light concrete with embedded eps beads 2

[ubrunjes]

Dear friends,

Next year I want to build my own house and at this time I'm in the process of defining the details. Among other things I want to incorporate eps beads in the floors, walls and perhaps ceilings. The reasons are that I want to insulate the house as well as possible, avoiding also rot, air leaks, etc., and participate in keeping eps out of the landfills. - Does anybody have experience with this construction method or can offer an "educated" opinion about the matter?

As a somewhat secondary subject I'm also interested in using lime instead of cement, if possible. As you know, lime hardens by carbonization, absorbing CO2 from the air and being therefore more environmentally benign. Trouble is, I don't know how to make it harden as strong and fast as cement. There are concrete hardeners (basically silicates) that react with the free lime in the concrete. Would they do the trick? How would I go about?

Thanks for your advice!

Uwe Brunjes

 

[RDK]

I’d stick to traditional methods of concrete construction.


EPS has a specific gravity around 0.16 Fresh concrete has a specific gravity of 2.5. All your EPS beads will be at the top.

Lime based cements are very weak compared to Portland cements. The performance would suffer greatly.

If you want to try something completely different and environmentally friendly try a straw house. It’s basically a post and beam construction with straw bales stacked up in the walls. The straw is covered with a fireproof coating (stucco) and is very easy to heat and cool because of the insulating poperties of the straw.

See

http://www.eere.energy.gov/EE/strawhouse/house-of-straw.html

for more details.




Rick Kitson MBA P.Eng

Construction Project Management
From conception to completion

http://www.kitsonengineering.com

 

[ubrunjes]

Hi Rick,

thanks for your reply! I'm aware of the difficulties you face when you want to combine two so different materials. That's why I asked for advice in the first place! Nevertheless, I know that has been done; sometimes succesfully, other times it was a flop. The reason is of course that we are dealing with a very novel technology, and mistakes are made. Those people who were succesful, normally are also very tight-lipped. So I hoped to get some advice from this forum, but apparently so far nobody knows how to make eps concrete. Tough!

Regarding the construction with strawbales, I know this system and I basically like it! The only thing that makes me worry is that you have to be very careful with the details. A little crack in an unconspicuous place, and your strawbale turns into a stinking heap of compost! And as I'm not related in any way to the building industry, I prefer to stay away from this system. It's just too easy for me to make mistakes!

Anybody else has comments on eps concrete?

Uwe

 

[clayR]

Uwe,

Cannot comment on eps concrete, but I believe it would come under the heading of light wt aggregate concrete, which is common.

I found your comments on Lime and silica interesting. What you discribe is called a pozzalonic reaction. Here, the function of the lime is to increase the pH for the formation of silica gel. It was used 2,000 years ago and is still used today, primarily is the acc market.

Typically, for modern autoclaved cellular concrete (acc)the raw materials consist of quick or hydrated lime with the addition of silica, such as fly ash or ground silica sand. Water is then added along with alumina powder. The light wt comes from the gas generated by the alumina reaction, creating bubbles in the mix and hence the light wt.

Another type of cellular concrete can be made simply by adding preformed foam to a cement paste. It is commonly used for light wt geotechnical fills, roof decks, tunnel lining and so forth. Since it can be cast in place, this could be something that may be of interest to you.

I'm glad you are looking at alternatives to normal wt concrete. The insulating properties certainly will result in lower energy costs, and savings in the long run.

 

[ubrunjes]

Hi "clayR",

It's good to see that your comments confirm what I already knew, as in the last case I might have to go with foamed concrete, if I can't get sufficiently precise info about eps concrete. - Could you recommend me any website, discussion list, specialist or whatever to find this info?

Uwe

 

[RiBeneke]

I have had little experience with foamed concrete - it is not used much here in South Africa, but it is used fairly commonly in parts of Europe (France, Germany).
Making foamed concrete requires special additives. These can be obtained from the specialist suppliers like Sika (Switzerland).
Foamed concrete also requires adaptation of the mixing and placing equipment - so the labour force would need to be trained.
I have seen expanded polystyrene foam used in small concrete items like garden ornaments etc. From a structural point of view, the strength of the concrete will be similar to the strength of a foamed or aerated concrete having the same percentage of air voids. Ideally some adjustment could be made to account for a different pore size and shape distribution, but this assumption of void percentage would be a good starting point for a structural calculation.
It certainly is a good idea to try and find uses for eps. Some years ago we experimented with these ideas in our construction business, but could not get anything economic that received support. We got as far as shredding eps using a hammermill of the type used to strip mielie-cobs (maize, corn-cobs in other lands). The static electric charges made the handling of the shredded material a problem. Also, by the time it is shredded and mixed into concrete, the pieces of eps are not little round balls, but tend to be squashed or split, reducing the mass reduction that could be possible using virgin eps balls.
You will need a well graded concrete mix with fine material (fly ash etc) and minimum water content to prevent the eps from floating. Mixes designed for pumping should work as a start.
Good luck with your research !
Richard Beneke

 

[ubrunjes]

Hi Richard,

thanks for your reply; we are beginning to get somewhere!

Regarding the voids, I am aware that from a structural point of view, eps has hardly any advantage over air. What I like about using eps is mostly that this way I'll keep it out of the landfill, and that no additional(!) unpleasant or harmful chemicals are used to create the voids.

To reconvert the used eps into beads, I was counselled to use a shredder, like those used for shredding wood (branches, etc.). If you adapt a mister to apply a little water, containing a very minute amount of dish detergent, static electricity shouldn't be an issue anymore.

Though all this is just theory; I need more hard data!

Uwe

 

[RiBeneke]

Your mister to reduce static electricity sounds a good idea.

Is there a Concrete Society/Association in your area who might be willing to make a small quantity of sample concrete (as a research project) and do strength and durability tests for you ?
Organisations like this are sometimes funded by the cement makers and other construction industry businesses.

 

[ubrunjes]

Hi Richard,

that's a very helpful tip I haven't thought about! Even if there is none in my area, distance shouldn't make a difference when it comes ot trying something new. Will try!

Uwe

 

[Ron]

ubrunjes...one point that I think you are still missing was made early on by RDK....the materials you are considering will not perform adequately in a classical structural sense. As an example, the thickness of concrete in structural members is related to its strength and its reinforcement. The reinforcement efficiency and effectiveness are closely related to the strength of the concrete. The thickness is kept lower by reinforcement and the reinforcement works because of the strength of the concrete, particularly in compression. These are basic interactions that cannot be ignored in concrete design.

With that said, the two concretes you have mentioned, first using EPS as an aggregate and secondly using "foamed concrete" will result in very low strength concretes, generally unsuitable for structural applications in a structural frame application. Foamed concrete has some good applications, but structural framing is not one of them.

 

[RiBeneke]

Ron

I agree fully with what you have said. Flat suspended concrete slabs do not work well in foamed concrete. Walls would need to be a little thicker, but could work in foamed concrete.

Here, as part of the process of innovative thinking, perhaps an unusual structural form would be necessary to work effectively with an unconventional material.

I can imagine that various arch-forms, even an igloo shaped house, would perhaps work well structurally, although it would be a headache for the interior fittings.

 

[WRMiller]

To All,
As usual, the "engineers" are acting on suppositions translated from other fields with no investigation of the state of the art in a specific application.

Expanded polystyrene concrete has been around since the 1950's in one form or another. It was first investigated by BASF shortly after they invented and patented eps! A number of suitable applications were subsequently developed commercially, using their ideas and practices, which they willingly placed in the public domain.

Concrete using expanded polystyrene as the aggregate is in general use through out Europe for homes and commercial construction projects. It is not used as a truly structural medium, except in road work and certain geo-thermal or geo-eco situations. In building construction, other elements are added or incorporated into the epsconcrete to carry the loads, but it is not a novelty.

In the United States, Rafsta, Tech-Block and others are building homes, offices, etc. with the product.

To search for applictions, uses, etc. on the web, construct a good boolan, starting with light weight concrete, then adding constrictive or expanding words.

As product development manager for Foam Lite Concrete, Inc.,I was chasing new developments when I ran across this site and the thread. Some of you guys don't do the engineering profession any good, by "assuming". I trust you all know what that word implies.

Oh, as an aside, Foam Lite Concretes (eps concretes) are sold through our distributor force through out the US, in Canada, Australia and Mexico.

Remember - Enjoy Life, This is Not Practice!

 

[DTGT2002]

Mr. Miller,

Lacking a supplier capable of providing an EPS mix with any history or guarantee of suitability, throwing some EPS into a concrete mixer and calling the EPS aggregate is irresponsible from a structural engineering point of view. I won't deny my ignorance of the "state of the art" of EPS concrete, just thousands of years of recorded history that lets some of us better understand the natural world.



The real questions may pertain to what capacity is truly required of the mix, and whether or not a reasonably economical mix can be safely made and installed.

Lightweight concrete or various forms is used all the time. Varying aggregates have varying strength, some greater than the matrix of the concrete - the cement paste, some weaker than the paste.

This is where the question comes in.

Can you reliably make a lightweight concrete with an EPS aggregate and get the capacity you need for it to function structurally.

Here in the south, I have known of no "Structural EPS Concrete". I have seen "Insulating Concrete" with EPS as the aggregate.

SO, if you want to save the earth and entomb some EPS, can you use a more normal concrete mix for major structural members and use your EPS mix as non load bearing filler walls between columns and under Cast in Place concrete beams, or the framing system you prefer?

Alternately, you could test your concept of EPS concrete mixes until you have a suitible solution you can replicate without question. At that point, you should probably go into business for yourself and patent your product.

Good luck with it all.

Daniel Toon

 

[dantheman222]

I have some web sites you might be interested in, and I want to use eps in concrete to build affordable housing. Hours searching on google revealed a few good sites. Also check out the curretn forbes article on page 166. Very interesting indeed! Here's what you are looking for I think, I have others you might be interested in:

http://www.b-lite.com/bsttext.htm

 

[Ron]

Sorry I missed Mr. Miller's statements earlier.

DTGT2002 is exactly right. I am speaking not from supposition or assumption, but from many years of experience, much of which has direct application to the subject at hand. I have designed numerous concrete mixes for insulation, for roadway structural applications, and for building structural applications. Further, I have analyzed and designed the structures involved as well. These applications have had the concrete and aggregates tailored to the need.

As several have said there has been no universal acceptance of the idea for several reasons, all of them good ones. Yes, EPS concrete has applications for which it is suitable, but a "fitness for purpose" assessment includes more than just the physical application. It also includes assessing the technology for economics, labor force training, availability, durability, longevity, and other variables.

Concrete technology makes advancements almost each and every day. Perhaps at some point the technology will include the general economical production of super lightweight concretes capable of general structural application that can substantially replace existing structural concretes in comparable volume and strength. It isn't there yet.