In the article,
"Sustainability", Missouri Asphalt Pavement Association (2013)
discusses the 'green' effects of asphalt. The article considers asphalt as
'green' for being non-disposable and reusable regardless of its age, but also
because it allows other waste products to be involved in the process. The
development of Recycled Asphalt Pavement (RAP) is revolutionary in asphalt
paving, as it uses cultivated old asphalt to be incorporated into new asphalt
using heat. The article highlights the lesser use of pristine resources and
reduction in spending and fuel usage which benefits both contractors and the
environment. Additionally, innovations such as Warm Mix Asphalt (WMA) and
porous pavements are beneficial to the environment. The article adds that halved
temperature emissions and reduced carbon footprints are resultant of WMA's
hybrid production and mentions the porous pavements' capability to drain
rainwater into recharge beds for soil absorption and replenishes aquifers
rather than forcing water into sewers.
The advancement of technologies used in
the paving industry empowers asphalt to be the most sustainable material for
road construction. With technologies such as RAP and WMA in asphalt production,
there is a need to discover other green materials that can substitute scarce
virgin aggregates. Aggregates such as coarse sand are part of a global trade
that is expanding at an exponential rate due to its widespread use and can
possibly be exhausted in the near future. In order to search for these green
materials, the need to comprehend asphalt’s composition and the material used
for its mixtures is crucial before exploring potential substitutes made from
non-pristine resources such as plastic and concrete waste to ensure
sustainability.
To look further into this, we must
first understand what asphalt is and how it is integrated when used for paving
roads. Asphalt is a petroleum-like matter, known as Bitumen, obtained from
natural deposits or as residue from petroleum distillation with a consistency of
either viscous liquid or glassy solid (Britannica Encyclopedia, 2019). For road
paving, asphalt is mixed with aggregates such as sand, gravel, and crushed rock
at manufacturing plants before being transported to the paving site to be
spread out and compacted (Speight, 2016). Hence, we understand that asphalt
itself is derived from unsustainable fossil fuel and as stated by MAPA (2013),
modern technologies have allowed asphalt to transform into recyclable material.
Aggregates such as sand, specifically coarse sand, is a raw material widely
used in construction that is actually finite. Growth of population, industry,
and urban developments fuels the explosive demand for sand and has pushed the
scale of sand mining at a rate of 5.5 percent yearly and is estimated to reach
60 billion tonnes by 2030 (Chatham House, 2019). Thus, it is imperative for the
industry involved in urbanization specifically in road construction and
maintenance to obtain greener materials or reusable waste which can reduce the
acquisition of virgin resources.
To start off, some green aggregates can
be acquired through the recycling of concrete debris. According to Kowalski
(2016), recycling construction and demolition waste (C&DW) through an
advanced processing concept named “Stone Recycling” can be the solution to
obtain pure aggregates from raw C&DW. The article mentioned that the
process goes through steps of crushing and sieving, sorting of ferric and
non-ferric parts, and finally scrutinized by a Near-Infrared (NIR) technology
to sort out unwanted elements. The resultant of this process is a high-grade
recycled pure concrete aggregate that can be re-integrated into asphalt for
road paving.
Furthermore, green materials can also
be obtained beyond the field of construction which reduces the limitation of
what can or cannot be implemented for sustainability. A case in point is the
solution created by the Singapore-based start-up, Magorium Pte Ltd, to turn
plastic wastes into an innovative synthetic that can partially replace binders
such as bitumen in asphalt mixtures of roads (Channel News Asia, 2020). The
article includes their innovation of producing plastic-like pellets that are
potential aggregate substitutes such as gravel. These pellets are implemented
at testbed roads near Tuas and Marymount to determine their performance under
natural climate conditions in which favorable results can lead to nationwide
implementation.
While producing aggregates from
non-biodegradable waste such as plastic are good green innovations, road
construction firms must not overlook the fact that there may be slight
drawbacks to such ideas. According to Conlon (2021), paving roads with plastic
materials can be harmful to roadworkers due to the heating process that is
involved. The heating of plastics causes the release of substances that are
carcinogenic and harmful gases such as carbon monoxide and formaldehyde which
can kill a person if ingested in large amounts. But, this issue can be overcome
if safety precautions are taken by the firms to ensure that workers’ safety is
not compromised in the paving process.
Fundamentally, with various
technologies and a sustainable target mindset, it is possible for road
construction firms to conceptualize and implement greener alternatives. By
exploring potential aggregate substitutes acquired through recycling waste,
these firms can achieve more eco-friendly outcomes and maintain the aspect of
sustainability in the industry.
References
Asphalt (2019, December 27). In Encyclopedia
Britannica. https://www.britannica.com/science/asphalt-material
Chatham House. (2019, May 30). Driven
to extraction: Can sand mining be sustainable? By Oli Brown and Pascal Peduzzi.
Sustainable Accelerator.
https://accelerator.chathamhouse.org/article/driven-to-extraction-can-sand-mining-be-sustainable
Conlon, K. (2021). Plastic roads:
not all they’re paved up to be. International Journal of Sustainable
Development & World Ecology.
https://pdxscholar.library.pdx.edu/cgi/viewcontent.cgi?article=1314&context=usp_fac
Kowalski, K. J., Król, J.,
Radziszewski, P., Casado, R., Blanco, V., Pérez, D., Viñas, V. M., Brijsse, Y.,
Frosch, M., Le, D. M., & Wayman, M. (2016). Eco-friendly Materials for a
New Concept of Asphalt Pavement. Transportation Research Procedia, 14,
3582–3591. https://doi.org/10.1016/j.trpro.2016.05.426
Missouri Asphalt Pavement Association.
(2013, May 23). Sustainability. https://moasphalt.org/why-asphalt/green-asphalt/
Speight, J. G. (2016). Asphalt
materials science and technology. Butterworth-Heinemann. https://doi.org.singaporetech.remotexs.co/10.1016/B978-0-12-800273-5.00001-5
Tang, S. K. (2020, Dec 7). This
Singapore start-up hopes to make roads with plastic waste. Channel News
Asia. https://www.channelnewsasia.com/climatechange/start-up-make-roads-with-plastic-waste-singapore-1340136
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