Between green and gray: decarbonization of Portland cement and durability of concrete – a critical review.

This paper presents a critical review of the decarbonization of Portland cement (PC) and its implications for concrete durability. The reduction of clinker content, a central strategy to mitigate CO₂ emissions, has been accompanied by physicochemical adjustments that increase PC reactivity, leading to higher heat of hydration and a greater risk of expansive reactions. Moreover, the lower alkaline reserve of low-carbon cement accelerates carbonation, increasing the probability of steel reinforcement corrosion. These and other issues must be considered in the decarbonization process, highlighting the need for systemic studies that address the trade-offs between CO₂ reduction and long-term durability over the service life of concrete structures.