Compaction Equipment - Part 2

Continuing from part 1...

The static roller compactors vary in the size and in the weight and different models can be found, from small static rollers to big rollers that can weigh up to 10-13 tones. The small static roller models are generally involved in smaller construction projects, such as for compacting small parking lots and driveways. The only variables that can be changed into the static roller are the weight of the ballast and the speed of the static roller. The static roller compactors are usually equipped with additional water tanks to prevent the asphalt material from sticking to the drums on the static roller. Such water system keeps the drums clean from picking asphalt materials during the compaction process. One important thing that needs to be highlighted when static rollers are used, is that the drums of the roller should always be faced towards the direction of the compaction operation. In this way the roller pulls the asphalt material under the drums and displacement or shoving is greatly reduced.

Pneumatic roller compactor. This roller is also known as rubber tired roller compactor. It uses static and manipulation force in order to compact the material. The pneumatic roller compactors are generally used for initial and breakdown compaction, as well as for intermediate compaction processes. Asphalt material is being compacted through tire pressure and through the ballast of the pneumatic roller compactor. The pressure in the tires ranges from 450 – 850 kPa depending on the number of piles in the tire construction. The inflation pressure in the tires in the key element for the proper operation of the pneumatic roller compactor. Higher tire pressure means higher compacting force transferred to the ground. For intermediate compaction the pressure in the tires is kept high for achieving proper compacting results. Overinflated tires can cause grooves to appear in the ground. Large tires are very effective in breakdown rolling. The same water spraying system is used with the pneumatic rollers. This system prevents the asphalt material from sticking to the tires.

Vibratory roller compactor. The vibratory roller combines the static and the impact force for more effective compaction. The compacting effort that is created from the static force is generated from the weight of the roller and from the drums. On the other hand, the compacting effort that is created by the impact force is generated by a rotating eccentric weight which is located in the drums. Dynamic force is being created as the weight rotates inside the drums.

The vibratory roller compactors can be found in different sizes and shapes. Most common are the single drum and the double or tandem drum vibratory roller compactors. The single drum roller is heavily used for soil and granular compaction. They are less used for asphalt material compaction. The tandem or double drum vibratory rollers are designed with rigid single or double articulated frame. These machines have the capability to work in any of the following modes: static with no vibrations, one static drum and one vibrating, and both drums vibrating.