his study aimed to derive practical empirical models of frost resistance for both normal-strength (NS) and high-strength (HS) concretes (NSC and HSC) using a comprehensive test program. For this purpose, the effects of the three key parameters of water-to-cement (w/c) ratio (at levels of 0.5, 0.6, 0.7, and 0.8), air content (at levels of 3, 4.5, 6, and 7.5%), and the number of freeze–thaw cycles, FTCs, (45, 100, and 150 cycles) were investigated on the frost resistance of NSC. To study the effect of key parameters on the frost resistance of HSC, the influence of water-to-cementitious materials ratio, w/cm, (0.25, 0.3, and 0.4), silica fume (SF) content (0, 5, 10, and 15%), type of coarse aggregate (limestone and quartzite), and number of FTCs (45, 150, and 200) was investigated. The experiments were performed using 720 concrete specimens divided into 288 NS and 432 HS concrete specimens. Finally, some models for predicting the frost resistance of NS and HS concretes were proposed. Validation of the proposed models using different parameters and previous studies showed their good capability to predict frost resistance of HS and NS concretes.
