DEPTH PROFILING AND PHASE DISCRIMINATION IN DETERIORATED CONCRTE UTILIZING SCANNING ELECTRON MICROSCOPY WITH AUTOMATED POINT COUNT ANALYSIS

摘要

Automated point count analysis utilizing scanning electron microscopy (SEM) associated with energy dispersive spectroscopy (EDS) allows for the discrimination of various phases by chemical composition. Phases are discriminated by energy dispersive spectroscopy with "rule" files developed for all phases of interest. Automatic control of the SEM stage and recording of coordinates also allows for the mapping of individual phases by location within a polished concrete section. In this manner, relative quantities of each phase (i.e. ettringite, monosulfate, CSH) may be plotted with respect to depth of the concrete from the surface. Automation of the analysis is achieved by fixing an array of points over selected "standard" magnified paste images. The computer then obtains EDS data from each point within a given image. Images and EDS point data can be electronically stored for subsequent review. Therefore, the frequency with which a given phase coincides within the regular grid system of points allows variations in paste composition to be observed. Comparisons of automated to manual SEM analysis are presented.