Friday, 6 April 2018

Reader Response, Final


In the article, “Porous Asphalt Is…,” on the website Pave Green (n.d), it was stated that porous asphalt is beneficial in terms of environment, safety and the cost. Porous asphalt earned its recognition from the Environmental Protection Agency and has been used all around the United States. It was indicated that porous asphalt roads or parking lots exclude small aggregates to allow water to pass through, acting like a filtration system. Superhighways also use porous asphalt because it helps to drain water, improve water quality, removes splashes and significantly reduce accident rates. The article also mentioned that porous pavement is beneficial in wintery climates because it allows snow to melt quicker which saves the cost of anti-icing agents, making it cost-effective and eco-friendly. Although the article states that the cost of porous asphalt is higher than conventional asphalt, the overall cost of construction balances out from the savings made from water pipes and inlets.

While I agree with the environmental aspect of stormwater management mentioned in the article, “Porous Asphalt Is…,” the article lacks any concrete information concerning the constraints and ineffectiveness which has led to the undermining of the article in naming porous asphalt the “king of the road”.

One characteristic contributing to the ineffectiveness of porous asphalt that the article has failed to mention is the critical downside of porous asphalt regarding the risk of skidding. In the research report, “Experiences with Porous Asphalt…,” Isenring, Koster and Scazziga (1990) stated that porous asphalt is not a suitable pavement choice for urban areas because of the low traffic speed. The same authors explained how the coefficient of friction is relative to the speed of vehicles and conclude that at higher speeds where the macro-texture is more important, the pavement will have better skidding properties. However, at lower speeds where the micro-texture is more relevant, the skid properties are much lower in comparison to conventional mix. The article highlighted that porous asphalt has high macro-texture but low micro-texture and is exposed to a higher risk in urban roads because of the decrease in traffic speed due to the densely populated residential areas. When vehicles travel at low speed in urban areas, the inadequate micro-texture will cause more skidding cases in urban areas especially in wintery climates.

Another negative aspect that was not mentioned in the original article is that porous roads require frequent maintenance and is problematic in urban areas due to the high traffic conditions. Isenring, Koster and Scazziga (1990) also mentioned that continual maintenance, it will contribute to a decrease in the permeability and porous asphalt will lose its noise reduction capability. Thus, the noise problem in urban areas generally cannot be solved with the use of porous asphalt. The same authors also mentioned that unlike the conventional mix, the binder coasting of the porous asphalt will have to be worn off before it can achieve its intended efficiency. Furthermore, porous asphalt at its pre-binder coasting state has even poorer micro-texture and normal repairing methods such as spreading of chippings will not be able to improve the situation.

Lastly, GreenBlue (2017) also state that porous asphalts will clog easily if no proper maintenance and regular checks are made. The void spaces in the pavement can be clogged by fine particles and sands and can only be removed using an industrial vacuum. Without fast maintenance, the permeability will decrease causing water and other pollutant to run off the surface which defeats the purpose of having permeable filtering pavement. The article also mentioned that the strength of porous asphalt cannot compete with traditional pavement. With consistent pressure from dynamic loadings such as heavy vehicles, it will cause pores of pavement to collapse. As a result, porous asphalt is not a recommended pavement for highways and airport runways.

In summary, the article by Pave Green (n.d) came across to me as being biased in the favor of porous asphalt as it only addresses the advantages. Porous pavements are not as perfect as it sounds, and like many other sorts of pavement, it has its own limits and restrictions and can only do so much.



References

Green Blue. (2017, January 25). Permeable Pavement: The Pros and Cons You Need to Know. Retrieve from https://www.greenblue.com/na/permeable-pavement-the-pros-and-cons-you-need-to-know/ 

Thomas, I., Harold, K., & Ivan, S. (1990). Experiences with Porous Asphalt in Switzerland. Retrieved from https://trid.trb.org/view/348603

Pave Green. (2018, February 5) Porous Asphalt Is King of Road. Retrieved from http://www.pavegreen.org/index.php?option=com_content&view=article&id=58:king-of-the-road&catid=35&Itemid=110


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