Preparation, characterization, and determination of mechanical and thermal stability of natural zeolite-based foamed geopolymers

This study is the first attempt to evaluate the effect of two foaming agents, aluminum powder and hydrogen peroxide (30 wt% water solution) on zeolite-based geopolymers and their possible use as building material according to Ecuadorian technical standards. These foamed geopolymers were prepared by alkali activation of an Ecuadorian natural zeolitic tuff and by alkali activation using NaOH (10 M), Ca(OH)(2) and Na4Si5O12 , with the use of two different foaming agents mentioned. In the case of aluminum powder, the experimental range was between 0.05 and 0.25 wt%; on the other hand, the percentages of hydrogen peroxide ranged from 0.5 to 4.0%. For characterization of the foamed geopolymer samples, quantitative X-ray diffraction (QXRD), thermogravimetric (TGA), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) techniques were used. The results of both foaming agents in zeolite-based geopolymers met Ecuadorian technical standards NTE INEN 643 and NTE INEN 638; nevertheless, the use of aluminum powder as foaming agent exhibited a better pore size distribution, suggesting a better performance. On the basis of these results, foamed geopolymers are suitable construction materials for the application of manufactured for masonry wall in houses. (C) 2018 Elsevier Ltd. All rights reserved.