RAPID METHOD OF CONCRETE. MIX PROPORTIONING USING DIFFERENT FLY ASH PERCENTAGES

Abstract

Fly ash is a ,firidi divided residue that results from the combustion of powdered coal. It is a major solid industrial waste and occupies a considerable amount of land and pollutes the air and water sources. Fly ash however, possesses several advantageous properties. It has vast potentialities as a construction material. Its utilisation not only produces technically very good concretes but also preserves and enhances the environment. The work reported herein is an experimentical study for the rapid method of concrete mix proportioning using different fly ash percentages. For that purpose four different water/binder ratios (0.3, 0.4, 0.5 and 0.6) wereaken and for each W/B ratio four different replacements of cement with fly ashux-re studied. A correlation is established between 28-day strength and accelerated strength. With the help of various correlations, one can directly determine the 28-day compressive strength of normal concretes and fly ash concretes only by knowing the accelerated strength for that particular mix. The accelerated strength can be determined by the boiling water method of curing by boiling the specimen for a period of 3 1/2 hrs just after 24 hours of casting. Therefore, the time required for mix proportioning of fly ash concretes as well as control concretes can be reduced significantly.