Properties of Gypsum Wallboards Containing Fly Ash

Abstract

In this study, the effect of replacing calcined gypsum in wallboards with fly ash was studied. Three types of fly ash produced in Alberta, Canada, were used for replacement of as much as 40% of the calcined gypsum in wallboards. All the three types of fly ash were pozzolanic as well as self‐cementitious. Wallboard specimens were prepared in the laboratory, placing gypsum, fly ash, pulp, starch, and foam slurry between two sheets of paper. Strength and other physical properties of wallboards, with and without fly ash, were determined. It was concluded that as much as 30% gypsum in the core of wallboards can be replaced by fly ash with very little detrimental effect on the properties of the wallboard. The results indicated there was only a slight loss in the compressive strength for 30% replacement of gypsum with fly ash. Wallboards containing fly ash developed high core hardness, nailhead pull resistance, and water resistance. They were also observed to have lower thermal conductivity than those containing only calcined gypsum.