Changes of thermal events of macrodefect-free (MDF) cements due to the deterioration in the moist atmosphere

Sulfoaluminate ferrite belite (SAFB) clinker premixed with Portland cement in mass ratio 85:15 was combined with hydroxypropylmethyl cellulose (HPMC) or sodium poly-phosphate (poly-P) for the macrodefect-free (MDF) process an d subsequent moisture treatment. Mass changes as the measure of the moistur e resistance and thermoanalytical traces of MDF cements gave useful informa tion. The mass change depends more on the humidity than on the composition (polymer and inorganic constituents) of the MDF cement or duration of the o riginal MDF cement synthesis. The values of mass changes at 100% relative h umidity (RH) and at ambient conditions are affected by the nature of the po lymer, poly-P being highly advantageous. Attack by environmental water and carbon dioxide increases the contents of C-4(A,F)(S) over barH(12)(AFm) and CaCO3, represented by thermogravimetry (TG) effects at 250 degreesC and di fferential thermal analysis (DTA) peaks at 600-700 degrees, respectively. I n contrast, the quantity of cross-linking, where the decomposition of Al(Fe )-O-C(P) bonds typically produces TG-DTA effects at 250-550 degreesC, remai ns intact during the moisture attack. (C) 2001 Elsevier Science Ltd. All ri ghts reserved.