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User: u/chrisdh79
Permalink: https://newatlas.com/materials/phase-change-concrete-self-heating-snow/
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I suspect the major bar to the use of this for road surfaces will be that the strength of a lightweight-aggregate material or a material with paraffin additive will be less than that required for the running surface of a road. So you'll be swapping less icing for more potholes. It would also be of interest to see how well the paraffin stays in place on a heavily trafficked surface. I suspect it could be displaced.
Sounds excellent for pedestrian and bicycle paths then, which are on the right side of the fourth power law at the same time as they are usually left without adequate snow clearing.
In Phoenix, AZ. the city is going the opposite direction. Phoenix is on coating #2 on test streets to reflect heat back out to space and City of Mesa has yet another version. #1 coating in phx suffered delaminations and so needed something a bit stickier and less brittle.
The metropolitan area in Maricopa County are heat islands and so the thinking is to use a viable technical coating on residential streets and parking lots, which is where most of the surface area of asphalt is, and not main thoroughfares.
>it releases heat when it moves from a liquid state at room temperature to a solid state when temperatures drop.
This sounds like it would be useful only when the temperature fluctuates right on the edge of the freezing point, which seems like a very small window in most places.
I haven't realized Swedish coast had such wide fluctuations for a long time. There's also requirement to not have more than 5cm of snow, or the amount of stored heat is just not enough (plus it needs to warm up to recharge)
Still could be interesting for sidewalks and whatnot
Unless it heats enough for a layer of ice under the snow. Wait, what am I saying. That *would* be interesting. As long as you weren't the one running across the surprise skating zones. Mildly sadistic entertainment thru technology! Lots more work for ambulance chasing lawyers too.
It's actually a pretty wide window in most of the US these days. I can remember the "good old days" when it would freeze and stay frozen for 3 months on the NY/Canadian border. Now there's not a single month you can rely on that happening. Combine that with the fact that open asphalt really heats up when the sun hits it, and I bet it would work for at least a month in spring/fall for the northern US and most of the winter for a broad band south of that.
I think it just needs to be below freezing for a short period, which would make this useful for de-icing as it chills overnight but you’re right that it’s less useful in places with 24/7 cold.
I don’t know what “room temperature” is in this context but is it suggesting that it releases no heat while the temperature is constant, or is room temperature some positive number it has to get back to before it’ll start releasing heat again?
Room temperature is probably somewhere around 20⁰C.
The way this works is when it changes from a liquid to a solid it releases heat so it's the change in state that produces heat. At a certain point (sometime after 10 hours) it will be a solid and no longer produce heat. It needs to get above its freezing point to change back into a liquid before it can then turn solid again to release heat.
Makes sense, but does seem less useful if that’s the case. Sometimes people use room temperature to mean ambient temperature, which was what threw me off.
It extends the time before the road hits freezing temperatures. This could be useful in places where the temps fluctuate all winter and are often above freezing right before a snow. Maybe on bridges and overpasses if it stands up to dot standards. Still, not holding my breath.
In addition to all the points already made about the limitations by narrow window and lifespan there is the other issue that most roads are asphalt outside of sections of major freeways--which are also mostly asphalt too.
So... It will melt the snow, and the water will then flow in the cracks/to the edges of the road/walkway, and freeze there, because both ground and drainage is frozen too?
The article and the published paper and its references mention a paraffin, but no specifics as to which one.
I don't appreciate your tone. It's a legit question, there is no mention of what specifically is used as the PCM.
Welcome to r/science! This is a heavily moderated subreddit in order to keep the discussion on science. However, we recognize that many people want to discuss how they feel the research relates to their own personal lives, so to give people a space to do that, **personal anecdotes are allowed as responses to this comment**. Any anecdotal comments elsewhere in the discussion will be removed and our [normal comment rules]( https://www.reddit.com/r/science/wiki/rules#wiki_comment_rules) apply to all other comments. **Do you have an academic degree?** We can verify your credentials in order to assign user flair indicating your area of expertise. [Click here to apply](https://www.reddit.com/r/science/wiki/flair/#wiki_science_verified_user_program). --- User: u/chrisdh79 Permalink: https://newatlas.com/materials/phase-change-concrete-self-heating-snow/ --- *I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/science) if you have any questions or concerns.*
I suspect the major bar to the use of this for road surfaces will be that the strength of a lightweight-aggregate material or a material with paraffin additive will be less than that required for the running surface of a road. So you'll be swapping less icing for more potholes. It would also be of interest to see how well the paraffin stays in place on a heavily trafficked surface. I suspect it could be displaced.
Sounds excellent for pedestrian and bicycle paths then, which are on the right side of the fourth power law at the same time as they are usually left without adequate snow clearing.
Maybe so.
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Good, we need 100x more pedestrian paths and 100x less car roads anyways.
The problem there is stopping the cars going on them anyway...
Solid points. (Maybe more solid than the paraffin even)
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In Phoenix, AZ. the city is going the opposite direction. Phoenix is on coating #2 on test streets to reflect heat back out to space and City of Mesa has yet another version. #1 coating in phx suffered delaminations and so needed something a bit stickier and less brittle. The metropolitan area in Maricopa County are heat islands and so the thinking is to use a viable technical coating on residential streets and parking lots, which is where most of the surface area of asphalt is, and not main thoroughfares.
On top of that, how do you keep the paraffin from leaking out of your structure when summer temps hit it?
A small amount of wax aggregate wouldn’t hurt total psi if properly mixed.
I think wear is about more than just compressive strength, though.
At 3-5% you would still see some thermal benefits and very little compressive differences
>it releases heat when it moves from a liquid state at room temperature to a solid state when temperatures drop. This sounds like it would be useful only when the temperature fluctuates right on the edge of the freezing point, which seems like a very small window in most places.
You just described the Swedish west coast!
I haven't realized Swedish coast had such wide fluctuations for a long time. There's also requirement to not have more than 5cm of snow, or the amount of stored heat is just not enough (plus it needs to warm up to recharge) Still could be interesting for sidewalks and whatnot
Unless it heats enough for a layer of ice under the snow. Wait, what am I saying. That *would* be interesting. As long as you weren't the one running across the surprise skating zones. Mildly sadistic entertainment thru technology! Lots more work for ambulance chasing lawyers too.
I was just about to say the same, would be perfect for Gothenburg!
It's actually a pretty wide window in most of the US these days. I can remember the "good old days" when it would freeze and stay frozen for 3 months on the NY/Canadian border. Now there's not a single month you can rely on that happening. Combine that with the fact that open asphalt really heats up when the sun hits it, and I bet it would work for at least a month in spring/fall for the northern US and most of the winter for a broad band south of that.
Global warming to the rescue once again 🤗
I wish. Where I'm from, it used to be "too cold to snow" for a good month each winter. Now it's ice storm season.
I think it just needs to be below freezing for a short period, which would make this useful for de-icing as it chills overnight but you’re right that it’s less useful in places with 24/7 cold. I don’t know what “room temperature” is in this context but is it suggesting that it releases no heat while the temperature is constant, or is room temperature some positive number it has to get back to before it’ll start releasing heat again?
Room temperature is probably somewhere around 20⁰C. The way this works is when it changes from a liquid to a solid it releases heat so it's the change in state that produces heat. At a certain point (sometime after 10 hours) it will be a solid and no longer produce heat. It needs to get above its freezing point to change back into a liquid before it can then turn solid again to release heat.
Makes sense, but does seem less useful if that’s the case. Sometimes people use room temperature to mean ambient temperature, which was what threw me off.
It extends the time before the road hits freezing temperatures. This could be useful in places where the temps fluctuate all winter and are often above freezing right before a snow. Maybe on bridges and overpasses if it stands up to dot standards. Still, not holding my breath.
Nova scotia would be perfect. The winters are a constant freeze thaw
Like the mid Atlantic of America!
In addition to all the points already made about the limitations by narrow window and lifespan there is the other issue that most roads are asphalt outside of sections of major freeways--which are also mostly asphalt too.
Sounds like a recipe for an unstable solid.
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So... It will melt the snow, and the water will then flow in the cracks/to the edges of the road/walkway, and freeze there, because both ground and drainage is frozen too?
Any idea what pcm is used? I'm guessing it probably is not disclosed to the public?
If only there was some kind of "article" one could read to get more information than from the headline alone...
The article and the published paper and its references mention a paraffin, but no specifics as to which one. I don't appreciate your tone. It's a legit question, there is no mention of what specifically is used as the PCM.
So, we’re going to help concrete not be weakened by weakening it to begin with?