Kemal Yucel | Suleyman Demirel University (original) (raw)
Papers by Kemal Yucel
The transport of fresh concrete by pumping is an important process and widely used in practical c... more The transport of fresh concrete by pumping is an important process and widely used in practical concrete technology. This process has been applied since the beginning of the twentieth century. More recent developments of pumping equipment and findings on mineral and chemical admixtures have prompted more sophisticated research on pumping concretes. While they do not elaborate upon standard specifications, many recommendations for the composition of pumping concretes which are very useful in applications, such as ACI-304.2R reports, are available. This paper reports the results of an experimental study into the effects of concrete components, namely cement content, aggregate type, mineral, fiber, and plasticizer admixtures, on the rheology of pumping concretes. The rheological properties of concretes are examined by the Two Point Workability Test Apparatus (CTPT) originally proposed by G. H. Tattersall. The present study shows that concrete workability is improved by increasing cement content and also shows that the aggregate type only effects the rheological parameters in low cement content mixtures. In addition, yield stress and plastic viscosity are generally lower in concrete mixtures that contain natural stone rather than crushed aggregates. In addition, this study shows that the effect of mineral, plasticizer and fiber admixtures depends on cement content and admixture type.
In this study, the dynamic stability problem of a cylindrical shell composed of non-homogeneous o... more In this study, the dynamic stability problem of a cylindrical shell composed of non-homogeneous orthotropic materials with Young's moduli and density varying continuously in the thickness direction under the effect of an axial compressive load varying with a parabolic function of time is considered. At first, the fundamental relations and the modified Donnell type dynamic stability equations of a non-homogeneous orthotropic cylindrical shell are set up. Applying the Galerkin method, first, and then the Ritz-type variational method, the closed-form solutions have been derived for the dynamic critical axial load and dynamic factor. Finally, carrying out some computations, the effects of the non-homogeneity of the orthotropy ratio and the axial loading parameter on the critical parameters have been studied. Comparing results with those in the literature validates the present analysis.
Reinforced concrete is a widely used construction material. Its properties depend on the bond bet... more Reinforced concrete is a widely used construction material. Its properties depend on the bond between the reinforcing bar and concrete as much as the compressive strength or properties of the reinforcing bar because of component of construction expose to both flexural and bond together compressive loads. In this paper, the bond properties of concretes with different mix designs were investigated according to the results of compressive, flexural, bond, and flexural-bond tests. The data mining (DM) process was used to determine relationships among the test results and DM algorithms. Seventeen modeling techniques within WEKA were applied to the experimental data for the prediction of bond properties.
Rheological measurements of a concentrated suspension can be used to describe the flow of concret... more Rheological measurements of a concentrated suspension can be used to describe the flow of concrete. The rheological constants (yield value and plastic viscosity) of the mortar can be determined with a co-axial viscosimeter, and this technique is applied in this study. If the efficiencies of the mortar phase with respect to the cohesion, fluidity, bleeding and the friction of the concrete with the pipe are taken into consideration, this approach can be recognized as beneficial and helpful. Rheological tests on mortars were carried out with a Mettler RM 180 Rheomat co-axial viscosimeter. The angular deformation rate (γ ) and shearing stresses (τ ) were determined, andγ -τ diagrams were drawn. All the mortars showed a tixotropic behavior conforming to the Bingham model. A linear regression of these parameters gave the yield value (τ o ) and the plastic viscosity (η pl ) of the mortars.
Transporting fresh concrete constitutes a significant part of the production process. Transferrin... more Transporting fresh concrete constitutes a significant part of the production process. Transferring ready-mixed concrete on-site is done using concrete pumps. Recent developments in concrete technology, and in mineral and chemical additives, have resulted in new developments in pumping techniques and the use of different concrete mixtures and equipment. These developments required further knowledge of the behavior of fresh concrete under pressure. Two criteria were determined for the pumpability of concrete: the power required to move the concrete or of the repulsive force; and the cohesion of the fresh concrete. It would be insufficient to relate pumpability to these two criteria; the values of segregation pressure, diffusion ability, water retention capacity, and side friction of the mixture are significant parameters in ensuring that concrete is pumped freely along the pipe. To solve the pumpability problem, friction stresses should be determined as a function of the linear pressure gradient, the pressure leading to segregation of the fresh concrete should be determined, and tests for the bleeding of concrete under pressure should be examined. The scope of the research is the examination of the behavior of fresh concrete under pressure. To determine the segregation pressures, a test apparatus was designed for the bleeding of concrete under pressure. The main purpose of the study is to determine whether the concrete can be pumped easily and whether it will lose its cohesion during the pumping, based on tests of concrete workability and bleeding of concrete under pressure. Int J Thermophys (2012) 33:885-894
The transport of fresh concrete by pumping is an important process and widely used in practical c... more The transport of fresh concrete by pumping is an important process and widely used in practical concrete technology. This process has been applied since the beginning of the twentieth century. More recent developments of pumping equipment and findings on mineral and chemical admixtures have prompted more sophisticated research on pumping concretes. While they do not elaborate upon standard specifications, many recommendations for the composition of pumping concretes which are very useful in applications, such as ACI-304.2R reports, are available. This paper reports the results of an experimental study into the effects of concrete components, namely cement content, aggregate type, mineral, fiber, and plasticizer admixtures, on the rheology of pumping concretes. The rheological properties of concretes are examined by the Two Point Workability Test Apparatus (CTPT) originally proposed by G. H. Tattersall. The present study shows that concrete workability is improved by increasing cement content and also shows that the aggregate type only effects the rheological parameters in low cement content mixtures. In addition, yield stress and plastic viscosity are generally lower in concrete mixtures that contain natural stone rather than crushed aggregates. In addition, this study shows that the effect of mineral, plasticizer and fiber admixtures depends on cement content and admixture type.
In this study, the dynamic stability problem of a cylindrical shell composed of non-homogeneous o... more In this study, the dynamic stability problem of a cylindrical shell composed of non-homogeneous orthotropic materials with Young's moduli and density varying continuously in the thickness direction under the effect of an axial compressive load varying with a parabolic function of time is considered. At first, the fundamental relations and the modified Donnell type dynamic stability equations of a non-homogeneous orthotropic cylindrical shell are set up. Applying the Galerkin method, first, and then the Ritz-type variational method, the closed-form solutions have been derived for the dynamic critical axial load and dynamic factor. Finally, carrying out some computations, the effects of the non-homogeneity of the orthotropy ratio and the axial loading parameter on the critical parameters have been studied. Comparing results with those in the literature validates the present analysis.
Reinforced concrete is a widely used construction material. Its properties depend on the bond bet... more Reinforced concrete is a widely used construction material. Its properties depend on the bond between the reinforcing bar and concrete as much as the compressive strength or properties of the reinforcing bar because of component of construction expose to both flexural and bond together compressive loads. In this paper, the bond properties of concretes with different mix designs were investigated according to the results of compressive, flexural, bond, and flexural-bond tests. The data mining (DM) process was used to determine relationships among the test results and DM algorithms. Seventeen modeling techniques within WEKA were applied to the experimental data for the prediction of bond properties.
Rheological measurements of a concentrated suspension can be used to describe the flow of concret... more Rheological measurements of a concentrated suspension can be used to describe the flow of concrete. The rheological constants (yield value and plastic viscosity) of the mortar can be determined with a co-axial viscosimeter, and this technique is applied in this study. If the efficiencies of the mortar phase with respect to the cohesion, fluidity, bleeding and the friction of the concrete with the pipe are taken into consideration, this approach can be recognized as beneficial and helpful. Rheological tests on mortars were carried out with a Mettler RM 180 Rheomat co-axial viscosimeter. The angular deformation rate (γ ) and shearing stresses (τ ) were determined, andγ -τ diagrams were drawn. All the mortars showed a tixotropic behavior conforming to the Bingham model. A linear regression of these parameters gave the yield value (τ o ) and the plastic viscosity (η pl ) of the mortars.
Transporting fresh concrete constitutes a significant part of the production process. Transferrin... more Transporting fresh concrete constitutes a significant part of the production process. Transferring ready-mixed concrete on-site is done using concrete pumps. Recent developments in concrete technology, and in mineral and chemical additives, have resulted in new developments in pumping techniques and the use of different concrete mixtures and equipment. These developments required further knowledge of the behavior of fresh concrete under pressure. Two criteria were determined for the pumpability of concrete: the power required to move the concrete or of the repulsive force; and the cohesion of the fresh concrete. It would be insufficient to relate pumpability to these two criteria; the values of segregation pressure, diffusion ability, water retention capacity, and side friction of the mixture are significant parameters in ensuring that concrete is pumped freely along the pipe. To solve the pumpability problem, friction stresses should be determined as a function of the linear pressure gradient, the pressure leading to segregation of the fresh concrete should be determined, and tests for the bleeding of concrete under pressure should be examined. The scope of the research is the examination of the behavior of fresh concrete under pressure. To determine the segregation pressures, a test apparatus was designed for the bleeding of concrete under pressure. The main purpose of the study is to determine whether the concrete can be pumped easily and whether it will lose its cohesion during the pumping, based on tests of concrete workability and bleeding of concrete under pressure. Int J Thermophys (2012) 33:885-894