PROJECT DESCRIPTION
BACKGROUND
Road construction, maintenance and renovation have a huge environmental impact, particularly asphalt pavements for primary and secondary roads. Road construction consumes large quantities of raw materials, including mineral elements, such as stones, grit and sand (aggregates), filler and bitumen. To produce one tonne of asphalt, approximately one tonne of natural resources, mainly aggregates, is needed. The demand for natural resources in road construction is therefore enormous, and requires the transport of natural resources from mining areas to asphalt plants and road construction sites. As a result, such production is responsible for large amounts of hydrocarbon emissions. The most important sources of these emissions are the combustion of fuels and vapours from heated bitumen. Extra hydrocarbons are emitted during the heating of reclaimed asphalt. At present, several innovations are taking place in different areas of the road construction sector: asphalt mixtures, construction techniques and the use of reclaimed materials. With regard to asphalt materials, for example, there are innovative developments in the areas of lower-temperature asphalt, low-traffic-noise asphalt and low-maintenance asphalt. However, these innovations occur on a product level and there is as yet no integration of the different innovations in order to realise optimal environmental performance of road (re)construction.
OBJECTIVES
The main objective of the LE2AP project was to demonstrate a convergence of cold asphalt technologies (a type of asphalt that retains its pliable properties when the temperature drops) and road construction technologies to significantly improve environmental performance of road construction and maintenance processes. The project aimed to demonstrate the following innovative asphalt technologies and paving techniques: dry decomposition of reclaimed asphalt, by milling and decomposing old asphalt layers with a cleaner dry process; and production of a new and greener cold asphalt mix that contains at least 80% reclaimed asphalt and can be produced and used at 80ºC.
RESULTS
The LE2AP project demonstrated a convergence of asphalt technologies and road construction techniques to improve environmental performance of road construction and maintenance. By doing so, it was able to achieve pollutant and greenhouse gas emission reductions, for hydrocarbons (CxHy), nitrogen oxides (NOx), carbon monoxide (CO), carbon dioxide (CO2), and odour. The project team's sustainable asphalt also achieved traffic noise reductions of at least 7 dB compared to conventional asphalt. LE2AP enabled the production of a recycled asphalt mix at 100°C-110ºC, a significantly lower temperature than used for the production of reference asphalt, yet above the 80°C targeted in the project objective. Asphalt mixtures containing up to 93% of decomposed reclaimed asphalt were produced and roughly 600 m2 of LE2AP road was constructed. The results laid the foundation for full-scale testing of LE2AP asphalt at two different road locations during the project.
Environmental and health benefits arise from the emissions reductions achieved using the new asphalts compared to a reference asphalt: 77% reduction for CxHy; 85% for NOx, 72% for CO2, and 51% for CO. Energy use was reduced by 51%, and odour by 77%. These reductions were, in most cases, higher than the percentages originally targeted.
Socio-economic benefits were quantified in terms of health, energy usage and climate change mitigation. LE2AP asphalt produced consistent cost savings (valuation per ton of LE2AP asphalt) compared to regular reference asphalt. This was calculated for health loss as €1.33 compared to €1.93 for regular asphalt; for energy use as €1.68 compared to €2.89 for regular asphalt; for climate change as €3.55 compared to €5.28 for regular asphalt; and for material use as €0.45 compared to €0.47 for regular asphalt. Total accumulated monetised savings on the basis of these criteria is 35%. Besides, research by the Technical University of Delft (TU Delft) showed that the achieved recycling of asphalt can have positive effects on employment (estimated at three full-time positions/100 000 tonnes of decomposed asphalt).
Several Dutch provinces have expressed interest in the construction of LE2AP test sections of roads and coordinating beneficiary BAM has invested in the construction of a new asphalt plant at Brabantse Asfaltcentrale in Helmond, which will take LE2AP lessons learned on board. This plant will produce asphalt mixtures with over 80% of reclaimed materials, with fewer emissions.
The LE2AP project enhanced recycling rates of porous asphalt mixtures, while the application of decomposed reclaimed porous asphalt material represents an innovative approach to more sustainable road building. Furthermore, reclaimed asphalt use exceeding 80% is considered ground-breaking in the current market.
