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For users of the VCCTL who do not have access to a scanning electron microscope (SEM) with X-ray imaging capabilities, a database of cement images has been created. Currently, the database contains 2-D images, quantitative image analysis results, and measured particle size distributions (PSDs) for 17 different cements produced in four different countries, as shown in Figure 2. The characterization process has been described in detail for two of the Cement and Concrete Reference Laboratory cements in a previously published report [6]. As new cements are processed at NIST, they will be added to the existing database. Typically, the PSD and quantitiative phase analysis information will be used as input to construct a starting 3-D microstructure for a specific cement.
Figure 2: Form to select a cement from the cement images database.
Upon entering the cement images database, the user will first be allowed to select a specific cement of interest using a fill-in form. Once this form is submitted, a 2-D color processed SEM/X-ray image will be returned along with the measured PSD for the chosen cement, as shown in Figures 3 and 4 for Cement 135, issued by the Cement and Concrete Reference Laboratory in January of 2000. The PSD is reported on a particle diameter basis, with both mass and number fractions reported. The number fractions have been obtained from the mass fractions based on the number of pixel elements present in digitized 3-D particles of each specific diameter [1]. For small diameters (3 pixels and 5 pixels), it should be noted that the volume of the digitized sphere is significantly greater than an equivalent diameter continuum sphere.
Figure 3: First half of page from cements image database for Cement 135.
Figure 4: Second half of page from cements image database for Cement 135.
Each cement page also contains two links to further information. The About this cement link directs the user to a secondary page that contains the quantitative image analysis results for this cement, including the names of the computed correlation files which can be used to create "equivalent" 3-D microstructures. Normally, this page will be printed by the user for later use with Menu Selection 7 to distribute the cement phases amongst the 3-D particles. The Access the ftp site for these files link directs the user to an anonymous ftp site from which the correlation and PSD files can be downloaded for personal use. Optionally, the measured PSD provided on the cement page can be printed and typed in by the user as input into Menu Selection 2) Create a particle size distribution file.
