The use of low temperature (LT) asphalt products can result in a significant decrease of temperature required for asphalt production. This reduces energy costs and consumption. Moreover, safety during asphalt production and laying improves because the amount of potentially harmful vapours and aerosols decreases. Temperature decrease, in addition to the above, reduces the short-term ageing of bitumen in the asphalt production process, and ultimately has a positive impact on the durability of pavements.
COLAS Group in Hungary considers propagating the use of low temperature sorts of asphalt in road construction in Hungary as a high priority innovation task
Between 2012 and 2014, COLAS Group equipped its asphalt mixers with units from different manufacturers, capable of producing foamed bitumen, at four COLAS Group mixing plants in Hungary.
This was followed by several test production runs and course laying with asphalt mixes containing foamed bitumen. Some of the foam asphalt mixes were produced and laid at low temperatures. The other part of the mixes were produced at conventional temperature and were layed after 2 - 2.5 hours of transport. The test asphalt mixtures were made with 50/70 and 10/40-65 modified bitumen also containing 10-20% RA.
We compared the compactability of foamed bitumen mixtures produced with four different foaming kits. We produced Marshall specimens at various compaction temperatures, tested the bulk densities of the specimens, then represented the bulk densities subject to the compaction temperature. We established the following:
the Marshall bulk density (better compactability) of foamed bitumen asphalt mixes is higher for all asphalt types compared to the normal bitumen mixtures,
higher Marshall bulk density of foamed bitumen asphalt mixes can be achieved both in normal (50/70) and modified bitumen mixtures (25/55-65,10/40-65),
better compactability of foamed bitumen asphalt mixes is independent of the type of the foaming kit. It works for all types of foaming kits.
The Defence Infrastructure Organisation requested a pavement evaluation on RAF Waddington and the results indicated that runway rehabilitation and reprofiling was needed in order to meet the physical design requirements set out in the Manual of Aerodrome Design & Safeguarding. The presence of tar in a layer of the old pavement promoted the option of cold recycling this material into the new structure. This paper presents the results from a laboratory investigation into the suitability of cold recycled foamed bitumen asphalt to be used in the structural layers of an airfield pavement.
Laboratory mixture designs with foamed bitumen, incorporating asphalt planings from RAF Waddington runway, were produced in URS Infrastructure and Environment Ltd. laboratory. Specimens were used to assess mix performance and in order to add confidence to the design. The last objective of the research was to demonstrate that asphalt planings from RAF Waddington could be recycled into foamed asphalt for incorporation in the runway rehabilitation works. The optimum binder content was determined from Indirect Tensile Stiffness Modulus tests and Indirect Tensile Strength tests, concluding that the optimum binder content was 3.3% by mass. As a common practice in the UK, up to 1.5% by mass of cement was added to the mixture to improve early life performance. To assess the foamed bitumen samples’ performance with time, specimens were prepared and cured for 28, 180 and 360 days at different temperatures. Post curing, the specimens were tested for a range of performance criteria including fatigue, stiffness and durability.
The study found that asphalt sampled from the runway at RAF Waddington can be recycled into foamed asphalt, meeting the requirements of Defence Infrastructure Organisation Specification 050.