Evaluation of the surfactant effect on the mechanical and pore properties of porous geopolymers

The formation and regulation mechanisms of pore structures in porous geopolymers (PGs) remain qualitatively unclear, posing significant challenges to their practical application and performance optimization. In this study, PGs were synthesized utilizing metakaolin as the primary raw material and hydrogen peroxide as the foaming agent. Three distinct surfactants—sodium dodecyl sulfate, hydroxypropyl methylcellulose, and cetyltrimethylammonium bromide—were incorporated to fabricate three unique categories of PGs. The mechanical properties that were evaluated to quantify the surfactant effect were total porosity, pore distribution, and pore size variations using techniques such as image analysis and mercury intrusion porosimetry. This analysis highlighted the significant influence of slurry viscosity on the evolution and modification of pore structure. The results illustrate that viscosity acts as a crucial determinant influencing pore deformation, coalescence, ultimate foaming height, and connectivity within PGs. In addition, this study investigates the correlation between pore structure and the macroscopic properties of PGs. The synthesized PG samples display a broad spectrum of compressive strengths (10.03–17.89 MPa), dry densities (0.87–1.09 g/cm³), and porosities (47.71%–57.41%). These findings provide valuable insights into the design and application of PGs.