Farklı inceliklerdeki uçucu külllerin betondaki performanslarının karşılaştırılması
Farklı inceliklerdeki uçucu külllerin betondaki performanslarının karşılaştırılması
Dosyalar
Tarih
1995
Yazarlar
Gökçe, Ahmet
Süreli Yayın başlığı
Süreli Yayın ISSN
Cilt Başlığı
Yayınevi
Fen Bilimleri Enstitüsü
Özet
Bu çalışmada Seyitömer Termik Santralından sağlanmış farklı inceliklerdeki uçucu küllerin betonun önemli bazı özellikleri üzerinde gösterdikleri etkileri karşılaştınlmıştır. Çalışma ana hatlarıyla altı bölümden meydana gelmiştir. Birinci bölümde çalışmaya giriş yapılarak konunun önemine değinilmiş, araştırmanın genel amacı ve kapsamı açıklanmıştır. İkinci bölümde uçucu küller ile ilgili genel bilgiler verilmiş ve önceden yapılan çalışmalar değerlendirilmiştir. Deneysel çalışmalar ile ilgili konulara giriş yapılan üçüncü bölümde ise öncelikle bu çalışmada üretilen betonlar için kullanılan malzemeler tanıtılmıştır. Seyitömer uçucu külü, çimento ve agregalar hakkında gerekli bilgiler aktarılmıştır. Üretilen betonlara ait karışım oranlan verilmiştir. Bu bölümde son olarak, yapılan taze ve sertleşmiş beton deneyleri anlatılmıştır. Deneysel çalışmalarda üretilecek serilerin karışım oranlan seçilirken belirli bir yaşta kontrol betonunun performansına ulaşmak gibi bir hedef koyulmamış, bu açıdan karışımlar basit ikame metoduyla, çimento ile uçucu külü bire bir yer değiştirerek oluşturulmuştur. İTÜ Yapı Malzemesi Laboratuvannda gerçekleştirilen araştırmada biri kontrol serisi (uçucu külsüz), üçü ince uçucu kül içeren seri, üçü orta incelikte uçucu kül içeren seri ve son üçü de iri uçucu kül içeren seri olmak üzere toplam 10 seri beton üretilmiştir. Her incelikte %10, %20 ve %30 olmak üzere üç ayn uçucu kül ikame oram ile çalışılmıştır. Kontrol betonu için çimento dozajı ve uçucu küllü betonlar için toplam bağlayıcı miktan (çimento+uçucu kül) 300 kg/m3 olarak seçilmiştir. Taze beton deneylerinde belirli bir işlenebilirlik değeri elde edebilmek için gerekli olan su miktarları araştırılmıştır. Sertleşmiş betonlar üzerinde basınç dayanımı, eğilme dayanımı, ultrases hızı, kılcal su emme, hacimsel su emme, birim ağırlık ve deniz suyu ortamına dayanıklılık deneyleri yapılmıştır. Dördüncü bölümde taze ve sertleşmiş beton deney sonuçlan toplu olarak sunulmuştur. Beşinci bülümde elde edilen bu toplu sonuçlann değerlendirilmesi ve irdelenmesi yapılmıştır. Son bölümde ise çalışmanın bütününden elde edilen bulgular ışığında ulaşılan sonuçlar açıklanmış ve üzerinde durulması gereken önemli noktalara dikkat çekilmiştir. İncelik faktörünün uçucu küllü betonlann özelliklerini bir çok yönden önemli ölçüde etkilediği ortaya çıkarılmışır.
Concrete technology has been changing rapidly. Industrial research has taken the lead in developing new innovative materials for the past 20 years, that, when used to their full potential, greatly enhance the properties of hydraulic cement concrete. Concrete is no longer a mixture of one, two, and three shovels of cement, sand, and coarse aggregate, respectively, but many changes have resulted from the development of technology in new mineral admixtures and chemical admixtures. The most often used mineral admixture in the modern concrete industry is the pozzolan. Two types of pozzolanic materials are readily available such as natural and artificial. The natural ones which are of volcanic origin such as trass, pumicites and perlite. Those of the second type are man-made pozzolans which include such by products as fly ash (the burning of coal), blast furnace slag (steel industry) and silica fume (silicon and ferrosilicon manufacture). Of the man-made pozzolans, fly ash is probably the most frequently used in concrete. Fly ash is " the finely divided residue resulting from the combustion of ground or powdered coal which is transported form the fire box through the boiler by flue gases " (ACI 116). It is generally classifed as Class F or Class C. Depending on the origin of coals burned, Class F is usually produced by burning anthracite or bituminous coal and Class C is normally produced by burning sub-bituminous coal or lignite. Fly ash provides many benefits in concrete, some of which are:. Improved workability. Reduced bleeding (which could be beneficial or not). Improved long-term strength. Generally reduced generation of heat. Reduced permeability In Turkey, 15 million tons of fly ash is provided from coal-fired electrical power plants. Unfortunately, this material almost is not used in construction sector in the country. It is well understood that in a country where cement production rate is 25 million tons annually, it should be kept in mind that 15 million tons of fly ash production is a very big potential. Many countries use almost all of the provided fly ashes in construction sector and also prevent the environmental pollution as a result. The concrete industry, which is rapidly developing in Turkey has reached to the economical and technological level of using this mineral admixture. xni The important thing to do is to characterize the fly ashes and use them consciously in construction sector and especially concrete industry of Turkey. The main object of this study is to add more information to the limited knowledge about the fly ashes in Turkey. The purpose of this study is to compare the performances of the fly ashes of three different fineness that have been obtained from Seyitömer Power Plant. The study is composed of 6 chapters; the first one is the introduction. In this part the attention is drawn on to the importance of the subject and general purpose of the study is explained. In the second chapter, general knowledge about the fly ashes is given and the former studies are compared. In the third chapter, the materials used in concrete production such as fly ashes, cement and aggregates, are explained. The mix proportions of concretes used were given. The fresh and hardened concrete experiments are described also in this chapter. The collected results that are maintained from the experimental studies are given in the forth chapter. In the fifth chapter, the results that are obtained are evaluated and discussed. In the last chapter, the conclusions drived from this study are summarized and attention is drawn to the important points that should be taken into consideration. By using fly ashes at different replacement ratios and finenesses, total of 10 series of concrete were produced. Table 1 shows the mix proportions of these concretes. Table 1. The mix proportions of the produced series XIV The results maintained from the study of experiments with fresh and hardened concrete are given below in tables. Table 2. Experimental results about fresh concrete properties Table 3. Compressive strenght results maintained from the experimental studies XV Table 4. Flexural strenght results maintained from the experimental studies Table 5. Pulse velocity results maintained from the experimental studies XVI Table 6. Experimental results about some physical properties of the hardened concretes Table 7. Comparison of the compressive strenghts of the specimens which have been kept in standart cure water and sea water XVll Table 8. Comparison of the flexural strenghts of the specimens which have been kept in standart cure water and sea water Table 9. Comparison of the pulse velocity values of the specimens in standart cure water and sea water Finally the following results are obtained by the evaluation of the experimental study : 1- The fineness factor affects the uniformity of the fly ash. The physical and chemical properties of fly ash from the same source change depending on this factor. 2- Pozollanic activity experiment carried out according to the TS 639 is thought to be inconvenient for fly ash like Seyitömer's which increases the water requirement by a considerable amount. 3- As the fly ash particles gets larger and the replacement ratio increases, the water requirement of fresh concrete also increases. The main reason of this increased water demand of fly ash is the stuructural change occured in it for larger particles, that is, as the size of particles gets larger, they loose their spherical forms and become XV1U shapeless, porous and rough. This structure naturally increases the water requirement. 4- It is understood that the fineness factor shows similar effects on the compressive and flexural strenght developments of the concrete. In the series at early ages the fly ash behaves like an inert compound and the influence of the fineness factor on the strength development does not appear. For this reason, the series with fly ash at the same replacement ratio at early ages take values close to each other independing of fineness. In strenght values of 28 th and 91 st days, the effect of the fly ash fineness appears in considerable levels. 5- From the data obtained by pulse velocity measurements, the effect of the fineness factor at early and later ages for ten percent replacement ratio can not be detected. In the other replacement ratios, also including the values of 7 days, the ultrasonic pulse velocities are affected by the fly ash fineness differences and as the replacement ratio increases, this effect appears more clearly. 6- It is understood that in the series with fine fly ash, generally at later ages,it shows positive contribution to the physical properties of concrete. On the contrary, a positive effect is not seen on physical properties of series including medium fine and large fly ash. 7- Depending on the fineness factor, in marine environment the series of fly ash exposed to wetting-drying cycles, the differentiating data cannot be obtained according to the performances shown to the above mentioned environments. The compressive and flexural strenghts and ultrasonic pulse velocity of the specimens kept in marine environment are smaller than those of the specimens which are kept in standart cur© conditions. But, the amount of the decrease depending on the fly ash fineness and replacement ratios is not clear enough to relate them among the series.
Concrete technology has been changing rapidly. Industrial research has taken the lead in developing new innovative materials for the past 20 years, that, when used to their full potential, greatly enhance the properties of hydraulic cement concrete. Concrete is no longer a mixture of one, two, and three shovels of cement, sand, and coarse aggregate, respectively, but many changes have resulted from the development of technology in new mineral admixtures and chemical admixtures. The most often used mineral admixture in the modern concrete industry is the pozzolan. Two types of pozzolanic materials are readily available such as natural and artificial. The natural ones which are of volcanic origin such as trass, pumicites and perlite. Those of the second type are man-made pozzolans which include such by products as fly ash (the burning of coal), blast furnace slag (steel industry) and silica fume (silicon and ferrosilicon manufacture). Of the man-made pozzolans, fly ash is probably the most frequently used in concrete. Fly ash is " the finely divided residue resulting from the combustion of ground or powdered coal which is transported form the fire box through the boiler by flue gases " (ACI 116). It is generally classifed as Class F or Class C. Depending on the origin of coals burned, Class F is usually produced by burning anthracite or bituminous coal and Class C is normally produced by burning sub-bituminous coal or lignite. Fly ash provides many benefits in concrete, some of which are:. Improved workability. Reduced bleeding (which could be beneficial or not). Improved long-term strength. Generally reduced generation of heat. Reduced permeability In Turkey, 15 million tons of fly ash is provided from coal-fired electrical power plants. Unfortunately, this material almost is not used in construction sector in the country. It is well understood that in a country where cement production rate is 25 million tons annually, it should be kept in mind that 15 million tons of fly ash production is a very big potential. Many countries use almost all of the provided fly ashes in construction sector and also prevent the environmental pollution as a result. The concrete industry, which is rapidly developing in Turkey has reached to the economical and technological level of using this mineral admixture. xni The important thing to do is to characterize the fly ashes and use them consciously in construction sector and especially concrete industry of Turkey. The main object of this study is to add more information to the limited knowledge about the fly ashes in Turkey. The purpose of this study is to compare the performances of the fly ashes of three different fineness that have been obtained from Seyitömer Power Plant. The study is composed of 6 chapters; the first one is the introduction. In this part the attention is drawn on to the importance of the subject and general purpose of the study is explained. In the second chapter, general knowledge about the fly ashes is given and the former studies are compared. In the third chapter, the materials used in concrete production such as fly ashes, cement and aggregates, are explained. The mix proportions of concretes used were given. The fresh and hardened concrete experiments are described also in this chapter. The collected results that are maintained from the experimental studies are given in the forth chapter. In the fifth chapter, the results that are obtained are evaluated and discussed. In the last chapter, the conclusions drived from this study are summarized and attention is drawn to the important points that should be taken into consideration. By using fly ashes at different replacement ratios and finenesses, total of 10 series of concrete were produced. Table 1 shows the mix proportions of these concretes. Table 1. The mix proportions of the produced series XIV The results maintained from the study of experiments with fresh and hardened concrete are given below in tables. Table 2. Experimental results about fresh concrete properties Table 3. Compressive strenght results maintained from the experimental studies XV Table 4. Flexural strenght results maintained from the experimental studies Table 5. Pulse velocity results maintained from the experimental studies XVI Table 6. Experimental results about some physical properties of the hardened concretes Table 7. Comparison of the compressive strenghts of the specimens which have been kept in standart cure water and sea water XVll Table 8. Comparison of the flexural strenghts of the specimens which have been kept in standart cure water and sea water Table 9. Comparison of the pulse velocity values of the specimens in standart cure water and sea water Finally the following results are obtained by the evaluation of the experimental study : 1- The fineness factor affects the uniformity of the fly ash. The physical and chemical properties of fly ash from the same source change depending on this factor. 2- Pozollanic activity experiment carried out according to the TS 639 is thought to be inconvenient for fly ash like Seyitömer's which increases the water requirement by a considerable amount. 3- As the fly ash particles gets larger and the replacement ratio increases, the water requirement of fresh concrete also increases. The main reason of this increased water demand of fly ash is the stuructural change occured in it for larger particles, that is, as the size of particles gets larger, they loose their spherical forms and become XV1U shapeless, porous and rough. This structure naturally increases the water requirement. 4- It is understood that the fineness factor shows similar effects on the compressive and flexural strenght developments of the concrete. In the series at early ages the fly ash behaves like an inert compound and the influence of the fineness factor on the strength development does not appear. For this reason, the series with fly ash at the same replacement ratio at early ages take values close to each other independing of fineness. In strenght values of 28 th and 91 st days, the effect of the fly ash fineness appears in considerable levels. 5- From the data obtained by pulse velocity measurements, the effect of the fineness factor at early and later ages for ten percent replacement ratio can not be detected. In the other replacement ratios, also including the values of 7 days, the ultrasonic pulse velocities are affected by the fly ash fineness differences and as the replacement ratio increases, this effect appears more clearly. 6- It is understood that in the series with fine fly ash, generally at later ages,it shows positive contribution to the physical properties of concrete. On the contrary, a positive effect is not seen on physical properties of series including medium fine and large fly ash. 7- Depending on the fineness factor, in marine environment the series of fly ash exposed to wetting-drying cycles, the differentiating data cannot be obtained according to the performances shown to the above mentioned environments. The compressive and flexural strenghts and ultrasonic pulse velocity of the specimens kept in marine environment are smaller than those of the specimens which are kept in standart cur© conditions. But, the amount of the decrease depending on the fly ash fineness and replacement ratios is not clear enough to relate them among the series.
Açıklama
Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 1995
Anahtar kelimeler
Beton,
Uçucu kül,
Concrete,
Fly ash