The compaction process of pavement materials like granular, asphalt and concrete is essential so that the strength and stiffness can be achieved. Recent studies have shown that lower ground compaction can lead to much lower strength and modulus of the pavement layer. The usage of special compaction machines such as the padfoot roller and the smooth drum roller has been beneficial for the ground stabilization process. Today, much heavier compaction machines are also available that provide static compaction so that effective density can be achieved in ground layers which are up to 250 mm in thickness. In some road constructions, the so called “spread and mix” operations can be subcontracted to specialists for a ground stabilization to achieve higher density. Generally, there are three main compaction methods for achieving density in stabilized materials: static compaction, dynamic compaction and impact compaction.
Static Compaction – With this compaction method, the weight of the compaction machine is applied directly to the soil to achieve higher pressure to the upper layers of the ground. The total weight of the compaction machine can be increased by additional steel weights that can be mounted at the rear end of the machine or by using water. The most commonly used compacting machines for the static compaction are:
- Three wheeled rollers
- Soil compactors
- Smooth drum rollers
- Padfoot rollers
- Pneumatic multi wheel rollers
Dynamic Compaction – Dynamic compaction is used for achieving rapid succession of impacts against the ground. Dynamic compaction machines when compared to the static compaction machines, are capable of providing higher compaction levels. The typical dynamic compaction machines used are:
- Single drum roller
- Tandem drum roller
- Padfoot rollers
Impact Compaction – This compaction method provides greater but less rapid impact compaction. The impact compaction machines need to be operated at significantly higher speed when compared with the vibratory and static compaction machines. Three compaction machines are used for impact ground compaction:
- Self propelled tandem roller
- Towed impact roller compactor
- Hand held roller compactor
For pavement materials which consist sand and gravel, the contractors will add certain amount of water in order to increase the moisture level. If the moisture level of the pavement materials is very dry, greater compaction effort is required. On the other hand, if the moisture level is bigger than the optimum moisture level, drying process is required. Clay materials generally require greater compacting effort than the granular materials. For these materials, a heavy static compacting roller should be used rather than the lighter padfoot roller compactors.