When exposed to attack by moisture, macroscopic defect-free materials (MDFs) undergo mass and phase changes. The nature of such changes was studied thermoanalytically. Attacked samples differ from non-attacked samples in the degradation of classical cement hydrates (TG, below 200C) and calcium carbonate (TG, DTA, 550-650C). Quantitative assessment favours the hypothesis of the impregnation/barrier effect due to the incorporation of polyphosphate glass into the structure of the MDFs. The identity of the thermal decomposition of attacked and non-attacked samples in the range 250-400C demonstrates the resistance of cross-linked sections of polymer and clinker constituents to the effects of moisture.