Plastic road

First recycled glass and plastic road in New South Wales, Australia at suburb Engadine

Plastic roads are roads made either entirely of plastic or of composites of plastic with other materials. Plastic roads are different from standard roads in the respect that standard roads are made from asphalt concrete, which consists of mineral aggregates and asphalt. Currently, there are no records of regular roads made purely of plastic. Plastic composite roads, however, have existed and demonstrate characteristics superior to regular asphalt concrete roads; specifically, they show better wear resistance. The implementation of plastics in roads also opens a new option for recycling post consumer plastics.

Construction

Since plastic roads are a relatively new idea, construction processes may vary. In Jamshedpur, India, roads are created from a mix of plastic and bitumen. These roads are made from recycled plastics, and the first step in constructing them is to collect and manage the plastic material. The plastics involved in building these roads consists mainly of common post-consumer products such as product packaging. Some of the most common plastics used in packaging are polyethylene terephthalate (PET or PETE), polyvinyl chloride (PVC), polypropylene (PP), and high and low density polyethylene (HDPE and LDPE). These materials are first sorted from plastic waste. After sorting, the material is cleaned, dried, and shredded. The shredded plastic is mixed and melted at around 170°C. Hot bitumen is then added and mixed with the melted plastic. After mixing the mixture is laid as one would with regular asphalt concrete.

So far, no large scale, systematic approach has been employed to build roads entirely of plastics. The plastic composite roads in Jamshedpur is not an ideal method, since the plastic is not exploited for all of its properties, which allow it to be formed into complex structure. An innovative concept proposed by a Dutch company, Volkerwessels, aims to create roads entirely of recycled plastic. Building roads entirely from plastic opens new possibilities in construction. Construction can be significantly more efficient, since roads can be created as individual pieces, which can be switched out in case of damages. This is different from traditional ways of road repair, which requires long time spent on site shaping asphalt to the desired shape. However, as of November, 2015 Volkerwessels has yet to release much detail on its proposed model.

Properties

Below are some of the pros and cons of plastic roads.

Pros

• On the proposed model by Volkerwessels, plastic roads can have hollow space built in to allow ease of wiring, connecting pipes, etc.
• Heating and power generation can be incorporated into plastic roads. Heating can prevent roads from freezing; it can also help evaporate water from the surface.
• Since plastics come with various chemical and physical properties, roads can be engineered to meet specific requirements (e.g. weather and wear resistance)

Plastic waste mixed in at 8% ratio to asphalt world-wide may solve the issue of plastics in landfills and oceans world-wide, soon becoming more valuable as a commodity in disadvantaged countries.

• Plastic roads can be made into interlocking pieces that can be quickly assembled or disassembled. This makes on-site construction much faster and convenient. Simplicity and speed of road work also correlates to lower cost.
• Plastic roads can be built from waste plastic --- the majority of which is usually put into landfill, incinerated, or polluted into the environment. Landfilling and incinerating plastic are both problematic methods of managing plastic waste. Plastics in landfills can leak pollutants into the surrounding soil; incinerating creates gaseous pollutants, such as carbon dioxide.
• Plastic-bitumen composite roads need not be especially discriminating with the plastics used, thus increasing the reuse of plastic. Most plastic waste is not recycled because it is usually mixed with different types of plastic and non-plastic (e.g. paper labels) and, so far, the segregation process is labor-intensive with no easy solution.
• Using less asphalt saves on resources. Asphalt concrete requires petroleum which is becoming more scarce.
• The use of plastic in road construction reduces the amount of asphalt used. This is beneficial to the environment since asphalt is responsible for 2% of global carbon emissions.
• Modular plastic pieces are much easier to work with than asphalt.
• The addition of plastic in asphalt can reduce the viscosity of the mix. This allows a lower working temperature, which lowers VOC and CO emissions.
• Plastic-bitumen composite roads have better wear resistance than standard asphalt concrete roads. They do not absorb water, have better flexibility which results in less rutting and less need for repair. Road surfaces remain smooth, are lower maintenance, and absorb sound better.
• Cost effective: using recycled, post-consumer plastics is cheaper than using asphalt.

Cons

• Pure plastic road requires using compatible plastics because, when melted, plastics of different types may phase-separate and cause structural weaknesses, which can lead to premature failure.