FI84341B - Anticorrosive mixture for steam-hardened porous concrete - Google Patents

Description

1 84341

The present invention relates to an anti-corrosion composition for steam-hardened aerated concrete. The mixture is specifically intended for use in protecting reinforcing bars in concrete. More specifically, the mixture is intended for use in protecting reinforcing bars in autoclaved lightweight concrete. The term "lightweight concrete" includes 10 aerated concrete, i. aerated concrete, which is made by adding a gas-generating substance, such as aluminum powder, to the aerated concrete mix so that it expands after pouring, and so-called foamed concrete, i.e. aerated concrete obtained by foaming the raw material mixture before pouring it. The invention relates in particular to a mixture for reinforcing steel bars in autoclaved lightweight concrete. This type of lightweight concrete generally has a density of 0.4 to 1.2 g / cm 3. The invention also relates to a method for producing steam-hardened concrete.

20

Autoclaved aerated concrete is prepared by mixing siliceous and calcareous raw materials with water, adding aluminum powder and other additives to the resulting mixture to form a slurry, or the like, and finally by hardening the cut concrete with steam using an auto-30 clave.

The autoclaved aerated concrete thus produced is a building material which is light and has superior thermal insulation and strength properties. However, it has the disadvantage that it is porous, which pores correspond to about 80% of its volume and pass moisture and corrosive substances through the autoclaved aerated concrete 2 84341 so that the reinforcing steel bars corrode.

To prevent corrosion, it has been customary to attach a suitable anti-corrosion compound to the reinforcing steel bars. Conventional 5 corrosion inhibitors are divided into three groups. (1) To the group in which cement is the main component, (2) to the group in which asphalt is the main component, (3) to the group in which the main component is resin emulsion or latex.

The first group of anti-corrosion compound is most widely used because it is inexpensive, adheres well to both autoclaved aerated concrete and steel bars (hereinafter referred to as "bonding" for simplicity) and has a moderately satisfactory anti-corrosion effect. On the other hand, it has some drawbacks. For example, its service life is limited; it is affected by variations in cement quality; it allows water to pass through; it forms a corrosion-resistant coating with poor flexibility; and it is difficult to attach to reinforcement bars 20 less than 5 mm in diameter used in thin plates made of autoclaved aerated concrete because of its poor flexibility. The anti-corrosion compositions of the second group generally eliminate the disadvantages of the compositions of the first group. However, it is still a bad commitment in terms of commitment.

The third group of anti-corrosion compound has the advantage that it has a long service life and its quality is stable. However, it varies greatly in terms of flexibility, binding and anti-corrosion effect depending on the type of emulsion or latex and the mixing ratio between the emulsion or latex and other additives. According to the information provided so far, the third group of anti-corrosion composition consists of synthetic rubber, thermo-35 plastic resin or thermosetting resin and inorganic powder; rubber latex, silicon powder and quicklime; or styrene-butadiene 3,834,31 from an ethylene rubber latex and an inorganic substance such as kaolin and slaked lime. This anti-corrosion mixture has the following disadvantages. It is more expensive than conventional mixtures with cement, although it provides a thinner anti-corrosion coating due to its relatively high resin or latex content. It does not always bind well enough and its flexibility is not always sufficient and another disadvantage is that cracks form in the relatively thicker coating part. For this reason, it is difficult to attach this special anti-corrosion composition in general to both reinforcing steel bars thicker than 5 mm for thick plates and steel bars or nets 15 to 3 mm thick for thin plates, because In general, the thicker the bars, the thicker the coating can be.

In addition to the three groups of anti-corrosion compositions described above, there are many known anti-corrosion compositions which contain a resin emulsion or latex and cement as the main component. Cement used with resin emulsion or latex inevitably shortens the service life. On the other hand, a method of forming an anti-corrosion coating by providing two different types of anti-corrosion coatings on top of each other has been provided, but this method has the disadvantage that it becomes complicated.

It is therefore an object of the present invention to provide an anti-corrosion composition for reinforcing steel bars in autoclaved aerated concrete which does not have the above-mentioned drawbacks.

The core of the present invention is an anti-corrosion composition for reinforcing bars in autoclaved concrete, comprising (a) a component having a mixture of 5 to 25% by weight (dry weight) of one or more types of styrene resin aqueous emulsion or latex; -15% by weight (dry weight) of an aqueous emulsion of asphalt, and (b) a component of a mixture of 60 to 90% by weight of at least one type of inorganic powder selected from 5 groups: flint, quartz sand, granite, andesite, slate ash, kaolin , feldspar, talc, mica, fly ash, slag, iron oxide and graphite.

The inorganic powder may also contain 1-10% by weight of 10 limestone powder.

Although this invention relates in particular to the formation of an anti-corrosion protective layer on reinforcing bars for autoclaved aerated concrete, it has also proven to be generally useful for protecting steel and iron surfaces from corrosion. It is therefore an object of the invention to provide a corrosion inhibitor composition for such surfaces.

One raw material of the anti-corrosion composition of this invention is an aqueous emulsion or latex of a styrene resin. Examples of styrene resins include polystyrene, styrene-butadiene, styrene-acrylonitrile resin, styrene rubber, polybutadiene-styrene and acrylonitrile-butadiene-styrene resin.

Another raw material is an aqueous emulsion of asphalt, which is commercially available. The two emulsions are used together to form one component.

The mixture ratio is 5-25% by weight (dry weight) for an aqueous emulsion of styrene resin and 5-15% by weight (dry weight) for an aqueous emulsion of asphalt. When the proportion of the aqueous emulsion of styrene resin is less than 5% by weight, the anti-corrosion effect of the obtained anti-corrosion mixture is very poor; when the proportion of the aqueous emulsion of the styrene resin is more than 25% by weight, an anti-corrosion mixture is obtained in terms of poor bonding and also anti-corrosion effect.

When the amount of asphalt emulsion in a similar manner is less than 5 pa ± no-% (based on solids), a corrosion-5 anti-corrosion composition is obtained with poor corrosion inhibitory effect, and when the asphalt emulsion amount is more than 15% by weight (solids), a corrosion anti-corrosion mixture is obtained.

10 When the amount of the inorganic powder is less than 60% by weight, a corrosion inhibitor composition is obtained with poor bonding, and when the amount of the inorganic powder is more than 90% by weight, a corrosion inhibitor composition is obtained with respect to the poor corrosion inhibitory effect.

15

The amount of inorganic powder is not explicitly limited as long as it is mainly stable during autoclave treatment. Inorganic powders are at least one type of inorganic powder selected from the group consisting of flint, quartz sand, granite, andesite, slate ash, kaolin, feldspar, talc, mica, fly ash, slag, iron oxide and graphite. The inorganic powder may also contain limestone powder.

If 1-10% by weight of limestone powder is mixed with the inorganic powder, the formed anti-corrosion composition provides a coating having a uniform surface and thickness, which prevents the inorganic powder from separating and forming pores and therefore enhances the anti-corrosion effect.

If the amount of limestone powder is less than 1% by weight, no effect is produced and if it is more than 10% by weight, the anti-corrosion effect of the obtained anti-corrosion mixture is poor.

In addition, when a small amount of the commonly used inorganic or organic compound is mixed with the inorganic powder: 35 6 84341 inhibitor improves the anti-corrosion effect of the obtained corrosion inhibitor.

The anti-corrosion compound of this invention for reinforcing steel bars can be used in its original form or to a suitable consistency after dilution with water. Reinforcing steel bars (2 mm or 5.5 mm in diameter) are immersed in a slurry anti-corrosion mixture, after which they are dried. Repeating this step 10 twice provides a coating with a mean thickness of about 200. The coating does not crack when the coated rod is bent at an angle of 45 °.

The bonding and corrosion-preventing effect of the treated reinforcing steel bars is good. The test was carried out as follows: The treated steel bars are placed in a mold, the raw mixture suitable for autoclaved aerated concrete is poured into a mold and is allowed to become semi-plastic. After the autoclave treatment has been carried out, the aerated concrete is cut so that the steel bars are included. Binding is measured by the ejection method and the anti-corrosion effect is investigated according to JIS A 5416.

The binding in this test was 20-26 kg / m2, which is significantly higher than the desired value of 15 kg / cm2 and the rust surface (corrosion protection) was 0.1-1.0%, which is much less than the maximum permissible value of 5% 5416.

30

The invention is explained in more detail below with reference to the following examples.

35 Example 1

Five types of anti-corrosion alloy were prepared by mixing the ingredients together for 30 minutes according to the following configurations: (a) 3-25% by weight (dry weight) of high molecular weight styrene SBR ("Croslene SPX-1"), Takeda Chemical Industries Co., 5 Ltd) an aqueous latex containing 70% by weight of polymerized styrene in the solids and 45% by weight of the solids in the latex.

(b) 3-20% by weight (dry weight) of an aqueous asphalt emulsion ("Flintkote No. 5", 10 product of Shell Petrochemical Co., Ltd.) containing 55% solids.

(c) 70-80% by weight of silicon powder manufactured by Tokai Kogyo Co., Ltd.

(d) 0.5% by weight of a dispersant ("Mighty 150R", a product of Kao Co., Ltd.).

15 (e) 0.1% by weight of antifoam ("Anti-Froth", Daiichi

Product of Kogyo Seiyaku Co., Ltd.).

(f) 10% by weight of additional water, calculated on the solids content.

(g) slaked lime powder (reagent grade, grade 1) sufficiently so that the pH of the slurry becomes 12.5.

Reinforcing steel bars with a diameter of 5.5 m were immersed in the anti-corrosion mixture prepared in this way, after which they were dried with hot air at a temperature of 80 ° C. The immersion and drying operations were repeated. Thus, an anti-corrosion coating with a mean thickness of 200 was formed on the reinforcing steel bars.

After the coated reinforcing steel bars were attached to the mold, autoclaved aerated concrete having a density of 0.5 to 30 kg / cm 3 was prepared in a conventional manner.

A specimen measuring 4x4x16 cm was cut from the autoclave-treated aerated concrete so that the reinforcing bar was located in the center of the cross-section and was parallel to the length of the prismatic specimen. This test cap

the palette was examined for binding by the ejection method and for anti-corrosion effect by JIS

s 84341 A 5416.

The anti-corrosion mixture was also tested for service life by storing it in two ways for 1 month to 5 months, i.e. the anti-corrosion mixture was allowed to be in a sealed container and was also stored by partially regenerating by removing 10% of the stored mixture and adding 10% fresh anti-corrosion mixture every day. After storage for a certain period of time, the change in viscosity, gelation and sediment feeding were examined. The stored anti-corrosion mixture was tested for bonding and anti-corrosion effect by preparing test specimens from reinforced autoclave-treated aerated concrete.

15 The coated reinforcing steel bars, which are not embedded in the concrete mass, were also cured in an autoclave, after which they were bent to 45 ° to detect any cracking.

20

The results are shown in Table 1, where they are compared with comparative examples.

Notes to the table.

25 Shelf life: O: No change after storage for 1 month or more or only slight sedimentation occurs, which decomposes easily on mixing.

Δ: Gelling occurs after 10-30 days of storage or sediment-35 habituation occurs, which cannot be broken down by mixing.

9 84341: Jelly is present after storage for less than 10 days or dimentation occurs which does not decompose on mixing.

5

Flexibility: Q: When the bar is bent at an angle of 45 °, there is no cracking.

10 X: When the bar is bent at an angle of 45 °, cracking occurs.

Binding (the value is obtained by dividing the maximum load-15 dimension during extrusion by the cross-section of the reinforcing bar).

: greater than 20 kg / cm2 Δ: 15-20 kg / cm2 20: less than 15 kg / cm2

Corrosion protection: (o): Less than 0.5% rusted surface.

25 Q: Rusted surface less than 2.0%.

^: Rusted surface more than 2.0%.

Based on Table 1, it can be stated that good results are obtained in all the experiments of Example 1 and the experimental results in the 30 comparative examples were found to be unsatisfactory for almost all the requirements.

ίο 8 4 341

Example 2:

The anti-corrosion mixture was prepared in the same manner as in Example 1 except that the amount of aqueous latex and asphalt emulsion was changed and the flint powder was replaced with kaolin powder as follows: (a) 15% by weight (dry weight) of a mixed aqueous latex consisting of solid) from an aqueous latex of SBR resin (50% by weight solids) containing 50% by weight of polymerized styrene.

(b) 10% by weight (dry weight) of an aqueous asphalt emulsion.

(c) 75% by weight of kaolin powder (reagent grade, class 1).

The obtained anti-corrosion mixture was tested for its effects in the same manner as in Example 1 by coating reinforcing steel bars with a diameter of 2 mm.

The coating results were good and met all the requirements.

25

Example 3:

Four anti-corrosion alloys were prepared in the same manner as in Example 1 with the following exceptions.

(a) 5-40% by weight (dry weight) of a mixed aqueous emulsion consisting of a styrene acrylonitrile emulsion, a polystyrene emulsion, and an asphalt emulsion in a weight ratio of 1: 1: 1 (dry weight).

35 (b) The remainder of the solid is flint powder.

(c) No pH adjusting agent is added.

11 84341

The obtained anti-corrosion mixture was tested for its bonding and anti-corrosion effect in the same manner as in Example 1. The results are shown in Table 2.

5 On the basis of Table 2, it can be stated that the upper limit of flint powder is 90% by weight and the best results are obtained at a level of about 80% by weight.

10 Example 4:

Five anti-corrosion alloys were prepared in the same manner as in Example 1 with the following exceptions.

(a) 20% of an emulsion mixture having the same composition as in Example 3.

(b) The inorganic substance is limestone powder and fine feldspar powder.

The obtained anti-corrosion mixture was tested for bonding and anti-corrosion effect in the same manner as in Example 1, except that the coating thickness was 150. The results are shown in Table 3.

Based on Table 3, it can be seen that an appropriate amount of limestone powder as part of the inorganic powder enhanced the anti-corrosion effect. However, an excessive amount of lime-stones produces the opposite result, as in experiment no. 5.

As discussed above, the anti-corrosion composition of the present invention has many advantages. It can be attached to reinforcing steel bars of any size. It gives a sufficient anti-corrosion effect with a coating thickness of 150 to 200. It has a long service life. It does not .35 cause any safety or health problems as it does not contain unhealthy organic solvents. It is cheaper than conventional mixtures.

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Claims (6)

14 84341 1- Anti-corrosion mixture for reinforced steam-hardened gas-5 concrete, characterized in that it comprises (a) a mixture of 5-25% by weight (dry weight) of one or more types of aqueous emulsions or aqueous latexes of styrene resin and 5-15% by weight (dry weight) asphalt aqueous emulsion and (b) 60-90% by weight of at least one type of inorganic powder selected from the group: flint, quartz sand, granite, andesite, slate ash, kaolin, feldspar, talc, mica, fly ash, slag, iron oxide and graphite, wherein the inorganic powder optionally contains 1-10% by weight of limestone powder. Corrosion inhibitor mixture according to Claim 1, characterized in that the aqueous latex of the styrene resin is a mixture of the aqueous latex of the polystyrene resin and the aqueous latex of the styrene-butadiene resin. Corrosion inhibitor mixture according to Claim 1, characterized in that the aqueous latex of the styrene resin is an aqueous latex of high molecular weight styrene SBR containing 65 to 75% by weight of styrene or an aqueous latex of styrene butadiene which has been modified and cured with an unsaturated carboxylate. . 4. A method of making reinforced steam-hardened aerated concrete comprising preparing an aqueous expandable and solidifiable slurry having one or more hydraulic binders and one or more siliceous materials, introducing reinforcing steel bars into a mold, pouring the slurry into this mold, casting into a molded part. expansion and solidification, possible cutting of the solidified body into smaller pieces and evaporation of the cast body or pieces, the reinforcing steel bars being treated with a corrosion-resistant composition, characterized in that the mixture comprises (a) a mixture of 5-25% by weight (dry weight); ) one or more types of aqueous emulsions or aqueous latexes of styrene resin and 5-15% by weight (dry weight) of an aqueous emulsion of asphalt and (b) 60-90% by weight of at least one type of inorganic powder selected from the group: flint, quartz sand, granite, andesite, shale ash, kaolin, feldspar, talc, mica, fly ash, slag, iron oxide and graphite, wherein the inorganic powder optionally contains 1-10% by weight of limestone powder. Process according to Claim 4, characterized in that the aqueous latex of the styrene resin is a mixture of the aqueous latex of the polystyrene resin and the aqueous latex of the styrene-butadiene resin. Process according to Claim 4, characterized in that the aqueous latex of the styrene resin is an aqueous latex of high molecular weight styrene SBR containing 65 to 75% by weight of styrene or an aqueous latex of styrene-butadiene which has been modified and cured with an unsaturated carboxylic acid . : 30 i6 8 4341