The road construction and traffic authority Landesbetrieb Mobilität (LBM) Cochem-Koblenz commissioned a pilot project in the course of their endeavours to further optimize the cold in-place recycling process (CIR). The aim was to examine the extent to which the layer thickness can be reduced, at least for roads which are less heavily used – such as district roads – looking at both economic aspects and the technical feasibility. For the purposes of the project, a 1,250-m stretch of road on the L 114 in Weibern, Rhineland-Palatinate, was rehabilitated using the resource-saving cold recycling process. The CIR layer was 12 cm thick rather than 18 to 20 cm, as is usually the case. The surface course paved on top was only 4 cm thick. The project was monitored by the State Ministry for Construction of Cochem-Koblenz – the responsible authority – while the laboratory for road and concrete construction, sbt, in Trier acted in the capacity of an independent testing laboratory. The first findings of the sbt laboratory are presented below.
Wirtgen GmbH – The pioneer of cold recycling technology
Featuring the recycling of all reclaimed material and its cost-effective processing, the cold recycling method is one of the most resource-saving processes in road construction. The demand for cold recycling technology has climbed sharply in recent years, spurred by rising prices for raw materials and energy. As the leading company in the sector, Wirtgen has been developing new means of optimizing the structural rehabilitation of roads for over 20 years now. Today, the mechanical engineering company offers its customers nine machines and plants for in-situ or in-plant cold recycling applications.
Invaluable savings on resources and costs
The WR 4200 – the most powerful machine in Wirtgen's cold recycler fleet – was used on the job site between Weibern and Engeln. The machine was able to mill the 7,200-m² road section and process it in a single pass within the space of just three days. Dipl.-Ing. Alexander Axt, the engineer in charge of the construction project for the company Kutter, says: "We are saving a vast amount of time on this job. The total construction time would normally have been six weeks, but we only needed three." What's more, unlike the conventional process involving the replacement of the surface and binder course, the cold recycling processes meant that the width of the roadway could be maintained without widening it, as would normally be required. Cold recycling not only saved valuable resources but also saved up to 10% on costs in comparison with ordinary rehabilitation methods. Moreover, construction projects using the two-layer rehabilitation method are eligible for state funding, fulfilling all the relevant criteria.
Check test findings fulfill basic statutory conditions
During the construction work, the laboratory sbt implemented an extended quality assurance program, both on the job site and in the laboratory. "All values investigated as part of the check test, both on the job site and in the laboratory, safely complied with the required specifications and statutory standards," says Dieter Thelen, head of the sbt laboratory in Trier. His team of experts will continue to monitor the project closely over a 10-year period of use. They will then pass their concluding judgement on the basis of the long-term empirical findings. Martin Diekmann, Cold Recycling Product Manager at Wirtgen, is optimistic about the outcome: "Our projects worldwide have shown that cold recycling is a technically mature and extremely economical process which offers an effective alternative under the right basic conditions. The check tests undertaken on this pilot project are already promising and I am confident that the final results will confirm this excellent first impression."