There are different ways to produce mineral foam. Air can be directly introduced by quick mixing of all components (binder, water, surfactant...) or an aqueous foam can be first produced and then added to a mineral suspension (prefoaming method). Another solution is to add mettalic foaming agents that react to produce gas bubbles.
In these three cases, to obtain light mineral foams (< 500 kg/m3) surfacant must be added to prevent coalesence between bubbles.There are plenty of surfactants to give very good results on classical binders such as oridnary Portland cement.
I tested two different surfactant (CTAB and Cetrimide) with geopolymer but it doesn't change samples density. As the alcaline solution and metakoalin suspension have a very high pH (= 13-14), if think it totally destroys the surfactant. I'm looking or surfactant that works on very high pH environnement.
Which type of surfactant can I use to produce geopolymer lightweight mineral foam ?
Best regards,
Gabriel SAMSON
Dear Gabriel, recently a paper was published on this topic: Synergistic effect of vegetable protein and silicon addition on geopolymeric foams properties, by L. Verdolotti et al., J. Mat. Sci. DOI 10.1007/s10853-014-8801-3
I hope it can be useful
Thanks. I am still waiting for effective admixtures for geopolymer formulations with fly ash and blast furnace slag
Dear Gabriel, when I used non-ionic surfactants (Tween 80 and Triton X-100) to produce geopolymer foams I considered their chemical characteristics. Taking in account the high level of cations scattered in the slurry is "better" use a surfactant with another mechanism of action and that does not undergo electronic interference of the scattered ions.
I have used oleinic acid for the similar problems, but not sure that was the best processing technological solution.
Dear Gabriel, instead of optimizing the surfactants, you had better to optimize the technique of hardening the geopolymer mixture. I would try to prevent the coalescence by the means of speeding up the hardening, by changing the Si/Al ratio and by raising the temperature of curing. I remember an experiment, during which the geopolymer had hardened in vacuum at 40°C creating porous foam.
Hi Gabriel, if your problem is related to reduce the density of the samples, there are different methods that you can use i.e. by modulating the formulation of geopolymer (silico aluminate source, grain dust etc..) and the curing (humidity/temperature) of samples or by adding foaming agents. In this respect and by considering the high pH of your systems, you can you use different approaches: templating technique, the addition of porous additives, the addition of metals (Al, Si..) and liquid proteins. The last one acts as a surfactant too, stabilizing the foamed system.
Hello everyone. Thank you very much for all your answers.
Letizia,yes, there are actually a lot of solutions to below geopolymer foam density. I aim to reach 150-200 kg/m3. At this low density, using surfactant is compulsory to prevent coalescence until setting. I tried to contact the laboratory that provide you the liquid protein you used in your article untitled "Synergistic effect of vegetable protein and silicon addition on geopolymeric foams properties". Unfortunately, they didin't reply. Do you know which kind of protein it is ?
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