Packing strength into the asphalt road.

Compaction is the final procedure in road construction, its goal being to produce a surface texture of high quality. What aspects need to be considered in asphalt compaction? When compacting an asphalt road, what impact will the road’s location or ambient temperatures have on the compacting operation?

The goal of asphalt compaction is to create a pavement that offers maximum evenness and stability, while simultaneously increasing both traffic safety and riding comfort. Compaction aims at producing a road surface of maximum regularity and skid resistance, and at creating a permanent bond between the various asphalt layers. Compaction by rollers results in an extremely tight interlock between the individual particles of the mineral aggregate, which enables a high degree of stability, excellent resistance to wear, and permanent evenness to be achieved. Rollers reduce the void content in the asphalt, making it more resistant to loads and more durable.

Questions to be clarified prior to commencing work

What type of mix will be compacted, and what are the thicknesses of the individual layers? Where’s the job location? On a motorway, in a residential area, on a bridge? The answers to these questions will determine the type of roller to be used for compaction. What will be the paving width and paving speed? That will determine the number of rollers to be used.

Getting the rollers ready

Rollers are heavy road construction machines used for compacting hot and therefore flexible asphalt pavements. To prevent them from causing damage to the new asphalt surface, they must not come to a halt during the compacting operation. For precisely that reason, machine maintenance is of particular importance. In addition to that, checks need to be carried out prior to commencing work to make sure that the drum is clean, that fuel and engine oil are available in sufficient quantities, and that the water tank has sufficient water for the drum spray system.

The effect of temperature on the compaction result

The basic rule applies that the higher the temperature of the paved mix, the better will be the compaction result. However, there are no generally applicable rolling temperatures. The ideal temperature range depends on the composition of the asphalt mix, layer thickness, and type of binding agent used.

The different roller passes

An experienced roller driver begins compaction at the seams – for instance, the lateral joints to the existing lane. Starting from there, he compacts along the edge of the pavement. In bends, the lane with the smallest radius is compacted first. The next pass is to press down the pavement. In most applications, dynamic compaction is used for the subsequent main compaction phase. Dynamic compaction means that the roller drums are made to vibrate either horizontally (oscillation) or vertically (vibration), thus achieving a significantly higher compaction effect. The operation is completed by a final roller pass that will “iron out” any remaining irregularities in the asphalt pavement or surface to produce a perfect surface finish.