Hızlandırılmış rötre ile hidrolik rötre arasındaki ilişkinin incelenmesi
Başlık çevirisi mevcut değil.
- Tez No: 46164
- Danışmanlar: PROF.DR. MEHMET UYAN
- Tez Türü: Yüksek Lisans
- Konular: İnşaat Mühendisliği, Civil Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1995
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 84
Özet
ÖZET Bu çalışmada hidrolik rötre ile etüvde kuruma rötresi arasında herhangi bir ilişki olup olmadığı incelenmiştir. Deneyler maksimum dane çapı 4 mm olan kum ve PÇ 32.5 çimentosu kullanılarak üretilen harçlar üzerinde yapılmıştır. Rötrenin etkilerini inceleyebilmek için üç çeşit su/çimento (E/C=0.5, E/C=0.6, E/C=0.7) oranı ve üç farklı çimento dozajı (C=350kg/m3, C=400kg/m3, C=450 kg/m3) seçilmiştir. Rötre deneyleri 40x40x160 mm boyutlarındaki prizmatik numuneler üzerinde yapılmıştır. Rötre deneyleri yanında boşluk yapısının etkilerini incelemek amacıyla kılcallık deneyleri yapılmıştır. Üç seri deney yapılmıştır. Birinci seri, hidrolik rötre deney metoduna (TS 3322} göre rötresi tayin edilen numuneleri içermektedir. Bu numuneler 20°C sıcaklıkta ve %50 bağıl nem altında tutulmuşturlar. İkinci ve üçüncü seri numuneler daha hızlı sonuca ulaşılabilen etüvde kuruma rötresi deney medoduna (TS 3453) uygun olarak test edilmişlerdir. Bu iki seriden biri 20°C sıcaklığında kirece doygun su içinde, diğeri ise 20°C sıcaklık ve %50 bağıl nem koşullarında saklanmıştır. 28., 56. ve 90. günlerde numuneler 50°C sıcaklığında etüve konulmuş ve uygun zamanlarda boyları ölçülerek kararlı hale geldiği zamanki rötreleri bulunmuştur. Bu rötre sonuçları ile hidrolik rötre deneyinden elde edilen sonuçlar karşılaştırılarak aralarındaki ilişki incelenmiştir. Rötre deneyi numunelerinin saklandığı iki farklı ortamda tutulan numuneler üzerinde yapılan kılcallık deneyleriyle ortam şartlarının yarattığı etkiyi bulmak amaçlanmıştır. Deneyler sonucu elde edilen sonuçlar aşağıda özet halinde verilmiştir. Çimento dozajının ve su/çimento oranının artmasıyla birlikte rötrelerin her iki yöntemde de artmaktadır. Çimento dozajının artması, su/çimento oranının rötreye olan etkisini azaltmaktadır. Hidrolik rötre deney sonuçları ile etüv rötresi deney sonuçlan arasında yakın ilişki gözlenmiştir. Her iki yötemin sonuçları birbirine yakın çıkmıştır. Bu nedenle uzun süre alan hidrolik rötre deneyleri yerine daha çabuk sonuç elde edilebilecek etüv rötresi metodununun kullanılabileceği kanısına varılmıştır. xı
Özet (Çeviri)
SUMMARY DETERMINATION OF RELATIONSHIP BETWEEN ACCELERATED DRYING SHRINKAGE AND HYDRAULIC SHRINKAGE Cracking due to restrained shrinkage in concrete structures such as highway pavements, slabs, retaining walls, long span bridges and dams can be critical. The importance of shrinkage is largely related to cracking. Drying shrinkage is defined as the time-dependent volume reduction in hardened concrete, as a result of water loss by evaporation. The rate of water loss is related to temperature and relative humidity. When the paste fraction in a concrete specimen looses moisture it shrinks, initially as a result of forces are set up in the solid fraction by capillary forces and subsequently because of the progressive removal of the adsorbed water layers on the pore walls which changes the surface energy of the solid so it contracts. Once the capilarity water has been lost, the withdrawal of adsorbed water takes place which causes shrinkage. The main parameters influencing the drying shrinkage are relative humidity of environment, water/cement ratio of mixture, hydration degree of cement, the elastic properties of the paste and aggregate, size and grading of aggregate admixtures, relative restrainment offered by the aggregate particles and unhydrated cement, and finally the age of concrete. The complexity of the subject is such that the effect of the mix design parameters on the equilibrium drying shrinkage of concrete and the fundamental shrinkage parameters of the paste have not been well understood. Whether a load is subjected or not, concrete shrinks on drying. Volume changes due to shrinkage is important because in practice, this movement is partly or wholly restrained, and as a result it induces stresses. The main danger generated by xnshrinkage is the presence of tensile stress induced because, of course, concrete is very weak in tension and sensitive to cracking. Cracks must be avoided or controlled and minimized because they impair the durability and structural integrity, and are also aesthetically undesirable. Therefore, it is necessary to take suitable countermeasures to prevent this cracking tendency. Some test methods are proposed in the literature to predict the ultimate drying shrinkage of concrete. In Turkish Standards two test methods for determining the drying shrinkage of concrete are given. The first, in TS 3322, needs long time periods to predict ultimate drying shrinkage of concrete specimen. The second one, in TS 3453, allows to get results more rapidly. The purpose of the present research was to clarify the relationship between these two methods mentioned above. In this study methods of TS 3322 and of TS 3453 are called hydraulic shrinkage and accelerated shrinkage respectively. This study is presented in five chapters. In the first chapter general information about the theme, related literature and the intent of the study are given. The second chapter involves experimental work and procedure of testing. The characteristics of the mortar compositions, the proportions of mortar mixes, and the methods of curing of specimens are also given in this chapter. The test results obtained from hardened concrete are listed together with essential explanations and techniques of calculations in the third chapter. The appraisals of test results with charts are presented in the fourth chapter. The conclusions obtained from this work are the subject of the fifth chapter. Three different water/cement ratios and cement contents were selected. Such as 0.5, 0.6, 0.7 for W/C, and 350 kg/m3, 400 kg/m3, 450 kg/m3 for cement content respectively. Ordinary Portland cement (PC 32.5) and sea sand was used in the production of mortars. Also two types of curing were applied on specimens. These were keeping in water at 20°C and in air with 50 percent relative humidity and 20°C temperature. Prismatic specimens of 40x40x160 mm were used for drying shrinkage tests. Three specimens were tested for each mix and testing process. The drying shrinkage rate of specimens are calculated by the basis of standards. The brief explanations of these two methods used in this study were given below: xiiiHydraulic shrinkage method : Shrinkage specimens are cured in a controlled room where the temperature and humidity were kept constant at 20°C and 50 % R.H. The duration of shrinkage test was 90 days and the length changes of specimens measured at certain ages. Shrinkage at nth day was calculated with the following expression (1): s=L1-LnxlQ0 (i) Ll wh ere: La= initial measurement of the specimen Ln=measurment after n days of drying S=the percent of shrinkage Accelerated shrinkage method : The following procedure was applied in this method. - Immersing of specimens in water at 23°C for 48 hours - Obtaining the initial length reading on the test specimen - Determining the saturated surface-dry weight of the test specimen. - After removing the specimens from the water bath storing them in oven at 50°C - At the end of drying period, removing specimens from oven and cooling to 23°C. Following cooling, obtaining specimen-length and weight, and also length of standard reference bar. - Returning test specimens to the drying oven for a second period of drying. The duration for the second, and subsequent drying periods were 48 hours. Following the second period of drying, repeating cooling, length measurements, and weight determinations as specified before. xiv- After a drying period in the oven for 48 h, cooling in specified environment until reaching the equilibrium condition and measuring length and weight of specimens. Equilibrium is considered to be prevailing condition when the average length change of the test specimen is less than 0.002 %, over a span of 6 days drying, and also when the average weight loss in 48 h drying is less than 0.2 % with respect to the last previously determined weight. Calculation of the drying shrinkage as a percentage of the gage length is as follows: S=4^xl00 (2) where: S = linear drying shrinkage, % AL= change in the linear dimension of the specimen due to drying from a saturated condition to equilibrium weight and length as specified above G = test specimen gage length In this study three sets of specimens were prepared for predicting ultimate drying shrinkage, and two sets of specimens for determining coefficients of capillarity. First set of the shrinkage specimens used to predict hydraulic shrinkage while the other two sets was used for accelerated shrinkage tests of two different curing conditions. One of the sets cured in 20°C water and other set was kept in air at 20°C and 50% R.H. The ultimate accelerated shrinkage results were obtained on 28, 56 and 90 days old specimens. By using to the results given in tables in the third chapter, charts were generated in the fourth chapter. The evaluations and discussions were based upon these graphs. Important results obtained from this research are grouped as follows: 1) Results of hydraulic shrinkage a) The magnitude of drying shrinkage depends on cement content and water/cement ratio. xvb) The greater the cement content, the greater the shrinkage. c) The influence of water/cement ratio on drying shrinkage decreases as the cement content increases. d) The weight loss of the specimens increases as the water/cement ratio reduces. 2) Results on coefficient of capillarity a) Coefficient of capillarity increases with the increase of water/cement ratio for both air cured and water cured specimens. b) Coefficient of capillarity decreases with the increase of cement content for both air cured and water cured specimens. c) For a given water/cement ratio, permeability increases up to 56 days of ages and than decreases. 3) Results of relationship between hydraulic shrinkage and accelerated shrinkage a) There is a strong relation between hydraulic shrinkage and accelerated shrinkage. One of these two methods can be used on prediction of drying shrinkage. b) Tendency of the two methods are the same and shows similar reactions. d) For air cured specimens accelerated shrinkage is lower than hydraulic shrinkage. e) For water cured specimens accelerated shrinkage is greater than hydraulic shrinkage. f) Increasing of cement content reduces effect of water/cement ratio on drying shrinkage. xvi
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