Effects of waste marble as partial replacement of cement and fine aggregate on the mechanical, durability and microscopic properties of concrete

Cement production significantly contributes to greenhouse gas emissions and global warming, underscoring the need for sustainable alternatives in the construction industry. One promising approach is the reuse of industrial by-products in concrete. The marble industry generates substantial amounts of waste, which, if disposed of improperly, can cause land contamination and ecological issues. In this study, the potential of marble powder (MP) as a partial cement substitute and marble fine aggregate (MFA) as a partial replacement for natural fine aggregate in M30 grade concrete was examined. Experimental mixes were prepared with incremental replacements of MP (5–15%) and MFA (5–15%), as well as combined substitutions, maintaining a water/cement ratio of 0.39. The mixes were evaluated for mechanical strength, durability and microstructural properties. The results showed that MP primarily functions as an inert filler, improving pore structure at lower replacement levels. At 28 days, the optimum performance was achieved with 10% MP, 10% MFA and a hybrid mix of 10% MP + 10% MFA, showing compressive strength gains of approximately 11%, 13% and 16%, respectively, compared with the control concrete. Microstructural analysis confirmed enhanced pore refinement owing to the filler effect of the MP. Overall, controlled use of MP and MFA improves concrete performance and supports sustainable and cost-effective construction.