Bitumen trends: new and existing technologies
A huge amount of research and development work is continually being carried out across Europe, exploring many areas that have potential to positively impact bitumen in different ways - including technologies, compositions, production methods and application techniques.
In this article, we explore some key trends under two important and related pillars: Sustainability and Performance.
Sustainability
Sustainability is defined as ‘meeting the needs of the present without compromising the ability of future generations to meet their needs’. In this section, we mainly focus on the work being done to minimise the consumption of non-renewable natural resources and reducing CO2 emissions.
In recent years there has been a significant increase in the use of reclaimed asphalt (RA). In Germany, where the average introduction rate of RA in new hot mixes has been above 25% since 2013, close to 90% of RA is re-used in hot mix asphalt production and more than 25% of the hot mix asphalt tonnage produced is RA. The average introduction rate is increasing in other countries too, and in France it rose to 18.4% in 2017.
Road pavements account for an estimated 80-85% of the bitumen consumed in Europe. The use of reclaimed asphalt in road pavements is set to continue and be a viable option, as long as there is RA available.
Research is underway across Europe regarding the development of bitumen binders and bitumen additives which allow the proportion of RA to increase, by enabling the asphalt containing RA to meet performance specifications of asphalt.
For example, where asphalt is already reclaimed and re-used multiple times, special binders are being developed to counter the effects of ageing caused by hot mix production, hot transportation, laying, then lifetime exposure to UV and other environmental impacts - all of which change the characteristics of the bitumen binder.
Other areas of investigation in this area are highly modified Polymer Modified Bitumen (PMB), softer binders, the use of other additives, and also the use of rejuvenating agents.
Another area of research concerns the maintenance of road pavements with bitumen emulsions, where emulsion techniques and formulations are being developed with new, more renewable fluxants - for surface dressing and slurry seal.
Meanwhile the trend for the use of warm mix asphalt, a process that allows for reducing the mixing temperature, continues.
Performance
A large amount of research is also being performed looking at potential ways to improve further the operational performance of bitumen in applications, especially within asphalt road pavements.
Reducing noise is a demand from the end users, but it is important that the solutions being developed also meet all the physical and mechanical performance requirements for the end application.
There is a lot of interesting research work regarding the further use of polymers to modify bitumen, in areas where traffic noise and pollution in towns and cities is a problem. For example, in France new high porosity asphalt formulations with high sound absorption properties are being developed. Meanwhile in Switzerland, intensive research and testing is being carried out to improve the durability of low-noise asphalt for road pavements.
The use of viscosity-modified binders - whether based on paving grades or PMB - has been prevalent for years in Germany, where PMB accounts for more than 30% of the paving market. The focus here, therefore, is on developing the next generation of binders and on new approaches to rheological testing in relation to performance characteristics. One example is the Binder Fast Characterization Test (Bitumen-Typisierungs-Schnell-Verfahren - BTSV), which can be used instead of conventional test methods to characterize unmodified and modified binders in the high service temperature range.
In the Netherlands there is a large research program called Asphalt Impulse, which involves authorities, contractors, binder producers, asphalt manufacturers, testing labs, etc. The ‘Grip on bitumen’ project will evaluate what can be done to further enhance binder quality and obtain a better understanding of the performance properties of asphalt mixes.
Meanwhile in the UK, research is underway to develop a premium asphalt surfacing system (PASS) that minimises air voids without compromising texture depth or durability, for use in the strategic road network. This research is about to move to trial phase on a motorway. There is also a push to develop a performance specification for warm mix asphalt.
Conclusion
Bitumen research and development is wide-ranging, with current trends including binders and additives that would enable the percentage of reclaimed asphalt in road pavements to be increased; better emulsion formulations and application techniques, to improve road maintenance; as well as projects covering noise reduction, durability and grip.
Within the industry we can be rightly proud of bitumen’s rich heritage, but more importantly we can look ahead with confidence to a bright future - because of the wealth of research and development being undertaken across Europe by and for the industry, particularly in relation to sustainability and performance.
