Abstract
EFFECT OF FLY ASH ON WATER DEMAND AND STRENGTH OF A CONCRETE MIX
*Adinna Boniface Okafor and Okonkwo John Chibuzo
ABSTRACT
The need to make concrete stronger, more workable and durable has led to increased research among scholars in the area of construction chemicals, especially cement dispersants or plasticizers. Fly ash seems to be the earliest, simplest and most common cement plasticizing compound; though not as active as the modern super plasticizers, but is still used in combination with them to achieve better results. This research studies the effect of fly ash on mixing water demand and 28-days strength of the hardened concrete at a constant consistency or slump. Five concrete mixes were studied containing 0%, 4%, 8%, 10% and 12% of class F fly ash, respectively, by weight of the cement content. The first mix containing 0% fly ash (control) was made with water-to-cement (w/c) ratio of 0.5, and it gave a slump of 30mm and a 28-days strength of 22.22N/mm2. For the remaining mixes, approximately the same slump (or consistency) was maintained by increasing the quantity of fly ash while reducing the quantity of water needed. At 8% fly ash content, maximum strength of 34.67N/mm2 and minimum water demand (effective w/c of 0.46) was obtained. Fly ash was then recommended to be used at 8%, by weight of the cement content, when used as a plasticizer alone, or in combination with other plasticizers, to achieve maximum results.
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