Comparative Study on Durability of Fly Ash Based Geopolymer Mortars in Sulphuric Acid and Nitric Acid

Geopolymers are a new promising binder manufactured by activation of a solid alumina silicate source material with a highly alkaline activating solution. Every year a huge amount of Fly ash is obtained from thermal power stations which is rich in silica and alumina and hence can be used with an alkaline fluid (mixture of Na₂SiO₃ and NaOH is used here) as a substitute of Cement. The process of hardening of the paste consists of formation of three dimensional polymeric chain and hydration does not take place in this case. So emission of CO₂ is very less in this case. An experimental study was conducted to study and compare the durability or acid resistance of fly ash based geopolymer mortar exposed to Nitric and Sulphuric acid. Compressive strength, weight of specimens and pH of acid solution is recorded at a regular interval. Residual alkalinity is tested at a regular interval by using 1% Phenolphthalein solution. The results are recorded and compared. Results obtained in the present study indicate that Geopolymers are highly resistant to both Sulphuric and Nitric acid.