Which type of material is most effectively compacted by a vibratory roller during base preparation?

The most effectively compacted material by a vibratory roller during base preparation is sand or gravel. This is because the design and operation of vibratory rollers are particularly suited to granular materials, such as sand and gravel, which have characteristics that make them responsive to vibratory forces.

As the vibratory roller moves, it imparts high-frequency vibrations that help rearrange the particles of the sand or gravel. This rearrangement leads to closer packing and an increase in density, which is essential for creating a stable base for construction. The empty spaces between the granular particles are efficiently filled in, resulting in a well-compacted layer that supports heavy loads and minimizes settlement.

In contrast, materials like clay and silt tend to have cohesive properties that do not respond as effectively to the vibratory action. These materials might require different techniques or equipment, such as static rollers or additional moisture, to achieve proper compaction. Loam, being a mixture of sand, silt, and clay, can also present challenges depending on its composition but typically does not achieve the best compaction results with a vibratory roller when compared to the straightforward compaction of coarse aggregates like sand and gravel.