Choosing Between Test Cubes and Cylinders for Concrete Compression Testing

In theory, both test cubes and test cylinders can be used for concrete compression testing on fresh pours. Simply fill up the molds with sample specimens, store under controlled conditions, and test at proper intervals. Compare the results to a standard core. However, when dealing with cured concrete, obtaining test cubes can be difficult. Core samples obtained by drilling provide 'as-built' comparisons and should ideally match the results.

Theoretical and Practical Considerations

Theoretical Approach: On a fresh pour, either test cubes or test cylinders can be used. You can fill molds with sample specimens, store them under controlled conditions, and test at proper intervals. The results can then be compared to a standard core. However, with cured concrete, it is often challenging to obtain cubes and thus core samples by drilling are necessary. These samples provide a more accurate 'as-built' comparison, hoping to align with the expected results.

Practical Approach: Cylindrical samples make more sense in practice for a few reasons. Firstly, the same testing machine can be used for both tests. Additionally, if you want to provide your results to an engineer or a statutory body, you must adhere to the norms and standard practices in your country. Different countries have varied preferences. For example, Australia and the USA use cylinders for concrete and cubes for grout, whereas Britain uses cubes for both.

Deciding Factors

Testing Agency and Building Codes: Practical speaking, this choice is determined by the testing agency and building codes. As a result, you have no control over the decision. Even if you have spare molds for cubes or cylinders, the choice should follow the established standards in your region.

Core saws are commonly used to cut out samples for testing, resulting in cylindrical samples. Other practices may be specified by road engineers, but typically, the norm is to use cylinders for concrete.

Conclusion

The choice between test cubes and test cylinders for concrete compression testing depends on the purpose of the test and the norms in your area. For accurate and meaningful results, especially in a professional or legal context, it's crucial to adhere to the standard practices.

For engineers and building professionals, understanding these differences and adhering to the appropriate standards is vital for ensuring the reliability and consistency of concrete compression testing results.