Assessment of CO2 Capture in FA/GGBS-Blended Cement Systems: From Cement Paste to Commercial Products

The cement industry’s intricate production process, including kiln heating and fossil fuel use, contributes 5–8% of global CO₂ emissions, marking it as a significant carbon emitter in construction. This study focuses on quantifying CO₂ capture potential in blended cement systems through the utilisation of phenolphthalein and thermalgravimetric methodologies. Its primary objective is to assess the CO₂ absorption capacity of these blended systems’ pastes. Initial evaluation involves calculating the carbon capture capacity within the paste, subsequently extended to estimate CO₂ content in the resultant concrete products. The findings indicate that incorporating ground granulated blast-furnace slag (GGBS) or an ettringite-based expansive agent did not notably elevate carbonation depth, irrespective of their fineness. Conversely, the introduction of fly ash (FA) notably augmented the carbonation depth, leading to a substantial 36.4% rise in captured CO₂ content. The observed distinctions in carbonation behaviour primarily stem from variances in pore structure, attributable to distinct hydration characteristics between GGBS and FA. Thermal analysis confirms the increased stabilisation of CO₂ in FA blends, highlighting the crucial influence of material composition on carbonation and emission reduction. Incorporating both GGBS and FA notably diminishes binder emissions, constituting almost half of PC-concrete emissions. Initially, 60% GGBS shows lower emissions than 50% FA, but when considering CO₂ capture, this emission dynamic significantly changes, emphasising the intricate influence of additives on emission patterns. This underscores the complexity of evaluating carbonation-induced emissions in cementitious systems.

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