Betonun hidrolik rötresinin iç yapıyla ilişkisi
Relationship between hydraulic shrinkage and its internal structure
- Tez No: 66472
- Danışmanlar: DR. OSMAN N. OKTAR
- 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: Yapı Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 130
Özet
ÖZET Bu çalışmada betonun hidrolik rötresinin iç yapıyla ve betonun diğer özellikleriyle olan ilişkisi incelenmiştir. Deneyler maksimum dane çapı 8 mm olan agrega kanşımı üzerinde yapılmıştır. Bunun için 3 ayrı granülometride ( A8-B8, B8, B8-C8 ) ; 3 ayn çimento dozajında ( 300, 350, 400 kg / m3 ) ve her bir granülometri ve dozajda 6 farklı su/ çimento oranında olmak üzere 54 karışım üretilmiştir. Ayrıca her bir su / çimento oram için de 3 adet numune üretilmiştir. Her bir karışıma ait numuneler üzerinde 63 günlük yaşa ulaşıncaya kadar rötre ve ağırlık ölçümleri yapılmıştır. Buna ilaveten bu karışımlardan alınan numunelerde, birim ağırlık, basınç dayanımı ve eğilme dayanımı da ölçülmüştür. Hidrolik rötre üzerinde, granülometri, çimento dozajı, su / çimento oranı ve çimento hamuru hacminin etkileri incelenmiş, ayrıca ele alınan özelliklerin çimento hamurunun boşluk yapısına duyarlılığı araştırılmıştır. Bundan başka hidrolik rötre değerleriyle çalışmada incelenen diğer özellikler arasındaki bağıntılar hesaplanmıştır. Çalışmada başlıca şu sonuçlar elde edilmiştir:. Su / çimento oranının yükselmesi ile hidrolik rötre oranlan artmıştır.. Hidrolik rötre deneylerinde dozaj önemli etkendir. Çimento dozajı arttıkça hidrolik rötrenin arttığı görülmüştür.. Agrega granülometrisinin hidrolik rötre üzerinde önemli bir etkisinin bulunmadığı görülmüştür.. Hidrolik rötre numune boy kısalma hızlan numune yaşlandıkça azalmaktadır. Bu hız sıfira doğru yönelmektedir.. Su / çimento oranının artmasıyla hidrolik rötre numune ağırlık kayıplan da artmaktadır.. Çimento dozajının artmasıyla birlikte ağırlık kaybı artmaktadır.. Betondaki hapsolmuş hava boşluklannın rötre ve ağırlık kayıplan üzerindeki etkisi, kılcal boşluklann etkisinin yanında ihmal edilecek düzeydedir.. Çimento hamuru hacmi rötre üzerinde önemli bir etkendir. İncelik modülü arttıkça rötre küçük bir miktar artmaktadır, ((c / (k*w+a)) negatif olduğu için bu değer büyüdükçe rötre azalmaktadır.Hesaplanan bağıntı: r63=0.000807*(c+w+a)'-0.0001488*[c/(k*w+a)]' + 0.000038*m'+ 0.00004645. Hidrolik rötre ile diğer beton özellikleri arasında şu bağıntılar bulunmuştur ve korelasyon katsayılan verilmiştir: r63 = 0.002338*fc63 (-°'22233) R=0.4486 r63 = 0.00233 1 *fe63 ("°31919) R=0.4221 r63 = - 0.0000096*fe63 + 0.00000195*^3 + 0.00091 R=0.4551 r63 = 1.094043 * r28 +0.000225 R=0.9556 r63 = 0.005749 * G63 + 0.000493 R=0.7548 X111
Özet (Çeviri)
SUMMARY RELATIONSHIP BETWEEN HYDRAULIC SHRINKAGE AND ITS INTERNAL STRUCTURE In this study, relationships between hydraulic shrinkage and its internal structure and the other properties of concrete are examined. Shrinkage is the decreasing in volume of hardened concrete, cement paste or cement slurry depending on temperature and relative moisture conditions. Shrinkage take places because of internal structure of cement. Excessive amount of cement in concrete, using of high heat cement and higher environmental temperature cause stronger shrinkage. Shrinkage makes important problems especially in mass concrete like dam body and road concrete. It is shown that the shrinkage of normal aggregate concretes is dependent primarily on only three parameters - the paste shrinkage, the aggregate shrinkage and the aggregate volume concentration. The observed dependence of concrete shrinkage upon original water content by weight, Young's modulus of the concrete and aggregate grading, for speciment of the same water -cement ratio, is shown to follow directly from the simply dependence of concrete shrinkage upon aggregate volume concentration. 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 conclussions obtained from this work are the subject of the fifth chapter. Experiments have been made over a mixture of aggregate the grain diameter of which is eight milimeters, producing fifty four distinct mixtures of three different granülometries (A8-B8, B8, B8-C8) and cement content (300, 350, 400 kg / m3) seperately, all having six various ratio of water / cement three samples have been produced shrinkage and weight measurements have been made on the samples of each mixture reaching to 63 days. Besides over the samples taken from the above mentioned mixtures unit weight, pressure strength, and bending resistance have been measured. The effects of granülometry, cement content, water / cement ratio, and volume of cement paste on the hydraulic shrinkage have been investigated, dealing with at the same time the sensitivity of the properties of the cement paste. On the other hand, the relations have been illuminated between the values of hydraulic shrinkage and the other properties being under consideration in this study. xivShrinkage specimens are cured in controlled room where the temperature and humidity were kept constant at 20 °C and 50 % relative humidity. The duration of shrinkage test was 63 days and the length changes of specimens measured at certain ages. Shrinkage at n* day was calculated with the following expression (1): Bd=(li-ld)xl00/l where li = initial measurement of the specimen, la = measurement after n days of drying Ba = the percent of shrinkage Results of the hydraulic shrinkage:. The greater the water / cement ratio, the greater the hydraulic shrinkage ratio.. Cement content is an important effect on hydraulic shrinkage. The greater the cement content, the greater the hydraulic shrinkage.. There is no important effect of granülometry of aggregate on hydraulic shrinkage.. The lengths of hdraulic shrinkage samples shorten in the first month and then the shortening speed of the samples are much more decreased.. The weight loss of the specimens increases as the water/cement ratio increases.. The weight loss of the specimens increases as the cement content increases.. The influance of the entrapped air pores on the shrinkage and weight loss in concrete is negligible compared with the influance of capillary pores.. Volume of cement paste has significant effecton shrinkage. The finenes modulus of aggregate increases as the shrinkage increases a small amount. Due to [c/(k*w+a)] is negative. In this value increases as the shrinkage decreases.Calculated relations on r63: r63= 0.000807*(c+w+a)' - 0.0001488*[c/(k*w+a) ]' + 0.000038*m'+ 0.00004645. It is found the equations between the hydraulic shrinkage and other properties concrete in below: r63 = 0.002338*fc63 (“°'22233) R=0.4486 r63 = 0.00233 1 *fe63 (-°31919) R=0.422 1 XVr63 = - 0.0000096*^3 + 0.000001 95*£ö + 0.00091 R=0.4551 r63 = 1.094043 * r28 +0.000225 R=0.9556 r63 = 0.005749 * G63 + 0.000493 R=0.7548 Coefficients and degrees of sensivity are introduced to define quantitively the sensitivity of concrete properties to the pore structure of cement paste. The following properties were determined in this study:. Coefficient of sensitivity Let Phi be a hardened concrete property and n; a parameter, and let us consider the values taken by Py in a sample large enough to representative of the concrete in relation to the variable. n* [1- (1.06-2.06s) t a.c / w ] w + a by given several values to ni. Suppose that for n; = n; * the highest coefficient of correlation [ R (nj J],T* is obtained. By obtaining this it can be thought that the variable used is the best representation of the influence of the pore structure of cement paste on the property. Thus, if nj * =1, this means that the volume of capillary pores and the volume of entrapped air effect the property equally. Hence, the property iş. insensitive. to.the pore structure of cement paste. If n; *= 1, than the volume of pores and their type affect the property, Which is said to be esensitive to the pore structure of cement paste. How far n; * takes a value different from an indication of the different effects of the two types of pores on the property. According to this, n; * may be called ”the coefficient of sensitivity to the pore structure of cement paste " of the property envisaged.. Sensitive and insensitive properties of concrete with respect to the pore structure of cement paste. If a specific property of concrete is effected by amount, but not by the type of pores ( Whether capillary or entrapped air) in cement paste, this property is said to be in sensitive to the cement paste pore structure; if the property is effected by both the amount and type of pores it is said to be sensitive to the paste pore structure.. Determination of sensitivity by comparision with unit weight. Generally it is difficult to determine the coefficient of sensivity defined above since a and s are probably not known exactly. But even so its possible to determine the sensitivity of a property to the pore structure of cement paste, by using an approaximate method which will be explained below. Let us call the unit weight of concrete as A, which is measured when the capilary pore are dried out completely. It is obvious that A must be an insensitive property xvito the cement paste pore structure, because the decrease in unit weight caused by pores is dependent only on their total volume and not on their shapes and dimensions. In this case, if we apply the method explained above to the unit weight ( A ), the result of n; * = 1 should be obtained, in other words if we take the variable on the horizontal axis as [1- (1.06-2. 06s) t a.c/w]w + a. We must obtain the greatest coefficient of correlation.. Type 1 sensitivity degree of property to the pore structure of cement paste. For any ( Pw ) concrete property, let us call k;*/ ko = ( SD ); = Type 1 sensitivity degree of this ( Py ) property. It was mentioned above that ko is a parameter of centreal tendency of [1 - ( 1.06 -2.06.s ) t a.c / w ] values and k;* is of n; * [1- (1.06-2.06. s ) t a.c / w ] values; ( nj * ) the coefficient of sensitivity, was constant for a certain concrete property. The Type 1 sensitivity degree ( SD ), is defined as: (SD^kj-VkoSni Thus, it can be seen that (SDI); Type 1 sensitivity degree of a concrete property Py is approximately equal-to nj * sensitivity coefficient ef the same property defined above.. Type 2 sensitivity degree of propertied) the pore structure of cement paste. For any Py property, the Type 2 sensitivity degree (SD2)i is defined as: (SD2> = R(ki*)/Ri(ko) where R (ki *) = the highest coefficient of correlation when the variation of the concrete property Phi is calculated with respect to (k*w+a) by allocating different values to the k parameter. Ri (ko)= the correlation coefficient obtained by allocating the value ko to parameter k in the same investigation of the Pw concrete property (ko gives the maximum correlation coefficient for unit weigth). According to this, (SD2); indicates how much the correlation of the Py is not taken account of and Py is considered as insensitive.. Sensitivity degrees of obtained according to various functions of c / (k*w+a). Lineer regression analysis has been done between the variables [c / (k*w+a)] and the properties Ph; in the form; Pw=A[c/(k*w+a)]+B xvuWhere A and B are regression constants. In these calculations the k parameter has been changed by increaments of 0.4; the k value giving the highest coefficient of correlation for unit weight has been called ko and k value which gives the highes coefficient of correlation for any other Phi property has been called k; *. Using [c / (k*w+a)] the equation above, k; * values and (SD1);, R (kj *), Ri (k0) and (SD2); were also calculated. Further, calculations used the following more developed functions of a: Pw = A ( c+w+a) +B [c / (k*w+a)] +C Phi = A ( c+w+a) +B [c / (k*w+a)] +C*m +D m being the fineness modulus of aggregate mixture and A, B, C, D being constants.. Comparison of functions used for expressing the properties.. Relations between properties and compositions with highest correlation coefficients. In this paper, it has been shown that sensitivity of concrete properties to the pore structure of cement paste can be^uantitively 4efined by sensitivity degrees. The second of the sensitivity degrees define^jhere, takes more stable values than the first for different functions, which related to properties of concrete to its internal structure, and thus it is more significant. In addition, the correlations between the concrete properties were investigated that to understand from which function the degree of sensitivity obtained is more significant. xvm
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