A new modelling platform, called mu ic has been developed to model the microstructural evolution of hydrating cement paste. The platform uses the vector approach and can be used for modelling particulate reactions including the hydration of many different cementitious systems involving millions of particles. In this paper, the ideas behind the development of mu ic and its main features are presented. The complexity of cement hydration and the gaps in our current understanding of cement played an important role in its design, so the platform has the primary objective of aiding, rather than replacing experiments. The platform is highly customisable as users can define materials, particles and reactions and choose or create external plugins to define models of microstructural development The platform can be used to test the validity of hypotheses by easily formulating them as input and comparing simulations with experimental results. This paper presents the design of mu ic and examples that demonstrate the important features of its performance and design. (C) 2008 Elsevier Ltd. All rights reserved.