5 August 2014 — Move over concrete and steel, there are new building materials in town transforming the industry and creating more sustainable buildings. These materials promise to lead to stronger, lighter, more sustainable buildings, and could even allow buildings to repair themselves from wear and bad weather, much in the same way that the human body can heal itself. This isn’t science fiction, it’s happening now.
The first is graphene. As The Guardian reports, graphene is more solid than steel and a better conductor than copper. How do you get it? You extract it from graphite, the material used in pencils. Like graphite, graphene is entirely composed of carbon atoms and one millimetre of graphite contains some three million layers of graphene. But graphite is a three-dimensional crystalline arrangement. Graphene on the other hand is a two-dimensional crystal only an atom thick. The carbons are perfectly distributed in a hexagonal honeycomb formation only 0.3 nanometres thick, with just 0.1 nanometres between each atom.
Graphene conducts electricity better than copper. It is 200 times stronger than steel but six times lighter. It is almost perfectly transparent since it only absorbs two per cent of light. It is impermeable to gases, even those as light as hydrogen or helium, and, if that were not enough, chemical components can be added to its surface to alter its properties.
Graphene could create paper-thin solar cells that can be painted over exterior walls and just about any surface. If it’s mixed with monolayers of transition metal dichalcogenides (TDMC), it creates something that can outperform traditional photovoltaic cells.
According to Science Daily, new cells that could be incorporated into a building’s exterior are in development. Graphene solar cells are one of industry’s great hopes for cheaper, durable solar power cells in the future.
“The dopant makes the graphene film more conductive and increases the electric field potential inside the cell,” said Xiaochang Miao, a graduate student in Florida University’s physics department. That makes it more efficient at converting sunlight into electricity. And graphene is stable so its effects are long lasting.
As reported here, graphene could save aging buildings and the cost of future repairs could be hugely reduced if the new facade is coated in a super-strong graphene-based paint – Graphenstone. This paint is made from a mixture of limestone powder and graphene. It could also help create a building better able to withstand the environmental changes – like hot and cold temperatures – which can lead to building deterioration, such as has been faced by the City of Arts and Sciences opera house in Valencia, Spain. The paint is already being sold, and has been used on older buildings in Spain.
Monash University research has found that the addition of graphene oxide improves the degree of hydration of cement paste and increases the density of the cement matrix, creating a more durable product.
Still, there are some reservations about graphene with some research finding that graphene becomes more mobile in waters like lakes or streams where the particles are more likely to cause negative environmental damage. Watch this space.
Graphene is only one innovation. There’s also 3D printed materials, which, according to research, could be programmed to later transform their shape in response to movement or environmental factors, such as the presence of water, air or temperature changes. With the addition of time to the mix, this is effectively 4D printing. No human interaction is required, and the transformation happens through passive energy, making it highly efficient. Researchers say the technology could combat major inefficiencies, energy consumption and excessive labour involved in elements of construction, and make it easier to build in extreme environments.
Then there are nano-particles, which could be used to replace steel cables by much stronger carbon nanotubes in suspension bridges and cable-stayed bridges. Nano-silica could be used to produce dense cement composite materials, resistive carbon nanofibres could be incorporated into concrete roads in snowy areas, nano-titania could produce photocatalytic concrete, nano-calcite particles in sealants could protect the structures from aggressive elements of the surrounding environment, nano-clays in concrete could enhance its plasticity and flowability and urban air quality could be improved by if the civil structures were treated with nano titanium dioxide. Nano-particle treatments applied to building facades can neutralise airborne pollutants, capture carbon dioxide and clean the air around each structure.
Another technology is the special bricks made by biotechnology start-up BioMason. These bricks are made from bacterial by-products that bind sand particles together in a matrix strong enough to be used in residential construction. All of the materials used in the production of biobricks are globally abundant, and can be extracted from various waste streams, such as urea and common bacteria grown with yeast and salt extracts. The Delft University of Technology in the Netherlands is working on the incorporation of bacteria into the concrete to have the ability to repair itself when it sustains modest damage and wear. The bricks also forego the carbon dioxide created with traditional cement-based masonry. In other words, we could be saving the planet and at the same building homes that could repair themselves, with the use of humble bacteria.
New concrete being developed at MIT could drastically reduce the carbon emissions currently associated with the manufacturing of this material, producing something strong enough to last for an incredible 16,000 years. This concrete will not only be stronger, but also lighter and thinner, so large-scale, lightweight structures require far less material. More durable concrete means that less building material and less frequent renovations will be required.
Spanish and Scottish researchers have developed woollen bricks. They’ve created a composite that’s sustainable and non-toxic, which would also improve the bricks’ strength. Just add wool and a natural polymer found in seaweed to the clay of the brick and you get a brick that’s 37 per cent stronger than other bricks, and more resistant to the cold, wet climate. They also dry hard, reducing the embodied energy as they don’t need to be fired like traditional bricks.
Then there’s bendable, self-healing concrete, which bends under five per cent tensile strain. While ordinary concrete would crumble under such pressure, the new material forms micro-cracks that can then auto-seal with the addition of water and carbon dioxide, ensuring the building lasts longer.
Novacem is a “carbon negative” cement substitute made of magnesium silicate that absorbs CO2 from the atmosphere. It could potentially achieve one of the single largest reductions in CO2 emissions in construction, cutting out 800kg of carbon emissions per ton of poured concrete and absorbing another 50kg.
Company Evocative creates packaging products using mushroom mycelium and agricultural waste that bind together to form a durable material. Arup recently took the technology to the next level, using Evocative’s recently created mushroom bricks to help architect David Benjamin of New York firm The Living construct a 12-metre tower called Hy-Fi. The bricks create almost no waste, requires no energy inputs and the production involves no carbon emissions. Arup said the material might not replace steel and concrete soon but the tower showed there was a place for this technology.