Picture of Styrofoam Concrete
There are many concrete projects, such as benches for sitting and walkway fill, that can be made using light-weight Styrofoam Concrete.  By substituting Styrofoam trash for store-bought gravel in the concrete mix, one saves on not only weight, but also on the cost of materials.  

To the best of my knowledge, Styrofoam is not a popular material for plastic recyclers.  Recycling it at home eliminates transportation costs for this bulky and low-value material. 

Many people don't own the property where they live, so maybe the incentive to build a castle for the owner over time is not there.  Instead of filling our dumps with this stuff, we could be building cities out of it, if we were motivated enough. 

I live on an island, and our dumps are filling up fast.  Taking waste and finding constructive uses for it is the best way to gracefully live with all the trash we generate. 

Styrofoam concrete probably has good thermal insulation, compared to rock concrete.  It might be a useful construction material in both hot and cold climates. 

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Step 1: An early experiment

This is a porous block of Styrofoam and cement.   By filing blocks of Styrofoam with special tool I made using lots of roofing tacks, I was able to make a supply of pea size particles. 

Using a soupy cement and water mix, I got the particles wet with the minimum amount of the mix needed to keep them stuck together.  By using the minimum amount of cement, the air space between the particles is not completely filled and the block is porous.  The block is fairly light weight.  It's strength is not what solid concrete would be, but sometimes the light mix is just fine for the job. 

I don't know what kind of uses this combination might have, but its porosity is interesting.  Perhaps, it could be a filter for air or water. 

Step 2: Another experiment

Picture of Another experiment

This experiment uses a regular mix of sand, cement and water, and the porosity between the gravel-size particles is saturated with the mix.   The resulting concrete is stronger than the earlier experiment, but also heavier.
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Really nice work. Do you have a certain formula you like, as far as the ratios of cement to styrofoam?



Thinkenstein (author)  ken.chambers.716924 days ago

Not really. If the Styrofoam comes in big solid pieces you can use big solid pieces. If not, you use little stuff, and more cement to hold it all together.

diy_bloke8 months ago

I need to poor some non standrad size tiles (otherwise I might have bought them and was using scrap already as filler ( medicine bottles, old cutlery), but I also got styrofoom. That might be an idea. I will be using the tiles at the side of my driveway so they wont need to carry much weight anyway

Maxmil1 year ago
Amazing - every instructable you have posted. Genius ideas and so conscientious of reusing what would be siting on our planet forever. I hope I can pose a question to you that you could help me with? We are on a tight (read: nonexistent) budget and want to install concrete countertops in our kitchen. It's our first house and we've tried to do almost everything by ourselves. We live nowhere as nice or warm as you-Chicago is brutal. And I've never seen an instructable for DIY cocncrete countertops using anything more than the "norm", and I'd be interested in any ideas you would be willing to offer using trash/recyclables and concrete to get our project done - as in expensively and beautiful as possible. I also wanted to include recycled glass in our concrete if that helps at all. Thanks for sharing these creative ideas!
Thinkenstein (author)  Maxmil1 year ago
There is an expanded sheet metal called Hirib that is especially for plastering with cement. You might find that useful for making the counter top and then tile it. I did a tile mosaic on my kitchen counter top that turned out well.

Remember that bent edges give reinforcement and extra strength, like ribs.

Good luck with your project.
i found out one time that if you want to make the styrofoam completely apart where you can see each little ball of foam, you can spray it with one of those hose nozzles and its strong enough to split apart each little ball of foam without ripping them and if you get the nozzle to spray a thin line you can roughly cut through the foam too
thequara4 years ago
The "Trash Rocks" is an interesting concept. I'm all for recycling and such, since we haven't had any significant plagues or anything lately to control the ever growing polulation... Grim thought, I know, but I can't help but think, isn't his just "hiding" non-recycleable trash until somebody else decides to get rid of this concrete and finds it full of trash? Don't get me wrong, great creativity and intent, just wish people would focus on trying to influence manufacturers to stop creating so much packaging and products that cause so much waste.
I have experimented with making things from plastic milk and water bottles. The easiest thing to make is chicken feeders and waterers by cutting a smooth hole between the top and the handle big enough for the chickens to comfortably put their heads in to eat or drink. I cut the hole from the back plate through the entire front so that up to 4 chickens can eat or drink a the the same time. I also cut the whole top off for water dishes for pets. The top can be a funnel or scoop. I had fun making christmas ornaments by cutting carasel shaped ponies out and decorating them with different shapes for their mane, tale, saddle etc then baking them, removing them before they stuck, cool and paint. Last experiments I did was to bake bread size bricks for future projects. I couldn't remove the darned things from my bread pans and ended up with door stops. What I learned from this was mostly the temperature you use determines the texture of the plastic. Quickly heating to 380 degrees gives you a pliable liquid that hardens like steel! I'll play with it more when I have the time.
How did your tinkering with plastic bricks turn out?
Did you find a reasonable and not too technical way of converting milk bottles etc to plastic bricks? If so I would love to see a step by step instructable on that.
Thinkenstein (author)  Websprinter4 years ago
Do you think you could make a plastic mesh out of recycled plastic; something that could be plastered with cement? Nylon fishnet is my preferred material, but I lost my source for free used stuff, and new fishnet is expensive. -- I was thinking of something that could be extruded under pressure through nozzles to make a mesh pattern, perhaps on a rotating teflon-coated drum, and peeled off as it cools and hardens. It would be nice to use up shopping bags, etc. in something constructive. -- Maybe a pressure cooker could be adapted somehow?
If you have a local green grocery near by the bag they ship onions and carrots is sometimes mesh and not organic. it would work as lathe, and if th eperson packing out like you they can cut it just right. I have used that stuff in garden projects. sparkie
Thinkenstein (author)  spark master4 years ago
Thanks for the idea, Sparkie. It seems to me that I tried onion sacks years ago. The center band, where the printing is, was solid and cement didn't stick to it. The remaining small pieces of mesh aren't very useful for stretching out and covering large areas. Plus they have to be overlapped, using up more surface area. -- Melting down the plastic and extruding it into a mesh pattern on a revolving non-stick drum would make mesh of endless length, with width limited only by the width of the drum. Plus, we could recycle more of our trash plastic that way. -- It's hard to beat fishnet. New fishnet is expensive, and used fishnet is in limited supply. I've lost my source for it.
What you describe is what inamtes do to make a plastic shiv to kill someone, they take hard plastics melt/form them with matches and produce weapons. Nifty except for all the blood. ciao
That would make prison inmates true environmentalists. Not only are they recycling toxic materials that would ultimately end up in a landfill, but they are doing it in a manner that produces high concentrations of isolated toxic fumes which they breath and thereby reduce their own lifespan; and the finished product of this labor is used to further reduce the felonious population. The ingenuity and inventiveness of prison inmates has always been amazing and it is a shame that such obvious talent only surfaces when they are confined under deplorable conditions, otherwise I am having a hard time finding anything negative about this.
I know it is nutty, but what can I say. Do a search for Xtal radios and look for pow radios. Simple recievers can be made, that will catch and decypher plain AM with little more then wire and the right rocks. You can even build a speaker or make one using a piezo Xtal loud enough to hear w/o a head phone. (of course where do you hide the thing, cuz you make a big cone to amplify the sound), but if you gt a single ear bud you are good to go. ciao sparkie
Thinkenstein (author)  thequara4 years ago
Yes, encapsulating the trash doesn't make it go away. Best would be to not have the trash to eliminate in the first place. Given the trash, the Trash Rocks are a cosmetic solution, but they can also be useful. Just trying to make the best of it.
tonygoffe2 years ago
Hi, tony in Jamaica... you could also attach wire mesh with staples and render that with cement... THAT would give you a steel componenet and more structural strength...You would want to use big syrofoam blocks, tho....
hardlec4 years ago
Have you considered putting medium sized chunks of foam in your concrete mixer with some sharp gravel to see if that might reduce the size of the chunks and may make them a more uniform size? I used a similar technique doing lapidary work with a rock tumbler. I'm also very interested on using concrete as a skim coat on a foam armature. Good stuff
A mulcher mower with bag would work great to break the styrofoam up smaller.

Thinkenstein (author)  hardlec4 years ago
No, I haven't tried that tumbling technique. I imagine running the mixer like that would consume a lot of energy for the amount of foam modification it would accomplish. I think the claw shaft and comb grate is probably the most energy efficient way of breaking it up. I don't know what you mean by a "skim coat" on a foam armature? Is that for sculpture? What is the skim coat for?
Sculpture, yes. Light weight is a real virtue even for lawn ornaments. Acetone, AKA fingernail polish remover, works really well dissolving Styrofoam and beaded foam. I've never considered using foam as a core I could dissolve out later.
IN metal casting we use styrofoam and concrete as an insulator in the outer layers of our refractory coat. The foam vaporizes leaving the concrete full of hollow insulating pockets. In our case the simple heat of the fire is enough to get rid of the foam itself, using something like acetone may dissolve the lime in the 'crete and degrade it's strength. Try heat exposure from a heat gun or something. The concrete itself WILL NOT burn for the first thousand+ degrees so just be careful to not burn the surrounding area.
thaicares3 years ago
I have another way to make things out of packing peanuts and virtually just the packing peanuts although they are only the organic one's so this is a great way to get rid of the other packing peanuts REALLY COOL :)
chaguin603 years ago
THINKENSTEIN have you allready used papercrete?IVE heard that that papercrete in a tropical island like PUERTO RICO rains a lot it tends to breakdown real fast ,is it true?Anybody that has tried in that kind of weather let me know.
Thinkenstein (author)  chaguin603 years ago
I have no experience with papercrete, nor have I heard of anybody using it here.
themadtreky4 years ago
I love close to the beach in Florida, recently I've seen a few buildings going up that the walls are concrete over recycled Styrofoam blocks. I'm not sure exactly how they did it, but it was interesting to see the beginning of the construct and the end results are strong and look just like stucco.
the materials that make up concrete do not break back down to their original state. Effectively you're encapsulating something that takes tens of thousands of years to decompose with something that will not decompose for hundreds of thousands of years. What about using Cob? Although as a fully decomposable building material, using Styrofoam would effectively pollute it.... I suppose if you don't mind never getting rid of your cement construct it's a great idea- but if you want to do anything to it- you've pretty much made THE un-recyclable material for the ages. Albiet a constructive use of styrofoam. I would be interested in the structure changes Styrofoam makes to the concrete, if it significantly lessens the integrity of the material. If not, using it for housing foundations would be a good idea- they stick around for a long time and are easily reused. Cheers!
Many of the piers along the coast of Southern California are made of gigantic styrofoam blocks encased in rebar cages and then covered with a thick layer of cement. I also seem to remember seeing something about freeform houses being made of a styrofoam substance shot onto a chickenwire frame and then coated with cement. Apparently the styrofoam does not affect the stuctural integrity of the cement. Environmentally, styrofoam may be a pain but chewing up trees to make plywood (which is probably as toxic as styrofoam) is not much better. I doubt that I would mix styrofoam chunks with cement because gravel is cheap and easy to come by. Besides that I favor smooth surfaces and styrofoam tends to float towards the top (even in cement).
Thinkenstein (author)  mstar4 years ago
For me, it solves a little bit of the general recycling problem we all share by taking care of what comes to me. -- Gravel is cheap, and heavy to transport. Styrofoam trash is free. If we all sucked up what was local to us and built out of it, it could be a very sculptural material to build an interesting city out of. -- Well, I know it has some uses. I don't know its limits.
I've actually got no problem with your use of styrofoam. I save a lot of the stuff myself and may try using it in a similar mannner for a couple of future projects like planter boxes and other garden things. Environmental considerations aside, styrofoam is everywhere, trash bins and landfills are full of it, it degrades slowly and there is no real way to get rid of it safely. Using it as fill material for sculptural cement is a novel idea but I would reduce the size of pieces to increase the overall strength of the material. The manufacturers of styrofoam packing parts and other items commonly run their "mistakes" through mechanical chippers connected to large collection bins or baghouses. That ground up styrofoam is then combined with unexpanded styrene balls in huge molds to produce styrofoam blocks that can be cut into slabs. The steam injected into the mold expands the new material and bonds the ground up materials into a single solid piece. Essentially you are doing the same thing but using cement as a binder. The larger the pieces are that you use the less structural integrity your finished product has, and if chunks of styrofoam are close to the surface there is the possibility that the cement will wear away and expose the styrofoam beneath. To avoid this, to ensure a better finish, and to improve the workability of the slurry I would run the styrofoam through some sort of chipper or leaf shreader to make smaller pieces. You could still use large blocks and chunks to build up the basic form, but then go with a finer ground mixture for the top coat. The finer ground slurry mixture would allow you to produce works with better detail capabilities and surface texture not possible with packing peanuts and large pieces. I imagine that you could mix a lot of of ground material with your cement before you reduced the quality of the surface or the sturctural intergrity of the finished work, but you would have to do some experimenting to find a good mix. I would not be afraid to use a three to one ratio to start with, but the smaller the styrofoam pieces, the better it will bind together and that equates to better detail and surface texture. Styrofoam may be an environmental disaster but there is a lot of it around, it is still being produced and that is not likely to stop any time soon. Finding alternatives to filling landfills with the stuff is a worthy pursuit and I think your idea is a pretty good starting place in that direction.
Think of it this way, your taking its toxicity out to some extent.
Wow, What is it with you people? Before even thinking about what you are saying you jump right in with all of this politically correct rubbish. (Now that is one kind of trash that should never be recycled but unfortunately it does, again and again). However, you seem to want your cake and be able to eat it too. Is it not the aim of all responsible people to recycle rather than send to a land-fill? That aside, you are totally wrong on several other accounts too. Organic fill would not be readily prepared and would be fibrous and useless as an aggregate unless it was something like wood shavings but that would be next to impossible to get any kind of smooth finish. As to the material being unrecyclable, wrong again. If the author chose to get rid of the material, it is easily crushed and used again as an aggregate as now the styrofoam is encapsulated in the cement slurry rather than light pieces which are the real pollutants as they will be easily blown about the landscape. The real howler is your psuedo knowledge of construction. Light weight screeds have been used as floor screeds for a long time (such as Boral-Lytag which uses 'blown' particles of lightweight material as an aggregate) as they are a very good insulators, but something as light weight as this material could never be used as a foundation as it would crushed under the building weight but suitably moulded into blocks (a wooden box will do), this material could be used for internal, non-load bearing walls and it's texture would easily over-coat with a decorative finish.
Thinkenstein (author)  jackoftheforest4 years ago
Old nylon-cement rubble and styrofoam-concrete rubble can all be used in road fills. -- To modify old structures with these materials is easy. The nylon-cement cuts easily with a cold chisel and a knife to cut the nylon. I have never broken up an old styrofoam-concrete structure, but I imagine all the old pieces could be mixed into a new batch of styrofoam-concrete and built with somewhere. -- The idea of the Termite Nest City, might be built using these materials. In such a city, very little of old structures would ever be demolished, since city growth is always upwards and outwards. Rubble would not be an issue.
Migs4 years ago
My company manufactures Styrofoam and concrete. There are additives you can add to the mix that promote the beads to mix more evenly. (I don't remember the names, and the names vary by country and market) As you all can imagine, until the concrete "wets" the beads, they are floating on top of the mix. (Problematic) One of the keys to a good mix is the mixer, which should be a slow pear type mixer that revolves the mix on itself (think bread dough). High speed mixers promote high shear, and this would destroy the Styrofoam beads. On a small scale this material works, but industrially speaking, there are better alternatives, including foams that are mixed with the concrete that leave large air bubbles in the mix.
Thinkenstein (author)  Migs4 years ago
Thanks for the info. Mixing it with a shovel on the patio is the way I usually do it, but on a windy day that gets a little out of control since the Styrofoam weighs so little. I was making a hand-cranked mixer inside a plastic 55 gallon drum once, with mixing paddles attached to the crank shaft. I figured for light-weight concrete it might work, but I never got around to trying it.
You might try plaster as well. If I recall, one could mix white glue with water, then pre-wet the eps (expanded poly styrene = Styrofoam) before adding it to the concrete mix. It all comes down to economics. We take in eps and add it to new block manufacture so we don't have any waste what so ever. You can also mix the eps with a solvent like Toluene and make glue. Or mix eps with styrene monomer to dissolve it and make other things. You can mix styrofoam with potting soil so it retains the moisture better. Styrofoam is a plastic that has many uses and creatively can be used for many things.
Thinkenstein (author)  Migs4 years ago
Potting soil using Styrofoam particles in it is one thing that I could never understand. Other than on its surface, I don't think that plastic particles in the soil can retain much water. The little white particles always seemed cosmetic to me, just to make the potting soil look more special to the customer than it really was. -- What with the Pacific gyre garbage patch and plastic entering the food chain anyway, it seems odd to dump plastic into our gardens, on top of everything else. -- I have heard of disolving Styrofoam with gasoline and using it as a roof sealer. Do you know how that holds up under UV radiation? It sounds like a poor man's sealer, with health risks using it, though.
It may not seem to make sense, but studies have shown that it really improves the soil's ability to retain water. Vermiculite is much better, but causes health problems in the areas where the raw material (mica) is mined (IIRC, it's found mixed in with asbestos, so the mining releases asbestos into the air). It also prevents the soil from clumping, as someone mentioned below, which helps with root growth & aeration.
perlite is mined in many areas which (currently , unless maybe chinese) that are asbestos free. In the past they easily could have had asbestos because people did not know th ehazards and when they did corporation played stupid . Due only to lawsuits out the ying yang it must be asbestos free.
I need some asbestos for a metal melting furnace, What is a good source?
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