Sülfo-kalsik ve siliko-kalsik uçucu küller iyileştirme ve rolkrit'de kullanımları

Abstract

Çalışmanın literatür bölümünde doğal ve yapay puzolanlar, puzolanik reaksiyon, uçucu külün malzeme özellikleri, TS ve ASTM ile karşılaştırmalı sınıflandırılması uçucu küllü betonların özellikleri, uçucu külle üretilen özel bir beton olan SSB hakkında geniş bir literatür taraması sunul muştur. Deneysel çalışmalar dördüncü bölümde üç ana alt grupta toplanmıştır. Birinci kısım uçucu külün niteliklerinin saptanmasına yöneliktir. Bu doğrultuda ÎTÜ İnşaat Fakültesi Zemin Mekaniği Laboratuvarında hidrometre analizleri, ÎTÜ Kimya Metalürji Fakültesi K-ışınları laboratuvarında X-ışınları difraksiyonu, ÎTÜ Nükleer Enerji Enstitüsünde radyasyon sayımları yapılmıştır. İkinci alt grup deneyler ise uçucu külleri iyileştirme Çalışmalarıdır. Serbest kireci yüksek Afşin-Elbistan küllerinin iyileştirilmesi için Centred ' Etudes et Recherches du Charbon (Cerchar, Fransa) kuruluşu ile işbirliğine gidilmiştir. Fransa'da iyileştirme prosesi uygulanan numuneler ÎTÜ înşaat Fakültesi Yapı Malzemesi Laboratuvarında şahit gurubu üretimlerle birlikte test edilmiştir. X-ışınları difraksiyonu ile etrenjit oluşumu incelenerek iyileştirmenin sülfat indirgeyip indirgemediği araştırılmıştır. üçüncü alt grup olan rolkrit üretimi için Yatağan külü kullanılmış ve bu külle yapılan üretimlerle kül/çimento, su/(kül+ çimento) ve basınç mukavemeti arasında ACI'da Amerikan külleri için verilen abak oluşturulmaya çalışılmıştır. Beşinci ve altıncı bölümler sonuçların değerlendirilmeleridir.

Interdiciplinary working is necessary for recycling industrial wastes. This effort does not only saving money but also preserves environment. Coal burning thermal power plants are sources of electric energy. About half of the total electricity by generated is obtained from thermal power plants. Coal burning power plant's wastes are very harmful for environment. The largest amount of the wastes is ash, esp. fly ash. People met fly ash the first time in 1930* s. In the begining it was just considered as a waste product. By the time it has been understood that it can be used in many areas, such as agriculture, chemical industry { plastics and paints), and construction industry. Actually pozzolan that is the name of group, including fly ash has been known and used for a long time in construction. As an example volcanic tuff of natural pozzolan has been used since Roman Empire. The Roman buildings, that are still in service, give an idea about durability of pozzolans. Fly ash, that is produced in very large amount is an artificial kind of pozzolans. A pozzolan is defined as siliceous or siliceous and aluminaous material which in itself possesses little or no cementitious value but which will, in finally divided form and in the presence of moisture, chemically reacts with calcium hidroxide at ordinary temperature to form compounds possessing cementitious properties. [6] The pozzolanic reaction is slow, so the rate of the strength development and heat of hydration associated with this reaction are low. Two basic properties, lime-consuming and low-heat of hydration are main advantages of fly ash in using mass concrete. Of course, material properties of fly ash must be known in order to be used as an acceptable material. In construction industry it is widely used such as treatment of soils and mix design of concrete. It hans many aspects in concrete technology. Using fly ash in concrete industry has many advantages such as cost reducing, quality increasing and preserving environment. Fly ash effects mechanical, chemical and conservative character of construction industry and no standardization of ash and no enough information of material properties are barriers in using fly ash widely. VHI If we compare consumption of fly ash of Türkiye and the developed countries we see that Türkiye is at the very behind of them although Türkiye has big capacity of fly ash production. The first step to incerease the comsumption of fly ash is to have the necessary information and knowledge about the material proportion of fly ashes. So analysis of fly ashes is one of the main subject of this study. If there are some disadvantages like a high volume free lime, treatment may be possible. The firm that we have worked togeather has a patented process about getting better high value free lime of any material. According to the method fly ash is prehydrated using cold water and the mixture has treated in a receptacle under pressure from superheated or saturated steam at temperature lying between 130°C and 250°C. The method is applicable to any substance containing quick lime that is to be slaked. As a first step we have studied the subject about natural pozzolans, fly ashes and using fly ash in concrete technology esp. Roller Compacted Concrete, literally. Fly ash usually has positive effects on almost all properties of concrete. In classification of Turkish fly ashes it is seen that only one of them(Çatalagzı) is F type in ASTM classification. The others, are in C type with high free lime ratio. High free lime content causes reducement of durability of concrete by expansion. In our experimental study we followed the procedure given below. 1) Study on some properties of fly ashes obtained from such Afşin-Elbistan, Orhaneli, Seyitömer and Yatağan Thermal Power Plants. a) Chemical and physical properties of the material b) Minerological analysis by X-Ray diffraction analysis. c) Radioactivity tests. 2) Treatment of high free lime and sulpho calsic fly ash of Afşin-Elbistan by collaboration with Cherchar from France The formation of ettringite is observed by X-ray diffraction analysis on high lime and treated fly ashes. 3) The recent and the most popular using of fly ash is RCC (Roller Compacted Concrete) There is enough information about chemical and minerological composition of Turkish fly ashes and these are enclosed literal division of our study. Our X-ray IX analysis is reputation of this fact. Everybody has doupt about high level of radioactivity Turkish fly ashes, so we have worked with Nuclear Energy Institute of Istanbul Technical University. Treatment of high level of free lime is very strategic. If it is succeed to treat the fly ash, with normally contains high level of free lime, it will be possible to use this method in big dam projects. That's why the treatment of free lime in fly ash is very strategic for Türkiye. For understanding these situation clearly sample from treated fly ash was untreated in ITÜ laboratory and the results were compared with the high lime fly ash test results. This results are shown on the table below. Strength at 28** day Strength at 28** day Strength at 90** day Strength at 90th day Trial for producing of RCC and obtaining a figure that gives a relation between the fly ash to cement ratio and water to cementitious ratio and compressive strength are the subjects of this study. This figure for ASTM type I and II cements is available in ACI-207.SR-80. In this study we have tried to obtain similar relation shown in the figure below by using Turkish fly ashes. RCC can be made from any of the basic types of portland cement and in combination with pozzolan. This method, which in many ways is more related to the procedures used in geotechnical engineering than to conventional concrete practice, depends upon the placement of layers of low workability concrete in the interior of dam and its compaction using vibratory rollers. RCC must be dry enough to support the weight of the vibratory equipment but wet XI enough to permit adequate distribution of paste binder throughout the mass during the mixing and vibration process (ACI-207 SR-80). The building of a gravity dam is made by superposition of layers of fresh concrete. With time the suspension of concrete transforms into a solid and the mechanical properties increase. Due to hydration of cement this evalution is combined with physico-chemical processes which induce an increase of temperature and lead to volumic variations of the expansion end shrinkage. The use of new RCC technic induces a fast construction and saving time and money. In our experimental study, mixture proportions have been calculated with maximum density approach. But there is no available relation between F/C and W/(F+C} and compressive strength for Turkish fly ashes. Determining some production points for F/C and W/F+C relation is much realistic in figure 4.14. We prepared 35 concrete groups, and for each of this group 23th day and 90th day compressive strengths were obtained. As a result of test carried out on the Turkish fly ashes, the mineralogical composition showed that amorphous and glass phases were the biggest proportions in the composition. Which is a good point for pozzolonic reactivity. A few ashes have high lime content. This situtation has to be considered in application. Radioactivity is the popular subject of fly ashes. Ashes are being used as an additive for some cement types, for this reason, radioactivity tests are needed for scientific research as well as public information. The results are found satisfactorily in regard of upper limits. Of course the radioactivity depends on the source of coal and concentration of radioactive elements in it.