This report presents results of work performed on aluminized underwater explosives within the project Energetic systems. The purpose of the work is to develop simulation models of the detonation process and the effect of non-ideal explosives. Particular nonideal explosives are produced by adding reactive material like aluminum to an ideal explosive. This initiates a combustion process taking place behind the detonation front. The late combustion contributes with extra energy which can give a stronger effect especially in underwater explosions where the detonation process is confined due to the surrounding water. Detailed modeling of the detonation and the late combustion in non-ideal explosives is a difficult task and an active research area. In the literature there exist different phenomenological models where measured material data and thermochemical calculations are fitted to the parameters of the models in order to be able to simulate the detonation and post-detonation combustion. Our study aims to evaluate and asses these models and if possible improve them. Initially we have focused on the 'GM-model', developed by Guirguis and Miller. We have tested the late combustion process in the GM-model in two different situations, in underwater experiments and in cylinder tests. The results of the simulations in both cases show good agreement with similar experiments reported in the literature. Thus this study shows that the late combustion model implemented in the GM-model is a potentially useful tool for simulation of the detonation and effect of non-ideal explosives.