KR101708879B1 - Method for repairing concrete structure with improved durability - Google Patents

Abstract

The present invention relates to mortar for repairing concrete, which ensures excellent durability and is intended to repair cross-sections or surfaces of concrete deteriorated in structures requiring concrete repair/reinforcement such as water and sewage pipes, sewage ducts, bridges, tunnels, tidal gates, agricultural irrigation canals, harbor facilities, dams, slabs, dammed pools, pillars, and foundations. The present invention further relates to a method for repairing concrete and, more specifically, a method for repairing concrete, which ensures excellent durability, increased contents of alumina, and increased fineness, by using a specific cement clinker instead of using common type 1 Portland cement.

Description

METHOD FOR REPAIRING CONCRETE STRUCTURE WITH IMPROVED DURABILITY [0002]

The present invention relates to a method for repairing and repairing a section or surface of a concrete which is deteriorated in a structure requiring repair and reinforcement of concrete such as a water supply and drainage pipe, sewage culvert, bridge, tunnel, drainage gate, agricultural waterway, port facility, dam, slab, beam, The present invention relates to a concrete repairing method having excellent durability and a durability, and more particularly, to a concrete repairing method using a special cement clinker instead of the ordinary Portland cement, which has high durability and increased alumina content.

Concrete structures are widely used as construction materials for semi-permanent structures due to their excellent durability. However, when these concrete structures are exposed to the marine environment for a long time, the concrete is eroded by the action of seawater (sea breeze), the rebar is corroded and the concrete is cracked and peeled by the volume expansion. As a result, . In winter, concrete may be damaged due to frozen and thawed concrete, and if it is exposed to automobile exhaust gas for a long time, the inner reinforcing steel may be corroded due to neutralization phenomenon, and concrete may crack or fall off .

In addition to these causes, the deterioration of concrete structures, neutralization, alkali aggregate reaction, plant wastewater and sewage can also cause corrosion of reinforcing bars and damage to concrete.

In the case that the inner reinforcing steel is corroded due to various causes and the concrete is cracked or dropped, it is necessary to restore it to a circular shape in order to continue to use the structure stably. Accordingly, various concrete structure circular restoration methods .

The general repair method of the concrete structure is done by applying the repair mortar (installation).

 Conventionally, one type of ordinary mortar is usually Portland cement.

One kind of Portland cement usually consists of hydrous C3S, C2S, C3A, C4AF (C = CaO, S = SiO2, A = Al2O3, F = Fe2O3) and a small amount of sulfate such as gypsum. Is the earliest reaction in the initial process where water and cement react, forming an aluminate gel, which reacts with the sulfate present in the cement and forms an ettringite which expands to the acicular structure. Aluminate gel is used as a mechanism to compensate the condensation of cement and to compensate the contraction of cement by using expansion structure.

However, after the cement is cured, the calcium aluminate reacts with the sulfate contained in the groundwater or seawater and reacts to form an expanded crystal, Ettringite. In other words, the late ettringite formed after the concrete is cured is called DEF (delayed ettringite formation), which causes a crack-like crack on the surface of the reinforced concrete after the concrete is cured due to the expansive crystal structure of the DEF crystal . As the crack continuously reacts with sulfate and grows in size over time, water or chloride penetrates into the structure through such cracks, resulting in a serious damage to the stability of the concrete structure.

In order to solve such a problem, conventionally, as described in the patent document (Korean Patent Registration No. 10-1616103), the shrinkability of cement is supplemented by blending an expandable CSA or a torsionally stiff CSA with one kind of ordinary Portland cement, Which is a product produced according to KS F 4042 quality, which is a mixture of KS F 4042 and KS F 4042.

That is, the conventional concrete repairing materials having excellent corrosion resistance against seawater and chemical resistance include 30 to 45% by weight of one kind of ordinary Portland cement, 10 to 15% by weight of calcium sulfoaluminate cement, 5 to 20% by weight of silica sand having an average particle diameter of 0.1 to 1.2 mm, 0.1 to 2% by weight of a fibrous reinforcement mixed with PP fiber and manila hemp having an average length of 65 to 75 탆 and an average length of 3 to 6 mm, 0.5 to 2% by weight of a fluidizing agent, 25 to 25% by weight of a pozzolan powder, 5 to 10% 3 to 5% by weight of waste glass powder having a particle size of 4000 to 4500 cm2 / g, 5 to 12% by weight of anhydrous gypsum, 1 to 5% by weight of an acrylic re-oiled resin, 5 to 8% Wherein the one or more kinds of ordinary Portland cement, calcium sulfoaluminate cement, silica sand, pozzolan powder, fiber reinforcing material, fluidizing agent, anhydrous gypsum, waste glass powder and acrylic- 0.1 to 0.3 parts by weight of tungstic acid and 0.1 to 0.3 parts by weight of calcium formate are added to 100 parts by weight of the mixture of the resin and the CSA-based swelling agent for shrinkage reduction.

However, since the conventional concrete repair material uses one kind of ordinary portland cement itself, the quality thereof is not constant and it is difficult to control the shrinkability of the cement, and the crack occurrence rate is high.

In addition, due to the nature of one kind of ordinary Portland cement, the adhesion performance is regulated by the content of the re-fusing powder resin, so the workability is lowered and the reusable powder resin powder (3000 to 3200 cm 2 / g) Falls.

In addition, since one kind of ordinary Portland cement is used as a main material, the content of alumina (Al2O3), which is one of the chemical composition, is very low (usually 4 to 5 wt%) and fire resistance is deteriorated.

In addition, since the blend design of one kind of ordinary portland cement places emphasis on the compressive strength, the flexural strength exhibiting direct reinforcement performance is lowered and the economical efficiency is lowered due to the large reinforced area and thickness in order to exhibit the performance.

Korean Patent Registration No. 10-1616103

It is an object of the present invention to provide a maintenance method which is easy to apply to a concrete structure requiring maintenance by deterioration or the like, and which has high strength, fire resistance and workability and is excellent in durability.

In order to achieve the above-mentioned object, the concrete repairing method according to claim 1 of the present invention is a concrete repairing method having excellent durability, comprising the steps of: performing a surface treatment for completely removing a deteriorated or eroded surface (such as a concrete section or a surface) step; A foreign matter removing step of completely removing foreign matter remaining on the surface after the surface treatment step; A primer applying step of applying a primer adhesive to the applied surface from which the foreign matter is removed to increase the adhesive force of the concrete; And restoring the construction surface by installing a concrete repair mortar having excellent durability after the application of the primer, wherein the concrete repair mortar having excellent durability comprises 36 to 44% by weight of special cement, 0.04 to 0.06% by weight of a fiber selected from the group consisting of polypropylene, polyethylene, nylon and PVA is mixed in an amount of 55 to 63% by weight, a re-oiled powder resin of 0.5 to 2.0% by weight, methylcellulose 0.03 to 0.06% The special cement is pulverized to a particle size of 4000 to 4500 cm2 / g by mixing 30% by weight or less of the blast furnace slag with 12% by weight or less of fly ash with respect to 100% by weight of the special cement clinker and the special cement clinker C ₂ S and anhydrous C ₄ A ₃ S obtained by calcining borax (35 to 55 wt%), limestone (10 to 20 wt%) and steel making slag (30 to 50 wt%) at 1300 to 1400 ° C, 5% by weight or less of calcium and 8% (FM) of 2.8 to 3.1, and the chemical composition of the special cement is 17.10% by weight of silica (SiO ₂ ), and the content of alumina (Al ₂ O ₃₎ 20.95% by weight of iron oxide (Fe ₂ O ₃₎ 2.35% by weight, calcium (CaO) 48.70% by weight of oxide, magnesium (MgO) 2.60% by weight oxide, titanium dioxide (TiO ₂₎ 1.55% by weight, of sulfur trioxide (SO ₃ ).

In the method of repairing concrete with excellent durability according to the second aspect of the present invention, there is provided a method for repairing concrete, comprising the steps of: applying a surface treatment agent for preventing concrete neutralization and salt damage to the surface having been restored; And applying the antifouling agent after applying the surface treatment agent for preventing neutralization and salt corrosion.

According to the present invention, the durability is remarkably improved due to the following effects when applied.

1 Specially, by using special cement excluding Portland cement, it is easy to control shrinkage and expansion originally, so that the occurrence rate of crack can be remarkably reduced.

In addition, it can be economically reinforced by reducing the reinforced area and the thickness of the construction surface by improving the strength by mixing sand fine aggregate and fiber.

In addition, while the type 1 ordinary Portland cement has a compressive strength of less than 60% at 600 ° C, the special cement having a high alumina content has a fire resistance of 900 ° C or more, so that the structure is not likely to collapse even in the event of fire.

In addition, since the specific surface area of the special cement clinker is high, it has a high moisture-holding ability and there is no decrease in the surface strength due to the surface roughness (unevenness), and due to the high powder, It sticks well and has less stickiness, so the work speed is fast and the beauty is very beautiful.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flowchart illustrating a concrete repair method using a concrete repair mortar having excellent durability according to a preferred embodiment of the present invention. FIG.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a flowchart showing a method of repairing concrete using a concrete repair mortar having excellent durability according to a preferred embodiment of the present invention.

The concrete mortar having excellent durability according to the present embodiment is composed of a fiber of any one of special cement, sand, re-oiled powder resin, methylcellulose, polypropylene, polyethylene, nylon and PVA .

That is, the concrete mortar having excellent durability is composed of 36 to 44% by weight of special cement, 55 to 63% by weight of sand, 0.5 to 2.0% by weight of re-oiled powder resin, 0.03 to 0.06% by weight of methylcellulose, , Nylon and 0.04 to 0.06% by weight of fibers of any one of PVA materials.

The special cement is prepared by mixing 30 wt% or less of blast furnace slag with 12 wt% or less of fly ash, and pulverizing it to 4000 to 4500 cm 2 / g with respect to 100 wt% of special cement clinker.

The sand is used to improve the pouring strength of the concrete repair mortar, and the particles having a maximum size of 1.5 mm and a minimum size of 0.3 mm are mixed with a fine aggregate (FM) ratio of 2.8 to 3.1.

The FM Fineness Modulus is a numerical representation of the mixing ratio of the most stable mixture of aggregate sizes, ie, large and small granules of the aggregate, in appropriate proportions. The test method is the value obtained by dividing the cumulative residual ratio by 100 divided by ten sieves sieving sieves of 80, 40, 20, 10, 5, 2.5, 1.2, 0.6, 0.3, 0.15 mm, and the assembly ratio of fine aggregate for concrete is 2.3 ~ 3.1 is the standard value, and coarse aggregate is about 6-8. The fine aggregate has a large influence on the strength, and the coarse aggregate does not affect the strength by itself. Therefore, the mixing design should be redone every time the fine aggregate granulation ratio changes by 0.2. There are several reasons why the granular aggregation rate affects the strength. The lower the granulation rate, the smaller the granules and the larger the surface area of the fine aggregate. As a result, the cement paste has a smaller thickness (coating) and weaker binding force. This is because air bubbles are contained and air bubbles act as voids to reduce the bonding force with cement. Therefore, in this embodiment, the reinforcing area and the thickness of the work surface are reduced with high strength by adopting a higher assembly ratio, thereby contributing to economical reinforcement.

The re-oiling type powder resin is mixed with special cement as a cement modifier and forms a film when the special cement is cured by hydration reaction and serves as a bond to add the characteristics such as tensile strength and adhesiveness of the polymer to the special cement. Special cement powder is very strong and moisture is very strong. Even if you do not use reusable powdered resin, it sticks well to the concrete matrix and it is fast and it is very clean.

The methylcellulose is used in a work for attaching a hard surface or tile to the mortar by improving the viscosity and the adhesive force to the mortar. It prevents the crack caused by expansion and contraction of the mortar after the construction, and has waterproof and antibacterial effect. In addition, it is a universal chemical pool for plastering and trowelling, which has good workability and is effective for homogeneous mixing of special cement and sand.

The fiber is made of polypropylene, polyethylene or nylon, and is a fillet type fiber, and contributes greatly to the improvement of the strength, particularly the bending strength, of the special cement.

On the other hand, the special cement clinker (clinker) are bauxite (35-55 wt%), limestone (10-20 wt%), C ₂ obtained by the slag (30-50% by weight) and baked at 1300 ~ 1400 ℃ S and anhydrous C ₄ A ₃ S to 5 wt% or less of calcium sulfate and 8 wt% or less of calcium oxide.

Special cement clinker is a lump obtained by calcining bauxite, limestone and steel slag at high temperature.

C2S is the most important component for solidification of special cement, and it is 2CaO, SiO2 component. Among the special cement components, the content is highest with C3S.

It is also used as an expansion agent to suppress the shrinkage and cracks that occur when special cement concrete cures by synthesizing special cement clinker minerals such as C4A3S and C2S.

Further, in order to increase the content of alumina, a special cement clinker is produced by reducing the amount of borosite and increasing the amount of steel slag.

As described above, in the present embodiment, C ₂ S and anhydrous C ₄ A ₃ S obtained by the special cement clinker are excluded from the one kind ordinary portland cement, and calcium sulfate and calcium oxide are mixed and pulverized. Table 1 shows the results obtained from the KS cement test.

Division Property Unit (weight) Results Chemical composition
Composition) Silica (SiO ₂₎ % 17.10 Alumina (Al ₂ O ₃₎ % 20.95 Iron oxide (Fe ₂ O ₃ ) % 2.35 Calcium oxide (CaO) % 48.70 Magnesium oxide (MgO) % 2.60 Dioxide, titanium (TiO ₂₎ % 1.55 Sulfur trioxide (SO ₃ ) % 6.15

As shown in Table 1, since the content of alumina is relatively large, the fire resistance is excellent and the compressive strength is relatively large.

The concrete repair method using the concrete repair mortar having excellent durability according to the present invention is as follows (see FIG. 1).

1. Construction Surface Treatment Process

The deteriorated or eroded surface (concrete section or surface, etc.) is completely removed by chipping or grinding with a tool or the like.

Remove the reinforced concrete part of the construction surface using tools suitable for the site conditions.

The soft part is removed with a wire brush, a grinder or the like.

2. Foreign matter removal process

After the surface treatment step, foreign substances such as sand and gravel remaining on the work surface are completely removed by using a blower or a high pressure washer.

3. Primer Adhesive Application Process

The primer adhesive is applied to the applied surface from which the foreign matter is removed to increase the adhesive force of the old and new concrete so that the concrete repair mortar can be bonded.

4. Construction Surface Recovery Process

After the primer application step, the concrete surface repair mortar having excellent durability is laid to restore the construction surface.

It is possible to apply concrete mortar by spraying method, and when the surface aesthetics is considered, the mortar is applied.

5. Application process of surface treatment agent for neutralization and prevention of saltiness

 A surface treatment agent for preventing concrete neutralization and salt corrosion is applied to the surface where the surface is restored.

6. Pollution prevention agent application process

After the surface treatment agent for neutralization and salt prevention is applied, the antifouling agent is applied and sufficiently dried.

<Examples>

1. Experiment 1

Strength change according to ratio of special cement and sand

The ratio of special cement to sand is varied to derive the most effective formulation for strength development. The water-mortar (W / C) ratio was fixed at 45%. Three cucumber molds of 5 × 5 × 5 size were prepared at each age and cured at a temperature of 20 ± 5 ° C one day later. Respectively.

Special cement
(weight%) sand
(weight%) W / C (%) Compressive strength (N / mm ^{2 )} 1 day 3 days 7 days 28th 90 days T1 36.0 64.0 45 25.1 34.4 43.2 58.1 63.1 T2 40.0 60.0 45 32.4 43.1 50.2 60.3 68.1 T3 44.0 56.0 45 39.4 49.6 56.4 70.4 76.5 T4 48.0 52.0 45 44.1 55.2 64.5 82.1 88.1

2. Experiment 2

According to the above results, 45% of W / C is used for 40% of special cement and 60% of sand, and the reusable powdered resin and MC (methylcellulose) are mixed to increase the adhesion strength. 3, the adhesion strength was improved.

Special cement
(weight%) sand
(weight%) Resuspended Powder Resin
(weight%) methyl
Cellulose
(weight%) Stickiness
(Visual inspection) Bond strength (N / mm ^{2 )} 3 days 7 days 28th T1-1 40.0 60.0 0.5 0.05 Good 0.4 0.9 1.2 T2-1 40.0 60.0 1.0 0.05 Good 1.1 1.9 2.1 (Parent Destruction) T3-1 40.0 60.0 1.5 0.05 Good 1.2 2.0 2.3 (Parent Destruction) T4-1 40.0 60.0 2.0 0.05 Bad 1.4 2.0 2.3 (Parent Destruction)

3. Experiment 3

In accordance with the above results, 45% of W / C is used for special cement 40% and 60% of sand, and 1% and 0.05% of reusable powder resin and MC (methylcellulose) The toughness PVA fibers were mixed in the range of 0.04 to 0.1, and the flowability was tested for improving the tensile strength and workability as shown in Table 4 according to the contents.

Special cement
(weight%) sand
(weight%) Re-oil type powder resin (% by weight) Methylcellulose
(weight%) PVA fiber (8mm) flow
(Mm) Tensile strength (N / mm ^{2 )} 3 days 7 days 28th T1-2 40.0 60.0 1.0 0.05 0.04 190 5.7 7.2 9.6 T2-2 40.0 60.0 1.0 0.05 0.06 185 7.1 8.6 11.1 T3-2 40.0 60.0 1.0 0.05 0.08 165 7.9 9.1 12.4 T4-2 40.0 60.0 1.0 0.05 0.1 155 8.3 10.8 13.5

In each of the three types of experiments, the content of special cement showed high strength up to 36 ~ 48%, which is not problematic in performance. However, considering economical efficiency, 40% is suitable, and re-melting type powder resin and methylcellulose have workability Considering the stickiness, 0.5 ~ 1.5% was good. However, considering economical efficiency, 1% is the most suitable in terms of minimum destruction of the matrix on the 28th day, and PVA fiber (based on 8mm length) shows high tensile strength as the content of PVA fiber is larger. However, 0.04 ~ 0.06%, which is more than flow, was the best.

<Comparative Example>

Table 5 shows the comparison between the optimum formulation of the present invention and a general product (a Portland cement-based product).

The mixing ratio of the cement (TB1) of this embodiment to Portland cement (TB2 to 4) of the general product was set to be the same as that of the special cement, sand, re-oiled powder resin, methylcellulose, PVA fiber, Respectively. Bleeding (phenomenon of water rising in still hardened concrete, mortar or grout) is carried out by putting the mortar up to the point of 15 cm in a plastic pack of 3 cm in width and 20 cm in depth and stitching the stomach. Respectively.

W / C 45% Special cement 1 species ordinary Portland cement Blast furnace slag powder CSA expander sand Resuspended Powder Resin methyl
Cellulose PVA fiber (8mm) Bleeding (mm) TB1 40.0 60.0 1.0 0.05 0.06 none TB2 40.0 60.0 1.0 0.05 0.06 3 TB3 24.0 16.0 60.0 1.0 0.05 0.06 2 TB4 36.0 4.0 60.0 1.0 0.05 0.06 3

[Strength Test]

delete

[Durability Test]

My alkalinity
(N / mm ² ) Neutralization
Resistance
(mm) Amount of water
(g) water
Absorption coefficient
(kg / (m ² .h ^{0 .5} ) Moisture permeation
Resistance
(S _d ) Chloride ion penetration resistance
(Coulombs) Length change rate
(%) standard 20 or more 2.0 or less 20.0 or less 0.5 or less 2m or less 1000 or less ± 0.15 or less TB1 60.1 0.3 3.1 0.1 0.9 443 -0.002 TB2 41.5 1.8 9.4 0.3 1.6 889 -0.19 TB3 42.2 1.6 9.6 0.3 1.4 749 -0.14 TB4 42.1 1.8 8.5 0.24 1.4 751 -0.08

From the results of the above tests, TB2 was evaluated according to KS F 4042 standard but the final length change rate was unsatisfactory. The remaining TB3 and TB4 passed the standard but all of them were lower than the invention in weather resistance tests such as crack resistance and waterproofing Respectively. Particularly, even though the same amount of powdered resin is mixed, the difference in adhesion strength seems to be influenced by the high degree of powderiness of special cement. Since there is no bleeding due to a rapid hydration speed, it does not affect the surface strength and has a very small volume change rate. Respectively.

As described above, the TB1 of the present example was superior to the TB2 to TB4 in terms of compressive strength, flexural strength, adhesion strength and tensile strength, and also showed excellent durability test.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims and their equivalents. It goes without saying that such changes are within the scope of the claims.

Claims (2)

A construction surface treatment step of chipping or grinding the deteriorated or corroded construction surface (concrete section or surface, etc.) with a tool or the like to completely remove it;
A foreign matter removing step of completely removing foreign matter remaining on the surface after the surface treatment step;
A primer applying step of applying a primer adhesive to the applied surface from which the foreign matter is removed to increase the adhesive force of the concrete; And
And restoring the work surface by installing a concrete repair mortar having excellent durability after the primer application step,
The concrete concrete mortar having excellent durability is characterized by comprising 36 to 44% by weight of special cement, 55 to 63% by weight of sand, 0.5 to 2.0% by weight of re-oiled powdery resin, 0.03 to 0.06% by weight of methylcellulose, 0.04 to 0.06% By weight,
The special cement is blended in an amount of more than 0 to 30% by weight of the blast furnace slag with 100% by weight of special cement clinker and a fly ash of more than 0 and 12% by weight or less and crushed to a particle size of 4000 to 4500 cm 2 /
The special cement clinker is composed of C ₂ S obtained by firing borax (35 to 55 wt%), limestone (10 to 20 wt%) and steel making slag (30 to 50 wt%) at 1300 to 1400 ° C Anhydrous C ₄ A ₃ S is mixed and pulverized with more than 0 to 5% by weight of calcium sulfate and more than 0 to 8% by weight of calcium oxide,
The sand was mixed with particles having a maximum size of 1.5 mm and a minimum size of 0.3 mm at a fine aggregate incorporation ratio (FM) of 2.8 to 3.1,
The chemical composition of the special cement was 17.10 wt% of silica (SiO ₂ ), 20.95 wt% of alumina (Al ₂ O ₃ ), 2.35 wt% of iron oxide (Fe ₂ O ₃ ), 48.70 wt% of calcium oxide (CaO) MgO), 1.55% by weight of titanium dioxide (TiO ₂ ), and 6.15% by weight of sulfur trioxide (SO ₃ ).
The method according to claim 1,
Applying a surface treatment agent for preventing concrete neutralization and salting to the surface of the work surface restored;
And a step of applying a surface treatment agent for preventing the neutralization and salting and then applying a surface treatment agent for preventing contamination.

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