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|X-ray emission analysis of portland cement. Report 1, Variance in analysis
|United States. Army. Office of the Chief of Engineers.
|Concrete Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
|Miscellaneous paper (U.S. Army Engineer Waterways Experiment Station) ; C-68-2 rept.1.
Abstract: A balanced statistical experiment was conducted to evaluate the effect of four factors on the X-ray emission analysis for calcium (Ca), silicon (Si), iron (Fe), aluminum (Al), magnesium (Mg) and sulfur (S) in portland cement. The factors evaluated were instrument conditions (optimized versus predetermined goniometer and counter-tube voltage settings); rounds; binders used to aid in grinding and pelletizing the cement (boric acid, sodium lauryl sulfate, Boraxo, and a Boraxo-cellulose mixture); and the sample pellet-making procedure. The experimental results indicate that pellets have a direct effect on the analysis of portland cement. Binders were found to have a direct effect on the elemental analyses, and the effect was determined to be due to sodium lauryl sulfate. However, the effect is negated by the use of a ratio method of analysis. Instrument conditions and rounds were both found to have an effect on the analytical results either as direct factors or in the form of interactions, particularly the interaction of pellets and rounds. The precision of the X-ray analysis is apparently increased when optimized instrument settings are used. Either sodium lauryl sulfate or Boraxo may be used as a binder for X-ray emission analysis. Only one pellet need be made with each sample. A replicate analysis will confound the pellet-round interaction with round variances, and the pellet effect will be confounded between samples. The decision as to whether the spectrometer is to be tuned prior to every analysis is deferred until the spectrometer calibration results are evaluated.
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