Investigation of geopolymer cement concrete samples from Elazığ Ferrochrome slag of sulfate resistance

The chromite deposits which are 10% of the world reserves located within the boundaries of Maden town-Alacakaya village of Elazığ are processed in Elazığ Ferrochrome Plants. Apart from the main product many by-products are produced in this factory. One of these by-products is Elazığ Ferrochrome slag (EFS). In this study, it is intended to produce a geopolymer material with binding property produced by grinding the EFS as fine as cement. Geopolymer paste samples were produced with 3 different silica modulus (0.50, 0.60 and 0.70) and 4 different Na2O concentration of (4, 7, 10 and 12%). The setting time, heat of hydration and compressive strength of geopolymer paste samples were examined. The setting time varies between 120 and 870 min, it shows variability depending on content of Na2O. The highest 28 day strength of the geopolymer paste sample was obtained from Na2O concentration of 7% and at silica modulu of 0.70. Geopolymer binding, instead of cement, mortar samples were produced with different water/binder (w/b) ratios (0.30, 0.35 and 0.40) and under 3 different curing conditions. Usually w/b is increased for decreasing the compressive strength of geopolymer mortar samples. The highest 28 day strength of the geopolymer mortar samples were obtained at 0.30 w/b ratio and samples were cured at laboratory conditions. Geopolymer concrete samples were produced by using this binding material aggregates (river sand and crushed sand). Compressive strength (3, 7 and 28 days) and sulfate resistance of geopolymer concrete samples were obtained experimentally. The highest compressive strength for geopolymer concrete samples were determined nearly 35 MPa. The compressive strength, change in weight, length of change, variation of pH solution and visual appearance of these samples were examined with different magnesium sulphate solution (by weight 3%, 5% and 7%). Samples of geopolymer concrete showed great resistance against magnesium sulfate solution. In addition, there were no visual signs of deterioration of the geopolymer concrete specimens. Keywords: Geopolymer cement, Elazığ ferrochrome slag, alkali-activator, sulfate resistance