Use of Fly Ash Based Aggregates for Sustainable Construction

Abstract

Modern industrialization has resulted in the production of huge quantities of fly ash, which is a waste and need to be discarded safely, as otherwise, it can cause disastrous consequences on the environment, and this has become a real dilemma for the environmentalists across the world. Fly ash is a high pozzolanic industrial waste which has the significant potential to replace Portland Cement, which is a major producer of Carbon Dioxide gas, and hence, can help decrease greenhouse gas emissions. The production of fly ash is increasing every year, however its utilisation is not even half of its production. The effective use of fly ash is currently restricted only to manufacture of bricks, producing fly ash based pozzolanic cement and use in pavements. To use the fly ash in large amounts, the inventive idea is to use fly ash as a replacement material for fine aggregates, in the form of pellets and angular aggregates, in structural concrete, such as in RCC Beams.
This study describes the manufacture of lightweight fly ash based aggregates and its partial replacement in structural concrete. Accordingly, the properties of these aggregates will be compared with conventional aggregates (gravel) and commercially available low density round aggregates (LDA pellets). Fly ash used in this experimental investigation is Class ‘F’ Fly Ash obtained from Bhushan Steel Plant, Sambalpur (Odisha, India). The production of these fly ash based angular aggregates involves blending of fly ash with water, following a certain water-to-fly ash ratio and then forming fly ash briquettes using a Briquette Machine. This is followed by sintering the briquettes at high temperature and crushing them to obtain aggregates of different sizes. The properties of both round pellets and angular lightweight aggregates – such as: crushing value, impact value, specific gravity and water absorption – are compared with the properties of the conventional aggregates (gravel). The Compressive Strength, Split Tensile Strength and Flexural Strength of M20 nominal mix with different percentages aggregate replacement by LDA Pellets and Fly Ash Angular Aggregates was found at 7-days and 28-days age of concrete to study the strength variation with aggregate replacement.