Manufacturing Ultra-High Performance Geopolymer Concrete (UHPGC) with Activated Coal Gangue for Both Binder and Aggregate

The use of coal gangue in the preparation of ultra-high performance concrete (UHPC) not only effectively solves the environmental problem, but also reduces the economic cost and carbon emission of UHPC manufacturing. In this study, calcined coal gangue aggregates and calcined coal gangue powder are used to prepare ultra-high performance geopolymer concrete (UHPGC). The result indicates that the higher concentration of Q3 (−101.1) [SiO4] structure and four- and five-coordinated Al, the higher the reactivity of calcined coal gangue. Active calcined coal gangue aggregate can compact the interface transition zone (ITZ) and reduce the porosity of UHPGC. The 28 d-compressive strength of UHPGC (C750F750) prepared from coal gangue aggregate calcined at 750 °C reaches 143.1 MPa. The width of the ITZ between aggregate and matrix of the C750F750 is 34 μm. Compared with traditional UHPC, UHPGC has a lower comprehensive cost and carbon emission. This study provides a low-carbon and low-cost UHPC, while also providing technical support for the resource utilization and high-value utilization of coal gangue.