What is the primary use of the sand cone method in construction materials testing?

The primary use of the sand cone method is to determine the in-place density and unit weight of natural soil deposits, aggregate, soil mixtures, or similar materials. This method is widely employed in construction for several reasons. It provides an effective means to measure how compacted soil is at a particular location, which is crucial for ensuring stability and strength of structures.

In the sand cone method, a known volume of sand is used, and it is carefully placed into a hole excavated in the soil. By measuring the amount of sand that fills the hole and knowing the density of the sand, one can calculate the in-place density of the soil. This information is critical for engineers and builders to verify compliance with project specifications and design criteria concerning soil compaction.

Understanding the in-place density helps to confirm whether the soil has been compacted adequately to support structures and to prevent future settlement issues. The reason other options do not apply is that while the sand cone method involves excavation and density measurement, it does not focus on moisture content determination, soil permeability assessment, or plasticity evaluation. Instead, these aspects are typically measured using different methods specifically designed for those purposes.