This is a simulation of the change in the water content within a cylinder of cement paste (4 mm radius) that is attacked by carbonic acid, as in the experiments performed by Andrew Duguid. This calculation shows that water molecules are depleted/created during the corrosion reactions. This should affect the transport of pore fluid (water advection), but that factor is not presently included (that is, the pressure gradient caused by the change in phase volume does not induce Darcy flow in the current implementation - but that will be done soon).