Monitoring Gypsum Plaster Setting in a Foam through Raman Spectroscopy

Abstract

We use Raman spectroscopy to probe in situ the hydration reaction of a foamed mineral binder, here gypsum plaster. We show the strong effect of the mixing process used for foaming on the hydration kinetics. On the contrary, we observe no effect of the cationic surfactant tetradecyltrimethylammonium bromide (TTAB) used as foaming agent, and of the foam structure. By tuning the hydration timescale with a setting retardant (citric acid) and measuring in parallel the characteristic bubble radius in the foam, we show that hydration kinetics control the arrest of the bubble size evolution in the fresh foam and the final pore size in the set gypsum.

Relation between oxidation kinetics and reactant transport in an aqueous foam

“…Key improvements compared to the literature -Despite great potential of foams as media for chemical reactions, the research in this domain is quite scarce. Most of the studies are dedicated to the investigation of the interplay between the foam stability and the rate of the chemical conversion within the foam liquid phase (42)(43)(44)(45)(46)(47)(48)(49), but the number of works considering the reaction involving both the liquid and the gas foam phases is very limited (13)(14)(15)(16). Furthermore none of these published articles neither controlled nor modeled precisely the transfers of reactants.…”

“…with α Henry's constant for O 2 . If both concentrations are expressed as molar concentrations, we have (49) . Henry's condition imposes a gaseous concentration at the contact with the Plateau borders which may differ from that in the `bulk' of the bubble: the corresponding difference generates an exchange flux which we now quantify.…”