Corrimal Coke Works Case Study: Concrete Crushing and Recycled Aggregate on a Heritage Demolition Site

The former Corrimal Coke Works sat in the middle of a suburb in the Illawarra for more than a century. Coke ovens, quench towers, steel stacks, a brick stack, conveyors, workshops and hardstand, with houses on the boundary and the railway line nearby. Legacy Property engaged Perfect Contracting as principal contractor for the demolition and land rehabilitation that cleared the way for the site's redevelopment, and this case study covers how it was done, with a close look at the part of the job that saved the most money and the most truck movements: crushing the demolition concrete and brick on site into recycled aggregate.

The short version. Over 95 percent of the demolition material was recycled. The heritage structures were documented by 3D scanning and selectively dismantled for restoration rather than knocked over. The steel stacks came down in sections by crane. The concrete and brick went through a tracked mobile crusher on site and came out as graded stockpiles ready for reuse, and the neighbours kept talking to us the whole way through.

The site and the brief

A coke works is an industrial demolition job with every complication in one place. The plant had been built, extended and patched for decades, so the drawings were a starting point rather than the truth. Parts of it were heritage listed and had to be kept or recorded. The ground carried the legacy of coal and coke handling. And unlike most heavy industrial sites, this one had residential streets on its boundary, so dust, noise, vibration and truck movements were a daily matter for real people rather than a line in a management plan.

The brief from Legacy Property was to take the redundant plant and buildings down, protect and document the heritage elements, deal with the hazardous materials, rehabilitate the land and hand over a site ready for the next stage of development. Perfect Contracting held the principal contractor role, ran the site and did the demolition, hazmat, crushing and earthworks with our own crews and plant.

Heritage first

Several structures on the site were historically significant. Before anything came down near them, we worked with heritage consultants, engineers and historians to record the features that mattered, using 3D scanning to capture them as built. Where a structure was to be retained it was protected and worked around. Where elements were to be removed for restoration they were selectively dismantled by hand and machine, set aside and stored under cover rather than processed as scrap.

The brick stack that stands over the site in most of our photographs is one of those retained structures. The steel stacks beside it were not, and they are a good example of how the method follows the site: with houses close and no room for a controlled fell, they were cut and lifted down in sections by mobile crane, with riggers at the cut line in an elevating work platform and an excavator processing each section on the ground. We have written up that method in our chimney and stack demolition guide.

Demolition with the neighbours in mind

The environmental management plan for the job was built around the boundary. Dust suppression ran on every machine that cut, broke or loaded, with water carts on the haul roads and monitoring at the fence. Noisy work was programmed to the hours that caused least trouble and the noisiest plant was kept as far from the houses as the sequence allowed. Waste was segregated at source into steel, timber, concrete and brick, hazardous materials and general waste, because mixed waste is the most expensive thing a demolition site can produce and the hardest to recycle.

Community engagement was not left to a letterbox drop. The site team gave regular updates, there was a way for residents to raise an issue and have it answered, and when the neighbourhood had its own emergencies during the project our people and plant helped where they could. The result was fewer complaints than a job this size next to houses would normally attract, and public support for what the site was becoming.

Why we crushed on site

A coke works is mostly concrete and brick by weight once the steel is out. Foundations, oven bases, slabs, retaining walls, hardstand, culverts and the brick from the ovens and buildings. There are two ways to deal with it. Load it out as demolition waste to a recycling facility and buy aggregate back in for the rehabilitation fill, or crush it where it lies and reuse it on site.

Loading it out means a truck movement for every load leaving and another for every load of fill coming back, through residential streets, for weeks. It also means paying gate fees on the way out and material costs on the way in. Crushing on site removes most of those truck movements, most of the gate fees and most of the imported fill, and it keeps the material under the project's control so it can be tested and placed to the engineer's specification. For a large site next to houses the decision makes itself, provided the crushing is run properly.

How the crushing was done

Sorting before the crusher

The crushed product is only as clean as what goes into the hopper. Demolition rubble arrives with reinforcing steel, timber, plastic, insulation and the odd thing nobody expected. At Corrimal an excavator worked the rubble piles ahead of the crusher, breaking oversize concrete down to a size the jaw could take, pulling out reinforcing bar for the scrap stream and picking out contaminants. Brick and concrete were kept in separate piles where the end use needed them separate.

The crusher

The machine was a tracked mobile jaw crusher, the standard choice for demolition concrete. A jaw crusher squeezes material between a fixed plate and a moving plate and lets it fall through once it is small enough, which suits hard, abrasive concrete and handles reinforcing bar better than an impact crusher does. A magnet over the discharge conveyor picks up the steel the sorting missed. The crusher was tracked around the site to the material rather than the material being carted to it, which is the point of a mobile unit.

A wheel loader fed the hopper, keeping the jaw choke fed so it ran efficiently and the product size stayed consistent. The crushed product came off the main conveyor into a stockpile, and the loader moved finished material to the stockpile field in graded rows. Dust suppression ran on the crusher and the stockpile area the whole time it worked, which next to houses is not optional.

Grading and stockpiling

Crushed concrete is not one product. The jaw setting and the screen decide what comes out, and the end use decides what is needed. Larger material suits bulk fill and drainage layers, a well graded product with fines suits road base and pavement sub base, and clean fine material suits bedding. At Corrimal the product was stockpiled in separate conical piles by grade, laid out in rows with room for a loader between them, so each pile could be sampled, tested and tracked to where it was placed. Good stockpile discipline is what turns a heap of rubble into an engineered material.

Testing and the rules

In NSW, crushed concrete and brick from a demolition site can be reused on that site or supplied to another one under the EPA's recovered aggregate resource recovery order and exemption, provided it meets the chemical and physical limits in the order and the sampling and record keeping are done. On a former coke works that matters more than usual: the material is sampled for the contaminants the site's history suggests, and anything that does not pass is kept apart from the clean product and dealt with as waste. The paperwork follows the material from stockpile to placement, so the end user can show where every load came from and what it tested at.

Concrete crushing technology: what the options are

Corrimal used a tracked jaw crusher because it suited the material and the site. It is not the only choice, and the right one depends on what is being crushed, what the product is for and how much room there is.

• Jaw crushers. Compression crushing between two plates. Best for hard concrete with reinforcing in it, high throughput, a coarser product. The usual primary crusher on a demolition site.
• Impact crushers. Material is thrown against breaker plates by a spinning rotor. Produces a more cubical, better graded product that suits road base, but wears faster on abrasive material and handles steel less well. Often used as a secondary stage after a jaw, or on its own for brick and softer concrete.
• Cone crushers. Compression crushing for secondary and tertiary stages where a fine, consistent product is needed. Less common on demolition sites than in quarries.
• Screens. A mobile screen splits the crusher product into size fractions and takes the fines out, which is how one crusher produces several graded stockpiles.
• Crusher buckets and pulverisers. Excavator attachments that break and size concrete in the bucket or jaws. Slow compared to a crusher but useful on small sites, in tight spaces and for pre breaking oversize before the crusher.
• Dust and noise control. Water sprays at the hopper, jaw and transfer points, misting cannons for the stockpile area, enclosure or positioning for noise, and real time monitoring at the boundary. On a residential boundary this is as much a part of the plant as the crusher itself.

For most industrial demolition sites the answer is a tracked jaw crusher with an overband magnet, a screen where graded product is needed, and an excavator with a pulveriser working ahead of it. That is what ran at Corrimal.

What it delivered

More than 95 percent of the demolition material from the site was recycled, between the steel that went to the mills, the salvaged items set aside for restoration and the concrete and brick that became recycled aggregate. The crushing removed a large share of the truck movements the job would otherwise have put through residential streets, cut the gate fees and the imported fill, and gave the rehabilitation an engineered, tested material produced from the site itself. The heritage elements were recorded and protected for the development that followed, and the community relationship held for the life of the project.

The lesson from Corrimal is not that crushing is clever. Every large demolition site should be crushing its concrete. The lesson is that the value only comes if the sorting, the dust control, the grading and the testing are run with the same discipline as the demolition. Done that way, the biggest waste stream on the site becomes its most useful product.

Frequently asked questions

Can crushed concrete from a demolition site be reused in NSW?

Yes. Under the NSW EPA recovered aggregate resource recovery order and exemption, crushed concrete and brick can be reused on site or supplied to another site as engineering fill, road base or drainage material, provided it is sampled and tested against the limits in the order and the records are kept. Material that fails is managed as waste.

What is the difference between a jaw crusher and an impact crusher for demolition concrete?

A jaw crusher compresses material between two plates and suits hard, reinforced concrete at high throughput, giving a coarser product. An impact crusher throws material against breaker plates and gives a more cubical, better graded product that suits road base, but it wears faster and handles steel less well. Many sites run a jaw first and an impact crusher or screen second.

How is dust controlled when crushing concrete near houses?

Water sprays at the hopper, the crusher and the conveyor transfer points, misting cannons over the stockpile area, water carts on haul roads, placing the crusher as far from the boundary as the site allows, programming the work to agreed hours and monitoring dust at the fence line in real time so the operation can be adjusted or stopped if levels rise.

How much of a demolition site can be recycled?

On an industrial site like Corrimal, over 95 percent by weight. Steel goes to the mills, concrete and brick are crushed into aggregate, timber and other streams are separated at source. What cannot be recycled is mainly contaminated material and mixed waste, which is why segregation at source matters so much.

Does Perfect Contracting crush concrete on other sites?

Yes. On site crushing is part of how we run large demolition and remediation projects across NSW and Queensland, from industrial plants to bulk earthworks. Send us the site details and we will tell you whether crushing on site stacks up for your job.

Talk to us about your site

Perfect Contracting carries out industrial demolition, heritage dismantling, hazardous materials removal, on site crushing and land rehabilitation across Australia from its Sydney and Brisbane bases. See the Corrimal Coke Works project page, read more about our industrial demolition, recycling and site remediation services, our Wollongong and Illawarra work, or send us the details.