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Spheres Can Make Concrete Leaner, Greener (phys.org)
An anonymous reader quotes a report from Phys.Org: 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. 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. He said the spheres are suitable for bone-tissue engineering, insulation, ceramic and composite applications as well as cement. The research appears in the American Chemical Society journal Langmuir.
In tests, the researchers used two common surfactants to make spheres and compressed their products into pellets for testing. They learned that DTAB-based pellets compacted best and were tougher, with a higher elastic modulus, than either CTAB pellets or common cement. They also showed high electrical resistance. [Rice materials scientist Rouzbeh Shahsavari] said the size and shape of particles in general have a significant effect on the mechanical properties and durability of bulk materials like concrete. He said increasing the strength of cement allows manufacturers to use less concrete, decreasing not only weight but also the energy required to make it and the carbon emissions associated with cement's manufacture. Because spheres pack more efficiently than the ragged particles found in common cement, the resulting material will be more resistant to damaging ions from water and other contaminants and should require less maintenance and less-frequent replacement.
In tests, the researchers used two common surfactants to make spheres and compressed their products into pellets for testing. They learned that DTAB-based pellets compacted best and were tougher, with a higher elastic modulus, than either CTAB pellets or common cement. They also showed high electrical resistance. [Rice materials scientist Rouzbeh Shahsavari] said the size and shape of particles in general have a significant effect on the mechanical properties and durability of bulk materials like concrete. He said increasing the strength of cement allows manufacturers to use less concrete, decreasing not only weight but also the energy required to make it and the carbon emissions associated with cement's manufacture. Because spheres pack more efficiently than the ragged particles found in common cement, the resulting material will be more resistant to damaging ions from water and other contaminants and should require less maintenance and less-frequent replacement.
I remember an article in Scientific American when I was a kid (decades ago) that described cement research. The one idea that stuck with me is that cement failure is precipitated by mechanical imperfections -- that much isn't so suprising -- which in cement are air bubbles. Remove the air bubbles and cement becomes as strong as aluminum, albeit considerably heavier. They demonstrated this remarkable property by making car springs out of void-free cement!
Put my fist through my alarm clock with its ding-dong death inside my ear. - The Blackjacks.
Why am I picturing these spheres as 1980s cartoon characters, complete with little capes?
The spheres can be prompted to self-assemble into solids that are stronger, harder, more elastic and more durable than ubiquitous Portland cement.
"We can't beat the creature alone! Spheres - assemble!"
This may prove useful for some specialty uses but Concrete doesn't need to be compacted to cure at this material does. It might be useful for some specialty prefab uses but clearly, it's not going to replace concrete in general use.
Democracy is a sheep and two wolves deciding what to have for lunch. Freedom is a well armed sheep contesting the issue
It's paywalled. But if practical and economic, this is one of the biggest changes for the better in two decades of Slashdot. Concrete is so ubiquitous that maintenance and GHG emissions are tremendously significant.
I'm guessing you aren't very familiar with construction techniques. Concrete is compacted using vibration because air pockets make concrete weak and causes cracking.
That is substantially different than the type of compaction they are taking about for this material. In common concrete compaction isn't strictly necessary, it is just a means of reducing entrained air, and in some mixes it is actually discouraged since you are attempting to retain air. Also in normal pours over compaction will actually segregate the particles making up the concrete and weaken it. The compaction they are talking about here seems to be required over the entire surface, and is necessary to cure the product. It could be useful for precast applications but wouldn't be useful for form and pour, or future 3D printing applications.
There are many kinds of cement, so don't assume that Portland Cement is the only kind out there. It's just the most common. We've been making concrete for thousands of years. I believe some Roman concrete was designed such that it gained strength in water over time instead of breaking down (I don't remember the details).
One issue with modern concrete is that adding steel increases the strength, but it also causes stress during temperature changes.
I believe there's lots of room for improvement in concrete, and I'm under the impression that it's an area of research that is still wide open. I would expect the concrete we use in construction in ten or twenty years will be significantly better than what we use today.
I can repaint it in any color I like once it cures, and I rarely choose green anyway. Green concrete looks nothing like the real green stuff, ecotards.
Wouldn't it be easier to toss green pigment into the mixer to make concrete greener?
I hope they're not creating another micro-something that will leach into water, animals, and eventually, us.
- The Kessel run is for nerf herders. I can circumnavigate the entire Central Finite Curve in a lot less than 12 parse
That's not compacting. That just makes the air bubbles rise to the top. TFS makes it seem like it needs to be actively compressed during curing to create the desired effects. Now that may be able to be done with post-tension cables like you would see in high rise towers. If not GP seems to be correct from the details I gathered in TFS.
Disclaimer: I am an electrician but have done a fair share of concrete work... And it sucks balls.
The paper is pay-walled and the other link was short on detail if they mean compaction (like used in concrete since they intend it to be used as such) and not compression then it's a non-issue otherwise it would be more like asphalt.
What Insurance company would want to underwrite this on a major project?
You would never build a Hoover Dam with this stuff.
Didn't the Romans use small vessels in the concrete of the Pantheon roof? Looked for a url but could not find one right away. In the case of the Pantheon roof, I thought that the small voids and the coffers used made the roof lighter.
;)
Just my 2 cents
I am pretty sure inhaling these spheres can kill you too.
Yeah but so can inhaling water so it's not a great measure.
Wanna buy a shirt?
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I'm guessing you aren't very familiar with construction techniques. Concrete is compacted using vibration because air pockets make concrete weak and causes cracking.
I'm guessing you aren't very familiar with construction techniques. Concrete is almost never compacted using vibration, because you actually want air bubbles in it in most applications. It's also very easy to over-vibrate the concrete, causing the aggregate and cement to separate (the rocks sink, the cement rises).
There are some situations where you want to compact cement, but cement is not concrete.
See, those building physics simulations using spherical cows where right after all. Cue up the Beach Boys', "I get around".
Table-ized A.I.
I'm guessing you made a false assumption further up the thread in trying to appear more knowledgeable than I am re: construction techniques. As Headw1nd & others have already stated, vibration isn't used to compress concrete generally, it's used to help air bubbles in the concrete flow to the surface to avoid voids. The vibration does little in regards to concrete curing as for concrete this is a chemical process.
Compare that to the material in TFA which needs to be physically compacted to cure -- which is quite clearly is the method used to form the pellets from the source materiel in the article.
Headw1nd, I & others were able to understand this essential difference. You appear to still have doubts.
Democracy is a sheep and two wolves deciding what to have for lunch. Freedom is a well armed sheep contesting the issue
Is it better than Hempcrete?
For millennia, we made concrete using the shells of creatures, and since those shells are literally carbon negative, storing carbon from the sea, they resulted in a far greener concrete.
Especially when grown amongst sea beds of kelp or sea grass or seaweed.
You can see it everywhere in ancient ruins that lasted thousands of years.
-- Tigger warning: This post may contain tiggers! --
Why not come up with something with similar properties that has a high carbon content, preferably extracted from the air?
The spheres can be prompted to self-assemble into solids that are stronger, harder, more elastic and more durable than ubiquitous Portland cement
Note that cost is not listed among the advantages here which is usually a sign that it is substantially more expensive. We use portland cement because it is CHEAP and generally works well. There are sometimes better performing materials available but seldom ones that have better price to performance ratios.
Not to be picky, but the definition of compaction in civil engineering is generally "taking the air out"... but officially concrete is consolidated, not compacted.
Then maybe somebody should read TFA and clarify for us whether they are referring to vibrating or actual compression. I am going to guess they mean actually compressing as they were talking about forming it into pellets. Then again I could be 100% incorrect.
Since you are an electrician, what do you think about the low conductivity this new material is supposed to have. Normally concrete is considered (for workspace clearance) as grounded.
227-3517
That actually concerns me because I immediately thought of the UFER we put in the slab to make sure you have a good earth connection. Very good question and if this material gets adopted widely it is going to force a change in the NEC grounding and bonding section and will most likely raise the price of any electrical service installation.
I guess only time can tell what happens with this material. It does sound interesting to say the least and if it's stronger and better for the planet I'm all for it.