Gypsum-Free Portland Cement, an Alkali-Activated Material Suitable for Acid Corrosion Protection

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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Investigating the Set and Strength Behaviors of Blast-Furnace Slag Blended Geopolymer Cement Based on Natural Pozzolan

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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Advancing the Use of Secondary Inputs in Geopolymer Binders for Sustainable Cementitious Composites: A Review

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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Method for Obtaining a Geopolymeric Binder Allowing to Stabilize, Solidify and Consolidate Toxic or Waste Materials

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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Were Ancient Structures Made 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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Desert 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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Ceramics for Molds, Tooling, High-tech

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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Functional Geopolymer Composites for Structural Ceramic Applications

Abstract
“Continuous fiber-reinforced ceramic matrix composites (CMCs) are attractive candidate materials for structural components in military/commercial airframe or engine/turbine components due to their high-temperature mechanical properties. However, currentCMCs have two major limitations that have prevented replacement of current materials, namely (1) very high processing/materials costs and (2) insufficient corrosion resistance under hydrothermal oxidizing conditions. Geopolymers, in whichamorphous/semi-crystalline aluminosilicates are dissolved into an inviscid, highly concentrated alkaline solution, offer an approach for the development of easily and cost-effectively processed matrix materials for alumina fiber composites. This Phase ISTTR proposal is targeted at demonstrating the feasibility of developing a geopolymer-based CMC with appropriate high-temperature performance. Our approach will include chemical design (i.e., aluminosilicate phase selection and solid-solution composition)and thermal processing of geopolymers so as to create, after firing, CMCs at chemical equilibrium (“petromimetics”) that, too, have more refractory behavior than current geopolymer systems. What is envisioned is a hybridization of present glass-ceramicand geopolymer processing. The work will establish a chemical processing and design/microstructure/property database for this relatively new class of materials, which will enable functional CMC design. Specifically, the role of a highly doped andreactive intermediate gel phase on properties of the final geopolymer will be studied. Cost-effective processing routes for CMCs with adequate high-temperature mechanical properties are attractive to a variety of applications where high-temperaturemechanical performance is required. The use of CMCs in aircraft or stationary engines and turbines have the potential to raise operating temperatures which will result in a significant step up in efficiency than is possible through marginal improvementsusing currently used materials such as nickel-based superalloys.

Source: SBIR.gov

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Geopolymers: Structures, Processing, Properties and Industrial Applications

Edited by J L Provis and J S J van Deventer, University of Melbourne, Australia
– discusses the synthesis and characterisation of geopolymers with chapters covering fly ash chemistry and inorganic polymer cements
– assesses the application and commercialisation of geopolymers with particular focus on applications in waste management
– reviews the latest research on and applications of these highly important materials

A geopolymer is a solid aluminosilicate material usually formed by alkali hydroxide or alkali silicate activation of a solid precursor such as coal fly ash, calcined clay and/or metallurgical slag. Today the primary application of geopolymer technology is in the development of reduced-CO2 construction materials as an alternative to Portland-based cements. Geopolymers: structure, processing, properties and industrial applications reviews the latest research on and applications of these highly important materials.

Part one discusses the synthesis and characterisation of geopolymers with chapters on topics such as fly ash chemistry and inorganic polymer cements, geopolymer precursor design, nanostructure/microstructure of metakaolin and fly ash geopolymers, and geopolymer synthesis kinetics. Part two reviews the manufacture and properties of geopolymers including accelerated ageing of geopolymers, chemical durability, engineering properties of geopolymer concrete, producing fire and heat-resistant geopolymers, utilisation of mining wastes and thermal properties of geopolymers. Part three covers applications of geopolymers with coverage of topics such as commercialisation of geopolymers for construction, as well as applications in waste management.

With its distinguished editors and international team of contributors, Geopolymers: structure, processing, properties and industrial applications is a standard reference for scientists and engineers in industry and the academic sector, including practitioners in the cement and concrete industry as well as those involved in waste reduction and disposal.

Source: Research and Markets.com

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Preparation and Characterization of Functional Geopolymer

The geopolymer has been prepared from fly ash, metakaolin and Quartz sand, by using the liquid sodium silicate as structural template and sodium hydroxide solution as activator. The effect of glass fiber on the properties of the geopolymer has been studied.

Source: Scientific.Net

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