[The images for this post were removed at the request of the blogger whose work we linked to]
Concrete that uses chunks or beads of expanded polystyrene (EPS) foam as aggregate has lots of interesting applications. It’s lighter, for one, so if you’re casting something intended to be portable (like Halloween yard tombstones) “EPScrete” can save you some lifting and groaning. It would also be expected to have better thermal insulation properties than plain-Jane concrete, and of course there’s the green angle: EPS is tough to recycle, and any that gets cast into concrete objects doesn’t end up in landfills (at least not immediately).
And while there is rather a lot of general discussion about EPScrete, online, there doesn’t seem to be much by way of hands-on instruction. That’s why I was pleased to discover this series of short posts from Nori Lamphere at her personal blog Our House, who did a great job, around this time last year, of keeping an online notebook describing her construction of an EPScrete wall using shredded foam slabs recycled from packing inserts. There are eleven posts in the series, which starts here.
Though you can make EPScrete using new polystyrene beads, Nori wanted to use directly recycled material, so she needed a way to grind up the foam slabs quickly. She started out using a wood chipper (which she does not recommend), but eventually switched to a homemade electric foam shredding machine, and developed a specific volumetric mix which includes recycled latex paint added to improve workability and flexural strength. Besides the recipe, she gives a detailed mixing protocol, and goes on to describe the construction of the wall itself.