The third analytical test I performed on the raw fly ash and the geopolymers was dilatometry a.k.a. thermo mechanical analysis (TMA). This is a measure of the deformation of a material under a constant stress over a temperature range. The result of this method is a plot of the length change of the material as it is heated to a high temperature. This technique is useful for detecting the kinetics of solid state phase transformations. Specifically, dilatometry can be a powerful tool for quickly analyzing the reactivity of different fly ash sources. The high-temperature expansion peak can be linked to the release of chemically bound water and geopolymer samples that exhibit this expansion at higher temperatures tend to have a higher strength. Other phenomena that can be observed from the dilatometry plot include dehydroxylation and viscous sintering.
Here are pictorial instructions on how to perform dilatometry measurements on geopolymers:
The final data will reveal whether the fly ash source and the activating solution have formed a strong, durable geopolymer matrix.