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GMAX42
Joined: 25 Nov 2006
Posts: 3
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 Posted: Tue Nov 28, 2006 1:15 pm Post subject: Green Concrete? |
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I have learned of a cement product that yields higher and earlier strenghts than conventional cement and utilizes mostly post consumer products as bulk fillers. Single application stuccos, flooring toppings and precasting for just about everything is the focus of this technology. My question: are conventional cement based product considered green? And is it possible to make something more green? What are the crtiteria in deciphering the green value of such products?
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Antisthenes
Joined: 28 Nov 2006
Posts: 604
Location: Phoenix
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| Posted: Tue Nov 28, 2006 1:19 pm Post subject: |
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Flyash?
i read the production of concrete is responsable for 30% of CO2 |
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lekizz
millennium club
Joined: 11 Jan 2006
Posts: 1070
Location: UK
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| Posted: Tue Nov 28, 2006 2:02 pm Post subject: |
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Generally, there are a number of ways to assess the envirnmental impact of building materials.
Calculating the embodied energy would be one - cement takes a great deal of energy to extract, heat, mix and refine.
And you would ask youself whether the materials were recyclable, or renewable. The extraction of cement leaves bl**dy great big, enormous chasms in the landscape. Once it is dug out it is not going to grow back!
It is possible to use cement substitutes, as antisthenes says, I believe up to 30-35% of the cement content in concrete can be replaced with flyash, or other industrial byproducts. But this slows the curing of the concrete, hence the construction time.
The use of lime instead of cement is coming back into fashion with some enviromentally concious people. Lime was used as a simple glue in buildings for centuries. It is flexible and breathable too, working with the elements and with time. |
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GMAX42
Joined: 25 Nov 2006
Posts: 3
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| Posted: Fri Dec 22, 2006 12:11 pm Post subject: Green(er) Concrete |
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All valid points and thanks for the feedback. With traditional portland cement production, high heat is used to drive off CO2 from the blended componets yeilding a new compound that we call cement powder.
The new blends need not to be sintered like portland saving the furnace energy and CO2 emissions. I am completely fascinated by this product and it's capabilities. Check out www.gigacrete.com and please give me some of your professional insight. I think it will be a welcome and responsible addition to current building practices since it largely uses recycled materials.
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scottmckean
Joined: 04 Jan 2007
Posts: 5
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| Posted: Fri Jan 19, 2007 7:56 pm Post subject: Sustainable Concrete |
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I am a civil engineering student, and doing a project on green concrete, so if anyone has anything else to add, it would be greatly appreciated:
Cement production accounts for 5% of green house gas emissions, and uses 2% of global energy (this is just the cement). Add to that aggregate mining, and the chemical reactions releasing CO2, and cement is a very energy intensive product.
Up to 60% supplementary materials like fly ash can be used according to Canadian Codes, and they include almost anything that reactive sillicates like silica fume, ash, volcanic debris etc...
There is also the density of concrete to consider, lighter concrete imposes less dead loads and thus requires less material (if it can develop the same strength).
Recycled aggregates are a possibility as well, by using demolished bricks, concrete and rocks for lower grade concrete (difficult to control).
Does anyone have any other ideas on how to make concrete more sustainable? I am really trying to brainstorm something amazing that won't blow economics out of the roof |
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Antisthenes
Joined: 28 Nov 2006
Posts: 604
Location: Phoenix
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| Posted: Mon Jan 22, 2007 12:00 am Post subject: |
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just use adobe clay?
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Scubasteve
Joined: 16 Jan 2007
Posts: 14
Location: Ireland
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| Posted: Mon Jan 22, 2007 11:24 am Post subject: |
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Concrete has been criticized alot lately for being energy intensive to produce and because of the emmisons that occur during its production. However alot of the statistics and studies that have yeilded negative results for concrete have been funded or in some way initiated by the TimberFrame Industry. There are other statistics which I discovered whilst doing a project on Concrete that seem to confirm that concrete is not much worse than any other building material.
For example
"figures produced by an independent group of show that one tonne of softwood contains 10 times the embodied energy and 8 times the embodied CO2 as one tonne of structural concrete"
and
"Comparing concrete to steel, steel consumes 30 times the amount of energy in its production than concrete for the same mass of product."
Here is the web address of the article I found these figures on, it might be of a little help to you?
http://www.localplanet.ie/index.php?option=com_content&task=view&id=86&Itemid=53 |
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Antisthenes
Joined: 28 Nov 2006
Posts: 604
Location: Phoenix
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| Posted: Tue Jan 23, 2007 3:56 pm Post subject: |
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kudos
4 that.
i just got out of a boxed lunch for manufactured stone. stronger than concrete 2000 psi stuff, with just steam and pressure
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The most necessary/useful piece of learning is that which unlearns what is untrue: 'evil'
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lekizz
millennium club
Joined: 11 Jan 2006
Posts: 1070
Location: UK
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| Posted: Tue Jan 23, 2007 5:55 pm Post subject: |
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| Quote: | There are other statistics which I discovered whilst doing a project on Concrete that seem to confirm that concrete is not much worse than any other building material.
For example
"figures produced by an independent group of show that one tonne of softwood contains 10 times the embodied energy and 8 times the embodied CO2 as one tonne of structural concrete"
and
"Comparing concrete to steel, steel consumes 30 times the amount of energy in its production than concrete for the same mass of product." |
That must be a different definition of "embodied energy" than the one I understand. To creat timber you chop down a tree and cut it to size. Relative to producing cement, timber involves hardly any energy in production. It is correct to say that timber contains a lot of carbon because, basically, that is what trees are made up of. But carbon is only released when the wood rots. If the wood is used in construction it is 'locked up' with (hopefully) no chance of it being converted into greenhouse gases anytime soon.
Steel is very energy intensive to produce but you require significantly less tonnage of steel beam to do the same job as a concrete beam, for example. And steel can be recycled.
There are apporopriate building materials for every project. |
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scottmckean
Joined: 04 Jan 2007
Posts: 5
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| Posted: Thu Jan 25, 2007 7:05 am Post subject: |
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Thanks LeKizz,
I believe you are totally right. Wood should have a net CO2 release of almost zero, since plants remove CO2 through photosynthesis, so wood may have quite a low embodied energy. The big problem with the whole evaluation of embodied energy is that is it very subjective, and can have HUGE local variations.
You raise a good point with the steel as well. We are using steel on most of our industrial facilities because it allows much less labor (Which is a huge problem in Alberta, Canada) on site, and the transportation of aggregate and ready-mix cement would be very energy intensive and costly, where as a pre-fabricated module uses much less energy by being constructed in a fab yard.
Like you said, every project has the right material, the right texture and the right construction approach, it just depends on where you are building and the functional requirements =).
I am continuing my research, and will post what I find up here upon completion |
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AP
Joined: 31 Mar 2005
Posts: 578
Location: UK
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| Posted: Thu Feb 01, 2007 4:14 am Post subject: |
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There is also an endurance factor to be considered. If, correctly protected, a concrete building can last centuries, then its energy/carbon costs should be viewed in that light, as an investment, compared to a steel structure designed to be replaced with newer in 60 years. Its a very different model of development.
I was also under the impression that whilst timber might be very ecologically sustainable, it has two inherent problems in and of itself;
1- sourcing it so that its not from endangered sources or being moved halfway round the globe, given the want for "strong" timber, or hardwoods for fire reasons
2- the great toxicity of the vast amount of chemicals that are used to laminate and fireproof timber to give it a structural integrity to allow performance comparable to concrete or steel fpr design purposes.
Feel free to correct if I'm mistaken, naturally. |
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GMAX42
Joined: 25 Nov 2006
Posts: 3
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| Posted: Mon Feb 19, 2007 8:50 am Post subject: 100% recycled material concrete |
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I saw Gigacrete listed in the March '07 issue of Poular Mechanics as being one of the top green building materials! It states that it integrates as much as 100% recycled materials as its filler while maintaining structural integrity. It appears that it is not designed to replace portland based concrete for foundations rather continue the rest of the building with pre fab panels for exterior walls, structural floor planking, interior wall partitions with finish treatments and exterior facades. I came across another website they have www.gigacreteusa.com that explains many more possibilities. It also states that it is bullet resistant and completely fireproof! Is this too good to be true? Has anyone used this stuff yet and if so what application was employed?
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Rearc22
Joined: 06 Jun 2004
Posts: 17
Location: China
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| Posted: Wed Mar 07, 2007 10:36 pm Post subject: how is timber ecologically sustainable? |
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how is timber ecologically sustainable?....
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Antisthenes
Joined: 28 Nov 2006
Posts: 604
Location: Phoenix
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| Posted: Thu Mar 08, 2007 10:38 am Post subject: |
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SFI etc
by care to the environment through practices that equally replenish it
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The most necessary/useful piece of learning is that which unlearns what is untrue: 'evil'
may be acquired, Happiness through virtue which is based on knowledge!/? |
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Adrian Lombardo
Joined: 16 Feb 2007
Posts: 8
Location: Canterbury, UK
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| Posted: Fri Mar 09, 2007 11:20 am Post subject: Re: how is timber ecologically sustainable? |
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| Rearc22 wrote: | | how is timber ecologically sustainable?.... |
It is sustainable by planting new trees when chopping down the old ones. released CO2 in the timber comes from the air in the first place anyway.
This is very interesting, I hope the discussion goes on. When it comes to fly-ash, it may contain very much heavy metals, according to wikipedia. |
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