Method for Direct Determination of Glassy Phase Dissolution in Hydrating Fly Ash‐Cement System Using X‐ray Diffraction

A method for quantitative X‐ray diffraction analysis is developed for direct determination of the glassy phase content of fly ash in a hydrating binary blend of cement and low‐calcium, siliceous fly ash. The intensity contributions of the unhydrated glassy phase of fly ash and the amorphous reaction products to the intensity pattern of the total amorphous phase in the hydrating binary blend are obtained by decomposition of the total intensity signature as a sum of component pseudo Voigt (PV) peaks. An experimental program involving binary blends with three different low calcium siliceous fly ashes and two different curing temperatures is reported. The centers of the component PV peaks of the fly ash glassy phase fitted to the overall intensity pattern are found to be invariant. The glassy phase content of hydrating binary blends determined from the XRD method were found to agree well with the values obtained from a selective dissolution method.