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". Additionally, he also 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 having
solar panels on top of roads could harvest energy. He noted that usage of such
energy generated could heat up roads during winter or lighting up the roads in
the night via motion sensors, thus improving on road safety and conserving
energy similar to how a “smart city” would be.
While there exist greener materials to be used in
replacement of asphalt as the author had mentioned, it is not a comprehensive
comparison. Comparing both materials, asphalt could still be the better
material to use as it has benefits such as being recyclable and as such, reducing
cost in the long term, while using plastic waste could be a liability as only certain
types could be utilized.
Firstly, asphalt is one of the “most recycled
material in the world”. According to a publication by Federal Highway
Administration (2005), the majority of all asphalt is recycled back into
“highway use”. From another publication by Federal Highway Administration
(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,
the Federal Highway Administration (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 the 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 are 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.
It is true that using plastic waste in road-making helps
reduce the total amount of plastic wastes, but only selected types of plastic could
be used. 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 Polymer
Handbook (4th edition) (1999;2005), most plastic (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 contributing factor is that some plastics, when
heated to its melting point, 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.
In summary, using asphalt and its recycled
counterpart has advantages that are comparable to adding plastic waste in
road-making. Quoting Joel (2008), basically “Recycled asphalt provides a better
product at a lower cost!”. On the other hand, plastic has issues with
integration, which results in non-integrable plastics still being wasted. Thus,
it would probably still take some time before greener materials, such as using
plastic waste, are able to replace asphalt in the road-making world.
Original blog post:
Decaux,
J. C. (2017, October 23). Mobility & Trends; New paths for the
roads of tomorrow
Retrieved
from
References:
Brandrup,
J. Immergut, Edmund H. Grulke, Eric A. Abe, Akihiro Bloch, Daniel R.. (1999;
2005). Polymer Handbook (4th
Edition). John Wiley & Sons.
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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
Mishra,
G. (2018, March 24). Steps in Bituminous Road Construction. The
Constructor.
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Harrington,
J. (2005). Recycled Roadways. (Publication Number:
FHWA-HRT-05-003) U.S. Department of Transportation Federal Highway
Administration.
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Joel. (2008,
September 17). What is Asphalt Recycling? Pavement
Recyclers. [Blog Post]
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Patterson, D. (2015, November
04). 5 Benefits of Recycled Asphalt
Pavement. Basic Constriction. [Blog Post]
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Patterson, D. (2015, November
30). Does Sustainable Asphalt Exist?
Basic Constriction. [Blog
Post]
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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.
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UN Environment. (2019,
May 02). Plastic bag bans can help reduce
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