ASTM D4535-21 PDF Download

ASTM D4535-21 is a standard that provides test methods for measuring the thermal expansion of rocks using a dilatometer. The information regarding the thermal expansion characteristics of rocks is crucial in the design of underground excavations, particularly in scenarios where the surrounding rock may be subjected to heat. This standard is applicable in various applications such as nuclear waste repositories, underground power stations, compressed air energy storage facilities, and geothermal energy facilities.

The coefficient of thermal expansion (a) of rocks is known to vary with temperature changes. These test methods enable the continuous measurement of thermal strain values as a function of temperature, providing information on how the coefficient of thermal expansion changes with temperature. It is important to note that rocks can also be anisotropic, meaning they exhibit different thermal strains depending on the direction of strain measurement. In such cases, specimens with different orientations need to be prepared and tested.

The standard emphasizes that the quality and reliability of the test results depend on the competence of the personnel conducting the tests and the suitability of the equipment and facilities used. Compliance with practice D3740 is recommended to ensure competent and objective testing. However, it states that compliance with this practice alone does not guarantee reliable results as many factors contribute to the accuracy of the measurements.

ASTM D4535-21 includes two methods for measuring thermal expansion: Method A for unconfined or benchtop measurements and Method B for confined conditions. These methods can be applied within a temperature range of 25°C to 300°C and can accommodate rocks with varying moisture content. The standard also provides guidelines for apparatus size, construction, and usage to ensure satisfactory results.

It is important to note that these test methods do not cover all possible test situations and may require technical knowledge related to heat flow theory, temperature measurement, and general testing practices. Additionally, the standard highlights guidelines for significant digits and rounding of observed and calculated values. However, it acknowledges that significant digits may vary depending on material variation, the purpose of obtaining the data, special studies, and user objectives, which are not within the scope of the standard.