Department of Civil Engineering
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Browsing Department of Civil Engineering by Author "Akış, Tolga"
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Item INFLUENCE OF WASTE FOUNDRY SAND (WFS) AND RICE HUSK ASH (RHA) ON THE MECHANICAL PROPERTIES OF POLYMER CONCRETE(2022-01-25) Alganad, Adnan Abdulghani Ali; Akış, Tolga; Şengönül, Cemal MerihPolymer concrete (PC) is a composite which contains aggregate, filler, bound together with a thermoset resin instead of cement and water. It is used as a repairing material due to its high bonding capability and good mechanical properties. On the other hand, it is quite expensive compared to ordinary concrete. The aim of this study is to investigate the effect of waste materials such as waste foundry sand (WFS) and rice husk ash (RHA) on mechanical properties of PC. RHA is used as a filler, while epoxy is used as a binding material in this study. The tests were conducted according to ASTM standards, where the compressive strength, splitting tensile strength, and flexural strength of the PC specimens were determined with various weight proportions of WFS, epoxy, and RHA. Firstly, five types of mixtures without RHA were prepared to determine the optimum proportion of epoxy and WFS. Secondly, the optimum proportion of RHA was determined for the optimum epoxy/WFS composition. The effect of normal sand (NS) in PC as a control was explored. The weight percent epoxy/WFS ratios were prepared as 10/90, 20/80, 25/75, 30/70 and 40/60, while RHA was tested for 5, 10, and 15% additions by weight. Scanning Electron Microscopy (SEM) was used to monitor the spatial distribution as well as adhesion between PC components. X-ray fluorescence (XRF) technique was performed to determine the chemical compositions of WFS and NS. Finally, Fourier Transform Infrared Spectroscopy (ATR-FTIR) was used in order to point out the chemical differences between WFS and NS. It was found that the average compressive strength, splitting tensile strength, and flexural strength values were all increased to their maximum for 25/75 epoxy/WFS ratio. On the other hand, the mechanical properties have been noticeably improved with 10% (by weight) RHA addition. Furthermore, using WFS as aggregate leads to better results in both compressive strength and flexural strength values compared to NS.Item INVESTIGATION OF WASTE FOUNDRY SAND MODIFIED POLYMER CONCRETE AS A RAPID REPAIR MATERIAL(2022-01-21) Aghi, Anas; Akış, Tolga; Şengönül, Cemal MerihPortland cement concrete (PCC) is a material composed of Portland cement, gravels, sand, and water and used for construction purposes. When it is damaged due to fire, sulfate attacks, or seismic forces, polymer concrete (PC) is one good candidate as a rapid repair material for PCC. PC is a material that consists of aggregates and a thermosetting resin as a binder. This present study investigates a special kind of PC composed of waste foundry sand (WFS), epoxy resin, and rice husk ash (RHA) as a repair material for PCC. In addition, the effect of surface roughness of PCC surface was investigated by applying different levels of artificial roughness on PCC substrates using various roughening techniques. Several mechanical tests, such as slant shear, splitting tension and bi-surface shear tests were performed in order to determine the bond strength between PCC and PC for four levels of substrate surface roughness. The surfaces were classified according to their roughness level as (a) smooth surfaces, (b) wire-brushed surfaces, (c) hole-drilled surfaces, and (d) sand-blasted surfaces. Overall, three types of failures namely, adhesive, cohesive and mixed failures were observed. It was found that not only the total surface roughness area but also the geometry of the roughness feature has an effect on the bond strength depending on the type of the applied stress and its direction. Furthermore, almost in all tested specimens, major or minor cracks were observed in PCC part and that reflects the significance of adhesive strength of the PC to the substrate.Item INVESTIGATION ON THE MECHANICAL BEHAVIOUR OF POLYMER CONCRETE FILLED ALUMINUM TUBES(2022-01-18) Alkarkhi, Ali Hafedh Mahmood; Akış, Tolga; Şengönül, Cemal MerihThis research focuses on the mechanical behaviour and confinement effect of aluminum tubes on a novel polymer concrete (PC) composed of recycled waste foundry sand (WFS), epoxy resin, and rice husk ash (RHA). In addition, we explored the effect of carbon fiber reinforcement (CFRP) on the axial load carrying capacity of polymer concrete-filled aluminum tubes (PCFATs) and determined the main influencing factors of both confinements. Specimens having dimensions of length 120, 150, 180, 210 mm, diameter 40, 50, 60, 70 mm, and thickness 2, 3, and 4 mm were prepared. We tested three specimens for each geometry under compression for three sets of experiments, where hollow circular aluminum tube (HCAT), PCFAT, and carbon fiber reinforced PCFAT (CFPCFAT) specimens were used. We employed two confinement models separately for the PCFAT and CFPCFAT. It is found that both diameter and thickness influence the composite tube’s axial load carrying capacity, and the thickness plays a significant role, especially in failure modes. The experimental results also showed the enhancement in the load-carrying capacity when CFRP was used. Moreover, test results show good agreement with the confinement model calculations for PCFAT specimens. On the other hand, the model for the CFPCFATs gives conservative results compared to the experimental ones.Item NUMERICAL ANALYSIS OF FIXED-ENDED MULTILAYER AND FGM ELASTIC TUBES UNDER THERMAL AND MECHANICAL LOADS(2022-02-15) Al-Mashhadani, Haithem; Akış, TolgaA numerical procedure is presented in this study in order to determine the elastic behavior of multilayer and FGM cylindrical thick-walled tubes with fixed ends under thermal and mechanical loads. In the first part of the study, using the symbolic computation software MATHEMATICA, the expressions of temperature distribution, stress components and radial displacement are derived for single layer tubes with different loading and boundary conditions. Then, using the numerical solution option of MATHEMATICA, the stress response of the fixed-ended multilayer tubes under thermal and mechanical loads are obtained by the simultaneous solution of a series of nonlinear equations. The validity of the numerical procedure is checked by comparing the solutions of several multilayer and FGM tube problems given in different studies with the solutions obtained by the proposed method. For multilayer tubes, almost identical results are obtained, while for FGM tubes, closer results are obtained when the numbers of the layers are increased. The proposed method is easy to be implemented and can be used especially for axisymmetric FGM tube, shaft, and disk problems where the analytical solutions cannot be obtained.Item PROPERTIES OF BURNT CLAY INCORPORATED CEMENTS(2022-02-16) Al-Noaimat, Yazeed Afet Adnan; Akış, TolgaThis study aims to compare the decomposition and pozzolanic reactivity of clays obtained from different regions of Turkey and from Guinea and to investigate their effects after calcination on the strength and water absorption properties of cement mortars when partially replacing Portland cement. Mineralogical and chemical compositions of the clay samples were determined using XRD (X-Ray Diffractometer) and XRF (X-Ray Fluorescence) tests, respectively. TG-DTA (Thermogravimetry - Differential Thermal Analyses) was used to determine the temperature profiles and the burning temperatures of the clays. Density and fineness of the burnt clays were also determined. In order to determine the optimum material properties, different burning temperatures and replacement levels (10, 20, and 30%) were considered. By applying compression tests, the strength activity index was calculated. Water absorption tests on 50 mm cube mortar specimens were also performed. It is found that for all temperatures, the selected burnt clays possess good pozzolanic activity. The highest compressive strength and lowest water absorption capacity were achieved when the clay determined as kaolinitic was burned at 700 °C and with 10% replacement level. While for the clay determined as montmorillonite, the optimum values were obtained at 700 °C with a 20% substitution level. Kaolinite was found to have higher pozzolanic activity and enhance the compressive strength and decrease water absorption more than montmorillonite. Moreover, it has compressive strength values even higher than cement.