An Australian company has started to make concrete which promises to dramatically cut the carbon dioxide ordinarily emitted during production. Concrete is the second most widely used material on earth, after water. Figures vary, but it’s estimated that the manufacture of cement, the reactive ingredient in concrete, is responsible for over 5% of the world’s CO2 emissions.
Using a technique to make geo-polymers similar to those found in some natural volcanic rocks, a concrete alternative called E-Crete is now being manufactured in Melbourne, which claims to have reduced the amount of CO2 ordinarily emitted in the manufacture process by an estimated 80–90%.
Narration: What’s the fast growing source of greenhouse gas?
You might be surprised but it’s cement.
Cement’s already the 3rd largest man-made source of carbon dioxide - more than two billion tonnes of it a year. That’s after fossil fuels and defrorestation.
And because of all the construction going on around the world, cement’s carbon footprint is growing rapidly.
We desperately need greener concrete.
Professor Jannie van Deventer’s team at the University of Melbourne has found one. And surprisingly it’s chemically similar to a cement used by the ancient Romans.
Professor Janine van Deventer: The good properties of geopolymeric concrete are also present in the old Roman structures, so old roman concrete be made along similar lines in terms of the chemistry.
Narration: Over time the Roman knowledge was lost. The cement we know and use was invented in the 19th Century. The problem with it is its fundamental chemistry.
Narration: 60% of the carbon emissions from cement manufacture come from the chemical reaction required to make it.
Calcium carbonate is heated until breaks down into calcium oxide – which is needed in the cement – and the by-product Carbon dioxide.
An environmentally-friendly cement will need a completely different chemical reaction.
Professor van Deventer: You have to change the intrinsic nature of the chemistry. Instead of having a calcium based system – as is the case with normal cement – you have to switch the chemistry to an aluminium silicon system.
You use reactive alumino-silicate materials such as ash that comes from power stations when you burn coal ash is generated in huge quantities, and you can also use slag which is a by product from the manufacturing of iron.
Narration: Jannie’s team explored the technique in the lab.
Professor van Deventer: You This is fly ash which comes from the combustion of coal, so coal fired power stations, and we add to that also in this case slag - a waste product from iron making
And that is available in abundance through out the world. I’m also putting in some sand just ordinary sand that we use in normal concrete, because that is what we use as a filler.
Then what we add is just some water and also a little bit of alkaline solution, which turns this mixture of ash and slag and sand into a concrete which will help to bind the particles together.
Narration: The activator dissolves out aluminium and silicon molecules from the slag and ash.
These molecules then link together, forming much longer molecules…they’re the geopolymers.
The geopolymers themselves link together, creating a vast three dimensional network. That’s what gives the cement its strength. And no carbon dioxide is produced.
Graham Phillips: Now what we’ve just been seeing in the lab is happening here on an industrial scale.
In fact this concrete slab I’m sitting on is made from geopolymer cement. Now, it looks like regular concrete, it feels like regular concrete and it seems as strong.
There are 200 tonnes of storage silo being supported by this slab.
Narration: Moving from the lab to the plant was not a simple matter says Peter Duxson.
Dr Peter Duxson: It’s not just a case of taking a small thing and doing it on a larger scale. In the lab we very rarely make concrete as such.
When you move to making concrete that involves rock and gravel, and then not only that but the application of that product. So you need to work with contractors and the way that material is used becomes the critical factor.
Narration: The first steps in the process are identical to making ordinary concrete. Sand and gravel are loaded into a storage hopper, then sent up to the cement mixing truck.
Now comes the difference. Slag and fly ash – from the silos - are fed into the truck, in carefully measured amounts.
When the truck gets to its destination the activator is added. The geopolymer concrete is then used exactly the same way as normal concrete.
But it’s all very well having a cement with a low carbon footprint… is it any good? For example, will it do what ordinary cement does, year in and year out?
Well it turns out a similar type of cement was developed in the Soviet Union in the 1950s and 60s.
Professor van Deventer: What we have is that the Ukrainians have developed a concrete based on alkali activation – so the same type of chemistry as we use – but they’ve used only slag not fly ash.
So those old slag structures that are based on the same chemistry have been standing there for forty, forty five years.
And we have taken samples of those structures, we have published now work with the Ukrainians, at the University of Kiev, and we have shown that these structures are strong, but we’ve also explained why they are strong and stable. So we have confidence that these materials will indeed stand the test of time.
Graham: When you consider how many concrete structures there are in the world, and the fact that many of those will eventually have to be replaced, plus all the new concrete structures that could be built, you get the feeling that geopolymer cement could play a very big role in reducing our carbon footprint in the future.
- Reporter: Graham Phillips
- Producer: Matthew Lovering
- Researcher: Ruth Beran
- Camera: Simon Green
- Sound: Simon Kennedy
- Editor: Andrew Scott
Professor Jannie van Deventer
Dr Peter Duxson
Zeobond – Ecrete
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08 Oct 2010 6:36:09am-
Kindly let me know how to increase the immunity of geopolymer cement against hydrogen sulfide attack when it is used in sewer pipe.
22 Oct 2010 7:31:55am-
u may get find a solution here..http://gpc.latech.edu/projects.htm#P1
11 Nov 2009 9:44:30pm-
Can any one assist with where I can find info on different types of "Eco cements" in relation to there strengths and recognized applications worldwide? Are any of these cement strengths verified to replace standard portland types; MP25/34/40etc?
Thanks in advance
04 May 2009 3:31:38pm-
with due respect to all the technical people involved ,whatever is described in your definition of "green cement" is nothing but referred to as"COMPOSITE CEMENT" across the globe and is internationally governed by EN 197 or by ASTM 150.
And ofcourse the activator you are referring to could be "OPC clinker" itself.
23 Sep 2008 10:11:31am-
I wish to know more about green cement .I am a cement sculptor and need to lighten up to world views on emissions .where can I get mix recipes or the product Regards Caroline Moss
09 Mar 2009 4:18:59am-
i wish to know a bout green cement. i am acement contractor from traditional constraction family. and i want to know a bout the new green cement .
regards filippos papanikolau
31 Aug 2009 9:26:11pm-
Just wondered if you got a reply to your query? as I am interested in the product as well. I am in Melbourne and noticed the Company is also a Melb company .
interested in hearing what you found out.
It sounds like the product is based on Alumina content and there are a few products on the market that have alumina content (am no chemeist tho) but the chemeical process is prob not as standardised as the "normal" concrete.
20 Nov 2009 1:24:10pm-
In the USA, Dr. Erez Allouche of Louisiana Tech University is researching geopolymers. They are characterizing various fly ash sources from across the USA and are determining how to get consistent, reliable physical properties from various sources. They've been doing some real pioneering research, and will hopefully be getting to field applications next year.