Standard Test Method for True Specific Gravity of Refractory Materials by Water Immersion

A water immersion technique is used to determine the true specific gravity of a ground specimen. A completely representative sample is required for the analysis.

$210 per specimen



The true specific gravity of a material is the ratio of its true density, determined at a specific temperature, to the true density of water, determined at a specific temperature. Thus, the true specific gravity of a material is a primary property which is related to chemical and mineralogical composition.

For refractory raw materials and products the true specific gravity is a useful value for: classification, detecting differences in chemical composition between supposedly like samples, indicating mineralogical phases or phase changes, calculating total porosity when the bulk density is known, and for any other test method which requires this value for the calculation of results.

This test method is a primary standard method which is suitable for use in specifications, quality control, and research and development. It can also serve as a referee test method in purchasing contracts or agreements.

Fundamental assumptions inherent in this test method are the following:

  • The sample is representative of the material in general,
  • The total sample has been reduced to the particle size specified,
  • No impurity has been introduced during processing of the sample,
  • The sample itself is not magnetic and all magnetic material introduced during processing of the sample has been removed,
  • The material is not hydratable or reactive with water, and
  • The test method has been conducted in a meticulous manner.
  • Deviation from any of these assumptions negates the usefulness of the results.

In interpreting the results of this test method it must be recognized that the specified sample particle size does not guarantee that all closed pores have been eliminated. The amount of residual closed pores may vary between materials or even between samples of the same or like materials, and the specified sample particle size is not the same as that specified for Test Method C 604. The values generated by this test method may, therefore, be close approximations rather than accurate representations of true specific gravities. Thus, comparisons of results should only be judiciously made between like materials tested by this test method or with full recognition of potentially inherent differences between the materials being compared or the test method used.


1.1 This test method covers the determination of true specific gravity of refractory materials under prescribed conditions. It is not applicable to materials attacked by water.


Extracted, with permission, from ASTM C135 Standard Test Method for True Specific Gravity of Refractory Materials by Water Immersion, copyright ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428. A copy of the standard may be purchased from ASTM International, phone 610-832-9555, e-mail:, website:


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