Chances are good that at this moment, close to wherever you live, there’s a pile of broken up concrete just waiting for a good home. Most often it started life as a sidewalk, driveway or parking area but was recently demolished and is now waiting to be carted off to the landfill. We call this material, “Urbanite” and love working with it.
New concrete is pricey and has a big environmental footprint (high embodied energy) what with all the mining and the heating involved to make Portland cement as well as its transport in big rigs. Therefore, urbanite is a good alternative for many projects. In this article I’ll share some tips and uses of this abundant, free, salvageable urban waste material. At our urban homestead I’ve used it for the bases of cob walls, foundations of earthen (cob) ovens, borders for our gardens and for our little front yard pond, paths, and as a parking surface. We use it regularly as stem walls on cob buildings, too.
Mostly I’ll see a pile somewhere in my travels around town and, if I’ve got a hankering for some, I’ll check it out and maybe come back with the truck to haul it home. Everyone (no exceptions!) is overjoyed to get rid of busted, heavy old concrete instead of lugging it to the dump and paying to dispose of it. Craigslist and Facebook Marketplace are also great options. Search for “concrete."
Be picky! Don’t just take all of someone’s pile unless it’s good stuff that you know you’ll use. Be clear and firm about that. Use your confident voice.
And...take extra. It’s good to have a variety of sizes and shapes so you can have options for what goes where. Hammers help with in making new shapes, too.
This stuff’s heavy and as a man slowly and reluctantly approaching middle age I am not fond of moving heavy objects. So, if the urbanite is too big to move around, I’ll tilt it up and let it crash down with the result that one heavy piece becomes two manageable pieces. However, depending on your project (maybe a parking or patio surface) large pieces may be very desirable so bring a burly young friend for help with those blocks.
Look for chunks that are all the same thickness. It’s a big pain and time suck to do just about anything with urbanite of varying thicknesses. Trust me - don’t take it unless they’re real close to equal.
Be aware of rebar and other metals poking out of the concrete. Wear gloves as even the rocky edges can be sharp. Keep that in mind when placing the urbanite - no one likes a bloodied shin.
Usually there’ll be one smooth side (what was the top) and one lumpy (formerly the bottom) with 4”-6” thick lumpy and sometimes jagged sides where it was broken. Consider what you’ll be doing with the chunks when you’re about to adopt them. Some pieces are really just trash and you should leave those behind.
Sometimes the smooth side will be painted and are you going for the painted urbanite look?
Cob Oven Foundations: Make your base with an urbanite ring several feet high and then fill in the void with rubble, sand bags, old tv sets, new tv sets…I use cob as a mortar when needed to hold some of the more recalcitrant pieces together. Regular mortar works, too, of course.
Paths: My friend Larry has the best urbanite paths I’ve ever seen. He spent a lot of time (a lot of time!) leveling the hunks by digging out the ground underneath and then filling with sand for a base as needed (he used urbanite of varying thicknesses, tsk, tsk). He also incorporated interesting and colorful rocks and detritus and then filled the gaps in with a little concrete mix that he broomed into place. To summarize, instead of buying sterile-looking pavers at Home Depot or tons of concrete he’s made a beautiful, aged-looking and artistic garden path with minimal new inputs. Magnifico! This all could be done for a larger patio, too.
Note: Pay attention to the width of the gaps and be consistent - it looks better. Also, mind how you place the triangular pieces with square pieces - blend them to create repeating patterns so the individual sections become an integrated whole.
Earthen Landscape Wall Bases: The urbanite keeps the cob off the ground so it stays dry, is super solid, and looks sexy a couple/few courses high.
Pond Wall: It’s just a way to cover the liner and make some usable space for birds, plants, a little height...We mixed urbanite with big rocks we had laying around. It’s good to bury some of the edge, too, when propping them upright. Muy estable!
Garden Retaining Wall: It retains soil, it retains heat, it’s decorative and metro-chic! Kathleen’s grapes (and vetch) thrive in front of her south-facing border wall. No, not that border wall, just a garden wall. The thermal mass helps ensure the plants don’t get damaged by one of our malevolent late spring frosts. Eck, they’re so malevolent. She did a great job artistically with the shapes, angles, heights, and double layers. A gold star for her! Buried edges, again.
Parking Surface: We’re building a “green” conventional home on a lot near our house and the city wanted another parking spot...alongside the other parking spot...behind the other two parking spots...which don’t count because of rules and stuff. But it’s fine. Really, I don’t mind the extra work or cost. It’s fine. In the plans we put down “permeable pavers” so rain could percolate into the ground instead of becoming runoff and what we’ve done is this:
• removed the topsoil
• leveled the subsoil surface
• laid down a weed barrier
• added a few inches of ¾” gravel
• placed the urbanite to level-ish
• added more gravel to fill in the gaps
• It’s coming out nice. We can park things there.
That’s it! I hope this article has turned you on to the possibilities of this oft-overlooked but abundant resource. No more is that just a giant mound of rubble: it’s now a giant mound of rubbly possibilities. Yee-haw!
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