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

  İncele
• 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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• 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

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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

  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
• MakaleAçık Erişim2022Scopus SJRQ2/r/bayburt/11977
  A novel internal curing method for 3D-printed geopolymer structures reinforced with a steel cable: Electro-heating

  Gökçe, H.S.; Güngör, O.; Öksüzer, N.

  Buildability and structural integrity are the inherent challenges of 3D printed geopolymer structures needed to be overcome. Reinforcing with steel cable ensuring a higher structural integrity of the printed structure can simultaneously improve the buildability due to the heating capability of this component. The controllable instant heating capability of steel cable was achieved by the use of a specific circuit system in the study. As a novel internal curing technique, electro-heating is recommended in the additive manufacturing of steel cable-reinforced geopolymer structures by the authors.

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  AtıfScopus4·WoS3·OpenAlex5

  İncele
• MakaleAçık Erişim2021Scopus SJRQ1/r/bayburt/13508
  Investigation of mechanical properties of high-performance hybrid fiber concretes adding nanomaterials using with coarse aggregate

  Öksüzer, Nurullah; Anil, Özgür; Aldemir, Alper; Şahmaran, Mustafa

  High-performance hybrid fiber cement composites have more ductility and higher strength than traditional concrete. This is because crack development is limited due to multiple small cracks are formed instead of a single large crack as the fibers enter the matrix. It is customary to produce these concrete composites with fine aggregates. In this study, concrete composites with coarse aggregates were strived to be produced to gain some feasibility. To this end, different mixtures composed of different aggregate/binder ratios and different fly ash/binder ratios were designed. In order to compare the effectiveness of the combination of different fibers were utilized in these mixtures. The volumetric ratios of fibers (excluding reference samples) were kept constant at a value of 2%. For each mixture, four-point bending and compressive tests were performed. The increase in the aggregate ratio was observed to cause a more ductile flexural behavior in mixtures composed of PVA and steel fibers. In contrast, the ductility was reduced in mixtures with Nylon-mono and steel fibers. In addition, the ductility values were enhanced with the increase in FA/PC ratio. In addition, the possibility to use the cheaper Nylon-mono fibers in hybrid fiber mixtures was proved with optimization of aggregate-binder (A/B) and FA/PC ratios, enabling more feasible high-performance concrete mixtures.

  AtıfScopus12·WoS9·OpenAlex13

  İncele
• Yüksek Lisans TeziAçık Erişim2016/r/bayburt/16969
  Farklı inceliklere sahip mermer ve Bayburt taşı atıklarının lif donatılı geopolimer bağlayıcılı sistemlerde kullanılması

  Nurullah Öksüzer

  Türkiye doğal taş bakımından oldukça zengin bir ülkedir. Birçok ilimizde endüstriyelleşmiş ya da endüstriyelleşmekte olan doğaltaş üretimi ülkemizin ekonomik kalkınmasında önemli bir rol üstlenmektedir. Ocak ve atölye işletmeciliği ile yapılan doğaltaş üretimlerinde yaklaşık %30-70 oranında atık ürün oluşturmaktadır. Bu atıkların bir kısmı inşaat sektörü başta olmak üzere birçok alanda değerlendirilmektedir. Ancak çoğunluğu atık sahalarında depolanmaktadır. Bu atık sahalarından rüzgâr ve yağmur erozyonu ile taşınan partiküller tarım arazilerini kirletmekte, içme sularını tahrip etmekte ve tozlaşma sonucunda doğa kirliliği oluşturmaktadır. Bayburt Taşı (BT) orijin olarak tüf/tüfit yapılı taş grubundadır. Kimyasal olarak yüksek oranda silis içermekte ve bu silissi yapı genel olarak zeolit minerallerinden meydana gelmektedir. Bayburt ilindeki rezervin yaklaşık miktarının 180 milyon metreküp olduğu MTA tarafından yapılan araştırmalarda belirtilmiştir. BT genel olarak dış duvar kaplaması, denizlik ve yüzey kaplamalarının yanı sıra çeşitli restorasyon işlerinde, köprü, cami ve çeşme gibi imalatlarda kullanılmaktadır. BT'nin ocak işletmeciliğinde modern yöntemlere geçilememesi sebebiyle %70'e varan verim kayıpları oluşmaktadır. Bu verim kaybı atık oranını artırarak tarım arazilerini ve havayı kirleterek çevre problemlerine sebep olmaktadır. BT üretimindeki atıklar depolama sorunlarını da beraberinde getirmektedir. Bu tez çalışmasında, yapı malzemesi biliminin son zamanlarda ilgi gören konularından, sürdürülebilirlik ve enerji tasarrufu sağlayan malzemelerden biri olan geopolimer malzeme üretilmesi amaçlanmıştır. Bu kapsamda çalışmada NaOH yapılı bir alkali aktivatör kullanılmış olup BT atıklarından yüksek dayanımlı kompozit yapı malzemesi üretilmesi planlanmıştır. Deneysel çalışmalarda Bayburt bölgesinde bulunan, farklı oranlarda mermer atıkları (MA) ile BT kullanılarak NaOH ile aktive edilmiş geopolimer kompozit malzemeler üretilmiştir. Çalışma üç aşamada tamamlanmıştır. BT ve MA 125 mikron ve 10 mikron olmak üzere iki incelikte öğütülmüştür. Ardından öğütülen malzemeler farklı oranlarda polipropilen mikro lifli ve lifsiz halde karıştırılarak 10 mol derişime sahip NaOH çözeltisiyle birlikte hamur haline getirildikten sonra kalıplara yerleştirilmiş ve 90 gün boyunca laboratuvar ortamında bekletilmiştir. Son olarak elde edilen sertleşmiş numuneler üzerinde 7, 28 ve 90 gün yaşlarında basınç dayanımı, eğilme dayanımı, birim hacim ağırlık, su emme, kapiler su emme, aşınma direnci ısıl iletkenlik ve yüksek sıcaklığın dayanım üzerindeki etkileri test edilmiştir. Ayrıca numuneler üzerinde civa püskürtmeli porozimetre (MIP), x-ışını oksidal spektrum analizi(XRF), x-ışını kırınımı yöntemi (XRD) ve taramalı elektron mikroskobuyla (SEM) mikro yapı görüntüleme analizleri de gerçekleştirilmiştir. Çalışmanın sonucunda %60 BT kullanımında 90 günde herhangi bir presleme işlemi yapılmaksızın lifsiz kompozitlerde yaklaşık 34 MPa, lifli kompozitlerde 39 MPa basınç dayanımına ulaşılmıştır. Görünür porozite değerleri yaklaşık % 25-45 oranlarında olan geopolimer kompozit malzemenin genel olarak su direncinin zayıf olduğu belirlenmiştir.

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