Evaluation of the use of potassium hydroxide in geopolymers aiming to prevent the formation of efflorescence

Abstract

The present study developed geopolymers through the combination of potassium hydroxide and silicate (KOH + SS) and potassium hydroxide and sodium silicate (KOH + SS) as activator mixture and residue of glass cutting and metakaolin as precursors, aiming to mitigate de efflorescence formation. X-ray diffraction (XRD) tests, visual analysis of the possible efflorescence formation and compressive strength tests were made on the produced geopolymers with the activator with molarity of 10, silica/alumina ratios of 3,5 and 4,0, subjected to thermal cures of 40 and 60 ºC, at the ages of 28 and 63 days. The XRD analysis showed that all pastes displayed quartz peaks in positions between 2θ = 20º e 30º, proving the presence of crystalline phases, but the geopolymers generated with sodium silicate presented peaks with higher intensity. None of the geopolymeric pastes had visual efflorescence formation. The mechanic tests made it possible to determine that the geopolymers that presented the best mean compressive strength were those made with the KOH + SS activator. The temperature of the cure that generated the best results was 40 ºC.

Keywords
Geopolymers; Potassium hydroxide; Residue of glass cutting; Metakaolin; Efflorescences