Results of an experimental investigation conducted to study the performance of fly ash based geopolymer paste specimens in sulphuric acid are presented. Class F fly ash was activated with a mixture of sodium hydroxide and sodium silicate solution containing Na2O in the range 5% to 8% of fly ash. Specimens were exposed to 10% sulphuric acid solution up to a period of 24 weeks. Performance of geopolymer paste specimens was evaluated in terms of visual appearance, residual alkalinity, changes in weight and compressive strength at regular intervals. There were no changes in colour and specimens maintained structural integrity. Surface corrosion was observed to increase with time of exposure. SEM micrographs showed deterioration of specimens due to acid attack. Formation of gypsum and ettringite was identified through X-ray diffractogram of exposed specimens. Loss of alkalinity was faster for geopolymer specimen having lesser Na2O content. Specimens revealed very low weight loss in the range of 0.52% to 1.43v%. However, residual compressive strengths were observed to be significantly low for the specimen with least Na2O content. Results obtained in the present study indicate that geopolymer manufactured with higher Na2O content perform much better on exposure to sulphuric acid.

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