Why recycled concrete? Concrete's active ingredient, portland cement, is pretty energy intensive to manufacture and so I thought I'd check out some alternatives to see if I could find something recycled or less energy consuming to produce. What I found is a portland cement replacement product called Eccorok that's made mostly from recycled coal ash. I also replaced the traditional aggregate (sand and stone) with recycled glass for a mix that's about 98% recycled. Coal ash is often used to replace a portion of the portland cement in a traditional mix, but this product is the first I've found that uses such a high percentage of it.
The photo above is a form containing the first four test pours that I did to check the proportions of my ingredients. The one below is the blocks after being removed from the form.
The first one on the left follows (with a couple of small changes) a recipe that was given to me by Tom Fischer of Fishstone, the company I bought the supplies from. It was a bit too dry, most likely because of a substitution I made in the mix - note how many voids remain. For the next one (second from left) I lowered the aggregate amount a bit and it flowed much better. This one is pretty close to the mix I'll cast the first project with. The third one from the left is a "light weight mix" test. I replaced 30% (by volume) of the aggregate with microspheres (very small empty glass spheres) to decrease the weight. It worked great, but I'm not sure the weight decrease is worth the cost increase for general use. More on that in a future post. The last block (on the right) is the same mix as #2 with the addition of black pigment, and again, this is really close to the mix I'll use for the first casting.
The next step is to clean these up, fill the voids and seal them. I'll show you how they came out in a future post. I'm hoping to have some pieces made with this mix ready for the Crested Butte Arts Festival. Come by and check them out.
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