JPS63162591A - Method of mending ferroconcrete - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for repairing reinforced concrete, and relates to a method for repairing deteriorated reinforced concrete, preventing progression of deterioration, or preventing deterioration of normal concrete.

[Conventional technology]

Recently, early deterioration of concrete structures has become a major social problem in Japan. This is said to be due to the use of concrete with a large amount of mixing water and the use of sea sand with a high salt content in order to increase construction efficiency.

Since cement (in this application, cement refers to Portland cement, blast furnace cement, fly ash cement, silica cement, etc.) is inherently alkaline, reinforcing bars inside concrete are difficult to corrode. However, reinforcing bars are susceptible to corrosion due to the neutralization of hardened cement and the action of salt in concrete. The reinforcing steel expands due to corrosion, and this expansion force causes cracks to occur in the concrete.

Cracks also occur in concrete due to drying shrinkage. The drying shrinkage of concrete increases as the amount of mixing water increases.
Moreover, if the amount of kneading water is large, the speed of neutralization will also be large.

When cracks occur in concrete, air and water can easily enter from the outside, accelerating corrosion of reinforcing bars and leading to destruction of concrete structures.

In order to prevent such a situation from occurring, measures have been taken to repair reinforced concrete or to prevent the progression of deterioration.

For example, prevention of corrosion by applying zinc-rich paint, epoxy resin, etc. to reinforcing bars exposed by cracks, or fa by injecting epoxy resin into concrete cracks.
′! This is a means to prevent the spread of A.

Measures have also been taken to prevent corrosion of reinforcing bars by coating the concrete surface with a hardened cement protectant such as an alkali imparting agent or a rust preventive agent, and allowing this to penetrate into the concrete.

[Problem that the invention seeks to solve]

However, zinc-rich paints are generally susceptible to alkali attack and are not effective in preventing long-term corrosion of reinforcing bars in concrete, and since epoxy resins are organic, they have problems with weather resistance, which also prevents corrosion over long periods of time. There is no effect of corrosion protection on reinforcing steel. Furthermore, measures such as applying zinc-rich paint or epoxy resin to exposed reinforcing bars in concrete, or injecting epoxy resin into cracks in concrete do not actively prevent corrosion of reinforcing bars, but rather slow the progression of reinforcing steel corrosion. It's nothing more than that.

The method of applying a hardened cement protectant and allowing it to penetrate into concrete is an effective measure to proactively change the chemical properties of concrete and prevent corrosion of reinforcing bars. However, with this method, these agents may be lost from the surface due to rainwater or the like. So, in order to eliminate this drawback, apply a cement hardening agent and apply it inside the concrete. =2 There are methods of coating the applied surface with cement paste after permeation, and methods of press-fitting a hardened cement protectant from the surface of the concrete. However, with these methods, there is a limit to the amount of chemical that can be applied to the concrete surface, and it is not possible to permanently supply the chemical into concrete.

The present invention has been made to overcome the drawbacks of conventional methods such as L.

- [Means for solving the problem] - Unexplored technical means for achieving the "Ashiguchi-tate" will be explained with reference to FIG. FIG. 1 shows a partial cross section of concrete to which the method of the present invention has been applied, and the surface of the concrete l containing reinforcing bars 2 is deteriorated concrete 3, and cracks 4 have occurred.

A water-absorbing substance such as a super absorbent resin is impregnated with a cement hardening agent, and this is mixed with cement and water to create mortar. This mortar is coated on the deteriorated reinforced concrete surface and impregnated with a cement hardening agent. This forms a mortar layer 5.

In this case, if the mortar layer 5 is weak and needs to be reinforced, it is reinforced with an admixture such as a fibrous material as necessary.

By applying the method described above, the hardened cement protectant impregnated with the water-absorbing substance permanently penetrates into the deteriorated reinforced concrete, changing the chemical properties of the concrete and preventing corrosion of the reinforcing bars in the concrete. It can be prevented.

When the deterioration of reinforced concrete progresses and immediate effect is required for repair, as shown in Figure 2, before applying the above repair method, apply a layer of cement hardening agent protective agent coating layer 6 to the concrete in advance.
Forming a protective agent and allowing the protective agent to penetrate will have a great effect.

In addition, if there is a possibility that the cement hardened body protective agent will dissipate from the mortar coated on the deteriorated reinforced concrete surface, it is covered with a cement paste layer 7 as shown in FIGS. 3 and 4. This coating layer covers the surface with a paste consisting of cement and water, or a paste consisting of cement and water with one or more selected from sand, fibrous substances, polymeric dispersions, and water reducing agents. This is what I did.

[Effect]

The reinforced concrete according to the present invention refers to RC structures, PC
Structures and other concrete reinforced with steel frames, etc., and reinforced concrete surfaces refer to the surfaces of mortar, tiles, paint, etc. that are adhered to the reinforced concrete surface for protection or decoration of the reinforced concrete, or those that are removed. It includes a surface.

In the present invention, uneven parts such as deteriorated and peeled surfaces of reinforced concrete, peeled off surfaces of tiles, paint, etc. can be filled with mortar containing a water-absorbing substance impregnated with a cement hardening body protection agent by the method of the present invention. . Furthermore, it is also possible to repair deteriorated parts of reinforced concrete by injection method of polymer resin such as epoxy resin before kL according to the method of the present invention.

An alkali imparting agent and/or a rust preventive agent is suitable as a cement hardening body protectant.

As the alkali imparting agent, any alkaline substance can be used as long as it is soluble in water and does not adversely affect the cured product. In particular, alkaline silica M salts have high solubility in water, have a large penetrating power into hardened cement, do not contain corrosive substances of salt, and do not cause harmful reactions to hardened cement such as alkaline aggregate reactions. suitable.

If the rust preventive agent has a rust preventive effect on reinforcing steel,
Although it can be used, it has a high solubility in water like an alkali-imparting agent, and has a high penetrating power into cement hardened bodies.
Alkaline earth metal nitrites such as calcium nitrite, which do not cause harmful reactions such as alkaline aggregate reactions, are preferred.

Although it is possible to use the alkali imparting agent or the rust preventive agent at the same time, it is advantageous to use them at the same time because the rust preventive effect on reinforcing bars increases when they are used together. If they are used simultaneously, it is desirable to impregnate the water-absorbing substance separately.

The water-absorbing substance used in the present invention can be used as long as it is insoluble in water, does not disintegrate during kneading, and does not have an adverse effect on the hardened cement such as expansion or contraction in the hardened cement.

In particular, superabsorbent resins are suitable because they are easy to handle and have a large ability to absorb water-soluble residues.

As explained above, according to the method of the present invention, a water-absorbing substance is impregnated with an alkali imparting agent and/or a cement hardening protectant such as a rust preventive agent, and this is mixed with cement and water or cement and water and a fiber material. By kneading the cement together with other materials to create mortar and coating the deteriorated reinforced concrete with this mortar, the cement hardening agent will permanently penetrate into the reinforced concrete, and by changing the chemical properties of the concrete, it will maintain the strength of the reinforced concrete over a long period of time. prevent corrosion.

〔Effect of the invention〕

According to the present invention, by changing the thickness of the mortar coated on the reinforced concrete surface, the blending amount of the mortar, the impregnating concentration of the cement hardened body protective agent into the water-absorbing substance, and the impregnating solution, the hardened cement body is supplied to the reinforced concrete. Since the amount of protective agent can be changed arbitrarily, it is possible to perform construction according to the degree of deterioration of the concrete, its composition, and the properties of the vehicle floor of the structure.

Furthermore, by applying the reinforced concrete repair method of the present invention to normal reinforced concrete, its life can be extended.

〔Example〕

Example-1 Tingtong cement 286 kg/rIf, water cement ratio 65%
Using concrete with a slump of 21 cm and an air content of 4%, a rectangular parallelepiped concrete test specimen of lO 10 x 10 x 40 was prepared, demolded after 2 days of age, and kept at 20°C until 7 days after demolding.
Cured in an aquarium at 20°C until wood age 211].
It was cured indoors at a relative humidity of 60%.

After curing, the entire surface of the specimen was coated with mortar to which an alkali imparting agent was added using the Mokkomei method to a thickness of 5 mm.

Mortar was prepared under the following conditions.

A super absorbent resin (Sumikagel R-30) having a particle size range of 1 to 4 mm was impregnated with a 20% aqueous solution of lithium silicate.

One part by volume of cement was added to one part by volume of the superabsorbent resin impregnated with lithium silicate, water was mixed at a weight ratio of 50% to the cement, and the mixture was kneaded with a Hobart mixer to prepare a mortar.

At the same time, the above concrete specimen was coated with a commercially available acrylic polymer cement paste to a thickness of 3 mm, a specimen coated with an epoxy resin to a thickness of 3 mm, a specimen coated with a 20% solution of lithium silicate, and concrete. An uncoated specimen was prepared for comparison.

These test specimens were heated to a carbon dioxide concentration of 10% after the 28th day of age.
It was further cured for one month indoors at a temperature of 20'C.

Table 1 shows the carbonation depth of each specimen. The depth of neutralization was measured by applying a 1% solution of phenolphthalein.

Example-2 Concrete specimens manufactured under the manufacturing conditions shown in Example-1 were subjected to carbon dioxide concentration of 10% and temperature of 20°C after the age of 28.
The carbonation depth of the specimen cured for 3 months indoors was 7.3.
It was mm. This test specimen was coated in the same manner as in Example 1, and was further cured for 3 months indoors at a RWA gas concentration of >io% and a temperature of 20°C.

The carbonation depth of the specimens after curing was measured.

Example 3 A test specimen in which two polished reinforcing bars were embedded was produced using fine aggregate containing 0.2% NaCl according to the formulation and production conditions stipulated in the JISA6205 rust preventive test for reinforced concrete. The entire surface of this specimen was coated with mortar containing a rust preventive agent according to the method of the present invention to a thickness of 5 mm. Mortar was prepared under the following conditions.

A superabsorbent resin having a particle size in the range of 1 to 4 mm was impregnated with a 20% aqueous solution of calcium nitrite. 3 parts by volume of cement for 1 part by volume of the super absorbent resin impregnated with calcium nitrate, and 50% ffl of water relative to the cement.
ffi ratio and kneaded with a Hobart mixer.

This test specimen and an uncoated test specimen similarly prepared by the method of JISA6205 were tested at a room temperature of 40°C and a relative humidity of 95%.
It was left indoors for one year.

After standing, the reinforcing bars were removed from the test specimens and the state of rust was observed. In the uncoated test specimens, the entire surface of the reinforcing bars was rusted, but in the test specimens coated with mortar using the method of the present invention, the reinforcing bars were slightly rusted. was at an acceptable level.

As shown in the examples below, according to the present invention, the alkalinity imparting agent restores the alkalinity of neutralized concrete, and the rust preventive agent prevents rusting of reinforcing bars.
By preventing corrosion of reinforcing bars in deteriorated reinforced concrete, it is possible to protect concrete structures from destruction.

[Brief explanation of the drawing]

1 to 4 are cross-sectional views of reinforced concrete repaired by the method of the present invention. 1... Concrete 2... Rebar 3... Deteriorated concrete 4... Microscopic cracks in concrete 5... Mortar layer impregnated with cement hardened body protection agent 6...
Cement hardened body protective agent coating layer 7...cement paste layer

Claims (1)

[Scope of Claims] 1. A water-absorbing substance is impregnated with an aqueous solution of a cement hardening body protective agent, and the water-absorbing substance is kneaded with cement and water, or with cement, water, and an admixture to prepare a mortar. A method for repairing existing reinforced concrete, characterized by coating the surface of the reinforced concrete and impregnating the inside of the reinforced concrete with a hardened cement protective agent. 2. The method for repairing reinforced concrete according to claim 1, wherein the cement hardening body protective agent is an alkali imparting agent and/or a rust preventive agent. 3. The method for repairing existing reinforced concrete according to claim 1, wherein the water-absorbing substance is a granular super-absorbent resin. 4. The method for repairing existing reinforced concrete according to claim 1, wherein the admixture comprises one or more selected from sand, fibrous substances, polymer dispersions, and water reducing agents. 5 A water-absorbing substance is impregnated with an aqueous solution of a cement hardening body protection agent, and the water-absorbing substance is kneaded with cement and water, or cement and water and an admixture to prepare a mortar, while a cement hardening body protection agent is applied to the surface of the reinforced concrete in advance. 1. A method for repairing existing reinforced concrete, which comprises applying a solution of an agent and allowing it to penetrate into the interior, and covering the surface of the reinforced concrete with the mortar. 6. The method for repairing reinforced concrete according to claim 5, wherein the cement hardening body protective agent is an alkali imparting agent and/or a rust preventive agent. 7. The method for repairing existing reinforced concrete according to claim 5, wherein the water-absorbing substance is a granular super-absorbent resin. 8. The method for repairing existing reinforced concrete according to claim 5, wherein the admixture comprises one or more selected from sand, fibrous substances, polymer dispersions, and water reducing agents. 9 Impregnate a water-absorbing substance with a cement hardening body protection agent, knead the water-absorbing substance with cement and water, or cement and water and an admixture to prepare a mortar, and apply the cement hardening body protection agent directly to the reinforced concrete surface or in advance. The method is characterized in that the mortar is coated on the surface of the reinforced concrete that has been coated and penetrated with the agent, and after it is cured, the mortar surface is further coated with a paste consisting of cement and water, or cement and water, and an admixture. Repair method for existing reinforced concrete. 10 Claim 9, characterized in that the cement hardened body protective agent is an alkali imparting agent and/or a rust preventive agent.
Reinforced concrete repair method described in section. 11. The method for repairing existing reinforced concrete according to claim 9, wherein the water-absorbing substance is a granular super-absorbent resin. 12. The method for repairing existing reinforced concrete according to claim 9, wherein the admixture comprises one or more selected from sand, fibrous substances, polymer dispersions, and water reducing agents.