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Archive for July, 2011

While the Roman buildings have endured 2,000 years or more, modern cement does not survive so well. Modern concrete can decay dangerously within decades. The problem was particularly significant in the Eastern bloc, where planners had seized on concrete as the ideal material to rebuild cities shattered by the war.

In 1957, Ukrainian scientist Victor Glukhovsky investigated why the ancient recipes were so much more durable than modern ones. From the earliest times, various additives were found to make a difference, and the ancients seem to have tried just about everything. The Romans are known to have used animal fat and milk, and more gruesomely, blood. Modern research has found that the blood altered the texture of the cement and introduced air bubbles, which help it to withstand the effects of freezing and thawing.

Glukhovsky discovered that superior cement could be obtained by mixing alkaline activators based on sodium and potassium, which occur in many natural minerals. His findings were quickly taken up in the Ukraine, but attracted little attention elsewhere. However, his work was important in inspiring Joseph Davidovits, a French chemical engineer. Davidovits developed a theory that the Egyptian pyramids were not constructed by assembling stone blocks as had always been assumed, but that the blocks were a type of artificial stone, made using reconstituted limestone, which had been cast in place.

In 1979, Davidovits discovered a new class of materials known as geopolymers, which are similar to Glukhovsky’s building cements and have aluminosilicate mineral powders added. Technically they are formed by condensation polymerisation and (unlike other cements) do not incorporate waters of hydration within their crystal structure. They are significantly stronger than other cements, impermeable to water, and much more durable to erosion caused by temperature change or chemical action. Geopolymers are only very slowly being accepted into the market in spite of their obvious advantages.

Source: Finding concrete evidence

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Hollow core blocks and bricks can be made with geopolymer.

Hollow core blocks and bricks can be made with geopolymer.


Scientists at Mexicos’s Cinvestav (Research and Advanced Studies Center), headed by Jose Ivan Escalante Garcia, have developed a geopolymer-based cement that actually results in producing reduced carbon-dioxide emissions and required lesser fossil fuel for the melting process plus it is even more durable and resistant than the regular cement that is used world-wide. This new cement variant that is geopolymer based can be manufactured at half the temperature (750 degrees Celsius) and the by-products during the manufacturing process can actually be incorporated while producing this cement. This new eco-friendly cement claims to reduce the total costs of producing the cement (upto 50%) and the CO2 emissions can actually be reduced by 80%

Source: Green Cleaning Idea

Stone textured hollow blocks

Stone textured hollow blocks


The line between geopolymer and stone becomes blurred when you start creating textured geopolymer that looks like stone, as in the blocks above. They’re actually made of concrete, but of course they could be made with geopolymer. This is another huge market opportunity. Hollow block lowers construction, reduces weight and materials and is extremely popular.

Source: Lyngso Garden Materials
(they have other products like garden ornaments that could be made with geopolymer)

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Hi Owen!
I’ve followed your (earthbag) blog for a while, and I really admire the way you’re THE earthbag guy; not the only one, but the broadest one. You’re doing important work; keep it up! I’m fascinated, as I can tell you are, by the prospects of casting a stone house. So I did a little casual price checking on ebay tonight, and it’s rather daunting.

Limestone Powder (Calcium Carbonate, CaCO3): $1/lb
Natron Salt (Soda Ash): $2/lb
Lime (CaO): Only one listing, but $8/lb
Caustic Soda (Sodium Hydroxide, Lye): $4/lb

These are all listed as reagents, in small quantities. Say you get them in bulk for less. Much less. Much, much less, maybe $1/lb for all of them averaged together. Am I wrong in estimating that a modest stone house weighs a couple hundred thousand pounds? That would make it a couple hundred thousand dollars just for the walls.

Can the cost really be so prohibitive? I had nothing to base it on, but I assumed casting stone would be cheap like earth building!
Thanks for getting this knowledge out there!

Owen:
This question goes to the heart of what this blog is about. You’re right about the expense if you buy commercially available processed products. What we hope to do is replicate what was done thousands of years ago. They didn’t buy anything. They gathered and used what was locally available — loose limestone, natron salt, etc. We’re trying to pull together various recipes so people can use what’s nearby and inexpensive. Things like crusher fines (the powder that’s washed off crushed gravel) come to mind. We’re also exploring weaker materials that are probably ‘good enough’ for many. Options like caliche, Alker technology and Low Strength Stone-like Material for Rural Areas may work for you. Did you see the article where an ancient civilization built with glutinous rice? We’ve had lots of articles on waste materials — fly ash, slag, rice hull ash, bagasse ash and other industrial wastes. There’s also cast earth and poured earth. Some stories (blog posts) have reported on geopolymer made with 100% fly ash or 100% waste materials. (Use the search engine on this site to find these blog posts.)

As for the weight of the building, that all depends on wall thickness and the size of the home. My first project will probably be ferrocement made with geopolymer — a thin shell of rebar and mesh plastered with geopolymer. So that’s one lightweight solution. You could make bricks or CEBs for fairly thin walls. Or you could make thicker walls with a weaker/lower cost material. Lots of options.

This open source blog is a journey. We’re not there yet. The strongest, most durable geopolymer products are pricey commercial products. They’re more sustainable than Portland because they create 80% less carbon dioxide, last longer, etc. But they’re out of reach price wise for many. Sometimes these products cost even more than Portland cement. It’s convenient to have off the shelf products we can utilize, but my real dream is to perfect simplified methods of making cast stone houses. Almost every day I read of ancient stone monoliths that were probably built with geopolymer and it gives me even more determination to figure out how it was done. What we really need now is a dedicated group to actively engage in testing and report the results. I’m slowly moving toward acquiring local materials for testing, but I’m extremely busy and can’t do as much as I’d like. This has to be a group effort.

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Sodium hydroxide (NaOH), also known as lye and caustic soda, is a caustic metallic base. It is used in many industries, mostly as a strong chemical base in the manufacture of pulp and paper, textiles, drinking water, soaps and detergents and as a drain cleaner.

Pure sodium hydroxide is a white solid available in pellets, flakes, granules, and as a 50% saturated solution. It is hygroscopic and readily absorbs water from the air, so it should be stored in an airtight container. It is very soluble in water with liberation of heat.

Of historic interest is the Leblanc process, which produced sodium carbonate, followed by roasting to create carbon dioxide and sodium oxide, which readily absorbs water to create sodium hydroxide. This method is still occasionally used. It helped establish sodium hydroxide as an important commodity chemical. The Leblanc process was superseded by the Solvay process in the late 19th century.

Sodium hydroxide is the principal strong base used in the chemical industry. In bulk it is most often handled as an aqueous solution, since solutions are cheaper and easier to handle. Sodium hydroxide, a strong base, is responsible for most of these applications. Another strong base such as potassium hydroxide is likely to yield positive results as well.

56% of sodium hydroxide produced is used by the chemical industry, with 25% of the same total used by the paper industry.

Sodium hydroxide is used in the home as a drain cleaning agent for clearing clogged drains. It is distributed as a dry crystal or as a thick liquid gel.

Safety warning:
Solid sodium hydroxide or solutions of sodium hydroxide may cause chemical burns, permanent injury or scarring if it contacts unprotected human, or other animal, tissue. It may cause blindness if it contacts the eye. Protective equipment such as rubber gloves, safety clothing and eye protection should always be used when handling the material or its solutions.

Dissolution of sodium hydroxide is highly exothermic, and the resulting heat may cause heat burns or ignite flammables. It also produces heat when reacted with acids. Sodium hydroxide is corrosive to some metals, e.g. aluminum, which produces flammable hydrogen gas on contact. Sodium hydroxide is also mildly corrosive to glass, which can cause damage to glazing or freezing of ground glass joints.

Source: Wiki

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Steel fiber reinforcement for concrete

Steel fiber reinforcement for concrete


Steel fibre reinforcement is widely used as the main and unique reinforcing for industrial concrete floor slabs, shotcrete and prefabricated concrete products. It is also considered for structural purposes in the reinforcement of slabs on piles, tunnel segments, concrete cellars, foundation slabs and shear reinforcement in prestressed elements.

Steel fibre reinforced concrete (SFRC) was introduced commercially into the European market in the second half of the 1970’s. No standards or recommendations were available at that time which was a major obstacle for the acceptance of this new technology. Initially steel fibres were mostly used as a substitute for secondary reinforcement or for crack control in less critical parts of the construction. Today steel fibres are widely used as the main and unique reinforcing for industrial floor slabs, shotcrete and prefabricated concrete products. They are also considered for structural purposes in reinforcement of slabs on piles, full replacement of the standard reinforcing cage for tunnel segments, concrete cellars, foundation slabs and shear reinforcement in prestressed elements. [Maybe metal shavings from lathes could be used where high strength geopolymer is required.]

Source: Steel fibre reinforced concrete (SFRC) – Quality, performance and specification
Image source: Alibaba.com

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Could this simple and inexpensive 4,500 year old technology be redeveloped for use today? We believe the answer to be a resounding yes! Research groups around the world, including our own, are well on their way to producing a geopolymer cement to rival the industry standard Portland Cement (PC) in compressive strength and cost.

Source: A White Paper by The Research Group of Dr. Michel Barsoum

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SYDNEY: A by-product from coal-fired power stations can be made into a stronger and much safer concrete with far less carbon dioxide emissions, researchers have found. They say this technology could “revolutionise the world’s building and construction industries” and they hope to move the technology towards a large-scale trial and commercialisation. Materials scientist William Rickard and his colleagues from Curtin University, in Perth, used waste materials called ‘fly ash’ to create the concrete.

Fireproof concrete may save lives
“The main benefit of using fly ash polymer cements is that they maintain their strength up to 1,200ºC whereas traditional cements start losing their strengths at about 600ºC … In the event of a fire, a building using traditional cement can lose its strength and collapse.
Buildings with fly ash concrete would have a much better chance of surviving a fire, Rickard says. Even coating exposed structural steel with it would reduce the heat that goes through the steel and prevent combustion. Each year there are approximately 100 fatalities and about 3,000 injuries from structural fires in Australia alone.

As well recycling, the fly ash cement will be good for the environment because it releases up to 80% less carbon dioxide than standard cement.
It could make a big different on a global scale. “[Currently] 5–8% of the world’s carbon emissions come from the manufacture of traditional cement,” says Rickard.

Source: CosmosMagazine

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