Browsing by Author "Yavuz, Demet"

Now showing 1 - 9 of 9

Çelik Lif Katkılı Alüminyum Tüp İçine Beton Doldurulmuş Kirişlerin Eğilme Dayanımlarının İncelenmesi
(2021) Yaltay, Namık; Güler, Soner; Yavuz, Demet
Çelik tüp içine beton doldurulmuş (ÇTBD) kirişlerin özellikle yüksek yapılarda ve köprü kirişlerinde kullanımı gün geçtikçe artmaktadır. Ancak, son yıllarda normal ve paslanmaz çelik yerine daha hafif ve ucuz olan alüminyum tüp içine beton doldurulmuş (ATBD) kirişler inşaat uygulamalarında yaygın bir şekilde kullanılmaktadır. Bu çalışmanın amacı çelik lif katkılı dikdörtgen en kesitli ATBD kirişlerin moment ve süneklik kapasitelerinin incelenmesidir. Çelik liflerin hacimsel lif oranları %0,5 ve %1,5 olarak, alüminyum tüp et kalınlıkları ise 2 ve 4 mm olarak seçilmiştir. Çalışma sonucunda, içi boş alüminyum tüplerin içine beton doldurulmasının ATBD kirişlerin dayanım ve süneklik kapasitelerini önemli oranda artırdığı belirlenmiştir. Çelik liflerin ATBD kirişlerin moment kapasitelerini arttırmada etkileri oldukça sınırlıyken, ATBD kirişlerin süneklik kapasitelerini arttırmada çok daha fazla etkili oldukları görülmüştür. Ayrıca, çelik lif hacimsel oranı %0,5’den %1,5’a çıkarıldığı zaman ATBD kirişlerin daha fazla elastik ötesi deformasyon yaptıkları ve bundan dolayı süneklik kapasitesindeki artışların daha belirgin olduğu belirlenmiştir
The Effect of Recycled Pervious Concrete Aggregate Substitution on Properties of Pervious Concrete
(Kare Publishing, 2024) Yavuz, Demet
Sustainability has gained significant importance in civil engineering and other areas in recent years. Numerous studies have been conducted on using recycled aggregates to demolish various structures in this context. However, almost all these studies have focused on recycled aggregates from traditional concrete. This study investigated the usability of recycled aggregates obtained from pervious concrete produced in a laboratory environment for use in pervious concrete production. Natural aggregate was substituted with recycled pervious concrete aggregate at weight ratios of 20%, 40%, 60%, 80%, and 100%. The concrete series' compressive, flexural, and splitting tensile strengths, water permeability coefficient, porosity values, and freeze-thaw resistance were examined. Additionally, the microstructure before and after the freeze-thaw effect was analyzed using scanning electron microscopy. The results showed that recycled aggregates increased the water permeability coefficient and porosity but negatively affected the mechanical properties.
Effect of Scoria Powder on the Strength and Porosity of Porous Concrete Produced With Recycled Porous Concrete Aggregate
(Elsevier - Division Reed Elsevier india Pvt Ltd, 2025) Yavuz, Demet
In recent years, there has been a significant increase in the cycle of demolition and reconstruction, driven by the growing demand for housing and urbanization in developing countries. As new buildings are constructed at a rapid pace, the resulting debris from older structures presents a considerable challenge, particularly because of limited storage capacity. This study focused on the production of porous concretes using recycled aggregates. To address the low strength associated with recycled aggregates, 5 % (by weight) of silica fume was incorporated, while scoria was used to replace cement at varying levels of 5 %, 10 %, 15 %, 20 %, 25 %, and 30 % by weight. The research also analyzed the pore structure and distribution within the porous concrete through computed tomography, with an emphasis on its mechanical properties, porosity, and water permeability. The results demonstrate that scoria serves effectively as a binder, successfully substituting for cement. Additionally, the integration of scoria enhanced the compressive strength of the porous concrete after a 120-day curing period, due to pozzolanic reaction caused by scoria, while also reducing water permeability.
Freeze-Thaw and Drop-Weight Impact Resistance of Fiber-Reinforced Pervious Concretes Produced Using Recycled Pervious Concrete Aggregate
(2024) Yavuz, Demet
Pervious concrete can rapidly drain stormwater from the top layer to the sublayer. However, the porous structure of this concrete also results in low mechanical properties, which prevent the widespread use of pervious concrete around the world. This study investigated the freeze-thaw and drop-weight resistances of pervious concrete produced with recycled pervious concrete aggregate. Two different aggregate types (limestone and recycled) and two different aggregate size fractions (15/25 mm and 5/15 mm) were used to examine the effect of aggregate type and gradation. Additionally, for improving mechanical and durability properties, polypropylene fibers were used at three different dosages by the volume of mixtures (0.1%, 0.2%, and 0.3%). Within the scope of the study, compressive, splitting-tensile, and flexural strengths, effective porosity, freeze-thaw, abrasion, and impact resistance of pervious concrete were determined. The results showed that concrete produced with recycled aggregate had some advantages in terms of porosity; however, its mechanical properties, freeze-thaw, and impact resistance were lower than those of pervious concretes produced with limestone aggregate. Additionally, fiber addition decreased the compressive strength and effective porosity of pervious concrete. However, up to a certain point (0.2%), fiber addition improved abrasion, freeze-thaw, and impact resistance, as well as splitting tensile and flexural behavior of pervious concrete.
Hybrid Fiber Reinforced Concrete-Filled Square Stub Columns Under Axial Compression
(Elsevier Sci Ltd, 2019) Guler, Soner; Yavuz, Demet; Aydin, Muhammet
The main aim of this study is to compare the axial load, ductility, and toughness capacities of square concrete-filled carbon steel (CFCST), stainless steel (CFSST) and aluminum tube (CFAT) columns filled with plain concrete, single (steel) and hybrid (steel + synthetic) fiber-reinforced concrete under axial compression. To this end, the enhancement in axial load, ductility and toughness capacities of steel and hybrid fiber-reinforced CFCST, CFSST, and CFAT columns were obtained with regard to fiber volume ratio (0.5 and 1.5%), compressive strength of concrete (30 and 70 MPa) and the steel tube thickness (2, 3 and 4 mm). A total of 99 hollow, steel and hybrid fiber-reinforced CFCST, CFSST, and CFAT columns were tested under axial compression. The results showed that although the use of steel and synthetic fibers in single and hybrid form is very limited for enhancement of the axial load capacities of CFAT, CFCST and CFSST columns, the enhancement in ductility and post-peak toughness capacities are notable especially for CFCST and CFSST columns. However, the effects of steel and synthetic fibers on post-cracking behavior of the CFAT columns are not significant due to early rupture of AL tubes that cause highly brittle behavior after first peak load. In addition to this, the use of steel and synthetic fibers in hybrid form is slightly better at improving the ductility and toughness capacities of most of the CFAT, CFCST and CFSST columns than the use of steel fibers in single form.
Incorporation of Eggshell Powder in Metakaolin-Based Geopolymer Concrete Exposed to Elevated Temperatures
(Springer, 2025) Yavuz, Demet
Recently, due to the high demand for concretes with a low carbon footprint during production, geopolymer concretes have been introduced. Metakaolin (MK) is widely used by researchers in the production of geopolymer concrete due to its ability to replace cement and its high silica content. This study investigated the mechanical properties and high-temperature performance of geopolymer mortars produced using eggshell powder (ESP), an organic waste, as a substitute for metakaolin (MK). Within the scope of the study, ESP was used to partially replace MK at 5%, 10%, 15%, 20%, 25%, 30%, 35%, and 40% (by weight), and the flexural and compressive strengths, as well as the water absorption values were determined. In addition, the samples were exposed to temperatures of 200 °C, 500 °C, and 800 °C to determine the residual compressive strengths of the samples and to examine the internal structures of the selected samples. The results showed that using ESP up to a specific rate increased the strengths of MK-based geopolymer mortars. Additionally, 25% ESP yielded the best results regarding the mechanical properties and high-temperature performance of geopolymers. © 2025 Elsevier B.V., All rights reserved.
Investigation of Fresh State, Mechanical and Durability Properties of Cementitious Systems Reinforced With Different Plastic Waste Fiber Materials: an Experimental Study
(Taylor & Francis Ltd, 2025) Yazici, Semsi; Pilsim, Goksu; Sahin, Hatice Gizem; Yavuz, Demet; Mardani, Ali
Utilization of fibers obtained from waste plastics in mortar mixtures was investigated in this study. For this purpose, fibers obtained from polyethylene terephthalate, high density polyethylene and polypropylene type plastic waste were used in mortar mixtures at the rate of 0.5%, 1% and 1.5% by volume. 10 mortar mixtures were produced. Flowability, unit weight, compressive strength and flexural strength of the produced mixtures were investigated. Also, water absorption and porosity ratio, capillary water absorption, sulfate resistance and abrasion resistance of some selected mixtures were investigated. Regardless of the waste plastic fiber type a decrease of 1.8% to 8% in flow performance of the mixture was detected. This effect became more pronounced for all waste fibers as the fiber content increased. Also, this negative effect is more dominant in polypropylene fiber mixtures. It was determined that the mixtures with the highest compressive strength value were the mixtures containing high density polyethylene fiber, and an increase of 3.8% was achieved compared to the control mixture. The transport properties of mortar mixtures were negatively affected by the use of fiber. Mixtures containing high density polyethylene fiber are more effective on mechanical performance of systems and more resistant to abrasion compared to other fibers.
Mechanical and Porosity Properties of Recycled Pervious Concrete Aggregate-Bearing Pervious Concretes
(Taylor & Francis Ltd, 2024) Yavuz, Demet; Gultekin, Adil
The recycling of construction wastes holds significant importance both environmentally and economically. While extensive research has been conducted on aggregates derived from various wastes, the recycling of pervious concretes (PC) has been largely overlooked. This study addresses this gap by examining the porosity and mechanical properties of PC manufactured using aggregates obtained from recycled PC. The investigation focuses on three key factors: aggregate size (5/15, 10/15, and 15/25 mm size fractions), fiber inclusion (dosages of 0.1%, 0.2%, and 0.3% by volume), and aggregate type (limestone aggregate and recycled aggregate). Through image processing techniques, void characteristics including amount, structure, and homogeneity were quantified. Results indicate that the use of recycled aggregate led to a decrease in compressive strength ranging from 29% to 65%, depending on aggregate size fraction and fiber content. Porosity assessments revealed higher porosity in concrete utilizing recycled aggregate, with computer-based methods yielding values closely aligned with volumetric results.
Strength Prediction Models for Steel, Synthetic, and Hybrid Fiber Reinforced Concretes
(Ernst & Sohn, 2019) Guler, Soner; Yavuz, Demet; Korkut, Fuat; Ashour, Ashraf
This paper proposes new strength models to predict compressive, splitting tensile and flexural strengths of steel, synthetic and hybrid fiber reinforced concretes. The strength models depending on fiber reinforcing index, concrete compressive strength, and fiber volume fraction have been developed by multiple regression analyses of the experimental results obtained from a comprehensive experimental program. Twenty-five concrete batches, one control and 24 fiber reinforced concrete with target compressive strength of 40MPa were produced. Steel and synthetic fibers, namely hooked-end steel (HF) and polyamide (PA) synthetic fibers of total volume of 0.25, 0.5, and 0.75% were added in single and hybrid forms to concrete mixes. Moreover, the predictions of the proposed strength models have been compared with the existing strength models in the literature. The test results clearly showed that the predictions of the proposed strength models are more accurate than the existing strength models for compressive, splitting tensile and flexural strengths of all the fiber types. Although the existing strength models may be applicable to the prediction of compressive strength of steel, synthetic, hybrid fiber reinforced concrete (FRC), they may not be safely used for splitting tensile and flexural strength of steel, synthetic and hybrid FRC.