Abstract

Characterizing and understanding the mechanisms underlying geopolymerization are critical in achieving the use of sustainable construction material, geopolymer, for widespread commercial production. Non-destructive ¹H NMR relaxometry can provide novel information about geopolymerization as it allows simultaneous detection of where the water goes and how the pore structure changes. Coupled with the development of single-sided NMR devices, NMR measurements are not limited by the specimen size and are therefore able to observe in-situ conditions of geopolymer synthesis. Here, the curing process of metakaolin-based geopolymers was monitored by ¹H relaxometry on a single-sided NMR device. The silica-to-alumina ratio (Si/Al) was found to affect reaction stages of the geopolymerization. After the dissolution of aluminosilicate precursor, the low Si/Al of 1 was found to generate three gelation/polymerization stages as well as a water-binding stage, and two gel phases appeared. When Si/Al varied in 1.5–2.5, two gelation/polymerization stages and only one gel phase was observed.