Sürdürülebilir Kalkınma Amaçları

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• MakaleAçık Erişim2026Scopus SJRQ1/r/bayburt/11301
  Performance level controlled efficiency of graphene nanoplatelets in cementitious composites

  Şahin, Yaren; Öksüzer, Nurullah; Kütük, Sezai; Gökçe, Hacı Süleyman

  Graphene nanoplatelets (nGP) have been widely reported as effective nano-reinforcements for cementitious composites; however, their optimal dosage remains inconsistent across existing studies. This variability is commonly attributed to nanomaterial-related parameters, whereas the influence of the cementitious matrix’s inherent performance is rarely systematically examined. In this study, cementitious matrices with distinct performance levels were designed by varying water-to-binder ratios (0.55, 0.40, and 0.30) and incorporating silica fume. Their interaction with nGP was experimentally investigated, with contents up to 2.4% being used. A total of 25 mix designs were evaluated for fresh-state behavior, mechanical performance, transport properties, and microstructural characteristics. The results indicate that the efficiency and optimal utilization of nGP are strongly governed by the matrix performance level. High-performance matrices (water-to-binder (w/b) = 0.30, 11% silica fume) achieved peak performance at 1.2% nGP, yielding compressive strength of 118.2 MPa and up to 50% reduction in capillary water transport, whereas low-performance matrices (w/b = 0.55) exhibited limited sensitivity to nGP incorporation. Microstructural observations confirmed that matrix densification improved nGP integration and hierarchical pore refinement by enhancing interfacial bonding, thereby restricting capillary water transport. The findings demonstrate that optimal nGP dosage cannot be treated as an intrinsic material parameter and should instead be defined in relation to matrix performance level, enabling performance-based dosage guidelines for nano-engineered composites in high-durability applications.

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  AtıfWoS1·OpenAlex1

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• MakaleYalnız künye2026Scopus SJRQ1/r/bayburt/11105
  Upcycling marble waste into construction materials and heavy metal adsorbents via hot-pressed geopolymerization technique

  Öksüzer, Nurullah; Uslu, Emin; Gökçe, H. Süleyman

  This study presents a sustainable approach to utilizing marble dust waste by producing bifunctional metakaolin-based geopolymers via a synchronized hot-pressing technique. In this study, the environmental footprint was minimized by designing mixtures in which marble waste constituted 50% of the total volume. Three stoichiometric series were investigated by varying the activator modulus (SiO2/Na2O = 3 and 4) and the Si/Al ratio (2 and 3) under two curing temperatures (150 and 300 °C) and three compaction stresses (5, 25, and 50 MPa). Thus, a high-volume industrial byproduct was transformed into a functional component. In this context, it investigated the transformation of industrial products into next-generation materials by using them to produce cementless composite geopolymers for civil engineering and to adsorb heavy metal (Cu2+). As a result of the research, an early compressive strength of 58 MPa was obtained through heat treatment and pressing applied at 300 °C and 50 MPa. This optimum strength was achieved in the SiO2/Na2O = 3, Si/Al = 3 series, whereas excess silica (SiO2/Na2O = 4) and excess aluminum (Si/Al = 2) limited the strength to 16.8 and 35.2 MPa, respectively. Microstructural analyses (SEM/EDS and FT-IR) revealed that marble dust was used as a filler material in the microstructure to produce an N-A-S-H-containing matrix. The produced materials were then ground after their service life and used to purify water containing heavy metals. More than 99.75% of Cu2+ was removed through ion exchange between copper ions used as heavy metals. The residual Cu2+ concentration fell below 0.25 mg/L from an initial concentration of 100 mg/L, and the released Na+-to-adsorbed Cu2+ molar ratio of approximately 1.8–2.3 confirmed an ion-exchange-dominated uptake mechanism. This structural and environmental impact demonstrates that marble waste, which is otherwise discarded as waste, is considered inert, offering an alternative model for the circular economy and environmental applications.

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• MakaleAçık Erişim2024Scopus SJRQ3/r/bayburt/12977
  Durability of slag-based alkali-activated materials: A critical review

  Gökçe, H.S.

  As the world becomes increasingly aware of the devastating effects of climate change, the need for sustainable building materials that are both durable and environmentally friendly increases. Geopolymer and alkali-activated materials formed by a chemical reaction between an alkaline activator solution and an aluminosilicate source have gained popularity in recent years. The alkaline activator solution dissolves the aluminosilicate source, which then undergoes a polycondensation reaction to form a three-dimensional geopolymeric gel network. The development of this network ensures the strength and durability of the material. Today, this phenomenon of durability has been studied in detail to enable the development of superior construction materials, taking into account degradation mechanisms such as carbonation, leaching, shrinkage, fire, freezing and thawing, and exposure to aggressive environments (chlorides, acids, and sulphates). Although there are many unsolved problems in their engineering applications, slag-based alkali-activated materials appear to be more advantageous and are promising as alternative materials to ordinary Portland cement. First of all, it should not be ignored that the cure sensitivity is high in these systems due to compressive strength losses of up to 69%. Loss of strength of alkali-activated materials is considered an important indicator of degradation. In binary precursors, the presence of fly ash in slag can result in an improvement of over 10% in compressive strength of the binary-based alkali-activated materials after undergoing carbonation. The binary systems can provide superior resistance to many degradation mechanisms, especially exposure to high-temperature. The partial presence of class F fly ash in the slag-based precursor can overcome the poor ability of alkali-activated materials to withstand high temperatures. Due to the desired pore structure, alkali-activated materials may not be damaged even after 300 freeze–thaw cycles. Their superior permeability compared to cementitious counterparts can extend service life against chloride corrosion by more than 20 times. While traditional (ordinary Portland cement-based) concrete remains the most widely used material in construction, geopolymer concrete’s superior performance makes it an increasingly emerging option for sustainable and long-lasting infrastructure.

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  AtıfScopus69·WoS63·OpenAlex70

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• 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
• MakaleYayıncıda açık erişim2023Scopus SJRQ4/r/bayburt/13057
  Development of Alkali-Activated Binders from Recycling Regional Tuff and Marble Wastes

  Tekin, İlker; Ciza, Baraka; Gökçe, H.S.

  The sustainability goals of the developing world have led many industries to recycle their wastes and reduce emitting greenhouse gases. To contribute to these environmental responsibilities, this study has focused on the development of eco-friendly binder materials from regional ground tuff and marble wastes by the activation of sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) or slaked lime (Ca(OH)2). The results of this study show that alkali-activated composites experienced expansion, drying shrinkage cracking, leaching, and efflorescence. The compressive strength values of the NaOH and Ca(OH)2-activated pastes reached up to 15 MPa and 9 MPa, respectively. A reduction in NaOH molarity improved the compressive strength, dimensional stability, and durability of tuff-based alkali-activated pastes.

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  AtıfScopus5·OpenAlex3

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• MakaleYalnız künye2023Scopus SJRQ1/r/bayburt/13016
  Gamma-ray and neutron shielding capability of blended cement-stabilized barite fillers developed by maximum density method

  Gökçe, H.S.; Öksüzer, N.; Kamiloğlu, H.A.; Yılmaz, F.

  The disposal of radiological wastes in the deep geological repositories has become an important issue for the reduction of hazardous risks on the human and biological environments. In this study, blended cement-stabilized barite fillers against gamma rays and neutrons have been developed with the use of the maximum density method by considering various amounts of water (100–300 kg/m3), binder (4–10%), and compaction energy (500–2000 kJ/m3). According to the experimental series of these filler materials, satisfactory response surface results have been achieved in the study. The experimental results revealed that compacted filling material can ensure an efficient shielding capability for gamma rays and neutrons when designed with a density of 3.064 g/cm3. An increase in binder content, water content, and compaction energy has improved the compressive strength of these materials up to 37 times according to that of the poorest series. Neutron and gamma-ray shielding capabilities were found to be 119 and 14% higher than those of the poorest filler material, respectively when theoretical and experimental results are considered in the study.

  AtıfScopus4·WoS3·OpenAlex5

  İncele
• MakaleAçık Erişim2023Scopus SJRQ1/r/bayburt/12939
  The effect of various industrial dust particles on the performance of photovoltaic panels in Turkey

  Güngör, Okan; Kahveci, Hakan; Gökçe, H. Süleyman

  The accumulation of dust is one of the main causes of power loss in photovoltaic (PV) farms, and the effect of dust particles’ size and chemistry on system performance is often overlooked. This study has focused on a comprehensive analysis of the effect of different dust particles collected from common industrial production facilities in Turkey on the performance of PV panels in the indoor laboratory environment. The collected dust samples were analyzed to determine the dust sample particles’ chemical properties, size, character, and topography. The data for dust samples at different weights with changes in maximum power point (MPP) of PV panel has been collected using the artificial solar irradiation source system. Thus, the mathematical correlations (R2≥0.965) between the PV panel Thevenin resistance (RTH), fill factor (FF), MPP, and pollution rate were obtained using these collected data and particle swarm optimization (PSO). According to the results of the obtained mathematical correlations, marble dust is 2.3, 3.4, and 4.2 times less polluting than cement, fly ash, and silica fume, respectively. Additionally, it was observed that smaller dust particles block more light than larger ones of the same weight and reduce MPP, FF while increasing the RTH.

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  AtıfScopus19·WoS14·OpenAlex21

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• MakaleAçık Erişim2023Scopus SJRQ2/r/bayburt/12900
  The Toughness of Polypropylene Fiber-Reinforced Foam Concrete under Various Uni- and Tri-Axial Compression Loads

  Gökçe, H.S.; Öksüzer, N.; Kamiloğlu, H.A.; Eyüboğlu, M.; Yılmaz, F.

  Foam concrete has recently become a key construction material in terms of meeting the special needs of modern engineering applications such as thermal insulation, absorption of static and dynamic loads. In this study, the effect of polypropylene fiber content and various uni- and tri-axial compression loads on the toughness response of polypropylene fiber-reinforced foam concrete was investigated. Up to a certain strain level (0.1 mm/mm), the ultimate compression stress of specimens under uni- and tri-axial loading increased from about 1 MPa to 16 MPa with the increased target densities of foam concrete. There was a strain-hardening capability of low-density foam concrete while the specimens failed by strain-softening in the high-density series. The optimum fiber amounts were found to be 3.9%, 4.6%, and 6.4% for low, medium, and high target densities of foam concrete, respectively. At low-density series, the bubbles were observed to be relatively bigger and mostly merged with each other. A reduction in foam content (vice versa, increasing target density of mixture) and the presence of fiber resulted in smaller pore size and a more homogenous distribution of them in the matrix. In conclusion, the desired pore structure and efficient bridging of fibers in the matrix allowed the production of favorable foam concrete with higher toughness.

  AtıfScopus14·WoS10·OpenAlex14

  İncele
• MakaleAçık Erişim2023Scopus SJRQ2/r/bayburt/12824
  Effect of elevated temperature on radiation shielding properties of cement and geopolymer mortars including barite aggregate and colemanite powder

  Kök, S.; Türetken, M.S.; Öksüzer, N.; Gökçe, H.S.

  This study aims to investigate the radiation shielding efficiency of cement and geopolymer-based mortars after exposure to elevated temperatures which may happen during the activation process of nuclear reactors. To contribute to the shielding properties, these binders were modified with the substitution of colemanite powder (5 and 10%), and barite aggregate was used to be an alternative to silica sand, as well. The produced specimens were exposed to 300 and 500 °C. While the colemanite powder resulted in significant retardation of setting time up to 183% for cement-based series, a set accelerator effect reaching 67% was found in the geopolymer series. Unlike expectation, the losses in mechanical and shielding properties have become more pronounced in geopolymer mortars at the applied temperatures. In particular, a significant increase reaching 28% in compressive strength of cement series was found after 300 °C exposure. It was noted that cement series with reaching a linear attenuation coefficient of 0.162 cm−1 presented more effective shielding against gamma rays when compared to that (0.134 cm−1) of geopolymers. To moderate thermal neutrons, geopolymer series reaching a linear attenuation factor of 2.799 cm−1, were found to be a more promising alternative according to cement series reaching 2.140 cm−1.

  AtıfScopus30·WoS27

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• MakaleAçık Erişim2023Scopus SJRQ1/r/bayburt/11488
  A bio-inspired solution to alleviate anisotropy of 3D printed engineered cementitious composites (3DP-ECC): Knitting/tilting filaments

  Zhou, Wen; McGee, Wes; Gökçe, H. Süleyman; Li, Victor C.

  Widely reported anisotropy in 3D printed cementitious structures has been a primary concern to structural integrity, especially for fiber-reinforced cementitious material, e.g., engineered cementitious composites (ECC). To alleviate the anisotropy present in 3D printed ECC (3DP-ECC), two innovative printing patterns, “knitting” and “tilting” filaments, were proposed, mimicking the natural crossed-lamellar structure of conch shells. 3D spatial paths were designed to allocate tensile/flexural resistance to multiple directions and to create an interwoven interface system to strengthen the structure. Four-point bending tests loading from three different directions were conducted. It was found that knitted and tilted filaments revealed superior or comparable bending performance to cast ECC in two favorable orientations. Furthermore, flexural performance in the weakest orientation was notably improved by knitting and tilting, with up-to-179% increases in flexural strength compared with that of parallel filaments. This novel approach holds great promise in alleviating anisotropy of 3DP-ECC without introducing additional reinforcement.

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  AtıfScopus45·WoS39·OpenAlex42

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