You may have seen different rollers out on jobsites and wondered exactly what is the difference? Which type should I utlise on my site and when? To run an efficient site it is important to use the right piece of machinery for the right job.
Compaction is a process to increase soil density. During compaction, soil particles are artificially rearranged and packed together by applying mechanical energy. The aim is to increase soil strength, stability and reduce permeability and erosion. Many different types of rollers exist in construction and earthmoving and each of them is designed to be used in a slightly different way.
Single Smooth Drum / Construction Roller
These are a common form of roller seen on roadworks and construction sites for granular soils, asphalt and gravel compaction. They create a flat surface for roading, sidewalks, driveways and foundations. The single drum at the front and rubber tyres at the back allow for good grip and traction.
Double Smooth Drum
The double-drum roller, similarly is good for finishing the upper surface of the soil. It is mostly used for asphalt compaction and other aggregate base materials. Great for projects involving roads, paths, playgrounds, and parking lots.
The double steel drums don’t give great traction. Be careful when loading and unloading transporters – especially in the rain or if the ramps are steel. Always load on a flat surface.
In NZ, single drum construction rollers are currently popular for health and safety reasons. The single drum at the front and rubber tyres at the back allow for much better traction and stability than their double drum counterparts. There has been a few high profile incidents with double drum rollers which have seen some contractors ban them from sites.
However, can you get the job done with single drum rollers? It has been argued that the weight on many single smooth drum rollers is over the tyres rather than the roller drum. This means doing many more static passes to reach compaction than you would need on a double drum roller and reducing efficiency. One case study I have seen reported during plateau testing for a carpark, an 18T single drum roller did 4 vibratory passes and 20 static passes and still couldn’t reach the 98% compaction required. Conversely, an 8T double drum roller reached 98% compaction with vibratory passes and only 6 static passes.
Rubber-tired, or pneumatic, rollers in certain applications provide contractors with a better base before paving.
They are used to manipulate asphalt to bring density and stiffness to the material. When completing chip seal projects, pneumatic rollers will set the rock chip in the oil without picking up and damaging the edges of the rock.
"Traditional steel drum rollers may tend to push some material as opposed to compacting it. The pneumatic-tire machines confine the material between the tires and with the kneading effect have a better opportunity to improve density in a tender zone. The kneading effect brings the oil up to the surface. It gives it that really nice, rich, black finish, which is what some contractors like to see." Steve Cole, vice president of the Western Region, Dynapac USA.
Padfoot Roller / Compactor
Padfoots normally have rubber tyres at the back and one vibrating steel drum on the front with knobbly steel pads. A padfoot roller should be used when you need to compact soils at greater depths and if the soils contain sticky, cohesive materials such as clay, silt or loam. The pads penetrate the soil to build up strength. These rollers normally range from 5T through to 18T and are designed to compact backfilled trenches and fills on most residential or commercial sites.
Compactors such as the CAT 836K are the giant versions of padfoot rollers. They have two steel padded drums, a blade and are used on massive earthworks and landfill sites for compacting and stabilising fill material.
Remote Control Trench Rollers and Plate Compactors
New remote control technology have created innovation in the compaction space. You can now get double drum padfoot trench rollers and plate compactors operated via remote control to assist with infrastructural service trench work. The infrared remote control systems provides maximum safety. The operator doesn’t have to get in the hole and is protected from vibrations, noise, dust and fumes.