Consolidation of Mineral Powders by the Geopolymer Binder Technique for Materials Use

Abstract

The geopolymer binder technique for monolithic materials production was briefly outlined. Monoliths can easily be prepared from mineral powders by mixing them with sodium silicate solutions at ambient temperature. Following 3 sources are necessary for preparation: geopolymer liquor, inactive filler and active filler. The first is sodium silicate solution working as binders. The second is ordinary mineral powders such as quartz, kaolin, pyrophyllite as well as waste powders such as fly ash, red mud and other type of slimes. The last is water quenched granulated blast furnace slag acting as a solidification agent and usually blended so as to be consisting of 10 ∼ 30 percent of total solid powders. Ratio of geopolymer liquor to solid powders were ranging from 0.45 to 0.80 depending on filler characters. Slurries cast into molds solidify in 1 ∼ 3 h to overnight due to slow polycondensation of geopolymer liquor subsequently occurring at ambient temperature. Generally over 4 MPa in flexural strength and over 10 MPa in compressive strength were reached at 28 d age and especially kaolin and pyrophyllite fillers showed extremely high strength, up to 19 MPa for flexural strength and up to 75 MPa for compressive strength. Furthermore, blending these minerals to waste powders such as fly ash was attempted to improve the weak monolith strength and it was found that pyrophyllite is the most effective mineral for such objectives