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Archive for November, 2011

Abstract
Investigation by scanning electron microscopy and X-ray energy dispersion measurements (X-ray line analyses) were perfor­med on a number of 90-day corroded gypsum-free Portland cement and ordinary Portland cement paste specimens placed in nitric acid solutions of respective pH of 1, 2, and 3. The results obtained show that the hardened paste specimens of gypsum-free and ordinary Portland cements are corroded by exactly the same mechanism. The only difference between the two types of cement is the corrosion rate. The absence of crystalline formations, typical of hardened OPC paste, together with the high density and degree of dispersion of hy­dration products are responsible for a relatively higher acid resis­tance in gypsum-free Portland cement.

Source: Clay Polymers.com

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Abstract
The effect of some parameters including sodium oxide, ground granulated blast-furnace slag, and W/C-ratio on the most important engineering properties of natural pozzolan-based geopolymer cement systems were investigated. The properties studied include 28-day compressive strength and final setting time. The results obtained reveal that the most effective parameter on strength behaviour is sodium oxide concentration. The geopolymer cement system comprising of 5 wt% blast-furnace slag and 8 wt% Na2O with a W/C-ratio of 0.30 exhibits the highest 28-day compressive strength, i.e. 36 MPa, along with almost acceptable final setting time. Systems exhibiting the highest 28-day compressive strengths were characterized using laboratory techniques of FTIR and SEM.

Source: Clay Polymers.com

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Abstract
Because of concerns over the construction industry‘s heavy use of cement and the general dissatisfaction with the performance of building envelopes with respect to durability, there is a growing demand for a novel class of ―green‖ binders. Geopolymer binders have re-emerged as binders that can be used as a replacement for Portland cement given their numerous advantages over the latter including lower carbon dioxide emissions, greater chemical and thermal resistance, combined with enhanced mechanical properties at both normal and extreme exposure conditions. The paper focuses on the use of geopolymer binders in building applications. It discusses the various options for starting materials and describes key engineering properties associated with geopolymer compositions that are ideal for structural applications. Specific properties, such as compressive strength, density, pore size distribution, cumulative water absorption, and acid resistance, are comparable to the specifications for structures incorporating conventional binders. This paper presents geopolymer binders, with their three dimensional microstructure, as material for structural elements that can be used to advance the realization of sustainable building systems.

Source: Ideas.Repec.org

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United States Patent 5349118
Abstract
The method of the invention provides a geopolymeric binder in powder, used for the ultra rapid treatment of materials, soils or mining tailings, containing toxic wastes. The geopolymeric binder has a setting time equal to or greater than 30 minutes at a temperature of 20° C. and a hardening rate such as to provide compression strengths (Sc) equal to or greater than 15 MPa, after only 4 hours at 20° C., when tested in accordance with the standards applied to hydraulic binder mortars having a binder/sand ratio equal to 0.38 and a water/binder ratio between 0.22 and 0.27. The preparation method includes the following three reactive constituents:

a) an alumino-silicate oxide (Si2 O5,Al2 O2) in which the Al cation is in (IV-V) coordination as determined by MAS-NMR analytical spectroscopy for 27 Al;

b) a disilicate of sodium and/or potassium (Na2,K2)(H3 SiO4)2 ;

c) a silicate of calcium where the molar ratios between the three reactive constituents being equal to or between ##EQU1## where Ca++ designates the calcium ion belonging to a weakly basic silicate of calcium whose atomic ratio Ca/Si is lower than 1.

Source: Free Patents Online.com

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No spaces between stones indicates they may have been cast in place with geopolymer.

No spaces between stones indicates they may have been cast in place with geopolymer.


There’s been a lot of interesting discussion on a previous blog post No Spaces Between Stones about building a model to show how ancient structures were made with geopolymer. To my knowledge this would be the first experiment of its kind. LeRoy Martinez, one of our readers, wants to build a small stone to test this theory. LeRoy has a background in mold making and believes he can pull this off using primarily local materials. Some of his comments are pasted below.

“I wish I had known of Davidovitz’s theory before I visited Machu Picchu. I would have certainly spent more time checking the stone texture and fit. I have a mold making background so I can see how some of these could have been cast in place.

Picture this: First they made a 4 sided box from wood and made it large enough so a person can get inside of it. There is no top or bottom. Then he covers the inside of the box with clay and he can be as artistic as he wants. He is making the reverse side of the rock. He only has to make the 4 sides of the stone. The bottom can be flat and the top is open. Then he will press decomposed granite or whatever stone they want to reproduce into the clay. When he has finished he climbs out of the box (mold) and laborers can make multiple pours of the decomposed granite and sodium carbonate solution being sure to coat all of the clay substrate that has the granite surface embedded in it. When it has cured the box (mold) is removed and the stone is finished and in place. All that remains to be done is to wash and brush off the clay.

The decomposed granite that was pressed into the soft wet clay has become the outside surface of the stone. It will provide the texture because it is decomposed granite reconstituted.

The mold can then be set on top of that stone and the procedure done all over again. No two stones will be the same because the sculptor is good at his trade and has his reputation at stake.”

You can read the entire discussion (still ongoing) here.

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Taliesin West stonework made with dry-pack concrete

Taliesin West stonework made with dry-pack concrete


Here’s the fascinating inside story of how they built Frank Loyd Wright’s famed School of Architecture at Taliesin West. Desert concrete or dry-pack is more sustainable than typical concrete because it uses free local sand and stone, no gravel and very little water. Large stones reduce use of cement. Using geopolymer instead of Portland cement would be even more sustainable.

“There was a query on the Frank Lloyd Wright Conservancy web site a while back about how the desert concrete at Taliesin West was constructed. The process is not all that complicated. We were working at a pretty primitive and labor intensive level. There was ample labor available, a scarcity of money, one little old concrete mixer, lots of sand and stone, and a great deal of talent and enthusiasm. We loved stripping the form work the next day to admire our artistry. We were, after all, working in the dark and the proof of the pudding was in the newly exposed wall. The secret, if indeed named such, was the mix of what is termed concrete. We used what really should be called dry-pack, a mixture of sand from the washes below Taliesin and cement. There was no aggregate; just sand, cement, and very little water. At my physical peak I could take a 5 yard dump truck down to the wash below Taliesin and fill it to the brim with sand on a 1/2/3/4 count without missing a beat. Well almost never.

The stone, like the sand, was free, also but very labor intensive to collect the best specimens. Our stone collecting tools were equally primitive, consisting of a Jeep, a small flatbed trailer and a 6 foot wrecking bar, lots of muscle, and above all, discriminating taste. We took our stone collecting very seriously. Our next wall was to be the best looking wall at the camp. We looked for size, color flatness and shape. We also probably ventured beyond the confines of the reservation in our stone collecting ventures, but in those days there was nothing around for miles.”

You can read the complete article at John Geiger’s site JGonWright.com
Image source: Shutter Mike

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Since 1986, the French aeronautic company Dassault Aviation is using geopolymer mold and tooling in the development of the Rafale fighter plane. In addition, we made for Northtrop Aviation a geopolymer composite tooling prototype (self-heated carbon/SiC/Geopolymite composite) used in the fabrication of carbon/APC2 composite designed for a new US Airforce bomber. More than a hundred tooling and items have been delivered for aeronautic applications (Airbus) and SPF Aluminum processing.

Source: Geopolymer.org

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