmental burden. This study used a statistical mixture design approach to systematically assess the effects of limestone and marble powders, with varying fineness levels, as partial cement replacements (up to 17%) on the rheological and mechanical properties of self-compacting concrete (SCC). The experimental findings revealed that the density of the SCC mixtures ranged from 2475 to 2487 kg/m³. Mixtures incorporating limestone powder exhibited superior flowability, achieving a slump flow of up to 69 cm, an 8% improvement compared to those containing marble powder. However, marble powder with a specific surface area of 330 m²/kg demonstrated significant improvements in compressive and tensile strengths, with increases of 18%. Statistical analysis using analysis of variance (ANOVA) validated the reliability of the predictive models developed, which demonstrated coefficients of determination (R²) that exceeded 0.94 and p-values below 0.05. These models enable precise predictions of critical performance metrics, including density, slump flow, box flow, compressive strength, and tensile strength, thus reducing the need for extensive experimental procedures.

The cement industry is a major contributor to global CO₂ emissions, driving the research for sustainable alternatives. Olive biomass ash (OBA), a byproduct from burning all types of biomass from the olive tree, has emerged as a potential supplementary cementitious material (SCM). This study investigates the effects of incorporating olive pomace ash (OPA) as a partial cement substitute (0% to 50% by weight) on mortar properties over extended curing periods. Workability, compressive and flexural strengths, water absorption, and freeze–thaw resistance were evaluated. Up to 20% OPA replacement improved workability while maintaining acceptable strength and durability. Beyond this level, mechanical properties and frost resistance decreased significantly. Correlation analyses revealed strong relationships between flow time and wet bulk density (R² = 0.93), an exponential relationship between 28-day compressive strength and water absorption (R² = 0.87), and linear correlations between pre- and post-freeze–thaw mechanical properties (R² ≥ 0.99 for both compressive and flexural strengths). The results demonstrate that optimal OPA incorporation enhances mortar performance without compromising structural integrity and provides a viable strategy for valorizing agricultural waste.