KR100888826B1 - Coating method of silica fume for high strength conctere - Google Patents

Abstract

A method of coating silica fume for manufacturing high-strength concrete is provided to reduce using amount of water by reforming surface of the silica fume, to achieve high intensity and to suppress aggregation reaction of the silica fume and the water. A method of coating silica fume for manufacturing high-strength concrete contains steps of: processing a surface of a silica fume with one or more surface modification agent selected from a group consisting of silanes, fatty acids, amines and surfactants; and drying and aging the surface-treated silica fume. A content of SiO2 of the silica fume is 70 weight% or greater and less than 100 weight% and a specific surface area is 150,000 to 250,000 cm^2/g.

Description

Coating method of Silica Fume for High Strength Conctere

The present invention relates to a silica fume coating method for producing high strength concrete, and more particularly, to a silica fume coating method for producing high strength concrete treated with silica fume with a surface modifier so that silica fume can be evenly dispersed in concrete without aggregation.

Silica fume is an industrial by-product of ultra-fine particles obtained by collecting SiO ₂ contained in the waste gas generated when manufacturing silicon (Si), ferrosilicon (FeSi), silicon alloy, etc. with a dust collector, and is composed of very fine amorphous silica. Due to the peculiarities of the arrangement, it reacts very quickly when reacting with cement. In addition, since the particle size of the silica fume is about 1/25 of the cement particles, it has a microfiller effect of filling the pores of the cement hardened body by reducing the porosity by performing the pozzolanic reaction that combines with calcium hydroxide from the beginning of hydration. This enhances the strength of cement, concrete or mortar.

In addition, it also contributes to reducing permeability and air permeability, and since the particle shape of silica fume is spherical, dispersibility can be improved by a ball bearing effect.

Silica fume, which has so many advantages, is a very useful material for high strength concrete and mortar, and is widely used as a substitute for cement and concrete products, refractory materials, polymers and other asbestos.

In order to make concrete or mortar with high strength (about 600Kgf / cm2 or more), water-cement ratio of about 20% or less, the use of polycarboxylic acid-based high performance admixtures, and capillary fillers (pore filling) such as silica fume are generally used.

Among them, when producing high-strength concrete using silica fume, silica fume has a very large specific surface area (about 200,000 cm 2 / g), and when used in concrete production by mixing with water, a large amount of water is used. It is known to use about 15% of the cement weight. If a large amount of water is used, it is not very effective in increasing the strength, and when it is used at 5% or less, it is difficult to manufacture high-strength concrete due to the small gap filling effect.

In addition, such silica fume requires very careful use. Since their chemical properties are amorphous and have silanol groups on the surface, when they are easily reacted with alkali and mixed with cement, they rapidly form CSH (calsium-silicate-hydrate) gels, which not only improve initial strength but also increase reaction heat. As the amount of water used increases, the drying shrinkage also increases, increasing the frequency of cracking.

Despite these shortcomings, recent concrete techniques use silica fume for the practical application of high strength of more than 1,000kgf / ㎠ and there is an urgent need for appropriate countermeasures.

So far, to solve this drawback, as disclosed in Patent Publication Nos. 10-1991-9602 and 10-453631, a method of mixing with slag or fly ash, etc. has been selected, but the silica fume has a very high ratio. It still had defects such as lowering of initial strength because it easily aggregated by the surface area and the large amount of water required thereby.

Therefore, it is required to overcome the above problems. In other words, by modifying the surface of the silica fume, it is necessary to suppress the property of agglomeration of the silica fume by reducing the large specific surface area and the amount of water added thereto, and to produce high-strength concrete by uniformly dispersing the silica fume in the concrete without agglomeration of the silica fume.

In order to solve the above problems, an object of the present invention is to treat silica fume with a surface modifier so that silica fume is uniformly dispersed in concrete or mortar without aggregation.

More specifically, by modifying the surface of the silica fume, while reducing the amount of water used, the filling of the pores in the concrete can be well achieved to achieve high strength, and to suppress the aggregation reaction of water and silica fume.

An object of the present invention as described above is the step of preparing a silica fume, treating the surface of the silica fume with a surface modifier selected from the group consisting of silanes, fatty acids, amines and surfactants and the surface-treated silica fume It is achieved by a silica fume coating method for producing high-strength concrete, comprising the step of drying and aging.

In addition, the silica fume contains 70 wt% or more of SiO ₂ and preferably has a specific surface area of 150,000 to 250,000 cm 2 / g.

In addition, the said silane is represented by following General formula (I).

R ₁ Si (OR) ₃ Formula (I)

In the formula (I), R ₁ represents a C ₁ to C ₈ straight or branched alkyl group, an amine or an epoxy group, and R represents a C ₁ to C 5 straight or branched alkyl group.

Preferably, the silanes of formula (I) are isooctyl methoxy silane, n-octyl methoxy silane, butyl methoxy silane, trimethyl ethoxy silane, tri epoxy ethoxy silane, isooctyl ethoxy silane, n- Any one selected from the group consisting of octyl ethoxy silane, butyl ethoxy silane and oligomeric siloxane.

In addition, the fatty acid is preferably at least one selected from the group consisting of oleic acid, fatty acid including palmitic acid and salts thereof.

The surfactants are preferably at least one selected from the group consisting of nonyl phenyls and sorbitan.

In addition, the surface modifier is preferably diluted with a diluent.

In addition, the diluent is preferably any one selected from the group consisting of solvents, alcohols, ethyl acetate and thinners.

In addition, the concentration of the surface modifier is preferably 10 to 50% by weight relative to the total weight of the surface modifier and diluent.

In addition, the surface modifier is preferably used less than 5% by weight based on the weight of the silica fume.

Therefore, even though silica fume has a large specific surface area, in the present invention, since the surface of the silica fume is modified to be hydrophilic or hydrophobic, a large amount of water is not required as in the prior art. It can be well filled in voids such as concrete or mortar and is suitable for producing high strength concrete.

In addition, according to the present invention, the surface-modified silica fume evenly disperses the particles of silica fume in concrete or mortar without agglomeration, thereby rapidly and completely reacting with cement, and not only increases slump, which is a measure of workability, but also compression. The strength is also improved.

Hereinafter, a method of coating the surface of the silica fume for producing high strength concrete according to the present invention.

First, prepare silica fume. The silica fume used in the present invention has a specific surface area of about 150,000 cm 2 / g to about 250,000 cm 2 / g, preferably about 180,000 cm 2 / g to about 220,000 cm ₂ / g, and also has a SiO ₂ content of about 70% by weight or more, preferably Preferably about 80% by weight or more.

Such silica fume is a general specification of compressed or uncompressed silica fume generally used in concrete or mortar in Korea, and in the case of compressed silica fume, it is used to compress particles to an appropriate size to prevent scattering of fine dust.

Thereafter, a surface modification process is performed to modify the surface of the silica fume for producing high strength concrete. As the surface modification treatment agent, silanes, fatty acids, amines and surfactants can be selected.

As the surface modification treatment agent, when silanes are used, silanes represented by the general formula (I) as defined above are used. In the general formula (I), R 'is a C ₁ to C ₈ linear or branched alkyl group, amines, epoxy groups are mainly used, the degree of hydrophobicity is determined by the number of carbon in the case of the alkyl group, the larger the carbon number has a strong hydrophobicity. On the other hand, amines or epoxy groups have strong hydrophilicity because they have an OH group which is a hydrophilic group. In the above formula, R is a C ₁ to C ₈ linear or branched alkyl group.

The silanes of formula (I) suitable for the present invention satisfying the above formula are, for example, isooctyl methoxy silane, n-octyl methoxy silane, butyl methoxy silane, isooctyl ethoxy silane, n-octyl ethoxy Silane, butyl ethoxy silane, oligomeric siloxane, trimethyl ethoxy silane (hereinafter referred to as TMES) and tri epoxy ethoxy silane (hereinafter referred to as TEES). Among these silanes, it is more preferable to use TMES and TEES.

Using TMES can give hydrophobicity to those of TEES. When using them as surface modifiers of silanes, it is preferable to use less than 5% by weight based on the unit silica fume amount. If 5 wt% or more is used as the surface modifier with respect to the amount of silica fume, the slump worsens and the compressive strength after 28 days also deteriorates when the surface modified silica fume is used in concrete production. This is presumably because the surface-modified silica fume becomes poor in reactivity with alkali in cement.

When fatty acids are used as the surface modifier, oleic acid, palmitic acid, or the like may be used. Fatty acids can be hydrophobized by reaction with cement but are hydrophilic prior to mixing with cement.

In addition, when amines are used as the surface modifier, triethanol, diethanolamine, diethylamine, and the like may be used.

In addition, when using surfactants as surface modifiers, most surfactants, such as nonyl phenyl and sorbitan, can be used. In the case of surfactants, they are often hydrophilic in nature, and when lowering the interfacial tension of water, the amount of entrained air may increase when mixed with concrete or mortar. However, any one or more of these may be selected, but they must be confirmed that the mixture does not react with each other and may be treated several times with different materials. However, if handled several times, the price may rise.

In order to treat silica fume with the above surface modifier, a spray (spray) method or a dipping method can be used. When spraying a surface modifier onto a surface such as silica fume using a spraying method, economical reduction can be obtained, but it is difficult to uniformly modify the surface. When surface modification of silica fume using the surface immersion solution immersion method is expensive to dry and the loss of surface modifier occurs a lot, the appropriate treatment method should be selected according to the situation.

The silica fume surface treated by spraying or dipping can then be dried and aged to obtain suitable properties. When surface treatment is carried out by the spray method, it is dried at about 50 ° C to about 70 ° C, preferably at 60 ° C. Surface modifiers must be aged for at least one day to exhibit proper properties, and may behave differently if used before aging, so the results may differ from two days later. This is because the performance of surface modifiers such as silanes is expressed, because a certain time is required. That is, in the case of silanes, since the polymer reaction (molecular polymerization) of silane is slow, an appropriate aging time is required. However, fatty acids, amines and surfactants may be used immediately after drying.

The silica fume modified with the surface modifier has a characteristic that evenly disperses the particles and reacts with the cement quickly and completely, thereby reducing the amount of water used when used in concrete or mortar, as well as improving the compressive strength. Modified.

Preferably the surface modifier should be easy to dry. This is because silica fume is quantified by dry weight after treatment, and in order to make uniform concrete or mortar using an appropriate amount of use, it must be well dried.

To this end, surface modifiers can be used diluted with a diluent. As the diluent, solvents, alcohols, ethyl acetate, thinners, and the like may be used. However, in order to be harmful to the environment and the human body, it is preferable to use C ₁ to C ₅ alcohols. More preferably ethanol is used. It is very useful because it not only can dry quickly but also does not react with surface modifiers.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are only for illustrating the present invention in more detail, and the scope of the present invention is not limited by these examples in accordance with the gist of the present invention to those skilled in the art. Will be self-evident.

Example 1 Silica Fume Coating Method

A silica fume containing at least 70% by weight of SiO _{2 and} having a specific surface area of 150,000 to 250,000 cm 2 / g is prepared. As the surface modifier, at least one of silanes, fatty acids, amines and surfactants is used.

It is preferable to use less than 5% by weight of the surface modifier relative to the amount of silica fume. If more than 5% by weight of the silica fume is used as the surface modifier, the surface-modified silica fume becomes poor in reactivity with the alkali in the cement. Thus, when the surface-modified silica fume is used for concrete production, slump and 28 days The compressive strength characteristic afterwards falls.

Surface modifiers and silica fume are treated by spraying or dipping.

When using the spray method, the silica fume is placed in a container and sprayed with a surface modifier from the top while stirring in a 60 rpm stirrer through a sprayer.In the case of the dipping method, the silica fume is poured into a plastic container and then the surface modifier is poured to wet the surface with silica fume. Reform

After that, the silica fume is dried and aged for at least one day in a dryer at about 60 ° C. and then used for concrete production.

Example 2: Surface Modifier Preparation Method and Silkyfume Surface Coating Method

In the second embodiment of the present invention, by adding a diluent to the surface modifier used in the first embodiment, using a surface modifier to improve the drying characteristics, it provides a silica fume surface coating method for high-strength concrete surface-coated silica fume.

 Table 1 below shows the components and contents of the surface modifiers with improved drying properties.

Name and content of material Material name TMES TEES Fatty acids Amines Surfactants ethanol NO. One 30 0 0 0 0 70 NO. 2 0 30 0 0 0 70 NO. 3 0 0 10 0 0 90 NO. 4 0 0 0 30 0 70 NO. 5 0 0 0 0 10 90

Note: The above content is weight percent.

In Table 1, TMES and TEES, which are silanes, were used by Wacker, Germany, and ethanol was used and manufactured by Daesung Chemical in Korea. As amines, triethanol amine of LG Chem was used.

The surface modifiers are prepared by mixing 99 to 1% of surface modifiers such as TMES and TEES, fatty acids, amines, and surfactants in an alcohol weight of 1 to 99%. Preferred concentrations of the surface modifier are 10 to 50% by weight relative to the total weight of the surface modifier and diluent. If the concentration of the surface modifier exceeds 50% by weight, it is difficult to control the modified state of the surface, and if the concentration of the surface modifier is less than 10% by weight, an economical loss occurs in evaporation upon drying.

1 L of the surface modifier of Table 1 was prepared, and 25 kg of silica fume was treated by spraying or dipping. In the case of the spray method, the silica fume was put in a container, and treated by stirring and spraying in a 60 rpm stirrer through a sprayer. In the case of the dipping method, silica fume was soaked in a plastic container and subjected to surface modification.

Subsequently, the surface-modified silica fume was dried and aged for at least one day in a dryer at about 50 ° C. to secure appropriate properties, and then used in concrete or mortar to confirm its performance during the process to confirm the completion of the process.

Table 2 below shows, according to the present invention, silica fume surface treated with TMES surface modifier (NO. 1), silica fume surface treated with TEES surface modifier (NO. 2), silica fume surface treated with oleic acid surface modifier (NO. 3) ), Silica fume (NO. 4) surface-treated with triethanolamine surface modifier and silica fume (NO. 5) surface-treated with nonylphenyl (NP) surface modifier, compared with conventional silica fume (comparative example 1) without surface treatment Presented for the experiment.

Exam number Name of material Remarks cement sand Pebble water Silica fume Surface Modifier Treatment NO. One 27 30 30 10 3 ○ - NO. 2 27 39 30 10 3 ○ - NO. 3 27 30 30 10 3 ○ - NO. 4 27 39 30 10 3 ○ - NO. 5 27 30 30 10 3 ○ - Comparative Example 1 27 30 30 10 3 × -

Note: The above content is weight percent.

When the silica fume treated with the surface modifier of the present invention is used in concrete having the above components, in order to confirm the effect of the surface-modified silica fume, the physical properties before curing and the physical properties after curing are compared It was confirmed.

That is, by applying to concrete or mortar to confirm the dispersibility by observing the change of the slump, which is a physical property of the concrete or mortar in the solidified state, the physical properties after curing after producing a cylindrical mold of 10 × 20㎝, Cured for 28 days, the compressive strength was measured to confirm the performance improvement after curing.

Table 3 below shows the physical properties of silica fume treated with surface modifiers (NO. 1 to NO. 5) and those not treated with surface modifiers (Comparative Example 1).

Before hardening After curing division Slump (cm) Compressive strength (kgf / ㎠) 3 days 7 days 28 days NO. One 14 213 298 314 NO. 2 16 275 314 334 NO. 3 10 208 267 315 NO. 4 12 198 276 327 NO. 5 9 222 245 333 Comparative Example 1 8 212 256 298

(week)

One). NO 1 and 2 are measured according to KS L 5105-'97 after curing in water for 28 days using silica fume surface-treated with the surface modifier according to the present invention.

2). Comparative Example 1 was measured according to KS L 5105-'97 after using silica fume not treated with a surface modifier and curing in water for 28 days.

3). Shear compressive strength is measured according to KS L 1592-'97.

As shown in Table 3 above, as a result of surface treatment of the silica fume with the surface modifier according to the present invention, the surface-modified silica fume evenly disperses the particles in concrete or mortar, thereby quickly and completely reacting with the cement. In addition to increasing the slump, which is a measure of workability, the compressive strength was also measured higher than that of the conventional comparative example.

Therefore, when the surface-treated silica fume is used for the production of concrete, it was possible to obtain a higher strength concrete.

Claims (10)

Treating the surface of the silica fume with at least one surface modifier selected from the group consisting of silanes, fatty acids, amines and surfactants, and Drying and aging the surface-treated silica fume, The silica fume is a silica fume coating method for producing high strength concrete, characterized in that the content of SiO ₂ is 70% by weight or more and less than 100% by weight, and the specific surface area is 150,000 to 250,000cm 2 / g. delete The method of claim 1, wherein the silane is a silica fume coating method for producing high strength concrete, characterized in that the compound represented by the following formula (I): R ₁ Si (OR) ₃ Formula (I) Wherein R ₁ represents a C ₁ to C ₈ straight or branched alkyl group, an amine or an epoxy group, and R represents a C ₁ to C ₅ straight or branched alkyl group. The silanes according to claim 3, wherein the silanes of the formula (I) are isooctyl methoxy silane, n-octyl methoxy silane, butyl methoxy silane, trimethyl ethoxy silane, tri epoxy ethoxy silane, isooctyl ethoxy silane , n-octyl ethoxy silane, butyl ethoxy silane and oligomeric siloxane is at least one selected from the group consisting of silica fume coating method for producing high strength concrete. The method of claim 1, wherein the fatty acid is at least one selected from the group consisting of oleic acid, fatty acid including palmitic acid and salts thereof. The method of claim 1, wherein the surfactants are at least one selected from the group consisting of nonyl phenyls and sorbitan. 2. The method of claim 1, wherein the surface modifier is diluted with a diluent. 8. The method of claim 7, wherein the diluent is any one selected from the group consisting of solvents, alcohols, ethyl acetate, and thinners. The method of claim 7 or 8, wherein the concentration of the surface modifier is silica fume coating method for producing high strength concrete, characterized in that 10 to 50% by weight relative to the total weight of the surface modifier and diluent. The method of claim 1, wherein the surface modifier is used in an amount of more than 0 wt% and less than 5 wt% based on the weight of the silica fume.