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The micron-scale micron-sized calcium silicate spheres developed at Rice University are a promising material that could lead to a stronger, more environmentally friendly concrete. Credit: Multiscale Materials Laboratory / Rice University
Scientists at Rice University have developed micrometric sized calcium silicate spheres that could lead to stronger, greener concrete, the most widely used synthetic material in the world.
Rice Materials Specialist Rouzbeh Shahsavari and graduate student Sung Hoon Hwang represent low-cost building blocks and promise to mitigate the energy-intensive techniques currently used to make cement, the most popular binder running in the concrete.
The researchers formed the spheres in a seed solution at the nanoscale of a common detergent type surfactant. Spheres can be encouraged to self-assemble into stronger, tougher, more resilient and more durable solids than ubiquitous Portland cement.
"The cement does not have the most pleasant structure," said Shahsavari, an assistant professor of materials science and nanoengineering. "The cement particles are amorphous and disorganized, making them a little vulnerable to cracking, but with this material we know our limits and we can channel polymers or other materials between spheres to control the structure of the material. bottom up and predict more precisely how he might fracture. "
He said the spheres are suitable for bone tissue engineering, insulation, ceramics and composite applications, as well as cement.
The research appears in the journal American Chemical Society Langmuir.
The work builds on a 2017 project led by Shahsavari and Hwang to develop self-healing materials with porous and microscopic calcium silicate spheres. The new material is not porous because a solid calcium silicate shell surrounds the surfactant seed.
The calcium silicate spheres synthesized at Rice University and packaged in a pellet are held together under compression. Spheres are building blocks that can be manufactured at low cost and promise to mitigate the energy-intensive techniques currently used to make cement, the most common binder in concrete. Credit: Multiscale Materials Laboratory / Rice University
But like the previous project, it is inspired by the way in which nature coordinates the interfaces between dissimilar materials, in particular mother-of-pearl (aka mother-of-pearl), material of the shells. The mother-of-pearl strength is the result of the alternation of inorganic organic platelets and soft and rigid. Because the spheres mimic this structure, they are considered as biomimetic.
The researchers found that they could control the size of spheres with a diameter of 100 to 500 nanometers by manipulating surfactants, solutions, concentrations and temperatures during manufacture. This allows them to be on the lookout for apps, Shahsavari said.
"These are very simple but universal building blocks, two essential features of many biomaterials," Shahsavari said. "They provide advanced features in synthetic materials, but there were earlier attempts to manufacture platelet or fibrous building blocks for composites, but this work uses spheres to create strong, resilient, and adaptable biomimetic materials.
"Spherical shapes are important because they are much easier to synthesize, assemble and evolve from the point of view of chemistry and large-scale manufacturing."
In the tests, the researchers used two common surfactants to make spheres and compress their products into pellets for testing. They learned that DTAB-based pellets compacted better and were more resilient, with a higher modulus of elasticity, than CTAB pellets or common cement. They also showed a high electrical resistance.
Shahsavari said particle size and shape in general have a significant effect on the mechanical properties and durability of bulk materials such as concrete. "It is very beneficial to have something you can control as opposed to material that is random in nature," he said. "In addition, spheres of different diameters can be blended to fill gaps between self-assembled structures, resulting in higher packing densities and thus mechanical and durability properties."
He said that increasing the strength of cement allowed manufacturers to use less concrete, reducing not only the weight, but also the energy needed to manufacture it and the associated carbon emissions in the manufacture of cement. Since the spheres condition more efficiently than the shredded particles present in the common cement, the resulting material will be more resistant to harmful ions of water and other contaminants and should require less maintenance. and a less frequent replacement.
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More information:
Rouzbeh Shahsavari et al, Synthesis controlled by size and shape of calcium silicate particles allowing self-assembly properties and improvement of mechanics and durability, Langmuir (2018). DOI: 10.1021 / acs.langmuir.8b00917
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