Synergistic effects of seaweed powder and rheology modifiers on the reaction mechanism and pore architecture of geopolymer

초록

This study investigates the feasibility of a sustainable unprocessed seaweed powder (USP) strategy for valorizing marine biomass waste, addressing the critical environmental issue of the high-water footprint inherent in conventional purifying processes. While seaweed powder offers renewable reinforcement potential, its direct application has been hindered by deleterious salts and organic impurities. Challenges that prior studies have addressed almost exclusively through water purification or pretreatment, rather than through chemical stabilization. Whether unprocessed marine biomass can be stabilized without any washing step has therefore remained unresolved. To resolve these challenges without freshwater consumption, this research developed a hybrid geopolymer system stabilized by a cellulose derivative rheology modifier (RM). A comprehensive, multi-scale characterization, including XRD, solid-state 27Al and 29Si MAS NMR, FTIR, μCT, and SEM, was conducted to elucidate the structure–property relationships. The results revealed that the direct use of 5 wt% USP caused a 33.7% reduction in 3-day compressive strength down to 29.92 MPa and increased water absorption to 11.32% due to chemical depolymerization and shrinkage-induced microcracking. However, the incorporation of RM effectively counteracted these adverse effects. NMR analysis confirmed that RM restored the degree of polymerization increasing the Si/Al ratio from 3.38 to 4.03 in the hybrid system, while μCT and SEM demonstrated a morphological transformation of pore defects from deleterious cracks to stable, isolated spherical voids, despite a 166.4% increase in total porosity. Consequently, the hybrid specimens achieved 28-day compressive strengths of up to 46.11 MPa, recovering 86% of the control's strength. This work validates that the USP and RM hybrid system offers a high eco-efficiency solution. By compensating for defects induced by impurities through microstructure remodeling and geopolymer network stabilization rather than physically removing them, this approach eliminates the massive freshwater consumption and wastewater generation of traditional methods, establishing a pathway for the cleaner production of marine waste-based construction materials.

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