Using recycled concrete – Urbanite

Modern, rectangular pavers are all the rage in Austin urban landscaping right now. Almost every client
considering a new entry way or patio refers to this style when discussing their yard.  They enjoy the clean lines and segmented nature that these pavers add to their space.

IMAG2045But regardless of aesthetic value,  this choice has several advantages compared to a poured concrete entryway.  Many clients have experience with cracks in their concrete, and they figure if the stone or concrete is segmented, then they won’t have to look at, or repair, cracks.  Modern reinforcing techniques of concrete have made it so that large cracks, on this scale, are generally avoidable these days, but the likelihood of a large crack on a small slab is even lower.

IMAG0720If you’re considering a pathway or driveway near large trees, especially if it will be built under the tree canopy, choosing a pathway that is segmented or porous greatly benefits the root system of the tree by allowing water through or around it.  Not to mention the cracking issue again; large slabs can be heaved and move as  tree roots grow underneath.  Smaller pavers aren’t immune to this movement; however, they usually won’t crack, and can be repaired simply by resetting them.  To see an example of our pervious driveways, click here.

Clients have a variety of materials to choose from but most choose either a poured concrete rectangle or sawn patio stone, usually 2 1/4″ limestone or lueder. Our preference is typically the limestone for several reasons:

  • Less volume of material – the limestone is 2 1/4″, the recommended minimum for the concrete is 3 1/2″
  • No steel – Built correctly, even small concrete pads should have reinforcement
  • Installation is simple – no form boards, no concrete mess to cleanup
  • Local – We have multiple limestone quarries in central texas so most of the material is coming from close to home, minimizing transport cost

But the main reason we prefer limestone is simply because we think it is better for the environment.  There are a lot of numbers out there, but most estimates say that cement & concrete manufacturing accounts for 5% of the global CO2 emissions.  Concrete is a great building material, but in this situation, we simply think it is not appropriate.

Yes, it requires diesel to dig up the limestone, and more diesel to move the limestone, and electricity to cut the limestone.  But it takes a similar amount of energy to move the raw materials of concrete.  Keep in mind, that concrete is three basic things – cement, gravel, & sand.  And during the production of cement, they take the limestone ( a key ingredient of cement) and other materials and heat them up to 1500 degrees C, to the point that they are molten and then let them cool.  Where does all that heat come from? Fossil fuels.

So, at this point, you may be asking why use concrete at all in this application?  Well, the limestone isn’t immune to cracks.  If you drive over it with your car, it could easily crack; a 4″ slab of reinforced concrete would stand a better chance in that situation.  But for most urban clients, their yard is so small that it is not a concern.

So, is there a way to do this even more sustainably?    Maybe.

During a consultation at a home in south Austin a client mentioned to me that they wanted a new walkwayto their front door, and as part of the landscaping project, they also wanted an old concrete pathway torn out.  The existing pathway was straight, went in the general direction they wanted and was in good shape, so why tear it out?  After some remodeling, the placement of the front door had changed, and they didn’t  want to direct guests away from the front door, not to mention that when it rained, the walkway was simply  a river, it had settled and become the low  spot in the yard.

So after some brainstorming, the solution became obvious, let’s reuse the old walkway!

We did some basic math to figure out how whether it was feasible to do their design with the existing walkway and it seemed like it would work.  We began cutting up the walkway into moveable rectangles with a 14″ concrete power cutter, shifted them around with some rock bars, leveled them with some shovels and surrounded them with gravel.

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Using recycled concrete, otherwise known as urbanite, should be a part of every landscaper’s repertoire.  The client ended up with a funky south austin modern landscape that not only saved them money, but substantially cut down on transport costs, disposal costs and CO2 emissions.

 

I see piles of urbanite all over the place.  Hopefully most of it is destined to become fill somewhere needed, IMAG0403but I also see large piles of it at the dump that have only grown larger since we’ve been in business, clearly separated and waiting for someone to invent a use for it.  Transport is a major obstacle for small landscaping companies without heavy equipment so keeping it onsite has clear advantages, but most people need to move it somewhere, so maybe we can harness that need to keep it out of the landfill.  So if you’re considering ripping out your aged driveway, or installing a stone patio or walkway, consider urbanite.

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