Study of Macro Mechanical Properties of High Strength Concrete (M70) by Partial Replacement of Cement with Fly Ash and Rice Husk Ash and Fine Aggregate with Steel Slag

High-strength concrete (HSC) is increasingly preferred in modern construction due to its superior mechanical

performance and improved service life. In the present study, an experimental investigation was carried out on M70 grade highstrength concrete incorporating industrial and agricultural by-products as partial replacements for conventional materials.

Cement was partially substituted with Fly Ash (10–30%) and, subsequently, the optimum FA level was maintained while Rice

Husk Ash (RHA) was introduced at 5%, 7.5% and 10%. Further, using this optimized binary blend, natural fine aggregate was

replaced with Steel Slag (SS) at 10%, 20%, 30% and 40% to examine its influence on overall strength characteristics. The mix

design for M70 concrete was prepared as per IS 10262:2019 and tested for compressive, split tensile and flexural strengths at 7

and 28 days. The findings clearly indicate that the mechanical behaviour of high-strength concrete can be significantly improved

when FA, RHA and SS are used in controlled proportions. Among all mixes, the blend containing 10% FA, 7.5% RHA and 30%

SS exhibited the highest strength values, producing a 28-day compressive strength of 89.2 MPa, split tensile strength of 5.40

MPa and flexural strength of 6.70 MPa, outperforming the conventional mix. Based on the obtained results, the optimized

ternary mix demonstrates superior macro-mechanical properties and presents a sustainable alternative to conventional highstrength concrete.