Ceramics-Silikáty 48 (4) 185-196 (2004)

INFLUENCE OF CURING TEMPERATURE ON THE PHYSICO-MECHANICAL, CHARACTERISTICS OF CALCIUM ALUMINATE CEMENT WITH AIR-COOLED SLAG OR WATER-COOLED SLAG

M. Heikal, M. mahmoud Radwan, M. Saad Morsy

The nature, sequence, crystallinity and microstructure of hydrated phases were analyzed using differential scanning calorimetry (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the formation of different hydrated phases was temperature dependence. The physico-mechanical and microstructural characteristics were investigated after curing at 20, 40 and 60° C. The results indicated that for the substitution of calcium aluminate cement (CAC) by air-cooled slag (AS) or water-cooled slag (WS) at 20° C, the compressive strength increases with slag content up to 10 wt.%, then followed by a decrease with further slag substitution up to 25 wt.%; but the values are still higher than those of the neat CAC pastes at different curing ages up to 60 days. After 28 days of hydration at 40-60° C, the compressive strength increases with the slag content. This is attributed to the prevention of the conversion reaction, which was confirmed by XRD, DSC and SEM techniques, and the preferential formation of stratlingite (gehleinte-like) phase. The SEM micrographs showed a close texture of hydrated CAC/slag blends made with AS or WS at 40°C due to the formation of C₂ASH₈ and C-S-H phases.

Keywords: Calcium aluminate cement, Curing temperatures, Physico-mechanical properties, Microstructure and phase compositions