Refractory Mortars Research Articles

A Statistical Approach for Green Conversion of the Amorphous E-waste into Glassy Refractory Mortar Subjected to High Temperature

A Statistical Approach for Green Conversion of the Amorphous E-waste into Glassy Refractory Mortar Subjected to High Temperature

Effect of ladle lining system refractories on the cleanliness of heavy-rail steel U75V

To understand the effect of refractories in the ladle lining system on the evolution of inclusions in the secondary refining process, refractory samples were taken from different locations in the ladle system (Slag lining bricks, Sidewall bricks, Refractory mortar, and Bottom bricks). Laboratory experiments were carried out using heavy-rail steel slab samples (Si-Mn-killed steel) and different refractory bricks. The four kinds of refractory bricks can be roughly divided into 3 categories: (1) MgO-Al2O3-C system (MAC, high MgO>55%); (2) Al2O3-MgO-C system (AMC, low MgO<13%); (3) Al2O3-SiO2 system (AS). The results show that after the reaction between molten steel and refractory materials, both AMC (slag lining bricks and sidewall bricks) and MAC (bottom bricks) will dissolve their component Al2O3, increasing [%Al] content in molten steel, forming MgO-Al2O3 type inclusions, and the dissolution of its component MgO depends on the content of MgO. When MgO>55%, MgO will dissolve. When MgO<13%, due to the low activity of MgO, MgO will not dissolve. MgO inclusions were found in the steel when the MgO content in the refractory was higher than 55%. MgO inclusions may originate from the refractory itself. The reduction of TiO2 in the AS (refractory mortar) by [%Al] and [%Si] in the steel increases the [%Ti] content of the steel, forming Ti-containing inclusions.

Experimental investigation on the influence of partially stabilised nano-ZrO2 on the properties of prepared clay-based refractory mortar

Abstract Buildings subjected to elevated temperatures or thermal shock can be exposed to many changes in their properties, such as phase transformation and weight loss; therefore, the thermomechanical stability of mortars is essential to maintain their properties. In this work, different ratios of partially stabilised nano-zirconium oxide (ZrO2) were used as a partial replacement by weight of kaolin to prepare a refractory mortar. Five ratios (5, 7.5, 10, 12.5, and 15%) of ZrO2, as well as unfired kaolin, water, and internal lubricant (potassium silicate) were applied to increase the specimen’s cohesion. The results showed that ZrO2 additives are suitable to be used for the production of refractory mortar as a result of increased physical and mechanical strength.

Study of the Mechanical and Thermal Properties of Refractory Mortars from Kaolin and Bentonite

In this paper, Mortar was prepared from medium alumina refractory grog, bricks crashed as a mean material to a particular size, and Iraqi raw (kaolin or bentonite) as binding materials. Refractory bricks were crushed, milled, then sieved to three particle sizes: fine as (1.18 >fine> 0) mm, medium as (2.36 > medium > 1.18) mm, crushed as (400 > coarse > 2.36) mm. Then these particle sizes were mixed with Iraqi raw kaolin or bentonite with selected ratios (10,15,20,30 and 40) %. Specimens were formed by the wetting method, then drying it at laboratory temperature for one day, followed by firing it at 1200 ℃. Results showed that the porosity of specimens decreases when increasing the clay ratio from 3-4% (kaolin or bentonite), and the bond strength between grog and clay increases when increasing the clay ratio from 2-3% (kaolin or bentonite). Also, the diametrical strength increases when increasing the clay ratio from 4-7% (kaolin or bentonite). The thermal shock results showed that K-mortar is better than B-mortar, depending on the results we obtained through the effect of temperature and diametrical strength. The SEM results showed that mortar structure was produced by adding 40% bentonite with small irregularly shaped. The mortar was produced by adding 40% of kaolin which possesses regular mullite crystals. Finally, the results of the test EDS that K-mortar were revealed in showed that there is no adsorption of carbon while B-mortar showed that there is adsorption of carbon atoms.

Physical, chemical and thermomechanical characterisation of glass textile-reinforced concretes (TRC): Effect of elevated temperature and of cementitious matrix nature on properties of TRC

In this paper, the thermomechanical behaviour of two glass textile-reinforced concretes (TRCs), with temperature levels ranging from 25 °C to 672 °C, was firstly characterised, compared and analysed. Each TRC had three layers of alkali-resistant glass grid but a different cementitious matrix (one with normal mortar and the other refractory mortar). The first novelty and achievement of this study, compared to existing studies in the literature, is that the size of particles within the cementitious matrix of TRC has a very important effect on the ultimate stress and the post-cracked composite stiffness of TRC under thermomechanical condition. The resistance of TRC with normal mortar is greater than that of the TRC with fire mortar because the size of particles within the cementitious matrix is finer for the normal mortar. The second novelty and achievement of this study is that the fire mortar, with refractory property, leads to greater thermal and mechanical stability of TRC when it is simultaneously subjected to a tensile pre-loading and exposed to increasing elevated temperature. The third novelty and achievement of this study is that the evolution of thermomechanical behaviour of the two TRCs before 300 °C has been experimentally justified and analyzed thanks to physical, chemical and thermal characterization that has been carried out on crushed hardened cementitious matrix or on small TRC specimens. Between 25 °C and 110 °C, the decrease of the ultimate stress and the post-cracked composite stiffness of TRC corresponds to dehydration of components of cementitious matrix. However, between 110 °C and 300 °C, with water molecules released, hydration of anhydrous particles of the cementitious matrix (mortar) occurs, a gain in the ultimate stress and the cracked-composite stiffness of glass TRC consequently occurs.

USING ARABIC GUM IN PRODUCTION OF REFRACTORY BONDING MORTAR

Refractory bonding mortar is a specially-engineered blend consists of non-metallic materials that give the mortar unique heat-resistance and thermal characteristics for use in high-temperature applications. The goal of this study was to determine the performance of refractory mortar that produced from local raw materials in this study; Iraqi clays were utilized as raw materials while Arabic gum was used as adhesive materials. Three proportion mixes were applied, (96:4), (93:7), and (90:10) as (grog: kaolin binding material) and the burning temperatures for specimens were 1500°C. In the present research, some physical test such as the percentage of apparent porosity, bulk density, and specific heat are studied. Also, some mechanical properties such as compressive strength, binding strength, and dimensional stability are investigated. Finally, thermal conductivity and thermal shrinkage as thermal properties are also surveyed. All refractory bonding mortar produced in this study which has been used local materials have a good quality and it has all the characteristics of an economical product.

Influencia de la incorporación de vidrio triturado en las propiedades y el comportamiento a alta temperatura de morteros de cemento

The incorporation of grounded construction and/or demolition wastes to cementitious conglomerates aims to achieve a positive environmental balance, so that the construction industry assumes wastes from different sources. Glass as a waste has a high recovery degree and numerous reuse possibilities. The glass residues incorporation to the cement mortar is studied in order to know its behavior as arid substitute and its capacity of modify the final product properties. The present work deals with the analysis of the modifications produced in a reference mortar 1:3 (cement/sand) by a partial replacement of sand with grounded domestic glass, in proportions of 25 and 50% by weight. Chemical, mineralogical, physical and mechanical characterization were developed. Subsequently, samples were subjected to heating to 600 and 800°C in order to evaluate their behavior after suffering similar conditions to those of a refractory mortar. The results have shown significant differences in the coefficients of thermal conductivity of the samples, which are reflected in a better performance for the materials with glass fractions in their composition.

The Mechanical Performance Experiments of Blast Furnace Hearth Ramming Material and Carbon Brick Refractory Mortar

In this paper, the mechanical properties experiments of BF hearth ramming material and carbon brick refractory mortar were carried out. The compressive strength experiments of refractory mortar at different curing temperatures and the resin and asphalt combined with ramming material at different molding pressures and curing temperatures were carried out respectively. The conclusions are as follows: (1) In the experiment temperature range, the compressive strength of resin combined with ramming material is significantly higher than that asphalt under the same conditions. (2) With the increase of temperature, the compressive strength of resin combined with ramming material and refractory mortar first increased and then decreased, while the asphalt combined with ramming material increases gradually.

Fused Refractory Oxides Increasing Nonferrous Metallurgy Unit Lining Life

Technology is developed for preparing periclase-chromite composition refractories based on fused grains of increased thermal-shock resistance. Technology is created for preparing periclase composition refractories based on fused grains exhibiting a high service temperature (up to 1900°C) and improved thermal shock resistance. Refractory material SHS-technology is developed on whose basis fused refractory objects, brickwork mortars, and torcrete mixes for hot torcreting are created. Refractory materials are turned out on an industrial scale in OAO Kombinat Magnezit. They are used for the most worn parts of linings such as the tuyere zone in horizontal converters, the slag belt of ore-roasting furnaces (ORF), in the reaction zone of a Waelz kiln, ORF outlet assemblies, Kivcet unit arches, and Vanyukov furnaces. Lining life is increased by a factor of 1.5 – 2.5.

Compaction and shear failure of refractory mortars – effects of porosity and binder hardening

With the aim to correlate the global properties of refractory mortars with the micro-mechanical processes, a series of uni-axial compression and shear tests was conducted. The test program was developed with the view that the shear grain slip and cracks are frequent failure mechanism under compressive loads. The micro-structural changes during compression were monitored by X-ray micro focus computed tomography. Discrete element modelling was used to highlight the effects of individual factors of influence. Mortars with a water glass binder of different maturity were tested. In compression the mortars demonstrated cracking and pore closure. Shear tests showed that the failure process consists of multiple local failure events. The combined effects of the porosity and immature binder promote increased tendency for crack branching and arrest. This results in low shear strength and high compressibility. Cohesion and interlocking between the grains prevents crack branching and increases the stiffness and the strength.

Durable Structures for the Lining of Electric-Arc Furnaces Used to Make Ferronickel and Granular Mattes

Results are presented from a study of the service conditions of the lining of electric-arc furnaces and the character of fracture of their lining. New compositions of refractory mortars and mixes were developed along with new lining systems. Extensive factory tests were conducted of new systems that employ high-quality refractory mortars and protective refractory mixes in the lining of the furnace roof. Implementation of the measures that were proposed have made it possible to increase the durability of the lining by a factor in the range 1.4 – 1.6.

Effect of binding system on the compressive behaviour of refractory mortars

Abstract In refractory masonry lining of industrial furnaces the compressibility of mortars is critical for the thermo-mechanical integrity of the structure. Compressive stress–strain behaviour of refractory mortars has been measured during drying at room temperature and in the service temperature range of 300–1400 °C. The results have been explained using fractographic analysis and distinct element method computer modelling. The mortar failure has been shown to occur due to formation of shear bands of micro-cracks. The propagation of cracks preferably follows the shortest path between larger pores and is influenced by grain cohesion and interlocking. Tests with mortars featuring calcium aluminate cement, mono aluminium phosphate, water glass and bentonite clay binders have indicated that besides increasing the cohesion between the grains the binder reduces the internal friction that promotes higher compressibility. It has been found that the mortar with clay has the highest compressibility. The mortar with cement shows the most stable behaviour.

Effect of Alumina Source and Soaking Time on Properties of Refractory Mortar Using as Slumping Mold

Slumping molds or sagging molds are utilized for shaping glassware containers and many kinds of slumped glass products from glass plates. In Thailand, a large number of slumped glass factories use such molds in their production because slumping process is easy and cheap; however, the major cost of this process is slumping molds. They are imported from other countries and are expensive. In this research, slumping molds are created from local raw materials using the basic method to reduce the cost of the production. One of proper materials for making slumping mold is refractory mortar which can be easily formed into various shapes and sizes. Consequently, it is interesting to prepare slumping molds from refractory mortar. In this study, the effect of different sources of alumina (calcined alumina and aluminum sludge) and soaking time on the properties of the refractory mortar were investigated. Dolomite clay, milled sand and white portland cement were mixed with sources of alumina in distilled water to form pastes. Super plasticizer was added to the pastes to adjust flow ability. Plastic containers were used as molds for specimen forming. Specimens were cured at room temperature for 24 hours and dried in air for 24 hours. After that specimens were dried in an oven at 110 °C for 24 hours and then fired at 1100 °C. The result showed that the suitable condition for making slumping mold is to use calcined alumina as a source of alumina with soaking temperature of 1100 °C for 4 hours. The physical properties, chemical properties and thermal properties were discussed.

Methods for evaluating effective mortars and protective coatings for laying a heating unit lining

Results are provided for the effective development of procedures for determining the properties of mortars, protective coatings, and bonding elements, consisting of refractory objects and mortars for lining a rotary Waelz kiln, horizontal converters, reverbatory furnaces, and other heating units. Optimum compositions are developed for refractory adhesives, mixes and cements using effective methods for evaluating mortars and protective coatings. The use of protective coatings and mortars makes it possible to prolong the working life of units by 25–50% and thereby reduce the number of ongoing and major repairs of a unit lining and to obtain a tangible economic effect.

Magic-angle-spinning NMR at 30 T with a Hybrid Magnet

Abstract Solid-state NMR measurements at 30 T have been performed with a hybrid magnet of National Institute for Materials Science. Spectral resolution less than 3 ppm was confirmed by 79Br magic-angle-spinning (MAS) NMR measurements of a reference material KBr. A small sample and an aluminum metal shield were used to reduce the effects of field inhomogeneity and fluctuation. As an example of application for an industrial material, 27Al MAS NMR of a refractory mortar was demonstrated.

Ultra-high Magnetic Field (21.8 T) Solid-state Nuclear Magnetic Resonance for Inorganic Materials

Abstract We hereby report that ultra-high magnetic field (21.8 T) solid-state nuclear magnetic resonance (NMR) spectroscopy is very useful in studies of quadrupolar nuclides in inorganic materials. The increase in signal sensitivity, especially for species with large quadrupolar products, and the decrease in signal width become significant with increasing magnetic field strength. An 27Al 5QMAS spectrum of a refractory mortar was considerably resolved at 21.8 T compared with 16.4 T, suggesting the effectiveness of the ultra-high field NMR in clarifying the local structures in complex materials.

An Air-Setting Refractory Mortar Using a Composite Binder

A composite binder composed of water glass with a hardener and a high-alumina cement is used to prepare an air-setting refractory mortar based on fireclay fillers. The physicomechanical characteristics of the mortar are determined. An analysis of strains induced in the mortar under the first heat-up conditions with allowance made for the change in mortar's mineral structure is given.

Development of compositions of highly refractory mortars

A composition of corundum mortar with a binder of technical Na(PO3)n or a composite binder of aqueous solutions of technical Na(PO3)n and Na3PO4 · 12H2O is suggested. A mortar with a basic composition with a sintering additive of Na5P3O10 is presented.

Use of SHS refractories for the lining of ferrous metallurgy units

Results of use of SHS materials as refractory mortars for the lining of ferrous metallurgy units are presented. It is shown that using Termok-3 SHS mortars increases substantially the durability of the linings of units operating in a medium of both basic and acidic slags.

Production tests of refractory bricklaying mortars

Production tests of refractory bricklaying mortars