JP7095837B2 - Drying shrinkage reducing agent for hydraulically cured material, shrinkage reducing method for hydraulically cured material, and cured hydraulic material with low shrinkage - Google Patents

Description

The present disclosure relates to a drying shrinkage reducing agent for a cured water-hard material, a method for reducing shrinkage of the cured water-hard material, and a cured water-hard material having low shrinkage.

Conventionally, when a cement composition obtained by kneading cement and water as a water-hardening material or a concrete composition containing an aggregate is further cured to obtain a cured product, a cured product placed in the air after curing is obtained. As the material ages, the water content in the cement composition or concrete composition evaporates, which may cause the cured product to shrink due to drying.
Shrinkage due to drying of a cured product obtained after curing of a composition containing a water-hardening material such as mortar or concrete (hereinafter, may be referred to as "dry shrinkage") causes cracks in the cured product, and thus civil engineering, There is a risk of reducing the strength, durability, etc. of the building structure.

Conventionally, as a method for reducing the drying shrinkage of a hydraulically cured material (hereinafter, may be simply referred to as “cured body”), a drying shrinkage reducing agent (hereinafter, simply “shrinkage reducing agent” is used for an uncured hydraulic material composition. The method of adding) was common. However, usually, when a shrinkage reducing agent is added to a hydraulic material, the content ratio of the hydraulic material involved in curing is relatively reduced.
As a method for reducing shrinkage, for example, a method for reducing shrinkage of a cured product by adding a shrinkage reducing agent containing a polyoxyalkylene group to a concrete composition has been proposed (see Patent Document 1). However, as described above, there is a problem that the relative content ratio of the hydraulic material is lowered by adding the shrinkage reducing agent to the hydraulic material, and the amount of the shrinkage reducing agent used is limited. Further, since the shrinkage reducing agent described in Patent Document 1 is hydrophilic and has air entrainment property, it may be difficult to adjust the amount of air at the time of preparing a hydraulic material.

Therefore, as a method of preventing the dried shrinkage of the cured product, a method of applying a shrinkage reducing agent to the cured product of a hydraulic material has been attempted.
For example, a method for reducing shrinkage has been proposed in which a cured product of a hydraulic material is impregnated with a solution containing urea (see Patent Document 2). Since urea has good water solubility and the material itself is non-volatile, in the method of Patent Document 2, drying shrinkage occurs due to the expansion pressure when urea permeated into the pores of the cured product crystallizes. It is thought to suppress it.

Japanese Patent Application Laid-Open No. 2003-171155 Japanese Patent No. 6163243

However, there is still room for improvement in the shrinkage reducing effect of the urea-containing solution described in Patent Document 2. Further, when the cured product is impregnated with an aqueous urea solution, urea crystals may precipitate on the surface of the cured product after drying, and the appearance of the cured product is significantly impaired. Further, the precipitation of hydrophilic urea crystals makes the surface of the cured product hydrophilic, which makes it difficult to finish the surface of the cured product, for example, waterproofing agent treatment, surface agent coating, and tileing. Inferior in sex.

The subject of one embodiment of the present invention is the shrinkage of the cured water-hard material, which is applied to the cured body of the water-hard material to reduce the drying shrinkage of the cured body of the water-hard material and suppress the cracking caused by the drying shrinkage. It is to provide a reducing agent.
An object of another embodiment of the present invention is to provide a method for reducing shrinkage of a cured water-hard material, which effectively reduces drying shrinkage of the cured water-hard material and suppresses cracking of the cured product due to drying shrinkage. It is to be.
An object of another embodiment of the present invention is to provide a low shrinkage water-hard material cured product containing a drying shrinkage reducing agent for a water-hard material cured product and suppressing cracks caused by drying shrinkage and drying shrinkage. be.

Means for solving the problem include the following embodiments.

<1> A shrinkage reducing agent for a cured water-hard material containing at least one compound selected from the group consisting of a urea derivative and a hydrophilic amine compound, and water.
At least one compound selected from the group consisting of urea derivatives and hydrophilic amine compounds exhibits good water solubility and excellent affinity with water. Therefore, the shrinkage reducing agent has a uniform composition, has good permeability to the hydraulically cured material, and is excellent in the shrinkage reducing effect of the hydraulically cured material.
Further, it has a secondary effect that the crystal precipitation of the above compound does not occur on the surface of the cured product after drying, and the finishing treatment of the cured product can be easily performed.

<2> At least one compound selected from the group consisting of a urea derivative and a hydrophilic amine compound is a compound represented by the following formula (I), a compound represented by the formula (II) and a compound represented by the formula (III). The shrinkage reducing agent for a cured water-hard material according to <1>, which is at least one compound selected from the group consisting of the represented compounds.

In formula (I), R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and the alkyl group may have a hydroxy group as a substituent. .. However, not all of R ¹ , R ² , R ³ and R ⁴ are hydrogen atoms.
In formula (II), R ⁵ , R ⁶ and R ⁷ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and not all of R ⁵ , R ⁶ and R ⁷ are hydrogen atoms. ..
At least one compound selected from the group consisting of the compound represented by the above formula (I), the compound represented by the formula (II) and the compound represented by the formula (III) is water-soluble. Yes, it can be easily obtained, and the shrinkage reducing agent containing these compounds has a better shrinkage reducing effect of the cured product.

<3> At least one compound selected from the group consisting of the compound represented by the following formula (I), the compound represented by the formula (II) and the compound represented by the formula (III), and water. A method for reducing shrinkage of a cured water-hard material, which comprises a step of applying a shrinkage reducing agent for the cured water-hard material to the surface of the cured water-hard material.

In formula (I), R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and the alkyl group may have a hydroxy group as a substituent. .. However, not all of R ¹ , R ² , R ³ and R ⁴ are hydrogen atoms.
In formula (II), R ⁵ , R ⁶ and R ⁷ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and not all of R ⁵ , R ⁶ and R ⁷ are hydrogen atoms. ..

By applying the above compound to the surface of the cured hydraulic material and allowing it to permeate, the shrinkage reducing agent permeates the pores of the cured body, and the pores are filled with the shrinkage reducing agent. Therefore, the inside of the pores is filled with the hydrophilic compound. Further, it is considered that a film derived from a compound is formed in the vicinity of the surface of the pores due to evaporation of water inside the pores over time, and when this phenomenon occurs, the drying shrinkage of the cured product is further reduced. , Dry cracking of the cured product due to drying shrinkage is effectively prevented.
In the shrinkage reducing method of the present disclosure, since the shrinkage reducing agent is applied after the formation of the hydraulic material cured product, there is no concern that the shrinkage reducing agent affects the strength of the hydraulic material cured product itself. Therefore, there is a high degree of freedom in prescribing the hydraulic material composition for obtaining the hydraulic material cured product.

<4> A cured product of a water-hard material having pores at least in the vicinity of the surface, and a compound represented by the following formula (I) existing in the pores in the vicinity of the surface of the cured product. A low shrinkage hydraulic material cured product containing at least one compound selected from the group consisting of the compound represented by (II) and the compound represented by formula (III).

In formula (I), R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and the alkyl group may have a hydroxy group as a substituent. .. However, not all of R ¹ , R ² , R ³ and R ⁴ are hydrogen atoms.
In formula (II), R ⁵ , R ⁶ and R ⁷ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and not all of R ⁵ , R ⁶ and R ⁷ are hydrogen atoms. ..
Since at least one of the above compounds is contained in the pores of the cured product and the pores are filled with the shrinkage reducing agent, the pores shrink due to the evaporation of water and the dry shrinkage due to the shrinkage of the pores occurs. It becomes a cured material of a hydraulically rigid material with suppressed low shrinkage.

In the present specification, the numerical range indicated by using "-" indicates a range including the numerical values before and after "-" as the minimum value and the maximum value, respectively.
In the present specification, the amount of each component in the composition is the total amount of the plurality of substances present in the composition when a plurality of substances corresponding to each component are present in the composition, unless otherwise specified. means.
In addition, in this specification, "at least one compound selected from the group consisting of a urea derivative and a hydrophilic amine compound" may be referred to as a "specific nitrogen-containing compound" below.
In the present specification, the term "process" is included in this term not only as an independent process but also as long as the intended purpose of this process is achieved even if it cannot be clearly distinguished from other processes.
In the present specification, the hydraulic material is a general term for materials that can be mixed with water and cured. For example, a cement composition that hardens by a hydration reaction with water, a mortar composition that further contains fine aggregate in the cement composition, a concrete composition that further contains fine aggregate and coarse aggregate, and no cement is used. It is used to include a so-called geopolymer composition which contains water, alkali silicate and coal ash such as fly ash and is cured by a polymerization reaction.

According to one embodiment of the present invention, when applied to a cured water-hard material, the shrinkage of the cured water-hard material is reduced, and cracks caused by the shrinkage of the water-hard material are suppressed. A reducing agent can be provided.
According to another embodiment of the present invention, there is provided a method for reducing shrinkage of a cured water-hard material, which effectively reduces the drying shrinkage of the cured water-hard material and suppresses cracking of the cured product due to the drying shrinkage. can do.
According to another embodiment of the present invention, it is possible to provide a hydraulic material cured product containing a drying shrinkage reducing agent for the hydraulic material cured product, in which cracks caused by drying shrinkage and drying shrinkage are suppressed.

3 is a graph showing the relationship between the drying period and the drying shrinkage strain of the hydraulically cured materials of Examples 1 to 3 and Comparative Examples 1 to 3.

<Shrinkage reducing agent for hardened hydraulic material>
The shrinkage reducing agent for the cured water-hard material of the present disclosure contains at least one compound (specific nitrogen-containing compound) selected from the group consisting of a urea derivative and a hydrophilic amine compound, and water.

As the specific nitrogen-containing compound, at least one compound selected from the group consisting of the compound represented by the following formula (I), the compound represented by the formula (II) and the compound represented by the formula (III) is used. It is preferable to include it.

In formula (I), R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and the alkyl group may have a hydroxy group as a substituent. .. However, not all of R ¹ , R ² , R ³ and R ⁴ are hydrogen atoms.
In formula (II), R ⁵ , R ⁶ and R ⁷ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and not all of R ⁵ , R ⁶ and R ⁷ are hydrogen atoms. ..

Although the action of the shrinkage reducing agent for the hydraulically cured material of the present disclosure and its application is not clear, it is considered as follows.
The specific nitrogen-containing compound has excellent solubility in water and exists uniformly dissolved in an aqueous solution without being decomposed into ions.
On the other hand, the drying shrinkage of the hydraulically hardened material is caused by the evaporation of the liquid component existing in the pores in the cured body. In particular, the pores near the surface of the cured product have a greater effect on drying shrinkage than the pores in the deeper region of the cured product.
The specific nitrogen-containing compound has the property of being easily dissolved uniformly in water. Therefore, when the shrinkage reducing agent of the present disclosure containing a specific nitrogen-containing compound is applied to the surface of a water-hard material cured product, it rapidly permeates from the surface of the cured product into pores at least in the vicinity of the surface, and is specified. The nitrogen-containing compound exists in the pores in the form of an aqueous solution dissolved in water. Therefore, the vapor pressure lowering action of the aqueous solution suppresses the evaporation of the liquid component in the pores that causes drying shrinkage. Further, since the specific nitrogen-containing compound is excellent in water retention and water evaporation inhibitory property, the evaporation inhibitory action becomes better.
Furthermore, the shrinkage reducing agent that permeated into the pores of the cured product dried from the surface side that was easily exposed to air, and a film was formed in the region where the water content decreased near the surface while holding the aqueous solution inside. It will be in such a state. Therefore, the evaporation of the shrinkage reducing agent that has penetrated deeper into the pores is more effectively suppressed. Further, due to this, unlike the case where urea is used, the specific nitrogen-containing compound does not precipitate crystals on the surface, and the rapid decrease in the water content in the pores of the cured product during drying is suppressed. It is considered that the drying shrinkage caused by the rapid decrease in water content is reduced.
Further, by applying the shrinkage reducing agent which is an aqueous solution of the specific nitrogen-containing compound, water is supplied to the cured hydraulic material and the evaporation of water is suppressed. Therefore, when the hydraulically hardened body contains cement, a secondary effect of promoting the hydration reaction and improving the strength can be obtained, and the reduction of drying shrinkage and the crack prevention property are further improved. Conceivable.
The present disclosure is not limited to the above estimation mechanism.

(Specific nitrogen-containing compound)
The shrinkage reducing agent of the present disclosure contains at least one specific nitrogen-containing compound selected from the group consisting of urea derivatives and hydrophilic amine compounds.
The specific nitrogen-containing compound is a compound that is hydrophilic and does not have ionicity, and is preferably an amphoteric or nonionic compound. Since the specific nitrogen-containing compound does not have ionicity, the aqueous solution obtained by mixing with water has an appropriate surface tension and has good permeability to a cured water-hard material.
As the specific nitrogen-containing compound, a compound selected from a urea derivative, a hydrophilic secondary amine compound, and a tertiary amine compound is preferable, and among them, the compound represented by the following formula (I) and the formula (II) are represented. At least one compound selected from the group consisting of the compounds to be formulated and the compound represented by the formula (III) is preferable.

In formula (I), R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and the alkyl group may have a hydroxy group as a substituent. .. However, not all of R ¹ , R ² , R ³ and R ⁴ are hydrogen atoms.
In formula (II), R ⁵ , R ⁶ and R ⁷ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and not all of R ⁵ , R ⁶ and R ⁷ are hydrogen atoms. ..
Hereinafter, preferred specific nitrogen-containing compounds in the present disclosure will be described.

[Compound represented by formula (I)]

The compound represented by the above formula (I) is one aspect of a urea derivative.
In formula (I), R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and the alkyl group is a hydroxyalkyl group having a hydroxy group as a substituent. You may. However, not all of R ¹ , R ² , R ³ and R ⁴ are hydrogen atoms. Among the compounds represented by the formula (I), R ¹ and R ³ are methyl groups or ethyl groups, and R ² and R ⁴ are hydrogen atoms, and R ¹ and R ² are methyl groups or. A compound that is an ethyl group and R ³ and R ⁴ are hydrogen atoms, a compound in which any one of R ¹ , R ² , R ³ or R ⁴ is a methyl group or an ethyl group and the other is a hydrogen atom. Is preferable.
Examples of the compound represented by the formula (I) include 1,3-dimethylurea (R ¹ and R ³ are methyl groups and R ² and R ⁴ are hydrogen atoms) and 1,3-diethyl urea. (R ¹ and R ³ are ethyl groups and R ² and R ⁴ are hydrogen atoms), 1,1-dimethylurea (R ¹ and R ² are methyl groups and R ³ and R ⁴ are hydrogen atoms). Compounds that are hydrogen atoms) and the like.

[Compound represented by formula (II)]

The compound represented by the above formula (II) is one aspect of a hydrophilic amine compound.
In formula (II), R ⁵ , R ⁶ and R ⁷ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and not all of R ⁵ , R ⁶ and R ⁷ are hydrogen atoms. ..
Of these, compounds in which at least one of R ⁵ , R ⁶ and R ⁷ is an alkyl group having 1 to 3 carbon atoms are preferable, and all of R ⁵ , R ⁶ and R ⁷ are alkyl groups having 1 to 3 carbon atoms. Certain compounds are more preferred.
As the alkyl group in R ⁵ , R ⁶ and R ⁷ , an alkyl group selected from a methyl group and an ethyl group is preferable.

[Compound represented by formula (III)]

The compound represented by the above formula (III) is hexamethylenetetramine, which is one embodiment of the hydrophilic amine compound.
Hexamethylenetetramine has good water solubility, and when used as a shrinkage reducing agent, a good shrinkage reducing effect can be obtained.

The shrinkage reducing agent of the present disclosure may contain only one specific nitrogen-containing compound, or may contain two or more of them in combination.

(water)
The shrinkage reducing agent of the present disclosure contains water in addition to the specified nitrogen-containing compound. That is, the shrinkage reducing agent takes the form of an aqueous solution of a specific nitrogen-containing compound.
The water is not particularly limited, and any of tap water, purified water, ion-exchanged water, pure water and the like can be used.
Above all, it is preferable to use tap water from the viewpoint of economy.

(Content of specific nitrogen-containing compound)
The content of the specific nitrogen-containing compound in the shrinkage reducing agent is not particularly limited, but from the viewpoints of easy preparation of a uniform aqueous solution and maintenance of good water retention in the pores of the cured product. The content of the specific nitrogen-containing compound in the shrinkage reducing agent is preferably 10% by mass or more, more preferably 20% by mass or more, and more preferably 40% by mass or more with respect to all the components of the shrinkage reducing agent. Is even more preferable. Since the specific nitrogen-containing compound has good water solubility, it can be expected that the effect increases as the content, that is, the concentration of the aqueous solution increases.
The upper limit of the content is not particularly limited and is not particularly limited as long as it can be uniformly dissolved, but it can be 60% by mass or less from the viewpoint of stability and workability of the aqueous solution.
When the content of the specific nitrogen-containing compound in the shrinkage reducing agent is within the above range, the permeability to the pores of the cured product becomes better, and the shrinkage reducing effect of the cured product can be sufficiently obtained.

<Method of reducing shrinkage of hydraulically hardened material>
The method for reducing shrinkage of the cured water-hard material of the present disclosure is selected from the group consisting of the compound represented by the following formula (I), the compound represented by the formula (II) and the compound represented by the formula (III). A step [step (A)] of applying a shrinkage reducing agent for a cured water-hard material containing at least one compound and water to the surface of the cured water-hard material is included.

The above formulas (I), (II) and (III) are synonymous with the formulas (I), (II) and (III) described in the above-mentioned shrinkage reducing agent, and the same applies to the preferred examples. be.

In the step (A), the shrinkage reducing agent of the present disclosure described above is applied to the cured hydraulic material. The method of applying the shrinkage reducing agent to the cured body of the water-hard material is arbitrary, and a known method, for example, a method of immersing the cured body in the shrinkage reducing agent, a method of applying the shrinkage reducing agent to the cured body, or a shrinkage reducing agent can be used. There are methods such as fixing a porous body such as a retained fiber mass to the surface of the cured body, creating a water tank with the surface of the cured body covered with a resin panel, and injecting a solution into the prepared water tank to allow it to permeate. Be done.
Above all, the method of immersing is preferable from the viewpoint that the shrinkage reducing agent easily permeates into the pores of the cured product.
On the other hand, when the shrinkage reducing agent is applied to the cured product, it may be applied in a plurality of times for the purpose of applying the required amount to the cured product. When the shrinkage reducing agent is applied a plurality of times, it is preferable to repeatedly apply the shrinkage reducing agent before it dries from the viewpoint of the effect.
The coating method when the shrinkage reducing agent is applied to the cured product by coating is not particularly limited, and examples thereof include a method of coating with a brush or a roller, and a method of coating using a known coating device.

(Other processes)
The method for reducing shrinkage of the hydraulically cured material of the present disclosure can include other steps.
Other steps include a step that can be performed after the step (A), for example, a step of drying the cured water-hard material to which a shrinkage reducing agent is applied, and covering the surface of the cured water-hard material with a sheet for curing. The process of doing this can be mentioned.

The cured hydraulic material to which the shrinkage reducing agent of the present disclosure is applied is not particularly limited, and the shrinkage reducing effect can be obtained by applying it to any cured hydraulic material.
For example, when the water-hardening material contains cement, by applying it to a cured product of a composition containing cement, the pores of the cured product are filled with a shrinkage reducing agent containing water, and shrinkage of the pores is suppressed. Moreover, due to the action of water contained in the shrinkage reducing agent, the hydration reaction of the cured product containing cement is promoted, and a secondary effect of further improving the strength can be obtained.
Further, when the geopolymer composition is used as the water-hardening material, the cured geopolymer composition is an amorphous shrink polymer and has pores inside, so that the composition containing the cement described above is contained. As in the case of the cured product, the shrinkage reducing agent permeates the pores and fills the inside of the pores, whereby the shrinkage reducing effect can be obtained.

<Low shrinkage hydraulic material hardened body>
The cured product of the low shrinkage water-hard material of the present disclosure is a cured product of the water-hard material, and is present in a cured product having pores at least in the vicinity of the surface and the following formulas existing in the pores in the vicinity of the surface of the cured product. It contains at least one compound selected from the group consisting of the compound represented by (I), the compound represented by the formula (II) and the compound represented by the formula (III).
The hydraulically cured material is not particularly limited, and is not particularly limited as long as it is a cured product obtained by using a material that can be mixed with water to form a cured product.
In general, in a hydraulic material cured product which is a cured product of a hydraulic material, pores are formed at least in the vicinity of the surface in the process of reaction curing. The manufacturing method of the present disclosure described above includes a step (A) of applying a shrinkage reducing agent to a cured hydraulic material. In the step (A), the shrinkage reducing agent applied to the hardened hydraulic material permeates the pores formed in the hardened body from the surface of the hardened body. Therefore, in the low shrinkage hydraulic material hardened body, among the pores formed in the hardened body, the shrinkage reducing agent permeated exists in the pores formed at least near the surface, and the shrinkage reducing agent is present in the pores. Due to the function of the shrinkage reducing agent present, cracks caused by pores are suppressed as described in the estimation mechanism described above.
Although it depends on the thickness of the cured product, the pores near the surface of the cured product are generally deeper than the surface (0 mm) of the cured product, considering the permeability of water into the pores of the cured product. It can be said that the pores exist in a range of up to 25 mm.
As described above, as the water-hardening material for forming a hardened body, a cement composition that cures by a hydration reaction with water, a mortar composition in which the cement composition further contains fine aggregate, and further fine aggregate and coarse Examples thereof include a concrete composition containing an aggregate. Further, a so-called geopolymer composition containing water, alkali silicate and coal ash (amorphous powder active in alkali) such as fly ash and cured by a polymerization reaction may be used.

(cement)
The cement which is a hydraulic material is not particularly limited, and can be appropriately selected from various cements according to the purpose of use of the hydraulic material cured product.
Examples of cement include early-strength Portland cement, ordinary Portland cement, moderate heat Portland cement, low heat Portland cement, sulfate-resistant Portland cement, mixed cement, that is, blast furnace cement, fly ash cement, silica cement, other eco-cement, and white Portland cement. , High sulfate slag cement, alumina cement, lime, sekkou and the like.

Hydraulic materials that can form a cured product include a mixture of cement and admixture. As an admixture that can be mixed with cement, blast furnace slag fine powder, fly ash, silica fume, expansion material, admixture for high strength, limestone fine powder, crushed stone powder, sludge powder, sewage sludge fine powder, silica Examples include admixtures and fine powder of waste concrete. Among these, blast furnace slag fine powder, fly ash, silica fume, limestone fine powder, sewage sludge fine powder, etc., which are amorphous powders active in alkali, should be used in combination with water glass (sodium silicate aqueous solution). It can also be a component of a geopolymer composition.

The content of the hydraulic material in the cured product of the hydraulic material is not particularly limited, and is appropriately selected in consideration of the purpose of use of the cured material of the hydraulic material and the like.
For example, in the case of obtaining a hardened cement, usually, the total amount of the hydraulic material can be contained in the cement composition as 270 kg / m ³ to 650 kg / m ³ and 320 kg / m ³ to 530 kg / m ³ . It is preferable to contain it. However, it is not limited to this example.

In addition to the above hydraulic materials, known additives other than water, aggregates, and specific nitrogen-containing compounds can be used in the production of the cured hydraulic material as long as the effects are not impaired.
Known additives include, for example, water reducing agents, air entraining agents, thickeners, defoaming agents, curing accelerators and the like.

In the hardened material of the low shrinkage water-hard material of the present disclosure, the inclusion of the shrinkage reducing agent of the present disclosure described above in the pores existing at least in the vicinity of the surface makes the hardened material of the low shrinkage water-hard material of the hardened material of the present disclosure. It can be confirmed by crushing the crushed material at regular depths from the surface, impregnating the obtained crushed material with water, and repeating the operation of analyzing the specific nitrogen-containing compound dissolved in water multiple times. ..
Specifically, the cured product is mechanically crushed at a depth of, for example, every 5 mm, and the crushing conditions are adjusted to obtain a crushed product having a particle size in the range of 0.5 mm or more and 5 mm or less.
50 g of the obtained crushed material is weighed, 50 g of the crushed material and 500 mL (milliliter) of pure water are put into a 1000 mL Erlenmeyer flask, and the mixture is continuously shaken with a shaker for 6 hours.
After shaking, the shrinkage reducing agent contained in the crushed material elutes in the dispersion. By filtration, the crushed material and the liquid are separated, and the water content of the obtained liquid is evaporated and concentrated. By analyzing the concentrated liquid with a Raman spectroscope and confirming the peak of the Raman spectrum, it is possible to identify the specific nitrogen-containing compound in the shrinkage reducing agent contained in the region of the cured product up to a depth of 5 mm.
By performing the above operation multiple times every 5 mm from the surface, the presence of the shrinkage reducing agent contained in the region of each depth can be confirmed, and if it is repeated further, it can be obtained by an operation of a certain depth or more. The presence of the shrinkage reducing agent from the crushed material cannot be confirmed.
By these operations, it was confirmed that the shrinkage reducing agent contained a specific nitrogen-containing compound at a certain depth from the vicinity of the surface, that is, the crushed material near the surface of the cured product, and the crushed material in the deep part of the cured product. By confirming that the specific nitrogen-containing compound is not contained in the above, it can be confirmed that the cured product as the subject is the cured product of the low shrinkage water-hard material of the present disclosure.

That is, when the specific nitrogen-containing compound is blended with the water-hard material, the specific nitrogen-containing compound is uniformly present in the depth direction of the cured water-hard material, whereas the low value obtained by the production method of the present disclosure is used. In the cured body of shrinkable water-hard material, a large amount of the specific nitrogen-containing compound is present near the surface of the cured body, but the specific nitrogen-containing compound is not detected in the deep part of the cured body in which the shrinkage reducing agent is difficult to penetrate. As a result, it is possible to distinguish between the cured product of the low shrinkage hydraulic material of the present disclosure and the cured product of the hydraulic material containing the specific nitrogen-containing compound.
In the above operation example, the crushing depth of the cured product is set to 5 mm, but the crushing depth for obtaining the crushed material in one operation is not limited to the above example, and the size of the cured product and the like. It can be appropriately selected according to the above. For example, in the case of a cured product having a thickness of about 30 mm to 100 mm, the crushing depth in one operation can be set to 5 mm to 7 mm, and in the case of a thicker structure, for example, a cured product having a thickness of 200 mm or more. The crushing depth in one operation can be 10 mm or more, and accurate confirmation can be performed in each case.

The hardened material with low shrinkage of the present disclosure can be used for various purposes such as structural materials and exterior materials because cracks caused by drying shrinkage and drying shrinkage are reduced.
Further, the shrinkage reducing agent contained in the cured body of a low shrinkage hydraulic material is present in the pores of the cured body at least in the vicinity of the surface, and precipitates on the surface of the cured body to affect the appearance or the physical characteristics of the surface. Does not affect.
Therefore, the low shrinkage hydraulic material cured product of the present disclosure has good post-treatability. For example, when applying a water absorption inhibitor or the like to the surface of a cured body for post-treatment such as waterproofing, it is possible to perform the coating work without any special treatment. Further, when the surface of the cured body is painted or tiled, there is an advantage that no special pretreatment is required.

Hereinafter, the shrinkage reducing agent of the present disclosure, the method of reducing shrinkage of the hydraulic material cured product, and the low shrinkage hydraulic material cured product will be described in detail with reference to specific examples, but the following examples are one embodiment of the present disclosure. Is shown. The present disclosure allows various variants as long as it does not deviate from the gist thereof, and is not limited to the following description.
Unless otherwise specified, the following "%" and "part" are based on mass.

[Example 1 to Example 3, Comparative Example 1 to Comparative Example 3]
A cured hydraulic material was prepared according to the formulation shown below, and the obtained cured hydraulic material was used for evaluation.

<Manufacturing of hardened hydraulic material>
Using the following materials, a cured hydraulic material (cement mortar) containing sand as a fine aggregate was prepared.
The composition of the hydraulic material composition using the following materials had a water-cement ratio (W / C) of 50% and a sand-cement ratio (S / C) of 2.5.
A hydraulically cured material was prepared by the method specified in JIS R 5201 (1997), and used as a cured product (standard test body) of Comparative Example 1.

(Material of hydraulic material composition)
-Hydraulic material: Ordinary Portland cement (density 3.16 g / cm ³ , specific surface area 3280 cm ² / g)
-Fine aggregate: Mountain sand from Kimitsu (absolute dry density 2.57 g / cm ³ , surface dry density 2.61 g / cm ³ , water absorption rate 1.59%)

<Evaluation of hydraulically cured material>
(1. Dry shrinkage and compressive strength)
The dried shrinkage and compressive strength of the obtained cured hydraulic material were measured.
The evaluation of the drying shrinkage of the cured water-hard material was carried out by measuring the drying shrinkage strain specified in JIS A 1129-3 (2010). The smaller the drying shrinkage strain measured according to JIS A 1129-3 (2010), the smaller the drying shrinkage.
The compressive strength of the cured water-hard material was measured according to the strength test specified in JIS R 5201 (1997) and used as an index of the compressive strength of the cured product.
The compressive strengths of Examples 1 to 3 and Comparative Examples 1 to 3 were measured using the test pieces treated and stored under the same conditions as the test pieces evaluated for drying shrinkage.
First, the drying shrinkage of Comparative Example 1 as a standard test piece was demolded at the age of 1 day, and then the drying shrinkage measurement was started in an environment of 20 ° C. and 60%, and drying in an environment of 20 ° C. and 60% was started. The shrinkage measurement was continued for 8 weeks, and the dry shrinkage strain after 8 weeks was recorded and evaluated.
Further, the compressive strength of the cured product of Comparative Example 1 treated and stored under the same conditions as the test body evaluated for drying shrinkage was measured at 4 weeks of age and used as an index of the compressive strength of the cured product.

-Application of shrinkage reducing agent-
The hydraulically cured material prepared by the same method as in Comparative Example 1 was demolded at the age of 1 day, and then the drying shrinkage measurement was started in an environment of 20 ° C. and 60%. Two days after the start of the dry shrinkage measurement, the hydraulically cured material was subjected to the shrinkage reducing agent or the comparative shrinkage reducing agent of the present disclosure described in Examples 1 to 3 and Comparative Examples 2 to 3 described later for 1 hour. It was soaked and impregnated with a shrinkage reducing agent. Then, a test piece treated with a shrinkage reducing agent (a cured body made of a low shrinkage water-hard material) was obtained, and the obtained test piece was again subjected to drying shrinkage measurement in an environment of 20 ° C. and 60% for 8 weeks from the start. The dry shrinkage strain after 8 weeks was measured. The results are shown in Table 1 below.
The dry shrinkage measurement was continued after 8 weeks and continued until 13 weeks. The relationship between the drying period and the drying shrinkage strain of the low shrinkage hydraulic material cured products of Examples 1 to 3 and the hydraulic material cured products of Comparative Examples 1 to 3 is shown as a graph in FIG. .. The change in the graph seen 2 days after the start of measurement is a change caused by impregnation with the shrinkage reducing agent.
In the graph of FIG. 1, the measurement of the dry shrinkage strain described above was continued even after 8 weeks, and the result of performing until 13 weeks was shown.
The compressive strengths of Examples 1 to 3, Comparative Example 2 and Comparative Example 3 were measured at 4 weeks of age using a cured product treated and stored under the same conditions as the test body evaluated for drying shrinkage. The results are shown in Table 1 below.

The composition of each shrinkage reducing agent is shown below.
(Shrinkage reducing agent used in Example 1)
-Shrinkage reducing agent (A-1): Urea derivative (density 1.14 g / cm ³ , molecular weight 88, compound represented by the formula (I), R ¹ and R ³ are methyl groups, R ² and A 40% aqueous solution of dimethylurea (where ^R4 is hydrogen).
(Shrinkage reducing agent used in Example 2)
-Shrinkage reducing agent (A-2): Betaine anhydrous (density 1.00 g / cm ³ , molecular weight 117, a compound represented by the formula (II), and R ⁵ , R ⁶ and R ⁷ are all methyl groups. A 40% aqueous solution of a compound).
(Shrinkage reducing agent used in Example 3)
-Shrinkage reducing agent (A-3): A 40% aqueous solution of hexamethylenetetramine (density 1.34 g / cm ³ , molecular weight 140 (compound represented by the formula (III))).

(Shrinkage reducing agent used in Comparative Example 2)
Comparative shrinkage reducing agent (CA-1): 40% aqueous solution of urea (density 1.32 g / cm ³ , molecular weight 60).
(Shrinkage reducing agent used in Comparative Example 3)
The test piece was immersed in water as a comparative shrinkage reducing agent (CA-2).

(2. Appearance evaluation)
The appearance of the test piece on which the drying shrinkage strain was measured was visually observed and evaluated according to the following criteria. The results are shown in Table 1.
-Appearance evaluation criteria-
A: As a result of visually observing the difference between the test piece of Comparative Example 1 and the test piece to be evaluated, no difference in appearance is visually observed.
B: As a result of visually observing the difference between the test piece of Comparative Example 1 and the test piece to be evaluated, a slight precipitate was observed in the appearance of the test piece to be evaluated, but the level was not a problem in practical use.
C: Crystalline precipitates were observed on the surface of the test piece to be evaluated, and the appearance was significantly inferior.

From the results shown in Table 1, the cured water-hard material of Examples 1 to 3 had a small dry shrinkage strain, and at 4 weeks of age, it was more than the standard cured water-hard material of Comparative Example 1. It can be seen that the compressive strength has improved.
On the other hand, Comparative Example 1 containing no shrinkage reducing agent had a large drying shrinkage strain, and tended to have lower compressive strength than Comparative Example 3 impregnated with each example and water.
The hydraulically cured material of Comparative Example 2 containing urea, which is a known shrinkage reducing agent, had a smaller drying shrinkage strain than Comparative Example 1 which was a standard test piece, and showed a certain degree of drying shrinkage reducing effect. However, the drying shrinkage strain was a larger value as compared with each of the cured products of Examples 1 to 3. Further, although the compressive strength is almost the same for each example, it can be seen that the precipitation of urea crystals on the surface of the cured product is remarkable and the appearance is very inferior.
Of the above Examples, the presence of the specific nitrogen-containing compound in the depth direction in the hydraulic material cured product obtained in Example 1 is analyzed by the method described above, that is, analysis of the crushed material at a depth of 5 mm of the cured product. Confirmed by. As a result, the presence of the specific nitrogen-containing compound was confirmed up to a depth of 10 mm, and the presence of the specific nitrogen-containing compound could not be confirmed in the deep part of the cured product exceeding the depth of 10 mm. From this, it was confirmed that in the low shrinkage hydraulic material cured product obtained by the production method of the present disclosure, the shrinkage reducing agent is present only in the pores near the surface and not in the deep part of the cured product. rice field. Therefore, in the cured product of Example 1, it is considered that cracks are suppressed by the shrinkage reducing agent that has penetrated into the pores from the surface of the cured product.

(3. Surface treatment)
An evaluation was made when surface-treating a hardened hydraulic material with a water absorption inhibitor.
That is, the obtained cured water-hardening materials of Examples 1 to 3 and Comparative Examples 1 to 3 were used as test bodies, and a water absorption inhibitor (silane coat HS (Kikusui Chemical Industry Co., Ltd.)) was applied to the surface of the cured body. ) Was applied, and the water repellency of the surface of the cured product by the surface treatment was evaluated.
That is, a water contact angle evaluation was performed in which water droplets were dropped on the surface and the contact angle was measured.
The contact angle was measured using a contact angle meter (Drop Master DM-501, manufactured by Kyowa Interface Science Co., Ltd.).
Since urea crystals were attached to the surface of the cured product of Comparative Example 2, the surface treatment was carried out with the urea crystals attached, and the surface treatment was carried out after removing the urea crystals in advance. The urea crystals were removed using a metal spatula.
The results are shown in Table 2 below.

The cured products of Examples 1 to 3 show almost the same contact angle as Comparative Example 1 which is an untreated standard test body and Comparative Example 3 impregnated with water only, and have high water absorption prevention property by surface treatment. It can be seen that the surface treatment property is good because (water repellency) is imparted.
On the other hand, since urea crystals are precipitated in the cured product of Comparative Example 2 containing urea, when the crystal removal treatment is not performed (Comparative Example 2 (a) in Table 2), a water absorption inhibitor is applied. However, the crystals adhering to the surface absorbed water and showed no water repellency, so measurement was not possible. In the case where the cured product of Comparative Example 2 is subjected to a crystal removing treatment in which crystals are scraped off with a metal spatula and then a water absorption inhibitor is applied (Comparative Example 2 (b) in Table 2), Comparative Example 1 It can be seen that the contact angle is slightly smaller than that of each example, and the surface treatability is lower than that of Comparative Example 1 and each example, which are standard test specimens.
From the above, the low shrinkage hydraulic material cured products of Examples 1 to 3 have better surface treatment properties than Comparative Example 2 when the surface treatment, which is a waterproof treatment, is performed. confirmed.

Claims (3)

Selected from the group consisting of urea derivatives and hydrophilic amine compounds selected from the group consisting of the compound represented by the following formula (I), the compound represented by the formula (II) and the compound represented by the formula (III). It is a shrinkage reducing agent for a cured product of a hydrophilic material containing at least one compound and water.
The content of at least one compound selected from the group consisting of the urea derivative and the hydrophilic amine compound with respect to the total mass of the shrinkage reducing agent is 20% by mass to 60% by mass, and the cured material is a water-hard material. A shrinkage reducing agent for a cured body of a water-hardening material used by applying it to the surface of .

In formula (I), R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and the alkyl group may have a hydroxy group as a substituent. .. However, not all of R ¹ , R ² , R ³ and R ⁴ are hydrogen atoms.
In formula (II), R ⁵ , R ⁶ and R ⁷ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and not all of R ⁵ , R ⁶ and R ⁷ are hydrogen atoms. .. Water containing at least one compound selected from the group consisting of a compound represented by the following formula (I), a compound represented by the formula (II) and a compound represented by the formula (III), and water. A shrinkage reducing agent for a hardened material, wherein the content of the compound with respect to the total mass of the shrinkage reducing agent is 20% by mass to 60% by mass. A method for reducing shrinkage of a cured water-hard material, which comprises a step of applying to the surface of the body.

In formula (I), R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and the alkyl group may have a hydroxy group as a substituent. .. However, not all of R ¹ , R ² , R ³ and R ⁴ are hydrogen atoms.
In formula (II), R ⁵ , R ⁶ and R ⁷ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and not all of R ⁵ , R ⁶ and R ⁷ are hydrogen atoms. .. The method for reducing shrinkage of a cured hydraulic material according to claim 2 , further comprising a step of applying a water absorption inhibitor to the surface of the cured hydraulic material.

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