A package of programs for simulating a hard core/soft shell microstructure in three dimensions has been presented. The programs allow for random particle placement, percolation assessment, volume fraction point sampling, and diffusivity estimation. The code has been developed in the C programming language, using linked list data structures and a modular program structure, to facilitate future modifications by the research community. The applications of the program to modelling the microstructure of cement-based materials are numerous and the programs should ultimately find applications to a diverse population of material systems.