Cement admixture and cement composition

Abstract: A cement admixture which is a substance obtainable by blending a CaO material, a Fe 2 O 3 material, a CaSO 4 material and, if necessary, an Al 2 O 3 material, followed by heat treatment, and which comprises (1) free lime, (2) calcium ferrite and/or calcium aluminoferrite, and (3) anhydrous gypsum.

Description: The present invention relates to a cement admixture and a cement composition which are to be used mainly in the field of civil engineering and construction. Reduction of cracks and improvement of the flexural strength of cement concrete are important from the viewpoint of e.g. reliability, durability and beauty of concrete structures, and a further progress in the technology of a cement admixture i.e. a cement expansive admixture, which is effective to improve such performance, is desired. Heretofore, as a cement admixture which presents expansibility to cement concrete, there has been, for example, a free lime/hauyne/anhydrous gypsum expansive admixture (JP-B-42-21840) or a free lime/calcium silicate/anhydrous gypsum expansive admixture (JP-B-53-31170). Further, a cement admixture containing calcium ferrite and/or calcium aluminoferrite, has also been proposed. For example, JP-A-49-81434 discloses a technique wherein a clinker comprising free lime, and calcium ferrite and/or calcium aluminoferrite, is produced and grinded, and then dihydrate gypsum is mixed thereto. However, such a cement admixture is not only inadequate in the expansion performance but also poor in the quality stability, as the free lime in the cement admixture is likely to be weathered. In recent years, for the purpose of high performance of concrete, development of highly superplasticized concrete or high strength concrete has been actively carried out. However, with such high performance concrete, it has been pointed out that no adequate effects of an expansive admixture tend to be obtained. Accordingly, it is desired to develop an expansive admixture which is capable of imparting high expansibility even with a small blend ratio of the expansive admixture. Further, when a conventional cement admixture capable of presenting expansibility is used, there has been a further problem that the strength of cement concrete tends to be low due to the expansion. Further, it is desired to develop a cement admixture which is not only capable of preventing a dimensional change due to shrinkage upon drying but also capable of preventing a dimensional change due to heat of hydration. The present inventors have conducted various studies to solve such problems and as a result, have found it possible to solve such problems by using a certain specific cement admixture. The present invention has been accomplished on the basis of such a discovery. Namely, the present invention provides a cement admixture which is a substance obtainable by blending a CaO material, a Fe 2 O 3 material, a CaSO 4 material and, if necessary, an Al 2 O 3 material, followed by heat treatment, and which comprises (1) free lime, (2) calcium ferrite and/or calcium aluminoferrite, and (3) anhydrous gypsum wherein the cement admixture has a silicate ratio of less than 1.0; such a cement admixture which further contains an alkanol amine; such a cement admixture which further contains dextrin; and a cement composition comprising cement and such a cement admixture. Now, the present invention will be described in detail. The cement admixture of the present invention is a substance obtainable by blending a CaO material, a Fe 2 O 3 material, a CaSO 4 material and, if necessary, an Al 2 O 3 material, followed by heat treatment, and comprising (1) free lime, (2) calcium ferrite and/or calcium aluminoferrite, and (3) anhydrous gypsum wherein the cement admixture has a silicate ratio of less than 1.0. The proportions of the respective components are not particularly limited. However, in 100 parts of a clinker comprising free lime, calcium ferrite and/or calcium aluminoferrite, and anhydrous gypsum, the free lime is preferably from 20 to 65 parts, more preferably from 30 to 55 parts, the calcium ferrite and/or calcium aluminoferrite is preferably from 10 to 55 parts, more preferably from 15 to 45 parts, and the anhydrous gypsum is preferably from 5 to 40 parts, more preferably from 10 to 30 parts. If the compositional proportions of the respective compounds in the clinker are not within the above ranges, there may be cases where excellent expansion performance cannot be obtained. The "parts" and "%" used in this invention to indicate the blend proportions, are represented by mass unit. In the present invention, the calcium ferrite means a CaO/Fe 2 O 3 type compound generally and is not particularly limited. Usually, however, when CaO is represented by C and Fe 2 O 3 is represented by F, a compound such as C 2 F or CF is well-known. Usually, it may be present in the form of C 2 F. In this invention, the calcium ferrite will hereinafter be abbreviated as C 2 F. In the present invention, the calcium aluminoferrite means a CaO/Al 2 O 3 /Fe 2 O 3 type compound generally and is not particularly limited. Usually, however, when CaO is represented by C, Al 2 O 3 by A and Fe 2 O 3 by F, a compound such as C 4 AF or C 6 A 2 F is well-known. Usually, it may be present in the form of C 4 AF. In this invention, the calcium aluminoferrite will hereinafter be abbreviated has C 4 AF. To produce the cement admixture of the present invention, a CaO material, a Fe 2 O 3 material, a CaSO 4 material and, if necessary, an Al 2 O 3 material, are blended and subjected to heat treatment to obtain a clinker comprising free lime, C 2 F and/or C 4 AF, and anhydrous gypsum, and the clinker is grinded to obtain the cement admixture. If a part or all of the free lime, C 2 F and/or C 4 AF, and the anhydrous gypsum, are separately prepared and mixed, the effects obtainable by the present invention, cannot be obtained. As a method of ascertaining whether or not a cement admixture is one produced by blending a CaO material, a Fe 2 O 3 material, a CaSO 4 material and, if necessary, an Al 2 O 3 material, followed by heat treatment to obtain a clinker, and grinding the clinker, for example, coarse particles, specifically particles larger than 100 µm, of the cement admixture may be inspected by e.g. a microscope to carry out the compositional analysis, whereby such can easily be ascertained by confirming that free lime, C 2 F and/or C 4 AF, and anhydrous gypsum exist in the particles. The temperature for the heat treatment to produce the clinker is preferably within a range of from 1,100 to 1,600°C, more preferably from 1,200 to 1,500°C. If it is lower than 1,100°C, the expansion performance of the resulting cement admixture tends to be inadequate, and if it exceeds 1,600°C, the anhydrous gypsum is likely to be decomposed. As the CaO material, limestone or slaked lime may, for example, be mentioned. As the Fe 2 O 3 material, various industrial by-products so-called molten slag, an industrial by-product so-called rolling scale, and commercially available iron oxide or iron powder, may, for example, be mentioned. As the CaSO 4 material, dihydrate gypsum, semi-hydrate gypsum and anhydrous gypsum may, for example, be mentioned. As the Al 2 O 3 material, bauxite and aluminum ash may, for example, be mentioned. Further, in the present invention, for a part or all of the Fe 2 O 3 material or the Al 2 O 3 material, iron sulfate, or aluminum hydroxide and/or aluminum sulfate, may also be used. In these materials, impurities are present. Specifically, impurities such as SiO 2 , MgO, TiO 2 , P 2 O 5 , Na 2 O, K 2 O, CuO and ZnO may be mentioned. They are not particularly problematic within a range not to substantially affect the purpose of the present invention. However, among them, particularly SiO 2 is at a level of a silicate ratio of less than 1.0. If the silicate ratio is 1.0 or higher, there may be a case where excellent expansion performance cannot be obtained. In the present invention, the silicate ratio is calculated by the following formula from the SiO 2 amount, the Al 2 O 3 amount and the Fe 2 O 3 amount in the clinker. Silicate ratio = SiO 2 /(Al 2 O 3 +Fe 2 O 3 ) Further, the SiO 2 amount in the clinker is preferably at most 5.0%, more preferably at most 3.0%. If it exceeds 5.0%, there may be a case where excellent expansion performance cannot be obtained. The particle size of the cement admixture of the present invention is not particularly limited, but usually, it is preferably from 1,500 to 9,000 cm 2 /g, more preferably from 2,500 to 4,000 cm 2 /g by the blaine specific surface area. If the particle size of the cement admixture is less than 1,500 cm 2 /g, the long-term durability tends to be poor, and if it exceeds 9,000 cm 2 /g, no adequate expansion performance tends to be obtainable. In the present invention, it is preferred to employ a grinding aid at the time of grinding the clinker, with a view to improving the grinding efficiency. The grinding aid is not particularly limited, but recently, a grinding aid has been developed which not only improves the grinding efficiency but also has an effect of increasing the strength, and it is advisable to use such a grinding aid. An alkanol amine is known as such a grinding aid having an effect of improving the strength. The alkanol amine of the present invention is not particularly limited. As a specific example, for example, USP 2,031,621 discloses a technique wherein triethanol amine is employed. JP-A-3-183647 discloses a technique wherein a higher trialkanol amine having a hydroxyl group and an amino group, such as triisopropanol amine, N,N-bis-(2-hydroxyethyl)-N-(2-hydroxypropyl)-amine or tris-(2-hydroxybutyl)-amine, is employed. Further, JP-A-10-324550 discloses an alkanol amine having an ionic functional group other than a hydroxyl group. Specific examples of the alkanol amine having an ionic functional group other than a hydroxyl group, include a 1-(bis-2-hydroxypropylamino)-2-propyl maleic acid ester, a 1-(bishydroxyethyl)amino-2-hydroxy-propylsulfonic acid, sodium 1-(bis-2-hydroxypropyl)aminopropionate, and sodium 1-(bishydroxyethyl)aminopropionate. Further, in the present invention, other than the above-mentioned alkanol amine or its sodium salt, the potassium salt, the calcium salt, the magnesium salt or the ammonium salt, may, for example, be employed. These alkanol amines have been proposed as a grinding aid for Portland cement clinker. Whereas, the present inventors have found surprisingly that when such alkanol amines are used as an additive or a grinding aid to the clinker at the time of preparing the cement admixture of the present invention, the compressive strength at 28 days old of the cement concrete employing the cement admixture of the present invention increases, and the expansion performance will also be improved. The amount of the alkanol amine is not particularly limited. However, it is usually preferably employed within a range of from 0.01 to 2 parts, more preferably from 0.05 to 1 part, per 100 parts of the clinker. If it is less than 0.01 part, the grinding efficiency or the strength-increasing effect will not be adequate, and if it exceeds 2 parts, such is not desirable from the economical viewpoint. In the present invention, in addition to an alkanol amine, dextrin may be incorporated to the clinker which is a substance obtainable by blending a CaO material, a Fe 2 O 3 material, a CaSO 4 material and, if necessary, an Al 2 O 3 material, followed by heat treatment, and which comprises free lime, calcium ferrite and/or calcium aluminoferrite, and anhydrous gypsum. The dextrin is used for the purpose of suppressing heat of hydration and suppressing a dimensional change due to heat generation. The effect of dextrin for suppressing heat of hydration varies substantially depending upon the solubility. The solubility of the dextrin is represented by the cold water soluble content. Here, the cold water soluble content means the amount dissolved in distilled water of 21°C. Specifically, 10g of dextrin is put into a flask having a capacity of 200 mℓ, and after adding 150 mℓ of distilled water at a temperature of 21°C, maintained at a temperature of 21 ± 1°C for one hour, followed by filtration, and the filtrate is distilled to dryness, whereupon the obtained dextrin is represented by the mass proportion based on the initial dextrin. The cold water soluble content of dextrin capable of providing the effect for suppressing heat of hydration is at most 70%. Accordingly, one having a cold water soluble content within this range is preferred, and more preferred is from about 10 to 60%. However, dextrin having a cold soluble content exceeding 70% has an effect for suppressing a slump loss although the effect for suppressing heat of hydration is low, and accordingly, such dextrin may be used for such a purpose. The amount of dextrin is not particularly limited. Usually, however, it is preferably from 1 to 10 parts, more preferably from 2 to 7 parts, per 100 parts of the clinker. If it is less than 1 part, the effect for suppressing heat of hydration tends to be inadequate, and if it exceeds 10 parts, setting may sometimes be substantially delayed. The amount of the cement admixture of the present invention to be used, is not particularly limited. Usually, however, it is preferably from 3 to 12 parts, more preferably from 5 to 9 parts, per 100 parts of a cement composition comprising cement and the cement admixture. If it is less than 3 parts, no adequate expansion performance tends to be obtained, and if it exceeds 12 parts, expansion tends to be excessive. As the cement for the present invention, various Portland cements such as ordinary, high-early-strength, ultra high-early-strength, low heat and moderate-heat Portland cements, various blended cements having blast furnace slag, fly ash and silica blended to such cements, and a filler cement having limestone powder mixed, may, for example, be mentioned. In the present invention, one or more among a water reducing agent, a high-range water reducing agent, an AE water reducing agent, a high-range AE reducing agent, a superplasticizer, a defoaming agent, a thickener, an corrosion inhibitor, an antifreezing agent, a shrinkage-reducing agent, a polymer emulsion, a setting accelerator, a setting retarder, a quick hardening admixture for cement, a clay mineral such as bentonite, an anion exchanger such as hydrotalcite, boric acid or its salts, may be used within a range not to substantially hinder the purpose of the present invention. In the present invention, the method of mixing the respective materials is not particularly limited, and the respective materials may be mixed at the time of application, or a part or all of them may preliminarily be mixed. As the mixing apparatus, any conventional apparatus may be used. For example, an gravity type mixer, an omnimixer, a Henschel mixer, a V-type mixer and a Nauta mixer may, for example, be mentioned. Now, the present invention will be described in further detail with reference to Examples. However, it should be understood that the present invention is by no means restricted to such specific Examples. EXAMPLE 1 A CaO material, an Al 2 O 3 material, a Fe 2 O 3 material and a CaSO 4 material were blended, mixed and grinded, and then subjected to heat treatment at 1,350°C for 3 hours to obtain a clinker having a composition as identified in Table 1. Using 0.05 part of grinding aid A per 100 parts of the clinker, the clinker was grinded to a blaine specific surface area of 3,500 ± 300 cm 2 /g by means of a ball mill, to obtain a cement admixture. The cement admixture was identified by a powder X-ray diffraction method, whereby it comprised free lime, C 2 F and/or C 4 AF, and anhydrous gypsum. The mineral composition of the cement admixture was calculated by a calculation based on the chemical composition. The chemical composition was obtained in accordance with JIS R 5202. Using the cement admixture in an amount of 7 parts in 100 parts of a cement composition comprising cement and the cement admixture, a mortar was prepared to have a water/cement composition ratio = 47% and a cement composition/sand ratio = 1/3, and the expansion ratio was measured. Further, for the purpose of comparison, similar tests were carried out also with respect to cement admixtures obtained by separately preparing part or all of the free lime, C 2 F, C 4 AF and the anhydrous gypsum, grinding and blending them to bring the mineral compositions to be the same as in Test No. 1-5, 1-15 and 1-16 for the present invention. The results are shown in Table 1. Materials used CaO material: Calcium carbonate as first grade reagent Al 2 O 3 material: Aluminum oxide as first grade reagent Fe 2 O 3 material: Ferric oxide as first grade reagent CaSO 4 material: Dihydrate gypsum as first grade reagent Grinding aid A: Triisopropanol amine Free lime: Prepared by heat treating the CaO material at 1,350°C for 3 hours. C 2 F: Prepared by mixing and grinding a blend material prepared by blending 2 mol of the CaO material and 1 mol of the Fe 2 O 3 material and then heat-treating it at 1,350°C for 3 hours. C 4 AF: Prepared by mixing and grinding a blend material prepared by blending 4 mol of the CaO material, 1 mol of the Al 2 O 3 material and 1 mol of the Fe 2 O 3 material and then heat treating it at 1,350°C for 3 hours. Anhydrous gypsum: Anhydrous gypsum obtained by calcining the dihydrate gypsum as first grade reagent at 1,350°C for 3 hours. Sand: JIS standard sand (in accordance with ISO679) Measuring methods Expansion coefficient: Measured in accordance with JIS A 6202. Test No. Cement admixture (parts) Expansion coefficient at material age of 7 days old (×10 -6 ) Notes Free lime C 2 F C 4 AF Anhydrous gypsum 1-1 0 0 0 0 10 Comparative 1-2 50 0 45 5 800 Invention 1-3 50 0 40 10 950 Invention 1-4 50 0 30 20 1070 Invention 1-5 50 0 25 25 1140 Invention 1-6 50 0 20 30 1170 Invention 1-7 50 0 10 40 1050 Invention 1-8 65 0 10 25 1080 Invention 1-9 55 0 20 25 1120 Invention 1-10 45 0 30 25 1090 Invention 1-11 35 0 40 25 930 Invention 1-12 20 0 55 25 670 Invention 1-13 30 0 45 25 810 Invention 1-14 40 0 35 25 1010 Invention 1-15 60 0 15 25 1120 Invention 1-16 50 20 0 30 1090 Invention 1-17 50 10 10 30 1100 Invention 1-18 50 20 0 30 490 Comparative 1-19 50 0 20 30 550 Comparative 1-20 50 10 10 30 520 Comparative 1-21 50 0 20 30 590 Comparative Test No. 1-1 represents a case where no cement admixture was added. Test No. 1-18 to 1-20 represent cases wherein the free lime, C 2 F, C 4 AF and the anhydrous gypsum were separately prepared and mixed. Test No. 1-21 represents a case where a clinker comprising the free lime and C 4 AF was prepared, and the anhydrous gypsum was mixed thereto. From Table 1, it is evident that mortars employing cement admixtures obtained by grinding a clinker prepared by simultaneously calcining the materials of the present invention and comprising the free lime, C 2 F and/or C 4 AF, and the anhydrous gypsum, exhibit excellent expansion performance as compared with mortars employing cement admixtures of Comparative Examples obtained by separately preparing the free lime, C 2 F, C 4 AF and the anhydrous gypsum and mixing them. EXAMPLE 2 A CaO material, an Al 2 O 3 material, a Fe 2 O 3 material and a CaSO 4 material, as industrial materials, were blended and calcined at a calcining temperature of 1,400°C by means of a rotary kiln to obtain a clinker having the chemical composition as identified in Table 2. The operation was carried out in the same manner as in Example 1 except that the cement admixture was prepared by using grinding aid A in an amount of 0.05 part per 100 parts of the clinker and carrying out the grinding by means of a ball mill to a blaine specific surface area of 3,500 cm 2 /g. The mineral composition calculated based on the chemical composition is shown in Table 3. For the purpose of comparison, the results with respect to the commercially available calcium sulfoaluminate type expansive admixture (hereinafter referred to simply as CSA) and the lime-type expansive admixture (referred to simply as FLE) are also presented. The results of measurement of the expansion coefficient are shown in Table 4. Materials used CaO material: Limestone produced at Oumi Kozan, Niigata Prefecture, Japan Al 2 O 3 material: Bauxite produced in China Fe 2 O 3 material: Rolling scale CaSO 4 material: Exhaust gas desulfurized dihydrate gypsum CSA: Commercially available calcium sulfoaluminate type expansive admixture, blaine specific surface area: 2,940 cm 2 /g FLE: Commercially available lime type expansive admixture, blaine specific surface area: 3,610 cm 2 /g Cement admixture Ignition loss (%) Chemical composition (%) SiO 2 Fe 2 O 3 Al 2 O 3 CaO SO 3 Others Present invention 1.5 1.4 6.4 4.1 67.3 15.6 3.7 CSA 1.1 1.2 0.6 16.1 51.3 27.5 2.2 FLE 2.5 8.7 1.4 2.0 67.9 15.6 1.9 Cement admixture Mineral composition (%) Free lime C 4 AF Anhydrous gypsum Hauyne C 3 S Present invention 47.5 19.4 26.5 - 5.3 CSA 19.0 1.8 39.8 31.3 4.6 FLE 30.8 4.4 26.5 - 25.0 Test No. Cement admixture Amount of SiO 2 (%) Silicate ratio Expansion coefficient at material age of 7 days old (×10 -6 ) Notes 2-1 Present invention 1.4 0.13 1250 Invention 2-2 CSA 1.2 0.07 470 Comparative 2-3 FLE 8.7 2.56 410 Comparative From Tables 2, 3 and 4, it is evident that mortars employing cement admixtures of the present invention exhibit distinctly superior expansion performance as compared with mortars employing commercially available expansive admixtures. EXAMPLE 3 The operation was carried out in the same manner as in Example 2 except that measurements of the expansion coefficient and the compressive strength were carried out by changing the type and amount of the grinding aid. The results are shown in Table 5. Materials used Grinding aid B: Triethanolamine Grinding aid C: 1-(bis-2-hydroxypropylamino)-2-propyl maleic acid ester Grinding aid D: Diethylene glycol Measuring methods Compressive strength: Measured in accordance with JIS R 5201. Test No. Grinding aid (parts) Expansion coefficient at material age of 7 days old (×10 -6 ) Compressive strength at material age of 28 days old (N/mm 2 ) Notes 3-1 0 1020 41.5 Invention 3-2 A 0.01 1210 51.0 Invention 2-1 A 0.05 1250 55.5 Invention 3-3 A 0.1 1270 58.0 Invention 3-4 A 0.5 1280 59.0 Invention 3-5 A 1.0 1300 59.5 Invention 3-6 A 2.0 1320 60.0 Invention 3-7 B 0.05 1210 51.0 Invention 3-8 C 0.05 1240 54.5 Invention 3-9 D 0.05 1070 45.0 Invention From Table 5, it is evident that the mortar employing the cement admixture of the present invention having a grinding aid incorporated, exhibits excellent expansion performance and compressive strength as the amount of the grinding aid increases. EXAMPLE 4 A cement admixture was prepared by blending a dextrin having a cold water soluble content as shown in Table 6 in a proportion as shown in Table 6 per 100 parts of the clinker. The operation was carried out in the same manner as in Example 2 except that the expansion coefficient, the compressive strength and the adiabatic temperature rise were measured by using the cement admixture in an amount of 6 parts per 100 parts of the cement composition comprising cement and the cement admixture. The results are shown in Table 6. Materials used Dextrin 1 ○: Cold water soluble content of 5% Dextrin 2 ○: Cold water soluble content of 10% Dextrin 3 ○: Cold water soluble content of 20% Dextrin 4 ○: Cold water soluble content of 30% Dextrin 5 ○: Cold water soluble content of 50% Dextrin 6 ○: Cold water soluble content of 60% Dextrin 7 ○: Cold water soluble content of 70% Measuring method Adiabatic temperature rise: Three litters of a mortar was put into a blowing styrol container, and a thermo couple was disposed at the center of the mortar, and the temperature was measured. The difference between the maximum temperature reached and the temperature upon mixing, of the mortar, was taken as the adiabatic temperature rise. Test No. Dextrin (parts) Expansion coefficient at material age of 7 days old (×10 -6 ) Compressive strength at material age of 28 days old (N/mm 2 ) Adiabatic temperature rise (°C) Notes 2-1 0 1250 55.5 31.0 Invention 4-1 3 ○ 1 1250 56.0 30.0 Invention 4-2 3 ○ 2 1260 56.5 29.0 Invention 4-3 3 ○ 3 1280 57.0 28.5 Invention 4-4 3 ○ 5 1300 58.0 28.0 Invention 4-5 3 ○ 7 1270 57.5 27.5 Invention 4-6 3 ○ 10 1240 56.0 27.0 Invention 4-7 1 ○ 5 1270 56.5 30.0 Invention 4-8 2 ○ 5 1290 57.0 29.0 Invention 4-9 4 ○ 5 1280 57.5 28.5 Invention 4-10 5 ○ 5 1260 56.5 29.0 Invention 4-11 6 ○ 5 1230 56.0 29.5 Invention 4-12 7 ○ 5 1200 55.0 30.0 Invention From Table 6, it is evident that mortars employing the cement admixtures of the present invention having dextrins incorporated, not only exhibit excellent expansion performance and compressive strength but also exhibit excellent effects for suppressing heat of hydration, as the adiabatic temperature rise lowers. EXAMPLE 5 The operation was carried out in the same manner as in Example 2 except that using the cement admixture used in Test No. 2-1 in Example 2 and changing the amount of the cement admixture as shown in Table 7. The results are shown in Table 7. Test No. Cement admixture (parts) Expansion coefficient at material age of 7 days old (×10 -6 ) Notes 5-1 0 10 Comparative 5-2 3 470 Invention 5-3 5 720 Invention 2-1 7 1250 Invention 5-4 9 2080 Invention 5-5 12 3150 Invention From Table 7, it is evident that as the amount of the cement admixture of the present invention increases, the expansion performance will be excellent. By using the cement admixture of the present invention, it is possible to obtain a cement composition which has excellent expansion performance and a strength-development, and which further has an effect for suppressing the heat of hydration.

Claims: A cement admixture which is a substance obtainable by blending a CaO material, a Fe 2 O 3 material, a CaSO 4 material and, if necessary, an Al 2 O 3 material, followed by heat treatment, and which comprises (1) free lime, (2) calcium ferrite and/or calcium aluminoferrite, and (3) anhydrous gypsum, wherein the cement admixture has a silicate ratio of less than 1.0. The cement admixture according to Claim 1, which further contains an alkanolamine. The cement admixture according to Claim 1 or 2, which further contains dextrin. A cement composition comprising cement and the cement admixture as defined in any one of Claims 1 to 3. Use of a cement admixture according to any one of claims 1 to 3 for the preparation of a cement composition.

Inventors: DAIMON MASAKI, HIGUCHI TAKAYUKI, HORI AKIHIRO, MORIOKA MINORU, NAKASHIMA YASUHIRO, OHASHI HIROYUKI, SAKAI ETSUO, TAKAHASHI MITSUO, TAMAKI TOSHIYUKI, DAIMON, MASAKI, HIGUCHI, TAKAYUKI, HORI, AKIHIRO, MORIOKA, MINORU, NAKASHIMA, YASUHIRO, OHASHI, HIROYUKI, SAKAI, ETSUO, TAKAHASHI, MITSUO, TAMAKI, TOSHIYUKI
Applicants: DENKI KAGAKU KOGYO KK, DENKI KAGAKU KOGYO KABUSHIKI KAISHA
Application year: 2001
Main classification: C04B22
IPC codes: C04B40, C04B22