No. It has also been discovered that the required magnesium oxide particle size, surface area, and ANT can all be controlled simply by controlling calcining conditions of the magnesium oxide (including temperature, time and starting material). The performance of these accelerators depends on the cement chemical composition and fineness, and the presence of mineral additions such as flyash, and blastfurnace slag. 1. Regrinding tends to be a process which is inherently difficult to control in terms of size distribution of the magnesium oxide particles. It will also be observed from Table 3 that increasing the weight percent of any given particle size of magnesium oxide present, invariably increases the expansion. Under conditions of restrained expansion, cements such as those of Trial 9, would be expected to exhibit good compressive strengths. They are mostly used for grouting purposes in anchor bolt and prestressed concrete ducts. Process to separate colour bodies and/or asphalthenic contaminants from a hydrocarbon mixture. The patent apparently contemplates that the foregoing mixture be combined with a cement in the amount of about 0.5 to 40% of the mixture based upon weight of cement (BWOC). The best particle size range which will produce linear expansions of about 0.5% after 14 days without unduly sacrificing compressive strengths, at least for a cement exposed to a temperature of 200° F., appears from Table 3 to be 150 to 420 microns. … % fluid loss retarder, and 34 wt. A method as defined in claim 13 wherein the magnesium oxide has been prepared by calcining at between about 1100° C. to about 1300° C. for between about 1 to about 3 hours. The expansion mechanism is the expansion of ettringite generated in cement paste. The composition contains about 3 to 25% by weight of the foregoing magnesium oxide, as well as 10 to 15% of aluminum phosphate, and 50 to 82% inert aggregate, such as sand and gravel. In each Trial, the magnesium oxide was sieved to be within the size range indicated. Further trials with the same type of cement compositions, were conducted at 200° F. (93° C.) and under a pressure of 3000 psi, using 0.5 wt. All expansions were measured with the cement exposed to a temperature of 200° F. (93° C.) for 7 and 14 days. Cement slurries were prepared with the resulting calcined magnesium oxides. An expandable cement composition useful for cementing a well casing within the bore of a well, comprising: 4. Magnesium oxide with a surface area of less than 1 m2 /g, is considered undesirable due to its separation to the outermost area of a mold during centrifugal molding of the composite product. of deionized water with 20 ml. Rapid Hardening Cement. The expansions of the cements at 7, 14, 21, and 28 days, both at 200° F. (93° C.) and 300° F. (149° C.) are shown in FIG. The results of the sieving to ascertain particle size, are tabulated in Table 6. No. It has also been discovered that cement compositions of the above-described type, containing magnesium oxide of the parameters already described, will not exhibit any significant expansion at lower temperatures, but when later exposed to higher temperatures, will then exhibit significant expansion. The cement slurry compositions which were used to obtain the expansions provided in Table 2 were the same as those used in connection with the Trials of Table 1, with the exception that the magnesium oxide was prepared under different conditions. In such cases, it is known that the thermal shock on the already set normal cement can result in the set cement becoming unsound (e.g., losing compressive strength). 9. It has now been discovered that cement compositions with consistently high rates of unrestrained linear expansion and good compressive strengths can be obtained by using magnesium oxide as an expansive agent in the composition. However, such is also accompanied by corresponding reductions in compressive strength. Trial 8, Table 9, used magnesium oxide calcined at approximately 1200° C., particle sizes between about 150 to about 425 microns(40 to 100 mesh)., surface area 1.49 m2 /g, ANT 16.8 minutes. The foregoing article deals primarily with the use of calcium oxide typically calcined at between about 850° C. and about 1400° C., as an expansive agent in amounts of between 7 and 15 percent (%). An expandable cement composition as defined in claim 6 wherein at least about 80% of the magnesium oxide particles have a diameter of between about 200 to 325 microns. for killing wells, Compositions for cementing, e.g. A method as defined in claim 17 wherein the bottom hole static temperature of the well is less than about 30° C. during placement of the cement, the method additionally comprising exposing the set cement to bottom hole static temperature of between about 70° C. and about 290° C. 21. Thus, it is apparent that increasing the calcining temperature of the magnesium oxide from 1000° C. to 1200° C., substantially increases the amount of expansion which can be produced in set cement exposed to temperatures of about 70° C. to 150° C. for periods of 14 days or more, or even periods as short as 7 days or less. This material is ground with sulfoaluminate clinkers. Expansion tests were obtained using a slurry of PERMANENTE Class G cement plus 0.3 wt. The magnesium oxide further preferably has an acid neutralization time for 1 g in 60 ml of deionized water with 20 ml added IN acetic acid, of between about 15 to about 30 minutes, and preferably between about 17 to about 25 minutes. 4,408,489 to Spangle, after the cement has cured for the stated time and at the stated temperature under a pressure of 3000 psi. 10. This type of cement has been developed by using an expansive agent and stabilizer. The expansions were 0.68 and 0.80% for the initial and final mix specimens, respectively (both from an average of two measurements). These types of cement have he quality to expand slightly with time. Expandable cement compositions using such magnesium oxide, and a method of using them in cementing of wells, are also disclosed. Expansive Cement. Chemical Composition of cement is: Lime 63% Silica 22% Alumina 06% Iron oxide 03% Gypsum 01 to 04% Suchismita Sahu, Asst. A method as defined in claim 14 wherein the BET surface area of the particles is between about 0.8 to about 1.8 m. 16. It will be seen from Table 5, that a good unrestrained linear expansion within the desirable range of 0.5 to 1.5% for cements used in cementing well casings, is obtained at temperatures of 200° F. (93° C.) and 300° F. (149° C.) after 14 days with only about 0.5 wt. Expansive cement shall conform to the physical requirements prescribed. Thus, from the general trend discussed in connection with Table 4 and reviewing the 300° F. (149° C.) expansions in Table 2, it appears that the best expansions are obtained with magnesium oxide samples having ANTs somewhere between about 20 to 30 minutes. Various weight percentages of this magnesium oxide was then used in a cement slurry containing PERMANENTE Class G cement, 0.3 wt. Shrinkage-Compensating concrete or artificial stone, e.g 13 and 14 ), were from. Inherently difficult to control in terms of size distribution use of inorganic materials as ingredients. Defined in claim 15 wherein the magnesium oxide invariably result in a well, comprising: 4 equal 1200°... For use at atmospheric temperatures, containing calcium oxide and/or magnesium oxide calcined at 1600° C. is as! Is suggested as an expanding additive about 0.8 to about 15 % calcium sulfate 300° F. ( C.. 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