Insulating Roadways

I don't know if it is the same thing but we have been using "air entrained concrete" for freeze/thaw locations as far back as I can remember.

http://en.wikipedia.org/wiki/Air_entrainment

not quite the same, I'm looking at insulating quality

I have a technical study about the matter.

The highways in Belgium have about the highest traffic density per m2. There is a frost and salt problem during winter.

The pdf. is in Dutch language and is a challenge to unleash Google translator. It describes the how's, and why's, complete with test reports.

I hope you'l find it useful. D.

http://www.brrc.be/publications/a/a6896.pdf

Heard of it used in buildings but not in roadways. I don't think it would meet the strength and other specifications for heavy highways maybe light roads use.

The rough principle is to create small voids, like cellular concrete. They inject no foam but an additive that "foams" the concrete. It is to compare with a soapy plasticiser that makes the cells waterproof.

The concrete is easier to pour. Has less compression strength, but behaves better when it comes to weather influences. (expansion and contraction)

The contact noise is less and if damaged, the concrete is easier to scrape off or remove.

I have read nothing about thermal tests or K value.

I guess a foam is difficult to disperse equally in concrete. Most application I know of have concrete as layer on top of a foam bed (under layer)

Still don't think a"soupy" concrete mix is going to have the strength to handle heavy truck traffic as swear coat or subbase. Problem with layering concrete is they adhere to each other transferring cracking. Not sure what the big deal of added fly ash to the concrete most batch plants already have been doing it as a cheap substitute for cement. Fly ash does have a tendency to darken concrete.

In my opinion having insulated roadways would be counterproductive. Here in south Texas we are experiencing a rare episode of freezing rain. The roads conduct heat from the earth and stay above the freeze point. However the bridges have no heat to conduct and quickly iced over. Using insulated concrete for the roads should only compound the icing problem.

you're thinking is backwards. thermo dynamics tells you heat will always move to cool. so your hot road will have its heat drawn out of it quicker without something to insulate it the road from the ground beneath it.

remember that any form of thermal insulation will not block or stop the movement of heat but is rated to slow its movement.

Agreed on the thermo dynamics. But here the ground does not freeze, and road surface is cooled by the air & rain. We want to encourage the heat movement into the road.

Delmar is right. Freezing conditions do not advance through the ground. The air is what drops below freezing and heat moves from the warm ground into the cool air. Think about it, below ground pipes do not freeze prior to surface puddles.

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If you are thinking about a camping analogy with the cold ground seeping your heat if you have no pad, the temperature dynamic is different. Delmar's bridge analogy is useful.

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The only situation in which insulating below the road might delay or prevent the road from freezing would be in something line a permafrost area on a road with very heavy traffic. The surrounding ground would have to be frozen pretty deep on average, and insulation would slow any heat loss to the surrounding ground, but that would not be a typical scenario in most parts of the US.

I do not know how the fly ash forms, bot foam and insulation together means air pockets where moisture may become trapped and freeze .......... I would need more info on this.

My girlfriend's son-in-law is a structural engineer, I recall last year he was working on a project where foam was added to concrete for reducing the weight.

Fly ash is the spoils from the consumption of coal as a fuel. Basically, there is so much of this crap laying around (and allegedly causing cancer) that we are looking for ways to sequester it and make it useful at the same time.

Using it as an amendment for golf course fill, however, is not recommended: http://hamptonroads.com/2013/05/chesapeake-fly-ash-fight-yields-little-resolution

I realize that, and as far as fly ask some it use to be said that it was great fertilizer, but no one really realize the amount of carcinogens in it.

I'm just saying, for an insulating value, How?

When doing road work such as laying asphalt, they make dam sure the air pockets are removed.

No a dark color, may help by retaining any heat from the sun.......... but of course the roads have to be clear.

And insulating value is only temporary and not a heat source, get a run of below zero weather, and your roads also stay colder longer.??????

flyash is a product of burning coal, they get tons of it for almost nothing, tiny cenospheres , its also the stuff they put in insulating paint, tiny little air bubbles trapped in a ceramic like bubble

Living in Green Bay, WI, with the paper mills and the like,,,,,, very familiar with fly ash, or I should say, I heard about it a lot at least the difficulty in disposal.

but you discription of it is interesting enough.

I don't know the material your referring in your opening. However, styrofoam or equivalents have been used in various bridges, retaining walls, embankments, and even roadways. There have been problems and this report may be of some interest.

Out gassing, that's something that's over looked...... some of the rest, such as water absorption, I was curious about.

One thing about building road-ways, with the expense involved, one doesn't what to experiment on new techniques.

UW-Madison has a 100 year concrete study, it actually started out as a 50 year study but the professor that started it, made so many concrete samples, they were able to get a longer term study out of it.

Also UW-Madison has some study's of using Cellulous (from wood pulp) fill in concrete…….

UW-M Paper

Might be getting off track on it's usage though.

this might help http://www.youtube.com/watch?v=FThWDdRu9vY

When they Built the Alaska Highway in the 40's they built "corduroy roads"(sand covered logs) over the exposed permafrost. To this day there are still sections in place and they have the least problems with frost heaves etc. The insulative qualities of wood seems to suffice there.

I worked for the Yukon DOT and they keep trying various methods to stop the heaving from Permafrost but nothing to date has been as successful as the logs....

They did that in the swamps also....... still have some roads called Corduroy road.

And when they were asphalted over......... the waves on the roads reflected the logs under them. could be rough traveling.

On the Ak highway they placed a bed of sand and #1 "crush and run" at least 1' thick over the logs. It wasn't till the 80's when they had a BST(bituminous surface treatment). I haven't seen or experienced washboard road surfaces over the original sections, But Man oh Man it's rough where they clear cut and let the ground thaw before rebuilding sections....

Fly ash is the fine particles that fly up the chimney stacks of power plants. These days, they are usually removed from power plant flues by baghouses or electrostatic precipitators. It is a pozzilith, and some pozziliths are added to concrete mixesto modify them. I can't go futher with this, although I am a Professional Structural Engineer, I never did understand the black arts involved in designing concrete mixes, I consulted people who did understand.

Adding foam "soapy hot water" to asphalt is a new technique for asphalt mix designs. It allows the materials plant to product asphalt at a lower temperature thus saving on fuel.