Factsheet 8.1; Calcium Silicate Masonry / Brick
(Factsheet Updated 12th August 2002)
Calcium Silicate Masonry
Calcium Silicate Masonry / Brick is manufactured by mixing high calcium lime with a very fine siliceous aggregate, & water, which is then moulded at high pressure, followed by high-pressure steam curing.
The result is the combination of the lime with part of the siliceous aggregate to produce Hydrated Calcium Silicate, which forms the binding medium.
The finished masonry brick is usually yellowish coloured, although inert inorganic pigments can be added during manufacture when different coloured bricks are required.
BS187 includes 'minimum properties' for Calcium Silicate bricks, including size, strength, & drying shrinkage.
Calcium Silicate Brick is sometimes viewed as an 'undesirable material' in structures, and thus there is often a requirement for laboratory identification.
A highly useful tool for such identification is X-Ray Diffraction Analysis.
XRD Procedure
X-Ray Diffraction is applied to determine the presence of crystalline compounds within the samples; the detection limit is typically 0.5%.
Identification is achieved by comparing the x-ray diffraction pattern, or 'diffractogram', obtained from the unknown sample with an internationally recognised database containing reference patterns for more than 70,000 phases.
Typical XRD Results -
Below is the XRD diffractogram of a sample of Calcium Silicate Brick.
Each mineral is identified by a pattern of 'peaks' relating to that mineral species.
The presence of Quartz and Calcite as the major components indicate that this sample is a calcium silicate brick. Vaterite, a high temperature polymorph of Calcite, is present as a minor component.
(Tobermorite is a binding component normally associated with calcium silicate bricks, but is often poorly crystallised and is therefore difficult to detect by XRD).
