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Öğe Durability characteristics of slag based geopolymer concrete modified with crumb rubber(Elsevier Sci Ltd, 2023) Orhan, Taha Yusuf; Karakoc, Mehmet Burhan; Ozcan, AhmetToday, due to the increasing demand in the building sector, the interest of researchers in sustainable building materials is increasing. Geopolymer concretes especially come to the forefront due to energy saving and recycling of waste materials. In this paper, slag based geopolymer concretes were produced by substituting crumb rubber (CR) in different proportions instead of fine aggregate. In the samples using 12 M potassium hydroxide (KOH) as alkali activator, river aggregate was used as aggregate. The 28-day compressive strengths of the samples were between 25.95 MPa and 38.17 MPa, between 9.8 MPa and 11.95 MPa at the end of 300F-T cycles, and between 40.65 MPa and 35.70 MPa in sulfate solutions at the end of 12 weeks. Sulfate (5% Na2SO4 and 5% MgSO4) and freeze-thaw (F-T) (100, 200 and 300 cycles) resistances of the samples cured in the laboratory were determined. As a result of durability tests, the compressive strength, weight changes, sorptivity, water absorption, visual and microstructure analysis of the samples were examined. While the compressive strength of the samples kept in sulfate solutions increased, the compressive strength of the samples exposed to F-T cycles decreased. Sodium sulfate solution caused more strength increase in the samples compared to magnesium sulfate solution. After 300F-T, the strength losses in the samples were over 60%. In general, although the CR slightly reduced the mechanical properties of the control samples, it reduced the permeability of the samples, which increased their durability.Öğe Effect of binder content and recycled concrete aggregate on freeze-thaw and sulfate resistance of GGBFS based geopolymer concretes(Elsevier Sci Ltd, 2021) Ugurlu, Ayse Ilayda; Karakoc, Mehmet Burhan; Ozcan, AhmetThe use of waste materials in concrete production is important because of the recycling of these materials. In this context, the use of both geopolymer binder and recycled concrete aggregate (RCA) becomes important. For this purpose, in this study, ground granulated blast furnace slag (GGBFS) based geopolymer concrete containing RCA was designed and freeze-thaw (F-T) and sulfate resistance of these samples were determined. In the production of geopolymer concrete, three different binder contents (300, 400 and 500 kg/m3) and five different ratios of RCA (0, 25, 50, 75 and 100%) were used. Samples that completed curing period were exposed to 100F-T cycles and two sulfate solutions (3% MgSO4 and 1.5% Na2SO4 + 1.5% MgSO4). Compressive strength, ultrasonic pulse velocity (UPV), weight change and sorptivity values of these samples were determined. At the same time, these results were interpreted together with microstructure analysis (SEM and EDS). An exponential relationship was found between Ca/Si and Si/Al ratios of the samples and their compressive strength. Increasing in Ca/Si ratio and decreasing in Si/Al ratio caused an increase in compressive strength. As the binder content amount increased, the resistance of the samples against F-T cycles and sulfate solutions increased. With the increasing RCA ratio in the samples, there were increases in strength losses, but these losses were low and indicated that RCA was suitable for use in geopolymer concrete production.Öğe Effect of binder dosage and the use of waste rubber fiber on the mechanical and durability performance of geopolymer concrete(Elsevier, 2022) Yolcu, Abdurrahman; Karakoc, Mehmet Burhan; Ekinci, Enes; Ozcan, Ahmet; Sagir, Mehmet AkifThis paper was designed to find solutions to the fact that the availability of natural aggregates in accordance with the standards used in concrete is gradually decreasing, the environmental problems caused by cement threaten our future, and the recycling of used tire waste is very difficult. The effects of three different binder dosages (300, 400 and 500 kg/m(3)) on the mechanical and durability properties of geopolymer concrete (GPC) samples were investigated in binder contents consisting of 98% granulated blast furnace slag (GBFS) and 2% nano silica. As for the aggregate composition, natural sand was used as the fine aggregate, while the waste rubber fibers (WRF) were substituted in different proportions (0%, 5%, 10% and 15%) of the coarse aggregate by volume. Following the solid part was obtained as described, the alkaline activation of GPC specimens was provided using a 12 M NaOH solution. At the end of 28-day curing period, compressive strength, flexural strength, splitting tensile strength, impact resistance, capillary permeability and elevated temperature performance properties were investigated in detail and the results obtained from the mentioned tests were also confirmed by microstructural analysis. Experimental findings revealed that the increase in binder dosage resulted in significant increases in all of the mechanical properties, and it was speculated that this was due to the formation of a denser and more compact microstructure compared to their counterparts produced using lower binder dosage. Besides the negative effects of WRF usage on compressive strength and resistance of elevated temperature, the other performance criteria such as flexural strength, impact resistance and splitting tensile strength values of GPC samples significantly improved with the usage of WRF. As a result, experimental findings demonstrated that the usage of waste rubber fibers in the production of GPC was advantageous in terms of some mechanical and durability properties.Öğe Effect of cooling regimes on compressive strength of concrete with lightweight aggregate exposed to high temperature(Elsevier Sci Ltd, 2013) Karakoc, Mehmet BurhanIn this study, the residual compressive strength of concrete with expanded perlite aggregate (EPA) and pumice aggregate (PA) after it was exposed 700 degrees C and then cooled in three cooling regimes (natural, water and furnace cooling) at w/b ratio for 0.25, 0.30, 0.35 was investigated. EPA and PA replacements of fine aggregate were used 10%, 20%, and 30%. Test results showed that the compressive strength of concrete cooled in water cooling after being exposed to the effect of different mixture with EPA and PA is higher than that cooled in natural and furnace. Based on the test results, the compressive strength of concrete cooled in water, furnace and natural cooling decreased by an average of 78%, 81% and 83%, respectively, when compared to control samples. (C) 2012 Elsevier Ltd. All rights reserved.Öğe Effect of silica fume and waste rubber on the performance of slag-based geopolymer mortars under high temperatures(Ernst & Sohn, 2023) Sagir, Mehmet Akif; Karakoc, Mehmet Burhan; Ozcan, Ahmet; Ekinci, Enes; Yolcu, AbdurrahmanIn this study, the fire resistance of slag-based geopolymer mortars was investi-gated and the effect of silica fume (SF) and waste rubber (WR) on this resistance was determined. In slag-based geopolymer mortars activated using 12M NaOH solution, 0%, 5%, and 10% by weight SF was substituted for slag; 0%, 5%, 10%, and 15% WR by volume were substituted for fine aggregate. The samples that completed the curing period were exposed to temperatures of 250 degrees C, 500 degrees C, and 750 degrees C for 1 h, and the mechanical (compressive, flexural and splitting tensile strengths, and impact resistance), physical (weight change and sorptivity) and microstructure (scanning electron microscopy [SEM] and energy dispersive spectroscopy [EDS]) properties of these samples were examined. The compres-sive strengths of the samples without WR were between 48.10 and 60.97 MPa, and the samples without SF were between 28.52 and 48.10 MPa. Strength losses at 750 degrees C were between 51.5% and 73.5%. As the SF substitution increased, the samples' mechanical and physical properties improved, whereas as the WR sub-stitution increased, the samples' mechanical and physical properties declined. While the SF substitution had a positive effect on the fire resistance of the sam -ples, the WR substitution had a negative effect. It is thought that the choice of geopolymer binder as a binder in the mortar and the use of waste tires as aggre-gate contribute to the literature in terms of both preventing environmental pollution and ensuring the recycling of these materials.Öğe Effects of elevated temperatures on the properties of ground granulated blast furnace slag (GGBFS) based geopolymer concretes containing recycled concrete aggregate(Taylor & Francis Ltd, 2022) Topal, Ozge; Karakoc, Mehmet Burhan; Ozcan, AhmetThe use of waste materials in concrete design draws the attention of researchers. Studies on the use of these materials both as binders and aggregates accelerate. In this study, ground granulated blast furnace slag (GGBFS) based geopolymer concrete was produced. 0, 25, 50, 75 and 100% recycled concrete aggregate (RCA) was used instead of river aggregate in the mixtures. These samples were exposed to temperatures at 100, 200, 400, 600 and 800 degrees C. The cooling process of these samples exposed to temperature was in 3 different forms: air, oven and water. Compressive strength, ultrasonic pulse velocity (UPV), weight loss, sorptivity and water absorption values of the samples were determined. At the same time, the changes in the microstructure of the samples under the elevated temperature were examined. Compressive strengths of the samples decreased with increasing RCA ratio in the mixture. Samples were severely affected due to elevated temperature, properties of the samples decreased. As the temperature degree increased, the weight loss and sorptivity values of the samples increased. As the temperatures to which the samples were exposed increased, there was a decrease in Ca/Si ratio and an increase in Si/Al ratio. The microstructure of the samples deteriorated at elevated temperatures.Öğe Fire resistance of geopolymer concrete produced from Elaz ferrochrome slag(Wiley, 2016) Turkmen, Ibrahim; Karakoc, Mehmet Burhan; Kantarci, Fatih; Maras, Muslum Murat; Demirboga, RamazanThis paper presents the effect of elevated temperatures up to 700 degrees C on compressive strength and water absorption of two alkali-activated aluminosilicate composites (one of them is river sand aggregate geopolymer concrete; the other one is crushed sand aggregate geopolymer concrete) and ordinary Portland cement based concretes. To obtain binding geopolymer material, Elaz ferrochrome slag was ground as fine as cement, and then it was alkali activated with chemical (NaOH and Na2SiO3). Geopolymer concrete samples were produced by mixing this binding geopolymer material with aggregates. At each target temperature, concrete samples were exposed to fire for the duration of 1h. Fire resistance and water absorption of geopolymer and ordinary Portland cement concrete samples were determined experimentally. Experimental results indicated that compressive strength of geopolymer concrete samples increased at 100 degrees C and 300 degrees C temperatures when compared with unexposed samples. In geopolymer concrete samples, the highest compressive strength was obtained from river aggregates ones at 300 degrees C with 37.06MPa. Water absorption of geopolymer concrete samples increased at 700 degrees C temperature when compared with unexposed samples. However, a slight decrease in water absorption of concrete samples was observed up to 300 degrees C when compared with unexposed samples. SEM and X-ray diffraction tests were also carried out to investigate microstructure and mineralogical changes during thermal exposure. Copyright (c) 2016 John Wiley & Sons, Ltd.Öğe 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, RamazanThe 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.Öğe The improvement of mechanical, physical and durability characteristics of volcanic tuff based geopolymer concrete by using nano silica, micro silica and Styrene-Butadiene Latex additives at different ratios(Elsevier Sci Ltd, 2019) Ekinci, Enes; Turkmen, Ibrahim; Kantarci, Fatih; Karakoc, Mehmet BurhanThis study aims to the improvement of volcanic tuff-based geopolymer concrete (GPC) with the addition of nano silica (NS), micro silica (MS) and Styrene-Butadiene Latex (SBL) at the different ratios. For this purpose, incorporating of volcanic tuff with NS (1, 2, 3%), MS (1, 3, 5%) and SBL (5, 10, 15%) was provided. GPC samples were produced with two different activation method (Na2SiO3 + NaOH and sole NaOH). 28-day compressive strength, freeze-thaw (FT) resistance, microstructure, water absorption, density, bulk density and apparent porosity values of volcanic tuff-based GPC samples were investigated. The results indicated that the compressive strength of NaOH-activated samples was much higher than similar ones activated with Na2SiO3 + NaOH. In both activation methods, the optimum NS and SBL ratios were determined as 2% and 5%, respectively. Also, the optimum additive of MS ratio was determined 5% and 3% for Na2SiO3 + NaOH and sole NaOH-activated samples, respectively. As well as the highest compressive strength losses as a result of 300 FT cycles were observed in pure samples for both activation methods, Na2SiO3 + NaOH-activated samples exhibited better resistance to FT effect than similar ones activated with sole NaOH. (C) 2018 Elsevier Ltd. All rights reserved.Öğe Investigation of the properties of two different slag-based geopolymer concretes exposed to freeze-thaw cycles(Ernst & Sohn, 2019) Ozdal, Mustafa; Karakoc, Mehmet Burhan; Ozcan, AhmetFerrochrome slag (FS) and ground granulated blast furnace slag (GGBFS) were used as resource material in geopolymer concrete mixtures. A mixture of 10 M sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) was used as the activator. After the two different slag-based geopolymer concrete (SGC) mixtures were prepared and molded. They were kept at 80 degrees C for 24 hr, and then the SGC samples were cured in 23 +/- 1 degrees C water for 27 days. Samples that completed the curing times were exposed to the 300 freeze-thaw (F-T) cycles. The compressive strength, ultrasonic pulse velocity, relative dynamic elasticity modulus values, weight changes, and appearances of the SGC samples were examined at the end of every 50 F-T cycles. Scanning electron microscopy analysis was performed to examine the microstructure changes of the samples after 300 F-T cycles. As the GGBFS proportion in the SGC mix increased, the mechanical properties of the samples against the F-T effect increased. Samples containing 100% FS and 75% FS fell apart at the end of 150 and 200 F-T cycles, respectively. The deterioration of the geopolymer gel structures of the samples exposed to F-T was decreased with increasing GGBFS ratio in the mix.Öğe Mechanical properties and setting time of ferrochrome slag based geopolymer paste and mortar(Elsevier Sci Ltd, 2014) Karakoc, Mehmet Burhan; Turkmen, Ibrahim; Maras, Muslum Murat; Kantarci, Fatih; Demirboga, Ramazan; Toprak, M. UgurMany researches have been done to investigate using raw materials in the production of geopolymer cements. This paper presents the effects of alkali dosage and silica modulus when using sodium metasilicate solution at different curing conditions on the geopolymerization of ferrochrome slag (FS). As alkali activation for geopolymerization, NaOH and Na2SiO3 solution were used. Geopolymer cement was produced using FS as raw material with 3 different silica modulus (0.50, 0.60 and 0.70) and 4 different Na2O concentrations (4%, 7%, 10% and 12%). The setting time, hydration heat and compressive strength of geopolymer paste samples and compressive strength of geopolymer mortar samples were obtained. The setting time varied between 120 and 870 min, it showed variability depending on Na2O content. The highest 28 day compressive strength of the geopolymer paste samples was obtained from one with Na2O concentration of 7% and silica modulus of 0.70. Geopolymer mortars were prepared for the determination of compressive strength by adding FS:sand:alkali activator ratio 1:2:0.30, 035 and 0.40. The specimens were cured at 60 degrees C and 80 degrees C kept for 20 h and the other mortar samples were stored under laboratory conditions. Compressive strength of the material decreased, when w/b (water/binder) ratio increased. The highest 28 day strength of the geopolymer mortar was obtained at 0.30 w/b ratio and laboratory temperature curing conditions. The hydration heat of geopolymer paste samples was found to be less than normal Portland cements. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were investigated to study the microstructural properties of the geopolymers. (C) 2014 Elsevier Ltd. All rights reserved.Öğe 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. UgurMany 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.Öğe Mechanical properties of high strength concrete made with pyrophyllite aggregates exposed to high temperature(Ernst & Sohn, 2020) Demez, Abdultaha; Karakoc, Mehmet BurhanThis paper presents the results of an experimental research on the assessment of the residual mechanical properties of high strength concretes (HSCs) made with pyrophyllite aggregate (PA) after high temperature. In the study, HSC mixtures with varying PA ratios (0, 25, 50, 75, and 100%) were subjected to elevated temperature (150, 300, 450, 600, and 750 degrees C) and then cooled in two different cooling regimes (air and water-cooling). The properties examined included compressive strength, weight loss, effects of cooling regime, and microstructure of HSC. The results of the study show that the increase in the PA ratios leads to a decrease in the compressive strength values. The results showed that weight loss of the specimens decreased with increasing PA ratios. It was found that the compressive strength values of HSC with PA cooled in air-cooling are higher than that cooled in water. When the compressive strength loss and the weight loss values are taken into consideration according to the control samples, the group with the highest resistance to high temperature (750 degrees C) effect was 100% PA group. Also, the internal structures of the samples exposed to high temperature were examined using scanning electron microscope and visual observations.Öğe Modeling of compressive strength and UPV of high-volume mineral-admixtured concrete using rule-based M5 rule and tree model M5P classifiers(Elsevier Sci Ltd, 2015) Ayaz, Yasar; Kocamaz, Adnan Fatih; Karakoc, Mehmet BurhanCompressive strength and UPV parameters are the methods that are used to determine high-volume mineral admixture concrete quality. But experiments for all levels of these parameters are expensive, difficult and time consuming. For determination of output values, classifiers with model extraction features can be used. In this study, classifiers, with the rule-based M5 rule and tree model M5P in the area of data mining are used to predict the compressive strength and UPV of concrete mixtures after 3, 7, 28 and 120 days of curing. The M5 rule and tree model M5P are tested using the available test data of 40 different concrete mix-designs gathered from literature [1]. The input of the model is a variable data set corresponding to concrete mixture proportions. The findings of this study indicated that the M5 rule and tree model M5P models are sufficient tools for estimating the compressive strength and UPV of concrete. 97% and 87% success is obtained in predicting compressive strength and UPV results, respectively. (C) 2015 Elsevier Ltd. All rights reserved.Öğe Modeling with ANN and effect of pumice aggregate and air entrainment on the freeze-thaw durabilities of HSC(Elsevier Sci Ltd, 2011) Karakoc, Mehmet Burhan; Demirboga, Ramazan; Turkmen, Ibrahim; Can, IbrahimThe objective of this work is to calculate the compressive strength, ultrasound pulse velocity (UPV), relative dynamic modulus of elasticity (RDME) and porosity induced into concrete during freezing and thawing. Freeze-thaw durability of concrete is of great importance to hydraulic structures in cold areas. In this paper, freezing of pore solution in concrete exposed to a freeze-thaw cycle is studied by following the change of concrete some mechanical and physical properties with freezing temperatures. The effects of pumice aggregate (PA) ratios on the high strength concrete (HSC) properties were studied at 28 days. PA replacements of fine aggregate (0-2 mm) were used: 10%, 20%, and 30%. The properties examined included compressive strength, UPV and RDME properties of HSC. Results showed that compressive strength, UPV and RDME of samples were decreased with increase in PA ratios. Test results revealed that HSC was still durable after 100, 200 and 300 cycles of freezing and thawing in accordance with ASTM C666. After 300 cycles, HSC showed a reduction in compressive strength between 6% and 21%, and reduction in RDME up to 16%. For 300 cycles, the porosity was increased up to 12% for HSC with PA. In this paper, feed-forward artificial neural networks (ANNs) techniques are used to model the relative change in compressive strength and relative change in UPV in cyclic thermal loading. Then genetic algorithms are applied in order to determine optimum mix proportions subjected to 300 thermal cycling. (C) 2011 Elsevier Ltd. All rights reserved.Öğe Performance of glass powder substituted slag based geopolymer concretes under high temperature(Elsevier Sci Ltd, 2022) Derinpinar, Aslihan Nida; Karakoc, Mehmet Burhan; Ozcan, AhmetGeopolymer concretes provide advantages in terms of recycling waste materials. Geopolymer concretes are advantageous in terms of both limiting the use of Portland cement and recycling waste materials. In this study, 5 different geopolymer concrete mixture groups were prepared by replacing slag with 0.5%, 10, 15 and 20% by weight glass powder (GP). Geopolymer concrete samples prepared by using 12 M sodium hydroxide solution as an alkali activator were cured in the laboratory environment. The samples, which completed their curing pe-riods, were kept at 150, 300, 450, 600 and 750 C temperatures for 1 h. Compressive strength, weight change and sorptivity values of these samples were determined. These results were interpreted together with the visual inspections and microstructure analyzes (SEM and EDS) of the samples. As the GP substitution rate increased, the mechanical properties of geopolymer concretes decreased. However, GP improved the performance of geo-polymer concretes exposed to high temperatures. Cooling in air affected the samples less negatively than cooling in water. While the Ca/Si ratios of the samples decreased at 450 C and above, the Si/Al ratio increased.Öğe Prediction of compressive strength and ultrasonic pulse velocity of admixtured concrete using tree model M5P(Ernst & Sohn, 2020) Kocamaz, Adnan Fatih; Ayaz, Yasar; Karakoc, Mehmet Burhan; Turkmen, Ibrahim; Demirboga, RamazanThe quality of concrete was assessed based on measurements of ultrasonic pulse velocity (UPV) and compressive strength. Portland cement (PC) was substituted with silica fume (SF), fly ash (FA) and blast furnace slag (BFS) as mineral admixtures. The compressive strength and UPV of concrete mixtures were estimated with classifiers alongside the tree model M5P in the data mining field. The compressive strength and UPV were modeled as a function of five input variables: day, cement, SF, FA, and BFS. It was found that UPV and compressive strength had an exponential correlation with SF, FA, BFS, SF + FA, SF + BFS and FA + BFS. However, additive-free admixture and PC-free substitution levels had a different constant in empirical work. According to the results obtained, both compressive strength and UPV of concrete mixtures could be reliably anticipated with the tree model M5P in a proportion of 97%. Hence, this model could be a potential new method for modeling mineral admixture concrete.Öğe The Resistance of Blast Furnace Slag- and Ferrochrome Slag-Based Geopolymer Concrete Against Acid Attack(Springer International Publishing Ag, 2019) Ozcan, Ahmet; Karakoc, Mehmet BurhanIn this study, blast furnace slag- (BFS) and Elazig ferrochrome slag (EFS)-based geopolymer concretes were produced. Samples were immersed in 5% phosphoric acid (H3PO4), hydrochloric acid (HCl), hydrofluoric acid (HF) and sulfuric acid (H2SO4) solutions for 12 weeks. The compressive strengths, ultrasonic pulse velocities, weight and length changes of the samples were determined in this process. At the same time, visual inspections of the samples were investigated. Scanning electron microscopy (SEM) analysis was performed for the microstructure analysis of the samples removed from the solutions. 5% H2SO4 solution had the most negative effect on the samples. As the EFS ratio in the geopolymer concrete mixture increased, the loss rate in the strength of the samples exposed to acid solutions decreased. H3PO4 solution caused less weight loss in samples than other acid solutions. It was seen that the samples immersed in H3PO4 and HCl solutions shrank and that the samples immersed in HF and H2SO4 solutions expanded. Softening, cracking and corruption occurred on the surfaces of the samples exposed to the acid solutions for 12 weeks. With increasing EFS ratio in the mixture, the deterioration of the samples' surfaces exposed to acid solutions decreased. Ettringite formations were seen in the SEM images of geopolymer concretes immersed in 5% H2SO4 solution.Öğe Sulfate resistance of ferrochrome slag based geopolymer concrete(Elsevier Sci Ltd, 2016) Karakoc, Mehmet Burhan; Turkmen, Ibrahim; Maras, Muslum Murat; Kantarci, Fatih; Demirboga, RamazanThis paper presents the study of the performance of a new geopolymer binding material exposed to sulfate attack. Geopolymer binding material was obtained by alkaline activating FS with chemical materials (NaOH and Na2SiO3). Geopolymer concrete samples were produced by mixing this binding material with river sand and crushed sand aggregates. Test specimens were immersed in magnesium sulfate solutions (by weight 3%, 5% and 7%) for various periods of time and the durability of geopolymer concrete was investigated. The residual compressive strength (90 and 180 days), change in weight and length of samples, pH variation of solution and visual appearance of these samples were obtained experimentally. It was concluded that compressive strength of both geopolymer and Ordinary Portland Cement (OPC) based concrete samples decreases with increasing in MgSO4 content and exposure duration. After exposed to 7% MgSO4 solution for 180 days, the minimum decrease in compressive strength was seen 25% in geopolymer concrete samples with crushed sand aggregates. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
