Trash Concrete





Introduction: 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. 

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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    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!

    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.

    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.

    Would it be okay use cans in this way?

    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.

    Sorry if this has been asked already, but how is it holding up over time?

    It's been holding up just fine. Not even any cracks that I can see.

    to keep the zombies out lol!!!

    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.

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