Concrete Products

FEB 2017

Concrete Products covers the issues that attract producers of ready mixed and manufactured concrete focusing on equipment and material technology, market development and management topics.

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Page 74 of 95 February 2017 • 73 TECHNICAL TALK RICE UNIVERSITY Once the calcite "seeds" form, they trig- ger the molecules around them to self-assem- ble into cubes, spheres and other shapes that are orders of magnitude larger. These can pack more tightly together in concrete than amorphous particles. 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, building upon work of the Massachusetts Institute of Technology team that decoded cement's molecular "DNA" in 2009, Shahsavari affirms. "There is currently no control over C-S-H shape," he adds. "The concrete used today is an amorphous colloid with significant porosity that entails reduced strength and durability." Concrete is one focus of the Rice lab, which has studied both its macroscale man- ufacture and intrinsic nanoscale properties. Because concrete is the world's most common construction material and a source of atmo- spheric carbon dioxide, university staff are convinced of the importance of developing a "greener" matrix. The new technique has several environ- mental benefits, says Shahsavari: "One is that you need less of it (the concrete) because it is stronger. This stems from better pack- ing 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 bet- ter job of protecting steel reinforcement inside." The research required the team to develop a method to test microscopic concrete particles for strength. Research- ers used a diamond-tipped nanoindenter to crush single cement particles with a flat edge. They programmed the indent- er to move from one nanoparticle to the next and crush it and gathered mechani- cal data on hundreds of particles of vari- ous shapes in one run. "Other research groups have tested bulk cement and concrete, but [none] had ever probed the mechanics of single C-S-H parti- cles and the effect of shape on mechanics of individual particles," says Shahsavari. Strat- egies developed during the project could have implications for other applications, he adds, including bone tissue engineering, drug delivery and refractory materials, and could impact such other complex systems as ceramics and colloids. Joining Rouzbeh Shahsavari on the research team and as Journal of Materials Chemistry paper co-authors are Professor of Chemisty Ken- ton Whitmire; Rice postdoctoral researcher Saki- neh Moghadda; graduate students Sung Hoon Hwang and Shuo Zhao; postdoctoral researcher Sreeprasad Srinavasan; undergraduate Benhang Shi; Aali Alizadeh, Vahid Hejazi and Joseph Mill- er of C-Crete Technologies in Houston; and, Irene Rusakova, a senior research scientist at the University of Houston. Rice University materials scientists have mapped the morphogenesis of cement hy- drates used in concrete. Their work could lead to finer control of the microscopic shape of cement particles for the manufac- ture of stronger, more durable concrete. ILLUSTRATION: Rice University Multiscale Materials Laboratory HORIZONTAL SHAFT TWIN SHAFT PLANETARY TURBIN GREAT PRODUCTS START WITH GREAT EQUIPMENT. Your mixer is the heart of your operations. That's why Mixer Systems offers four types of Mixers – Turbin, Horizontal Shaft, Planetary and Twin Shaft. With this lineup, we can perfectly match your requirements for capacity, speed and economy. Contact us to find the right mixer for your business. Concrete equipment. Concrete solutions. PO Box 10, 190 Simmons Avenue, Pewaukee, WI 53072-0010 262-691-3100 Visit us at the Precast Show Booth #919

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