Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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Author: search.filters.author.Erdem, Tahir Kemal

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Now showing 1 - 4 of 4
  • Master Thesis
    Mechanical Behavior of Hybrid Fiber Reinforces Concrete Under Direct Tension
    (Izmir Institute of Technology, 2020) Çetin, Fatma Şirin; Saatçi, Selçuk; Erdem, Tahir Kemal
    Using different fiber types together, called hybrid fiber reinforced concrete, may cause a mutual synergic response between fiber matrixes. Due to these synergic effects of different fiber combinations, the mechanical behavior of concrete may perform differently than single fiber reinforced concrete. In this study, the effects of fiber hybridization in the direct tension behavior of concrete mixtures obtained by using three different types of steel fiber and polyvinyl alcohol (PVA) fiber were investigated. In this scope, total of 50 dog bone shaped, notched specimens were cast for 10 different mixtures and tested under direct tension. Average tensile stress-crack width responses of concrete specimens were investigated. It was found that the addition of PVA fiber to 35 mm long single hook end and 60 mm long double hook end steel fiber mixtures with a volume ratio of 0.75% did not considerably change the tensile behavior post cracking. As a result of adding PVA fibers to 60 mm single hook steel fiber mixtures with a volume ratio of 1.25%, cracking stresses were decreased and post cracking behavior was adversely affected. Addition of PVA fibers to 60 mm single hook steel fiber mixture with 0.75% volumetric ratio was found to increase post cracking stress levels.
  • Master Thesis
    Use of Excess Paste Theory and Image Analysis To Investigate Properties of Pervious Concrete
    (Izmir Institute of Technology, 2019) Bilgiç, Esra; Erdem, Tahir Kemal
    Pervious concrete is a type of special concrete that is formed with interconnected pores. It is able to pass the stormwater through its pores in order to control surface runoff and groundwater effectively. Due to the environmental benefits of pervious concrete, the usage of it has been increased day by day. In this thesis, the properties of pervious concrete by using excess paste theory and image analysis method were investigated. Concrete mixtures were prepared with four different aggregate gradations by combining three aggregate sizes (4-8 mm, 8-12.5mm and 12.5-16 mm), three different volume of paste to the volume of aggregate ratios (0.39, 0.42, and 0.45) and superplasticizer in three different ratios (0.5%, 0.7%, and 0.9%). For the determination of paste thickness in pervious concrete, excess paste theory and image analysis were used. For the determination of surface area of aggregate AutoCAD ReCap and some models were used. For the determination of fresh properties of pervious concrete, slump test, the density test of fresh pervious concrete and rheological measurements of cement paste were done. Permeability, compressive and flexural strength, abrasion resistance, density test, and void content tests were performed on hardened pervious concrete. To sum up, just as paste thickness results, the ratio volume of paste to the volume of aggregate, aggregate gradations, and the usage ratios of superplasticizer affected the performance of concrete. Results showed that increasing paste to aggregate ratio and superplasticizer dosage caused more workable concrete, more paste thickness, less permeability, less void, and more compressive strength.
  • Master Thesis
    Develepment of a New Test Method To Evaluate Dynamic Stability of Self-Consolidating Concrete
    (Izmir Institute of Technology, 2014) Alami, Mohammad Musa; Erdem, Tahir Kemal
    Self-consolidating concrete (SCC) is a new generation of concrete with high performance. It is able to flow under its own weight and fills the formwork without any external vibration. Stability is the most important plastic and crucial property for successful application of SCC and it refers to segregation of constituent in fresh state. Dynamic stability is the segregation resistance of SCC during transportation and placement. Evaluation of dynamic stability is one of the most investigated topics of SCC. Many different test methods have been proposed to evaluate the dynamic stability of SCC. No single and widely accepted method exists for the evaluation of the dynamic stability of SCC. In this thesis a new apparatus for testing the dynamic stability of SCC was developed. The effect of different mix design parameters such as water-to-cement ratio w/c, slump flow diameter, coarse aggregate-to-total aggregate ratio (CA/TA), and maximum size of aggregate (Dmax) were evaluated on the dynamic stability of SCC. Several fresh concrete tests were carried out on the SCC mixtures: slump flow, T500 time, Visual stability index (VSI), V-funnel, L-box, static sieve segregation (GTM), rheometer, and new proposed method (DSST). Several correlations were established between the test results. It was found that the new proposed test is a suitable method to evaluate the dynamic stability of SCC. Limits were proposed for a dynamically stable SCC.
  • Master Thesis
    Effects of Thixotropy on Self Consolidating Concrete Surface Properties
    (Izmir Institute of Technology, 2012) Ersöz, Hasan Yavuz; Erdem, Tahir Kemal
    Self-consolidating concrete is a high performance concrete that does not require vibration for placing and compaction. It is able to flow under its own weight compeletly filling the formwork and achieving full compaction. Self consolidating concrete reduces construction time and cost, also faults resulting from the poor workmanship. In this thesis, the effects of thixotropy on surface properties and durability were investigated. Concrete Mixtures were produced with different three slump flows (55 cm , 65 cm , 72 cm). Rheology and thixotropy of fresh concrete were examined by Contec 4SCC concrete rheometer. To obtain different surfaces, following parameters were changed: Thixotropy (by changing slump flow), release agent (six different types), formwork type (steel, plexiglas, plywood) and pressure application (equivalent to the weight of 10 m high fresh SCC) on specimens during setting. Concrete specimen surfaces were captured and digitally recorded on a hard drive. Digital images were analyzed by an image processing software, Image J. Compatibility of mixture type, material and release agent varieties was studied to minimize voids on surfaces. In the last stage of the thesis, durability and permeability of selected mixtures were investigated by performing sorptivity permeability, salt scaling and chloride ion penetration tests. It was found that, the surface quality depends on both thixotropy and release agent. Moreover, the release agent has to be selected according to the formwork material. In other words, for best surfaces release agent, formwork material and thixotropy have to be considered simultaneously. In general plywood formworks resulted in better surfaces in comparison to steel and plexiglas. Furthermore surfaces exposed to pressure gave better results. At the end of this work a table was prepared to make surface categorization which can be used as a reference for future works.