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!
Scientists channel graphene to understand filtration and ion transport into cells
11.12.2017 | National Institute of Standards and Technology (NIST)
Successful Mechanical Testing of Nanowires
07.12.2017 | Helmholtz-Zentrum Geesthacht - Zentrum für Material- und Küstenforschung
Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.
To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...
The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.
Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...
With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong
Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...
An interdisciplinary group of researchers interfaced individual bacteria with a computer to build a hybrid bio-digital circuit - Study published in Nature Communications
Scientists at the Institute of Science and Technology Austria (IST Austria) have managed to control the behavior of individual bacteria by connecting them to a...
Physicists in the Laboratory for Attosecond Physics (run jointly by LMU Munich and the Max Planck Institute for Quantum Optics) have developed an attosecond electron microscope that allows them to visualize the dispersion of light in time and space, and observe the motions of electrons in atoms.
The most basic of all physical interactions in nature is that between light and matter. This interaction takes place in attosecond times (i.e. billionths of a...
11.12.2017 | Event News
08.12.2017 | Event News
07.12.2017 | Event News
11.12.2017 | Physics and Astronomy
11.12.2017 | Earth Sciences
11.12.2017 | Information Technology