Mineral katkılar kullanılarak üretilen kendiliğinden yerleşen betonların mekanik özeliklerinin ve dayanıklılığının incelenmesi

06.03.2018 tarihli ve 30352 sayılı Resmi Gazetede yayımlanan “Yükseköğretim Kanunu İle Bazı Kanun Ve Kanun Hükmünde Kararnamelerde Değişiklik Yapılması Hakkında Kanun” ile 18.06.2018 tarihli “Lisansüstü Tezlerin Elektronik Ortamda Toplanması, Düzenlenmesi ve Erişime Açılmasına İlişkin Yönerge” gereğince tam metin erişime açılmıştır.Bu çalışma, mineral katkıların çimento ile değişik ikame oranlarında kullanılmasıyla üretilen KYB'lerin taze haldeki işlenebilirlik, sertleşmiş halde ise mekanik ve dayanıklılık özelliklerinin incelenmesi amacıyla gerçekleştirilmiştir. Bu sebeple ilk olarak uçucu kül, yüksek fırın cürufu (YFC), doğal zeolit, kalker tozu, bazalt tozu ve mermer tozunun farklı yer değiştirme oranlarında kullanılması ile üretilen betonların taze beton deneyleri ile kendiliğinden yerleşebilirlik özelliklerini sağlayıp sağlamadıklarına bakılmış ve bu özelliği sağlamayan mineral katkıların değişik ikame oranlarındaki karışımları elenerek bu özelliği sağlayan betonların ise mekanik ve dayanıklılık özellikleri incelenmiştir.Taze beton deneyleri olarak çökme-yayılma (slump-flow), T50 süresi, V hunisi ve L kutusu deneyleri yapılarak mineral katkıların çimento ile farklı ikame oranlarındaki karışımlarının ?kendiliğinden yerleşebilirlik? özellikleri araştırılmıştır. Mekanik özellikler ise, basınç dayanımı, ultrases geçiş hızı ve elastisite modülü deneyleri ile belirlenmeye çalışılmıştır. Laboratuvar ortamından çıkarak sahada bu betonların ?kendiliğinden yerleşebilirlik? özelliklerini incelemek amacıyla farklı karışımlarda, büyük boyutlu (300x150x20cm), L şekilli ve sıkı donatılı yapısal perde elemanları üretilmiştir. Bu elemanların değişik bölgelerinden karot numuneler alınarak, yatayda ve düşeyde kendi ağırlığı ile herhangi bir sıkıştırma uygulanmadan sıkı donatılı kalıbına yerleşen betonların döküm noktası uzaklığına göre dayanım değişimleri, birim ağırlıkları ve su emme oranları incelenmiştir. Ayrıca bu perde elemanlara Schmidt çekici uygulanarak yatay ve düşeyde dayanımın üniformluluğu belirlenmeye çalışılmıştır.Dayanıklılık deneyleri olarak su emme, hızlı klorür geçirgenliği, basınçlı su derinliği (impermeabilite), yüksek sıcaklık etkisi ve sülfat direnci deneyleri gerçekleştirilmiştir.Deney sonucu elde edilen veriler değerlendirildiğinde, YFC'nin çimento ile % 60 oranında ikame edilmesiyle üretilen karışım işlenebilirlik deneylerinde en yüksek işlenebilirlik değerleri vermiştir. Erken yaş dayanımı olarak (7. gün) en yüksek dayanımı çimentonun mermer tozu ile % 10 oranında ikame edilmesiyle üretilen karışım, 400 günlük numuneler üzerinde yapılan basınç dayanımı sonucunda ise en yüksek dayanımı uçucu külün çimento ile % 25 oranında ikame edilmesiyle üretilen karışım vermiştir. Farklı bileşimde üretilip perde elemanlarına yerleştirilen KYB'lerin dar ve sıkı donatılı kalıplar içerisinde homojen olarak yayıldığı görülmüştür. Durabilite deneyleri sonucunda, uçucu kül ve YFC ikameli karışımların diğer karışımlara göre daha iyi performans sergilediği gözlemlenmiştir.In this study, it was investigated that the effect of different mineral additives on the workability, mechanical and durability properties of self compacting concrete. For this reason, fly ash, granulated blast furnace slag (GBFS), natural zeolite, limestone powder, basalt powder and marble powder were used in different substituation rates and it was carried out the workability tests to determine `?self compactibility?? and the mixtures which provided this qualification, tests proceeded to determine mechanical and durability properties of SCC.As workability tests, slump-flow, T50, V-funnel and L-box tests were performed and `?self compactibility?? were determined. Mechanical properties were determined by compressive strength tests, ultra-sound velocity tests and elastic modulus tests. Moreover, large-sized (300x150x20 cm), L-shaped and double-sided reinforcement mesh equipment which was designed often combined with a special pre-screen in the form of equipment and placed in molds and different SCC mixtures were produced. Afterwards, by taking into account reinforcement points, the different height levels of the curtain wall core samples taken and these samples were made on the compressive strength, unit weight and water absorption tests.Impermeability tests, rapid chloride ion permeability tests, high temperature effect tests and sulphate resistance tests were performed as durability tests on the SCC.When test results were evaluated it can be seen that, the best results were obtained in the workability tests by granulated blast furnace slag 60% substituation rate with cement in SCC. As early age compressive strength, marble powder has shown the best performance by 10% substituation rate with cement. According to 400 days compressive strength test results, fly ash shown the best performance by 25% substituation rate with cement. It can be seen that self compacting concretes consolidated by its own weight homogeneously in the narrow curtain wall reinforcement construction elements. Finally, GBFS and fly ash SCC mixtures performed better performance than other mixtures as durability properties

Molecular characterization of cereal yellow dwarf virus-RPV in grasses in European part of Turkey

Yellow dwarf viruses (YDVs) are economically destructive viral diseases of cereal crops, which cause the reduction of yield and quality of grains. Cereal yellow dwarf virus-RPV (CYDV-RPV) is one of the most serious virus species of YDVs. These virus diseases cause epidemics in cereal fields in some periods of the year in Turkey depending on potential reservoir natural hosts that play a significant role in epidemiology. This study was conducted to investigate the presence and prevalence of CYDV-RPV in grasses and volunteer cereal host plants including 33 species from Poaceae, Asteraceae, Juncaceae, Geraniaceae, Cyperaceae, and Rubiaceae families in the Trakya region of Turkey. A total of 584 symptomatic grass and volunteer cereal leaf samples exhibiting yellowing, reddening, irregular necrotic patches and dwarfing symptoms were collected from Trakya and tested by ELISA and RT-PCR methods. The screening tests showed that 55 out of 584 grass samples were infected with CYDV-RPV in grasses from the Poaceae family, while none of the other families had no infection. The incidence of CYDV-RPV was detected at a rate of 9.42%. Transmission experiments using the aphid species Rhopalosiphum padi L. showed that CYDV-RPV was transmitted persistently from symptomatic intact grasses such as Avena sterilis, Lolium perenne and Phleum exratum to barley cv. Barbaros seedlings. PCR products of five Turkish RPV grass isolates were sequenced and compared with eleven known CYDV-RPV isolates in the GenBank/EMBL databases. Compared nucleotide and amino acid sequences of CYDV-RPV isolates showed that the identities ranged from 40.38 - 95.86 % to 14.04 - 93.38%, respectively. In this study, 19 grass species from the Poaceae family and two volunteer cereal host plants were determined as natural reservoir hosts of CYDV-RPV in the cereal growing areas of Turkey. © 2020 Authors

Optimización de las propiedades de durabilidad del hormigón que contiene ceniza, utilizando el enfoque Taguchi y análisis Anova]

In this study, optimization of durability properties of the concretes was performed by using Taguchi method and Anova analysis. The durability performance of the concretes was evaluated using measurements of rapid chloride ion permeability, freezing-thawing resistance and sorptivity tests. The degree of freezing-thawing resistance was assessed the change of weight, ultrasonic pulse velocity (UPV) and flexural strength after 300 cycles. The use of fly ash improved the rapid chloride ion permeability and sorptivity of concrete. The best resistance to chloride ion permeability was obtained from a combination of type of class C fly ash content of 102 kg/m(3) with PC content of 332 kg/m(3). There was a remarkable reduction in the UPV after the specimens are subjected to freezing-thawing cycles. The amounts of flexural strength loss have been measured in the range of 6.70 - 29.83%. The use of type of class C fly ash positively affected freezing-thawing resistance of concrete. The Anova analysis indicated that the cement dosage has an utmost importance on the sorptivity level, chloride ion permeability and ultrasonic pulse velocity loss. Furthermore, the fly ash percentage has an utmost importance on the weight loss and flexural strength loss

Behaviour of Geopolymer Mortars after Exposure to Elevated Temperatures

In this study it was investigated the behavior of class F fly ash based geopolymer mortars subjected to elevated temperatures. Geopolimer composites were prepared with CEN-sand, water, fly ash as the binder, nSiO2Na2O and NaOH mixture combination as alkali activator. After mixing fresh geopolymer mixture, prismatic specimens were prepared using 40 mm × 40 mm × 160 mm prism molds. After molding, fresh geopolymer mortar samples with their mold were subjected to heat curing at 50 °C, 60 °C, 70 °C, 80 °C, 90 °C and 100 °C temperature for 48 hours in an oven. After 48 hours initial heat curing, the hardened samples were taken out of their mold. Then, they were further cured by leaving them in laboratory environment at about 22 ± 2 °C temperature, until 28 days together with heat curing duration. At the end of 28 days, geopolymer mortar samples developed flexural strength values between 2,9 MPa and 8,51 MPa. Geopolymer mortar samples developed compressive strength values between 7,63 MPa and 50,64 MPa. High temperature experiments were conducted to observe behaviour of geopolymer mortars at elevated temperatures. The control cement mortar mixtures were also prepared and subjected to high temperature exposure in comparison to geopolymer mortar mixtures. Control cement mortars were cured at laboratory environment for 28 days without initial temperature curing. Control cement mortar mixtures and geopolymer mortar mixtures were exposed to elevated temperatures of 200 °C, 400 °C, 600 °C and 800 °C temperature. The unit weight, ultrasonic pulse velocity, flexural and compressive strength of all mixtures were measured before and after high temperature exposure. Scanning electron microscope (SEM) images of the mixtures were taken and X-ray fluorescence (XRF) spectrometer analyses were carried out. It was observed that there was an increase in the flexural and compressive strengths of some geopolymer mortars after high temperature exposure. In general, geopolymer mortars exhibited better performance at elevated temperatures in comparison to control cement mortar mixture. DOI: http://dx.doi.org/10.5755/j01.ms.24.4.18829</p

Self-compacting concrete incorporating filler additives: Performance at high temperatures

An experimental investigation was conducted to evaluate the performance of self-compacting concrete (SCC) subjected to elevated temperatures. For this purpose, Portland cement (PC) was replaced with limestone powder (LP), basalt powder (BP) and marble powder (MP) in various proportioning rates. Half of the total specimens for each mix type were studied by adding polypropylene (PP) fibers to improve the understanding of the effect of PP fibers on the behavior of SCCs subjected to high temperatures. SCC mixtures were prepared with water to cement ratio of 0.33 and polypropylene fibers content was 2 kg/m(3) for the mixtures containing polypropylene fibers. Specimens were heated up to elevated temperatures (200, 400, 600 and 800 degrees C) at the age of 56 days. Then, tests were conducted to determine loss in weight and compressive strength. Moreover, the change of ultrasonic pulse velocity (UPV) was determined and surface crack observations were made after being exposed to elevated temperatures. Experimental results indicate that a severe strength loss was observed for all of the SCC mixtures after exposure to 600 degrees C, particularly the concretes containing polypropylene fibers though they reduce and eliminate the risk of the explosive spalling. At higher replacement levels of LP. BP and BP further lower resudial strength was observed. In terms of percent residual properties, control mixture specimens performed better than filler additive specimens for all heating cycles. (C) 2011 Elsevier Ltd. All rights reserved

Taguchi and Anova approach for optimisation of design parameters on the compressive strength of HSC

In this study, the effect of cement type, cement dosage, superplasticiser type and mineral admixture on the compressive strength of high-strength concrete (HSC) was investigated experimentally and statistically. The concrete mixtures were prepared using two different cement types (ordinary Portland cement and white Portland cement), two different cement dosages (450 and 550 kg/m(3)), two different superplasticisers (polycarboxylate based and modified polycarboxylate based) and two different mineral admixtures (silica fume and fly ash). After being cured under the standard conditions for 2, 7, 28 and 90 days, the specimens were tested for the compressive strength. The Taguchi method was used to determine the optimum conditions and to reduce the number of experiments. Five control factors such as time, cement type, cement dosage, superplasticiser and mineral admixture were used for this study. The results showed that the parameter that most influenced the compressive strength properties of HSC was time

The influence of coarse aggregate type on mechanical properties of fly ash additive self-compacting concrete

This paper presents the results of an experimental investigation carried out to evaluate the effectiveness of various types of coarse aggregates on fresh and hardened properties of self-compacting concrete (SCC). For this purpose, five different coarse aggregate types (basalt, marble, dolomite, limestone and sandstone) were used to produce SCC containing fly ash. The water to binder ratio is maintained at 0.33 for all mixtures. The examined properties include workability, abrasion, compressive strength, static and dynamic elastic moduli and ultrasonic pulse velocity. Workability of SCC was determined using slump-flow, T-50 time and V-funnel tests. The results show that it is possible to successfully utilize various types of coarse aggregates in producing SCC. The abrasion depths were within the range of 0.98-3.02 mm and mass losses were within the range of 0.71-3.24% after exposure to abrasion. The highest compressive strength values were measured in SCC mixture prepared with basalt aggregate while the lowest compressive strength values were noted in SCC mixture prepared with limestone aggregate at 28 d, 56 d and 90 d. Ultrasonic pulse velocity has increased by increasing compressive strength for all SCC mixtures. It was concluded that among the various types of coarse aggregates considered, the best performance has been obtained for the mixture containing basalt aggregate as hardened properties of SCC. (C) 2012 Elsevier Ltd. All rights reserved

The influence of coarse aggregate type on mechanical properties of fly ash additive self-compacting concrete

This paper presents the results of an experimental investigation carried out to evaluate the effectiveness of various types of coarse aggregates on fresh and hardened properties of self-compacting concrete (SCC). For this purpose, five different coarse aggregate types (basalt, marble, dolomite, limestone and sandstone) were used to produce SCC containing fly ash. The water to binder ratio is maintained at 0.33 for all mixtures. The examined properties include workability, abrasion, compressive strength, static and dynamic elastic moduli and ultrasonic pulse velocity. Workability of SCC was determined using slump-flow, T-50 time and V-funnel tests. The results show that it is possible to successfully utilize various types of coarse aggregates in producing SCC. The abrasion depths were within the range of 0.98-3.02 mm and mass losses were within the range of 0.71-3.24% after exposure to abrasion. The highest compressive strength values were measured in SCC mixture prepared with basalt aggregate while the lowest compressive strength values were noted in SCC mixture prepared with limestone aggregate at 28 d, 56 d and 90 d. Ultrasonic pulse velocity has increased by increasing compressive strength for all SCC mixtures. It was concluded that among the various types of coarse aggregates considered, the best performance has been obtained for the mixture containing basalt aggregate as hardened properties of SCC. (C) 2012 Elsevier Ltd. All rights reserved