1. Introduction
Sulphate attack is a common durability concern for concrete structures in coastal and industrial environments, and alkali-activated geopolymer binders have been proposed as a more resistant alternative due to their distinct reaction chemistry compared to calcium-silicate-hydrate systems in OPC.
2. Methodology
Geopolymer mixes were prepared with fly ash to GGBS ratios of 100:0, 70:30 and 50:50, activated with a sodium silicate and sodium hydroxide solution, alongside an OPC control mix of equivalent 28-day design strength. Cube specimens were cured for 28 days then immersed in 5 percent sodium sulphate solution, with compressive strength and mass change measured at 28, 90 and 180 days of exposure.
3. Results
The 50:50 fly ash-GGBS blend retained 92 percent of its pre-exposure compressive strength after 180 days, compared with 87 percent for the 70:30 blend, 81 percent for the fly-ash-only mix, and 76 percent for the OPC control, with corresponding trends observed in mass loss and surface spalling.
4. Conclusion
Increasing GGBS content in fly-ash-based geopolymer concrete improves resistance to sulphate attack, supporting its use in aggressive exposure environments. Future work will examine chloride-induced reinforcement corrosion in the same mix series.
References
[1] Davidovits J., Geopolymer Chemistry and Applications, Institut Geopolymere, 2008. [2] Bakharev T., Resistance of geopolymer materials to acid attack, Cement and Concrete Research, 2005. [3] Provis J. L. and van Deventer J. S. J., Alkali Activated Materials, Springer, 2014.