Rice University scientists develop 'programmable' cement particles to attain enhanced properties
Bringing order to disorder is key to making stronger and greener cement, the paste that binds concrete.
Rice University materials scientists have mapped the morphogenesis of cement hydrates used in concrete. It could lead to a way to 'program' cement particles for the manufacture of stronger, more durable and more environmentally friendly concrete.
Credit: Multiscale Materials Laboratory/Rice University
Scientists at Rice University have decoded the kinetic properties of cement and developed a way to "program" the microscopic, semicrystalline particles within. The process turns particles from disordered clumps into regimented cubes, spheres and other forms that combine to make the material less porous and more durable.
Their study appears in the Royal Society of Chemistry's Journal of Materials Chemistry A.
The technique may lead to stronger structures that require less concrete -- and less is better, said Rice materials scientist and lead author Rouzbeh Shahsavari. Worldwide production of more than 3 billion tons of concrete a year now emits as much as 10 percent of the carbon dioxide, a greenhouse gas, released to the atmosphere.
Through extensive experiments, Shahsavari and his colleagues decoded the nanoscale reactions -- or "morphogenesis" -- of the crystallization within calcium-silicate hydrate (C-S-H) cement that holds concrete together.
For the first time, they synthesized C-S-H particles in a variety of shapes, including cubes, rectangular prisms, dendrites, core-shells and rhombohedra and mapped them into a unified morphology diagram for manufacturers and builders who wish to engineer concrete from the bottom up.
"We call it programmable cement," he said. "The great advance of this work is that it's the first step in controlling the kinetics of cement to get desired shapes. We show how one can control the morphology and size of the basic building blocks of C-S-H so that they can self-assemble into microstructures with far greater packing density compared with conventional amorphous C-S-H microstructures."
He said the idea is akin to the self-assembly of metallic crystals and polymers. "It's a hot area, and researchers are taking advantage of it," Shahsavari said. "But when it comes to cement and concrete, it is extremely difficult to control their bottom-up assembly. Our work provides the first recipe for such advanced synthesis.
"The seed particles form first, automatically, in our reactions, and then they dominate the process as the rest of the material forms around them," he said. "That's the beauty of it. It's in situ, seed-mediated growth and does not require external addition of seed particles, as commonly done in the industry to promote crystallization and growth."
Previous techniques to create ordered crystals in C-S-H required high temperatures or pressures, prolonged reaction times and the use of organic precursors, but none were efficient or environmentally benign, Shahsavari said.
The Rice lab created well-shaped cubes and rectangles by adding small amounts of positive or negative ionic surfactants and calcium silicate to C-S-H and exposing the mix to carbon dioxide and ultrasonic sound. The crystal seeds took shape around surfactant micelles within 25 minutes. Decreasing the calcium silicate yielded more spherical particles and smaller cubes, while increasing it formed clumped spheres and interlocking cubes.
Once the calcite "seeds" form, they trigger the molecules around them to self-assemble into cubes, spheres and other shapes that are orders of magnitude larger. These can pack more tightly together in concrete than amorphous particles, Shahsavari said. Carefully modulating the precursor concentration, temperature and duration of the reaction varies the yield, size and morphology of the final particles.
The discovery is an important step in concrete research, he said. It builds upon his work as part of the Massachusetts Institute of Technology team that decoded cement's molecular "DNA" in 2009. "There is currently no control over C-S-H shape," Shahsavari said. "The concrete used today is an amorphous colloid with significant porosity that entails reduced strength and durability."
Concrete is one focus of Shahsavari's Rice lab, which has studied both its macroscale manufacture and intrinsic nanoscale properties. Because concrete is the world's most common construction material and a significant source of atmospheric carbon dioxide, he is convinced of the importance of developing "greener" concrete.
The new technique has several environmental benefits, Shahsavari said. "One is that you need less of it (the concrete) because it is stronger. This stems from better packing of the cubic particles, which leads to stronger microstructures. The other is that it will be more durable. Less porosity makes it harder for unwanted chemicals to find a path through the concrete, so it does a better job of protecting steel reinforcement inside."
The research required the team to develop a method to test microscopic concrete particles for strength. The researchers used a diamond-tipped nanoindenter to crush single cement particles with a flat edge.
They programmed the indenter to move from one nanoparticle to the next and crush it and gathered mechanical data on hundreds of particles of various shapes in one run. "Other research groups have tested bulk cement and concrete, but no group had ever probed the mechanics of single C-S-H particles and the effect of shape on mechanics of individual particles," Shahsavari said.
He said strategies developed during the project could have implications for other applications, including bone tissue engineering, drug delivery and refractory materials, and could impact such other complex systems as ceramics and colloids.
Rice postdoctoral researcher Sakineh Moghadda is lead author of the paper. Co-authors are Rice graduate students Sung Hoon Hwang and Shuo Zhao, postdoctoral researcher Sreeprasad Srinavasan, undergraduate Benhang Shi and Kenton Whitmire, a professor of chemistry; visiting scientists Vahid Hejazi and Joseph Miller of C-Crete Technologies in Houston; Aali Alizadeh of C-Crete Technologies and Irene Rusakova, a senior research scientist at the University of Houston.
The National Science Foundation and the Department of Energy supported the research.
Read the abstract at http://pubs.
This news release can be found online at http://news.
Follow Rice News and Media Relations via Twitter @RiceUNews
Multiscale Materials Laboratory home page: http://rouzbeh.
George R. Brown School of Engineering: http://engineering.
Rice Department of Civil and Environmental Engineering: http://www.
Rice Department of Materials Science and NanoEngineering: https:/
Images for download:
Rice University scientists created microscopic cubes and other shapes of cement and crushed them to test their mechanical properties. The shapes may serve as "seeds" for the bottom-up manufacture of stronger, more durable concrete. (Credit: Multiscale Materials Laboratory/Rice University)
An isolated cement cube created by the lab of Rice materials scientist Rouzbeh Shahsavari. Microscopic cubes and other shapes may serve as "seeds" in programmable cement for stronger, less porous and more environmentally friendly concrete. (Credit: Multiscale Materials Laboratory/Rice University)
Rice University materials scientists have mapped the morphogenesis of cement hydrates used in concrete. Their work could lead to finer control of the microscopic shape of cement particles for the manufacture of stronger, more durable and more environmentally friendly concrete. (Credit: Multiscale Materials Laboratory/Rice University)
Rice University materials scientists have mapped the morphogenesis of cement hydrates used in concrete. It could lead to a way to "program" cement particles for the manufacture of stronger, more durable and more environmentally friendly concrete. (Credit: Multiscale Materials Laboratory/Rice University)
Rouzbeh Shahsavari (Credit: Jeff Fitlow/Rice University)
Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,910 undergraduates and 2,809 graduate students, Rice's undergraduate student-to-faculty ratio is 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for happiest students and for lots of race/class interaction by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger's Personal Finance. To read "What they're saying about Rice," go to http://tinyurl.
David Ruth | EurekAlert!
The stacked colour sensor
16.11.2017 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt
Counterfeits and product piracy can be prevented by security features, such as printed 3-D microstructures
16.11.2017 | Karlsruher Institut für Technologie (KIT)
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.
Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...
Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
17.11.2017 | Physics and Astronomy
17.11.2017 | Health and Medicine
17.11.2017 | Studies and Analyses