Strength and durability performance of a sustainable OPC–GGBS quaternary binder incorporating calcined seashell powder and biomass ash

The high carbon emissions associated with ordinary Portland cement (OPC) production necessitate the development of sustainable alternative binder systems incorporating industrial and waste-derived materials. This study investigates a quaternary blended binder comprising calcined seashell powder (CSSP), micronized biomass silica (MBS), and ground granulated blast furnace slag (GGBS) as partial replacements for OPC. Seven binder formulations were developed with 40–50 % OPC replacement, maintaining a constant MBS content of 15 % while varying CSSP and GGBS proportions. A control mix with 100 % OPC was used for comparison. Fresh properties were evaluated through consistency, setting time, and packing density tests, while reaction degree was determined using selective dissolution. Microstructural characterization using X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy confirmed the formation of calcium silicate hydrate gel. Mechanical and durability performance were assessed through compressive strength, ultrasonic pulse velocity, water absorption and exposure to aggressive environments. Among all mixes, M13 (50 % OPC, 15 % MBS, 15 % CSSP, and 20 % GGBS) demonstrated optimal performance, achieving compressive strengths of 29.5 MPa and 33.55 MPa at 28 and 56 days, respectively, along with improved durability. Strength reductions of 48.5 %, 28.5 %, and 9.5 % were observed under H₂SO₄, HCl and seawater exposure. Sustainability analysis revealed significant reductions in carbon emissions and cost with M13 exhibiting the highest eco-efficiency. The study highlights the synergistic potential of agro–aqua–industrial waste materials in developing sustainable, durable, and low-carbon cementitious binders.