Summary Reader Response #Draft 2

 The article “Porous Asphalt Is King of the Road” (PaveGreen, n.d.) presents the benefits of porous asphalt surfaces and explains its utility in improving stormwater management and road safety. Rainfall naturally sinks into the soil and is filtered through it. However, in cities, rainfall or “runoff” causes flooding on roads and parking lots, along with contaminants, such as oils and minerals. It then flows straight into drains without being filtered naturally. The article states that porous asphalt is a natural material consisting of rocks combined with asphalt cement and fewer fine aggregates as compared to conventional roads. This frees up space for water to pass through open spaces between large aggregates. Underneath, a “recharge bed” composed of spaced-out stones retains rainwater until it is filtered into the soil, hence cleaning it. 

During storms, accidents are greatly reduced as there are fewer puddles on the road. During winter, it reduces the need for “deicing”, where “chlorine-laden” chemicals remove ice from roads to make them less slippery. Hence, risks of accidents are reduced in both rainstorms and winter climates. The article points out that the stone bed underneath costs more than a conventional road, but is typically outweighed due to substantial savings in reducing stormwater pipes and inlets. These benefits cut costs and protect the environment. 

While the article fails to address the disadvantages such as higher maintenance and surface abrasion resistance, the benefits of using porous asphalt outweigh the negatives.

Firstly, since porous asphalt is required to remain porous to function, there are concerns about the upkeep and maintenance over the long run as it gets blocked by contaminations. The article  “Assessment of Restorative Maintenance Practices on the Infiltration Capacity of Permeable Pavement. Water” (Danz, M., Selbig, W., & Buer, N.,2020) it is stated that sediments would get trapped in the pores of the asphalt over time. Most of the clogging occurs “within 1.5 to 2.5 cm” of the asphalt. Once the top layer is clogged, the cleaning and draining effect of the porous road is diminished. Defeating the purpose of installing a porous road. Reverting to original condition requires pressure washing and vacuuming using special machines designed specifically for this task such as the “Cyclone CY5500®” (Cycloneclean, 2020). The schedule for maintenance varies with pavement age, joint space and intensity of usage. Additional costs for equipment and a complex maintenance structure would have to be drawn up to be able to use porous asphalt on a wider scale. 

Secondly, as porous asphalt is loosely packed, it is more prone to come loose under hard repeated loads. Frequent reapplication of the top layer would be required in such cases, which is not cost-effective. This also means that there is a limitation to the areas that porous asphalt can be applied. In the article “Porous Asphalt and Concrete Pose Big Problems” (TrueGrid, 2019), it is stated that resistance to abrasion is a concern in using porous asphalt. In areas where there is a high traffic count with heavy vehicles, it is observed that the top layer of the road surface came loose. This greatly shortens the lifespan of the road. So there is a limit to the application of porous asphalt. It is not suitable for use in areas where vehicles perform hard braking and acceleration such as highway exit and entry ramps or heavy vehicle parking lots.

On the other hand, an overlooked benefit of using porous asphalt is the decrease in usage of land as a drainage basin. In many built-up areas, towns are required to reserve open land areas for water retention purposes. This is due to most surfaces being covered by conventional asphalt/concrete which are not porous. This remains true, especially in land-scarce countries such as Singapore. There are many open spaces left empty in well-built areas such as "Tampines Central" and "Jurong East". The article “How It Works: Porous Asphalt Pavements” (Lombardo, 2020)  states that there is a significant cost advantage by being able to use parcels of land for commercial purposes rather than as a “detention basin”. Using porous asphalt in areas with limited land would be financially beneficial in the long run.

After weighing the pros and cons. I can confidently conclude that there are more advantages to using porous asphalt than a conventional road. When properly installed and maintained, porous asphalt pavements help to lower accident rates, act as a natural filtration system and increase the efficiency of the land used. These are benefits that outweigh the initial costs required for installation and maintenance. We should use porous asphalt wherever possible.

References

PaveGreen. (n.d.) Porous asphalt is king of the road.     http://www.pavegreen.org/index.php?option=com_content&view=article&id=58%3Aking-of-the-road&catid=35%3Aporous-asphalt&Itemid=110

Danz, M. E., Selbig, W. R., & Buer, N. H. (2020, May 30). Assessment of restorative maintenance practices on the infiltration capacity of Permeable Pavement. MDPI.

https://www.mdpi.com/2073-4441/12/6/1563/htm

Cycloneclean. (2020, November 18).

https://www.cycloneclean.com/cy-5500/

Paver, T. R. U. E. G. R. I. D. (2019, September 5). Porous asphalt and concrete pose big problems. TRUEGRID Pavers.

https://www.truegridpaver.com/porous-asphalt-and-concrete/

Lombardo, J. (2020, May 21) How it works: Porous asphalt pavements - for construction pros. https://www.forconstructionpros.com/asphalt/article/21134321/how-it-works-porous-asphalt-pavements