Cellular Lightweight Concrete - Effect of Fly Ash As a Filler and Foaming Agent

The cellular lightweight concrete (CLC) has been a widely used material for site reconstruction & low-rise structures. In CLC, the air bubbles embedded in the concrete make it lighter & stronger than conventional dense concrete. Hence, it is a cost effective material and also provides thermal insulation for the building. In addition to this, the cellular concrete has the property of good water resistance & is termite proof.

In order to improve the workability, consistency & cohesiveness of the CLC mix, different types of fillers & foaming agents have been tried. Among the many materials that are used, fly ash is found to be particularly useful because of its fine granularity. This enables the uniform embedding of the air bubbles & gives the resulting cellular concrete good strength.

However, the proportion of the coarse granularity in the cellular concrete affects its properties. When there is a large proportion of coarse granularity, the pore structure tends to become non-uniform & consequently the concrete becomes weak. On the other hand, with a high proportion of fine granularity, the pore structure is more uniform & the resulting cellular concrete has a good strength.

In this study, the effect of various filler contents on the properties like density, flow behavior, porosity and compressive strength of cellular concrete has been studied by using constant water to binder ratio of 0.5 and unit weight of 800 kg/m3. Different mixes were prepared replacing cement with fly ash in proportions of 0, 10, 20 and 30 percent by weight of the binder. The compressive strengths of the samples were tested at curing ages of 3, 14, 28 and 60 days.