How many blows per layer are used in a standard proctor test?

How many blows per layer are used in a standard proctor test?

• A. 56 blows per layer.
• B. 30 blows per layer.
• C. 20 blows per layer.
• D. 25 blows per layer.

Answer: (B)

In a standard Proctor test, the goal is to apply a consistent amount of energy to compact the soil so you can compare dry densities reliably. The soil is put into a mold in three equal layers, and a fixed number of hammer blows are delivered to each layer with a light, measured energy. For the standard Proctor, you apply 25 blows per layer using a 5.5-pound hammer dropped from 12 inches. This setup (mold about 4 inches in diameter, three layers, 25 blows per layer) yields a repeatable compaction energy that represents typical field compaction for many soils. The key reason for this specific number is to strike a balance: enough energy to compact the soil to a representative density without overworking it. A different, higher-energy procedure—the modified Proctor—uses a heavier hammer and greater drop height, resulting in a higher density and a different number of blows per layer.

In a standard Proctor test, the goal is to apply a consistent amount of energy to compact the soil so you can compare dry densities reliably. The soil is put into a mold in three equal layers, and a fixed number of hammer blows are delivered to each layer with a light, measured energy. For the standard Proctor, you apply 25 blows per layer using a 5.5-pound hammer dropped from 12 inches. This setup (mold about 4 inches in diameter, three layers, 25 blows per layer) yields a repeatable compaction energy that represents typical field compaction for many soils.

The key reason for this specific number is to strike a balance: enough energy to compact the soil to a representative density without overworking it. A different, higher-energy procedure—the modified Proctor—uses a heavier hammer and greater drop height, resulting in a higher density and a different number of blows per layer.