Ponza katkılı tuğla üretimi ve bu tuğlaların mekanik ve boşluk özelliklerinin incelenmesi
The Production of bricks with pumice additive and the investigation of the mechanical and pore properties of these bricks
Yazar: AYŞE GÜL GÜZEL
Danışman: PROF. DR. EROL GÜRDAL
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü
Derece: Doktora, 1993
Konu: Mimarlık = Architecture
Dizin: Kil = Clay ; Ponza = Pumice ; Seramikler = Ceramics ; Tuğla = Brick

Özet:
Bu çalışmada hafif doğal bir taş olan ponza katkısı ile hafifletilmiş tuğla üretim koşullarının araştırılması ve elde edilen ürünlerin fiziksel ve mekanik özelikleri üzerinde etken olan boşlukluluk ve mikroyapı özeliklerinin incelenmesi amaçlanmıştır. Tez altı bölümden oluşmaktadır. İlk bölüm giriş bölümü olup konunun kısa bir tanıtımı yapılmakta üretimde kullanılan malzemelerin seçiminde etken olan faktörlere değinilmektedir. İkinci bölümde seramikler, pişmiş toprak malzemelerin ana maddesi olan kil mineralleri ve gerek hafifletme gerekse de başka amaçlarla kile katılan katkılar ve hafifletme yöntemleri hakkında genel bilgiler verilmektedir. Üçüncü bölümde öncelikle hafifletici katkılar olmak üzere çeşitli katkıların tuğla kiline ilavesi ile ilgili çalışmalar hakkında yayın taraması yapılmıştır. Üretimde kullanılan malzemelerin özeliklerinin tanımlanması, ponza katkılı tuğla üretimi ve üretilen numuneler üzerinde yapılan deneyler dördüncü bölümde açıklanmıştır. Beşinci bölümde ise, üretilen pişmiş toprak malzemenin, fiziksel t mekanik, mineorolojik petrografik ve mikroyapı özelikleri, def lokulan ve ponza katkısı, pişme sıcaklığı ve ponza hacim oranı gibi parametrelerin etkisi açısından incelenmekte ve elde edilen sonuçlar irdelenmektedir. Genel sonuçları içeren altıncı bölümde ponza katkılı tuğlaların saptanan özelikleri ve bu özelikler arasındaki ilişkiler toplu olarak değerlendirilmiştir. Ponza katkısı ile gelen düşük basınç dayanımı değerlerinin, def lokulan ve özellikle 0.5 mm den küçük dane çaplı ponzalarında kullanılması ile arttırılabileceği ve böylelikle basınç dayanımları da kontrol altına alınmış hafif ve termal yalıtım özelikleri geliştirilmiş tuğla üretiminin ponza katkısı ile de mümkün olduğu sonucuna varılmıştır.

Abstract:
Especially in recent years the development of modern construction systems and prefabrication, rapid urbanization and the construction of higher buildings necessitated to save weight particularly on the external walls and inner partitions of the building. Therefore this makes it necessary either to give up or modify the traditional heavy construction materials such as clay brick. The bricks which were made lighter by the perforations are partially adequate for this necessity. But it is a well-know fact however that a decrease in the brick density by increasing the perforation volume generally do not improve the thermal insulating properties which are the basic cause for the need of lightweight bricks. Thus, it seems more plausible and worth examining to reduce the brick's bulk density by pore-forming of the ceramic body. In foreing countries, the production of light weight bricks by adding organic materials particularly like polystyrene, sawdust, and paper making sludge is quite widespread. But the use of these organic and combustible materials bring about some disadvantages. The incomplete combustion of these materials can stimulate organic material emissions in the pre-heating zone of the tunnel kiln. These especially comprise organically bonded pollutant carbon compounds, benzol, phenol and formaldehyde and diffuse into the atmosphere via the exhaust gases. In Turkey the production of light weight brick through this way is only substantiated with polystyrene and under the commercial title of izotugla. In addition, even in foreign countries, the use of inorganic materials as pore-forming and lightening additives is a new application. These natural inorganic materials are rather artificial aggregates that are produced with added energy from natural materials such as perlite and vermiculite. Whereas in Turkey pumice which is a natural lightweight aggreagate is abundantly available. When we handle the subject from a different point of view, that is, from the view of the effective use of existing sources, it seems possible that admixture of this light weight aggregate to brick clay, makes it possible to use this aggregate economically and to produce lightweight bricks with improved thermal insulation properties. And with this application, energy and housing deficit - xx -problems of Turkey under existing socio-economic circumstances can be solved partially. Because one of the most important advantages that is brought about with the use of lightweight bricks is the energy conservation through thermal insulation properties. In the light of the above identified reasons, the investigation of the production conditions of the bricks with pumice additive as an alternative for the other pore-forming materials and lihgtweight bricks is the main goal of this study. Beside this, with porous materials like brick and concrete, the importance of the pore system developed in the materials body and the microstructures type that affects the other properties of the material is known. For this reason, in this investigation too, the experiments and the investigations about the bricks with pumice additive handles the porosity, pore size distrubution and micro-structure beside the utility of these bricks. The study is presented in six chapters. The first chapter is the introduction part in which a short explanation of the subject matter is made and the factors that affect the selection of the materials used in the production are mentioned. In the second chapter the general knowledges about the ceramics, clay minerals which are the raw material of the fired clay materials and their characteristics are given. The most important clay properties are listed as plasticity, cohesion, thixotrophy, shrinkage and colour. Also in this section in addition to the essential clay minerals the accessory minerals they contain that influence the behaviour and utility of a clay, are dealt with. It is stated that, the most common minerals among these are quartz, feldspars and minerals costaining iron, lime, alkali and soluble salts. Again in this chapter, the materials that are added to clay with different purposes are classified generally. Among those the materials that lighten the brick and develop the thermal properties of it are emphasized and the pore-forming methods are stated since they are related to the subject matter of the study. These methods are : 1) The addition of inorganic materials which themselves are also porous and lightweight or organic materials that leave behind pores in the ceramic body by corbanizing during firing. 2) Pore-forming by chemical and mechanical foaming methods and techniques. - xxi -In the third chapter there is an overview of the relevant literature. The studies dealt with in this chapter are classified in three categories. These studies are about the adding of the below materials to brick clay:. Pore-forming additives,. Opening additives,. Industrial wastes with no pore-forming effect. The properties of the materials used in the pro duction, the production of the bricks with pumice additive and the experiments on the produced speciemens are explained in the fourth chapter. In the analysis done for the determination, of the properties of the clay used, it is found that the 57 % of clay cansists of particles smaller than 2/x, its true density is 2.70 gr/cm, the plastic limit is 23 % and the liquid limit is 54 %. As a result of X-Ray analysis it is found that, it is a clay mineral of the kaolinite group and beside this, it contains a great proportion of quartz mineral. In the experiments on the pumice lightweight aggregate extracted in the vicinities of Nevşehir region, the true density of this aggregate is determined as 2.41 gr/cm, the bulk density of pumices of the 2/4 mm particle group is determined as 0.93 gr/cm in dry state and the compressive strength of. them is 8.3 N/mm2 In this study the effects of pumice additive on the mechanical and physical properties of the brick are examined in two different aspects; 1) The effect of pumice particle size; a) From the pumices with different particle sizes fitting the existing sieve set is obtained three groups of 1.2, 2/2.36, 2.36/3.35 mm. It is accepted that smaller than 1 mm. particle size has no effect on the bulk density and accordingly it is not used, b) Since it is thought that by using each of the particle groups one by one it would be quite difficult to make production in natural conditions, to mix all the particle sizes with the biggest aggregate size as being 4 mm. is planned. With this purpose, the aggregate granulometre suitable the Fuller parabola which is taken as the referance curve in the concrete mix design is accepted as the basis; and with the idea that the aggregate smaller than 1 mm particle size would increase the strength by getting into the pores between the particles, adding powdered pumices with small particle sizes to this mixture seemed suitable - xxii -2) The effect of pumice volume; All of the below as being in fired state;. 50 % pumice, 50 % fired clay by volume. 53 % ", 47 % " " " ". 60 % ", 40 % " " " ". 70 % », 30 % " " " " fractions and in the 1/2, 2/2.36, 2^36/3.35 mm particle groups are produced. In these groups it was not possible to produce more than 70 % by volume fraction of pumice with the extrusion method. In the mixtures made according to Fuller parabola, since there is aggregate with finer sizes it is thought that the volume fraction smaller than 60 % would not provide enough reduction in the bulk density; accordingly, the mixtures were first begun with 60 % pumice volume fraction and then by increasing 10 by 10 there obtained four different mixtures up to 90 % pumice volume fraction. The clay-pumice mixtures, prepared with above listed ratios and particle sizes are shaped by extrusion method and it is formed prismatic samples with the dimensions of 4x4x16 cm. To research the effects of firing temperature on the properties they are fired at temperatures of 800°C, 850°C, 900 C, 950 C and 1000 °C. In the preparation of clay, a second method is tested; the clays are dispersed in the water by using def locculants. Deflocculant proportions are 0,867 gr phosphor pentoxide (P2O5) against 1.29 gr sodium hydroxide (NaOH) and they are added to clay so as to make the total additive proportion 2.12 %. For examining the effects of deflocculant additive on the physical and mechanical properties of the bricks, P2O5 and NaOH added clay is produced with the above mantioned pumice mixture fractions and firing temperatures. The linear drying shrinkages of all the prepared specimens are calculated and the dilatometric analysis is applied only on the specimens produced according to Fuller parabola. The physical tests that performed on the fired specimens are shrinkage, capillary absorption, absorption in atmospheric pressure, absorption by boiling 2 hours and true density. After these tests the bulk density, capillary pore percents, apparent and true porosities and saturation coeffecient of the specimens are also calculated. Thermal conductivity experiment is performed on only the non-pumice added bricks fired at 850 °C and 950 °C and bricks produced according to the Fuller parabola. - xxiii-The cylindrical specimens of 8x50 mm dimensions with the same mix design but fired at 800 °C are again dilatometrically analyzed and linear expansion coefficients are calculated. Related to the micro- structure on some of the selected specimens Mercury Intrusion Porosimetry (MIP), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometer (EDAX) tests are made; and for the determination of the petrographic and mineralogical structure a number of researchs are performed with polarised microscope and X-Ray Dif f ractometer. Firstly the longitudinal resanance freguency and then the ultrasound velocity of all the prismatic specimens are measured with ultrasonic instrument. From these measurements two different elasticity moduli, Eu and Er are calculated. The mechanical tests applied are simple beam flexure and compressive strength tests. On the two of the each three compressive strength test applied specimens, modulus of elasticities are recalculated through the readings of compactions in length by means of a comparator. In calcuting the elasticity moduli the following method is followed : By disregarding some first points in the stress-strain curves, linear regression according to least sguares method is performed up to the point they show linear behaviour and the slope of the regression line is specified as elasticity moduli. In the fifth chapter, the physical, mechanical, mineralogical, petrographic and microstructural properties of the bricks are examined from the view of the four parameters which are the deflocculant and pumice additive, firing temperature and pumice volume fraction and the obtained results are evaluated and discussed through graphics. In the sixth chapter covering the general results, the properties of the bricks with pumice additive and the relations between these properties are evaluated substantially and the important results are grouped as follows : 1) The results related to physical, mechanical and micro-structural properties :. The physical properties of all the produced pumice added and without pumice brick series react against the change of firing temperature in the same way. As the firing temperature increases, shrinkage, bulk density and ultrasound velocity increase, normal and boiling absorption capacities and porosity decrease. The - xxiv-capillarity and sorptivity increase as the firing temperature increases in most of the specimens. However, as seen in the deflocculant added reference bricks and bricks produced with pumices granulometrically suitable Fuller parabola with a 90 % volume fractions, when the firing temperature increases, vitrification and as a consequence of this, with the closing of capillary shaped pores, the capillarity decreases. Sometimes by incomplete fusion the pores existing in the material's structure becomes finer instead of closing and capillarity increases. As a result is found that capillarity and capillary absorption is not only affected from the firing temperature and porosity but also the geometrical shape and size of pore structure.. In the researchs done with the scanning electron microscopy it is seen that with pumice additive, the pores in the brick's body are generally formed between pumice and matrix and many times they appear as circular or continious capillary pores which are developed as a result of the shrinkage: of the clay getting into the pores of pumice. From the results of the measurements done with mercury intrusion porosimetre, it is found that firing temperature and pumice additive factors, affects and modifies the sizes and distrubutions of the pores: By pumice additive and by increasing firing temperature, the maximum of penetration shifts in the direction of larger pores.. Because of the interior fissures caused by the production defects, in the bricks produced with the pumices that have diameters of 1/2, 2/2.36, 2.36/3.35 mm, firing temperature has no effect on the mechanical strength : Whereas including the reference bricks and with a few exceptions in the bricks produced with pumices granulometrically suitable Fuller parabola, compressive strength increases as the firing temperature increases.. The effects of deflocculant and pumice additive on the properties of the bricks without additive are totally different from each other: Deflocculant additive makes the clay body fuse and vitrify and then the bulk density, ultrasound velocity and compressive strength of the fired product increases while the porosity decreases. Whereas with pumice additive the apparent pores, pore sizes, porosity and termal insulating capacity of the with and without deflocculant bricks increase while the bulk density and mechanical strength decrease.. With the bricks produced with pumices granu lometrically suitable Fuller parabola, as the volume fraction of pumice increases, as an effect of less than - xxv -0,5 miti partide sized pumices, bulk density, ultrasound velocity and mechanical strength increase while porosity and absorption decrease. This effect is much more clear on the bricks without deflocculant additives. In the bricks with deflocculant, with an increase in the volume fraction of pumice additive, there is a substantial increase in compressive strength, while the physical properties and flexural strength is not changed. 2) General Results :. While the bricks without deflocculant produced in the 1/2, 2/2.36, 2.36/3.35 mm particle sizes are much more effective in reducing the bricks bulk density in camparison to the other types, many of them couldn't provide limiting compressive strength values of a masanry brick should posses. Therefore these bricks can only be produced with deflocculant additive. In the same production conditions, since the mechanical strengths of the deflocculant added bricks usually decrease at high firing temperatures for these also the optimum firing temperature is determined as 850 °C..Beside all these, the use of the bricks produced with pumice 60 % and 70 % volume fractions and granulometrically suitable Fuller parabola should be preferred since their compressive strength limits are more dependable and they give nearly the same bulk density and termal conductivity values with the bricks produced with single type particle size pumices.. With the bricks prepared with pumices of 80 % and 90 % volume proportion granulometrically suitable Fuller parabola and with firing at high temperatures like 950 °C and 1000 °C, there is a little decrease in the bulk density; while it is possible to produce bricks with low porosity and water absorption even lower than bricks without pumice additive. With the suitable chosen places the use of the bricks of this quality would be very beneficial in making use of small particle size pumices which are quite widespread in Turkey.. The low strengths as a results of pumice additive, can be increased with deflocculant additive and with the use of different sized and particularly smaller than 0,5 mm. particle size pumices. Consequently it is concluded that, through the use of deflocculant and the change of the size distribution of pumice added to clay, it is possible to produce light weight bricks with improved insulating properties and sufficient compressive strength. -