The aim of the present work is to study the effect of low grade aluminosilicate refractory bricks (ASRBs) with metakaolin (MK) on the hydration properties and the fire resistance of composite cement pastes at elevated temperature up to 800 oC. The composite cement are composed of constant proportion of ordinary Portland cement (OPC) (80 wt%) with variable amounts of ASRBs and MK. The substitution of 20% ASRBs with MK increases the water of consistency and retarded the initial as well as the final setting times, whereas the free lime contents and the bulk density decreases with MK. The compressive strength increases with MK content which enhanced the early and long term strength. It acts also as micro-filler that accelerates initial cement hydration. The fire resistance of composite cement pastes was evaluated up to 800 oC with rate of firing 5 oC/min. and soaking time for 2 h. The physico-mechanical properties such as, weight loss, bulk density and compressive strength were determined at each firing temperature. Moreover, some selected samples were investigated by using XRD, DTA/TG and SEM techniques analyses. Cement pastes containing 20 wt% ASRBs (PC-A) is the optimum composite cement paste which gives high bulk density and compressive strength. It can be concluded the cement paste PC-A has a good fire resistance paste.
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