Determining which compaction equipment is best suited to specific conditions.
The general type of material is the starting point. For example there is a large difference between compacting soil and asphalt. Other things to consider are the width of the area to be compacted, the final density required, the grade of the area to be compacted, the type of asphalt mix, soil type, as well the type of materials that lie below the material being compacted. Other aspects such as weight, frequency, amplitude and centrifugal force will also influence the final density achieved. In this first of a series of articles, Case assists us with the type of roller, compaction width and weight.
- Smooth drum, pad-foot drum or pneumatic for soil compaction? Granular materials such as sand and gravel require a smooth drum or a pneumatic roller. The smooth surfaces of the roller will allow granular materials to consolidate more efficiently. A vibratory compactor will allow for deeper compaction depths than a pneumatic roller. More cohesive materials, like clay, need a vibratory pad-foot drum. These soils stick together and slip over each other during compaction. It is therefore critical to shear the soil with the pad-foot drum in order to achieve the desired compaction density.
- Compaction width: One normally tries to achieve optimal compaction in the least amount of passes, but a wider compaction footprint isn’t always better. For example, one might think that an 84 in (210 cm) drum would be more productive than a 66 in (170 cm) drum, but the narrower drum may be better for getting the job done in a comparable number of passes while optimizing overlap, which helps reduce over-compaction.
- Weight: One should consider the compaction depth required and desired final compaction density. Weight is critical with pneumatic machines. The machine should preferably have a variety of weight configurations to maximize the number of applications the machine can be used for. With vibratory rollers, the static weight of the machine and the force generated by its eccentric motor creates centrifugal force, which helps determine the achievable compaction depth. If a very heavy machine is used on a thin layer it can result in over-compaction, and a machine that is too light can cause the base of the layer to not be compacted properly. Soil compaction on very deep layers needs a heavier machine with greater centrifugal force to reach the proper depths. With asphalt, frequency is more important than centrifugal force. One of the common mistakes is using a machine that is too light or layers that are too deep. Source: http://www.casece.com/en_us/News/Pages/Compaction-Technology-Specifying-the-Right-Roller-for-the-Job.aspx