Combating the increasing need for road materials coincides with increasing supply of plastic waste. Inclusion of recycled plastic in the aggregate for the transport infrastructure is of growing interest. Testing plastic waste in both asphalt and concrete paving mixtures showed promising results and the need to examine long-term performance and durability.
The availability of high -quality overall materials for local roads and highways is often not sufficient to satisfy the increasing demand. However, the deliveries of plastic waste are plentiful. Plastic contributes significantly to the US waste flow. Less than 10% of the material are recycled. The conversion of plastic waste into useful material such as plasters could have numerous ecological and economic advantages.
However, there are many questions about the feasibility and material performance of plastically reinforced paving mixtures. Local agencies and mnds were interested in investigating whether upcycling plastic with plastic produces a product of a higher value from the waste – in road applications, specifications and benefits can meet and at the same time contribute to the sustainability goals of the agencies and the accumulation of plastic waste.
What did we do?
A comprehensive review of existing practices, pilot efforts and other research on the inclusion of recycled plastic waste in asphalt and concrete road paving examined the properties, the performance and durability of proprietary and non-proprietary products such as binders, additive, fiber amplification and seals.
Two online surveys of more than 30 recovery systems and suppliers of a variety of recycled plastic material, including fibers from wind turbines, helped identify and characterize researchers to identify plastic waste for testing. Interviews with selected respondents, which were developed about the characteristics of products, disposal methods and capacities for recycling different plastic types and challenges in connection with the processing of plastic waste.
“This research was very informative about the advantages and disadvantages of the inclusion of plastic content in bituminous and concrete sidewalks. Understanding the long-term performance of plastic fibers in concrete would support the livelihood of a sustainable road option,” said Jim Johnson, Public Works Administrator, City of Chisholm.
In the laboratory, the researchers assessed the effects of adding plastic waste to asphalt and concrete mixtures. Asphalt tests included the involvement of recycled plastic in pellet shape from two separate sources in a typical Mndot binder to determine the appropriate mixing time, performance and separation tendency. Finally, asphalt mixtures with and without the plastic attached binders were tested for temperature cracks and susceptibility to moisture.
The researchers then evaluated concrete mixtures with a virgin and three recycled plastic materials – both fibers and sand – as a replacement. The tested fresh and hardened properties included the processing and the air content, pressure and bending strength as well as durability.
What did we learn?
In this project, plastic suppliers sought -after an increasing trend of tending plastic materials into the transport infrastructure described the examination of the long -term performance and durability of sidewalks that were constructed with these materials. Companies encounter with food and liquid contamination of materials, high processing costs and technical complexity in recycling and reprocessing of plastics as well as a limited market to support production.
The optimal mixing time for upcycling waste plastic in asphalt binder was 15 minutes. Since some plastic were separated from the modified binder, the researchers came to the conclusion that the binder should be mixed and used immediately and should not be saved. The amount of plastic material that was added to the binder was 1.5% based on the weight of the virgin binder and led to a reduced crack resistance of the mixture.
By including waste in the concrete mixture, processability was reduced by approx. 50%. The plastic fibers led to a higher pressure and bending strength than the mixture of control, while the plastic sand modification mixture showed a lower compressive strength. The plastic waste improved the durability of the concrete mixtures. These materials replaced 20% of the unit, which has significantly used more waste material than in the asphalt mixtures.
What's next?
The concrete mix modified with upcycled plastic showed a high potential for the same or improved performance and could have significant environmental advantages. However, further research and field tests are required. Potential research problems included the variability of plastic quality and processing technologies, the asphalt separation problems and long -term performance.
Related research in both Minnesota and in other countries will drive the level of knowledge, move local agencies and be integrated closer to the integration of waste in sustainable sidewalks.