JPH0812467A - Method for durable finishing of concrete - Google Patents

Abstract

PURPOSE:To improve durability of a concrete and application efficiency, since a cement composition can be applied without waiting its hardening, by applying the cement composition containing a nitrite on the surface of a hardened concrete and coating the concrete with a coating material containing an epoxy resin having bonding ability to a lubricated surface. CONSTITUTION:A cement composition to be used in this method can be a pasty one applied in thin coating, a mortar applied in slightly thick coating, etc. A hardened concrete to be coated can be a new one just after casting and an old one aged with time. As a nitrite, a single nitrite selected from lithium nitrite, calcium nitrite, etc., or a mixture thereof is used. The nitrite is added to the cement in 1-25 wt. % based on the cement. An adhesive epoxy resin for a lubricated surface to be used after coating the cement composition containing a nitrite is a composition comprising an epoxy-group containing component such as a condensate of bis-phenol A and epichlorhy drin and a hydrophilic curing agent (e.g. diethylenetriamine).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a finishing method for improving the durability of concrete. More specifically, the present invention relates to a method for preventing deterioration of concrete caused by penetration of a harmful substance from the surface of hardened concrete into the interior thereof or caused by a harmful substance already entering the concrete. The deterioration referred to here is a phenomenon of carbon dioxide infiltration into concrete to lower the alkalinity of concrete, a corrosion phenomenon of rebar in concrete due to chloride ions, sodium ions in concrete and potassium ions of certain types. This refers to the expansion phenomenon of concrete due to the alkali-aggregate reaction that occurs with aggregate, and the weathering phenomenon in which the cement components exposed outdoors are lost.

[0002]

2. Description of the Related Art Conventionally, in order to improve the durability of hardened concrete, surface coating with various coating materials has been performed. Further, a method for preventing deterioration of concrete by impregnating nitrite from the concrete surface or applying a cement composition containing nitrite to the concrete surface is disclosed in JP-A-60-204, respectively.
No. 683 and JP-A No. 1-103970. Furthermore,
JP-A-63-021270 discloses a method of impregnating the surface of a hardened cementitious material with an aqueous solution of a nitrite and then coating it with an epoxy resin for a wet surface.

[0003]

The problem to be solved by the present invention is to prevent the elution of nitrite to the outside from the cement composition containing the nitrite applied to the surface of the hardened concrete. The goal is to shorten the construction period. If the mortar containing nitrite is left as it is, it can be easily imagined that the nitrite ion is eluted to the outside through rainwater, condensed water, or the like. Therefore, it is necessary to apply some kind of surface coating. Although various coating materials can be used after the mortar has hardened, it must be left for a long time until it hardens, and if there is rainfall during that time, the nitrite contained in the cement composition will elute outside. To do. In addition, there was a problem that the construction period was extended. JP 63
No. -021270 discloses a method of impregnating the surface of a hardened cementitious material with an aqueous solution of nitrite and coating it with an epoxy resin for a wet surface. Application of aqueous solution is not easy. JP-A-1-103970 proposes application of a nitrite-containing mortar, but coating with a finishing material is necessary for aesthetic appearance, prevention of elution of nitrite, and prevention of invasion of water and carbon dioxide gas. However, a mortar containing a high concentration of nitrite has a problem that the surface has a large water content, the curing is slow, and it takes several days to apply the finishing material, and the construction period is inevitably long. When the surface to be coated as in the present invention is uncured, it is easy to peel off at the interface between the cement-based material and the finishing material in the usual finishing material, and the effect of applying the cement composition containing nitrite is sufficiently expressed. It's hard to do.

[0004]

The method for durable finishing of concrete according to the present invention comprises applying a cement composition containing nitrite to the surface of hardened concrete and then wetting the surface of the cement composition in an uncured state. It is characterized by coating with an epoxy resin-containing coating material having surface adhesiveness.

The cement composition to which the method of the present invention is applied is a paste which is used in a thin coating, a mortar which is applied slightly thickly, and a concrete which is mixed with coarse aggregate. . The hardened concrete to which these are applied can be applied to everything from immediately after pouring to those that have deteriorated over time.

As the nitrite used in the method of the present invention, lithium nitrite, sodium nitrite, potassium nitrite, calcium nitrite and the like can be used alone or in combination. Sodium salt and / or potassium salt are
Lithium nitrite and / or calcium nitrite are preferable because they also cause an alkaline aggregate reaction. The amount of nitrite added to cement is generally 1 to 25% by weight.

The wet surface-adhesive epoxy resin applied to the surface of the cement composition containing nitrite is hydrophilic with conventional epoxy group-containing components such as a condensate of bisphenol A and epichlorohydrin. It is a compound with a curing agent. More preferably, in order to improve hydrophilicity, an epoxy resin and a carboxyl group-containing polymer chemically mixed with a nonionic surfactant such as Epan (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) and dispersed in water with a mixer are chemically used. Epoxy resin that can be self-emulsified by reaction, or self-emulsifiable by polymerizing carboxyl group-containing monomers such as acrylic acid and methacrylic acid and copolymerizable vinyl and acrylic monomers in the presence of epoxy resin What is made into a graft copolymer etc. is used. These manufacturing methods are described, for example, in Japanese Patent Laid-Open No. 1-110517.

As a curing agent, diethylenetriamine,
Polyethylene amine produced by condensation reaction of polyamines such as triethylene tetramine and tetraethylene bentamine and synthetic dimer acid, or polyether diamine, pentaethylene hexamine, stearyl amine,
Long chain aliphatic amines such as xylenediamine are mentioned. Further, a part of these amine curing agents which has been previously modified with a ketone to be ketiminized is also preferably used. An amine salt surfactant having a water displacement action can also be used in combination. The amount of these amine curing agents used is preferably such that the active hydrogen atoms are in a molar ratio of 1.6 to 2.4 with respect to the epoxy groups. In addition, mercaptans such as polythiols, a complex of a dimer or trimer of a drying oil fatty acid described in JP-A-49-93497 and a polyamine, and JP-A-49-93496 Modified aromatic amines can also be used as a curing agent.

As the coating material containing the wet surface adhesive epoxy resin used in the present invention, in addition to the epoxy resin alone, calcined gypsum, Portland cement, mixed cement, or the like may be mixed with a component that absorbs water. It is possible to achieve the desired object. Further, as long as the object of the present invention is achieved, activated alumina, silica alumina, calcium carbonate, bentonite, etc. may be used as the filler.

It is desirable that the curing rate of the wet surface adhesive epoxy resin be equal to or less than the strength development of the cement composition. If the curing of the epoxy resin is too fast, the cohesive force of the epoxy resin exceeds the strength of the cement composition, causing peeling at the interface between the epoxy resin and the cement composition, which is not preferable.

The method for applying the wet surface adhesive epoxy resin is not particularly limited to trowel coating, brush coating, roller coating, spray coating and the like, but the cement composition as the base is in an uncured state. If the viscosity of the epoxy resin is too high, it may cause difficulties during application. Therefore, the viscosity at the time of use after mixing with the curing agent is preferably 20000 cps or less. The curing rate of the epoxy resin and the viscosity at the time of use can be adjusted to desired conditions by appropriately mixing the types and amounts of the curing agent and the filler.

The interval between the application of the cement composition and the application of the wet surface adhesive epoxy resin is preferably after the initiation of setting of the cement, but the cement composition can be prepared by properly blending the epoxy resin, the curing agent and the filler. Even after the application, it can be performed without any trouble. On the surface after curing the epoxy resin, cement composition such as cement paste or mortar, urethane resin, acrylic resin,
A solvent-based paint such as an epoxy resin or a vinyl chloride resin, a water-based paint, or an impregnating material or a coating material such as a silane compound or a polysiloxane resin can be applied and finished as desired.

[0013]

The above-mentioned epoxy resin-containing coating material has sufficient adhesive strength even when the surface to be coated is a wet surface, and the curing rate can be adjusted according to the curing rate of cement.
After application of the cement composition containing nitrite, the cement composition can be coated before setting. As a result, it is possible to form a finishing layer in which the cement composition containing nitrite and the epoxy resin are integrated after curing. By applying the durable finishing method of the present invention, the epoxy resin exhibits water impermeable property after solidified by its curing reaction, so that the nitrite ion in the cement composition is prevented from eluting to the outside and the concrete. Can be diffused and penetrated only inside. Also, it prevents the invasion of harmful substances such as carbon dioxide and chloride ions from the outside, so that the diffusion and permeation of nitrite ions into the interior is prevented, the progress of neutralization is prevented, and the corrosion of reinforcing steel in concrete is prevented. , Remarkably acts to prevent the progress of alkali-aggregate reaction and improves the durability of concrete.

[0014]

【Example】

Example 1 A 30 × 30 × 6 cm hardened concrete plate was prepared as a test substrate, and ordinary portland cement, sand, water, a 40% aqueous solution of lithium nitrite, and 45 were used as materials for mortar.
% Styrene butadiene rubber dispersion prepared,
Sand / cement ratio of 2, water / cement ratio of 0.5 by weight,
Knead so that the lithium nitrite (solid content) / cement ratio is 0.1 and the resin (solid content) / cement ratio is 0.1,
It was applied with a trowel to a thickness of about 5 mm. Immediately after applying the mortar, the main material bisphenol A glycidyl ether type epoxy resin and the epoxy resin for the wet surface using the long-chain aliphatic amine curing agent and ordinary Portland cement in a weight ratio of 4: 1.
1 mm of the coating material containing epoxy resin mixed with the spatula
It was applied thickly. 48 hours after applying the epoxy resin-containing coating material,
An adhesion strength test was carried out with a Kenken-type adhesion tester. Then, a 5 × 5 × 6 cm block was cut out from the part of the test plate that was not subjected to the adhesion strength test (the 5 × 5 cm part is the finished surface), and the quick-drying epoxy resin adhesive (coni Sealed with a trade name, Quick Mender Co., Ltd.), placed in a 1 liter beaker, poured about 800 ml of pure water, and soaked so that the finished surface as the upper surface was completely immersed in water. After 24 hours, the concentration of nitrite ions eluted from the immersion liquid was measured by a colorimetric method using diazo coupling.

Comparative Example 1 A test substrate was coated with a lithium nitrite-containing mortar having the same composition as in Example 1 but without the epoxy resin-containing coating material.
After standing for 48 hours, the nitrite ion concentration of the immersion liquid was measured in the same manner as in the example. The test results of Example 1 and Comparative Example 1 are shown in Table 1.

[Table 1] Table 1 Adhesive strength Nitrite ion concentration in immersion liquid kgf / cm ² ppm Example 4.5 Non-detection comparative example ─── 1000 or more

[0016]

According to the present invention, it is possible to prevent nitrite from being eluted from the cement composition containing nitrite to the outside,
Since it can be efficiently diffused and penetrated into concrete, it has a high effect of improving the durability of concrete. Further, since the work can be performed without waiting for the cement composition to harden, the work efficiency is high.

Further, since the surface of the cement composition is immediately covered with the resin film, there is an effect of preventing the occurrence of efflorescence. Further, since various coating materials can be suitably applied on the coating film in which the epoxy resin is solidified,
Even a material such as urethane resin that turns yellow when it comes into contact with nitrite ions can be overcoated without any problem.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Yuji Nakazawa 1-3-1, Kodai, Adachi-ku, Tokyo Tajima Roofing Co., Ltd. (72) Inventor Sugio Fukuda 1-3-1, Kodai, Adachi-ku, Tokyo No. 72 Tajima Roofing Co., Ltd. (72) Inventor Takahiro Hori 1 722, Tsuboi-cho, Funabashi-shi, Chiba Central Research Laboratory, Nissan Chemical Industries, Ltd. (72) Inventor Tadashi Naito 3-7-1, Kandanishiki-cho, Chiyoda-ku, Tokyo Nissan Inside Chemical Industry Co., Ltd. (72) Inventor Satoshi Yamazaki 722-1, Tsuboi-cho, Funabashi City, Chiba Prefecture

Claims (1)

[Claims] 1. A cement composition containing 1 to 25% by weight of nitrite with respect to cement is applied to the surface of hardened concrete, and the surface of the uncured cement composition has wet surface adhesiveness. A durable finish method for concrete, characterized by coating with a coating material containing epoxy resin.