Decades of research has led to new design guidelines for concrete-to-concrete connections, enabling design optimisation and delivering sustainability benefits.
The quality and strength of the adhesive chemicals used for post-installed rebar have significantly improved over the last 20 years, opening up a range of exciting new possibilities and repair options for designers.
But, despite such impressive technological advances, the qualification guidelines surrounding their performance remained stubbornly unaltered, becoming more outdated and unrealistic as every year passed.
For construction firms connecting new reinforced concrete to old, adhering to the outdated technical approvals has meant using way more materials than necessary and, on many occasions, having to demolish buildings instead of simply repairing them.
But groundbreaking research in Europe has now convinced industry regulators that the cutting-edge adhesives on the market today mean those rules can finally be updated, a decision with potentially transformational repercussions.
Need for change
The traditional design method meant the bond strength of the chemical anchor couldn’t be used. The guidelines often dictated that holes had to be drilled much deeper than the concrete itself, resulting in the design not being viable.
Suddenly, what appeared to be a straightforward extension or upgrade that would have taken a few weeks became a mammoth undertaking over several months.
“It’s been a challenging situation for structural engineers for a long time,” said Baz Kaknics, Hilti’s Codes and Approvals Manager. “The old qualification guidelines for post-installed rebar did not acknowledge the actual performance of the adhesive, often resulting in unfeasible designs.
“Finally, with the help of the new approvals and new design method, the drilling depth can be optimised while maintaining ultimate safety in the designs.”
Despite the solid body of research, changes in codes and regulations have taken time. The long-awaited updates will therefore be welcomed by many. Kaknics believes the impact will be substantial for designers in Australia
“It removes the roadblocks that had been holding us back for years,” he said. “At last, design challenges that were impossible under the previous legislation become viable options, resulting in optimised results for clients.”
To help use those solutions, Hilti has become the first company to develop specialised software for the new methodology that calculates exactly what engineers need to do to ensure each project complies with the relevant standards.
Its Profis Engineering Anchor Design Software is a cloud-based solution that enables analyses and design of both steel-to-concrete and concrete-to-concrete connections based on the latest Australian standards, such as AS5216:2021 and AS3600:2018.
“The reaction in Australia has been overwhelmingly positive,” Kaknics said. “The industry had been desperate for a solution so there’s enormous relief that we finally have one. It will be adopted very quickly as it allows better building designs that can be completed in a shorter timeframe and for less money.”
It also has huge benefits in terms of sustainability. Worldwide, concrete manufacture accounts for between four and eight per cent of carbon dioxide emissions, so organisations targeting net zero are under increasing pressure to reduce consumption.
“Clearly, if you can just join a new piece of concrete to an existing one instead of demolishing the building and starting again, the impact on the environment will be substantially less,” Kaknics said.
“Properties can be repaired, enlarged or upgraded in a way that minimises the need for freshly-made concrete. There are also health and safety benefits as you no longer need blocks of concrete with spikes jutting out to be left on sites for weeks while a new structure is built from scratch.”
Learn how Hilti helps transform post-installed rebar projects for Australian engineers, and don’t miss an upcoming webinar on innovation in post-installed rebar design, organised by Engineers Australia in partnership with Hilti.