Browsing by Author "Yaltay, Namik"

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Nuclear Radiation Shielding and Mechanical Properties of Colemanite Mineral Doped Concretes
(Taylor & Francis Ltd, 2019) Oto, Berna; Madak, Zekiye; Kavaz, Esra; Yaltay, Namik
The present research focused on the investigation of photon and fast neutron shielding parameters of colemanite mineral doped and undoped concretes. The fabricated concretes have been exposed to gamma rays at 59.5 and 81 keV energies and the measurements have been carried out with NaI(Tl) detector. The parameters of effective atomic number (Z(eff)) and electron density (N-el) have been determined experimentally and theoretically. The exposure buildup factor (EBF) and energy absorption buildup factor (EBF) have been computed utilizing the Geometric progression (G-P) fitting method. In addition to the photon shielding parameters, the macroscopic effective removal cross-section calculations for fast neutron (sigma(R)) were performed. As a result, it was observed that the concretes doped with colemanite mineral are not very effective in gamma radiation shielding. On the contrary, it was observed that concretes with colemanite were more effective in shielding fast neutrons and the fast neutron removal cross-section values increased with increasing colemanite concentration in the concrete. Additionally, compressive strength values (MPa) of concretes were tested using ALFA TESTING (B001-PC) 200 tons capacity device.
Properties of Pumice-Fly Ash Based Geopolymer Paste
(Elsevier Sci Ltd, 2022) Hamid, Maadh Abdulmuttaleb; Yaltay, Namik; Turkmenoglu, Mehmet
Invention of a new and improved binding material has become an urgent need in order to reduce reliance on Portland cement while minimizing environmental pollution and energy consumption associated with its manufacture. Geopolymer could be a possible alternative in the future. This study investigated some mechanical and durability properties of pumice-fly ash geopolymer paste, including six pumice + fly ash percentages, six alkaline activating solution-to-binder (A/B) ratios, and three curing times in the oven at 60 degrees C for 2, 4, and 6 days. Several laboratory tests such as consistency, strength tests, and UPV tests were used to investigate the behavior of various geopolymer mixtures. The results confirmed that pumice powder with fly ash can be utilized to create good geopolymeric binders with optimum compressive strengths of 31.02 to 69.90 MPa and optimum flexural strengths of 6.14 to 9.40 MPa. The highest strengths were obtained during the 6-day curing time. The results revealed that the strength of P-FA geopolymer specimens increases by increasing the A/B to a certain value (representing the optimum-active A/B ratio for each type of mixture), the strength decreases more or less than this value. Furthermore, the compressive strength of geopolymer samples with a high content of FA was increased before and after exposure to elevated temperatures.
Strength and Elevated Temperature Resistance Properties of the Geopolymer Paste Produced With Ground Granulated Blast Furnace Slag and Pumice Powder
(Elsevier, 2024) Mohammed, Deeman Talaat; Yaltay, Namik
The production of cement results in large amounts of CO2 emissions. In order to reduce the energy consumption and gas emissions associated with cement production, a new technology called geopolymerisation has been developed to produce concrete without the use of cement by using aluminosilicate materials as raw materials. The purpose of this study is to evaluate the effect of various parameters on the geopolymer based slag/pumice paste. Slag (GGBFS) and pumice powder were used as binders in different slag/pumice ratios (100:0, 90:10, 80:20, 70:30 and 60:40) and activated with sodium hydroxide (NaOH) at 12 and 14 M concentration and cured for 3 and 7 days at 65 degrees C temperature. The effect of these parameters on compressive strength and resistance to elevated temperatures was investigated. Microstructural (SEM, EDX) and chemical (FT-IR, XRD) analyses were also carried out to determine the effect of slag/pumice ratio, NaOH concentration and curing time on the properties of the geopolymer pastes. The results showed that the use of slag significantly increased the compressive strength, while the use of pumice with slag increased the resistance of geopolymer pastes to elevated temperatures. For the geopolymer paste produced with slag, high compressive strength can be obtained by a long period of oven curing, whereas for pumice a short period of oven curing and a long period at low temperature can be used. In conclusion, the most effective of the different parameters was the percentage of slag/pumice in the first degree and then the molarities of NaOH, while the least effective parameter was the curing time.
Structural Performance of Masonry Buildings Under Harsh Climate and Seismic Loads
(Springer int Publ Ag, 2022) Erdil, Baris; Korkut, Fuat; Aydin, Mahsum; Yaltay, Namik
Masonry buildings in Van which is a city located at the eastern border of Turkey exposed to several earthquakes in 2020 while continuously being subjected to harsh weather conditions. Two earthquakes with Mw = 5.9 occurred on the same day and four months after another one hit the region. Besides the earthquakes 124 freeze-thaw cycles occur annually and the region has snow and rain approximately 103 days. Both continuously and periodically applied environmental exposures due to harsh weather conditions and earthquakes that is significant in a short period, affects the structural performance of the masonry buildings adversely. During the field investigations after the earthquakes, it was realized that none of the buildings comply with the available codes, foundations, and walls damaged due to the environmental exposures and those damages either increased or end up with total collapse due to the seismic loading. Besides the damaged buildings, it was observed that some buildings were strengthened locally at the corners. L shaped reinforced concrete columns were added to the cracked corners to increase the lateral capacity of the walls. That strengthening seemed to be adequate for low seismicity because no significant damage was seen.