For how long must a sample be placed in a mechanical shaker?

The specified duration for placing a sample in a mechanical shaker is crucial to ensure proper separation and classification of aggregate particles according to their sizes. When the sample is shaken for 7-10 minutes, it provides sufficient time for the mechanical action to effectively break apart any clumps and allow finer particles to pass through meshes, while larger aggregates remain on top. This time frame is optimal to achieve a consistent and accurate gradation analysis without risking excessive wear on the mechanical shaker or potential alterations in the sample's size distribution due to over-shaking.

The duration is designed to strike a balance between efficiency and thoroughness in the shaking process, which is essential for obtaining reliable results. Too short of a duration may result in incomplete separation, while an overly extended time might lead to degradation of the sample or skewed results.