EVALUATING THE POTENTIAL APPLICATION OF FLY ASH/ BLAST ... 21 EVALUATING THE POTENTIAL APPLICATION OF FLY ASH/ BLAST FURNACE SLAG GEOPOLYMER MATERIAL FOR INHIBITING ACID CORROSION, A COMPARATIVE STUDY Ali Allahverdi 1 , FrantiŠek Škvára 2 1 College of Chemical Engineering Iran University of Science and Technology 2 Department of Glass, Ceramics, and Inorganic Binders Institute of Chemical Technology, Czech Republic Abstract. The response of hardened paste of a geopolymer cement to acid attack has been investigated and compared to that of ordi- nary Protland cement. The geopolymer cement was produced by activating a mixture of fly ash and blast furnace slag using a proportioned solution of NaOH and Na 2 SiO 3 . At relatively lower pH values (pH2), sulfuric acid is less corrosive than nitric acid because of the inhibition caused by gypsum crystals depositing on the acid- exposed surface or inside the corroding layer. The corrosion process very soon becomes diffusion controlled owing to the formation of relatively thick corroded layers. At relatively higher pH values (pH3) and for relatively short exposure time periods ( 90 days), mecha- nism of attack by sulfuric acid approaches that of nitric acid attack. The total rate of deterioration is more effectively controlled by the po- rosity and the nature of corroding phases than the protective effect of a relatively very thin corroded layer. Keywords. Geopolymer cement, Acid resistance, Nitric acid, Sulfuric acid 1 Introduction The deteriorating effect of acid media (e.g. acid rains, acid ground-wa- ters, etc) on cement-based construction materials has attained more importance in the recent decades. Hardened paste of Portland cement that is a highly alkaline material with pH above 12.5 is severely attacked by acid media. Authors discussed and reviewed the phenomenon of acid corrosion of hydrated cement-based materials and the literature pub- lished during the last two decades thoroughly [1], [2]. At the same time, development of geopolymer cements with improved properties necessi- tates more detailed investigations.