Quantitative X-Ray Diffraction Analysis of Handmolded Brick.
Quantitative X-Ray Diffraction Analysis of Handmolded
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
bricks; x ray diffraction
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