Experimental Study on M40 Concrete with Partial Cement Replacement Using Silicon Carbide and Carboxymethyl Cellulose Hybrid Matrix

The growing demand for high-performance and sustainable construction materials has accelerated the development of advanced cementitious composites with enhanced mechanical and microstructural properties. This study presents an experimental investigation on M40 grade concrete incorporating a hybrid matrix composed of Silicon Carbide (SiC) and Carboxymethyl Cellulose (CMC) as a partial replacement of cement. The hybrid system was introduced at replacement levels of 2%, 4%, 6%, and 8% by weight of cement to evaluate its influence on fresh and hardened properties. The experimental program included workability assessment using the slump cone test and compressive strength evaluation at curing ages of 7, 14, and 28 days, in accordance with relevant Indian Standard codes. The results indicate a consistent reduction in workability with increasing hybrid content, attributed to the high surface area of SiC particles and the viscosity-modifying behavior of CMC. However, a significant improvement in compressive strength was observed up to an optimum replacement level of 6%, beyond which strength declined due to possible particle agglomeration and disruption in hydration mechanisms. At 6% replacement, the concrete achieved a maximum compressive strength of 47.8 MPa, representing an increase of approximately 14.9% compared to conventional M40 concrete. The enhancement in mechanical performance is primarily attributed to the synergistic interaction between SiC and CMC, where SiC acts as a micro-filler improving particle packing density, while CMC enhances dispersion, hydration control, and interfacial bonding within the cement matrix. This combined effect leads to a denser microstructure and improved load transfer efficiency. The study concludes that the SiC–CMC hybrid matrix offers a viable approach for optimizing strength and material performance while reducing cement consumption. Although the inclusion of hybrid additives increases the overall cost, the improved structural efficiency makes it suitable for high-performance and specialized construction applications. This research contributes to the advancement of hybrid composite technology in concrete and provides a foundation for future studies on durability and large-scale implementation.