MIT students fortify concrete by adding recycled plastic

Newsfeed said:
MIT students fortify concrete by adding recycled plastic


Discarded plastic bottles could one day be used to build stronger, more flexible concrete structures, from sidewalks and street barriers, to buildings and bridges, according to a new study.
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This has been trade before even in South Africa. Plastic has a too high thermal expansion coefficient and induces to much stress with seasonal changes. We already use plastic fibres, but they are largely limited to places that has similar temperatures. No seriousl structural engineer will use this.
 
Nicodeamus said:
This has been trade before even in South Africa. Plastic has a too high thermal expansion coefficient and induces to much stress with seasonal changes. We already use plastic fibres, but they are largely limited to places that has similar temperatures. No seriousl structural engineer will use this.
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Did you read the article?
 
I have great respect for MIT student projects, but this idea stretches the real-world bounds of practicality, scale and economics, and public relations:

MIT undergraduate students have found that, by exposing plastic flakes to small, harmless doses of gamma radiation, then pulverizing the flakes into a fine powder, they can mix the irradiated plastic with cement paste and fly ash [snip]
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Schaefer and Ortega manually sorted through the flakes to remove bits of metal and other debris. They then walked the plastic samples down to the basement of MIT’s Building 8, which houses a cobalt-60 irradiator that emits gamma rays, a radiation source that is typically used commercially to decontaminate food.
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If this has real potential, the cement manufacturers will be onto it quickly. There are dozens of cement institutes, cement associations, portland cement associations etc who would no-doubt gladly sponsor research.
 
Saw this on SKY the other day. I'm stunned that there is no concern of this plastic leeching off into the storm drains and inevitably ending our in our water system.
 
This may be kind of petty, not a scientist, but, wouldn't changing the crystalline structure, ie what makes a substance a substance, no longer make it that substance? ie, nuking plastic to change it into something that is stronger and no longer has the properties of plastic means they're not actually using plastic in concrete, they're using plastic to create a material for use in concrete?
 
PAYBACK said:
Saw this on SKY the other day. I'm stunned that there is no concern of this plastic leeching off into the storm drains and inevitably ending our in our water system.
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How would plastic leach out of concrete?

Have you observed stone and sand leaching out of concrete?
 
buka001 said:
How would plastic leach out of concrete?

Have you observed stone and sand leaching out of concrete?
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The plastic particles exposed on the surface of said concrete might indeed leach some molecules out, especially when it rains, thus into the water system, on that I can agree with him.
 
supersunbird said:
The plastic particles exposed on the surface of said concrete might indeed leach some molecules out, especially when it rains, thus into the water system, on that I can agree with him.
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Have you observed molecules of cement, fly ash or GGBS that are exposed on the surface of said concrete also leaching out? Especially when it rains?
 
buka001 said:
Have you observed molecules of cement, fly ash or GGBS that are exposed on the surface of said concrete also leaching out? Especially when it rains?
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The human eye tends to not be able to see things on the molecular level.
 
buka001 said:
Have you observed molecules of cement, fly ash or GGBS that are exposed on the surface of said concrete also leaching out? Especially when it rains?
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Well, it does erode, so yes, I'm sure it does leach away over time. Now whether the composition of those molecules are bad is then the issue.
 
FoXtroT said:
The human eye tends to not be able to see things on the molecular level.
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Exactly my point.

And yes the molecular constituents of concrete do leach. Especially when concrete is cracked. This is evident by the salt deposits visible along crack lines.

Concrete exposed to aggresive environments (sea, chemicals - especially sulphates and carbonates).

The constituents of concrete that do leach are as harmful, if not more harmful than the molecules in plastic.
 
I'd pick the slowly leaching plastic over the below, but who knows maybe it's worse than this?

maxresdefault.jpg
 
supersunbird said:
The plastic particles exposed on the surface of said concrete might indeed leach some molecules out, especially when it rains, thus into the water system, on that I can agree with him.
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Normally you add a cover layer on top of concrete to prevent leeching. As I mentioned earlier, we already use plastic in concrete. I am still not convinced that the thermal expansion wont cause interior cracks.
 
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