A concrete example

There’s an article in the current issue of New Scientist about this fantastic new type of concrete being made right here in ol’ Melbourne town.

It is essentially concrete without Portland cement. The stuff is called ‘e-crete’ (my goodness words with randomly added e’s at the beginning annoy me) and it is made by a company called Zeobond. Instead of regular cement it uses fly ash or mineralogical slags for the required bonding of the concrete. The problem with cement is that to make it you need to cook the hell out of limestone (calcium carbonate), which not only requires a huge amount of energy, but the chemical reaction that occurs when you cook the limestone results in not only the quicklime (calcium oxide) that you need for the cement, but carbon dioxide, which as well all know is a greenhouse gas.

Cement production worldwide accounts for about 4-5% of total man made greenhouse gas emissions. For each kilogram of cement produced, approximately 800 grams of carbon dioxide is released into the atmosphere with the majority of this, about 500 grams, coming from the actual chemical reaction itself and the rest from fossil fuels used to provide the heat to drive the reaction.

But the Zeobond stuff uses geopolymers (like fly ash) instead of Portland cement, which don’t release anywhere near the amount of carbon dioxide and don’t require heating either, hurrah!

Unfortunately you can’t specify this for a slab just yet. At the moment e-crete is only able to be used in non-structural applications. Still, it’s something to look out for in the (hopefully near) future.

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6 Responses to A concrete example

  1. lauren says:

    huzzah!
    and while e-crete’s a pretty bad name, they could’ve done worse and called it C-crete.

  2. markham says:

    Its possible that e-crete is a flawed piece of thinking.
    The geopolymer fly ash is not replacement of an “ungreen” material with a “green” one.
    Its the sequestration of waste produced by the steel industry.
    Its a filler in the concrete or landfill for the steel industry.
    It does improve the strength of the concrete as its filling it with metal but only up to limits.
    It does not replace the cement – the cement is the key “villain” in concrete in terms of energy use to manufacture. It is in fact a carbon offset – and carbon offset principles are not necessarily at this time aligned with reuse/recycling principles.
    The steel industry needs to clean up to produce less or no fly ash – which to an extent they are doing. The concrete industry needs to examine the sources of its energy for the production of cement – or find a fundamentally new process/material to replace cement.

    The question for geopolymers is do they allow the concrete to be recycled 100% into more concrete creating a cradle to cradle loop. Given that they are inorganic this may not be so,

  3. boffin says:

    markham, I think you missed the point. According to their website, they make concrete without using any portland cement. Geopolymers are a different type of binder that does not use cement at all.

    secondly, inorganic materials can be reused… um.. ah… like glass maybe! I think you need to do a little more thinking yourself!

  4. ari says:

    i agree that it would be best if fly ash didn’t exist in the first place, but seeing as it does recycling it seems a better option than just dumping it. this e-crete stuff doesn’t HAVE to use fly ash though, it is simply a good source of aluminosilicate, which it does need and which can be gotten out of rocks. far better to recycle something than mine for it.

    also, cradle to cradle is a great philosophy, but nothing that is recycled will be 100% the same materials as it was before. if you recycled something and the resulting product was the same exact weight as the original item, you would have a perpetual motion machine which is impossible because it would necessitate a breach of the second law of thermodynamics.

  5. markham says:

    I don’t do any thinking boffin.
    I’m not certain I said inorganic materials can’t be recycled.
    I looked again at my comment!!??
    But I know asked a question.
    The question is still unanswered here or anywhere else I’ve looked.
    Traditional concrete is 100% recyclable into itself – just like your obvious example of glass.
    What is interesting about both of them is they are simple materials – well understood chemically and they don’t sequester waste from other processes which can result in possibly perverse interdependencies. I’m a purist – I put that down to not being educated in Melbourne.

    There are issues, granted, with traditional concrete in terms of the amount/type of energy that has to be employed to make portland cement. Thats not an impossible hurdle to jump – and it strikes me that jumping that hurdle is fundamental to a lot of materials – not just concrete. Think Steel, think aluminium.

    I remain a skeptic, rather than a spruiker of E-crete – until its proven to me that I’m not putting a material into a building that a future generation cannot remanufacture or recycle into itself or return safely to the biosphere.

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