Advancing Carbon-Negative Reactive Magnesia-Based Composites for Scalable CO2 Curing, Phase Stability, and Long-Term Durability in Construction

Annual global cement production is ~4.5 billion tonnes and contributes about 8% of global CO2 emissions, making it one of the most pressing challenges for climate neutrality. Among decarbonisation pathways, Carbon Capture and Utilisation/Storage (CCUS) are widely recognised as having the greatest potential to bridge the ‘emissions gap’ toward net zero goals. Integrating CCUS into construction materials is impactful, enabling carbon sequestration at scale while creating durable infrastructure. Among candidate materials, reactive magnesium oxide (MgO) binder (RMB) stands out as a promising solution. Produced at lower calcination temperatures (700–1000 ºC versus 1450 ºC for conventional cement), it absorbs more CO2 than it emits, making it a TRUE carbon-negative binder. But its adoption has been limited by critical gaps: incomplete carbonation leaving unreacted MgO, formation of metastable phases prone to transformation, and poor understanding of long-term durability and scale-up performance under real environmental and industrial conditions. Carbon-X has the ambition to bridge a significant portion of the ‘emissions gap’ (X) preventing the construction sector from reaching net zero targets. The project addresses the mentioned barriers through four work packages: (1) optimising carbonation kinetics to achieve rapid and complete reactions, (2) controlling phase evolution toward stable carbonates, (3) testing long-term durability under environmental stresses, and (4) integrating data into predictive models and pilot-scale proof-of-concept demonstrations using industrially relevant CO2 streams.The project will deliver open datasets, predictive models, and practical curing protocols for industry. Wider benefits include advancing EU Green Deal and net zero targets by enabling scalable carbon-negative construction materials, reducing billions in potential CO2 emissions, and positioning EU as a global leader in sustainable construction innovation.