Asphalt anti-aging Scientists from Braunschweig and Swansea extend life of road surfaces with nanoparticles
Reduced energy consumption, lower CO2 emissions and a better working environment for road builders: Warm mix asphalt (WMA) is becoming increasingly important as a more sustainable technology. Unlike conventional asphalt, WMA is more susceptible moisture and aging. To solve this problem, researchers from Technische Universität Braunschweig and the University of Swansea in the UK have now developed an anti-ageing binder for asphalt using nanoparticles. They have published their results in the scientific journal “Nanotechnology Reviews”.
View through field emission scanning electron microscopy: The distribution of nanocomposites on the surface of asphalt binders. Picture credits: ISBS/TU Braunschweig
The production of asphalt is a hot business: the building material is usually mixed at around 160 degrees Celsius. Warm mix asphalt (WMA), on the other hand, is produced at temperatures up to 40 degrees Celsius lower than conventional hot mix asphalt. WMA technology not only lowers temperatures and energy consumption in asphalt production, but also reduces vapors and greenhouse gas emissions. As a result, CO2 emissions can be reduced by up to 15 per cent. For the UK, this would mean: Converting to WMA could save around 61,000 tonnes of CO2 every year. This is roughly equivalent to the amount of CO2 produced by about 300 million car kilometres driven.
Susceptible to moisture and ageing
Dr. Gِoshtasp Cheraghian, project manager at Braunschweig Pavement Engineering Center (ISBS) of TU Braunschweig, cites as further advantages of WMA asphalts the better compaction on the road, and the ability to haul paving mixtures for longer distances. “Even in less than ideal weather conditions, WMA can be paved well, thus extending the paving season,” says Dr Cheraghian. The disadvantage: high susceptibility to moisture and ageing make WMA asphalts less robust.
To solve the problem of limited durability, the team from the ISBS and the Energy Safety Research Institute (ESRI) at Swansea University in Wales uses nanoparticles of clay and fumed silica. These are added to the bituminous binder. On the one hand, the nanocomposite lowers the temperature in the WMA process, but it also makes the asphalt less susceptible to moisture and ageing, thus extending the life of road pavements.
Cost-effective and non-toxic material
The results of this research, recently published in Nanotechnology Reviews, focus on the impact of nanocomposites on the aging resistance of road asphalt binders. “The used nanoparticles act like a shield against moisture and aging, thus making the asphalt mixture less prone to brittleness and cracking,” explains Professor Michael P. Wistuba, head of ISBS. For the development of the next generation of road asphalt materials, the modification of asphalt binders by nanoparticles could be of great benefit, he adds. “Clay/fumed silica nanocomposite with a large surface area is an ideal candidate as a cost-effective and non-toxic material that can meaningfully impact on shielding asphalt in WMA technology,” says Dr Cheraghian. “In addition, our findings on the concept of the molecular interaction between nanoparticles and asphalt binders can open new avenues for the application of nanotechnology in asphalt engineering.”