As a major solid waste in coal-fired power plants, circulating fluidized bed fly ash (CFBFA) has a high content of SO3 and f-CaO, leading to a lack of avenues for its resource utilization. Using the characteristic of it, this study combined it with ground granulated blast furnace slag (GGBFS) to produce an ecofriendly cementitious material (CGL) without cement. At the CFBFA/GGBFS ratio of 3:2, the lime content of 20 wt% and the water–solid ratio of 0.45, the unconfined compressive strength of CGL mortar could achieve 33.44 MPa at 28 d. With the prolongation of curing age, high polymerized C-(A)-S-H gel with a foil-like morphology, as well as ettringite and hydrotalcite were continuously generated and filled the pores, resulting in a continuous decline of the porosity. Simultaneously, the proportion of small pores (<50 nm) increased continuously. In addition, CGL had significant environmental and economic advantages. Compared with Portland slag cement (32.5R), the energy consumption, carbon emissions, and production costs of CGL reduced by 73.51 %, 75.76 %, and 25.93 %, respectively. Therefore, this work offered a practical and novel way for resource utilisation of CFBFA.