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Öğe Effect of fibre characteristics on physical, mechanical and microstructural properties of geopolymer concrete: A comparative experimental investigation(Wiley, 2023) Kantarci, FatihThe main aim of this work is to comparatively reveal the effect of fibre type, length and content on compressive strength and microstructure of structural geopolymer concrete (GPC) produced under constant mixture and curing parameters in order to address the significant gap in present literature. Firstly, GPCs with different NaOH concentrations (i.e., 6, 9, 12 and 15 M) and activator solution/binder (a/b) ratios (i.e., 0.45 and 0.55) were produced in ambient curing condition, and optimum production parameters were determined based on the preliminary evaluations. Then, glass and polypropylene fibres in 6-mm length (GS6 and PP6) and polyamide and polypropylene fibres in 12-mm length (PY12 and PP12) were included in GPCs at ratio of 0.4%, 0.8% and 1.2% (by volume). Compressive strength, apparent porosity, bulk density, ultrasonic pulse velocity (UPV), X-ray diffraction (XRD) and scanning electron microscope (SEM) analysis of GPC samples were carried out comparatively. The inclusion of GS6 fibre enhanced the compressive strength thanks to fibre surface being covered by geopolymer gel and the strong adhesion between GS fibre and geopolymer matrix. SEM images of fibre reinforced GPC (FRGPC) also confirmed the experimental findings, which were attributed to improvement in compressive strength. Regardless of the fibre type, the maximum compressive value strength was obtained from GPC specimens with 0.4% fibre and then decreased. Higher fibre inclusions led to poor compaction, workability issues and inhomogeneous fibre dispersions. A very good relation (R-2 = 0.98) was acquired between UPV and compressive strength values of GPC/FRGPC samples.Öğe Effects of acid-base solutions on some Turkish natural building stones: physico-mechanical and color changes(Springer Int Publ Ag, 2022) Ozdemir, Engin; Kantarci, Fatih; Eren Sarici, DidemNatural stones are exposed to various physical, chemical and environmental interactions during service life. It is quite important to determine physico-mechanical properties of natural stones for specific applications. This paper presents an experimental study conducted to explore effect of acid and sulfate shocks on some physico-mechanical properties and color of natural stones. For this purpose, five different building stones used as marble (Malatya Beige, Agri Onyx, Adiyaman Crystal Emperador, Diyarbakir Black Pearl, Elazig Rosso Levanto) were supplied from eastern region of Turkey. Point load strength, Schmidt hardness rebound, unit weight, porosity, water absorption and color measurements were conducted on provided natural stones. Additionally, mineralogical properties of natural stones were investigated with XRD and XRF analyses. Then, these natural stones were exposed to chemical shocks with 5% H2SO4 and Na2SO4 solutions for 0, 10, 20 and 30 cycles. Changes in Schmidt hardness, point load strength, porosity, dry weight and color after chemical shock cycles were investigated. Experimental results showed that Diyarbakir Black Pearl (DBP) and Malatya Beige natural stones might be used in aggressive H2SO4 and Na2SO4 environments for structural and ornamental purposes. After 30 cycles of H2SO4 and Na2SO4 shock, minimum decrease in point load values was obtained from DBP samples with 5.97% and 9.15%, respectively. Similarly, decrease in Schmidt harness values of DBP was minimum. Among natural stones exposed to H2SO4 and Na2SO4 shocks, AO sample that had the greatest strength loss was 17.36% and 9.68%, respectively.Öğe Enhancing acid resistance of geopolymer concrete composites by utilising styrene-butadiene latex, nano-silica and micro-silica powder(Taylor & Francis Ltd, 2023) Kantarci, Fatih; Turkmen, Ibrahim; Ekinci, EnesThe acid resistance of geopolymer binder, a promising alternative to ordinary Portland cement with clean technology option, needs detailed investigations for widespread use in different applications and severe acidic conditions. The aim of this work is to enhance acid resistance of geopolymer concretes (GPCs) by employing styrene-butadiene latex (SBL), nano-silica (NS) and micro-silica (MS) powders. The residual compressive strength, weight loss, visual appearance and microstructure properties of GPC samples were evaluated after exposed to hydrochloric acid (HCl) solutions with different concentrations (3%, 5% and 7%) for 90 and 180 days. The addivites increase residual compressive strength by preventing acid liquids to ingress the interior areas thanks to additional pozzolanic and filler effect leading to more compact and denser microstructure. Any apparent damage was not observed at the outer surface of GPC specimens.Öğe Fabrication of Novel Geopolymer Grout as Repairing Material for Application in Damaged RC Beams(Springer Int Publ Ag, 2022) Kantarci, Fatih; Maras, Muslum MuratIn this study, a new grouting composite, called geopolymer grout, with high compressive strength (> 107 MPa, cured at ambient conditions) was developed and injected into damaged reinforced concrete (RC) beam. This investigation was planned in two steps: (1) determination of optimum geopolymer grout composite depending on viscosity, compressive strength, and SEM findings; (2) injection of optimum geopolymer grout to damaged RC beam. Geopolymer grouts were fabricated with different NaOH concentrations (i.e., 8, 10, and 12 M) and Ca(OH)(2) contents (1, 3, 5 and 7% of slag weight). A remarkable advance in fresh and hardened characteristics of geopolymer grouts was acquired with changing of NaOH concentration and Ca(OH)(2) content. A reference RC beam was subjected to bending test and the load-displacement curve was obtained. The determined optimum geopolymer grout was injected into this damaged RC beam and exposed to reloading test. The strengthened RC beam specimen was compared with reference RC beam in terms of failure modes, load capacity and crack patterns. After damaged RC beam was strengthened, it showed higher mechanical performance compared to reference RC beam. The experimental findings revealed that geopolymer grouts could be a suitable alternative for repair and strengthening of damaged RC beam due to their low viscosity, eco-friendliness, good bonding and superior compressive strength.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 Formulation of a novel nano TiO2-modified geopolymer grout for application in damaged beam-column joints(Elsevier Sci Ltd, 2022) Kantarci, Fatih; Maras, Muslum MuratThe aim of this study is to develop a nano TiO2-modified geopolymer grout and to confirm application in damaged beam-column joints (BCJs). The experimental study was planned in two stages: i) fabrication of an optimal geopolymer grout depending on compressive strength, viscosity, UPV and SEM investigations, ii) injection of the optimal geopolymer grout to damaged BCJ to confirm application. Geopolymer grouts were produced with different NaOH concentrations (8, 10, 12 M) and nano TiO2 contents (5, 10 and 15% of slag weight). The obtained optimal gopolymer grout was injected into the damaged BCJ and subjected to reloading test. Significant improvements in fresh and hardened properties of geopolymer grout samples were provided with modification of NaOH concentrations and nano TiO2 contents. It was also explored that the application of nano TiO2-modified geopolymer grout on the damaged BCJ increased load carrying capacity and ductility in comparison with the reference sample. As a result, a novel eco-friendly geopolymer grout with effective viscosity and high compressive strength was developed and confirmed for utilising in damaged BCJs.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 Improving elevated temperature performance of geopolymer concrete utilizing nano-silica, micro-silica and styrene-butadiene latex(Elsevier Sci Ltd, 2021) Kantarci, Fatih; Turkmen, Ibrahim; Ekinci, EnesGeopolymer binders (GPBs) have gained an increasing research potential in recent years due to their environmental, economic and durability advantages. This paper aims to improve elevated temperature performances of volcanic tuff (VT) based geopolymer concrete (GPC) by utilizing nano-silica (NS), micro-silica (MS) and styrene-butadiene latex (SBL). To this end, NS, MS and SBL additives were added to GPC samples at 2%, 2% and 5% ratios by weight of binder, respectively. GPB was obtained by activating ground VT with 12 M NaOH solution. Produced GPC samples were exposed to elevated temperatures (100, 300, 500 and 700 degrees C) for 1 h after reaching the target temperature. Changes in compressive strength, water absorption, visual appearance, weight and microstructure of GPC samples were investigated after the influence of elevated temperatures. The experimental findings displayed that compressive strength of GPCs increased up to 300 degrees C independently of the type of additive used, but higher temperatures than 300 degrees C caused decrease in compressive strength values. As a result of mechanical tests and microstructure investigations, it was determined that MS additive significantly increased the elevated temperature performance of GPCs. Additionally, color of GPC samples turned gray after elevated temperatures due to dehydration of GPB and microstructural transformations occurring in aggregates. (c) 2021 Elsevier Ltd. All rights reserved.Öğe Improving performance of bituminous pavement layers with vermiculite, perlite, lime and calcite additives(Springer Int Publ Ag, 2022) Temiz, Huseyin; Kantarci, Fatih; Keklik, MesutThe bearing resistance of asphalt pavements decreases due to the high temperature and long loading times and many distortions occur with tracks. Mineral additives are used to prevent the formation of wheel marks and other deformations in bituminous hot mixtures. Some of the additives are used to improve the blend properties by modifying the bitumen and some are directly involved in the admixture to enhance the engineering characteristics of the pavement layer. In this study, vermiculite, perlite, lime and calcite minerals were added directly to the mixture at the ratio of 0.5%, 1%, 1.5%, 2% and 2.5% of aggregate weight. Bitumen content, porosity, stability and flow values of the samples were determined by Marshall method. The values obtained from doped samples were compared with the reference sample. As a result of experimental study, it was revealed that vermiculite, perlite, lime and calcite mineral additives increased the durability of the asphalt mixtures and these additives may obstruct the wheel tracks on the surface.Öğe Influence of blast-furnace slag on behaviour of dolomite used as a raw material of MgO-type expansive agent(Elsevier Sci Ltd, 2015) Temiz, Huseyin; Kantarci, Fatih; Inceer, M. EminThe content of MgO in cement is restricted to less than 5% (by weight) because of its expansive character. However, the cement, called dam cement, containing MgO more than 5% is used in both research activities and industrial applications. Turkey is rich in dolomite reserves and dolomite is abundantly found in several regions of the country. In this study, influence of blast-furnace slag (BFS) on expansion properties of dolomite was explored. Portland Cement (CEM I 42.5R) was replaced with dolomite up to 40% and blast-furnace slag up to 20%. Hydration heat, setting times, soundness and micro-structures of paste samples and compressive strength and length change of mortar samples were measured. As a result of experimental studies, dolomite used instead of cement caused up to 1.75 mm expansion. The results are in accordance with the values indicated in the standards. As a conclusion, it is possible to use blast-furnace slag in balancing the expansion properties of dolomite. (C) 2015 Elsevier Ltd. All rights reserved.Öğe Influence of fiber characteristics on sulfate resistance of ambient-cured geopolymer concrete(Ernst & Sohn, 2022) Kantarci, FatihThe brittle nature of geopolymer concretes (GPCs) and curing process required in their production are factors that limit their practical applications. It was not detected any study investigating the effect of polypropylene (PP) fiber length and fiber content on sulfate resistance of GPC. The aim of this study is to investigate the effect of PP fibers used in different content and length on sulfate resistance of GPC cured under laboratory conditions. For this purpose, 6 and 12 mm length PP fibers were added to GPC at rate of 0.5, 1.0, and 1.5% by volume of concrete. Samples were cured in laboratory conditions for 28 days, and then exposed to 5% MgSO4 solutions. After the sulfate effect, the changes in physical and mechanical properties of GPC such as compressive strength, tensile strength, weight, ultrasonic pulse velocity (UPV), apparent porosity, and external appearance were investigated. In addition, microstructural analyzes were carried out with scanning electron microscope (SEM). As a result, it was determined that PP fiber additive at rate of 0.5% by volume significantly increased the sulfate resistance by preventing crack growth thanks to bridging function occur between binder phase and interface regions. Since the increased fiber length made it difficult to distribute the fibers homogeneously, 6 mm long PP fibers were more effective in improving the sulfate resistance.Öğe Influence of various factors on properties of geopolymer paste: A comparative study(Ernst & Sohn, 2020) Kantarci, Fatih; Turkmen, Ibrahim; Ekinci, EnesA comprehensive experimental study was conducted to investigate effect of different production parameters such as activator type, activator concentration and curing temperature on fresh and hardened properties of volcanic tuff based geopolymer paste (GP) samples. Volcanic tuff obtained from Nevsehir (Central Anatolia, Turkey) was ground to particle size less than 45 mu m, after that alkali activation process was provided with two type of alkali activators such as NaOH and NaOH+Na2SiO3(SH and SH + SS) solutions. Produced geopolymer samples were cured at different temperatures ranging from 23 to 150 degrees C. Compressive strength, setting time, hydration heat of GP samples were investigated. Additionally, microstructural investigations were performed with SEM and XRD analyzes. As a result of modification of experimental parameters, compressive strength development reached to 41.43 MPa was obtained from GP samples, which did not harden in laboratory conditions. It was also determined that the alkali activation of volcanic tuff with SH exhibited better mechanical and microstructural properties than alkali activation with SH + SS.Öğe Investigation of durability of CEM II B-M mortars and concrete with limestone powder, calcite powder and fly ash(Elsevier Sci Ltd, 2014) Temiz, Huseyin; Kantarci, FatihIn this study, a new binding material obtained by mixing limestone, calcite powders and fly ash in various ratios were used instead of mineral admixture in CEM II/B-M. Mechanical and physical properties of the samples were tested. Results showed that an increase which agreed with the standard requirements was observed in the setting times and volume expansion of paste samples with increasing amount of limestone and calcite powder. Also, the compressive strength of mortar samples decreased with increasing the amount of limestone and calcite powder. Compressive strength of samples with fly ash had a significant increase after 28 days. When samples with limestone and calcite powder were immersed in chemical solutions, compressive strength of samples decreased and weight loss increased. (C) 2014 Elsevier Ltd. All rights reserved.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 Optimization of production parameters of geopolymer mortar and concrete: A comprehensive experimental study(Elsevier Sci Ltd, 2019) Kantarci, Fatih; Turkmen, Ibrahim; Ekinci, EnesGeopolymers are a new type of material offered as an alternative to traditional Portland cement. Geopolymers, produced by activation of natural and waste pozzolans with alkali activators such as NaOH (SH) and Na2O center dot 3SiO(2) (SS) solutions, have been widely supported and investigated due to environmental and economic advantages. In this study, a detailed experimental program was conducted to investigate the influence of activator type, activator concentration and curing temperature on mechanical and microstructural properties of volcanic tuff based geopolymer mortar (GPM) and concrete (GPC) samples. A total of 1080 GPM and GPC samples were produced and a number of parameters were investigated with 360 combinations. Maximum compressive strength was obtained as 37.09 MPa in 90-day samples in which the SH concentration was 16 M, activator/binder (a/b) ratio was 0.45 and the curing temperature was 120 degrees C. As a result of optimization of the production parameters, a considerable development in mechanical and microstructural properties of GPM and GPC samples was obtained. Experimental results demonstrated that alkali activation with sole SH bring about superior characteristics compared to alkali activation with SH + SS. Higher a/b ratio led to higher UPV values because of more dense and compact microstructure resulting from increase in gopolymerization reactions. This is also supported by compressive strength and microstructure findings. (C) 2019 Elsevier Ltd. All rights reserved.Öğe Structural behavior of RC beams strengthened using fiber-reinforced polymer U-jackets(Ernst & Sohn, 2023) Maras, Muslum Murat; Kantarci, FatihThe study aims to identify flexural behavior of RC beams strengthened using three different fiber-reinforced polymers (FRPs) with differential cross-sections configuration (i.e., middle and support sections). The experimental and calculations results of strengthening methods for RC beams were investigated utilizing FRPs under flexural loading. The strengthening FRP materials (CFRP, AFRP, and GFRP) were externally attached to the surface of the samples with U-wrapped shape at the three different regions of the beams. The experimental results were compared with the fiber polymer systems of the American Concrete Institute according to the ACI 440.2R-08 standards. The results demonstrated that RC-9 specimen reinforced using AFRP exhibited higher load capacity performance than the others. The RC beams strengthened at both middle and support area exhibited more ductile behavior, which depends on the failure mode. Less crack formation was seen in the RC-10 beams reinforced with AFRP, both in the middle and in the support area, compared with reference sample. The experiment revealed that FRP U-jackets could be a promotive alternative to improve structural performance greatly and provide reliable and suitable solutions for sustainable buildings.Öğe Structural Performance of Reinforced Concrete (RC) Moment Frame Connections Strengthened Using FRP Composite Jackets(Springer Heidelberg, 2021) Maras, Muslum Murat; Kantarci, FatihThis study investigates structural behaviors of reinforced concrete (RC) moment frame connections strengthened using three different FRPs with different cross section configurations. The novelty of this research is the strengthening of a beam-column connection with FRP composites, where the joint consists of a weak column and a strong one that plays a vital role in the RC element. It is also rare in engineering to use inorganic composites in retrofit configurations (X shape, U shape, and T shape retrofit configurations). That is why we aimed to apply fiber-reinforced composite materials in different configurations (cross, diagonal, and parallel configurations). The experimental performance of strengthened samples was investigated using carbon fiber-reinforced polymer (CFRP), aramid fiber-reinforced polymer (AFRP), and glass fiber-reinforced polymer (GFRP) under loading systems. The strengthened RC specimens (SBWC-2-SBWC-7) were compared with a control specimen (SBWC-1) in terms of load capacity, ductility index, failure modes, and crack patterns. The strengthening of the SBWC-2 and SBWC-3 specimens using CFRP increased the ultimate loads up to 12.5% and 11.4% compared to reference sample, respectively. The first cracks in SBWC-4 and SBWC-5 beam-column joint specimens were found at loads of 35.4 kN and 33.8 kN, respectively. The results indicate that SBWC-2 specimen strengthened by AFRP displayed higher strength and ductile behavior than other specimens, as it depends on failure mode more than its counterparts. The reinforced X shape beam-column connection sample was protected from diagonal cracks. Strengthening with CFRP decreased visible-width shear cracks compared to control samples. The experiments revealed that CFRP composites could be a suitable alternative for greatly improving structural performance and providing suitable and reliable solutions for sustainable structures.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.
