Spheres Can Make Concrete Leaner, Greener (phys.org) 98
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.
Why do I care if the damned thing is greener? (Score:2)
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.
cement is amazing (Score:5, Interesting)
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!
Re:cement is amazing (Score:5, Interesting)
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!
Yes, concrete is a fascinating substance. They've figured out what makes Roman opus caementicium concrete so strong http://www.sciencemag.org/news... [sciencemag.org]
The secret was aluminum tobermorite, which is what was formed in situ by seawater dissolving the volcanic ash and forming the tobermorite, was what did the trick. Being a silicate also, these might just be sharing the same mechanism in this modern version of concrete?
Anyhow, a fun bit of research for a Thursday morning.
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Yup, that fancy Roman concrete was badass because the environment (sea water) caused the concrete to chemically react advantageously, adding to its strength and longevity.
We ought to follow in those shoes, creating structures that react likewise.
Considering the longevity of such things, it makes sense to make them large and pretty, which, to me at least, would make our cities/landscapes easier on the eyes than the econo-throwaway crap that seems so ubiquitous.
Re:cement is amazing (Score:4, Interesting)
If you talk about "material science" then it is extremely important to note: concrete != cement!!!
There is a small faction of sailors who build yachts with cement hulls. Seems to be tricky, but it is considered more robust than aluminium hulls (because of corrosion).
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That's only true in the US, or actual pavement engineering. In the rest of the English speaking world the binder is called bitumen and the product asphalt. Asphalt "Concrete" is also a bit of a misnomer in the engineering sense, because it is really in a different class of materials to lime/pozzolanic concretes.
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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!
1) air bubbles in the concrete is intentional - it provides frost protection in cold climates. Without air entrainment, concrete cracks very easily. sidewalk and other concrete exposed to frost conditions usually contain around 7% air
2) jagged aggregate provides more contact area between aggregates (sand & stone) and the cement particles.
3) I believe they are talking just about making the cement particles spherical in order to increase the packing in between the aggregate
Re: cement is amazing (Score:2)
You can get cement slabs cured in nitrogen atmosphere for high water table areas , they make great leak free basement walls
need coffee (Score:2)
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!"
Major difference, Cement doesn't need compacting (Score:2)
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.
Re:Major difference, Cement doesn't need compactin (Score:5, Informative)
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.
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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.
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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
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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.
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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.
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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.
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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.
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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.
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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.
this is huge (Score:2, Informative)
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.
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It lasts longer, so you can justify a higher cost on that basis alone. Plus it's stronger, which may mean you need thinner sheets of concrete made this way for a given strength.
But three times the lifespan times twice the strength (numbers pulled out of my ass) means it'll sell if it costs no more than six times as much as conventional concrete.
So, does this stuff meet the test of being more economically efficient? If so, I f
Re:this is huge (Score:4, Informative)
But three times the lifespan times twice the strength (numbers pulled out of my ass) means it'll sell if it costs no more than six times as much as conventional concrete.
You are not considering secondary effects. Let's say you are constructing a building. If it is twice as strong, you need half as much for the same strength. But if you need half as much on the upper floors, then you need less concrete on the lower floors to support the weight ... so you end up using much less than half as much. The reduced weight will also bring savings on the steel rebar and steel frame ... but maybe more cost for wind vibration damping.
There are also secondary effects of the longer life. If you are building a bridge, and the concrete is 50% of the cost, then a 3x lifetime increase saves you 6x not 3x (assuming concrete is the critical path item for longevity).
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I am pretty sure inhaling these spheres can kill you too.
Yeah but so can inhaling water so it's not a great measure.
Lots' of Cement Options (Score:5, Interesting)
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.
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Based on my recollection, the Romans found that mixing a certain kind of volcanic ash, which IIRC had aluminum silicates in it, into the cement caused it become what is called hydraulic cement, or cement that hardens in water.
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If rust were an issue before the steel became exposed, then they would use galvanized steel to reduce the problem. A quick search indicates that galvanized rebar is often used. Concrete is porous, so water and oxygen can permeate it to reach the steel.
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Modern rebar is frequently coated to help avoid corrosion, but the best defense is generally depth - keeping rebar away from the surface. Once the rebar begins to corrode, rust jacking will introduce additiona
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True. I'm just under the impression that we're still learning a lot about concrete, so the best concrete for a given job will likely be better in a decade than what is considered best now. But I'm just a non-expert making suppositions, so who knows?
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One issue with modern concrete is that adding steel increases the strength, but it also causes stress during temperature changes.
Actually one of the reasons steel reinforced concrete works so well is that steel and concrete have very similar thermal expansion coefficients and thus aren't subject to a lot of stress from temperature changes. I would love to see a citation for your temperature induced stress issue.
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I was repeating what I've heard. It appears that I heard wrong. Thanks for enlightening me.
Colored Concrete... (Score:2, Troll)
Is this like micro-plastics? (Score:2)
I hope they're not creating another micro-something that will leach into water, animals, and eventually, us.
Insurance (Score:2)
What Insurance company would want to underwrite this on a major project?
You would never build a Hoover Dam with this stuff.
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You would never build a Hoover Dam with this stuff.
No, because the point of the concrete in Hoover Dam isn't the strength, it's the weight.
The strength comes from the shape and the bedrock. Granted, a good amount of strength does come from the concrete itself, but weight is the primary driver. The natural strength of the arch directs the forces into the cliffsides.
Now Grand Coulee Dam, on the other hand, is just a giant slab. Weight is even more significant for Grand Coulee.
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A common misconception, but even Hoover Dam works on just weight alone. It is arch shaped, but it is more for aesthetics as it's not required to hold back the water. A straight dam the same weight as Hoover Dam would work just as well.
Is this a variation of an old idea? (Score:2)
Just my 2 cents
Say mooo, you spherical cows (Score:2)
See, those building physics simulations using spherical cows where right after all. Cue up the Beach Boys', "I get around".
Hempcrete (Score:1)
Or we could just use sea shells (Score:2)
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.
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Second, common [cement.org] ingredients used in production of portland cement include limestone, shells, chalk, clay, etc. (though I'm guessing shells are not that common)
Third, the process of turning shells into portland cement includes using heat to disassociate and drive off water and carbon dioxide, so still not very green from an AGW point of view. (Though some carbon dioxide will be re-absorbed as the cement ages.)
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Heat is a waste byproduct of many green energy methods - biofuel, nuclear fission, ethanol conversion, industrial and commercial manufacturing - in fact, one of the reasons we're "upset" at China is they converted their highly polluting inefficient coal plants to modern (circa 1980s) coal plants with water scrubbers and heat cogeneration.
Recapture of the water and CO2 is an important thing to do, however.
Why not carbon? (Score:2)
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Is it cheap? (Score:2)
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.