Reader Response, Draft #1

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. Thus, this reduces flooding and erosion. 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 liquify quicker which saves the cost of anti-icing agents, making it cost-effective and eco-friendly. Although the cost of porous asphalt is higher, the overall cost of construction balances out from the savings made from water pipes and inlets.

The article by Pave Green is biased in the favor of porous asphalt as it only addresses the advantages. I believe that porous asphalt does not always make the best pavement choice for being environmentally friendly and cost effective. There are many factors in which the article has failed to consider. In the research report, “Experiences with Porous Asphalt…,” Isenring (1990) has proved that porous asphalts are not so ideal in urban areas with the aid of the skid trailer Skiddometer BV8. From the same article, figure 3 is a graph which shows the low coefficient of friction relative to the speed. It concludes that porous asphalt has high macro-texture but low micro-texture. 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 matters more, the skid properties are much lower in comparison to conventional mix.

Due to the nature of the densely populated residential areas surrounding urban roads, it will cause a decrease in traffic speed. Having low speed, the inadequate micro-texture will cause more skidding cases in urban areas during wintery climate. Porous roads require frequent maintenance and is problematic in urban areas due to the high traffic conditions. Along with the lack of maintenance, this will contribute to the decrease in 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. 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 poorer micro-texture and normal repairing methods such as spreading of chippings cannot be used to improve the situation. Porous asphalt must also have strict criteria such as aggregates of high quality with good resistance to polishing and with sharp edges due to the specific surface structure of porous asphalt.

GreenBlue (2017) also states that porous asphalts are more prone to clogging if no proper maintenances are conducted. The void spaces in between the pavers can be clogged by fine particles and can only be removed using an industrial vacuum. During wintery climates, sand can also cause clogs. Without instant maintenance, permeability will decrease causing water and other pollutant to run off the surface which defeats the purpose of having permeable pavement. The article also mentioned that the strength of porous asphalt cannot compete with traditional pavement. Consistent pressure from dynamic loadings such as heavy vehicles will cause pores of pavement to collapse. Due to this fact, porous asphalt is not a recommended pavement for highways and airport runways.

In conclusion, porous asphalt is limited to very little types of roads and have to be under maintenance constantly.

Reference:

1. 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

2. Isenring, Thomas. Harald, Koster. Ivan Scazziga. (1990). Experiences with Porous Asphalt in Switzerland. Retrieved from http://onlinepubs.trb.org/Onlinepubs/trr/1990/1265/1265-005.pdf

3. 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/