Concrete Recycling & Concrete Reclaiming
Posted on Thu, Jul 21, 2011 @ 02:00 PM
I've been away from blogging for 2 weeks now to enjoy the summer (and get some work done), and I thought I'd return to one of my favorite subjects: recycling concrete. What's it all about?
First, let's make a distinction between concrete recycling and concrete reclaiming. To me, concrete recycling usually involves the reutilization of hardened concrete that has been already used for another purpose, such as old sidewalks, curbing, pavements, buildings, etc. Your options are fairly limited for that material - it should be recycled into an aggregate material (sometimes called recycled concrete aggregate), and then used in a suitable manner. The best options seem to be using recycled concrete aggregate for base and sub-base materials under new roads and parking areas. By the way, very environmentally friendly and sustainable, since you are conserving landfill space (where the old concrete might otherwise go), and are prolonging the life of stone or other aggregate materials from mines and quarries which might go towards better uses in the future. A great option.
But what about "unhardened" concrete - we might call it leftover concrete, excess concrete, brought-back concrete - whatever. It's the extra, unhardened concrete that was ordered and has come back to the concrete plant that has to be dealt with at the plant. Note that this is a very common practice, particularly in the US, occurring when customers regularly overorder concrete rather than facing a potential shortage on the job. Need 8 yard of concrete? Order 10 to make sure we have enough - what we don't use the concrete producer will have to worry about. Not fair, but a fact of life. When you add this to rejected loads, it can come to a lot of concrete. How much comes back to concrete plants in the US? Estimates are anywhere between 2% and 10% of total annual production - when you consider all concrete produced in the US, this totals millions of yards of concrete needs to be managed annually.
What to do with it? Here's a quick rundown of the options:
- Dispose of it in a landfill. Bad idea. It's too costly, a huge waste of resources, and takes up vital landfill space. Avoid this.
- Use it for on-site purposes, such as paving and curbs. Great idea, provided you have the need. But really, how much need do you have on your site? How much curbing can you pour, and who is going to do the placement? Not a long-term solution.
- Give it away. Why do this? Aren't concrete producers in the job of selling concrete? And what about lost sales, quality concerns, etc. Another bad idea, and certainly not a long-term solution.
- Make blocks. Not a bad idea - but do you really have the market for blocks? Are you selling them to cover the costs of handling, storage, etc? Many do, but a lot of sites accumulate a lot of blocks, hoping for sales. Seems to be a decent idea for a small volume of returned concrete, but not for most producers in the long run.
- Batch on top - take that 2 yards of returned concrete, add 8 yards on top, and then sell 10 yards. Viewing only the technical aspects of this practice, might there be quality concerns? While not insurmountable, this doesn't seem to be the favored choice for most producers.
In my next blog article, I'll cover some better choices - hydration control admixtures, hardened concrete recycling, and the use of reclaimers.
Whatever choice is made, concrete should be recycled and reused in a positive, environmentally friendly and sustainable manner, and hopefully one that provides a good financial return.
In the meantime - what are you doing with returned concrete?
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