A promising alternative to form engineered barriers for high level nuclear waste repositories is the use of pellets-based material because high dry densities can be achieved with no or minimal compaction effort. It is also planned to subject these materials to temperatures significantly higher than 100ºC. The paper reports the results of coupled THM analyses of a heating-hydration test performed on a granular assembly of MX-80 bentonite pellets. The goal is to characterize the material under conditions akin to those of an engineered barrier. It is shown that the numerical analyses are able to reproduce satisfactorily the observations of the test. This enhances the confidence placed on the computational tool for predicting the behaviour of actual engineered barriers constructed with pellets-based materials.