In the world of retaining walls, bigger is not just better but more efficient. But with great height comes greater hazards, risking derailing commercial or residential construction projects.
Projects requiring taller retaining walls can face setbacks, such as unstable foundations, the potential for water damage and installation technology that does not support taller structures.
However, one company has addressed these pain points, with the imminent launch of a new large-format, interlocking block system that promises to safely scale new heights.
Austral Masonry, part of building products manufacturer and investment company Brickworks, has developed the Keystone KeyMass system that allows retaining walls to reach 15 m and higher, well above traditional retaining walls.
KeyMass is a collaboration between Austral Masonry and Keystone, a leading creator of innovative retaining wall systems based in the United States. The new system is expected to reverse the traditional flow of construction technology design that typically is exported from the US to Australia. This time, an Australian company has been an integral part of developing a solution expected to be in demand in the local and overseas markets.
Bridging the gap in retaining wall solutions
According to Nick Warrier, a consulting engineer who collaborated on the project, the KeyMass system bridges the divide between current materials available on the market.
“There’s always been a gap in the market,” Warrier said. “On one end, we have the standard size dry cast blocks – Keystone is one of them – and on the other side we have these massive wet cast blocks.
“They both have their pros and cons, but there was nothing that really bridged the gap between them.”
The KeyMass system features blocks that are four times larger than standard retaining wall blocks, measuring 1000 mm long, 400 mm high and 600 mm deep. Despite their size, they maintain the production efficiency of dry cast products.
“This means that it can be produced quickly, which is always an issue with wet-cast products because they have to be cast in a mould,” Warrier said. “It can be stacked on pallets and delivered to the site with absolute certainty.”
Installation efficiency drives construction safety and savings
There are strong efficiency gains with the KeyMass system. “When you install one KeyMass block, it is equal to installing four standard Keystone blocks,” Warrier said. “This gives you efficiency on the job site and reduces the time to install.”
The large blocks require specialised machinery to install, which Warrier said boosts safety.
“The standard Keystone blocks are 36 kg, which is at the limits of manual handling,” Warrier said. “KeyMass blocks are larger and heavier, requiring specialised equipment for handling, which eliminates manual lifting. In our opinion, it triples the installation efficiency.”
This translates to time and cost savings. “If you can finish the job in two weeks instead of three, that’s one week of operational cost savings straight away,” he said.
Versatile system adapts to wide range of projects
The KeyMass system has been designed primarily for large commercial applications, though it can be adapted to other residential projects.
“This is targeted at large commercial jobs because of the size of it,” Warrier said.
The system’s versatility is one of its key strengths, allowing for different configurations depending on wall height and site conditions.
“A perfect job site for this will be a development where you have varying wall heights and with varying loading conditions,” Warrier said. “So you have smaller wall heights starting from 1.2 m, and then you have to go higher up to 15 m.”
Walls up to 4.4 m in cut condition are cost effective when designed as gravity systems using the KeyMass extender. Walls in fill condition are generally suited for soil reinforced systems using Keymass with geogrids.
For shorter walls, the system can also be configured as a gravity wall using the KeyMass extender, which dovetail interlocks onto the back of the block. For taller walls, soil reinforcement with geogrid becomes necessary.
In confined spaces or where excavation limits are restricted, a hybrid system can be implemented to maximise the benefits of both gravity and soil-reinforced retaining wall systems. This generally starts with a soil reinforced system at the base and transitions to a gravity system at the top to allow for services and plantation behind the wall. The same block faces seamlessly transitions between systems without compromising aesthetics. This is critical for engineers, providing both design flexibility and optimised efficiency.
The KeyMass system uses Keystone’s proprietary fibreglass pin connection system that is lightweight with a tensile strength stronger than steel. This flexibility allows for easy alignment and adjustment during installation.
The team is also testing a positive connection system to reduce the length of the geogrid. This either reduces excavation, backfilling and compaction effort, resulting in cost savings, or increases the load carrying capacity of the system to cater for more challenging scenarios not suitable for traditional dry-cast modular blocks.
The system’s adaptability makes it less susceptible to damage in poor soil conditions compared to rigid in-situ retaining walls.
“In terms of poor soil conditions, these blocks are interlocked but they’re flexible,” Warrier said. “They can move around and adjust to varying soil settlements within tolerance along different lengths.”
Sustainable manufacturing reduces carbon footprint
Sustainability has been a key focus in the development of the KeyMass system. Taka Numata, R&D and technical manager at Brickworks, said significant progress has been made in reducing the product’s environmental impact.
“We’ve been working on a concrete mix in the plant to reduce the embodied carbon,” Numata said.
The manufacturing process incorporates recycled materials such as fly ash from power stations and the hollow core design reduces the overall amount of concrete used in the blocks.
Up to 20 per cent of the energy used in production comes from solar sources, an estimate that was authenticated by environmental certification group the Good Environmental Choice Agency (GECA). Austral Masonry is also working on an Environmental Product Declaration, an independently verified and registered document that provides information about the environmental impact throughout a product’s lifecycle.
Resources for engineers and contractors
To support adoption of the KeyMass system, Austral Masonry offers a range of resources for engineers and contractors.
“Austral Masonry has been supplying the existing Keystone system to the market for more than 10 years in Australia, so they have a lot of in-house capabilities,” Warrier said. “A lot of questions get answered straight away.”
The company also provides the Key Wall Pro software system, which engineers are already familiar with from working with standard Keystone blocks. “It’s a very easy, streamlined software, for the engineers to download and KeyMass will be incorporated in the same system.”
