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Conference Presentations by Yılmaz Akkaya
Concrete is widely used in construction sector and as a resource its consumption is the second la... more Concrete is widely used in construction sector and as a resource its consumption is the second largest on the planet after water, whereas having significant negative impacts on the environment. Regulatory authorities, concrete and cement industries are aware of environmental impacts of concrete and in most cases are making attempts to reduce them. Optimized solution for the concrete industry to have eco-friendly concretes is to obtain a balance between environmental impact and economy. In this research, a comparative study will be made for different types of concretes and results will be evaluated in terms of i) raw materials, ii) production, and iii) transportation, in order to make a detailed CO2 emission identification and classification. The main objective of this study is to identify the key emission sources contributing to CO2 emissions from concrete. First of all, a reporting boundary was selected, where there are three main scopes (Scope 1, 2 and 3) of emissions that will need to be examined within each activity of concrete production stages. Following this, a quantification of the emissions resulting from the production of a cubic meter of concrete is carried out. And finally, various concrete mixtures from 6 differeent concrete plants were compared in terms of CO2 emissions. As a result of this study, the equivalent CO2 emissions generated by a particular concrete with known mix proportions can be estimated using the emission contributions from the several different constituents of concrete.
Papers by Yılmaz Akkaya
Composite materials such as Fiber Reinforced Cement or Concrete (FRC) are designed to prevent bri... more Composite materials such as Fiber Reinforced Cement or Concrete (FRC) are designed to prevent brittle fracture. FRC is characterized by enhanced ductility and distributed crack formation prior to failure. Mitigation of progressive crack propagation and localization of cracks and stresses are result of the even distribution of fibers throughout the matrix. This chapter presents the utility of full field optical methodology for tracking the progressive development of cracking in cement based FRC. A full field imaging approach is used to better understand the link between microstructural properties, and sequence of cracking. We present the application of Electronic Speckle Pattern phase measurement interferometry (ESPI) for the identification of crack locations, size and progression, and how these features are linked to the uniformity of fiber distribution in the matrix.
Teknik Dergi, 2012
Yuksek performansli beton uretiminde puzolanik ozelikleri nedeniyle mikron boyutunda taneciklere ... more Yuksek performansli beton uretiminde puzolanik ozelikleri nedeniyle mikron boyutunda taneciklere sahip olan ucucu kul ve silis dumani kullanilmaktadir. Bu calismada, endustriyel bir urun olan mikrokalsit ile ucucu kul ve silis dumani katkili beton karisimlarinda taze beton deneyleri, priz suresi, sicaklik gelisimi, dayanim gelisimi, kirilma enerjisi, gecirimlilik ve sulfat dayanikligi deneyleri yapilmistir. Mikrokalsitli betonlarda islenebilirlik kaybi ve prizin hizlandigi gorulmustur. Erken yas dayanim gelisimi ucucu kul ve silis dumani katkili betonlardan daha hizli olmakla beraber ileri yas dayanim degerindeki artis ve sulfat hasarina direnci dusuktur.
Construction and Building Materials
Cement and Concrete Composites, Feb 1, 2007
ABSTRACT This paper reports the results of a study to determine the effects of supplementary ceme... more ABSTRACT This paper reports the results of a study to determine the effects of supplementary cementitious materials (SCMs) on the chloride binding of portland cement pastes. The results show that SCMs with significant quantities of alumina increase the binding capacity of cement paste. Pastes with metakaolin (45% Al2O3) showed the greatest chloride binding capacity and pastes with silica fume (< 0.5% Al2O3) showed the least binding. The chemical binding in solutions of high chloride concentration is mainly attributed to the formation of Friedel's salt, C3A·CaCl2·10H2O. When pastes originally exposed to high chloride concentrations are subsequently exposed to chloride-free solution, a portion of the bound chloride is released, but a significant portion remains irreversibly bound. There is some evidence that Friedel's salt may partially convert to Kuzel's salt, C3A·(0.5CaCl2)(0.5CaSO4)·12H2O, under these conditions. The binding relationships were best described by the Freundlich isotherm and binding coefficients are given for all the binders tested.
Journal of Materials in Civil Engineering, Aug 1, 2000
ABSTRACT
Aci Materials Journal
This paper presents the development of a rheological model for self-consolidating concrete (SCC).... more This paper presents the development of a rheological model for self-consolidating concrete (SCC). The developed model is based on the paste rheology criteria, which include minimum apparent viscosity, minimum flow, and optimum flow-viscosity ratio to achieve self-...
The amount and geometry of pores in hardened cement paste phase, that affect the mechanical behav... more The amount and geometry of pores in hardened cement paste phase, that affect the mechanical behaviour of concrete, have been considered in the form of two different parameters: porosity and capillary sorptivity coefficient (or water/cement ratio) where the latter represents the geometry of pores in hardened concrete. A mathematical model based on the damage mechanics approach has been developed to relate the compressive strength of concrete to these two parameters. Equations developed in this model have been applied to the values obtained in an available experimental work, in which porosities, sorptivity coefficients and strengths were measured for 40 different concrete mixtures. For indirect determination of the water-cement ratio in both hardening and hardened concretes, a petrographic examination method using optical fluorescence is presented. Additionally, five concrete mixtures with different water-cement ratios were used to determine their fluorescence intensities, sorptivity ...
Measuring, Monitoring and Modeling Concrete Properties, 2006
The mixture design, workability and mechanical properties of the steel fiber reinforced self comp... more The mixture design, workability and mechanical properties of the steel fiber reinforced self compacting concrete mixtures were studied. Nine mixtures were cast without fibers and with fibers, of low and high strength. The compressive and splitting tensile strengths and energy absorption capacities of self compacting concretes with different cementitious material contents, fiber contents and fiber strengths were compared. According to
Vibrational Spectroscopy, 2006
Materials and Structures, 2000
Materials and Structures, 2003
Concrete is widely used in construction sector and as a resource its consumption is the second la... more Concrete is widely used in construction sector and as a resource its consumption is the second largest on the planet after water, whereas having significant negative impacts on the environment. Regulatory authorities, concrete and cement industries are aware of environmental impacts of concrete and in most cases are making attempts to reduce them. Optimized solution for the concrete industry to have eco-friendly concretes is to obtain a balance between environmental impact and economy. In this research, a comparative study will be made for different types of concretes and results will be evaluated in terms of i) raw materials, ii) production, and iii) transportation, in order to make a detailed CO2 emission identification and classification. The main objective of this study is to identify the key emission sources contributing to CO2 emissions from concrete. First of all, a reporting boundary was selected, where there are three main scopes (Scope 1, 2 and 3) of emissions that will need to be examined within each activity of concrete production stages. Following this, a quantification of the emissions resulting from the production of a cubic meter of concrete is carried out. And finally, various concrete mixtures from 6 differeent concrete plants were compared in terms of CO2 emissions. As a result of this study, the equivalent CO2 emissions generated by a particular concrete with known mix proportions can be estimated using the emission contributions from the several different constituents of concrete.
Composite materials such as Fiber Reinforced Cement or Concrete (FRC) are designed to prevent bri... more Composite materials such as Fiber Reinforced Cement or Concrete (FRC) are designed to prevent brittle fracture. FRC is characterized by enhanced ductility and distributed crack formation prior to failure. Mitigation of progressive crack propagation and localization of cracks and stresses are result of the even distribution of fibers throughout the matrix. This chapter presents the utility of full field optical methodology for tracking the progressive development of cracking in cement based FRC. A full field imaging approach is used to better understand the link between microstructural properties, and sequence of cracking. We present the application of Electronic Speckle Pattern phase measurement interferometry (ESPI) for the identification of crack locations, size and progression, and how these features are linked to the uniformity of fiber distribution in the matrix.
Teknik Dergi, 2012
Yuksek performansli beton uretiminde puzolanik ozelikleri nedeniyle mikron boyutunda taneciklere ... more Yuksek performansli beton uretiminde puzolanik ozelikleri nedeniyle mikron boyutunda taneciklere sahip olan ucucu kul ve silis dumani kullanilmaktadir. Bu calismada, endustriyel bir urun olan mikrokalsit ile ucucu kul ve silis dumani katkili beton karisimlarinda taze beton deneyleri, priz suresi, sicaklik gelisimi, dayanim gelisimi, kirilma enerjisi, gecirimlilik ve sulfat dayanikligi deneyleri yapilmistir. Mikrokalsitli betonlarda islenebilirlik kaybi ve prizin hizlandigi gorulmustur. Erken yas dayanim gelisimi ucucu kul ve silis dumani katkili betonlardan daha hizli olmakla beraber ileri yas dayanim degerindeki artis ve sulfat hasarina direnci dusuktur.
Construction and Building Materials
Cement and Concrete Composites, Feb 1, 2007
ABSTRACT This paper reports the results of a study to determine the effects of supplementary ceme... more ABSTRACT This paper reports the results of a study to determine the effects of supplementary cementitious materials (SCMs) on the chloride binding of portland cement pastes. The results show that SCMs with significant quantities of alumina increase the binding capacity of cement paste. Pastes with metakaolin (45% Al2O3) showed the greatest chloride binding capacity and pastes with silica fume (< 0.5% Al2O3) showed the least binding. The chemical binding in solutions of high chloride concentration is mainly attributed to the formation of Friedel's salt, C3A·CaCl2·10H2O. When pastes originally exposed to high chloride concentrations are subsequently exposed to chloride-free solution, a portion of the bound chloride is released, but a significant portion remains irreversibly bound. There is some evidence that Friedel's salt may partially convert to Kuzel's salt, C3A·(0.5CaCl2)(0.5CaSO4)·12H2O, under these conditions. The binding relationships were best described by the Freundlich isotherm and binding coefficients are given for all the binders tested.
Journal of Materials in Civil Engineering, Aug 1, 2000
ABSTRACT
Aci Materials Journal
This paper presents the development of a rheological model for self-consolidating concrete (SCC).... more This paper presents the development of a rheological model for self-consolidating concrete (SCC). The developed model is based on the paste rheology criteria, which include minimum apparent viscosity, minimum flow, and optimum flow-viscosity ratio to achieve self-...
The amount and geometry of pores in hardened cement paste phase, that affect the mechanical behav... more The amount and geometry of pores in hardened cement paste phase, that affect the mechanical behaviour of concrete, have been considered in the form of two different parameters: porosity and capillary sorptivity coefficient (or water/cement ratio) where the latter represents the geometry of pores in hardened concrete. A mathematical model based on the damage mechanics approach has been developed to relate the compressive strength of concrete to these two parameters. Equations developed in this model have been applied to the values obtained in an available experimental work, in which porosities, sorptivity coefficients and strengths were measured for 40 different concrete mixtures. For indirect determination of the water-cement ratio in both hardening and hardened concretes, a petrographic examination method using optical fluorescence is presented. Additionally, five concrete mixtures with different water-cement ratios were used to determine their fluorescence intensities, sorptivity ...
Measuring, Monitoring and Modeling Concrete Properties, 2006
The mixture design, workability and mechanical properties of the steel fiber reinforced self comp... more The mixture design, workability and mechanical properties of the steel fiber reinforced self compacting concrete mixtures were studied. Nine mixtures were cast without fibers and with fibers, of low and high strength. The compressive and splitting tensile strengths and energy absorption capacities of self compacting concretes with different cementitious material contents, fiber contents and fiber strengths were compared. According to
Vibrational Spectroscopy, 2006
Materials and Structures, 2000
Materials and Structures, 2003
Journal of Materials in Civil Engineering, 2000
ABSTRACT