This article presents the further development of a tool for multi-phase reactive mass transport modelingfor durability estimation of cement-based materials, by the addition of the gas phase, adopting a trulyseparate two-phase moisture transport approach. The governing system of equations are based on phys-ically sound hybrid mixture based version of the Poisson-Nernst-Planck system of equations includinggaseous transport in the air-filled space, ionic transport in the liquid phase, electro-migration of ionicspecies, a two-phase moisture transport model, and sorption. The addition of the gas phase and thetwo-phase moisture description enables the user of the model to investigate individual and combinedeffects of different degradation processes in unsaturated systems. The altering of hydrated cement underthree different environments were studied representing an accelerated carbonation environment, a sub-merged marine environment and a cyclic drying-wetting zone in a marine environment, to illustratesome of the model’s capabilities.