Methodology for the determination of <63 µm free mica fines in sand and within the cement matrix of hardened concrete blocks using scanning electron microscopy and energy dispersive spectroscopy

We propose a method for quantification of the percentage of <63 µm muscovite fines (termed free mica) in mixed sand fines and the identification/semi-quantitative analysis of free mica in the cement matrix of hardened concrete blocks. In recent times homeowners in County Donegal, Ireland reported structural problems in their buildings and concern that it is due to high concentrations of free mica within the concrete blocks. Our method requires the generation of high-resolution backscattered electron (BSE) images using field emission scanning electron microscopy (FE-SEM), where the characteristic needle-like morphology of mica can easily be identified. Additional information on the size, shape and chemical composition of the free mica fines, is gathered using energy dispersive spectroscopy (EDS or EDX). The combination of high-magnification images, high-resolution elemental maps, and mineral liberation software allows accurate identification and quantification of free mica within the sand fines and cement matrix.Supplementary material: Information pertaining to the measurements by SEM-EDX are reported in Supplementary Tables 1 and 2, available at https://doi.org/10.6084/m9.figshare.c.4709390