How many lifts and blows are required for a 4" mold during a standard proctor test?

During a standard Proctor test, the procedure involves compacting soil in a cylindrical mold to determine its maximum density and optimal moisture content. For a 4-inch mold, the standard practice is to perform the compaction in a specific number of lifts and blows.

The identified correct procedure calls for compacting the soil in three lifts, applying 25 blows to each lift. This setup helps ensure uniform compaction throughout the soil sample, which is essential to simulate field conditions accurately. Each lift is compacted separately to avoid any inconsistencies that might occur if too much soil were placed into the mold at once. The use of 25 blows is based on empirical research that has determined this to be an appropriate level of energy to achieve maximum density for the material being tested, without over-compacting it.

In contrast, other options either propose a different number of lifts or an incorrect number of blows per lift, leading to variations in the density measurement that would not accurately reflect the soil’s characteristics. By adhering to this procedure, results obtained from the standard Proctor test can be reliably used for engineering purposes.