Binary and Ternary Blends of Construction and Demolition Waste and Marble Powder as Supplementary Cementitious Materials

Portland cement is widely used in construction, but it contributes significantly to global CO₂ emissions. This study evaluates the potential use of construction and demolition waste (CDW) and marble powder (MP) as supplementary cementitious materials, in line with circular economy goals. Both wastes were ground finer than cement and characterised chemically and physically. Binary and ternary blends with 5% and 10% replacement were tested in pastes and mortars for fresh properties, mechanical performance, and durability. Setting time, soundness, and workability remained within standard limits. Compressive strength decreased moderately, with 28-day activity indices between 82 and 88%, confirming the low reactivity of the supplementary cementitious materials. Sorptivity decreased in all mixes, and chloride resistance improved in the 10CDW and 10MP blends. However, the ternary mix showed increased chloride migration. Carbonation depth increased in all mixes, indicating the need for protective measures in carbonation-prone environments. Replacing 10% of cement with CDW or MP can avoid 70–80 kg of CO₂ per tonne of binder and reduce landfill waste. These materials can be used as low-carbon fillers in cement-based systems, provided that their durability limitations are considered in design.