Plant recycling with bitumen emulsion
Definition
Recycling with bitumen emulsions, in for example an asphalt mix plant or Grave Emulsion type plant, consists of treating milled and screened asphalt planings materials obtained from the demolition of old pavement layers.
Application area
Plant-recycled asphalt aggregates can be used as base, bonding or rolling layers.
Formulation
A recycling operation is only possible if the “deposit” of recycled asphalt mix is well defined and sufficiently homogeneous in terms of the nature of the aggregates, gradation and aged binder- content and properties.
The new binder added is chosen to restore the aged binder properties such as flexibility and adhesiveness. The bitumen emulsion is formulated to match the particle gradation and surface properties of the fine aggregate material. The resulting recycled asphalt mix design formulation and performance depends on the anticipated stresses on the recycled mix (traffic, climate, base layers, position in the structure etc).
Technical, economic and environmental benefits
Technical advantages
- good initial behaviour and improvement over time under traffic of recycled mix cohesion,
- restructuring of degraded layers that could not be satisfactory re-instated,
- ability to significantly delay cracking due to shrinkage,
- improved mechanical performance,
- accepts variations in composition and thicknesses without subsequent evolution of the structural profiles,
- flexible behaviour of the bituminous mix material,
- improved longitudinal uniformity, transverse profile and homogeneity of the pavement, despite relatively weak initial compaction,
- good performance in cold or hot mix wearing courses
Economical benefits
- savings in raw materials, aggregates and transport,
- eliminates platform widening and limits ancillary work (shoulder re-instatements, etc.).
Environmental benefits
- energy-efficient, dust-free, cold technology supporting sustainable development
- instant re-opening for traffic
- reduced inconvenience to road users.
In-place cold remixing of old pavements
Definition
This technique consists of in place remixing, all or part of a roadusing a bitumen emulsion. The binder can regenerate the aged binder, or be a compounded binder (emulsion of bitumen + hydraulic binder). Addition of fresh mineral aggregate is optional.
We distinguish mainly :
- Pavement reprocessing of untreated material with a low bitumen coverage (often wear coursesup to 4 cm thick).
- Reprocessing of bituminous road layers over 4 cm thick on pavements with (un)treated or hydraulic stabilised foundations.
Formulation
When remixing predominately bituminous old pavement regeneration treatment with a bitumen emulsion is preferred.
Remixing hydraulically bound old pavement requires a specific bitumen emulsion. In all cases, the cases the type of binder and the formulation of the emulsion are adapted to the particular case (traffic, climate, granulometry, fines, etc.), so as to satisfy the criteria of coating and breaking speed.
Advantages of the technique
Environmental benefits
- In place reuse of materials, no site waste,
- energy efficient cold technique and dust free,
- instant re-opening for traffic
- reduced inconvenience to road users.
- eliminates platform widening and reduces ancillary work (shoulder re-instatements, etc.).
Technical advantages
Similarly to all cold bituminous application technologies,remixing with bitumen emulsions tolerates variations in compositions and thicknesses, without any subsequent evolution of the profiles, and very effectively delays recovery of shrinkage cracks of the underlying layers.
- Restructuring of damaged layers leads to:
- Interfacial and crack remediation
- Improvement of pavement layer impermeability,
- potential regeneration of the binder. Simple reinstatement would not solve these problems.
- Homogenization of the mechanical characteristics of the remixed surface layer and improvement of the mechanical performances
- Treatment with a bitumen emulsion allows better compaction and workability.
- Improvement of longitudinal eveness, transverse profile and overall homogeneity of the pavement.
Economical advantages
- saving new raw materials, aggregates and transport; less fatigue of road network by the transport of raw materials due to in-situ re-use of the construction materials,
- reduction of the shoulders, accesses, thresholds, curbs,
- treatment per single lane only and reshaping the roadway
- rapid execution, rate from 5 to 8000 m2 / day.
