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Spheres Can Make Concrete Leaner, Greener (phys.org)

Posted by BeauHD on from the well-rounded dept.

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.

11 of 98 comments (clear)

  1. cement is amazing by pz · · Score: 4, 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!

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    1. Re:cement is amazing by Ol+Olsoc · · 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...

      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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    2. Re:cement is amazing by angel'o'sphere · · Score: 3, 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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    3. Re:cement is amazing by Anonymous Coward · · Score: 2, 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!

      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

  2. this is huge by Anonymous Coward · · 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.

    1. Re:this is huge by CrimsonAvenger · · Score: 2
      MIllion dollar question: how much does this cost compared to normal concrete?

      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 foresee a bright future for the stuff. Otherwise, it'll be yet another minor factor in building a variety of special-purpose stuff....

      --

      "I do not agree with what you say, but I will defend to the death your right to say it"
    2. Re:this is huge by ShanghaiBill · · Score: 3, 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).

  3. Re:Major difference, Cement doesn't need compactin by pr0fessor · · Score: 4, 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.

  4. Lots' of Cement Options by crow · · Score: 4, 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.

    1. Re:Lots' of Cement Options by marquis111 · · Score: 3, Interesting

      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.

  5. Re:What if we inhale or eat this? by stealth_finger · · Score: 2

    I am pretty sure inhaling these spheres can kill you too.

    Yeah but so can inhaling water so it's not a great measure.

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