Digital Exclusive: Executive viewpoint-Recycled plastic used in roads as Aramco adopts the circular economy
Using recycled plastic waste in the construction of new highways aims to reduce emissions and costs, while improving the quality of road infrastructure by utilizing circularity principles
Khalid Y. Alqahtani, Aramco Senior Vice President of Engineering Services, Dhahran, Saudi Arabia
Aramco is a pioneer in adopting circularity solutions that tackle different challenges, including plastic waste accumulation. The company has rolled out an innovative approach to utilize plastic waste in building roads.
Accumulation of plastic waste is a result of traditional linear practices of take, make and dispose, which has caused plastic use to increase by about 20-fold in the past half century. Shifting towards adopting circular economy business models can help enhance reuse. In line with the circularity principle of turning waste into resources, Aramco has utilized recycled plastic as a binding material in asphalt pavements.
Asphalt consists of gravel, sand and crushed rocks, which are bound together by bitumen, a sticky substance produced from crude oil. Minimizing the amount of bitumen in asphalt by replacing it with recycled plastic contributes to carbon dioxide (CO2) emissions reduction associated with the production of asphalt. This approach improves the performance of asphalt production by using recycled plastic and extending materials’ lifecycles, which supports Aramco’s ambition to become a prominent circular economy player in the energy industry.
Aramco’s journey in plastic road development. Aramco’s move into building “plastic roads” started in 2019 with a trial of a 250-m stretch of highway in Hawiyah, Saudi Arabia, that is used for company operations. The highway’s recycled plastic was imported by a company that was assessing the use of plastic in asphalt pavement construction. The trial was a success, but importing waste plastic was not a desirable long-term strategy, so a plan was developed to utilize local waste plastic. Aramco now uses plastic waste that comes from domestic waste treatment plants and meets technical requirements.
Sample of recycled plastic used in asphalt.
Once sorted into different types, the plastic waste is melted down and turned into pellets or flakes that can be used in asphalt binder, where it replaces up to 10% of traditional binder.
Since the first pilot, other roads in Jeddah and King Salman Energy Park (SPARK), in Saudi Arabia’s Eastern Province, have been built using recycled plastic. At SPARK, recycled plastic was incorporated into a 1-km industrial access road frequently used by heavy trucks.
Based on this success, recycled plastic is now specified as an option in Aramco’s Engineering Standards for asphalt production. The standards set out the method of production to be adopted, the percentage of waste plastic to be used, and viscosity and melting point, among other things.
Creating engineering standards. Road building is based on a set of technical standards for preparing the design mix and meeting minimum performance requirements, depending on a road’s geographical location and exposure to traffic loading. Governments and standards organizations maintain detailed manuals specifying what materials can be used, how they should be mixed and the specific performance requirements that must be met.
To standardize recycled plastic pavement construction, Aramco tested various locally available recycled plastics to ensure the minimum standard requirements were met. After several trial-and-error attempts, a recipe to create and prepare the design mix was established. A pilot project in Jeddah was selected to apply the design mix and asses road performance under heavy traffic loading. Construction of the pilot project using locally sourced recycled plastic was then carried out. The road was assessed after one year in service and was found to be performing well in meeting the Kingdom’s temperature and loading requirements.
Based on the experience with the pilot project and lessons learned, a design mix, proportions and recycled plastic specifications were developed and added to the company’s set of technical standards. Creation of a well-established asphalt mix formula in the standard has encouraged and increased the use of recycled plastic in pavement construction. In addition, Aramco has conducted awareness campaigns in its engineering communities for project management professionals, proponents, and designers to increase the formula’s deployments in the company and in Saudi Arabia.
As a result of Aramco’s efforts, a number of deployments have been achieved. Recently a large-scale deployment of a new 12-km road at the company’s Jafurah gas facility in the Eastern Province has been completed and is in service. Up to 10% of its bitumen binder replacement was accomplished by the use of approximately 160 metric tons of recycled plastic.
This practice serves to enhance the circularity of road construction by reducing the consumption of raw materials and reintroducing plastic waste to the flow of resources.
Building better quality roads. In addition to providing constructive uses for recycled plastic, the approach also results in better road quality. Roads laid with recycled plastic materials have unique characteristics compared to those constructed with conventional bitumen. The recycled plastic can strengthen the road and improve its resistance to pavement deformation (rutting) and cracking (fatigue). It can also make roads stand up well to high temperatures and help them to sustain the load of heavy truck traffic. It can additionally enhance water and skid resistance and provide stability and integrity.
Road constructed at SPARK with the use of recycled plastic
The use of plastic also contributes to road durability by increasing the periodic maintenance timeframe from approximately four years to seven years. Recycled plastic is not just a solution for new roads, as it can be used for maintenance and repairs, helping to reduce existing quantities of domestic plastic waste. In addition, after its useful pavement life, asphalt containing plastic can be reintroduced as a resource by recycling it into new products.
Aramco’s plastic roads initiative is part of a wider program, initiated under “Lower Carbon Construction Materials,” to use industrial waste in a range of construction applications. Other road-building techniques being developed include rubberized asphalt, sulfur asphalt and warm mix asphalt. Rubberized asphalt uses recycled shredded tires in the production of asphalt concrete. The warm mix and sulfur asphalt can reduce the temperature for mixing asphalt concrete ingredients by approximately 20°C compared to conventional asphalt production
To summarize, the aim of these technologies is to reduce energy use, reduce greenhouse gas emissions, increase reuse of waste materials and conserve natural resources. Use of recycled plastic can help reduce plastic waste, improve road performance, provide social value, and create industry and employment for local communities. There is now a need to widely adopt these new methods of road construction, and to include them in international standards for wider acceptance by the engineering community.
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