Pore characteristics of Ca(OH)2 foams: Impact of surfactant–mineral interaction

Slake lime (Ca(OH)2) foams were prepared via a mechanical foaming and gelcasting method. The Ca(OH)2 foams were systematically characterized in terms of pore size and porosity according to expansion ratio (ER). The results showed that the physical properties of the Ca(OH)2 foams increased with ER. Additionally, the Ca(OH)2 foams with ER = 4 showed considerably larger pore size (727.5 μm) as compared to those with smaller ER (8.8 and 20.1 μm for ER = 2 and 3, respectively). In order to further elucidate the mechanism, SiO2 and Al2O3 foams with same ER were prepared and compared. Additional experiments were also conducted, such as rheological behavior of slurry, electrical property of starting materials, and surfactant (sodium lauryl sulfate, SLS)–mineral adsorption capacity. The results showed that the pore size of the SiO2 and Al2O3 foams was much smaller than that of the Ca(OH)2 foams. The discrepancy in the pore size between three foams was due to the difference in the adsorption capacity of SLS onto mineral surfaces. Specifically, the loss of SLS from aqueous phase by the SLS–Ca(OH)2 interaction resulted in the decrease in the surface tension of the Ca(OH)2 slurry, and consequently led to the increase in bubble size (i.e., final pore size).