What kind of tests are performed on concrete in highway construction?

In highway construction, the slump test and the compressive strength test are fundamental methods used to evaluate concrete quality. The slump test assesses the workability and consistency of the concrete mix. It provides an indication of how easily the concrete can be placed and compacted. A proper slump ensures that the concrete will flow well into forms and around rebar, leading to better compaction and strength.

The compressive strength test, on the other hand, is crucial in determining the concrete's ability to withstand loads. This test measures the maximum load that a concrete sample can bear before failure, which is essential for ensuring that the concrete meets the structural requirements of a highway.

Other tests mentioned in the other options, such as water absorption and flexural strength, are not standard primary tests for highway construction concrete. While tests like thermal conductivity and tensile strength also have their applications, they are not typically prioritized for the immediate quality assessment of concrete in highway contexts. Elastic modulus and pH tests have different purposes and are not standard tests during the initial concrete evaluation process in highway construction. Hence, the combination of slump and compressive strength tests provides a comprehensive assessment of both workability and structural integrity, making it the most relevant choice.