Ceramics-Silikáty 50, (3) 167 - 177 (2006) |
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EFFECT OF TEMPERATURE ON THE STRUCTURE AND STRENGTH PROPERTIES OF CEMENT PASTES CONTAINING FLY ASH ALONE OR IN COMBINATION WITH LIMESTONE |
Heikal Mohamed |
Chemistry Department, Faculty of Science, Benha University, Benha, Egypt
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Keywords: Thermal treatment, Microstructure, Compressive strength, Fly ash and blended cement |
This study aimed to investigate the effect of heat treatment on microstructure and phase composition of pastes containing fly
ash (FA) and limestone (LS). Two groups of cement pastes were prepared. In the first group, Portland cement (OPC) has been
partially replaced by 10, 20 and 30 wt.% FA (M.0, M.10, M.20, M.30). The second group of specimens is constituted by samples
derived from M.20, in which, FA has been replaced by 5, 10, 15 and 20 wt.% LS (L.5, L.10, L.15 and L.20). After 28 and
366 days of water curing, the hardened cement pastes were dried at 105°C for 24 hours, subjected to thermal treatment for 3
hours at 250, 450, 650 and 800°C, then cooled to room temperature in the furnace switched off. The compressive strength and
weight loss were determined. Scanning electron microscopy, differential scanning calorimetry and X-ray diffraction were used
for identification of the changes occurring in the microstructure of the formed or decomposed phases. The results show that
additional hydration of unhydrated cement grains, recrystallization, deformation and transformation of CSH phases were
occurred. The changes in physical state of cement pastes were studied by measuring deterioration in the compressive strength
with temperature. |
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