JPH0712985B2 - Neutral resistant concrete structure - Google Patents

Description

TECHNICAL FIELD The present invention relates to a cement concrete or cement mortar structure (hereinafter referred to as a concrete structure) having excellent resistance to neutralization. More specifically, "Free calcium hydroxide and calcium silicate generated in the cement hardening process are caused by reacting with acidic water and acidic rain generated in the presence of an appropriate amount of water and acidic water, and the surface of the hardened cement The present invention relates to a concrete structure resistant to the neutralization reaction that progresses from.

It is generally understood that the neutralization reaction is a phenomenon in which a concrete structure chemically reacts with carbon dioxide gas in the air to gradually carbonate. With the neutralization reaction, concrete structures not only change the physical properties, but also fundamentally change the chemical properties. This phenomenon gradually progresses from the surface of the concrete structure and the portion near the surface of the capillary void.

Recently, the concentration of acidic gases such as carbon dioxide gas, sulfurous acid gas, nitrous acid gas and acidic mists such as sulfuric acid mist and nitric acid mist has been increasing as acid rain along with the consumption of coal, oil and city gas. When these acid gases and mist increase in the air and become mixed with the moisture in the air or the residual moisture in the concrete structure and come into contact with the surface of the concrete structure or the surface of the inside of the capillary, the free gas existing in the concrete structure is released. Calcium hydroxide or calcium silicate chemically reacts with the acidic water to cause so-called neutralization of concrete.

When the concrete becomes neutral, it causes volume expansion and dissolution of cement, which lowers the strength of the concrete, causes deterioration of the strength over time, and causes crevices. cause. With the progress of neutralization, the hardening reaction due to the hydration reaction is interrupted, and the initial strength does not appear.

The pH of concrete decreases, the neutralized part becomes brittle, and stress concentration occurs.

When the surface of the capillaries inside the concrete is neutralized, the pH around the steel frame decreases and rust develops on the steel frame.

When the steel frame rusts, that part causes system expansion, causing crevices in the concrete.

(Prior Art) Conventionally, the following four methods have been roughly classified as methods for secondarily preventing neutralization by kneading or coating concrete.

Lattex kneading method Acrylic ester-based latex, styrene / butadiene-based latex, ethylene / vinyl acetate-based latex is kneaded with cement to obtain a concrete structure Latex curing method Acrylic ester-based latex, styrene / butadiene-based latex, ethylene / Vinyl acetate-based latex,
A method to prevent the excessive evaporation of water by applying a diluted liquid of vinylidene chloride-based latex before the concrete surface is dried. Inorganic coating method An aqueous dispersion of colloidal silica (also called silica sol or water glass) is applied to the concrete surface. Method of water repellent treatment Method of applying water or organic solvent dispersion of silicone resin or fluorine resin to concrete surface.

In both cases, a protective layer is provided inside or on the concrete surface to prevent moisture in the atmosphere from entering the concrete surface or the inner surface of the capillary, condensing, and permeating acidic gas or mist. So there are some difficulties and drawbacks.

Lattex kneading method Acrylic ester-based latices, styrene / butadiene-based latices, ethylene / vinyl acetate-based latices themselves, which are commonly used binders, have low barrier properties against oxygen gas or water vapor, and condense water inside concrete or acid water. It is difficult to prevent generation. It has been reported that "Polymer Cement" (published by CMC in February 1984) improves the resistance to carbonation of concrete due to the effect of the binder contained on CO ₂ infiltration. Since it is virtually impossible to eliminate all of them, the effect of preventing neutralization is insufficient, and the effect is not expressed unless a large amount of binder of 20% by weight or more is kneaded, and the cost increases. Atsuta

Latex curing method Since the diluted latex is applied before the concrete surface dries, a discontinuous film is formed on the concrete surface with the latex blocked. If a continuous film without voids was not formed, the acid gas and water would permeate freely, which was not effective in preventing the neutralization of concrete.

Inorganic paint method When water glass is dried, it forms a continuous film by sintering, but the film has a large number of microporous capillaries and water or acid mist does not enter, but acid gas and water vapor can enter freely. It has a drawback that it allows the permeation of acid gas and water vapor into the concrete to generate acid water.

Water-repellent treatment method The application of a water-repellent substance can prevent the adhesion of acidic mist and water to the concrete surface, but it also has drawbacks such as inability to prevent the intrusion of acidic gas and water vapor, which have poor durability.

(Problems to be solved by the invention) For many years, a neutralization-resistant concrete structure having a structure capable of substantially preventing adhesion or infiltration of acidic water on the surface or inside of concrete, permeation of acidic gas or water vapor, and condensation of acidic water It was requested over.

(Means for Solving Problems) An essential requirement for a neutralized concrete structure is that the concrete structure has a coating film that substantially blocks permeation of acid gas and water vapor.

The coating film has a continuous coating structure that does not substantially have capillary-like communication holes.

Do not generate enough acidic water for neutralization on the concrete surface and inside.

The coating should adhere to the concrete surface.

The coating should not discolor due to sunlight.

The coating film is tough.

The coating film is flame retardant. Etc. were requested.

In order to satisfy these requirements, the inventors of the present invention have earnestly studied and as a result, permeation of acidic gas and water vapor into the concrete surface or inside, production of acidic water, adhesion of acidic water, and other requirements for substantially blocking infiltration. In order to satisfy the performance, it has been found that the application of a polymer coating with a specific composition is effective for the neutralized concrete structure.

It is known that a copolymer containing vinylidene chloride and vinyl chloride as main components is a barrier resin for gas such as steam and carbon dioxide. It is also known to prevent carbon dioxide and water from entering and contacting the concrete as a measure for neutralizing the concrete.

The present invention is to provide a neutralized concrete structure in which a copolymer having a specific composition containing vinylidene chloride as a main component and a coating film of the composition have particularly excellent performance.

The organic polymer composition used in the present invention means vinylidene chloride (A) 50 to 90%, monomer component (B) 10 to 15% by weight of (A) copolymerizable weatherability and flexibility controllability.
And a composition containing, as a main component, a synthetic polymer composed of 0 to 3% by weight of an adhesiveness imparting monomer component (C) copolymerizable with the monomer component (A) and / or (B). Additives such as commonly used polymer thickeners, polymer cross-linking agents, organic or inorganic colorants, ultraviolet absorbers, plasticizers and the like can be used in combination as auxiliary components. For aqueous dispersions, as a polymer thickening agent, it is described in “New Augmented Water-Soluble Polymer” by Chemical Industry Co., Ltd., April 1984, edited by Yukio Nakamura. Polyvinyl alcohol, sodium polyacrylate, polyacrylamide, polyethylene oxide. , Carboxymethyl cellulose, methyl cellulose, sodium polyalginate and the like.

As a polymer cross-linking agent, Shinzo Yamashita, Tosuke Kaneko, "Crosslinking Handbook," edited by Taisei Co., Ltd., October 56 edition, is described in Crosslinking of paints and crosslinks of adhesives. Examples include water-soluble phenol, melamine, urea, resorcinol resin , Water-dispersed raw polyurethane, epoxy, unsaturated polyester and the like. Additives such as organic or inorganic colorants, ultraviolet absorbers, plasticizers, flame retardants and the like are preferably mixed as an aqueous dispersion. Acrylate ester-based latex, natural rubber and synthetic rubber latex, ethylene-
Vinyl acetate, ethylene-vinyl chloride, ethylene-vinyl chloride-vinyl acetate-based latex may be used in combination as an extender, but in order to prevent the barrier properties from being substantially reduced, a subcomponent and / or an extender is the main component. It is better not to exceed 50% by weight with respect to 50% by weight.

The above-mentioned subcomponents and extenders can be similarly used in the organic solvent dispersion.

As the anti-blocking agent, colloidal silica, diatomaceous earth, inorganic powder of calcium silicate, nitrocellulose or fine cellulose powder can be used.

The case where the above composition is used in combination with an inorganic filler and / or cement is described below. The combined use of inorganic filler and cement is adopted when it is desired to significantly reduce the cost of the neutralizing paint or when the hardness of the coating film is required. As an inorganic filler, inexpensive calcium carbonate, china clay, talc, mica powder, perlite, finely powdered silica, diatomaceous earth, calcium silicate, synthetic calcium silicate, etc. As cement, edited by Kazuo Kondo Shizuo Kondo "Concrete Handbook" Asakura Shoten Showa It is described in the September 32 edition, and for example, Portland cement blast furnace cement, silica cement, and alumina cement can be used. 30-100% by weight of a composition mainly composed of a gas barrier synthetic polymer having a specific composition, and these inorganic fillers and / or
Alternatively, a composition consisting of 0-70% by weight of cement is in a range suitable for substantially blocking acid gas and water vapor. If the inorganic filler or cement exceeds this, not only will the barrier synthetic polymer composition not be able to form a continuous film, but the coating film will also become brittle, the pot life after adjustment will be shorter, uneven coloring will occur, and fading will occur. Easier to do. Especially when cement is used together, it has a drawback that it is itself eroded by acidic water. Barrier synthetic polymer composition 50-100% by weight,
Inorganic fillers and cements 0 to 50% by weight are preferred, 70 to 100% by weight of the composition, and inorganic fillers and cements 0 to 30% by weight are more preferred.

As a specific composition of the barrier polymer composition, 50 to 90% by weight of vinylidene chloride (A) for obtaining high barrier properties,
(A) 60 to 50% by weight of the monomer component (B) copolymerizable with (A), and 0 to 3% by weight of the functional monomer component (C) copolymerized with (A) and / or (B). 80% by weight,
20 to 40% by weight of (B) and 0 to 2% by weight of (C) are preferable from the viewpoint of weather resistance, strength and adhesiveness. When compounded with an inorganic filler or cement, the component (C) plays an important role. These fillers and cement compounds serve to prevent the formation of voids when forming a coating film.

As components (B) and (C), Pol edited by Brandrup Immergut
It is described in the ymer Hand book 2nd edition, for example (B)
Ingredients: vinyl chloride, acrylonitrile, vinyl acetate, vinyl methyl ether, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyne acrylate, methyl methacrylate, ethyl methacrylate, ethylene, methylpropylene, methylbutene, butadiene, chloroprene And so on.

(C) component: acrylic acid, methacrylic acid, itaconic acid,
Fumaric acid, maleic acid and their acid amides N-methoxy N-butoxy acrylic acid amide, hydroxyethyl acrylate, glycidyl acrylate and methacrylate can be mentioned.

The coating film of the Bayer synthetic polymer composition specified as described above has a carbon dioxide permeability (CO ₂ T) in order to prevent neutralization.
R) It is essential to have barrier properties of 3 × 10 ³ cc · μ · / m ² day · atm or less and water vapor transmission rate (WVTR) of 2 × 10 ³ g · μ / m ² · day or less.

The coating film of the synthetic barrier polymer composition of the present invention must have a yellowness of 65 or less in terms of weather resistance. Preferably 50
Or less, more preferably 40 or less.

The composition can be used as an aqueous dispersion or an organic solvent dispersion to form the composition film layer. In the case of an organic dispersion, the film layer is generally flexible and exhibits excellent adhesiveness even on a highly water-absorptive substrate, but on the other hand, since a large amount of organic solvent is used, handling and painting workability are reduced. It is much inferior to the water dispersion.

Organic solvent dispersions are used in special cases, especially when the thin film layer is used as a topcoat or primer coat.

The thickness of the composition film layer is determined by the required performance of finishing, for example, flat finishing or three-dimensional finishing, and the degree of demand for imparting neutralization resistance in addition to cost, but it covers unevenness on the outer surface of concrete. 50μ or more is required to form a substantially void-free film layer, and preferably 200μ or more.
μ or more is required. The upper limit of the thin layer is not to exert the effect of the present invention, but to reduce the cost of finishing twice and finishing three times. It is not practical to finish the film of 1000μ or more once to form the film layer, especially for finishing the vertical wall. In order to reduce the three-dimensional finish and cost, it is preferable to superpose a thin film layer of the synthetic polymer alone on the outer surface of the composition film layer as a concrete outer surface or a top coat.

As a method of forming a substantially void-free film layer on the outer surface of concrete, Soichi Muroi, "Application of Polymer Latex in Architectural Paint", 1983, VIII-XI
The flat layer-like finish, the sand wall-like finish, the hard three-dimensional pattern finish, and the elastic three-dimensional pattern finish method can be used to form a film layer by using a trowel, a spray or various rollers.

For example, when decorativeness in appearance is required, the neutralized concrete structure of the present invention may be used in combination with a conventional cosmetic paint or the like.

(Action) The organic polymer composition membrane layer of the specific composition of the present invention has the action of substantially preventing permeation of acidic gas or water vapor to prevent these gas bodies from adsorbing or penetrating into the concrete surface or inside. . The presence of this membrane layer on the outer surface of concrete is considered to substantially prevent the permeation of these acidic gases and mists to the concrete surface, and these gas bodies and mists condense below the temperature change or water dew point. It is considered that acid water becomes on the surface or inside the concrete and substantially prevents the so-called neutralization reaction. Therefore, the membrane layer should be substantially free of capillary-like communicating pores that allow the passage of gas.

(Examples) Examples will be shown below, but the essence of the present invention is to utilize the barrier property of a synthetic polymer having a specific composition as a coating film of a neutralized concrete structure. It is not limited to

WVTR measurement method WVTR (Water Vaper Transmission Rute) is JIS-Z-02
It was measured by 08 (cup method). About 3μ of water dispersion or organic dispersion of barrier resin was applied on 12μ polyester film (Torel mirror), fixed on a cup containing anhydrous calcium chloride, and stored at 40 ° C and 90% RH for 24 hours. . From the change in weight before and after storage, WVTR was calculated as the WVTR of the barrier resin alone using the formula below.

P ^W = WVTR of barrier resin layer (calculated value) P _* ^W = Overall WVTR (measured value) P ₀ ^W = WVTR of polyester film (measured value) P ₀ ^W : 53 g / m ² .day (40 ° C., 90% RH) P ^W (g / m ² .day) obtained from (a) was converted per 1 μ thickness.

CO ₂ TR measurement method The same sample as WVTR was sandwiched in a cell kept at 20 ° C. 1
Flow 1 atm CO ₂ gus at 10 ml / min under saturated water at 20 ° C, flow N ₂ gus at 10 ml / min to the other side of the sample, and sample 10 ml of CO _{2 in} N ₂ into the autosampler at regular intervals. . The quantification of CO _{2 in} N ₂ was performed by converting it into CH _{4 using a} Ni catalyst column, quantifying it from a calibration curve by gas chromatography, and calculating it as CO ₂ TR when the steady-state CO ₂ concentration was reached.

P ^C = CO ₂ TR of barrier resin layer (calculated value) P _* ^C = overall CO ₂ TR (measured value) P ₀ ^C = CO ₂ TR of polyester film (measured value) P ₀ ^C = 800cc / m ² . day.atm and (20 ℃ 100% RH) P C determined from (i) (cc / m ² .day.atm) converted per 1μ thick.

Measurement of yellowness The coating film after the neutralization resistance test was measured by the reflection method using JIS K7103-1977 "Suga Testing Machine SM-3-CH".
Yellowness was calculated by the following formula.

Y _I : Yellowness X, Y, Z: Tristimulus value of test sample under standard light C Cement neutralization evaluation method (1) Mortar sample preparation method Cement physical test method JIS ・ R ・ 5201 hand,
It was prepared with the following composition.

Cement 100 parts by weight (appearance) Standard sand 200〃 Water 65〃 Defoamer 0.2〃 The flow value of this mixture was 196-202. It is poured into a mold and cured at room temperature (20 ℃, 90% RH or above) for 2 days, then 40
It was cured in water at 7 ° C for 7 days.

(2) Method of forming a barrier organic polymer composition film layer on the dried outer surface of the mortar sample of (1) An aqueous dispersion of a barrier polymer or an organic solvent dispersion should have a dry weight of 50 g / m ^2. It was applied 3 to 5 times with a brush.

(3) Neutrality measurement method The sample having the barrier polymer composition film layer formed in (2) above was immersed in water saturated with carbon dioxide for 1 month at room temperature and then for 1 month in the room. I left it for a while. Cut the sample and cut 1% of phenolphthalein
The position where the color changed to red after applying the ethyl alcohol solution was measured from the surface, and the length was indicated as the neutralization depth (m, m). If the neutralization depth is short, the shorter the neutralization depth, the more the neutralization is prevented.

Example 1 A mixture of the monomer compositions shown in Table 1 was polymerized by the emulsion polymerization method shown below to obtain an aqueous dispersion of a barrier resin.

Using a pressure resistant polymerization vessel with an internal volume of 4 l, t was used as a polymerization initiator system.
-Butyl hydroperoxide / formaldehyde sodium sulfoxylate Redox system is adopted at 55 ℃.
Polymerization was carried out.

Sodium diphenyl ether disulfonate (Dow FAX 2A1 made by Dow Chemical) as an emulsifier in 550 g of deionized water 5
Mix 5g of wt% aqueous solution and add 50g of monomer mixture
0.08 wt% t-butyl hydroperoxide aqueous solution
40 g and 0.2 g of a 0.2% by weight aqueous solution of sodium sulfoxylate dihydrate in 20% were added at a speed of 40 g / Hr, and seed polymerization was completed in 2 hours. 90 g / Hr of the remaining 950 g of the same monomer mixture and 180 g of the same emulsifier
15 g / hr, 195 g of the same Redox polymerization initiator aqueous solution is 15 g / hr
Was continuously added, and the polymerization was completed in 13 hours. When calculated from the solid content of the obtained aqueous dispersion, the polymerization rate was 97% or more. Table 1 shows the results of measuring the depth of neutralization by applying it to mortar according to the procedure of CO ₂ TR, WVTR of this latex and neutralization evaluation method.

As a comparative example, (a) uncoated and (b) Table-1 NO.1 latices are diluted 3 times with water and coated as curing latices 1 day after mortar molding (dry weight 20 g / m ² discontinuous film)
Further, (c) Table 1 shows the neutralization depth when the No. 1 lattex in Table 1 was kneaded in a dry weight of 20 parts per 100 parts of cement when the mortar was prepared. As is clear from Tables 1 and 2, it can be seen that the concrete structure having the continuous membrane layer of Example-1 is neutralized.

Figures 1 and 2 show continuous membrane layers of Example 1 (Table 1) No. 1 and comparative examples (Table 2) applied to the surface of a concrete structure.
The electron microscope photograph of the discontinuous film layer of No. 1 is shown.

Example-2 500 g of a mixture of the monomer compositions shown in Table 1 was dissolved in 1000 g of dimethylformamide, 0.5 g of azobismethylvaleronitrile was added as a polymerization initiator, and polymerization was performed at 50 ° C for 15 hours to obtain a polymerization rate of 90-. 95% polymer was obtained. Table 3 shows the results of measuring the neutralization depth after applying this polymer solution to mortar and drying at 150 ° C for 30 minutes. All show excellent neutralization resistance performance compared to the uncoated one.

(Effects of the Invention) The effects of the present invention are summarized as follows.

(1) A concrete structure that substantially prevents the penetration of acid rain or acid water that inhibits or delays the hardening reaction of cement.

(2) A concrete structure in which volume expansion or partial dissolution of cement caused by a discontinuation reaction is substantially prevented.

(3) A concrete structure in which generation of rust of a steel frame due to a neutralization reaction is substantially prevented.

(4) A neutralized concrete structure that is aesthetically or aesthetically painted.

(5) The surface of a concrete structure having a synthetic polymer composition membrane layer containing vinylidene chloride as a main component is flame-retardant.

(6) A concrete structure having good durability and good wettability with the surface of a concrete foundation.

[Brief description of drawings]

1 and 2 are electron micrographs showing the surface particle structures of the continuous film layer of Example 1 and the discontinuous film layer of Comparative Example, respectively.

Claims (2)

[Claims] 1. Vinylidene chloride (A) is 50 to 90% by weight,
Olefinic unsaturated monomer copolymerizable with (A) (B)
Of 10 to 50% by weight of (A) and / or (B) and 0 to 3% by weight of the functional monomer (C) copolymerizable with (A) and / or (B). The outer surface is covered with a continuous membrane layer, and this membrane layer has a carbon dioxide gas permeability of 3 × 10 ³ cc · μ / m ² · day · atm or less and a water vapor permeability of 2 × 10 ³ cc · μ / m ²・ Day-atm or less, membrane layer thickness: 50 μ or more and less than 1000 μ, Yellowness: 65 or less, neutralized concrete structure. 2. The neutralized concrete structure according to claim 1, wherein the organic polymer composition film layer is formed from an aqueous dispersion or a solvent dispersion.