4.1 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.

4.2 This test method is particularly useful for hydratable materials that are not suitable for test with Test Method C135.

4.3 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 that requires this value for the calculation of results.

4.4 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.

4.5 Fundamental assumptions inherent in this test method are the following:

4.5.1 The sample is representative of the material in general,

4.5.2 The total sample has been reduced to the particle size specified,

4.5.3 No contamination has been introduced during processing of the sample,

4.5.4 The ignition of the sample has eliminated all free or combined water without inducing sintering or alteration,

4.5.5 An inert gas (helium) has been used in the test, and

4.5.6 The test method has been conducted in a meticulous manner.

4.5.7 Deviation from any of these assumptions negates the usefulness of the results.

4.6 In interpreting the results of this test method, it must be recognized that the specified sample particle size is significantly finer than specified for Test Method C135. Even this finer particle size for the sample does not preclude the presence of some closed pores, and the amount of residual closed pores may vary between materials or even between samples of the same or like materials. The values generated by this test method may, therefore, be very 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.