JPH0497929A - Water-soluble fine particle silica dispersed body for admixture for cement - Google Patents

Abstract

PURPOSE:To obtain a dispersed body having excellent stability and giving a hardened body excellent in strength in the case of blending with cement, mortar or the like by uniformly dispersing prescribed amounts of each specified silica powder, a water-soluble silica sol, bentonite and a water-soluble organic high polymer material into water. CONSTITUTION:By pts.wt., 100 fine silica powder having particle size finer than that of cement, a water-soluble silica sol having 2 to 200mu average particle size by 0.1 to 100 as SiO2, 0.05 to 10 bentonite and 0.05 to 5 water-soluble organic high polymer material (e.g. xanthan gum) are uniformly dispersed into water to form the dispersed body. Furthermore, the total of the solid content in the above components is regulated to 10 to 80wt.%.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is directed to the improvement of an aqueous fine-particle silica dispersion used as an admixture for cement, mortar, concrete, etc., and in particular, to an aqueous fine-particle silica dispersion that is stable for a long period of time. Regarding.

(Prior art) It is known that adding fine silica powder when mixing cement, mortar, concrete, etc. improves the strength, watertightness, durability, etc. of hardened materials such as cement, mortar, concrete, etc. ing.

Japanese Patent Publication No. 60-59182 discloses a method of increasing the strength of a hardened cement body by filling silica dust, colloidal silica, etc. between closely packed cement particles.

JP-A-2-102152 discloses a method of filling the voids of closely packed cement particles with silica hume particles and fine particles having a continuous particle size distribution.
Japanese Patent No. 180741 proposes an aqueous slurry of silica hume particles comprising silica hume, a higher fatty acid or a salt thereof, and a nonionic surfactant and/or an anionic surfactant.

(Problem to be Solved by the Invention) The above-mentioned Japanese Patent Publication No. 60-59182 not only does not disclose the preferred combination ratio of silica dust and colloidal silica, but also provides stable fine particle silica that can be easily added to cement. Aqueous dispersions are not disclosed. The above-mentioned Japanese Patent Application Laid-Open No. 2-102152 also does not disclose a stable aqueous fine-particle silica dispersion having a preferable combination ratio of silica dust and colloidal silica.

When the water slurry disclosed in JP-A-62-180741 is added when mixing cement, mortar, concrete, etc., the surfactant contained in this water slurry acts as an air-entraining agent, causing cement, mortar, concrete, etc. The strength of the cured product does not improve significantly.

The present invention solves the difficulties of these conventional techniques, and when mixing cement, mortar, concrete, etc.,
To provide an aqueous fine particle silica dispersion that can be easily added to these materials, can significantly improve the strength of hardened materials such as cement, mortar, concrete, etc., and is stable for a long period of time. This is what I am trying to do.

(Means for Solving the Problems) The aqueous fine-particle silica dispersion of the present invention comprises 100 parts by weight of fine-particle silica powder having a particle size smaller than that of cement;
0.1 to 100 parts by weight of a silica aqueous sol with an average particle size of 2 to 300 mm as SiO□, 0.05 to 10 parts by weight of bentonite, and 0.0 parts by weight of a water-soluble organic polymer substance.
5 to 5 parts by weight are dispersed in water, and the total solid content of these components is 10 to 80% by weight.

The cement mixture to which the aqueous fine-particle silica dispersion of the present invention is added is a conventional hydraulic cement paste, mortar, concrete, etc., and the hydraulic cement used is also a conventional hydraulic cement, such as ordinary Portland cement, Early strength cement, blast furnace cement, etc. may be used. Typically, the particle size of these cements is on the order of 1-100 microns.

The particulate silica powder used in the aqueous particulate silica dispersion of the present invention has a particle size smaller than that of the above-mentioned cement particles, and is usually about 5 mm to 100 microns. These silica powders are easily available as commercial products, such as silica hume, which is a by-product during the production of ferrosilicon,
Examples include fly ash, silica powder produced by vapor phase hydrolysis of silicon halide, and precipitated silica powder produced by acid neutralization of an aqueous water glass solution.

The aqueous silica sol used in the present invention includes colloidal silica with an average particle size of 3 to 200 millimicrons and 5iO
Preferably, particles with a Z concentration of 1 to 50% by weight are stably dispersed in water, and particularly preferred examples include particles with an average particle diameter of 5 to 10%.
0 millimicron silica SiO2 concentration 5-30% by weight
Examples include moderately alkaline aqueous sol.

Such an aqueous silica sol can be easily obtained by a known method. Examples include a method in which an aqueous solution of water glass is dealkalized with a cation exchanger and then stabilized with an alkali, or a method in which precipitated silica produced by adding an acid to an aqueous solution of water glass is peptized with an alkali. Examples include methods. It can also be easily obtained as a commercial product.

The bentonite used in the present invention may be an ordinary commercially available product containing montmorillonite as a main component. Further, the water-soluble organic polymer substance may be a conventional synthetic or natural substance, and examples thereof include commercially available polyvinyl alcohol, polyacrylamide, nonionic cellulose ether, xanthan gum, and the like.

The fine particle silica aqueous dispersion of the present invention contains 100 parts by weight of the above fine particle silica powder and 5102 parts by weight of the above silica aqueous sol.
0.1 to 100 parts by weight, preferably 5 to 60 parts by weight of the bentonite, 0.05 to 10 parts by weight, preferably 0.5 to 8 parts by weight of the bentonite, and the water-soluble organic polymer substance. It can be easily obtained by adding 0.05 to 5 parts by weight, preferably 0.1 to 2 parts by weight, to water and mixing uniformly. During this mixing, the total solid content of the above mixed components in the aqueous dispersion obtained by this mixing is 10 to 80% by weight.
, preferably 40 to 65% by weight, but this concentration adjustment can be done by adding water to the aqueous dispersion obtained by the above mixing, or by adding water to the aqueous dispersion obtained by the above mixing. This can also be done by concentrating the aqueous dispersion.

The order in which the above components are added to water is not particularly limited and may be arbitrary. The mixing temperature is preferably higher than the freezing point of water and at a temperature at which the obtained aqueous dispersion does not thicken or gel, usually from 0 to 100° C., preferably at room temperature. The above-mentioned mixing can be carried out by mixing for about 60 to 180 minutes using an ordinary stirrer.

The aqueous fine-particle silica dispersion of the present invention may contain, in addition to the above-mentioned components, any other component as long as the object of the present invention is achieved. For example, a small amount of a dispersant, antifoaming agent, surfactant, etc. can be added.

By the above mixing, the viscosity at 20°C is 100~2
000 cps of the fine particle silica aqueous dispersion of the present invention is obtained, and this aqueous dispersion has a stability that hardly changes for more than 30 days at room temperature.

(Function) In the aqueous fine-particle silica dispersion of the present invention, the interaction of the added components has not yet been completely elucidated. However, if any of the aqueous silica sol, bentonite, and water-soluble organic polymeric substance is missing, a stable aqueous fine-particle silica dispersion cannot be obtained. It is thought that the synergistic effect contributes to the stabilization of the aqueous fine-particle silica dispersion.

During mixing, if the silica aqueous sol exceeds 100 parts by weight with respect to 100 parts by weight of fine-particle silica powder, the aqueous fine-particle silica dispersion tends to have an excessively high viscosity; If the amount is too small, a stable aqueous fine-particle silica dispersion cannot be obtained.

If the amount of bentonite exceeds 10 parts by weight per 100 parts by weight of fine-particle silica powder, the resulting aqueous fine-particle silica dispersion will have too high a viscosity.On the other hand, if it is less than 0.1 part by weight, the aqueous fine-particle silica dispersion will not be stable. I can't get it. If the water-soluble organic polymer substance exceeds 5 parts by weight per 100 parts by weight of fine-particle silica powder, the viscosity of the fine-particle silica aqueous dispersion will be too high; It tends to settle and a stable aqueous fine particle silica dispersion cannot be obtained.

Furthermore, when the total solid content of these fine particulate silica powder, silica aqueous sol, bentonite, and water-soluble organic polymer substance exceeds 80% by weight in the fine particulate silica aqueous dispersion, the fine particulate silica aqueous dispersion has an excessively high viscosity. . If the total solid content is less than 10% by weight of the aqueous fine-particle silica dispersion, it is not preferable to add a large amount of the aqueous fine-particle silica dispersion when adding it to cement as a cement admixture.

The excessively high viscosity of the aqueous fine-particle silica dispersion makes measuring and other handling difficult when it is used as a cement admixture, making the aqueous fine-particle silica dispersion impractical.

When a fine silica aqueous dispersion, which is a combination of fine silica powder with different particle sizes and colloidal silica in a silica aqueous sol, is used in cement formulation, it further increases the filling density of the voids in the cement particles and increases the strength of the cement. It is convenient for improving.

(Example) The prepared mixed components are all commercially available products, and the fine-particle silica powder is silica hume, and the silica aqueous sol is colloidal silica with a particle size of 8 millimicrons and an alkaline aqueous sol with a 3102 concentration of 20% by weight. 80 to 100 mesh was used as the bentonite, and xanthan gum was used as the water-soluble organic polymer substance.

Example 1 Aqueous dispersions Nos. 1 to 13 listed in Table 1 were obtained by mixing the mixed components in a mixer for 2 hours with the compositions listed in Table 1. No. 1 to 9 are examples of the present invention, and N
o, 10 to 13 are comparative examples.

Next, the viscosity of the obtained aqueous dispersion was measured at 20°C immediately after its production and after 28 days of sealed storage at 20°C, and the results shown in Table 1 were obtained.

The results of the Examples and Comparative Examples in Table 1 show that the aqueous dispersion of the present invention exhibits good storage stability, whereas the aqueous dispersion of the Comparative Example thickens during storage and is not stable. This shows that it is stable.

Example 2 In this example, the particulate silica aqueous dispersion obtained in Example 1 was blended into concrete. The materials used are as follows.

Cement --- Ordinary Portland cement coarse aggregate --- Crushed stone with a surface dry specific gravity of 2.65 200
5 Fine aggregate ・〜・・−・−River sand AE with surface dry specific gravity 2.60
Agent...--Hozolith No. 70 Water reducing agent
...Mighty-150 Table 2 shows the unit compositions of concrete (A) to (F). Table 3 also includes water/cement ratio (W/C) as well as JIS A 6
Regarding the physical properties of these concretes, test results of slump value, air content, and compressive strength are shown in accordance with the measurement method specified in 204. In addition, concrete (C) and (F) are
This is a comparative example in which no fine particle silica aqueous dispersion was blended.

The results in Table 3 show that the hardened concrete containing the aqueous fine-particle silica dispersion of the present invention has extremely high strength.

(Effects of the Invention) According to the present invention, a stable aqueous fine-particle silica dispersion can be obtained by simply mixing fine-particle silica powder, aqueous silica sol, bentonite, and a water-soluble polymeric substance in water.

When this stable aqueous fine-particle silica dispersion is blended into cement, mortar, concrete, etc., cured products of extremely high strength can be obtained.

Claims (1)

[Claims] 100 parts by weight of fine silica powder with a particle size smaller than that of cement, 0.1-100 parts by weight of SiO_2 of an aqueous silica sol with an average particle size of 2-200 millimeters, and 0.05-10 parts by weight of bentonite. , 0.05 to 5 parts by weight of a water-soluble organic polymer substance are uniformly dispersed in water, and the total solid content of these components is 10 to 80 parts by weight.
Particulate silica aqueous dispersion for cement admixtures in weight %.