JPH058151B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for preventing deterioration of concrete-based structures and a method for repairing deteriorated areas such as cracks. Apply and impregnate the body sequentially, or mix both components in advance and apply.
The present invention relates to a highly practical method for improving the strength of concrete structures by impregnating them to prevent deterioration of concrete structures or to effectively repair and strengthen areas where deterioration has progressed. [Prior art and its problems] In recent years, aging deterioration of cement-based structures has become a major social problem. The main reasons for this are the use of undesirable sea sand and crushed stone as aggregates due to resource depletion, and the need to provide fluidity in line with the construction requirements for pumping hydraulic cementitious compositions. This is thought to be due to the fact that more water than necessary was added to the composition. In such cement-based structures, for example, (1) rusting of internal reinforcing bars due to carbonation of the structure, (2) promotion of rusting of reinforcing bars due to salt in the raw materials used or salt entering from the outside, (3) Inconvenient phenomena such as cracks in structures due to expansion and pop-outs occur due to the use of expandable aggregates, and these phenomena appear to accelerate the deterioration of cement-based structures. be. Conventionally, as a means to prevent such deterioration,
Reinforcing bars to be buried in concrete are pre-galvanized or coated with organic polymer materials such as epoxy resins, but galvanized reinforcing bars have poor coating resistance due to the high alkalinity of concrete. Not only is this a problem, but it also has the disadvantage of being easily damaged during processing;
It is industrially undesirable because it requires a coating film with a certain thickness or more and the material is expensive. In addition, attempts have been made to protect the surface of concrete structures by coating them with epoxy resin, but this method is not necessarily satisfactory, as organic coatings generally have problems with durability and are easily damaged. Furthermore, attempts have been made to dissolve silicone or silicone oligomers in organic solvents and apply them to the concrete surface to take advantage of their water-repellent properties to block water, but due to their large molecular weight, they cannot sufficiently penetrate into the pores. Since the protection is limited to the surface layer, many products are unsatisfactory in terms of protective effect and durability of the effect, and improvements are desired. Furthermore, methods of coating and impregnating alkyltrialkoxysilanes have been used as waterproofing and salt-proofing measures for concrete and stone. These silanes have low viscosity and low surface tension, so they have good permeability into pores and easily penetrate deep into the pores, but the silanes that have penetrated completely fill and block the porous voids. Therefore, the ingress of water can be prevented by the water-repellent action of the alkyl group, but there is a drawback that the protective effect against pressure water is extremely low due to the presence of porous voids. On the other hand, a modification method is known in which monomers such as methyl methacrylate or styrene are applied, impregnated, and polymerized to concrete structures. Since it requires operations such as pressurization and impregnation, it cannot be practically adopted for large structures. The purpose of the present invention is to improve the waterproofness, salt-blocking property, and durability of concrete structures by using a hydrolyzed silanol layer that penetrates deep and a polymer layer of acrylic monomer that penetrates shallowly. The purpose of the present invention is to provide a modification method that significantly improves Another object of the present invention is to provide a reinforced and repaired concrete structure that is prevented from deteriorating over a long period of time. [Means for Solving the Problems] As a result of repeated experiments and research on effective methods for achieving the above objectives, the present inventors have discovered a practically highly desirable method for effectively achieving the above objectives. . That is, the present invention involves applying and impregnating an alkyltrialkoxysilane compound onto the surface of a concrete structure, and then applying a polymerizable acrylic monomer together with a polymerization initiation catalyst, or applying an alkyltrialkoxysilane compound to the surface of a concrete structure. and a polymerizable acrylic monomer together with a polymerization initiation catalyst, which is applied and impregnated, and the acrylic monomer that has penetrated into the structure is polymerized and hardened. and provide repair methods. In the method of the present invention, the target concrete structure is mainly a large-scale structure or construction made of concrete that includes reinforcing bars or steel frames inside. However, since the method of the present invention can be applied to various porous structures to effectively prevent their deterioration and strengthen them, the concrete structure of the present invention can be applied to various types of porous structures, such as It also includes porous structures such as stone, nitrogen-based materials, ALC, lightweight aggregates and wood. The alkyltrialkoxysilane used in the method of the present invention is a compound represented by the following general formula: R ₁ -Si(OR ₂ ) ₃ , and preferably R ₁ in the formula has 3 to 3 carbon atoms. 14 alkyl groups, and OR ₂ is a methoxy group or an ethoxy group. Such compounds include, for example, propyltrimethoxy(ethoxy)silane, butyltrimethoxy(ethoxy)silane, amyltrimethoxy(ethoxy)silane, hexyltrimethoxy(ethoxy)silane, octyltrimethoxy(ethoxy)silane, decyltrimethoxy(ethoxy)silane, Examples include trimethoxy(ethoxy)silane, dodecyltrimethoxy(ethoxy)silane, tetradecyltrimethoxy(ethoxy)silane, octadecyltrimethoxy(ethoxy)silane, and the like. These can be used alone or in combination of two or more. In order to apply these silane compounds to the surface of a porous structure, they may be applied directly, but usually,
The silane compound can be applied, for example, by preparing a 10 to 50% aliphatic lower alcohol solution. The silane compound that has penetrated into the porous structure is
It is hydrolyzed by the moisture present inside the structure to form silanol, and this silanol group is dehydrated and condensed by reaction with the OH group on the surface of silica, etc. in the structure, or other silanol groups, and becomes strong. It forms a siloxane bond. In the present invention, after the alkyltrialkoxysilane compound is applied and impregnated onto the surface of the porous structure, a polymerizable acrylic monomer is further applied together with a polymerization initiator, or the alkyltrialkoxysilane By pre-mixing a silane compound and a polymerizable acrylic monomer, applying the mixture together with a polymerization initiation catalyst, impregnating it, polymerizing and curing, the silanol layer penetrates deep and is hydrolyzed, forming a silanol layer in shallow parts. A water-blocking protective layer in which the porous voids are densely filled is effectively formed by the polymer layer of the acrylic monomer infiltrated into the acrylic monomer. Examples of acrylic monomers preferably used in the method of the present invention include methyl methacrylate (MMA), butyl acrylate (BA), glycidyl methacrylate (GMA), 2-ethylhexyl methacrylate (2-EHMA), and cyclohexyl methacrylate (CHMA). ), 2-hydroxypropyl methacrylate (2-HPMA), tetrahydrofurfuryl methacrylate (THFMA), isobornyl methacrylate (IBMA), and the like. These may be used alone or in combination of two or more. In addition, in the method of the present invention, it is preferable that the acrylic monomer is applied in the form of a composition mixed with a polymerization initiation catalyst in advance, but it is preferable to apply the acrylic monomer after dissolving a predetermined amount of the catalyst in an appropriate solvent. Afterwards, an acrylic monomer or a liquid containing the same may be applied and impregnated. The polymerization initiator used with the acrylic monomer is a commonly known polymerization catalyst, and representative examples thereof include benzoyl peroxide, cumene hydroxy peroxide, methyl ethyl ketone peroxide, etc. I can do it.
Further, the amount of the polymerization initiator to be used is conveniently within a generally known amount range, and the amount is appropriately selected depending on the desired polymerization curing time and pot life.
Further, a small amount of a polymerization aid or polymerization promoter can be used in combination with such a polymerization initiation catalyst. Such accelerators include, for example, paradimethylbenzoic acid isoamyl ester,
Examples include acetylacetone cobalt salt and naphthenic acid cobalt salt. [Operations and Effects] According to the method of the present invention, a silane compound is mainly immobilized in the inner layer of the porous void impregnated part of a concrete structure by siloxane bonding,
A filling layer mainly made of an acrylic polymer having good weather resistance is effectively formed on the surface layer of the impregnated portion. As a result, a concrete-based structure having a protective layer with excellent waterproofness and salt-blocking properties, excellent deterioration resistance, and long-term stability is provided. [Example] Next, the present invention will be explained in more detail with reference to Examples. Note that parts and percentages in the examples are by weight unless otherwise specified. In addition, in order to test the performance of various factors regarding deterioration prevention and repair effects by the method of the present invention, mortar of various shapes as shown below, which are typical for concrete-based structures, was made and these were used as specimens in various combinations. Various physical properties were measured for those to which the treatment agent was applied. [Mortar specimen for measurement] The mixing ratio of cement: sand: water is 1:2:0.5
The mixed preparation composition was poured into the molds of various test specimens, removed from the mold after 2 days, and then kept at a temperature of 20 ± 2.
The specimens were cured for four weeks at a temperature of 65±5% and a relative humidity of 65±5%. Next, using these specimens, the deterioration prevention properties of various deterioration prevention methods were evaluated by the following test method. (a) Penetration depth A predetermined amount of impregnated material is applied to the entire surface of a cured 4 x 4 x 16 cm mortar specimen, and the temperature is 20±
After being left for 7 days at 2°C and relative humidity of 65±5%, the specimen is split open, the split surface is wetted with water, and the depth (mm) of the water-repellent area is measured. However, when a silane-based material was not applied, a dye was added to the coating material in advance to color it, and the penetration depth was examined. (b) Water absorption rate A predetermined amount of impregnation coating material was applied to the entire surface of a cured 4 x 4 x 16 cm mortar specimen, and the temperature was 20±
After being left for 7 days at 2°C and relative humidity of 65±5%, the sample was submerged in water, and the water supply rate (%) was determined from the weight increase after 30 days. (c) Water permeability test-1 A predetermined amount of impregnation coating material was applied to one side of a cured mortar specimen measuring 10 x 10 x 20 cm, and the temperature was 20°C.
The sample was left for 7 days at ±2°C and relative humidity of 65±5%, and the amount of water permeation (cc) after 24 hours was measured using the JIS A6910 water permeability test method. (d) Water permeability test-2 In this test, a specimen is prepared in accordance with the provisions of JIS A1404, and the pressurized water permeability is measured using the following method. [Preparation of specimen] 5 kg of Portland cement, 5.5 kg of Iwaki silica sand
Add water to a mixture of No. 10 kg and 5 kg of Iwaki silica sand No. 6.
Add 3.25Kg and mix (flow value: approx. 150-155),
This was poured into a cylindrical frame with an inner diameter of 15 cm and a height of 4 cm, and placed indoors at a temperature of 20°C ± 3°C and a relative humidity of 80% or more.
After leaving for 48 hours, demold. After demolding, for another 19 days,
Cured in the same room, then at a temperature of 35℃ and relative humidity.
The specimen was left in a 60% room for 7 days. [Pressure water permeability test] A predetermined amount of the material to be impregnated is applied to the top surface of this specimen, the sides are sealed with polyurethane resin, and after being left for 7 days at a temperature of 20°C and a relative humidity of 65%, the coated surface is Attach the mortar to a water permeability tester specified in JIS A1404 with the mortar facing up, and press clean water into the mortar from the top at a water pressure of 3 kg/cm ² to measure the increase in weight of the mortar after 5 hours. (e) Salt-blocking test A predetermined amount of impregnating material was applied to the entire surface of a 4 x 4 x 16 cm mortar specimen, and after being left for 7 days at a temperature of 20 ± 2°C and a relative humidity of 65 ± 5%. The specimen was fully immersed in saturated saline solution, and the weight increase was measured after 3 months, and the specimen was split open after 6 months of immersion to determine the penetration depth of chlorine ions into the interior (mm).
is measured by fluorescein color reaction. (f) Alkali immersion test A predetermined amount of material is applied to the entire surface of a 4 x 4 x 16 cm mortar specimen, and the temperature is 20 ± 2 °C and the relative humidity is 65 ±.
After being left for 7 days under the condition of 5% calcium hydroxide, the sample was completely immersed in a saturated calcium hydroxide solution, and the weight increase of the sample after 3 months was measured. (g) Underground reinforcement effect test A predetermined amount of material was applied to the top surface of a 7 x 7 x 2 cm mortar specimen, and after being left for 7 days at a temperature of 20°C and a relative humidity of 65%, it was tested according to JIS A6909.5.5. Measure the specified vertical tensile strength. (h) Crack filling adhesion effect test A gap was created between two mortar specimens measuring 7 x 7 x 2 cm and 4 x 4 x 2 cm using a 0.3 mmφ wire.
Place a 100g weight on top. When a material is applied to the peripheral edges of these two specimens, the material enters the gap by capillary action. This coating operation was repeated three times at 60 minute intervals, and the temperature was 25
After leaving it for 7 days at ℃ and 65% relative humidity, two grooves with a width of 2 mm and a depth of 2 mm are made vertically and horizontally, and the tensile strength is measured according to the provisions of JIS A6909.5.5. Examples 1 to 5 and Comparative Examples 1 to 2 Modifications obtained by first coating and impregnating alkyltrialkoxysilane on the surface of a specimen, then coating, impregnating, and curing a polymerizable acrylic monomer The above-mentioned various tests were conducted on the body. The measurement results are summarized in Table 1. Incidentally, decyltriethoxysilane (abbreviated as _C10 ) was used as the alkyltrialkoxysilane, and IBMA,
THFMA, 2-EHMA and 2-HPMA were selectively used, and cumene hydroxyperoxide was used as a polymerization initiation catalyst in an amount of about 0.5% based on the total amount of monomers. The amount of C ₁₀ applied, the types of acrylic monomers used, their combinations, and the amount of each application are shown in Table 1 below. In addition, the specimens were coated and impregnated with _C10 only (Comparative Example 1), those coated with IBMA, impregnated, and cured (Comparative Example 2), and the specimens themselves to which none of these were applied (blank). The measured values of each are also listed for reference.

[Table] Examples 6 to 9 Decyltriethoxysilane and isobornyl methacrylate were used as the alkyltrialkoxysilane compound and the acrylic monomer, and mixed compositions were prepared in various weight proportions. The composition was applied to the surface of the specimen in an amount of 300 g/m ² , impregnated, and cured to obtain a modified specimen with each composition. Table 2 summarizes the measurement results of each test conducted on the obtained concrete structure. From Tables 1 and 2, it can be seen that the method of the present invention has a significantly excellent deterioration prevention effect and repair effect on concrete structures. In addition, a two-step method in which a silane compound is first applied to a concrete-based porous structure and then a polymerizable acrylic monomer is applied, and a composition in which both components are mixed in advance is applied.
The one-step application method of impregnating and curing has similar water-blocking properties,
It can be seen that it exhibits salt blocking properties and pressurized water resistance, and also has a good filling adhesive effect against cracks and the like.

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Claims (1)

[Scope of Claims] 1. After applying and impregnating an alkyltrialkoxysilane compound on the surface of a concrete structure, a polymerizable acrylic monomer is applied together with a polymerization initiation catalyst, or an alkyltrialkoxysilane compound is applied to the surface of the concrete structure. Prevention of deterioration of concrete structures, characterized by coating and impregnating a mixture of a compound and a polymerizable acrylic monomer together with a polymerization initiation catalyst, and polymerizing and hardening the acrylic monomer that has penetrated into the structure. and repair methods. 2. The method according to claim 1, wherein the silane compound is an alkoxysilane compound having an alkyl group having 3 to 14 carbon atoms and an alkoxy group selected from a methoxy group and an ethoxy group.