In our former paper, based on a published 3D reactive transport model at microscale with the capability of simulating the chemical reactions involved in ASR, the location of expansive ASR gel related to the reactivity of aggregate, temperature, aggregate porosity and silica content in aggregate, is clarified. Based on the simulation results, in this paper, the cracking process at mesoscale in concrete induced by ASR in the early stage is investigated. The results show that the cracking process can be divided into four stages and three cracking routes are generalized with the behind chemical exposed environments specified. The cracking routes are found to be comparable with the experimental observed routes. For the first time, the cracking patterns induced by ASR in concrete at mesoscale is linked with the chemical reactions at microscale, which is the first step towards building a complete computational tool to predict ASR as realistic as possible.