Organosilicon functionality modification mechanisms in geopolymer and the improvement of carbonation resistance

Abstract

This study explores a routine of improving carbonation resistance of geopolymer by CO 2 -H 2 O-gel interface modification using organosilicon functionality.In this study, three organosilicon modifiers with distinct non-hydrolysable groups, including PMS, S823, and KH570, were added into geopolymers. The carbonation behavior of the geopolymers was comparatively evaluated under different drying conditions. Fresh-state properties, wettability, carbonation depth, and compressive strength were evaluated. To clarify the modification mechanism, gel structure evolution, carbonation products, and water-state changes were characterized by XRD, FTIR, TGA, LF 1 H NMR, and MIP. The results show that differences in organosilicon functional groups govern the carbonation resistance of geopolymers through distinct interfacial chemistries: the long hydrophobic alkyl group of S823 promotes the formation of a lowsurface-energy interfacial environment and disrupts the effective CO 2 -H 2 O-gel reaction interface, thereby most effectively suppressing carbonation; KH570 mainly influences local crystallization and carbonate phase evolution through its polar methacrylate functionality; whereas PMS, containing only a small methyl group, shows limited improvement because it primarily participates in aluminosilicate network reorganization rather than establishing a strongly hydrophobic interfacial environment.This work provides a basis for the functionality-guided design of organosiliconmodified geopolymers with enhanced carbonation resistance, and contributes to their practical development for durable applications in CO 2 -rich service environments.