Tag Archives: cement

Buildings grown by bacteria — it’s not as crazy as it sounds, and it’s actively researched

Buildings are not unlike a human body. They have bones and skin; they breathe. Electrified, they consume energy, regulate temperature and generate waste. Buildings are organisms – albeit inanimate ones.

A block of sand particles held together by living cells. Image credits: University of Colorado Boulder College of Engineering and Applied Science.

But what if buildings – walls, roofs, floors, windows – were actually alive – grown, maintained and healed by living materials? Imagine architects using genetic tools that encode the architecture of a building right into the DNA of organisms, which then grow buildings that self-repair, interact with their inhabitants and adapt to the environment.

Living architecture is moving from the realm of science fiction into the laboratory as interdisciplinary teams of researchers turn living cells into microscopic factories. At the University of Colorado Boulder, I lead the Living Materials Laboratory. Together with collaborators in biochemistry, microbiology, materials science and structural engineering, we use synthetic biology toolkits to engineer bacteria to create useful minerals and polymers and form them into living building blocks that could, one day, bring buildings to life.

In one study published in Scientific Reports, my colleagues and I genetically programmed E. coli to create limestone particles with different shapes, sizes, stiffnesses and toughness. In another study, we showed that E. coli can be genetically programmed to produce styrene – the chemical used to make polystyrene foam, commonly known as Styrofoam.

Green cells for green building

In our most recent work, published in Matter, we used photosynthetic cyanobacteria to help us grow a structural building material – and we kept it alive. Similar to algae, cyanobacteria are green microorganisms found throughout the environment but best known for growing on the walls in your fish tank. Instead of emitting CO2, cyanobacteria use CO2 and sunlight to grow and, in the right conditions, create a biocement, which we used to help us bind sand particles together to make a living brick.

By keeping the cyanobacteria alive, we were able to manufacture building materials exponentially. We took one living brick, split it in half and grew two full bricks from the halves. The two full bricks grew into four, and four grew into eight. Instead of creating one brick at a time, we harnessed the exponential growth of bacteria to grow many bricks at once – demonstrating a brand new method of manufacturing materials.

Living building materials can be formed into many shapes, like this truss. Image credits: University of Colorado Boulder College of Engineering and Applied Science.

Researchers have only scratched the surface of the potential of engineered living materials. Other organisms could impart other living functions to material building blocks. For example, different bacteria could produce materials that heal themselves, sense and respond to external stimuli like pressure and temperature, or even light up. If nature can do it, living materials can be engineered to do it, too.

It also take less energy to produce living buildings than standard ones. Making and transporting today’s building materials uses a lot of energy and emits a lot of CO2. For example, limestone is burned to make cement for concrete. Metals and sand are mined and melted to make steel and glass. The manufacture, transport and assembly of building materials account for 11% of global CO2 emissionsCement production alone accounts for 8%. In contrast, some living materials, like our cyanobacteria bricks, could actually sequester CO2.

A growing field

Teams of researchers from around the world are demonstrating the power and potential of engineered living materials at many scales, including electrically conductive biofilmssingle-cell living catalysts for polymerization reactions and living photovoltaics. Researchers have made living masks that sense and communicate exposure to toxic chemicals. Researchers are also trying to grow and assemble bulk materials from a genetically programmed single cell.

While single cells are often smaller than a micron in size – one thousandth of a millimeter – advances in biotechnology and 3D printing enable commercial production of living materials at the human scale. Ecovative, for example, grows foam-like materials using fungal mycelium. Biomason produces biocemented blocks and ceramic tiles using microorganisms. Although these products are rendered lifeless at the end of the manufacturing process, researchers from Delft University of Technology have devised a way to encapsulate and 3D-print living bacteria into multilayer structures that could emit light when they encounter certain chemicals.

The field of engineered living materials is in its infancy, and further research and development is needed to bridge the gap between laboratory research and commercial availability. Challenges include cost, testing, certification and scaling up production. Consumer acceptance is another issue. For example, the construction industry has a negative perception of living organisms. Think mold, mildew, spiders, ants and termites. We’re hoping to shift that perception. Researchers working on living materials also need to address concerns about safety and biocontamination.

The National Science Foundation recently named engineered living materials one of the country’s key research priorities. Synthetic biology and engineered living materials will play a critical role in tackling the challenges humans will face in the 2020s and beyond: climate change, disaster resilience, aging and overburdened infrastructure, and space exploration.

If humanity had a blank landscape, how would people build things? Knowing what scientists know now, I’m certain that we would not burn limestone to make cement, mine ore to make steel or melt sand to make glass. Instead, I believe we would turn to biology to help us build and blur the boundaries between our built environment and the living, natural world.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Bacteria-laden materials point the way to living, growing, healing buildings

New research at the University of Colorado Boulder (UCB) aims to pave the way to living, breathing buildings by mixing concrete with bacteria.

One of the shapes the team used to test their material.
Image credits UCB College of Engineering & Applied Science.

Walls that heal, scrub the air clean, or even glow on demand — that’s what the team envisions for the future. Led by engineer Wil Srubar from the UCB, they’re trying to make it happen by mixing living bacteria with sand and gelatin and then having them produce concrete on the spot, out of thin air. In addition, such an approach would help scrub CO2 out of the atmosphere.

Tiny building blocks

“We already use biological materials in our buildings, like wood, but those materials are no longer alive” said Srubar, an assistant professor in the Department of Civil, Environmental and Architectural Engineering at the UCB.

“We’re asking: Why can’t we keep them alive and have that biology do something beneficial, too?”

The bacteria-laden material isn’t commercially available just yet. However, the little bugs have survived in the hardened mixture for several weeks, suggesting that the approach is viable.

Mineralization comparison of the gelatin scaffold for the experimental (A, B) and bacteria-free control (C, D) bricks.
Image credits Chelsea M. Heveran et al., (2020), Matter.

Srubar and colleagues experimented with cyanobacteria belonging to the genus Synechococcus. Under the right conditions, these green microbes absorb carbon dioxide gas to help them grow and make calcium carbonate—the main ingredient in limestone and, it turns out, cement. The researchers bred colonies of these cyanobacteria and injected them into the sand and gelatin matrix, which serves to provide the shape and other materials required for the desired piece of concrete.

With the right tweaks, the calcium carbonate mineralizes with the gelatin that binds the grains of sand together, producing a brick.

“It’s a lot like making rice crispy treats where you toughen the marshmallow by adding little bits of hard particles,” Srubar said.

The material effectively acts as carbon storage, because it scrubs the gas from the air and chemically binds it into a stable compound. Because the bacteria don’t die off after crystallization, they could be used to repair any cracks or similar damage sustained by the brick (or a whole building), much like the living cells in our bones. The team managed to keep around 9-14% of the bacterial colonies in their material alive for 30 days, having spent three different generations in brick form.

“We know that bacteria grow at an exponential rate,” Srubar said. “That’s different than how we, say, 3-D-print a block or cast a brick. If we can grow our materials biologically, then we can manufacture at an exponential scale.”

But are they any good as far as bricks go? It seems so — the team found that the bacteria-laden bricks have similar strength to Portland cement-based mortars humidity conditions. In the future, they see their material as being delivered in bags on-site, where it would just be mixed with water and shaped, then allowed to develop.

 Cyanobacteria growing and mineralizing in the sand-hydrogel framework.
Image credits UCB College of Engineering & Applied Science.

The team also hopes to help slash emissions and energy use related to construction material manufacturing. Cement and concrete production for roads, bridges, skyscrapers and other structures generates nearly 6% of the world’s annual emissions of carbon dioxide, they explain.

However, there is still a lot of work to be done before such material becomes commercially available. One of the team’s goals right now is to grow cyanobacteria that is more resistant to dry conditions (the team’s bacteria currently need humid conditions to survive) so that they can be employed in hotter, drier areas.

The paper “Biomineralization and Successive Regeneration of Engineered Living Building Materials” has been published in the journal Matter.

Astronauts mix cement in space station, pave way for buildings on other worlds

Humans have been using concrete for thousands of years to erect all sorts of buildings, from small homes to today’s skyscrapers. Concrete is very durable, strong, and cheap, which explains its widescale success — and, in the future, it might become a crucial constructions material on other words too.

A huge step in this direction was recently made by researchers working on a NASA project that mixed cement on the International Space Station (ISS).

European Space Agency astronaut Alexander Gerst works on the MICS experiment aboard the International Space Station. Credit: NASA.

As part of the experiment, called Microgravity Investigation of Cement Solidification, researchers sent tricalcium silicate, hydrated lime, and distilled water — the basic building blocks of cement — to the ISS. Once there, these ingredients were mixed and allowed to harden. The resulting structure was compared to cement mixed on Earth under normal gravity conditions.

The lack of gravity proved to play an important role in how the cement hardened. Surprisingly, the space cement has a uniform density while Earth-based cement has a more layered structure due to gravity-based sedimentation.

This uniform density makes the cement stronger. But this strength may be counter-balanced by the development of large air pockets in space cement, making it more porous than the Earth-mixed counterpart. This increased porosity makes the cement weaker.

Cement pastes mixed in space (above) and on the ground (below). The sample from space shows more porosity, which affects concrete strength. Meanwhile, crystals in the Earth sample are more segregated. Credit: Penn State Materials Characterization Lab

So, what is the net effect? That’s something that a strength test will have to determine. The researchers are planning to destroy the samples later this year after they’ve finished conducting their microstructural analysis. Ultimately, this fail test will determine which of the two types of cement is stronger.

Concrete is made by mixing two components: aggregates and paste. In the composition of modern concrete, there are various materials that are used by the industry as aggregates. These include sand, gravel, or crushed stone.  The paste is most of the time cement — a mix of limestone, clay, gypsum, and various other minerals or chemicals.

Concrete is highly attractive as a building material in space because of its good thermal and radiation insulating properties. In fact, it’s the go-to material when it comes to shielding radioactive waste.

“On missions to the Moon and Mars, humans and equipment will need to be protected from extreme temperatures and radiation, and the only way to do that is by building infrastructures on these extraterrestrial environments,” said principal investigator Aleksandra Radlinska of Pennsylvania State University. “One idea is building with a concrete-like material in space. Concrete is very sturdy and provides better protection than many materials.”

Concrete could also be mixed on off-world sites with local resources. Lunar regolith, also known as moon dust, is composed of jagged and fine dust grains that could decrease the porosity of the concrete. Radlinska and colleagues have already performed preliminary tests on lunar regolith, the results of which have been submitted for an upcoming publication.

This is why the present evaluation of microgravity-mixed cement is so important. First and foremost, it showed that it can be done.

“Even though concrete has been used for so long on Earth, we still don’t necessarily understand all the aspects of the hydration process. Now we know there are some differences between Earth- and space-based systems and we can examine those differences to see which ones are beneficial and which ones are detrimental to using this material in space,” said Radlinska. “Also, the samples were in sealed pouches, so another question is whether they would have additional complexities in an open space environment.”

Next, the researchers plan on studying various binders that are particularly suitable for various degrees of gravity, from zero gravity to Mars gravity and in between.

The findings were published in the journal Frontiers in Materials.

Building houses with bacteria

Houses of the future might be built with bacteria – at least partially. It may sound like science fiction, but a Spanish company located in Madrid is working to make that a concrete reality.

Image via Eco-Cement.

It all starts with a common type of soil bacterium being. Put it in some soil, provide it with nutrients, and keep the temperature steady at about 30 degrees, and then let it work its magic; after a while, add it to a mix of sand, industrial cement waste and the ash of rice husks.. Piero Tiano, a biologist with the Italian Institute for the Conservation and Preservation of Cultural Heritage told euronews how it works:

“Inside this mix, bacteria starts to develop; they basically grow in number. The bacteria has to reach a certain quantity in order to make cement. After around three hours of fermentation, our mix is ready for use”.

OK, but why would they want to do this? Well, about 5% of global carbon emissions originate from the manufacturing of cement. Furthermore, the global production of cement in 2030 is projected to grow to a level roughly 5 times higher than its level in 1990, with close to 5 billion tones worldwide This project aims to make cement not only cheaper and easier to make, but also more sustainable.

“Our raw materials are basically all waste. So we don’t have added costs,” said Laura Sánchez Alonso, a mining Engineer and Eco-Cement project coordinator. For instance, we don’t need to extract and transport the limestone commonly used to produce cement. And we also save the energy costs”

Less heat means lower amounts of energy invested and less emissions. To put some figures down, this technology can reduce greenhouse gas emissions by 11%, and production costs by 27%. This might not seem like much, but again – consider the massive quantities of cement fabricated throughout the world. This are also only the initial results – researchers are working to make the technology even more efficient and eco-friendly.

“In ordinary cement, they have to use very high temperatures, up to 1,400-1,500 degrees Celsius in order to turn limestone into cement. That is part of the process. And that takes an awful lot of energy. Here we only need bacteria to multiply at 30 degrees. So that is a massive difference. And that amount of heat energy is saved because we are using a biological process to bind the particles together”.

The bacteria basically produces limestone, but if it’s not carefully planned, it may produce too much or too little.

“It’s important to know the ideal density of bacteria in the mix,” said Linda Wittig, an industrial chemist with Fraunhofer-IFAM.

To make things even more interesting, the resilience, resistance and sturdiness of the resulting structure means that researchers can also use this bacteria to create mortar.

“We decided to use this material as mortar and not as concrete because it is not as strong as traditional concrete. But it can be easily transformed. This is the reason why we decided to use this material as mortar,” said Nikos Bakas, a civil engineer at Neapolis University in Greece.

Realistically speaking, the technology is still a few years away before actually hitting the shelves – but developing a cheaper, easier and more sustainable system of creating cement… sign me up any day!

Electrons (the blue blobs) trapped inside calcium oxide cages. (c) PNASElectrons (the blue blobs) trapped inside calcium oxide cages. (c) PNAS

Modern ‘alchemy’ turns cement into semiconducting metal

Sure, this transmutation might not be as spectacular as that of lead into gold, but it most certainly would have made even the alchemists at King Arthur’s court envious. Using an innovative technique, an international team of researchers has transformed cement, a sturdy insulator (especially electrical), into a semiconductor metal. Apart from being a remarkable display of science, the findings could open up new opportunities for developing  thin films, protective coatings, and computer chips.

Truth be told, the transformed cement isn’t actually a metal, but rather a glass-metal. Previously, however, only metals were proven to be able to transition into glass-metals. The researchers achieved this with cement (calcium and aluminum oxides) by first heating it to  2,000 Celsius degrees with a high-power laser until it turned liquid. Then a special tool called  the levitator keeps the hot liquid from touching any container surfaces and forming crystals. True to its name, this remarkable tool pumps out inert gas through its nozzles and literally levitates the liquefied cement. This let the liquid cool into glassy state that can trap electrons in the way needed for electronic conduction.

Electrons (the blue blobs) trapped inside calcium oxide cages. (c) PNASElectrons (the blue blobs) trapped inside calcium oxide cages. (c) PNAS

Electrons (the blue blobs) trapped inside calcium oxide cages. (c) PNAS

Remember, a metal is so good at conducting electricity because it has a bunch free electrons running around which can be used to pass energy from one atom to other. Normal cement can’t do this, obviously, however the new transmuted glass-metal cement has free electrons tapped inside cages made of calcium oxide – something only previously seen in ammonia solutions. This is because trapping electrons inside a crystal’s structure is fairly new, and seeing how this works for cement, there’s no reason to believe other materials can’t behave in much or the same manner. This opens the possibility of turning other solid normally insulating materials into room-temperature semiconductors, something which by itself can pose huge implications in the industry.

“This new material has lots of applications including as thin-film resistors used in liquid-crystal displays, basically the flat panel computer monitor that you are probably reading this from at the moment,” said Chris Benmore, a physicist from the U.S. Department of Energy’s (DOE) Argonne National Laboratory who worked with a team of scientists from Japan, Finland, and Germany to take the “magic” out of the cement-to-metal transformation. Benmore and Shinji Kohara from Japan Synchrotron Radiation Research Institute/SPring-8 led the research effort.

Findings were reported in the journal Proceeding of the National Academy of Sciences.