THE EFFECT OF RED HEARTS IN FIRE CLAY BRICK1

Laboratory tests made on two brands of fire clay brick indicate that red hearts, which are normally considered as being detrimental, add to both the hot and cold strength and would not be objectionable except in furnaces operated at a low temperature, and in which spalling is an important item. Results of load, reheating and spalling tests are given, together with porosity and iron oxide determinations. A short discussion of the causes of red hearts is also included.     

USE OF THE SIMULATIVE TEST FURNACE AS A MEANS OF MAKING COMPARATIVE TESTS OF FIRE BRICK1

The Navy Simulative Service Test for refractories is described, specifications for the test and the furnace used being given. The simulative service furnace has found application in making comparative tests of different brands of refractories, development of and improvement of standard fire brick, and as a control test for maintaining quality of the product.     

Experimental and numerical study on compressive performance of perforated brick masonry after fire exposure

This paper discusses the compressive performance of perforated brick masonry after fire exposure. Compressive strength tests of the mortar, clay perforated brick, and perforated brick masonry specimens were performed in accordance with ISO834 fire tests of different durations. The temperature distribution of the masonry materials and specimens was simulated using the finite element software ABAQUS, with the thermal parameters of masonry materials recommended by European standard Eurocode 6 and related literature. The compressive strength reduction factors of mortar and clay perforated brick exposed to different fire durations were calculated via the layered method suggested by European standard Eurocode 1. In addition, the compressive strength reduction factors after cooldown were obtained from the experimental data of the masonry materials, and by considering further reductions in the compressive strength after cooling from high temperatures. Experimental data of the masonry specimens were compared with the numerical results obtained using the reduction factors proposed in this work. The comparison revealed an overall acceptable approximation. Thus, the method presented in this paper can be used to evaluate the residual capacity of masonry structures after fire.     

HIGH TEMPERATURE LOAD AND FUSION TESTS OF FIRE BRICK FROM THE PACIFIC NORTHWEST IN COMPARISON WITH OTHER WELL-KNOWN FIRE BRICK1

Seventeen samples of fire-clay brick from the Pacific Northwest have been tested with twenty-seven other commercial brands of fire clay, silica, magnesia, chromite, zirconia, diaspore, silicon carbide and crystalline alumina, as well as china clay and crystalline sillimanite products made at the University of Washington. The tests show that the fire-clay brick of the Pacific Northwest vary considerably in quality. According to the high temperature load test, the majority of the local brick are among the upper grades, some are to be classed with the best fire-clay brick and one equal to the best diaspore brick. The brick tested is not the best which can be made from Pacific Northwest materials, for the kaolins in eastern Washington and northwestern Idaho give opportunity for the production of an all-kaolin fire brick. A method is suggested for testing super-refractory materials under load at high temperatures similar to the standard load test for fire clay and silica brick except that the temperatures are measured by cones, and are raised until 10% linear deformation of the brick is obtained. The rate of heating and soaking varies with the brick under test, and the principles learned from the cone fusion test are used in the application of heat. A numerical value, expressing the area under the cone-shrinkage curve, affords an easy method for comparing the high temperature load resistance of various refractories. The brick which are best able to resist deformation at high temperatures are composed of crystalline materials which have developed a recrystallized bond of the same composition. These are crystalline silica, silicon carbide, corundum and sillimanite, and they resist deformation at temperatures close to their melting points. Amorphous materials like fire clay, diaspore, bauxite or even the very refractory crystalline materials lie chromite and periclase, which depend on amorphous silicates for a bond or are contaminated with silicate impurities. will fail with the softening of the bond of the amorphous impurities. The cone fusion of the brick as a whole can not be depended upon to indicate the resistance to load at high temperatures.     

EFFECT OF WEATHER UPON THE STRENGTH OF REFRACTORY BRICK1

Magnesia and silica brick should be protected from the action of the weather. Open textured fireclay brick (usually having end cold crushing strengths of less than 1500 pounds per square inch) should be afforded protection from the action of the weather. Finely ground, dense, hard-burned firebrick , especially those of medium or low refractoriness. may be exposed to the action of weather with a reasonable amount of safety. These are usually made from one clay which is shaped on a dry press or auger machine and have an end cold crushing strength approximating 5000 pounds per square inch.     

PROGRESS REPORT ON INVESTIGATION OF FIRECLAY BRICK AND THE CLAYS USED IN THEIR PREPARATION1

This is a progress report of an extensive study of fire clays and fireclay brick. It includes the results of a preliminary study of clays representative of those used in the manufacture of refractories throughout the United States. Chemical analyses and a summary of physical tests are given of both fire clays and the brick manufactured from them. The thermal expansion behavior of the fire clays fired at 1400°C and those of the fire brick “as received” from the manufacturer and also after firing at 1400°C, 1500°C, and 1600°C were studied and the materials classified into groups having characteristic thermal expansions. The moduli of elasticity and rupture were determined at 20°C, 550°C, and 1000°C. The resistance of the brick to spalling in a water-quenching test is expressed in an empirical relation correlating the elasticity, strength, coefficient of expansion, and percentage of grog used in compounding the brick batches. Data are presented on individual bricks made by the same manufacturer showing probable reasons for great differences in the number of quenchings required to cause spalling in the water-dip test.     

Effective thermal inertia in relation to normalized heat load

Normalized heart load, obtained by dividing heat absorption by thermal inertia, is a quantity useful in building design for relating fire severity in fully developed compartment fires to fire severity in standard fire resistance tests. Harmathy has shown how normalized heat load may be used for determining required fire resistance in projected buildings. The present work describes how effective values of thermal inertia can be calculated for such important materials as brick and concrete, both normal and lightweight, for which thermal properties depend strongly upon temperature.     

THE BEHAVIOR OF FIRE BRICK IN MALLEABLE-IRON FURNACE BUNGS1

Purpose. —An investigation was conducted to study the requirements of fire clay and bodies used for fire brick in malleable-iron furnace bungs. Tests were made on complete bungs holding forty sample brick in malleable-iron furnace bungs with twenty different fire brick. Laboratory tests were also made in conjunction with them. Results. —The spalling tests bear the closest relation to the service test; those brick losing less than 10% withstand more than fifteen heats. There is also a relation between the porosities and densities of fire brick, which lie between 15 and 28% and 1.5 and 2.6%, respectively, for the best brick. There is no close relation between the load test and softening-points of fire brick and their lifetime in malleable furnace bungs, so these tests are no criterions in judging the serviceability of brick, provided the brick are sufficiently refractory to support the arch at furnace temperatures. Methods for Improving Fire Brick. —The resistance of a brick to spalling may be governed by: (1) the selection of the proper clays, (2) the size of grain and the proportioning of the non-plastic ingredients, (3) the fineness of grain of the bond clay, (4) the manner of molding, and (5) the temperature of firing.     

RELATION OF CRUSHING STRENGTH OF SILICA BRICK AT VARIOUS TEMPERATURES TO OTHER PHYSICAL PROPERTIES*

The failure at elevated temperatures under constant load for silica brick is reported using the Iupuy load test apparatus. The crushing strength at 1500°F, 1800°F. 2100°F, and 2400°F is recorded, as well as the crushing strength at room temperature. The size of test piece utilized normally was 1 by 1 by 2′/2 inches. A definite relationship is shown to exist between the strength at room temperature and that at elevated temperatures. The effect of variation in lime content, bats content, and fluxes is also reported. Data were obtained on brick made from three different quartzites. Additional physical data are reported to give information concerning the properties of the brick tested.     

Ignitability Analysis of Siding Materials Using Modified Protocol for Lift Apparatus

This paper reports on the ignitability of common siding materials that could be exposed to wildland fires. When exposed to brands or fires, structures will experience piloted ignition, which is requisite for sustained ignition involving burn-through and surface flame spread in various directions. In this study, the Lateral Ignition and Flame Spread Test (LIFT) apparatus (ASTM E1321 and E1317) was used to test various siding materials (plywoods, softwoods, and vinyl), some of which were painted, humidified, or sawed. A recently developed protocol provided useful, accurate values of the following thermophysical properties: surface emissivity, surface ignition temperature, thermal conductivity, and thermal diffusivity. Full consistency was achieved with independent literature values of these properties and can be used directly in the database of fire growth models.     

COMPARATIVE TESTS OF SOME AMERICAN AND GERMAN FIRECLAY BRICK1

The Bureau of Standards has recently completed a short investigation comprising comparative tests of five brands of German-made brick and six brands of American-made brick. The results indicate that the Ge man-made brick are practically the equal of the American brick.     

THE COMPRESSIVE AND TRANSVERSE STRENGTH OF BRICK1

This paper reports the compressive strength flat and on edge and the transverse strength of twenty-seven makes of brick covering a range of conditions in method of manufacture and degree of firing. The attempt is made to correlate the variation in ratios of these different measures of strength with the various structural features of the check.     

COMPARISON OF HOT AND COLD MODULUS OF RUPTURE FOR SILICA BRICK

Purpose of the Investigation .—(1) To obtain relative values for the cross-breaking strength of silica brick at temperatures encountered in coke oven practice. (2) To correlate the hot modulus of rupture test, if possible, with the cold modulus of rupture, or cold crushing test, either of which is cheaper and more easily conducted. This report gives the method of making the test, difficulties encountered and results obtained. The report shows a comparison of cold crushing, cold modulus of rupture and hot modulus of rupture on a series of silica brick made from special mixes, commercially burned. Conclusions .—The modulus of rupture of a silica brick at 1350°C is approximately one-third the strength at atmospheric temperature. For this series it averaged from 130 to 189 lbs. per square inch. Too rapid or eccentric heating up to red heat may cause such weakening of the structure or bond that the brick will break under very low pressure. Cross-breaking strength decreases as the temperature increases. Hot modulus of rupture test appears to give results, in most respects, comparable to the cold test, and for routine testing it would seem advisable to use the cold test since it can be made in much shorter time.     

Forsterite refractory brick produced by talc and magnesite from Thailand

This research focuses on refractory material synthesized from precursors of talc and magnesite in Thailand. They were mixed at a molar ratio of 1:5 with mechanical activation at 5 h and calcined at 1300 °C for 1 h to create forsterite. The resulting forsterite crystals were round with less than 1-μm particle size. Synthetic forsterite refractory was formed into refractory bricks and studied at various sintering temperatures of 1200, 1300, and 1400 °C with a dwell time of 2 h. The characteristics and properties of refractory samples were tested in physical properties, cold crushing strength, thermal conductivity, thermal shock, and corrosion resistance from various substances. The results showed that increasing the sintering temperature increases the physical properties and cold crushing strength values. Also, the sintering temperature increases will increase thermal conductivity. The best condition of forsterite refractory brick sintering was 1400 °C for 2 h (FB-14), which showed the following desirable properties: firing shrinkage of 18%, bulk density of 3.03 g/cm³, the apparent density of 3.26 g/cm³, both apparent porous and water absorption values of zero, and cold crushing strength of 72.18 MPa. The FB-14 brick has excellent resistance to corrosion and penetration from lead silicate frit and copper slag. There was minor weight loss from the corrosion of the chemical solutions used in sodium hexametaphosphate production, whereby weight loss will begin on the 18^th cycle. Consequently, the FB-14 brick can be used for blast furnace walls to slow down corrosion, which will allow the blast furnace to have a longer life cycle.     

Development of fireclay aluminosilicate refractory from lithomargic clay deposits

Lithomargic clay until now has not been utilised to produce refractory bodies due to its low plasticity. In this work, the development and evaluation of fireclay refractory material produced from lithomargic clay deposit has been studied by addition of clay binder. Three formulations were prepared by mixing, semi-dry moulding, drying and firing at temperatures ranging from 1200 to 1400 °C. The fired samples were investigated to determine their physical properties such as bulk density, apparent porosity, linear firing shrinkage, and cold crushing strength. The chemical and mineralogical compositions were also determined. The results show that the linear firing shrinkage values were within limits acceptable for refractory clays. The cold crushing strength increases as temperature increased to 1400 °C. Cold crushing strength increased with increasing binder content. The increase of the highly refractory phases (cristobalite and mullite) and the densification of the bricks due to the presence of fluxing agents were responsible for the high cold crushing strength values. The investigated properties indicate that lithomargic clay underlying bauxite deposits could be used to produce fire clay aluminosilicate refractories.     

A STUDY OF HEATING AND COOLING RATES OF CHECKER BRICK*

A test simulating the heat absorption and emission of checker brick was developed. The results of such tests on fire brick of two sizes, made by three different processes and procured from four fireclay districts, are given and correlated with the bulk specific gravity and porosity of the brick.     

STUDIES ON THE THERMAL CONDUCTIVITIES OF SOME REFRACTORY MATERIALS1

The method used was a modification of that described by Hepplewhite. The changes made were for the purpose of insuring greater accuracy. An effective means for preventing lateral flow of heat was devised. The coefficients obtained for the several materials studied were (c. g s. units) silica brick .00099, fire clay brick .00169, fire clay slab .00203, light weight fire clay brick .00251, sillimanite brick .00432, electrically sintered magnesia brick .00665, “Alundum” fire brick .00833, “Crystolon” silicon carbide brick .00982. [The work for this paper including the design, erection and operation of the apparatus, most of the calculations and the preparation of the detailed report was done by 0. S. Buckner.]     

ELASTIC BEHAVIOR AND CREEP OF REFRACTORY BRICK UNDER TENSILE AND COMPRESSIVE LOADS*

Specimens cut from 9-in, brick of nine brands of firebrick, including two high-alumina, four fire-clay, two siliceous fire-clay, and one silica, were subjected to tensile and compressive creep tests at eleven temperatures from 25° to 950°C., inclusive. The duration of each test was approximately 240 days. Small length changes, independent of stress direction (that is, compressive or tensile), occurred at the lower temperatures. The lowest temperatures at which creep was significant were (a) high-alumina brick, 700° to 850°C.; (b) fire-clay brick, 600° to 700°C.; and (c) siliceous and silica brick, 950°C. Creep results under compressive stress could not be correlated with results under tensile stress. Specimens of different brands, at 950° C. showed greatly different capacities to carry load. Repeated heatings caused growth of silica brick of approximately 0.27%. Moduli of elasticity at room temperature were determined before and after the various heat-treatments and resultant changes were recorded. The changes in moduli were 15% or greater for silica and siliceous brick and 4% or less for the fire-clay brick. The moduli of elasticity at room temperature were approximately 2.7–4.3 × 10⁶ for high-alumina brick, 0.6–1.9 × 10⁶ for fire-clay brick, 0.3–1.7 × 10⁶ for siliceous fire-clay brick, and 0.4 × 10⁶ for silica brick.     

Crushing characteristics

A method of measuring the basic characteristics of comminution was developed. These characteristics are expressed by the major comminution functions: crushing probability function, energy function and breakage function. The crushing probability function is the strength distribution of particles of a given size. The energy function is the strength of the particles as a function of their sizes. And finally, the breakage function is the size distribution of the crushed material. The functions are defined mathematically. Several natural minerals were tested by drop tests in order to determine their individual comminution functions. From the tests, several crushing properties of the particulate materials can be derived. The comminution functions given in this paper would be the basic elements in developing mathematical models for various crushing and grinding processes.