Geopolymer Summary

Previous blog posts have introduced basic information about geopolymer. Let’s summarize what we’ve covered so far.

– Geopolymer is a term covering a class of synthetic aluminosilicate materials with potential use in a number of areas, essentially as a replacement for Portland cement and for advanced high-tech composites, ceramic applications or as a form of cast stone.
– This amazing video by Prof. Davidovits is what first caught my attention to the possibilities of building with geopolymer.
– Stone houses have always been in high demand, including by those who can afford to pay a premium price. Stone is expensive is quarry, cut and ship, and labor costs are high because of the slow, skilled nature of the work. But what if you could build your own stone home much more quickly with few specialized skills? And what if you used local, low value materials to reduce costs? You’d have all the benefits of a stone house at a fraction of the cost. This is the allure of geopolymer cast stone houses.
– Geopolymer is carbon neutral and doesn’t need a large amount of energy to produce, can be produced by batching processes similar to those used for Portland cement, can be applied as shotcrete or by hand, has rapid set binders, is resistant to corrosive elements such as sea salt, is not dissolved by acidic solutions, has excellent frost resistance and withstands repeated freeze thaw cycles
– Because they don’t have water in their structure, they do not suffer from vapor spall and they resist very high temperatures.
– Geopolymer can reduce the amount of pollution by 90% and last much longer than Portland cement.
– Geopolymer can be made from low cost waste materials like fly ash and slag.
– Cement with slag has better workability and finishability, higher compressive and flexural strengths, and improved resistance to aggressive chemicals.
– Ancient pyramids, statues and other objects may have been made with geopolymer.
– Geopolymer can be used for architectural uses, including countertops, sculptural tile, fireplaces, fountains, picnic tables, benches, pots, etc.
– Glass, colorful stones, seashells and other materials can be embedded in geopolymer.
– Sculpted forms will create geopolymer with stone-like texture.
– Geopolymer can be used to make blocks and bricks of various sizes and shapes, and replace Portland cement in cultured stone veneer.
– Some eco cements are actually carbon negative – they utilize industrial wastes and absorb more CO2 than they release.
– Building materials can be made from low cost, sustainable materials such as rice hull ash, gypsum, clay, sand, coconut coir dust, sugar cane ash and sugar cane filter cake, diatomaceous earth
– Products made of fly ash and rice hull ash are lower cost than Portland cement.
– Ultra-fine fly ash allows for a lower water-cement ratio and stronger concrete, additional resistance against early age stress development and restraint cracking, and decrease in permeability.
– Rice hull ash, which is extremely high in silica, improves workability, strength and impermeability of concrete mixes, while making the concrete durable to chemical attacks, abrasion and reinforcement corrosion, increasing the compressive strength by 10% – 20%.
– Bricks can be made with 100% fly ash at room temperature at lower cost than traditional clay bricks – see the “Greenest Brick”
– Gypsum and lime stabilized soil (Alker technology) produces inexpensive, durable, strong building materials that, even though not hard as stone, are adequate in many cases.
– Cast earth with gypsum binder can be poured just like Portland cement. Klaus Leiss suggests borax or citric acid as a retarder to slow the setting time.
– Professor Davidovits has demonstrated Low Temperature Geopolymeric Setting
– Some off-the-shelf geopolymer products such as E-Crete and Pyrament are now available. Pyrament can support the heaviest of aircraft after only six hours.
– It’s probably best to start geopolymer experiments with off-the-shelf processed materials until you’ve worked out your recipes.
– Calcined source materials, such as fly ash, slag, calcined kaolin, demonstrated a higher final compressive strength when compared to those made using non-calcined materials.
– People have been developing a wide range of cast stone formulas for many years, no doubt because they understood the value of ‘liquid stone’.
– Dr. Michel Barsoum’s electron microscope studies have provided extremely compelling evidence that some ancient structures such as the pyramids were partially built with geopolymer.
– Thin shell structures that use minimal materials can be made with geopolymer.
– Air entrainment additives create tiny air spaces in geopolymer to increase its insulation value and resist damage from freezing.
– You can add scoria, pumice, perlite, vermiculite or rice hulls to reduce the weight and increase insulation values.
– Geopolymer can be stamped, stained, polished, enhanced with overlays, inlays, exposed aggregates, etc.

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Ecologic Tech “Greenest Brick”

Ecologic Tech “Greenest Brick” made with 100% fly ash

Here’s more information on the 100% fly ash bricks from a previous post. This new information explains how they make the bricks without binders.

“Greenest Brick” is the trade name of a special type of bricks invented and made by the EcologicTech, using fly ash as the raw material. The Greenest Brick has many advantages over conventional clay bricks in that: (1) It requires much less energy to manufacture, (2) it does not emit any pollutant and greenhouse gas during and after manufacturing, (3) it costs about 20% less than manufacturing clay bricks, (4) it is more uniform in size and shape, and hence saves labor cost in laying bricks.
Fly ash can be utilized to make bricks and blocks in one of several ways:
(a) To substitute for a portion of the cement and/or aggregates in making concrete bricks and blocks. This is a common use nowadays not only in the U.S. but also in many other countries.
(b) To substitute for a portion of the clay used in making clay bricks. This uses the same process for making clay bricks, requiring heating the adobes (green bricks) in kilns to more than 2,000 degree F, which consumes much fossil fuel and generates air pollutants and carbon dioxides due to the combustion of the fossil fuel
(c) To substitute for all the clay used in making clay bricks, using the same process for making clay bricks which requires burning fossil fuel to heat adobes in kilns at over 2,000 degrees F. This uses the same process and has the same drawback of (b) except that 100% fly ash is used in making bricks.
(d) Use 100% fly ash to make bricks without firing adobes in kilns. This process to make Greenest Bricks is the focus of the remaining questions and answers. Henceforth, when mentioning “fly ash brick” or “Greenest Brick” in this document, it means “the 100% fly ash brick made without cement or any other binder, and without kiln firing or autoclave curing.” The curing method used for fly ash bricks uses much less energy than either kiln firing or autoclave curing.

For fly ash that contains a large amount of calcium (e.g., Class C fly ash), the fly ash is cementious (i.e the fly ash reacts chemically with water in the same way that Portland cement does with water — a synonym of “cementious” would be “self-cementing.”) in nature, and no binder is required to make bricks or blocks at room temperature using such fly ash, and using ET’s patent pending process, which we chose to call it “Greenest Brick”. However, for fly ash that is low in calcium (ex. Class F fly ash), the fly ash is not cementious. It consists of mostly inert materials that don’t react chemically with water. In this case, it is necessary to add certain binder before bricks can be made at room temperature. Therefore, it is much easier and less costly to make fly ash brick using the room-temperature process (Greenest Brick) than if the fly ash is Class C rather than Class F.

In the United States, approximated 50% of the fly ash is Class C. The Class C ash is generated by burning Western coals, usually subbituminous or lignite. For instance, the largest coal source and reserve in the United States – Powder River Basin Coals – produces Class C fly ash. For bituminous coals produced in Eastern states, they normally produce Class F fly ash. However, if such coals are burned with limestone in fluidized boilers in order to remove the sulfur from the coals, or if powdered limestone is injected into the exhaust flue gas using a clean coal technology called “flue gas desulfurization (FGD)”, the fly ash produced from such a system, regardless of the type of coal used, will contain high amount of calcium oxide (CaO). Therefore, there is plenty of high-calcium fly ash in the United States for making fly ash bricks, more so in the Western states than Eastern states.

Color: The natural color of fly ash bricks made of low-carbon fly ash is a neutral buff color. For fly ash bricks made of high carbon fly ash, the brick is gray or dark grey. Simply adding a small amount (1%-2%) of color pigment leads to fly ash bricks of different colors, as shown in the photo.

Fly ash bricks have the following advantages:
• Cost less to produce – at least 10% less than concrete bricks and 20% less than clay
bricks. Details on cost will be addressed later in this document.
• Save construction cost – Due to the uniform shape and size of the fly ash brick, it saves labor in laying bricks by about 15%. This translates into an estimated 7 cents reduction in labor cost in laying each brick.
• Use less energy – Much energy is consumed in firing clay bricks in kilns. By using fly ash bricks instead of clay bricks, much energy is saved in brick manufacturing. Details on energy saving will be addressed later in this document.
• Reduce air pollution – Much fossil fuel is used in heating clay bricks in kilns. Burning such fuel generates air pollution and greenhouse gas (CO2), contributing to global warming. By manufacturing fly ash bricks (at room temperature) instead of clay bricks (at over 2,000 degree F), emission of air pollutants and greenhouse gas is avoided at brick plants, which helps to reduce air pollution and global warming. More on the environmental benefits will be addressed later in this document. Based on the above benefits, the fly ash brick is not only a low-cost, high-quality brick, it is also the “Greenest brick” of the future. Widespread use of the Greenest brick in the future would contribute not only to lower construction cost for housing but also to a cleaner and healthier environment.

The term “Greenest Brick” is derived from the fact that there are other bricks made of fly ash and they are Green (environmentally friendly). However, since other fly ash bricks either require the use of cement or lime as binder, or require burning fossil fuel in kilns, they are not as Green as the bricks developed by ET, which use 100% fly ash (no cement or lime), and which does not require burning fossil fuel in kilns which generates pollutants and greenhouse gas. Therefore, this is certainly the Greenest type of fly ash brick, deserving the trademark name “Greenest Bricks”.

Source: Ecologic Tech

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Designer CEBs and Bricks

Designer CEBs and Bricks

This designer compressed earth block is a sampling of the possible colors and designs you can create, using the materials and methods covered on this blog and our Earthbag Building Blog. In this example, broken glass is mixed with geopolymer and the mixture is compressed in a block press.

Star Top CEB Presses

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$300 Geopolymer CEB House

$300 Geopolymer CEB House (click to enlarge)

I’ve added a third entry in ‘The $300 House Open Design Challenge’. CEBs are popular and practical, and some of you may be thinking of using them for columns, next to wood stoves, interior walls or as a design element. They would make a great center column in a roundhouse. Geopolymer CEBs turn to actual stone as explained in several previous posts.

Please vote on my projects. It’s shocking how few people have voted. This means a handful of votes changes the ranking considerably. Here’s the direct link to the $300 Geopolymer CEB House.

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