What shape should the ends of the tamping rod be for the slump test?

The ends of the tamping rod should be rounded to a hemispherical tip for the slump test because this design helps to ensure uniform compaction of the concrete inside the mold without causing segregation or excessive disturbance of the mixture. The rounded tip allows the rod to penetrate easily through the concrete, making it effective at consolidating the material evenly, which is crucial for obtaining accurate and reliable slump measurements.

Using a flat or pointed end could lead to uneven compaction or damage the concrete sample, affecting the consistency and reliability of the test results. A conical shape would also impede uniform application of force, making it difficult to achieve the desired level of compaction. Thus, a hemispherical tip supports the purpose of the slump test, which is to assess the workability of concrete by measuring how much it slumps when the mold is removed, ultimately providing crucial information about the mix's properties.