Using XRD to Assess the Strength of Fly-Ash- and Metakaolin-Based Geopolymers

Compressive strength testing is usually the first test applied to alkali-activated materials or geopolymers after their manufacture to gauge the success of the selected formulation. If the compressive strength is found to be acceptable, then a raft of other tests can be applied to assess the suitability of the geopolymer for its anticipated application. It is proposed that a rapid X-ray diffraction (XRD) test can provide an indication of the strength of geopolymers via the measurement of the difference between the amorphous precursor peak position and the position of the amorphous peak of the geopolymer material. The proposed XRD method provides complementary data to mechanical strength testing and provides evidence that a geopolymer has formed.