JPS582191B2 - Rust-preventing film forming agent for reinforcing reinforcing bars for lightweight cellular concrete - Google Patents

Description

[Detailed Description of the Invention] Generally, lightweight cellular concrete is made by mixing water in an appropriate ratio with crushed calcareous substances such as cement and lime, and silicic substances such as silica sand and silica stone, and adding aluminum powder, etc. to this mixture. It is manufactured by adding air bubbles by adding metal powder and stirring or mixing air, solidifying and hardening, and causing a hydrothermal reaction by curing in high-temperature, high-pressure steam in an autoclave. .

In order to use this lightweight aerated concrete as a building material, reinforcing steel bars are embedded within it.

If the reinforcing reinforcing bars were buried in the raw material, the lightweight cellular concrete would have a high porosity and low basicity, so the reinforcing bars would corrode due to moisture in the air, reducing the strength of the concrete panel. It is common practice to form a rust-preventive coating on reinforcing bars in advance.

Conventionally, methods for forming this anti-rust coating include casein,
A mixture of a colloidal binder such as gelatin or a cellulose compound, cement, one of rubber latex, ethylene-vinyl acetate copolymer resin emulsion, vinyl acetate-acrylic copolymer resin emulsion, or acrylic resin emulsion, and water. A method of forming a rust-preventing film using the above method is known.

In order to uniformly form these anti-rust coatings on the surface of reinforcing reinforcing bars for lightweight aerated concrete, these mixtures are kept in the form of a viscous slurry and then sprayed, brushed or dipped, and then dried. This is done by doing this.

Therefore, in order to apply the formation of a rust preventive film as a step in the production of lightweight cellular concrete, it is necessary to maintain the slurry viscosity of the rust preventive film forming agent at an appropriate level for a long period of time without condensation.

Conventional rust inhibitors for cement-synthetic resin emulsion mixtures contain starch, cellulose, sugar, calcium gluconate, iron gluconate, glucose, etc. as coagulation inhibitors to suppress cement coagulation and maintain appropriate viscosity. However, starch and cellulose have little effect on suppressing aggregation and are only effective for a few hours, so if they are used in large amounts, the strength of the film formed becomes weaker, and sugar and other gluconic acids have a Although there was an effect of inhibiting coagulation for one week, it was not enough time and was unsatisfactory.

Furthermore, sodium boroheptonate described in JP-A No. 52-40446 has a short coagulation inhibition time of about 2.5 weeks when not used in combination with sugars, and even when used in combination with sugars, it takes a long time for pseudo-coagulation to occur immediately after mixing. However, there were disadvantages such as long drying time, long drying and curing times, and insufficient film strength.

In order to correct the above-mentioned drawbacks, the inventors conducted various tests and found that the setting suppression time could be maintained for approximately one month, and the strength of the coating was 20 kg per 1 cm2 of surface area of the reinforcing bars, which is the adhesion strength between the lightweight cellular concrete anticorrosive film and the reinforcing bars. The present invention was achieved by discovering the combination of sodium heptonate and sugar as an additive that maintains the above strength.

That is, the present invention provides cement, an ethylene-vinyl acetate copolymer resin emulsion or a vinyl acetate-acrylic acid ester copolymer resin emulsion having a resin content of 1 to 55% by weight based on the cement, and 0.1-20% by weight of hydroxyethylcellulose or ethylhydroxyethylcellulose, 0.1-0.5% by weight of sodium heptonate, 0.1-0.5% by weight of sugar, and water. The mixed slurry liquid is used as a rust-preventing film forming agent for reinforcing reinforcing bars for lightweight cellular concrete.

If the resin content of the ethylene-vinyl acetate copolymer resin emulsion or the vinyl acetate-acrylic acid ester copolymer resin emulsion is as low as 1% by weight or less based on the cement, the dried and solidified coating will have many pores, making it difficult for reinforcing steel. The adhesion force also decreases, and its performance as a rust-preventing film disappears.If the resin content exceeds 55% by weight, the ability to passivate the reinforcing steel surface due to cement hydrate decreases, and the adhesion force to concrete decreases. descend.

The addition of hydroxyethylcellulose or ethylhydroxyethylcellulose has the effect of protecting the uniform dispersion of the synthetic resin emulsion in the mixed slurry and prolonging the usable shelf life, and the addition amount is 0.0% relative to the cement.
If it is less than 1% by weight, hydration of the cement in the anticorrosive film forming agent tends to proceed, shortening the usable time.
．． If the amount exceeds 0% by weight, the anticorrosion film forming agent becomes too sticky and it becomes difficult to maintain the required thickness of the film.

Sodium heptonate, which is added as a setting inhibitor, is highly effective in inhibiting the setting of film-forming agents.
．． It is effective in combination with 1 to 0.5% by weight.

Addition amount of sodium heptonate is 0.1 to cement
If it is less than 0.5% by weight, the viscosity of the slurry will increase in a short period of time and it will harden. If it is added in an amount greater than 0.5% by weight, the viscosity of the slurry will drop too much and it will be difficult to obtain a suitably homogeneous film.

One way to prevent a drop in slurry viscosity is to adjust the amount of water used, but if the amount of water is reduced, it will be sensitive to other external factors, such as fluctuations in cement activity.
It becomes difficult to control the viscosity and has a negative effect on pot life.

Immersing the reinforcing steel in the antirust film forming agent according to the present invention, or
Alternatively, after brushing and drying, a film of appropriate thickness is formed on the surface of the reinforcing bars.

To prevent collapse due to external forces, drying of the film formation stage is performed with hot air at room temperature to about 80°C to harden the film.
Attach to reinforcing steel.

The coated reinforcing bars are then set in a concrete molding form, and a slurry containing raw materials for producing lightweight cellular concrete is poured into the concrete, followed by foaming, curing, and molding.

After that, this was heated in an autoclave to 4 to 12 cm/cm2.
Lightweight aerated concrete with reinforcing reinforcing bars is obtained by curing with high temperature and high pressure steam.

Examples of the present invention will be described below.

The ethylene-vinyl acetate copolymer resin emulsion and vinyl acetate-acrylic acid ester copolymer resin emulsion used in each example were commercial products Sumikaflex (manufactured by Sumitomo Chemical Co., Ltd.) and Wallpol (manufactured by Dainippon Ink & Chemicals Co., Ltd.), respectively. Co., Ltd.), and sodium heptonate and sodium boroheptonate were manufactured by Croda Chemical Co., Ltd. and were in the form of aqueous solutions with pure content of 50% by weight and 45% by weight, respectively.

The ratio of ethylene to vinyl acetate in this ethylene-vinyl acetate copolymer resin emulsion is 2:8 to 8:2, and the ratio of vinyl acetate to acrylate in the vinyl acetate-acrylic ester copolymer resin emulsion is 2:8 to 8:2. It is from 85:15 to 80:20.

Example 1 Boltland cement 100 parts by weight Ethylene-vinyl acetate copolymer resin 10 parts by weight Emulsion (resin content 55% by weight) Hydroxyethyl cellulose 0.4 parts by weight Sodium heptonate (purity) 0.1 parts by weight Sugar
0.1 parts by weight water
30 parts by weight of the above substances were mixed to prepare a viscous slurry film forming agent solution.

This slurry could be stored for a long time to form a good film on the surface of the reinforcing bars, that is, the usable time was about 4 weeks.

Reinforcing bars were immersed in this slurry, pulled out and dried to form a film on the surface of the reinforcing bars.

The adhesion strength of this film was as strong as 28 kg/cm2.

After the coating was formed, it was placed in a formwork, and a slurry-like lightweight cellular concrete raw material mixture was poured into it, foam-molded, and then heated at 185°C in an autoclave at 11.5 kg/c.
As a result of a weather resistance test on the concrete that had been cured with steam for 5 hours, it was found that the anti-corrosion performance was extremely good, and as a result of observing the occurrence of rust on the reinforcing bars embedded in the concrete, almost no rust appeared. I hadn't.

Example 2 Boltland cement 100 parts by weight Ethylene-vinyl acetate copolymer resin 5 parts by weight Emulsion (resin content 55% by weight) Hydroxyethyl cellulose 0.4 parts by weight Sodium heptonate (pure content) 0.5 parts by weight Sand
Sugar 0.5 parts by weight Water
The usable period of the mixed solution of 35 parts by weight of the above substances was extremely long, about 5 weeks, and the adhesion strength of the film was as good as 22 kg/cm 2 .

Example 3 Boltland cement 100 parts by weight Vinyl acetate-acrylic acid ester copolymer resin emulsion (
Resin content 55 parts by weight > 5 parts by weight Hydroxyethyl cellulose 0.4 parts by weight Sodium heptonate (pure part) 0.3 parts by weight Sugar
0.3 parts by weight water
35 parts by weight The usable period of the mixed solution of the above substances is approximately 5 weeks, and the adhesion strength of the film is 25 kg/cm.
2, which was good.

Example 4 Boltland cement 100 parts by weight Vinyl acetate-acrylic acid ester copolymer resin emulsion (resin content 55% by weight) 20 parts by weight Ethyl hydroxyethyl cellulose 0.4 parts by weight Sodium heptonate 0.4 parts by weight Sugar
0.4 parts by weight water
25 parts by weight The usable period of the mixed solution of the above substances is approximately 5 weeks, and the adhesion strength of the coating is 27 kg/kg.
cm2, which was good.

Comparison 1 Boltland cement 100 parts by weight Ethylene-vinyl acetate copolymer resin 5 parts by weight Emulsion (resin content 55% by weight) Hydroxyethyl cellulose 0.4 parts by weight Sodium heptonate (purity) 0.05 parts by weight Sand
Sugar 0.1 parts by weight Water
35 parts by weight Sodium heptonate in the mixed solution of the above substances was unstable and the usable period was only about two weeks.

Comparison 2 Boltland cement 100 parts by weight Ethylene-vinyl acetate copolymer resin 5 parts by weight Emulsion (resin content 55% by weight) Hydroxyethyl cellulose 0.4 parts by weight Sodium heptonate (purity) 0.5 parts by weight Water
35 parts by weight The mixed solution of the above substances did not contain sugar, and the usable period was a little long at about 3 weeks, but it was not sufficient.

Comparison 3 Boltland cement 100 parts by weight Ethylene-vinyl acetate copolymer resin 5 parts by weight Emulsion (resin content 55% by weight) Hydroxyethyl cellulose 0.4 parts by weight Sodium boroheptonate (pure content) 0.3 parts by weight Sand
Sugar 0.3 parts by weight Water
35 parts by weight Sodium boroheptonate is used as the mixed solution of the above substances, and it can be used for a long time of about 5 weeks. The adhesion strength of the film was 16 kg/cm2, which was insufficient.

Note: The adhesion strength measurement method is based on the research report of the ALC study group (1937).
According to the "Adhesion Strength Measurement Method" published in March 2013).

Claims (1)

[Claims] 1 Cement and a pair of cement have a resin content of 1 to 1
55% by weight of ethylene-vinyl acetate copolymer resin emulsion or vinyl acetate-acrylic acid ester copolymer resin emulsion, and 0.1 to 20% by weight of hydroxyethylcellulose or ethylhydroxyethylcellulose, also calculated based on the cement. , also 0.1
~0. A rust-preventing coating forming agent for reinforcing reinforcing bars for lightweight cellular concrete, which is made of a slurry mixture of 5% by weight of sodium heptonate, 0.1 to 0.5% by weight of sugar, and water.