Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) as a potential on site tool to test geopolymerization reaction

Abstract

Geopolymers, synthesized starting from aluminosilicate precursors activated with alkaline solutions, constitute a class of materials of high interest as potential substitutes of traditional, cementitious, binders. Infrared spectroscopy is one of the routine analytical techniques employed to study these materials and to verify the occurrence of geopolymerization; on the other hand, its portable version working in diffuse reflection is not enough exploited for their characterization. The aim of this work is therefore to assess the potentiality of Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) in the study of geopolymers. The combination of this technique with Principal Components Analysis (PCA) statistical treatment was used to search for criteria able to discriminate the successful products from those which require a correction in their formulation. Mainly, two groups of geopolymers were studied, based respectively on clay sediments and ceramic waste precursors, in the latter case with the possible addition of metakaolin. These samples were studied both after maturation, comprising several variables in their mix-design and curing, and during the first hours of solidification of the slurry. The results allowed to identify the best formulations within the analyzed groups. Besides, the extension of this study to a wider selection of geopolymers, such as the pumice-, volcanic paleo-soil- and/or metakaolin-based ones, already studied with other techniques, further confirmed the efficacy of DRIFT spectroscopy in the identification of the geopolymerization reaction.

Keywords: Alkali activated materials; Diffuse reflectance infrared spectroscopy; Geopolymers; Nondestructive analysis; Principal component analysis.