Studying the effect of thermal and acid exposure on alkali activated slag Geopolymer

Housing and Building National Research Centre (HBNRC) 87 El-Tahreer St. Dokki, Giza, P.O. Box 1770 Cairo

e-mail: Hkhater4@yahoo.com

Abstract

This article reports a study about thermal stability as well as acid resistance of geopolymer materials prepared from Ground Granulated Blast Furnace Slag (GGBFS), Air Cooled Slag (ACS), Silica fume (SF) and cement kiln dust (CKD) using 6% (weight) of equal mix from alkaline sodium hydroxide and sodium silicate activators. Study of addition of ACS, SF and CKD as partial replacement of GGBFS is investigated so as to improve the mechanical and microstructural properties of geopolymer mixes. Compressive strength and SEM were utilized in these studies. Materials were prepared using water/binder of 0.30 at 38°C and 100% RH. Results showed that geopolymer materials prepared using alkali activated slag exhibit large changes in compressive strength with increasing the firing temperature from 300 to 1000°C and exhibit an enhancement in thermal stability as compared to concrete specimens. Materials prepared by replacing GGBFS by 15% ACS resist thermal deterioration up to 1000°C. It was suggested to be suitable for refractory insulation applications as well as for production of nuclear concrete reactors. On the other hand, geopolymer mixes exhibit low stability upon subjecting to different concentration from the mix of nitric and hydrochloric acid in equal ratio (1:1). Current studies of geopolymer microstructure were focused on the morphology as well as the relationship between compositions and mechanical properties.