Toward Low-Carbon Cement: Comparative Assessment of Industrial and Plant-Based SCMs for Cleaner Cement Production

Abstract

The environmental impact of cement production has to be lowered since normal Portland cement generates approximately 0.8 kg CO₂ per kilogram and produces approximately 10% of all emissions worldwide. This paper explores the effect of partial replacement of cement by addition of cementitious materials (SCM) which are fly ash, bagasse, silica fume, quartz powder and calcium carbonate on performance as well as sustainability. Water to binder ratios of 0.30 and 0.40 were used to prepare cement pastes with dosage of 5% to 25% by mass of SCM. Indirect tensile strength were conducted and estimated CO₂ savings. The dominance patterns globally are indicated by the slope graphs of the winners at each W/C. The global dominance patterns are captured by the heatmaps with isocontours. The findings indicate that when quartz and bagasse ash content in low to moderate amounts (10–15percent) were replaced, tensile strength rose by 23–88 percent than in controls and clinker demand was minimized by as much as 15 percent. Silica fume showed the greatest uplift of +58% at 5–10 per cent mixes of high water-to-cement but showed no improvement at low W/C. Calcium carbonate showed more modest and broader, with maxims of 15–20 per cent replacement. Fly ash has always had a low performance on early age controls because of the slow pozzolanic reaction. The calculated sustainability indices showed that a 15 percent cement replacement will reduce CO2 emissions by approximately 0.12 per tonne of binder, which depicts significant environmental advantages. Results show that quartz powder (10–15%) and bagasse ash (10–15 %) significantly enhance early age tensile strength (up to 88%), while a 15% cement replacement reduces embodied CO₂ by approximately 0.12 t per tonne of binder, demonstrating a direct performance sustainability synergy. This work shows that the direct correlation of mechanical performance with embodied CO₂ reductions can be used to generate cleaner and sustainable binders through optimized use of agro-industrial wastes and filler type SCMs to promote both performance objectives and cleaner production strategies.