Performance enhancement of concrete using Dokhan volcanics powder as cement replacement and nano‐banded iron formation as additive: Individual and combined effects

Abstract The construction industry's reliance on Ordinary Portland Cement (OPC) contributes global CO 2 emissions, necessitating sustainable alternatives that maintain or enhance structural performance. This study investigates Dokhan Volcanics Powder (DVP) as a partial cement replacement and Nano‐Banded Iron Formation (NBIF) as a supplementary cement addition, evaluating their individual and combined effects on concrete performance. DVP was incorporated at replacement levels of 3%, 6%, 9%, 12%, and 15% by cement weight, while NBIF was added at dosage levels of 0.5%, 1%, 1.5%, 2%, and 2.5% by cement weight. Fresh properties, mechanical performance, and microstructural analysis were evaluated to assess consistency, strength development, and hydration mechanisms. DVP incorporation progressively increased water demand and retarded setting times, while NBIF significantly accelerated hydration. Both materials reduced workability, with NBIF producing more pronounced reductions owing to its ultra‐fine particle size and high surface area. Hardened density peaked at 2471 kg/m 3 for optimal 6% DVP and reached 2513 kg/m 3 for the combined formulation, compared to 2452 kg/m 3 for the control. The optimal 6% DVP replacement improved compressive strength by 27.2%, 19.7%, and 16.1% at 7, 28, and 90 days, respectively. NBIF addition at 1.5% delivered enhancements of 36%, 34.6%, and 34.1% at corresponding ages. The combined formulation (6% DVP + 1.5% NBIF) demonstrated superior synergistic effects, achieving improvements of 51%, 43.6%, and 39.8% in compressive strength, 28.1% in splitting tensile strength, and 23.3% in flexural strength. SEM–EDX analysis confirmed denser microstructures with abundant calcium silicate hydrate (C–S–H) formation and reduced void content, with the combined mixture achieving the lowest Ca/Si ratio.