SPLITTING OF SOFT-MUD BRICK*

A study was made of the cause and methods of preventing the splitting of Hudson River soft-mud brick. The splitting occurred in the kiln and paralleled the 8- by 4-in face of the brick and was found to be associated with black coring. Tests made on various portions of the brick showed that the black portions were more vitreous and had lower thermal expansions than the outer, more oxidized portions. On cooling, the stresses resulting from the difference in thermal expansion were such as to tend to split the brick Modification of brick mixes and method of setting are recommended to overcome black coring.     

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.     

TENSILE TESTS OF GLASSES*

A machine was designed to place tensile loads on glass fibers having diameters from 0.6 to 0.8 millimeter (0.024 to 0.032 inch). The results of tests on twelve glasses of known chemical compositions are given. The fractured surfaces exhibited characteristic smooth and rippled areas which were measured and correlated with the breaking loads. In order to compare the various glasses, it is convenient to use that value of the load per unit area which exists in a fiber whose fractured surface shows a smooth area that is 1% of the section. For the twelve glasses tested, these values ranged from 23.0 to 33.0 kg. per mm.² (32,500 to 47,000 1b. per sq. in.) when the load on the fiber was increased at the rate of 1 pound per minute.     

OF ANALYTICAL CONTROL FOR SILICA BRICK*

The prevalent use of silica brick has focused attention upon the need for control and improvement in quality. A review of the methods available reveals that many laboratory tests have been developed to avert expensive trial testing. It is significant, however, that the chemical knowledge of this product has lagged owing to (1) difficulty in sampling, (2) the tedious and time-consuming aspects of wet chemical methods, and (3) the consequent lack of knowledge of the deleterious effects of certain secondary constituents. One of the newer analytical tools is the spectrograph. A total-energy method has been developed to permit analysis of A1₂O₃, MgO, Fe₂O₃, CaO, Na₂O, TiO₂, K₂O, ZrO₂, MnO₂, and Li₂O. Thirty minutes are required for sample preparation and twenty-five minutes for the spectrographic process. Present accuracy is well within production limits. This method is also suitable for the analysis of glass sand.     

IMPROVING THE QUALITY OF EXTRUDED MILL BRICK*

In the production of extruded brick for lining ball mills, unevenness of the brick such as (1) bow, (2) diagonal twist, (3) sunken faces, (4) depressed and bulged ends, and (5) underfired and cracked centers were reduced by (1) adjusting the die, (2) using grids behind the die, (3) controlling the drop from the die to the cutting table, (4) adjusting the tilt of the cutting table, and (5) stacking the brick during drying. The specific gravity was increased as much as 3.3% by using improved methods of setting the brick in saggers.     

THE SHALES AND BRICK CLAYS OF GEORGIA*

A résumé is given of the geology, general ceramic properties, and uses of the shales and alluvial clays of Georgia, based on a study by the Georgia Geological Survey. The conclusions were derived from seven months of field work and from ceramic tests on 115 samples from private properties and active plants.¹     

FACTORS INFLUENCING THE STAINING OF SILICA BRICK*

The staining of silica brick was found to occur in a critical temperature range of 900°‘ to 1000°C. Concurrently the brick had to be “soaked“ in this temperature range and exposed to an oxidizing atmosphere. Stained brick could be “cleaned up” or staining prevented by manipulation of the foregoing set of conditions as well as by additions of 4.5% or more of lime. The experimental data examined in the light of the system CaO-Fe₂O₃-SiO₂ suggest that the colorant is the mineral dicalcium ferrite.     

CFRP-PCPs复合筋混凝土柱偏压柱受力性能的试验研究

通过15根碳纤维预应力棱柱体复合筋(Carbon Fiber Reinforced Plastics Prestressed Concrete Prisms,简称"CFRPPCPs复合筋")混凝土柱进行偏心受压试验,考虑相对偏心距、复合筋配筋率、CFRP筋张拉控制应力和普通钢筋配筋率4个变化参数对复合筋混凝土柱受力性能的影响。观察了试件的受力过程及破坏形态,获取了试件开裂荷载、极限承载力、荷载-侧向变形曲线等重要数据,分析了4个变化参数对CFRP-PCPs复合筋混凝土柱偏心受压作用下的开裂荷载和极限承载力的影响规律。研究结果表明:CFRP-PCPs复合筋混凝土偏压柱与普通钢筋混凝土偏压柱的受力过程及破坏形态相似,试件的开裂荷载和极限承载力均随相对偏心距的增大而降低;提高CFRP筋张拉控制应力、增大复合筋配筋率和普通钢筋配筋率均能有效提高CFRP-PCPs复合筋混凝土柱的开裂荷载和极限承载力。     

COMPARATIVE TESTS OF POROSITY AND SPECIFIC GRAVITY ON DIFFERENT TYPES OF REFRACTORY BRICK1

Comparative data of porosity and specific gravity on several types of refractory brick are presented. Apparent porosity is obtained directly by the water absorption and air expansion methods. Total porosity is calculated from the true specific gravity and apparent specific gravity is calculated from the observed porosity values. The results indicate (1) a more accurate measurement of open pore space in bricks by means of the air expansion method than by water absorption, and (2) the absence of sealed pores in some types of refractory brick.     

CORRELATION OF ELECTRICAL AND THERMAL PROPERTIES OF BUILDING BRICK *

A relationship has been found to exist between the electrical and thermal conductivities of certain ceramic materials. This relation appears to be both a direct and an approximately linear function of the porosity of the material and, for the materials used, independent of chemical composition. Current-voltage relations bear out the generally accepted assumption that solid, non-metallic dielectrics, such as ceramic materials, exhibit electrical conductivity by virtue of a movement of ions. Current-time’relations indicate that the materials used in this study exhibited an appreciable polarization current, the magnitude and time of decay of which were closely associated with the porosity. The latter, time of decay, is of particular interest. From these observations, it is evident that the effective direct-current resistance of a ceramic insulator may not be its final steady-state resistance but some much lower value.     

AN X-RAY STUDY OF THE TOUGHNESS OF PAVING BRICK*

X-ray diffraction photographs of paving brick were compared with those of pure materials. The most important result obtained in this work is the discovery of a line in the X-ray diffraction pattern of paving brick which is characteristic of high-grade shale paving brick. This line, produced by an undetermined crystal, is more intense in the tougher than in the weaker brick. The line falls at 2.03 ± 0.01 Ångström units. A further result of this investigation is the proof that cristobalite, mullite, sillimanite, alumina, and cyanite are not present in the paving brick studied. This also shows that mullite is not produced in ceramic materials at the relatively low temperature at which paving brick are fired.     

EFFECT OF MOLTEN ALUMINUM ON VARIOUS REFRACTORY BRICK*

To study the effect of molten aluminum on refractory brick with a view toward explaining some of the brick failures in aluminum melting furnaces, the following test was conducted. Brick of different compositions and from various manufacturers were placed on end in the bottom of an electrically heated ladle to which molten aluminum was added. After holding the molten aluminum in contact with the brick for thirty-five days, it was poured out and the ladle was allowed to cool slowly to room temperature. A study of the brick revealed that some failed by penetration of the aluminum into the brick accompanied by a reaction between the aluminum and the brick. This penetration was less with the denser brick than with the more porous ones. Of the brick tested, there was the least reaction between aluminum and the chrome brick and most between aluminum and silica brick. Many other factors, however, must be considered when deciding which brick is the most economical to use in aluminum melting.     

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.     

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.     

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.     

TESTS FOR HOT-WATER RESISTANCE OF TANK ENAMELS*

The resistance to attack by hot water of a representative group of commercial enamels, designed especially for use on hot-water tanks, and of several nontank enamels was measured by the following three types of test: (A) loss of gloss after periods up to several hours in a conventional autoclave with distilled water, (B) loss of gloss after one day to two weeks in apparatus which kept the specimens in contact with constantly changing, boiling distilled water, and (C) loss in thickness after periods up to 5000 hours (208 days) in a modified autoclave with circulating aerated tap water under pressure. The tests are described in detail, comparisons are made, and the loss-of-gloss test with boiling distilled water as used in Commercial Standard CS115–44 is discussed.