Enhancing ambient-temperature performance of GGBS-based geopolymer with calcium oxalate: setting time reduction and strength optimization

This study investigates the ambient-temperature properties and mechanistic behavior of calcium oxalate (CO)-modified ground granulated blast furnace slag (GGBS) geopolymer to eliminate high-temperature activation. Results showed that the setting time decreased significantly with increasing CO content, with a reduction of 73 % and 68 % in initial and final setting times at 10 % CO, respectively. 2 % CO yielded the highest compressive strength, with 31.45 % and 24.52 % increases at 28 and 90 days, respectively. TGA (Thermogravimetric Analysis) and DTG (Derivative Thermogravimetry) results indicated enhanced portlandite formation at 400–500 °C, confirming accelerated hydration. Fourier Transform Infrared Spectroscopy (FTIR) showed intensified C–S–H gel formation at 1496 cm⁻¹, particularly at early curing stages. Isothermal calorimetry confirmed CO's role in boosting hydration kinetics, with a secondary heat peak appearing 1-hour post-mixing. These findings highlight CO's potential in optimizing geopolymerization without heat curing, improving sustainability and practical applications.