Advancements in WMA and HMA Pavement Technology
The development of Warm Mix Asphalt (WMA) has revolutionised asphalt technology, enabling the pavement industry to mitigate the negative impact of asphalt production on the environment. This eco-friendliness can be attributed to the lower temperature at which WMA is produced (about 20 – 40 °C lower than HMA). A range of techniques, including organic and chemical additives and foaming, have been developed to decrease the temperature required for mix production.
How can WMA take us one step closer to a carbon-neutral future?
At the heart of WMA’s sustainability is its lower temperature at which it is made, placed, and compacted. This decreases fuel usage and emissions from such fuels. Reducing the production temperatures by 30°C can lead to a decrease in greenhouse gas emissions by 12-15% (AfPA 2022). Furthermore, by substituting hydrated lime with liquid adhesion agents and minimising aggregate moisture, additional reductions of greenhouse gas emissions can be achieved. Additionally, lowering mixing temperatures by 30°C during production reduces the carbon footprint by 24,000 tonnes across the board. This is equivalent to the carbon emitted from burning 10,918,076 pounds of coal (AfPA 2022).
Figure 1 shows the sustainability advantages of WMA.
Figure 1: A quick comparison of WMA and HMA.
Now, let’s have a look at how WMA performs on the field when compared with HMA.
How does WMA compare with HMA?
WMA’s performance when compared with HMA can be summarised as follows:
Studies have indicated that warm mix asphalt (WMA) performs equally or potentially better than hot mix asphalt (HMA) and both materials have comparable versatility. Both can be used in different asphalt surface mixes and on roads with heavy traffic.
WMA has been utilised in various mixes such as dense-graded, stone matrix, mastic, and open-graded friction-course mixes, and with polymer-modified binders.
WMA has been applied in pavements with traffic anticipated to surpass 30 million 18-kip-equivalent single-axle loads and in various layer thicknesses.
WMA has been paved at bus stops, airfields, and port facilities, and has displayed similar or better performance in all these applications.
WMA offers improved compaction, comparable stiffness and rutting resistance, enhanced resistance to fatigue and thermal cracking, and greater durability than HMA.
Conclusion
The asphalt industry's remarkable adoption of WMA technologies since its introduction almost two decades ago is a strong indication that they are on track to become the standard for producing asphalt mixtures in the near future. When combined with other sustainable construction materials like reclaimed asphalt pavement, this asphalt mixture can further enhance the sustainability of pavement construction.
Further Reading
The continuous research on warm mix asphalt consistently provides evidence of considerable economic, environmental, performance, and social advantages. We recommend reading the reference paper by Tutu and Tuffour which offers a great review of WMA sustainability. Please see below for links.
References
Tutu, K.A. and Tuffour, Y.A. (2016) Warm-Mix Asphalt and Pavement Sustainability: A Review. Open Journal of Civil Engineering, 6, 84-93. <http://dx.doi.org/10.4236/ojce.2016.62008>
AfPA. (2022) Technical Talk – Warm Mix Asphalt – A pathway to reduce the carbon footprint towards a carbon neutral future. <https://www.afpa.asn.au/wp-content/uploads/2022/03/2022-03-15-AfPA-Technical-Talk-%E2%80%93-Warm-Mix-Asphalt-.pdf>