Normal ortam koşullarında gözenekli beton üretimi ve niteliklerinin incelenmesi

Abstract

Bu tezin konusu, çağdaş yapı malzemelerinden gazbetonun; Üretim safhalarını incelemek ve deneme üretimleri yaparak, bu malzemenin doğru karışım oranlarını deneysel olarak tespit etmektir. Gazbeton ile, yapı malzemeleri ve yapı elemanları olmak üzere iki farklı uygulama sınıfında üretim yapılabilir. Yapı malzemeleri, iki farklı üretim içerir. Birincisi, prefabrikasyonda kullanılabilen, gerekirse donatılı olarak üretilebilen ve taşıma gücü yüksek olan, basınçlı buhar kürüne tabi tutularak yüksek mukavemet kazandırılan ürünlerdir. Diğeri ise, şantiyede üretilebilen ve sadece normal hava şartlan ile sertleştirilen, bu nedenle mukavemeti diğer ürün gibi yüksek olmayan, - yalıtım, dolgu malzemesi ve bölme duvarı olarak kullanılabilen- ürünlerdir. Yapı elemanları ise daha çok prefabrikasyonda görev alan hazır yapı birimleri şeklinde üretilir. Bundan dolayı donatı içerirler. Bu tipteki üretimin sertleştirilmesinde, basınçlı buhar kürü sağlamak için otoklav kullanılması zorunludur. Bu çalışmanın deney safhasında, yapılan gazbeton üretimi tamamen endüstriyel üretime uygundur. Ancak, laboratuvarda otoklav bulunmadığından, üretimin son kısmı olan kür safhasında eprüvetler sadece normal ortam şartları altında sertleşme işlemine tabi tutulmuşlardır. Bu Sebeple gerçek mukavemetleri tespit edilememiştir. Üretilen örnekler ilk önce üretim esnasında, özellikle harç genleşmesi safhasında, daha sonrada homojen gözenek yapısı, silindirik gözenekler ve optimum genleşme elde etmek üzere incelenmişlerdir. Bu inceleme sonunda hedeflenen fiziksel yapıyı sağlayabilecek karışım oranları yaklaşık olarak tespit edilmiştir. Daha sonra en doğru karışım oranını tespit edebilmek ve karışıma giren malzemelerin farklı oranlarının gazbeton üretimi üzerindeki etkilerini belirlemek için, 27 adet farklı karışım oranı ile 6 şar adet üretim yapılmıştır. Daha sonra fiziksel niteliklerinin tespiti için Basınç Mukavemeti, Su Emme, Kapilarite, deneylerine tabi tutulup, özgül ağırlıkları tespit edilmiştir. Elde edilen veriler değerlendirildiğinde şu sonuçlara varılmıştır: Çimento / Kum oranı 0.8 iken, karışım ağırlığının % 23' ü kadar su ile ıslak harç elde edildikten sonra karışıma, homojen dağılımını sağlamak koşulu ile %o75 oranında Alüminyum tozu katılarak üretilen eprüvet, en iyi gözenek yapısına, en homojen genleşmeye, optimum mukavemete sahip olmuştur. Su emme miktarıda diğerlerine göre daha düşük seviyede olan bu eprüvetin karışım oranlarının, en doğru oranlar olduğuna karar verilmiştir.

In our century, building sector has been affected by rapidly changing and developing world conditions as in all sectors. And as a result, big changes and developments have taken place especially in the field of building materials and elements. Today, in building sector, the traditional materials which are being used for centuries, left their place to contemporary building materials and elements which can answer the multi-dimensional needs and can be economically produced. The most important of all, this contemporary building materials and elements have cheap raw materials and can be maintained in large amounts without giving any damage to nature. These materials are called " ideal materials " and supposed to have the following criteria; - to have high strength, - to have the qualities to be nailed, screwed, pierced cut, etc. - to ensure sufficient heat, sound and water isolation, - to have fire resistance and to be stable in volume, - to be in accordance with the materials used together, - to have the abilty of both carrying loads and covering at the same time, - to make âs less addition as possible to building loads and to be appropriate for prefabrication, - the raw material to be maintained easily and cheaply without giving any damage to nature, - and to supply the above functions at minimum cost and with optimum output. The subject of this thesis is to determine the manufacturing stages, the effects of variable amounts of materials used in the production and viii the most suitable mixture proportions of aerated concrete building material which has all the ideal qualities listed above by doing experiments on various test mixture proportions that will be produced. The manufacture of aerated concrete primarily actuallized in 1925, in Sweden; as a fabrication by the series of operations invented by Axel Ericson. The reason of the development of this material in Sweden is its being productive as a material having high heat resistance in such a country that a long period of year passes under snow. Besides, because of being alternative to a valuable and useful material as wood, great investments have been made on the development researches of aerated concrete. Aerated concrete is a ligtweight material. It is unlike other concretes in as much as it does not normally contain aggregate, and can be regarded as an aerated mortar. Aerated concrete can be described as a porous, lightweight concrete obtained by the result of hghweighting with the addition of a material forming pores and hardening by steam curing of the mixture prepared by ground siliceous aggregate and inorganic cementitious material ( lime or cement ). In fabricational production; pulverized quartzite, pulverized fuel ash and fine sand rich in silica, aluminium powder as a material forming pores, cement and lime as cementious material, are used. Preference of fine sand rich in silica used as a siliceous aggregate, ground quartzite or pulverized fuel ash brings only an economical difference. Apart from this, the use of pulverized fuel ash is important in respect of evaluation of industrial waste. In situation of using sand, grain sizes must not be over than 5 mm. There are two forms of aerated concrete, the in situ type and the precast products. The latter are usually cured in high-pressure steam. Precast aerated concrete is made in the form of load bearing blocks and reinforced wall, roof and floor units in densities of 500- 1000 kg/m3. In situ types, because of being dried only by air and not being autoclaved, they don't have accessible strength and density. During the experiments, materials are produced of three different proportions. Each material ratio is modified while keeping the amount of the others fixed. In this way, the effects of the proportions of materials to the manufacturing and the mixture proportions of the best aerated concrete sample, are determined. The effects of water-addition in ratios of % 20,23 and 26 - to the production, and the most compatible amount of water are identified. IX When % 20 water is added to the mix, it is observated that after aerated mortar completed its expansion, the reaction period, the period of turning back to its beginning temperature is shortened and the amount of expansion is decreased. Expansion occurs by hydrogen gas driven off from the chemical reaction of Al, H2 and cement in mortar. The maximum temperature is measured 54 °C during reaction and the reaction period took 37 minutes. When % 23 water is added, the reaction period is 43 minutes and the maximum temperature is 48 °C. The amount of expansion is more than the amount in % 20 water. When % 26 water is added to the mix, the maximum expansion occurs. Measured maximum temperature is 41 °C, and the reaction period is 47 minutes. The reaction that expands aerated concrete is explained by the following chemical formula; 2 Al + 3 Ca(OH)2 + 6 H2O -> 3 CaO. AI2O3. 6 H2O + 3 H2 Aluminium powder is another material consists in the mixture. This material is lastly added to the mortar. Its function is to make the hydrogen gas be driven off by its chemically combining with CaOH. Thus, depending on the presence of hydrogen gas in mortar, the porous structure; the main structural characteristic of aerated concrete is to be formed. Aluminium powder is added to the mix in 3 different amounts; 5, 7.5 and 10 gr. The effects of these various amounts of aluminium powder on the physical structure of aerated concrete and the best amount are determined. When 10 gr. aliminium powder is added to the mix, it is observed that the expansion of the sample becomes larger than the others. In spite of this, a dense and heterogenous pore structure appears. The pores are ill-shaped and irregular. With another expression, this amount of aluminium powder is too much for the mixture. When 7.5 gr. aluminium powder is added, the sample product has a more homogenous structure. However, the pore structure is dense, it is formed by regular pores in cylindrical shape. According to the results of the physical observation, the best production is provided by the mixture of this amount of aluminium powder. When 5 gr. aluminium powder is added, it is noticed that the pore structure of the sample is rarely dispersed and is formed of pores in small sizes. And because of hydrogen gas not being competent, it is shapeless formed. In this production, the sample having the least amount of expansion is formed. Other inputs of aerated concrete are sand and cement. Manufacturing is made by mixing these materials in 3 different proportions of each other Samples in which the cement-sand ratio is 0.33, the amount of expansion occured in normal sizes. It is observed that the sand piled on the lover part of the sample because of the amount of 750 gr. sand being too much for the mixture. For this reason, a homogenous structural mixture couldn't be produced. The expansion of the sample remained on the upper limits of the mould. This amount of expansion is normal when the other samples are taken into account. By the result of the experiments, the compressive strength of the sample is found low; depending on the dosage of cement being low. The sample in which the cement-sand ratio is 0.5, completed its expansion 0.5 cm over than the upper limits of the mould. The pore structure of the sample is the most homogenous one according to the others. The pores were cylindrical and larger than the others. The sample in which the cement-sand ratio is 0.80, the amount of expansion were lower than the others. Pores were small and shapeless but homogenously dispersed, compressive strengths of these samples were higher than the others', because of the cement dosage being highest. The manufacture of aerated concrete realizes under very sensitive environmental conditions and as a result of serious of orderly operations. It is observed that the reaction which hydrogen gas especially affects the formation of pores and expansion is driven off is easily affected by the environmental conditions. Two samples; consisting of the same materials with the same amounts in its mixture; is manufactured in two different environmental conditions with the aim of determining the effects of the environmental conditions. When the sample which is produced at 13.30 and 22 °C completed its expansion, the top of the mortar is 0.5 cm over than the limits of the mould. The maximum temperature measured is 54 °C and reaction took 37 minutes. When the second production of the same mixture is done at 19.00 the temperature is 18 °C. The reaction lasted 42 minutes. The expansion remains 0.4 cm lower than the upper limits of the mould. The maximum temperature measured during the reaction is 41 °C. These data show that the increasing temperature increases the severity of the reaction and the expansion,and it also show that in providing the standardization in manufacturing of aerated concrete,the standart conditions are needed. xi This standart manufacturing is available only by the moulds which the environmental conditions can be taken into control and by sensitive dosaging. According to the results of the experiments, the compressive strength of the samples are between 2.32-6.07 N/mm2. It is observed that the samples having large amounts of cement in their mix have also high strengths. The sample having the highest strength contains more amounts of cement and less amounts of water (T311). The sample having the lowest strength have less amounts of cement and large amounts of water in its content (T113 ). The second experiment is made for obtaining the amounts of water absorption of the samples. The samples used were taken off from the moulds in sizes of 4x4xl6cm. The samples kept in drying out cupboard at 105 oc for 24 hours and their dry weights are determined. Later, the weigths with saturated water of the samples waited 24 hours in water are obtained. And by the following equation the amounts of water absorption are calculated. These results are reached when the data are appreciated: cement-sand ratio is 0.8 and after making mortar with the %23 mixture weight water, by affording homogenous dispersion, aluminium with the ratio of %75 is added and the sample which has the best pore structure, most homogenous expansion and optimum strength is produced.The mixture proportions of this sample,which has thee lower amount of absorption of water, are decided to be the true proportion Also physical and chemical effects of different proportions of the ingredients that enter the mixture to produce aerated concrete have been explained.