Durability of Geopolymer Materials in Sodium and Magnesium Sulfate Solutions

Geopolymers are synthetic minerals that are similar to those that form in the Earth's crust. They possess high strength, thermal stability, high surface smoothness and precision, and high surface hardness. This article reports on a study of the durability of geopolymer materials manufactured using class F fly ash (FA) and alkaline activators in sodium and magnesium sulfate solutions. Three tests were used: immersions for a period of 5 months into 5% solutions of sodium sulfate and magnesium sulfate, and a solution of 5% sodium sulfate+5% magnesium sulfate. The evolution of weight, compressive strength, products of degradation and microstructural changes were studied. In the sodium sulfate solution, significant fluctuations of strength occurred, with strength reduction 18% in the 8FASS material prepared with sodium silicate and 65% in the 8FAK material prepared with a mixture of sodium hydroxide and potassium hydroxide (K) as activators. A 4% strength increase was measured in the 8FA specimens activated by sodium hydroxide. In the magnesium sulfate solution, 12% and 35% strength increase was measured in the 8FA and 8FAK specimens, respectively; and 24% strength decline was measured in the 8FASS samples. Diffusion of alkali ions into the solution caused significant stresses and formation of deep vertical cracks in the specimens prepared using a mixture of sodium and potassium hydroxides. The author concludes that the geopolymer specimens had very different durabilities when exposed to sulfate solutions. Material prepared using sodium hydroxide had the best performance, which is attributed to its stable cross-linked aluminosilicate polymer structure.


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  • Accession Number: 01002949
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Aug 4 2005 11:32AM