The optimum water content and maximum dry density of a certain soil or pavement material vary with the compaction work.

For the same soil or the same graded aggregate, when the compaction work increases, the optimum water content decreases, while the maximum dry density increases.

The same is true when rolling with a road roller on a construction site. If we keep the quality of the roller unchanged and increase the number of rolling passes; or increase the quality of the road roller without changing the number of rolling passes, we can get the moisture content density relationship curve with the same nature as the indoor test.

Therefore, as the mass of the road roller increases, the optimum moisture content of the soil or pavement material decreases, while the maximum dry density increases. However, there are limits to this phenomenon. exceed this limit. Continuing to increase the number of rolling passes or using a heavy roller will not significantly reduce the optimum moisture content and increase the maximum dry density significantly. When the moisture content of the material is close to the optimum moisture content at the time of compaction of the road roller, minimum compaction work is required.