Picture of Trash Concrete
I wanted to extend a hillside patio area.  Hauling in dirt fill by hand was more work than I wanted to do, and it would probably settle over time.  Cement was better. 

The gravel in regular concrete is heavy and costs money.  I decided to replace it with free plastic bottles and pieces of Styrofoam trash.  Sand and cement were the only purchased materials. 

Although the air cavities from the bottles don't have the compression strength of solid cement, the spaces between them create interior columns, walls and arches which are load bearing.  The top layer was more solid, with pieces of foam and cement to help spread out the weight.  The patio only needs to support foot traffic, and it does that just fine. 
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Step 1: Collecting the Trash

Picture of Collecting the Trash
I don't drink soda pop, or use vast quantities of Chlorox.  Going against the normal flow of things, I went to our city's recycling department and was given bottles that they had collected.  I also put the word out locally and helped clean up our barrio of locally generated bottles. 

Step 2: Basic Structure

Picture of Basic Structure
I laid some fishnet down first, with enough skirt left over to fold up over the layer of trash concrete.  That way, the mass would have a skin holding it all together if it ever does decide to fragment. 

Bottles went down first, with richer amounts of Styrofoam toward the top.  I already knew that Styrofoam cement makes a pretty non-compressive layer for walking on.  That layer helps spread one's weight out over the foam-like bottle and cement layer below.   Foot pressure is not concentrated on a small area. 

It supports my weight well now, and I am expecting no problems. 
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RoBear61311 months ago

While the Clorox bottles may be a bit extreme, this concept actually dates back to the originators of concrete, the Romans. They mixed small clay post into the concrete to lighten the weight while maintaining strength.

And placing the bottles on their sides does maintain a natural circular arch, while placing them upright would probably create a weaker load bearing arch.

Thinkenstein (author)  RoBear61311 months ago

On their side, you get the advantages of arches. Vertically gets the advantages of columns. Bottle necks placed vertically probably combine both because of their shapes.

Interesting about the Romans including clay pots in their mix. Thanks.

melliott111 year ago

Would it be okay use cans in this way?

Thinkenstein (author)  melliott111 year ago

I would lean toward aluminum cans, set vertically with the openings facing downward to avoid collecting water inside should water penetrate the cement through cracks. Even if it did, though, you would probably never have mosquito problems. Iron cans would probably rust away over time.

foobear1 year ago
Sorry if this has been asked already, but how is it holding up over time?
Thinkenstein (author)  foobear1 year ago
It's been holding up just fine. Not even any cracks that I can see.
Schmidty162 years ago
to keep the zombies out lol!!!
Lokisgodhi2 years ago
This is an interesting method of recycling bottles.

One should remember there are different ways of recycling/reusing materials

You can reuse the material to make other containers.

You can use the preexisting form in another manner.

You can reuse the material in another form.

The only downside I can see in this particular use is that if you live in a populated area, your neighbors are unlikely to appreciate you collecting a large number of bottles over a long period of time in order to have enough material for a project like this.

I read a similar instructable a few years back using stacked 5 gal pails to build walls. Great idea, but collecting enough is likely to raise the whole neighborhood's ire long before you got the stucco on the completed wall.
Thinkenstein (author)  Lokisgodhi2 years ago
Maybe one should be able to order trash plastic bottles from the dump when needed, instead of collecting piles slowly over time.
Definitely better than braving hordes of irate neighbors brandishing torches and pitchforks. ;-)
Thinkenstein (author)  Lokisgodhi2 years ago
To eliminate the dump, it would be nice if trash pick up trucks could just deliver bottles directly to construction sites on trash pick-up days. That would take a load of work off the recycling centers. Delivered in a big mesh sack, the bottles wouldn't blow around the neighborhood. It would be nice if the mesh, itself, could be used in construction.
The thing is in a lot of places, soft drink plastic bottles are redeemed with machines which shred the bottles as they're collected.

Shredded PET can probably be used as a concrete filler material but I don't know how or if the residue of the contents would affect the concrete. Might require a separate washing step. That would require a lot of water.
Thinkenstein (author)  Lokisgodhi2 years ago
I don't like the idea of shredded plastic bottles in the cement especially. The main advantage of using the bottles is the air inside them that makes for light weight, and cheap fill material.
323maderas3 years ago
It just occurred to me that this would be a good place to put discarded computer cases-stack them w cement between like they were bricks, layer or two of mesh over all of it, and finish-crete it. I know it's metal that can be recycled, but if you need a little more weight-bearing base for a bench or something, this would work.
Thinkenstein (author)  323maderas3 years ago
It's weight bearing until the metal rusts away. I'm sure it would work for a while, though; probably a long while.
vincent75204 years ago
Shouldn't we call that pollution ???…
Concrete you can do away with. Grind it in pieces and it makes material such as gravel for new roads …
But concrete with foam and plastic ? Both the latter will pollute for a hundred years, maybe more … 
And this just when we and some governments are trying to prevent these material to spread with coherent recycling methods and enforcement.
I must confess I am somewhat at loss with this instructable.
Don't you think there were other methods for efficiency, economics and light work, the combination of the three being perfectly acceptable ?…
What other members think ? …
Best wishes to all.
Thinkenstein (author)  vincent75204 years ago
All the plastics seem to eventually end up polluting, even if they are recycled a few times along the way. At present, the percentage of plastics recycled is not very impressive. Maybe there is not enough profit in it. Not producing or using plastics is probably the only clean way of solving that problem with them.

There are technologies for turning them back into oil, or fuel, but I don't know how energy efficient they are. Also, burn the fuel and you again are polluting.

As far as road fill goes, I kind of wish we had done something like elevated monorails instead from the beginning. It would have scarred our mountainsides less. Road cuts here in the mountains invite landslides, which mean constant maintenance. Roads also spread asphalt over topsoil, which seems somehow insulting to nature.

Busted up plastic bottles and cement could always be used as aggregate for more plastic bottle and cement floors and patios, instead of roads. The plastic may still break down, but it does so more slowly when locked up in cement.
Ok, plain and simple we need other methods of recycling. We need to find other processes of breaking down and reusing these "Non-Recyclable" plastics and polymers and hopefully at some point leave polymers behind in place for something strong and biodegradable. This may be one possible alternative solution for now but, by no means is this a "solution" or in my opinion a good alternative at that. We need to change our ways if we want to change this planet. But i do commend you and everyone else who are at least trying to address the problem and come up with solutions. Keep fighting the fight guys..
COuldn't agree less than 200% with you !!!…
Thinkenstein (author)  vincent75203 years ago
Me too, but until the replacement chemistry comes along, I think this is a reasonable way to turn waste into a resource.
-- Cheers!
I don't agree with you on this point : by using the waste so liberally you spread it and it will be not reclaimed when chemistry will allow to treat it …
My idea would be to dispose of it in dumps made for that and let it sit there until it can be "bio-degraded".
Then again I know it is a somewhat wishful thinking, still containing those "non-recyclable" plastics in specific places is essential to me.

As for you way of living : please keep on the good inventive life you lead. We need a whole lot more people like you !!!…
Thinkenstein (author)  vincent75203 years ago
There is already some technology that, with heat and pressure can convert plastics to fuel, lubricants, and ash. If it was so good, though, you would think it would spread faster than it has. No sign of it here, yet.
Well that's a good sign anyway…
We're going in the right direction
Best wishes
I agree thinkenstien , the more plastic you lock up in concrete the less ends up floating out there in our water ways. I seen on pbs there is an island of plastic the size of new england, floating out in the middle of the pacific ocean.
OK, I understand your point and basically I agree with you, especially about roads.
Nonetheless I think (but it maybe only my "aesthetics" feeling, whatever that means !… LOL) it really bothers me to see all this plastic not being recuperated one way or another

Best wishes … 
You sure don't want to talk to anyone that works in the recycle industry, you'd be blown away by what really takes place.
Remember all that computer crap that went to China for recycling?
You really don't want to know what they do.
This is a great use of material, besides it takes a lot of ENERGY to move it, clean it, separate it, melt it all down, yada, yada, yada....
The reality is, recycling is a FOR PROFIT business, they don't do if for puppy dogs & rainbows.

I always thought this would have great insulation properties too.
hi there see my answer to you and and bricabracwizard and jpinney below
have a good day
Yes, you definitely wouldn't want to know how much the west dumps on third world countries and how they dispose of it and what happens to the locals!!
hi there see my answer to you and jpinney below
have a good day
But Vincent, it is being reused. When most still ends up in the landfill or along the sides of our highways and byways, this starts to look like a better use.
Hello there ! … this is an answer to Bricabracwizard, bluumax and jpinney :

I do know the strain we put on poor countries, and I feel it's a shame (and it is not solely environmental … ).
But if I agree not to dump my junk in our neighbor's backyard I don't either want to see mine filled up to the brim …
To me recycling is not hiding non recyclable stuff in constructions that will be uncovered by future generations who will have to face highly polluted soil (think of the food chain …) but creating low environmental impact materials that can either be reused for the same or other practical purposes or that will dissipate in nature at a reasonable pace so that future generations will not have to endure our misgivings.

Also I do know what's going on in the recycle industry : not really ethical, to say the least… Can even tell you of a funny story (from my country !…)
well, at the moment its not entirely profitable as you say, but they've discovered a type of bacteria that when plastic is heat treated is capable of breaking down the molecular structure of the plastic rendering it completely re-usable without lowering the quality of the plastic. this actually means that in the next couple of years like with glass bottles we will be paid for our plastic refuse. jobs and work will be created from collecting plastic from dumps, landfills and other such places, and converted into building materials. i read an article in the irish times about plans to develop a 'plastic island' holiday resort! damn interesting stuff!
The thing about this recycling technique is that it has only been discovered in the last year at the start of 2010, by a UCD student in dublin. so full implementation will take a bit of time!
Be careful. Don't forget what happened to Haiti.
nachsan4 years ago
I agree with Thinkenstein it's a good way to use plastic. If it's gonna last 100 years it can be 50 under your feet, and you don't waste other materials, don´t forget that the making of cement is a very pollutioning proccess.

For the next extension you could fill the bottles with water, it make them more resistant. And don´t use the foam, it will compact in a few years and the concrete could break!!!!

P.S.: sorry for my english, ha, ha
1161858 nachsan3 years ago
why not just fill them with dirt being enclosed in the bottles they wont sag from seeping water and wont expand and evaporate like water and im sure there is plenty of dirt laying around
Thinkenstein (author)  11618583 years ago
Dirt is cheap, but it is difficult and time consuming to pack a small-mouth bottle with dirt. Also, unless the dirt is really compact, the bottle can still compress under pressure. It doesn't compress, though, because the cement is rigid. If the cement doesn't break, the bottles won't compress, hollow or otherwise. If they don't compress hollow, there is no reason for filling them with water, or dirt. Hollow bottles make a lighter-weight mix, which is sometimes a good quality. The cement has not broken thus far. One can assume that the bottles and foam inside have not compressed.

It helps to have a fairly rigid top layer, which spreads one weight out over a larger area and prevents localized failures.
Zovits nachsan4 years ago
I was also thinking about water-filled bottles. But in winter water would freeze and expand in the process, that could crack the concrete.
I'm thinking he probably doesn't worry about his patio freezing In Puereto Rico
just fill em half way.
ken24004 years ago
So in the end one want to lighten the mix.
I wonder if air could be injected into the mix while it is setting and making blocks with a number of small air holes then use the full mix to put them together.

I thought of using peanuts but have not done so yet.

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