Browsing by Author "Baradan B."

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    Use of recycled concrete aggregates in Hot-Mix Asphalt
    (American Concrete Institute, 2006) Topal A.; Öztürk A.U.; Baradan B.
    The rubble from construction is generally used in landfill or thrown to natural areas at the end of their service life. Because continuously increasing production of concrete consumption, recycling of concrete waste materials will provide environmental protection and economical benefits. In this study, effects of fine and coarse recycled concrete aggregates on Hot-Mix Asphalt (HMA) performance were investigated. In performed experiments, Marshall Mixtures were prepared by using recycled concrete aggregates in the proportion of 10%, 20%, and 30% by mixture weight for the replacement of limestone in suitable gradation. Six different bitumen ratios were added to each mixture, respectively. Void %, flow and stability values were examined on 54 specimens. Furthermore, indirect tensile strength experiments were examined on the specimens having optimum 4.5% bitumen content and 30% recycled concrete aggregates. The results indicate that waste concrete can be used in HMA as aggregate to obtain the required Marshall stability and indirect tensile strength of the mixtures. However, the void percent of the mixture are not desirable due to the dense gradation of aggregate. Hence, gradation change is needed to Marshall Design criteria. © 2006 American Concrete Institute. All rights reserved.
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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.