When is a correction factor established in a standard proctor test?

In a standard Proctor test, a correction factor is established when the test specimen contains more than 5% of oversize fractions. This situation arises because the presence of oversize particles can significantly affect the density and moisture content measurements. The Proctor test is designed to evaluate the compaction characteristics of soil, and having a standard method for addressing oversize materials ensures that the resulting values are accurate and representative of the soil's compaction properties.

When oversize particles exceed 5%, they can disrupt the uniformity of the soil matrix being tested, leading to a potential misrepresentation of the soil’s density after compaction. By applying a correction factor at this threshold, engineers and technicians maintain the integrity of the test results, allowing for more reliable design and analysis of soil in construction projects. This correction is crucial in ensuring that the test results are valid for determining the optimal moisture content and maximum density for proper soil compaction.