Slurry rheological behaviors and effects on the pore evolution of fly ash/metakaolin-based geopolymer foams in chemical foaming system with high foam content

Interstitial slurry rheology significantly influences the pore structure of chemically foamed geopolymer foams (GPFs). However, the relationship between these two factors has not been elucidated completely. To achieve a range of slurry rheological properties, different metakaolin/fly ash ratios were used, and a high-foam-content system was realized using a H2O2 solution. The slurry rheological properties, foaming properties, and pore structures of the GPFs were tested to establish the influence mechanism of rheology on bubble behavior and pore structures from the perspective of foaming systems. Moreover, equations describing the relationship between the internal and external bubble pressure, extrusion pressure, and slurry yield stress are discussed from the perspective of a single bubble. Four sequential phases of bubble deformation were identified during the foaming process, namely, bubble nucleation, extrusion, expansion, and solidification. The intrinsic relationship between the interstitial slurry rheology and final pore structure of the GPF established herein will provide essential guidance for designing and synthesizing porous cementitious materials.

Automated summary

This study investigates the influence of interstitial slurry rheology on the pore structure of chemically foamed geopolymer foams (GPFs). Different metakaolin/fly ash ratios were used to achieve a range of slurry rheological properties, and a high-foam-content system was created using a H2O2 solution. The study tests the slurry rheological properties, foaming properties, and pore structures of the GPFs to understand the effect of rheology on bubble behavior and pore structures. Equations describing the relationship between bubble pressure, extrusion pressure, and slurry yield stress are discussed, and four sequential phases of bubble deformation during the foaming process are identified. The findings of this study provide essential guidance for designing and synthesizing porous cementitious materials.