Cold-recycling in-situ

Cold in-situ recycling is environmentally friendly and cost-effective

Once the bearing capacity of the asphalt surface layer has been compromised, the road structure must be completely rehabilitated. The trend is currently moving towards environmentally friendly and cost-effective solutions that involve recycling the damaged road surface.

How does cold recycling work?

During the cold in-place (or in-situ) recycling process, the reclaimed material does not leave the construction site at all, but is processed on the spot and reused immediately. This not only eliminates the need for trucks to make frequent trips to the processing station, but also reduces construction times.

"Resource-saving technologies are in demand. The cold recycling process from WIRTGEN has been proven for years – and already meets tomorrow's requirements."

WIRTGEN Cold recyclers

One Technology, Numerous Methods

As a pioneer in cold recycling, WIRTGEN offers different technologies and processes that can be used in accordance with the conditions on site. The basic technology is the same for all cold recyclers, however: small quantities of cement are spread out ahead, the asphalt layer is granulated to the desired depth, the granulate is mixed with the binding agent and water as well as bitumen emulsion or foamed bitumen, then repaved and compacted.

The difference lies in the method of paving:

When using the WIRTGEN cold recyclers of the CR series, an asphalt paver is usually used. The homogeneous material prepared by the cold recycler is transferred directly to the asphalt paver’s material hopper, where it is paved and pre-compacted.

With the WR series of cold recyclers, an additional paver is not required. Before compaction, the material is finely profiled by a grader.

All cold recyclers are supplied by water and, if necessary, emulsion or bitumen tank trucks driving ahead of them.

Recycling with cold recyclers CR

The WIRTGEN cold recycler transfers the RAP directly to the paver's material hopper for paving. This is followed by compaction.

Paving option – recycling train with WR series soil stabiliser and cold recycler

The WR uses its powerful milling and mixing rotor to granulate the damaged pavement layers, simultaneously mixing in the pre-spread cement and injecting water and bitumen emulsion into the mixing chamber. The resulting homogeneous construction material is finish-graded by a motor grader and then compacted by different HAMM rollers.

The cold recycling process carried out by a tank truck, WR 240 cold recycler, and HAMM compactor leaves behind a stable surface that can be opened to traffic without a new surface layer, if necessary.

Foamed bitumen first choice as a binding agent in cold recycling

Foamed bitumen is manufactured by injecting small amounts of water and air into heated bitumen under high pressure. The water then evaporates and causes the bitumen to foam up abruptly to between 15 and 20 times its volume. The foam is then added directly to the mixer via injection nozzles and thoroughly blended into cold and moist aggregates. The quality of the foamed bitumen is primarily defined by the parameters “expansion” and “half-life.” This is because the greater the expansion and the longer the half-life, the easier it is to process the foamed bitumen.

WIRTGEN ancillary equipment: Preliminary testing for determining the mix quality

Asphalt rehabilitation as mobile roadworks using the cold recycling method

Cold recycling using foamed bitumen as a binding agent has become an established method world-wide that has already increasingly moved into the focus of road authorities and construction companies for the rehabilitation of roads and is already being tendered as a standard procedure in some countries. It makes it possible to produce flexible and long-lasting layers. These create the perfect foundation for the final asphalt layer with reduced thickness. Foamed bitumen is produced from normal bitumen at a temperature of approx. 175°C using state-of-the-art technology. In the in-situ design, microprocessor-controlled injection systems built into the WIRTGEN CR series as well as the WR series of cold recyclers precisely inject the binding agent into the aggregate. This means the project can be carried out as a moving construction site.

Environmental Protection
Cost Efficiency
Short construction time
Cold in place recycling is very popular

Interview with Martin Diekmann, Product Manager Cold Recycling by WIRTGEN

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Road rehabilitation
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