Porous Asphalt and Infrastructure Resilience

Porous asphalt is a pavement material that is made to let water pass through it rather than gather on the surface. Because of this distinctive quality, it is a well-liked option for infrastructure projects as it can lessen the effects of severe rain and flooding.

This material is constructed of a significantly coarser aggregate than conventional asphalt,

as a result, water can penetrate the pavement and enter the subsurface soil or drainage system [5].

Figure 1 - Asphalt road.

Benefits

One of the main benefits of porous asphalt is its ability to reduce the amount of runoff that is generated during heavy rainfall events. This can help prevent flooding and reduce the strain on local stormwater systems. Additionally, because water is allowed to filter through the pavement, it can help to recharge groundwater supplies [6].

Figure 2 - Porous pavements vs traditional pavements[1].

Another benefit of porous asphalt is that it can help to reduce the urban heat island effect [7]. This occurs when urban areas become significantly warmer than surrounding rural areas due to the heat-absorbing properties of pavement and buildings. By allowing water to filter through the pavement, porous asphalt can help to cool the surrounding environment.

Figure 3 - Air temperature in and around London [2].

Take a look at the video below which shows how effective this material is at absorbing liquid!

Figure 4 - Video of porous asphalt absobring water [3].

Drawback

Despite these benefits, there are also some potential drawbacks to using porous asphalt. For example, it may not be suitable for high-traffic areas or areas with heavy industrial activity, as it can be more prone to damage and wear than traditional asphalt [8]. Additionally, because it is more porous, it may require more frequent maintenance to prevent clogging and ensure proper drainage. These two reasons are why this material is often found in areas experiencing low traffic e.g. carparks or airport taxiway shoulders.

Figure 5 - Aiport taxilane and aprons.

Compared to traditional Marshall asphalt, porous asphalt generally has lower strength and durability. This is due to the coarser aggregate used in its composition, which can make it more prone to damage and wear. However, new developments in porous asphalt technology are continuously being made to improve its strength and durability.

Climate change In terms of its relation to infrastructure resilience in the face of climate change, porous asphalt can play an important role in helping communities to adapt to the impacts of more frequent and severe weather events. By reducing the amount of runoff and flooding that occurs during heavy rainfall, it can help to protect homes and businesses from water damage and reduce the strain on local infrastructure systems.

In order to effectively adapt to the impacts of climate change and improve the resilience of our infrastructure systems, it is important to recognize the importance of loosely coupled systems. Loosely coupled systems are characterized by their ability to operate independently and adapt to changing conditions without disrupting the overall functionality of the system.

Figure 6 - Example of traditional drainage (slot drain) [4].

Porous asphalt pavements can supplement traditional drainage methods. These usually rely on non-porous surfaces, such as concrete and asphalt, to direct rainfall to centralized collection systems. Porous asphalt allows water to pass through and filter into the soil beneath, this creates a more harmonious relationship with the existing nature. We can leverage this innovation in combination with traditional techniques to produce a more resilient and sustainable drainage system equipped for changing climate conditions.

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References:

[1] Speight JG. Chapter 8 - Uses of Asphalt. In: Asphalt Materials Science and Technology. 2015.

[2] Turton P, Coppel A. Reducing urban heat risk. London: Arup;

[3] City of Burnsville. City demonstrates porous asphalt [Internet]. YouTube. YouTube; 2013 [cited 2023Mar19]. Available from: https://www.youtube.com/watch?v=_-5S9LIyYvQ&embeds_widget_referrer=https%3A%2F%2Fmanage.wix.com%2F&embeds_euri=https%3A%2F%2Fwww.clim8delta.com%2F&embeds_origin=https%3A%2F%2Fwww.clim8delta.com&feature=emb_imp_woyt

[4] High capacity slot drain [Internet]. High Capacity Slot Drain | BPDA. [cited 2023Mar19]. Available from: https://www.precastdrainage.co.uk/page/high-capacity-slot-drain

[5] Hodgson L. What is "porous pavement"? [Internet]. Laidback Gardener. 2019 [cited 2023Mar19]. Available from: https://laidbackgardener.blog/2019/01/27/what-is-porous-pavement/

[6] Nunn M, Robinson H. Storm water control using porous asphalt pavements [Internet]. Agg. 2006 [cited 2023Mar19]. Available from: https://www.agg-net.com/resources/articles/asphalt/storm-water-control-using-porous-asphalt-pavements

[7] Bates T. How roads can help cool sizzling cities [Internet]. Rutgers CAIT. Rutgers CAIT; 2019 [cited 2023Mar19]. Available from: https://cait.rutgers.edu/how-roads-can-help-cool-sizzling-cities/

[8] Hashim TM, Ali AH, Al-Khafaji R, Al-Khazraji AA, Zahra Dharb FR. A comparison study between porous and conventional asphalt concrete mixtures. IOP Conference Series: Materials Science and Engineering. 2021;1090(1):012041.