CO2 sequestration through mineral carbonation of sugarcane bagasse ash-blended cement pastes and mortars

Incorporating CO₂ into cement-based materials and utilizing industrial waste as supplementary cementitious materials offer promising approaches for reducing greenhouse gas emissions, alleviating landfill disposal burdens, and promoting sustainable development in the construction industry. This study investigates the effects of early-stage carbonation on cementitious systems incorporating 15 % sugarcane bagasse ash, examined at both mortar and paste levels, with CO₂ introduced during the first five minutes of mixing in dosages ranging from 0 to 3.75 wt% of binder. At the mortar level, moderate CO₂ dosages (1.5–2.25 wt%) increased both early- and later-age compressive strengths, with the effect being more pronounced at early age due to accelerated hydration and calcium carbonate (CaCO₃) precipitation. Within the investigated CO₂ dosage range, ultrasonic pulse velocity and water absorption remained stable across all mixes, confirming that pore structure integrity was preserved. At the paste level, pH measurements indicated only minimal changes, with all mixes maintaining alkalinity above the steel corrosion threshold. Thermal analysis (TG-DTA) confirmed partial consumption of portlandite (CH) alongside CaCO₃ formation, while the persistence of CH in the carbonated specimens indicated that the carbonation mixing technique did not hinder the development of this common hydration product. Microstructural analyses (XRD and SEM) further revealed the simultaneous presence of carbonation and hydration products. Overall, the findings suggest that controlled early-stage CO₂ incorporation in sugarcane bagasse ash-blended mortars can enhance material performance, while also facilitating effective CO₂ capture and utilization, thereby offering end users environmentally friendly construction materials