SUMMARY/READER RESPOND DRAFT #3: POROUS ASPHALT IS KING OF ROAD
The article “Porous Asphalt Is Kind of The Road”
(PaveGreen n.d.) introduces the features and application of porous asphalt, a
type of road surface used to improve safety, diminish water pollution and
decrease erosion. The article states that porous asphalt is made up
of rocks glued together with asphalt cement while lowering the amount of fine
aggregate added. With lesser fine aggregate, more space is created in between
rocks, rainwater is able to seep into the space and limit the flow of water on
the surface. On highways, it reduces the amount of water flowing on the surface.
Thus, reducing the chances of splashes caused by vehicles, thereby, improving visibility
and safety.
It was further stated in the
article that during the winter season porous asphalt requires less application of anti-icing
to keep the road free from ice. With reduced usage of anti-icing, lesser chloride
which is toxic to aquatic life is released into the environment.
According to the article, the cost of porous
asphalt roads is relatively the same as conventional asphalt (or roads). Typically,
porous asphalt is used with a base layer such as a stone recharge bed
to achieve an optimal result. However, this results in a higher cost for
installing porous asphalt. On the other hand, the
cost difference can be offset by the reduced amount of stormwater
pipes being built.
The article mentioned the benefits and
multi-purpose applications of porous asphalt. However, porous asphalt requires routine
assessment and maintenance to be in optimal working condition. The high void
content in porous asphalt is essential to achieving its high permeability characteristics
causing the durability of porous asphalt to be lower compared with traditional
asphalt roads.
While the article mentions the benefits of porous
asphalt, there are constraints that limit its applicability of porous asphalt. When
constructing porous asphalt roads, assessments have to be conducted by specialists
personally to determine the suitability of the location. Porous asphalt can be
a more ecological and greener alternative to the traditional road when constructed
under favourable conditions.
Firstly, when rainwater hits the ground it will be mixed with
contaminants such as oils and minerals on the surface of the ground. While
porous asphalt reduces surface runoff due to its permeability, containment will
enter the porous asphalt with the flow of rainwater. Over time, containment tends
to get trapped in the pores and reduces the permeability of porous asphalt. Hence,
routine assessment is essential to understand the clogging situation and to schedule
maintenance when necessary. If left unchecked and untreated the pores of porous
asphalt roads eventually be clogged by containment. According to Ma, et
al. (2020) the clogging characteristic of porous asphalt roads is a common
problem owing to the deposition of sediments on the surface of the road. Thus,
over a period, the roads will be clogged, which causes 59% - 75% reduction in
permeability.
Research done by Razzaghmanesh et al. (2018) mentioned
that there is no one fit for all methods of assessment and monitoring porous
asphalt. Assessment and monitoring should be conducted early after
installation even if there are no signs of blockage. It will provide a
better understanding of the in-situ clogging mechanisms for the region. Routine
assessment of porous asphalt roads condition will (also?)provide the clogging
statistics. Subsequently, maintenance can be scheduled for porous
asphalt roads. Early assessment enables timely intervention to keep porous
asphalt in ideal working condition. In comparison, traditional
roads do not require such in-depth routine assessment or maintenance.
Secondly, the high permeability due to high void content
between pores led to a weaker internal structure of porous asphalt. According
to Alberet al (2017), the high void content of porous asphalt is designed
into porous asphalt intentionally to achieve the high permeability
characteristic. In order to achieve more void, less aggregate will be added
when constructing porous asphalt roads. The internal structure will be weaker as
the support from aggregate will be replaced by void spaces. Therefore, leading to
material deterioration, such as the ravelling and increased physical aging
effect. In locations that experience high traffic flow such as expressways,
porous asphalt is more likely to lose its durability and collapse more often than
traditional dense asphalt. In such areas, the lifespan of porous asphalt roads
will be greatly reduced. The building
of porous asphalt roads in such locations have to be avoided.
Lastly, the key characteristic
of porous asphalt that is often overlooked is the ability to reduce noise
generated. Noise-reducing characteristic is especially useful in countries and areas
where land is limited such as Singapore. In Singapore, roads and expressways
are generally in the vicinity of HDB flats. According to Kondo et al (2000), porous asphalt
pavement is one of the
most effective countermeasures for countering traffic noise. Result shows
that noise reduction on the porous pavement is about 3-4dB lower compared with
traditional roads. Generally, noise is mainly caused by vehicles on the roads,
porous asphalt roads can be built in the residential area to reduce the noise
generated by vehicles, this can improve the quality of life of the resident in
the area.
In conclusion, there are
multiple benefits of porous asphalt when compared with traditional roads.
However, assessment and planning based on the climate and location should be
done diligently as the applicability of porous asphalt varies with different
conditions.
References
Alber, S., Ressel, W., Liu, P., Wang, D., Oeser,
D., Uribe, D., & Steeb, H. (2017) Investigation of microstructure
characteristic of porous asphalt with relevance to acoustic pavement
performance. International Journal of Transportation and Technology, 7,(
3).
https://doi.org/10.1016/j.ijtst.2018.06.001
Kondo, N., Ohnishi, H., Hattori, H., Ishikawa, K.,
& Nakano, T. (2000) Noise reduction effect on double-layer porous pavement.
Liu, M., Huang, X., & Xue, G. (2016)
Effects of double layer porous asphalt pavement of urban street on noise
reduction International Journal of Sustainable Built Environment, 5, (1).
https://doi.org/10.1016/j.ijsbe.2016.02.001
Ma, Y., Chen, X., Geng, Y., & Zhang, X.
(2020). Effect of Clogging on the Permeability of Porous Asphalt Pavement Article 4851291
https://doi.org/10.1155/2020/4851291
Pavegreen.
(n.d).Porous Asphalt is king of the road
Thanks for the rewrite.
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