Time to rethink plastics

No doubt, waste plastic is a significant contributor to Australasian waste generation with way too much of it going to landfill.

But there is good argument also for including the use of plastics and composites in our circular economy ambitions.

For example, there is growing interest in exploring the viability of using recycled plastic in roads with advantages to the environmental and the development of sustainable

road making materials.

A report late last year by Austroads, a collective of Australian and New Zealand transport agencies, found that waste plastic can act as a partial aggregate replacement in bituminous mixes and a binder extender without having any significant influence on the properties of the asphalt mix.

While there may be environmental benefits associated with the use of recycled plastic, there are concerns regarding the potential health and safety hazards, mainly relating to the workers using the material.

Not all recycled plastics are suitable for bitumen modification at high temperatures. For example, heating poly-vinyl chloride (PVC) at high temperatures can result in dangerous chloride emissions. In addition, alternative In 2018, a series of road trials took place around Australia, mainly involving two proprietary products from suppliers MacRebur and Downer EDI. The report provides details and performance testing results reported by the manufacturers of these two products. It was found that soft plastics were the predominant material used in road trials in Australia. Soft plastics are those that can be scrunched into a ball such as plastic shopping bags, bread bags, cereal bags, bubble wrap, fruit and vegetable bags, packaging, netting.

materials such as reclaimed asphalt pavement, crumb rubber, glass and crushed concrete have been increasingly used for road pavement construction.

All of the commercial products available in the Australian and New Zealand market are made from different classes of plastics and little is known about the manufacturing process.

Since the Australian trials with recycled plastic only commenced in 2018, it is important that the performance of these pavements be monitored over the longer term, the report says

Still, if recycled plastic can be successfully incorporated into pavements it will enhance road-building material options and lessen the reliance on virgin non-renewable resources.

There will be environmental and, potentially, commercial benefits arising from reduced landfill and the benefits associated with a consistent and reliable source of recycled materials for the road building industry.

The use of recycled plastics will improve sustainability through climate and infrastructure resilience benefits.

The most commonly recycled plastics are PET, HDPE, LDPE and PP which comprise more than 85 percent of all reprocessed Australian plastics.

The report suggests the use of HDPE, LDPE and polyethylene terephthalate (PET) are most prevalent for binder and asphalt modification. PET also has a high potential for reuse.

Some plastics are more difficult to reprocess owing to their chemical properties, resulting in increased proportions being sent to landfill.

Downer, Hume City Council, Close the Loop, Sustainability Victoria and RED Group worked in partnership to build the first ever Australian road with soft plastics, glass and toner.

The same day, the project was the first to be funded under the A$2.5 million Resource Recovery Market Development Programme of the Australian state to support market development for recovered resources materials.

Downer’s expertise in building infrastructure and facilities combined with the ability of recycling companies such as Close the Loop allowed for the use of materials such as glass and printer cartridge toner to manufacture asphalt, effectively keeping it out of Australia’s waste stream.

Through the REDcycle program (hosted by the RED Group), unwanted plastic shopping bags and other soft plastics such as food packaging were collected from bins placed at major supermarkets to be re-used in an environmentally responsible manner.

It is not limited to only using recently banned plastic bags. Sustainability Victoria estimates that 170,000 tonnes of soft plastic waste is created in Victoria each year, with only 17,000 tonnes or 10 percent recovered

The programme is not limited to only using recently banned plastic bags. Sustainability Victoria estimates that 170,000 tonnes of soft plastic waste is created in Victoria each year, with only 17,000 tonnes or 10 percent recovered.

Close the Loop transforms the soft plastics collected by the REDcycle program along with waste toner collected through programs such as Cartridges 4 Planet Ark to develop an asphalt additive called TonerPlas.

TonerPlas is then mixed with glass and Reclaimed Asphalt Pavement (RAP) to produce the final proprietary product named Reconophalt.

Downer commissioned an internal research and development program to assess product performance, occupational health and safety

risks and scalability in a real-world application.

There is no risk of releasing microplastics into the environment. The asphalt is made up of 95 percent aggregate and five percent bituminous binder.

The bituminous binder is the ‘glue’ that bonds and waterproofs the aggregates. The soft plastics additive melts and becomes part of the bituminous binder.

Because of this process it is not possible for the additive to separate out creating microplastics.

This method involves returning plastic waste to its original polymer state which is used as a substitute for virgin petrochemical products which are normally mined for use in road construction.

The roads industry has used virgin polymers since the 1990s and this soft plastics initiative follows a similar vein; where asphalt manufactures modify a road construction material to improve long term performance.

The sustainable, cost-competitive road has a 65 per cent improvement in fatigue life and a superior resistance to deformation allowing it to better handle heavy vehicle traffic.

When scaled up from the Melbourne trial, every kilometre of two-lane road paved with plastic and glass modified asphalt would use about 530,000 recycled plastic bags and packaging, 170,000 recycled glass bottles, toner from 12,500 used printer cartridges, 130 tonnes of reclaimed road (asphalt) re-used with the inclusion of 20 percent RAP.

It is not limited to only using recently banned plastic bags. Sustainability Victoria estimates that 170,000 tonnes of soft plastic waste is created in

Fulton Hogan, in partnership with Christchurch Airport, conducted a trial with recycled plastic modified asphalt mix. PlastiPhalt®, which was developed by Fulton Hogan and used to pave half of Christchurch Airport’s fire station. PlastiPhalt® is made from used oil containers collected through Fulton Hogan’s Recovering Oil Saves the Environment (ROSE) scheme. Previously, these containers could not be reused due to the residual oil left on the inner surface. In 2014, the company began its research program by shredding these plastic containers to an ideal size before incorporating them into an asphalt-grade bitumen. PlastiPhalt® is used to modify the asphalt mix required to meet the performance requirements of any given site. Once it is blended and ready to be used, it is sampled and laboratory tested to ensure the level of modification is achieved. Additional plastic material can be added to fine-tune the mix, if required.

Victoria each year, with only 17,000 tonnes or 10 percent recovered.

However, it costs 2-5 percent more than standard asphalt due to the additive production and transport costs. Despite this, it was claimed that it was still 25% cheaper than PMB-modified. Alex Fraser has recently resurfaced two municipal streets in the City of Yarra, Victoria with its proprietary product, PolyPaveTM. The resurfacing of Stanley and Margaret Streets in Richmond was reported to contain recycled glass, asphalt and HDPE plastic (hard plastic/bottles), amounting to almost 100 tonnes of recycled waste. The city has re-engaged Alex Fraser to repair and repave several more streets.

In September 2018, a 30-metre-long bicycle path called PlasticRoad, composed of recycled plastics, was installed in Zwolle, Netherlands. The innovation was the result of collaboration between three companies, an engineering firm KWS (a VolkerWessels company), Wavin (a subsidiary of the plastic piping company Mexicham), and an energy company Total. The first pilot trial in Zwolle involved the use of 70 percent of recycled plastic, including plastic bottles, beer cups, cosmetic packaging, plastic furniture and the like. Besides the effective use of waste plastic that would otherwise have been incinerated or dumped into landfill, the construction of the path was fast and easy. This was because the road design incorporated prefabricated and lightweight modular pieces put together like Lego. The path was installed in a matter of days, thus reducing of the normal downtime and traffic obstruction often related to traditional road construction methods. The modular design also resulted in a reduction of in the levels of greenhouse gas emissions typically associated with conventional road construction methods. PlasticRoad is hollow. As a result, it offers many benefits, including the ability to cater for utility services such as pipelines and cables for high-speed internet, and the storage of rainwater to mitigate flooding. It was reported that this concept offers opportunities for further innovation such as solar roads, light poles and traffic loop sensors. A second pilot trial was established by the same partnership in November 2018 in the town of Giethoorn. Similar to the first trial, this was also a 30-metre long bicycle track but smaller and smaller and lighter equipment was used to ‘pick and drop’ the fabricated pieces. After more than 18 months of testing, learning and continued development into a design suited for industrial production, the circular economy technology known as PlasticRoad is now ready for commercial launch.

At the time of their installation in 2018, both test roads in the Netherlands were fitted with sensors that enabled 24/7 monitoring of their use and behaviour.

It has become clear from practical tests and data that the PlasticRoad is also a match for heavier loads like garbage trucks and maintenance vehicles.

Further improvements to the design mean that the definite version will be more rugged and 2.5 times stron-

ger than the test sections.

This makes the PlasticRoad suited at this stage for applications like parking lots, and the first pilot project for this application is underway.

The eventual realisation of the first PlasticRoad for cars and other road traffic has become more likely than ever, the project team says.

“The PlasticRoad has proven able to handle heavy loads and offers an effective solution for water management with heavy precipitation and periods of drought.

It holds up under a wide range of conditions and the group behind the PlasticRoad initiative are “exceptionally satisfied with the results of the pilot project and look forward to seeing the first PlasticRoad element roll off the production line.”

Marcel Jager and Anne Koudstaal of the PlasticRoad project team say “ we have proven that our ground-breaking circular concept – a prefab road based on recycled plastic – is feasible in practice.

“An initiative that started in 2018 with two pilot projects is now ready for industrial production – a feat that we are incredibly proud of.”

Each pilot contained about 1000 kg of recycled plastics, the equivalent of 218,000 plastic cups.

The pilot version of the PlasticRoad has already cut carbon emissions by between some 50 percent and 70 percent compared to conventional bike paths made from asphalt or concrete.

The group says this percentage stands to increase even further when the finalised design is taken into industrial production in 2021.

The circular characteristics of the finalised product have been optimised by further developing the road’s structural design – an achievement that has been confirmed by an independent circular audit.

Extreme precipitation and heavy showers are becoming increasingly common as a consequence of climate change.

In many cases, current infrastructure struggles to accommodate all the excess water – with flooded streets as the result.

The hollow sections under the PlasticRoad’s surface are intended to quickly store this sudden precipitation and then gradually allow it to infiltrate the subsoil.

This climate-adaptive solution turns out to work very well in practice.

“Before the two test sections were installed, both locations used to be affected by water storage problems,” the group says.

“But with PlasticRoad, even the heaviest showers proved to have a minimal impact on local storage capacity.

“The highest water level measured within the PlasticRoad was only 48 percent of the available storage capacity at one test site.

The water subsequently infiltrates the subsoil within the next two days – exactly as predicted. The project looks certain to encounter strong interest from the market. Based on the convincing results recorded in the pilot projects, the PlasticRoad team are taking he production line into operation. The PlasticRoad is available for orders immediately with initial deliveries in the first quarter of 2021. Working together with clients and contractors, PlasticRoad will be launching a variety of applications that can help make cities and towns climate-adaptive and carbon-neutral. For example, the PlasticRoad planning includes bike paths, parking lots, pavements and schoolyards. The team will initially be focusing on clients in the Netherlands and neighbouring countries, after which they expect to scale up to markets in other parts of the world.

www.plasticroad.eu

In 2015, a commercial plastic waste recycling venture was released in Scotland.

The idea behind the product was inspired by practice in Southern India of retrieving waste plastic to fill up potholes.

Diesel was then poured over it and the mix set on fire until the plastic melted into the craters and formed a makeshift plastic pothole filler.

India has been using plastic in the construction of roads since the turn of the century, following a process developed by Rajagopalan Vasudevan, a chemistry professor at Thiagarajar College of Engineering in the South Indian state of Tamil Nadu.

Vasudevan's process involves scattering shredded plastic over hot stones to form a thin, primer coat. This is then added to bitumen, resulting in a strong bond.

To date, this method has been used on an estimated 100,000 kilometers of roads across India.

In late 2015, the Indian road transport ministry made it mandatory to construct roads using waste plastic in most urban areas.

MacRebur has now produced three products (MR6, MR8 and MR10) made from domestic and industrial waste plastic.

These products have a melting point lower than that of typical asphalt and binder production temperatures, enabling it to melt into the binder to extend and modify it.

These three products come in a different colours and forms:

• MR6 – comes in pellet form and is intended to be incorporated directly into the asphalt production plant. It modifies the asphalt by increasing its tensile strength and the softening point. It is flexible but rigid and unbreakable.

It is reported to work well in hot conditions (like Australia) as it has a melting point of 110 °C. • MR8 – a shredded plastic. It was developed to be a more economical bitumen extender without any performance enhancement. It is a cheaper version of MR6. • MR10 – comes in pellet form (looks similar to MR6). It was developed to provide a more crack-resistant binder. In contrast to MR6, it is flexible in a solid form - it rebounds when flexed.

It was reported that it worked well in colder climates such as the UK, Canada and Russia.

In 2017, Cumbria County Council was the first highway authority in the UK to trial MacRebur’s plastic-based material.

An equivalent of 500,000 plastic bottles and over 800,000 one-time-use plastic bags were recycled for a 400m long by 20m wide strip of road.

MacRebur says the company aims to use a ratio of 50/50 domestic and commercial waste for local road applications.

In Australia, MacRebur performed a road trial for Brisbane in 2018.

There is limited information about this trial in the public domain although it is understood that a series of performance tests has been conducted by Brisbane City Council’s Pavement Division in association with the University of Sunshine Coast, Boral and Fulton Hogan. Testing was undertaken to compare the behaviour of a binder that had been supplemented with the MacRebur products -- MR6, MR8 and MR10. When 4.5 percent of MR6 was added to the C170 binder, the properties were similar to a A35P bitumen with good torsional recovery and an increased softening point to about 78 degrees celsius. This was in line MacRebur’s claims that MR6 mimics a plastomeric polymer and MR10 an elastomeric polymer. However, the MR10 blend was much stiffer, which contradicted the claim. There was no significant difference in the properties when the MR8 was added to the C170 bitumen. Six per cent (by mass of bitumen) of MR6 and MR10 was added to the C320 bitumen through a batch plant. Another two batches of asphalt were prepared which were C320 and Multigrade M1000 control mixes. The deformation resistance of the MR6 mix was superior to the M1000 mix. However, the tensile strength of both the MR6 and MR10 mixes dropped drastically when the mix was exposed to moisture. The addition of MR6 to the C320 mix resulted in an increase in stiffness similar to the M1000 mix, but very little difference with the MR10 mix. However, the fatigue results for the MR6 were poor, suggesting no improvement to the life cycle of the asphalt. The fatigue life of the MR10 mix, on the other hand, was slightly higher but minimal compared to the results for the C320 and M1000 mixes. It was suggested that this behaviour could be due to the poor digestion of the waste plastic material in the samples, as some pellets were still visible. An asphalt mix containing British pen grade 40/60 bitumen (equivalent to C320) modified with 6 percent MR6, MR8 and MR10 was undertaken. Testing was conducted according to British Standard EN 13108-5:2016 and it was found that the addition of all three products resulted in an improvement in deformation resistance and overall structural contribution. MR10 had the highest stiffness modulus, whilst MR6 had the most significant effect on asphalt fracture resistance and deformation resistance. This contrasted with the original intention of MR6 to exhibit plastomeric properties rather than MR10. The tests also suggested that the addition of MR6 and MR10 resulted in improved fracture toughness and fatigue life.