Properties of Ground Perlite Geopolymer Mortars

Perlite is a volcanic aluminosilicate abundant in several countries that are major producers of portland cement. The amorphous nature and silica-to-alumina ratio of ground perlite indicate that it can be activated with alkaline solutions. This study presents the strength development of mixtures containing only ground perlite as their powder binder, activated with sodium hydroxide and/or sodium silicate solutions, at room temperature or using oven curing. The structure of the formed geopolymers is investigated using X-ray diffraction, Fourier transform infrared spectroscopy, and nuclear magnetic resonance spectroscopy. The thermal stability and acid resistance of the mixtures are evaluated. Sodium silicate-activated mixtures slowly reach moderate strengths at room temperature but sodium hydroxide-activated ones do not develop strength regardless of activator concentration. Both activators produce geopolymers with high strengths with 100 degrees C dry oven curing. Sodium silicate-activated specimens are more resistant to high temperatures but less resistant to a sulfuric acid solution than are sodium hydroxide solution-activated specimens. Being natural and having a more consistent chemical composition compared with most artificial pozzolans make perlite an attractive geopolymer raw material.