JP2006124232A - Method of repairing reinforced concrete structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming a repairing layer for reinforcement which efficiently suppresses neutralization of reinforced concrete having insufficient covering depth and copes with the additional placement of concrete. <P>SOLUTION: The repairing method is that a 1st polymer mortar composition which contains cement, 40-300 pts.mass aggregate per 100 pts.mass cement and 20-70 pts.mass synthetic resin having 0 to -45°C glass transition point and has 10-30 cm flow value is applied on the surface of the concrete of the reinforced concrete structure to form a 1st layer having 2-5 mm thickness and a 2nd mortar composition which contains cement, 100-400 pts.mass aggregate per 100 pts.mass cement and 2-30 pts.mass synthetic resin having 10 to -15°C glass transition point is applied thereon to form a 2nd layer having 5-50 mm thickness. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a repair method for a reinforced concrete structure with insufficient cover thickness, and more particularly to a repair method with a mortar composition that suppresses neutralization of concrete and compensates for a lack of cover thickness of a reinforced concrete structure.

  Reinforced concrete originally has excellent strength and durability as a noncombustible structural material, and is widely used in buildings. The concrete layer shrinks with time, or easily cracks due to external forces in nature, and air and moisture enter it.In particular, on the outdoor wall, rainwater enters and the alkaline concrete layer is Easily neutralized. It is said that the neutralization of the concrete layer progresses to the inside in proportion to the square root of age even in the part without cracks. When the concrete becomes neutral, the reinforcing bars are oxidized and corroded, and the strength of the structure is significantly reduced. Therefore, it is an extremely important issue for reinforced concrete structures to suppress such neutralization, in particular, the generation of cracks.

  In Japan, as a measure to repeatedly change building standards or reduce construction costs, many structures with thin cover thickness of reinforced concrete structures have been built so far, but for reinforced concrete structures with insufficient cover thickness. However, the above problem is a more serious problem, and there is a demand for development of a technique for repairing the structural defect. Japanese Patent Publication No. 5-71550 (Patent Document 1) is known as a prior art relating to a neutralization of reinforced concrete, in particular, a protective layer that suppresses the occurrence of cracks.

  The technology of this Patent Document 1 relates to a construction method for forming a laminated thin layer of a coating material having a flame retardance on a reinforced concrete cement ground surface, particularly for cracking of the ground surface. On the other hand, a coating shielding method comprising a combination of a flexible undercoat thin layer containing a large amount of an acrylic resin that does not cause the same crack and a top coat thin layer imparting flame retardancy is disclosed. However, each coating material is adjusted to a viscosity suitable for roller application and is sequentially applied to the concrete base by a porous hand roller, so that the formed laminate is as thin as about 1 to 2 mm in each of the upper and lower layers. It is a sheet-like coating layer. This covering layer stably covers and shields the surface of a reinforced concrete structure without cracking due to its flexibility even when cracking the concrete ground surface, but it is difficult to expect a long-term protective effect due to the thin layer, It does not substantially contribute to the reinforcement of Moreover, since the application work with the porous hand roller is inferior in workability, it is not particularly suitable for large-scale work and the like, and is industrially disadvantageous.

  In recent years, improvement in the durability of reinforced concrete houses has become socially important, and the provision of stable houses that can suppress the neutralization of concrete over a long period of time has become a major technical issue. With regard to the extension of the service life of reinforced concrete houses, the standards for concrete deterioration prevention measures, which are based on three-generation dwellings that ensure stability over a long period of 75 to 90 years, are `` The Law on Promotion of Housing Quality Assurance. On the other hand, according to Article 79 of the Building Standard Law Enforcement Ordinance, in order to delay the neutralization, the cover thickness of the reinforcing bars was stipulated as 3 cm or more for bearing walls, columns and beams.

  However, in order to extend the life of existing reinforced concrete buildings with insufficient cover thickness as described above, it is optimal to reinforce concrete with increased cover thickness. Not only that, but because it is extremely disadvantageous economically, it cannot be practically adopted.

The inventors of the present invention develop a method for effectively repairing the lack of cover thickness as a repair method comparable to the increase in the concrete while suppressing the neutralization of reinforced concrete having a thin cover thickness, for example, less than 3 cm. We examined as much as possible. In the study, firstly, a neutralization-suppressing layer with good adhesion without risk of peeling and dropping applied to the concrete surface of a reinforced concrete structure, and secondly, a structural repair layer formed on that layer. Research was conducted on the combination of two types of mortar compositions.
Japanese Patent Publication No. 5-71550 (especially, claims)

  Accordingly, an object of the present invention is to provide a method of forming a repair layer that can effectively suppress the neutralization of reinforced concrete with insufficient cover thickness and can also be expected to have structural reinforcement that can cope with the additional striking of concrete. It is in. Another object is to provide a thick laminated repair layer with excellent adhesive strength, in which the application layer does not easily peel off from the wall surface of the concrete structure. Still another object of the present invention is to provide a reinforced concrete repair layer that is excellent in applicability to the outdoor wall of reinforced concrete and is economically desirable. Other problems and technical features of the present invention will become more apparent from the following description.

  In order to solve the above problems, the present invention provides a cement, 40 to 300 parts by weight of aggregate and 100 to 100 parts by weight of cement and 20 to 70 parts by weight of a glass transition point in the range of 0 to −45 ° C. A first polymer mortar composition containing a resin and having a flow value specified in JASS15M-103 adjusted within a range of 10 to 30 cm is applied to the concrete surface of a reinforced concrete structure to have a thickness of 2 to 5 mm. On the first layer formed and solidified, cement, 100 to 400 parts by weight of aggregate and 2 to 30 parts by weight of 10 to -15 ° C per 100 parts by weight of cement Provided is a method for repairing a reinforced concrete structure with insufficient cover thickness, in which a second mortar composition containing a synthetic resin having a glass transition point is laminated and formed as a second layer having a thickness of 5 to 50 mm.

  The first polymer mortar composition for the lower layer formed on the concrete surface of the reinforced concrete structure by the method of the present invention comprises 40 to 300 parts by mass of aggregate and 20 to 70 parts by mass of 0 per 100 parts by mass of the cement. A composition containing a synthetic resin having a glass transition point in the range of ˜−45 ° C. and having a flow value specified in JASS15M-103 in the range of 10 to 30 cm is applied to the concrete surface of the reinforced concrete structure. The flow value of this composition is usually prepared by adding water, for example, by roller brushing or spraying to a first mortar layer (priming layer) having a layer thickness of 2-5 mm, preferably 3-4 mm. It is formed. For the coating layer, any generally known method such as a spraying method or a coating method can be adopted.

  Further, the second mortar composition applied on the undercoat layer in the method of the present invention comprises cement, 100 to 400 parts by weight of aggregate and 2 to 30 parts by weight of aggregate per 100 parts by weight of cement. A composition comprising a synthetic resin having a glass transition point in the range of 10 to -15 [deg.] C., wherein the second layer has a thickness of 5 to 50 mm on the first primer layer by spraying or troweling. The upper layer (overcoat layer) is laminated. This layer thickness is selected particularly depending on the lack of cover thickness of the reinforced concrete to be repaired, and it is important that the thinner the cover thickness, the thicker the cover layer is. Preferably, it is the range of 5-30 mm.

  The mortar laminating repair layer formed by the method of the present invention is highly resistant to neutralization of concrete because it has excellent covering shielding properties over a long period of time without cracking due to cracks over time of the concrete base. It can be stably suppressed. In addition, the method of the present invention is an extremely practical repair method that can be sprayed or applied in a simple manner without increasing the concrete thickness in order to increase the cover thickness of an existing reinforced concrete building. Therefore, it can be applied to repair work for reinforced concrete houses for three generations.

  In the method of the present invention, the cement used in the first polymer mortar composition and the second mortar composition is not particularly limited, but Portland cement, fly ash cement, blast furnace cement and alumina cement are preferably used. These may be used alone or in combination of two or more. Practically, Portland cement is preferably used.

  In the method of the present invention, the aggregate used in the first polymer mortar composition is a fine granular material adjusted to a particle size of 0.6 mm or less, and as such an aggregate, for example, Examples include dredged sand, calcium carbonate, slag crushed sand, perlite, and ethylene / vinyl acetate copolymer chips. These aggregates may be used singly or in combination of two or more. The amount used is in the range of 40 to 300 parts by mass with respect to 100 parts by mass of cement in the first mortar composition. If it is less than 40 parts by mass, it is difficult to ensure a coating thickness of 2 to 5 mm mortar. On the other hand, if it exceeds 300 parts by mass, not only the strength and flexibility of the layer will be lowered, but also the curing rate will be slow, and the working efficiency will be reduced, which is disadvantageous in practice. The preferable usage amount range varies depending on the type and specific gravity of the aggregate, but is in the range of 120 to 250 parts by mass. A more preferable range is 150 to 220 parts by mass.

  The aggregate used in the second mortar composition for top coating is in the range of 100 to 400 parts by weight per 100 parts by weight of cement. If it is less than 100 parts by mass, the drying shrinkage rate is increased, and it is difficult to ensure a thick coating, which is not preferable. On the other hand, when the amount exceeds 400 parts by mass, the water / cement ratio increases, so that the neutralization suppressing ability is lowered and the strength of the layer is also lowered. The preferable amount of use varies depending on the type and specific gravity of the aggregate, but is 200 to 400 parts by mass.

  In the first polymer mortar composition and the second mortar composition of the present invention, a part of the aggregate can be replaced with an inorganic powdery admixture with finer particles. Examples of such admixtures include fly ash, calcium carbonate, blast furnace water slag, and talc. They are used in replacement amounts in the first polymer mortar composition of up to 80% by weight of the aggregate and in the second mortar composition of up to 50% by weight. If the ratio is exceeded, it is not preferable because it is difficult to ensure the thickness of each coating material layer. The upper limit of the desired substitution amount is 60% by weight for the first polymer mortar composition and 30% by weight for the second mortar composition.

  Next, the synthetic resin used in the first polymer mortar composition is a synthetic resin having a glass transition point (Tg) in the range of 0 to -45 ° C. Examples include acrylic resins, ethylene / vinyl acetate resins, vinyl acetate / versaic acid ester resins, and styrene / butadiene rubber (SBR) resins. When Tg is higher than 0 ° C, the undercoating mortar layer formed on the concrete surface has insufficient elongation and flexibility at low temperatures, and when it is lower than -45 ° C, the softening temperature of the mortar layer becomes low, and the coating layer This is not preferable because the hardness is insufficient and the adhesiveness is also lowered. When importance is attached to the flexibility of the coating layer to be formed, those having a Tg in the range of −10 to −40 ° C. are preferably used.

  The usage-amount of the synthetic resin added to a 1st polymer mortar composition is 20-70 mass parts per 100 mass parts of cement. If it is less than 20 parts by mass, the flexibility of the undercoat mortar layer, that is, the elongation performance is insufficient, which is inappropriate, and if it exceeds 70 parts by mass, the physical strength of the layer is lowered and the adhesion durability with time is also lowered. Therefore, it is not preferable. The preferred usage range is 30 to 60 parts by mass, but 40 parts by mass or more is preferable when emphasizing elongation performance. These synthetic resins can be added as a powder, preferably as a re-emulsifying powder, but can also be added as an emulsion. In the case of an emulsion, the resin solid content is adjusted so as to be within the above range.

  It is important that the synthetic resin used in the second mortar composition has a Tg in the range of 10 to -15 ° C. Examples of such synthetic resins include acrylic resins, ethylene / vinyl acetate resin systems, acetic acid / versaic acid ester resins, and styrene / butadiene rubber (SBR) resins. If the Tg is higher than 10 ° C, the resin film-forming bondability at the time of forming the mortar layer is poor. Therefore, the formed overcoating layer tends to break, and if the Tg is lower than -15 ° C, This is not preferable because the physical strength of the layer is lowered. Considering the function of the coating layer to be formed, the Tg of the resin is preferably within a range of 5 to -15 ° C, and particularly a resin having a Tg within the range of 0 to -10 ° C is preferably used. .

  These synthetic resins are added to the second mortar composition in an amount ranging from 2 to 30 parts by mass per 100 parts by mass of cement. The overcoat layer preferably has a drying shrinkage ratio as small as possible and desirably has a high physical strength, and an improvement in the safe coating shielding performance of the first undercoat layer can be expected. However, if the amount of resin used is less than 2 parts by mass, it is difficult to improve the neutralization suppressing performance of the laminated coating layer. Moreover, when it exceeds 30 mass parts, since workability is inferior and it becomes a cost increase, it is industrially disadvantageous. A preferable usage amount is in the range of 5 to 15 parts by mass.

  The composition containing cement, aggregate and synthetic resin is adjusted to a mortar composition for layer formation by adding water. The first polymer mortar composition applied to the surface of the reinforced concrete is applied to the vertical surface of the reinforced concrete and adjusted to a softness (viscosity) suitable for forming an undercoat layer with a thickness of 2 to 5 mm. Is done. The softness suitable for the formation of such an undercoat layer is measured by the method stipulated in JASS15M-103 (quality standards for self-leveling materials) described in the Building Construction Standard Specification / Explanation (The Architectural Institute of Japan). The flow value is within the range of 10-30 cm. The flow value is the maximum diameter of a circular shape with a 50 mm inner diameter and 51 mm high vinyl chloride pipe placed on a 5 mm thick polished glass, filled with kneaded mortar, pulled up, and the mortar spread stationary. And the diameter perpendicular to it is measured, and the average length is displayed in cm.

  If the flow value of the first polymer mortar composition is less than 10 cm, the fluidity is insufficient, and it is extremely inappropriate to form a layer having a thickness of 2 to 5 mm by operations such as roller coating and spraying with a sprayer. It is. In addition, when the flow value exceeds 30 cm, it is difficult to form a layer having a thickness of 2 to 5 mm on the vertical wall surface because the viscosity is too low, and the composition applied to the vertical surface may flow down or in some cases. This is inconvenient because moisture separates and causes a bleeding phenomenon. A preferred flow value range is 15 to 25 cm, and a particularly preferred range is 18 to 22 cm. The adjustment of the flow value is mainly adjusted by the amount of water, but according to an expert, it can be easily adjusted to a composition having a desired flow value while injecting and mixing water. The mortar composition having this flow value can be applied with a trowel or sprayed with a spraying machine, but spraying is excellent in workability and extremely industrially advantageous.

  In addition, the second mortar composition is sprayed by a spraying machine on the dried and solidified undercoat layer after the first polymer mortar composition is applied to the concrete surface. Usually, it adjusts by adding water to a solid content composition. Here, solidification of the undercoat layer refers to a solidified state in which the second mortar composition is cured to such an extent that it is not easily affected by deformation such as spraying.

The second mortar composition is adjusted to a viscosity or plasticity suitable for forming a layer thickness of 5 to 50 mm by spraying or troweling, but is changed and adjusted according to the desired laminated thickness. The viscosity is, for example, Japanese Industrial Standard
It is preferable that the flow value when measured by the method defined in JIS R 5201 is adjusted within the range of 150 to 250, particularly 170 to 220. If the flow value is less than 150, the fluidity is poor and it is too hard to be sprayed by a sprayer. On the other hand, if it is higher than 250, the composition sprayed on the first mortar layer flows down due to low viscosity, and the desired layer thickness cannot be ensured. The above flow value range of this composition is suitable for spraying a relatively thick topcoat layer of about 5 to 50 mm. The layer thickness formed by spraying is about 20 to 25 mm in relation to plasticity. Therefore, in order to secure a layer thickness of 25 mm or more, it is usually necessary to spray twice.

When adjusting the first polymer mortar composition and the second mortar composition, various regulators which are usually used in the technical field and the coating technical field can be added and used. Such regulators include, for example, thickeners, shrinkage reducing agents, water reducing agents, antifoaming agents and fibers. These regulators use the performance of each to adjust the flow value and viscosity of the composition suitable for spraying, etc., and to reduce the medium moisture of the composition, and thus the coating layer. It is used to adjust the desired state such as reduction of drying shrinkage and defoaming. Further, the fibers contribute to improvement of the physical strength and flexibility of the layer. As such a fiber material, synthetic resin fibers having excellent temporal stability such as vinylon, polyester, acrylic, and alkali-resistant glass fibers are preferable, and relatively short synthetic resin fibers are preferably used. The Examples of the drool preventive agent include silica fume and fly ash.
These fibers are used by adjusting to a short fiber length of about 1 to 15 mm, for example. Those additive regulators are appropriately selected and used by a skilled person in a relatively small amount that is generally used.

  When applying the first composition, it is desirable to wet the surface of the concrete before the application, and an improvement in the adhesion of the first layer can be expected. A method of forming a thin resin undercoat film layer by spraying a resin emulsion is also effective. Such undercoat resin emulsions are not particularly limited, but practically desirable undercoat emulsions include, for example, the stability of resins such as ethylene / vinyl acetate copolymer (EVA) and acrylic resins. Can be mentioned.

  Although the laminated coating layer formed by the method of the present invention itself provides a long-term stable shielding protective layer, a top coat having good weather resistance can be further provided on the surface of the second coating layer. This top coat is effective in preventing the cement whitening phenomenon and improving the stain resistance of the concrete, and as a result, further improving the neutralization suppressing effect of the reinforced concrete. As such a coating material, for example, silicone resins and acrylic resins are preferably used. These are usually applied by spraying in the form of dilute solutions or resin emulsions and provided with a thin protective film.

Hereinafter, the present invention will be described in more detail with reference to specific examples. In addition, the number of parts and% in a specific example are based on weight unless there is particular notice. Various performances of the reinforced concrete mortar laminated repair layer formed by the method of the present invention include zero span tension elongation (mm), neutralization depth (mm), standard bond strength (N / mm ² ), and hot and cold repetition. The subsequent adhesion strength (N / mm ² ) and crack resistance were tested and their measured values were evaluated. The measurement methods for the various performances are as follows.

Zero span tension elongation (mm):
This was in accordance with the performance test method of the Independent Administrative Institution Urban Renewal Organization (hereinafter abbreviated as Urban Organization) “Inorganic coating waterproofing material”. Cut a flexible board with a thickness of 5.0 mm specified in JIS A 5430 to produce two 50 x 75 mm rectangular boards, but the short sides of both boards are butted together and the back side is fixed with adhesive tape to make a base The first polymer mortar composition is applied to the surface to a layer thickness of 3 mm, and the second mortar composition is applied to a thickness of 7 mm on the surface to form a laminate, which is formed at 20 ° C. and 65% relative humidity ( Cured for 28 days under the conditions of (RH). This test body was attached to a tensile tester, the adhesive tape was cut and pulled at a tensile speed of 5 mm / min, and the increase in the distance between the holding chucks when the test body was broken was measured to obtain zero span tension elongation. This zero span tension elongation is considered to be effective if it is 0.6 mm or more (preferably 0.8 mm or more) in order to cope with a crack of about 0.5 mm.

Neutralization test:
The test was conducted according to the test method of the urban organization “Premix polymer cement mortar for initial repair”. First, 60% water / cement ratio water is added to a 1: 3 mass ratio mixture of cement: river sand (particle size 2.5 mm or less), and the composition is kneaded to form a 100 × 100 × 400 mm mold. A concrete piece of 100 × 100 × 100 mm was produced by placing the frame in a frame and cutting the plate. A mortar composition was applied to one surface of the concrete piece, and an epoxy resin paint was applied to the four surfaces in contact with the surface to form a coating layer to prepare a base plate. A mortar composition was applied and formed on the one surface of the base plate, and this was cured at 20 ° C. and 65% RH for 14 days. This was further stored on a shelf in a neutralization promotion test chamber at 30 ° C., 60% RH and CO ₂ concentration of 5% for 30 days, and the neutralization depth was examined. The mortar layer of the curing sample was split at right angles, and a 1% phenolphthalein solution was sprayed on the split surface, and the depth of the portion not colored red was determined as the neutralization penetration depth.

Standard adhesive strength (N / mm ² ) and adhesive strength after repeated heating and cooling (N / mm ² ):
A measurement sample was prepared according to the test method of the Urban Organization “Premix Polymer Cement Mortar for Initial Repair”, and the adhesive strength was measured according to the provisions of JIS A 6909. The sample to be measured is a 70 × 70 × 20 mm mortar plate, and a 3 mm first polymer mortar subbing layer and a 7 mm second mortar layer are formed on the plate surface. After curing for 24 hours, Was measured for 28 days in an atmosphere (standard condition) at 20 ° C. and 65% RH as the standard time adhesive strength. In addition, a sample prepared in the same manner and cured in a standard condition of 20 ° C. and 65% RH for 28 days is further immersed in 20 ° C. water for 18 hours, taken out, and immediately kept at a constant temperature of −20 ° C. Cooled in a bath for 3 hours and kept in a thermostatic bath at a temperature of 50 ° C for 3 hours. Repeated 10 times, left in standard condition for 2 days, and measured as adhesive strength after repeated heating and cooling. To do. The bond strength at the standard time and after repeated heating and cooling is preferably 0.6 (N / mm ² ) or more, and the interface fracture rate is preferably 50% or less.

Crack resistance:
The cracking property test by initial drying was performed according to JIS A 6909. Based on JIS A 5430 4 mm thick flexible plate cut to 300 x 150 mm, the first polymer mortar composition and the second mortar composition are adjusted immediately to 3 m / sec. Place the specimen in parallel with the airflow, remove the specimen after 6 hours, and examine the surface for cracks. This test is important for maintaining the neutralization inhibiting performance and durability of the second mortar layer.

[Preparation of various polymer mortar compositions for first layer (primer)]
Undercoat materials comprising various components shown in Table 1 below were prepared. The numbers are mass percentages. In Table 1, the used cement is Portland cement, and the aggregate is No. 6 cinnabar. Synthetic resin is acrylic resin with Tg of 0 ° C A 0, -40 ° C A-40, -50 ° C A-50, styrene acrylic resin -20 ° C SA-20 is indicated, and ethylene / vinyl acetate is T0 0 ° C E 0, -10 ° C E-10, -20 ° C E-20, -25 ° C E-25 And those at 10 ° C. are indicated by E10. The e added after that indicates that it was added in the emulsion, but the numerical value is the resin solid content in the emulsion. In addition, about 0.2 mass% of methylcellulose was added to each composition as a viscosity modifier.
Moreover, about hardening time, adhesive strength, elongation performance, and applicability | paintability, it evaluated as follows.

[Curing time]
○: Cured after 20 hours at 20 ° C.
X: Cured within 20 hours at 20 ° C.
[Adhesive strength]
○ ... 0.6 N / mm ² or more × ... less than 0.6 N / mm ² [elongation performance]
○: Zero span tension elongation of the first layer material alone is 0.8 mm or more ×: Zero span tension elongation of the first layer material alone is less than 0.8 mm [Coating property]
○: It is possible to paint well with one or two rollers. × ... With one or two rollers, painting is insufficient.

  Table 1 summarizes the main component constitutions of the 17 polymer mortar compositions for the first layer and the layers formed, and the physical properties of each. Lower 1, lower 8, lower 9, lower 11-13, lower 16 and lower 17 in the table are compositions outside the scope of the present invention.

[Preparation of mortar compositions for various second layers (coating materials)]
A top coating material comprising various components shown in Table 2 below was prepared. The numbers are mass percentages.
In the table, the used cement is Portland cement, and the aggregate is No. 4 and No. 5 mixed dredged sand. The synthetic resin was the same as the display shown in Table 1.
In addition, about the compressive strength of this composition, shrinkage | contraction rate, and thick coating property, it measured as follows and attached the evaluation criteria.

[Compression strength]
It measured based on JIS A6203. This value is preferably 20 N / mm ² or more.
[Shrinkage factor]
The measurement was performed according to JIS A 1141.
[Thickness]
Excellent ... Possible up to 20mm at a time Possible ... Possible up to 15-20mm at a time Impossible ... Possible up to less than 10mm at a time

  Table 2 summarizes the main component constitutions of the 10 types of mortar compositions for the second layer thus adjusted and the physical properties of these layers. Top 1, top 5, top 6, top 9 and top 10 in the table are compositions outside the scope of the present invention.

(Examples 1-8 and Comparative Examples 1-5)
Various performances of the laminated repair layer by various combinations of the undercoat material and the topcoat material were measured by the test method. The results and evaluation are summarized in Table 3 below. In addition, the upper and lower material numbers in the column of the undercoat material and the overcoat material in the table are the respective coating materials described in Tables 1 and 2 above. In addition, the crack resistance of the test items to be measured is crack resistance, the neutralization depth (mm) is the neutralization depth, the standard bond strength (N / mm ² ) is the standard bond strength, and the standard interface fracture rate ( %) Standard interfacial break, bond strength (N / mm ² ) after hot / cold repetition, hot / cold bond strength, interface fracture rate (%) after hot / cold repeat, hot / cold interfacial break, compressive strength (N / mm ² ) was abbreviated as compressive strength and zero span tension elongation (mm) as elongation. In addition, the physical properties of each specific example were measured by applying a primer to a thickness of 3 mm, curing for 24 hours, and then forming a repair layer 23 mm on which a top coat was laminated to a thickness of 20 mm. Was measured. The layer thickness (mm) of each coating material is shown in parentheses.

Comprehensive evaluation: standard bond strength is 1.0 N / mm ² or more, standard interface fracture rate is 50% or less, bond strength after repeated heating and cooling is 0.7 N / mm ² or more, interface fracture rate after repeated heating and cooling The criteria for pass / fail were: 50% or less, zero span tension elongation of 0.6mm or more, no cracks, and no applicability.

  As apparent from Table 3, when the aggregate amount of the undercoat layer of the first polymer mortar composition is small, it is difficult to ensure the layer thickness and the crack resistance is inferior (Comparative Example 1). On the other hand, if the amount is too large, the strength is lowered and the adhesive strength is extremely reduced (Comparative Example 2). From Comparative Examples 3 to 5, it is understood that long-term stable repair effects of reinforced concrete structures cannot be expected when deviating from the respective limiting requirements of the first polymer mortar composition for undercoating and the mortar composition for overcoating in the present invention. Let's be done.

  The laminated mortar repair layer formed by the method of the present invention more stably shields the concrete outer surface of the reinforced concrete structure with insufficient cover thickness, highly suppresses the neutralization of the concrete, and provides a second mortar composition. Since the solid surface layer is repaired and reinforced, the life of the structure is greatly extended. In addition, the laminated repair layer according to the method of the present invention is excellent in physical properties such as adhesive strength, interfacial fracture rate, and delamination resistance, and stably protects and repairs reinforced concrete structures over a long period of time. Can be provided.

Claims (1)

Containing cement, 40-300 parts by weight of aggregate and 100-mass of the cement, and 20-70 parts by weight of synthetic resin having a glass transition point in the range of 0--45 ° C, specified in JASS15M-103 The first polymer mortar composition having a flow value adjusted within a range of 10 to 30 cm is applied to the concrete surface of the reinforced concrete structure to form a first layer having a thickness of 2 to 5 mm and solidified. On top of one layer, containing cement, 100 to 400 parts by weight of aggregate and 100 parts by weight of cement and 2 to 30 parts by weight of synthetic resin having a glass transition point in the range of 10 to -15 ° C. A method for repairing a reinforced concrete structure with insufficient cover thickness, wherein the second mortar composition is laminated as a second layer having a thickness of 5 to 50 mm.