Author : Dr.Mudimby Andal 1
Date of Publication :7th December 2016
Abstract: Use of fly ash in concrete as replacement to cement is an established practice accepted all over the world. The reason is mainly due to the fact that replacement or addition of fly ash reduces the cement consumption and make the concrete economical. Flyash concretes are more durable than conventional concretes. However, the addition of fly ash in concrete decreases the pH of concrete and reduction in pH value disturbs the passivation layer formed around the rebars. The passivation layer is formed around the rebars in concrete due to the higher alkalinity of concrete. Thus the addition/replacement of cement by fly ash affect the pH and thereby the alkalinity. This article describes the effect of replacement of cement by fly ash on the pH value of the end product i.e., fly ash concrete. Fly ash concrete and mortar specimens are cast and tested for pH. It is found that replacement of cement by fly ash reduces the pH of the matrix. With the increase in the age of fly ash concrete reduction in pH value is found to be more. This indicates that the reaction of fly ash with Calcium Hydroxide present in concrete with time reduces the pH value. It is concluded that the treated flyash would be more effective and beneficial than replacement of cement with untreated fly ash..
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