Reducing CO2 emissions from the cement industry is challenging because a large share of the emissions arises from core chemical processes, and the further handling of the CO2 depends highly on regional CO2 storage availability. We provide the first quantitative, system-wide comparison of oxygen-from-electrolysis, CO₂ grid, and flexible grinding for cement decarbonisation, based on an endogenous linear optimisation model quantifying the system-cost and technology-mix implications. The analysis focuses on Baden-Württemberg, an industrial region without established geological storage and with constrained renewable resources. It therefore offers insights for similarly constrained regions. The study investigates the role of carbon capture technologies in future carbon management strategies, including both CO2 storage and its utilisation for fuels and chemical products. Across six scenarios, the viability of carbon management options depends strongly on the availability of CO2 transport and storage infrastructure; where these are absent, on-site carbon capture and utilisation becomes essential. The study further examines the use of co-product oxygen from electrolysers in oxyfuel combustion. It also assesses flexible cement grinding as an implicit demand-side response option. Comparing the three technological options—CO2 network availability, oxygen from electrolysis, and flexible cement grinding—shows that oxygen utilization reduces average cement prices by up to 30 %, a CO2 grid by 5 %, and flexible cement grinding by 1.2–6.6 %.
Increased use of supplementary cementitious materials (SCMs) is limited by variability in their compositions and reactivities, since these factors significantly affect concrete properties and durability. Traditional durability testing is time-consuming, making it infeasible to apply widely to emerging SCMs. This paper develops and applies a computational method to screen many blended cements containing coal fly ash and granulated blast furnace slag to identify those that have higher potential to produce high freeze-thaw resistance and low CO2 emissions concrete, varying SCM chemical composition, reactivity, and replacement levels. This is achieved using the Panoramix algorithm, which integrates thermodynamic modelling, random sampling, grid search algorithm, a freeze-thaw prediction model, and life cycle assessment (LCA) to probabilistically explore the design space, thereby rigorously accounting for uncertainties in raw material properties. A novel SCM reactivity database is developed and used here, enabling application of Panoramix to blended cement concretes. The modelling results show that at constant air content (4%), increasing the replacement levels of coal fly ash and granulated blast furnace slag decrease the mean value of the freeze-thaw resistance indicator but increase its variance, due to their broader chemical composition ranges than Portland clinker. At constant air void system quality and content, higher values of the freeze-thaw resistance indicator are calculated at increased SCM reactivity levels, and reduced climate change impacts are calculated at increased SCM substitution levels. The results indicate that a balance between higher freeze-thaw resistance and lower CO2 emissions can be approached using high reactivity SCMs and low clinker-to-cement ratios. The methodology used here facilitates multi-objective concrete selection considering environmental impacts and durability performance.
The hydration mechanism of the low-clinker binders (cement ≤ 45%) incorporating either calcined clay or natural pozzolana together with limestone were investigated in this study. The reactivity of calcined clay and natural pozzolana were evaluated using synthetic portlandite (CH) pastes, to clarify the influence on microstructural development kinetics and corresponding early and later age strength performance.Calcined clay in low clinker mixtures exhibited rapid early reaction, promoting the formation of hydration products such as AFm and C-(A)-S-H within the first 7 days. This accelerated reaction enhanced microstructural densification and early compressive strength. While mixtures incorporating natural pozzolana demonstrated slower hydration kinetics, with more pronounced hydrate formation occurring after 7 days. By 90 days, significant increases in AFm and C-(A)-S-H phases were observed, aligning with continued strength development. In this paper it was found that natural pozzolana mixtures formed higher total hydrate volumes at later ages than calcined clay mixtures. Sodium sulfate addition enhanced early age strength by accelerating hydration, while later strength was unchanged or slightly reduced, likely due to limited availability of saturated pore space for continued hydration. Nevertheless, the presence of reactive SCMs largely compensated for this effect.
