Enhancement in acid resistance of 3D-printed geopolymer-stabilized earth through organic-mineral interactions

3D-printed geopolymer-stabilized earth is a low-carbon alternative to conventional Portland cement-based materials. However, its durability under acidic conditions remains unexplored. This study investigates an organic-mineral interaction pathway by using sucrose, added at 0.50 – 1.5% by weight of blast furnace slag (GGBS) and fly ash (FA), to enhance the durability of 3D-printed geopolymer-soil exposed to sulfuric acid solutions of pH = 2.0 and 0.50, respectively. Findings show that sucrose additions of 1–1.5% significantly mitigate the linear expansion associated with gypsum formation and reduce the depth of acid attack in the 3D-printed geopolymer-soil by 30–40%. These improvements are linked to 35–50% reductions in sorptivity and in the volume of small- and medium-capillary pores in sucrose-modified materials. Depending on the sucrose dosage, leaching from sucrose-modified 3D-printed geopolymer-soil decreases by 9.50 – 43%, while relative mass losses are reduced by 33–55% and 17 – 72% after exposure to pH = 0.50 for 28 days and 120 days. The enhanced performance is attributed to sucrose-induced structural changes mitigating decalcification and dealumination of the binder hydrates under acidic conditions, confirmed by 27 Al and 29 Si NMR. After exposure to pH = 2.0 for 120 days and pH = 0.50 for 28 days, sucrose-modified 3D-printed materials exhibit 19–35% and 75% higher compressive strengths, respectively. However, the beneficial effect of sucrose on strength retention is not prominent after 120 days of exposure to pH = 0.50. Overall, the research provides a pathway for developing durable 3D-printed stabilized earth materials for environments where pH ≥ 2 is encountered.