Afşin-Elbistan uçucu külünün beton ve çimento katkısı olarak kullanabilirliğinin çimento hamuru ve harçlarının üzerinde yapılan deneylerle araştırılması

TEZ4685Tez (Doktora) -- Çukurova Üniversitesi, Adana, 2003.Kaynakça (s. 297-307) var.xxxvii, 307 s. ; 30 cm.…Bu çalışma Ç.Ü. Bilimsel Araştırma Projeleri Birimi Tarafından Desteklenmiştir. Proje No:fbe 2002 d 17

İki eksenli eğilme momenti ve eksenel yük altındaki kolonların sonlu parçalar metodu ile analizi

TEZ2625Tez (Yüksek Lisans) -- Çukurova Üniversitesi, Adana, 1997.Kaynakça (s. 103-104) var.v, 106 s. ; 30 cm.…Bu çalışma Ç.Ü. Bilimsel Araştırma Projeleri Birimi Tarafından Desteklenmiştir. Proje No: FBE 96. 109

Traffic Safety at Median Ditches: Steel vs. Concrete Barrier Performance Comparison Using Computer Simulation

In Turkey, concrete V-shaped ditches are formed at the median section of divided highways to provide drainage. Recent accidents show that these ditches actually present safety risks to vehicles entering the medians. Vehicles either cross over the ditch, roll over, or become trapped in the ditch, depending upon the mass, size, speed, and angle of the entering vehicle. To overcome this safety risk and reduce the severity of these accidents, longitudinal barriers are installed along these ditches. Currently, in Turkey, steel barriers are extensively used to improve traffic safety at median ditches. In this paper, the crash performances of steel and concrete barriers used at medians with ditches are compared. A model of a standard steel EDSP-1.33 barrier and a model of a newly developed concrete C470 barrier were constructed, and impact simulations were performed for when they are installed at a ditch slope break point. A nonlinear finite element program, LS-DYNA, was used for the analysis. A 13,000 kg bus model was used to impact both barriers in accordance with European standard requirements for crash tests. Simulation results show that when the steel EDSP-1.33 barrier is used, the bus has the potential for excessive penetration of the ditch, with significant barrier deformation. Moreover, the barrier damage is extensive, resulting in increased maintenance costs. On the other hand, the concrete C470 barrier successfully contains and redirects the 13,000 kg bus impact, with minimal barrier deformation and safety risk. Even though the concrete barrier slides toward the inside of the ditch, the bus does not enter the ditch area and exits the barrier in a stable manner. Therefore, to increase traffic safety at ditches located at the median section of divided highways in Turkey, utilization of the newly developed concrete barrier C470 is recommended

THE PROPERTIES OF SODIUM SULFATE-ACTIVATED CEMENT MORTARS CONTAINING FLY ASH

Portland çimentosunun icadından önce mineral katkılar sönmüş kireçle karıştırılarak harç imalinde bağlayıcı olarak kullanılmıştır. Günümüzde de mineral katkılar, ekonomik olduklarından ve özellikle taze ve sertleşmiş beton ile harcın bazı özelliklerinde faydalı değişiklikler sağladıklarından, çimentoyla birlikte kullanılmaktadır. Çalışmada, Portland çimentosuna yüksek oranda kalsiyum içeren uçucu kül ve aktifleştirici susuz sodyum sülfat (Na2SO4) ilaveleriyle üretilmiş harç numunelerinin dayanımları incelenmiştir. Uçucu kül, çimento ile ağırlıkça % 10, % 20, % 30 ve % 40 oranlarında ikame edilerek kullanılırken, sodyum sülfat ise toplam bağlayıcı miktarının % 0, % 2 ve % 4 oranlarında kullanılarak kum/çimento oranı 2,75 ve su/çimento oranı ise 0,485 olan harç numuneleri üretilmiştir. Uçucu kül katkılı harç numunelerine susuz sodyum sülfatın aktivatör olarak ilavesinin, harç numunelerinin boşluk oranlarına ve basınç ile eğilmede çekme dayanımlarına etkileri 3, 7, 28 ve 90 günlük kür süreleri sonunda tespit edilmiştir. Bulgular, uçucu külün % 20 ikame oranına kadar kullanılabileceğini, erken yaş dayanım kayıplarının ise bağlayıcı miktarının en fazla % 2'si kadar Na2SO4kullanılarak telafi edilebileceğini göstermiştir.Prior to the invention of Portland cement, mineral admixtures had been used by blending with calcium hydroxide in the production of mortar mixtures. Today, since the mineral admixtures are economic and ensure useful alterations in some properties of fresh and hardened concrete and mortar, they have been used with Portland cement. In this study, the strengths of cement mortars containing high calcium fly ash and sodium sulfate (Na2SO4) as activator were examined. While fly ash was used at 10%, 20%, 30% and 40% replacement by weight of cement, sodium sulfate was used 2% and 4% by mass of binder. The mortar mixture proportions were 1:2.75:0.485 by weight of cement, sand and water, respectively. The effects of addition of sodium sulfate into cement mortars were investigated through the porosity, compressive and flexural strength tests at 3, 7, 28 and 90 days. The findings showed that fly ash could be used in the cement mortars up to 20% replacement ratio, and that the early term strength losses could be compensated by using 2% sodium sulfate in the mixture

Compressive strength prediction models for cementitious composites with fly ash using machine learning techniques

In this study, it was proposed a novel prediction model to predict compressive strength of mortar samples having different properties. For this purpose, 8 different fly ashes were used in mortar mixture as a replacement of cement by weight. Mortars including different ashes were prepared with addition of 10%, 20%, 30% and 40% fly ash. Compressive strength of the produced mortar samples were evaluated at 1, 3, 7, 28, 90 and 365 days. Totally 196 test samples were produced and mechanically tested. The relation between compressive strength values (dependent value) and SiO2 + Al2O3 + Fe2O3 content, age, and fly ash replacement ratios (independent values) were predicted by machine learning techniques such as Artificial Neural Networks (ANN) and Adaptive-Network Based Fuzzy Inference Systems (ANFIS). The findings were compared with traditional statistical method Multi-Linear Regression (MLR) to prove proposed models. According to test results it has an incentive effect for future studies to know that GA based Antis model produce better results to estimate compressive strength using chemical composition of fly as in terms of SiO2 + Al2O3 + Fe2O3, fly ashsubstation ratio in the mortar and age of the sample. (C) 2020 Elsevier Ltd. All rights reserved

Design of a linear to circular polarization converter integrated into a concrete construction for radome applications

© 2021 The Author(s). Published by Cambridge University Press in association with the European Microwave Association.In this paper, we present a linear to circular polarization converter integrated in a concrete structure to eliminate signal transmission problem originated from the concrete buildings in microwave regime. Two polarization converter samples and a control specimen made by traditional concrete are designed and their signal transmission responses are compared experimentally. Axial ratio values which can be calculated by the ratio between the co-polar transmission and cross-polar transmission results of the proposed samples are below 3 dB and highly sufficient for linear to circular polarization conversion activity. The operating frequency for the proposed sample 1 is between 6 and 6.5 GHz with 500 MHz of bandwidth. The proposed sample 2 exhibits dual-band operation covering frequency bands, 4.58-5.13 and 6.0-6.4 GHz with bandwidths of 550 and 400 MHz, respectively. Operating frequencies of the samples are in the WIMAX frequency bands. In addition, the liner to circular polarization converter design integrated to concrete has a huge potential to improve reflection and directivity parameters of many antennas if it is considered as a radome

Metamaterial sensor application concrete material reinforced with carbon steel fiber

In this paper, a rectangular split ring resonator-type metamaterial (MTM) sensor application is demonstrated in order to examine concrete materials. First, different types of concrete materials including carbon steel fiber with the purity ratio of 0.5%, 1% and 1.5% were prepared by using cement and water and their electrical properties were determined via Nicolson-Ross-Weir tehcnique. After that, compatible MTM-based sensor structure was designed and proposed. In order to find out the effect of the humidity on the concrete material, all samples were kept in the water pool for 28 days, the samples were then taken out and the temperature effect on the concrete materials was observed by increasing the heat up to 30 degrees and 70 degrees in the oven. The simulated resonance frequency shifts were observed at 910 MHz for concrete material sensor, 120 MHz for humidity sensor validation and 400 MHz for temperature sensor applications. By having large bandwidth in different fiber contents and validating the physical sensor applications as temperature and humidity, it was shown that the proposed study has novelty in the area of MTM-based sensor applications when it is compared with current state-of-the-art