Addition of solid sodium silicates is now implemented in geopolymer concrete. I was wondering about the precautions needed while using this chemicals in mixing. More specifically saying, in two part counterparts one of the major setback or disadvantage is the usage of corrosive alkalis. Does this concern from toxicity viewpoint is encountered by the one part counterparts?
If yes, how so?
Dear Jayashree,
Geopolymer binders are made using user friendly liquid reagents, so MR isn’t corrosive and these hardeners are classified only irritant for skin and eyes like for Portland cement and lime. Silicates with lower MR can be used only for research project.
To obtain Geopolymers, alkaline reagent should be in liquid form not anhydrous because mix design of Geopolymer materials is completely different from Portland technology.
The most important things are the selection of the best amorphous allumino silicate powder precursor (taking in account reactive mineralogy, sizes of particles and chemistry) , the use of well balanced alkaline system and following the correct mixing method (isn‘t hydraulic reaction but chemical reaction between amorphous mineral reactive sources at room temperature). It isn’t really necessary metasilicate that is strongly corrosive (pH 14!). Check at prof. Davidovits work to understand better my words if aren’t enough clear.
To work with Geopolymer materials you have to use the same rubber gloves , goggles and usual clothes used when work with Portland cement or lime based materials.
Toxicity is parameter linked to organic polymers like polyester, polyurethane or epoxy that are totally different binders from Geopolymer binders that are completely mineral so inorganic (from natural or artificial/waste sources).
Geopolymers aren’t toxic don’t worry.
Alkali activated materials aren’t polymers because obtained using hydraulic systems so are more similar to Portland technology ,than Geopolymer technology, even though some raw materials can be used with different roles in all systems.
In conclusion, Geopolymer materials are 2 components non hydraulic, but about safety there are no problems (no toxicity, no corrosive materials, just irritant like Portland or lime based), of course we are speaking about products for professional use only as ever.
Portland cement and Alkali Activated Materials are hydraulic and one component. Portland is only irritant like Geopolymers, while usually AAM are more alkaline so corrosive (check Glukovsky and others) so you must take care also about your breathing apparatus and clothes must be more protective.
All best
Alex Reggiani
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