What should be done if the core thickness is impossible to obtain?

When the thickness of a core sample is impossible to obtain, ensuring that the length-to-diameter (L/D) ratio equals 1 and documenting the reason is the correct course of action. This is because the L/D ratio is crucial for ensuring that the sample is representative and that the results of the testing meet the required standards for reliability and accuracy.

By maintaining the L/D ratio of 1, the integrity of the sample is preserved, which helps in achieving consistency in testing conditions. Documentation of the reason for any deviations is vital not only for quality control but also for providing context for the test results. This approach aligns with standard testing protocols, which emphasize precision and accountability in sample preparation.

In contrast, using any thickness that fits, ignoring the requirement, or testing regardless of size would compromise the validity of the test results and violate established standards in concrete testing.