JP2512538B2 - Lightweight cement composition and method for producing lightweight cement molded product using the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a lightweight cement composition capable of advantageously preparing a lightweight cement molded article suitably used as a building member, and a method for producing a lightweight cement molded article. .

(Prior Art) Light-weight cement compacts are used as building materials such as exterior materials, interior materials, and ceiling materials for homes. A lightweight cement molded product of this type is prepared, for example, by pouring a cement composition containing Portland cement, lightweight aggregate and water, and optionally other components, into a desired mold and curing. The above cement molded product is taken out of the mold when it hardens to a certain extent and hardens sufficiently, but continuous production cannot be performed and production efficiency is poor.

Therefore, a method of preparing a cement molded product by extrusion molding (dry method) is adopted. When a cement molded product is obtained by extrusion molding, it is necessary to improve fluidity in the manufacturing process. It is considered to increase the amount of water in order to improve the fluidity of the cement composition, but even if the amount of water is increased, only the water will flow out before the composition material is extruded by pressure, resulting in poor molding. Further, even if a molded product having a desired shape is extruded, the molded product loses its shape and the desired cement molded product cannot be obtained.

Therefore, asbestos has been usually added to the cement composition used. This asbestos is added for the purpose of enhancing the fluidity of the mud-like cement composition during the manufacturing process and maintaining the shape of the extruded uncured compact. Asbestos also plays a role of improving the strength of the obtained cement compact. However, asbestos is designated as a specific chemical substance, and its carcinogenicity is a problem. Although a standard for use is set when manufacturing an asbestos-cement molded product, a cement molded product that does not use asbestos is currently desired due to the problem of dust generation during manufacturing and use.

Therefore, glass fiber, vinylon fiber, pulp, etc. are used as a reinforcing material in place of asbestos. However, reinforcing fibers such as glass fibers, vinylon fibers, and pulp tend to be oriented in the longitudinal direction of the molded product, and have a problem of weak strength in the lateral direction.

As the lightweight aggregate contained in the cement composition, an inorganic lightweight aggregate such as pearlite or shirasu balloon is used. Then, such a lightweight aggregate is subjected to high external stress such as shearing, compression, and bending by a kneader or an extruder. As a result, there is a problem that the lightweight aggregate is crushed, the extrusion moldability is deteriorated, and the weight of the obtained cement molded product is not sufficiently reduced.

(Problems to be Solved by the Invention) The present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to facilitate extrusion molding, and to obtain longitudinal and lateral strength and impact resistance of the obtained cement molded product. To provide a lightweight cement composition having excellent properties, surface smoothness, and weather resistance, and containing no harmful asbestos, and a method for producing a lightweight cement molded product.

(Means for Solving the Problems) The lightweight cement composition of the present invention comprises cement, calcium metasilicate, an inorganic aggregate composed of spherical particles having an average particle size of 1 to 100 μm, a lightweight aggregate, a reinforcing fiber and a cellulosic admixture. A lightweight cement composition containing, wherein the inorganic aggregate is 5 to 100 parts by weight of cement.
Parts by weight, 5 to 100 parts by weight of the calcium metasilicate based on 100 parts by weight of cement, a lightweight cement composition. The method for producing a lightweight cement molded product of the present invention is characterized in that a plastic kneaded product obtained by kneading the above cement composition is extruded under pressure to cure the obtained molded product. The above object is achieved by the above configuration.

In the present invention, as the cement, known cements such as Portland cement, blast furnace cement and alumina cement are used.

Calcium metasilicate is mainly used to improve the strength difference in the vertical and horizontal directions and the weather resistance of the molded body, is represented by the chemical formula of CaSiO ₃ , and is also called wollastonite or wollastonite. It is usually present as a contact metamorphic mineral associated with limestone, and is white, gray, and yellowish in color, and is produced in the form of fibers and lumps.
The main component contains almost equal amounts of silicic acid (SiO ₂ ) and lime (CaO), and a small amount of alumina, iron oxide, etc. as impurities. Further, it can be manufactured by melting silicon dioxide and calcium oxide. The crystal structure has two modifications, α-type and β-type, and particularly β-type is obtained as a fibrous natural mineral and is preferably used.

Due to its shape, such calcium metasilicate is sufficiently dispersed in the cement composition and has reactivity to increase the strength of the obtained molded body. Calcium metasilicate is contained in a ratio of 5 to 100 parts by weight with respect to 100 parts by weight of cement. If the amount is too small, the strength of the obtained cement molded product will decrease. If it is excessive, the moldability will be poor and the strength of the molded product will also be reduced.

The inorganic aggregate composed of spherical particles is mainly used for improving the fluidity of the kneading composition, and the average particle size thereof is 1
~ 100 μm. If the average particle size of this aggregate is too small, the fluidity during extrusion molding will not improve much, and if it is too large, the fluidity will decrease. As such an inorganic aggregate, fly ash of pulverized coal combustion ash collected by a dust collector of a lime thermal power plant, microsilica, silica fume, spherical calcium silicate and the like are preferably used. The above inorganic aggregate is contained in an amount of 5 to 100 parts by weight with respect to 100 parts by weight of cement. If the amount is too small, the moldability will be poor, and if it is excessive, the strength of the obtained molded product will decrease.

The lightweight aggregate is used to reduce the specific gravity of the molded body and reduce the weight. For example, fly ash balloons, perlite,
Inorganic lightweight aggregates such as shirasu balloons and organic lightweight aggregates made of styrene resin balloons, vinylidene chloride balloons, synthetic resin foam particles such as phenol resin balloons are used. Such a lightweight aggregate is a hollow body or a porous body having an average particle size of generally 0.01 to 3 mm, preferably 0.1.
~ 1mm. If the average particle size is too small, the lightness and heat insulating properties are reduced, and if it is too large, the fluidity of the composition is reduced.
The lightweight aggregate preferably has a bulk specific gravity of 0.03 to 0.8 and a 50% breaking hydrostatic pressure of 50 kg / cm ² or more.

In particular, when the inorganic lightweight aggregate and the organic lightweight aggregate made of synthetic resin expanded particles are used together as the lightweight aggregate, the flow of the kneading composition is improved by the synthetic resin expanded particles, and the synthetic resin expanded particles are also improved. Since it is less likely to be broken, the weight of the molded product can be favorably reduced.

The above lightweight aggregate is generally contained in the composition in an amount of 1 to 100 parts by weight, preferably 5 to 50 parts by weight, based on 100 parts by weight of cement. If the amount is too small, the lightweight property and the heat insulating property are poor, and if the amount is too large, the strength of the obtained molded article is lowered.

In particular, when the inorganic lightweight aggregate and the organic lightweight aggregate composed of synthetic resin foamed particles are used together, the inorganic lightweight aggregate has an average particle size of 0.1 to 0.5 mm and a bulk density of 0.1 to 0.8 and 100 parts by weight of cement. 1 to 100 parts by weight of the organic lightweight aggregate made of synthetic resin foam particles, an average particle size of 0.01 to 3 mm, a bulk density of 0.03 to 0.1 of 0.01 to 100 parts by weight of cement
It is preferable to contain 10 parts by weight.

Reinforcing fibers are mainly used to improve the bending strength and impact resistance of the molded body. For example, polypropylene fibers, polyethylene fibers, vinylon fibers, pulp, glass fibers, and other organic and inorganic fibers are used. In particular, polypropylene fibers have good heat resistance, alkali resistance and dispersibility, and since they do not absorb, they also have good dimensional stability and are preferably used. Reinforcing fiber diameter is 1 to 100 μm, fiber length is 3 to 2
0 mm is suitable. This reinforcing fiber is contained in the composition in a ratio of 0.1 to 10 parts by weight with respect to 100 parts by weight of cement.
When the amount of reinforcing fibers is too small, the strength of the obtained molded product decreases. If it is excessive, the dispersibility when the composition is mixed is poor, and as a result, the strength and surface smoothness of the resulting molded article deteriorate.

The cellulosic admixture is used to impart appropriate viscosity and improve moldability when the composition is extrusion-molded. As the cellulose-based admixture, methyl cellulose, hydroxy cellulose and the like are preferably used. This cellulosic admixture is preferably contained in the composition in a proportion of generally 0.1 to 10 parts by weight relative to 100 parts by weight of cement. If the amount is too small, the viscosity when kneading the composition is low, and if the amount is too large, the viscosity is high.

The cement composition contains 100% clay minerals.
Generally, 50 parts by weight or less can be contained with respect to parts by weight. When the clay mineral is contained, the moldability, shape retention and appearance of the cement molded product are further improved. If it is excessive, problems such as drying shrinkage may occur with respect to dimensional stability.

As such clay minerals, a structure group having a layer lattice as a basic unit such as an allophane group, a kaolin group, a halosite group, a montmorillonite mineral, a vermiculite mineral, and a mica mineral, and a double chain structure such as an apulgite, sepiolite, and palygorskite as a basic unit. There are structural groups.

In order to produce a lightweight cement compact using the lightweight cement composition of the present invention, the same steps as those for producing a conventional cement compact can be adopted. For example, first, the above cement, calcium metasilicate, an inorganic aggregate composed of spherical particles,
An appropriate amount of lightweight aggregate, reinforcing fiber, cellulosic admixture, and clay mineral are dry-blended. An appropriate amount of water, for example 100 to 100 parts by weight of the above cement, generally 20 to 1
Wet blending is performed by adding 00 parts by weight of water, and then kneading is sufficiently performed using a kneader.

The resulting plastic kneaded product is introduced into an extruder having a desired mold, and extrusion molding is performed under pressure. The extruded compact having the desired shape can be formed under certain conditions (for example, temperature
It is dried and solidified by being left (cured) for 30 to 80 ° C. and a humidity of 80 to 100% for 15 to 100 hours, for example. General-purpose equipment is used for the blending step, kneading step and extrusion molding step.

(Operation) When the lightweight cement composition of the present invention is used to perform extrusion molding by the method of the present invention, for example, the kneaded product has sufficient fluidity in the extruder, the flow rate is uniform, and the uncured extruded product is uncured. The molded product of (1) has sufficient shape retention until curing proceeds, and crushing of the lightweight aggregate is prevented.

Since such a good property contains the inorganic aggregate composed of spherical particles in the composition, it exhibits the effect of a bearing under pressure, and the inorganic aggregate and the reinforcing fiber are contained. It is considered that this is mainly due to the fact that the shape retention property is sufficient after extrusion.
Further, since the kneaded product contains a cellulosic admixture, an appropriate viscosity is imparted, and even when molding is performed with a mold having a complicated irregular cross-section, the conventional dehydration step is not required and the kneaded product can be easily obtained. Molding is performed.

Furthermore, since the composition contains calcium metasilicate together with reinforcing fibers, it eliminates the difference in strength in the vertical and horizontal directions due to the orientation of the fibers at the time of extrusion molding, has sufficient strength and impact resistance, and has excellent weather resistance. And surface smoothness. Further, since the lightweight aggregate is included, the lightweight property and the heat insulating property are improved.

(Example) Below, the Example and comparative example of this invention are shown.

Example 1 (A) Preparation of lightweight cement composition Cement (Portland cement) 100 parts by weight Calcium metasilicate (fibrous wollastonite with an aspect ratio of 35) 30 parts by weight Lightweight aggregate (styrene resin balloon having an average particle diameter of 1 mm) 1 part by weight Inorganic aggregate consisting of spherical particles (fly ash with an average particle size of 50 μm) 40 parts by weight Polypropylene fiber (thickness 48 μm, length 10 mm) 4 parts by weight Methylcellulose-based admixture (methylcellulose) 2 parts by weight Water 45 parts by weight Each component of the lightweight cement composition of the above formulation other than water was placed in a mixer (Shinagawa universal mixer: manufactured by Sanei Seisakusho) and mixed for 3 minutes. After adding water to this and mixing for another 3 minutes, a kneader (Auger type extrusion kneader MP-100 type:
(Miyazaki Tekko Co., Ltd.) was sufficiently kneaded to obtain a plastic kneaded product.

(B) -1 Manufacture of flat plate-like lightweight cement molded product The kneaded product obtained in (A) is used as a vacuum extrusion molding machine (vacuum extrusion molding machine equipped with a flat plate prototype mold (opening width 250 mm x thickness 15 mm)). It was supplied to a hopper of an extrusion molding machine MV-FM-A-1: manufactured by Miyazaki Iron Works Co., Ltd., and a long uncured flat cementitious compact having a width of 250 mm and a thickness of 15 mm was prepared by extrusion molding.
At this time, the extrusion pressure and the extrusion amount per unit time were measured. As the extrusion pressure, the pressure of the resistance portion from the barrel of the extruder to the mold was measured with a Bourdon tube pressure gauge. The extrusion amount per unit time is indicated by the volume of the uncured flat plate-shaped cement molded product extruded from the tip of the mold.

This uncured flat cement product was left for 5 hours at room temperature (preliminary curing), and then kept for 12 hours (primary curing) in an atmosphere of 50 ° C. and RH 95% or higher. This flat cement molded product was immersed in water at 20 ° C. for 4 weeks to be sufficiently hydrated and hardened.

(B) -2 Manufacture of Light-weight Cement Compact with Cross Section Ω As shown in FIG. 1 (a), the inner mold 11 and the projection 11a in which the projections 11a having a trapezoidal cross section are arranged along the longitudinal direction. A mold having an outer mold 12 in which a recessed groove portion 12a into which the upper part of is fitted is arranged along the longitudinal direction was prepared. The protrusion of this inner mold 11
The width of the top of 11a is 7 cm, and the width of the bottom is 9c.
m, and the height is 6 cm. The widthwise dimension of the opening of the concave groove portion of the outer mold 12 is 11.5 cm, the widthwise dimension of the inner back portion is 9.5 cm, and the depth is 5 cm. Separately, an uncured flat cement product (25 cm x
1.5 cm x 35 cm) was obtained.

This uncured flat plate cement molded body 3 is shown in FIG. 1 (a).
As shown in, each side portion in the width direction is placed on a pair of support plates 21 and 22 that are arranged to face each other with the ridge 11a of the inner mold 11 interposed therebetween,
As shown in FIG. 1 (b), an uncured cross-section Ω-shaped cement molded body shown in FIG. 1 (c) was pressed by an inner mold 11 and an outer mold 12 (pressure 10 kg / cm ² for 10 seconds). Got 30 This uncured compact was cured according to paragraph (B) -1, and as shown in FIGS. 2 (a) and 2 (b), a cement compact 31 having a cross section of Ω having a recess protruding upward. Got

(C) -1 Performance evaluation of lightweight cement molded product (B) Longitudinal sample (longitudinal direction to extrusion direction) and lateral sample (perpendicular to extrusion direction) elongated sample from flat plate molded product obtained in section 1 Cut (width: 25mm, length: 240mm), put in a gear oven at 105 ℃ and dry for 48 hours, then
It was left to cool for 4 hours. The two types of samples were supported at intervals of 200 mm, and a force was applied to the central portion thereof at a bending speed of 2.5 mm / min to measure bending strength in the longitudinal direction and the transverse direction. The specific gravity of this sample was measured.

In addition, the flat plate molded body obtained in (B) -1 is 250 m wide.
m, length 250mm (cut perpendicular to the extrusion direction),
Oven treatment was performed as described above. This sample is placed on a flat river sand, and a 1 kg steel ball is dropped from the height of 2 m in the center of the sample, and it is observed whether or not any abnormality is found in the sample.
The impact resistance was evaluated.

In addition, the rate of change in thickness and the average surface roughness of the flat plate-shaped molded product obtained in (B) -1 were measured and within 10% and
Those having a surface smoothness of 50 μm or less were judged to have passed the surface smoothness, and the result was judged. The rate of change in thickness was calculated by the following formula.

Average surface roughness conforms to JIS B-0601, measuring length 8 cm
Was measured 5 times, and the pass / fail was determined by the average value.

In addition, the flat plate molded body obtained in (B) -1 is JIS A-
According to 1415, the above-mentioned measurement of bending strength after 1000 hours of irradiation time was carried out, and those having a strength decrease of 20% or more of the strength before irradiation were judged to have failed weather resistance, and pass / fail was judged.

Furthermore, the Ω-shaped molded body 31 having a cross section obtained in (B) -2 is cut into a length of 30 cm at right angles to the longitudinal direction, and the depth X of the recess is determined.
(Shown in Fig. 2 (b)) was measured with a caliper, and X was 4.5 cm.
The above was passed as the shape retention property, and the pass / fail was determined. The above results are shown in Table 1.

Example 2 Instead of 1 part by weight of a styrene resin balloon as a lightweight aggregate, a fly ash balloon (breaking hydrostatic pressure 100 kg / cm ² ,
Example 1 was repeated except that 20 parts by weight of an average particle size of 150 μm) and 50 parts by weight of water were used. The results are shown in Table 1.

Example 3 1 part by weight of a styrene resin balloon as a lightweight aggregate, a fly ash balloon (breaking water pressure 100 kg / cm ² , average particle size 1
The same procedure as in Example 1 was carried out except that 20 parts by weight of 50 μm) was used together and 53 parts by weight of water was used. The result is first
Shown in the table.

Example 4 40 parts by weight of fly ash (average particle size 50 μm) as an inorganic aggregate composed of spherical particles was used in combination with 10 parts by weight of silica fume (average particle size 1 μm), and sepiolite (trade name: Serbora) as a clay mineral. Example 1 was repeated except that 10 parts by weight and 50 parts by weight of water were used. The results are shown in Table 1.

Comparative Example 1 Example 1 except that calcium metasilicate was not used, 4 parts by weight of vinylon fiber was used instead of 4 parts by weight of polypropylene fiber, and 35 parts by weight of water was used.
It carried out similarly to. The results are shown in Table 1.

Comparative Example 2 The procedure of Example 1 was repeated except that calcium metasilicate was not used, 4 parts by weight of pulp was used instead of 4 parts by weight of polypropylene fiber, and 40 parts by weight of water was used. The results are shown in Table 1.

Comparative Example 3 Extrusion was carried out with the same composition as in Example 2 except that fly ash was not used as the inorganic aggregate composed of spherical particles and 45 parts by weight of water was used. Could not be molded.

(Effects of the Invention) As described above, according to the present invention, a cement molded product that is lightweight, has high strength, is excellent in impact resistance, and has an excellent strength balance can be obtained by extrusion molding with good moldability and high efficiency. Such a lightweight cement molded product is suitably used as a floor material such as a deck material and a corridor material of an apartment house. Also,
Since it does not contain asbestos, there is no risk of carcinogenesis due to dust generation in asbestos during the manufacturing process and during use.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 (a) to (c) show an example of a step of pressing an uncured flat plate-shaped cement compact obtained by extrusion using the cement composition of the present invention. Explanatory drawing, FIG.2 (a) and (b) are the perspective views and sectional drawings of the hardened | cured cement molded object of cross section Ω shape. 3 ... Unhardened flat cement molding, 11 ... Inner mold, 12
…… Outer mold, 21,22 …… Support plate, 30 …… Unhardened section Ω-shaped cement molded body, 31 …… Hardened section Ω-shaped cement molded body.

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Claims (1)

(57) [Claims] 1. An inorganic aggregate comprising cement, calcium metasilicate, spherical particles having an average particle diameter of 1 to 100 μm, a lightweight aggregate,
A lightweight cement composition containing reinforcing fibers and a cellulosic admixture, wherein the inorganic aggregate is 100 parts by weight of cement, 5 to 100 parts by weight, the calcium metasilicate is 100 parts by weight of cement, Light weight cement composition characterized by comprising 5 to 100 parts by weight