PARTIAL REPLACEMENT OF CEMENT WITH FLY ASH - OPTIMUM BLENDS.
The SiO//2 in Fly Ash (FA) combines readily with Ca(OH)//2 in cement paste. Hence, when cement is partially replaced with FA, not all of the potential strength of the replaced cement is lost. Less cement is not only a saving, but has also other attributes such as lower heat production and greater resistance against alkali aggregate reaction (AAR) and sulphates. Physically, FA enhances workability, plasticity, placeability and pumpability of wet mixtures. A prerequisite for durability is dense concrete. A study on the effect of cement and blended cement on packing of the solids in a mixture revealed that an optimum percentage binder which is rather low, exists. Binder contents should therefore be kept low, and preferably below 20% for best packing. A new and a more functional concept of bleeding is also presented.