As part of an on-going research project, a model being developed to simulate ASR in concrete is described. The formulation consists of the three main diffusion/reaction field equations for the concentrations of Alkali, Calcium and Silicate ions in the pore solution, complemented by a number of evolution equations for the local ingredients involved (e.g. local concentration of reactive silica, local availability of portlandite, etc.). A new experimental set-up to study the expansion mechanisms at the level of a single matrix-aggregate interface, using sandwich-like cylindrical specimens of cement paste/mortar and glass are exposed to 1 M NaOH solution at 60¿°C, is also presented along with typical free expansion curves and subsequent SEM images and EDX analysis of the reaction.