Showing papers on "Calcium oxide published in 1989"

Strength and deformation characteristics of lime-treated soft clays

Abstract: the effect of lime on the strength and deformation characteristics of soft Bangkok clay has been investigated by unconfined compression tests, oedometer tests and undrained triaxial tests. The unconfined compression tests revealed that the undrained strength can be increased nearly tenfold by the addition of 5% lime. Under the oedometer test condition the preconsolidation pressure of the lime-treated clays showed a marked increase and the overconsolidation ratio increased, thus improving the compressibility characteristics. The reduction in compressibility was also accompanied by an increase in the coefficient of consolidation. The undrained triaxial tests further confirm the overconsolidated nature of the lime treated clay in the effective stress paths, stress-strain curves and pore pressure characteristics. Both the cohesion and the angle of shearing resistance are also increased in a substantial manner with the addition of lime. These results form an interesting basis to develop the appropriate stress-strain theory for lime-treated clays. (Author/TRRL)

A CO2 negative ion source for 14C dating

Abstract: A negative ion source has been developed capable of producing 20 to 30 μA of 12 C − ions from CO 2 gas with an ionization efficiency of close to 10%. Memory effects have been shown to be low (comparable with sputter sources using solid targets) and, with reasonable care, it is possible to date samples with ages up to at least 76000 years. A novel feature of the source is that the flow of CO 2 is metered into the source, not by a needle valve, but rather by controlling the temperature of a reservoir containing calcium carbonate. The reservoir may contain natural materials, such as limestone, dolomite, seashell, foraminifera, etc., or artificial carbonates prepared by absorbing sample CO 2 in heated calcium oxide. Since the total sample can be used very efficiently it is feasible that a 1 or 2% measurement can be made on a modern sample containing as little as 10 μg of carbon.

Process for preparing overbased calcium sulfonates

Abstract: In the preparation of an overbased calcium sulfonate, it has been found that adding the calcium hydroxide during the carbonation reaction reduced solid waste. An initial charge of 15 to 25 wt % of the total calcium hydroxide is added to initiate the carbonation reaction. The balance is added by a process whereby calcium hydroxide concentration remains low in the reaction admixture to reduce amorphous calcium carbonate residence time. In the process, calcium hydroxide is added in amounts whereby the molar ratio of carbon dioxide to the sum of calcium hydroxide and calcium oxide is about 0.8.

Lime addition and curing effects on the index and compaction characteristics of a montmorillonitic soil

Abstract: The effects of amount of lime added and of the curing period on the liquid limit, shrinkage limit and compaction characteristics of a montmorillonitic soil are investigated. Incremental additions of lime result in a progressive decrease in liquid limit, increase in shrinkage limit, decrease in maximum dry density and increase in optimum moisture content of the soil on immediate testing. Curing the soil with lime also has a distinctive influence on its properties. On extended equilibration for a given lime addition, liquid and shrinkage limits increase with time, while the maximum dry density and optimum moisture content values show a decrease. The physico-chemical mechanisms which alter the montomorillonitic soil properties on addition of lime and subsequent curing are highlighted.(A)

Process of producing colloidal zirconia sols and powders using an ion exchange resin

Abstract: A method of preparing colloidal zirconium oxide sols having substantially uniformly spherical particles in the size range of from about 0.01 to about 2.0 microns is described. The process comprises the steps of (A) preparing a liquid mixture comprising at least one zirconium salt and a compatible liquid vehicle; (B) contacting said liquid mixture with an anion exchange resin for a period of time sufficient to form a zirconium hydrate sol having a pH of at least about 5.0; and (C) recovering the zirconium hydrate sol from the resin. Colloidal size zirconium oxide powders can be prepared from the colloidal zirconium oxide sols by drying and calcining the sols at an elevated temperature. The zirconium oxide powders obtained in accordance with the present invention can be stabilized by the incorporation of certain stabilizers such as yttrium oxide, lanthanum oxide, cerium oxide, calcium oxide and magnesium oxide.

Property changes induced in clay soils when using lime stabilization

Abstract: Lime is being used increasingly to modify and stabilize soils for numerous engineering applications such AS Embankments, road subgrade and sub-base stabilization and foundations for small buildings. It is therefore important that engineers using this technique are aware of the nature of the changes imparted to soils by the addition of lime, and of the modifications which are brought about in the physical and mechanical properties of soils by lime treatment (soil strength, permeability, frost resistance and plasticity). This paper reviews the current state of knowledge regarding the way in which lime modifies the properties of soils, and reports on the observed changes on a Devonian red marl when mixed with lime and cured in different environments. The results of the work suggest that more effective stabilization may be achieved, even at normal ambient temperatures, by the use of further chemical additives in addition to lime. (TRRL)

Synthesis of bi-ca-sr-cu-o superconductive material

Abstract: A mixture comprised of an alkali chloride solvent and reactants comprised of bismuth sesquioxide, calcium oxide, strontium oxide and copper oxide, or precursors therefor, wherein the reactants are formulated to produce a superconducting reaction product, is heated to melt the chloride solvent in which the reactants then dissolve and react precipitating a Bi-Ca-Sr-Cu-O superconductive material which is comminuted to produce a sinterable powder

Method for producing porous sintered apatite material

Abstract: A method for producing a porous sintered apatite material comprising the steps of: sintering a calcium-excess apatite at 800° C. or more so as to form a sintered apatite material having a calcium oxide content of from 0.5 to 60 wt % by phase separation of calcium oxide; and removing the calcium oxide from the sintered apatite material so as to form a porous sintered apatite material.

Frost resistance of lime-stabilized clay soil

Abstract: A frost-susceptible soil (red marl) was treated with various amounts of lime (calcium hydroxide) and cured for up to 24 weeks at different temperatures. Frost resistance of the cylindrical specimens was determined by measuring the frost heave in a controlled freezing environment. Soil-lime specimens with 2 wt% lime were more susceptible to frost action than soil alone--regardless of curing time and curing temperature. However, cured specimens with relatively high lime contents (greater than 2 wt%) showed significant improvement in frost resistance. From previous studies by the authors, it was found that cementitious gel forms and develops in these specimens during curing--increasing the degree of interparticle bonding and producing greater strength. It is suggested that this restricts ice segregation and prevents heave and that frost resistance is dependent on the extent of the formation and growth of the cementitious gel within the cured soil-lime composites.

Studies on time-granulated blast furnace slag as an alternative binder to cement

Abstract: This paper deals with the activation of granulated blast furnace slag (GBFS) and slag-fly ash/burn clay pozzolana mixes in presence of lime and lime with gypsum. The paper highlights the effectiveness of lime- GBFS mix with and without additives as an alternative binding material. It includes mortar studies and stabilisation of alluvial soil with lime-GBFS mixes. Investigations showed that strength development of 1:3 mortar was highest when 7.5 per cent gypsum was also added to lime-GBFS mix. The alluvial soils could be satisfactorily stabilised with both lime-GBFS and lime-GBFS with 7.5 per cent gypsum or by replacing 20 per cent of GBFS with fly ash. (A)

Calcium, An Overview-1989.

Abstract: An overview of calcium is presented including introduction, pre-history, chronology of the research recorded in the literature, discussion, summary, recent references, literature cited, acknowledgments, and appendix. Elemental calcium began with the Earth's formation. Calcium was used for utilitarian purposes in B.C. times. In the 12th and 13th centuries A.D., calcium oxide was formed by roasting limestone to form calcium carbonate. A test for calcium was found in the 17th century, and "stones" were observed in humans (see appendix). In the 19th century, calcium was isolated and chemically identified by electrolysis, and later in that century calcium was found to be needed in a physiological solution similar to the ionic content of blood. In the 20th century it was found that, in the absence of calcium, living cells pulled away from one another. Anesthesia was produced by massive injection of magnesium salts into a mammal-conciousness could be restored by the addition of calcium, which neutralized the magnesium. Finally, calcium out of control in necrosis has an invasive action. Calcium antagonists and their mode of action were described in 1986.

Zirconium oxide sinter for forming thin film thereof and method for production of the same

Abstract: of the Disclosure: Zirconium oxide sinter for use in forming a thin film thereof by vapour deposition etc., having a purity not less than 99.0 % by weight with unavoidable hafnium oxide and a density more than 4.9 g/cm3. Desirably the sinter further contains calcium oxide in an amount from 50 to 2000 ppm. The sinter can produce a uniform zirconium oxide thin film which can be used in optical applications with superior characteristics.

Potential uses of Jordanian spent oil shale ash as a cementive material

Abstract: Retort residue ash of El-Lajjun oil shale from central Jordan has been studied for its cementitious and pozzolanic properties and potential uses in construction. During the preliminary phase, properties of the ash were determined and some tests were performed on pastes of ash, cement and their mixtures. According to X-ray diffraction and thermogravimetric studies, the ash mainly consisted of calcite and silica and some lime silicates, providing cementitious character. Its hydration resulted in ettringite and lime silicate gel formation. The ash paste had relatively low setting times and hardened into a lightweight porous structure. Its 28 day strength was about half of the cement paste value for the same water content. The ash had weak pozzolanic activity. In blended pastes, addition of ash up to 30% caused some reductions in 28 day strengths. There seemed to be optimum ash contents which improved compactibility while causing minimum strength reductions. The results indicated that the ash could be used to...

Method for cleaning gases

Abstract: In the cleaning of flue gases formed during the combustion of coal, preferably pulverised coal, the flue gases in a first step are cleaned of particulate pollutants, so-called fly ash, in a first separator (5). In a subsequent step, the flue gases are cleaned of gaseous, acidifying pollutants by mixing the flue gases with a sorbent in the form of a dry powder or fine water droplets in a contact reactor (21). The resulting reaction products are then separated together with unreacted sorbent as a dry powder from the flue gases in a second separator (41). Water is added to the fly ash separated in the first separator (5). The fly ash is then milled in a mill (11) in order to convert the calcium oxide and silicon dioxide present therein into calcium hydroxide and calcium silicates. Also, the fly ash is mixed with burnt or slaked lime and/or silicon dioxide prior to or after milling. The thus treated material is then used as sorbent in the subsequent cleaning step.

Chemical heat pump

Abstract: The regeneration temperature of a chemical heat pump of closed system utilizing reversible reaction between calcium oxide and water is lowered by using an aqueous solution of a salt in an absorber-condensor provided separately from a reactor filled with calcium hydroxide

Some Physico-Chemical Aspects of Dry Sorbent Injection for Removal of HCI and HF from Waste Incinerator Flue Gases

Abstract: As part of a study on the uses of dry sorbent injection to control emissions of hydrogen chloride and hydrogen fluoride from waste incinerators, we investigated the properties of some calcium-based sorbents at incinerator temperatures. Decomposition of such a sorbent with formation of calcium oxide causes a marked increase in its surface area. At higher temperatures, however, this effect is offset by sintering.

Alkoxylation using heterogeneous calcium catalysts and products therefrom

Abstract: This invention relates to heterogeneous (organic polymer-supported) calcium-containing catalysts and the use thereof in the preparation of alkoxylation products, i.e., condensation reaction products of alkylene oxides and organic compounds having at least one active hydrogen. In another aspect of this invention, processes are provided for preparing heterogeneous (organic polymer-supported) calcium-containing catalysts for alkoxylation using calcium oxide or calcium hydroxide as sources for the catalytically-active calcium. In a further aspect of this invention, alkoxylation products are provided that have beneficial, narrow molecular weight ranges and are essentially neutral in pH and free from catalyst residues.

Method of making a composite filter material and its use in treating edible oils

Abstract: A substantially dry filtering media for rejuvenating glyceride oils is formed by admixing a calcined metallic oxide and an expanded silicate in a tumbler having grounded, electrically conducting walls for a period of time to electrostatically produce an agglomerate. Specific examples of metallic oxides are calcined magnesium oxide, calcined aluminum oxide, calcined potassium oxide, calcined calcium oxide, calcined zinc oxide and calcined ferric oxide. Examples of the silicate are expanded perlite and expanded pumice. The agglomerate so formed is of sufficient size to facilitate filtering of the oil, and subsequent removal of the media from the rejuvenated oil.

Biomedical material and method for making the same

Abstract: A biomedical material for use as artificial bone and dental root is provided which takes the form of a sintered composite body comprising a crystalline calcium phosphate matrix and inorganic whiskers dispersed therein. The inorganic whiskers contain at least one oxide selected from the group consisting of silicon oxdie, aluminum oxide, calcium oxide and magnesium oxide. The matrix of tricalcium phosphate or apatite preferably has a grain size of 0.05 to 30 µm. The whiskers, typically anorthite and diopside whiskers occupy 0.5 to 95% by area of a cross section of the sintered body, and preferably have a length of 0.05 to 30 µm and an aspect ratio of from 1.2 to 100, with the ratio of matrix grain size to whisker length being 10/1 to 1/10. The material has physical toughness and strength and biomedical affinity. The material is prepared by mixing calcium phosphate and a whisker-forming material or whiskers and sintering the mixture at a temperature of 800 to 1600°C.

Fabric development in lime treated clay soils

Abstract: A regeneration of interest in the use of lime stabilised clay soils for subgrade capping material in highway construction has led to renewed consideration of the physical changes involved. It has generally been held that the long-term development in strength of lime stabilised soil is due to a gradual increase in the degree of crystalline order. The author describes work on illite and lime, kaolinite and lime and montmorillonite and lime carried out at high temperatures and for periods of up to two years. The formation of a calcium silicate aluminate hydrate gel is described which also occurs at lower temperatures but at a slower rate. TEM micrographs show the gel which is also seen in a sample taken from the lime-stabilised foundations of a 400 year old bridge in Iran. The author suggests that stability comes from the gradual formation of the gel product and development of the gel-clay particle microstructure rather than from crystallisation of the gel. The effect on permeability and how this increases or decreases with age are considered.

Magnesia-calcium oxide refractories

Abstract: Disclosed are a magnesia-calcium oxide refractory product comprising (i) about 100 parts by weight of a refractory aggregate consisting essentially of about 20 to about 95% by weight of MgO and about 80 to about 5% by weight of CaO and (ii) about 0.5 to about 5 parts by weight of aragonite-type calcium carbonate, and a process for preparing the same.

Zirconia-based sintered material and process for producing the same

Abstract: There are disclosed a process for producing a zirconia-based sintered material, which process com­prises heating an amorphous material consisting of zirconium oxide containing about 9.5 - about 10.5 mol % (in terms of oxide) of cerium oxide and about 0.4 - about 3.0 mol % (in terms of oxide) of calcium oxide, to a temperature not lower than the temperature of crystallization of the amorphous material but not higher than about 1,200°C, crushing the resulting material to obtain a powder containing a tetragonal phase in an amount of about 90% by weight or more, and then subject­ing the powder to molding and sintering, and a sintered material thus produced.

Manufacture of high purity metallic chromium

Abstract: PURPOSE:To advantageously manufacture the title chromium by mixing chromium oxide powder and calcium hydride powder, bringing it into a heating reaction in a hydrogen atmosphere and separating the generated metallic chromium. CONSTITUTION:The chromium oxide powder and the metallic calcium powder are preliminarily mixed and charged to a reaction furnace; the atmosphere in the reaction furnace is reduced to the hydrogen atmosphere and the mixture is gradually heated and is retained to 200-300 deg.C for prescribed times to substantially obtain the mixed powder of chromium oxide and calcium hydride. The mixed powder is then successively heated to 700-1200 deg.C in the hydrogen atmosphere and is brought into a heating reaction to melt calcium oxide away by an acid (acetic acid, etc.,). By this method, high purity metallic chromium is obtd. directly as fine powder.