What must test specimens in compression meet before testing?

For test specimens in compression, it is essential that they meet requirements for uniform diameter, planeness, and perpendicularity. This ensures that the compressive strength test results are reliable and valid. When a specimen has a uniform diameter, it allows for an even distribution of stress across the surface during testing. Planeness refers to the flatness of the specimen faces, which is critical as it helps ensure that the load is applied uniformly without introducing bending moments or stress concentrations that could affect the test outcome. Perpendicularity is important for the alignment of the specimen during testing, ensuring that the load is applied directly and evenly along the axis of the specimen. Failing to meet these requirements can lead to inaccurate test results and misinterpretation of a material’s compressive strength.

Other options, while relevant to the overall quality control and assessment of concrete, do not specifically pertain to the criteria that must be met before conducting compression tests. For instance, moisture content affects the curing and strength of concrete but is not a physical property of the specimen itself at the moment of testing. Similarly, criteria for surface finish and requirements for weight and thickness are important in different contexts but do not directly relate to the factors that influence the fundamental mechanics of compression being tested.