JPH1053448A - Cement admixture and cemental composition for molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition for extrusion molding, capable of improving the fluidity of a cemental composition and having excellent moldability. SOLUTION: This cemental composition for molding is obtained by adding a cement admixture to a composition for molding containing at least a cement. The admixture has 0.5-300Pa value of shear stress A at 10s<-1> in a test on flow characteristics carried out by stirring a mixture of 27.5 pts.wt. cement with 27.5 pts.wt. silica sand No.7, 1.1 pts.wt. pulverized pulp having 3mm size, 0.1 pt.wt. admixture and 20 pts.wt. water for 60min and increasing the shear rate from 0 to 100s<-1> at a constant rate per min by using a viscometer. The admixture includes hydroxyalkyl alkyl celluloses (hydroxypropyl methyl cellulose or hydroxyethyl methyl celluose) and hydroxyalkyl celluloses (hydroxyethyl cellulose). The admixture may be used with a surfactant in combination.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cement admixture which is excellent in moldability (particularly extrusion moldability) and is useful for obtaining extruded articles such as molded articles for building materials, and cement-based extrusion molding containing this admixture. The present invention relates to a composition for use and a method for molding a cement-based composition.

[0002]

2. Description of the Related Art A mortar composition or a concrete composition prepared by adding an aggregate (silica sand or silica stone powder) and, in some cases, reinforcing fibers to cement and mixing with water include:
A water reducing agent or a dispersant is added as an admixture. Such an admixture has a cement dispersing effect, and can be used as a mortar or concrete composition having excellent fluidity even with a small amount of water added, as a cause of a decrease in strength during the hardening process. The amount of excessive water can be reduced. However, these dispersants generally have an effect of dispersing cement particles, but are inferior in adhesion between the cement and the added aggregate or reinforcing fiber. Therefore, separation of aggregates and reinforcing fibers occurs in the cement composition.

In order to suppress the separation of aggregates and reinforcing fibers, a water-soluble organic binder is added. Further, in the composition for extrusion molding of cement, a binder is added in order to suppress separation of components of the composition even under high stress during molding. As this kind of binder, a cellulose derivative or the like having excellent adsorption performance to cement particles, separation resistance of aggregate, or water retention is used. However, depending on these admixtures, the fluidity of the composition for extrusion molding is reduced, so that extrusion molding becomes impossible, and the extruded product has rough surfaces, cracks, and bends. Furthermore, these admixtures reduce the extrudability under high temperature conditions such as in summer. for that reason,
Extrusion molding cannot be performed stably throughout the year, and the productivity of molded articles decreases.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a cement admixture and a cement molding composition capable of improving not only flow characteristics but also moldability. Another object of the present invention is to provide an admixture and a cement-based molding composition capable of imparting high extrusion moldability to a cement-based composition even under high temperature conditions such as in summer. Still another object of the present invention is to provide an admixture and a cement-based molding composition that have high surface smoothness and are useful for preventing occurrence of cracks, curls, and the like in molded articles. Another object of the present invention is to provide a molding method capable of producing a uniform concrete molded product without roughening with high productivity.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, when an admixture having an A value of 0.5 to 300 Pa in the following flow characteristic test is added, cement-based The present inventors have found that the flowability and moldability (particularly, extrusion moldability) of the molding composition can be greatly improved, and have completed the present invention. That is, the admixture of the present invention,
An admixture added to a cement-based molding composition containing at least cement (particularly, an extrusion molding composition), which is composed of 27.5 parts by weight of cement and 27.
5 parts by weight, 1.1 parts by weight of 3 mm ground pulp, admixture 0.
1 part by weight of a mixture of 20 parts by weight of water and stirred for 60 minutes, using a viscometer, shear rate 10s in flow characteristics test to increase the shear rate to 1 minute at a constant rate up to 0s ^-1 ~100s ^{-1 -} The shear stress A value at ¹ is 0.5 to 300
Indicates Pa. The cement-based molding composition of the present invention (particularly, an extrusion-molded composition) is a cement-based composition containing at least cement and an admixture, wherein the admixture is 27.5 parts by weight of cement and No. 7 silica sand. 5 parts by weight, 1.1 parts by weight of 3 mm ground pulp, 0.1 parts by weight of admixture and 20 parts of water
The mixture of parts by weight and stirred for 60 minutes, using a viscometer, shear stress at a shear rate of 10s ^-1 at the flow characteristic test of increasing the shear rate in 1 minute at a constant rate up to 0s ^-1 ~100s ^-1 A The value is between 0.5 and 300 Pa. In this composition, the admixture includes a water-soluble cellulose-based binder, for example, a hydroxyalkylalkylcellulose,
And hydroxyalkyl cellulose.
The admixture may be used alone, or may be used in combination with a surfactant.

In the method of the present invention, a molded product is obtained by adding the above-mentioned cement admixture to a cement-based composition containing at least cement and extruding the mixture. As used herein, the term "surfactant" refers to a unit having a surface activity, improving workability by dispersing cement particles in concrete, and obtaining a predetermined consistency and strength. And an AE (Ai) for improving workability, freeze-thaw resistance, etc. by generating a large number of closed microbubbles in concrete by a dispersing agent (water reducing agent) for reducing the amount of unit cement.
r Entraining agent, a compound called a water-reducing AE agent having the effects of the water-reducing agent and the AE agent.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The admixture of the present invention is added to a molding composition containing at least cement, in particular, an extrusion molding composition. The cement-based molding composition of the present invention containing this admixture has high fluidity and moldability (extrusion moldability),
It can be used effectively for extrusion molding. The admixture has a shear stress “A value” at a shear rate of 10 s ⁻¹ of 0.5 to 300 P in a flow property test using the following model composition.
a, preferably 1 to 300 Pa (for example, 10 to 300 Pa
Pa), preferably 50 to 300 Pa (for example, 150 Pa).
３００300 Pa).

[Flow characteristics test] A powder composition (27.5 parts by weight of cement) previously prepared was added to an aqueous solution (concentration: 0.5% by weight) of 0.1 parts by weight of an admixture and 20 parts by weight of water under stirring. No. 7, 27.5 parts by weight of silica sand, 3 mm ground pulp 1.1
(Parts by weight), the mixture was stirred for 60 minutes, and the shear rate was increased to ^{0 s -1} to 1 minute at a constant rate using a viscometer.
In a flow property test to increase to 100 s ⁻¹ , a shear stress A value at a shear rate of 10 s ⁻¹ is measured. In addition, as No. 7 silica sand, for example, No. 7 silica sand manufactured by Kumamoto Silica Sand Mining Co., Ltd. can be used, and ordinary Portland cement is used as cement, and 3 mm ground pulp has an average fiber length of 3 mm and an average fiber diameter of 10 μm. Ground wood pulp (for example, Hattori Co., Ltd., PK pulp) can be used. A three-one motor (manufactured by Shinto Chemical Co., Ltd.) can be used for stirring the aqueous solution of the admixture, and a double cylinder viscometer (manufactured by Haake, Germany) can be used as a viscometer. The measurement temperature is 25 ° C. "A value"
The composition for molding (composition for extrusion molding) can be obtained by adding an admixture having a viscosity of more than 300 Pa or an admixture after stirring the model composition so that the sample cannot be filled in the gap of the double cylinder of the viscometer. Is poor in flowability, and molding (especially extrusion molding) becomes impossible, and cracks and the like occur in molded products after molding. On the other hand, the “A value” is not less than the value of the shear stress at a shear rate of 10 s ⁻¹ of a 0.5% aqueous solution of the admixture, and the “A value” of the admixture exhibiting high moldability (extrudability).
Is 0.5 Pa or more. The “A value” is an index for selecting an admixture that imparts high moldability (extrusion moldability) in a molding composition (composition for extrusion molding).

The admixture having the above properties includes a water-soluble cellulose-based binder (a water-soluble cellulose derivative), particularly a cellulose ether. Such admixtures include, for example, alkylcellulose (eg, methylcellulose, ethylcellulose, etc.), carboxyalkylcellulose (eg, carboxymethylcellulose, carboxyethylcellulose, etc.), hydroxyalkylalkylcellulose [eg, hydroxypropylmethylcellulose, hydroxyethylmethylcellulose, Examples thereof include hydroxy C _2-4 alkyl-C _1-4 alkyl cellulose such as hydroxypropylethyl cellulose and hydroxyethyl ethyl cellulose, and hydroxyalkyl cellulose [eg, hydroxy C _2-4 alkyl cellulose such as hydroxyethyl cellulose and hydroxypropyl cellulose]. . These admixtures can be used alone or in combination of two or more. In particular, when hydroxyalkylalkylcellulose and hydroxyalkylcellulose are used in combination, even when one of the components alone cannot improve the flow characteristics and extrudability, the combination provides higher fluidity and moldability (especially extrusion moldability). Can be given.

Preferred admixtures include hydroxyalkyl alkylcellulose (particularly hydroxy C _2-3 alkyl-C _1-2 alkyl cellulose such as hydroxypropyl methylcellulose and hydroxyethyl methylcellulose;
Especially hydroxy C _2-3 alkyl-methyl cellulose),
And hydroxyethylcellulose.

The average degree of substitution in the cellulosic binder can be selected within a range that can maintain the curing retardation and high moldability of the molding composition. The degree DS is 1.2 to 1.6 (preferably about 1.3 to 1.6, more preferably about 1.3 to 1.5), and the substitution degree MS of the hydroxyalkyl group is 0.1 to 1.6.
0.3 (preferably about 0.15 to 0.3, more preferably about 0.15 to 0.25) and the total degree of substitution (DS + M
S) is 1.5 to 1.7 (preferably about 1.5 to 1.65). The degree of polymerization of the hydroxyalkylalkylcellulose can be selected from a range that does not impair fluidity and moldability, for example, from about 50 to 300. Hydroxyalkyl cellulose (such as hydroxyethyl cellulose) has a 1% by weight aqueous solution viscosity (20 ° C.) of 10,000.
cps or more (for example, 10,000 to 50,000 cp)
s, preferably about 10,000 to 25,000 cps), and the substitution degree MS of the hydroxyalkyl group (particularly, hydroxyethyl group) is 1.5 to 2.5 (preferably 1.
6-2.4).

The amount of the admixture used is within a range capable of improving flowability and moldability, for example, 0.1 to 20 parts by weight, preferably 0.2 to 10 parts by weight, more preferably 0.2 to 10 parts by weight per 100 parts by weight of cement. It can be selected from the range of about 0.5 to 5 parts by weight, and is often about 0.3 to 3 parts by weight.

The cellulose ether (hydroxyalkylalkylcellulose, hydroxyalkylcellulose, etc.) can be produced by a conventional method. For example,
Hydroxyalkylalkylcellulose is obtained by subjecting an alkali cellulose (cellulose sodium) to an alkylation step of introducing an alkyl group by a reaction with an alkyl halide (eg, methyl chloride) or a dialkyl sulfate (eg, dimethyl sulfate); and an alkylene oxide (eg, ethylene oxide). , propylene oxide, can be obtained by passing through the C _2-4 and alkylene oxide) and hydroxyalkylated step of introducing a hydroxyalkyl group by reaction, such as butylene oxide, order of the steps is not particularly limited. Further, the alkylation step and the hydroxyalkylation step may be performed simultaneously. Hydroxyalkyl cellulose can be obtained by reacting cellulose with an alkylene oxide (for example, the above-mentioned C _2-4 alkylene oxide). As the alkylene oxide, ethylene oxide and propylene oxide are often used.

The admixture of the present invention (especially the water-soluble cellulose)
Binder) may be used alone, and other components may be used.
Use in combination with surfactants, especially dispersants
You can also. The surfactant includes a fluidizing agent, a water reducing agent.
Agents, AE agents and water reducing AE agents [eg, ligninsulfonic acid
Salt, sulfite pulp waste liquor, and substituents such as alkyl groups
Arylsulfonate (benzenesulfur)
Fonates, alkylbenzene sulfonates, naphthalene
Sulfonate) and melamine sulfonate
Alkaline gold of pine and other ingredients such as fonate and abietic acid
Water reducing agent, AE water reducing agent, high performance reducing
Liquid agent, high-performance AE water reducing agent] and the like. Especially semen
Surfactants such as dispersants that have a curing retardation effect, such as
For example, a lignin sulfonate surfactant (lignin sulfonate)
Sulfonic acid, sulfuric acid pulp waste liquor), oxycarboxylic acid
Salt-based surfactants (eg, tartaric acid, citric acid, humic
Acid, gluconic acid or their salts), triazine-based surfactants
Melamine sulfonate, melamine sulfonate
A formalin condensate having a molecular weight of 2,000 to 20,000
A highly condensed melamine sulfonate of about 00 (for example, melamine
Min-based high-performance water reducing agent, manufactured by Kao Corporation, Mighty 150v
-2) and the like, and polycarboxylic acid surfactants (Polyac
Lylic acid or its salt, styrene-maleic anhydride copolymer
Or a salt thereof, isobutylene-maleic anhydride or a salt thereof
), Aromatic aminosulfonic acid surfactants (anili
Of formic acid sulfonate and aniline sulfonate
Compound, at least anilinesulfonic acid and phenols
Formalin co-condensate), alkyl group is substituted
Formalin condensates of aryl sulfonates
(Benzenesulfonate, alkylbenzenesulfonic acid
Salt, lignin sulfonate, naphthalene sulfonate
Which formalin condensate), polyoxyethylene alkyl
Anionic surfactant such as phenol ether sulfate
Agent, polyol surfactant (glycerin C_10-24fat
Acid ester, sorbitan C_10-24Fatty acid esters,
Sugar C_10-24Polyhydric alcohol such as fatty acid ester-C
_10-24Fatty acid esters), polyether-based surfactants
Agent (C_8-24Alkyl polyoxyethylene ether, C
_6-18Alkyl phenyl polyoxyethylene ether, C
_8-24Alkylcarbonyloxypolyoxyethylene, C
_10-24Fatty acid-polyhydric alcohol ester polyoxyethylene
Lenether, polyoxyethylene-polyoxypropyl
Nonionic surfactants such as ren block copolymers
For example).

The salts include alkali metal salts (such as sodium and potassium salts), ammonium salts, organic amine salts, and the like, and alkali metal salts are often used. These concrete surfactants or dispersants can be used alone or in combination of two or more. Furthermore, when an admixture (such as a water-soluble cellulose-based binder) and a formalin condensate of an aryl sulfonate (particularly naphthalene sulfonate) which may be substituted with an alkyl group are used in combination, high temperature conditions such as summertime High extrudability can be ensured even below. The ratio of admixture to surfactant can be selected in a wide range, for example, admixture / surfactant = 5/9
5 to 95/5 (% by weight), preferably 10/90 to 90
/ 10 (% by weight), more preferably 30/70 to 70 /
It can be selected from a range of about 30 (% by weight).

[0016] The cement includes, for example, air-hardened cement (lime such as gypsum, slaked lime and dolomite plaster); hydraulic cement (eg, Portland cement, early-strength Portland cement, alumina cement, rapid-hardened high-strength cement, calcined gypsum) Self-hardening cement; lime slag cement, blast furnace cement, etc .; mixed cement). Preferred cements include, for example, dolomite plasters and hydraulic cements. The cement-based molding composition of the present invention may contain at least the cement and the admixture together with the surfactant as necessary, but may contain other components.

For example, the cement may be used as a paste composition with water (cement paste), and may be used as an aggregate (eg, fine aggregate such as sand, quartz sand, perlite, vermiculite, lightweight aggregate, crushed stone). , Gravel and other coarse aggregates)
May be used as a mortar composition or a concrete composition containing. The paste composition and the mortar composition include reinforcing agents such as organic fibers (eg, pulp, olefin fibers such as polyethylene and polypropylene, polyester fibers, nylon or polyamide fibers, rayon fibers, etc.), and inorganic fibers (eg, glass). Fiber, rock wool,
(Silica fiber, carbon fiber) and the like. Fibrous reinforcing agents are often used as short fibers. The paste composition and the mortar composition are, as necessary, a coloring agent, a curing agent, a curing accelerator such as calcium chloride, a coagulant composed of polyacrylamide, etc., carboxymethyl cellulose, methyl cellulose, ethyl cellulose, and polyvinyl alcohol. It may contain various additives such as a thickener, a foaming agent such as aluminum powder, a waterproofing agent such as a synthetic resin emulsion, and a plasticizer.

Since the cement-based molding composition of the present invention has high fluidity and moldability, concrete products can be obtained by various molding methods such as pouring. In particular, the cement-based molding composition of the present invention to which the cement admixture is added has excellent extrudability, so that a high-quality concrete product can be efficiently produced by extrusion. This molding method is useful for the production of concrete products, for example, concrete panels such as curtain walls and wall materials, concrete blocks, etc., particularly for the production of precast concrete plates, and can improve the molding efficiency and production efficiency of concrete products. it can. Extrusion of the cement-based molding composition is carried out by a conventional method, for example, using an extruder at 5 to 30 kgf / cm.
It can be carried out by extruding at a pressure of about ² into a predetermined shape such as a plate, a hollow plate, a column, a hollow column, and a tube. Extruded molded articles can be obtained by conventional methods (for example,
Curing by normal temperature / normal pressure curing, normal pressure steam curing, underwater curing, autoclave curing, etc.) can produce a molded product. The extruded product can be used in various applications depending on the shape and the like, for example, as a molded product for building materials such as flooring materials, interior materials, exterior materials, and sound insulation materials.

[0019]

Industrial Applicability The cement admixture and the cement-based molding composition of the present invention can greatly improve not only flow characteristics but also moldability, particularly extrusion moldability. In addition, it has a high surface smoothness, can prevent the occurrence of cracks and curls, and is useful for efficiently producing a uniform molded product having no rough surface, particularly an extruded molded product. In addition, when the admixture of the present invention and a surfactant are combined, the extrusion moldability can be greatly improved even under high temperature conditions such as in summer. In the molding method of the present invention,
Since the cement composition to which the cement admixture is added is molded by extrusion molding, a uniform concrete molded product without roughness can be produced with high productivity.

[0020]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. Examples 1 to 5 and Comparative Examples 1 to 3 As shown in Table 1, the following components were mixed using a mixer [Omnimixer OM-30A, manufactured by Chiyoda Giken Kogyo Co., Ltd.], and a kneader [Miyazaki Iron Works] Extruder [manufactured by Honda Iron Works Co., Ltd., DE-75].
D], a solid extruded plate having a width of 60 mm and a thickness of 12 mm was formed. The temperature of the kneader and the extruder was adjusted with circulating water at a temperature of 15 ° C.

Cement: 40 parts by weight of ordinary Portland cement (Tokuyama Corporation, ordinary Portland cement) Aggregate: 55 parts by weight of fine silica sand (Tsuruga Cement, fine silica sand, silica 37, specific gravity 2.65, specific surface area 3) , 880 cm ² / g, average particle size 1
8-21 μm) Lightweight aggregate: 5 parts by weight perlite N-3 (Hokushin Co., Ltd., N-3, bulk specific gravity 0.16-0.19k)
g / L) Reinforcing fiber: 3 mm pulverized pulp 4 parts by weight (Hattori Co., Ltd., PK pulp, average length 3 mm, diameter 10 μm)
m) Admixture: admixture composed of the following components: 0.7 parts by weight Water: 32 parts by weight tap water The particle size distribution of the lightweight aggregate (Perlite N-3) by a sieve is as follows. Aperture (μm) Passage (% by weight) 1,200 100 600 96-98 300 75-87 150 55-71 7.4 34-55 The following admixtures were used in Examples and Comparative Examples.
Further, regarding these admixtures, the above-mentioned ordinary Portland cement (Tokuyama Corporation, ordinary Portland cement), No. 7 silica sand (Kumamoto silica sand mining, No. 7 silica sand), 3
The shear stress A value at a shear rate of 10 s ^-1 was measured by the flow characteristics test using mm-milled pulp (Hattori Co., Ltd., PK pulp) and water. The particle size distribution of the above No. 7 silica sand by the sieve is as follows.

Mesh (opening μm) Remaining amount on the mesh (% by weight) 45 (297) 0.43 60 (210) 18.43 100 (149) 35.52 150 (105) 29.63 200 (74) 13.62 270 (53) 1.44 Remaining 0.93 Comparative Example 1: Hydroxypropyl methylcellulose [Aquacell R1000, DS = 1.48, MS, manufactured by Daicel Chemical Industries, Ltd.]
= 0.27] Comparative Example 2: hydroxypropyl methylcellulose [Aquacell R150, manufactured by Daicel Chemical Industries, Ltd., DS = 1.59, MS =
0.28] Comparative Example 3: Hydroxypropylmethylcellulose [Aquacell R1000, manufactured by Daicel Chemical Industries, Ltd., DS = 1.48,
MS = 0.27] Hydroxyethyl cellulose [manufactured by Daicel Chemical Industries, Ltd., MS = 2.0, 1% viscosity (20 ° C.) 6,000 cps] A mixture of 70 parts by weight of the above component and 30 parts by weight of the component

Example 1 Hydroxypropyl methylcellulose [Aquacell R100, manufactured by Daicel Chemical Industries, Ltd.]
0, DS = 1.48, MS = 0.27] Hydroxyethyl cellulose [manufactured by Daicel Chemical Industries, Ltd., MS = 1.8, 1% viscosity (20 ° C.) 11,000 cps] A mixture of 70 parts by weight of the above component and 30 parts by weight of component Example 2: Hydroxypropyl methylcellulose [Daicel Chemical Industries, Ltd., Aquacell R1000, DS = 1.48,
MS = 0.27] A dispersant mainly composed of a complex of modified lignin and an oxycarboxylic acid compound [Pozoris Co., Ltd., Pozoris N
o. 89] A mixture of 90 parts by weight of the above component and 10 parts by weight of the component. Example 3: Hydroxypropylmethylcellulose [DS
= 1.40, MS = 0.19] Example 4: Hydroxyethylmethylcellulose [DS =
1.32, MS = 0.20] Example 5: Hydroxypropyl methylcellulose [Daicel Chemical Industries, Ltd., Aquacell R1000, DS = 1.48,
MS = 0.27] Lauryl group-containing polyether [Mighty AE03, manufactured by Kao Corporation] Mixture of 90 parts by weight of the above component and 10 parts by weight of the component

At the time of extrusion molding, extrusion moldability was evaluated as follows. Also, the extruded product is kept at room temperature
Cured in the air overnight in a constant temperature room at 60 ° C and 60% humidity, water temperature 20 ° C
After curing in water for 27 days in water tank, the bulk density and flexural strength after drying were measured. [Extrusion Moldability] (1) Extrusion Pressure The extrusion pressure was measured by a pressure gauge attached to the upstream side of the die. (2) Extrudability Extrudability was evaluated based on the following criteria. ：: The molded article is uniform and the surface smoothness is high. ：: Cracks are formed in the molded article. X: Cracks are formed in the molded article.
After drying at 05 ° C. for 24 hours, the density of the molded article was measured. [Bending strength] It was measured according to JIS A1408.
Table 1 shows the results.

[0025]

[Table 1] As is clear from Table 1, in the comparative example, a high extrusion pressure was required, the fluidity was small, and the extruded product had cracks and cracks, and the extrudability was not sufficient. On the other hand, in the example, a uniform molded article can be obtained with a low extrusion pressure, and the extrusion moldability is high.

Examples 6 to 10 and Comparative Examples 4 to 6 Cement (Tokuyama Corporation, ordinary Portland cement), aggregate (Kumamoto silica sand mining, No. 7 silica sand), reinforcing fiber (Hattori Co., Ltd., 3 mm) Ground pulp, PK pulp,
(Average length 3 mm, diameter 10 μm), the admixtures and tap water used in Examples 1 to 5 and Comparative Examples 1 to 3 were used at the ratios shown in Table 2, and Examples 1 to 5 and Comparative Examples 1 to 3 were used. Extrusion molding was performed in the same manner as in Example 1 to produce a concrete molded plate.
Extrusion moldability and properties of a concrete molded board were evaluated in the same manner as described above. Table 2 shows the results.

[0027]

[Table 2] As is clear from Table 2, in the example, as compared with the comparative example,
A uniform molded product can be obtained at a low extrusion pressure without cracks or cracks in the extruded product, and the extrudability is high.

Example 11 and Comparative Examples 7 to 8 Cement (Tokuyama Corporation, ordinary Portland cement), aggregate (Kumamoto silica sand mining, No. 7 silica sand), reinforcing fiber (Hattori Co., Ltd., 3 mm crushed pulp) , PK pulp,
Extrusion molding was performed in the same manner as in Examples 1 to 5 and Comparative Examples 1 to 3 using the following admixture and tap water in the proportions shown in Table 3 to obtain a concrete molded plate. . The temperature of the kneader and the extruder was adjusted with circulating water at 15 ° C. and 55 ° C., and the influence of the temperature was examined. Also,
Extrusion moldability and properties of a concrete molded board were evaluated in the same manner as described above. Table 3 shows the results. Example 11: Hydroxypropylmethylcellulose [Aquacell R1000, manufactured by Daicel Chemical Industries, Ltd., DS = 1.
48, MS = 0.27] Sodium salt of naphthalenesulfonic acid formalin condensate [Leveron P, manufactured by Sanyo Chemical Industry Co., Ltd.] A mixture of 80 parts by weight of the above component and 20 parts by weight of the component Comparative Example 7: Comparative Example 1 Comparative Example 8: Same as Comparative Example 3.

[0029]

[Table 3] As is clear from Table 3, in the example, as compared with the comparative example,
Even under high temperature conditions, no cracks or cracks are formed in the extruded product, a uniform molded product can be obtained at a low extrusion pressure, and the extrudability is high.

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Claims (14)

[Claims] 1. An admixture added to a molding composition containing at least cement, comprising 27.5 parts by weight of cement, 27.5 parts by weight of No. 7 silica sand, and 3 mm crushed pulp.
Parts, the mixture of admixture 0.1 parts by weight 20 parts by weight of water and stirred for 60 minutes, using a viscometer, is raised to 0s ^-1 ~100s ^-1 at a constant speed shear rate per minute flow A cement admixture having a shear stress A value at a shear rate of 10 s ^-1 of 0.5 to 300 Pa in a property test. 2. A cementitious composition comprising at least cement and an admixture, wherein 27.5 parts by weight of cement,
A mixture of 27.5 parts by weight of No. 7 silica sand, 1.1 parts by weight of 3 mm ground pulp, 0.1 parts by weight of an admixture and 20 parts by weight of water was stirred for 60 minutes, and the shear rate was reduced to 1 minute using a viscometer. cement-based molding compositions shear stress a value is 0.5~300Pa at a shear rate of 10s ^-1 at the flow characteristic test to increase at a constant rate until 0s ^-1 ~100s ^-1. 3. A shear stress A value at a shear rate of 10 s ⁻¹ is 5
The cement-based extrusion molding composition according to claim 2, further comprising an admixture of 0 to 300 Pa. 4. The cement-based molding composition according to claim 2, wherein the admixture is a water-soluble cellulose-based binder. 5. The cement molding composition according to claim 2, wherein the admixture is at least one selected from hydroxyalkylalkylcellulose and hydroxyalkylcellulose. 6. An admixture wherein the admixture is hydroxy C _2-4 alkyl-
3. The cement molding composition according to claim 2, which is at least one water-soluble cellulose derivative selected from C _1-4 alkyl cellulose and hydroxy C _2-4 alkyl cellulose. 7. The hydroxyalkylalkylcellulose has an alkyl group substitution degree DS of 1.2 to 1.6, a hydroxyalkyl group substitution degree MS of 0.1 to 0.3, and a total substitution degree (DS + MS). The cement-based molding composition according to claim 5, wherein is 1.5 to 1.7. 8. The cement molding composition according to claim 5, wherein the 1% by weight viscosity of the hydroxyalkyl cellulose is 10,000 to 50,000 cps, and the substitution degree MS of the hydroxyalkyl group is 1.5 to 2.5. Composition. 9. The cement-based molding composition according to claim 5, wherein the hydroxyalkylalkylcellulose is hydroxypropylmethylcellulose or hydroxyethylmethylcellulose. 10. The cement molding composition according to claim 5, wherein the hydroxyalkyl cellulose is hydroxyethyl cellulose. 11. A cement-based molding composition according to claim 2, wherein the admixture comprises a combination of the cellulosic binder according to any one of claims 5 to 10 and a surfactant. . 12. The surfactant may be a lignin sulfonic acid surfactant, an oxycarboxylate surfactant, a triazine surfactant, a polycarboxylic acid surfactant, or an aromatic aminosulfonic acid surfactant. The cement-based molding composition according to claim 11, wherein the composition is at least one selected from an agent, a polyol-based surfactant, and a polyether-based surfactant. 13. The cement molding composition according to claim 11, wherein the surfactant is a formalin condensate of an aryl sulfonate optionally substituted with an alkyl group. 14. A molding method comprising adding the cement admixture according to claim 1 to a cement composition containing at least cement, and extruding the mixture.