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. Thus, exploring potential substitutes made from non-pristine resources such as plastic and concrete waste is the ideal method 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.
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.
Fundamentally, with various technologies and a sustainable target mindset, it is possible for road construction firms to conceptualize and implement greener alternatives to achieve more eco-friendly outcomes and maintain the aspect of sustainability in the industry.
References
Missouri Asphalt Pavement Association. (2013, May 23). Sustainability. https://moasphalt.org/why-asphalt/green-asphalt/
Asphalt (2019, December 27). In Encyclopedia Britannica. https://www.britannica.com/science/asphalt-material
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
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
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
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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