Mineral foams like gypsum plasterboard, foamed concrete or artificial bone are porous materials obtained by foaming a hydraulic binder (cement, plaster, etc.), i.e. a reactive suspension. They are sought for their lightness, their porosity or their absorbing or insulating properties. These properties are largely determined by the pore morphology, which results from the balance between aging of the fresh liquid foam due to coarsening, i.e. gas transfer between bubbles, and setting, i.e. solidification following a dissolution-precipitation reaction.
To understand this competition, we combine Raman spectroscopy and bubble size measurements in a plaster foam obtained by direct foaming of a suspension. We thus probe at the same time the kinetics of reaction, and the arrest of coarsening due to the stiffening of the liquid foam structure. We first evidence the strong effect of the foaming process on the reaction kinetics. By using a setting retardant, we also show that the reaction timescale controls the final pore size in the solid foam.