The paper presents a summary of the work concerning the prediction of cracking risk in reinforced concrete structures at early age that has been carried out by our team at the LMDC laboratory during the last ten years. It focuses on the principles that must be taken into account in numerical simulations (evolution of characteristics, behaviour law, numerical implementation, effect of reinforcement, etc.) in order to be able to predict the cracking pattern caused in structures by the thermal loading induced by hydration at early ages