Work package 1
WP1: Advanced mix design of cold-recycled bitumen stabilized material
WP leader: Fátima Batista (LNEC)
The Extensive laboratory study will concentrate on elaboration of a harmonized advanced mix design procedure among European countries, considering different bituminous binders (bituminous emulsion, foamed bitumen eventually foamed emulsion) and combinations of these with traditional hydraulic binders (cement, lime) or alternatives (e. g. fly-ashes), namely in terms of:
- Laboratory compaction methods
- Laboratory curing methods
- Performance test methods (tensile and compressive strength, stiffness, water susceptibility, thaw-frost effect, voids content or Proctor Standard)
- Mix design requirements (characterization of input materials, material characteristics tolerances, recommended control testing during and after construction, performance based requirements)
Provide recommendations on the use of different binders and additives.
Summarize effects of inhomogeneous material properties of reclaimed material on mix design and performance (sensitivity study).
Analyze relations between performance based requirements and real data from existing construction sites of different age (at least from 3 countries with different binder used).
Work package 2
WP2: Durability of cold-recycled bitumen stabilized materials (laboratory study)
WP leader: Jan Valentin (CTU)
Determination of suitable procedures for stiffness assessment for cold-recycled mixtures (resilient modulus, retained resilient modulus after water immersion, dynamic complex modulus including master curve, stiffness test with continuous loading): Application of test methods used for stiffness according to EN 12697-26 and 13286-43 will be experimentally compared for cold recycling mixtures. Effect on mixtures tested within WP2 work program will be evaluated. Partial issues of interest are namely:
- Specification of most appropriate curing period and definition of test conditions (temperature, Poisson ratio etc.) most suitable for stiffness assessment
- Recommendation on threshold limit for retained stiffness modulus (after water immersion or thaw-frost cycles)
- Requirements for implementation of dynamic modulus testing and utility of master curve approach as a modern tool for quality control
- Influence of stiffness values on mix design and pavement design
- Early age performance of cold-recycled mixtures as an important characteristic of this type of mixtures (mainly concerning its permanent deformation resistance), analyzing consequences on pavement design
Comparison of laboratory stiffness values with in-situ testing on targeting trial sections and with data on selected existing construction sites (coring, FWD testing where feasible).
Laboratory determination of fatigue characteristics for various cold-recycled mixtures (only bituminous binder and/or combination with hydraulic binder). Using two different test methods according to EN 12697-24 (4PB – more for scientific and experimental reasons, ITFT – applicable as a more practical method).
Evaluation of testing resistance to cracking in low temperature range. Defining usable test methods (crack propagation according to EN 12697-44, TSRST – depending on the ability of specimen preparation) and experimental assessment on selected mixes used within the WP 1 work program.
Ageing effect of cold-recycled mixtures.
Moisture effect assessment of cold-recycled mixtures.
Work package 3
WP3: Pavement design with cold-recycled bitumen stabilized road base
WP leader: Petr Mondschein (CTU)
Propose simple concept of standardized application of cold-recycled bitumen stabilized material in base or binder course within the pavement design manuals.
Propose conditions for incorporating the concept of fully recyclable asphalt pavement with use of cold-recycled bitumen stabilized material in base and/or binder course and with HMA wearing course containing RAP.
Decide if pavement structures containing cold-recycled mixture can be by default mechanistically calculated or pavement catalogues should be preferred.
Work package 4
WP4: Recyclability of recycled bitumen-stabilized material applications
WP leader: Konrad Mollenhauer (UK)
Role of RA binder in bitumen stabilised material: elaboration of differences between reclaimed asphalt and reclaimed unbound / hydraulic concrete in cold-recycled mixes
Rate of activity of the bituminous binders in previously recycled bitumen stabilized materials including the influence of combined effect of bituminous and hydraulic binder
Recyclability of bitumen stabilised materials in new hot-mix asphalt: can the binders (original RA and bitumen emulsion / foam bitumen) be activated during hot-mix recycling
Work package 5
WP5: Environmental compatibility of recycled bitumen stabilized material applications
WP leader: Ciaran McNally (UCD)
The objectives of this work package are to determine the full extent of potential environmental benefits associated with the use of cold-mixed bitumen stabilized materials by cold-recycling techniques. While there are obvious benefits with respect to cold recycled mixtures and cold asphalt mixtures in terms of energy savings, there are other possibilities which to date have not been fully quantified. These would include the use of materials for cold-recycled mixtures that would not ordinarily be permitted for use in road construction. An example of this would be a tar containing asphalt, a material which is prohibited from hot or warm recycling in most of the European countries. This material is rightly prohibited from use in hot-mix asphalt as the heating process would lead to the release of fumes which are harmful to those working with the material. Cold-recycled bitumen stabilized materials offer a potential way around this as the tar would not need to be heated, thus avoiding harmful emissions. However, concerns still exist that the material may leach PAHs or heavy metals into the local groundwater. There is the possibility that the encapsulation of the tar within cold-recycled material by bitumen is sufficient to stabilise the material. This approach has been used in some countries (Germany,Czech Republic), but has not yet been quantified especially for cement-rich mixes requiring grooving to avoid wild cracking.
Another aspect of long-term eco-stability is minimized carbon footprint of pavement rehabilitation or new constructions. Several calculators are available across Europeand ERA-Net project CEREAL focuses on development of a harmonized European tool. Therefore it is not the intention to develop a new tool or procedure. Within this partial objective data should be collected on achievable savings in the field of production energy demand, transport distances and transport volumes as well as the effect of embodied energy in once used materials which are locally reused with minimized requirements on their customization. The data should be then shared with the CEREAL project to get a precise calculation for correctly evaluate the recycling strategies. As part of eco-balance evaluation and assessment of emissions and harmful substance related to PAHs content in tar it is not primarily expected to perform in-situ SO2, CO2 and NOx measurements. Eventual possibility of doing such surveying will be decided during the first project year.
Work package 6
WP6: Dissemination and management
WP leader: Jan Valentin (CTU)