JP2010070403A - Method for suppressing drying shrinkage crack of fresh concrete and crack reducing agent, and method for plugging crack of existing concrete and crack plugging agent - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for cheaply and easily suppressing a drying shrinkage crack of a fresh concrete, which is durable in freezing and thawing and usable in a cold district, and capable of giving densifying property and water retentivity to suppress the evaporation of inside water. <P>SOLUTION: In a method for suppressing a drying shrinkage crack of a fresh concrete structure or a fresh concrete secondary product, the method is characterized by containing a process for suppressing a drying shrinkage crack by applying a lithium silicate-based surface modifying material to a fresh concrete which is wet-cured after demolding and after bringing the wet-curing to an end. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a drying shrinkage cracking suppressing method and cracking inhibitor for new concrete (new concrete structure or new secondary concrete product), and a crack closing method and cracking for existing concrete (existing concrete structure or existing concrete secondary product). It relates to an occlusive agent.

  In recent years, many cases of deterioration of concrete structures and concrete secondary products have been reported, which has become a social problem. One of the possible causes of early deterioration in actual structures is the cracks that occur on the surface of concrete in the early stages of age. As a result, various deterioration mechanisms such as frost damage, neutralization, and salt damage are promoted locally from the cracked portion, and the durability is lowered and corrosion of the reinforcing steel in the concrete is considered to occur.

  In particular, in the case of structural concrete with thin members such as walls and floors and large surrounding constraints, or when only the surface layer is dried early due to insufficient curing, cracks are likely to occur due to drying shrinkage of the concrete. When this crack width becomes large, problems such as water leakage occur. Further, when recycled aggregate concrete is used as a measure for depletion of aggregate resources and effective utilization of resources in recent years, it is necessary to have crack resistance comparable to that of concrete using general crushed stone. However, when recycled aggregate is used, dry shrinkage cracks are generally likely to occur, and there is concern about the use of the parts such as the upper structure subjected to drying. Furthermore, when using high-fluidity concrete, this formulation increases the viscosity of the mortar by increasing the amount of powder or using a separation reducing agent in order to increase the material separation resistance. There is a tendency to reduce the amount. For this reason, it is feared that the high fluidity concrete has a large self-shrinkage and drying shrinkage and is likely to be cracked as compared with normal concrete.

Here, as a method for suppressing drying shrinkage cracking of new concrete, a method of applying a shrinkage reducing agent or an expanding agent has been proposed. Furthermore, as a technique for suppressing drying shrinkage cracking of new concrete, the use of curing mats, water-permeable molds, and coating curing agents, and further increasing the diameter of embedded reinforcing bars (Non-patent Document 1) (Non-patent document 2), increase the water cement ratio or use low heat cement (Non-patent document 3), mix blast furnace slag fine powder that is said to have frost resistance and salt barrier properties (Non-Patent Document 4) has been proposed.
Annual Report of Concrete Engineering 12-1 1990 “Experimental Study on Crack Control Effect of Rebar during Drying Shrinkage” Annual Report of Concrete Engineering Vol. 22, no. 2,2000 “Dry Shrinkage Cracking Properties of Recycled Aggregate Concrete with Different Aggregate Quality” Annual Report of Concrete Engineering Vol. 22, no. 2,2000 "Experimental Study on Resistance to Drying Shrinkage Cracking of Ultralight Concrete" Annual Report of Concrete Engineering Vol. 26, no. 1,2004 "Study on the effect of cracks introduced in the early days on the durability of concrete"

  However, among the conventional dry shrinkage cracking control methods for new concrete, if a shrinkage reducing agent is used, air that is important for frost resistance tends to deviate from the concrete after placement, and on the other hand, there is insufficient proper restraint by reinforcing bars, etc. Even if an expanding agent is used under such conditions, cracks due to repeated freezing and thawing are likely to occur (usually it is necessary to withstand repeated tests about 300 times, but only about 30 times). Therefore, it cannot be used in a cold region, and the place where it is used is limited. In addition, when the reducing agent is used, the drug that has entered the inside does not densify the tissue and does not have a water retention capability, so that the moisture in the inside tends to evaporate, and the effective life of the reducing agent is usually about 4 weeks. There is a problem that it is very short. Curing mats are inexpensive and easy to construct, but have little water retention effect, especially poor on the vertical surface (in the water retention effect test of the mat, water is retained for 4 days on the horizontal surface and only 2 days on the vertical surface). There is a disadvantage that it is impossible to keep water on all sides. Permeable formwork reduces the water-cement ratio in the vicinity of the surface, improving the strength and durability of the concrete itself, and its effects have also been clarified, but it takes time for construction, the surface becomes slightly blackish, etc. It is necessary to pay attention to this point. In the case of coating curing agent, it is cheap and easy to implement, but the quantitative evaluation of the effect is unclear, and it is difficult to manage the process because it cannot be applied to the wet surface, and the duration of the effect is unsatisfactory. There are disadvantages such as being clear and difficult to control the thickness of the coating film. Further, in the case of a technique such as increasing the diameter of the embedded reinforcing bar or changing the composition of the concrete material, it is necessary to devise the concrete itself or the reinforcing bar inside thereof, which leads to high cost. Therefore, the present invention is resistant to freezing and thawing and can be used even in cold regions, and it can be made dense and water-retaining in order to suppress moisture evaporation inside, and at low cost and easily, A first object is to provide means for suppressing drying shrinkage cracks.

  Furthermore, when dry shrinkage cracks have occurred in the existing concrete, the blockage of cracks with a width of 0.2 mm or more can be dealt with by conventional methods such as injection or coating of resin or the like. Here, it has also been proposed to use an epoxy-based injecting agent as a method for closing cracks. However, the clogging of fine cracks with a width of 0.2 mm or less has a problem that if a resin-based injecting agent (epoxy-based injecting agent, acrylic injecting agent or the like) is used, the viscosity is high and the fine cracks cannot enter. More specifically, the use of the resin-based injecting agent is limited to use in a dry state because water cannot be used. Therefore, since air exists in the crack, it is difficult for highly viscous resin to enter. Therefore, when a crack is closed using a resin-based injecting agent, it is necessary to perform a troublesome work such as sealing on the crack and vacuuming from the opposite side. Furthermore, if a resin-based injectant is used, cracks can be prevented in the part where the agent is applied, but cracks occur in other areas that are fragile, particularly near the interface of the resin-based injectant. There is also a problem that cannot be prevented. Therefore, the present invention provides a long-term durability of these effects by suppressing the clogging of fine cracks with a width of 0.2 mm or less and the occurrence of secondary cracks for which the clogging method has not been developed in order to extend the life of existing concrete. The second purpose is

The present invention (1) is a method for inhibiting dry shrinkage cracking in a new concrete structure or a new concrete secondary product,
Including a drying shrinkage cracking inhibiting step of applying a lithium silicate surface modifier to the new concrete after performing wet curing after demolding of the new concrete and terminating the wet curing (preferably within 14 days). It is a characteristic method. Here, the term “wet curing” in the claims and the present specification means curing for keeping concrete in a moist state, and it is kept for a predetermined period (from 3 days to 10 days depending on the type of cement). More than a day), watering, water spraying, etc., including maintaining high humidity.

This invention (2) is a durability improvement process (or water retention effect reinforcement | strengthening process) which applies a silane type or a silane siloxane type water repellent to the said new concrete after the said drying shrinkage crack suppression process.
The method of the invention (1), further comprising:

  This invention (3) is the method of the said invention (1) or (2) in which concrete is densified and the durability of concrete itself improves in the said drying shrinkage crack suppression process.

  The present invention (4) includes a lithium silicate-based surface modifier, and is subjected to wet curing after demolding of the new concrete, and after the wet curing is terminated (preferably within 14 days). It is a drying shrinkage cracking inhibitor for new concrete structures or new secondary concrete products for application to concrete.

  This invention (5) is a drying shrinkage cracking inhibitor of the said invention (4) which functions also as a concrete durability improvement agent which densifies concrete and improves durability of concrete itself.

  The present invention (6) further includes a new concrete to which the drying shrinkage cracking inhibitor of the invention (4) or (5) is applied, characterized by containing a silane-based or silane-siloxane-based water repellent. It is a new concrete durability improver (or water retention effect enhancer) for application.

The present invention (7) is a method for closing cracks in an existing concrete structure or an existing concrete secondary product,
It is a method characterized by having a crack closing step of applying a lithium silicate surface modifying material and a calcium carbonate filler to existing concrete.

  The present invention (8) is the method of the invention (7), wherein the calcium carbonate filler is rod-shaped or plate-shaped.

  The present invention (9) is the method according to the invention (7) or (8), wherein the calcium carbonate filler is derived from an unfired shell.

The present invention (10) has the crack closure durability improving step of applying a silane-based, siloxane-based or silane-siloxane-based water repellent to the existing concrete after the closing step, according to the inventions (7) to (9). One of the methods.

The present invention (11) further includes a concrete durability improving step in which the lithium silicate surface modifying material is applied to a portion other than the cracked portion to densify the concrete and improve the durability of the concrete itself. ) To (10).

  The present invention (12) is a crack plugging agent for an existing concrete structure or an existing concrete secondary product, characterized by comprising a lithium silicate surface modifier and a calcium carbonate filler.

  The present invention (13) is a crack plugging agent for an existing concrete structure or an existing concrete secondary product according to the invention (12), wherein the calcium carbonate filler is rod-shaped or plate-shaped.

  The present invention (14) is the crack plugging agent according to the invention (12) or (13), wherein the carbonated calcium filler is derived from an unfired shell.

  The invention (15) is any one of the inventions (12) to (14), wherein the lithium silicate-based surface modifier functions as a concrete durability improver that densifies the concrete and improves the durability of the concrete itself. Is one cracking plug.

  The present invention (16) is a silane-based repellent for further application to an existing concrete structure or an existing concrete secondary product to which any one of the crack plugging agents of the inventions (12) to (15) is applied. It is a crack closure durability improver containing a liquid agent.

  According to the present invention (1) and (4), after the new concrete is demolded, wet curing is performed, and after the wet curing is terminated (preferably within 14 days), the lithium silicate surface modifier is applied to the new concrete. Compared with conventional methods such as increasing the diameter of embedded reinforcing bars or changing the composition of concrete materials, such as increasing the diameter of the embedded reinforcing bars, it is cheaper and simpler. There is an effect that drying shrinkage cracking of the new concrete can be suppressed. Furthermore, according to the present invention (1) and (4), the lithium silicate surface modifying material and the calcium component in the concrete react with each other, and the calcium silicate has a densification performance of the concrete structure and water retention. Hydrates (C—S—H) are formed. Therefore, as a result of suppressing evaporation of moisture inside, there is also an effect that drying shrinkage can be suppressed. In addition, according to the present invention (1) and (4), the place where calcium silicate hydrate can be formed is originally a fragile place (place where tensile stress due to drying shrinkage is concentrated and easily cracked) and is fragile. By reinforcing the portion, the entire structure is made uniform, and as a result, the tensile stress due to drying shrinkage is dispersed and does not lead to large cracks, and it is possible to further prevent drying shrinkage. Furthermore, according to the present invention (1) and (4), the penetration of moisture, which is the main cause of freezing and thawing, is suppressed by densification and prevention of microcracking. There is an effect that there is. Even with the same silicic acid-based surface modifier, the penetration effect is small in the case of sodium-based and potassium-based materials, and the modification effect is small. Moreover, by containing lithium, the water retention effect is higher than the hydrate derived from sodium or potassium.

  According to the present invention (2) and (6), in addition to the above effects, a silane-based water repellent is further applied to improve the durability after drying shrinkage cracking suppression. It becomes possible to reinforce the dry and wet repeated durability. Thus, the effect of reinforcing the surface with a silane-based water repellent provides a remarkable effect that the effect of suppressing the drying shrinkage cracking lasts for a long time.

  According to the present invention (7) and (12), by applying a crack plugging agent, which is a combination of a lithium silicate surface modifying material and a calcium carbonate filler, to existing concrete, a plugging method has not been developed. An effect is obtained that it is possible to close fine cracks having a width of 0.2 mm or less. In addition, unlike conventional resin-based injectants, these agents are used in the presence of water, so there is no need to perform intrusion of injectants due to the presence of air or complicated work, and for a short period of time. It also has the effect of being able to work with. In addition, since calcium carbonate is used as a filler, it has a high affinity for calcium hydrate, which is the main component of cement hydrate. As a result, the modifier is stably held inside the crack. There is an effect.

  According to the present invention (8) and (13), in addition to the above effects, since the calcium carbonate filler is rod-shaped or plate-shaped, these rod-shaped or plate-shaped members overlap to form a space inside, The production of the reaction product by the modifier is not hindered and the effect of maintaining a space for relaxing the external force is achieved. FIG. 27 is a secondary electron image obtained by a scanning electric microscope (SEM) of a rod-like calcium carbonate-based filler derived from a shell and a mechanism of action of the present invention. In the figure, 1 shows a state in which a space is formed between powders in a state where cracks are filled with a calcium carbonate-based filler derived from a shell. 2 shows a state where 1 is impregnated with a lithium silicate surface modifier and easily penetrates into the space formed between the powders. 3 shows a state in which a calcium ion eluted from calcium carbonate after 2 and a lithium silicate surface modifier component react to form a network between the crack inner surface and the powder by the generated reaction product.

  According to the present invention (9) and (14), in addition to the above-mentioned effects, since a shell carbonate-derived material is used as the calcium carbonate filler, it has higher strength and bending toughness than mineral calcium carbonate. In addition, because it uses unfired trace protein (shell carbonate-specific calcium carbonate and trace protein complex) remains, as a result of having higher strength and bending toughness, There is an effect that a further crack closure can be achieved.

  According to the present invention (10) and (16), in addition to the above effects, a silane-based, siloxane-based or silane-siloxane-based water repellent is further applied to improve durability after crack closure, It becomes possible to give surname, salt barrier property, and dry and wet repeated durability. In this way, a crack of 0.2 mm or less is closed with a silicic acid-based modifier and a filler, and the surface is reinforced with a silane-based water repellent, so that the repair effect lasts for a long time. There is an effect.

  Furthermore, according to the present invention (3), (5), (11) and (15), the new or existing concrete to which the lithium silicate surface modifying material is applied is resistant to freezing and thawing and salt damage deterioration. The effect is that it can be used in cold regions and coastal areas. Here, the reason will be described below. First, the present inventors prevented the deterioration due to freezing and thawing, salt damage, and composite deterioration due to the relatively simple construction method of simply applying a lithium silicate surface modifying material to the surface of a new and existing concrete structure. Or the technique to suppress has already been proposed (PCT / JP2005 / 003122). Hereinafter, the mechanism of action will be described in detail.

  First, the surface modifying material imparts the property of reducing moisture permeability and salt permeability to concrete. Specifically, the alkali metal-containing lithium silicate in the agent reacts with calcium hydroxide, which is a pore solution component of water or concrete present on the aggregate interface or in the internal voids, to form a gel. This gel formation results in densification of the voids. As a result, it inhibits the invasion of water, which is a factor that promotes various deteriorations. With respect to chloride ions that cause salt damage, the charge on the gel surface increases with densification. Diffusion is also suppressed by becoming negative and electrically repelling. Furthermore, by taking in void water inside the concrete that causes freezing and thawing during gelation, voids that are not filled with water increase, and a space is created to release the pressure when water and gel freeze and expand.

  Second, the surface modifying material has the property of penetrating deeper into the concrete (for example, to a depth of about 40 mm). The reason for this is understood to be that the reaction rate is very slow compared to conventional ones (such as water glass modifiers) (so that it can penetrate deep into the concrete). In various conventional research reports, there have been many reports that lithium compounds are effective in preventing various deterioration of concrete. However, since this component can penetrate only about 1 to 2 mm from the surface, it can only be used as a concrete admixture or a surface coating material. The surface modifying material is epoch-making in that it provided an osmotic surface coating agent based on this second property of deep penetration.

  For ease of understanding, the mechanism of action by the surface modifying material will be described with reference to FIG. FIG. 28A is a schematic view of a concrete cross section, showing a mortar matrix 1 including fine aggregate, coarse aggregate 2, pores, cracks, and the like 3. And the figure which expanded the square enclosure part in Fig.28 (a) is FIG.28 (b)-(d). In FIG. 28 (b), 3 also indicates a fragile tissue portion at the aggregate interface, 4 is a fine aggregate, and 5 is a hardened cement paste. Inside 3 is a pore solution containing ions such as calcium. When the surface modifier is applied to the concrete surface, it penetrates into the interior through cracks, voids, and aggregate interfaces. FIG. 28C shows a state in which the surface modifying material 6 has permeated into the voids and the like. The surface modifying material that has permeated into the voids reacts with calcium hydroxide and water in the pore solution to form a gel. FIG. 28D shows a state of the gel 7 generated from the surface modifying material. FIG. 28 (e) shows the actual state of the square box in FIG. 28 (d).

  To summarize the above, when the surface modification material is applied to the concrete surface, the agent mainly composed of alkali metal-containing lithium silicate is transmitted through the continuous voids, cracks and aggregate interfaces, and penetrates deep into the concrete. Furthermore, it penetrates into fine voids in the rough portion of the composition in contact with the interface. Further, when gelling by reacting with water and calcium hydroxide present on the interface or inside the voids, the reaction rate is very slow compared to the prior art, and therefore, it can penetrate deep into the concrete. As a result, the present invention is a relatively simple construction method that is simply applied to the surface of new and existing concrete structures, and prevents or inhibits deterioration due to freezing and thawing and salt damage and composite deterioration due to these without changing the surface design. There is an effect that can be done.

  The best mode of the present invention will be described below. The technical scope of the present invention is not limited to the best mode. Hereinafter, the dry shrinkage cracking suppression technology for new concrete will be described first, and then the crack closure technology for existing concrete will be described.

《Technology for controlling drying shrinkage cracking of new concrete》
The technique applies to young age concrete where hydration is ongoing. Here, when cracks occur in young age concrete that is undergoing hydration, deterioration progresses very quickly, so it is important to suppress cracks at the young age, and long-term durability of the concrete structure It greatly affects sex. According to the present invention, the reduction of drying shrinkage cracks suppresses the permeation of substances such as water, salinity, and carbon dioxide, which cause deterioration. The technique will be described in detail below.
(Dry shrinkage cracking inhibitor for new concrete)
The novel concrete drying shrinkage cracking inhibitor according to the best mode includes a lithium silicate surface modifier. As described above, the drying shrinkage cracking inhibitor also functions as a concrete durability improver that densifies new concrete and improves the durability of the concrete itself. Hereinafter, the drying shrinkage cracking inhibitor will be described in detail.

-Composition of drying shrinkage cracking inhibitor This drying shrinkage cracking inhibitor contains a lithium silicate (lithium silicate) surface modifying material. Here, a suitable lithium silicate surface modifying material is obtained by blending an alkali metal ion source with an aqueous lithium silicate solution. Hereinafter, the configuration requirements of the present invention will be described. In this specification, “Li ₂ O”, “Na ₂ O”, and “K ₂ O” are equivalent oxide equivalents.

The “aqueous lithium silicate solution” refers to a kind of colloidal silica in which the alkali portion is lithium. Here, the “aqueous solution” does not mean that these raw material components are completely dissolved, but indicates a state in which at least a part of the raw materials is dissolved in some form. Therefore, even if one of the raw materials (especially SiO ₂ ) exists in a colloidal state, even if a part of the raw material is dissolved and a part is in a colloidal state, all of these states are included. Moreover, these raw materials may exist in any form in the liquid.

The “lithium silicate aqueous solution” can be produced by boiling silica in an aqueous solution of sodium hydroxide or potassium hydroxide and replacing Na and K in the resulting colloidal silica with Li. Examples of commercially available products include lithium silicate 45 manufactured by Nissan Chemical Industries, Ltd. {20.0 to 21.0 parts by weight of SiO _{2 with} respect to 100 parts by weight of aqueous solution, 2.1 to 2.4 weights of Li ₂ O. Part, SiO ₂ / Li ₂ O molar ratio 4.5} can be used.

  "Alkali metal ion source" is not particularly limited as long as it causes alkali metal ions to be present in an aqueous lithium silicate solution when added to water. For example, a substance that dissociates into alkali metal ions when added to water, Examples thereof include water-soluble alkali metal-containing substances such as alkali metal hydroxides, alkali metal oxides or alkali metal salts (for example, alkali metal carbonates), alkali metals themselves, and alkali metal ion aqueous solutions. The “alkali metal ion” is not particularly limited, and may be any of lithium, sodium, potassium, rubidium, and cesium. Furthermore, the alkali metal ion source to be blended in the lithium silicate aqueous solution is not necessarily one type, and is a plurality of types (for example, a combination of sodium hydroxide and sodium carbonate) in which the same alkali metal ion is present in the lithium silicate aqueous solution. Alternatively, a plurality of types (for example, a combination of sodium hydroxide and potassium hydroxide) in which different alkali metal ions are present in an aqueous lithium silicate solution may be used.

  A preferred alkali metal ion is a combination of sodium and potassium ions. In particular, the molar ratio of potassium ions to sodium ions is preferably 0.02 to 2.7, more preferably 0.04 to 1.8. In this case, a suitable alkali metal ion source is a combination of sodium hydroxide and potassium hydroxide. With respect to these combinations, the preferred blending ratio of sodium hydroxide and potassium hydroxide is 1.3 to 2.5 (more preferably 1.7 to 2.2) in weight ratio (sodium hydroxide / potassium hydroxide). ).

Furthermore, the addition amount of the alkali metal ion source is preferably 0.08 to 1.8, more preferably 0.12 to 1 with respect to SiO _{2 in} terms of molar ratio (calculated as alkali metal ions). .2.

-Method for Producing Drying Shrinkage Cracking Inhibitor Next, a method for producing a stock solution of a lithium silicate surface modifying material, which is an essential component of the drying shrinkage cracking inhibitor, will be described. The stock solution of the modifying material is produced by blending an alkali metal ion source and water with an aqueous lithium silicate solution. Further, in the production, the mixing method and the order of introducing the materials are basically not limited.

Here, a suitable aqueous solution of lithium silicate is such that the total weight of SiO ₂ and Li ₂ O is 15 to 30% by weight (more preferably 20 to 25% by weight) with respect to the total weight of the aqueous solution. Is added to water at a molar ratio (SiO ₂ / Li ₂ O) of 3 to 8 (more preferably 4 to 5).

  When an alkali metal hydroxide is used as the alkali metal ion source, since there is an exothermic reaction, the alkali metal hydroxide is added little by little to the lithium silicate aqueous solution.

  Add the alkali metal ion source to the lithium silicate aqueous solution and stir well, then add the required amount of water, or add the alkali metal ion source to the lithium silicate aqueous solution with the required amount of water added beforehand and stir well The stock solution of the modifier according to the present invention can be obtained. This water is added for the purpose of reducing the viscosity. The water to be used is preferably pure water or ion exchange water.

  It should be noted that the lithium silicate aqueous solution, which is a raw material, is gelled in a sub-freezing environment and becomes cloudy at + 80 ° C. or higher, so it is preferable not to use such a modified material. . When the aqueous lithium silicate solution is stored or when the present modifying material is produced, the liquid temperature is preferably controlled in the range of +5 to 60 ° C. (more preferably +5 to 25 ° C.).

  The stock solution thus obtained preferably contains 65 to 85% by weight (more preferably 70 to 80% by weight) of water based on the total weight of the stock solution. Moreover, the suitable specific gravity (measured with a float-type hydrometer, 20 degreeC) of the said undiluted | stock solution is 1.210-1.270 (more preferably 1.230-1.250).

  Moreover, the suitable viscosity (measured with a tuning fork type vibration viscometer, 20 ° C.) of the stock solution thus obtained is 1.0 to 15 mPa · s (more preferably 6.5 to 9.5 mPa · s). ).

  Furthermore, the pH of the stock solution thus obtained is preferably in the range of 11.0 to 13.5, and more preferably in the range of 11.9 to 12.6. Further, it is preferable that the pH of the diluted solution is generally within the above range.

Durability improver composition Durability improver according to the best mode includes a silane, siloxane or silane / siloxane water repellent as an essential component, and if necessary, appropriate amounts of various emulsifiers, preservatives, pH It may contain a conditioner, a filler and the like. Here, the silane-based water repellent is an alkylalkoxysilane represented by the general formula: R—Si— (OR ′) (R is an alkyl group having 1 to 15 carbon atoms, R ″ is 1 to 6 carbon atoms). The main component is an alkoxy group), and the use or non-use of a solvent is not a problem. Also, the molecular weight is not particularly limited, and applications from low molecular weight to high molecular weight are possible. Further, the siloxane-based water repellent is a polyorganosiloxane represented by the general formula, R ₁ aR ₂ bR ₃ cSiO (4-abc) / 2 (R ₁ is a methyl group, R ₂ is an aminoalkyl group) , R ₃ represents a hydroxyl group or an alkoxy group and has a relationship of 0 <a + b + c <3) as a main component, and does not specify the use, nonuse, or molecular weight of a solvent. A silane / siloxane water repellent mixed with silane and siloxane may also be used. Here, the active ingredient (alkoxysilane, polyorganosiloxane, etc.) in the water repellent is preferably in the range of 50 to 90% by weight. The weight ratio of alkylalkoxysilane to polyorganosiloxane in the silane / siloxane water repellent is preferably 2: 1 to 10: 1. The durability improver may be liquid, emulsion, gel, aqueous, or solvent-based.

  These water repellents can be obtained according to known production methods. For example, as for the method for producing the water repellent, as for the silane water repellent, for example, Japanese Patent Laid-Open No. 63-69779, Japanese Patent Publication No. 4-68274, Japanese Patent Laid-Open No. 4-300961, Japanese Patent Laid-Open No. 9-9 189030 and the like. The siloxane water repellent is described in, for example, the above-mentioned Japanese Patent Publication No. 4-68274. Further, the silane / siloxane water repellent is described in JP-A-2006-36586. Commercially available products include alkylsiloxysilanes such as Protectsyl BHN, EnviroSeal (BASF Pozzolith Co., Ltd.), Nippa Quad Seal 200S / 500S (Nippon Paint Co., Ltd.), Spanguard (manufactured by Showbond Construction Co., Ltd.), Tossbarrier 100 (), Hydrosilane (Ryoyo Co., Ltd.), Silane Coat (Kikusui Chemical Co., Ltd.), etc., siloxane as hydrosilane CG (Ryoyo Co., Ltd.), silane siloxane as Magical Repeller (Kajima Marino Bait), Aquapel (Product name) and the like.

(how to use)
-New concrete to be applied The new concrete to which the drying shrinkage cracking inhibitor according to the present invention is applied is not particularly limited as long as it is new concrete, and includes both new concrete structures and new concrete secondary products. Also, the type of concrete is not particularly limited. For example, ordinary concrete, high strength concrete, low heat generation concrete, underwater non-separation concrete, underwater concrete, factory product concrete, marine concrete, shotcrete, fiber reinforced concrete, prepacked concrete , High fluidity concrete, lightweight (aggregate) concrete, steel concrete composite structure, prestressed concrete, recycled aggregate concrete and the like. In addition, for example, admixtures such as fly ash, blast furnace slag fine powder, and silica fume may be mixed. In particular, it is more effective to apply the drying shrinkage cracking inhibitor according to the present invention to walls and floors where cracks tend to occur.

-Application method (1) Application method of drying shrinkage cracking inhibitor Next, an application method of the drying shrinkage cracking inhibitor according to the present invention will be described. Wet curing is performed after demolding of the new concrete, and the agent is applied to the new concrete preferably within 14 days after the completion of the wet curing. Here, the reason for “preferably within 14 days after the end of the wet curing” is that the drying gradually proceeds after the end of the wet curing, and depending on the conditions, the drying shrinkage occurs after 14 days. This is because cracks occur. More preferably, it is within 10 days after the end of the wet curing. Hereinafter, the detail (an example) of the application method of this drying shrinkage cracking inhibitor is demonstrated.

First, the stock solution of the drying shrinkage cracking inhibitor according to the present invention is diluted as necessary (hereinafter described by taking a 2-fold dilution as an example) and stirred well (step 1). And before apply | coating this inhibitor to concrete, water is sprinkled in order to make the concrete of an application | coating surface into a moist state (process 2). Thereafter, the wet state of the concrete is confirmed, and the present inhibitor diluted twice with water is applied with a low-pressure sprayer, brush, roller or the like (selected according to the construction site conditions) and allowed to penetrate into the concrete surface (step 3). Here, the usage-amount of this modifier per 1 m < ² > of concrete is 100 ml / m < ² > (what was diluted 2 times), for example, and is 50 ml / m < ² > on a stock solution basis. Next, after application, before drying, water is sprayed at 50 ml / m ^{2 at} a low pressure and wet-cured (step 4). Step 2 to Step 4 are repeated (Step 5). It is confirmed whether the present inhibitor remains on the surface (step 6). As a final step, water is sprayed at a low pressure (50 ml / m ² ), and when remaining is confirmed in step 5, it is washed by brushing or the like so as not to remain on the concrete surface (step 7). Thereafter, it is naturally dried (step 8). Moreover, at the time of construction, it is preferable that the outside air temperature is + 5 ° C. or more, and when it is less than + 5 ° C., it is preferable to control the temperature by heating and curing.

(2) Method of applying durability improver Next, a method of applying the durability improver according to the present invention will be described. First, after the application step of the drying shrinkage cracking inhibitor is completed, a step of drying the surface moisture content to about 8% is preferably executed. However, it may be applied continuously after the step of applying the drying shrinkage cracking inhibitor, and it is preferable to apply the durability improver at least the next day. The application step of the durability improver is carried out by applying a predetermined amount (100 to 300 ml / m ² ) of a silane-based, siloxane-based or silane-siloxane-based water repellent and penetrating the concrete. After application, dry curing is performed so that moisture is not supplied until the surface is completely dried.

《Cracking technology for existing concrete cracks》
(Old concrete cracking plugging agent)
The crack plugging agent of the existing concrete according to the best mode is composed of a lithium silicate surface modifying material and a shell rod-like or plate-like calcium carbonate. Here, the crack plugging agent according to the best mode is a so-called two-component type, and is composed of a calcium carbonate-based filler (A agent) and a lithium silicate-based surface modifier (B agent). However, the present invention is not limited to this, and a so-called one-pack type may be used. In addition, a powder capable of eluting divalent or higher cation such as calcium hydroxide and cement may be contained (in the case of a two-component type, either or both). In addition, the lithium silicate type modifier according to the agent B also functions as a concrete durability improver that densifies existing concrete and improves the durability of the concrete itself, as described above. Hereinafter, the crack plugging agent will be described in detail.

-Composition of crack plugging agent First, the lithium silicate-based surface modifier (B agent) according to the best mode is the same as that described in the above-mentioned dry shrinkage cracking inhibitor, and thus the description thereof is omitted.

  Next, as long as the calcium carbonate-based filler (agent A) according to the best mode can contain calcium carbonate as a main component and penetrate into cracks of 0.2 mm or less, the size thereof such as rod-like, plate-like, granular, etc. The sheath shape is not particularly limited. Moreover, the kind of calcium carbonate is not limited, For example, any of biological origin, such as a shell, eggshell, and bone, mineral origin, and a synthetic product may be sufficient.

  However, the preferred calcium carbonate filler is a rod or plate. In particular, those having an average particle diameter of 3 to 100 μm and an average aspect ratio of about 1 to 30 in the case of a rod shape are suitable. When such a rod-like or plate-like filler is used, the rod-like members or plate-like members overlap to form an internal space. As a result, the production of the reaction product by the modifier is not inhibited, and a space for relaxing the external force is maintained. Here, the measurement of an average particle diameter is an average particle diameter obtained from the cumulative distribution calculated | required using the standard sieve of JIS. The aspect ratio indicates a value measured and calculated based on an SEM image of 100 arbitrary fillers.

  In addition, a preferred calcium carbonate filler is one in which the calcium carbonate filler is derived from an unfired shell. Here, as shellfish used as raw materials, shellfish belonging to bivalves that are hexagonal calcite-type calcium carbonate in the middle part of shells having a three-layer structure are suitable and are used for food because they are used for food. Easily available materials include scallops, oysters, hoki, clams, swordfish, etc., and scallops are optimal because of their large shells and excellent materialization efficiency. Shellfish belonging to the snails can also be used. Furthermore, among the calcium carbonate-based fillers derived from shells, an unfired one in which a trace amount of protein remains is more preferable. This is because, due to the presence of the calcium carbonate peculiar to the shell and the trace protein complex, the filler has higher strength and bending toughness, and as a result, further crack closure can be achieved. A particularly suitable calcium carbonate-based filler derived from a shell is composed of 96 to 98% calcium carbonate, 1 to 3% mineral such as sodium and magnesium, and 1% or less protein. In the case of scallops, calcium carbonate is the main component (about 98%), and contains trace amounts of proteins (0.8 to 0.01%) and other trace minerals (about 1%).

-Manufacturing method of crack plugging agent Among the crack plugging materials according to the present invention, the lithium silicate surface modifying material is the same as that described in the above-mentioned dry shrinkage cracking inhibitor, and thus the description thereof is omitted. Next, regarding the calcium carbonate filler, when using a shell as the filler, it is washed with water, sterilized by heating at a low temperature (100 to 250 ° C.), and then pulverized with a hammer mill, pin mill, screen mill, jet mill or the like. Manufactured (Japanese Patent Laid-Open No. 10-257850).

-Composition of crack closure durability improving agent The composition of the crack closure durability improving agent according to the best mode is the same as that described in the above-mentioned dry shrinkage cracking inhibitor, and thus the description thereof is omitted.

-Manufacturing method of crack closure durability improvement agent The manufacturing method of the crack closure durability improvement agent which concerns on this best form is the same as what was demonstrated by the dry shrinkage cracking inhibitor mentioned above, Therefore It abbreviate | omits description.

(how to use)
-Existing concrete to be applied The existing concrete to which the crack plugging agent according to the present invention is applied is not particularly limited as long as it is existing concrete, and includes both existing concrete structures and existing concrete secondary products. Also, the type of concrete is not particularly limited. For example, ordinary concrete, high strength concrete, low heat generation concrete, underwater non-separation concrete, underwater concrete, factory product concrete, marine concrete, shotcrete, fiber reinforced concrete, prepacked concrete , High fluidity concrete, lightweight (aggregate) concrete, steel concrete composite structure, prestressed concrete, recycled aggregate concrete and the like. In addition, for example, admixtures such as fly ash, blast furnace slag fine powder, and silica fume may be mixed. In particular, it is more effective to apply the crack plugging agent according to the present invention to existing concrete in which cracks of 0.2 mm or less, which could not be solved by the prior art, have occurred.

-Application method (1) Application method of crack plugging agent Next, an example of the application method of the crack plugging agent according to the present invention will be described. First, from the first method example, 5-30% (preferably 10-20%) of the calcium carbonate-based filler (A agent) is suspended in water, injected by a dropper, a syringe, or the like, or sprayed. Using a brush, roller or the like, the cracked portion is impregnated. Here, since the volume of the filler decreases with the absorption of water, the impregnation step is repeated several times so that the cracks are closed until the water is dried. Next, a 2-fold water dilution of the lithium silicate surface modifying material (agent B) was filled with the calcium carbonate filler using a syringe, syringe, or the like, or using a spray, brush, roller, or the like. Impregnate cracks. The amount of impregnation varies depending on the scale of cracks, but is about 1 to 10 ml (preferably 3 to 8 ml) per 100 mm length when the crack width is 0.2 mm and the crack depth is 100 mm. Next, a second method example will be described. A calcium carbonate filler is suspended in water for 5 to 30% (preferably 10 to 20%) and injected by a dropper, a syringe or the like, or spray, brush, roller -Impregnate the cracked part using etc. Once water is absorbed, a 2 times water dilution of lithium silicate surface modifier (B agent) is injected with a dropper, syringe, etc., or spray, brush, roller, etc., calcium carbonate type Impregnate the cracks filled with filler. After the surface is dried, the above process is repeated for the unoccluded portion of the cracked portion to block the crack. A more specific application example is given below.
1. When the crack width is narrow (0.1 mm or less), a method of using a 10% suspension of HTC (see Examples) before mixing a 20% suspension of equal amounts of HTC and HTC-20 (see Examples).
2. If the crack width is narrower and almost invisible (about 0.03 mm or less), only the B agent (lithium silicate modifier) is applied.
3. A method in which HTC, HTC-20, and calcium hydroxide are mixed in equal amounts and used as a 10% suspension to increase the reactivity with the lithium silicate surface modifier.

In addition, although the above-mentioned first method and second method are construction methods that impregnate and apply only to the cracked part, if only the cracked part is repaired, there is a possibility that dry shrinkage cracking may occur after the closing process. is there. In order to prevent this, the entire surface of the construction surface is made uniform by applying and impregnating the lithium silicate surface modifying material (B agent) to the entire concrete surface where cracks are generated at the same time as repairing the cracked portion. It is possible to suppress the occurrence of cracks that lead to deterioration. Therefore, the third method example of the crack plugging agent according to the present invention will be described. In the first and second methods, after the crack portion is plugged, the lithium silicate surface modifier (B agent) is cracked. 200 ml / m ^{2 is} applied to the entire concrete surface where cracks are generated, and the cracks newly generated after the crack closing process are suppressed.

(2) Method for Applying Crack Closure Durability Improvement Agent The method for applying the crack closure durability improver according to the present best mode is the same as that described for the dry shrinkage crack inhibitor described above, and thus the description thereof is omitted.

  Hereinafter, the present invention will be specifically described with reference to examples. The present invention is not limited in any way by the examples.

Production Example Lithium silicate 45 ( manufactured by Nissan Chemical Industries, Ltd., 20.0 to 21.0 parts by weight of SiO _2, 2.1 to 2.4 parts by weight of Li ₂ O, 100 parts by weight of aqueous solution, SiO ₂ / Li ₂ Weigh out 85.70 g of O molar ratio 4.5) in a beaker, and add 412 g of sodium hydroxide (manufactured by Kanto Chemical Co., Inc., purity 97%) well with a glass rod. We added sequentially. After all of the sodium hydroxide has dissolved, add 1.96 g of potassium hydroxide (manufactured by Kanto Chemical Co., Inc., 86% purity) little by little, and gently add 8.22 g of ion-exchanged water to the place where it has completely dissolved. By thoroughly stirring with a stick, a stock solution of a lithium silicate surface modifying material according to this production example was obtained (viscosity: 7.32 mPa · s). In addition, the composition of each component is shown in Table 1 (here, values of lithium oxide, sodium oxide and potassium oxide are converted to equivalent oxides).

<< Example 1 (Dry Shrinkage Cracking Inhibition Test of New Concrete) >>

(1) Crack suppression confirmation test <Outline of experiment>
Wet curing after demolding of new concrete (tunnel), within 14 days after discontinuation of wet curing, after applying a dry shrinkage cracking inhibitor on the new concrete surface, the presence or absence of visual cracks, Cracks were confirmed by applying a fluorescent agent, and changes in the air permeability coefficient were confirmed. For comparison, an uncoated area was also provided. Further detailed information is described below.
Site name: Donan district tunnel (about 5km from the sea)
Construction time: November 2007 Construction location: Near the sea side exit (apply 64M from the exit)
Status check: August 2008 (9 months from construction)

<Drying shrinkage cracking inhibitor>
A modifier obtained by diluting the stock solution obtained in the production example with water twice.

<Application method>
After washing the concrete on the coated surface by high-pressure water jet and performing wet curing, the modifier 100ml / m ² is sprayed uniformly as a primary application using a low-pressure spray and takes about 45 minutes. Infiltrated. Thereafter, about 50 ml / m ^{2 of} water was sprayed with a low-pressure spray and moistened for about 30 minutes. As a secondary application, the modifier 100 ml / m ² was sprayed and permeated in the same manner as the primary application, and further wet curing was performed with 50 ml / m ² of water. The modifier remaining on the surface after secondary curing was removed by watering and brushing to complete the construction.

<Result>

-Visual condition In the crack confirmation by visual observation, the crack of about 0.2 mm was confirmed in the non-application part (FIG. 1), but there was no crack in a construction part (FIG. 2).

・ Check for cracks below the visual range (check by UV irradiation after impregnation with fluorescent agent)
The fine crack (FIGS. 3 and 4) confirmed at the non-coated portion is long and linear, and is likely to develop into a large crack when drying proceeds in the future. On the other hand, the fine cracks (FIGS. 5 and 6) confirmed at the construction site were short in length and branched. In addition, the crack width appeared to be large under ultraviolet light emission, but the non-application was about 0.2 mm, whereas the application with this agent was as small as about 0.1 mm. It was shown that the stress distribution effect of drying shrinkage due to the homogenization of the tissue by the modification effect by applying this agent.

-Change in air permeability coefficient The density of the surface concrete was confirmed by the torrent air permeability coefficient test at the place where cracks were confirmed. The air permeability coefficient is an index indicating that the smaller the numerical value is, the more difficult it is to pass air, and the durability of the surface layer that affects the concrete life. The measurement results are shown in Table 2. The non-application air permeability coefficient of 0.34 is reduced to about 1/2 by 0.18, which indicates that densification was achieved by application.

(2) Surface strength change confirmation test by suppressing cracks <Outline of experiment>
After demolding the new concrete (pier), wet curing was performed, and within 14 days after the completion of the wet curing, a strength estimation test was conducted after a predetermined period of time had elapsed since the drying shrinkage cracking inhibitor was applied to the new concrete surface. . For comparison, an uncoated area was also provided. Further detailed information is described below.
Site name: Road pier construction in the mountainous region of the Douo region Timing: October 2007 Construction location: Confirmation of the entire pier situation up to 5M height from the ground: August 2008 (10 months from construction)

<Drying shrinkage cracking inhibitor>
A modifier obtained by diluting the stock solution obtained in the production example with water twice.

<Application method>
After washing the concrete on the coated surface by high-pressure water jet and performing wet curing, the modifier 100ml / m ² is sprayed uniformly as a primary application using a low-pressure spray and takes about 45 minutes. Infiltrated. Thereafter, about 50 ml / m ^{2 of} water was sprayed with a low-pressure spray and moistened for about 30 minutes. As a secondary application, the modifier 100 ml / m ² was sprayed and permeated in the same manner as the primary application, and further wet curing was performed with 50 ml / m ² of water. The modifier remaining on the surface after secondary curing was removed by watering and brushing to complete the construction.

<Result>
The concrete surface layer strength estimation test was performed by the mechanical impedance method. Changes were confirmed before and after construction and after 10 months. The measured values in the figure indicate that the strength is higher as the numerical value is larger as the strength index value. FIG. 7 (left) shows the strength distribution before construction, FIG. 7 (right) shows the strength distribution immediately after construction, FIG. 8 (left) shows the strength after 10 months after construction, and FIG. 8 (right) shows the strength distribution after 10 months after no application. Only one day has passed between FIG. 7 (right) and (left), and there is almost no change, but the strength is greatly improved after 10 months from the construction shown in FIG. 8 (left). On the other hand, in the non-application part, it is almost the same as before construction. An improvement in the overall strength of the application of the modifier is considered to mean an improvement in durability due to a crack suppression effect. In addition, the numerical value shown under these figures is the estimated intensity | strength (N) which derived | led-out using the conversion formula (Fc = STR * 6.97-87.7) and the inside of [] the intensity | strength index value (STR). / Mm ² ).

(3) Crack suppression effect improvement test with silane water repellent <Outline of experiment>
Wet curing is performed after demolding of the new concrete internally constrained with a steel ring, and within 14 days after the termination of wet curing, a dry shrinkage cracking inhibitor is applied to the surface. Applied. After coating, the film was dried in a constant temperature and humidity chamber, and the amount of shrinkage due to drying was measured using a strain gauge to confirm the time until cracking occurred.
Specimen: The composition is OPC concrete with 50% W / C, and the dimensions are shown in Table 3 and FIG.
Drying conditions: + 20 ° C, humidity 60%

<Drying shrinkage cracking inhibitor>
A modifier obtained by diluting the stock solution obtained in the production example with water twice.

<Durability improver>
Silane-based water repellent (trade name: Protectsill BHN) based on alkylalkoxysilane

<Application method>
The placing surface and bottom surface of the specimen were brushed to remove dirt and latency, and then sprayed with water to perform wet curing. Thereafter, 100 ml / m ² of the drying shrinkage cracking inhibitor was applied uniformly using a brush as a primary application and allowed to penetrate for about 45 minutes. Thereafter, about 50 ml / m ^{2 of} water was applied with a brush and moistened for about 30 minutes. As a secondary application, 100 ml / m ² of the above-mentioned drying shrinkage cracking inhibitor was applied and infiltrated in the same manner as the primary application, and further wet-cured with 50 ml / m ² of water. After the drying shrinkage cracking inhibitor was applied, it was dried for one day, and 200 ml / m ^{2 of the} durability improver was applied and impregnated.

<Result>
Table 4 shows the results of measurement of the drying shrinkage strain of the concrete. The crack generation time was 472 hours with no coating applied, while the lithium silicate surface modifier (silicated Li in the figure) used as a dry shrinkage cracking inhibitor applied 589 hours and 128% with no coating. Suppressed. In addition, in the case where a durability improver (silane-based water repellent) is applied to the top coat of a lithium silicate surface modifier (in the figure, silicate Li + silane), 735 hours (vs. non-application ratio 155%), Cracking was suppressed for a long time. The suppression effect of dry shrinkage cracking by the lithium silicate surface modifier was confirmed. It was also confirmed that the effect was further improved by applying a silane water repellent after the lithium silicate surface modifier was applied.

(4) Verification of frost damage resistance by suppressing drying shrinkage cracks <Experimental overview>
A dry shrinkage cracking inhibitor was applied on the age of 7 days. A one-side freeze-thaw test was performed. The surface peeling (scaling) durability was confirmed using salt water, and the freeze-thaw action was repeated up to 56 cycles with + 20 ° C to -20 ° C / 12 hours as one cycle.
Test standard: RILEM-CDF test formulation: W / C0.5 OPC concrete and W / C0.45 BB concrete Dimensions: 100 × 100 × 200mm

<Drying shrinkage cracking inhibitor>
A modifier obtained by diluting the stock solution obtained in the production example with water twice.

<Application method>
200ml / m ² applied to one side of the mold at 7 days of age. After application, wet curing until age 28 days.

<Result>
The results are shown in FIG. 11 and FIG. First, as shown in FIG. 11, normally a result of performing up to 56 cycles of 2 times the period of the standard modifier applied for peeling amount 0.26 kg / m ² of non-coated at OPC50 concrete and 0.04 kg / m ² Reduced to 16% of no application. Further, as shown in FIG. 12, the peeling amount of free coating is BB45 concrete exceed 1.5 kg / m ² limit amount 42 cycle time, but became 2.03kg / m ² to 56 cycles, modifier The application was reduced to 0.40 kg / m ² and 19% without application. If there is a crack on the surface, the lithium silicate-based surface modifier has an inhibitory effect on scaling deterioration, which deteriorates remarkably.

<< Example 2 (crack blockage test of existing concrete) >>
(1) Crack closure test (simulated crack)
<Outline of experiment>
Simulated by cutting existing concrete (φ100 × 100 cylinder) vertically from the center, specifying the opening width to 0.05, 0.1, 0, 2, 0.3mm and fixing the outside with aluminum tape The cracks were closed by applying and impregnating the cracks with a crack closing agent composed of a calcium carbonate filler (agent A) and a lithium silicate surface modifier (agent B). After coating, an acrylic cylinder was bonded to the top of the crack, and the change in the amount of water injected into the cylinder was measured to determine the water absorption rate per unit time.

<Lithium silicate surface modifier>
A modifier obtained by diluting the stock solution obtained in the production example with water twice.

<Calcium carbonate filler>
HTC (manufactured by Hokkaido Kyodo Lime Co., Ltd.) and rod-shaped calcium carbonate fine powder derived from shells and having an average particle size of 5 μm and HTC-20 (product name) having an average particle size of 30 μm were mixed with water in the proportions shown in Table 5. thing.

<Application method>
The cracked portion was impregnated with the calcium carbonate filler using a dropper. Table 6 shows the type and amount of agent A applied to each crack width. After each suspension was overflowed to the upper part of the crack, the step of impregnating each solution was further repeatedly filled in the portion where the volume decreased due to moisture absorption. Next, 1.2 ml each of a 2-fold water dilution of a lithium silicate surface modifying material (agent B) was impregnated with a dropper.

<Result>
FIGS. 13, 14 and 15 show changes in the water absorption amount before, after and after the blockage, and Table 7 shows the water absorption rate obtained from the water absorption amount for 2 hours from the start of the test. Before clogging, 40 ml of water was 0.05 mm, 20 minutes permeated, and in others, it passed in 1 or 2 minutes. After clogging, there was no penetration of water into the cracks after 2 hours at any crack width, and the water absorption rate Became 0. Similar results were obtained in the second measurement after occlusion. The third measurement showed a slight water absorption only with a width of 0.2 mm, but it showed a good effect of cracking by the plugging agent.

(2) Crack blockage test (actual crack of about 0.2 mm)
<Outline of experiment>
With respect to dry shrinkage cracks generated in a full-scale structure simulating a wall surface, the cracks were closed using the crack plugging agent. The effect of the blockage was confirmed by measuring the water absorption rate.
Specimen and crack outline: W / C 60% of width 200 x height 900 x length 10,000 mm with embedded slit for inducing the occurrence of dry shrinkage cracking, exposed to OPC concrete for 10 weeks. The width of the crack is 0.05 to 0.2 mm, and the crack length is about 350 mm.
FIG. 16 shows the entire specimen and the cracked portion.

<Coating agent>
10% suspension of HTC (A-1), 20% suspension of HTC and HTC-20 equivalents (A-3), 30% suspension of HTC and HTC-20 equivalents Four types of liquid (A-4) and a lithium silicate surface modifier (B agent) were used.

<Application method>
About 10 ml of the A-1 agent was impregnated into the cracked portion using a dropper and a roller. The drying process and impregnation were repeated to close the cracked part up to about 0.05 mm. Thereafter, about 10 ml of the A-2 agent was used, and the crack portion up to about 0.1 mm was closed in the same manner as the A-1 agent. Furthermore, about 10 ml of the A-3 agent was used, and the cracked part up to 0.2 mm was closed by the same method as that of the A-1 agent. Thereafter, the B agent 200 ml / m ² coating with a roller, impregnated into the wall (to the left and right 300mm cracking) including cracking. The cracked portion was permeated more until the B agent was not absorbed. FIG. 17 shows a cracked part before and after closing.

<Test results>
FIG. 18 and Table 8 show changes in the water absorption rate of the cracked part before and after the blockage and the sound part without cracking. In the healthy part, the water absorption for 20 minutes was only 1.4ml, but the cracked part absorbed 6ml in 3 minutes. On the other hand, the water absorption of the cracked portion after the blockage was 1.1 ml in 20 minutes, indicating a higher water barrier than the healthy portion, and the blockage effect of the crack due to the plugging agent was confirmed.

(3) Crack closure test (actual crack of 0.05 mm or less)
Subsequent drying shrinkage crack progress suppression effect and surface performance improvement effect by applying the above-mentioned crack plugging agent to fine cracks were confirmed.

<Summary>
A crack-blocking agent B was applied to a column of a concrete outdoor structure that had passed 2 years after placement (Fig. 19), and changes in properties due to the exposure period of 2 years were confirmed by measuring the cracked state, surface strength, and moisture content. . FIG. 19 shows the situation when the B agent is applied to the pillar (the front is the west side).

<Test body>
The target pillar is 500mm square, and is Portland cement concrete with a design strength of 24N. When 3 years have passed since the installation, 200 ml of cracking plugging agent B (lithium silicate-based modifier) in a band with a height of 350 mm is placed around 1 m above the ground on the west, north, and south surfaces that will be raining. / m ^{2 was} applied and impregnated. After that, she was exposed to an exposure environment with rainfall, sunshine, wind, and temperature changes for 23 months.

<Measurement item>
Cracked state (visual and fluorescent agent applied), surface strength distribution (concrete tester CTS-02), moisture content

<Test results>
(Crack change)
The occurrence of cracks was suppressed on all of the west, north, and south surfaces where the B agent was applied, compared to the uncoated part. FIG. 20 shows a photo of the crack measurement location by visible light, and FIG. 21 shows a photo of the fluorescent material applied to the same location and irradiated with ultraviolet rays. From FIG. 20, cracks can be confirmed without application, but cracks are not confirmed with application of B agent. In FIG. 21, the fluorescent agent particles are as small as 2 μm, and the cracks in the visible range are difficult to be confirmed by irradiation with the fluorescent agent, but the finer cracks are uniformly introduced compared to the case where the B agent application is not applied. It can be seen that the stress is distributed.

(Surface strength change)
The surface intensity changes on the west and north surfaces are shown in FIGS. The numerical value in the figure indicates that the surface strength is high when the numerical value is high, and the surface strength is low when the numerical value is small, but it does not indicate the compressive strength itself, but is an index value, both from the non-application shown on the left side Many places with high strength can be seen by applying B agent. Also, in terms of compressive strength converted from the average value, the West side is 23.1 N / mm ² with no application, the B agent application is 24.1 N / mm ² , and the north side is also 24.7 N / mm ² with 26.5 N / mm ² Strength improvement was seen.

(Change in moisture content)
On the day before the measurement, the moisture content of the concrete was large due to rainfall, but as shown in Fig. 24, the moisture content of the surface layer was lower with the B agent application than with no application, and the moisture transfer to the inside due to the clogging effect of the cracked part. A state of suppression is shown.

(4) Durability improvement test with silane <Test method>
A silane-based water repellent (mainly alkylalkoxysilane) as a durability improver after clogging with a crack plugging agent, A and B in a 0.2 mm wide simulated crack in the same test method as in Example 2 (Product name: Protect Sil BHN) was applied to the cracked portion in an amount of 0.4 ml.

<Result>
FIG. 25 shows the first and second changes in water absorption after the blockage. The measurement was carried out for up to 20 hours. In the case of clogging with only the crack plugging agents A and B, the water absorption was 2 ml at the first time and 3.5 ml at the second time. The water absorption was zero at the second round, and the durability improvement effect of the silane water repellent was confirmed.

(5) Freezing damage test <Overview>
A one-side freeze-thaw test was carried out by applying to concrete that had undergone frost damage for about 50 years in Hokkaido. The concrete in question is subject to frost damage due to long-term exposure, and the structure has many fine cracks. After applying and impregnating a 10% suspension of calcium carbonate filler (agent A) to this, a lithium silicate surface modifier (agent B) is applied to the entire test surface, and a one-side freeze-thaw test is performed. did.
Test standard: RILEM-CIF (Pure water freezing and thawing test)
Specimen: Mixture unknown Diameter 50 mm Height 100 mm Application test on cut surface: Wet curing was performed for 14 days after application, and the test was started.
Freezing and thawing conditions: Freezing and thawing was repeated up to 42 cycles with one cycle of + 20 ° C to -20 ° C / 12 hours.
<Result>
The results are shown in FIG. As can be seen from the figure, 42 cycles result of carrying up to, non-coating peeling amount 3.28kg / m ² relative to the lithium silicate-based surface modifier (B agent only) free coating with 1.48kg / m ² in coating It has been reduced to 45%. However, when calcium carbonate filler (A agent) and lithium silicate surface modifier (B agent) are used in combination, the peel rate is very small at 0.11 kg / m ^2, and it is reduced to only 3% with no coating ratio. Has been. It was effective to use agent A for blocking fine cracks, and the effect of improving freeze-thaw durability was also demonstrated.

FIG. 1 is a result of visually confirming cracks in Example 1 (uncoated portion). FIG. 2 is a result of visual confirmation of cracks in Example 1 (construction location). FIG. 3 shows the result (uncoated portion) of crack confirmation (confirmation by ultraviolet irradiation after impregnation with a fluorescent agent) below the visual range in Example 1. FIG. 4 is a result (uncoated part) of crack confirmation (confirmation by ultraviolet irradiation after impregnation with a fluorescent agent) below the visual range in Example 1. FIG. 5 shows the result (construction location) of crack confirmation (confirmation by ultraviolet irradiation after impregnation with a fluorescent agent) within the visual range in Example 1. FIG. 6 shows the result (construction location) of crack confirmation below the visual range in Example 1 (confirmation by ultraviolet irradiation after impregnation with a fluorescent agent). FIG. 7 shows the results of a surface strength change confirmation test by suppressing cracks in Example 1. FIG. 8 shows the results of a surface strength change confirmation test by suppressing cracks in Example 1. FIG. 9 shows a specimen for a crack suppression effect improvement test using a silane-based water repellent in Example 1. FIG. 10 shows the results of the crack suppression effect improvement test using the silane-based water repellent in Example 1. FIG. 11 shows the results of a frost damage resistance verification test by suppressing drying shrinkage cracks in Example 1. 12 shows the results of a frost damage resistance verification test by suppressing drying shrinkage cracks in Example 1. FIG. FIG. 13 shows the results of a crack closure test (simulated crack) in Example 2. FIG. 14 shows the results of a crack closure test (simulated crack) in Example 2. FIG. 15 shows the results of a crack closure test (simulated crack) in Example 2. FIG. 16 is a diagram showing the whole specimen and a cracked portion in a crack closure test (actual crack of about 0.2 mm). FIG. 17 is a diagram showing a state of a cracked part before and after closing in the crack closing test (actual crack of about 0.2 mm) in Example 2. FIG. 18 shows the result of a crack closure test (actual crack of about 0.2 mm) in Example 2. FIG. 19 is a diagram showing a state of a crack closure test (actual crack of 0.05 mm or less) in Example 2. FIG. 20 is a diagram showing the results of a crack closure test (actual cracks of 0.05 mm or less) in Example 2 (photographs of visible portions of cracks). FIG. 21 is a diagram showing the results of a crack closure test (actual cracks of 0.05 mm or less) in Example 2 (photos of applying a fluorescent agent to a crack measurement location and irradiating with ultraviolet rays). FIG. 22 is a diagram showing a result (surface strength change) of a crack closure test (actual crack of 0.05 mm or less) in Example 2. FIG. 23 is a diagram showing a result (surface strength change) of a crack closure test (actual crack of 0.05 mm or less) in Example 2. FIG. 24 is a diagram showing the result (water content change) of a crack closure test (actual crack of 0.05 mm or less) in Example 2. FIG. 25 shows the results of a durability improvement test using silane in Example 2. FIG. 26 shows the results of a frost damage resistance test in Example 2. FIG. 27 is a secondary electron image of a scanning electric microscope (SEM) of a rod-like calcium carbonate-based filler derived from a shell and an action mechanism diagram of the present invention. FIG. 28 is an explanatory diagram of the mechanism of action of the present invention using a surface modifying material.

Claims (16)

In the method for inhibiting dry shrinkage cracking in new concrete structures or new secondary concrete products,
A method comprising a drying shrinkage cracking suppression step of applying a lithium silicate-based surface modifier to a new concrete after performing wet curing after demolding the new concrete, and terminating the wet curing. The method according to claim 1, further comprising a durability improving step of applying a silane-based, siloxane-based, or silane-siloxane-based water repellent to the new concrete after the drying shrinkage cracking suppressing step.   The method according to claim 1 or 2, wherein in the drying shrinkage cracking suppressing step, the concrete is densified and the durability of the concrete itself is improved.   A new concrete structure or a new concrete secondary, characterized by containing a lithium silicate-based surface modifier, for performing wet curing after demolding of the new concrete and applying it to the new concrete after cutting off the wet curing Inhibitor of dry shrinkage cracking of products.   The drying shrinkage cracking inhibitor according to claim 4, which also functions as a concrete durability improver that densifies concrete and improves the durability of the concrete itself.   A novel concrete for further application to a new concrete to which the drying shrinkage cracking inhibitor according to claim 4 or 5 is applied, comprising a silane-based, siloxane-based or silane-siloxane-based water repellent. Durability improver. In the method of blocking cracks in existing concrete structures or existing concrete secondary products,
A method comprising a crack closing step of applying a lithium silicate surface modifying material and a calcium carbonate filler to existing concrete.   The method according to claim 7, wherein the calcium carbonate filler is rod-shaped or plate-shaped.   The method according to claim 7 or 8, wherein the calcium carbonate-based filler is derived from an unfired shell. The method according to any one of claims 7 to 9, further comprising a crack closing durability improving step of applying a silane-based, siloxane-based, or silane-siloxane-based water repellent to existing concrete after the closing step. 11. The concrete durability improving step of applying the lithium silicate surface modifying material to a portion other than the cracked portion to further improve the durability of the concrete itself by densifying the concrete. the method of.   A crack plugging agent for an existing concrete structure or an existing concrete secondary product, characterized by comprising a lithium silicate surface modifier and a calcium carbonate filler.   The crack blocking agent for an existing concrete structure or an existing concrete secondary product according to claim 12, wherein the calcium carbonate-based filler is rod-shaped or plate-shaped.   The crack plugging agent according to claim 12 or 13, wherein the calcium carbonate-based filler is derived from an unfired shell.   The crack plugging agent according to any one of claims 12 to 14, wherein the lithium silicate surface modifying material also functions as a concrete durability improver that densifies the concrete and improves the durability of the concrete itself. A silane-based, siloxane-based, or silane-siloxane-based water repellent for further application to an existing concrete structure or an existing concrete secondary product to which the crack plugging agent according to any one of claims 12 to 15 is applied. A cracking blockage durability improving agent containing an agent.

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