How many lifts and blows should a 6" mold be compacted during a standard proctor test?

During a standard proctor test, the procedure involves compacting a specified soil sample within a mold to determine its optimal moisture content and maximum dry density. For a 6-inch mold, the established standard according to ASTM D698 (Standard Test Method for Laboratory Compaction Characteristics of Soil Using Standard Effort) specifies that the soil is to be compacted in three layers, or lifts. Each lift is then compacted with 25 blows of a standard 5.5-pound hammer dropped from a height of 12 inches.

When analyzing the answer of three lifts with 56 blows each, it's important to see that while the lift count aligns with the standard for a 6-inch mold (which is indeed three lifts), the blow count deviates from traditional practice. The total blows should accumulate to approximately 25 per lift for a standard test.

This is why this choice is noted; it adheres to the correct lift count specified for a standard proctor test. Nonetheless, the blow count is not accurate per the established norms, which emphasizes the need to refer to the current testing standards to ensure clarity regarding blow counts and lifts.