Summary/Reader Response Draft #2: "Porous Asphalt Is King of the Road" (b)

   The article “Porous Asphalt Is King of the Road'' (Pavegreen, n.d.) introduces the features and uses of porous asphalt mixture (PAM). It is a type of road surface used to improve safety, diminish water pollution and decrease erosion. The Environmental Protection Agency had identified it as the leading practice for stormwater management. The article states that porous asphalt is made up of rocks glued together with asphalt cement while reducing the fine aggregates used. This allows rainwater to seep through the space between the rocks which decreases the surface runoff. The rainwater within will then slowly filter out reducing the amount of pollutants that goes into the earth. Porous asphalt can be built above a stone recharge bed or a conventional road base. The article mentions that during winter climates, porous asphalt requires less anti-icing agents. This reduces the amount of chloride from the agents which are toxic to aquatic life in the runoff. In highways the porous surface absorbs rainwater preventing splashes thus improving visibility and safety for vehicles. The article noted that porous asphalt costs relatively the same as conventional asphalt. However, the stone recharge bed is more costly than the traditional base. This cost difference can be offset as the number of stormwater pipes and inlets needed are reduced. In my opinion, the use of porous asphalt should be increased as it has benefits to safety, pollution and sustainability when compared to the conventional road surface.

Firstly, when it comes to safety PAM helps more than by just reducing splashes. A scholarly article “Design and performance of porous asphalt mixture for predestrian/cyclist applications in Singapore” (Chen, 2016) mentioned that this thin layer of water can cause bright lights to be reflected and tires to lose traction and skid. However, porous asphalt is able to drain and sometimes prevent this thin layer of water from forming thus reducing glare and improving traction. This helps drivers to control their vehicles better during heavy rain and reduces accidents.

The article “Asphalt Environmental Impact – An Eco Friendly Paving Material” (Pavingfinder, n.d) stated that flowing rainwater over an impermeable surface exposes the water to asphalt, pollutants and surface debris. This polluted water will flow into drains and emptied out into rivers, streams and lakes. Porous asphalt mitigates this by filtering the water through its permeable surface. Porous asphalt helps to mitigate sound pollution. As Chen (2016) noted, “As compared to dense asphalt mixture, PAM reduces noise level by around 3 dB(A) on average” (p.30). This is done as the noise generated by rolling tires is reduced as the sound that travels into the ground is greatly absorbed by the air voids in the porous asphalt. These air voids help to reduce traffic noise and increase the comfort of people living within the vicinity of these roadways.

To combat the amount of solid waste generated by the construction industry, concrete aggregates are recycled. The journal article “Porous asphalt mixture with 100% recycled concrete aggregate” (Chen & Wong, 2013) pointed out that using recycled concrete aggregates can decrease the demand for quarrying as well as decrease the magnitude of waste disposal. The article mentioned that it will still maintain its drainage function and can be used in low-strength applications like pedestrian and cyclist pathways. When this mixture is modified by adding enhanced asphalt binder, it can even meet the requirements set by Singapore’s Land Transport Authority to be used in normal highways. By being able to use recycled concrete aggregates in its construction, porous asphalt becomes a lot more sustainable and reduces the amount of waste generated thus freeing up space in landfills as well.

While porous asphalt can be viewed as sustainable and green it does require more frequent maintenance when compared to conventional asphalt roads. According to a study by Knut and Juned (2011, as cited in Chen, 2016), the unit costs of single layer PAM and double layer PAM are about 69% and 161% higher than conventional asphalt road respectively. The unit cost represents the cost of paving, delays and warning based on a dual carriageway with the average daily traffic condition. In my opinion, these traffic delays will increase vehicle emissions that pollute the air. This also proves that more materials are required to maintain PAM roads that will increase the amount of solid waste generated.

In conclusion, the benefits to safety, pollution and sustainability prove that porous asphalt should be used to help the experience of users on the road.

Reference:

Chen, M. & Wong, Y. D. (2013). Porous asphalt mixture with 100% recycled concrete aggregate. Road Materials and Pavement Design, 14(4), 921–932. https://doi.org/10.1080/14680629.2013.837839

Chen, M. (2016). Design and performance of porous asphalt mixture for predestrian/cyclist applications in Singapore. Doctoral thesis, Nanyang Technological University, Singapore. https://hdl.handle.net/10356/67037

(Pavegreen, n.d). Porous Asphalt is King of the Road. Pavegreen. http://www.pavegreen.org/index.php?option=com_content&view=article&id=58:king-of-the-road&catid=35:porous-asphalt&Itemid=110

(Paving Finder, n.d). Asphalt Environmental Impact – An Eco Friendly Paving Material. pavingfinder. https://pavingfinder.com/expert-advice/asphalt-environmental-impact/