Flash Recycling of Waste Cement

Ordinary Portland cement (OPC) production accounts for ~8% of global anthropogenic CO2 emissions, while the hydrated cement paste (HCP) fraction of demolished concrete is largely landfilled worldwide. Here, we introduce an electrified flash recycling process (FRP) that directly converts waste HCP into OPC-like clinker within 60 s, fully restoring mineralogy, hydraulic reactivity, and mechanical performance. FRP employs intense Joule heating to raise temperatures above 1,600 °C within seconds, enabling rapid dehydration and regeneration of reactive clinker phases. Life-cycle assessment shows that flash-recycled cement exhibits ~40% lower energy use and ~60% lower CO2 emissions than OPC, with further reductions under renewable electricity or in OPC-slag blended systems. Techno-economic analysis indicates ~35% lower production costs than OPC, with additional gains where waste tipping fees apply. By regenerating standard OPC chemistry, FRP enables immediate compatibility with existing specifications while supporting decentralized, electrified waste recycling, establishing FRP as a viable pathway for circular, lowcarbon cement production.