The following extract is from The Fifth Estate’s latest ebook, Visit Tomorrowland: Buildings for a Sustainable Future.
Technology and human ingenuity have brought us new construction materials that a decade ago seemed inconceivable – well to the average person at least. Researchers and scientists have been aware for decades of the potential for new materials to dramatically improve building performance and reduce greenhouse gas emissions. Just like climate change these materials are not of the future – they are here now. And their development must be accelerated if we want to reach zero carbon or better.
Along with advances in the construction materials we know so well, such as timber, concrete, steel and glass, there are new ones that have the potential to generate power, such as the super thin perovskite solar cells that can be part of the building structure or algae facades that act as biodigesters to generate gas.
Or those that enhance existing materials, such as graphene – 200 times stronger than steel and impermeable – making it a super material for construction and already being used in a wide range of applications from walls to lighting, touch panels, sensors, generators, batteries and solar panels. And geopolymers, new materials for fire- and heat-resistant coatings and adhesives that have wide-ranging uses, including for lower carbon cements.
Timber hailed as the low carbon answer
Probably the biggest push in new materials is coming from the timber industry. Timber is a material loved by builders, engineers, architects and, most importantly, by building occupants. And thanks to new production techniques and engineered products, timber is being hailed as the answer to many of the sustainability issues in construction. It has the ability to store carbon, it can be produced reasonably sustainably, new engineered products are stronger than steel but much lighter, and prefabrication of timber panels can dramatically cut down on construction times. And, because of their high thermal performance, timber buildings also offer social and financial benefits through lower utility bills and greater comfort.
A game changer for timber in Australia is the establishment of a cross laminated timber, or CLT, manufacturing plant in Albury by XLam. The company has been manufacturing CLT in New Zealand for five years and exporting to Australia. The opening of the plant means CLT specifically made for Australia will be available for the first time.
Alex Sinickas, head of research & development with Arup, says the new plant will really ramp up the use of timber in Australian buildings. The push for timber, though, is largely as a result of desire for the product from the market.
“People want to work in beautiful buildings and timber is a very attractive material that people enjoy being around,” Sinickas says.
Gerard Neylan, lead program development manager of Wood Solutions’ mid-rise advisory team, agrees that people love timber buildings. The mid-rise advisory team is Wood Solutions’ response to recent changes to the National Construction Code (NCC) that make it easier to use lightweight and massive timber building systems in mid-rise construction.
A pilot advisory program comprising a team of design, engineering, construction and property specialists, it is a free service focused on buildings up to eight storeys. In addition to making the marketplace more aware of changes to the NCC, the project aims to educate industry specialists on what timber products are available.
“We want to give designers and specifiers confidence about how to use new timber products,” Neylan says. “Nobody likes to be a pioneer. When the tilt slab came in people said that would never work. The fact is big companies like Lend Lease are pursuing timber and are already using it for multi storey buildings.”
Lendlease has been at the forefront of engineered timber buildings in Australia. The six-storey International House at Barangaroo was the first engineered timber office building in Australia and the company’s third Australian CLT building, the other two being Forte apartments and the public building Library at The Dock, both in Melbourne.
The company is also building 5 King in Brisbane – the first engineered timber building in Queensland and Australia’s tallest so far, at 10 storeys, as well as the Community Hub at Jordan Springs in Western Sydney, NSW’s first public CLT building.
Neylan points to the numerous benefits timber offers on building sites – faster and safer construction, a cleaner site with no welding or steel cutting, and less disruption to surrounding buildings and streets. He believes benefits to occupants are even higher.
“Studies have shown that occupants of timber buildings are calmer, have lower blood pressure and are less prone to absenteeism. In some schools in the US where timber is used there is even less graffiti.”
But what about the sourcing of timber? How can we be sure the growing demand for timber won’t mean more clearing of old growth forests and vital habitat for numerous species?
Michael Lord, head of research at Beyond Zero Emissions (BZE), says that’s unlikely due to the large quantity of timber that currently goes to landfill and also used for packaging and pallets. Much of this can be re-used in timber production while timber used for pulp could also be redirected to the construction industry.
“We can also grow forests on marginal land that has already been cleared. We’ve quantified that the area needed [to supply the timber construction industry] is less than that put aside for chickpea farming,” Lord says.
Low carbon cement and geopolymers
Much work has been done globally to improve the carbon intensity and production methods of concrete. A key area of research is in the production of concrete that does not contain Portland cement, traditionally used in concrete and very carbon intense. BZE recently launched its Rethinking Cement plan, which recommends five strategies for industry to move towards a zero carbon cement industry over the next 10 years.
The BZE report recommends four strategies that can be applied over the next 10 years using already commercialised technologies, such as geopolymer cements, high-blend cements and mineral carbonation, and another strategy that could achieve positive carbon results once the production method has been proven commercially.
Lord says the need to reduce carbon emissions in cement production is urgent as it accounts for eight per cent of global carbon emissions, equal to all the cars on the road.
“Virtually all the cement in the world right now is Portland cement. And 55 per cent of the emissions from the cement industry in Australia come from the carbonisation process used in making Portland cement,” Lord says.
“Our first two strategies involve replacing Portland cement, in the first strategy with geopolymer cement. Geopolymer cement is made in a very different way to Portland cement and it doesn’t release carbon dioxide. Our second strategy involves mixing Portland cement with other materials such as fly ash and slag rather than clinker to reduce its carbon intensity.”
Currently materials added to cement to reduce carbon emissions account for about 20 to 30 per cent of the content. The plan recommends raising the proportion of replacement material to 70 per cent using fly ash, slag, clay and ground limestone to create a “new generation of high-blend cements”.
The fourth strategy is to use less cement. By designing structures to use concrete more efficiently, utilising high strength cement, and replacing concrete with timber, BZE says overall cement consumption could be reduced by around 15 per cent in 10 years.
Not enough effort is going into replacing cement at scale, Lord says.
“Structural engineers don’t put enough effort into minimising the amount of material. It’s easier to standardise things, so they tend to use block shapes. It is often possible to use much less concrete and cement.”
BZE would like to see a national policy which puts a price on cement carbon emissions, including imported cement. The plan says a national target by the federal government to reduce carbon intensity of cement, which becomes progressively more stringent, would be a powerful stimulus for change.
The target could be supported by public investment into research and deployment of low-carbon cements, similar to the support for renewable energy provided by the Clean Energy Finance Corporation and the Australian Renewable Energy Agency.
Lord says governments should also introduce new regulations or incentives to encourage the use in cement production of stockpiled fly ash and other waste materials such as waste glass, red mud and bagasse ash.
So far response to the report has been much better than expected.
“The reaction has been really good and the government and private sector are definitely interested in what we are saying,” Lord says. “The cement industry has been a little lukewarm but that’s not surprising given the amount of investment they have in current technology.”
Some in the cement industry are already producing low-carbon concrete.
Professor Stephen Foster, head of school in the School of Civil and Environmental Engineering at University of NSW, has been involved in research on geopolymer concrete for decades, and is working on a project with the CRC for Low Carbon Living. He says the stage of research is now nearing standardisation for geopolymer concrete, which will allow engineers and councils to specify its use with confidence.
“The main issue is durability. We need to know that if we build with the material it is going to be there in 50 years time as normal concrete would be and, if not, what design parameters do we need. Also mechanical issues – if we add steel to it does it perform the same as conventional concrete and if not what is different and how do we quantify that?
“We’ve got to the stage where we have a handbook that is in drafting stage for designers, engineers and specifiers so they know how to design with the material and specify it.”
Geopolymer concrete covers a very broad range of materials, Foster says. The major advantage of geopolymer concrete is it has half the carbon emissions of conventional concrete. Globally the use of geopolymer concrete is very small.
“It is very early days for the product. Australia is miles ahead in terms of research.”
There is a wide range of applications with geopolymer concrete. Whether it is made with predominantly fly ash or with a mixture of fly ash and slag or, less common in Australia at present, with metakaolin, it performs differently, particularly with durability but also with shrinkage and creep.
One of the biggest potential uses for geopolymer concretes is in pavements, which accounts for 70 per cent of all concrete. These could be any pavements from buildings to airports and carparks.
The issue of creep – or flow – while a problem if it is too high in concrete used in building features such as structural beams – is not such an issue in pavements. In geopolymer concrete creep can be higher, the amount dependent on the mix used in the product and whether it is heat treated or not. These issues are currently being tested and quantified.
“Creep can be a good thing. From a structural aspect it can relieve areas of high stress and in pavements what happens with conventional concrete is you get shrinkage and that causes tension and cracking. If you have more creep it reduces that tension and potentially the amount of cracking. That can be a positive,” Foster says.
The world’s largest geopolymer concrete project to date is at Brisbane West Wellcamp Airport, Australia’s first privately funded public airport. Located at Toowoomba, the airport was built by the Wagner Group for farmers to take their produce to international markets. All the taxi-ways at the airport are made from geopolymer concrete. Wagner Group used its own Earth Friendly Concrete (EFC) to build the airport in order to dramatically shrink its carbon footprint.
When the airport opened in 2014 Wagner Group’s John Wagner said Wellcamp would be “the greenest airport in the world.”
“One tonne of regular cement produces one tonne of CO2 – we reduce that by 90 per cent just by using the EFC concrete for all the pavements, the terminal and the car park. There will be no normal concrete used in this project,” Wagner said.
“What we have discovered through our R&D process is EFC has far superior flexural strength, which is very important in airport pavement, and low shrinkage… We’ve got a product which is not only the same price [as regular cement], it has a very low carbon footprint.”
Using recycled glass in concrete is another idea being investigated by a research team at the University of Melbourne. As reported recently by The Fifth Estate, the team is working on a solution for making strong, lightweight and cheap concrete panels using waste glass instead of sand, which is a dwindling resource.
Project manager for the project, Associate Professor Tuan Ngo, said that as the world ran out of sand, waste glass was an obvious choice to target for replacement. He believes the new product has great commercial potential.
“Our work has shown it has excellent sound, thermal insulation and fire-resistant characteristics,” he said. “We are looking forward to working with the cement and concrete industries and building standard regulators to prove the viability of using these products in traditional concrete structures.”
- Read the rest of the article in Visit Tomorrowland