What does Standard Optimum Water Content refer to?

Standard Optimum Water Content refers to the specific moisture level at which a given soil type can be compacted to achieve its maximum dry unit weight. This concept is critical in soil mechanics and is established through laboratory tests such as the Proctor test. During this test, different moisture contents are tested to find the point where the maximum density is achieved without excess water, which often reduces the soil's ability to bond during compaction. Achieving this optimum water content ensures better stability and strength in construction while minimizing issues related to over-saturation, such as reduced load-bearing capacity or susceptibility to shifting.

The other options do not accurately describe the concept. While they touch on related ideas within soil behavior and compaction, they do not specifically define Standard Optimum Water Content as the ideal moisture percentage for achieving maximum dry density in compacted soil.