Structure of 'Concrete Disease' Solved

Previously undocumented sheet-silicate crystal structure

Date: November 5, 2015
Source: Swiss Federal Laboratories for Materials Science and Technology (EMPA)
Summary: When bridges, dam walls and other structures made of concrete are streaked with dark cracks after a few decades, the culprit is AAR: the alkali-aggregate reaction. AAR damages concrete structures all over the world and makes complex renovations or reconstructions necessary. Researchers have now solved the structure of the material produced in the course of AAR at atomic Level.


Researchers from the Paul Scherrer Institute (PSI) teamed up with colleagues from the Swiss Materials Science Lab Empa to study a degenerative sign of ageing in concrete: the so-called alkali-aggregate reaction (AAR). In the course of AAR, a material forms that takes up more space than the original concrete and thus gradually cracks the concrete from within as the decades go by.

The researchers have now explored the exact structure of this material. They managed to demonstrate that its atoms are arranged extremely regularly, making it a crystal. They also showed that the structure of this crystal is a so-called sheet-silicate structure. This specific structure had never been observed before. The researchers made their discovery thanks to measurements at the Swiss Light Source SLS at PSI. The research results could help towards the development of more durable concrete in future.

A Global Problem

AAR is a chemical reaction that affects outdoor concrete structures all over the world. It happens when concrete is exposed to water or moisture. For instance, numerous bridges and up to twenty per cent of the dam walls in Switzerland are affected by AAR. With AAR, the basic ingredients in the concrete are actually the problem: cement -- the main component of concrete -- contains alkali metals such as sodium and potassium. Any moisture infiltrating the concrete -- stemming for example from rainwater -- reacts with these alkali metals, leading to an alkaline solution.

The second main ingredient in concrete is sand and gravel, which in turn are composed of minerals, such as quartz or feldspar. Chemically speaking, these minerals are so-called silicates. The alkaline water reacts with these silicates and forms a so-called alkali calcium silicate hydrate. This is itself able to absorb more moisture, which causes it to expand and gradually crack the concrete from within. This entire process is referred to as AAR.

AAR takes place extremely slowly, so that the cracks are initially only tiny and invisible to the naked eye. Over the course of three or four decades, however, the cracks widen significantly and eventually jeopardise the durability of the entire concrete structure.

A New Crystal

Even if the chemical processes involved in AAR have long been known, nobody had identified the physical structure of the alkali calcium silicate hydrate formed in the course of AAR. The researchers at PSI and Empa have now managed to fill this knowledge gap. They studied the substance of a Swiss bridge constructed in 1969, which has been affected heavily by AAR. Researchers from Empa cut out a material sample from the bridge and ground down a small piece of it until they were left with a wafer-thin sample that was merely 0.02 millimetres thick. The sample was then taken to the Swiss Light Source SLS and irradiated with an extremely narrow x-ray beam, fifty times thinner than a human hair. Performing so-called diffraction measurements and a complex data analysis, the PSI researchers were eventually able to determine the crystal structure of the material with pinpoint precision.

They found that the alkali calcium silicate hydrate has a previously undocumented sheet-silicate crystal structure. "Normally, discovering an uncatalogued crystal structure means you get to name it," explains Rainer Dähn, the first author of the study. "But it has to be a crystal found in nature, therefore we didn't get that honour," says the researcher with a smile. Andreas Leemann, Head of the Concrete Technology Group at Empa, had the idea for the current study. The researchers from PSI then brought their knowledge of the x-ray beam method to the table. "In principle, it's possible to add organic materials to the concrete that are able to reduce the build-up of tension," explains materials scientist Leemann. "Our new results provide a scientific basis for these considerations and could pave the way for the development of new materials.

Story Source: Swiss Federal Laboratories for Materials Science and Technology (EMPA). "Structure of 'concrete disease' solved: Previously undocumented sheet-silicate crystal structure." ScienceDaily. ScienceDaily, 5 November 2015. .

Wastewater to Irrigate, Fertilize and Generate Energy

Date: September 3, 2015
Source: Fraunhofer-Gesellschaft
Summary: To meet the requirements of Asian cities, researchers are adapting an idea they have already applied in Germany for comprehensive water management: developing a concept for reducing water use, treating wastewater and extracting fertilizer for a strip of coastline in the Vietnamese city of Da Nang

Agricultural areas in the Vietnamese city of Da Nang: in the future, residents can use purified wastewater to water their crops.
Credit: © Fraunhofer IGB

To meet the requirements of Asian cities, researchers are adapting an idea they have already applied in Germany for comprehensive water management: They are developing a concept for reducing water use, treating wastewater and extracting fertilizer for a strip of coastline in the Vietnamese city of Da Nang.

Urbanization is in full swing. Particularly in Asia, solutions are needed for feeding the growing population, supplying water and energy, and cleverly recycling waste wherever possible. In Vietnam, researchers from the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB in Stuttgart have adapted a wastewater treatment concept they developed in the DEUS 21 project to support the supply of water, energy and fertilizer.

Under the auspices of the German Society for International Cooperation GmbH (GIZ), the "Integrated Resource Management in Asian Cities: The Urban Nexus" project will now implement the innovative infrastructure along a strip of coastal land with some 200,000 residents in the Vietnamese city of Da Nang. Starting in the fall, 110 plots -- home to around 500 people -- are to be connected to a novel sewage network made up of vacuum pipes, which have a significantly smaller diameter than standard pipes. Wastewater is extracted with pumps, similar to the process used in trains and aircraft.

Until now, Da Nang's wastewater often flowed untreated into leaky ditches. Not only does this risk contaminating beaches, it also leaves untapped a valuable resource that the Fraunhofer researchers are now making accessible. Now for the first time, wastewater will be processed together with hotel kitchen waste; the resulting biogas will be used for cooking in hotel kitchens. Treated water will be used for urban agriculture -- meaning farmers will require less groundwater, reserves of which are at risk of becoming ever more saline as seawater is drawn in to replace the excessive volumes of freshwater being extracted during periods of drought. A further advantage is that nutrients found in the processed wastewater work as a natural fertilizer. So the novel system connects the pressing issues of supplying water, energy and food with little effort -- and the researchers achieve good results in each area. For example, with biogas: "At 45 liters per resident per day, our solution produces twice as much biogas as with traditional water treatment plants in Germany," says group manager Dr. Marius Mohr from the IGB.

Even the Wastewater Energy is Used

This concept sees wastewater purified biologically. "At the heart of the system are anaerobic bioreactors in which the organic component of wastewater ferments into biogas," Mohr explains. Bioreactors can also be combined with membrane filtration so that all larger particles, including the bacteria, remain inside the bioreactors. For cost reasons, this is not part of the initial plan for Da Nang.

The DEUS 21 concept was developed to maximize the recycling of wastewater and of the resources it contains. Not only can the biogas created in the anaerobic bioreactor be used for cooking, it can also be used to supply electricity and heat or to power vehicles. And because the wastewater remains relatively warm after processing, it is possible to draw additional thermal energy from it and supply this to households in cooler regions via a district heating network. "As another product of wastewater treatment nitrogen-phosphorus fertilizer can be won through a process of precipitation and ion exchange," Mohr explains.

The system could be implemented in many different regions, in particular where there is no sewer system or sewage treatment. "It's also suitable for export to areas with little water because it can be adapted to fit the needs of arid and semi-arid regions," Mohr adds.

Story Source:

The above post is reprinted from materials provided by Fraunhofer-Gesellschaft.

Fraunhofer-Gesellschaft. "Wastewater to irrigate, fertilize and generate energy." ScienceDaily. ScienceDaily, 3 September 2015. .

Crowd Computing to Improve Water Filtration

The research was conducted by 150,000 volunteers

Date: July 6, 2015
Source: American Friends of Tel Aviv University
Summary: Scientists propose a novel nanotechnology-based strategy to improve water filtration. The project was an experiment in crowdsourced computing -- carried out by over 150,000 volunteers who contributed their own computing power to the research.

Nearly 800 million people worldwide don't have access to safe drinking water, and some 2.5 billion people live in precariously unsanitary conditions, according to the Centers for Disease Control and Prevention. Together, unsafe drinking water and the inadequate supply of water for hygiene purposes contribute to almost 90% of all deaths from diarrheal diseases -- and effective water sanitation interventions are still challenging scientists and engineers.

A new study published in Nature Nanotechnology proposes a novel nanotechnology-based strategy to improve water filtration. The research project involves the minute vibrations of carbon nanotubes called "phonons," which greatly enhance the diffusion of water through sanitation filters. The project was the joint effort of a Tsinghua University-Tel Aviv University research team and was led by Prof. Quanshui Zheng of the Tsinghua Center for Nano and Micro Mechanics and Prof. Michael Urbakh of the TAU School of Chemistry, both of the TAU-Tsinghua XIN Center, in collaboration with Prof. Francois Grey of the University of Geneva.

Shake, Rattle, and Roll

"We've discovered that very small vibrations help materials, whether wet or dry, slide more smoothly past each other," said Prof. Urbakh. "Through phonon oscillations -- vibrations of water-carrying nanotubes -- water transport can be enhanced, and sanitation and desalination improved. Water filtration systems require a lot of energy due to friction at the nano-level. With these oscillations, however, we witnessed three times the efficiency of water transport, and, of course, a great deal of energy saved."

The research team managed to demonstrate how, under the right conditions, such vibrations produce a 300% improvement in the rate of water diffusion by using computers to simulate the flow of water molecules flowing through nanotubes. The results have important implications for desalination processes and energy conservation, e.g. improving the energy efficiency for desalination using reverse osmosis membranes with pores at the nanoscale level, or energy conservation, e.g. membranes with boron nitride nanotubes.

Crowdsourcing the Solution

The project, initiated by IBM's World Community Grid, was an experiment in crowdsourced computing -- carried out by over 150,000 volunteers who contributed their own computing power to the research.

"Our project won the privilege of using IBM's world community grid, an open platform of users from all around the world, to run our program and obtain precise results," said Prof. Urbakh. "This was the first project of this kind in Israel, and we could never have managed with just four students in the lab. We would have required the equivalent of nearly 40,000 years of processing power on a single computer. Instead we had the benefit of some 150,000 computing volunteers from all around the world, who downloaded and ran the project on their laptops and desktop computers.

"Crowdsourced computing is playing an increasingly major role in scientific breakthroughs," Prof. Urbakh continued. "As our research shows, the range of questions that can benefit from public participation is growing all the time."

The computer simulations were designed by Ming Ma, who graduated from Tsinghua University and is doing his postdoctoral research in Prof. Urbakh's group at TAU. Ming catalyzed the international collaboration. "The students from Tsinghua are remarkable. The project represents the very positive cooperation between the two universities, which is taking place at XIN and because of XIN," said Prof. Urbakh.

Other partners in this international project include researchers at the London Centre for Nanotechnology of University College London; the University of Geneva; the University of Sydney and Monash University in Australia; and the Xi'an Jiaotong University in China. The researchers are currently in discussions with companies interested in harnessing the oscillation know-how for various commercial projects.

Story Source: American Friends of Tel Aviv University. "Crowd computing to improve water filtration: The research was conducted by 150,000 volunteers." ScienceDaily. ScienceDaily, 6 July 2015. www.sciencedaily.com/releases/2015/07/150706123738.htm.

Climate Engineering May Save Coral Reefs, study shows

Date: May 25, 2015

Source: University of Exeter

Summary: Mass coral bleaching, which can lead to coral mortality, is predicted to occur far more frequently over the coming decades, due to the stress exerted by higher seawater temperatures. Geoengineering of the climate may be the only way to save coral reefs from mass bleaching, according to new research.

Current coral bleaching in Fiji.
Credit: Professor Peter J Mumby, University of Queensland

Geoengineering of the climate may be the only way to save coral reefs from mass bleaching, according to new research.


Coral reefs are considered one of the most vulnerable ecosystems to future climate change due to rising sea surface temperatures and ocean acidification, which is caused by higher atmospheric levels of carbon dioxide.

Mass coral bleaching, which can lead to coral mortality, is predicted to occur far more frequently over the coming decades, due to the stress exerted by higher seawater temperatures.

Scientists believe that, even under the most ambitious future CO₂ reduction scenarios, widespread and severe coral bleaching and degradation will occur by the middle of this century.

The collaborative new research, which includes authors from the Carnegie Institution for Science, the University of Exeter, the Met Office Hadley Centre and the University of Queensland, suggest that a geoengineering technique called Solar Radiation Management (SRM) reduces the risk of global severe bleaching.

The SRM method involves injecting gas into the stratosphere, forming microscopic particles which reflect some of the sun's energy and so help limit rising sea surface temperatures.

The study compared a hypothetical SRM geoengineering scenario to the most aggressive future CO₂ reduction strategy considered by the Intergovernmental Panel on Climate Change (IPCC), and found that coral reefs fared much better under geoengineering despite increasing ocean acidification.

The pioneering international study is published in leading scientific journal, Nature Climate Change.

Lead author Dr Lester Kwiatkowski of the Carnegie Institution for Science said "Our work highlights the sort of climate scenarios that now need to be considered if the protection of coral reefs is a priority."

Dr Paul Halloran, from the Geography department of the University of Exeter added: "The study shows that the benefit of SRM over a conventional CO₂ reduction scenario is dependent on the sensitivity of future thermal bleaching thresholds to changes in seawater acidity.

This emphasises the need to better characterise how warming and ocean acidification may interact to influence coral bleaching over the 21st century."

Professor Peter Cox, co-author of the research and from the University of Exeter said: "Coral reefs face a dire situation regardless of how intensively society decarbonises the economy. In reality there is no direct choice between conventional mitigation and climate engineering but this study shows that we need to either accept that the loss of a large percentage of the world's reefs is inevitable or start thinking beyond conventional mitigation of CO₂ emissions."

This work shows the very different impacts on coral bleaching of different measures to tackle climate change. These different techniques will also have different effects on other impacts such as regional crop growth or water availability.

Story Source: University of Exeter. "Climate engineering may save coral reefs, study shows." ScienceDaily. ScienceDaily, 25 May 2015. www.sciencedaily.com/releases/2015/05/150525120430.htm.

Engineers Purify Sea and Wastewater in 2.5 Minutes

Date: April 17, 2015
Source: Investigación y Desarrollo
Summary: A group of engineers have created technology to recover and purify, either seawater or wastewater from households, hotels, hospitals, commercial and industrial facilities, regardless of the content of pollutants and microorganisms in, incredibly, just 2.5 minutes, experts say.

Credit: Image courtesy of Investigación y Desarrollo

A group of Mexican engineers from the Jhostoblak Corporate created technology to recover and purify, either seawater or wastewater from households, hotels, hospitals, commercial and industrial facilities, regardless of the content of pollutants and microorganisms in, incredibly, just 2.5 minutes, researchers say.

The System PQUA, works with a mixture of dissociating elements, capable of separating and removing all contaminants, as well as organic and inorganic pollutants. "The methodology is founded on molecularly dissociating water pollutants to recover the minerals necessary and sufficient in order for the human body to function properly nourished," technical staff explained.

Notably, the engineers developed eight dissociating elements, and after extensive testing on different types of contaminated water, implemented a unique methodology that indicates what and how much of each element should be combined.

"During the purification process no gases, odors nor toxic elements that may damage or alter the environment, human health or quality of life are generated," said the Mexican firm.

The corporation has a pilot plant in their offices that was used to demonstrate the purification process, which uses gravity to save energy. We observed that the residual water in the container was pumped to reactor tank, where it received a dosing of the dissociating elements in predetermined amounts.

In this phase solid, organic and inorganic matter as well as heavy metals are removed by precipitation and gravity; and a sludge settles at the bottom of the reactor. The latter is removed and examined to determine if it is suitable to use as fertilizer or manufacture construction materials.

Subsequently, the water is conducted to a clarifier tank, to sediment the excess charge of dissolved elements; then the liquid reaches a filter to remove turbidity and is finally passed by polishing tank that eliminates odors, colors and flavors. The treated water is transported to a container where ozone is added to ensure its purity, and finally is ready to drink. Indeed, the resulting liquid is fresh, odorless and has a neutral taste.

"We have done over 50 tests on different types of wastewater and all have been certified and authorized by the laboratories of the Mexican Accreditation Agency (EMA). Also, the Monterrey Institute of Technology and Higher Education (ITESM), the College of Mexico and the National Polytechnic Institute (IPN) have given their validation that the water treated with our technology meets the SSA NOM 127 standard, which indicates the parameters and quality characteristics for vital liquid to be used for human consumption," says the Corporate Jhostoblak.

Moreover, they report that this development is protected under trade secret in America and soon will get the same record in Switzerland. Its implementation in the market will depend on the needs of users and the issue of new laws regarding use, consumption and water discharge.

Story Source:
The above story is based on materials provided by Investigación y Desarrollo; nvestigación y Desarrollo. "Engineers purify sea and wastewater in 2.5 minutes." ScienceDaily. ScienceDaily, 17 April 2015.

Chlorine Use in Sewage Treatment Could Promote Antibiotic Resistance

Date: March 22, 2015

Source: American Chemical Society

Graduate student Nicole Kennedy measures the antibiotic activity of various samples in the lab.
Credit: Olya Keen

Chlorine, a disinfectant commonly used in most wastewater treatment plants, may be failing to completely eliminate pharmaceuticals from wastes. As a result, trace levels of these substances get discharged from the plants to the nation's waterways. And now, scientists are reporting preliminary studies that show chlorine treatment may encourage the formation of new, unknown antibiotics that could also enter the environment, potentially contributing to the growing problem of antibiotic resistance.

The research, which will be presented today at the 249th National Meeting & Exposition of the American Chemical Society (ACS), suggests that a re-evaluation of wastewater treatment and disinfection practices is needed.

"Pharmaceuticals that get out into the environment can harm aquatic life, making them react slowly in the wild and disrupting their hormone systems," notes Olya Keen, Ph.D. She adds that increased antibiotic exposure, even at low levels in the environment, can lead to development of antibiotic-resistant microbes and a general weakening of antibiotics' abilities to fight bacterial infections in humans.

"Treated wastewater is one of the major sources of pharmaceuticals and antibiotics in the environment," says Keen. "Wastewater treatment facilities were not designed to remove these drugs. The molecules are typically very stable and do not easily get biodegraded. Instead, most just pass through the treatment facility and into the aquatic environment."

But besides failing to remove all drugs from wastewater, sewage treatment facilities using chlorine may have the unintended consequences of encouraging the formation of other antibiotics in the discharged water. Keen, graduate student Nicole Kennedy and others in her team at the University of North Carolina at Charlotte ran several lab experiments and found that exposing doxycycline, a common antibiotic, to chlorine in wastewater increased the antibiotic properties of their samples.

"Surprisingly, we found that the products formed in the lab sample were even stronger antibiotics than doxycycline, the parent and starting compound," she adds. Keen has not yet identified all the properties of these "transformation products," and that research is now underway. She notes that these compounds could turn out to be previously unidentified antibiotics.

Keen explains that the best solution may be to decrease the amount of these drugs that reach a treatment plant in the first place. Currently, disposal of pharmaceuticals is not regulated, however. So she urges a greater emphasis on collecting and incinerating old pharmaceuticals, rather than dumping them down the drain or placing them in the trash, which can lead to harmful environmental exposures.

In addition, this research has applications to drinking water treatment systems, most of which also use chlorine as a disinfectant, she says. To purify drinking water, chlorine must remain in the distribution piping system for hours, which blocks microbes from growing. But this also provides ample time for chlorine to interact with pharmaceuticals that may be in the water, encouraging development of new antibiotic compounds.

Story Source: "Chlorine use in sewage treatment could promote antibiotic resistance." ScienceDaily. ScienceDaily, 22 March 2015. www.sciencedaily.com/releases/2015/03/150322080204.htm

Earth's Climate is Starting to Change Faster, New Research Shows

Date: March 9, 2015

Source: Pacific Northwest National Laboratory

Summary: Earth is now entering a period of changing climate that will likely be faster than what's occurred naturally over the last thousand years, according to a new article, committing people to live through and adapt to a warming world.

The rate of temperature change is rising and will continue to do so, as seen here with the thick gray line. This model depicts rates measured in 40-year windows of time, a time frame that reflects lifespans of people.
Credit: Image courtesy of Pacific Northwest National Laboratory

An analysis of changes to the climate that occur over several decades suggests that these changes are happening faster than historical levels and are starting to speed up. The Earth is now entering a period of changing climate that will likely be faster than what's occurred naturally over the last thousand years, according to a new paper in Nature Climate Change, committing people to live through and adapt to a warming world.

In this study, interdisciplinary scientist Steve Smith and colleagues at the Department of Energy's Pacific Northwest National Laboratory examined historical and projected changes over decades rather than centuries to determine the temperature trends that will be felt by humans alive today.

"We focused on changes over 40-year periods, which is similar to the lifetime of houses and human-built infrastructure such as buildings and roads," said lead author Smith. "In the near term, we're going to have to adapt to these changes."

See CMIP Run

Overall, the Earth is getting warmer due to increasing greenhouse gases in the atmosphere that trap heat. But the rise is not smooth -- temperatures bob up and down. Although natural changes in temperature have long been studied, less well-understood is how quickly temperatures changed in the past and will change in the future over time scales relevant to society, such as over a person's lifetime. A better grasp of how fast the climate might change could help decision-makers better prepare for its impacts.

To examine rates of change, Smith and colleagues at the Joint Global Change Research Institute, a collaboration between PNNL and the University of Maryland in College Park, turned to the Coupled Model Intercomparison Project. The CMIP combines simulations from over two-dozen climate models from around the world to compare model results.

All the CMIP models used the same data for past and future greenhouse gas concentrations, pollutant emissions, and changes to how land is used, which can emit or take in greenhouse gases. The more models in agreement, the more confidence in the results.

The team calculated how fast temperatures changed between 1850 and 1930, a period when people started keeping records but when the amount of fossil fuel gases collecting in the atmosphere was low. They compared these rates to temperatures reconstructed from natural sources of climate information, such as from tree rings, corals and ice cores, for the past 2,000 years.

Taken together, the shorter time period simulations were similar to the reconstructions over a longer time period, suggesting the models reflected reality well.

While there was little average global temperature increase in this early time period, Earth's temperature fluctuated due to natural variability. Rates of change over 40-year periods in North America and Europe rose and fell as much as 0.2 degrees Celsius per decade. The computer models and the reconstructions largely agreed on these rates of natural variability, indicating the models provide a good representation of trends over a 40-year scale.

Now Versus Then

Then the team performed a similar analysis using CMIP but calculated 40-year rates of change between 1971 to 2020. They found the average rate of change over North America, for example, to be about 0.3 degrees Celsius per decade, higher than can be accounted for by natural variability. The CMIP models show that, at the present time, most world regions are almost completely outside the natural range for rates of change.

The team also examined how the rates of change would be affected in possible scenarios of future emissions. Climate change picked up speed in the next 40 years in all cases, even in scenarios with lower rates of future greenhouse gas emissions. A scenario where greenhouse gas emissions remained high resulted in high rates of change throughout the rest of this century.

Still, the researchers can't say exactly what impact faster rising temperatures will have on the Earth and its inhabitants.

"In these climate model simulations, the world is just now starting to enter into a new place, where rates of temperature change are consistently larger than historical values over 40-year time spans," said Smith. "We need to better understand what the effects of this will be and how to prepare for them."

This work was supported by the Department of Energy Office of Science.


Story Source:
The above story is based on materials provided by Pacific Northwest National Laboratory. Pacific Northwest National Laboratory. "Earth's climate is starting to change faster, new research shows." ScienceDaily. ScienceDaily, 9 March 2015. www.sciencedaily.com/releases/2015/03/150309134642.htm.