Geopolymers

Geopolymerization is the process of polymerizing silica and alumina containing minerals with the use of alkali solvents. Discovered (or rediscovered) by Josheph Davidiots, geopolymer cements are likely similar to materials used in antiquity. Although cements are the most common application of geopolymerization, a range of refractory and structural products have been produced. The products of geopolymerization are called poly-silates.

The vast majority of minerals on the earth's surface exist as aluminosilicate crystals (for example: clays, feldspars, quartz). By disolving these and then allowing them to recondense, materials with longer range crystalline structure than its components may be formed.

The simplest inorganic polymerization process uses abundant kaolin clays and silica rich industrial wastes, which are partially dissolved in an alkali solution. The dissolved aluminosilicates condense upon dehydrolization into a micro crystalline structure. Kaolin and other materials have been mixed with potassium hydroxide to make bricks and cements many times stronger than Portland cement (which lacks any long range crystalline structure). At temperatures and pressures exceeding the earth's surface conditions, much more structured polymers can be produced which will never combust at any temperature (due to a lack of carbon to react with oxygen), and which also have very low thermal expansion coefficients.

Currently, much of this research is strictly closed source and proprietary. Room temperature setting cements, refractory mineral foams and non-combustible panels for airplanes are amongst the products being researched, and possibly already being widely produced. As the field progresses, more advanced geopolymers and geopolymerizing processes will likely emerge.

The Geopolymer Institute has many useful technical papers on the subject, including low temperature setting geopolymer (LTGS) bricks for fabrication with limited infrastructure.

This group has also released several collections of papers from "geopolymere" (french) confrences.