Since 1974, Delta Group has established itself as an industry leader in demolition projects across Australia. Its core activities include civil works, excavation, landscaping, commercial bin hire and heavy equipment hire and its clients have included construction companies, government departments, municipal councils and developers.
In the last decade, Delta?s demolition division has been involved in some of Australia?s landmark redevelopments. These include the Northern Stand at the Melbourne Cricket Ground and the Crown Casino Promenade in Melbourne, the Australian Taxation Office and Federal Department of Immigration and Multicultural Affairs buildings in Canberra, White Bay Wharf and the Hyundai headquarters in Sydney, the IKEA outlet in Slacks Creek, near Brisbane, and Perth?s William Street Overpass.
Delta Group actively recycles over 85 per cent of all materials that it collects from its demolition projects. Its metal recycling plant in Altona, near Melbourne, recycles non-reusable ferrous and non-ferrous materials and retails a range of salvaged metal and steel products with varying applications. Delta is also a dedicated timber recycling specialist and retailer.
However, of most interest to the quarrying industry is Delta?s concrete and brick recycling division. This division has formed a very successful joint venture with Boral Quarries in Victoria and New South Wales to crush, process and treat commercial demolished concrete into a new product called Envirocrete which is used as a pavement material – the equivalent of various grades of quarry products – for roadworks, carparks, factory sites and landscaping purposes.
The Delta/Boral partnership encompasses a fixed concrete recycling plant in Sunshine, in Melbourne?s western suburbs, as well as mobile operations at multiple sites elsewhere in Melbourne and Sydney. The throughput rate of the Sunshine plant is around 250 tonnes per hour (equating to 500,000 tonnes per year). Delta not only crushes and processes the recycled concrete aggregate from its demolition projects, but accepts construction and demolition (C&D) waste from other demolition and civil contractors, infrastructure suppliers, and major projects at sites throughout Melbourne and Sydney.
THE AGE OF RECYCLING
Delta Group first became involved in the recycled construction materials business in 1999. The recycled concrete market is only slightly older – no more than 20 years – and it is universally agreed that one of the first companies to profitably recycle and sell C&D waste as an alternative quarry product was the Alex Fraser Group, based in nearby Laverton North. Today both Alex Fraser and Delta Group are the leaders in the recycled concrete marketplace, which is believed in Melbourne alone to have an output of two to three million tonnes per year.
Chris Cox, the contract crushing and national recycling manager of Delta Group, states that 20 years ago most C&D waste material went straight to landfill or less regulated sites. However, in the last three decades, market forces, coupled with State and local government regulation and a push towards more sustainable policies by clients, have inadvertently combined to drive the demand for alternative recycled products.
?Landfill costs and government policy to zero waste are the forces that made people initially look at recycling,? Chris says. ?When you consider all the reinforced steel alone that was in the concrete product that was just going straight into landfill, in dollar terms it was 30 to 40 tonnes of steel on a daily basis.?
It is therefore far cheaper, not to mention more environmentally friendly, for clients to take their C&D waste to recycling plants like Delta than it is for them to send it to landfill and pay tipping fees and government levies for its disposal. According to Chris, recycled concrete production potentially could add to the sustainability of quarry deposits.
?By having this product here, it extends the life of the quarry deposits,? he says. ?It?s more and more difficult to open new quarries. They are not as easy to open now because of the structure of the local government assessment process and some community pressures. Over many years, Melbourne has been very well served with quality rock reserves, as it sits on a basalt flow and is so plentiful. As a result, the Victorian quarry industry has quarried the high quality rock, and haven?t utilised all the resources efficiently. In Sydney, by comparison, because rock resources are low and because the average cart for quality quarry products is about 100 kilometres to the Sydney market, there is a greater acceptance of alternative products. The Sydney market has had to engineer better products or make use of whatever is available. Recycled aggregate is one of those.?
The Delta/Boral partnership is itself, Chris says, a recognition by Boral that its resources are finite within Victoria and that there are strong benefits to be had from having both recycled concrete products and a full range of quarry products. ?When Delta first started its recycling business, it had a limited customer base,? Chris recalls. ?Boral had a strong customer database and wanted to be involved in recycling to compliment their product range and the opportunity arose for both companies to work together and utilise their particular expertise.
Together, we?ve achieved considerable success in the product development, that is, with the blending of low grade quarry products and recycled products to improve the quality. Once again it?s about extending the life of quarry deposits, particularly Boral?s high quality reserves. This is the critical issue. Melbourne?s been very well served with quarries over the years, but to get the approval now for new ones – or even to extend existing ones – is going to be a challenge.?
RECYCLED PRODUCTS FOR SUSTAINABILITY
Chris explains that recycled concrete products, and particularly the Envirocrete, has similar properties to extracted rock products – ?After all, concrete is made up of quarry products? – and has been very successful in the application of pavement products in road construction, particularly in low traffic sub-divisions. ?As most quarry people know, there is a high clay content in scalping materials and normally it will finish up as waste. What generally happens with products with a lot of clay is they can produce an unstable sub-base. However, when you add crushed brick or crushed concrete to the mix, it breaks down the clay and stabilises the lower grade product. It becomes a far stronger, more suitable product because the actual cement properties neutralise the plasticity of the clay.
?If you blend crushed brick or cement or concrete with clay, it then breaks up all those molecules of clay so you don?t have all that same wetting, drying impact. We recently had great success by blending low grade quarry products with crushed brick to make a suitable sub-grade material for the lower base of the Deer Park by-pass. The low grade quarry product was provided by Boral Deer Park Quarry Products and we provided our own crushed brick materials.?
Chris adds there has been success for recycled concrete to be utilised for lower strength concrete production. ?It?s a quarry product, it?s high quality aggregate, so you can always potentially recycle it. We split the materials up, take the sand and the aggregate out and send them back to concrete plants, or some companies add 30 per cent of the total crushed product into their concrete mixes.?
However, Chris explained that there are restrictions on the use of recycled construction materials in higher grade concrete. ?Twenty megapascals (MPa), 25 MPa or 32 MPa are the lower strengths of concrete that could incorporate recycled materials,? he said. ?The end use of recycled construction materials is mainly in the lower sub-base areas of road construction, landscaping in parks and gardens, council work and in commercial developments such as factories and car parks. It can also be used in site preparation for large concrete slabs. By blending excavation rock and concrete, top of the range specified recycled products are produced. Recycled aggregates are seldom used in high strength concrete.?
THE PROCESSING CIRCUIT
Like a regular quarry operation, Delta Group?s concrete and brick recycling division employs very similar fixed plant and mobile equipment for the crushing of the C&D waste, including the crushing and separation of the reinforced steel. The fixed plant at the Sunshine site utilises a 54? x 42? William Group jaw crusher (similar in shape and size to a Kobe jaw crusher) as the primary. It is complemented by two Kawasaki 1350 and 1200 cone crushers and two 20? x 6? screens, assisted by two additional, smaller screens for separation.
?The fixed plant in Sunshine services the needs of the Melbourne CBD and inner Melbourne, and the mobile crushing plant moves around the Boral sites crushing concrete,? Chris explains. ?The mobile plant is at Boral Lysterfield at the moment, and will move to Wollert and Coldstream, according to demand and raw feed availability. We are crushing in South Australia at a Boral site with another mobile plant and we crush in NSW at three plants in Parramatta, St Peters, near Sydney Airport, and in Newcastle.?
Magnets are located at most transfer points to remove reinforced steel amongst the C&D waste. Other non-ferrous metals and smaller quantities of wood, plastic and steel are removed by hand as C&D materials pass through a picking shed during processing.
Through this fixed circuit and mobile equipment, Delta produces a minus 20mm fine crushed material for road base materials and a 7mm fine dust for use on walking tracks in parks and gardens from concrete and crushed brick. Chris describes the production process as very similar to hard rock quarry crushing, except ?with the addition of several magnets in the system and several picking sheds?. He also emphasises that the C&D waste is not so much crushed as ?unstuck?, that is, ?what you do is unstick and separate because you?re not actually breaking up the rock again. What you?re doing is breaking the bond of the sand and the cement in the aggregate. It?s different with the crushing of bricks?. This therefore means that compared with hard rock, there is potentially less wear from recycled products on the processing equipment, compared with conventional hard rock.
The processing equipment also suffers less because Delta insists that clients separate foreign materials such as timber and plastic from their C&D waste even before it is delivered. Chris recalls that in the past some producers would carelessly tip ?everything into the plant, leaving a fairly mixed product? to sort through. To maintain quality control in the finished product, Delta dictates that C&D waste should not contain more than three per cent of foreign materials when it is ultimately loaded onto the first conveyor.
?The most difficult thing in the processing is the removal of non-acceptable materials in the product, materials that will be detrimental to the specified product,? Chris Cox says. ?In order to have better control of the quarry product, you need to be more diligent in the acceptance of the raw feed and the sorting prior to processing. Customers have now started to sort that themselves because they know if they turn up with a lot of wood and plastic in their concrete, extra fees will apply or the loads will be rejected, so they then make the effort to separate it. So, raw feed costs are used as a control item on the acceptance of recyclable products. Mixed brick and concrete attracts higher fees than just straight concrete. Straight, clean concrete is a minimum charge. There are all sorts of mechanical means of removing timber and plastic, but if you don?t put it in at the start it helps.?
FROM C&D TO R&D
Chris Cox believes that the quarrying industry traditionally has been slow to embrace recycled aggregates mainly because there are concerns that the end product is not as robust as natural rock. However, he is confident that the contemporary generation of quarry professionals have become more accepting of the development of alternative quarry products and realised that it is both sustainable and practical.
He added that the blending of crushed concrete and bricks with natural quarry products has offered the potential over time for recycling businesses such as Delta to develop a more superior product. ?The recycled aggregates industry itself has had to be vigilant and monitor its performance over a long time so that we have a higher standard of product quality,? Chris explains. ?In the early days, some of the recycled material was very poor and impure and that caused problems because end users had bad experiences with the final product, especially recycled concrete. Now we are making more and more products, we are doing some interesting things such as the development of drainage aggregates with crushed brick.
?We have a NATA registered laboratory on site testing production every hour, which is a massive advancement today and we are producing a finished product that meets the VicRoads specifications for Class 2, 3 and 4 products.?
The recycled aggregates industry has also worked closely with VicRoads to develop specifications and the Victorian Government?s Department of Sustainability and Environment (DSE) has provided grants on a 1:3 basis for recycled aggregate businesses when they have been establishing new sites and plants. In 2009, the DSE, in conjunction with Swinburne University and the Australian Road Research Board, funded some research into the end uses of recycled construction materials in road base. Both Delta Group and Alex Fraser Group participated in the study which exemplified how much the Government is ?continually working to assist the industry in building an acceptance of recycled products as a quarry alternative product?.
?The key to running a successful recycled aggregates operation is strict control of the material and a constant supply of the raw feed,? Chris says. ?The C&D waste recycling business is a perfect marriage for Delta with its core demolition business because there is always a solid, constant supply of raw feed. Whether or not other quarry businesses follow Boral?s lead and enter into similar partnerships like ours, I?m not sure. That will come with time.?
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