JP7415532B2 - Repair method for concrete structures - Google Patents

Description

The present invention relates to a method for repairing a concrete structure in which deteriorated portions have occurred on the concrete surface including the lower surface.

Traditionally, there has been a demand for longer lifespans for concrete structures, and in order to achieve this, we have developed ultra-high strength materials that have high strength and high durability against carbonation, salt damage, freezing damage, etc. High strength fiber reinforced concrete has been developed. Ultra High Strength Fiber Reinforced Concrete (UFC) is a durable, durable concrete made of ultra high strength mortar and high strength steel fibers that give the ultra high strength mortar high toughness and crack prevention functions. It is a high-performance concrete that can last for 100 years.

However, the ultra-high-strength mortar constituting ultra-high-strength fiber-reinforced concrete generally requires heat curing in order to develop high compressive strength. For this reason, it is often used as a secondary product rather than cast on-site, and is used in many repair methods for concrete structures, for example, as a repair panel material.

Under these circumstances, high-strength mortar compositions shown in Patent Documents 1 to 5 have been developed as ultra-high strength mortars that can exhibit high compressive strength even when cured at room temperature. The high-strength mortar composition of Patent Document 1 includes cement having a specific particle size distribution and containing C ₃ S and C ₃ A, fine aggregate and inorganic fine powder having a specific particle size, silica fume, and a water reducing agent. By combining this with an antifoaming agent, it is possible to improve fluidity and improve strength by curing at room temperature.

Patent No. 5336300 Patent No. 5702608 Patent No. 5592806 Patent No. 5592807 Patent No. 5997807

The ultra-high-strength fiber-reinforced concrete obtained by adding high-strength steel fibers to the ultra-high-strength mortar compositions of Patent Documents 1 to 5 can be cured at room temperature, so if it is cast on-site by pouring, For example, it can be applied to repair methods for concrete structures, such as top cross section repair work, to ensure high durability of the repaired concrete structure while reducing wall thickness.

On the other hand, when trying to apply the above-mentioned ultra-high-strength fiber-reinforced concrete to the lower surface cross-section repair work, such as repairing the lower surface of a concrete slab, the methods of placing the concrete include plastering, spraying, and floor slabs. Examples include pouring method for filling from the top or side, and press-in filling method. However, with the plastering method, it takes a lot of manpower and work time to repair a wide area under the concrete slab, and with the spraying method, dust and rebound materials are easily scattered around the construction site, making it difficult to preserve the environment. I have an issue with this. In the method of filling and pouring from the top or side of the slab, construction is performed from the top of the slab, which limits the ability to carry out construction while using the upper part of the slab. Furthermore, when press-fitting mortar with normal compressive strength, it is difficult to ensure the necessary durability through cross-sectional repair.

The press-in filling method is a method that can solve these problems, but the high-strength steel fibers that make up ultra-high-strength fiber-reinforced concrete may get stuck in the hose used for pumping or become clogged with fiber clumps, resulting in press-in filling. Work will be hindered. As described above, many problems arise when using ultra-high-strength fiber-reinforced concrete as is for repairing the lower section.

The present invention was made in view of the above problems, and its main purpose is to extend the service life while keeping the cross-sectional thickness to the same level or less when repairing the concrete surface including the bottom surface of a concrete structure. It is an object of the present invention to provide a repair method for concrete structures using a press-in filling method, which is possible.

In order to achieve such an objective, the concrete structure repair method of the present invention involves chipping away the degraded portions that have occurred on the concrete surface, including the bottom surface of the concrete structure, and then placing a formwork opposite the chipped surface. A method for repairing a concrete structure in which a repair material is press-filled between the formwork and the lifting surface, wherein the repair material comprises a cement composition having a compressive strength of 100 N/mm ² or more, a shrinkage reducing material and/or or an expansion material and a non-ferrous fiber , the unit amount of the shrinkage reducing material per m ³ of the cementitious composition is 10 to 60 kg/m ³ , and the expansion per m ³ of the cementitious composition is The unit amount of the material is 10 to 40 kg/m ³ , and the amount of the non-ferrous fiber is 0.01 to 4.0 vol. relative to the cement composition. %, the cementitious composition contains cement, silica fume, water, a water reducing agent, an antifoaming agent, fine aggregate, and an inorganic fine powder, and the mixture of the fine aggregate and the inorganic fine powder has a granular content. Contains 40 to 80% by mass of grains with a diameter of 0.15 mm or less, and 30 to 80 mass% of grains with a grain size of 0.075 mm or less, and contains inorganic materials based on 100 mass% of the total amount of cement and silica fume. It is characterized by containing 10 to 60% by mass of fine powder .

According to the repair method for concrete structures of the present invention, a cement composition with a compressive strength of 100 N/mm ² or more and a material containing a shrinkage reducing material and/or an expanding material are used as the repair material as an ultra-high strength mortar. . As a result, even if the filling thickness is reduced and thin-wall construction is performed when press-fitting the repair material, the self-shrinkage and drying shrinkage cracks that tend to occur in the repair material after curing can be avoided by using shrinkage-reducing materials and/or expansion materials. It can be suppressed. Since it further contains non-ferrous fibers, the cross-linking effect of the non-ferrous fibers makes it possible to suppress peeling even if cracks occur due to an unexpected situation. Furthermore, unlike high-strength steel fibers, there is no increase in weight, so it is possible to maintain a reduction in weight while increasing the durability of the cement composition. Furthermore, since durability can be ensured, the cover thickness of reinforcing bars can be reduced. In addition, the rust on the exposed iron fibers on the surface of the cross-sectionally repaired structure will not impair its aesthetic appearance.

Therefore, it is possible to suppress the intrusion of deterioration factors such as moisture and salt, and without using high-strength steel fibers, the repaired concrete structure has the same level of durability as when ultra-high-strength fiber-reinforced concrete is used as the repair material. This makes it possible to ensure the quality of the product. Furthermore, since the weight can be reduced by making the wall thinner, there is no need to change the design load of the repaired concrete structure.

Furthermore, since high-strength steel fibers are not used, a small pump such as a squeeze pump can be used for press-fitting the repair material. This makes it possible to perform repair work efficiently even in a restricted environment such as a narrow work space. In addition, unlike when high-strength steel fibers are used, fiber clumps are less likely to form and the hose is not damaged, making it possible to significantly improve the workability of press-fit filling work on site.

In addition, since the repair material is press-filled using formwork, there is no rebound material or dust scattered around, compared to when repairing using the spraying method. Even in the case of concrete floor slabs, it is possible to carry out repair work that takes into consideration the preservation of the surrounding environment without polluting the sea area. Furthermore, compared to the plastering method, it is possible to press-fit and fill a wide area in one operation, making it possible to greatly contribute to shortening the construction period and reducing construction costs.

The concrete structure repair method of the present invention is characterized in that the formwork is placed closer to the chisel surface than the concrete surface.

According to the method for repairing concrete structures of the present invention, it becomes possible to reduce the dead weight of the repaired concrete structure compared to before repair, thereby reducing the weight. It becomes possible to suppress this. Furthermore, the amount of concrete used can be reduced, making it possible to reduce the environmental load.

The method for repairing concrete structures of the present invention is characterized in that the water-powder ratio of the cement composition is 30% or less.

According to the method for repairing concrete structures of the present invention, by setting the water-powder ratio of the cement-based composition to 30% or less, the viscosity increases, so bleeding is suppressed, so that repair materials for concrete structures can be used. It is possible to improve the adhesion performance and also to improve the strength of the repair material.

In the concrete structure repair method of the present invention, the cement contains 40.0 to 75.0% by mass of C ₃ S and less than 2.7% by mass of C ₃ A, and has a 45 μm sieve residue of 25% by mass. It is characterized by being less than .0% by mass. Further, the repair material is characterized in that a mortar flow value is 150 mm or more.

According to the method for repairing concrete structures of the present invention, the cement-based composition is a material that can quickly develop high compressive strength just by curing at room temperature. It becomes possible to ensure high compressive strength. Furthermore, since bleeding water can be suppressed, the repair material can be reliably attached to the concrete surface.

According to the present invention, a cement composition with a compressive strength of 100 N/mm ² or more and a material containing a shrinkage reducing material and/or an expanding material are used as the repair material, and self-shrinking and self-shrinking are achieved without using high strength steel fibers. In order to suppress drying shrinkage cracks, it is possible to use the press-in filling method, and it is also possible to extend the life of the repaired concrete structure while keeping the cross-sectional thickness to the same level or less.

It is a figure showing the procedure of the repair method of the structure in an embodiment of the present invention. FIG. 4 is a diagram showing the formulation of the repair material when the press-fitting test was conducted in the embodiment of the present invention, and the formulation in which the autogenous shrinkage strain of Comparative Examples 1 and 2 and Examples 1 to 6 shown in FIG. 4 was measured. It is a figure showing the main components of the added expansion material, shrinkage reducing material, and non-ferrous fiber in the embodiment of the present invention. It is a figure showing the relationship between autogenous shrinkage strain and material age in an embodiment of the present invention.

The present invention relates to a press-in filling method, which is one of the methods for repairing concrete structures, and is applicable to a compressive strength of 100 N/mm, which is applied as an ultra-high-strength mortar constituting ultra-high-strength fiber-reinforced concrete. A material containing ^two or more cementitious compositions and a shrinkage reducing material and/or an intumescent material is used as a repair material. As a result, while making it possible to press-fit the repair material, it has the same effect as when UFC is used as the repair material, that is, it suppresses cracking and peeling of the repair material on the repaired concrete structure. This achieves the effect of ensuring 100 years of durability without increasing the cross-sectional thickness.

The details of the repair method for concrete structures will be explained below using Figures 1 to 4, taking as an example the case of repairing the lower surface of the concrete slab of a pier. Note that the concrete surface to be repaired may not only be the lower surface of the concrete structure, but also a wide area extending from the lower surface to the side edges of the concrete structure.

≪Concrete structure repair method≫
As shown in FIG. 1(a), the concrete floor slab 1 of the pier has deteriorated parts 12 such as peeling of concrete on the lower concrete surface 11. Therefore, as shown in FIG. 1(b), this degraded portion 12 is lifted off to expose the reinforcing bars 13. In this embodiment, the concrete in the degraded portion 12 is removed by jetting high-pressure water or using a machine such as a breaker until the reinforcing bars 13 are exposed.

Next, as shown in FIG. 1(c), the deteriorated portion 12 is removed so that it faces the lifting surface 14 formed by removing it, and is lower than the position where the concrete surface 11 of the concrete slab 1 was. The formwork 2 is installed close to the reinforcing bars 13, that is, at a position where the cover thickness of the reinforcing bars 13 is reduced. Note that the exposed reinforcing bars 13 are coated with a rust preventive material or the like, if necessary.

Thereafter, as shown in FIG. 1(d), a repair material 5 is press-fitted between the chiseling surface 14 and the formwork 2 via a pressure hose 4 from a small pump 3 such as a squeeze pump. In this embodiment, the repair material 5 is press-fitted from the bottom to the top by providing an insertion hole for the pressure hose 4 in the formwork 2. However, the present invention is not limited to this. 2 may be press-fitted from the side.

According to the repair method for a concrete structure described above, the cover thickness of the reinforcing bars 13 can be reduced while ensuring higher durability than the concrete slab 1 before repair. In addition, since all processes are performed on the underside of the concrete slab 1, repair work can be carried out on the concrete slab 1 of the pier while it is open to traffic, etc. In addition, reinforcing materials such as reinforcing steel bars, mesh members (steel fibers, non-ferrous fibers, stainless wire mesh), and continuous fibers are installed at necessary locations between the lifting surface 14 and the formwork 2, and then these are buried. Then, the repair material 5 may be filled.

In addition, as shown in FIG. 1(c), since the repair material 5 is press-fitted using the formwork 2, the mortar material and dust are not scattered around, compared to the case of repair using the spraying method. Even if the target of repair is the concrete slab 1 of the pier, it is possible to carry out the repair work in consideration of preserving the surrounding environment without polluting the sea area. Furthermore, compared to the plastering method, it becomes possible to press-fit and fill a wide area in one operation, making it possible to greatly contribute to shortening the construction period and reducing construction costs.

≪Repair materials≫
The repair material 5 used in the repair method for the concrete slab 1 described above is a cement-based composition with a compressive strength of 100 N/mm ² or more, and either an expanding material or a shrinkage-reducing material, or an expanding material and a shrinkage-reducing material are added. This is what I did. Furthermore, non-ferrous fibers are added as needed.

Any cement composition may be used. Examples of high-strength mortar compositions that can be used as cement compositions included in the repair material 5 are shown below.

≪High-strength mortar composition (cement-based composition)≫
The high-strength mortar composition includes cement, silica fume, water, a water reducing agent, an antifoaming agent, fine aggregate, and fine inorganic powder.

The mineral composition of the cement is such that the amount of C ₃ S is 40.0 to 75.0% by mass, and the amount of C ₃ A is less than 2.7% by mass. The amount of C ₃ S in the cement is preferably 45.0 to 73.0% by mass, more preferably 48.0 to 70.0% by mass, and still more preferably 50.0 to 68.0% by mass. The amount of C ₃ A is preferably less than 2.3% by weight, more preferably less than 2.1% by weight, even more preferably less than 1.9% by weight. If the amount of C ₃ S is less than 40.0% by mass, compressive strength tends to be low, and if it exceeds 75.0% by mass, firing of the cement itself tends to become difficult. Furthermore, if the amount of C ₃ A is 2.7% by mass or more, the fluidity will be poor. Note that the lower limit of the amount of C ₃ A is not particularly limited, but is approximately 0.1% by mass.

Further, the amount of C ₂ S in the cement is preferably 9.5 to 40.0% by mass, more preferably 10.0 to 35.0% by mass, and even more preferably 12.0 to 30.0% by mass. . The amount of C ₄ AF is preferably 9.0 to 18.0% by weight, more preferably 10.0 to 15.0% by weight, even more preferably 11.0 to 15.0% by weight. If the mineral composition of the cement is within this range, high compressive strength and high fluidity of the high-strength mortar composition can be ensured.

The particle size of the cement is such that the 45 μm sieve residue is at the upper limit less than 25.0% by weight, preferably less than 20.0% by weight, more preferably less than 18.0% by weight, even more preferably 16.0% by weight. It is 0% by mass. The lower limit of the 45 μm sieve residue is 0.0% by mass or more, preferably 1.0% by mass or more, and more preferably 2.0% by mass or more. If the particle size of the cement is in this range, high compressive strength can be ensured, and the mortar slurry prepared using this cement has a moderate viscosity, so when fibers are added, it has sufficient dispersibility. Can be secured.

Silica fume is a by-product obtained by collecting dust in the exhaust gas generated during the production of metal silicon, ferrosilicon, fused zirconia, etc., and the main component is an amorphous substance that dissolves in an alkaline solution. It is _SiO2 . The average particle diameter of silica fume is preferably 0.05 to 2.0 μm, more preferably 0.10 to 1.5 μm, and still more preferably 0.18 to 0.28 μm. By using such silica fume, high compressive strength and high fluidity of the mortar composition can be ensured.

The silica fume content, based on cement, is preferably 3 to 30% by weight, more preferably 5 to 20% by weight, even more preferably 10 to 18% by weight. Further, the unit amount of silica fume per m ³ of the high-strength mortar composition is preferably 35 to 380 kg/m ³ , more preferably 58 to 253 kg/m ³ , and even more preferably 116 to 228 kg/m ³ .

As the water reducing agent, lignin-based, naphthalene sulfonic acid-based, aminosulfonic acid-based, polycarboxylic acid-based water reducing agents, high performance water reducing agents, high performance AE water reducing agents, etc. can be used. From the viewpoint of ensuring fluidity at a low water-to-cement ratio, it is preferable to use a polycarboxylic acid-based water reducing agent, a high-performance water reducing agent, or a high-performance AE water-reducing agent as the water-reducing agent. It is more preferable to use

The water reducing agent is preferably 0.5 to 6.0 mass %, more preferably 1.0 to 4.0 mass %, and even more preferably 1.8 to 3.0 mass %, based on 100 mass % of the total amount of cement and silica fume. It is 0% by mass. Further, the unit amount of the water reducing agent per m ³ of the high-strength mortar composition is preferably 7 to 86 kg/m ³ , more preferably 13 to 58 kg/m ³ , and even more preferably 18 to 43 kg/m ³ .

Examples of antifoaming agents include special nonionic surfactants, polyalkylene derivatives, hydrophobic silica, and polyethers. In this case, the antifoaming agent is preferably 0.01 to 2.0 mass%, more preferably 0.02 to 1.5 mass%, and still more preferably 0.01 to 2.0 mass%, based on 100 mass% of the total amount of cement and silica fume. 03 to 1.0% by mass.

The unit amount of the antifoaming agent per m ³ of the high-strength mortar composition is preferably 0.13 to 29 kg/m ³ , more preferably 0.26 to 22 kg/m ³ , even more preferably 0.39 to 15 kg/m 3 It is ³ .

Examples of fine aggregate include river sand, land sand, sea sand, crushed sand, silica sand, limestone aggregate, blast furnace slag fine aggregate, ferronickel slag fine aggregate, copper slag fine aggregate, electric furnace oxidation slag fine aggregate, etc. can be used. Note that the particle size of the fine aggregate is such that all of the fine aggregate passes through a 10 mm sieve, and 85% by mass or more passes through a 5 mm sieve.

As the inorganic fine powder, limestone powder, silica powder, crushed stone powder, etc. can be used. Inorganic fine powder is a fine powder obtained by crushing or classifying limestone powder, silica stone powder, crushed stone powder, etc. until the specific surface area becomes 2500 cm ² /g or more, and is blended to supplement the fine particulate content of fine aggregate and has high strength. The fluidity of the mortar composition can be improved.

The mixture of fine aggregate and inorganic fine powder according to the present embodiment contains 40 to 80% by mass, preferably 45 to 80% by mass, and more preferably 50 to 75% by mass of particles having a particle size of 0.15 mm or less. %including. Further, the above mixture contains 30 to 80% by mass, preferably 35 to 70% by mass, and more preferably 40 to 65% by mass of particles having a particle size of 0.075 mm or less.

If the content of the inorganic fine powder is 30% by mass or less, the viscosity of the mortar slurry will be too low, so there is a risk that the non-ferrous fibers will not be sufficiently dispersed. If the content of the inorganic fine powder exceeds 90% by mass, the amount of fine powder is too large, resulting in high viscosity, and it is necessary to increase the water-cement ratio in order to produce a predetermined flow, which may lead to a decrease in strength.

It is preferable to contain 10 to 60 mass % of fine aggregate and 10 to 60 mass % of fine inorganic powder, based on 100 mass % of the total amount of cement and silica fume, and 15 to 50 mass % of fine aggregate and fine inorganic powder. It is more preferable to contain 15 to 50% by mass of fine aggregate, 15 to 30% by mass of fine aggregate, and even more preferably 15 to 30% by mass of fine inorganic powder. Further, the unit amount of fine aggregate and inorganic fine powder per 1 m ³ of the high-strength mortar composition is preferably 140 to 980 kg/m ³ , more preferably 300 to 900 kg/m ³ , even more preferably 600 to 900 kg/m 3 It is ³ .

Water is preferably contained in an amount of 10 to 25% by weight, more preferably 12 to 20% by weight, and even more preferably 13 to 18% by weight, based on 100% by weight of the total amount of cement and silica fume. The unit water amount per m ³ of the high-strength mortar composition is preferably 180 to 280 kg/m ³ , more preferably 190 to 270 kg/m ³ , even more preferably 200 to 250 kg/m ³ .

The above-mentioned high-strength mortar composition suppresses bleeding water and can improve fluidity and strength by curing at room temperature. Therefore, as shown in FIG. 1(d), even if the lifting surface 14 is on the lower surface of the concrete slab 1, the repair material 5 can be reliably attached to the concrete slab 1 without being affected by bleeding water. becomes possible.

The details of the high-strength mortar composition, such as the specific surface area of the cement contained in the high-strength mortar composition, the manufacturing method, and the specific surface area of the inorganic fine powder, are given in Japanese Patent No. 5997807.

Next, the shrinkage reducing material, expansion material, and non-ferrous fibers that are added together with the high-strength mortar composition will be explained below.

≪Shrinkage reduction material≫
Shrinkage reducing materials include wollastonite, quartz, etc. for inorganic materials, and lower alcohol alkylene oxide adducts, ether type nonionic surfactants, etc. as shrinkage reducing agents for organic materials. can be used. The unit amount of shrinkage reducing agent per m ³ of the high strength mortar composition is from 10 to 60 kg/m ³ , preferably from 10 to 40 kg/m ³ . When the amount of the shrinkage reducing agent is less than 10 kg/m ³ , a sufficient shrinkage reducing effect cannot be obtained, and when it is more than 60 kg/m ³ , the viscosity of the repair material 5 increases and air is drawn in, resulting in a decrease in compressive strength. Additionally, the time required for curing is significantly delayed.

≪Expansion material≫
As the expanding material, quicklime, gypsum, magnesia, lime, ettringite, etc. can be used. The unit amount of expanding material per m ³ of the high-strength mortar composition is 10 to 40 kg/m ³ , preferably 15 to 30 kg/m ³ . If the amount of the expanding material is less than 10 kg/m ³ , the expansion effect will be small, the final shrinkage strain of the repair material 5 will be large, and the crack suppressing effect will not be obtained. Moreover, if it exceeds 40 kg/m ³ , delayed expansion occurs and the compressive strength decreases.

By using the above-mentioned shrinkage reducing material and expansion material, it is possible to enhance the effect of suppressing self-shrinkage and drying shrinkage cracking without using high-strength steel fibers. Further, since high-strength steel fibers are not added, the repair material 5 can be press-filled using a small pump such as a squeeze pump. Note that either the shrinkage reducing material or the expansion material may be added alone, or both may be added together.

≪Non-ferrous fibers≫
As non-ferrous fibers, polypropylene fibers, nylon fibers, vinylon fibers, polyethylene fibers, glass fibers, carbon fibers, aramid fibers, cellulose fibers, PBO fibers, basalt fibers, jute fibers, etc. can be used singly or in combination. . The non-ferrous fiber has a volume of 0.01 to 4.0 vol. relative to the repair material 5. %, preferably 0.05 to 2.0 vol. %including. The non-ferrous fiber has a volume of 0.01 vol. %, sufficient peeling-reducing effect and shrinkage-reducing effect cannot be obtained; %, fiber clumps will occur and the pump will become clogged, and the fluidity of the repair material 5 will decrease.

The fiber length of the non-ferrous fibers is preferably shorter than the diameter and cross-sectional repair thickness of the pressure hose 4.

By further including non-ferrous fibers, the repair material 5 can suppress peeling even if cracks occur due to an unexpected situation due to the cross-linking effect of the non-ferrous fibers. In addition, unlike in the case of high-strength steel fibers, the appearance of the structure is not spoiled due to rust on the exposed iron fibers on the surface of the cross-sectionally repaired structure. Note that the non-ferrous fibers do not necessarily need to be added to the cement composition.

≪Method for producing repair material≫
The above-mentioned repair material 5 is prepared by adding cement, silica fume, fine aggregate, inorganic fine powder, antifoaming agent, and expanding agent (if added) to a twin-screw forced mixing mixer, dry-mixing, and then mixing with a water-reducing agent and shrinkage agent. Kneading water containing the reducing agent (if added) is put into the mixer and kneaded for several minutes. After that, non-ferrous fibers are further added and stirred to produce the product. In addition, when employing a shrinkage reducing agent instead of the shrinkage reducing agent, it is added during the dry kneading process.

In the repair material 5 thus produced, the mortar flow value (0-stroke mortar flow value according to the mortar flow test specified in JIS R 5201) is preferably 150 mm or more, and more preferably 200 mm or more.

Further, the air content (according to "Pressure test method for air content of fresh concrete - air chamber pressure method" specified in JIS A 1128) is preferably 3.5% or less.

Furthermore, the compressive strength (according to the "Compressive strength test method (draft) for mortar or cement paste using cylindrical specimens" stipulated in JSCE-G 505) is 100 N/mm ² or more when tested on the 28th day of material age. is preferable, and 120 N/mm ² or more is more preferable.

Note that the water-powder ratio of the high-strength mortar composition (cement-based composition) is preferably 30% or less from the viewpoint of mortar viscosity and strength. This is because when the water-powder ratio becomes 30% or less, the viscosity of the mortar increases, which suppresses bleeding, which improves the adhesion performance of the repair material 5 to the concrete slab 1, and also improves the adhesion of the repair material 5 to the concrete slab 1. The strength can be improved. Here, the powder used to calculate the water-powder ratio includes cement, silica fume, inorganic fine powder, an expanding material, and a shrinkage reducing agent, and the water includes water, a water reducing agent, and a shrinking reducing agent.

≪Press-in construction test of repair material≫
Below, a press-fitting construction test was carried out on the repair materials 5 of Case 1 and Case 2 produced with the formulation shown in FIG. 2, and it was confirmed that they could be normally press-fed. In addition, in FIG. 2, the special premix powder refers to a material in which cement, silica fume, and inorganic fine powder are mixed in advance.

In the repair material 5, nylon fibers (organic fibers A) were added as non-ferrous fibers in case 1, and nylon fibers (organic fibers A) and polypropylene fibers (organic fibers B) were added as non-ferrous fibers in case 2. In addition, in both Case 1 and Case 2, an expanding agent (EX) is added as part of the powder and a shrinkage reducing agent (SR) is added as part of the water to the high-strength mortar composition.

≪Compressive strength of repair material≫
The above repair material 5 was poured into a predetermined mold to produce a specimen, and a compressive strength test was conducted. Looking at FIG. 2, it can be seen that the compressive strength of both Case 1 and Case 2 greatly exceeds 100 N/mm ² .

≪Self-shrinkage strain of repair material≫
As shown in FIG. 2, six types (Examples 1 to 6) of repair materials 5 were prepared in which a shrinkage reducing agent, an expansion material, and an organic fiber were added in appropriate combinations. FIG. 3 shows the main components of the shrinkage reducing agent (A, B), expansion material, and organic fiber (A, B) used in Examples 1 to 6. Furthermore, for these Examples 1 to 6, the relationship between material age and autogenous shrinkage strain is shown in FIG.

Regarding Examples 1 to 6 and Comparative Examples 1 to 2 above, looking at FIG. 4, we can see that Comparative Example 2 using only a high-strength mortar composition and Comparative Example 1 adding high-strength steel fiber to the high-strength mortar composition There was a difference of about 350μ at the age of 28 days and about 450μ at the age of 182 days. However, even if high-strength steel fibers were not added, in Examples 1 to 6, in which shrinkage-reducing materials, expansion materials, and organic fibers were appropriately added, the self-shrinkage strain was lower than that of high-strength steel fibers. The result was approximately converged to the value of Comparative Example 1.

In particular, it can be seen that in Example 4, the autogenous shrinkage strain is reduced compared to Comparative Example 1 after the material age is 98 days. It can also be seen that in Example 2, in which no organic fibers were added, the self-shrinkage strain approached the value of Comparative Example 1, in which high-strength steel fibers were added, as the material age increased. Furthermore, when comparing Example 1 and Example 4, even when the same amount of shrinkage reducing agent is added, as in Example 4, shrinkage reducing agent B whose main component is a glycol ether derivative is added. It can be seen that a higher shrinkage reduction effect can be obtained.

In addition, looking at Examples 5 and 6, even if two types of non-ferrous fibers, nylon fibers (organic fiber A) and polypropylene fibers (organic fibers B), are mixed as in Example 6, nylon fibers as non-ferrous fibers No major difference was observed between Example 5 in which only fiber (organic fiber A) was added, and it can be seen that the non-ferrous fiber to be added may be either nylon fiber or polypropylene fiber.

As described above, the repair material 5 is made of a high-strength mortar composition constituting the UFC, and a material containing a shrinkage reducing material and/or an expansion material, or a material to which non-ferrous fibers are further added. As shown in Figures 1(a) to 1(d), even if a thin wall construction with a filling thickness of 30 mm is performed using a press-in filling method using a small pump 3 such as a squeeze pump, the cost is high. Compressive strength can be ensured, and self-shrinkage strain can be reduced to suppress self-shrinkage cracks and drying shrinkage cracks that tend to occur in the repair material 5 after curing.

Therefore, it is possible to suppress the intrusion of deterioration factors such as moisture and salt, and without using high-strength steel fibers, the concrete floor slab 1 after repair can achieve the same level of performance as when ultra-high-strength fiber-reinforced concrete is used as the repair material. It is possible to achieve durability, that is, 100 years of durability without increasing the cross-sectional thickness.

Further, since the weight can be reduced by making the wall thinner, there is no need to change the design load of the concrete slab 1 after repair. Furthermore, since a small pump 3 such as a squeeze pump can be used for press-fitting the repair material 5, it is possible to carry out repair work efficiently even in a restricted environment such as a narrow work space. Become. Furthermore, unlike when high-strength steel fibers are used, fiber clumps are difficult to form and the pressure feed hose 4 is not damaged, making it possible to significantly improve the workability of press-fit filling work on site.

The repair material 5 of the present invention and the method of repairing a structure using the repair material 5 are not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention.

For example, one or more types of setting accelerators, setting retarders, thickeners, polymer emulsions, polymer dispersions, etc. may be added to the repair material 5 as necessary.

Furthermore, in this embodiment, the surface to be repaired is the lower surface of the concrete slab 1, but it is not limited to this, and may be the upper surface of the concrete slab 1, or the wall surface of another structure. etc. may be used.

1 Concrete floor slab (concrete structure)
11 Concrete surface 12 Deteriorated part 13 Reinforcement bar 14 Hanging surface 2 Formwork 3 Small pump 4 Pressure feed hose 5 Repair material

Claims (5)

After chipping off the degraded parts of the concrete surface, including the bottom surface of the concrete structure, a formwork is placed opposite the chiseled surface, and a repair material is press-fitted between the formwork and the chiseled surface. In the repair method of concrete structures,
The repair material includes a cement composition having a compressive strength of 100 N/mm ² or more, a shrinkage reducing material and/or an expanding material, and a non-ferrous fiber ,
The unit amount of the shrinkage reducing material per m ³ of the cementitious composition is 10 to 60 kg/m ³ ,
The unit amount of the expanding agent per 1 m ³ of the cement-based composition is 10 to 40 kg/m ³ ,
The amount of the non-ferrous fibers is 0.01 to 4.0 vol. relative to the cement composition. % mixed,
The cement composition includes cement, silica fume, water, a water reducing agent, an antifoaming agent, fine aggregate, and inorganic fine powder,
The mixture of the fine aggregate and the inorganic fine powder contains 40 to 80% by mass of particles with a particle size of 0.15 mm or less, and 30 to 80% by mass of particles with a particle size of 0.075 mm or less. ,
A method for repairing concrete structures , comprising 10 to 60% by mass of inorganic fine powder based on 100% by mass of cement and silica fume . In the concrete structure repair method according to claim 1,
A method for repairing a concrete structure, characterized in that the formwork is placed closer to the lifting surface than the concrete surface. The method for repairing a concrete structure according to claim 1 or 2,
A method for repairing a concrete structure, characterized in that the water/powder ratio of the cement composition is 30% or less. In the method for repairing a concrete structure according to any one of claims 1 to 3,
The cement contains 40.0 to 75.0% by mass of C ₃ S and less than 2.7% by mass of C ₃ A, and has a 45 μm sieve residue of less than 25.0% by mass. Repair method for concrete structures. In the method for repairing a concrete structure according to any one of claims 1 to 4,
A method for repairing a concrete structure, characterized in that the repair material has a mortar flow value of 150 mm or more .

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