Study on the Freeze-Thaw Deterioration Mechanism of Activated Coal Gangue Cementitious Concrete

As a typical industrial solid waste-based concrete material, activated coal gangue cementitious concrete is prone to the freeze-thaw cycle in cold-region engineering applications, leading to durability degradation that severely limits its service performance. In this paper, freeze-thaw cycle tests were designed to reveal the influence of different ratio designs on the freeze resistance of materials. Scanning electron microscopy and nuclear magnetic resonance spectroscopy were employed to observe the microstructural changes in the internal pores of activated coal gangue cementitious concrete after freeze-thaw degradation. The optimal replacement ratio for activated coal gangue powder was analyzed. The results showed that, as the number of freeze-thaw cycles increased, the pore structure within the activated coal gangue cemented concrete deteriorated significantly, though the degree of deterioration varied. With the gangue powder content increasing, both the number of pores and porosity within the concrete initially decrease and then increase. According to the test results, when the activated coal gangue powder content was 35% in the concrete mix, the freeze-thaw resistance performance was optimal. This mixture maintained a good pore structure and superior porosity, indicating that the concrete with 35% activated coal gangue powder content was the best mix design. The result provides a reference for enhancing the freeze-thaw resistance of activated coal gangue cementitious concrete in cold environments.