How many layers should the slump mold be filled in during testing?

The correct response is that the slump mold should be filled in three layers during testing. This method is designed to ensure that the concrete is given adequate compaction and uniform consolidation throughout the mold. Each layer should be about one-third of the mold's height.

Filling the mold in three layers allows for the use of a tamper to compact each layer effectively, which helps to eliminate air pockets and ensures a consistent and representative measurement of the concrete's workability. Each layer should be rodded a specific number of times, usually 25 times, to achieve proper consolidation. This three-layer approach reflects standard practices in concrete testing, providing reliable and reproducible slump results that are critical for assessing the consistency and performance of the concrete mix.