In the blog post “New paths for the
roads of tomorrow”, Decaux (2017) observed that developments in smart
infrastructure can be applied to roads, which will further improve roads to be
more “smart, connected and safer”. The author mentioned that roads are made of
asphalt, which is a costly material and encourages the formation of "heat
islands during heat waves in cities". In contrast, he stated that there
had been developments to create greener materials which would improve the
quality of roads. Such materials include "recycled plastic" that
helps to make roads more resilient and cigarette butts which are mixed with
asphalt that reduces the "heat island" formation. Decaux also found
that installing solar panels on top of roads could harvest energy. He noted two
applications of such energy: heating up roads during winter, and lighting up
the roads in the night via motion sensors. He further mentioned that these
applications of the generated energy will result in an improvement in road
safety and energy conservation similar to how a “smart city” would be.
Within this blog post, the author had given
examples of greener materials that can be used in replacement of asphalt in
road-making. However, he did not provide other valid points to make a comprehensive
comparison such as the advantages of using asphalt waste, the reduction of cost
and emissions as a result of that usage and the limitations of using plastic as
an alternative.
Firstly, most asphalt waste can be
recycled and reused when making new roads. According to a publication by
Harrington (2005), the majority of all asphalt is recycled
back into “highway use”. From a research publication by Turner-Fairbank Highway Research Center (2008), the process begins when pavements have broken down and
are “reprocessed” into the form known as “Reclaimed Asphalt Pavement (RAP)”. RAP
is then added back into the mixture that makes roadway structures. This also
has many benefits, such as improving the strength of new roads. In that same
publication, Turner-Fairbank Highway Research Center (2008) states that when RAP is
added to the foundation mixture, it makes the resulting roads stronger over a
period of time.
Another benefit of recycling asphalt is
that it is a penny-wise process. Adding recycled asphalt into mixtures reduces
the amount of raw asphalt needed in new mixes. In a blog post, Patterson (2015)
states that RAP reduces the tax from “American taxpayer by $1.8 billion per
year”. Furthermore, as lesser raw asphalt would be required, this would also
lessen the need for mining, manufacturing and transporting of raw asphalt which
is known to be expensive tasks, with the added benefit of easing carbon
emissions. In another blog post, Patterson (2015) states that recycled asphalt
has “cost lower than traditional asphalt as processes are eliminated”. Also, he
mentioned a notable decrease of “greenhouse gas emissions” due to avoidance of
gas usage needed in obtaining raw asphalt.
As the author had highlighted, using plastic waste in road-making may sound like a good idea, but not all plastic waste can
be utilized. As there are many forms of plastic, the melting point of each type
of plastic differs. This is important to note as the integration of plastic
waste to road-making mixtures requires the process of melting. According to Brandrup, Immergut, Grulke, Abe, & Bloch (2005),
most plastics (polymers) melts at a temperature above 200 Degree Celsius. In
comparison, this is higher than the heating of bitumen that is used in mixtures
for road-making. According to Mishra (2018), Bitumen is heated to “150 – 177
Degree Celsius.” in the process of mixing. Another problem with using plastic
wastes is that when heated to their respective melting point, most would
produce toxic fumes. According to the UN Environment (2019), plastic
incineration creates harmful fumes that are a hazard not just to human, but also
plantations and wildlife.
To conclude, although Decaux mentioned
the problems with using asphalt, there are still considerable benefits that
asphalt and its recycled counterpart provides. Similarly,
he has stated the possible use of plastic waste as a replacement material but in truth, plastic waste has limitations in usage. Thus, it would probably still take some
time before greener materials, such as using plastic waste, are able to replace
asphalt by a significant scale in the road-making world.
References:
Brandrup, J., Immergut, Edmund H., Grulke, Eric A., Abe, Akihiro &
Bloch, Daniel R.. (2005). Polymer
Handbook (4th Edition). John
Wiley & Sons.
Retrieved from
https://app.knovel.com/hotlink/toc/id:kpPHE00026/polymer-handbook-4th/polymer-handbook-4th
https://app.knovel.com/hotlink/toc/id:kpPHE00026/polymer-handbook-4th/polymer-handbook-4th
Decaux, J. C. (2017, October 23). Mobility & Trends; New
paths for the roads of tomorrow. [Blog Post]
Retrieved from
Harrington, J. (2005). Recycled Roadways. (Publication
Number: FHWA-HRT-05-003) U.S. Department of Transportation Federal Highway
Administration.
Retrieved from
Joel. (2008, September 17). What is Asphalt Recycling? Pavement
Recyclers. [Blog Post]
Retrieved from
Mishra, G. (2018, March 24). Steps in Bituminous Road Construction. The Constructor.
Retrieved from
Patterson, D.
(2015, November 04). 5 Benefits of Recycled Asphalt Pavement. Basic
Constriction. [Blog Post]
Retrieved
from
Patterson, D.
(2015, November 30). Does Sustainable Asphalt Exist? Basic
Constriction. [Blog Post]
Retrieved
from
Turner-Fairbank Highway Research Center (2008). Reclaimed Asphalt
Pavement. User
Guidelines for Waste and Byproduct Materials in Pavement Construction. (Publication
Number: FHWA-RD-97-148) U.S. Department of Transportation Federal Highway
Administration.
Retrieved from
UN
Environment. (2019, May 02). Plastic bag bans can help reduce toxic
fumes.
Retrieved
from
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