EMC Greener Cement

[EdEarl]

EMC compared to Portland Cement saves over 90% CO2 emission and energy use. It can be used in 70% of construction instead of Portland Cement, with an estimated annual savings of 2.4G tons CO2 and 2.3T KW energy.

 

When there are many plants to make EMC, the climate may improve. At least, the climate will not degrade as quickly.

[Sato]

I think it would be like leaning on your side while skiing down a steep, icy slope. That's still better than not though.

[studiot]

The first recorded use of Pozzolanic materials was by the Romans, although the Etruscans may have used them before.

 

So they have been known for a long time.

 

The added durability of properly designed mass concrete containing pozzolans is worth having.

 

However there are one or two caveats in the structural use of the material.

 

1) The rate of strength gain by the curing concrete is lower with pozzolanic cement replacement than with straight OPC. The eventual strength is the same but you have to be careful with formwork striking times.

 

2) The resultant concrete has a lower pH than with OPC, resulting in decreased protection against carbonation. Whether this will affect the longevity of structures containing reinforcement has yet to be seen.

Edited September 8, 2013 by studiot

[EdEarl]

The first recorded use of Pozzolanic materials was by the Romans, although the Etruscans may have used them before.

 

So they have been known for a long time.

 

The added durability of properly designed mass concrete containing pozzolans is worth having.

 

However there are one or two caveats in the structural use of the material.

 

1) The rate of strength gain by the curing concrete is lower with pozzolanic cement replacement than with straight OPC. The eventual strength is the same but you have to be careful with formwork striking times.

 

2) The resultant concrete has a lower pH than with OPC, resulting in decreased protection against carbonation. Whether this will affect the longevity of structures containing reinforcement has yet to be seen.

 

If there are any Roman buildings still standing that used Pozzolanic material, what can we learn from them. I assume your concern is for the steel rebar. I've seen some references to using carbon fiber rebar, which probably would not deteriorate due to carbonation.

[studiot]

 

If there are any Roman buildings still standing that used Pozzolanic material, what can we learn from them.

 

Here is an extract from my copy of Neville, but first I posted a reply to your question in the parabola thread.

 

Did you look at it, you never came back.

 

 

The use of cementing materials is very old. The ancient Egyptians used calcined impure gypsum. The Greeks and Romans used calcined limestone and later learned to add lime, water, sand, crushed stone or brick or broken tiles. This was the first concrete in history.

Lime mortar does not ahrden under water, and for construction under water the Romans ground together lime and a volcanic ash or finely ground burnt clay tiles. The active silica and alumina (MY words compare with the EMC above) in the ash and the tiles combine with the lime to produce wjat became known as pozzolanic cement from the name of the village of Pozzuoli, near Vesiuvius, where the ash was first found.

The name pozzolanic cement is used to this day to describe cements obtained simply by the grinding of natural materials at normal temperatures.

Some of the Roman structures in which masonry was bonded by mortar, such as the Coliseum in Rome and the Pont Du Gard in Nimes and concrete structures such as the Pantheon in Rome have survived to this day with thecementitious material still hard and firm. In the ruins of Pompeii the mortar is oftern less weathered than the rather soft stone.

 

Note1) The Romans did not use steel reinforcement.

 

Note2) Carbon fibre reinforcement brings its own issues with it, not least that of bond strength within the matrix. That is the transfer of the loads from the matrix to the fibres. Carbon fibres are very slippery compared to steel.

[EdEarl]

 

Here is an extract from my copy of Neville, but first I posted a reply to your question in the parabola thread.

 

Did you look at it, you never came back.

 

 

Note1) The Romans did not use steel reinforcement.

 

Note2) Carbon fibre reinforcement brings its own issues with it, not least that of bond strength within the matrix. That is the transfer of the loads from the matrix to the fibres. Carbon fibres are very slippery compared to steel.

Yes, I just replied in the parabola thread.

 

Steel is slippery, too, which is why rebar is made with ridges. I assume carbon fiber rebar could be made rough too.

[studiot]

 

Steel is slippery, too, which is why rebar is made with ridges. I assume carbon fiber rebar could be made rough too.

 

 

Not all steel reinforcement is textured. And I did say carbon fibre is slippery compared to steel.

 

Just as a matter of interest how would you make textured carbon fibre reinforcement?

 

Steel is cold worked to produce the texture. You can't do this with CF.

[Moontanman]

When I make light weight concrete I use crushed lava rock but I only make small amounts to make artificial reef rocks...

[EdEarl]

 

Not all steel reinforcement is textured. And I did say carbon fibre is slippery compared to steel.

 

Just as a matter of interest how would you make textured carbon fibre reinforcement?

 

Steel is cold worked to produce the texture. You can't do this with CF.

At least one way would be to wrap monofilament in a spiral around the cylinder of rebar and apply resin. Perhaps, a spiral in each direction would be better. Sand blasting the resin surface would provide a fine rough texture.

Edited September 9, 2013 by EdEarl

[studiot]

Quite energy intensive then?

[EdEarl]

Quite energy intensive then?

You mean sand blasting? Compared to what, making steel rebar? I don't think so.

[studiot]

But you had steel bar in your recipe.

 

However we seem to be digressing. You are right that pozzolanic materials are significantly less energy intensive than OPC cements.

 

Another plus point is that they are generated on a large scale from former waste products. In this guise they are known as PFA or fly ash.

[EdEarl]

 

2) The resultant concrete has a lower pH than with OPC, resulting in decreased protection against carbonation. Whether this will affect the longevity of structures containing reinforcement has yet to be seen.

studiot, you said the above, which made me think you were talking about steel rebar reinforcement. But, yes we digress.

[studiot]

I did talk about reinforcement.

 

Western structures use reinforcement in general.

 

But carbonation can be a good thing as it leads to a stronger harder mass material, even if that does not protect any steel present.

 

Scientific American did an article a few years back on this, showing some amazingly strong Aztec structures and citing modern research into artificially inducing carbonation in mass concrete by using carbon dioxide injection. Sorry but I don't have the reference any longer but it was in the mid 1990s.

[Danijel Gorupec]

EdEarl, in your OP you provided an advertising article. So I took a look at Wikipedia, and also found an 'undercover' advertising article there... Anyway I have a hard time finding anything non-advertising about this. The technology is patented (I have mixed feelings about patenting)... Any more realistic information source?

[EdEarl]

EdEarl, in your OP you provided an advertising article. So I took a look at Wikipedia, and also found an 'undercover' advertising article there... Anyway I have a hard time finding anything non-advertising about this. The technology is patented (I have mixed feelings about patenting)... Any more realistic information source?

Sorry, no I do not. I sympathize with your feelings about patents. In this case, the patent may help generate the capital to spread the technology quickly in the Western world, if so, it is good. Moreover, China is about the biggest user of cement in the world, and they usually do not honor patents. I suspect China will begin making and using EMC without paying royalties, which goes along with the spirit of not patenting

[Brice]

Reply to Danijel Gorupec: I also took a look at the wikipedia article http://en.wikipedia.org/wiki/Energetically_modified_cement

 

I did not find it to be an advertisement in a "commercial sense" at all. It seems to me it was a very informative article about the science behind it etc., that has 20 years development in the academic community. The only reference to commercialization was a single reference to the technology being patented - and I do not see who that debases the article. It is about 5 words out of what must be several thousand.

 

I have found a load of other academic articles about the subject too, so do not understand the comment from Danijel "Anyway I have a hard time finding anything non-advertising about this". Number one, this is not true from even my brief research and if so, so what? Does that make the technology any less "worthy"? I do not think so. Why should it?

 

Regarding patenting, then it is very often required to ensure quality in the process: loads of Universities and colleges own substantial portfolios of patents. The point being that if something is patented, then unless you have a license you can use the method that's been patented. I would have thought that is prudent. It allows those who understand the technology to control its usage - and at the end of the day we do not want to build bridges and wotnot that collapse because the material was dodgy because someone had ripped-off technology they had not fully understood. I suspect that the patent protection is there to ensure quality.

 

If I were Chinese, I would want the license. Because I would also want the know how that comes with it and that's always going to be more valuable than not having that for the reasons covered.