Which factor affects the results of Proctor tests significantly?

The moisture content of the soil is a critical factor in Proctor tests as it directly influences the compaction characteristics and the maximum dry density that can be achieved. The Proctor test is designed to determine the optimum moisture content at which the soil can be compacted to its maximum density.

When moisture is added to soil, it acts as a lubricant, allowing particles to move closer together while compacting. If the moisture content is too low, the soil particles cannot adequately pack together, resulting in a lower dry density. Conversely, if the moisture content is too high, the excess water can prevent soil particles from effectively interlocking, also leading to lower density. Thus, the correct determination of moisture content is essential for achieving the most accurate results during the testing process, as it profoundly impacts the soil's behavior and properties when compacted.

While factors such as temperature, color of the soil, and age of the sample may have some influence on the material properties, they do not play as significant a role as moisture content in the outcome of Proctor tests. Temperature can affect the rate of moisture evaporation but does not directly dictate compaction results in the same way. The color of the soil generally has no bearing on physical properties related to compaction,