Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The First Seconds in a Building’s Life

20.04.2012
X-ray diffraction studies of cement hydration on the millisecond scale

No matter if it is a giant complex, a high-rise, or an underground project, modern architecture cannot get along without concrete. The component in concrete that holds the other components together is cement.

In order to control the properties of concrete, it is important to know what occurs as it hardens. German scientists have now successfully watched the first few seconds in the “life” of cement by means of X-ray diffraction. In the journal Angewandte Chemie, they explain the role of the superplasticizers added to concrete.

Concrete is made from sand, gravel, additives, water, and cement. Portland cement is a complex mixture of finely ground limestone, clay, sand, and iron ore—mainly calcium silicate with fractions of aluminum and iron compounds and sulfates. Once mixed with water, chemical reactions occur between the components of cement, and it solidifies and hardens. When the process is finished, it remains solid and stable, even under water.

The enormous stability of concrete comes from crystalline needles that form during this process and are firmly interlocked with each other. Various additives are used to optimize the properties of concrete, including a class of superplasticizers based on polycarboxylate (PCE). These improve the flow of the concrete, making it easier to pour. The water content can be reduced to improve the concrete’s compressive strength.

“Detailed insight into the different stages of the hydration process is essential for a more complete understanding of how these processes can be effectively influenced,” explains Franziska Emmerling of the BAM Federal Institute of Materials Research and Testing in Berlin (Germany). “In particular, the phase development at the beginning of hydration is not yet well understood.” The very rapidly initiated reaction of the cement clinker component C3A (Ca3Al2O6) with sulfate (SO42-) to form ettringite (Ca6Al2(SO4)3(OH)12•26H2O) seems to be critical. By means of high-resolution X-ray diffraction experiments, Emmerling’s team has now been able to follow this reaction on the millisecond timescale. The deflections experienced by X-rays as they pass through a material provide information about its crystal structure. In order to prevent interference from any supporting material, the sample is held in suspension by acoustic waves.

This has also made it possible to clarify the function of PCE superplasticizers. Says Emmerling: “Immediately after water contacts the cement, the PCE adsorbs onto the surface of the clinker C3A; the particles remain in suspension because they then repel each other. The PCE is then gradually replaced by sulfate ions, which retards the incipient ettringite crystallization. This leaves more free water in the system, dissolving more crystalline components—the resulting concrete can thus flow for a longer period and becomes more dense.”

About the Author
Dr. Franziska Emmerling leads the department of Structure Analysis at the Federal Institute for Materials Research and Testing (BAM) in Berlin. Her main research areas include the in-situ analysis of different material systems using synchrotron radiation. Besides that, she lectures since two year at the Humboldt University in Berlin in the field of anorganic and solid state chemistry.
Author: Franziska Emmerling, BAM Federal Institute of Materials Research and Testing, Berlin (Germany), http://www.bam.de/de/kompetenzen/fachabteilungen/abteilung_1/fg13/fg13_ag1.htm
Title: First Seconds in a Building’s Life—In Situ Synchrotron X-Ray Diffraction Study of Cement Hydration on the Millisecond Timescale

Angewandte Chemie International Edition, Permalink to the article: http://dx.doi.org/10.1002/anie.201200993

Franziska Emmerling | Angewandte Chemie
Further information:
http://pressroom.angewandte.org

More articles from Materials Sciences:

nachricht Researchers invent process to make sustainable rubber, plastics
25.04.2017 | University of Delaware

nachricht Nanoimprinted hyperlens array: Paving the way for practical super-resolution imaging
24.04.2017 | Pohang University of Science & Technology (POSTECH)

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

NASA's Fermi catches gamma-ray flashes from tropical storms

25.04.2017 | Physics and Astronomy

Researchers invent process to make sustainable rubber, plastics

25.04.2017 | Materials Sciences

Transfecting cells gently – the LZH presents a GNOME prototype at the Labvolution 2017

25.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>