Physical and chemical characteristics of fly ash using automated scanning electron microscopy

• ASEM simultaneously measures size, shape, and chemistry of fly ash particles.
• ASEM showed consistent performance with repeat investigations.
• The bulk composition from ASEM and XRF analysis compared well.
• Particles of a certain chemistry are shared by both Class C and F ashes.

Currently, bulk chemical analysis techniques are typically used to determine the composition of fly ash. While bulk analysis provides useful information, the bulk averaging process of a method removes the specificity of the data. Since the individual particles in the fly ash are participating in different reactions, the information about individual particles may be more useful for predicting the performance of fly ash within concrete. This paper presents a method to characterize fly ash on a particle-by-particle basis using automated scanning electron microscopy (ASEM). This technique can simultaneously measure the particle size and chemical composition. The data compares well with bulk powder measurements while also providing single particle information on thousands of samples. This paper also presented advanced characterization of fly ashes using this ASEM method, which cannot be observed from the bulk measurement of fly ash.