Introduction


CRABfor OERE project is part of the CEDR Transnational Road Research Programme and is one of the three projects funded under the Call 2017 "New Materials & Techniques". The project is funded by the road administrations of Austria, Belgium-Flanders, Denmark, Germany, Netherlands, Nordway, Slovenia, Sweden and the United Kingdom.

 

The project Managers for the project are Reinhard Lohmann-Pichler of ASFINAG (Austria) and Oliver Ripke of BASt (Germany).

 

Hot recycling is the recycling procedure for the use of old asphalt materials reclaimed from existing road pavements most often applied in Europe. In terms of economic value, hot recycling is usually considered as the best option for reducing the need for new resources of high-quality aggregates and bitumen. However, in several regions within Europe, the technical and economic capacities for reuse of reclaimed asphalt (RA) by approx. 30 % have been reached. For further increasing the recycling rate special installations are required (parallel recycling drums) within asphalt plants. Larger plant ground area for optimised RA management is needed also to improve the RA quality in terms of homogeneity. Inadequate characteristics of the RA binder demands for the addition of rejuvenating additives. Especially highly-aged binders and/or applied modifications within the reclaimed asphalt prohibit the use of these resources in hot-mix asphalt. These reached capacity limits result in increasing storage stockpiles for less recyclable reclaimed asphalt sources.

 

As an alternative, recycling of RA in cold recycling materials (CRM) is applied internationally with success. Also in Europe (especially Italy and the UK) significant proportions of incurred RA are already cold recycled by application of foamed bitumen, bitumen emulsion in combination with mineral binders. Good experience regarding mechanical properties and durability was further made with CRM for recycling of tar-contaminated pavements, for example in Germany. Generally, RA contents ≥ 75 % are reached within CRM. In France, annually ~1,5 mil. tons of cold asphalt mixtures based on natural aggregates and bitumen emulsion are applied since centuries in base layers (EAPA 2017). Due to the mix preparation at ambient temperature, CRM demand for comparably less energy. Therefore, Cold recycled asphalt bases (CRAB) can be considered as pavement of optimal energy and resource efficiency (OERE).

Recently, harmonised test procedures and material requirements were proposed for cold asphalt mixtures with bitumen emulsion within CEN 336/WG1 (prEN 13108-31, prEN 12697-53 to -56). However, for the wider use especially in countries with less experience in cold recycling some aspects of these road materials needs to be assessed. The short-term performance which is highly dependent on the development of moisture within the CRM layer and therefore of climatic conditions is not fully understood so far and therefore cannot be properly adopted during mix design properly. Furthermore, durability as well as failure modes need to be examined in order to introduce sustainable pavement design procedures.  

 

Within CRAB for OERE, following steps further for establishing harmonised standards for cold recycling technologies can be reached:

 

1. Assessment of long-term performance of existing cold recycling and/or cold asphalt pavement structures

 

2.  Validation and - if necessary - adaption of existing test methods and qualification procedures for RA aggregates. 

 

3. Validation of laboratory curing and performance assessment procedures for cold recycled materials

 

4. Demonstration of harmonised mix design procedures based on prEN 12697-53ff and prEN 13108-31

 

5. Demonstration of pavement design procedures for pavements with structural layers composed of cold recycling materials

 

6. Scientific supervision of new test pavements with optimised energy efficiency allowing the application of sensors and monitoring of      short-term performance

 

7. LCA- and Risk analysis for assessment of environmental and economic benefits by using cold recycled materials and evaluate              application risks (e. g. weather during construction, RA variability)