Microstructural Assessment of the Effect of Sulfate Environments on the Mechanical Properties of GeopolymerConcrete

Geopolymer concrete is a new material in the construction industry with optimal performance and efficiency. On the other hand, geopolymer concrete has mechanical characteristics and durability against chemical attacks. Microstructural changes on the mechanical properties of geopolymer concrete in sulfate environments can be strongly affected. Accordingly the present study is a microstructrul analysis of the influence of sulfate environmental condition on the mechanical propertiese of geopolymer concrete.

In this regard, for the production of geopolymer concrete-based slurry, a sodium bicarbonate solution with sodium concentration of 10 M and sodium silicate as activating material have been used. This study evaluated about 200 concrete samples. The samples were preserved for 3 months in simulated environments with 0.1%, 0.25%, 0.5%, 1%, 2.5%, 5% and 7.5% sulfuric acid concentrations. Compressive strength, weight percentage, ultrasonic wave, permeability and pH change tests were then performed after 1, 3, 7, 14, 28 and 90 days on all the samples in the preserving environment.

The results indicate that the strength of samples preserved in the sulfate environment compared to the control sample depended on the amount of sulfate. After 90 days, the compressive strength of samples preserved in the 7.5% concentration sulfuric acid sulfate environment was reduced by about 45% compared to control samples. This reduction in compressive strength is inversely related to the results from the ultrasonic test of samples preserved in the 7.5% percent concentration sulfate environment.