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    Fire Resistance of Geopolymer Concrete Produced From Ferrochrome Slag by Alkali Activation Method
    (Ieee, 2013) Turkmen, Ibrahim; Karakoc, Mehmet Burhan; Kantarci, Fatih; Maras, M. Murat; Demirboga, Ramazan
    The effect of high temperatures up to 700 degrees C on compressive strength and water absorption of two alkali-activated aluminosilicate composites (one of them with river sand aggregates, the second crushed sand aggregates) and ordinary Portland cement (OPC) concretes is analyzed in this paper. Binding geopolymer material was obtained after grinding the Elazig Ferrochrome slag (EFS) as fine as cement and alkaline activating with chemical materials (NaOH-Na2SiO3). Geopolymer concrete samples were produced by using this binding material with aggregates. Produced concrete samples were exposed to temperature for 1 hour, after reaching the maximum temperature. Fire resistance and water absorption of geopolymer and OPC concrete samples was obtained experimentally. Compressive strength of river aggregates and crushed sand aggregates concrete increased at 100 and 300 degrees C temperatures compared to unexposed samples, and the maximum compressive strength for these geopolymer concrete sample was obtained at 300 degrees C. Water absorption of all concrete samples increased at 700 degrees C temperature compared to unexposed samples. But there appeared to be a slight decrease of water absorption in the all concrete samples up to 300 degrees C temperatures compared to unexposed samples. Scanning electron microscopy and XRD tests were also conducted to examine microstructure and mineralogical changes during the thermal exposure.
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    Mechanical Properties and Setting Time of Geopolymer Paste and Mortar Produced From Ferrochrome Slag
    (Ieee, 2013) Karakoc, Mehmet Burhan; Turkmen, Ibrahim; Maras, M. Murat; Kantarci, Fatih; Demirboga, Ramazan; Toprak, M. Ugur
    Many researches have been done to investigate using raw materials in the production of geopolymer cements. The aim of this paper is the effect of dosage of alkali and silica modulus when using sodium metasilicate solution at different curing conditions on the geopolymerisation of ferrochrome slag (FS). As alkali activation for geopolymerization, NaOH and Na2SiO3 solution were used. Geopolymer cement was produced using FS and 3 different silica modulus (0.50, 0.60, and 0.70) and 4 different Na2O concentrations (4, 7, 10, and 12%). The setting time, heat of hydration and compressive strength of geopolymer paste samples and compressive strength of geopolymer mortar samples were obtained. The setting time varies between 120 and 870 min, it shows variability depending on content of Na2O. As a result of the highest 28 day strength of the geopolymer paste sample was obtained at Na2O concentration of 7% and at silica modulu of 0.70. Geopolymer mortars were prepared for the determination of compressive strength by adding FS: sand: alkali activator ratio 1:2:0.30, 0.35 and 0.40. The specimens were cured at 60 degrees C, 80 degrees C kept in 20 hours and the other mortars were stored under laboratory conditions. Compressive strength of the material decreases, when w/b ratio increases. The highest 28 day strength of the geopolymer mortar was obtained at 0.30 w/b ratio and at curing temperature laboratory conditions. The hydration heat of geopolymer paste samples was found to be less than normal Portland cements. Microstructural changes in the specimens were studied with SEM and XRD.