What must be avoided when raising the slump mold?

When raising the slump mold, it is crucial to avoid rotating or twisting the mold. This is because any rotational movement can compromise the integrity of the concrete sample being measured. The slump test is designed to assess the workability of concrete, and introducing any motion that disturbs the sample can lead to inaccurate measurements.

The primary goal during this step is to maintain the vertical orientation of the mold and to lift it straight upwards. This ensures that the cone shape of the concrete is preserved and that the resulting slump is a true representation of the concrete's consistency. Proper technique is essential to achieve reliable test results, which are vital for quality control in concrete work.

Although there are other considerations such as the speed at which the mold is raised, the amount of force used, and the removal of excess concrete, these concerns do not impact the integrity of the slump measurement as directly as improper rotation or twisting does. Therefore, avoiding rotation or twisting is key to maintaining the accuracy and reliability of the slump test.