Concrete Products

AUG 2013

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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NEWS SCOPE ancient Roman Al-tobermorite doublelayer silicate structure likely provides cavities for Na+ and K+ cations derived from the alkali-rich volcanic ash and seawater-saturated lime. This contributes to charge balancing and stability in the maritime environment, which is important for long-term durability. However, the large interlayer spacing also increases compressibility relative to ideal tobermorite with 11.3 Å spacing. "Even so, this study shows that Al-tobermorite has increased mechanical performance relative to poorly-crystalline C-A-S-H. Romans were able to produce massive seawater concrete structures with Al-tobermorite as the principal crys- talline cementitious product. If we could translate Roman expertise to modern concrete structures, then we could conceivably improve the mechanical and material properties of pozzolanic concretes." The research began with funding from King Abdullah University of Science and Technology (KAUST) in Saudi Arabia, which has an abundance of potentially concretegrade volcanic ash. In addition to the Berkeley Lab's ALS, researchers deployed Berlin Electron Storage Ring Society for Synchrotron Radiation in their analyses. Jackson adds that the release of the Roman concrete investigation findings has spurred other proposals for using ancient Roman principles in innovative cement or concrete research. "We have received numerous messages from folks actively involved in developing products, especially block concrete, in aluminous pozzolanic systems, some of which are autoclaved to produce Al-tobermorite," she says. "We are in the first stages of discussing our research results regarding C-A-S-H and Altobermorite with some of these people, to explore how we can apply Roman principles of concrete construction with volcanic pozzolans to specialty concrete products." Other possible avenues opened up by these findings include the study of natural pozzolan from different parts of the world and the utilization of waste products to produce green concrete. BRIGHT IDEAS IN X-RAY SPECTROMICROSCOPY RESEARCH AT ADVANCED LIGHT SOURCE The Advanced Light Source (ALS) is a third-generation synchrotron, a specialized particle accelerator that generates bright beams of x-rays for scientific research. It is located in a building originally designed in the 1930s by Arthur Brown, Jr.—architect of the Coit Tower in San Francisco—to house Ernest O. Lawrence's 184-in. cyclotron. In 1987, a $99.5 million construction project, funded by the U.S. Department of Energy's Office of Basic Energy Sciences, began to reconfigure the building to accommodate the ALS accelerator and beamlines. Completed in 1993, the ALS is a national user facility that now attracts more than 2,000 researchers and students annually from around the world. Electron bunches traveling nearly the speed of light, when forced into a circular path by magnets, emit bright ultraviolet and x-ray light that is directed down beamlines to experiment end stations. The ALS produces light in the x-ray region of the electromagnetic spectrum that is 1 billion times brighter than the sun. This extraordinary tool offers opportunities for state-of-the-art research in biology, chemistry, physics, and materials, energy, and environmental sciences. Ongoing research includes semiconductors, polymers, superconductors, magnetic materials, biological macromolecules (proteins, etc.), 3-D biological imaging, chemical reaction dynamics, and atomic and molecular structure. UC Berkeley Civil and Environmental Engineering Research Engineer Marie Jackson explains the differences between ALS's processes and more tradi- WWW.CONCRETEPRODUCTS.COM tional microscopy practices: "In petrographic microscopy, a digital camera photographs an image through a traditional polarized light microscope; in scanning electron microscopy with energy dispersive spectroscopy compositional analyses, a focused beam of electrons scans a sample and produces a high-resolution image with information about the morphology at the micron scale and qualitative chemical analysis, mainly as major elements in atomic percent or in weight percent oxides; and in synchroton radiation applications, electromagnetic radiation emitted by high-energy particles accelerated to relativistic speeds in a magnetic field are focused on a sample to determine diverse aspects of its material characteristics at the nanoscale. "The Scanning Transmission X-ray Microscopy analyses performed at ALS beamlines 5.3.1 and 5.3.2 (described in the American Mineralogist article) investigate the very fine scale bonding environments of aluminum and silicon (also carbon and calcium) in poorlycrystalline C-A-S-H and crystalline Altobermorite in relict lime clasts. The high-pressure X-ray diffraction analyses performed at ALS beamline 12.2.2 (discussed in the Journal of the American Ceramic Society article) describe mineral structure of the Al-tobermorite in a relict lime clast and its mechanical properties, computed as bulk modulus. The micro X-ray diffraction analyses performed at ALS beamline 12.2.2 (also described in the Journal of the American Ceramic Society article) show the min- eral structure of Al-tobermorite and phillipsite in the cementitious matrix of the ancient seawater mortar." X-ray spectromicroscopy also can study the hydration process in-situ (under water). This unique feature permits researchers to characterize complex reactions with very high spatial resolution (~20 nm). Together with ALS scientists, the Berkeley team is exploring the use of diffraction imaging, which can revolutionize the understanding of the early-age reactions. Advanced Light Source Beamline 12.2.2 end station is equipped with diamond anvil cells to test tiny amounts of materials under tremendous pressures. UC Berkeley staff has deployed the ALS in research on the crystal structure of cement. AUGUST 2013 | 15

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