Case Study: Cracked C6 Concrete Footings and Walls Repair at Coal Mine in Australia

Case Study Data

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Site
Coal mine
Location
Australia
Repair Type
Concrete repair
Defect
Cracks and other visible surface damage caused by mine subsidence

Products Used

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Sylmasta AB Original Epoxy Putty Stick
Epoxy putty which is ceramic-filled for super strength used to seal cracks and rebuild significant areas of damaged concrete

Case Study PDF

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Case Study Details

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The coal mine was relatively new. It was one of many built in response to the Australian mining boom of the mid-2000s, which at one point made the country the world’s biggest exporter of coal.

Even when the boom came to an end, the industry continued to grow and new mines came online. By 2020, mining represented 10.4 percent of national GDP and mineral exports contributed 62 percent of total export revenue.

To help manage construction costs at the mine, low-strength C6 concrete was used for many above ground, non-structural and non-load bearing applications. These included fillings voids and encasing footings.

Various surveys took place before and during construction to assess the potential stability of the mine. But once it opened and coal production began, the ground began moving more than expected.

Within five years, unsightly cracks began appearing alongside visible surface damage where large chunks of C6 concrete had broken off and crumbled away.

Whilst the mine itself was structurally safe and requited no remediation, the mine owners wanted to make superficial repairs to improve the appearance of the concrete.

Sylmasta representatives in Australia had worked with the coal mine before and suggested using AB Original Epoxy Putty for the repair of concrete footings and other areas of damage.

10kg of AB Original Sticks were delivered to the site. The mine maintenance team attended known areas of concrete damage, cutting enough putty from each stick to repair a specific area of damage and kneading it by hand.

Whilst still soft, AB Original was forced into the crack or gap until the missing concrete was fully replaced. The two-hour cure of AB Original offered plenty of time for the team to mix and apply the putty without the threat of it setting before the concrete had been accurately rebuilt.

Once applied, AB Original was smoothed off with a little water to give it a more concrete-like appearance. 24 hours later and it reached maximum properties.

The application was so seamless, that it was impossible to tell afterwards which areas were original concrete and where repair had taken place.

This process was repeated across the entire mine over two days, helping to cover up all visible cracks and damage caused by subsidence.

The mine were pleased with the huge cost saving compared with replacing all damaged footings – especially as new footings would be at risk of cracking themselves through future ground movement.

With further subsidence likely leading to more superficial damage to C6 concrete, Sylmasta are working with the coal mine to manufacture a trowelable version of AB Original at the request of the maintenance team.

Reducing the consistency of AB Original by reformulating it from an epoxy putty into a paste will allow the mine to apply by tool rather than hand, speeding up repairs by enabling large areas of damage to be covered much more quickly.