How many layers is the standard compaction sample compacted in?

The standard compaction sample is typically compacted in three layers. This method of compaction is based on ensuring uniformity and accuracy in density measurements, as each layer can be compacted to a consistent degree. By using three layers, it allows for a more comprehensive assessment of the material's response to compaction forces, achieving a more representative density throughout the sample.

The practice of compacting in multiple layers helps to avoid variations that might occur if the sample were to be compacted in one single layer, which could lead to inadequate density in some parts of the sample. The three-layer approach is standard in many testing procedures, as it ensures that all areas of the sample receive equal treatment during compaction, leading to reliable and repeatable results for the evaluation of aggregate bases.