Effective properties of a fly ash geopolymer: Synergistic application of X-ray synchrotron tomography, nanoindentation, and homogenization models

Microstructural and micromechanical investigation of a fly ash-based geopolymer using: (i) synchrotron X-ray tomography (XRT) to determine the volume fraction and tortuosity of pores that are influential in fluid transport, (ii) mercury intrusion porosimetry (MIP) to capture the volume fraction of smaller pores, (iii) scanning electron microscopy (SEM) combined with multi-label thresholding to identify and characterize the solid phases in the microstructure, and (iv) nanoindentation to determine the component phase elastic properties using statistical deconvolution, is reported in this paper. The phase volume fractions and elastic properties are used in multi-step mean field homogenization (Mori–Tanaka and double inclusion) models to determine the homogenized macroscale elastic modulus of the composite. The homogenized elastic moduli are in good agreement with the flexural elastic modulus determined on macroscale paste beams. The combined use of microstructural and micromechanical characterization tools at multiple scales provides valuable information towards the material design of fly ash geopolymers.