Değişik ortamlarda kür uygulanmış translı portland çimentolu betonların özellikleri
Concrete properties of portland and pozzolanic cements curing on different conditions
- Tez No: 66666
- Danışmanlar: PROF. DR. MEHMET UYAN
- Tez Türü: Yüksek Lisans
- Konular: İnşaat Mühendisliği, Civil Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1997
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: İnşaat Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 104
Özet
ÖZET Mineral katkı maddeleri puzolanik özeliklere sahip doğal veya suni maddeler olup, beton teknolojisinde çeşitli amaçlarla yaygın kullanım alanı bulmaktadırlar. Bu amaçların başında da betonun dayanıklılığının iyileştirilmesi ve nihai dayanımının artırılması gelmektedir. Ayrıca katkı maddelerinin çimento endüstrisinde kullanımı da ekonomik ve çevresel birtakım faydalar sağlamaktadır. Bu çalışmada, Traslı Çimentolarla üretilen beton numunelerin sabit sıcaklıklardaki ve değişebilen hava koşullarındaki kür şartlarının, betonun dayanımına ve dayanıklılığına etkileri incelenmiştir. 300 ve 350 dozlu beton numuneler üretilmiştir. Numunelerde TÇ-32.5 ve PÇ-42.5 tip bağlayıcılar kullanılmıştır. Üretim boyunca serilerin granülometrisi değiştirilmemiştir. Maksimum dane çapı olarak 16 mm seçilmiştir. Üretilen serilerin akıcı kıvamda olmaları istenmiş olup, çökmelerinin 14 cm olmasına çalışılmıştır. Bu amaçla her seri için ayrı ayrı su/ çimento oranları, deneme betonları üretildikten sonra hesaplanmıştır. Toplam 20 seri beton dökülmüş olup, 320 adet numune üretilmiştir. Numune boyutu, 70x70x280 mm prizma olmuştur. Üretilen numuneler 90 gün boyunca 5°C ( % 90 bağıl nem) ile 10°C ( %80 b. n.), laboratuvar ortamında (20 °C ve %65 b.n.), dış ortamda ve suda (20 °C± 2°C) bekletilmiştir. Küre tabi tutulmuş numuneler üzerinde çekme dayanımı, basınç dayanımı, su emme ve kılcallık deneyleri yapılmıştır. Eğilme ve basınç deneyleri 3., 7., 14., 21., 28. ve 90. günler sonunda numuneler üzerinde uygulanmışken; su emme ve kılcallık olayları 28. gün sonunda numuneler üzerinde incelenmiştir. Deneyler sonucunda kısaca; traslı çimentoyla üretilmiş serilerin karma suyu ihtiyacının inceliğe bağlı olarak artmış olduğu, serilerin dozajı arttıkça su/çimento oranlarının azalmış olduğu, su ortamındaki serilerin basınç ve eğilme dayanımlarının diğer ortamlara nazaran daha iyi gelişmiş olduğurözellikle traslı serilerde düşük sıcaklıklarda dayanım gelişiminin^yavaş olduğu.yine traslı serilerin kontrol serilerini 90. gün sonunda yakalayamamış oldukları, laboratuvar ve su ortamında kürlenmiş olan traslı serilerin şahitlerine göre daha az kılcal su emmiş oldukları gözlenmiştir. ^ Bu sonuçların ışığında; yaygın olarak üretilen traslı çimentoların ortam şartlarına bağlı olarak mekanik özelikler kazanmasından ve betonda karışım suyu ihtiyacını artırabileceğinden ötürü, bu tip çimentoların inşaatların taşıyıcı kısımlarında düşük sıcaklıklarda mümkünse kullanılmaması ya da sıcaklığın 10°C nin altına düştüğü durumlarda kalıp alma sürelerinin bir veya birbuçuk misli uzatılmasının yararlı olacağı ileri sürülebilir. ıx
Özet (Çeviri)
Mineral admixtures have been used over 100 years in the cement technologic Because of energie consumption and economic reasons, many countries have been procuding blended pozzolan Portland cements. In ACI 1 16R a pozzolan is defined as a siliceous or siliceous and aluminuous material, which in itself possesses little or no cementitious value but will, in finely divided form and in the presence of moisture, chemically react with calcium hydroxide at ordinary temperatures to form compounds possessing cementitious properties. The pozzolan which is used in the cement may be a natural or an artifical one. A natural pozzolan is a raw and also a calcined natural material that has pozzolanic materials such as volcanic ash or pumicite, opaline chert and shales, tuffs, and some diatomaceous earths. Every pozzolan has a different petrographic origine and mineralogical structure influencing the qualities of the cement. It is mainly divided into four categories, i.e., unaltered volcanic glass, volcanic tuff, calcined clay or shale, and raw or calcined opaline silica. Typical chemical analyses and mineralogical analysis of some natural pozzolans are given below. Table S.1 Mineralogical analysis of some natural pozzolans [ 5 ] XTable S.2 Typical chemical analyses of some natural pozzolans [ 5 ] Some countries like Greece, Italy, France, Germany, Spain, U. S. A., C. S. I. China, Mexico, Japan, India have a good opportunity to get valueable natural sources. In these countries natural pozzolans are used in great amounts. A lot of dams, bridges, aqueducts, sewers, marine structures have been built concretes containing pozzolan concretes or mortars in this century and now many of them are showing good service ability. Using natural pozzolan blended cements in concretes, have many important advantages according to the scientific publications. They briefly are : - reducing heat of hydration, - resisting to aggressive agents such as pure and acidic waters, chlorides, and sulphates, - preventing expansion caused by alkali- aggregate reaction, - increasing ultimate strength, - decreasing thermal shrinkage, - improving extensibility or resistance to cracking, - lower susceptibility to dissolution and leaching - improving workability. However, pozzolanic cements have also some disadventages. The most important disadventage is, slower early strength gain. It is obvious that, this problem affects curing time. Since 1960's, pozzolanic cements have been produced in Turkey. On the petrographical map of Turkey, it is observed that pozzolanic areas are covered 75% percentages of total solid area. Because of this reason, today the number and the production rate of pozzolanic cements were rapidly increased between 1985 and 1995 and according to the offical informations it reached a peak in 1995. The share of blended and pozzolanic cements was over % 80 in the total production in 1995. Neverthless, consumers have some dissapointments using these cements in constructions, because of prolonging the construction time, despite of their low costs. XIThe study is composed of six 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. The aim of thesis, which is the experimental comparison of the properties of pozzolanic cement concretes with those of portland cement ones, is explained in this chapter. General informations about natural pozzalans and former studies related with this subject are also given in this chapter. In the second chapter, materials which had been used in the experimental study were explained and also the test methods were briefly mentioned. Two type of cements were used during this study. One of them was pozzolanic cement ( TÇ-32.5) and the other one was normal portland cement (PÇ-42.5). The physical testing of these cements were carried out in the I.T.U. Laboratory of Material Science whereas the chemical properties were investigated in the laboratory of AKÇİMENTO cement factory. During experiments the grading of aggregates was kept constant and the maximum aggregate dimension was 16 mm. The water/ cement ratios of concretes were determined to have flow consistency and the slump was 14cm. Five different curing conditions had been chosen such that the temperatures of 5°C and 10°C, humidity conditions of indoor, outdoor, and also in water. The specimens which had 300 kg/m3 and 350 kg/m3 cement content were kept in these conditions for 90 days. On these specimens at 3, 7, 14, 21, 28 and 90 days, tensile and compressive strengths were determined. Water absorption and permeability tests were done on the one of the specimens of 28 days age. Prismatic specimens of 70x70x280 mm were used in this study and 16 specimens were prepared for each mix. Totally 320 specimens were tested. Mix proportions and fresh concrete properties are shown in the Table 3 given below. In the third chapter, the test results were presented and they are repeated in Tables given below. In the fourth chapter, the obtained results were evaluated and considered with regard to graphics. And finally in the last chapter, the results were briefly written, and some advices were given for the further studies. XllXU1Table S. 4 Compressive strengths of hardened concretes Table S. 5 Tensile strengths of hardened concretes xivTable S.6 Results of water absorbtion and capillarity The results of this study are given below: 1) Fresh concrete results - The high fineness of pozzolanic cement caused an increase of water requirement. - For both pozzolanic cement concrete and the reference one, water / cement ratio decreased while cement content increased at constant workability. 2) Hardened concrete results a) Compressive strengths depending on curing conditions - Curing in water was the most positive and effective condition for all kind of specimens. XV- The second higher strengths at three days of age were obtained on the specimens of TÇ-300 series ( containing 300 kg/ m3 pozzolanic cement ) cured in the laboratory. The strength gains in the laboratory and water conditions were 31% and 34%, respectively. The 3% difference occured both in TÇ-300 and TÇ-350 series. However, strength gain rate decreased after 28 days, probably because of unsufficient curing conditions. - Early strength gain for both pozzolanic and portland cement concretes was occured slow at 5°C, 10°C and outdoor conditions due to the slow rate of the hydration process. b) Compressive strengths depending on type of cement - In all conditions, the low pozzolanic cement content series gave the lowest strengths. - Strength development of pozzolanic series cured in low temperature conditions increased after 14 days. At 14 days, compressive strength of PÇ-350 series ( containing 350 kg/ m3 portland cement control concrete ) was 37% more than that of TÇ-350 one and the difference declined to 18% at 21 days. - Strength gain of portland and pozzolanic cement concrete series containing 300 kg/ m3 cement and cured at 5°C, were similar. - Portland cement concrete with a dosage of 350 kg/ m3 had highest strengths in all conditions. - Pozzolanic series had lower three months strengths than the control ones. c) Tensile strengths depending on curing conditions - Curing in water was the most positive and effective condition for the tensile strengths like compressive ones. - The laboratory condition affected early tensile strengths of pozzolanic series positively like compressive ones. - Under low temperature conditions the pozzolanic cement concretes showed inordinary early strengths. d ) Tensile strengths depending on type of cement - Portland cement concrete containing 350 kg/ m3 cement had higher strengths than the others in all conditions. XVI- The three month strengths of pozzolanic cement concretes were lower than those of the others. - Concretes containing 350 kg/ m3 pozzolanic cement showed high development than others after 14 or 21 days. 3) Results of water absorption and capillarity - Pozzolanic series containing 300 kg/ m3 cured in water and laboratory had less water absorption in weigth than the control series. - Under low temperature conditions pozzolanic series had much more capillary water absorption than the control series. - In laboratory and water conditions, pozzolanic series had much smaller capillary water absorption than the control series. XVll
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