المستخلص: |
Large quantities of by-pass cement dust are accumulated as a solid waste during cement manufacture using the dry process which is a big environmental problem. In this investigation, it was used as an alkaline activator for burnt clay (B.C.), obtained by firing Libyan clay at 650, 750 and 850°C, as an artificial pozzolana. Hardened pastes were prepared from. 75% (w/w) B.C and 25% (w/w) by-pass cement dust at these temperatures. Another series of pastes were made form 75% (w/w) B.C. and 25% (w/w) calcium hydroxide . The pastes were made using 0.50 by weight water/solid ratio and hydrated for 1, 3, 7, 28 and 90 days. At each interval, every paste was tested for compressive strength, hydration kinetics, phase composition and microstructure. The results of the hydration kinetics, phase composition and microstructure could be related as much as possible to the development of compressive strength of the hardened pastes. The relatively high hydraulic character of by-pass cement dust reflects the high strength values relative to B.C. – CH pastes, at the early ages of hydration. While the hardened B.C. – by-pass cement dust pastes possess lower strength values than those of B.C. – CH pastes at the later ages of hydration; due to the lack of free lime, which acts as an activator, available for the pozzolanic interaction with B.C.
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