It is generally possible to consider modeling of ASR damage in concrete in two main groups: modeling of gel formation and its expansion; modeling of ASR related damage. In this paper, authors take an attempt to combine both: simulating the correct crack formation and the connected concrete expansion. It is aimed to simulate ASR damage in a cementitious material bearing reactive aggregates. The model that is used is a 3D lattice type model. It models concrete on a meso-scale in which particles embedded in a cement matrix are taken into account. The particle structure is obtained by CT-scanning of samples. With the model the concrete expansion can be simulated. One of the inputs in the model is the local expansion of the gel. For that the mechanical properties of the gel should be known, which are obtained from an experimental procedure developed by the authors.