Their refinements to our understanding of how cement and concrete actually work, reported this week in Nature Materials,* ultimately may make possible improvements in the formulation and use of cement that could save hundreds of millions of dollars in annual maintenance and repair costs for concrete structures and the country’s infrastructure.
Cement may be the world’s most widely used manufactured material—more than 11 billion metric tons are consumed each year—but it also is one of the more complex. And while it was known to the Romans, who used it to good effect in the Colosseum and Pantheon, questions still remain as to just how it works, in particular how it is structured at the nano- and microscale, and how this structure affects its performance.
Cement is something of a paradox. It requires just the right amount of water to form properly—technically it’s held together by a gel, a complex network of nanoparticles called calcium silicate hydrate (C-S-H) that binds a significant amount of water within its structure. But once the cement has set, the C-S-H structure retains a tough, unchanging integrity for centuries, even in contact with water. To date, attempts to pinpoint the amounts and different roles of water within the C-S-H in cement paste have required taking the water out, either by drying or chemical methods. The NIST/Northwestern researchers instead combined structural data from small-angle neutron scattering experiments at the NIST Center for Neutron Research and from an ultrasmall-angle X-ray scattering instrument built by NIST at the Advanced Photon Source at Argonne National Laboratory. Their experiments are the first to classify water by its location in the cured cement.
As a result, the researchers were able to distinguish—and measure—the difference between water physically bound within the internal structure of the solid C-S-H nanoparticles and adsorbed or liquid water between the nanoparticles. They also measured a nanoscale calcium hydroxide structure that co-exists with the C-S-H gel. The new data, which imply significantly different values for the formula and density of the C-S-H gel than previously supposed, have implications for defining the chemically active surface area within cement, and for predicting concrete properties. They also may lead to a better understanding of the contribution of the nanoscale structure of cement to its durability, and how to improve it.
Michael Baum | EurekAlert!
Novel sensors could enable smarter textiles
17.08.2018 | University of Delaware
Quantum material is promising 'ion conductor' for research, new technologies
17.08.2018 | Purdue University
New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference
Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...
Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...
Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.
When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...
Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.
Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....
Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.
Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...
17.08.2018 | Event News
08.08.2018 | Event News
27.07.2018 | Event News
17.08.2018 | Physics and Astronomy
17.08.2018 | Information Technology
17.08.2018 | Life Sciences