The article “Porous Asphalt Is King of the Road,” on the website Pave Green (n.d.), stated that porous asphalt is advantageous to the environment, enhances safety and is cost-effective. Porous asphalt is manufactured such that gaps are present for water to pass through and to a filtration bed underneath. As a result, it prevents flooding, filters contaminants in the water and enhances water standard. The article also mentioned that water spatter from vehicles vanishes, hence improving visibility for motorists, and reducing traffic accidents. Maintenance during winter is low, in view that minimal salt is required to remove snow on roads since snow liquefies at a faster rate on porous asphalt. Consequently, the use of pollutive de-icing agents is eliminated. The article also stated that porous asphalt costs about the same as standard asphalt. However, the overall construction cost is lower due to the reduced need for building of pipes and ground excavation.
While the article addressed the boons offered by porous asphalt (PA) by mentioning the material’s extensive usage in the US and its contribution to road safety in winter, its susceptibility to climate change sullies its own reputation. There are several factors of climate change that can negatively affect PA’s behaviour, thus undermining the article’s claim to PA’s ‘King of the Road’ status.
One major factor of climate change that can affect PA is the increase in moisture due to heightened precipitation. Though the article noted the comparable functionality of PA pavements to storm drains, it overlooked a consequence of moisture on the material itself. Makkonen et al. (2007) forecasted that the most affected area where precipitation is likely to rise in Europe due to increased heavy rain spells, is in northern European regions in contact with the Atlantic Ocean, and mountainous and elevated areas. The impact of additional precipitation on PA will be dependent on the ability of the underlying mixture of the pavement. If this mixture is not well prepped and becomes impermeable, water underneath the surface will swell and cause scouring, which is the loss of soil, of the lower layer mixture (Solaimanian et al., 2003). Most importantly, stripping, which is the functional deterioration of a pavement mixture by the loss of adhesive bond between asphalt binder and aggregate surface due to moisture, will occur. This will threaten the strength and durability of the layer. In due time, PA pavements in these highly precipitated areas will incur damage as a result of climate change.
Another factor of climate change that can affect PA is the increase in temperature. The article hinted on PA’s attribute in withstanding sub-zero temperatures, albeit without mentioning the effects of temperature increases. Thodesen and Hoff (2010) said that temperature rise may cause PA pavements to deform permanently if the pavement temperatures exceed the design temperatures. This may lead to uneven road compaction and the release of trapped water from within the air void structure. They also concluded that continued temperature fluctuations can also lead to cyclic loading of the saturated pavement, hence leading to the development of heightened pore pressures and stripping in the layers underlying the porous section of the pavement when using porous pavements.
In conclusion, what the article did not mention regarding the careful attention given toward the behaviours of PA in light of climate change should not be overlooked. Ultimately, as with all other pavement types, the success of PA is dependent upon proper design and construction. When properly designed and built, the PA surface can be a viable option when working in tandem with an integrated pavement system to serve a more deserving recognition for the title of ‘King of the Road’.
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References
Makkonen, L., Ruokolainen, L., Räisänen, J., & Tikanmäki, M. (2007). Regional climate model estimates for changes in Nordic extreme events. Geophysica, 43(1-2), 19-42. Retrieved February 19, 2018, from https://www.researchgate.net/profile/Lasse_Makkonen/publication/254947036_Regional_Climate_Model_Estimates_for_Changes_in_Nordic_Extreme_Events/links/02e7e534eb3c8e7ff7000000.pdf
Pave Green. (n.d.). Porous Asphalt Is King of the Road. Retrieved February 4, 2018, from http://www.pavegreen.org/index.php?option=com_content&view=article&id=58%3Aking-of-the-road&catid=35%3Aporous-asphalt&Itemid=110
Solaimanian, M., Harvey, J., Tahmoressi, M., & Tandon, V. (2003). Test Methods to Predict Moisture Sensitivity of Hot-Mix Asphalt Pavements. In Moisture Sensitivity of Asphalt Pavements – A National Seminar (pp. 77-110). San Diego, California, USA: Transportation Research Board. Retrieved February 19, 2018, from http://onlinepubs.trb.org/onlinepubs/conf/reports/moisture_seminar.pdf
Thodesen, C., & Hoff, I. (2010, June). Study of Water Effects on Asphalt and Porous Asphalt (Research Report No. 5). Retrieved February 4, 2018, from http://www.cedr.eu/download/other_public_files/research_programme/eranet_road/call_2008_climate_change/p2r2c2/08_Deliverable-N5.pdf
umar abdul aziz 