Studies on influence of characteristics of surfactant and foam on foam concrete behaviour

Abstract

This paper describes an extensive laboratory-based investigation conducted to evaluate the relative performance of foam produced with two different synthetic surfactants namely Sodium lauryl sulphate (SLS) and Nonylphenol ethoxylate (NPE) along with an additive Carboxymethyl cellulose sodium salt (CMC) for use in foam concrete. The different essential characteristics of foam and surfactants such as initial foam density, foam stability, average bubble size and viscosity of surfactant solution are investigated in the present study through systematic experimental design based on response surface methodology. Further, based on studies on microstructure of foam concrete, it is found that selection of surfactant and CMC concentration have significant influence on foam characteristics and hence on the air void size distribution of foam concrete. In addition, the dependence of the compressive strength and water permeation characteristics of foam concrete on the air void size parameters of concrete is also investigated. Experimental outcomes indicate that increase in surfactant concentration from 3% to 6% results in 24%–44% reduction in median air void diameter in concrete which eventually led to 29%–37% enhancement in compressive strength of foam concrete mixes. In the same line, addition of CMC to surfactant solution enhances viscosity of surfactant solution significantly and thereby results in improvement of foam microstructure, concrete air void microstructure and eventually improves compressive strength of foam concrete. Further, improved microstructure with smaller air voids in foam concrete with NPE + CMC results in 10%–25% relatively higher compressive strength than SLS + CMC foam concrete mixes.