Introduction: Styrofoam Concrete

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. 

Step 1: An Early Experiment

Picture of 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.

Step 3: Chunking Up Scrap Styrofoam

Picture of Chunking Up Scrap Styrofoam

The city's recycling department used to save me sacks of Styrofoam packing material that people threw in the trash.  I made a hand-powered machine kind of like a tree limb chipper to rip it into smaller pieces. 

Basically, it had a hand crank at the end of a pipe shaft.  The shaft had some pretty wicked iron claws welded to it that dug into the foam that was fed into the machine.  The teeth went between parallel sections of rebar, which formed a comb-like grate in the floor of the bin.  The foam, caught between the claw teeth and the rebar got ripped to shreds and fell through the rebar grate to be caught in sacks below. 

Although I no longer have the complete machine, you can see what the claw shaft is like, and what is left of the wood hopper. 

Step 4: Bench Seat

Picture of Bench Seat

This bench is made of Styrofoam concrete.  I used mostly Styrofoam packing peanuts to make it.  As the cement was hardening up, I found I was able to carve it easily with a sharp machete. 

''The "rocks" on either side of it are hollow "Trash Rocks", filled with some of my unrecyclable trash from years ago.  See my other instructable on trash rocks here:

Step 5: Sculpture Uses

Picture of Sculpture Uses

Styrofoam in the cores of cement sculptures helps cut down on the weight a lot. 

This is a statue of my neighbor, Bartolo, emptying his coffee picking basket into a sack.  I donated it to the town many years ago and it is located near the plaza.  The armature is PVC pipe.  The rest is a combination of materials, but Styrofoam is a big part of it.  The reduced weight of this life-size cement sculpture allowed Bartolo, himself, to carry it quite a long distance from my house out to the road (just the figure, not the rock-like base, which was made on location). 


Migs (author)2010-06-23

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)Migs2010-06-23

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.

Migs (author)Thinkenstein2010-06-23

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)Migs2010-06-23

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.

3rajames (author)Thinkenstein2017-10-15

Isn't styrofoam with gasoline napalm? That's what a friend told me her Mom used to let her and her brother experiment wth on their farm.

ydlv (author)Thinkenstein2017-05-26

I know this is 7 years later replying but better later than never if the saying is applicable at all here... Anyway, the white things in potting soil used to bug me too until I started growing my own food and pot. It's actually not styrofoam but perlite, "a form of obsidian characterized by spherlulites formed by cracking of the volcanic glass during cooling, used as insulation or in plant growth media." Hope it makes your day or anyone reading this by chance.

Thinkenstein (author)ydlv2017-05-26

Thanks for the info.

ydlv (author)ydlv2017-05-26

Oh. and I love your experiments with concrete. It lends to progress in practicality, many thanks. Good for you and us.

Ketroot (author)Thinkenstein2016-09-06

The reason I understand is that it prevents the soil from packing, and increases the volume without adding much weight, never known of any one that thinks it might look good but it could be the similarity in the appearance to premium soils made with perlite.

Broom (author)Thinkenstein2010-06-27

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.

spark master (author)Broom2010-07-01

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.

xarlock667 (author)spark master2010-07-01

I need some asbestos for a metal melting furnace, What is a good source?

what your looking for is a refractory ceramic that contains a zirconium as this is you heat refractory. by all means dont use asbestose as the particles are friable in other words easily air born and can be considered carsengenes that cause cancer and asbestose udse should be banned totally.

They would not become airborne as I would place them in with my refractory compound, which is about like cement or concrete. If they can get loose from that, we are all screwed anyway.

KellyCraig (author)xarlock6672010-07-01

I don't know much about metal and the temperatures you require, but boilers and such use diatomaceous earth for insulation. It will take a lot of heat. If memory serves (there's a first time for everything), water filters use a crystallized form, which is created by heating it to around a couple thousand degrees. Even that would still have insulating properties. I believe it melts around four thousand degrees. If you need small quantities for an experiment, stop at an auto supply store and check out the oil absorbents. Many are diatomaceous earth and it's fairly cheap.

spark master (author)xarlock6672010-07-01

HI, you can not buy asbestos, or if you can its gotta be very regulated. You can get other things and there are different types of firbrick, there are insulator bricks that look like a fire brick, but do not hold conduct heat back. Good mason yard will have them as well as castable refractory, then there are the sodium silicate boards and foam glass (I do not thing foam glass will help you though. Mineral wool might, you need to find the temps it can take b4 melting. what will be the ultimate use of the asbestos? One gent who responded works with cement and sells the stuff, ask him for best info. gotta go Sparkie

Broom (author)spark master2010-07-01

Thanks, spark master. Didn't know that. Maybe now they'll bring back the plaster-perlite fill compound that is so awesome for filling holes in walls & ceilings... Can't find it anywhere anymore!

spark master (author)Broom2010-07-01

I stuff holes with plastic bags (clean, no odor, bugs can smell too), all crumpled up. Smearin the plaster, then if it is a depression , (not a hole, from say a door knob), I do several layers of patch using brown paper shopping bags or, cotton shirt, (clean and roled in dry plaster), My last piece is ever so slightly lowwer then the depression and dries well then roughed then final coat of plaster mixed with joint compund. I had a room in a very old apartment where the walls had a "wave" (only seen on edge 16 inch period wave . The I put up chair rail, almost 1/2 inch deep throughts 8 feet tall for 10 feet. I fixed it. When I sold my aprtment I was told th enew owner hated me. I had fixed ABOVE the chair rail only . You could never see it from because the chair railing separated it enough to fool the eye.

Thinkenstein (author)Broom2010-06-27

I have probably released more Styrofoam to the ground than most people have, through construction and sculpture projects. I'm not real afraid of having it in the ground around me. It just doesn't seem natural is all. It's the sort of thing I would rather not encounter on a nature hike. -- The world is somewhat plasticized already, and it looks like we just have to live with it because it is so spread out. Maybe we can stay healthy around it. I hope so.

redplanet (author)Thinkenstein2010-06-27

The stuff in potting soil that looks like styrofoam is called perlite. It is an expanded mineral and used mainly for water retention purposes.

spark master (author)redplanet2010-07-01

not usually, usually it is styrofoam, pearlite is different . the round spherules are plastic, burn a few sniff the cyanide like gas it makes

redplanet (author)spark master2010-07-01

I don't know where in the world you are, but I have never heard of potting soil that contains styrofoam in my life. I know it looks like styrofoam, but it's perlite. No, really.

spark master (author)redplanet2010-07-02

Next time I get something with them I will look, (spear a bunch and set fire to them, if they burn and stink they are plastic). I know some batches were strofoam because hte beads were connected and I burned a few , they smelled like plastic. Pearlite is used as a heat stop insulator in ovens , so it doesn't burn. I trust you, but I will look around for some potted plants after the season is over and I will pop a few pots open. I haven't bought potting soil in years and years. I use peat moss and lawn clippings. I am in NYC area, you are located where? (do not take anything I wrote/write as a flame, it is not intendedthat way sparkie

Thinkenstein (author)redplanet2010-06-27

"Expanded mineral" sounds a little more Earth-friendly to me than "plastic". Here's the Wikipedia entry for those who may be interested.

xarlock667 (author)Thinkenstein2010-07-01

DO NOT EVER DO THIS!!! That is not a recipe for roof sealant, that is a mixture for damned NAPALM!!! Do not coat your roof with napalm!!! I don't know who told you to do that but they CLEARLY did NOT like you!

That might work, though I have done similar experiements and the result is a very flammable, and very difficult to extinguish material. It also isn't very malleable, but more putty-like. It hardens almost like platic when it dries. It is still very flammable, though.

Migs (author)Thinkenstein2010-06-23

It turns out eps is fairly innocuous and non toxic if you don't eat it. What it does is absorb water. That slows down the water loss in the soil. I personally think lots of "health risks" are a bit overrated. Common sense is the key. For a potted plant it's OK but maybe not for your tomatoes. I really don't know, but in our chemistry lab we have lots of plants which are fed the reactor water from the Styrofoam reactions and they are quite healthy. Some also have Styrofoam in the soil. No problem. As for UV resistance, it probably wont do too well. Water damage will probably get to it sooner than the UV. The solvent diluted Styrofoam is like regular plastic: Very strong, tough and hard. I would use something simple and proven like tar. On the other hand your experiments can lead to useful discoveries. That tinkering is the motor of innovation. In an industrial environment we do the same thing. Then we sell it!

Fred82664 (author)Migs2010-06-25

lol Yes I am ready to order I will have the EPS sand-witch with a slab of PVC and those fake bate souse. there are those on this site that would push the health risks way beyond the realms of real life use. my post is in good joking

macrumpton (author)Migs2010-06-24

EPS is fairly benign until you get it hot enough to burn, and then it releases a gas that has some cyanide component that is very toxic to breath. At least that is what the guy who taught me to do metal casting said. We had a process at RISD (art school) where you could build stuff out of styrofoam, pack it in a clay rich sand and pour molten aluminum into the styrofoam, which vaporized as soon as the metal got near. It was a surprisingly good process for making quick castings, and a lot easier than investment casting to clean up. You could even make the finished surface smooth by covering the foam with tape and/or paper. The finished castings picked up details as small as the wrinkles in masking tape.

Thinkenstein (author)macrumpton2010-06-24

That sounds cool. I have seen aluminum casting of Styrofoam models, but I have never had the opportunity to try it. -- Styrofoam is also good for making hollow silicone rubber squeeze bulbs, squeaky toys, etc. Just cover the Styrofoam with a layer of silicone, let it harden and then introduce some lacquer thinner, or other solvent inside to eat away the foam.

macrumpton (author)Thinkenstein2010-06-25

I had not heard of the silicone/eps casting method. I will definitely try that. I don't have a foundry so I have not done metal casting in decades (though I have often wanted to).

macrumpton (author)Thinkenstein2010-06-25

I think the idea of the pellets in soil is to prevent the solidifyiing of the soil into a hard surface that is hard for roots to get through. The pellets weaken the adhesive bonds in the earth by providing less stuff to stick to, and make the soil lighter. At least that is my theory.

Thinkenstein (author)macrumpton2010-06-25

As good a theory as any. I'd still rather keep it all organic farming, though.

overblast (author)Migs2016-04-20

Could old bad gasoline or other VOCs be used for the solvent? That would be a way to put it to use and keep it out of the environment.

jackoftheforest (author)2010-07-02

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!

mstar (author)jackoftheforest2010-07-02

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)mstar2010-07-03

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.

overblast (author)Thinkenstein2016-04-20

What would happen to the Kool-Aid Man if he tried to break into the city by running into the walls? OH YEAH!! :)

mstar (author)Thinkenstein2010-07-06

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.

natman3400 (author)mstar2010-08-12

Think of it this way, your taking its toxicity out to some extent.

Pader (author)jackoftheforest2010-07-17

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.

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.

JimS86 (author)2015-11-27

Hyper Tufa, is mixing Portland cement "not concrete" together with peat moss for a light weight mix, makes great pots and bricks for garden borders. You can also mix concrete with pearlite to make a light but very insulated concrete slab. I used this mix for the cladding over the fire bricks on my bread oven. Build a fire inside and drag out the ashes, the oven stays very hot for days.

pparker4 (author)2015-09-16

that's so cool

ken.chambers.7169 (author)2014-11-26

Really nice work. Do you have a certain formula you like, as far as the ratios of cement to styrofoam?



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_bloke (author)2014-04-13

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

Maxmil (author)2013-07-20

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)Maxmil2013-07-23

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

About This Instructable




Bio: I'm a refugee from Los Angeles, living in backwoods Puerto Rico for about 35 years now and loving it. I built my own home ... More »
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