User-friendly geopolymer cements
Although geopolymerization does not rely on toxic organic solvents but only on water, it needs chemical ingredients that may be dangerous and therefore requires some safety procedures. Material Safety rules classify the alkaline products in two categories:
- corrosive products
- irritant products
The two classes are recognizable through their respective logos displayed below.
The Table lists some alkaline chemicals and their corresponding safety label. The corrosive products must be handled with gloves, glasses and masks. They are User-hostile and cannot be implemented in mass applications without the appropriate safety procedures. In the second category one finds Portland cement or hydrated lime, typical mass products. Geopolymeric mixes belonging to this class may also be termed as User-friendly.
When we started the research on geopolymer cements, we decided to select alkaline conditions that are User-friendly. (Na,K,Ca)-Poly(sialate-siloxo) and K-Poly(sialate) products (resins, binders and cements) have starting molar ratio SiO2:M2O ranging from 1.45 to 1.85. Unfortunately, this is not followed by other scientists and technicians involved in the development of so-called alkali-activated-cements, especially those based on fly ashes, with molar ratio in average below 1.0. Looking only at low-costs consideration, not at safety and User-friendly issues, they propose systems based on pure NaOH (8M or 12M). For example in a “State of the Art” on alkali-activated fly-ash cements, wrongly named geopolymer technology, published in 2007, several scientists claimed that the pure NaOH system should be considered as the reference for fly-ash-based cements (see: Duxson P., Fernandez-Jimenez A., Provis J.L., Lukey G.C., Palomo A. and van Deventer J.S.J., Geopolymer technology: the current state of the art, J. Mater. Sci., 42, 2917-2933, 2007). These are User-hostile conditions for the ordinary labor force employed in the field.
Finally, companies refuse to support the liability and pay high insurance fees based on such out-of-date processes. Indeed, laws, regulations, and state directives push to enforce for more health protections and security protocols for workers’ safety. Further details on fly-ash-based geopolymer cement in the page GEOASH, a project aimed to develop a real industrial process driven by these constraints.