Physicotechnical properties are provided for concretes based on mechanically-activated phosphate suspensions previously modified with magnesium and aluminum hydroxides and silicic acid. The results obtained demonstrate the efficiency of using modifying additions in order to increase the strength and heat resistance of corundum concretes. Development and improvement of the manufacturing technology for refractory materials using phosphate binders has promoted high physicotechnical and engineering properties for these refractories, strong adhesive bonds between particles of the filler within them, simplicity of production, not requiring significant energy and capital expenditure.Analysis of results of studies in the field of forming the material structure, the technology and properties of refractory concretes based on phosphate binders has revealed the efficiency of their use. Use of phosphate binders makes it possible to prepare high quality components [1]. Of the many forms of refractory concretes the best properties are exhibited by corundum concretes based on orthophosphoric acid, magnesium-and aluminophosphate binders. With the optimum content of 80% H 3 PO 4 these concretes after heat treatment at 800°C have high strength (ultimate strength in compression 60 MPa) and the greatest heat resistance (>50 thermal cycles). Addition of 9 -40% alumina hydrate does not improve the properties of corundum concrete, the strength is reduced, and there is an increase in its shrinkage and porosity. Corundum concretes based on magnesium phosphate binders with addition of 10% raw ground technical grade alumina are distinguished by high apparent density, strength and heat resistance [1].The properties and operating characteristics of corundum refractories are improved by introducing into their composition small amounts of modifiers [2]. In refractory concrete technology based on phosphate binders there is use not only of orthophosphoric acid, but also mechanically activated binding suspensions with different modifiers. Here a combination of mechanical activation and chemical reaction markedly improves the strength of castings with an increase in concentration of the phosphate-ion in the surface layer of corundum crystals [3].Mechanical activation of corundum charges with heat treatment at 180°C of an aluminoborophosphate binder reduces open porosity to 23% and increases the ultimate strength in compression to 115 MPa for corundum concretes after firing at 1300°C [4].The hardening mechanism for refractory concrete mixes based on phosphate binders is quite complicated. Within them there is chemical reaction of phosphates with the filler, polymerization and polycondensation, and also adhesion [5]. Here hardening processes change from chemical reaction of phosphate binders with the surface of filler grains to their simple adhesive gluing. Hardening of the main oxides (MgO, BeO, Y 2 O 3 ) is due to primarily to their chemical reaction with phosphate binders that leads to formation of new chemical compounds. The hardening mechanism f...
Ceramic lining brick is the most eco-friendly material and it is widely spread in modern construction. To date, the brick of light colors is of particular interest among consumers (peach, straw, beige, etc.). One of the main problem of brick constructions which impair technical and aesthetical properties is the salt weathering on the ceramic masonry surface. The reasons for this phenomenon are various-high content of water-soluble salts in clay raw materials, migration of salts from cement masonry, water hardness, etc. There are plenty methods to reduce damage and protect lining brick from salt efflorescence but raw materials selection and preliminary analysis of its liability to salt weathering is of particular importance. This paper addresses to the occurrence causes and microstructure of vanadium salts on the light-tone lining brick. The mineral composition, physical and molding properties of raw clay materials from Bolshaya Karpovka, Talalaevskoe, Chasov-Yarskoe deposits is analized from the standpoint of vanadium salt efflorescence. It is found that salt formation on the test sample surface consists of alkalis sulphates and calcium vanadates from the greenish-yellow to orange colors. The paper provided recommendations for using above-mentioned clays in light-tone ceramic brick manufacturing.
Coatings and materials based on aluminum phosphate suspensions are studied that have high strength in a raw state and are suitable for carrying out combined firing of a refractory and coating. An aluminum phosphate binder provides preparation of high physicomechanical properties in the firing temperature range. Use of traditional mixes with a protective aluminum phosphate coatings, and also ceramic concrete based on this binder provide increased material corrosion resistance, and consequently an increase in object operating life and period between repairs for metallurgical and glass melting units.Phosphate binders are used traditionally both as a binder in preparing refractory ceramic concretes and in the form of protective coatings [1 -5]. Their use makes it possible to reduce the firing temperature during preparation of refractory concrete materials, and to increase refractory concrete life in service. The purpose of protective coatings on refractories is very varied. There are coatings that are chemically resistant, antiburning, gas protective, etc. The service life of a coating depends on operating conditions and is from several seconds to many days. The choice of a protective coating in each specific case should be made in relation to the nature of the corrosive medium and the nature of the material being coated, Coatings should be refractory and resistant sharp temperature variations and mechanical action [6].Phosphate binders are highly refractory substances, prepared as a result of chemical reaction that occurs between orthophosphoric acid and finely ground aluminum-, chromium-, aluminum-chromium-containing or aluminum silicate materials [4]. In this work in order to prepare modifying coatings a suspension of aluminum phosphate composition was used, which has increased strength in a raw condition, and therefore it becomes possible to heat treat an object and coating simultaneously.In developing protective coatings three types of materials and binders were studied:-aluminum phosphate binders, which are used as a protective coating, and also a ceramic concrete matrix;-ceramic concretes based on an aluminum phosphate binder developed using high alumina chamotte as a filler; -composite materials prepared on the basis of a ramming grade MMK-80 (plant control composition) produced in OAO Semiluk Refractory Plant.Aluminum phosphate binders were prepared by combined grinding of components in a ball mill of periodic operation with a volume of 8 liters with orthophosphoric acid with an apparent density of 1140 kg/m 3 in a ratio of 75% solid and 25% liquid phase. The solid phase used was electromelted corundum with an Al 2 O 3 content not less than 97%. Binder dispersion was specified by a content of particles on a 0063 screen (less than 63 mm) not more than 2%. Combined milling of binder components provided with mechanical activation improvement of the suspension quality obtained.Ceramic concretes based on aluminum phosphate binder were prepared on the basis of an experimental composition, containing 65% high alumi...
Composite refractories and heat insulation materials of corundum, aluminosilicate and carbide ceramic compositions with improved operating properties have been prepared by modifying dispersed binder materials at different levels.
The results of studies of the reotechnological properties of plastic refractory masses based on bauxite suspensions plasticized with refractory clay are presented. The regularities of the influence of the filler diameter and the content of the binder in the mass on the structuralmechanical and operational properties of samples based on it are established. Samples from the developed masses intended for molding at low pressure (up to 10 MPa) are characterized by high compressive strength (100‒110 MPa) and relatively low porosity (up to 20‒21%) after heat treatment at 1300 oC. Ill. 5. Ref. 20. Tab. 4.
For centuries, ceramic brick is the main building material in the construction of low-rise residential buildings and utility rooms. In addition, durability, high artistic features and the absence of toxicity characterize building ceramics. The volumes of construction in the Republic of Sakha (Yakutia) and the demand for bricks are increasing every year. Ceramic brick imported from outside the republic is used in the construction of facilities in Yakutsk. The Republic of Sakha possesses a good raw material base of clay and loam for the production of ceramic products. The study of basic properties of clay raw materials for obtaining a quality product is of particular importance. The results of studies on the use of raw materials from the Sannikovskoye clay deposit located in the Republic of Sakha (Yakutia) for the further production of ceramic bricks are presented. The chemical and mineralogical compositions of the clay raw materials are determined. Compositions of ceramic masses with the addition of waste cullet in different percentages are designed to reduce the amount of solid waste. The cullet used is tare and transparent. The technological and basic physicomechanical properties of the obtained samples are investigated.
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