Wirtgen scores a first in road recycling

Ireland’s first road recycling scheme is under way in Co Cork, with Wirtgen’s WR2400 taking the lead role. Chris Webb visited the site in September where the 3.5km trial could literally pave the way for future road rehabilitation in the Republic.

The busy N71 is a three-lane carriageway where it winds its way from Cork to the peninsula in the south west of Ireland which is so popular with tourists. The N71, or at least a stretch of it between the towns of Inishannon and Bandon, is playing host to a reconstruction project that could change the way Ireland’s roads are rebuilt in the future. The 3.5km trial, commissioned by the National Roads Authority, features a Wirtgen WR2400 self-propelled soil stabiliser/recycler owned and operated by Staplestown Ground Stabilisation of Murrintown, Co. Wexford.

Staplestown is the first Irish owned company to purchase the WR2400, which has hitherto been involved in a number of soil stabilisation projects across Ireland. The N71 trial marks a significant departure in the use of the machine in the country and looks set to open the way for greater activity in the use of recycling for pavement rehabilitation, cutting costs reducing the use of virgin materials and preserving the environment.

In charge of the project for Staplestown is director, David O’Connor. “We are reclaiming and recycling the material from the existing pavement and, in places, changing the camber of the new road at the same time,” he explains.

To do this, the carriageway is being prepared in advance of the WR2400 with the help of a Vögele 1803-2 paver, on demonstration to Arkil Ltd., of Co. Kildare, from Wirtgen Ireland. The paver is laying a granular material on top of the existing pavement to correct the road camber, aid drainage and improve road safety.

Essentially, the process involves the reworking of the existing road construction consisting of a bituminous surface and granular base to a depth of around 300mm. The WR2400 recycler machine pulverises the material to the required depth, mixes and re-lays the materials in a single pass.

On some sections of the road a patented polymer additive is also mixed in with the cement to improve flexural strength, while water is also added where necessary, depending on the optimum water content of the existing material. When the additives are mixed in the compaction of the layer is carried out in the normal way to achieve the required density. Staplestown is using a Hamm 3520 single drum sheepsfoot vibratory compactor for this exercise. The recycled stabilised layer is then surfaced with a bituminous base and wearing course.

Wirtgen WR 2400

The Wirtgen WR 2400 is a compact cold recycler designed for recycling entire carriageway structures while adding various binding agents, such as bitumen emulsion or foamed bitumen, to microprocessor controlled accuracy. Its powerful 420kW engine and working width of 2.4m, which is standard worldwide, make it suitable for working on tight construction sites or, as is the case on the N71, adjacent to live carriageways. The machine is capable of milling and recycling to a depth of up to 500mm.

All-wheel drive and ample ground clearance ensure the machine copes readily with challenging ground conditions. The recycler’s dynamic four-column hydraulically operated lifting system ensures the milling operation proceeds at the correct level whatever the undulations of the existing base, promoting a smooth and precise operation in all situations.

A large front-mounted cab gives the operator good all-round visibility; the operator’s cab can be displaced to the right side of the machine, permitting an uninterrupted view of the milling edge and precise, flush-to-kerb milling. For maximum manoeuvrability, the Wirtgen WR 2400 offers four different working modes as each axle can be steered independently while travelling forward or in reverse.

The machine’s milling drum features quick change picks, using Wirtgen’s patented tool replacement system, while the capacity of mixing chamber itself adjusts to depth of the carriageway being milled, and hence the volume of material being mixed.

In total, some 28,000m2 of road surface is being recycled on the N71 trial, representing some 8,400m3 of material. At the time of going to press, the contract was due to be completed in early October.