Freeze–Thaw Resistance of Class C/Class F Fly Ash Geopolymer Mortars with Different Ash-to-Sand Ratios. - Li, Xiaodong; Chu, Zhenyu; Zhu, Ge; Yu, Tao; Su, Hengqiang; Shao, Yueyong; Li, Xueying; Jiang, Zhenpeng; Jiao, Zhenzhen (Buildings (2075-5309), 2026)