Sürdürülebilir Kalkınma Amaçları

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• 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/12103
  A Comprehensive Assessment for the Aftershock Sequence of August 11, 2012 Varzaghan-Ahar Doublet Mainshocks, NW Iran

  Öztürk, Serkan; Yaghmaei-Sabegh, Saman

  In this study, an evaluation of regional, temporal and magnitude properties of the August 11, 2012 Varzaghan-Ahar aftershock sequence was performed based on the different variables such as the Gutenberg-Richter b-value, the Modified Omori p-value, fractal dimension Dc-value and the maximum aftershock magnitude Mamax value which commonly used to describe aftershock behaviors. b-value was computed as 0.73 ± 0.03 for the study area where catalog has a completeness magnitude Mc = 2.0. This b-value is relatively small from typical b≈1 and it can be due to the abundance of aftershocks larger than Mw = 4 in the region. Structural heterogeneity of the seismic source along with the compressive stress situation of the aftershock area could be another reason for this finding as well. p-value was estimated as 1.00 ± 0.03 where c-value took 0.342 ± 0.106 according to the analysis which shows that the number of aftershocks of the Varzaghan-Ahar mainshock shows a relatively fast decrease. Dc-value was computed as 1.84 ± 0.07. This large value indicates homogeneously distributed aftershocks and more clustering in smaller areas or larger scales. As a result, the smallest b-values (< 0.7) and Mamax values larger than 5.0 were obtained around the mainshock. In addition, the biggest p-values (> 1.2) were found in and around the mainshock including Varzaghan. The areas having the biggest p-value and the lowest b-value have great coseismic deformation and stress, respectively. Hence, we can say that coseismic deformation and stress distributions are very effective on the b- and p-value changes. Thus, particular attention on assessing the aftershock hazard may be directed on the understanding of these spatio-temporal aftershock variables.

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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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