Study of Mechanical Properties of M40 Grade Concrete Incorporating Ground Granulated Blast Furnace Slag and Silica Fume as Partial Replacement of Cement

Based on the experimental investigation conducted on M40 grade concrete containing different proportions of Ground Granulated Blast Furnace Slag (GGBS) and Silica Fume (SF) as partial replacements of cement, the following conclusions can be drawn: 1.      The incorporation of GGBS and Silica Fume significantly influenced the fresh and mechanical properties of M40 grade concrete. 2.      The workability of concrete increased with increasing replacement percentages of GGBS and Silica Fume. The maximum slump value of 88 mm was obtained for the M6 mix, indicating improved flow characteristics of ternary blended concrete. 3.      The density of concrete generally increased with the incorporation of GGBS and Silica Fume due to better particle packing and reduction of internal voids. The highest density of 2533.82 kg/m³ was observed for the M6 mix. 4.      The compressive strength of ternary blended concrete was enhanced up to an optimum replacement level. The maximum 28-day compressive strength of 46.65 MPa was achieved by the M1 mix containing 5% Silica Fume and 20% GGBS, which exhibited approximately 30.85% higher strength than conventional concrete. 5.      The split tensile strength also followed a similar trend, where the M1 mix achieved the highest 28-day split tensile strength of 5.58 MPa, showing an improvement of approximately 19.49% over the control mix. 6.      The maximum 28-day flexural strength of 4.02 MPa was obtained for the M1 mix, representing an improvement of approximately 18.24% compared with conventional M40 concrete. 7.      The improvement in mechanical properties is attributed to the combined effect of Silica Fume and GGBS. The ultra-fine Silica Fume particles fill the micro-pores and promote secondary C-S-H gel formation, while GGBS contributes to a denser and more durable cementitious matrix. 8.      Higher replacement levels of GGBS and Silica Fume beyond the optimum percentage resulted in a reduction in strength due to a decrease in effective cement content and slower hydration reactions. 9.      The optimum combination identified in the present investigation was 5% Silica Fume and 20% GGBS (M1), which provided the best balance between workability and mechanical performance. 10.   The partial replacement of cement with GGBS and Silica Fume provides a sustainable approach for concrete production by reducing cement consumption, utilizing industrial by-products, and decreasing the environmental impact associated with cement manufacturing. Overall, the study demonstrates that the combined utilization of GGBS and Silica Fume can effectively produce sustainable high-performance M40 concrete with improved mechanical characteristics.

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