JP5009233B2 - Repair method for cracks in cement-based structures mixed with fibers - Google Patents

Description

The present invention relates to method of repairing fine cracks of structures made of cement-based material obtained by mixing fibers.

  Water-stopping methods caused by cracks in structures made of cement-based materials, such as concrete structures, include the injection method, filling method, surface impregnation method, and surface coating method. Generally, the crack width is large and the cracks in the future. These methods are selected depending on the presence or absence of the behavior.

  The injection method and the filling method are methods for repairing the generated cracks in units of one, and are often applied when the crack width exceeds 0.2 mm.

  The surface impregnation method and the surface coating method are methods of repairing the entire surface including the cracked part, and are often applied to a crack width of 0.2 mm or less.

  The materials used in these four methods include those that use organic solvents depending on petroleum resources, such as epoxies, acrylics, and urethane resins, and those that feature strong alkalinity such as silicates. Commonly used.

  Conventionally, the performance aspect of the water-stopping effect is prioritized, and there is a problem that the present situation has been reached without consideration for safety and environmental aspects such as ensuring safety during construction, effective use of resources, and reducing environmental impact. .

  In addition, a surfactant, a highly water-absorbing polymer, a water-absorbing polymer gelling agent and a water leakage preventing agent containing water are injected from a water leakage preventing agent inlet provided in advance in a structure made of cementitious material to prevent water leakage. There is a method of stopping (see, for example, Patent Document 1).

  However, in this method, since a gel substance obtained by adding a gelling agent to a superabsorbent polymer is used as a water leakage preventing agent, it is difficult to penetrate into fine cracks having a crack width of 0.2 mm or less.

  Further, there is a water leakage preventing agent mainly composed of kaolin-based minerals, three or more kinds of hydrophilic polymers, colloidal silica, and alkylene glycol derivatives (see, for example, Patent Document 2).

However, this method has a high viscosity of 940 to 3,300 mPa · s, as clearly shown in the examples, so that it penetrates into fine cracks unless a special device is used. Is difficult.
JP-A-11-190133 JP 2004-182869 A

  The conventional crack repair method for a structure made of cement-based material described above has problems in terms of material safety, effective use of resources, and environmental load. Penetration into fine cracks is impossible unless a special device is used, and therefore there is a problem that it is difficult to properly achieve the purpose of water stoppage.

  The present invention provides a technique for closing fine cracks in a structure made of a cement-based material by using an environment-conserving material that has excellent workability, high safety during construction, and does not depend on petroleum resources.

The present invention relates to alginic acid extracted from seaweed and its salt after pretreatment by pre-infiltrating a calcium solution into cracks generated in a structure using a cement-based material mixed with fibers, (Sodium alginate, potassium alginate, ammonium alginate) or a propylene glycol ester of alginate (hereinafter referred to as alginic acid) is impregnated, and the reaction of the impregnated alginic acid with calcium of the calcium solution and calcium of cement is carried out. Thus, gel-like calcium alginate is formed inside the crack, and the gel-like calcium alginate is retained by a large amount of the above-mentioned fibers appearing on the fracture surface, thereby preventing water from cracking.

  By impregnating the crack generation site with a dilute solution of alginic acid made mainly of seaweed such as seaweed and kelp, the calcium and alginic acid, which are the main components of cement mortar and concrete, react to cause the gel-like calcium alginate to crack. This makes it possible to stop the water at the cracked portion.

  Since the diluted solution has a low viscosity, it can easily penetrate into fine cracks, can improve the effectiveness of water stopping, and can be easily repaired.

  Both alginic acid and calcium alginate are recognized as food additives. This has made it possible to provide a method for repairing cracks using materials that are safe and environmentally friendly and do not contain petroleum resources or organic solvents.

According to the present invention, it is possible to effectively achieve the purpose of improving water stoppage due to fine cracks generated in a structure composed of a cement-based material mixed with fibers by using a seaweed substance recognized as a food additive, It is possible to effectively solve various problems such as ensuring the safety of the conventional water-stopping material, that is, the repair material itself, effectively using resources, and reducing the environmental load.

  If the present invention can block fine cracks in a concrete structure and increase the water-stopping property, the water-stopping structure of the structure can be improved, the usefulness of the structure can be increased, and the application range can be expanded.

  For example, in waterways and water supply facilities, the economic effect due to the reduction of water leakage from cracks is great. In addition, in a structure that stores harmful water solubility, the impact on the environment can be reduced by increasing the water resistance of cracks.

  Alginic acid used in the present invention is a polysaccharide contained in kelp and the like, is used as a food additive, has little influence on the human body, and has high safety.

By contributing to the restoration of functionality of structures made of cement-based materials mixed with fiber, such as various concrete structures in roads, rivers, harbors, airports, and water and sewage facilities, etc. Can contribute to fulfillment.

  The best mode for carrying out the present invention will be described below with reference to FIGS.

  The structure 1 made of a cement material to be repaired in the present invention is various concrete structures in roads, rivers, harbors, airports, water and sewage facilities, agricultural waterways, and the like. These various concrete structures are made of cement-based material 2 in which cement is used as a hardener and various aggregates are blended therein.

  As the cement-based material 2 in the above structure, fiber reinforced cement mortar (including fiber reinforced polymer cement mortar) in which reinforcing fibers such as synthetic resin fibers, ceramic fibers, metal fibers, and glass fibers are blended is used. It is like that.

The present invention relates to a method for preventing cracks in a structure made of a cement-based material mixed with fibers, that is , as shown in FIGS. It is effectively implemented as a water method, that is, a repair method.

  The crack 3 is a crack 3 reaching from the front surface to the back surface of the structure 1 or a crack 3 generated on the surface layer of the structure 1.

  That is, a dilute solution 4 of alginic acid, a salt thereof (sodium alginate, potassium alginate, ammonium alginate), or propylene glycol alginate (hereinafter referred to as alginic acid) mainly made from seaweeds such as seaweed and kelp is contained in the crack 3. By impregnating, the alginic acid and calcium, which is the main component of the cement-based material 2, react to generate gel-like calcium alginate 4 'inside the crack 3, thereby achieving the purpose of water stopping at the cracked portion.

  The diluted solution 4 of alginic acid is obtained by diluting alginic acid with water. Since this diluted solution has a low viscosity, it easily penetrates into fine cracks of 0.2 mm or less.

  The diluted solution 4 of alginic acid has a sufficient effect at a dilution concentration of 0.1% to 0.25%, and the dilution concentration is arbitrary. For example, it can be used at a dilution concentration of about 0.1% to 80%.

  As described above, alginic acid and calcium alginate are both recognized as food additives, and they do not use petroleum resources and do not contain organic solvents. Can provide.

  FIG. 1 is a graph showing the relationship between the concentration of the sodium alginate solution and the viscosity, and FIG. 2 is a graph showing the relationship between the concentration of the sodium alginate solution and the amount of penetration.

  A 40 mm thick concrete and a 10 mm fiber reinforced cement mortar were laminated and integrated, and the concentration and the amount of penetration were determined using a specimen into which innumerable fine cracks were introduced by double loading.

  The crack width at this time was 0.589 mm for the concrete layer and 0.040 mm at the maximum for the fiber-reinforced cement mortar layer.

  From these things, although it is an example, when the crack is about 0.04 mm, the viscosity of 2 mPa · s is the upper limit value that can penetrate, and the penetration when using a gelled and high viscosity is used. Sex was almost unpredictable.

  When cracks occur in a structure using a cement-based material in which fibers are mixed, the fibers appear by bridging between the crack fracture surfaces. For this reason, the alginic acid solution after permeation and the generated gel (calcium alginate) after reaction are held by a large amount of fibers in the cracked cross section, and are difficult to flow out. The mixed fiber plays a major role in improving water stoppage.

  Cement-based materials have the property that neutralization gradually progresses from the surface toward the inside due to the influence of carbon dioxide in the air.

  As a specific example of the repair method according to the present invention, the amount of calcium alginate that is effective for water-stopping is reduced in application to those that have become neutralized, so that calcium acetate, calcium nitrite, calcium hydroxide, When the calcium solution is preliminarily infiltrated into the cracks and pretreatment is performed, and then the alginic acid solution is infiltrated into the cracks, the water-stopping improvement effect is enhanced.

  Calcium acetate and the like are recognized as food additives overseas and are highly safe materials.

  Alginic acid or alginate is mass-produced as a food additive and exhibits a sufficient water-stopping effect even in low-concentration products of 0.1 to 0.25%. High construction is possible.

  After using a low-viscosity solution to infiltrate fine cracks of 0.2 mm or less using a seaweed substance with high safety and low environmental impact, gel calcium alginate is reacted with calcium in the cement component. Water stoppage is improved by forming the gel inside the crack and holding the gel by a large amount of fibers appearing on the fracture surface.

Seaweed material to improve the water cut-off due to fine cracks in cementitious materials obtained by mixing the fibers, alginate and sodium alginate, potassium alginate, either good alginates of ammonium alginate and propylene glycol alginate.

  What is necessary is just to adjust the density | concentration of the alginic acid, alginates, and alginic acid propylene glycol ester which are penetrated to a fine crack so that the solution viscosity after dilution may be 2-30 mPa * s.

  The fine cracks can be penetrated or filled with a brush such as a roller brush, an impregnation method using low-pressure spray, or in a water storage tank or the like, a predetermined concentration of alginic acid solution can be stored in the water storage tank to improve water stoppage. .

  Since alginic acid used for improving waterstop is also highly safe, construction by such a water storage method is also possible.

<Example 1>
A specimen having a concrete layer thickness of 40 mm and a fiber-mixed mortar layer thickness of 10 mm was integrally combined to produce a specimen having a total thickness of 50 mm, and cracks were introduced by double pulling loading. The maximum crack width after introduction was 0.140 mm for the concrete layer and 0.062 mm for the fiber-mixed mortar layer.

  After impregnating the cracked portion with a 0.1% sodium alginate solution using this specimen, the wet and dry cycle was repeated a total of 4 times for a total of 10 days, and then a water permeability test was conducted. The water permeation test was evaluated by the time required for the water head to drop from 250 mm to 200 mm, and the test apparatus was attached to the fiber-mixed mortar layer.

  The effect of improving the water stoppage by the treatment with alginic acid was about 123 minutes due to the difference in water permeation time, and the ratio was about 308 times, and a high water stoppage improvement effect was recognized.

<Example 2>
A specimen having a concrete layer thickness of 40 mm and a fiber-mixed mortar layer thickness of 10 mm was integrally formed to prepare a specimen having a total thickness of 50 mm, and cracks were introduced by double pulling loading. The maximum crack width after introduction was 0.655 mm for the concrete layer and 0.027 mm for the fiber-mixed mortar layer.

  After impregnating the cracked portion with a 0.10% sodium alginate solution using this specimen, the wet and dry cycle was repeated a total of four times for a total of 10 days, and then a water permeability test was performed. The water permeation test was evaluated by the time required for the water head to drop from 250 mm to 200 mm, and the test apparatus was attached to the fiber-mixed mortar layer.

  The effect of improving the water stoppage due to the treatment with alginic acid was about 22 minutes due to the difference in water permeation time, and the ratio was about 5 times, and a high water stoppage improvement effect was recognized.

  In addition, a large amount of calcium hydroxide was observed in the large cracked part of the concrete layer, and it was also confirmed that the self-occlusion action of cracking by alginic acid treatment was high.

  The method of extracting alginic acid from the seaweed is based on a method of dissolving seaweed with an alkali, and is divided into an “acid method” and a “calcium method” depending on the treatment method after filtering the solution. Since both the acid method and the calcium method are well known, the details are omitted.

  Alginic acid extracted from seaweed is in a powder state, and the alginic acid powder is diluted with water or the like to obtain an alginic acid solution.

In addition, calcium and alginic acid in the cement-based material form an insoluble calcium alginate gel by replacing Na in alginic acid with Ca in cement. The reaction chemical formula is as shown in the following chemical formula 1.

  As described above, the present invention is a method for repairing a crack having an unprecedented feature that is excellent in workability and takes safety and environmental aspects into consideration. In particular, it is an optimal repair method for water supply facilities, agricultural water tanks, irrigation canals, and other structures related to the supply of drinking water and crops directly related to human health.

The relationship figure of the density | concentration and viscosity of a sodium alginate solution. The relationship figure showing the density | concentration of a sodium alginate solution and the penetration | invasion amount to a crack. A is an enlarged cross-sectional view of a crack generated in a structure made of a cement-based material, B is an enlarged cross-sectional view showing a state in which a solution of alginic acid is impregnated in the crack, and C is a reaction between cement and alginic acid in the crack. The expanded sectional view which shows the state by which the gelatinized calcium alginate was produced | generated.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Structure, 2 ... Cement-type material, 3 ... Crack, 4 ... Diluted solution of alginic acid, 4 '... Gel-like calcium alginate.

Claims (1)

After pretreatment by pre-infiltrating the cracks generated in the structure using the cement-based material mixed with fibers with a calcium solution, the cracks are impregnated with a solution of alginic acid or its salts or propylene glycol alginate. Then, the gelled calcium alginate is formed inside the crack by obtaining a reaction between the impregnated alginic acid or a salt thereof or propylene glycol alginate and calcium of the calcium solution and calcium of the cement. A method for repairing cracks in a cement-based structure mixed with fibers, characterized in that the cracks are retained by the fibers appearing on the fracture surface of the cracks to prevent water from cracking.

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