The ageing of French nuclear power plants raises many research issues in nuclear safety analysis. The phenomena involved in the ageing of structures can lead to concrete degradation and more specifically to the cracking of the corresponding structures. In order to be able to predict further degradation, it is necessary to carry out numerical simulations using complex mechanical codes. However, each simulation is costly in term of computational time. This remains a strong limitation for industrial applications where a large number of simulations are often required to perform the whole mechanical analysis. Therefore, in order to circumvent this limitation, this work is devoted to the construction of a new fast-to-evaluate Markov chain model to predict the cracking trajectory in a microstructure. The analysis of its performances is then conducted. It exhibits the agreement between the predictions and the computer code simulations (Xper in our study). Moreover, one can observe a significant reduction of the computational time compared to the Xper simulation. The new model is finally successfully applied to a three-point bending beam test. It requires coupling the model to a Finite Elements mechanical code.