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Quantitative X-Ray Diffraction Analysis of Handmolded Brick.


pdf icon Quantitative X-Ray Diffraction Analysis of Handmolded Brick. (803 K)
Livingston, R. A.; Stutzman, P. E.; Schumann, I.

Foam Conservation of Historic Brick Structures. Chapter 11, Donhead Publishing Ltd., Shafesbury, UK, Baer, N. S.; Fritz, S.; Livingston, R. A., Editor(s)(s), 105-116 pp, 1998.

Keywords:

bricks; x ray diffraction

Abstract:

The durability of brick is related to its microstructure and mineralogy. It has been proposed that the ratio of cristobalite to quartz would be a reliable predictor of durability. To test this theory, quantitative X-ray diffraction analysis was applied to samples of historic brick from the United States and Europe. The quantitative method was based on finding the reference intensity ratios (RIR) for cristobalite and for quartz relative to an internal standard of corundum (A12O3). Known amounts of corundum were added to the ground brick samples, and replicate X-ray diffraction patterns were taken. The intensities of the cristobalite, quartz, and corundum peaks were calculated after correcting for background. The cristobalite/quartz ratio agreed with the relative durability of bricks from Colonial Williamsburg in the United States. However, cristobalite was not detected in brick samples from Germany. Among other mineralogical differences observed, the German brick contained plagioclase feldspars while the American bricks did not. Also, one set of less durable bricks from Germany had detectable amounts of illite or mica. This suggests that the mineralogy of bricks made in Germany was fundamentally different as a result of either the raw materials used or the firing procedure. Consequently, the cristobalite index may be usable only for bricks with chemical compositions similar to those of Colonial Williamsburg. This study also revealed that corundum may not be the most suitable choice for the internal standard because of overlaps with quartz and feldspar peaks.