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Öğe Combined Use of Natural and Artificial Slag Aggregates in Producing Self-Consolidating Concrete(AMER CONCRETE INST, 2016) Oz, Hatice Oznur; Gesoglu, Mehmet; Guneyisi, Erhan; Mahmood, Swara FuadThis study addresses properties of self-consolidating concrete (SCC), in which natural coarse aggregates had been substituted by artificial slag aggregates (ASAs). For this, 90% groundgranulated blast-furnace slag and 10% portland cement by weight were pelletized in a tilted pan through cold-bonded agglomeration process. Then, the hardened coarse aggregates (ASA) were tested for specific gravity, water absorption, and crushing strength. Thereafter, they were partially used in producing SCCs in which ASA replaced the natural coarse aggregates at 0, 20, 40, 60, 80, and 100% by volume. Therefore, six SCCs with 0.32 water-binder ratio (w/b) were designed and cast using both natural and/or ASA. Hardened concrete properties were tested for compressive and splitting tensile strengths, modulus of elasticity, drying shrinkage, freezing-and-thawing resistance, chloride ion permeability, gas permeability, and sorptivity. Test results indicated that SCCs with ASA displayed better performance than the control mixture in terms of durability-related properties. Incorporating ASA in SCCs increased the compressive strength and elastic modulus (up to 60%) but decreased the splitting tensile strength. However, ASA provided gradual reduction in sorptivity coefficient, chloride ion, and gas permeability especially at 60% replacement level and 56 days.Öğe Comparison of Glass Powder and Fly Ash Effect on the Fresh Properties of Self-Compacting Mortars(Iop Publishing Ltd, 2017) Oz, Hatice Oznur; Yucel, Hasan Erhan; Gunes, MuhammetThis study is aimed to determine effects of glass powder on fresh properties of self-compacting mortars. Self-compacting mortars incorporating glass powder (SCMGPs) were designed with a water/binder ratio of 0.40 and a total binder content of 550 kg/m(3). At first, the control mixture was produced with 20% fly ash and % 80 cement of the total binder content without using the glass powder. Then, glass powder was used in the proportions 5%, 10%, 15% and 20% instead of fly ash in the mortars. Mini-slump flow and mini-v funnel tests experimentally investigated on SCMGPs to compare the effect of fly ash and glass powder. With increasing the amount of glass powder used in SCMGPs increased the amount of superplasticizer used to obtain the desired mini-slump flow diameter. So, the use of glass powder reduced the flow ability of SCMGPs in comparison to fly ash. Additionally, the compressive strength and flexural strength of the mortar mixtures were determined at the 28th day. The test results indicated that the mechanical characteristics of SCMGPs improved when the fly ash was replaced with glass powder in SCMGPs.Öğe Durability and Shrinkage Characteristics of Self-Compacting Concretes Containing Recycled Coarse and/or Fine Aggregates(HINDAWI PUBLISHING CORPORATION, 2015) Gesoglu, Mehmet; Guneyisi, Erhan; Oz, Hatice Oznur; Yasemin, Mehmet Taner; Taha, IhsanThis paper addresses durability and shrinkage performance of the self-compacting concretes (SCCs) in which natural coarse aggregate (NCA) and/or natural fine aggregate (NFA) were replaced by recycled coarse aggregate (RCA) and/or recycled fine aggregate (RFA), respectively. A total of 16 SCCs were produced and classified into four series, each of which included four mixes designed with two water to binder (w/b) ratios of 0.3 and 0.43 and two silica fume replacement levels of 0 and 10%. Durability properties of SCCs were tested for rapid chloride penetration, water sorptivity, gas permeability, and water permeability at 56 days. Also, drying shrinkage accompanied by the water loss and restrained shrinkage of SCCs were monitored over 56 days of drying period. Test results revealed that incorporating recycled coarse and/or fine aggregates aggravated the durability properties of SCCs tested in this study. The drying shrinkage and restrained shrinkage cracking of recycled aggregate (RA) concretes had significantly poorer performance than natural aggregate (NA) concretes. The time of cracking greatly prolonged as the RAs were used along with the increase in water/binder ratio.Öğe Effect of nano silica on the workability of self-compacting concretes having untreated and, surface treated lightweight aggregates(ELSEVIER SCI LTD, 2016) Guneyisi, Erhan; Gesoglu, Mehmet; Azez, Oday Ali; Oz, Hatice OznurThis paper presents the fresh properties of self-compacting lightweight aggregate concrete (SCLC) made with cold bonded fly ash (FA) lightweight aggregate (LWA) at a wide range of water-to-binder (w/b) ratios. For this, three concrete series including eighteen SCLCs were designed with w/b ratios of 0.25, 0.37 and 0.50, respectively. Each series have 6 different mixes in which two type of coarse LWAs (surface treated or not) and three nano silica (nS) replacement levels (0, 2.5% and 5.0%) are considered. The properties of SCLCs were observed in terms of slump flow diameter, T-500 slump flow time, V-funnel flow time, and L-box height ratio. The compressive strength test was also conducted to obtain the strength level at 28 days. It is found that the fresh SCLCs have good fluidity, passing ability, uniform aggregate distribution and resistance to segregation. Incorporating treated coarse LWA5 increased the workability characteristics of SCLCs. However, appreciable improvement in the consistency of SCLCs by nS addition was observed. The SCLCs made with treated LWAs and 5% nS were found to be the harder samples in this research. (c) 2016 Elsevier Ltd. All rights reserved.Öğe Failure characteristics of self-compacting concretes made with recycled aggregates(ELSEVIER SCI LTD, 2015) Gesoglu, Mehmet; Guneyisi, Erhan; Oz, Hatice Oznur; Taha, Ihsan; Yasemin, Mehmet TanerThis study addresses the properties of self-compacting concretes (SCCs) produced with recycled coarse aggregates (RCAs) and/or recycled fine aggregates (RFAs) compared to SCCs with natural aggregates (NAs). The SCC mixtures were designed with a constant slump flow of 680 +/- 30 mm and two water/binder (w/b) ratios of 0.3 and 0.43. Silica fume (SF) was also used at two replacement levels of 0% and 10%. Hardened properties of the SCCs were evaluated in terms of compressive strength, splitting tensile strength, static modulus of elasticity, and net flexural strength after 56 days of water curing. Failure mechanism of the concretes was also monitored via three-point bending test on the notched beams. The results indicated that failure occurred throughout the recycled aggregates (RAs) which in-turn decreased the mechanical properties of SCCs. However, SCCs with both fine and coarse RAs (RCAs + RFAs) had relatively worse performance than those with only RCAs or RFAs such that the reduction in strength was about 30% as compared to the corresponding reference mixes. Moreover, incorporating SF and decreasing w/b ratio improved the mechanical properties of SCCs. (C) 2015 Elsevier Ltd. All rights reserved.Öğe Fly-ash-based geopolymer composites incorporating cold-bonded lightweight fly ash aggregates(Elsevier Sci Ltd, 2021) Oz, Hatice Oznur; Yucel, Hasan Erhan; Gunes, Muhammet; Koker, Turan SevkiIn this study, effects of cold-bonded lightweight fine aggregate (LWFA) on the geopolymer composites (GCs) were investigated in terms of fresh, physical, mechanical and durability properties. LWFA and different diameters quartz aggregates were used in the production of fly-ash-based GCs. However, LWFA was only replaced with the quartz aggregate of 1.2-2.5 mm. A mixture of 12 M NaOH and Na2SiO3 solution was prepared as 1/2.5. Unit weight, specific gravity, water absorption, apparent porosity, compressive and flexural strengths, ultrasonic pulse velocity and water sorptivity coefficient of GCs were determined. According to the test results, workability of GCs improved as the usage rate of LWFA increased. Due to the surface characteristics of LWFA, the mechanical properties of GC were enhanced by the geopolymerization reaction conducted between LWFA with alkali activators. Thus, the compressive strength of GC with 25% LWFA was 39.6% higher than that of the control GC at 28th day. This conclusion supported by TGA/DTA and FTIR analysis indicated that N-A-S-H gel of GC incorporating 25% LWFA was higher compared to control mixture. Also, GCs incorporating 40% and higher LWFA showed lower performance than control GC. (C) 2020 Elsevier Ltd. All rights reserved.Öğe Internal Curing of High-Strength Concretes Using Artificial Aggregates as Water Reservoirs(AMER CONCRETE INST, 2015) Gesoglu, Mehmet; Guneyisi, Erhan; Ismael, Ali Nooruldeen Ismael; Oz, Hatice OznurThis paper investigates the shrinkage cracking performance of high-strength concrete (HSC) containing artificial fly ash (AFA) and artificial blast furnace slag aggregates (ASAs) used as water reservoirs to provide internal curing. Artificial aggregates (AAs) were produced through cold bonding pelletization of 90% fly ash or slag with 10% portland cement. At a constant water-cement ratio (w/c) of 0.28, a total of nine HSCs incorporating varying amounts of AFA or ASA (0%, 5%, 10%, 15%, and 20%) by total aggregate volume were designed. The hardened concretes were tested for compressive strength, splitting tensile strength, and modulus of elasticity at 28 days for assessment of mechanical properties. Drying shrinkage accompanied by water loss, restrained shrinkage, and autogenous shrinkage were also monitored for a drying period of 57 days. Test results indicated that the highest mechanical properties were achieved for HSC with 20% ASA. Using ASA extended the cracking time of the HSCs and resulted in finer cracks associated with the lower free shrinkage. Moreover, there was a marked decrease in the autogenous shrinkage for all HSCs including artificial aggregates.Öğe Life cycle assessment and shrinkage properties of high performance mortars incorporating synthetic wollastonite microfibers(Emerald Group Publishing Ltd, 2023) Oz, Hatice Oznur; Gunes, Muhammet; Yucel, Hasan Erhan; Ersoy, Orkun; Sever, Yunus; Demirel, SevgiIn this study, the use of an alternative material as supplementary cementitious material was researched for the design of high-performance mortars (HPMs). Synthetic wollastonite microfibres (SWMs) were produced from calcite and quartz sand. The SWMs were then replaced at ratios of 0, 3, 6, 9 and 12% by cement weight to investigate the fresh, mechanical and shrinkage properties of HPMs. Test results showed that the mechanical and shrinkage properties of HPMs improved up to 9% inclusion of SWMs. The compressive strength, flexural strength, modulus of elasticity, fracture toughness and fracture energy of HPM incorporating 9% SWM was higher than that of the control mixture by 8.8-9.1%, 7.5-9.9%, 4.7-6.7%, 8.9-4.6% and 13.2-2.5% at 28-90 days, respectively. Similarly, the ratios for maximum drying shrinkage and average crack width were determined as 10.5% and 58.3%, respectively, at the end of 60 days. These findings were also supported by microstructural analysis. Moreover, the potential environmental impacts resulting from the production of 1 kg SWM and HPM incorporating 9% SWM were evaluated using the life cycle analysis software (LCA) SimaPro 8.5.0.0. Based on the LCA results, SWMs can be used as an alternative material to develop sustainable concrete structures.Öğe Physico-mechanical properties of self-compacting concrete containing treated cold-bonded fly ash lightweight aggregates and SiO2 nano-particles(ELSEVIER SCI LTD, 2015) Guneyisi, Ethan; Gesoglu, Mehmet; Azez, Oday Ali; Oz, Hatice OznurIn this experimental study, the physico-mechanical properties of self-compacting lightweight aggregate concrete (SCLC) containing artificial lightweight aggregate (LWA) made from fly ash (FA) through cold-bonded process are investigated. Coarse LWAs were treated with a soluble solution of sodium silicates (WG) in order to enhance quality. However, the binary and ternary use of fly ash (FA) and silicon dioxide nanoparticles (nS) were considered in the production of SCLC. For this, a total of 18 SCLC mixtures were designed at three different w/b ratios of 0.25, 0.37 and 0.50, and total binder contents of 600, 550 and 450 kg/m(3), respectively. The physical properties were tested for water sorptivity, gas permeability and water permeability, as well as for drying shrinkage. The use of treated instead of untreated LWA reduces the negative effect of w/b ratio increment of the drying shrinkage of SCLCs. The results showed that using 5.0% nano-silica and treated aggregate decreased the drying shrinkage as much as 23%. However, a significant reduction in SCLC permeability was achieved by including nS and/or treated LWAs, specifically, a reduction of up to 70% for gas permeability at 90 days. Moreover, a lower compressive strength resulted due to the use of untreated aggregate and higher w/b ratio. As a general result, it was determined that a better performance is revealed at 90 days for SCLCs containing 5% nS and treated LWAs, regardless of w/b ratio. (C) 2015 Elsevier Ltd. All rights reserved.Öğe Production of geopolymer composites by using different alkaline solution/material ratio(Iop Publishing Ltd, 2019) Dogan-Saglamtimur, Neslihan; Oz, Hatice Oznur; Bilgil, Ahmet; Suzgec, Elif; Vural, TurkanThis study reports an experimental program to optimize mix design parameters of fly ash-based geopolymer engineering composites. Fly ash (FA) supplied from Catalagzi Thermal Power Plant (Zonguldak, Turkey) and Rilem Cembureau Standard Sand were used together with a constant ratio of 0.50 for producing geopolymer. In the first step, two different alkaline solution/material ratio (FA+standard sand) (L/M) were determined as 0.20 and 0.40, respectively. After that, sodium silicate ((Na2SiO3) and 12M sodium hydroxide (NaOH) were utilized at a ratio of 1, 2, and 3, respectively. 6 mixtures obtained by using different design parameters were cured at 70 degrees C for 24 hours, respectively, and then they were stored at room temperature until testing age. While the physical properties of the samples were measured by the bulk density and water absorption tests at 28 days, mechanical properties were tested via the compressive and flexural strength tests at 90 days, respectively. The results indicated that the highest compressive strength for geopolymer materials was found as 36.5 MPa in the mixture produced with the ratios of L/M=0.2 and Na2SiO3/NaOH=2 (by weight). However, less alkali reaction caused by using excessive activator solutions decreased the strength characteristics of geopolymer.Öğe Rheological and microstructural properties of FA+GGBFS-based engineered geopolymer composites (EGCs) capable of comparing with M45-ECC as mechanical performance(Elsevier, 2023) Oz, Hatice Oznur; Gunes, Muhammet; Yucel, Hasan ErhanIn this study, it has been aimed to obtain the fly ash + ground granulated blast furnace slag (FA GGBFS)-based engineered geopolymer composites (EGCs) having similar bearing strength and deformation capacity with the engineered cementitious composite (M45-ECC) known as M45. EGCs incorporating 70% FA and 30% GGBFS as binder were developed under three different groups in which the different ratios of alkali liquids/binder (AL/Bi) with the different content of AL + Bi. All of eight FA + GGBFS-based EGCs designed with 2.5 ratio of Na2SiO3/NaOH. FA GGBFS-based EGCs, which were kept in the mold under laboratory conditions for 24 h imme-diately after production, were kept in water at 60 degrees C until the test age. The fresh, rheogical, mechanical and microstructural properties of FA + GGBFS-based EGCs were determined. Test results indicated that FA + GGBFS-based EGCs can be developed with similar or higher compressive strength and ductility than that of M45-ECC. However, the flexural strength of M45-ECC was higher than those of all other composites. In addition, TGA/DTA and FTIR analysis supported that the excessive amount of AL + Bi content would not improve the characteristics of FA + GGBFS-based EGCs after the optimal production of C-S-H and N-A-S-H gels which acquired in geopolymerization. However, ductility continued to improve significantly as the AL + Bi content increased. Moreover, reduction of AL/Bi ratio increased the total gel content and thus, the compressive strength of composites developed.Öğe Rheological properties, strength characteristics and flexural performances of engineered cementitious composites incorporating synthetic wollastonite microfibers with two different high aspect ratios(Elsevier Sci Ltd, 2021) Yucel, Hasan Erhan; Oz, Hatice Oznur; Gunes, Muhammet; Kaya, YasinIn this study, synthetic wollastonite microfiber (SWM) with high aspect ratio (44:1/SWM-I) developed with a special technique was used in different proportions instead of cement (C), fly ash (FA) and cement + FA (C-FA) in Engineered Cementitious Composites (ECC). SWM-I decreased the workability as a result of interlocking during flow due to its acicular particle structure. When SWM-I was used instead of C, it was determined that the compressive strength decreased and the ductility improved significantly due to the increased SWM-I content. The use of SWM-I instead of FA improved the mechanical performance up to 6% in terms of compressive strength and flexural performance. However, the mixtures prepared by using SWM-I instead of C-FA provided optimum data, considering both ''increasing deformation capacity'' and ''maintaining the bearing strength by fiber bridging after crack''. Therefore, the effect of SWM-II (30:1) was tested by using instead of C-FA. SWM-I with a higher aspect ratio has been improved the mechanical properties of ECC and reduced the workability of ECC more than that of SWM-II. Increasing FA content in ECC has been provided higher ductility but decreased significantly the compressive strength. The bearing strength and deformation capacity of the ECC designed with finer aggregate has been achieved the higher levels compared to larger aggregate size. As a result of all obtained findings, the data of the optimum mixture has been determined as follows: the compressive strength, flexural strength and ductility of ECC incorporating 6% SWM-I instead of C-FA have been reached higher levels than that of 19.0%12.5%, 12.0%-8.2% and 56.2%-25.5% at 7-28 days, respectively.Öğe Self-Consolidating Concretes Made with Cold-Bonded Fly Ash Lightweight Aggregates(Amer Concrete Inst, 2017) Oz, Hatice Oznur; Gesoglu, Mehmet; Guneyisi, Erhan; Sor, Nadhim HamahAn experimental program was conducted to investigate the mechanical, fracture, and physical properties of self-consolidating lightweight concretes (SCLCs) made with cold-bonded fly ash (FA) aggregates. A total of 17 SCLCs were designed with a water-binder ratio (w/b) of 0.32, in which the natural aggregates were partially replaced with cold-bonded lightweight fine aggregate (LWFA) and lightweight coarse aggregate (LWCA) at different volume fractions of 10, 20, 30, 40, and 50%. Hardened properties of the SCLCs were tested for bond strength, fracture energy, characteristic length, drying shrinkage, weight loss, and restrained shrinkage cracking. It was observed that the SCLCs had relatively lower compressive and splitting tensile strengths with increasing LWFA and/or LWCA in the mixtures. Bond strength of the SCLCs decreased gradually with the replacement level of LWA because the bond strength directly depended on the quality of the cement paste and aggregate. Although SCLCs had significantly poorer restrained shrinkage cracking performance than the control concrete, the time to cracking greatly lengthened as the replacement level of LWA increased.Öğe Shear thickening intensity of self-compacting concretes containing rounded lightweight aggregates(ELSEVIER SCI LTD, 2015) Gesoglu, Mehmet; Guneyisi, Erhan; Ozturan, Turan; Oz, Hatice Oznur; Asaad, Diler SabahThis paper investigates the rheological behavior of self compacting concrete (SCC) made by replacing normal-weight aggregates (NWAs) with cold bonded lightweight fly ash aggregates (LWAs). Dry powder mixture of 90% fly ash and 10% Portland cement by weight was pelletized through moistening in a revolving tilted pan at ambient temperature to produce lightweight fly ash aggregates which were then cured for 28 days. Seventeen concrete mixtures were produced to have a fixed slump flow by using varying amounts of High-Range-Water-Reducing-Admixture (HRWRA). Increasing replacement level for fine and/or coarse LWA simultaneously decreased density and plastic viscosity which made the concretes less susceptible to shear thickening. Meanwhile, the increasing percentage of LWA used reduced the HRWRA needed for gaining constant workability. With full replacement by lightweight fly ash aggregates, 25% reduction was achieved in the fresh density of self-compacting concrete produced. (c) 2015 Elsevier Ltd. All rights reserved.Öğe The effects of synthetic wollastonite developed with calcite and quartz on high performance mortars(Ernst & Sohn, 2020) Oz, Hatice Oznur; Gunes, MuhammetIn this study, the effects on high performance mortar (HPM) of synthetic wollastonite (SW) mineral were researched. Through this work, firstly, wollastonite was synthetically obtained by a particular production method. Secondly, SW was utilized as cement replacement material from 0 to 12% by 3% steps of increment in the production of HPM. After determination of slump flow diameters of HPMs, mechanical and durability properties were observed at 28 and 90 days. Additionally, microstructural performance properties of HPMs designed with SW in the ratios 0, 9, and 12% was specified with TGA/DTA and FTIR analysis as well as SEM/EDX and XRD analysis. The test and analysis results showed that SW decreased the workability of HPMs. The improvement of the mechanical and durability properties of HPMs proceeded up to 9% of SW. Microstructural analysis showed that development effect of SW on the HPM can be attributed to its needle-shaped structure.Öğe Using of thermal power plant fly ash to produce semi-lightweight aggregate and concrete(Yildiz Technical Univ, 2023) Azez Altayawi, Oday Ali; Oz, Hatice Oznur; Mermerdas, KasimThis article introduced a zero waste management of pulverized fuel ash in construction sectors via two different approaches. The first one was represented by production of spherical lightweight aggregates from fly ash (FA). The second approach was introduced by producing a non-conventional concrete type namely self-compacting concrete incorporated a high FA content. The production of aggregate and concrete was adopted through the use of lower consumptions of electrical energy. To this aim, fresh aggregate particles were self-cured at ambient temperature for 28 days, whilst no electrical or mechanical vibrators have been used in casting process. The quality of produced aggregate and concrete was examined by different experimental tests. The general conclusion of this study revealed that the use of FA in the production of lightweight aggregate and concrete can be tapped to protect the environment from the side effects of FA. In addition, the produced concrete can be utilized for structural purposes as the lower compressive strength was found to be higher than 55.1 MPa.Öğe Utilization of cold bonded fly ash lightweight fine aggregates as a partial substitution of natural fine aggregate in self-compacting mortars(ELSEVIER SCI LTD, 2015) Guneyisi, Erhan; Gesoglu, Mehmet; Altan, Inan; Oz, Hatice OznurIn this study, lightweight fly ash fine aggregates (LWFAs) were used as a partial replacement of natural fine aggregate to investigate the fresh and hardened states of self-compacting mortars (SCMs). For this, a powder mixture of 90% fly ash (FA) and 10% Portland cement (PC) by weight were pelletized in a tilted pan through a cold-bonded agglomeration process. Thereafter, a total of five mixtures of SCMs were prepared in which natural fine aggregate was replaced by LWFA partially started from 0% to 100% by 25% increment. Subsequently, tests carried out on the fresh mortar involved mini-slump flow, mini-V-funnel flow time and viscosity while the hardened properties of SCMs were evaluated using the compressive strength, ultrasonic pulse velocity, gas permeability and sorptivity tests. The hardened characteristics of SCMs were determined at different ages up to 56 days. It was observed that the increased percentage of LWFA improved the workability and the flowability of SCMs. On the other hand, the strength and permeability properties of SCMs had a negative effect due to the substitution of LWFAs for natural fine aggregate, especially at higher replacement level. (C) 2014 Elsevier Ltd. All rights reserved.
