Rice University scientists have developed micron-sized calcium silicate spheres that could lead to stronger and greener concrete, the world's most-used synthetic material.
To Rice materials scientist Rouzbeh Shahsavari and graduate student Sung Hoon Hwang, the spheres represent building blocks that can be made at low cost and promise to mitigate the energy-intensive techniques now used to make cement, the most common binder in concrete.
The researchers formed the spheres in a solution around nanoscale seeds of a common detergent-like surfactant. The spheres can be prompted to self-assemble into solids that are stronger, harder, more elastic and more durable than ubiquitous Portland cement.
[...] The work builds on a 2017 project [DOI: 10.1021/acsami.7b12532] [DX] by Shahsavari and Hwang to develop self-healing materials with porous, microscopic calcium silicate spheres. The new material is not porous, as a solid calcium silicate shell surrounds the surfactant seed.
Size- and Shape-Controlled Synthesis of Calcium Silicate Particles Enables Self-Assembly and Enhanced Mechanical and Durability Properties (DOI: 10.1021/acs.langmuir.8b00917) (DX)
Related: Biologists Create Self-Healing Concrete
Probing Ways to Turn Cement's Weakness to Strength
Roman Concrete Explained
The Rock Solid History of Concrete
Fungi Can Help Concrete Heal Its Own Cracks
Related Stories
A team of microbiologists from the Delft University of Technology claims to have invented "bioconcrete" — concrete that heals cracks and breaks using bacteria. The goal was to find a type of bacteria that could live inside concrete and also produce small amount of limestone that could re-seal cracks. This is a difficult prospect because concrete is quite dry and strongly alkaline. The bacteria needed to be able to stay alive for years in those conditions before being activated by water. The bacteria also need a food source — simply adding sugar to concrete will make it weak. The scientists used calcium lactate instead, adding biodegradable capsules of it to the concrete mix. "When cracks eventually begin to form in the concrete, water enters and open the capsules. The bacteria then germinate, multiply and feed on the lactate, and in doing so they combine the calcium with carbonate ions to form calcite, or limestone, which closes up the cracks."
One thing that is left out of the articles mentioned above is the amount of time needed for a given crack to "heal" closed.
Concrete isn't thought of as a plastic, but plasticity at small scales boosts concrete's utility as the world's most-used material by letting it constantly adjust to stress, decades and sometimes even centuries after hardening. Rice University researchers are a step closer to understanding why.
The Rice lab of materials scientist Rouzbeh Shahsavari performed an atom-level computer analysis of tobermorite, a naturally occurring crystalline analog to the calcium-silicate-hydrate (C-S-H) that makes up cement, which in turn holds concrete together. By understanding the internal structure of tobermorite, they hope to make concrete stronger, tougher and better able to deform without cracking under stress.
Their results appear this week in the American Chemical Society journal ACS Applied Materials and Interfaces .
Tobermorite, a key element in the superior concrete Romans used in ancient times, forms in layers, like paper stacks that solidify into particles. These particles often have screw dislocations, shear defects that help relieve stress by allowing the layers to slide past each other. Alternately, they can allow the layers to slip only a little before the jagged defects lock them into place.
The researchers built the first computer models of tobermorite "super cells" with dislocations either perpendicular to or in parallel with layers in the material, and then applied shear force. They found that defect-free tobermorite deformed easily as water molecules caught between layers helped them glide past each other.
But in particles with screw defects, the layers only glided so far before being locked into place by the tooth-like core dislocations. That effectively passed the buck to the next layer, which glided until caught, and so on, relieving the stress without cracking.
-- submitted from IRC
Researchers have unlocked the chemistry of Roman concrete which has resisted the elements for thousands of years.
Ancient sea walls built by the Romans used a concrete made from lime and volcanic ash to bind with rocks.
Now scientists have discovered that elements within the volcanic material reacted with sea water to strengthen the construction.
[...] This new study says the scientists found significant amounts of tobermorite growing through the fabric of the concrete, with a related, porous mineral called phillipsite.
The researchers say that the long-term exposure to sea water helped these crystals to keep on growing over time, reinforcing the concrete and preventing cracks from developing.
Source: BBC News
American Mineralogist DOI: 10.2138/am-2017-5993CCBY
The story of concrete is so ancient that we don't even know when and where it begins. It is a story of discovery, experimentation, and mystery. Emperors and kings became legends for erecting great concrete structures, some of which are still a mystery to engineers today. Many of history's most skilled architects found inspiration in slabs of the gray building material. Common bricklayers advanced the technology, and a con man played a crucial role in the development of concrete recipes.
Today, the world is literally filled with concrete, from roads and sidewalks to bridges and dams. The word itself has become a synonym for something that is real and tangible. Press your handprints into the sidewalk and sign your name to history. This is the story of concrete.
[...] Let's get this out of the way right here: cement and concrete are not the same thing. Cement, a mixture of powdered limestone and clay, is an ingredient in concrete along with water, sand, and gravel.
So ubiquitous and fundamental, that nobody thinks about it. Its inventor is unknown, but that person changed history.
Related: Volcanic Rocks Resembling Roman Concrete Explain Record Uplift in Italian Caldera
Roman Concrete Explained
[researchers] have found an unusual candidate to help concrete heal itself: a fungus called Trichoderma reesei.
We initially screened about 20 different species of fungi in order to find one that could withstand the harsh conditions in concrete. Some we isolated from the roots of plants that grew in nutrient-poor soils, including from the New Jersey Pine Barrens and the Canadian Rocky Mountains in Alberta.
We found that as calcium hydroxide from concrete dissolved in water, the pH of our fungal growth medium increased from a close-to-neutral original value of 6.5 all the way to a very alkaline 13.0. Of all the fungi we tested, only T. reesei could survive this environment. Despite the drastic pH increase, its spores germinated into threadlike hyphal mycelium and grew equally well with or without concrete.
We propose including fungal spores, together with nutrients, during the initial mixing process when building a new concrete structure. When the inevitable cracking occurs and water finds its way in, the dormant fungal spores will germinate.
As they grow, they'll work as a catalyst within the calcium-rich conditions of the concrete to promote precipitation of calcium carbonate crystals. These mineral deposits can fill in the cracks. When the cracks are completely caulked and no more water can enter, the fungi will again form spores. If cracks form again and environmental conditions become favorable, the spores could wake up and repeat the process.
The spores wake up when cracks form in concrete and admit moisture.
(Score: 1, Funny) by Anonymous Coward on Thursday September 27 2018, @02:12AM (4 children)
... cancer, at least in the State of California.
(Score: 1, Interesting) by Anonymous Coward on Thursday September 27 2018, @04:42AM (1 child)
Yeah, Silicates and Lungs aren't best friends.
(Score: 3, Insightful) by c0lo on Thursday September 27 2018, @12:37PM
Now, have you ever took a lungful of Portland cement?
I bet cement is as health damaging as that calcium silicate dust and yet it is used all around us.
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 2, Informative) by realDonaldTrump on Thursday September 27 2018, @05:07AM (1 child)
They call it Nano. Also known as MICRONIZED. If you have rosacea, very important to use sunscreen. You go out in the sun, no sunscreen, boom. Your face turns red -- very quick. So you do the sunscreen. But, you want the Nano. Because it's invisible. Nobody knows you're wearing it. You know. But nobody else. The regular, it makes you look like a clown. White nose, white everything. People laughing at you. Not the reaction you expected. And not what you wanted. And many people say, "oh, the Nano maybe makes Cancer." But many people say it's fine. I don't think anyone knows 100%. I say, go with Nano. With Micronized. Because you look fabulous. The old sunscreen, you look horrible -- white clown face. No sunscreen, you get the flare up, you look horrible. And possibly, Skin Cancer that way. Not a pretty sight!
We want very strong concrete. And the approvals are going to come very fast on that one. Tell the Rice People, just bring me the papers. I'm waiting, pen in hand. Look what happened at Florida International University. They did a bridge in concrete, they had a crack. And they lost the whole bridge. Along with, many people dieing (RIP!!!). Very sad situation, right? And Genoa. Beautiful bridge, they got a lot of use out of that one. But they didn't take care of it, because of politics. They didn't pay attention to the politics of it. Or to taking care of it. So many people died (RIP!!!). And if we had better concrete, stronger concrete, maybe those bridges would still be standing. And maybe they'd be much slimmer. Lighter. Cheaper. And more environmental. I'm known as The Environmental Hero. I've won many awards for environmental. Trust me, nobody has received more environmental awards than I have. We love environmental!!! amazon.com/Donald-J-Trump-Environmental-Hero/dp/1535456868 [amazon.com]
(Score: 0) by Anonymous Coward on Saturday September 29 2018, @04:09AM
My experience has been that trustworthy people have no need to say "trust me."
(Score: 0, Insightful) by Anonymous Coward on Thursday September 27 2018, @02:53AM (3 children)
I'm an old rich American boomer. Taxes are theft of money out of my pocket that I did nothing at all to earn. I like my concrete infrastructure crumbling in disrepair. Poor people don't deserve roads because if they did then they would pay for their own roads with their own money instead of my money.
- Every Soylentitled
(Score: 0, Redundant) by Anonymous Coward on Thursday September 27 2018, @03:33AM (2 children)
(Score: 3, Insightful) by realDonaldTrump on Thursday September 27 2018, @04:28AM (1 child)
You know why our roads are so tremendously expensive? Regulations. I’ve reduced regulations terrifically. It would take, as an example, to build a highway. It would take 17 to 20 years to get approvals. And at the end of 20th year, in many cases, they voted it down. Do you approve? No. So they wasted tens of millions of dollars. There’s a highway in Maryland where it took exactly 17 years. And the original numbers were very little, and it ended up costing hundreds of millions of dollars for a very small, short highway. And we can’t have that.
So we’re trying to bring that number down from anywhere from 13 to 20 years. We’re trying to bring it down to one year. You want to build a road? You want to build a highway? You want to build a school? You want to build a factory or a plant? You’re going to have your approvals very, very quickly.
Now, you may be rejected quickly, too. But that’s OK, if you’re rejected quickly. You don’t want to be rejected at the end of the 17th year. I approved a power plant. Which has been under consideration for 11 years, and they gave up, and I approved it. And it’s a $7 billion plant. And the state wanted it and the local community wanted it, but they had environmental restrictions. And now it’s being built. We're #BuildingAStrongerAmerica [twitter.com]!!!! #InfrastructureInAmerica [twitter.com]
(Score: 2) by RandomFactor on Thursday September 27 2018, @04:32AM
It is my shame that i really just haven't figured you out yet.
В «Правде» нет известий, в «Известиях» нет правды
(Score: 4, Interesting) by RandomFactor on Thursday September 27 2018, @04:29AM (2 children)
There are those who might argue Congress is a prefered binding agent for Concrete
В «Правде» нет известий, в «Известиях» нет правды
(Score: 2, Informative) by Anonymous Coward on Thursday September 27 2018, @04:40AM (1 child)
And far greener.
(Score: 5, Funny) by c0lo on Thursday September 27 2018, @12:42PM
I have this hunch some politicians will feel offended in being called Green after being Reps/Dems all their life.
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 0) by Anonymous Coward on Thursday September 27 2018, @05:55PM (2 children)
The pyramids and other megalithic structures around the world have lasted for thousands of years. Why not build using that method rather than these new ones that require a total redo every couple decades?
(Score: 0) by Anonymous Coward on Thursday September 27 2018, @10:21PM (1 child)
The issue with modern concrete is the rebar added to work in tension. Some formulas of concrete last a lot, in compression. We have Roman things that use concrete and they are rather fine after 2000 years give or take. Reinforced concrete is the one failing in decades.
So find designs that only use compression (not gonna happen), or a replacement for steel based rebar (when iron rusts, it expands and flakes, cracking the concrete from inside). I have heard about some fibers, or even coating the steel, yet nothing final. Also remember greed fueled by apparent unlimited avaliability of energy of modern times: last centuries for some extra %, or fully remake in decades, costing >100% of demolish and build again?
(Score: 2) by PocketSizeSUn on Saturday September 29 2018, @07:23AM
Not sure when this 'it's the steel reinforced concrete bar' meme started but shows a deep willful ignorance of the engineering and economic reality of road and building construction.
Using steel is required for spanning and helpful in significantly reducing the amount of concrete needed in compression applications (piers and foundations).
As far as 'replacement for steel based rebar' there is none. Steel works because the thermal expansion of steel and concrete are matched. Any replacement would require the same thermal expansion co-efficient .. and there is none.
As for 'rust' that is easily prevented by using high strength concrete 6000 psi (42 Mpa) and water repellent coatings.