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https://nap.nationalacademies.org/catalog/27432/critical-issues-in-transportation-for-2024-and-beyond

Low Energy Asphalts

The ever-increasing price of energy encourages a change of thinking and habits and the promotion of new coating technologies. Coating processes at lower temperatures and hence economical and energy saving, have been appearing for some years. Less energy needed for manufacture likewise implies a smaller discharge of CO2. These road-surfacing materials coated and used at lower temperatures, accordingly offer a dual advantage in terms of both economy and the environment. However, the new generation of low-temperature and low-energy asphalts must have the same performance as traditional hot-mix asphalts; their development is therefore subject to laboratory and in-situ verification of their mechanical performance. The current paper describes a process involving low energy asphalts (LEA) which fits into the context of protecting the environment at the stage of carrying out work of maintenance and construction of new roads. The innovative nature of the process is characterized by the following features: the auto-expansion of bitumen, i.e. natural formation of bitumen foam by taking advantage of the (free and bound) natural humidity of aggregates. The formation of foam on the contact of hot bitumen with (cold or warm) humid aggregates questions the common use of vaporized bitumen foam on the aggregates; the adaptability of the two variants of sequential coating at any kind of plants without costly modifications of the industrial equipment, unlike some existing warm and half-warm coating processes; the adaptability of both variants to any type of hydrocarbon mixture, any form of aggregate formula (continuous or discontinuous, rich or poor sandy fraction, with or without RAP, etc), aggregates of any mineralogical type, any binder; the optimization of the foaming capacity of binder by the use of special additives; the determination of energy savings by (fuel or natural gas) meters of plants: 35 to 50% according to the plant, the materials and their degree of humidity, temperature, etc.; the potential saving of CO2 emissions : 35 to 50%; a potentially longer time of storage and transport than those of a hot mix asphalt (HMA). In the case of accidental rain or for any other reason, loaded lorries can remain on stand-by for some hours before re-supplying the finisher, thus avoiding possibly costly discharging; the maintenance of the plants and equipment used is facilitated by the formation of a fine skin of steam condensed in the form of fine droplets on the surfaces. This brings about a reduction of soiling and consequently a reduction in the amount of solvent used; the disappearance of harm caused to application teams and of nuisance to neighbours due to the great reduction of odours, emissions and risk of burns; a more rapid return to traffic than in the case of hot (160degreesC) or warm mix asphalts (130degreesC); the normal properties are obtained after cooling; a risk of smoke and formation of a fog much smaller in the case of rain after realization, thus improving site safety; and the preservation of mechanical properties equivalent to those of hot mix asphalts. For the covering abstract see ITRD E139491.

  • Authors:
    • OLARD, F
    • NOANC, L E
  • Publication Date: 2007

Language

  • English

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 01116967
  • Record Type: Publication
  • Source Agency: TRL
  • Files: ITRD
  • Created Date: Dec 22 2008 9:07AM