Showing papers on "Calcium oxide published in 1988"

Lime-Induced Heave in Sulfate-Bearing Clay Soils

Abstract: Expansive reactions between lime and sulfate-bearing clay soils have attracted little attention until relatively recently. Lime treatment of Stewart Avenue in Las Vegas, Nevada, had induced heave in excess of 12 in. Heaved areas are found to contain abundant thaumasite, a complex calcium-silicate-hydroxide-sulfate-carbonate-hyd rate mineral. Thaumasite forms a solid solution series with ettringite, a calcium-aluminum-hydroxide-sulfate-hy drate mineral. In the presence of aluminum, ettringite forms first and is replaced by thaumasite only at temperatures below 15°C. The mechanism of heave is a complex function of available water, the percentage of soil clay, and ion mobility. Only the long-term possolanic chemistry of normal lime-soil reactions is disrupted. Cation exchange, agglomeration, and carbonation are unaffected. With the present state of knowledge, lime-induced heave is difficult to predict for all but most obvious conditions.

Stabilisation and treatment of clay soils with lime. part 1 - basic principles

Abstract: Clay soil can be stabilised by the addition of a small percentage, by weight, of lime. This produces an improved construction material. Generally the amount of lime needed to modify a clay soil varies from 1 to 3 per cent, whilst that required for cementation varies from 2 to 8 per cent. Montmorillonitic clay soils respond more rapidly to lime treatment than do those in which kaolinite is the dominant clay mineral. When lime is added to clay soils, calcium ions are combined initially with or adsorbed by clay minerals which leads to an improvement in soil workability, that is, to an increase in the plastic limit of the clay and generally to a decrease in its liquid limit. The optimum lime additive for maximum increase of the plastic limit of the soil is referred to as the lime fixation point. Lime added in excess of the fixation point is utilised in the cementation process and gives rise to an increase in soil strength. The initial increase in strength has been attributed to the formation of poorly ordered reaction products which surround the clay materials. However, the development of long-term strength appears to be due to the gradual crystallisation of structurally-ordered new minerals from the initial disordered reaction products. The principle uses of the additions of lime to clay soils is for, firstly, stabilisation of subbases and subgrades in pavement construction and, secondly, to dry out wet soils. Lime treatment also has been used to stabilise embankments and canal linings, and to improve foundation soils. In the latter instance soil is stabilised beneath strip or raft foundations, or lime piles or columns are formed. (TRRL)

Reaction mechanism for the CaO-Al and CaO-CaF2 desulfurization of carbon-saturated iron

Abstract: The desulfurization of carbon-saturated iron with CaO is inefficient due to the formation of solid reaction products on the CaO particles which inhibit sulfur transfer. It has been shown in full scale and pilot plant studies that Al improves desulfurization with CaO. The present results indicate that Al affects the rate at 1450 °C, but not at 1350 °C, and that zirconium, which has a stronger affinity for oxygen than Al, does not increase the rate as much as aluminum. Alternate methods of producing a liquid reaction surface, such as desulfurization with CaO-CaF2 or a premelted calcium aluminate flux, also increase the rate. From these results, it is concluded that it is critical to have a liquid reaction surface for effective desulfurization. Aluminum in the metal, reacting with oxygen and CaO, provides a liquid calcium aluminate surface. An optimum aluminum level of about 0.1 to 0.3 pct was found. At lower levels, the Al is consumed and eventually solid calcium silicate forms, and at higher levels, possibly an alumina-rich solid phase forms.

Effects of pulverization on the strength and durability of highly active clay soils stabilized with lime and portland cement

Abstract: This paper presents the results of a laboratory investigation exploring the effects of varying degrees of pulverization, from laboratory-quality gradations to field gradations, on the strength and durability of highly plastic clay soils stabilized with lime and portland cement. Background information is presented on the mechanisms of stabilization and on previously reported studies of other materials. A 6-cu yd sample was used to provide 198 large specimens, which were tested in unconfined compression and wet-dry tests. Considerable differences were found in the strength of a highly active clay soil, depending on the gradations used to make specimens. Significant differences were found in the durabilities of specimens, depending on the stabilizer and the gradations used. Lime appears to be a more effective stabilizer for durability and portland cement more effective for strength, provided the gradation is fine enough. Recommendations, subject to further research, include longer curing times and the use of field gradations for all mix designs.

Method for recycle and use of contaminated soil and sludge

Abstract: Process for recycle and reuse of soil, sludge, sand, or rock containing: (a) at least about 16 wt % calcium oxide, about 5 wt % silica, about 1 wt % alumina, about 0.5 wt % Fe 2 O 3 , or about 0.76 wt % magnesia; and (b) at least about 5 ppm arsenic, about 100 ppm barium, about 1 ppm cadmium, about 5 ppm chromium, about 5 ppm lead, about 0.2 ppm mercury, about 1 ppm selenium, or about 5 ppm silver. The process comprising mixing the soil, sludge, sand, or rock with an amount of inorganic constituents to form a raw material mix having a chemical composition suitable for the manufacture of Portland cement, charging the slurry to a cement kiln, heating the slurry in the kiln to a temperature sufficient to form a cement clinker, and removing the cement clinker from the rotary kiln.

Tetrafluoroethylene resin composition

Abstract: PURPOSE: To obtain the title composition outstanding in creep resistance, lubricity and wear resistance in addition to the excellent characteristics inherent in the resin, suitable as a sliding member by incorporating a tetrafluoroethylene resin with calcium fluoride and/or calcium oxide. CONSTITUTION: The objective composition can be obtained by incorporating (A) 100 pts.wt. of a tetrafluoroethylene resin, i.e. tetrafluoroethylene homopolymer with (B) 5-90 pts.wt. of calcium fluoride and/or calcium oxide (with reaction with the moisture in air suppressed by e.g., treatment of the surface), pref. ≤50 (esp. ≤30)μm in average granular size, and, if needed, (C) a heat-resistant polymeric material (e.g., polyamideimide resin), heat-resistant inorganic fiber (e.g., glass fiber), heat-resistant organic fiber (e.g., aromatic polyamide fiber), etc. COPYRIGHT: (C)1989,JPO&Japio

Sintered body of aluminum nitride

Abstract: Sintered bodies of aluminum nitride are produced by adding, as a sintering aid, an oxide mixture consisting essentially of calcium oxide, yttrium oxide and one or more oxides of tungsten oxide and molybdenum oxide or a mixture of compounds (precursors) capable of being converted into said oxide mixture by firing to aluminum nitride as a main component in such proportions that total amounts of the sintering aid is in the range 01 to 20% by weight (calculated as oxides of CaO, Y₂O₃, WO₃, and MoO₃) based on the sum of the weight as the oxide forms of the sintering aid and aluminum nitride, molding the resulting composition and sintering the molded composition The composition can be sintered at relatively low temperature The black sintered bodies thus obtained are especially useful as materials for insulating substrate, heat sink, packaging for semiconductor device, etc, due to their high density and good thermal conductivity

Structural properties of plasma-sprayed zirconia-based electrolytes

Abstract: Zirconia-based electrolytes, stabilized either with yttrium oxide or calcium oxide, were prepared in 100 to 200 μm thick layers by plasma spraying and densified by high-temperature vacuum sintering. The structure and the microstructure were investigated by optical microscopy, scanning electron microscopy, X-ray diffraction and Raman spectroscopy. The results are compared with the data we obtained on the powders used for plasma spraying and on single crystals. In the zirconia-yttria system, dense and fully stabilized zirconia films with structural properties similar to the corresponding single crystals were obtained. On the other hand, cracks and deformations were observed on calcia-stabilized films. This phenomenon is explained by the dramatic increase of monoclinic phase content due to the preferential evaporation of calcium oxide which occurs during high-temperature vacuum sintering.

Calcium sulfate process for the coproduction of Portland cement clinker and concentrated sulfur dioxide adequate to manufacture sulfuric acid

Abstract: This invention isolates in separate furnaces the three thermochemical processes required in manufacturing Portland cement and sulphur dioxide from a calcium sulfate source so as to yield improved pyrometallurgical treatment for each individual process Separating these processes facilitates selection of the most kinetically suitable reactions by enabling the maintenance of optimum conditions for each process without compromising the thermal or kinetic efficiencies of the other processes Only one fourth of the calcium sulfate is reduced to calcium sulfide in a separate ad hoc reduction furnace specifically designed for achieving enhanced reduction parameters which results in minimized reduction equipment size Treating most of the calcium sulfate elsewhere works to avoid side reactions and allows Portland cement raw mix components to have an enhanced synergistic catalytic effect on reduction kinetics Compounds deleterious to both Portland cement and sulfuric acid, such as alkalies and fluorides, are removed with the reduction furnace gases while high concentrations of sulphur dioxide are achieved in the gases reporting to the sulfuric acid plant Three fourths of the calcium sulfate is made to react separately and simultaneously in a flash calciner with the calcium sulfide to produce sulphur dioxide and calcium oxide At the flash calciner heat of radiation from exothermic combustion reactions is applied directly to the highly endothermic desulfurization of calcium sulfate under an oxidizing atmosphere The calcium oxide and other Portland cement components are then discharged onto a short rotary kiln where only clinkering reactions take place at high thermal efficiencies for enhanced throughput, minimized furnace size, and lower burning zone temperatures

Effect of lime on a highly plastic clay with special emphasis on aging

Abstract: A laboratory study was undertaken to evaluate the effect of aging on the properties of Regina clay treated with 2 and 4 percent quicklime. Aging is generally referred to as the time interval between the addition of lime and water to the soil and the compaction of the mixture. Regina claly, a highly expansive clay, was selected for this study because it forms a common subgrade material in Saskatchewan. As a result of this study, it was found that aging had a pronounced effect on the properties of the treated soil. The properties also depended on the percentage of lime. The results indicate that both density and strength decreased as a result of an increased aging period for the treated samples prepared using constant compactive effort. However, the reduction in strength could be eliminated or could even result in an increase if the treated specimens with low percentages (e.g., 2 percent) were subjected to an increased compactive effort. Nevertheless, the results show that increasing the compactive effort could not eliminate the reduced strength for samples treated with higher percentages of lime (e.g., 4 percent) and increased aging (e.g., 24 hr). Increased compaction may well lead to a lower strength as a consequence of overcompaction. Aging appears to have had no significant effect on swell for treated samples prepared by both constant and increased compactive efforts, and little effect as well on the plasticity index.

Method of capturing sulfur in coal during combustion and gasification

Abstract: A method of reducing the amount of gaseous sulfur compounds released during combustion of sulfur-containing fuel, comprising the steps of: (a) preparing a mixture of sulfur containing particulate fuel and a sulfur absorbent, such as calcium oxide, calcium hydroxide, calcium carbonate, lime, limestone, dolomite, or mixtures thereof; (b) exposing the mixture to a reducing atmosphere at a temperature of at least about 1500° F., so as to convert at least a portion of the particulate fuel into a gaseous portion and a solid, char portion; and (c) combusting the char portion, thereby forming an ash containing sulfur fixed therein.

Producing molten glass and batch components therefor

Abstract: A method of producing molten glass wherein silica is heated with a batch component comprising a sodium alkaline earth silicate which includes a major portion of the sodium in the resultant molten glass. There is also disclosed a batch component for use in glass manufacture, comprising sodium calcium silicate, and, optionally, sodium magnesium silicate. There is further disclosed a method of producing a batch component comprising sodium calcium silicate for use in glass manufacture, the method comprising heating a mixture of (i) a source of sodium oxide and (ii) (a) a source of calcium silicate or (b) a source of calcium oxide and a source of silica, at a temperature of greater than about 800° C.

Glass composition and batch blend for its production

Abstract: A glass composition, especially suitable for glass fibre manufacture and having good fiberizing characteristics and good physical properties, typically contains, by weight, 40.0% to 65.0% silica, 4.0% to 11.0% alumunum oxide, 6.0% to 20.0% sodium oxide, 5.0% to 8.0% magnesium oxide, 6.0% to 17.0% calcium oxide, 4.0% to 12.0% ferrous and ferric oxides, and 0.0% to 7.0% potassium oxide.

Glaze for coating

Abstract: This invention presents a glaze for coating which is suitable for clay brick, white porcelain brick,cement surface and metal surface. It is mainly consisted of silicon dioxide, calcium oxide, sodium oxide, magnesium oxide, aluminium trioxide, lithium oxide, boron trioxide, copper, potassium oxide, iron oxide and cerium oxide. They can be obtained from waste glass, silica sand, borax, bentonite, limestone,feldspar and dolomite whose cost is low. The prescription of glaze is simple and without any poisonous mater. No oxidates of noble metals or only a little of them are used. The softening temp. is low, colour is bright. The products with glaze coating can beautify environment. It is damproof, anticorrosive and used extensively in buildings.

Method for producing non-reducible dielectric ceramic composition

Abstract: A method for producing non-reducible dielectric ceramics of the kind comprising a basic composition of a three component system BaTiO 3 -CaTiO 3 -CaZrO 3 or a four component system BaTiO 3 -CaTiO 3 -CaZrO 3 -MgTiO 3 and containing additives composed of at least manganese oxide and silicon dioxide. The method comprises the steps of separately preparing calcined powders of at least three perovskite compounds including BaTiO 3 , CaTiO 3 and CaZrO 3 , mixing the calcined powders to prepare a mixture for a basic composition, adding additives composed of at least manganese oxide and silicon dioxide to the mixtures for the basic composition, and then firing the resultant mixture in a reducing atmosphere. One of the oxides, magnesium oxide, calcium oxide, strontium oxide and barium oxide is additionally incorporated into the mixture for the basic composition together with manganese oxide and silicon dioxide.

Dielectric ceramic composition

Abstract: A dielectric ceramic composition having a high relative dielectric constant a high quality factor and a small temperature coefficient of resonance frequency, consisting essentially of calcium oxide, strontium, oxide, bismuth oxide and titanium oxide, and having a composition represented by the formula: (CaO)suba(SrO)subb(Bisub2 Osub3)subc(TiOsub2)subd wherein 0≦a<30, 0

New Cubic Structure in the Ca‐Si‐O‐N System

Abstract: Subsolidus-phase studies in the calcium-silicon-oxygen-nitrogen system have been conducted using the reactive precursors calcium nitride, calcium oxide, and silicon nitride. A new structure has been isolated with a large, face-centered cubic lattice, a=1.4864 nm, which coexists with several new CaSiON phases as well as Ca3Si2O4N2 and the unknown “D’ phase, reported previously by other workers. The new structure is not isotypic with any known mineral oxide. The highest degree of phase purity has been obtained using a 1.1 calcium nitride:silicon nitride starting mixture. Structural and approximate compositional analyses were conducted by X-ray diffraction and TEM energy dispersive spectroscopy.

White fabric having heat insulating property

Abstract: PURPOSE:To obtain the subject fabric, constituted of fibers containing specific white fine particles, excellent in heat insulating properties and suitable as winter or sports clothes without problems in cost increase, unevenness in performance, etc., in post-processing. CONSTITUTION:The objective fabric constituted of fibers containing white fine particles, having the ability to absorb light energy and emit far infrared rays [preferably fine particles of stannic oxide doped with antimony oxide or fine particles obtained by coating another inorganic substance (e.g., titanium oxide, zinc oxide, calcium oxide or alumina) with stannic oxide doped with antimony oxide]. Furthermore, nylon, polyester, PE, PP, acrylic, vinyl, polyurethane, rayon, etc., are cited as the fibers.

Method of making magnesium oxide and hydrates thereof

Abstract: A process for producing magnesium oxide and/or hydrates thereof from predominantly magnesium or magnesium-calcium raw materials, and optionally producing calcium carbonate, whereby the raw material is roasted if necessary to form a mixture of magnesium oxide and calcium oxide. The calcium oxide is then dissolved from the mixture using an aqueous solution containing an organic amine and a salt of an organic amine with an acid capable of forming a soluble calcium salt with said organic amine. Separating the solution from the undissolved magnesium oxide and treating the solution with carbon dioxide will cause the dissolved calcium to be precipitated and calcium carbide.

Aluminium nitride sintered body formed with metallized layer and method of manufacturing the same

Abstract: A metallized layer comprising:- tungsten and/or molybdenum; at least one of nitride, oxynitride, oxide of aluminium; and calcium oxide; is formed on the surface of a sintered aluminium nitridebody. Preferably the layer contains 40% to 98% by weight of metal, 1% to 25% by weight of the aluminium compound and 1% to 35% by weight of calcium oxide. The method comprises coating a pre-fired aluminium nitride body with a metallizing paste of teh above composition and firing in an inert atmosphere.

Low temperature sintered ceramic capacitor having a high resistivity and bending strength and method of manufacture

Abstract: A monolithic capacitor having a dielectric ceramic body cosintered with at least two base metal electrodes buried therein. The ceramic body is composed of a major ingredient expressed by the formula, (Ba.sub.1-v-w Me.sub.v Mg.sub.w O).sub.k (Zr.sub.1-x-y Ti.sub.x Si y )O 2 where Me is either or both of strontium and calcium, and v, w, x, y and k are numerals in specified ranges. To this major ingredient is added a minor proportion of a mixture of lithium oxide, silicon dioxide, and one or more metal oxides selected from among barium oxide, magnesium oxide, zinc oxide, strontium oxide and calcium oxide. For the fabrication of capacitors the mixture of the above major ingredient and additives in finely divided form are formed into moldings of desired shape and size, each with at least two electrodes buried therein. The moldings and electrodes are cosintered in a reductive or neutral atmosphere at temperatures of less than 120° C. and then are reheated at a lower temperature in an oxidative atmosphere.

Cement manufacturing process.

Abstract: METHOD FOR PRODUCING CEMENT. METHOD FOR PRODUCING CEMENT, BY COOKING AT HIGH TEMPERATURE OF A MIXTURE OF CALCAREA AND CLAY, OR A MIXTURE OF SILICA, CAL, alumina and iron oxides, ADDITION OF PLASTER TO CLINKER RESULTING FROM THIS BAKING AND GROUND OF THE FINAL MIX THUS OBTAINED, IN WHICH ADDS A MIXTURE OF INGREDIENTS OF DEPARTURE OF PRODUCING clinker a product obtained by granulation pressure of a homogeneous mixture powder containing a higher GARBAGE GROUND, practically free of metallic bodies pROPORTION, AND A PROPORTION LESS THAN AT LEAST A MINERAL MATERIAL CONTAINING CALCIUM OXIDE IN FREE OR COMBINED TATE AND HEAT TREATMENT granules thus formed at a temperature between 130 and 230GC, for a period such that its water content CARRIED to a value of 0.1 to 1% by weight.

Magnesium calcium acetate products, and process for their manufacture

Abstract: Finely divided ore blends containing chemically active magnesium oxide and calcium oxide are physically combined with a critical amount of water prior to reaction with acetic acid. Intermediate products range in physical consistency from putty-like masses to viscous liquors, depending upon the relative fraction of magnesium oxide in the ore feed. Intermediate products freeze to form hydrates of magnesium calcium acetate, the freeze times being dependent upon a number of chemical and physical parameters. Product drying requirements range from minimal drying to none at all, depending upon the magnesium fraction in the products. Products are non-friable and have excellent crush strength, and are suitable for storage, shipping and application in chemical deicing as well as other end use applications where crude low-cost materials are called for. A unique situation centers around the composition corresponding to the magnesium mol fraction of 0.8. This material requires no drying and exhibits an extraordinary high crush strength. Additionally, as much as 75% by weight of traction agent (sand) can be successfully incorporated into this material without the aid of chemical binders.