JPH085702B2 - Cement composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a cement composition suitable for extrusion molding of a high-strength cement-forming material that is preferably used as a building member.

(Prior Art) In recent years, a cement molded product by extrusion molding has been used as a building member such as a housing exterior material, interior material, and ceiling material. This type of cement molded product contained asbestos fibers in the composition in order to improve moldability, shape retention and product strength. However, asbestos fiber is considered to be a carcinogen, and its production and use are regulated. Therefore, a reinforcing fiber instead of this has been included in the composition. As the reinforcing fibers, glass fibers, metal fibers such as steel fibers, and high-strength synthetic fibers typified by vinylon have been used. However, glass fibers cause alkali resistance, metal fibers cause damage to the extruder and mold, and synthetic fibers cause problems such as moldability due to poor dispersion. Therefore, as an alternative to the cement composition containing these reinforcing fibers, a cement composition has been proposed which improves the product strength by densifying the molded body. The cement composition is, for example, one in which the amount of water relative to the cement component in the composition is reduced to reduce voids due to excess hydration water, or by adding silica fume, a microfiller of the silica fume. There are some which are designed to utilize the effect and high hydration activity (see, for example, JP-A-58-132505).

(Problems to be solved by the invention) However, in the case of a cement composition in which the amount of water with respect to the cement component in the composition is reduced, the extrusion pressure becomes high in extrusion molding, which causes deterioration of fluidity and friction during extrusion molding. Inconveniences such as heat curing of the material occur. Also, in the case of a cement composition to which silica fume is added, due to the ultrafine powder property and high hydration activity of silica fume, the stickiness of the material becomes unnecessarily large when added in a large amount, and the pot life (pot life) However, there is a problem in extrusion moldability such as shortening of the length.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a cement composition capable of producing a densified high-strength cement molded product by extrusion molding.

(Means for Solving the Problems) The cement composition of the present invention comprises a cement and the cement.
Average particle size with a specific surface area of 8000 cm ² / g or more per 100 parts by weight
It is composed of 5 parts by weight or more of silica fine powder having a particle size of 10 μm or less, an inorganic powder mainly composed of spherical particles, a reinforcing fiber and a fluidity-imparting agent.

(Function) Cement and specific surface area 8 with respect to 100 parts by weight of the cement
5 parts by weight or more of silica fine powder having an average particle diameter of 10 μm or less at 000 cm ² / g or more, and an inorganic powder mainly composed of spherical particles,
The reinforcing fiber and the fluidity-imparting agent are uniformly mixed, and extrusion molding is performed using this cement composition. At this time, since the silica fine powder is a crystalline inorganic powder, the disadvantage that the pot life is shortened due to the high hydration activity does not occur. Further, by setting the average particle size of the silica fine powder to 10 μm or less, the silica fine powder surrounds the cement particles and other materials in the composition so as to be filled, and the compacted compact of the cement compact by the microfiller effect is provided. Promote the transformation. Further, by setting the specific surface area of the silica fine powder to 8000 cm ² / g, the water supply of the silica fine powder is improved and the fluidity of the composition is improved. In addition, since the inorganic powder composed of spherical particles is spherical when kneaded under pressure in an extruder, it substantially alleviates rough friction and improves the fluidity of the composition. Furthermore, the reinforcing fibers improve the moldability and impact strength of the molded body.

(Example) Hereinafter, the Example of this invention is described with reference to drawings.

Cement in the present invention is not particularly limited as long as it is usually used, for example, Portland cement,
Blast furnace slag cement, alumina cement, etc. are used.

Silica fine powder has a specific surface area of 8000 cm ² / g or more and an average particle size of 10
It is preferable that the silica fine powder has an average particle diameter of 10 μm or less, so that the silica fine powder surrounds the cement particles and other materials in the composition so as to be filled, and the micro filler effect is exerted. It is possible to promote the densification of the cement molded body. Further, by setting the specific surface area of the silica fine powder to 8000 cm ² / g, the water supply of the silica fine powder can be improved and the fluidity of the composition can be improved.

The inorganic powder composed of spherical particles is preferably 200 μm or less, and fly ash is particularly preferable. Also,
Since silica fume is also spherical, it may be mixed as long as it does not adversely affect the pot life. further,
If the amount of this inorganic powder used is too small, the formability is poor, and if it is too large, the strength of the formed body is reduced. preferable.

The reinforcing fiber is used to improve the moldability and the impact strength of the molded product. As a fiber that satisfies this,
For example, defibrated pulp and organic fibers are suitable. Since defibrated pulp has water retention property, it improves moldability during extrusion molding. In addition, this addition can be expected to improve the bending strength of the molded body. On the other hand, the organic fiber improves the impact strength of the molded product. In particular, polypropylene fibers are preferable, have better heat resistance and dispersibility than other organic fibers, and have no dimensional stability because the fibers themselves do not have hygroscopicity. If the amount of these reinforcing fibers used is too small, the impact strength of the molded product is reduced, and if it is excessive, the surface smoothness of the product is deteriorated.Therefore, it is mixed in a range of 10 parts by weight or less relative to 100 parts by weight of cement. Preferably.

As the fluidity imparting agent, a cellulosic admixture is suitable. This is used for the purpose of imparting an appropriate viscosity during extrusion of the composition and improving the fluidity. As the admixture, a cellulose derivative such as methyl cellulose or hydroxymethyl cellulose is used. If the amount of the admixture used is too low, the viscosity becomes low and the moldability deteriorates.If the amount is too large, the viscosity becomes too high and the moldability deteriorates. It is preferable to mix in a weight ratio of 0.5 to 5 parts by weight.

The amount of water used with respect to cement is such that it is generally used in the production of lightweight cement compacts, and it is preferable to use 30 parts by weight or more per 100 parts by weight of cement, for example.

The above-described cement composition of the present invention can be manufactured as a cement molded product, for example, through the same steps as the conventional cement extrusion molding. That is, first, the above composition is dry blended. To this, an appropriate amount of water is added, wet blending is performed, and then kneading is sufficiently performed using a kneader. The thus obtained plastic kneaded product is introduced into an extruder having a desired mold, and extrusion molding is performed under pressure. The extruded molded body having a desired shape can be formed under predetermined conditions (for example,
It is dried and solidified by leaving it at a temperature of 30 to 80 ° C and a humidity of 80 to 100% for 5 to 100 hours. Note that general-purpose equipment can be used for each of the above steps.

Next, the cement composition of the present invention and a molded product molded from the cement composition are divided into (a) preparation of the cement composition, (b) molding of the molded product, and (c) performance evaluation of the molded product in order. explain. Further, a comparative example of a conventional cement composition is shown as a comparison target.

[First Experimental Example] (a) Preparation of cement composition Each component other than water of the lightweight cement composition of the above formulation was put into a mixer (Eirich mixer VR02 type: manufactured by Nippon Eirich Co., Ltd.) and mixed at 1000 rpm for 2 minutes. Water was added to this, and the mixture was further mixed for 1 minute, and then sufficiently kneaded with a kneader (Auger type extrusion kneader mp-100: manufactured by Miyazaki Tekko Co., Ltd.) to obtain a plastic kneaded product.

(B) Molding of molded body A vacuum extruder (type MV-FM-A-1: type MV-FM-A-1: It was supplied to a hopper of Miyazaki Tekko Co., Ltd. and extruded. At this time, the pressure applied to the mold resistance portion and the discharge speed were measured, and as shown in the figure, the discharge amount per unit time (/ Hr was calculated from the measured values of the thickness a and the width b of the molded flat plate sample 1). ) Was asked.

Q = a ・ b ・ c × 0.06 Q: Amount of discharge per hour (/ Hr) a: Thickness of sample (cm) b: Width of sample (cm) c: Length of flat plate sample discharged in 1 minute (Cm / min) (c) Performance evaluation of molded product The flat plate sample 1 obtained in (b) is left indoors (preliminary curing) for 5 hours, and steam curing chamber (50 ° C, RH 95% or more)
I put it in and cured it for 12 hours. Next, this flat plate sample 1 was immersed in water for about 4 weeks, and then cut into a width of 2.5 mm and a length of 240 mm (cut at a right angle to the extrusion direction), and then a drier (105
(° C) for 2 days and cooled to about room temperature. The thus-obtained test piece 2 was supported at intervals of 200 mm, and an autograph (manufactured by Shimadzu Corporation) was used in the center thereof to apply a force at a bending speed of 2.5 mm / min, and the bending strength was measured by the following formula.

Bending strength (kgf / cm ² ) = 3PL / 2dt ² P: Maximum load (kgf) L: Support distance (cm) d: Specimen width (cm) a: Specimen thickness (cm) The test piece 2 used for the measurement was measured for each of the lateral direction 2a cut in the direction perpendicular to the extrusion direction of the flat plate sample and the longitudinal direction 2b cut along the extrusion direction. Further, the surface smoothness of the product was visually observed.

 Table 1 shows the above results.

[Second Experimental Example] In the first experimental example, 10 parts by weight of silica fume was added to the cement composition, and the other conditions were the same, and the experiment was conducted.

 Table 1 shows the above results.

<First Comparative Example> In the first experimental example, the silica fine powder in the cement composition was removed, the amount of water was reduced from 40 parts by weight to 30 parts by weight, and the other conditions were the same.

 Table 1 shows the above results.

<Second Comparative Example> In the second example, the experiment was conducted under the same conditions except that silica fine powder in the cement composition was removed, 50 parts by weight of silica fume was added.

 Table 1 shows the above results.

<Third Comparative Example> In the first experimental example, the experiment was conducted under the same conditions except that the average particle size of the silica fine powder in the cement composition was changed from 4 μm to 100 μm.

 Table 1 shows the above results.

From the results of the first experimental example, the second experimental example, and the first comparative example to the third comparative example described above, the cement composition of the present invention can extrude a high-strength molded article with good moldability. I understand.

(Effects of the Invention) As described above, according to the present invention, it is possible to provide a cement molded product having high strength and excellent moldability. In addition, it is safe because it does not use carcinogens such as asbestos.

[Brief description of drawings]

The figure shows a drawing of a flat plate sample extruded with the cement composition of the present invention.

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Claims (1)

[Claims] 1. Reinforcement with cement, 5 parts by weight or more of silica fine powder having a specific surface area of 8000 cm ² / g or more and an average particle size of 10 μm or less with respect to 100 parts by weight of the cement, and an inorganic powder mainly composed of spherical particles. A cement composition comprising a uniform mixture of fibers and a fluidity-imparting agent.