The Geotechnical Research Centre is currently completing contract research testing steel fibre reinforced concrete (SFRC) tunnel lining segments for the Toronto Transit Commission Spadina subway extension. These SFRC lining rings are being tested for structural and durability criteria in the Department of Civil Engineering research laboratories. The objectives of the research program are to characterise the compressive and tensile strength of the SFRC, subject to chloride exposure, and to assess the flexural resistance of the SFRC segments. This will provide experimental data that can be used to develop strength parameters and improved analytical models used for designing SFRC segments for tunnels. The photograph shows the delivery and offloading of the SFRC segmental tunnel linings to the Structural Engineering laboratory. Each segment is nominally 3 metres long by 1.5 metres wide, and weighs approximately 3 metric tons. This work is being supervised by GRC research director Dr. Tim Newson, and associate members of the GRC Drs. Sean Hinchberger and Moncef Nehdi, who specialises in concrete durability.
O'Carroll: Environment, just one beneficiary of nanotechnology revolution
By Dennis O'Carroll, October 27, 2011
Nanotechnology has generated significant public and scientific excitement due our abilities to design and synthesize nanoparticles at the nano scale. A nanoparticle is considered a particle with one of its three dimensions less than 100 nanometres. There are a wide variety of engineered nanoparticles on the market or currently in development. They are designed to have a wide range of very unique properties that are much more significant than larger particles of the same composition. In the environmental community there is considerable interest in harnessing the tremendous potential of nanotechnology for environmental restoration and water purification.
Environment Canada estimates that 29% of the population consumes groundwater as their domestic water so protection of this resource is essential to the health and well being of Canadians. Historically, the subsurface was thought to act as a natural filter of wastes injected into the ground. The potential for these wastes to persist in the subsurface for decades, potentially contaminating drinking water sources was ignored. Oils are one class of waste liquids that were subject to improper disposal practices. These liquids are extremely difficult to remove from subsurface aquifers (zone below the ground with considerable amounts of water that can be pumped out).Nanoiron particles are one promising innovative groundwater remediation technology that can convert these contaminants into less toxic or nontoxic materials. They are particularly useful because of their size a single human hair is 500 to 5,000 times as wide. At that scale, they can move through microscopic flow channels in soil and rock, reaching and destroying groundwater pollutants that larger particles cannot.We have had tremendous success in laboratory experiments using nanoiron to rapidly degrade a wide range of environmental pollutants. However one problem that has hampered the widespread implementation of nanoiron is poor subsurface mobility. That is when nanoiron is injected into the subsurface it did not originally flow through microscopic flow channels in soil and rock, as anticipated. To overcome this problem we have developed formulations and processes that make nanoiron mobile in the subsurface. One part of this recipe has been the use of starches or flour in our nanoiron in our formulation. We are currently working with researchers at the University of Toronto to take the nanoiron that we have developed in our laboratories to the field scale. In November 2010 and in February 2011 we took our technology to the field to clean up two contaminated sites. At the first field experiment we injected 1000 litres of a nanoiron solution into a very contaminated region in the subsurface. Continued site monitoring has found considerable decreases in subsurface contaminants. The second field trial in February 2011 was equally successful. This work has generated significant public and media attention. Our February 2011 field trial will be the subject of the October 27, 2011 edition of the CBC’s The Nature of Things. We are very excited with these success stories and anticipate moving forward with commercial applications of nanoiron.
Nanotechnology holds unbelievable potential that will revolutionize the products we use on a daily basis. With these advances comes significant potential for nanotechnology based technologies to improve the environment.
Dr. Jason Gerhard, November 2011
A team at the University of Toronto, one of the selected universities, approached Gerhard thanks to his soil remediation research at Western.
“They had a lot of good ideas, but did not know how they were going to deal with the solid waste after separation of the liquids,” says Gerhard, Canada Research Chair in Geoenvironmental Restoration Engineering. “The reinvented toilet requires total disinfection within 24 hours, so biological methods would not work.”
A member of Toronto’s team saw one of Gerhard’s STAR (Self-sustaining Treatment for Active Remediation) presentations and asked if it could apply to human waste.
STAR is an innovative technology for remediation of contaminated soils Gerhard co-founded with Jose Torero from the University of Edinburgh.
The working principle involves the smoldering combustion of contaminates in soil. Smouldering is the process by which combustion takes place in the absence of flame (for example, a glowing red charcoal briquette in a traditional barbecue). It converts organic material, plus oxygen, into water, carbon dioxide and heat.
“It is self-sustaining, which means once you get it going then it generates enough energy to keep itself going until all the fuel (organic matter) is gone,” Gerhard says.
There are many organic liquids that pollute our environment, such as coal tar and oil, for which no acceptable cleanup options are available. “By smouldering the oil, we can clean up contaminated soil and polluted sites using very little energy,” he continues.
Routinely, greater than 99 per cent of contaminant mass is destroyed in the process.
But can STARs technology be transferable to this latest project?
“Theoretically, it should be possible. But it has never been proven,” Gerhard says.
The team will try to adapt the process for destroying the organic waste in the toilet, allowing the waste to be disinfected without using much energy or water.
Gerhard and Torero, also invited to join the Toronto team, will conduct the initial work at the University of Edinburgh combustion laboratory.
“It is a new application of combustion science to environmental engineering problems, and crosses this unusual boundary between fire and water,” Gerhard says.
While excited to push STAR’s capabilities, Gerhard recognizes the bigger picture.
“One of the reasons we got involved in this project is the potential impact for billions of people,” he says. “The majority of my career has been spent on cleaning up industrial pollution, which is a serious problem, but one that primarily affects first world countries.
“We are working on many different ‘fun’ challenges. But for this work, I am particularly excited to be part of a project which such important positive implications for the developing world.”
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Updated January 31, 2012 by cquintus
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