Evaluating the Impact of Marble Waste and Fly Ash as Sand Replacements on Concrete's Compressive Strength and Workability

The rapid expansion of infrastructure, urbanization, and industry has intensified the global demand for concrete, straining natural resources and posing ecological threats. In response to these challenges, integrating recycled materials into concrete formulations offers a sustainable solution without compromising quality. This study is focused on evaluating concrete characteristics by substituting natural sand with marble dust and fly ash as fine aggregates. Three series of mixes were prepared, S1 replaced sand with marble dust from 10% to 50%, increasing incrementally by 10%, S2 substituted sand with fly ash under similar conditions, and S3 utilized a blend of marble dust and fly ash at various substitution rates to compare their effects. Results indicated that in the three series of mixes, and at all ages, the compressive strength increased by 49.94%, 49.15%, 49.53%, and 53.08% compared to the control mix at days 7, 14, 28, and 56, respectively, peaking at 20% marble dust and 30% fly ash replacement. However, higher levels of marble dust reduced workability compared to standard concrete. This research underscores the potential benefits of incorporating waste marble powder and fly ash in concrete production, highlighting their role in enhancing material properties while promoting sustainable practices in construction.