Low-Carbon Concrete Development: Integrating Silica Fume, Glass Powder and Recycled Aggregates

Low-carbon concrete has an essential role in the reduction of the environmental impact of the building industry. Ordinary concrete manufacture is a significant contributor of carbon emissions due to high amount of energy that is needed in the processing of cement. The use of industrial by-products and recycled materials will offer a green solution to this problem. The research aims at exploring the use of silica fume (SF), waste glass powder (GP), and recycled coarse aggregate (RCA) as partial cement and natural aggregate replacements in developing eco-friendly concrete with reduced carbon footprint. A total of 16 concrete mixes (K0-K15) were designated with a mix ratio of 1:1:2 and a water-cement ratio of 0.45. Workability, compressive strength and tensile strength of different mixtures were tested. It was found that SF and RCA reduced workability because of the higher water demand, whereas GP increased it at low replacement levels, but the opposite happened at high GP contents e.g., in mix C30R100 (34 mm slump). The strength was significantly lowered by the porosity and poor bonding of RCA, but to a certain extent, SF countered this impact via pozzolanic responses. As an example, Mix C20R50 (20% cement replacement, 50% RCA) had about 85% of the strength of the control mix (C0) with 90 mm slump and 28-day compressive strength of 39.6 MPa, demonstrating that a reasonable trade-off between performance and sustainability is possible. A right combination of these materials may facilitate sustainability without compromising the structural performance. Mix C20R50 attained the best balance and showed better strength retention and reasonable workability without chemical admixtures. The study contributes to low-carbon concrete technologies by promoting the use of industrial byproducts, and recycled materials in construction.