JPH0552394B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for repairing cement-based structures. The purpose of the present invention is to prevent the progression of deterioration and improve the durability of cement-based structures by improving the strength of the repaired surfaces of cement-based structures that have deteriorated and become brittle or spalled, and by suppressing corrosion of internal reinforcing bars. An object of the present invention is to provide a method for repairing cement-based structures. [Prior Art] Conventionally, the method for repairing deteriorated reinforced concrete or inorganic materials is to apply and impregnate the surface with a solution of a water-soluble silicate compound, and then coat the surface with cement paste ( Special Publication No. 57-11988) has been proposed. [Problem to be solved by the invention] Foreign matter such as moisture, oil, sand, dust, etc. is attached to the surface or cracks of deteriorated reinforced concrete or inorganic materials, so water-soluble silicate compounds are attached to the surface of the deteriorated reinforced concrete or inorganic material. If the solution is simply applied, it will not easily penetrate into the main body, and the effect of inhibiting corrosion of the internal reinforcing bars will not be sufficient. As described above, the conventional method has the disadvantage that the effects obtained using the water-soluble silicate compound solution are not sufficient. [Means for Solving the Problems] Therefore, the present inventors have conducted repeated research in order to improve these drawbacks, and have applied an aqueous solution of a water-soluble silicate compound (hereinafter sometimes simply referred to as a chemical solution) to the repaired surface.
By pre-penetrating the area with an alkaline solution before applying it, the depth of penetration of the chemical solution into the main body becomes greater, sustaining the effect of inhibiting corrosion of internal reinforcing bars, and improving the strength of the repaired surface. The present invention was completed based on the discovery that this can be done. That is, the present invention provides a method for repairing a cement structure using a water-soluble silicate compound, in which an alkali metal carbonate, phosphate,
After infiltrating in advance a liquid containing at least one compound selected from the group consisting of polyphosphate, aluminium-hydrochloric acid, and hydroxide, an aqueous solution of a water-soluble silicate compound is applied or injected to form the structure. The gist of this article is a method for repairing cement-based structures, which is characterized by infiltration into the body of the object. The present invention will be explained in detail below. A feature of the method of the present invention is that before applying an aqueous solution of a water-soluble silicate compound to the surface to be repaired, an alkaline agent-containing solution is infiltrated in advance. Generally, many years have passed since the object to be repaired was constructed or manufactured, so it may be exposed to moisture, dust, dirt, etc.
Foreign matter such as colloids, oil, and salt adheres to the surface or gets stuck inside the cracks. For this reason, even if a chemical solution is simply applied to the surface and attempts to penetrate the inside of the main body, it may take a long time or may not penetrate at all. By infiltrating the repaired surface with a solution containing an alkaline agent in advance, the depth of penetration of the chemical solution into the interior of the object to be repaired is increased, and the anticorrosion effect of the reinforcing bars inside the main body is maintained, and the strength of the repaired surface is improved, which improves the strength of the object to be repaired. The progress of deterioration can be prevented. Cement structures targeted by the repair method of the present invention include reinforced concrete, secondary concrete products, etc., and hydraulic inorganic materials such as ordinary Portland cement, early strength cement, ultra early strength cement, moderate heat Portland cement, Portland cements such as sulfate-resistant Portland cement and white Portland cement, mixed cements such as blast furnace cement, silica cement, fly ash cement, alumina cement, ultra-fast hardening cement (rapid hardening cement, jet cement), colloid cement, etc. The main raw material is one or more types of special cements such as cement, expanded cement, calcium silicate, hemihydrate gypsum, anhydrite, lime, fly ash slag, etc., which have been ground into micrometers.
Includes materials made by adding various aggregates, cement admixtures, etc. as necessary, kneading with water, and then hardening. In the present invention, the water-soluble silicate compound used to alkalize the neutralized part of the repair target and suppress corrosion of the reinforcing steel is: Silicic acid represented by the general formula: M ₂ O・nSiO ₂ Refers to a single salt or a mixture thereof. In the above general formula, M represents an alkali metal element such as Li, K, Na, or Cs, specifically lithium silicate, potassium silicate, sodium silicate,
Alkali metal silicate salts such as cesium silicate can be mentioned. Molar ratio (SiO ₂ /M ₂ O): n
The value of is in the range 1-100, preferably 1-10. In the above general formula, compounds in which M can be represented as an ammonium component can be used, and examples of such compounds include methylamine silicate, ethylamine silicate, dimethylamine silicate, cyisopropylamine silicate, trimethylamine silicate, Silicate amines such as triethanolamine silicate; in addition to ammonium silicate, quaternary ammonium silicates such as monomethyltriethanolammonium silicate and tetraethanolammonium silicate can be mentioned. In addition, the water-soluble salt salt compound used in the present invention has the general formula: Si(OR) ₄ , [R: represents an alkyl group]
It includes tetraalkoxysilanes (siliceous esters) represented by the following, and specific examples thereof include tetramethoxysilane (methyl silicate), tetraethoxysilane (ethyl silicate), and the like. In order to improve the water resistance of the water-soluble silicate compound after drying and curing, a curing agent such as an organic ester or an aldehyde may be added to the chemical solution within a range that does not adversely affect workability and permeability. Although the concentration of the silicate compound in the chemical solution is not particularly limited, it is preferably in the range of 10 to 30% by weight. If the concentration is lower than this range, curing will be small, and if it is higher than this range, the permeability will decrease, which is not preferable. Moreover, in order to further improve the anticorrosive effect on reinforcing bars, an anticorrosive agent can be added to the chemical solution in the method of the present invention. Inorganic anticorrosive agents used in the present invention include one or two alkali metal salts such as sodium and potassium of acids such as chromic acid, nitrous acid, phosphoric acid, polyphosphoric acid, molybdic acid, and tungstic acid. The above can be used. Further, examples of the organic type include commonly used amine type, thiourea type, mercaptan type and the like. The amount of the anticorrosive agent to be used is not particularly limited, but it may be added in an amount of about 10 to 1000 ppm based on the chemical solution. Examples of the alkali agents used in the present invention include alkali carbonates, alkali phosphates, alkali polyphosphates, alkali aluminates, and alkali hydroxides having aqueous solutions. Specifically, the alkali carbonates include sodium carbonate, potassium carbonate, lithium carbonate, etc., the alkali phosphates include trisodium phosphate, tripotassium phosphate, etc., and the alkali polyphosphates include sodium tripolyphosphate. , potassium tripolyphosphate, sodium metaphosphate, potassium metaphosphate, etc., alkali hydroxides such as sodium hydroxide, potassium hydroxide, lithium hydroxide, etc., and alkali aluminates such as alkali against Al ₂ O ₃ . Molar ratio (Nn ₂ O or K ₂ O/
Examples include water-soluble sodium aluminate and potassium aluminate with Al ₂ O ₃ ) of 1 or more. These can be used alone or in combination of two or more. Although the mechanism of action of the alkaline agent used in the present invention is not clear, it is thought to be as follows. Cement structures contain Ca(OH) ₂ , CaO, CaSO ₄ ,
Contains compounds such as NaCl and _MgCl2 that can gel an aqueous solution of silicate compounds, so if the silicate compound applied to the repaired surface comes into contact with these compounds, silicate will form within a short period of time. A gel is generated, which closes the voids in the surface layer of the repaired surface and prevents the chemical solution from penetrating into the interior of the main body. The presence of an alkaline agent suppresses the formation of silicic acid gel produced by the reaction between the above-mentioned compounds contained in the cement structure and the silicate-based compound, thereby improving the permeability of the chemical solution. it is conceivable that. It is practical to use these alkaline agents in the form of an aqueous solution. The concentration is not particularly limited, but if the concentration is too high, the permeability will decrease, and if it is too dilute, the effect will be small.It is usually in the range of 0.01 to 10% by weight, preferably 0.1 to 3% by weight. These alkaline agent-containing liquids may be applied or injected by a conventional method to penetrate into the repaired surface. A surfactant or a metal anticorrosive agent may be added to these alkaline agent-containing liquids as appropriate. Note that even if the alkaline agent and the silicate compound aqueous solution are mixed and applied or injected onto the repaired surface at the same time, the effects of the present invention cannot be obtained. In order to prevent the elution of the chemicals that have penetrated into the repaired surface and to maintain their effects, a waterproof coating material can be laminated on the surface of the object to be repaired after the chemicals have penetrated into the repaired surface. In this case, after the chemical solution has penetrated into the main body, the chemical solution adhering to the surface of the repaired area and its dried and cured film are removed to expose the surface of the repaired object, and then the coating material is laminated. This can prevent a decrease in adhesive strength to the wall surface. As the waterproof covering material, one or more of organic adhesives, cement paste, cement mortar, polymer cement paste, polymer cement mortar, resin concrete, etc. can be used. A fibrous material can be added to the waterproof coating material of the present invention for the purpose of preventing cracking, increasing strength, preventing peeling, etc. Examples of the fibrous material used in the present invention include steel fibers, glass fibers, alkali-resistant synthetic fibers such as vinylon, nylon, and polyester, carbon fibers, and asbestos, which are commonly used for cement addition. In addition, before laminating the covering material, various laths, nets, etc. can be attached to the repaired surface as a supporting material for the covering material, if necessary. [Effects of the Invention] The present invention has the following effects. (1) It is possible to increase the penetration depth of the chemical solution applied or injected to the repaired surface of a cement structure into the main body, thereby improving the effect of inhibiting corrosion of internal reinforcing bars. (2) When injecting a chemical into the repaired surface of a cement structure, the injection pressure of the chemical can be lowered. (3) The compressive strength of the surface of cement-based structures can be increased. (4) Due to the above synergistic effect, the durability of cement-based structures can be improved. [Example] The present invention will be described below with reference to Examples and Comparative Examples. Note that % indicates weight %. Examples 1 to 12, Comparative Examples 1 to 15 Redemix concrete (nominal strength: 300
Kg/ ^cm2 , slump 12cm, coarse aggregate 25mm),
Assuming salt damage, an amount equivalent to 1% NaCl was added and mixed with appropriate water to prepare a 50 x 50 x 20 cm concrete block, cured to prevent cracks, and left at room temperature for about 2 years. A specimen that had been left alone was used. Using a brush, apply 500 c.c. of the various alkaline aqueous solutions shown in Table 1 to one surface of the specimen per ¹ m2.
Infiltrated. Next, a silicate-based compound is applied to this surface.
A 20% aqueous solution was applied using a brush at a rate of 1/m ² and allowed to penetrate. One week later, the concrete specimens were cut into 4mm thick pieces and analyzed for silicate.
Determine the penetration depth. In addition, for comparison, a case where the silicate compound aqueous solution was directly applied to the above specimen without applying the alkaline agent of the present invention, and a case where the alkali agent and the silicate compound aqueous solution were mixed and applied simultaneously. The penetration depth of each chemical solution was investigated. In addition, the compressive strength of the concrete specimen surface after chemical treatment in each case was measured. The results are shown in Table-1. By the method of the present invention, the depth of penetration of the aqueous silicate compound solution into the body can be increased to 2 to 3 times that by conventional methods. When an alkaline agent and an aqueous silicate compound solution were mixed and applied simultaneously, no effect of the alkaline agent was observed. (Comparative examples: 13, 14, 15) The compressive strength of the concrete specimen surface is expressed as an index with the value when no chemical treatment is taken as 100.
When the method of the present invention was used, the result was 105 to 108, indicating an increase in compressive strength. In the comparative example, the exponent is 101
~103, the strength is lower than that obtained by the method of the present invention.

【table】

[Table] Example 13 A 1% aqueous solution of lithium hydroxide was applied as an alkaline agent at 0.5/m ² to the deteriorated exterior wall surface of a three-story RC building that had been constructed for 25 years. After that, potassium silicate ( n=3.3): A 18% aqueous solution was injected at 1/m ² . The injection pressure at this time was 0.05 to 0.1 Kg/cm ² -G. The penetration depth of the potassium silicate aqueous solution was determined by drilling holes in areas with no cracks, cutting them every 3 mm from the surface, and analyzing them. The average depth was 12.
It was warm in mm. On the other hand, for comparison, the same potassium silicate aqueous solution as above was injected at 1/m ² directly onto the outer wall surface without applying an alkaline agent. Adjust the injection pressure of the chemical solution to 0.05~
The penetration depth of the chemical solution at the location set to 0.1Kg/cm ² -G is:
The average diameter was 4 mm. The injection pressure is 0.2 to 0.25 kg/high compared to the method of the present invention described above.
By setting cm ² -G, the penetration depth of the chemical liquid could be set to an average of 12 mm, which is the same as in the present invention. After the injection work is completed, the exterior wall surface is dried, the hardened potassium silicate film adhering to the surface is scraped off, and an aqueous SBR latex solution (solid content: 20%) is applied to the exposed concrete surface as a waterproof coating.
After applying 500 c.c./cm ² of 500 c.c./cm 2 , a synthetic resin net was placed over the peeled off part, and the solid content was applied to the rapidly hardening cement.
It was covered with a cement mortar made by mixing 10% equivalent SBR latex and twice the amount of sand to the cement. Next, it was finished by covering it with an acrylic rubber waterproof exterior material. When the reinforcing bars were exposed and inspected one year after construction, the concrete around the reinforcing bars remained highly alkaline, and no rusting was observed on the reinforcing bars. In addition, an investigation was conducted after 3 years had passed, but no abnormalities were found. For comparison, in areas where an aqueous potassium silicate solution was injected without applying an alkaline agent, the concrete around the reinforcing bars tended to become neutralized, and rust was observed on the surfaces of the reinforcing bars.

Claims (1)

[Claims] 1. In a method of repairing a cement structure using a water-soluble silicate compound, the repaired surface is coated with an alkali metal selected from the group consisting of carbonates, phosphates, polyphosphates, aluminates, and hydroxides. A cement structure characterized in that a liquid containing at least one selected compound is infiltrated in advance, and then an aqueous solution of a water-soluble silicate compound is applied or injected to infiltrate the main body of the structure. How to repair.