What should be done if a concrete specimen fails the strength test?

When a concrete specimen fails the strength test, the appropriate course of action is to recast the specimen and test again. This step is crucial because it allows for a fresh evaluation of the concrete mixture under controlled conditions. Recasting helps to eliminate any potential issues related to the original test specimen, such as improper curing or handling that could have affected the results.

Recasting also presents an opportunity to investigate the mix design and ensure that it meets the project's requirements. By retesting a new specimen, the technician can confirm whether the initial failure was a one-time anomaly or indicative of a more systemic issue with the concrete mix.

The other options do not address the fundamental problem of the failed test in a manner that aligns with best practices in concrete testing. Ignoring the results would compromise the integrity of the construction project, while testing with a different type of aggregate or changing the water content introduces variables that could lead to further inconsistencies without properly assessing the original mix's performance. Recasting maintains the integrity of the testing process and ensures reliable and accurate results.