Trash Concrete




About: 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 from discarded nylon fishnet and cement.

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. 

Step 1: 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

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. 

Step 3: Mixing the Cement

For those who have never mixed cement, all you need is a flat area to mix on, a water source, and a shovel.  A square nosed shovel is preferred to a pointed shovel.   One part of cement is mixed with three parts of sand. 

Mix the sand and cement dry first.  Make a hole in the middle of the pile and add water.  It is better to add less water at first and creep up on the proper consistency little-by-little.  Mix with the shovel, trying to not let water escape the ring of dry material.  If you get it too soupy, the bottles will float in it and the cement doesn't behave well as mortar between the bottles.   If you make a ball of mortar, it may sag some, but it should not run. 

Use rubber gloves to protect your hands.  Cement is caustic to skin.  Use a trowel for smoothing the cement. 

Step 4: The Finished Project

The patio was extended two, or three feet.  It was a small patio to begin with.  This extension makes it much more comfortable. 



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    136 Discussions


    2 years ago

    Great job at thinking on how to get some of that trash out of the dumps, where they are piling up faster than recycling companies can actually reuse them. My yard is in need of a few planters and a wall, and I am going to follow your idea and use all the cans/bottles I have been saving. Concrete additions/fixes/planters/ect are far too expensive for broke people to afford and this is a great way to help them improve their properties as well. And yes, the plastic doesn't degrade as fast as it would in a dump, but have you actually ever been to one in a big city?! They are ridiculously over filled with plastic products that someone "just figured that a company would recycle it for them". To find ways to recycle plastic (and not just in flimsy art projects that will be eventually thrown out) is commendable! Props to you sweetie!


    5 years ago on Introduction

    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.

    1 reply

    Reply 5 years ago on Introduction

    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.


    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.


    6 years ago on Introduction

    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.

    5 replies

    Maybe one should be able to order trash plastic bottles from the dump when needed, instead of collecting piles slowly over time.


    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.


    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.


    7 years ago on Introduction

    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.

    1 reply

    It's weight bearing until the metal rusts away. I'm sure it would work for a while, though; probably a long while.


    8 years ago on Step 4

    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.

    3 replies

    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..