Surface Structure Modification of Portland Cement Via Semidry Carbonation with Flue Gas for Mitigating Early Hydration Heat

An eco-friendly surface structure modification method using semidry carbonation treatment on Portland cement (PC), based on cement kiln flue gas utilization, is proposed to mitigate rapid heat release during early hydration. The results show that the heat release of 1 d is reduced by 75.6%, accompanied by a 72.7% reduction in the hydration degree. This is attributed to the formation of carbonation product particles on the clinker surface, which significantly reduce the reactive surface area and impede clinker dissolution, resulting in lower Ca and Si concentrations in the pore solution and further inhibiting the formation of portlandite and C–S–H. Despite these reductions, carbonation treatment has a minimal long-term impact on the hydration products content (<7%). Meanwhile, prolonged hydration leads to a denser interfacial transition zone between clinker particles and hydration products, ensuring negligible effects on compressive strength. Additionally, thermodynamic simulations are conducted, accurately predicting the early hydration process and phase evolution, offering further insight into the hydration kinetics of PC subjected to semidry carbonation. Moreover, semidry carbonation enables CO2 sequestration from flue gas, reducing the CO2 intensity of cement mortars by up to 8.4%, and offers a sustainable strategy for low-carbon and low-heat cement production.