Sürdürülebilir Kalkınma Amaçları

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• MakaleAçık Erişim2024Scopus SJRQ1/r/bayburt/11742
  Production of high strength and colored concrete using textile waste reactive dyestuffs as superplasticizers

  Erdem, Emin; Aydın, Gülsüm Merve; Kılınçarslan, Rafet

  Herein, we are reporting the effect of reactive dyestuffs, currently widely used in textile industry, on the hydration of Portland cement and their usability as water-reducing additives. For this purpose, solutions containing various ratios (0,005- 0,016 g/100 ml tap water) dyestuffs as superplasticizers were used as mixing water for cements. The effects of these dyes on the hydration of Portland cement were determined by physical tests and DSC-TG-DTG, FT-IR and X-ray diffraction techniques. It was found that the dyestuff added to the cement reduced the cement water/cement ratio (2–7%) and increased the compressive strength (8–13%), depending on the molecular size and structure, and it was also determined that it had no negative effect on cement hydration.

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  AtıfScopus4·WoS4·OpenAlex5

  İncele
• Derleme MakaleYalnız künye2023Scopus SJRQ1/r/bayburt/10755
  Nanomaterial and fiber-reinforced sustainable geopolymers: A systematic critical review

  Ünal, M. T.; Gökçe, H. S.; Ayough, P.; Alnahhal, A. M.; Simsek, O.; Nehdi, M. L.

  Global cement production is associated with a colossal environmental footprint due to its considerable carbon emissions, energy consumption, depletion of natural resources, and waste accumulation. Geopolymer based concretes (GCs) have emerged as revolutionary alternatives to ordinary Portland cement concrete with enormous potential ecological benefits. However, they suffer from deficiencies, such as their brittle behavior under flexural and tensile loads. Using different types of fiber reinforcement and nanomaterial additions in geopolymer composites (GCs) has recently gained considerable attention to enhance various engineering properties, improve crack resistance, toughness, and ductility of the geopolymer matrices. This systematic and critical review analyses the effects of different reinforcing fibers and nanomaterials on the compressive and tensile strengths, modulus of elasticity, and impact resistance of GCs, and highlights the associated microstructural features. It is shown that carbon, basalt, and steel fibers can impart considerable improvement in mechanical strength, modulus of elasticity, and impact resistance of GCs. Furthermore, the introduction of polyethylene fibers has been shown to induce complex cracking behaviors, thereby contributing to the strain-hardening capability of geopolymer matrices. The integration of nanomaterials into GCs has emerged as a powerful strategy for achieving substantial enhancements in mechanical performance. Optimal nanomaterial dosages, typically around 2%, have been identified, with the specific surface area of nanoparticles proving to be a crucial determinant of the resulting mechanical properties. Notably, nano-silica has exhibited pronounced macro-scale reinforcement effects, whereas nano-titanium has displayed the potential to significantly enhance gel micromechanical characteristics. Additionally, synergistic combinations of nanomaterials and fiber reinforcements have led to the development of novel and distinctive mechanical properties within GCs. The synthesis of these findings underscores current best practices, highlights areas requiring further investigation, and emphasizes the need for concerted research efforts to advance the knowledge and implementation of sustainable geopolymers. This review offers a comprehensive analysis of the effects of fiber reinforcements and nanomaterials on geopolymer composites, providing valuable insights for researchers and practitioners.

  AtıfScopus43·WoS37

  İncele
• MakaleAçık Erişim2022Scopus SJRQ1/r/bayburt/13171
  Improvement of mechanical and transport properties of reactive powder concrete using graphene nanoplatelet and waste glass aggregate

  Arslan, S.; Öksüzer, N.; Gökçe, H.S.

  In this study, the use of graphene nanoplatelet (GNP) and waste glass aggregate (WGA) was investigated to improve the mechanical and transport properties of reactive powder concrete (RPC), which is an ultra-high strength concrete type. The co-addition of 0.14% GNP and 30% WGA resulted in a significant increase in the compressive strength of RPC from 192.9 to 258.9 MPa and flexural strength from 16.2 to 38.7 MPa. In the study, the most significant improvement (138.6%) was obtained for the flexural strength values of RPC. Considering the strength aspects, the relevant amounts of GNP and WGA enable production of RPC ensuring a conducted electrical charge of less than 100 Coulombs; that is, with negligible chloride ion permeability. Accordingly, the highest improvement (59.8%) after flexural strength was found for the resistance of the specimens against chloride ion penetrability. In conclusion, the findings of this study show that eco-efficient production of RPC with superior mechanical and durability characteristics can be achieved using GNP and WGA, with lower cement consumption per unit value of these studied characteristics, reaching 59%.

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  AtıfScopus31·WoS26·OpenAlex32

  İncele
• MakaleYalnız künye2022Scopus SJRQ1/r/bayburt/13076
  Performance of fly ash-blended Portland cement concrete developed by using fine or coarse recycled concrete aggregate

  Şimşek, O.; Pourghadri Sefidehkhan, H.; Gökçe, H.S.

  The recycling of concrete and industrial wastes in the production of new concrete structures has increased its share due to the growing environmental concerns of the world. In this study, the use of recycled concrete aggregate at various replacement amounts (0–100 %) was investigated to be fine or coarse aggregate sources instead of crushed natural aggregate to understand better its effects on the dimensional stability and durability aspects of fly ash-blended Portland cement concrete. In the presence of recycled concrete aggregate, fly ash was very important for eliminating possible mechanical losses of concrete at 90 days. The use of coarse recycled concrete aggregate resulted in better compressive strength values of concrete exposed to with and without wetting–drying and freezing-thawing cycles when compared to fine ones. While the free drying shrinkage of concrete increased at significant amounts (68 and 79 %) for fine and coarse recycled concrete aggregate, the restrained drying shrinkage crack widths were reduced up to by 13.5 %. In conclusion, it should be noted that the amount and size of recycled concrete aggregate need to be designed by considering the residual quality and dimensional stability of concrete, which exposes weathering actions in place.

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  AtıfScopus57·WoS50·OpenAlex54

  İncele
• Derleme MakaleAçık Erişim2021Scopus SJRQ1/r/bayburt/13308
  Alkali-activated and geopolymer materials developed using innovative manufacturing techniques: A critical review

  Gökçe, H.S.; Tuyan, M.; Nehdi, M.L.

  The manufacturing of geopolymers and alkali-activated materials for precast and cast in-situ construction applications could be achieved using suitable production techniques, such as one-part production, pre-setting pressure and hot pressing, two-stage concreting, and 3-dimensional printing. Adequate selection and tailoring of the manufacturing methodology are imperative for overcoming characteristic application problems of these materials and achieving eco-efficiency and superior engineering properties. With distinctive benefits including rapid solidification, lower cost, saving natural resources, less energy consumption, and reduced carbon footprint, alkali-activated and geopolymer composites have emerged as a strong contender for replacing conventional concrete in diverse construction applications. Critical analysis of the literature on innovative production methods indicates that the one-part production technique is promising for the eliminating design complexity of these mixtures. The pre-setting pressure and hot pressing applications would allow the achievement of superior physical and mechanical characteristics in a short period of time, especially for the precast industry. The workability and setting problems of alkali-activated materials could be overcome using the two-stage concreting methodology. To be used in 3D printing of alkali-activated and geopolymer materials, remarkable development is required in terms of rheological aspects. Accordingly, this paper surveys pertinent and recent literature and critically reviews the state-of-the-art of alternative production techniques of alkali-activated and geopolymeric materials, along with its use in recent applications, identifies pertinent knowledge gaps, and defines future research directions.

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  AtıfScopus155·WoS137·OpenAlex167

  İncele
• MakaleYalnız künye2021Scopus SJRQ1/r/bayburt/12118
  Physical, mechanical, and radiation attenuation properties of serpentine concrete containing boric acid

  Zayed, A.M.; Masoud, M.A.; Shahien, M.G.; Gökçe, H.S.; Sakr, K.; Kansouh, W.A.; El-Khayatt, A.M.

  Serpentine and boric acid are effective materials to produce the radiation-shielding concrete (RSC) for attenuating the fast and thermal neutrons, respectively. Therefore, this study investigates the effect of boric acid (0, 1, and 3% by cement weight) on the physical, mechanical, microstructural, and radiation shielding properties of serpentine concrete. The results showed that the addition of boric acid hindered the hydration of cement through the generation of amorphous borate material, which encapsulates the cement phases and retards their transformation into hydration products. Such a retardation process negatively influenced the mechanical properties of boric acid-bearing concrete and contributed to the thicker and less condensed interfacial transition zone. Furthermore, unlike total γ-rays, boric acid enhanced the attenuation properties of serpentine concrete against thermal and fast neutrons favoring the former. There was a satisfying agreement between the theoretical and measured values of fast neutron attenuation parameters. However, negligible variations in the theoretical values of photon interaction parameters showed that porosity was the principal reason for the reduction in gamma-ray attenuation as a result of boric acid addition.

  AtıfScopus91·WoS88·OpenAlex93

  İncele
• MakaleYalnız künye2020Scopus SJRQ1/r/bayburt/13266
  Simulation and optimization of gamma-ray linear attenuation coefficients of barite concrete shields

  Şensoy, A.T.; Gökçe, H.S.

  The remarkable increment in radioactivity risks of today's industrial world is required to the efficient design of shielding structures. In the present study, the optimal design parameters of barite concrete shields for providing the highest gamma radiation shielding capability were researched by using a hybrid technique of the Box-Behnken Design based response surface method and Particle Swarm Optimization. Barite aggregate fraction, water-to-cement ratio and cement content of the shields were limited as 0:100 (by weight), 0.30:0.70 (by weight) and 200:600 (kg/m3) in the optimization problem, respectively. The regression equation derived from the regression learning process presented an excellent correlation to define the XCOM linear attenuation coefficients. A nonlinear response surface fitted to the regression equation was used as the validation of the PSO results obtained from MATLAB. The results of this study have shown that the proposed method provides satisfactory predictions for the barite concrete radiation-shielding capability depending on the design parameters. In addition, it was found that the linear attenuation coefficient could be increased by 102% by the design of the best shield according to the poorest mixture.

  AtıfScopus77·WoS66

  İncele
• MakaleAçık Erişim2020Scopus SJRQ1/r/bayburt/12047
  Gamma ray and neutron shielding characteristics of polypropylene fiber-reinforced heavyweight concrete exposed to high temperatures

  Demir, İ.; Gümüş, M.; Gökçe, H.S.

  The residual properties of shielding structures need to be redefined after exposure to elevated temperatures due to their probable radiological hazards on biodiversity. In this study, the effect of high temperatures on mechanical, gamma ray and neutron attenuation characteristics was determined for limestone, barite and siderite concrete shields reinforced with polypropylene fiber. The increase in temperature up to 600 °C reduced the ultrasonic pulse velocity and compressive strength values of these shields by 59% and 62%, respectively. A good linear correlation (R2 ≥ 0.97) was found between these values. While the gamma ray linear attenuation coefficients increased by 9% for barite concrete, and reduced by 15% for normal concrete and by 17% for siderite concrete at 600 °C, trivial fluctuations (from −1% to +7%) were observed at 300 °C. The neutron attenuation factors of these shields gradually reduced up to 31% with the increase of temperature. The performance of siderite concrete was found to be slightly better than that of barite concrete in terms of strength and neutron shielding characteristics. With the satisfactory linear attenuation coefficients at all energy levels of gamma rays, barite concrete seems to be the most suitable concrete type under high temperature risks.

  AtıfScopus142·WoS132·OpenAlex150

  İncele
• MakaleYalnız künye2020Scopus SJRQ1/r/bayburt/12044
  Natural radioactivity of barite concrete shields containing commonly used supplementary materials

  Gökçe, H.S.; Canbaz Öztürk, B.; Çam, N.F.; Andiç-Çakır, Ö.

  The recycling of hazardous materials within new composites has a sustainable importance as it contributes on the reduction of high radionuclide concentrations. In this study, the effect of cementitious materials i.e. viscosity modifier, silica fume and fly ash on the 226Ra, 232Th and 40K activity levels of barite concrete shields was researched by using different mixing compositions in terms of binder content, w/b ratio and the amount of supplementary cementitious materials. In comparison to cement, silica fume and fly ash used in the production of concrete shields were found to have significantly higher activity levels of 40K, as well as 226Ra, 232Th and 40K, respectively. The 226Ra, 232Th and 40K activity levels of concrete shields range between 2.2 and 20.7 Bq kg−1; 2.6 and 7.0 Bq kg−1; 51.5 and 89.3 Bq kg−1, respectively. These activity values were found similar or less than those of building materials in the world. These satisfactory results are mostly caused by the barite source which has lower radioactivity levels. The concrete mixture details used in the study caused significant variation in the natural radioactivity of barite concrete shields. The introduction of silica fume which has high 40K activity levels and fly ash with high 226Ra, 232Th and 40K activity levels compared to cement and barite aggregate, significantly increased the radiological hazard parameters, although all results were found to be below the limits recommended by international reports. In conclusion, 226Ra activity levels of the concrete shields were significantly increased (up to 8.4 times) by the variation of mix design parameters used in comparison with concrete mixtures that have the least 226Ra activity level. The 232Th and 40K activity levels were as well increased in relatively less amounts (1.7 and 0.73 times higher, respectively).

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  AtıfScopus22·WoS20·OpenAlex23

  İncele
• MakaleAçık Erişim2019Scopus SJRQ1/r/bayburt/12349
  Effect of fly ash and silica fume on hardened properties of foam concrete

  Gökçe, H. Süleyman; Hatungimana, Daniel; Ramyar, Kambiz

  In this study, the effects of foam content as well as fly ash and silica fume inclusion on some physical and mechanical properties of foam concrete, subjected to various curing regimes, were researched. Totally, forty-five series of foam concrete mixtures were prepared at three replacement levels of fly ash and silica fume (0, 10 and 20%, by weight of cement), at three foam contents (0, 31 and 47%, by volume) and at three curing regimes (7- and 28-day standard water curing and autoclave curing). Density, water absorption, compressive strength and thermal conductivity values of the mixtures were determined on prismatic specimens with dimensions of 40 × 40 × 160 mm. The density (oven dry), water absorption, compressive strength and thermal conductivity results of the foam concrete were found to be between 873–1998 kg/m3, 3.5–35.9%, 1.5–88.1 MPa and, 0.239–0.942 W/m.K, respectively. A balanced benefit with regard to both compressive strength and water absorption of foam concrete was found in the mix with density of 1320 kg/m3. Particularly in the mixtures having high foam content, silica fume introduction resulted in superior compressive strength values and greater compressive strength/thermal conductivity ratios than fly ash introduction.

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  AtıfScopus271·WoS237·OpenAlex276

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