Sürdürülebilir Kalkınma Amaçları

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• MakaleYalnız künye2025/r/gumushane/16739
  Modeling the Compressive Strength of Fiber-Reinforced Alkali-Activated Concrete Using Non-Destructive Methods in Short Curing Periods

  Aksüt, Yavuz Selim; Çullu, Mustafa; Yetgin, Sukru

  The indirect assessment of concrete compressive strength using non-destructive techniques, including the Schmidt rebound hammer and ultrasonic pulse velocity methods, is crucial for evaluating and tracking the strength of structural concrete used in construction and rehabilitation projects. However, studies focusing on alkali-activated concrete (AAC) remain insufficient. This study investigates the mechanical properties of fiber-reinforced alkali-activated concretes (FAACs) produced with short curing times, addressing this gap in the literature. Ground blast furnace slag (GBFS) was used as the binder, and waste volcanic rock dust (RD), produced in a natural stone processing plant, served as a fine filler. These materials were activated with sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) to produce alkali-activated concrete, both without fibers (AAC) and with fibers (FAAC). Steel fiber (SF) and polyester fiber (PYF) were used separately and in hybrid forms at 0.25%; 0.50%; 0.75%, and 1.0% volume fractions, resulting in a total of 117 cubic specimens (15x15x15 cm). The specimens' mechanical properties were evaluated using regression analyses based on data from Schmidt rebound number (RN), ultrasonic pulse velocity (UPV) non-destructive methods and uniaxial compressive strength (UCS) destructive tests. Optimized functions predicting compressive strength based on RN and UPV measurements were developed, highlighting the significant effects of fiber type, ratio, and mode of use. Additionally, multivariate prediction models were statistically developed using data from the three test methods.

  İncele
• MakaleAçık Erişim2025/r/gumushane/14352
  Optimal Ratio of Steel and Polyester Fibers on the Mechanical Behavior of Alkali-Activated Concrete Produced by Industrial Waste Minerals

  Aksüt, Yavuz Selim; Çullu, Mustafa; Yetgin, Şükrü

  Alkali Activation Concretes (AAC) have many superior properties compared to Ordinary Portland Cement Concrete (OPC). However, it shows traditional concrete behavior with its brittleness. In this case, the tensile strength and flexural strength which are weak in addition to ductility is being studied to be increased by using various artificial and natural fibers. In this context, it is inevitable to conduct multifaceted research to improve the behavior of Fiber Alkali Activated Concrete (FAAC). In this study, 13 different mixes were made using steel and polyester fibers in different proportions by volume (0%; 0.25%; 0.50%; 0.75%; 1%) separately and hybrid. The mechanical properties of cubic (150 × 150 × 150 mm), cylindirical (100 × 200 mm) and prismatic (150 × 150 × 600 mm) specimens were determined including compressive strength, modulus of elasticity and poison ratio, splitting tensile strength and flexural strength (toughness-energy absorption capacity and modulus of rupture). crack formation in concrete occurs early and a significant decrease in strength is observed due to the high flexibility and low flow resistance of polyester fibers. Steel fibers with high strength and higher yield strength were used in hybrid form to solve this problem. It was revealed that the blend ratio that contributed the most to the mechanical behavior of the specimens was the case where the fibers were used as hybrid at a ratio of 1% by volume evaluation from both the experimental results and the optimization.

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• MakaleYalnız künye2025/r/gumushane/13973
  Durability properties of fiber-reinforced geopolymer concrete with natural and industrial waste mineral admixtures

  Aksüt, Yavuz Selim; Çullu, Mustafa; Yetgin, Şükrü

  In this study, ground granulated blast furnace slag (GGBFS) and quarry rock dust (RD), both industrial and natural mineral wastes were used as binder materials in geopolymer concrete. The influence of these mineral admixtures on the concrete’s durability under aggressive environmental conditions was investigated. Steel, polyester, and hybrid fibers were incorporated at volume fractions of 0%, 0.25%, 0.50%, 0.75%, and 1.0% to further enhance durability performance. Freeze-thaw and sulfate resistance tests were carried out to evaluate the effects of fiber type and content on the durability behavior of the geopolymer concrete. The test results showed that the mineral waste-based binder system itself offered considerable durability while the addition of fibers significantly improved resistance to freeze-thaw cycles and sulfate attacks. Among all types, the geopolymer concrete with 0.5% polyester fiber exhibited the highest resistance to freeze-thaw while hybrid fiber usage provided a balanced enhancement across both test environments.

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• MakaleAçık Erişim2024/r/gumushane/11956
  Performance of different fibre types in alkaline-activated concrete produced with industrial wastes: volcanic rock powder and blast furnace slag

  Aksüt, Yavuz Selim; Külekçi, Gökhan; Çullu, Mustafa; Yetgin, Şükrü

  The objective of the study is to determine the effects of different fibre types and ratios on the mechanical and physical properties of alkali-activated concrete (AAC) and to optimise important properties such as workability, unit weight, water absorption, compressive strength, modulus of elasticity and abrasion resistance of these concretes. Concrete samples were produced using steel and polyester fibres at ratios of 0.25%, 0.50%, 0.75% and 1%. The fibre ratios were varied, and various tests were conducted to determine the mechanical and physical properties of the concrete samples. The experiments clearly revealed the effects of fibre types and ratios on the performance of concrete. These results clearly demonstrate the effects of different fibre types and ratios on the mechanical and physical properties of AACs. Particularly noteworthy is the water-retaining property of polyester fibres, their effect on workability and their enhancing effect on abrasion resistance. The effects of steel fibres on compressive strength and modulus of elasticity are more pronounced, but they may present disadvantages in terms of workability and abrasion resistance. It is observed that mixed fibre usage provides a good balance in some properties. This study provides a roadmap for evaluating sustainable material options in the concrete industry and guiding future research.

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• MakaleYalnız künye2023/r/gumushane/14493
  Effect of Reduced Fineness of Fly Ash Used on the Alkali–Silica Reaction (ASR) of Concrete

  Eker, Hasan; Demir Şahin, Demet; Çullu, Mustafa

  This study aimed to determine the effect of fly ash added to concrete with high calcium content (C class) and different fineness on durability properties such as the alkali–silica reaction (ASR). By substituting ultra-fine fly ash for cement at specific proportions in concrete mixes and increasing the fly ash fineness, fly ash filled the spaces between cement grains or aggregates in concrete and accelerated the hydration process. Thus, the mechanism of ASR development was reduced. Class C Afşin Elbistan ash was used and was ground in a ball mill for 0, 10, 20, 30, and 45 min, and Blaine fineness values of 1555, 1632, 2347, 2589, and 2766 cm2/g were obtained, respectively. For each fly ash fineness, the effect of mixtures with 10%, 30%, and 50% replacement of cement on the ASR mechanism was observed during curing periods of 3, 7, 14, and 28 days compared to concrete without fly ash admixture. Furthermore, the effect of the increased fineness and substitution rate of fly ash with high calcium content in cement on the microstructure was revealed by microscopic mineralogical images. The prepared fine fly ash added to concrete mixes at different replacement ratios showed ASR reducing properties compared to the concrete mix without additions. The fly ash fineness and the substitution rate in the concrete had a reducing effect on the ASR, and this effect resulted in values lower than the reference concrete value.

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• MakaleYalnız künye2023/r/gumushane/12741
  Mechanical Properties of Shotcrete Produced with Recycled Aggregates from Construction Wastes

  Külekçi, G.; Çullu, M.; Yilmaz, A.O.

  Abstract: This study examines the usability of concrete wastes generated from buildings demolished for various reasons in shotcrete. The strength properties of shotcrete produced from recycled aggregates (RA), cylinder specimen and plate specimen were tested. it was observed that as the ratio of RA used instead of natural aggregate increases, the strength of the cylinder specimen decreases, ultrasonic pulse velocity increases. The toughness value has increased in the concrete samples prepared by replacing the natural aggregate with 50% or more RA. It was observed that the fiber amount and load carrying capacity were proportional in fiber reinforced plates prepared using RA. As a result, it has been observed that the interaction of RA with fiber is positive and it can be used in shotcrete. It has been revealed that RA can contribute to the reduction of environmental pollution caused by construction and wreckage wastes and can be presented as an alternative to natural aggregate.

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• MakaleAçık Erişim2022/r/gumushane/17325
  Uçucu kül inceliğinin betonun sülfat direnci üzerine etkisi

  Demir Şahin, Demet; Çullu, Mustafa; Eker, Hasan

  Beton bileşiminden biri olan çimentonun hidratasyonu ile sülfat iyonları arasında oluşan kimyasal reaksiyon sonucu sülfat korozyonu oluşmakta ve bu oluşum betonda bozulmalara neden olmaktadır. Sülfatın beton üzerinde oluşturduğu hasarı azaltmak ya da en aza indirmek için çimento yerine uçucu kül gibi puzolanlar kullanılmaktadır. Bu çalışmada betonun ana bileşenlerinden biri olan çimento yerine çimentoya yakın bileşene sahip olan Afşin Elbistan Termik Santralinden temin edilmiş uçucu kül atığı kullanılmıştır. Uçucu külün (UK) bilyalı değirmende 0, 10 ve 20 dk öğütülmesi ile elde edilen farklı inceliklere sahip örnekler % 10 UK ikame oranı ile hazırlanarak uçucu kül katkılı beton örnekleri oluşturulmuştur. Daha sonra bu örnekler; % 5 ve % 10 katkılı sülfat çözeltisine maruz bırakılmış ve beton örneklerinin sülfat direnci üzerine etkisini araştırmak için basınç dayanımı ve ultrasonik dalga hızı ölçümü testlerine tabi tutulmuş, ağırlık kayıpları incelenmiştir. Elde edilen sonuçlara göre uçucu kül öğütme süresine bağlı olarak % 5 ve % 10 sülfat çözeltisine maruz bırakılmıştır ve daha sonra katkılı beton örneklerindeki basınç dayanım değerlerinde artışlar gözlenmiştir. Sülfat çözeltisi miktarının artmasıyla birlikte beton örneklerinin basınç dayanımının azaldığı ve bu beton örneklerinin referans örneğine göre daha yüksek basınç dayanımı değerine sahip olduğu görülmüştür. Bununla birlikte; öğütme süresinin artmasıyla ağırlık kayıplarının azaldığı görülmüştür. Ayrıca; öğütmenin etkisi ile uçucu külün inceliğinin artması sonucu ultrasonik dalga hızı değerlerinin de arttığı belirlenmiştir.

  İncele
• MakaleAçık Erişim2021/r/gumushane/16761
  The investigation of mechanical properties of polypropylene fiber-reinforced composites produced with the use of alternative wastes

  Külekçi, Gokhan; Çullu, Mustafa

  Various studies on the disposal or storage of the wastes generated due to mining activities have been carried out until today. With the developing technology, the use of alternative products instead of aggregates in Composite and the effect of fiber addition were investigated. The most common of these studies is the bending strength tests on the beam sample. In this study, solid wastes generated by mining operations were used instead of aggregate used in Composite. Beam samples were poured with the dimensions of 40x40x160 mm by adding 4-6 kg/m(3) polypropylene fiber to the mixture obtained by using these solid wastes; then, its effects on ultrasonic pulse velocity test, tensile test, and compressive strength tests were conducted. According to the results of these tests, it was found that the fibers had a positive effect on compressive strength and bending strength. Also, it was found that water absorption rates and densities did not have an effect, while the ultrasonic pulse velocity decreased with increasing fiber content.

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• MakaleYalnız künye2021/r/gumushane/14609
  Experimental Investigation of Usability of Construction Waste as Aggregate

  Kulekci, Gokhan; Yilmaz, Ali Osman; Cullu, Mustafa

  The aim of this work is to obtain recycled aggregate (RA) from construction debris in order to reduce the rapid consumption of aggregate resources and the environmental impact of these resources. In order to fulfill this aim, the density, porosity, Schmidt hardness test, uniaxial compression resistance, carbonation depth, and ultrasonic p-wave velocity experiments were conducted on different construction debris transported by trucks from 9 different points in Turkey. In addition, the debris samples taken were broken down to the size of the aggregate and subjected to the tests of density, porosity, moisture content, freeze-thaw, and impact resistance. As a result of the conducted experiments, the lowest mass loss as a result of freezing-thawing was in GRA with 9.36%, the highest mass loss was in ORA with 22.58%, the highest ORA average aggregate impact strength index was 21.27%, and the lowest TRA aggregate impact strength index was found to be 18.26%. İt was determined that most of the physical properties of RA obtained from the construction wreckage was within the limit values specified in the literature and that the recycled aggregates could be used instead of natural aggregate. With this work and these results, RA obtained could be used in many areas such as concrete aggregate in the construction sector, underground filling in mining, filling material in gunned concrete, and filling materials on highways.

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• MakaleYalnız künye2020/r/gumushane/17916
  The effect of different fineness values of Afşin Elbistan fly ash on permeability in concrete

  Demir Şahin, Demet; Çullu, Mustafa; Eker, Hasan

  Too much CO2 is released during cement production. In many researches, the use ofnatural or recycled compounds plays an important role in the cement composition.The use of these components contributes both to reducing the amount of waste andto protecting the environment in nature. It is possible to produce an environmentallyfriendly concrete, thanks to its being a fly ash thermal power plant waste and its useas mineral additive in terms of its composition. In this study, it is aimed to produceimpermeable concretes with the use of C type fly ash as substitutes for cement in concrete composition in substitution rates of 10 %, 30 % and 50 %. In order to reduce thepermeability of concrete in this direction, as a result of grinding the fly ash in the ballmill for 0, 10, 20, 30, 45 and 60 minutes, concrete samples were prepared with andwithout admixture (Reference). Capillarity test was performed to determine the permeability at the end of cure periods of 28 and 90 days on concrete samples. Accordingto the results obtained at the end of 28 days, the best impermeability was achieved inthe mixture with 50 % fly ash replacement and 60 minutes grinding time. In 90 days,the best impermeability was obtained in the mixture with 30 % fly ash replacementand 0 minutes of grinding time. As a result, it was seen that permeability decreasedwith increasing thinness and substitution rate of fly ash in concrete composition.

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