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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.
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.