Low-carbon precast concrete: optimising mixture design and renewable-energy steam curing

Precast concrete production commonly relies on clinker-intensive mixtures and steam curing, resulting in high carbon dioxide emissions and potential deterioration of long-term performance under excessive thermal exposure. This study presents an optimisation strategy combining mixture design and renewable steam curing for precast concrete production. Concrete mixtures were first screened under baseline steam curing, and the shortlisted mixtures were then evaluated under systematically varied curing parameters. The results show that a mixture with 15% ground granulated blast-furnace slag, combined with a controlled curing regime of 12 h precuring, 15°C/h heating/cooling, 60°C isothermal temperature and 12 h holding, provided the best overall balance between early strength, long-term mechanical performance and durability. Compared with the reference concrete, the optimised system increased 28-day compressive strength by 16.3% and reduced chloride migration by 41.2%. These improvements in precast concrete performance can be attributed to pore refinement and interfacial transition zone densification. Plant-scale validation further demonstrated the practical feasibility of the proposed approach and its potential to reduce equivalent carbon dioxide emissions by 71.7–76.4 kg/m³, coal and natural resource consumption by 121.9 kg/m³ and costs by 2.1–7.8 US$/m³ in precast concrete production.