Which roller is not recommended for use on clean sands?

The steel-wheel roller is not recommended for use on clean sands primarily due to the characteristics of clean sand and the functionality of the roller. Steel-wheel rollers are designed to compact cohesive materials effectively, where their weight and smooth surfaces can apply effective pressure to achieve density in those types of soils. However, clean sands are granular materials that do not have cohesion, which means that the effectiveness of a steel-wheel roller is significantly reduced.

Clean sands often require a different type of compaction approach because they do not bond together like clay or silt. The weight of a steel-wheel roller can displace the sand particles without effectively compacting them together, leading to potential issues such as uneven surfaces or insufficient density.

In contrast, other options such as vibratory rollers are effective on clean sands due to their ability to introduce vibrations that help the sand particles settle and compact better together. The responsibility of choosing the right roller type is critical in ensuring optimal compaction and stability for specific soil types, highlighting why the steel-wheel roller is not suitable for clean sands.