Heat-resistant concrete based on aluminothermic slags of the Klyuchevskii Ferroalloys Plant

Substance and grain compositions, parameters of physicochemical properties, and ranges of application of heat-resistant concretes produced on the basis of aluminothermic slags are presented. A wide range of fillers and lime-aluminate cements of refractory and heat-resistant concretes is considered. Experience in the use of slag concretes in linings of various heating units is described. __________ Translated from Novye Ogneupory, No. 12, pp. 15–18, December, 2007.     

New refractory concretes and binding systems: Basic trends of development, production, and use of refractories in the 21st century. Part III. Spinel and cast (self-flowing) concretes

The state-of-the-art in the field of creation and use of spinel, spinel-forming, and corundum-spinel concretes in the world is analyzed. In contrast to foreign-made concretes of this calss produced using high-alumina cement Russian specialists have developed cementless spinel concretes of the type of ceramic castables. Achievements in the field of low-cement self-flowing (cast) concretes, which are often more effective than vibrocompacted ones, are considered. The factors that determine their quality are analyzed. Concretes of this class can be obtained on the base of ceramic binders (HCBS). Due to their diminished (compared to low-cement concretes) water demand the materials can possess a lower porosity. Translated from Ogneupory i Tekhnicheskaya Keramika, No. 4, pp. 12‐18, April, 1998. Parts I and II have been published in Nos. 2 and 3, 1998. To be continued.     

New forms of unmolded refractory materials produced by OOO Keralit

New forms of refractory materials are presented, produced by OOO Keralit: heat-insulating concretes, refractory concretes with low and normal cement contents, torcrete-mixes for heating furnace walls, and magnesia torcrete-mixes for hot repair of arc furnaces. Properties and fields of application for unmolded materials are provided. Translated from Novye Ogneupory, No. 7, pp. 21–23, July 2008.     

Petrographic investigation of the pore structure of alumina-silica refractory concretes

The results of a petrographic study of the pore structure of chamotte filler, the binder of alumina-silica refractory concretes, and stamped chamotte brick are presented. It is established that the pore structure of vibrationally cast alumina-silica concretes produced at the Semiluki Refractory Works consists mainly of round, closed pores. __________ Translated from Steklo i Keramika, No. 5, pp. 26–28, May, 2007.     

Preparation and properties of corundum HCBS and ceramic concretes. Part 3. Casting and volume constancy of ceramic concretes

Vibration casting and casting from a self-spreading mix with an original moisture content of molding systems of 3.8 – 4.2% are used to prepare coarse-grained (D _max = 10 mm) and medium-grained (D _max = 3 mm) corundum ceramic concretes with a corundum-mullite matrix system. Depending on the heat treatment temperature, the amount of their open porosity is 11 – 15%, and the ultimate strength in compression reaches 160 MPa. Both cast and compacted ceramic concretes have high volume constancy during heating or firing, and also in service. Linear shrinkage does not exceed 0.2 – 0.5%.     

Integrated shrinkage,relative humidity,strength development,and cracking potential of internally cured concrete exposed to different drying conditions

Internal curing (IC) technology using prewetted lightweight fine aggregates (LWFAs) as additives has been proved an effective means for mitigating both autogenous shrinkage and early-age cracking under sealed curing conditions. However, for practical structures in the field, concrete experiences more complex environmental conditions compared to under sealed curing. To better utilize internal curing technology for durable concretes, this study conducts comprehensive investigations on both control and internally cured concretes at water/cement (w/c) ratio of 0.3 and 0.4 in terms of the influence of age when concrete is exposed to drying and the drying duration on the developments of integrated shrinkage, internal relative humidity, compressive and flexural strengths, mass loss, and cracking potential. The results are beneficial for producing internally cured concrete with increased resistance to early-age cracking and enhanced durability for infrastructure applications.     

Properties of aluminophosphate concretes containing various types of orthophosphoric acid

Conclusions The type of orthophosphoric acid has the maximum influence on the properties of corundum concretes, a lower influence on high-alumina concretes, and practically no influence on quartz-clay concretes. It is desirable to use wet-process orthophosphoric acid for refractory concretes. The excellent properties of concretes in the system A1₂O₃-SiO₂ based on this acid which is also cheaper enabled us to recommend it for preparing refractory concretes.The advantage of using H₃PO₄ of various types for corundum concretes is determined by the requirements placed on them in actual working conditions.Translated from Ogneupory, No.6, pp. 58–61, June, 1970.     

Properties of cast magnesial refractory concretes

Conclusions The rheological and physical properties of cast magnesial concretes and the relationship between these properties have been studied.It is established that with an increase in the compressive load, the shear deformation of the cast concretes decreases sharply and the concretes become more rigid. In the concretes studied, when rapid elastic deformation predominates, slow elastic deformation is observed to a lesser extent; and the plastic deformation of the cast concretes is quite insignificant. The viscosity of the experimental concretes is virtually the same and is independent of the composition of the concrete.The cast concretes are characterized by an adequate ultimate compressive strength, adequate thermal shock resistance after drying, a low deformation temperature under a load of 2 kgf/cm², and by very low gas permeability.Translated from Ogneupory, No. 6, pp. 36–41, June, 1979.     

Strength of corundum concretes

Conclusions Studies were made of the strength properties of corundum concretes containing a hydraulic bond, and an assessment was made of bending strength in relation to the heat-treatment temperature.It is shown that the concretes investigated belong to nonlinearly deformable materials. We determined the true strength of the concretes, which with rise in temperature increases; the strongest are concretes with a bond from hydraulically setting cement — Talum cement.We determined the maximum bending deformation of the concretes. It is shown that the lower the elastic deformation shown by the refractory material before failure then the less catastrophically will the destruction occur.We determined the densities of the full energy of deformation and the elastic energy at temperatures of 120, 1400, and 1750°C. It was established that concretes characterized by maximum strength possess the greatest stock of densities of full and elastic energy.On the basis of the deformation diagrams obtained for nonlinear-elastic concretes we determined the magnitudes of static and dynamic elasticity moduli. The strongest concretes are characterized by the maximum modulus values.Translated from Ogneupory, No. 6, pp. 9–14, June, 1986.     

Scale resistance of some refractory concretes

Conclusions The scale resistance of refractory concretes when the latter interact with molten scale varies, and is primarily determined by the composition of the concretes. The highest scaleresistance is found in the dunite concretes and the lowest in the high-alumina; the chromemagnesite, chromite, and corundum concretes occupy the intermediate position.The scale in the solid state hardly interact with the concretes at all.The wear of the high-alumina and corundum concretes by molten scale occurs as the result of the formation of FeO·Al₂O₃ hercynite which forms a low-melting eutectic with the iron oxides (hercynite-wustite eutectic at 1330°C); hercynite is next replaced by magnetite and hematite which, after changing into FeO, form low-melting fayalite 2FeO·SiO₂ with SiO₂. The process of hercynite-formation and its replacement by iron oxides are accompanied by an increase in volume of roughly 16% and this leads to the swelling and deformation of the concretes.The wear of the chrome-magnetite and chromite concretes is accompanied by the appearance of new formation of the magnomagnetite and high-iron chrome-spinel type.Translated from Ogneupory, No. 1, pp. 43–47, January, 1979.     

Deflocculated refractory concretes with a high cement content

Dependences are provided for the spreadability and mechanical characteristics of deflocculated concretes on the content of microsilica, deflocculant and water. The effect of microsilica on hydration of calcium aluminate cements is discussed. __________ Translated from Novye Ogneupory, No. 1, pp. 44–48, January 2008.     

Thermal,mechanical properties,and low‐temperature performance of fibrous nanoclay‐reinforced epoxy asphalt composites and their concretes

Epoxy asphalt (EA) concretes have been widely used in the pavement of orthotropic steel bridge decks. The objective of this study was to figure out the enhanced effects of natural fibrous attapulgite (ATT) as a reinforced nanofiller in ATT/EA nanocomposites through a comparison of the properties of the composites with a series of various nanoclay loadings. The rheological properties, glass transition, thermal stability, mechanical properties, and morphology of the ATT/EA composites were characterized. Furthermore, the low‐temperature flexibility of the ATT/EA concretes was investigated. The test results show that the addition of ATT had no significant effect on the rotational viscosity of EA in the initial stage of the curing reaction. In addition, the ATT/EA composites showed better performance than the neat one in thermal stability with a higher glass‐transformation temperature. The tensile strength and elongation at break of the ATT/EA composites at a loading of 0.5 wt % ATT were 21 and 22% higher than those of the neat EA. The addition of ATTs also enhanced the low‐temperature flexibility of the EA concretes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41694.     

New-generation refractory concretes. Thermal processes,structure and high-temperature properties

Regularities of the processes of drying and heat treatment (firing) of new refractory concretes (ceramic concretes, low-cement refractory concretes, etc.) are considered. The conditions for the appearance of the effect of their explosive cracking (destruction) in drying are analyzed. Changes in the porous structure and some characteristics of the concretes (porosity, strength, shrinkage, expansion) are considered as functions of the temperature of their preliminary treatment. Regularities in the formation of the zonal structure and the stress state in use of refractory concretes are described. Data on the thermal conductivity and thermal expansion of refractory concretes of the Al₂O₃-SiO₂ system are presented for a wide temperature range.Translated from Ogneupory, No. 6, pp. 5–12, June, 1995.     

Strain model for traditional and self‐compacting concrete during fire

In this paper, a complete strain model is derived that describes the strains developed during fire (up to 400 °C) and is based on the model of Anderberg et al., published in 1976. This model describes the total measured deformation as a superposition of four strain types: free thermal strain, instantaneous stress‐related strain, creep strain and transient strain. The strains are derived from loading tests on cylinders with dimensions Ø106 × 320 mm, submitted to load ratios of 0%, 20% and 30% of the initial strength before heating. For damage to the oven to be avoided, the instantaneous stress‐related strain is found from Young's modulus tests immediately after cooling. All tests occurred at a heating rate of 5 °C/min, and the specimens were pre‐dried to avoid explosive spalling. The investigated concretes are a traditional and a self‐compacting concrete with a testing age of about 30 months. Only small differences between both concrete types are found for the transient strain despite the different fracture of cement matrix. For the studied test conditions, the modern siliceous concretes such as self‐compacting concrete yielded similar results as the traditional siliceous concretes tested in the 1970s. Copyright © 2012 John Wiley & Sons, Ltd.     

Reactive powder based concretes: Mechanical properties, durability and hybrid use with OPC

The basic mechanical properties, frost durability and the bond strength with normal strength concretes of the ultra high strength (UHS) mortars and concretes were studied. The produced mixes had plastic or fluid-like consistency. The 28-day compressive strength varied between 170 and 202 MPa for the heat-treated specimens and between 130 and 150 MPa for the non-heat-treated specimens. The shrinkage values were two times higher for the UHS mortars in comparison with the UHS concretes. After the initial shrinkage, swelling was noticed in the UHS mortars. The lowest creep values were measured for the non-heat-treated UHS concretes. The frost-deicing salts durability of the UHS mortars and concretes appeared to be very good even despite the increased water uptake of the UHS concretes. The study of the hybrid concrete beams indicated the formation of low strength transition zone between the UHS mortar and normal strength concrete.     

High-alumina concretes and objects based upon them used for metal pouring

High-alumina concretes have been developed in OOO MetOgneupor for the production of objects for siphon steel pouring. Information is provided about the objects developed and their operating experience under ZAO MRK (mechanical repair unit) OAO MMK conditions. Translated from Novye Ogneupory, No. 3, pp. 11 – 12, March 2009.     

Effect of binder content on the performance of alkali-activated slag concretes

This paper assesses the mechanical and durability performance of concretes produced using alkali silicate-activated ground granulated blast furnace slag as sole binder. Alkali-activated concretes are formulated with 300, 400 and 500 kg slag per m³ of fresh concrete, and their performance is compared with reference concretes produced using Portland cement (OPCC). Regardless of the binder content, the alkali-activated slag concretes (AASC) develop higher compressive strength than the comparable reference concretes. A higher binder content leads to increased strength in both AASC and OPCC at 28 days. However, at 90 days, the performance penalty for low binder content is more significant in the OPCC than AASC samples. Permeability, water sorption and carbonation resistance properties are also improved at higher binder contents. By controlling mix design parameters, it is possible to produce AASC with mechanical strength and durability comparable to conventional Portland cement concretes.     

Properties of hot aluminosilicate concretes with various binders

Conclusions On the basis of results of a study of aluminosilicate concretes in the heated state, the following recommendations can be made for the use of these concretes, depending on the form of the binder and on the concentration of Al₂O₃ in the filler.Semiacid concrete in APB has fairly good strength and deformation properties, a high thermal-shock resistance, and can be used up to temperatures of 1350°C.Chamotte concrete in HAC is clearly not economical to manufacture. For performance, it can be totally replaced by chamotte concrete in AC or APB. The chamotte concrete in APB has better characteristics in the heated state than the concretes in other binders. It can be successfully used under conditions where there are sudden variations in the temperature and mechanical action.Aluminosilicate concretes in WG can reasonably be used in conditions of fairly intense abrasive action up to temperatures of 800°C. In places where the concrete is not subject to the action of molten metal or slag, it would not be reasonable to use concretes in WG containing >60% Al₂O₃.The high-alumina concretes in HAC have greater strength at high temperatures and therefore they must be used in those conditions; analogous concretes in APB can reasonably be used where there are sudden variations in temperature.The properties considered here of the concretes in HAC and APB are improved by increasing the concentration of Al₂O₃ and therefore the form of the filler for the concretes must be chosen in relation to the actual conditions of use.Translated from Ogneupory, No. 7, pp. 52–60, July, 1980.     

A method for repairing tunnel furnace cars

The NPF Alineka company has developed refractory construction concretes BRSB20I11 based on water glass and concretes BRAB50I13 and BRAB50I15 with the traditional content of aluminate cement, which have a high class of thermal resistance (T₁40–T₁80) and the maximum application temperature of 1100–1500°C, as well as heat-insulating lightweight plates of size 300 × 200 × 80 mm and density 400 kg/m³, with a maximum application temperature of 1150°C. These materials can be used as lining of tunnel furnace cars for firing wall ceramics, as well as porcelain and faience products. The experience in repairing a furnace car is described. __________ Translated from Novye Ogneupory, No. 5, pp. 15–19, May, 2007.     

Abrasion resistance of refractory concretes and linings

Results are provided for determination of the abrasion resistance of refractory concretes of different composition according to the standard ASTM C-704. Principles are considered for constructing abrasion-resistant linings in order to protect heating units in various branches of industry. __________ Translated from Novye Ogneupory, No. 3, pp. 81–85, March, 2007.