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Recycled concrete

Recycled concrete appears as an aid to tackle the rampant consumption of concrete in our society.

The world loves concrete. We create an enormous amount of it. In fact, we produce 10 billion tonnes of it every year. That is one whole cubic metre of concrete for every man, woman and child on the planet. Every year! Over the next 40 years we expect to produce 230 billion square meters of concrete. That is adding about the same construction as the whole of Paris every week for the next 40 years.

As old concrete crumbles through time and wear then it must be replaced but what do we do with all that old concrete? We produce 900 million tons of concrete waste each year. The shameful thing is that 83% of that is dumped into landfill sites never to be used for anything useful ever again. Is the right thing to do? Surely not.

We produce 900 million tons of concrete waste each year

In this short article we look at concrete recycling, how it is used, how is it processed and what are the benefits of doing it.

Why throwing away old concrete is a bad idea.

Firstly, it costs money. Getting rid of old concrete to a landfill site costs approximately $35 per tonne. That can add up for a large demolition job. In many countries, recycling centres will pick up  used concrete for free.  

Perhaps more importantly is the fact that making concrete is bad for the environment. Two thirds of concrete is aggregate and that is usually mined from the ground. In the US alone that amounts to 1.96 billion tons of aggregate, 10 metric tons for every man, woman and child in the country. Aside from the damage to natural landscapes vast quantities of fossil fuels are used in the mining, construction and mixing.

What can we do with old concrete?

Well we can recycle old concrete it to make new concrete! Old concrete can be processed to produce aggregate that can be used alongside traditional excavated aggregate. Unfortunately, using 100% recycled concrete as aggregate doesn’t make good concrete. It is less durable and decays easily. However, a mix of 35% recycled concrete and 65% excavated aggregate makes very good concrete indeed.

Now we know that about 70% of concrete is aggregate and we use around 7 billion tones (70% of 10 billion tonnes of new concrete) each year. Given that we throw away 750 million tonnes of concrete each year then there is space to recycle every single bit it and reduce the demand for fresh aggregate by that same 750 million tonnes and still have space to use more.

How do we recycle concrete

It is relatively simple to recycle concrete. The concrete is crushed and smashed using mechanical crushers and impactors. Magnets are used to remove any metal from the crushed concrete. The resultant rubble is then washed and graded for use to produce different types of aggregate for remixing to make new concrete.

Benefits of recycling concrete

Recycling concrete reduces the demand for fresh aggregate and extends the life of landfill sites.  

In many countries standards exist, like LEED, to certify that the company is fulfilling environmental requirements in the conduct of its construction work. Using recycled concrete will score points in this type of evaluation.

Using recycled concrete reduces the cost of aggregates and so money is saved.  

Tests like those performed by the University of British Columbia Engineering Department in a five year study demonstrate that using recycled concrete as 35% of the aggregate has no detrimental effect on the concrete. In fact, the concrete produced is lighter than normal concrete and can be used effectively in the construction of buildings.

Here at BECOSAN we know that using recycled concrete as the aggregate in new concrete is good for the purse strings and good for the planet. We also know that concrete floors made using recycled concrete can also be made to look good too. The BECOSAN® treatment of grinding, densifying and polishing concrete can create a floor that will match any floor made with traditional aggregate.

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