Conbextra EP65 Plus enables rapid restoration of critical rail infrastructure Mt Lawley, WA

A collaborative approach to product selection

During routine bridge inspections, the PTA identified a defect on the abutment of the bridge under a bridge bearing. Working under contract to the PTA, Enviro Infrastructure was asked to explore possible repair solutions.

“Once the team at Enviro Infrastructure inspected the issue on the Mt Lawley bridge, they brought the project to Fosroc ANZ for a product recommendation and specification," said Fosroc ANZ Account Manager, Nakita Tuffin.

She added that Enviro Infrastructure has a long-standing working relationship with Fosroc, enabling the project team to quickly assess the repair requirements and develop an appropriate solution.

The repair presented several challenges. The ageing support pillar beneath the bridge had begun to crumble and required urgent reinforcement. Working beneath an active rail bridge meant both access and time were limited, while the proposed product and repair methodology required approval from the PTA's engineering team before work could commence.

Engineering the right repair solution

Initially, a conventional cement-based repair mortar was considered as a solution, however, this type of system would have required the rail line to remain closed for three to four days at a minimum. That was not an option.

Following an onsite assessment with Enviro Infrastructure, Fosroc ANZ Concrete Repair Specialist, Dennis Murray, recommended Conbextra® EP65 Plus.

"I suggested an epoxy-based product to meet the time constraints,” Dennis said. “The team originally requested a cement-based mortar solution, but that was going to take too long to cure."

As a high-flow, fast-curing epoxy grout, Conbextra EP65 Plus offered the best solution to achieve a strong, durable bond to the existing concrete within the strict timeframe.

After extensive consultation, the PTA engineers approved the epoxy-based repair system, recognising that while it represented a higher initial cost, it was the safest and most practical solution for this time-sensitive project.

A quick return to service

Dennis said choosing the right repair product was only part of the challenge. With more than 200 rail services operating in a single direction each weekday, the repair also had to be installed correctly the first time to avoid any unexpected delays in returning the line to service.

"It was a very difficult job with not a lot of space to work under the bridge. They had to form it up, make it completely watertight, then pour the grout from above at rail level. It was a very tricky situation."

Formwork installation and associated preparation works took approximately three to four days. Although the repair itself was completed in around three hours, the rail shutdown allowed a further three hours for the grout to achieve the required compressive strength before the results were assessed.

"You can't pour a fresh grout and then have trains roll over it too quickly because the vibration isn't good for the repair,” Dennis said. “The team allowed another 3 hours for it to get to the required compressive strength."

Capable of developing 30–35 MPa within six hours, Conbextra EP65 Plus allowed train services to safely resume while providing the long-term structural performance required for a bridge subjected to constant dynamic loading.

The product's excellent bond strength meant no primer was required, helping maximise the limited construction window. Its highly fluid consistency also allowed the applicator to securely form the damaged pillar using watertight form ply before pouring the grout through the rail platform, maintaining the required hydrostatic head to ensure complete filling of the repair. In addition to its rapid strength gain, Conbextra EP65 Plus delivers ultra-high compressive, tensile and flexural strengths together with excellent resistance to repetitive dynamic loading, making it ideally suited to critical transport infrastructure.

Keeping the network moving

Careful engineering, close collaboration and timely technical support were essential to delivering a successful repair while maintaining the demanding operational requirements of the rail network.

"Whilst it was a small volume pour, the project was highly technical and the support and timely feedback was appreciated by both Enviro Infrastructure and the PTA," Nakita said.

Nakita said minimising disruption remained a key objective throughout the project, but product performance was just as crucial.

"We needed to minimise downtime. We had a six-hour window to conduct the repair work on a Sunday. With vibrations over the top from returning trains, the repair was held in place with the formwork and then removed on the following Wednesday."

"Fosroc's technical data sheets gave the engineers confidence that Conbextra EP65 Plus would achieve the required performance. As long as the product was mixed and applied correctly, it would reach the required compressive strength in that timeframe.”

The successful repair allowed train services to resume within 24 hours while providing a durable structural solution for the ageing bridge. More importantly, it demonstrated how close collaboration between the asset owner, contractor and manufacturer – combined with technical expertise and the right product selection – can minimise disruption while delivering reliable, long-term outcomes for critical transport infrastructure.