During compression testing, what is the purpose of aligning the concrete specimen within the testing machine?

Aligning the concrete specimen within the testing machine is critical primarily to ensure uniform load distribution during the compression test. When a concrete sample is subjected to compression, it is essential that the load applied is evenly distributed across the entire surface area of the specimen. Proper alignment helps achieve this uniformity, which ensures that the test results reflect the true strength of the concrete rather than variations that could be introduced by misalignment.

If a specimen is misaligned, it may experience uneven forces during the test, which could lead to premature cracking or failure at specific points, potentially skewing the data and resulting in unreliable strength measurements. Therefore, correct alignment of the specimen is a fundamental aspect of achieving accurate and repeatable test results in concrete strength testing.