Modified gypsum compositions

BACKGROUND OF THE INVENTION
This invention relates generally to improvement of the engineering properties of hydraulic cements and, more particularly, to set control compositions having a modified gypsum component.
It is well-known in the cement/concrete industry that cementitious materials are prepared by combining the sintered product of the oxides of calcium, silicon, iron and aluminum (commonly abbreviated C, S, F and A, respectively, in the industry) with a calcium sulfate material. Subsequent addition of water to the cement provides a workable material which hardens and gains strength as hydration proceeds to completion. Varying the proportions of the initial oxide and sulfate materials and the process conditions affects the physical properties and performance of the resulting mortar or concrete. More specifically, these properties and subsequent performance are, in large part, determined by the relative amounts of, interaction between and hydration of the sintered oxide products: tricalcium silicate, dicalcium silicate, tricalcium aluminate and tetracalcium aluminoferrite (abbreviated C.sub.3 S, C.sub.2 S, C.sub.3 A and C.sub.4 AF, respectively, in the industry). Generally, C.sub.3 S contributes to early and later compressive strengths, while the contribution of C.sub.2 S is limited to later strengths. C.sub.3 A contributes to early strength, but is sulfate susceptible. While C.sub.4 AF is also sulfate susceptible and adds little to early strength, it does enhance later strength. It is understood that while these four oxides and their products of sintering are those basic to the preparation and function of cementitious materials, other chemical components will also be present depending upon the source and/or identity of the raw materials used.
As mentioned above, the sintered product, clinker, is finally ground with an appropriate amount of a calcium sulfate material, usually gypsum. The resulting mixture is a hydraulic cementitious material, of which portland cement is a well-known representative. The principal function of the sulfate material is to control the set time of the cement upon mixing with water and through the course of hydration. Although the final setting of most cement materials is predominately influenced by the reaction of the C.sub.3 S phase, it is generally believed that the particulate surfaces of this phase can be quickly covered by hydrated reaction products, slowing additional reaction and development of early strength. In contrast, initial reaction of the aluminate phases with water is immediate and characterized by vigorous formation of crystalline hydrate. Unless aluminate hydration is moderated an undesirable flash set condition occurs. In the presence of a calcium sulfate material, among other effects, an insoluble sulfoaluminate coating forms on the particulate surfaces and slows the rate of hydration.
In contrast to flash set, false set conditions--initial, rapid rigidity--can also occur. During grinding with the clinker material, calcium sulfate dihydrate can be dehydrated to hemihydrate or soluble anhydrite forms. When the cement is mixed with water, rehydration can form an initial mass of dihydrate crystals, causing an initial rigidity, which appears to resemble actual set conditions.
False and flash set control conditions illustrate the importance of a sulfate component to a cementitious material. A set control composition should have a chemical profile which facilitates an appropriate degree and rate of hydration. Furthermore, a set control composition must be compatible with a particular cement to achieve acceptable strengths and/or related performance parameters.
It is desirable, therefore, to have an inexpensive set control composition that is compatible with various cementitious materials, which can be interground with clinker material or admixed with the ground product and that will meet or enhance the various physical, chemical and/or performance standards recognized through out the industry, both here and abroad, especially as they apply to the portland cements as specified under various ASTM, B.S., DIN and equivalent standard specifications.
SUMMARY OF THE INVENTION
The present invention is directed to set control compositions with a sulfate component modified by inclusion of magnesium sulfate in an amount of from about 0.5 to about 12 percent by weight.
Generally, the magnesium sulfate can be present in concentrations of about 1 percent by weight or greater, such as, for example about 2 or 4 percent by weight. While concentrations of up to about 12 percent by weight have been found operable, lesser quantities, such as, for example about 9 percent by weight and even about 6 or 3 percent by weight are quite effective.
One particularly economical source of magnesium sulfate that has been found effective is the solid oxidation product from oxidizing a mixture comprising carbon (particularly a hydrocarbon), sulfur and magnesium with the sulfur and magnesium in a molar ratio of sulfur to magnesium in the range of from about 1 to about 200, preferably at least about 10 or even about 25. Generally, it is not necessary to have a ratio of greater than about 100, or even about 50. Usually the combined sulfur and magnesium content of the mixture comprising carbon, sulfur and magnesium which is oxidized is in the range of from about 0.1 to about 5 percent by weight of the mixture comprising carbon, sulfur and magnesium which is oxidized and can be from as low as about 0.05 up to as high as 6 or 7 percent by weight. The magnesium component in the oxidation product, predominantly magnesium sulfate, is generally present in a weight ratio to unoxidized carbon of greater than about 5, and preferably greater than about 20, or even about 50.
Such oxidation products generally have a magnesium content, measured as elemental magnesium, of about 4 to about 12 percent by weight, preferably about 8 to about 11 percent by weight. Usually, the unoxidized carbon in the oxidation product is less than about 4 percent by weight and preferably lower, for example 2 or even 1 percent by weight. It will be understood that the lower unoxidized carbon content in the oxidation product is desired and zero is ideal. Typically, the oxidation product has a magnesium sulfate to unoxidized carbon molar ratio of greater than about 5, preferably greater than about 20 and even greater than about 50. To express it another way, the molar ratio of sulfur to magnesium in the oxidation product is less than about 10 and generally is in the range of from about 1 to about 5, or from about 1 to about 2.
It is particularly preferred to employ as the mixture comprising carbon, sulfur and magnesium which is oxidized an aqueous emulsion of naturally occurring asphalt from the Orinoco Belt of Venezuela containing from about 100 to about 1500 ppm by weight of magnesium in the form of a water-soluble magnesium salt. When employing such a material as the mixture comprising carbon, sulfur and magnesium which is oxidized, the oxidation product can be incorporated as an additive, whether interground or admixed, over a range of concentrations, for use in the preparation of a variety of cement, mortar and concrete compositions, and the like. Typically the oxidation product can be incorporated into the cement material in quantities in the range of from about 0.1 to about 7.5 or 8 percent by weight based upon the overall composition.
Another source of magnesium sulfate that can be employed in this invention comprises at least one or more of the halides, hydroxides, carbonates and sulfates of Group IA and IIA metals. Mixtures such as these can be conveniently obtained from the waste solids produced in the aqueous scrubbing of flue gases. These mixtures should be limited in the amount employed due to the fact that they contain significant quantities of halides, particularly chlorides. Accordingly, we find that limiting the concentration of such mixtures in the total cementitious composition to about 1 percent by weight keeps the halide level below that set by various specifications and standards.
Thus, such mixtures will normally comprise less than about 6, and usually less than about 5, percent by weight of the set control compositions of this invention. The lower limit is set by the quantity of magnesium it is desired to include in the set control composition or the final cementitious composition. When employed, we typically tend to use these mixtures at a level of at least about 2 percent by weight of the set control composition of this invention, and typically greater than about 3 percent by weight of the set control composition. It will be understood that these mixtures can be used alone or in conjunction with other sources of magnesium sulfate, such as the oxidation products mentioned above or magnesium sulfate, per se. A typical combination set control composition of this invention can contain from about 2 to about 4 percent by weight of the mixture with about 6 to about 3 percent by weight of the above described oxidation product.
More particularly, the present invention provides a set control composition for use in a hydraulic cement, in which the set control composition includes (1) from about 85 to about 99.9 percent by weight of a calcium sulfate material, and (2) from about 0.1 to about 15 percent by weight of a solid oxidation product of a naturally occurring asphalt from the Orinoco Belt of Venezuela which asphalt also contains from about 100 to about 1500 ppm of magnesium. In preferred embodiments, the oxidation product is obtained from the combustion of an aqueous emulsion of an asphalt from the Orinoco Belt of Venezuela in which the magnesium is present in the form of a water soluble salt. Such an emulsion is commercially-available as Orimulsion.RTM. fuel. Generally, the oxidation product is utilized in the range from about 5 to about 12 percent by weight.
As described above, the inventive set control and/or sulfate compositions have incorporated therein an oxidation product of a naturally occurring asphalt from the Orinoco Belt of Venezuela, preferably an aqueous emulsion of such asphalt. Generally and as will be well known to those skilled in the art made aware of the invention, the preparation of such an oxidation product includes contacting the asphalt material with air and/or another oxygen-containing stream, through any one of several recognized processes or variations thereof, to provide the oxidation product in addition to combustion by-products such as heat, carbon dioxide and water. The oxidation product is the solid residuals subsequently collected downstream from the point of combustion/oxidation.
The oxidation product of the present invention can be generated in such a manner as to include the introduction of one of several auxiliary processes and/or additives upstream, downstream or at the point of combustion, to meet various process or combustion requirements, relating but not limited to emission control, reduced corrosion or enhanced operability. Depending upon the nature of these processes and/or additives, the combustion residue or by-products thereof can become intimately commingled with an oxidation product described above and can be, where appropriate, considered part of, integral to, and used with the present invention.
Illustrative of an auxiliary process and/or additive is the incorporation of a flue gas clean up device--such as a wet lime-limestone scrubber--downstream from the combuster. Scrubber residues can be returned and/or reintroduced to the combustion/oxidation line at a point upstream of the final particulate separator, such that the residues are mixed with and incorporated into the oxidation product. Again, considering a scrubber process as illustrative of a number of available auxiliary processes, one skilled in the art will recognize that the identity/composition of the scrubber residues are a function of the identity of the particular scrubbing reagent, whether it be lime, limestone or a related scrubbing reagent, and the compositional components and their relative concentrations of the make-up of water used in the scrubber.
An asphalt precursor to the oxidation product of this invention is commercially available from Bitor America Corporation, Boca Raton, Fla., under the Orimulsion.RTM. trademark. Without limitation, this commercial product is currently prepared by initial injection of steam into the asphalt formation until the viscosity is reduced to a point permitting it to flow into a well bore. A primary aqueous emulsion is prepared which further reduces asphalt viscosity and facilitates handling and transportation. The primary emulsion is then broken with the water substantially removed, leaving an asphalt material with less than 2 percent water.
Alternatively, the asphalt in the formation can be dissolved or suspended in a light hydrocarbon solvent, such as for example, kerosene, and the kerosene-containing bitumen removed to the surface where separation of the bitumen and kerosene can be effected.
Fresh water is reintroduced and the asphalt is emulsified with a surfactant under strictly controlled protocols. For example, for a shear rate of 20 s.sup.-1, a viscosity of about 450 mPas is achieved by handling the Orimulsion.RTM. at 30.degree. C. This and comparable production methods and techniques provide an aqueous emulsion with no more than 2 percent of the droplets having a diameter higher than 80 micrometers. The Orimulsion.RTM. material is further characterized by density (.about.1,010 kg/m.sup.3 at 15.degree. C.), flash point (.about.130.degree. C./266.degree. F.), and concentrations of vanadium (.about.300 ppm), nickel (.about.73 ppm), magnesium (.about.350 ppm), carbon (.about.60.0 weight percent), hydrogen (.about.7.5 weight percent), sulfur (.about.2.7 weight percent), nitrogen (.about.0.50 weight percent) and oxygen (.about.0.20 weight percent).
It will be understood by those skilled in the art that the set control compositions of the present invention are not necessarily restricted by incorporation of an oxidation product of any one aqueous emulsion which contains magnesium of the type profiled above. Whereas a commercially-available Orinoco asphalt material might be described as a 30 percent aqueous emulsion prepared with a non-ionic surfactant, the compositions of the present invention can suitably comprise, consist of, or consist essentially of the oxidation product of such material and/or oxidation products of other comparably emulsified Orinoco-type asphalts. Each such oxidation product is compositionally distinguishable, characteristically contrasted, and can be practiced in conjunction with the present invention separate and apart from another. Accordingly, it should be understood that the inventive compositions, as illustratively disclosed herein, can be prepared and/or practiced in the absence of any one oxidation product and/or species which may or may not be specifically disclosed, referenced or inferred herein, the absence of which may or may not be specifically disclosed, referenced or inferred herein.
While other components, preparations, mixtures or formulations involving a naturally-occurring Orinoco-type asphalt and which contain magnesium can be used herewith, a useful source of oxidation product is available under the PCS trademark, available from Pure Air, a division of Air Products and Chemicals, Inc. of Allentown, Pa. As described above, the compositional profile of an oxidation product will reflect any process, operation and/or additive auxiliary to the asphalt and/or combustion process. However, any such oxidation product-while compositionally distinguishable, characteristically contrasted, and separately practiced--will reflect either the absolute or relative vanadium and nickel concentrations characteristic of a naturally-occurring asphalt from the Orinoco Belt of Venezuela.
Whereas various calcium sulfate materials can be used, a preferred material consists essentially of a dihydrate of calcium sulfate. Irrespective of the identity of the calcium sulfate material utilized, the set control composition can further include materials comprising a Group IIA halide, hydroxide and/or carbonate. The corresponding Group IA halides, hydroxides, sulfates and/or carbonates can also be incorporated into the composition in quantities which will not later adversely affect the structural integrity of a cement material or concrete reinforcement. Where such auxiliary, optional and/or additive materials are utilized, the oxidation product of this invention can be present in the range from about 4 to about 9 percent by weight.
In part, the present invention is an interground blend of materials including (1) a clinker material, and (2) a set control material containing from about 85 to about 99.9 percent by weight of a calcium sulfate composition, and about 0.1 to about 15 percent by weight of a solid oxidation product of an aqueous emulsion of a naturally occurring asphalt from the Orinoco Belt of Venezuela, which aqueous emulsion includes from about 100 to about 1500 ppm of magnesium in the form of a water-soluble salt of magnesium. Likewise, as described more fully above, a preferred oxidation product is obtained from the combustion of an aqueous emulsion of the naturally occurring Orinoco Belt asphalt, such as Orimulsion.RTM. fuel which contains magnesium, and can be utilized in concentrations ranging from about 5 to about 12 percent by weight. Irrespective of the source and concentration of the inventive oxidation product, a preferred calcium sulfate composition is a dihydrate.
The interground blend of the present invention preferably has chemical and physical properties meeting ASTM C 150 standard specifications for portland cement, or C 595 and/or C 1157 standard specifications for blended cements. However, interground blends prepared in accordance with this invention can also have chemical and physical properties equivalent to ASTM C 150 standard specifications for portland cement and/or C 1157 standard specifications for blended cements. See Tables A-G below, as discussed in a co-pending application entitled "Modified Cement and Concrete Compositions" filed contemporaneously herewith and incorporated by reference herein in its entirety.
The aforementioned chemical and physical requirements can also be met by inclusion of a material comprising a Group IIA halide, hydroxide and/or carbonate. Such materials can also include the corresponding Group IA halides, hydroxides and/or other Group IA or Group IIA compounds at concentrations below those which would bring the physical/chemical parameters outside the standard specifications or adversely affect the structural integrity of any concrete material subsequently prepared with the interground blend.
As such, where the present invention is utilized in the preparation of a cementitious concrete, the improvement in the concrete includes a set control composition of about 85 to about 99.9 percent by weight of a calcium sulfate material and about 0.1 to about 15 percent by weight of a solid combustion product of a naturally occurring asphalt from the Orinoco Belt of Venezuela which contains magnesium. In particular, the improvement in such concrete materials can usually be realized most effectively when the calcium sulfate material is a dihydrate of calcium sulfate and the oxidation product is obtained from the combustion of an aqueous emulsion of the naturally occurring Orinoco asphalt which contains magnesium, such as the commercially available Orimulsion.RTM. fuel, and utilized at a concentration of about 5 to about 12 percent by weight. Improvements in accordance with the present invention are also available by inclusion of at least one of a Group II halide, hydroxide and carbonate, and/or one or more of the corresponding Group IA halides, hydroxides and carbonates, or other Group IA or Group IIA compounds.
TABLE A______________________________________ASTM C 150 Standard Chemical Requirements III I and II and andCement Type IA IIA IIIA IV V______________________________________Silicon dioxide (SiO.sub.2), min, % . . . 20.0 . . . . . . . . .Aluminum oxide (Al.sub.2 O.sub.3), . . . 6.0 . . . . . . . . .max, %Ferric oxide (Fe.sub.2 O.sub.3), max, % . . . 6.0 . . . 6.5 . . .Magnesium oxide (MgO), 6.0 6.0 6.0 6.0 6.0max, %Sulfur trioxide (SO.sub.3),max, %When (C.sub.3 A) is 8% or less 3.0 3.0 3.5 2.3 2.3When (C.sub.3 A) is more than 8% 3.5 N/A 4.5 N/A N/ALoss on ignition, max, % 3.0 3.0 3.0 2.5 3.0Insoluble residue, max, % 0.75 0.75 0.75 0.75 0.75Tricalcium silicate (C.sub.3 S) . . . . . . . . . 35 . . .max, %Dicalcium silicate (C.sub.2 S) . . . . . . . . . 40 . . .min, %Tricalcium aluminate (C.sub.3 A) . . . 8 15 7 5max, %Tetracalcium alumino- . . . . . . . . . . . . 25ferrite plus twice thetricalcium aluminate(C.sub.4 AF + 2(C.sub.3 A)), or solidsolution (C.sub.4 AF + C.sub.2 F), asapplicable, max, %______________________________________
When expressing compounds, C=CaO, S=SiO.sub.2, A=Al.sub.2 O.sub.3, F=Fe.sub.2 O.sub.3. For example, C.sub.3 A=3CaO.Al.sub.2 O.sub.3.
There are cases where optimum SO.sub.3 (using Test Method C 563) for a particular cement is close to or in excess of the limit in this specification. In such cases where properties of a cement can be improved by exceeding the SO.sub.3 limits stated in this table, it is permissible to exceed the values in the table, provided it has been demonstrated by Test Method C 1038 that the cement with the increased SO.sub.3 will not develop expansion in water exceeding 0.020% at 14 days. When the manufacturer supplies cement under this provision, he shall, upon request, supply supporting data to the purchaser.
The expression of chemical limitations by means of calculated assumed compounds does not necessarily mean that the oxides are actually or entirely present as such compounds.
Titanium dioxide and phosphorus pentoxide (TiO.sub.2 and P.sub.2 O.sub.5) shall be included with the Al.sub.2 O.sub.3 content. The value historically and traditionally used for Al.sub.2 O.sub.3 in calculating potential compounds for specification purposes is the ammonium hydroxide group minus ferric oxide (R.sub.2 O.sub.3 --Fe.sub.2 O.sub.3) as obtained by classical wet chemical methods. This procedure includes as Al.sub.2 O.sub.3 the TiO.sub.2, P.sub.2 O.sub.5 and other trace oxides which precipitate with the ammonium hydroxide group in the classical wet chemical methods. Many modern instrumental methods of cement analysis determine aluminum or aluminum oxide directly without the minor and trace oxides included by the classical method. Consequently, for consistency and to provide comparability with historic data and among various analytical methods, when calculating potential compounds for specification purposes, those using methods which determine Al or Al.sub.2 O.sub.3 directly should add to the determined Al.sub.2 O.sub.3 weight quantities of P.sub.2 O.sub.5, TiO.sub.2 and any other oxide except Fe.sub.2 O.sub.3 which would precipitate with the ammonium hydroxide group when analyzed by the classical method and which is present in an amount of 0.05 weight % or greater. The weight percent of minor or trace oxides to be added to Al.sub.2 O.sub.3 by those using direct methods may be obtained by actual analysis of those oxides in the sample being tested or estimated from historical data on those oxides on cements from the same source, provided that the estimated values are identified as such.
When the ratio of percentages of aluminum oxide to ferric oxide is 0.64 or more, the percentages of tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium aluminoferrite shall be calculated from the chemical analysis as follows:
Tricalcium silicate=(4.071.times.% CaO)-(7.600.times.SiO.sub.2)-6.718.times.% Al.sub.2 O.sub.3)-1.430.times.% Fe.sub.2 O.sub.3)-2.852.times.% SO.sub.3)
Dicalcium silicate=(2.867.times.% SiO.sub.2)-(0.7544.times.% C.sub.3 S)
Tricalcium aluminate=(2.650.times.% Al.sub.2 O.sub.3)-(1.692.times.% Fe.sub.2 O.sub.3)
Tetracalcium aluminoferrite=3.043.times.% Fe.sub.2 O.sub.3
When the alumina-ferric oxide ratio is less than 0.64, a calcium aluminoferrite solid solution (expressed as ss(C.sub.4 AF+C.sub.2 F) is formed. Contents of this solid solution and of tricalcium silicate shall be calculated by the following formulas:
ss(C.sub.4 AF+C.sub.2 F)-(2.100.times.% Al.sub.2 O.sub.3 +(1.702.times.% Fe.sub.2 O.sub.3)
Tricalcium silicate=(4.071.times.% CaO)-(7.600.times.% SiO.sub.2)-(4.479.times.% Al.sub.2 O.sub.3)-(2.859.times.% Fe.sub.2 O.sub.3)-(2.852.times.% SO.sub.3).
No tricalcium aluminate will be present in cements of this composition.
Dicalcium silicate shall be calculated as previously shown.
In the calculation of all compounds the oxides determined to the nearest 0.1% shall be used.
All values calculated as described in this note shall be reported to the nearest 1%.
For Type IV cements, C.sub.3 S, C.sub.2 S and C.sub.2 A requirements do not apply when the heat of hydration limit on Table D is specified.
For Type V cements, C.sub.3 A and (C.sub.4 AF+2(C.sub.3 A)) requirements do not apply when the sulfate expansion limit in Table D is specified.
TABLE B__________________________________________________________________________ASTM C 150 Optional Chemical Requirements I II III and and andCement Type IA IIA IIIA IV V Remarks__________________________________________________________________________Tricalcium aluminate (C.sub.3 A), . . . . . . 8 . . . . . . for moderate sulfatemax, % resistanceTricalcium aluminate (C.sub.3 A), . . . . . . 5 . . . . . . for high sulfatemax, % resistanceSum of tricalcium silicate and . . . 58 . . . . . . . . . for moderate heat oftricalcium aluminate, max, % hydrationAlkalies (Na.sub.2 O + 0.658 K.sub.2 O), max, % 0.60 0.60 0.60 0.60 0.60 low-alkali cement__________________________________________________________________________
When expressing compounds, C=CaO, S=SiO.sub.2, A=Al.sub.2 O.sub.3, F=Fe.sub.2 O.sub.3. For example, C.sub.3 A=3CaO.Al.sub.2 O.sub.3.
These optional requirements apply only if specifically requested. Availability should be verified. See note in Section 4.
The expression of chemical limitations by means of calculated assumed compounds does not necessarily mean that the oxides are actually or entirely present as such compounds.
When the ratio of percentages of aluminum oxide to ferric oxide is 0.64 or more, the percentages of tricalcium silicate, dicalcium silicate, tricalcium aluminate and tetracalcium aluminoferrite shall be calculated from the chemical analysis as follows:
Tricalcium silicate=(4.071.times.% CaO)-(7.600.times.% SiO.sub.2)-(6.718.times.% Al.sub.2 O.sub.3)-(1.430.times.Fe.sub.2 O.sub.3)-(2.852.times.% SO.sub.3)
Dicalcium silicate=(2.867.times.% SiO.sub.2)-(0.7544.times.% C.sub.3 S)
Tricalcium aluminate=(2.650.times.% Al.sub.2 O.sub.3)-(1.692.times.% Fe.sub.2 O.sub.3)
Tetracalcium aluminoferrite=3.043.times.% Fe.sub.2 O.sub.3
When the alumina-ferric oxide ratio is less than 0.64, a calcium aluminoferrite solid solution (expressed as ss (C.sub.4 AF+C.sub.2 F)) is formed. Contents of this solid solution and of tricalcium silicate shall be calculated by the following formulas:
ss(C.sub.4 AF+C.sub.2 F)=(2.100.times.% Al.sub.2 O.sub.3)+(1.702.times.% Fe.sub.2 O.sub.3)
Tricalcium silicate=(4.071.times.% CaO)-(7.600.times.% SiO.sub.2)-(4.479.times.% Al.sub.2 O.sub.3)-(2.859.times.% Fe.sub.2 O.sub.3)-(2.852.times.% SO.sub.3).
No tricalcium aluminate will be present in cements of this composition.
Dicalcium silicate shall be calculated as previously shown.
In the calculation of all compounds the oxides determined to the nearest 0.1% shall be used.
All values calculated as described in this note shall be reported to the nearest 1%.
The optional limit of heat of hydration in Table D shall not be requested when the sum of C.sub.3 S and C.sub.3 A is requested.
The limit on alkalies may be specified when the cement is to be used in concrete with aggregates that may be deleteriously reactive. Reference should be made to Specification C 33 for suitable criteria of deleterious reactivity.
TABLE C______________________________________ASTM C 150 Standard Physical RequirementsCement Type I IA II IIA______________________________________Air content of mortar,volume %:max 12 22 12 22min . . . 16 . . . 16Fineness, specific surface,m.sup.2 /kg (alternative methods):Turbidimeter test, min 160 160 160 260Air permeability test, min 280 280 280 280Autoclave expansion, max, % 0.80 0.80 0.80 0.80Strength; not less than thevalues shown for the agesindicated below:Compressive strength,psi (MPa): 1 day . . . . . . . . . . . . 3 day 1800 1450 1500 1200 (12.4) (10.0) (10.3) (8.3) 1000 800 (6.9) (5.5) 7 days 2800 2250 2500 2000 (19.3) (15.5) (17.2) (13.8) 1700 1350 (11.7) (9.3)28 days . . . . . . . . . . . .Time of setting(alternative methods):Gillmore test:Initial set, min, not less than 60 60 60 60Final set, min, not less than 600 600 600 600Vicat test:Time of setting, min, 45 45 45 45not less thanTime of setting, min, 375 375 375 375not more than______________________________________Cement Type III IIIA IV V______________________________________Air content of mortar,volume %:max 12 22 12 12min . . . 16 . . . . . .Fineness, specific surface,m.sup.2 /kg alternative methods):Turbidimeter test, min . . . . . . 160 160Air permeability test, min . . . . . . 280 280Autoclave expansion, max, % 0.80 0.80 0.80 0.80Strength; not less than thevalues shown for the agesindicated below:Compressive strength,psi (MPa): 1 day 1800 1450 . . . . . . (12.4) (10.0) 3 day 3500 2800 . . . 1200 (24.1) (19.3) (8.3) 7 days . . . . . . 1000 2200 (6.9) (15.2)28 days . . . . . . 2500 3000 (17.2) (20.7)Time of setting(alternative methods):Gillmore test:Initial set, min, not less than 60 60 60 60Final set, min, not less than 600 600 600 600Vicat test:Time of setting, min, 45 45 45 45not less thanTime of setting, min, 375 375 375 375not more than______________________________________
Compliance with requirements of this specification does not necessarily ensure that the desired air content will be obtained in concrete.
Either of the two alternative fineness methods may be used at the option of the testing laboratory. However, when the sample fails to meet the requirements of the air-permeability test, the turbidimeter test shall be used, and the requirements in this table for the turbidimetric method shall govern.
The strength at any specified test age shall not be less than that attained at any previous specified test age.
The purchaser should specify the type of setting-time test required. In case he does not so specify, the requirements of the Vicat test only shall govern.
The second set of 3 and 7 day strength parameters for Types II and IIA apply when the optional heat of hydration or the chemical limit on the sum of the tricalcium silicate aluminate is specified.
The time of setting is that described as initial setting time in Test Method C 191.
TABLE D______________________________________ASTM C 150 Optional Physical RequirementsCement Type I IA II IIA______________________________________False set, final penetration, 50 50 50 50min, %Heat of hydration: 7 days, max, cal/g (kJ/kg) . . . . . . 70(290) 70(290)28 days, max, cal/g (kJ/kg) . . . . . . . . . . . .Strength, not less than thevalues shown:Compressive strength,psi (MPa)28 days 4000 3200 4000 3200 (27.6) (22.1) (27.6) (22.1) 3200 2560 (22.1) (17.7)Sulfate expansion, 14 days, . . . . . . . . . . . .max, %______________________________________Cement Type III IIIA IV V______________________________________False set, final penetration, 50 50 50 50min, %Heat of hydration: 7 days, max, cal/g (kJ/kg) . . . . . . 60 . . . (250)28 days, max, cal/g (kJ/kg) . . . . . . 70 . . . (290)Strength, not less than thevalues shown:Compressive strength,psi (MPa)28 days . . . . . . . . . . . .Sulfate expansion, 14 days, . . . . . . . . . 0.040max, %______________________________________
The optional limit for the sum of the tricalcium silicate and tricalcium aluminate shall not be requested when the heat of hydration limit is requested for Types II and IIA. These strength requirements apply when either heat of hydration or the sum of tricalcium silicate and tricalcium aluminate requirements are requested.
When the heat of hydration limit is specified for Type IV cement, it shall be instead of the limits of C.sub.3 S, C.sub.2 S, and C.sub.3 A listed in Table A.
When the sulfate expansion is specified, it shall be instead of the limits of C.sub.3 A and C.sub.4 AF+2 C.sub.3 A listed in Table A.
TABLE E______________________________________ASTM C 595 Chemical Requirements I(PM), I(SM), I(PM)-A, I(SM)-A, P, PA, IP,Cement Type IS, IS-A S,SA IP-A______________________________________Magnesium oxide (MgO), max, % . . . . . . 5.0Sulfur reported as sulfate (SO.sub.3), 3.0 4.0 4.0max, %Sulfide sulfur (S), max, % 2.0 2.0 . . .Insoluble residue, max, % 1.0 1.0 . . .Loss on ignition, max, % 3.0 4.0 5.0Water-soluble alkali, max, % . . . 0.03 . . .______________________________________
When it has been demonstrated by Test Method C 563 that the optimum SO.sub.3 exceeds a value of 0.5% less than the specification limit, an additional amount of SO.sub.3 is permissible provided that, when the cement with the additional calcium sulfate is tested by Test Method C 265, the extractable calcium sulfate in the hydrated mortar at 24.+-.1/4 h, expressed as SO.sub.3, does not exceed 0.50 g/L. When the manufacturer supplies cement under this provision, he will, upon request, supply supporting data to the purchaser.
TABLE F__________________________________________________________________________ASTM C 595 Physical Requirements I(SM)-A, IS- I(SM), IS-A, A(MS) IS, I(PM)-A, IS(MS) IP-Cement Type I(PM),IP IP-A IP(MS) A(MS)__________________________________________________________________________Fineness (See Below)Autoclave expansion max, % 0.50 0.50 0.50 0.50Autoclave contraction, max % 0.20 0.20 0.20 0.20Time of setting, Vicat test:Set, minutes, not less than 45 45 45 45Set, h, not more than 7 7 7 7Air content of mortar (Method C 185), 12 max 19 .+-. 3 12 max 19 .+-. 3volume %Compressive strength, min, psi (MPa): 3 days 1800 1450 1500 1200 (12.4) (9.9) (10.3) (8.3) 7 days 2800 2250 2500 2000 (19.3) (15.5) (17.2) (13.8)28 days 3500 2800 3500 2800 (24.1) (19.3) (24.1) (19.3)Heat of hydration: 7 days, max, cal/g (kJ/kg) 70 70 70 70 (293) (293) (293) (293)28 days, max, cal/g (kJ/kg) 80 80 80 80 (335) (335) (335) (335)Water requirement, max weight % . . . . . . . . . . . .of cementDrying shrinkage, max, % . . . . . . . . . . . .Mortar expansion:At age of 14 days, max, % 0.020 0.020 0.020 0.020At age if 8 weeks, max, % 0.060 0.060 0.060 0.060Sulfate Resistance 0.10 0.10Expansion at 180 days max, %__________________________________________________________________________Cement Type S SA P PA__________________________________________________________________________Fineness (See below)Autoclave expansion max, % 0.50 0.50 0.50 0.50Autoclave contraction, max % 0.20 0.20 0.20 0.20Time of setting, Vicat test:Set, minutes, not less than 45 45 45 45Set, h, not more than 7 7 7 7Air content of mortar (Method C 185), 12 max 19 .+-. 3 12 max 19 .+-. 3volume %Compressive strength, min, psi (MPa): 3 days . . . . . . . . . . . . 7 days 600 500 1500 1250 (4.1) (3.4) (10.3) (8.6)28 days 1500 1250 3000 2500 (10.3) (8.6) (20.7) (17.2)Heat of hydration: 7 days, max, cal/g (kJ/kg) . . . . . . 60 60 . . . . . . (251) (251)28 days, max, cal/g (kJ/kg) 70 70 (293) (293)Water requirement, max weight % . . . . . . 64 56of cementDrying shrinkage, max, % . . . . . . 0.15 0.15Mortar expansion:At age of 14 days, max, % 0.020 0.020 0.020 0.020At age if 8 weeks, max, % 0.060 0.060 0.060 0.060Sulfate ResistanceExpansion at 180 days max, %__________________________________________________________________________
With regard to fineness, both amount retained when wet sieved on 45-.mu.m (No. 325) sieve and specific surface by air permeability apparatus. cm.sup.2 /g, shall be reported on all mill test reports requested under 14.4.
Time of setting refers to initial setting time in Method C 191.
Heats of hydration are applicable only when moderate (MH) or low (LH) heat of hydration is specified, in which case the strength requirements shall be 80% of the values shown in the table.
The test for mortar expansion is an optional requirement to be applied only at the purchaser's request and should not be requested unless the cement will be used with alkali-reactive aggregate.
TABLE G______________________________________ASTM C 595 Requirements for Pozzolan for Use in BlendedCements and for Slag for Use in Slag-modified portland CementsPozzolanFineness: 20.0Amount retained when wet-sieved on 45-.mu.m(No. 325) sieve, max, %Alkali reactivity of pozzolan for use in Types 0.05I(PM) and I(PM)-A cements, six tests, mortar barexpansion at 91 days, max, %Slag or pozzolan activity index: 75with portland cement, at 28 days, min, %______________________________________

EXAMPLES OF THE INVENTION
The following nonlimiting examples and data illustrate various aspects and features relating to the compositions and/or methods of this invention, including the utility of the inventive set control compositions, and the resulting cements, mortars and concretes.
Example 1
A specific surface (Blaine) of 350.+-.10 m.sup.2 /kg was targeted for the gypsum and/or set control materials of this example. To that effect each was ground at a temperature (230.degree. F.) adequate to dehydrate about 50% of the gypsum or gypsum component (CaSO.sub.4.2H.sub.2 O) to the hemihydrate. The actual Blaines are as shown in the following Tables.
Mixing times for all the physical tests, summarized below in the following Tables, are specified in the aforementioned ASTM methods. For the C 109 strength test, place the dry paddle and the dry bowl in the mixing position in the mixer, then introduce the materials for a batch into the bowl and mix in the following manner: 1) Place all the mixing water in the bowl. 2) Add the cement to the water; then start the mixer and mix at the slow speed (140.+-.5 rev/min) for 30 seconds. 3) Add the entire quantity of sand slowly over a 30-sec period, while mixing at slow speed. 4) Stop the mixer, change to medium speed (285.+-.10 rev/min), and mix for 30 sec. 5) Stop the mixer and let the mortar stand for 11/2 minutes. During the first 15 sec of this interval, quickly scrape down into the batch any mortar that may have collected on the side of the bowl; then for the remainder of this interval, cover the bowl with the lid. 6) Finish by mixing for 1 min at medium speed (285.+-.10 rev/min). 7) In any case requiring a remixing interval, any mortar adhering to the side of the bowl shall be quickly scraped down into the batch with the scraper prior to remixing.
For the C 185 Air Content Test, the mixing procedure is substantially the same as for the C 109 strength test.
For the C 191 Vicat Set Time and the C 151 Autoclave Expansion Tests, place the dry paddle and the dry bowl in the mixing position in the mixer, then introduce the materials for a batch into the bowl and mix in the following manner: 1) Place all the mixing water in the bowl. 2) Add the cement to the water and allow 30 sec for the absorption of the water. 3) Start the mixer and mix at the slow speed (140.+-.5 rev/min) for 30 sec. 4) Stop the mixer for 15 sec and during this time scrape down into the batch any paste that may have collected on the sides of the bowl. Start the mixer at medium speed (285.+-.10 rev/min), and mix for 1 min.
For the C 359 Mortar False Set Test,: mix at one time 600 g of cement, 300 g of graded standard sand, 300 g of 20-30 standard sand, and 180 ml of water for all cements except Types III and IIIA, for which the amount of water shall be 192 ml. The mixing shall be done in the mechanical mixer as follows: 1) Place the sand and the cement in the dry bowl, and mix the dry materials for a few seconds with the spoon. 2) Place the bowl in the mixer, set the paddle in place, and mix the dry materials for 10 sec at slow speed (140.+-.5 rev/min). 3) With the mixer operating at slow speed, add the entire quantity of mixing water within 5 sec. Stop the mixer, quickly change to a medium speed (285.+-.10 rev/min), and continue the mixing for 1 min, timing from the first addition of water. 4) Stop the mixer, scrape the sides of the mixing bowl with the rubber scraper, and quickly place the thermometer in the mortar. Allow it to stand undisturbed for the remainder of a 45-sec interval from the time of stopping the mixer. 5) Read the temperature, remove the thermometer, start the mixer, and mix for 15 sec at a medium speed. If the mortar temperature is not in the range from 23.+-.1.7.degree. C. (73.4.+-.3.degree. F.), discard the batch and adjust the temperature of the water or sand, or both, to give the required temperature.
Immediately after the particular mixing described for each test, 1) remove the bowl from the mixer and with a spoon, uniformly distribute a portion of the mortar into the container until the container is heaping full. Quickly and gently place each spoonful of mortar in the container. When removing the mortar from the bowl, do not remove the material pushed up on the side of the bowl by the paddle. After the container has been filled, reassembled the mixer, cover the bowl with a lid, and retain the remaining mortar for a remix test to be performed later. To compact the mortar in the container, lift the container approximately 80 mm (3 in) from the table with both hands and rap it twice against the surface of the table. 2) With the leading edge slightly raised, strike off the mortar with one stroke of the trowel along the length of the container. Then remove the excess mortar by means of a sawing motion with the straightedge of the trowel along the length of the container in a direction opposite to that used in striking off. Then, smooth the surface of the mortar with a single stroke of the trowel.
For completion of the mortar false set test, 1) after filling the container, immediately place the 10-mm plunger of the Vicat apparatus, FIG. 1 of Test Method C 187, in contact with the surface of the mortar at the midpoint of the container on the longitudinal center line. Set the movable indicator at zero. Release the plunger 3 minutes after the beginning of the wet mixing and record the initial penetration in millimeters to which the plunger has settled below the surface 10 sec after being released. Generally, the plunger will settle to the bottom of the container, and the initial penetration will, accordingly, be recorded as 50+ mm. 2) Immediately withdraw and clean the plunger. In a similar manner, determine, after moving the Vicat apparatus to the desired location, the penetrations at intervals of 5, 8, and 11 min after the beginning of mixing. Do not move the filled container until these measurements are completed. Make all penetrations along the longitudinal center line of the container. Obtain 5 and 8-min penetrations at a distance of approximately 40 mm (11/2 in.) from each end of the container, respectively, and determine the 11-min penetration at a point approximately midway between the points at which the initial and 5-min penetrations were determined. 3) At the completion of the measurement of the 11-min penetration, immediately return the mortar in the container to the bowl. Start the mixer, raise the bowl into mixing position, and remix the contents of the bowl at medium speed (285.+-.10 rev/min) for 1 min. Fill a clean container as outlined above, and determine the penetration 45 sec after completion of mixing.
In the following examples the material designated as "OP 1" was comprised totally of the oxidation product obtained from Orimulsion fuel described previously, while the material designated "OP 2" was comprised of 40 percent by weight of the mixture of Group IA and IIA solids and 60 percent by weight of the oxidation product obtained from Orimulsion fuel.
TABLE 1a______________________________________Comparative Mortar Compressive Strengths (ASTM C 109) Fineness, Compressive Strength,Cement m.sup.2 /kg psi (days of hydration)Type Gypsum (Blaine) 1 3 7 28______________________________________I Control 1 356 2280 3820 4460 5080 Control 2 351 1640 3160 4020 4720 Control 3 2000 3530 4760 6180 MgSO.sub.4 * 2250 3600 5350 6475 Gypsum/OP 1 350 2050 3380 4060 4780 Gypsum/OP 2 2770 3700 4400 5080II Control 1 358 1370 3680 4810 5650 Control 2 355 1640 3930 4900 5800 Gypsum/OP 1 362 1270 3970 5000 5430V Control 1 348 1130 2920 3980 5090 Control 2 352 1350 3470 4270 5410 Gypsum/OP 1 351 1280 3880 4700 5520______________________________________ *-MgSO4 is compared to Control 3 All others are compared to Controls 1 & 2
TABLE 1b______________________________________Relative Mortar Compressive Strengths (ASTM C 109) Fineness,Cement m.sup.2 /kg Percent of ControlType Gypsum (Blaine) 1 3 7 28______________________________________I Control 1 356 100 100 100 100 Control 2 351 72 83 90 93 Control 3 100 100 100 100 MgSO.sub.4 * 113 102 112 105 Gypsum/OP 1 350 90 88 91 94 Gypsum/OP 2 121 97 99 100II Control 1 358 100 100 100 100 Control 2 355 120 107 102 103 Gypsum/OP 1 362 93 108 104 96V Control 1 348 100 100 100 100 Control 2 352 119 119 107 106 Gypsum/OP 1 351 113 133 118 108______________________________________ *-MgSO4 is compared to Control 3 All others are compared to Controls 1 & 2
TABLE 1c______________________________________Autoclave Expansion (ASTM C 151) Expansion,Cement Type Gypsum % Length______________________________________I Control 1 0.02 Control 2 0.02 Gypsum/OP 1 0.03II Control 1 -0.04 Control 2 -0.04 Gypsum/OP 1 -0.08V Control 1 -0.04 Control 2 -0.05 Gypsum/OP 1 -0.05______________________________________
TABLE 1d__________________________________________________________________________Motar False Set (ASTM C 359)Cement mm PenetrationType Gypsum Initial 5-min. 8-min. 11-min. Remix__________________________________________________________________________I Control I 50 47 20 11 50 Control 2 50 40 15 10 50 Control 3 22 12 9 10 13 MgSO.sub.4 10 5 5 4 4 Gypsum/OP 1 50 14 61/2 4 50 Gypsum/OP 1* 22 4 2 1 21 Gypsum/OP 2 50 50 15 10 50II Control 1 50 50 45 45 50 Control 2 50 50 50 50 50 Gypsum/OP 1 50 45 10 5 50V Control 1 50 50 44 5 50 Control 2 50 50 48 47 50 Gypsum/OP 1 50 50 48 25 50__________________________________________________________________________ *Ground at reduced temperature to reduce dehydration.
TABLE 1e______________________________________Time of Set, VICAT (ASTM C 191)CementType Gypsum Init.-Hr:Min. Fin.-Hr:Min.______________________________________I Control 1 2:16 4:00 Control 2 2:46 4:45 Control 3 2:46 4:15 MgSO.sub.4 2:29 4:15 Gypsum/OP 1 2:55 5:00 Gypsum/OP 2 2:12 3:45II Control 1 3:05 4:30 Control 2 2:46 4:30 Gypsum/OP 1 4:15 5:45V Control 1 3:00 5:00 Control 2 3:15 4:45 Gypsum/OP 1 4:00 6:30______________________________________
TABLE 1f______________________________________Mortar Air Contents (ASTM C 185)Cement Type Gypsum % By Volume______________________________________I Control 1 9.3 Control 2 11.1 Gypsum/OP 1 10 Gypsum/OP 2 9.7II Control 1 6.6 Control 2 6.2 Gypsum/OP 1 6V Control 1 9.9 Control 2 9.5 Gypsum/OP 1 9.7______________________________________
The mortar specimens of this example were prepared with the indicated portland cement types, as prepared from clinkers with low (<5%, Type V), intermediate (.about.6%, Type II) and high (>12%, Type I) levels of tricalcium aluminate, by way of illustrating the effects available through use of the set control compositions of this invention. The gypsum materials tested with each cement type are as indicated. Control 1 is commercially available natural gypsum; Control 2 is a gypsum material commercially available from Air Products and Chemicals, Inc. under the Power Chip gypsum trade designation; the gypsum material indicated as gypsum/OP 1 is about 9 weight percent oxidation product in calcium sulfate dihydrate and commercially available from Pure Air, a division of Air Products and Chemicals, Inc. under the Cement Grade Power Chip trade designation; and gypsum/OP 2 is Power Chip gypsum including about 5.4 weight percent oxidation product, which is commercially available under the PCS trademark, as described above. The concentration of magnesium sulfate, per se, utilized in these Examples was 7 percent by weight of the set control composition (equivalent to 0.35% of total cementitious material). The amount of gypsum used with each clinker/cement material was chosen to provide reasonable set control, strength development, and volume stability within the parameters of the referenced ASTM test methods. As discussed above, higher gypsum levels with corresponding increases in the oxidation product component, can be used to extend the results of this example.
The C 109 mortar strength results are provided in Table 1a and compared percentage-wise with Control 1, in Table 1b. Control 2 provided greater compressive strengths than Control 1 with Types II and V cement, but showed less strength over 28 days of hydration than Control 1 with Type I cement. Gypsum/OP 1 exhibited superior strengths with Type V mixes, was substantially equivalent to Control 1 with Type II cement, but exhibited slightly reduced strengths (compared to Control 1) with Type I cement. Gypsum/OP 2 performed well with Type I cement in mortar, with high one day strengths, but was otherwise substantially equivalent to Control 1.
Both gypsum/OP were observed to be dry, compared to Control 1. The oxidation product of this invention is somewhat hygroscopic. The high water demand causes the mortar to dry rather fast. As a result, various counteracting admixtures can be introduced, including a superplasticizer such as a naphthalene sulfonate, such admixtures are also considered to be within the scope of this invention.
Referring to Table 1c, autoclave expansions are negligible and substantially unchanged with respect to either Control 1 or Control 2. Referring to Table 1d, gypsum/OP 1 induced minor false setting conditions when used in conjunction with Type II mixes, intensified slightly the false set observed with Type I mixes, and somewhat reduced the false set conditions with the Type V mixes. The gypsum/OP 2 performed in a manner comparable to Control 1, with respect to false set. As indicated, a lower grinding temperature reduced false set, suggesting that a hemihydrate species may be influencing mortar behavior for this particular cement.
As shown in Table 1e, gypsum/OP 1 delayed setting times when used in Type I, II and V cements, but the retardation is observed to be minimal. In contrast, gypsum/OP 2 eliminated the retardation. As shown in Table 1f, cements made with the gypsum materials including inventive oxidation products exhibit air contents comparable to those with Controls 1 and 2.
Example 2
The Type I and V cements described in the previous example were analyzed for insoluble residue, according to the procedures described in ASTM C 114. The results summarized in Table 2 show that the residue problem associated with coal fly ash materials (i.e., an unacceptably high concentration of materials which can not be dissolved in either acid or alkali, usually due to the presence of aluminosilicates) is not evident with the oxidation products of this invention. In all cases the residue was well below the 0.75 weight percent limit specified by C 114.
TABLE 2______________________________________Cement Type Gypsum Insol. Res. (wt. %)______________________________________I Control 1 0.21 Control 2 0.36 Gypsum/OP 1 0.25V Control 1 0.11 Control 2 0.08 Gypsum/OP 1 0.06______________________________________
While the principles of this invention have been described in connection with specific embodiments, it should be understood clearly that these descriptions, along with the chosen tables and data therein, are made only by way of example and are not intended to limit the scope of this invention, in any manner. Other advantages and features of the invention will become apparent from the following claims, with the scope thereof determined by the reasonable equivalents, as understood by those skilled in the art.
Example 3
In part, the results of the compositions of Example 1 were extended to Type V cement in concrete. Utilizing, generally, the procedures described in Example 2 of the aforementioned co-pending application, entitled "Modified Cement and Concrete Compositions," the concrete of this example was prepared with laboratory grinds of Type V clinker and the gypsum/OP 1 material described above.
Compressive strengths were determined according to standard ASTM C 39 procedures at 1, 3, 7, 28, 56 and 90 days and compared to a control prepared with a laboratory grind of the same clinker and a commercially-available natural gypsum. The results are provided in Table 3, below.
TABLE 3______________________________________ Compressive strength, psi (days of hydration)Concrete 1 3 7 28 56 90______________________________________Control 1050 1930 2750 3970 4230 4610w/gypsum/OP 1 890 2190 2890 4170 4370 4580% of Control 85 113 105 104 103 99______________________________________
As summarized in Table 3, a Type V concrete prepared using an oxidation product of the type described herein was observed to have compressive strengths very comparable to, and in general exceeding, those of the control. In accordance with this invention and as described above, the results of this example can be extended to include concrete compositions prepared with other cements and set control compositions of the sort disclosed herein.
Example 4
Set control compositions and the cements and concretes in which they are employed are prepared in the manner described above, but employing the mixture of blow down solids from the aqueous scrubbing of flue gas as the source of magnesium sulfate. A typical analysis of such mixture is set forth in Table X, below.
TABLE 4______________________________________Material Concentration wt. %______________________________________MgSO.sub.4.H.sub.2 O 56Ca.sub.2 SO.sub.4 12NaCl 11.7AI(OH).sub.3 7.6Fe(OH).sub.3 5.0Na.sub.2 SO.sub.4 4.8KCl 2.9______________________________________
Several batches of set control compositions are prepared using various concentrations of the solids mixture (WES) ranging from about 2 to about 6 percent by weight and including compositions prepared using combinations of the solids mixtures together with other sources of magnesium sulfate, including blends with the above described oxidation products, in proportions ranging from about 10 to about 40 percent by weight solids mixture, with the balance being oxidation products. Similarly, the solids mixture is blended with commercial grade magnesium sulfate, with the solid mixture being present in an amount of about 10 to about 50 percent by weight of the blend.
The results obtained with these batches are equivalent to the results shown above in Examples 1 through 3.

Number	Name	Date
814490	Weiss	Mar 1906
3885980	Noone	May 1975
4193971	Kawamata et al.	Mar 1980
4381207	Olander et al.	Apr 1983
5084255	College et al.	Jan 1992

Number	Date	Country
55-162426	Dec 1980	JPX
58-179539	Oct 1983	JPX
58-179558	Oct 1983	JPX

Modified gypsum compositions

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

Field of Search

US

International Classifications

Abstract

Description

Claims

US Referenced Citations (5)

Foreign Referenced Citations (3)