Science
World-wide increase in geopolymer research
Twenty five years long, geopolymer science was studied in very few laboratories and institutions. It is only during the last five years that we notice a strong increase in geopolymer research. The actual situation was presented by Prof. J. Davidovits in his 2010 Geopolymer Camp Keynote: State of the Geopolymer 2010. The following map shows [...]
What is a geopolymer? Introduction
Geopolymers are chains or networks of mineral molecules linked with co-valent bonds. They comprise following molecular units (or chemical groups): -Si-O-Si-O- siloxo, poly(siloxo) -Si-O-Al-O- sialate, poly(sialate) -Si-O-Al-O-Si-O- sialate-siloxo, poly(sialate-siloxo) -Si-O-Al-O-Si-O-Si-O- sialate-disiloxo, poly(sialate-disiloxo) -P-O-P-O- phosphate, poly(phosphate) -P-O-Si-O-P-O- phospho-siloxo, poly(phospho-siloxo) -P-O-Si-O-Al-O-P-O- phospho-sialate, poly(phospho-sialate) -(R)-Si-O-Si-O-(R) organo-siloxo, poly-silicone Geopolymers are presently developed and applied in 9 main classes of [...]
About geopolymerization
In 1937 W. L. Bragg published a method for classifying all kinds of silicates and their crystal structures based on the concept of the ionic theory by L. Pauling. The fundamental unit is a tetrahedral complex consisting of a small cation such as Si4+, or Al3+ in tetrahedral coordination with four oxygens (Pauling’s first rule). [...]
Scientific means of investigation
X-rays diffraction spectra of hardened geopolymeric materials (resins and cements) do not supply accurate information (amorphous structure). High-resolution MAS-NMR (Nuclear Magnetic Resonance) spectroscopy of 29Si and 27Al is a very powerful tool that provides useful structural data. For more updated information, see in Davidovits’ book, Geopolymer Chemistry & Applications, the Chapter 4. You may also [...]
Examples of geopolymer frameworks
Geopolymerization forms aluminosilicate frameworks which are similar to those of rock-forming minerals. Yet there are major differences. At low temperature, generally below 300°C, geopolymers contain hydroxyl groups -OH as well as bounded water (so-called zeolitic water), and the structures shown in the figure below must be edited accordingly, with the exception of the sodalite framework. [...]
Chemical Structure and Applications
The atomic ratio Si:Al in the poly(sialate) structure determines the properties and application fields. A low ratio Si:Al (1,2,3) initiates a 3D-Network that is very rigid. A high ratio Si:Al, higher than 15, provides polymeric character to the geopolymeric material. One third of Davidovits’ book, GEOPOLYMER Chemistry & Applications, is dedicated to applications. See the [...]
Technical Data Sheet
Technical Data Sheet for Geopolymeric cement type (Potassium, Calcium) – Poly(sialate-siloxo) / (K,Ca) – (Si-O-Al-O-Si-O-), Si:Al=2:1 Further details in Davidovits’ book, GEOPOLYMER Chemistry & Applications, Part III, Properties, Chapters 15 to 18, GEOCISTEM , GLOBAL WARMING, and also previous papers in the Geopolymer Library. Tested on standard sand mortar prisms: setting: 10 hours at -20°C [...]
Cements, Concretes, Toxic Wastes, Global Warming
Applications with geopolymer cements and concretes are described in the section Geopolymer Cement with special emphasis on the introduction of user-friendly systems. It is striking to notice that Geopolymer cements manufacture emits 80 to 90% less CO2 (greenhouse effect gas) than Portland Cement. See in GLOBAL WARMING. They are perfect examples of Green Chemistry and [...]
Portland Cement Chemistry vs. Geopolymer Chemistry
Left: hardening of Portland cement (P.C.) through simple hydration of Calcium Silicate into Calcium Di-Silicate hydrate and lime Ca(OH)2. Right: hardening (setting) of Geopolymer resin (GP) through poly-condensation of Potassium Oligo-(sialate-siloxo) into Potassium Poly(sialate-siloxo) cross linked network.
Ceramics, Binders and Composites
Geopolymeric binders, used either with rock aggregates to produce rock-concretes or with carbon fibers to produce non-flammable composites, have a variety of important industrial uses. The same geosynthesis that produces geopolymeric rock-cements is used industrially for making binders for advanced composite materials and ceramics. Updated research is presented in Davidovits’ book, Geopolymer Chemistry & Applications, [...]
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