GRC (Glass Reinforced Concrete) is proving to be the most popular substitute for ACP (Aluminium Composite Panels)
Singapore ZOO, BIRD PARK WATERFALL
Owner: Mandai Project Development
A court case concerning a fire in 2014 at the Lacrosse building in Melbourne’s Docklands was recently settled on the 28 February 2019. This was the project in Australia that confirmed there were issues with ACP cladding. The terrible Grenfell Tower fire in London in June 2017 alerted the World to the dangers of ACP cladding even though there had been a fire in the Torch Tower in Dubai on the 21 February 2015 (with a further fire on the 4 August 2017). A further fire occurred on a building in Spencer Street, Melbourne in February this year. Through the intervening period since 2014, authorities World Wide have been grappling with how to deal with the many thousands of square metres of façade already built (note, not just in Australia). Contracts are already being let in Australia to substitute solid aluminium sheeting in lieu of ACP. Manufacturers of ACP are desperately seeking to produce a modified or alternative ACP product. NCC2018 (National Construction Code) has been revised in recognition of the problems with ACP and further revision is anticipated in NCC2019 later this year. In the meantime, Fire Consultants are working overtime to ensure that ongoing projects comply with the latest regulations.
At a time when energy should enjoy far greater significance in the design of our buildings, it is logical to suggest why aluminium remains an optimum solution. In the last five years, Rickard Engineering have been involved in nearly fifty different projects all over Australia utilising GRC.
Glass Reinforced Concrete (GRC) was invented in the 1960s by the Building Research Establishment (BRE) in the UK, though it dates back to Ancient Greece and Rome who used horse hair to reinforce mortar. They found a way to coat glass fibre in “zirconia” to make it resistant to alkali attack. Pilkington Bros Ltd was the company who created a commercial product ready for market, but only after they completed exhaustive testing around the world.
GRC can be used as:
- Façade on a new building.
- Renovate as an over-cladding on an old façade on existing buildings.
- Permanent formwork on which you pour concrete, thereby gaining a very durable long-term soffit surface to your slab.
- Used to form sculptured structures: the 37-metre-high Merlion on Sentosa Island, Singapore or The Big Ram, The Big Prawn and The Big Oyster in Australia.
- Awnings or sunscreens on the face of a building.
- In or above ground drainage pits; oil or grease separators.
- Robust on the ground service ducts planter boxes .
- Street furniture.
- Computer flooring systems.
- A big attractive advantage of the material is that you can create a fire-resistant structural product to suit any shape, subject to engineer approval.
It is typically made in a thickness of around 12mm, either framed with steel or using GRC integral ribs. This typically gives a panel weight less than 50 kilograms per square metre. You compare that with conventional reinforced concrete, which weighs 360kg per square metre from a 150mm panel. This means that the GRC panel will be seven times lighter.
GRC can achieve a fire rating. A single skin of GRC can achieve a fire rating of up to one and a half hours. A greater fire rating is achieved through introducing a Styropor (polystyrene beads, sand and cement) core to create a sandwich panel that can provide a fire rating of up to three hours. (Refer to PCI (USA), GRCA (UK) or NPCAA (AUS) codes for further details).
It is an extremely durable product: GRC has the compressive strength of typically 60mpa, which therefore makes it the perfect material for an exposed application. It has durability far better than most reinforced concrete and note, no steel reinforcement to create spalling. Credit Lyonnais Bank building in London has a GRC façade, built in the 1970s. When cleaned after 50 years in the UK climate, it was found to be in perfect condition.
GRC is made in a mould, so one can create any shape you wish within reason, dictated only by engineering design to utilise its inherent ability. In fact, the biggest restriction on the successful commercial use of GRC has been the fact that people too often try to emulate solutions possible in a different material, instead of aiming for a solution that is unique to the ability of the material. Recent developments in technology now allows the GRC product to be used in a full structural application, subject to engineering design. Note the energy footprint of a building can be significantly improved by an “overclad” in GRC.
The disadvantages of GRC
The material is relatively fragile and requires great care in transportation and erection. It is a labour-intensive product and therefore is not cheap to manufacture.
It is very important to rationalise design to maximise repetition of shape.
Some key points that one should think about when utilising GRC:
- Innovative design techniques utilising prestressing allows very thin elements of GRC to span large distances.
- The lightweight nature of GRC enables it to be a very successful material for the use of over cladding on existing buildings. Generally, engineers will allow a 25% increase in load on existing building foundations subject to appropriate investigation and justification of the existing structure. The lightweight nature of GRC allows this to be added on the existing façade, subject to appropriate detailing without the need for expensive strengthening.
- A very recent innovative development with GRC has been to design a new building utilising an inner skin to seal the building which can be done more rapidly than waiting for the final external skin to be added to the building. Thereafter, the external GRC skin is added off the critical path.
We recommend that the GRC be used generally as a rain screen with a ventilating cavity between the inner and outer skin. Recent developments have seen a fixing technique which does not require internal access to the rear of the GRC panels.
Who makes GRC in Australia?
There are five major manufacturers of GRC is Australia:
- Asurco have been manufacturing GRC in Australia since the 1980s. This company is headed by Mr Des Pawelski and based in Adelaide. Recent major projects by them include The Geelong Library, NRT Stations in Sydney and The Green Square project in Sydney.
- Precast Concrete in Brisbane makes all manner of precast which also includes GRC. This company is headed by Mr Colin Ginger and Mr David Raetz. A major project by them was the Museum of Contemporary Art project in Sydney in 2011 and they continue to service the market.
- GRC Environments, established in 2006, has already built a substantial reputation in its hometown of Melbourne. Significant projects include ACU, PLC School, Monument Park and 108 Flinders Street. They are the largest manufacturer of GRC bathroom floors in Australia.
- Mascot Engineering are based in Sydney but supply all over Australia. They have been making precast GRC pits since the 1980s. They have diversified their product into permanent formwork for concrete to cover the heaviest possible loading classifications. They also supply planter boxes.
- Robin Johnson Engineering (RJE) have evolved from the manufacturer of substations manufacture to be a general GRC supplier in the industry.
If you are looking for design assistance in GRC, Rickard Engineering is recognised to be one of the most experienced designers, not just in Australia, but also around the world. Based in Sydney, the company’s principal Charles Rickard, has been designing GRC since the 1980s and was the Technical Secretary for the original publication of the National Precast Concrete Association of Australia document entitled “Design, Manufacture and Installation of Glass Reinforced Concrete (GRC).” Rickard Engineering offer free tender support, subject to a written agreement that if the project goes ahead, then Rickard Engineering will be the consulting engineers for the GRC. Rickard Engineering not only support GRC manufacturing companies, but also architects and clients who are looking at different design options. The fee arrangement for that service is assessed on a job-by-job basis. Rickard Engineering are now working with GRC manufacturers, not just in Australia, but also in the USA, Oman, UAE, Singapore, Bhutan, UK, Kazakhstan, China and India.
So why GRC?
- There are five manufactures in Australia who can provide a competitive professional service in a tender situation.
- The material is lightweight and can be used, not only as a new façade, but as an overclad of an existing building.
- The material can be used for all manner of different products, such as drainage chambers, planter boxes, permanent formwork, sewer liners, street furniture as well as façades.
- The product is relatively expensive, unless one utilises its advantages to reduce overall costs. One needs to maximise repetition but more importantly, look for a finish in GRC that cannot be readily achieved in a different material.
- There is no limitation on the different textures/features that can be built into GRC.
- The product is incredibly durable. The absence of aggregate in the mix means the lines of the panels are very sharp and the surface of the panels can be very smooth.
- The product can provide an immediate upgrade to an existing building as well as significantly improving the energy performance of that building.
- A popular use of the material has proved to be in creating “monuments” eg The Merlion in Singapore and Monument Park in Melbourne.
Rickard Engineering offers engineering design services in all facets of façade, diagnostic structural and civil works. Charles Rickard and his professional team are renowned for their expertise in the design of building facades, in particular for curtain wall construction and the design of glass reinforced cement (GRC).
For further information, please call our Sydney office on +61 2 9904 5610