Surface Area

SURFACE AREA MEASUREMENT STANDARD REFERENCE MATERIAL The surface area of cement is a measure of cement fineness. In Australia, the surface area of cement is determined in accordance with AS 2350.8 Fineness Index by Air Permeability Method, known as Blaine test. There are several types of equipment that are employed in the test. All of these need to be calibrated by a Standard Reference Material. A Standard Reference Material (SRM) is produced under strictly controlled conditions and is subjected to extensive testing by a large number of certified laboratories. The national Institute of Standards and Technology in the USA (NIST) is the predominant supplier of SRMs and the only supplier of the SRM for surface area calibration. Typically a developed SRM batch is in use for a period of 7-10 years depending on the quantity prepared and the demand for it. Early in 2005 NIST produced a new batch of the SRM 114 used for surface area calibration. The new batch is designated SRM 114q to differentiate it from the previous batch SRM 114p. The new SRM 114q is very different from the previous SRM 114p. As a consequence the measured surface area of the same cement calibrated by SRM 114q appears coarser than when calibrated by the previous SRM 114p. The difference is around 10m2/kg. For example, when testing a cement using an equipment calibrated by the two SRMs, the following results were obtained: Calibration SRM 114p 114q

Measured surface area (m2/kg) 370 360

Note: The actual surface area has not changed.