Abstract
Cell size and shape and closed or open configurations were found to greatly influence the compressive strength, density, water absorption, and insulative properties of two sintered fly ash/acid materials. In one case, finely ground fly ash, mixed with a water/phosphoric acid solution and alumina, is sintered to produce an open microstructure consisting of a large number of small pores dispersed relatively uniformly throughout the material. The material has a density of 0.8 gm/cm3 (800 kg/m3), very low bending strength, a compressive strength of under 800 psi (5000 KPa), and thermal conductivity of .17 W/mK. In the second case, the material had a lower density of 0.52 gm/cm3 (520 kg/m3) a higher compressive strength of 800-1000 psi (5000-7000 KPa), and thermal conductivity of .11 W/mK. This con sisted of larger closed spherical cells mixed within the other material. In a third case, theoretical studies lead us to predict values of density (696 kg/m3), improved com pressive strength (6500-9100 KPa), thermal conductivity (.099 W/mK), and less water absorption for a material consisting of closed cell/close packing structure ob tained by a different sintering process, one using a vacuum to expand the spheres to close pack them. These materials are for use as exterior applied insulation on build ings.
Get full access to this article
View all access options for this article.