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

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

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

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

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:    https://www.instructables.com/id/TRASH-ROCKS-Eliminate-Unrecyclable-Trash

Step 5: 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). 

Comments

[Doc_Boomslang]

I love your fake rocks. You mentioned they were porous. How do they hold up to the weather? In a climate where it gets colder, I would be concerned that the airspace could get waterlogged and freeze and expanding water would blow apart whatever had been created.

I poured a wall at my house using straight concrete mix. I noticed my gloves that had become saturated were solid like rock the next day. So I threw some old pink fiberglass insulation in the mix as well. I figured the strands of shredded fiberglass would give it more strength.

What ratio did you use? 1% portland, 3% sand, 3% styrofoam? I'm thinking 1-gallon bucket of portland, (3) 1-gallon buckets of sand, (20) 1-gallon buckets of styrofoam fluff, (5) 1-gallon buckets of shredded pink fiberglass insulation.

[danf371]

I hope you’re still around to read this.

There are LOTS of fake rocks out there. They’re such good fakes that few people think they’re fakes.

I helped build Universal Studios Florida. I was very surprised at how some of the really ornate design features of the buildings were made.

Styrofoam chunks were glued to concrete block walls and covered in a concrete-like substance that was scooped on and troweled into final shape. If you see what looks like a concrete sculpture, it is more than likely Dry-Vit (proprietary name for the coating).

The big “rocks” around the lagoon are rebar covered in what looked like burlap, covered with the mix, and painted to look like rocks.

Two men were easily able to lift them into place. It took two men, not because of the weight, but because they were very large and bulky. Setting them in place was much easier that way.

Here’s a link to the Dry-Vit website. https://www.dryvit.com/#menu

I’m still fascinated by the process and how well it works.

Stay safe!

[Thinkenstein]

The fake rocks are sacks sewn of fishnet, filled with trash, with the fishnet then plastered with cement (1:3 mix cement to sand). If water gets in through a crack, it should hopefully find its way out through a crack, or you could drill drain holes in them. I have never noticed the rocks being full of water; definitely not enough to fill the whole rock. The insulation fiber sounds like a good idea, except for the possibility that the wet cement might react with it during curing. Some fibers, like basalt, need buffering by some chemical to protect them from the caustic cement while it is curing.

If you don't know about basalt fiber products, check out basalt rebar on Youtube. It also comes in chopped fiber, twine, and cloth forms. From what I have seen, it is a stronger fiber than fiberglass is.

[hazex75]

What is the ratio of the mix, it's not possible to try this without the ratio.

[jnnnyhsiao]

Hi, I have a basic question I cant seem to find an answer to online

When using foam to lighten the overall cast's weight -- how do you prevent the foam from floating to the top (and interrupting the surface? especially after vibrating out bubbles) ?

Thanks!

[Thinkenstein]

I don't worry so much about small bubbles anyway, since I'm going for light weight. I mix the Styrofoam and cement with a thicker mix, so the foam tends not to float. It can even be built up like masonry, to use larger chunks of foam.

[msm1981]

I am so impressed with you sculpture of Bartolo, it is beautiful! I came here for the styro recycling idea, but so appreciated seeing your artwork...

[Thinkenstein]

Thank you. Check out my YouTube channel to see more of my work: https://www.youtube.com/channel/UCMTXd_-nLlNtoq6gIidVVlw

[JimS86]

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.

[betonaloka]

betonaloka: like it

[shalnachywyt]

I've never had any luck with Hypertufa, no matter what recipe I use. It always falls apart when I pick it up.

[PatienceL5]

can you share examples pictures of your creations? [e-mail]

[pparker4]

that'absolutely brilliant and beautiful

[betonaloka]

yes i like it too

[shalnachywyt]

I've been making "fake rocks" with concrete and those styrofoam containers that you get with meat and fish from the grocery store. I simply cover foam piece with concrete using a trowel then, when it's dry about 12 hours later, I flip it over and continue to add concrete to the rest of the foam. I've made at least a dozen of these to use in what will eventually be my Zen garden to cover the clay and (expletive deleted) Johnson grass which is almost impossible to get rid of any other way. I first place recycled plastic bags that topsoil came in on top of the ground, then put the "fake rocks" on top. Eventually gravel will go on top of that. They're lighter than real rocks and do the job.

"Styrofoam at the core of sculptures helps cut down on the weight a lot." This is what I was taught in a college sculpture class. Of course it's more complicated in that you have to place concrete lattice (the kind used to anchor concrete to the side of buildings) in order for the concrete to stick to the foam, and then you have to make sure that the thickness of the concrete is at least 1/2 inch or the stuff flakes off as has happened with one of my attempts at making a sculpture. (Now I have to go and "repair" the sculpture by adding more concrete.) (see pic attached of the "concrete Tori")

Thanks for the idea about using styrofoam packing peanuts. I hate those things, but now I have a way to dispose of them and make something useful as well!

[jackoftheforest]

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]

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]

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.

[mstar]

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.

[Xaymaca]

Hi mstar; I know it is sometime since you commented here. Wanted your take on using styrofoam and cement for a slab roof. We live in Jamaica and must use serious amts. of steel in our structures because of earthquakes. Would you suggest what ratios to use and what levels to pour the cement. Trying to use the styrofoam as a heat break in the slab roof and for it to be structurally sound. If you have some questions to gain clarity on what I trying to achieve, just ask. Hoping for a reply and thanks.