Incorporation of self-ignited coal gangue in steam cured precast concrete

Abstract Steam curing is commonly adopted in the production of precast concretes (PC) for modern industrialized buildings. To propel recycling of harmful waste and reduce carbon emission for prefabricated construction, this study aims to provide insights into the role of steam curing in performance of PC incorporating self-ignited coal gangue (CG) particles. Mechanical strength and transport properties of concretes with variable CG dosages and different curing conditions were evaluated. Cement paste matrices were employed to analyze microstructure and mineral phases. Results showed that the CG incorporation degraded early-age strength and increased porosity and water absorption under standard curing condition, but improved the resistance to chloride ion or gas penetration. Steam curing can significantly activate the pozzolanic reaction of CG particle and alleviate the negative impact arising from CG addition. Both steam curing temperature and duration had a direct bearing on early-age and long-term performance of CG-PC. An excessive steam curing tended to induce an evident deterioration on CG-PC strength and anti-permeability, especially at later ages. Overall, CG-PC cured at 60 °C for 18 h showed substantially low transport behaviors and refined pore structure, merely with a negligible loss of ultimate strength. Therefore, it is concluded that the combination of a suitable steam curing regime and a proper CG content could realize the production of green concretes with excellent durability, low cost and substantial environmental benefit.