A coupling model reflecting the interaction between freeze–thaw cycles (FTCs) and alkali–silica reactions (ASRs) is established from the microscale to the macroscale under the consideration of non-uniform environmental and mechanical conditions. At both material and structural levels with/without reinforcement, the deformation and damage patterns of specimens under single and coupled FTCs and ASRs were simulated by multiscale finite element analysis and partially verified by experiments. Furthermore, following different sources of damage actions, the remaining fatigue life of reinforced concentrate (RC) slabs under traffic loads was investigated. The results show that ASR-driven expansion is mainly governed by the arrangement of reinforcing bars, whereas FTC damage is mainly initiated from corners, edges, and surfaces of RC slab parts and closely relies on water supply. In addition, the severity of coupled damage (FTC and ASR) can be significantly greater than that of the sum of single ASR and FTC damage due to the gel-filling of pores and entrained air. Finally, in terms of the remaining fatigue life, the ASR could be occasionally beneficial for bridge decks under moving traffic loads due to gel-filled cracks and chemical prestressing. However, if cracks are empty or filled by condensed liquid water, the overall fatigue life will be significantly reduced.