Poly-Foam

[J_M_Tungsten]

I posted this question on the Rush University Medical Center forum, but was thinking it might get more attention over here. I'm really curious about the integrity of this poly foam stuff (thats the name I found when I did a little research?), it seems like such a brilliant idea. Reduce weight loads while still elevating the terrain! awesome! How will this stuff hold up long term, and how does it interact with plant life ( can tree roots grow into it/ weaken it?)

Does anyone know anything about "poly-foam"? The entire terrain south of the ortho building to the power plant was filled with 7-8ft of these giant white cubes. I imagine that they are put there to reduce the weight load on the connecting tunnel structure below as dirt and rocks would be an enormous amount of weight added with the road over head. I looked into it a little bit and read that a good portion of Millennium Park had used poly-foam for the same reason of weight reduction. Does any one know what this stuff is made of or how much it weighs per cubic ft vs dirt?

You can see more pictures of the road paved over the poly foam at the Rush page on this site.

http://forum.skyscraperpage.com/show...=169510&page=2

[1ajs]

they use it as insulation

[J_M_Tungsten]

8 feet of terrain raising insulation? I know its used to raise the terrain, and can see how it could somewhat be used as insulation, but its purpose has to be more than to just insulate. I was wondering more on the integrity of the stuff, and how it interacts with tree roots and what not.

[Tecumseh]

Originally Posted by J_M_Tungsten

I posted this question on the Rush University Medical Center forum, but was thinking it might get more attention over here. I'm really curious about the integrity of this poly foam stuff (thats the name I found when I did a little research?), it seems like such a brilliant idea. Reduce weight loads while still elevating the terrain! awesome! How will this stuff hold up long term, and how does it interact with plant life ( can tree roots grow into it/ weaken it?)

Does anyone know anything about "poly-foam"? The entire terrain south of the ortho building to the power plant was filled with 7-8ft of these giant white cubes. I imagine that they are put there to reduce the weight load on the connecting tunnel structure below as dirt and rocks would be an enormous amount of weight added with the road over head. I looked into it a little bit and read that a good portion of Millennium Park had used poly-foam for the same reason of weight reduction. Does any one know what this stuff is made of or how much it weighs per cubic ft vs dirt?

You can see more pictures of the road paved over the poly foam at the Rush page on this site.

http://forum.skyscraperpage.com/show...=169510&page=2

Mods: Odd coincidence...someone posted this http://rankings.big-boards.com/?sort=pageviews&p=4 on another message board that I frequent. I saw this board and was interested because of my line of work, and I signed up. I soon saw JM's question. I am not here to solicit. If this post is inappropriate, please feel free to let me know, or delete it.


I work for a company that manufactures this type of foam. I do not want to violate the T.O.S., but I'll answer your questions generically.

1st, Poly-Foam is a brand name. The industry term is geofoam. You'll have better results googling that term.

As a brief overview, geofoam is expanded polystyrene foam, which is the same type of foam that "styrofoam" cups are made from. (Styrofoam cups aren't actually styrofoam. Styrofoam is a Dow brand name for extruded polystyrene, rather than expanded polystyrene. Anyhoo...)

Expanded polystyrene is very commonly used as insulation, but the purpose in a geofoam application is to serve as a structural fill. As you noted, it adds very little weight, is very strong, and takes up a great deal of space.

Geofoam comes in varying densities, which can weigh from .7lbs cu ft up to more than 3lbs cu ft. Higher density=higher compressive strength. Normal dirt weighs approx. 120-130lbs cu ft.

The geofoam is generally fine with grass and small plants, because the root structure is not deep enough to get to the foam. In the case of larger plants or trees, a root ball is required.

You are correct about Millenium Park. Additionally, the largest geofoam installation in the world is underneath a huge section of I-15 in downtown Salt Lake City.

I'd be happy to answer any other questions that you have.

[J_M_Tungsten]

Thank you Tecumseh, that was beautifully answered.

So this stuff will not have problems say 20-30 years up the road when the concrete road above has been driven on over and over? Also, is there any kind of adhesive they use to bind the pieces together, or will it just stay together from the weight above (maybe some shifting from the earth settling or repetitive forces from above)?

I find this geofoam fascinating, as its purpose is an ingenius way to raise the terrain AND reduce weight loads on the structures below!

[Tecumseh]

Originally Posted by J_M_Tungsten

Thank you Tecumseh, that was beautifully answered.

So this stuff will not have problems say 20-30 years up the road when the concrete road above has been driven on over and over? Also, is there any kind of adhesive they use to bind the pieces together, or will it just stay together from the weight above (maybe some shifting from the earth settling or repetitive forces from above)?

I find this geofoam fascinating, as its purpose is an ingenius way to raise the terrain AND reduce weight loads on the structures below!

The foam does not degrade over time, and as long as the loads are engineered properly, the projects won't experience "creep" (continued compression) over time.

As far as holding the pieces together, the only time that this is really an issue is during the actual construction process. Obviously having the blocks shift would not be helpful, so to address that, the manufacturer should be able to supply geo-gripper plates, which are 4" x 4" galvanized steel plates, with spikes on both sides. The plates are embedded in the foam, and each plate is capable of resisting up to 60lbs of lateral pressure.

[arkhitektor]

I remember seeing a story about these foam blocks on the news a few months back because the UTA (Utah Transit Authority) is using them in construction of a new light rail line. Link to the story

[harryc]

Tecumseh thank you for the concise, authoritative, and simple explanation. I had always thought it looked and felt like normal "Styrofoam".

[J_M_Tungsten]

Thanks Arkh, that cross section is a nice image to show the layering of this stuff.

[GWHH]

That a nice job spotting that operation. Look like they are building something with life size lego blocks.

[SFUVancouver]

They have been using the stuff quite a lot recently in Vancouver in new waterfront parks. Much of Vancouver's waterfront is, at least partially, fill. Large tracts were deposited by the Canadian Pacific Railway when they gradually filled in the edges of a waterbody called False Creek to expand their railyards and the land they had available to lease to industry. The new parks that have been built above this century-old fill rely heavily on this geofoam to allow for naturalistic rolling terrain and terracing without the associated weight.

In areas of the city with a high watertable due to the Fraser River geofoam is an attractive alternative to costly and time consuming pre-loading areas that will only be landscaped.

Lastly, our new convention centre has an immense 6 acre green roof and a fair number of 'green slopes' above the exhibition hall and parking garage. Geofoam was used extensively both as an insulator on the roof and for mass on the green slopes connecting to the adjacent park.

[SFUVancouver]

A recent webcam photo of a new piece of highway infrastructure in a suburb of Vancouver that is utilizing geo-foam for an embankment.

Originally Posted by officedweller

Pitt River Bridge - Mary Hill Bypass ramp webcam pic from today - note the foam blocks...

[Kelvin]

It will be interesting to see what they do to provide the side faces to the geofoam fill in the ramp. They don't have enough room laterally to use a natural side slope (as in the train section shown previously) at locations near the structure, but may not be able to use MSE wall or other conventional retaining walls either.

[J_M_Tungsten]

This stuff must literally be cheaper than dirt if they are using it for above grade use only, without having to use it for weight reduction to a structure below.

[Tecumseh]

Originally Posted by J_M_Tungsten

This stuff must literally be cheaper than dirt if they are using it for above grade use only, without having to use it for weight reduction to a structure below.

It's not. There could be unstable soils, underground utilities, or another reason to need a light weight solution. Alternatively, it could be a time issue, since Geofoam doesn't have to surcharge nearly as long as conventional materials.

[ChicagoChicago]

^^^
I wonder if they are using the poly-foam to reduce lateral earth pressure from the embankment?

[mersar]

I've noticed they've been using it in Calgary for a couple LRT projects, though a slightly different application. In the downtown they are rebuilding all the LRT stations, the majority of the platform is made of precast concrete sections, however two of the stations back right against an existing building. So they build a footing that the precast rests on, then another footing against the building. Then they filled the gap (about 2' or 3' deep, 5' wide and roughly 300' long with foam blocks, then laid out the rebar lattice that will be in the concrete they've yet to pour to complete off the platform for the one. On the other theres just a small section that resulted from the one restaurant who's main door was at street level that didn't want to renovate when they built the new platform, so they've done a similar process to fill in the gap where the entrance used to be

[Jasonhouse]

Fascinating stuff... Something I've wondered for years is why foam isn't used in more varied ways in the construction of highrise buildings... One would think that the allure of weight savings, increased insulation and sound/vibration reduction would be compelling.

[aic4ever]

Originally Posted by J_M_Tungsten

This stuff must literally be cheaper than dirt if they are using it for above grade use only, without having to use it for weight reduction to a structure below.

Interestingly enough, it is not. In fact, the companies that do it quite literally price it exactly the same as dirt.

They have little competition amongst each other, and keep an eye on the prices of dirt. At the end of the day, they will quote you basically exactly what your price for dirt would have been anyway, relying on superior performance for their advantage.

I researched this stuff for a substitution in some foundation work once upon a time. After finding some information about how much it actually costs them to produce these huge blocks of foam, I was confounded when they priced the work to me at nearly exactly what my excavators priced.

Very smart on their part to know their market, and to capitalize on it.

Anyone who knows better, feel free to re-educate me, but this is my observation and belief of the material.

[XSpringfieldGuy]

Stupid.. Metallurgist would know different. Go figure. Not good for wind load or Siesmeic activity at all..thats just me though. I guess poly makes it possible. Who had Dow as a rep on this?