Recycled roads on the rise

Main Roads Western Australia is increasing its use and implementation of recycled construction and demolition waste in road construction and maintenance through a new pilot project and product testing scheme.

With a review of its waste strategy last year, the Western Australian Government has outlined some key targets in its draft Waste Strategy 2030 that aim to take the state’s waste management processes to the next level.

One target included in the strategy is for construction and demolition (C&D) waste, the aim of which is to increase material recovery to 75 per cent by 2020.

Main Roads Western Australia (MRWA) is already setting the benchmark for increasing the use of C&D waste in new and sustainable ways and taking up the challenge laid down in the strategy.

For MRWA Principal Advisor Sustainability Louis Bettini, the hierarchy of sustainability known as “reduce, reuse, recycle” is an ethos that informs and helps guide the road authority’s decision-making processes.

“The most effective way to increase sustainability is to reduce the amount of waste in the first place. Main Roads can contribute to this by ensuring it maximises the lifespan of its roads through good design and construction using durable materials, and encouraging the reuse of materials wherever possible,” Mr. Bettini explains.

Much of the state’s road network is rehabilitated or strengthened with in-situ recycling processes to reuse the existing materials, rather than replace them, when they reach their end of life.

Crushed recycled concrete (CRC) has been used on a number of MRWA projects in the past, which Mr. Bettini explains has performed well.

“The material makes an excellent sub-base under full depth asphalt pavements, providing a stiff underlying layer that will help extend the life of the pavement,” he says.

The authority also uses plastics in asphalt and other bituminous products while encouraging suppliers to source recycled plastics where possible. “Different plastics have different effects on the bitumen and asphalt and must meet quality requirements to prevent detrimental impacts on service life,” Mr. Bettini adds.

Late last year, the Department of Water and Environmental Regulation (DWER) approved the new Recycled Construction Products Program Specification, which has allowed the Main Roads department to include CRC as an approved sub-base for road projects. The move has set in motion a new pilot project that will see the recycled C&D waste product rolled out on one of the state’s busiest road corridors – the Kwinana Freeway.

In November last year, Western Australian Environment Minister Stephen Dawson and Transport Minister Rita Saffioti announced the Roads to Reuse (RtR) pilot.

The RtR supports MRWA in using recycled C&D for road construction, namely through a pilot project set to take place on the Kwinana Freeway Northbound Widening Project.

The project will see 25,000 tonnes of CRC used on the Kwinana Freeway works between Russell Road and the Roe Highway in early 2019.

CRC will be used as road sub-base under full depth asphalt on the project. This will involve laying a 150-millimetre-thick layer of the product, which will form the stiff support layer under approximately 250 millimetres of asphalt.

The material is a granular material mixture of fine-grained and coarse soils and crushed aggregate up to 20 millimetres in size, which will be placed by grader – like conventional quarry crushed rock-base material.

Aside from the environmental benefits of using the CRC as a sub-base, Mr. Bettini says it includes positive engineering properties, including strength.

“Previous experience with the product found it requires less water for compaction and requires less work to achieve compaction than limestone during construction,” he says.

“The residual cement in the crushed recycled concrete is partially reactivated and begins to re-cement over time. This is beneficial under full depth asphalt due to the increased stiffness and strength.”

He says the material can also be used as a base-course layer with thin asphalt layers on low traffic roads, as demonstrated by a number of local government authorities.

The Kwinana Freeway project is part of a greater push not just from MRWA, but other organisations and government bodies to increase the recycling of C&D waste in the state.

“Main Roads, the DWER, the Waste Authority and the Waste Recycling Industry have been collaborating for some time to develop an overall system for the use of recycled C&D waste in WA,” Mr. Bettini explains.

“Main Roads’ role is as the end user and, to ensure the success of the pilot trial, the Waste Authority is providing some seed funding to assist the industry supply recycled product competitively.”

DWER has provided the new Recycled Construction Products Program Specification, which includes a new product testing scheme with extensive testing by the supplier too ensure the product is safe and that hazardous contaminants are below maximum permissible levels set by the Department of Health. In addition to supplier testing, DWER will also undertake random independent audit testing to ensure the reliability of supplier testing and processes.

As part of the project, a new product testing scheme is being used to help C&D recyclers with costs associated with the sampling and testing required to ensure all product meet appropriate specifications and are free of contaminants.

Mr. Bettini says, in the first instance, the product testing scheme will provide end users confidence in the end product, assist the industry to improve processes to manage contamination over time and assist in dealing with issues of contamination if they do occur.

“The product testing scheme and the independent audit testing will assist industry by demonstrating contamination is being managed for the safety of the community and workforce working with the product,” he says.

“It involves extensive testing by the supplier to ensure hazardous contaminants do not exceed maximum permissible levels set by the Department of Health.”

The testing is focused on ensuring contamination is reliably managed below permissible maximum limits, and that testing will be undertaken and assessed during the trial.

The road authority has previously trialled and used the material successfully to the extent that, while performance and engineering properties will be monitored for a number of years, those results are not required before expanding use to other projects.

Mr. Bettini says there are a number of steps required for suppliers for CRC to gain approval for their quality processes, but supply is anticipated to commence in early 2019, when the pilot project is expected to commence.

There has been a significant push for the project to go ahead, Mr. Bettini explains, considering the million tonnes of C&D waste that goes unrecycled in Western Australia each year. The initiative also complements the direction MRWA is taking with regards to the consideration of safety, environmental, economic and community benefits and impacts as a whole.

The road authority has a long history of minimising use of raw materials and reusing and recycling materials where possible, which Mr. Bettini says has been driven by the need to reduce costs and to preserve finite sources of good road building materials – a sound notion, from both economic and sustainability perspectives.

“For example, crumbed scrap rubber has been used by Main Roads in bitumen sealing for over 30 years to extend the life of seals in certain applications. Similarly, CRC is expected to be a cost-effective material as its usage increases,” he says.

“The seed funding to get the industry up and running will accelerate take-up considerably.”

MRWA has already identified an ongoing program of projects that can utilise the recycled material if the trial’s successful.

The authority also has other projects targeted for early 2019 to trial the use of CRC as aggregate in new concrete and is already looking at trials of retaining wall blocks manufactured from the product.

“We recognise that consistently using the product will help provide confidence to local governments in using increased quantities of CRC, instead of virgin quarry materials,” Mr. Bettini adds.

“Main Roads recognises the need to take the lead to help demonstrate high-quality recycled products can be produced and used in WA. This project is a small step towards greater ongoing use of the product in WA by Main Roads and local government authorities.”