Browsing by Author "Ozturk A.U."

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    Effects of admixture type and dosage on microstructural and mechanical properties of cement mortars
    (2011) Ozturk A.U.; Baradan B.
    Effects of admixture type and dosage have been investigated in the scope of this study. The influence of incorporation of chemical admixtures at different dosages on the development of pore structure of cement mortars has also been investigated. A delay on the development rate of strength by incorporation of chemical admixtures at early ages has been determined. The highest strength values were obtained for the cement mortars prepared by naphthalene sulphonate based chemical admixture. The strength values of specimens prepared with overdosage were lower than those of control specimens. Therefore, setting time and flow values were investigated related to admixture dosage and type. Increase in dosage of admixtures results in an increase of setting time and flow values. The pore structure development was given by time and dosage. Maximum pore area ratio values are determined for cement mortars prepared with overdosage. Pore area ratio values decrease by time, as compressive strength values increase. © 2011 Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg.
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    Microstructure - Macro property model proposal
    (2011) Ozturk A.U.; Onal O.; Baradan B.
    A relationship between the microstructure formation and compressive strength of cement mortars has been established within this study. Microstructure properties such as pore area ratio, total pore length, total dendrite length and average roundness of pore phases were determined by microstructural investigations. In addition, the hydrated part area, calcium hydroxide phase area and unhydrated part area ratios were calculated based on image analysis. Six parameters (pore area ratio, total pore length, total dendrite length, average roundness, hydrated part area ratio and unhydrated part area ratio) were correlated to the compressive strength values of different mixtures. Multiple linear regression investigations indicated that determination of only two parameters (total dendrite length and hydrated part area ratio) is sufficient enough to represent the relationship of microstructural formation-compressive strength confidently. This analysis indicates that the connected channel system of pore phase is more effective on strength than the amount of pore phase. © 2011 Thomas Telford Ltd.
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    Effects of micro pore characteristics on strength of cement mortar using artificial neural network
    (Nova Science Publishers, Inc., 2011) Ozturk A.U.; Onal O.
    Cementitious materials comprise a great part in construction process of structures such as buildings, bridges, roads and dams. The most expected properties of structural members prepared with cement mortar or concrete, are strength and durability. These structural members are supposed to have strength values determined in the structural analysis and to be durable against aggressive media in their service life. These characteristics are the most effective criteria in civil and material engineering. Therefore, these two parameters depend mainly on the pore structure and its characteristics of structural members. Nowadays, scientists and engineers are using new computer technologies, simulations and experimental techniques try to perform to characterize the inner structure of structural materials in order to define microstructural formations and the effects of microstructural phases such as pores on macro properties. New image capturing tools and their improved magnification capacity induced researchers to have an expanded view on investigation of microstructures. In addition, the results of these studies are simply not enough to realize the simulation of effects of inner structure. Some numerical and statistical methods performed by computers are needed at this stage. Artificial neural network (ANN) is one of these methods. In last decades, artificial neural network applications have become more considerable issue in engineering applications. In the scope of this chapter, pore area ratio values represent total pore area amount in a polished section of cement mortars were determined. Also, some pore characteristics representing the probability of channels between pores are investigated. The pore amounts and these pore characteristics are related to compressive strength values of cement mortars in order to establish a microstructure - macro property relationship. Thus, nondestructive methodologies and artificial neural network have been used in the prediction of a macro property, which only be determined by destructive testing techniques. © 2011 by Nova Science Publishers, Inc. All rights reserved.
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    Early age corrosion of mild steel in aggressive media
    (2012) Ozturk A.U.; Gucuyen E.; Erdem R.T.; Seker S.
    Effects of the time of holding, type of section, and concentration of the solution on the early age corrosion of mild steel are studied. Section types for steel specimens were box, tube, and corner. They were subjected to 3.5%, 5.0%, and 7.0% NaCl solutions. It was established that the concentration of the solution affects the corrosion until reaching the saturation value. © 2012 Springer Science+Business Media New York.
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    Prediction of effects of microstructural phases using generalized regression neural network
    (2012) Ozturk A.U.; Turan M.E.
    In the scope of this study, microstructure-macroproperty relationship of cement mortars has been established in order to define the effects of microstructural phases on strength. Microstructural studies have been become great issue in materials engineering. Nowadays, to characterize the microstructural phase properties and to improve and modify them are performed by scientist to forecasting and enhancing. According to this objective, cement mortars incorporating with chemical admixtures were prepared to constitute different microstructural graphs. These micrographs were analyzed to determine the amounts of unhydrated cement part, undifferentiated hydrated part and capillary pore phases in the cement mortar sections. Afterwards, the amounts of these microstructural phases were related to strength values of each cement mortar specimen. The relationship was established by using generalized regression neural network analysis. © 2011 Elsevier Ltd. All rights reserved.
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    Numerical analysis on corrosion resistance of mild steel structures
    (2013) Erdem R.T.; Seker S.; Ozturk A.U.; Gucuyen E.
    Corrosion resistances of mild steel specimens according to artificial neural network (ANN) analysis were investigated in the scope of this study. Corrosion rate values were taken into numerical analysis as a result of experimental studies under corrosive aggressive media. Mild steel specimens were selected according to the section type varieties such as box, tube and cornier. All steel specimens were subjected to the aggressive media formed using sodium chloride (NaCl with 99.8 % purity) solutions with 3.5, 5.0 and 7.0 % ratios per one liter distilled water and only distilled water. The reduction in corrosion rate has been observed and considered according to some corrosion loss respects. Corrosion rate prediction models were established between corrosion rate and parameters such as mass loss obtained by experimental studies using ANN. ANNs are computing systems that simulate the biological neural systems of the human brain. In this study, ANN analysis was generated to predict the corrosion rate values after experimental studies. Experimental and predicted values were compared by each other and it is seen that a strong relationship was established between them. © 2012 Springer-Verlag London Limited.
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    Identification of water/cement ratio of cement pastes, basing on the microstructure image analysis data and using artificial neural network
    (2013) Ozturk A.U.; Onal O.
    Artificial Neural Network (ANN) analysis has been established to forecast the Water/Cement (w/c) ratio values of cement pastes by using image analysis techniques in the scope of this study. W/c ratio values have reasonably great effects on the performance of cement based structural members. The service life or ultimate performances such as strength and durability characteristics are strongly affected by w/c ratios of cementitious materials. In this study, the relationship between microstructural phases such as unhydrated cement part, hydration products, capillary porosity, and w/c ratios predicted by ANN analysis, has been established. The predicted values are compared with estimated values obtained by proposed method in the literature. The study indicated that, using a contemporary data analysis technique, which is capable of searching nonlinear relationships more thoroughly, would result in more realistic prediction of the w/c ratios compared to the proposed method. © 2013 Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg.
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    Effectiveness of micro phases on water/cement ratio
    (2013) Ozturk A.U.
    Multiple linear regression (MLR) analysis has been performed to determine the effects of microstructural phases formed during hydration period of cement pastes to forecast their water/cement ratios. Image analysis methods have been used to determine the properties of microstructural phases in order to predict water/cement (w/c) ratio of cement pastes. Water/cement ratio has a great effect on strength and durability characteristics of cement-based structural members in their service life. In this study, the relationship between microstructural phases such as anhydrated cement part, hydration products, capillary porosity, and w/c ratios predicted by MLR analysis, has been established. The predicted values are compared with estimated values obtained by proposed method in the literature. MLR model indicates that volumetric ratios of microstructural phases in cement paste are effective in predicting w/c ratios of cement pastes.
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    Abrasion Resistance and Mechanical Properties of Waste-Glass-Fiber-Reinforced Roller-compacted Concrete
    (Springer New York LLC, 2018) Yildizel S.A.; Timur O.; Ozturk A.U.
    The potential use of waste glass fibers in roller-compacted concrete (RCC) was investigated with the aim to improve its performance and reduce environmental effects. The research was focused on the abrasion resistance and compressive and flexural strengths of the reinforced concrete relative to those of reference mixes without fibers. The freeze-thaw resistance of RCC mixes was also examined. It was found that the use of waste glass fibers at a rate of 2 % increased the abrasion resistance of the RCC mixes considerably. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.