The building industry gets smart
While the construction industry has been lagging behind other sectors in the adoption of new technologies, this gap is starting to close as companies work to improve efficiency and achieve energy and cost savings.
There have been a number of new breakthroughs in modern building material developments and 3D print applications in recent years, driven by growth in the green building industry. Rising energy costs, concerns about greenhouse gas emissions and diminishing raw materials are forcing companies to explore alternative building products, as well as new building designs and construction techniques.
As a result, there are increasing opportunities for builders to embrace innovation.
From advances in materials we know such as timber, steel and concrete to the invention of new materials that have the ability to generate power or act as bio-digesters, construction technologies are evolving rapidly.
Despite being in their infancy, these ‘building materials of tomorrow’ look set to have a dramatic impact on the construction industry, improving building performance and reducing greenhouse gas emissions.
Below, we look at some of these advances and how they’re helping to reduce construction costs and time.
Self-modifying window coating
RMIT University has developed an ultra-thin coating for windows that responds directly to changes in temperature and has the ability to change glass’ infrared opacity. Made using vanadium dioxide, the self-modifying coating transforms from an insulator into a metal when heated to 67°C, becoming a versatile optoelectronic material that is controlled by, and sensitive to, heat.
Basically, this means that while the coating appears transparent to the human eye, it goes opaque when exposed to infrared solar radiation, which is caused by exposure to direct sunlight. This change in the glass’ infrared opacity blocks heat from getting through.
While most coatings for smart windows are electrochromic, which cause windows to change opacity when an electrical voltage is applied across them, the RMIT coating operates passively.
“Whereas electrochromic window coatings control heat in response to electricity, the coating we’ve developed is thermochromic, meaning it responds to heat from direct sunlight. The colour of the window doesn’t change but it stops letting infrared go through so it goes from being infrared transparent to infrared opaque,” says RMIT School of Engineering associate professor Madhu Bhaskaran.
“The coating works in both directions so if the inside is hotter then it helps to keep the heat in, whereas if the outside is hotter then it automatically keeps the heat out.”
According to the Australian Window Association, up to 40% of a home’s energy for heating can be lost through windows and up to 87% of a home’s heat gain in summer can be through windows and skylights. The RMIT coating could help to significantly reduce these, enabling windows to naturally regulate the temperature inside buildings.
The researchers have filed a patent in the US and Australia for the coating, which can be applied directly onto windows after manufacturing or used on nearly any surface.
Madhu says the coating is not yet at the commercialisation stage but the researchers are looking for industry partners to start down this path.
“We’re looking to start testing whether the coating works on a larger scale. Realistically, if we find the right industry partner then this technology could be out to the market in around five years.”
Although cement-bonded wood products have been around for more than 100 years, these have previously only been used for non-load bearing purposes. Now, the Institute of Construction and Environmental Technologies (iTEC), which is an institute of the School of Engineering and Architecture of Fribourg (a department of the University of Applied Sciences and Arts of Western Switzerland), has developed a cement-bonded wood product that can be used in larger structural applications.
Entitled WooCon, the compound material is a pourable, wood-based, lightweight, structurally applicable concrete mixture that can improve the acoustic and thermal insulation, storage capacity and fire protection properties of building materials. It provides a greener, lighter and easier to recycle, low-tech concrete.
“Cement-bonded wood products usually use relatively large-scale wood components, such as strands and long fibres, which are pressed to prefabricated panels. The cement primarily works as an adhesive for the wood components and as fire protection, while the wood components are often treated in elaborate manners to improve chemical bonding between wood and cement,” says iTEC head, Professor Dr Daia Zwicky.
“Our recipe combines cement with small wood particles to provide a pourable, possibly self-compacting mix where cement and other minerals are the major component and the wood particles primarily serve as weight-reducing filler. As untreated wood particles can be applied, no additional economic disadvantages are introduced.”
Daia says WooCon provides the same benefits as prefabricated cement-bonded panels but because WooCon is pourable, it allows for structural applications more easily.
“Our goal is to prove that this kind of construction material, which can be thermally recycled, can also be applied in structural elements to provide additional physical and ecological benefits to buildings.”
While it has not been designed to replace concrete and timber in the construction process, Daia says as consciousness for the ecological impacts of building construction increases around the world, alternative methods are becoming more attractive.
“We targeted the application of WooCon in composite action with timber elements to replace heavy concrete with lightweight, largely wood-cement compounds. WooCon’s stiffness and strength is considerably lower than what we are used to from regular concrete so larger construction element dimensions or composite construction is usually required.
“However, considering high-rise buildings are currently being constructed in pure timber, I cannot see why we should not be able to develop appropriate WooCon solutions as well.”
WooCon has gone through initial stress tests that found it’s suitable for slab and wall elements, and can provide load-bearing function. However, it is not yet at immediate industrial commercialisation.
“We are currently working on eliminating the existing disadvantages of this material in the framework of internal as well as international research projects,” says Daia.
“As the construction industry is very conservative, large-scale introduction of new materials and construction elements into the market is not evident. Still, I hope to see a pilot application of WooCon-based construction elements in practice in the early 2020s.”
3D printed concrete
The Technical University of Munich (TUM) has been studying 3D printed concrete to develop new ways to bring direct digital fabrication of single parts with a high geometric freedom into the building industry.
TUM chair of Timber Structures and Building Construction Dr. Klaudius Henke has published research on the issue that shows 3D printing can provide automatically fabricated, free-formed building elements optimised to structure and building-physics.
The research, which was presented at the International Association for Shell and Spatial Structures (IASS) Annual Symposium 2017, explored selective binding and extrusion processors to create structures.
The selective binding method involves depositing a mixture of cement and water over thin layers of aggregate and binders in the pattern of the final part to be created. Once the layers have set, the excess aggregate is removed, leaving a concrete structure behind. The researchers were able to build lightweight, thin and strong pipes with an intricate bracing structure using this method.
Material testing showed that the pipes can withstand forces up to 50 newtons per square millimetre, making them as stable as conventionally cast concrete.
Extrusion processors focused on the extrusion of wood chip concrete, which involved mixing Portland limestone cement and untreated softwood chips in a ratio by volume of 1:1. The ingredients for fresh concrete are combined in a mixer before being transported by a conveyer within the extruder to a nozzle. The concrete is then dispensed in a continuous strand onto a building platform or on top of previously dispensed strands. Several test objects were built and testing found the concrete has a compressive strength of 10 newtons per square millimetre and a bending tensile strength of four newtons per square millimetre. The researchers say this lies in the area of lightweight concrete with mineral aggregates.
The 3D printed concrete structures produce almost no waste, can be fabricated in any shape and made from local materials. As a result, demand for 3D printed concrete is predicted to grow as technology continues to improve.
“There are several companies developing commercial products, including machines and materials, for use in 3D printed construction to be launched to the market before long,” says Klaudius.
Canberra-based start-up Mineral Carbonation International (MCi), which is a joint venture between Newcastle Innovation, Orica and GreenMag Group, has developed a carbon utilisation platform of technology. This will enable the development of the large-scale transfer of carbon dioxide (CO2) into building and construction products.
The platform is based on the natural mineral carbonation process that transforms CO2 from a gas into a permanent solid over millions of years. MCi’s technology has significantly sped up this process, producing carbonate and silica that can be used in building products such as bricks, pavers and plasterboard.
“The platform has a range of different technologies integrated but at the core is a carbonation reactor that takes CO2 and combines it with feedstock in a continuous process that permanently binds the CO2 in solid carbonates,” says MCi chief executive Marcus St. John Dawe.
“We’ve been working with building product companies to then formulate new products using the carbonates and the silica by-products, including new Portland cement formulations, plasterboards and high performing cements, bricks, building blocks and other cementitious products.”
The technology has been developed in commercial secrecy so MCi does not disclose specifics of the process such as optimum conditions or the integration of the process routes. However, the company demonstrated the hour-long process at the launch of its carbonation research pilot plant at the Newcastle Institute for Energy and Resources in August 2017.
Serpentine was crushed, heated and then mixed with water and pressurised with CO2 to speed up the natural carbonation reaction, which forms stable magnesium carbonate powder and sand. If this process is used at an industrial scale around the world, Marcus says millions of tonnes of CO2 could be permanently and safely stored away. This would have a significant impact on Australia’s greenhouse gas emissions, which recorded the second highest quarterly results in five years in Q1/FY 2018, according to NDEVR Environmental.
MCi has already produced a report that shows mineral carbonation is feasible both economically and environmentally, and is looking to open a commercial plant within the next three years.
“We are keen on opening this in Australia but it really depends on policy incentives and the appetite of industry to adopt new technology,’ says Marcus.
“The interest is there, especially among consumers, and it’s clear that we need technology like this to help decarbonise the cement and steel industries. It’s been difficult to get better products to market in Australia but we’re hoping this is starting to change now.”