Hafif betonlarda agrega konsantrasyonunun mekanik özelliklere etkisi
Infuluence of aggregate volume concentration on the mechanical properties of lightweight concretes
- Tez No: 39711
- Danışmanlar: DOÇ.DR. M. ALİ TAŞDEMİR
- Tez Türü: Yüksek Lisans
- Konular: İnşaat Mühendisliği, Civil Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1994
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 65
Özet
ÖZET Beton, înşaat Mühendisliğinde en önemli ve vazgeçilemez yapı malzemesidir. Beton un iç yapısının bilinmesi ondan en iyi şekilde yararlanmamızı sağlar. Bu alanda yapılan araştırmalar betonun en güvenilir ve en ekonomik biçimde kullanılmasını hedefler. Bu çalışmada hafif betonlarda agrega hacim konsantrasyonunun betonun kısa süreli elastik ve elastik olmayan davranışına etkisi araştırıldı. Daha önce normal ve yüksek mukavemetli betonlarda incelenen aynı problemin sonuçlarıyla karşılaştırmalar da yapıldı, üretilen hafif betonların elastisite modülü, iki fazlı bir kompozit malzeme modeli ile hesaplanıp deney sonuçlarıyla karşılaştırıldı. Bu çalışmada, sekiz değişik agrega bölümü seçildi. Bunlar % 0 dan başlayıp, % 8'er arttırılarak % 56 ya kadar değiştirilmesiyle oluşturuldu. Tüm betonlarda aynı granülometrik bileşim kullanıldı. Bütün betonlarda en büyük agrega boyutu ve etkin su/çimento oranı (0.2 8) sabit tutuldu. Üretilen hafif betonların agregası ponza taşı olup bütün betonlarda sadece bu agrega kullanıldı. Kum kullanılmadı. Agregalar kullanılmadan önce 105°C de değişmez ağırlığa gelinceye kadar kurutuldu ve beton karışımından önce yarım saatlik ön emdirme uygulandı. Yapılan deneyler sonunda hafif betonlarda agrega hacim konsantrasyonunun artmasıyla basınç dayanımı, elastisite modülü ve kırılma işinin azaldığı görüldü. üretilen hafif betonların elastisite modülü ve iki fazlı bir kompozit malzeme modeli ile hesaplanan elastisite modülü birbirine oldukça yakındır. Bu çalışmada kullanılan Hashin-Hasen modelinin hafif betonlar için oldukça iyi sonuçlar verdiği görüldü. vi
Özet (Çeviri)
SUMMARY INFLUENCE OP AGGREGATE VOLUME CONCENTRATION ON THE MECHANICAL PROPERTIES OF LIGHTWEIGHT CONCRETES In concrete construction, self-weight represents a very large proportion of the total load on the structure, therefore there are considerable advantages in reducing the density of concrete. The main advantages are the possibility of using of smaller sections and the corresponding reduction in the sizes of foundations. Furthermore, with lighter concrete, the formwork need withstand a lower pressure than would be the case with ordinary concrete, and also the total weight of materials to be handled is reduced with a consequent increase in productivity. Lightweight concretes are more fire resistant than normal weight concretes because of their lower thermal conductivity and lower thermal expansion. On the other hand lightweight concrete has some limita tions: Greater care may be required in controlling water content, mixing and supervision to maintain strength and workability requirements. They have low compressive strength and modulus of elasticity than ordinary concrete lightweight concrete also show higher and shrinkage. There are three broad methods of producing lightweight concrete. In the first method, porous lightweight aggregates are used instead of ordinary aggregate. The second method relies on introducing large voids in the concrete, like foamed or gas concrete. The last method is omitting the fine aggregate from the mix so that a large number of interstitial voids is present which is called no-fines concrete. The scope of the subject can readily be seen from the following table. This thesis investigates the influence of aggregate volume concentration on the elastic and inelastic behavior of lightweight concrete. The modulus of elasticity of lightweight concretes measured experimentally and compered with the one estimated by using two phases composite material models. For this purpose, eight different types of aggregate volume concentrations have been chosen, starting from % 0 to % 56, by an increase of % 8. The aggregate grading of -concrete, water cement ratio and the maximum particle size for all sizes have been kept constant. The water/ cement ratio and the maximum size of aggregate were 0.2 8 and 19. 1 mm respectively. The aggregate of lightweight concretes was pumice. All lightweight aggregates were dried at 105 C xxp viiH(\f1,J' m vo t> VXX1to obtaining a constant weight before use. The lightweight aggregates are subjected to a process of pre-obsorption prior to the production of concretes; thus the water obsorbed by the aggregate is not included in the mix composition- No sand has been used in the mixture Turkish portland cement type I was used. The compressive strength and modulus of elasticity experiments were carried out on (JİSO x 300 mm cylinders and the splitting tensile strength tests carried on 150 x 190mm cylinders. The modulus of elasticity was calculated based on the stress corresponding to 30 percent of ultimate stress and the longitudinal strain produced by this stress. The vales of fracture energy up to peak point have been found with the calculation of areas under the stress-strain curves. Relative fracture energy values have been obtained after non-dimensional is at ion öf curves. This study cons its of six parts: In the first part, an introduction is made to the subject matter of the investigation and definitions of some relevant terms and a classification of lightweight concretes are given. In the second part, a summary of the previous investiga tions found in the literature dealing with the effect of the agregate on elastic and inelastic behavior of concrete are given. The third part is devoted to experimental work. The tests carried out on the materials used, the type and mixture of concretes produced are listed. In the fourth part experimental results are given. In the fifth part the experimental results are discussed and evaluated. In the last part the conclusions drived from the results obtained in this work are summarized. The experimental results obtained in the experimental work can be outlined in the following six groups: ix1. The properties of fresh concrete:. As the aggragate concentration increases the density of fresh concrete and density of oven dry concrete decrease. 2. Results related to the elastic behavior:. Aggragate concentration has an important effect on the moduls of elasticity. The modulus of elasticity decreases as the aggregate concentration increases.. The modulus of elasticity of lightweight concretes can be estimated from the modulus of lightweight aggragate and cement paste phases by using composite materials models. The predicted values showed reasonable approxima tions to the experimental result.. The modulus of elasticity can be calculated as function of comprossive strength and unit weight of the concrete. 3. The results related to inelastic behavior. As the lightweight aggragate concentration the compressive strength of the lightweight concrete decreases. For normal weight concretes, the compressive strength first decreases as the aggregate concentration increases, then passes in minimum point and finally increases. For high strength concrete an increase in the aggragate concentration increases the compressive strength.. As the unit weight of the lightweight concrete increases the compressive strentgh of the concrete also increases..The strains at maximum stresses decrease as the aggregate concentration increases. 4-. The experimental results related to the splitting tensile strength:. With increasing the aggragate concentration the splitting tensile strength decreases.. There is a relationship between the compressive strength ana the splitting tensile ' strength of the lightweight concrete; with the increase of the former strength the latter strength also increases. 5. The experimental results related to the stress- strain curves of the concretes:. A decrease in aggragete concentration shifts the curves leftwards and makes the slopes more steep.. The fracture energy and the relative fracture energy decrease as the aggregate concentration increases, 6. The results related to the ultrasonic pulse velocity:. As the aggragate concentration increases the ultrasonic pulse velocity decreases.. As the compresive strength, modulus of elasticity and splitting tensile strength increase the ultrasonic pulse velocity also increases. xi
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