Investigation of silica fume as foam cell stabilizer for foamed concrete

Abstract

Foamed concrete, classified as lightweight concrete, has been commonly used in construction applications for saving energy and reducing production transportation and labor costs during construction. However, due to the tendency of coalescence and disproportionation of foam cells during the preparation process, the maintenance of the fine cellular structure has become difficult. The use of a particle-stabilized foam (PSF) is an effective way to pertain or even improve its fine cellular structure and related performance. In the paper, silica fume particles with the ability to stabilize foam were used in foamed concrete. Effect of silica fume on volumetric stability of the foam sample was investigated by the relative height of foam volume change. Effect of addition of silica fume in different stages on properties of foamed concrete was explored by viscosity, density, water desorption, compressive strength, strength/weight ratio, scanning electron microscope (SEM) and pore size distribution analysis. The result showed that the volume with a whole and fine cell pores within the foam was more stable due to addition of silica fume in the liquid foaming stage. Silica fume is beneficial for stabilizing foam, but the stabilization effect varies when it is added in different stages of the paste. Sample that was prepared with addition of silica fume in the liquid foaming stage (F1) was verified to have best strength/weight ratio against the control sample without silica fume (F0) and the sample with addition of silica fume in the preparing paste stage (F2). Mechanistic model of the various cell stabilization effect on the foamed concrete that occurred by addition of silica fume at different stages was proposed and analyzed to explain the advantages of silica fume stabilized foam concrete.