Durability of mortars of white cement against sulfate attack in elevated temperatures

摘要

In this study, white cement CEM 1-32,5 & white limestone cement CEM Ⅱ-A/LL, with 15% limestone substitution, were investigated. Mortars were made from these types of cement and the durability of these mortars against sulfate attack as well as the effect of temperature (50 ℃) were investigated. During the experiment, the mortar samples were being observed visually on a regular basis using the Heine Delta 20~® LED Illuminated Loupe 10× device. After a period of 90 days, the mortar samples' com-pressive strength was determined and the deterioration products which affected the durability were identified. The identification of the deterioration products was made through means of X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM-EDAX), Thermogravimetry (TG), Infra-Red Spectroscopy (FT-IR) and Mercury Porosimetry (MP). The results of this study clearly displayed that the rate of sulfate attack to the cement with limestone substitution was lower compared to that of pure cement. Furthermore, it was shown that this type of cement is three times more durable than pure cement of the same category. It was also identified via different methods of analysis that the cause of the deterioration was the development of microcrystalline ettringite which caused microcracks and degradation of the specimens. In conclusion, it is shown that in the case of same class cement with limestone substitution, such a microstructure is developed which does not allow the penetration by sulfate ions. This is demonstrated through the higher resistance of this specific mortar despite the adverse conditions in which these mortars were exposed to.