ScholarWorks@중앙대학교

초록

This study explores how variations in the silicon-to-aluminum (S/A) ratio affect the compressive strength of metakaolin-based geopolymer. Increasing the S/A ratio from 1.8 to 2.0 resulted in a 20% decrease in compressive strength, although the underlying reasons remain unclear. Nanoindentation tests confirmed the formation of low-stiffness polymers (less than 10 GPa), disrupting the homogeneity of the N-A-S-H gel structure. Additional test results, including desorption isotherm, X-ray CT scan, energy-dispersive X-ray spectroscopy (EDS), and vacuum pycnometer measurement, also supported that the generation of weak N-A-S-H gels was the primary factor responsible for the observed strength reduction. Based on these findings, the study proposes a new conceptual model to describe the changes in N-A-S-H gel structure as a function of varying S/A ratios. This model challenges the traditional inference that sodium silicate densifies the N-A-S-H gel and thoroughly explains the variation in compressive strength in metakaolin-based geopolymers as the S/A ratio changes. © 2025 Elsevier Ltd

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