Chances are you’re within a few meters of some right now.
I’m talking about concrete, the sturdy yet humble building block used since the days of the ancient Romans. You probably don’t give this ubiquitous substance a second thought – that is, unless you’re Craig Tenney, a chemical engineer at Sandia National Laboratories who is looking to solve one of concrete’s biggest problems.
Concrete Contamination
In 1995 a group of Japanese terrorists unleashed a deadly nerve agent called sarin into the Tokyo subway system, killing 12 people and injuring thousands more. An often overlooked consequence of this tragedy is the potentially lingering effects of contamination in the concrete comprising the subway.
This is because concrete’s ubiquity belies its chemical and physical complexity . Full of microscopic pores, concrete is intricately spongy. It’s capable of absorbing chemicals and even “breathing” them back out. Cleaning just the concrete surface is like going through a car wash – it makes your car look nice and shiny on the outside, but it does nothing about the mess on the inside.
A Concrete Solution to Chemical Contamination
A chemical attack on a transportation hub today could shut it down for weeks, creating a huge economic impact in addition to the initial horror. Moreover, there’s no easy solution in place if this were to occur.
“We can’t just rip out and replace the affected concrete — that would be too expensive,” said Tenney. “We need to decontaminate it and make it safe. The public has to be confident enough to come back and use the affected facility.”
Tenney and his team are using computer simulations to study how chemical agents soak into concrete and become bound within it. They modeled several long-lasting chemical agents and monitored how molecules of these agents act within nanometer-sized pores such as those found in concrete. So far, the team has determined how strongly various chemical agents stick to concrete pores as well as which ones clump together.
By comparing their results to the small amount of experimental data available, the team was able to validate their findings, an encouraging starting point for further research. While there is still work to be done, Tenney is confident that the computational models may lead to more accurate field tests and improved decontamination techniques.
“Yes, it would be great from a scientific perspective to just understand what’s going on, but from an engineering point of view, it would also be darn nice if we could take that understanding, tailor our approach for decontamination and make it better,” said Tenney. “This is a national lab-scale problem and there are lots of little pieces that need to be put together to solve a big problem. If the unfortunate ever does happen, at least we [will be] prepared.”
For more news from the world of concrete, this flexible concrete won’t crack under pressure .