A non-fired ceramsite construction material with enhanced lightweight high strength properties

•The ceramsite was prepared by low-activity circulating fluidized bed fly ash (CFBFA) with 73% utilization.•The ceramsite was non-fired without pretreating CFBFA.•The ceramsite behaved the strength of 5.5 MPa and porosity of 51.86 % synchronously.•Both quicklime and desulfurized gypsum can promote the formation of CSH in the system.•The preparation process is simple, green and energy-saving.