For Standard Proctor testing, what is the role of the hammer?

The role of the hammer in Standard Proctor testing is to compact the soil through dynamic impact. This test is designed to determine the optimal moisture content at which a specific type of soil achieves its maximum density when compacted. The hammer applies a predetermined weight and height during compaction, resulting in a controlled amount of energy being transferred to the soil as the hammer strikes down into the mold. This repeated dynamic impact compacts the soil particles more tightly together, which is crucial for understanding the soil's behavior under load and its potential use in construction projects.

The other roles mentioned, such as holding the mold securely, measuring moisture content, or increasing the weight of the soil, do not align with the primary function of the hammer in this testing method. The hammer's primary focus is solely on achieving proper compaction.