Building A Future-Proof Future
By itself, the construction industry is responsible for more than 10% of the world’s CO2 emissions—five times more than global air travel. One of the biggest sources of this heavy carbon footprint is concrete and its main ingredient, cement. If the global cement sec-tor were a separate country, it would be the world’s third-largest CO2 emitter after China and the United States. The good news is that a radical rethink of the built environment is already underway to drastically reduce its carbon footprint and move from the current model to a sustainable, closed-loop system.
The good news
Much progress is being made to develop and bring to market a wide range of new materials and approaches to the built environment to make it sustainable for today and tomorrow. This includes the next-generation of ecologically friendly cement and concrete that not only can radically reduce carbon emissions but, over time, has the potential to make concrete a carbon-negative material. Teams around the world are also engaged in ground-breaking work to develop special-ised alternative concretes that can do things like capture, store, and transmit solar energy as either electricity or light without operational costs or harmful emissions.
Natural materials like wood are also getting a rethink as part of the solution for the built environment. Advances in engineered wood make it not just struc-turally possible but also economically viable to build high-rise buildings with engineered wood beams rather than steel. Engineered wood has other benefits, including carbon capturing, passive cooling and the general well being that the natural material engenders.
Adding to the list, new developments in nano-technologies are enabling the roll-out of self-regulating building facades, while breakthroughs in HVAC sys-tems are making it possible to reduce energy consumption significantly. No one solution holds the key. This is a case where the more good ideas we have, the better. Making the concrete jungle green Concrete is everywhere. Each year, over 10 bil-lion tonnes of it are consumed worldwide, mak-ing it the most-used manmade material on the planet—and the second-most used substance on Earth after water.
To meet the growing global demand for concrete, currently more than 4.5 billion tonnes of cement are produced each year. And cement production—at least in the way that most of the industry-standard Portland cements are made today—is an energy-intensive process that emits massive amounts of CO2.
The main source of emissions is the produc-tion of clinker, which requires heating limestone to temperatures of up to 1,500 Celsius—around twice as hot as molten lava. While the energy used comes mostly from fossil fuels, as much as 60% of the carbon emissions come from the chemical reactions that take place during the production of clinker.
One solution for cement is to replace clinker with another, more benign material. Researchers at Princeton University have shown that it is possi-ble to make cement-like materials using recycled by-products from industrial activities, including steel slag, fly ash from coal-fired power plants, and certain clays. While still in the developmental phase, this technique—which has the added benefit of recycling industrial waste and cap-turing carbon—could reduce CO2 emissions by as much as 80% compared to the production of traditional Portland cement.
Another possible solution in develop-ment at the Laboratory for the Chemistry of Construction Materials at UCLA is a unique cement-like material produced by upcycling C02 from industrial carbon emissions with-out the need for further processing. The ma-terial, which the UCLA team calls “CO2N-CRETE”, is produced by taking the captured CO2 from flue gas and combing it with other elements to trigger a chemical reaction, which is then fabricated using 3D printers. The cur-rent pilot project is producing up to 10 metric tonnes a day and in phase two, output should reach 100 tonnes per day.
In the UK, researchers at the University of Aberdeen are working on something they call the Carbon Capture Machine. The device captures CO2 and converts it to materials that can replace ground calcium carbonate— another CO2-intensive ingredient used to pro-duce concrete. While still in the early stages of development, the technology could play an important role in eliminating CO2 from the production of concrete.
Fixing the cracks
One big problem with modern concrete is that it doesn’t last. Many modern concrete structures begin to degrade within 50 years. Repairs are costly and many structures are simply demolished without effective recy-cling. But what if concrete could fix itself?
The idea is not farfetched—the ancient Romans developed self-healing concrete mix-tures more than 2,000 years ago that have stood the test of time. Recent analysis reveals that the Romans made their concrete from a mix of volcanic ash and rocks, lime, and sea-water. The process—which modern science has not fully been able to replicate—causes a rare hydrothermal mineral to grow, which strengthens the concrete over time.
Researchers today are working on solu-tions to develop self-healing cement to meet the needs of the modern world. A team from Delft University in the Netherlands has tak-en the lead in developing a concrete mixture infused with bacteria that enables the con-crete to heal its own cracks and fissures. The bacteria naturally produce limestone when exposed to air and water. Thus not only does this new material eliminate the need for costly repairs, it actually strengthens concrete structures over time. The material can be used not only for new buildings but also for repairs to existing structures. Mixing the bac-teria into specialised gels before it is added to the cement enables the self-healing process to go on for centuries.
Do you see the light?
Another eye-opening innovation in the world of cement and concrete—one with numerous potential applications—is the development of light-emitting or phosphorescent cement: cement that literally glows in the dark.
Researchers in Mexico have invented a cement mixture that can absorb and store sunlight during the day and then emit light (currently in hues of blue or green) for 12 hours during the night. The material can be used to illuminate things like highways, bike paths and buildings using only the energy ab-sorbed from sunlight during the day. It has a lifespan of 100 years.
The team figured out an ingenious way to transform the crystalline micro-structure of regular cement (which makes it opaque) into a gel that can absorb and emit light. The material is also ecological, as it is made from sand, dust or clay and the only emission during the production process is steam. The project has garnered international attention and several companies are starting to roll out production.
Another futuristic innovation is cement that can conduct electricity. Conductive cement is already in use for things like electrical grounding, lightening protection, electro-magnetic interference and thermoelectric power generation. Now, several teams of researchers around the world are working on various ways to enhance the conductivi-ty of concrete to take its applications to the next level.
Researchers at Leeds University in the UK have developed a cement compound that uses potassium ions to conduct energy. This en-ables concrete structures to act as batteries to store and emit energy wirelessly. That means that our homes and offices could, in effect, power themselves.
Another breakthrough in the works is a graphene-infused cement mixture that its developer, the Australian company Talga, claims acts like the heating element of an electric stove. The potential applications of this “energised” concrete are immense: from heated floors to heated roads and walkways, which would create a safe and environmen-tally friendly way to clear ice in winter.
Perhaps the most exciting possibility is that conductive cement could enable elec-tric vehicles to be charged wirelessly—either while they are being driven or when they are parked—using the solar energy absorbed by the concrete surface of the motorway or car park.
This is the kind of game-changing tech-nology that would make it possible in the not-so-distant future for electric vehicles to replace fossil-fuel-burning cars and trucks, eliminating a huge source of CO2 emissions.
Ferrock to the rescue?
Ferrock—a revolutionary, rust-coloured con-crete-like material developed accidentally a few years ago by an environmental chemist in the United States—is a simple yet amazing substance. Made mainly from iron dust and silica (crushed glass), both of which are read-ily available from recycling, Ferrock actually absorbs rather than emits CO2 during its pro-duction process, making it a carbon-negative building material.
Research is still on-going into how the material does what it does, but in essence CO2 reacts with rust to form iron carbonate, locking in the greenhouse gas from the atmosphere. Additionally, Ferrock is produced without the need for high temperatures and also strengthens when exposed to seawater. Ferrock is five times stronger than Portland cement and much more flexible, making it better suited than traditional concrete to withstand seismic activity and industrial processes. Still in development, commercial production is expected soon.
From Earth to Mars and back again
A team of architects and designers in the US working to develop a prototype habitat to support human life on Mars may have devel-oped the ultimate sustainable building mate-rial for the future here on Earth.
The design firm AI SpaceFactory won a half-million dollars from NASA for its Mars habitat prototype MARSHA. The space- age design uses a bespoke construction ma-terial called biopolymer basalt composite, which is made from crops like corn and sugar cane and fabricated using 3D printing technology. The material has been certified by NASA to be 50% stronger and more durable than concrete.
Inspired by MARSHA, the team focused their attention back here at home and came up with TERA, an Earth-bound version of MARSHA using the same plant-based poly-mers. TERA is proof-of-concept for the build-ings of the future. The construction material is 100% recyclable and compostable, while at the same stronger and more durable than traditional concrete.
Wood is the new concrete
Another traditional building material getting a re-think for the 21st century is wood, which is making a comeback as a construction ma-terial for all the right reasons. With proper forest management, wood is a sustainable building material that absorbs and locks in CO2 from the atmosphere.
The big change in the world of wood is the on-going development of engineered timber—a super-wood that it is stronger, lighter and more fire-resistant than steel. Some architects now describe it as the concrete of the future.
One of the most important of these is cross-laminated timber (CLT). First devel-oped in Austria in the 1990s, CLT is basically a super-plywood made by taking planks from different woods and binding them togeth-er at right angles. CLT constructions can be pre-fabricated offsite to a great deal of pre-cision, allowing them to be put together al-most like Lego blocks at the building site by a relatively small crew.
The speed and ease of construction saves both time and money.
Although not exactly new, the use of en-gineered wood for construction has acceler-ated in recent years. In 2003, consumption of CLT worldwide was only 2,000 cubic metres. In 2018, over one million metric tonnes were used.
Castles made of CLT
Currently most CLT is used for the construction of low- and mid-rise residential and industrial buildings, including offices and warehouses. But as the use of engineered wood continues and building codes are revised to allow for taller wooden structures, we are going to be seeing more of something we haven’t seen much of before: wooden skyscrapers.
The newest contender for world’s tallest wooden structure is the recently announced Canada Earth Tower in Vancouver. Plans for the 40-storey building include 200 apartments and outdoor vertical gardens. Canada—with its large supply of sustainable timber— currently has over 500 mid-rise wooden building projects under construction.
Japan is another pioneer in timber sky-scrapers. Last year Sumitomo Group an-nounced plans to build the world’s tallest wooden skyscraper in Tokyo. The 70-storey building, called W350, will be 350 metres tall at completion and will be made from a hybrid of wood and steel.
In addition to its ecological and cost ben-efits, there’s another good thing about wood: people like it. While more research is needed, wood has long been known to make people feel better: it reduces stress, improves air quality and fosters overall well being.
Nano-wood is cool
Another fascinating innovation in wood is “nano-wood” developed by researchers at the University of Maryland. This new material
has wide-reaching implications as a passive cooling agent for both new and existing buildings.
Although it sounds high-tech, nano-wood turns out to be relatively simple: the team developed a low-cost way to take ordinary recycled wood and remove the compounds that make it brown and hard. What remains is a woody material made only of cellulose nano-fibres and the natural spaces that trans-port water and nutrients inside a living tree. This material is then compressed to restore its strength, and a hydrophobic compound is added to make it water repellent.
The result is a bright white “wood” that is both extremely effective at reflecting and dissipating heat and extremely strong: ten times stronger than wood, and three times stronger than steel. These dual properties make nano-wood ideal as a building material, especially for roof tiling and facades. Tests show it to be 10% more effective at blocking heat than Styrofoam or silica aerogel and up to 30 times more durable. The natural nano-structure of the material enables it to stay up to 4 degrees Celsius cooler than the air around it, even during the hottest part of the day.
Nano-wood is inexpensive to produce (currently around USD 7 per square metre) and is ideal for both new constructions and for renovating existing buildings. Studies have shown that for buildings built after 2004, it can reduce energy costs by more than 20%. For older buildings, the savings are even higher.
Face of the future
All-glass facades have come to define much of the modern urban landscape. Such buildings may be stylish and sleek, but they are also, in effect, giant greenhouses heated up by the sun that require massive amounts of energy to cool.
According to the International Energy Agency, the amount of energy used for cool-ing buildings has doubled since 2000 and now accounts for around 14% of all energy usage. The high environmental cost of all-glass facades has triggered a growing cam-paign of prominent voices calling for them to be banned. While the debate is underway, new breakthroughs may offer the solution.
Homeostatic (self-regulating) facades could be a game-changer when it comes to the buildings of the future.
Developed by an architectural team in the US, the system uses a high-tech ribbon woven inside the cavity of double-skin glass that contracts or expands depending on the temperature outside. The flexible ribbon is made of a special polymer material called dielectric that can be polarised with very little energy consumption. The ribbons react to changes in temperature and either contract to let warmth in or expand to block sunlight.
Another twist on the façade of the future is to literally make it green. Vertical gardens are increasingly seen by architects and developers as an ideal way to reduce cooling costs while providing a signifi cant contribution to CO2 reduction and cleaning urban air.
A good example is Milan’s award-win-ning Bosco Verticale (Vertical Forest) project designed by Stefano Boeri Architects. Com-pleted in 2014, the twin residential towers rise to heights of 116 metres and 76 metres and contain more than 800 trees and 14,000 plants representing over 100 species.
The team also won the commission to de-sign the Liuzhou Forest City in China—the world’s most ambitious vertical forest project to date. Plans call for the creation of apart-ments for 30,000 people within a series of plant-covered skyscrapers involving 40,000 trees and one million plants.
Each year the trees at Liuzhou Forest City are expected to absorb 10,000 tonnes of CO2 and 57 tonnes of air-borne pollutants while producing around 900 tonnes of oxygen. The project will decrease average air temperature in the area, create noise barriers, and boost biodiversity by creating a habitat for birds and insects.
A less eye-catching but no less important de-velopment for the built environment is a new breakthrough that makes existing climate control systems for buildings exponentially more effi cient.
Heating, ventilating and air conditioning (HVAC) systems using turbulent heat exchange is how the majority of the world’s buildings regulate their internal climates. These systems are major contributors to the energy usage of the built environment worldwide.
A joint team of researchers from the US and China are making waves in the world of HVACs with a relatively small innovation with big potential. The team took an organic compound known as HFE, which is the sole fluid used in some heat exchange systems, and added it to a water-based heat exchange system to see what would happen.
After three years of tinkering, the results are impressive. The team determined that adding 1% HFE to a water-based heat exchange HVAC system can increase its effi cien-cy by an astounding 500%, as the droplets of HFE in the water speed the process of heat exchange throughout the system.
One current limitation with this break-through is that it only works for vertical heat exchange. Adaptions are underway to modify the technique for horizontal heat exchange systems.elastomers coated with silver.