Air-void characterisation of foam concrete

The pore structure of cementitious material, predetermined by its porosity, permeability and pore size distribution, is a very important characteristic as it influence the properties of the material such as strength and durability. The pore parameter could therefore be a primary factor influencing the material properties of foam concrete and an in depth look into this aspect is required to establish relationships between this and material properties. In order to evaluate these relationships it was necessary to develop parameters to explain and quantify the air-void structure of foam concrete. This paper discusses the investigations done to characterise the air-void structure of foam concrete by identifying few parameters and influence of these parameters on density and strength. A camera connected to an optical microscope and computer with image analysis software were used to develop these parameters. It is found that out of the air-void parameters investigated, volume, size and spacing of air voids have influence on strength and density. Mixes with a narrower air-void size distribution showed higher strength. At higher foam volume merging of bubbles seems to produce larger voids, results in wide distribution of void sizes and lower strength. Air-void shape has no influence on the properties of foam concrete. (C) 2006 Elsevier Ltd. All rights reserved.