JPH04214059A - Production of hardened body of cement - Google Patents

Abstract

PURPOSE:To offer a precast concrete having high bending strength and excellent in flame resistance, water resistance, etc. CONSTITUTION:Fine aggregate, filler, etc., are arbitrarily added in addition to 1-20 pts.wt. of water dispersive polymer and 5-25 pts.wt. of water, to 100 pts.wt. of powder prepared by arbitrarily mixing hydraulic compound with gamma-C2S, then these are kneaded, and the resulting cement composition is molded and is the treated at 40-180 deg.C at 20-70% relative humidity and/or under 5-15atm to undergo hardening, by which a precast concrete is produced. If the above- mentioned kneaded cement composition is hermetically sealed in this stage, it can be preserved in a state without losing its plasticity over several months.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a hardened cement body.

0002

BACKGROUND OF THE INVENTION Cement products obtained by curing cement compositions do not necessarily have high bending strength. The flexural strength of products obtained by curing hydraulic cement compositions of conventional particle sizes and water/cement ratios is on the order of 5-10 MPa. It is known that the flexural strength of cement products can be increased by including fibrous substances in cement compositions, but the flexural strength rarely exceeds 40 MPa, and moreover, the formability of the cement composition deteriorates. . In addition, it has been proposed to increase the bending strength of cement products by regulating the size and proportion of pores in cement products, by regulating the viscosity conditions of cement compositions, etc. However, the cement products with improved bending strength according to these proposals have drawbacks in flame resistance (heat resistance, fire resistance), water resistance, etc., and there are problems in putting them into practical use. Furthermore, since these cement products mainly use portland cement or other hydraulic cement, the products are gray in color and have problems in appearance.

0003

[Problems to be Solved by the Invention] In view of the above-mentioned prior art, an object of the present invention is to provide a method for manufacturing cement products that have high bending strength and are excellent in flame resistance, water resistance, etc. do.

0004

[Means for Solving the Problems] In order to achieve the above object, in the present invention, 1 to 20 parts by weight of a water-dispersible polymer is added to 100 parts by weight of a powder prepared by mixing γ-C2S with an optional hydraulic compound. In addition to 5 to 25 parts by weight of water, a cement composition is prepared by adding fine aggregate, filler, etc., and kneading the mixture.
After molding, relative humidity 20-70% or (and) 5
It is treated and hardened at temperatures of 40 to 180°C under ~15 atmospheres to produce cement products. If the cement composition kneaded above is sealed at that stage, it can be stored for several months without losing its plasticity. Therefore, the above-mentioned cement composition can be sealed and stored as a product material as it is or as a molded semi-finished product, later opened, and heat-treated and hardened as described above to produce a cement product.

In the present invention, γ-C2S is used as cement particles.
Use. Conventionally, since γ-C2S usually does not exhibit hydraulic properties, it has been thought that it is preferable to include it as little as possible as a cement constituent compound. However, the inventors
Surprisingly, a hardened cement obtained by adding a water-dispersible polymer and water to γ-C2S powder, kneading it, and heat-treating it under conditions of low humidity or high pressure has high bending strength and other excellent properties. The present inventors have discovered that this is an epoch-making product that shows the characteristics of the invention, and have come up with the present invention.

[0006] The characteristics of this cured product are that γ-C2S
tobermolite-like hydration product (C
SH) Because a very small amount of gel forms the matrix of the cured product and it is stabilized by the polymer, it has excellent mechanical strength including high bending strength, as well as high water resistance. Further, it has characteristics such as low water permeability, excellent heat resistance and fire resistance, and little deformation. FIG. 1 is a diagram illustrating the internal structure of the cured product according to the present invention.
A mixture of CSH gel and polymer fills the space between the S particles 1 and the filler 2 as a matrix 3. On the contrary,
FIG. 2 is a diagram showing the internal structure of a conventional hardened Portland cement body, in which particles such as unhydrated material 5, external hydrated material 6, calcium hydroxide 7, etc., whose surfaces are surrounded by internal hydrated material 4 are shown. are combined to form tissues.

The present invention is characterized in that a cured product is obtained by using γ-C2S and hydrating it under specific conditions, and the above-mentioned advantages are achieved by using γ-C2S. However, hydraulic compounds may optionally be incorporated. When a hydraulic compound is mixed, the mixing ratio is not particularly limited, but is generally 40% or less of the total weight with γ-C2S. As a hydraulic compound, it is usually sufficient to mix so-called hydraulic cement, for example, portland cement, mixed portland cement (
Blast furnace cement, flyfish cement, silica cement, etc.), alumina cement, hydraulic lime, Roman cement, natural cement, and mixed lime cement (slag cement, volcanic ash cement, etc.). Also, early-strengthening cement, super-fast-hardening cement, oil well cement, etc. may be used. In particular, alumina cement itself is known to provide a hardened product with high bending strength, and mixing of alumina cement is preferred.

A water-dispersible polymer is added to the cement composition of the present invention to provide a lubricating or dispersing effect and plasticity to particles such as γ-C2S during molding or processing. Water-dispersible polymers include, for example, vinyl acetate polymers and copolymers; amide-substituted polymers such as acrylamide and methacrylamide polymers and copolymers; nonionic polymers such as hydroxypropyl methyl cellulose and oxypropyl methyl cellulose. alkyl or hydroxyalkyl cellulose esters; polyalkylene oxide derivatives such as polyethylene oxide; polyalkoxy derivatives; sulfone group-containing polymers such as lignosulfonate and sulfonated naphthalene salts; do. The water-dispersible polymer is added in an amount of 1 to 20 parts by weight, preferably 1 to 5 parts by weight, per 100 parts by weight of the powder consisting of γ-C2S and an arbitrary hydraulic compound.

[0009] Fine aggregate, filler, etc. may be optionally added to the cement composition of the present invention. It is preferable that these particles have a particle size of 1 mm or less. Examples include sand, quartz sand, and silica such as fine amorphous silica, titania, olivine, slate powder, fly ash, slag, gypsum, and the like. Further, although the cement product according to the present invention achieves high bending strength without incorporating fibers, it does not exclude the inclusion of fibers. Furthermore, pigments can be added to the present cement compositions. The hardened cement product according to the present invention has an aesthetically superior white color because the γ-C2S powder is white, and therefore also has the advantage that it is easy to add pigments to obtain clear coloring. There is.

[0010] When kneading the cement composition of the present invention, a powder consisting of γ-C2S and optionally a hydraulic compound is used.
Only 5 to 25 parts by weight, preferably 7 to 15 parts by weight of water is added per 100 parts by weight, and the amount of water mixed is extremely small. This is to limit the hydration rate of the cement while keeping the density high and reducing the total voids by reducing the water space voids. In order to uniformly knead such a composition with a very small amount of mixed water, it is preferable to knead it under high shear force using a two-screw kneader, a two-roll mill, etc., alone or in combination.

The kneaded cement composition is formed by extrusion molding, roll molding (sheet form), pressure molding (irregular shape, rod shape, conical shape, etc.), and then machined (cutting, etc.) to form various shapes. It is a semi-finished product in the shape of a part. As mentioned above, the cement composition of the present invention can be stored while retaining its plasticity by sealing it after kneading or at the stage of a molded semi-finished product. In this way, the molded semi-finished product or the semi-finished product opened after hermetically sealed storage has a relative humidity of 20 to 70, preferably 2.
Under low humidity of 0 to 60% or/and high pressure of 5 to 15 atmospheres, preferably 5 to 10 atmospheres, approximately 40 to 180
It is cured by treatment at a temperature of preferably 80 to 150°C. By such curing, it is possible to harden the cement composition of γ-C2S powder, which does not exhibit hydraulic properties under normal conditions.

[0012] In order to improve the bending strength of the cement product, it is also effective to adjust the pores of the cement product in the cement product of the present invention (Japanese Unexamined Patent Publication No. 56-144
(See Publication No. 65). For example, 2% or 0.5% of the total volume of the product has a maximum dimension of 100 μm or 50 μm.
m, or occupied by pores larger than 15 μm. Generally, the smaller the proportion of relatively large pores, the greater the strength of the cement product. Obtaining such a dense product is possible by adjusting the size distribution of the particles. In particular, it is advantageous to adjust the particle size formulation so that there is a multimodal distribution, ie a plurality of peaks in the particle size distribution curve. For example, as a bimodal distribution, (a) particle size 60
~ 110 μm at 50 wt% or more, preferably 70 to 9
(b) 5 wt% or more, preferably 10 to 30 wt% of particles with a particle size of 1 to 10 μm, and (c) 20 wt% or less of particle sizes other than the above, preferably 10 wt% or less, more preferably 5 wt% or less is considered suitable. Other dual-mode distributions, triple-mode distributions, etc. can be used to achieve desirable porosity products. Of course, a single mode distribution may also be used. In general, the γ-C2S used in the present invention is easily pulverized, so it is easy to prepare more dense products.

[0013] When selecting the components of the cement composition, it is also effective to conduct a capillary rheometer test and select those whose shear stress increases by more than a certain level as the shear rate increases (Japanese Patent Laid-Open No. 129853/1983). (see publication). For example, if a test composition is extruded into a capillary rheometer and the shear rate of the test composition is increased by a factor of 10 at a shear rate in the range of 0.1 to 5/sec, Flexural strength can be increased by selecting the components and composition of the composition such that the shear stress of the composition is increased by at least 25%. This method of increasing bending strength was originally proposed for ordinary hydraulic hardened cement products, but by applying it to the cement products of the present invention, the bending strength of the hardened products of the present invention can be dramatically increased. It is possible to increase The present inventors
I think it is possible to some extent. Similarly, methods for achieving high Young's modulus have also been proposed.

Next, γ used in the cement product of the present invention
-C2S powder is made of calcium oxide, calcium hydroxide, and/or calcium carbonate powder with a purity of 99 wt% or more, and silicon oxide powder with a purity of 99 wt% or more, and the molar ratio of CaO/SiO2 is 1.90. ~2.05
, preferably 1.98, 1000~
It can be produced by firing at a temperature of 1500°C, preferably 1400°C, and slowly cooling to room temperature. The above CaO
source and SiO2 source are compounds or compositions that become CaO and SiO2, respectively, under calcination conditions;
The purity of the compound or composition is greater than or equal to 99 wt%. Both must not contain more than a certain amount of specific components as described below.

[0015]

[Table 1]

CaO sources include quicklime, slaked lime, calcium carbonate, etc., and SiO2 sources include silica stone, silica sand, and siliceous substances as industrial by-products. CaO source and S
The iO2 source powder has a powder density of Blain 1500cm2/g.
Use particles with a particle size of 0.1 mm or more or 0.1 mm or less. In the case of slow cooling after firing, the cooling rate is generally from 500°C to room temperature at a cooling rate of 15°C/min or less, preferably 10°C/min or less. The C2S phase produced by the calcination undergoes a polymorphic transition from a β to a γ crystal structure through this slow cooling, and as a result, a γ-C2S fine powder is obtained. This is because volume expansion occurs with polymorphic transition from β to γ. The obtained γ-C2S powder has a diameter of about 0.5 to 100 μm (
It is a fine powder with many small particles) and therefore does not require a mechanical grinding process to be used as cement powder. This constitutes a major advantage of the cement product of the present invention using γ-C2S powder, which allows for significant cost reductions.

[0017]

[Examples] Examples of the present invention will be described below. (Example 1) 100 parts by weight of quicklime powder (particle size of 0.1 mm or less) and 54 parts by weight of siliceous powder (particle size of 0.1 mm or less) were mixed. In both powders, the impurities are Al2O3 on a weight basis.
0.10% or less, Fe2O3 0.05% or less, MgO
0.20% or less, TiO2 0.05% or less, B
2O3 0.02% or less, P2O5 0.02% or less, Na2O 0.05% or less, K2O 0.05% or less, Al2O3 and others 0.02% or less. This powder mixture was fired at about 1400° C. for 2 hours in an electric furnace and slowly cooled. In particular, the cooling rate was set at 10°C/min from 500°C to room temperature. After slow cooling, a white powder with a particle size of 0.3 to 95 μm was obtained, which was confirmed to be γ-C2S by X-ray diffraction.

(Example 2) γ-C2S powder prepared in Example 1 (composition is γ-C2S
is 98wt%, powder particle size composition is Blaine 1500
cm2/g, particle size 88μm or more 0.04wt%, 63μ
m or more 1.57 wt%, 44 μm or more 4.47 wt%,
30μm or more 30.28%, 20μm or more 58.0
polyvinyl acetate (saponification degree 78.5-81.
5%) and 12 parts by weight of pure water were premixed using a hover mixer, then kneaded using a two-roll mill, and the resulting sheet was further pressurized at 30 kg/cm2 and held for 10 minutes. Test specimen (thickness 3mm x length 200mm)
mm x width 150 mm). This test specimen was immediately transferred to a constant temperature and humidity bath adjusted to a relative humidity of 45% and a temperature of 100° C., and was heat-treated for 1 hour to be cured.

The following values were obtained for the physical properties of the cured test specimen. However, the bending strength was measured using an Instron universal testing machine using a test piece with a width of 5 cm and a span of 10 cm. The heating bending strength is the same bending strength after being held at 300°C for 1 hour. The water absorption rate and length change rate were determined from the weight change and length change after the sample was saturated with water and then absolutely dried at 105°C. Regarding flame retardancy, it was determined whether or not it passed the Ministry of Construction certified noncombustible material according to JIS A1321.

[0020]

[Table 2]

(Example 3) To 100 parts by weight of cement powder consisting of 95 wt% γ-C2S and 5 wt% talc, 7 parts by weight of polyacrylamide and 15 parts by weight of pure water were added, and the same procedure as in Example 2 was followed. Kneaded, molded, heat treated and tested. The results were as follows.

[0022]

[Table 3]

(Example 4) A product kneaded and molded in the same manner as in Example 2 was sealed in a polyethylene bag and opened after 6 months, and there was no problem with the plasticity and machinability of the cement composition. Ta. When this was heat treated and tested in the same manner as in Example 1,
I got the following results.

[0024]

[Table 4]

[0025]

As is clear from the above description, according to the present invention, it is possible to obtain a hardened cement body which has significantly improved bending strength (50 MPa or more), which was a major drawback of conventional hardened cement bodies. Furthermore, this cured product can achieve low porosity, high Young's modulus, and high fracture energy. In addition, it is a practical hardened product without the drawbacks of poor water resistance, flame resistance, etc. that have been observed in hydraulic cement hardened products that have been proposed to achieve high bending strength. Moreover, since this cured product is white, it has an excellent aesthetic appearance and can be easily colored. Furthermore, the cost of the γ-C2S powder used in this cement product is low because fine powder can be obtained without going through a mechanical pulverization process. Therefore, the cost of hardened cement using this is also reduced. Applications that take advantage of these characteristics of this cement product include not only general building materials, but also sealants, electrical material parts, vehicle tire rims and wheel kips, and substitutes for plastics, ceramics, and non-ferrous metal materials. It can be used in a wide range of applications as a material. Furthermore, the present invention also provides a cement composition for providing the cement product as described above, and a method for producing γ-C2S powder.

[Brief explanation of the drawing]

FIG. 1 is a diagram of the structure of a hardened cement body according to the present invention.

FIG. 2 is a diagram of the structure of a conventional hardened cement body. 1...γ
-C2S Unhydrated 2...Filling 3...Matrix 4...Internal hydrate 5...Unhydrated 6...External hydrate 7...Calcium hydroxide

Claims (1)

[Claims] [Claim 1] γ-Dicalcium silicate (γ-C2S)
Powder consisting of a hydraulic compound arbitrarily mixed with 100
Based on parts by weight, 1 to 20 parts by weight of water-dispersible polymer, 5 parts by weight of water
~25 parts by weight and optionally fine aggregate, filler, etc. are added, kneaded, shaped, and treated at a temperature of 40 to 180 °C under a relative humidity of 20 to 70% or (and) 5 to 15 atm. A method for producing a hardened cement body, characterized by: