JPH0674160B2 - Mortar, concrete structure quality improvement method and admixture - Google Patents

Description

TECHNICAL FIELD The present invention relates to a mortar, a method for improving the quality of a concrete structure, and a mortar and a concrete admixture used in the method. More specifically, the present invention aims to prevent white mortar from mortar and concrete secondary products, suppresses neutralization of mortar and concrete structures, reduces drying shrinkage, and prevents corrosion of reinforcing bars, mortar and concrete structures. The present invention relates to a method for improving durability.

Conventional technology Generally, cement compositions such as mortar and concrete are
Exhibits various fatal defects with curing and drying. For example, white sinter that occurs on the surface of a hardened product of a cement compound has a bad influence such as impairing the appearance of a building or peeling or discoloring a finishing material such as a tile or a paint. Although various methods for preventing white fluff have been proposed in the past, the present situation is that a method for preventing white fluff that exhibits a sufficient effect has not yet been developed.
As one of the reasons why it is difficult to prevent efflorescence, there are usually two causes of efflorescence. That is, as described in JP-A-60-16843, one of the causes of the occurrence of white sinter is that the calcium hydroxide existing inside the hardened body is carbonated on the surface of the hardened body to become calcium carbonate and crystal growth. Another cause is that the alkali metal and sulfate radicals are eluted on the surface of the hardened body to form an alkali metal sulfate, which causes crystal growth. Therefore, even a whitening preventive agent capable of preventing whitening based on one cause cannot necessarily prevent whitening based on the other cause, and therefore cannot completely prevent whitening.

Next, regarding the durability of concrete structures, it has been conventionally believed that the life of reinforced concrete structures is about 50 to 60 years. The reason for this is that when carbonation from the surface of the concrete into the interior of the concrete progresses, and when this neutralization area reaches the position of the reinforcing bar, the reinforcing bar rusts and the reinforced concrete member loses its proof strength. It is due to.

In addition, the cement composition causes a decrease in volume as it hardens and dries, but this drying shrinkage causes cracks in concrete structures and the like. These cracks reduce the strength of concrete structures, etc. and allow carbon dioxide gas to penetrate from the cracks into the interior, promoting the neutralization of concrete and causing rusting of reinforcing bars, which significantly reduces the durability of concrete structures. Let As countermeasures against such neutralization and cracking, conventionally, 1) reduce the water / cement ratio of the cement mixture, 2) apply a finishing material with excellent airtightness such as paint to the concrete surface, And so on. However, when the water / cement ratio is reduced, the workability is significantly impaired, and moreover, there is a drawback that cracks occur due to the increase in the heat value of curing. Further, even if the use of a finishing material such as the above paint is effective in the short term, there is a problem in the durability of the finishing material itself. Therefore, neither of the methods 1) and 2) can be said to be satisfactory.

Further, a factor that deteriorates the durability of the concrete structure is corrosion of the reinforcing bars in the concrete due to the iron-corrosive chloride. More specifically, it is the corrosion of reinforcing bars due to the increasing use of sea sand in recent years and the penetration of iron-corrosive chloride carried by the sea breeze into the concrete structures along the coast into the concrete. As a countermeasure,
Conventionally, additives that promote initial hardening and additives that enhance watertightness have been proposed, but they are not always satisfactory, and in particular, the content of iron-corrosive chloride in aggregate sand is Na.
In the case of 0.01% by weight or more in terms of Cl, no particularly suitable rust preventive agent is found.

DISCLOSURE OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION The present invention aims to provide a method for improving the above-mentioned mortar, the drawbacks specific to a concrete structure, and providing a mortar and a concrete structure which are excellent in prevention of sinter phenomenon and durability. To do.

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above problems.
As a result, they have found that the water-soluble amino resin is effective not only for preventing white sinters based on the above two causes but also for suppressing neutralization and rust prevention of reinforcing bars.

The present inventor further comprises the above water-soluble amino resin and at least one of a higher fatty acid metal salt and a nonionic surfactant,
It has been found that the above-mentioned effects of the water-soluble amino resin can be enhanced and, in addition, the drying shrinkage can be suppressed by using the water-soluble amino resins in appropriate amounts. The present invention has been completed based on these new findings.

That is, the present invention is a mortar, a mortar formed from concrete, a method for improving the quality of a concrete structure, in the kneading of the mortar and concrete, a mortar characterized by blending a water-soluble amino resin, a concrete structure It provides a way to improve the quality of.

Further, the present invention, a mortar, a mortar formed from concrete, a method for improving the quality of a concrete structure, at the time of kneading the mortar and concrete, a water-soluble amino resin, a higher fatty acid metal salt and a nonionic surfactant. It also provides a method for improving the quality of mortar and concrete structures, which is characterized by mixing at least one kind.

According to the present invention, when the above water-soluble amino resin is used alone, efflorescence prevention, neutralization prevention and rust prevention of reinforcing bars are effectively performed.

Further, according to the present invention, the above action is enhanced by using the water-soluble amino resin and at least one of the higher fatty acid metal salt and the nonionic surfactant in an appropriate amount.

More specifically, the combined use of the water-soluble amino resin and a higher fatty acid metal salt enhances the effect of preventing white sinter and the effect of suppressing neutralization.

When the above water-soluble amino resin and a nonionic surfactant are used in combination, the anti-whitening effect, the neutralization suppressing effect and the drying shrinkage suppressing effect are enhanced, and when both are used in a specific amount, the anti-whitening effect, It exerts a remarkably excellent effect in all of the neutralization suppressing action, the drying shrinkage suppressing action, and the reinforcing rod rust preventing action.

When the above water-soluble amino resin, higher fatty acid metal salt and nonionic surfactant are used, at least partial effects of anti-white flower effect, neutralization inhibitory effect, drying shrinkage inhibitory effect and reinforcing bar rust preventive effect are obtained. When these three are used in a specific amount, they prevent white bloom, suppress neutralization,
It exerts a remarkably excellent effect in all of the drying shrinkage suppressing effect and the reinforcing bar rust preventive effect.

As the water-soluble amino resin used in the present invention,
It is a water-soluble resin at the prepolymer stage, which is mainly composed of dimers and trimers obtained by the reaction of amino compounds or amide compounds such as melamine and urea with aldehydes such as formaldehyde, and is wide as long as it is water-soluble. Those in the range are included, and those having a special free methylol group are preferable. Amino resins that are water-insoluble due to the etherification of the methylol group cannot sufficiently exhibit the desired quality improvement effect. In the present invention, among the above water-soluble amino resins, water-soluble urea resins, melamine resins, urea / melamine resins and the like can be preferably used. Such urea resin is
1 to 2.5 moles of formaldehyde to 1 mole of urea,
In particular, it is methylolated at a ratio of about 1.5 to 2 mol, and the melamine resin is methylolated at a ratio of about 1.5 to 3.5 mol, particularly about 2 to 3 mol of formaldehyde to 1 mol of melamine.
More preferred is a water-soluble resin obtained by condensation reaction,
The urea / melamine resin is more preferably a mixture or cocondensation product of such a specific urea resin and melamine resin. These may be prepared separately, or commercially available products may be used. Generally, the water-soluble amino resin is in the form of an aqueous solution.

In the present invention, the water-soluble amino resin, when used alone, is used in an amount of 0.4 to 1.5 parts by weight, preferably 0.5 to 1.0 parts by weight, based on 100 parts by weight of cement. If it is less than 0.4 parts by weight, the effect becomes insufficient, and if it exceeds 1.5 parts by weight, the curing is sometimes impeded, and the antirust effect of the reinforcing bar tends to be impaired.

As described above, in the present invention, at least one of the above water-soluble amino resin, higher fatty acid metal salt and nonionic surfactant is used.
When used in combination with a seed, the action of the water-soluble amino resin can be enhanced.

Various types of higher fatty acid metal salts can be used,
An alkali metal salt or an alkaline earth metal salt of a higher saturated or unsaturated monocarboxylic acid having 6 to 24 carbon atoms is preferably used. In particular, an alkaline earth metal salt of a higher saturated monocarboxylic acid having 9 to 21 carbon atoms is inexpensive and more preferable from the viewpoint of alkaline aggregate reaction. Among the higher fatty acid metal salts used in the present invention, calcium stearate, magnesium stearate, calcium myristate, calcium palmitate, calcium laurate and the like can be particularly preferably used.

Although various nonionic surfactants can be used, typically, the following general formulas RO (CH ₂ CH ₂ O) _n H (1) or RO (CH ₂ CH ₂ O) _n R (2) [ In the formula, R represents an alkyl group having 6 to 22 carbon atoms or an alkyl group having 1 to 16 carbon atoms as a substituent or a phenyl group which may have a halogen atom, and n is an integer of 4 to 30. ] Or a general formula R ¹ COO (CH ₂ CH ₂ O) _m H (3) or R ¹ COO (CH ₂ CH ₂ O) _m COR ¹ (4) [wherein R ¹ has 6 carbon atoms] ~ 22 alkyl groups, m is 4
It is an integer of ~ 30. ] Or a general formula [In the formula, R ² represents an alkyl group having 6 to 22 carbon atoms, and R ³ represents a hydrogen atom or a 2-hydroxyethyl group. ] What is represented by these is preferable.

The higher fatty acid metal salt or nonionic surfactant as described above does not exhibit any effect of preventing white sinter, neutralization suppression, drying shrinkage reduction, and reinforcing bar rust prevention by itself, and the water-soluble amino resin When used in combination, the water-soluble amino resin enhances the effect of preventing efflorescence, the effect of suppressing neutralization, and the effect of reducing drying shrinkage. Therefore, in the case of such a combined use, the water-soluble amino resin may be used in a smaller amount as compared with the case where it is used alone, and is generally about 0.2 to 1.5 parts by weight as a dry solid content relative to 100 parts by weight of cement, preferably About 0.3 to 1.0 parts by weight may be used. When used in combination with the water-soluble amino resin, the higher fatty acid metal salt is generally about 0.02 to 0.1 parts by weight, preferably 0.03 to 0.08 parts by weight with respect to 100 parts by weight of cement.
The nonionic surfactant is generally used in an amount of about 0.004 to 0.08 parts by weight, preferably about 0.005 to 0.05 parts by weight, based on 100 parts by weight of cement.

0.2 parts of the above water-soluble amino resin per 100 parts by weight of cement
~ 1.5 parts by weight (dry solid content equivalent) and higher fatty acid metal salt
When it is used in an amount of about 0.02 to 0.1 part by weight, the white-water preventing effect and neutralization suppressing effect of the water-soluble amino resin are enhanced. When the amount of the higher fatty acid metal salt used is less than 0.02 part by weight, the effect of enhancing the effect of preventing white sinter and the effect of suppressing neutralization is small.
On the other hand, if it exceeds the weight part, white liquor tends to occur.

0.2 parts of the above water-soluble amino resin per 100 parts by weight of cement
The combined use of about 1.5 parts by weight (on a dry solids basis) and about 0.004 to 0.08 parts by weight of a nonionic surfactant enhances the anti-white flower action, the neutralization inhibitory action and the dry shrinkage inhibitory action. When the amount of the nonionic surfactant used is less than 0.004 parts by weight, the effect of enhancing the neutralization inhibitory effect and the drying shrinkage inhibitory effect is small, and when it exceeds 0.08 parts by weight, the anti-white flower action and the neutralization inhibitory effect The strengthening effect tends to decrease.

0.2 parts of the above water-soluble amino resin per 100 parts by weight of cement
~ 1.5 parts by weight (as dry solids), higher fatty acid metal salt 0.02 ~ 0.1 parts by weight and nonionic surfactant 0.004 ~
When about 0.08 parts by weight is used, all of the anti-white flower effect, the neutralization inhibitory effect, the drying shrinkage inhibitory effect and the rust preventive effect of the reinforcing bar are at least partially enhanced.

In order to obtain a remarkably excellent effect in terms of prevention of white sinter, neutralization suppression, drying shrinkage and rust prevention of reinforcing bar, cement 10
About 0.3 to 1.0 parts by weight of the above water-soluble amino resin (dry solid content) and 0.
0.03 parts by weight or about 100 parts by weight of cement, about 0.3 to 1.0 parts by weight of the above water-soluble amino resin (dry solid content), about 0.03 to 0.1 parts by weight of higher fatty acid metal salt and non- It is recommended to use about 0.005 to 0.03 parts by weight of an ionic surfactant.

Further, according to the present invention, in addition to improving the above-mentioned white sinter prevention effect, neutralization suppressing effect, drying shrinkage suppressing effect and rust preventive effect of the reinforcing bar, the mortar and the waterproofness of the concrete structure are also improved. To do.

The cement which is the subject of the method for preventing white flower of the present invention,
Commonly used ones can be used without particular limitation, and examples thereof include Portland cement, alumina cement, fly ash cement, blast furnace cement and silica cement.

When the water-soluble amino resin is used in combination with at least one of the higher fatty acid metal salt and the nonionic surfactant, these may be added separately to the cement mixture, or they may be mixed in advance to achieve the desired quality. It may be added as a composition. When the composition is made to meet the desired quality, the composition may be appropriately determined in light of the above-mentioned amount used, but generally, 100 parts by weight of the water-soluble amino resin (as a dry solid content), higher fatty acid metal It is desirable to prepare a composition containing about 5 to 25 parts by weight of salt, preferably about 7.5 to 20 parts by weight or / and about 1 to 20 parts by weight, preferably about 1.5 to 7.5 parts by weight of a nonionic surfactant. .

Therefore, the present invention comprises (a) 100 parts by weight of a water-soluble amino resin (as a dry solid content), and (b) 5 to 25 parts by weight of a higher fatty acid metal salt and / or 1 to 20 parts by weight of a nonionic surfactant. It also provides a mortar-concrete admixture characterized by containing.

According to the present invention, the water-soluble amino resin alone or the water-soluble amino resin and at least one of the higher fatty acid metal salt and the nonionic surfactant are blended in a cement mixture such as mortar and concrete to form a uniform mixture. Then, when this is poured into a formwork and then cured to produce a building wall or floor surface, a bridge or other mortar, or a concrete structure, the quality of such structure is improved as described above. Further, by applying or spraying the above-mentioned homogeneous mixture onto the surface of the already completed mortar or concrete structure, it is possible to prevent or suppress the whitening and neutralization.

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples.

Example 1 (1) Admixture Material The water-soluble amino resin used in this example is as follows.

a: Water-soluble urea resin (trade name "Igetalime" manufactured by Sumitomo Bakelite Co., Ltd.)
In the series, 1 mol of formaldehyde to 1 mol of urea.
Methylolation of 7 moles and condensation reaction) b: Water-soluble melamine resin (Sumitomo Bakelite Co., Ltd. product name "Igetalime")
In the series, 2.6 mol of formaldehyde was converted to 1 mol of melamine and subjected to condensation reaction. C: Water-soluble urea melamine resin (the above-mentioned water-soluble urea resin a and the above-mentioned water-soluble melamine resin 3: 7 ( (Weight ratio) Mixture) As the higher fatty acid metal salt, the following were used.

I: Calcium stearate II: Calcium palmitate The following nonionic surfactants were used.

(2) Test method 1) White flower acceleration test Using the above water-soluble amino resin, higher fatty acid metal salt and / or nonionic surfactant, the use ratio is changed as shown in Table 1 below, and ordinary Portland cement is used. Added to
Mortar with a sand / cement weight ratio of 3 (using Toyoura standard sand) and a water / cement weight ratio of 0.7 was molded into a 10 × 10 × 10 cm cement mortar prism and aged at 20 ° C. × 90% RH for 24 hours in wet air. I demolded later.

Then, apply these cement mortar prisms 2c in the longitudinal direction.
It cut | disconnected by m width and obtained the cut piece of 10x10x2cm. The obtained cut piece was dried at 80 ° C. for 24 hours, and the side surface was coated with paraffin to prepare a test piece for a white fluff generation test.

Separately, an aqueous solution containing 2% by weight of sodium sulfate and an excess of calcium hydroxide was placed in a bath to float the oil in order to prevent carbonation. This bath is 7 ℃ x 55% RH, wind speed 0.2 ~
The test piece was placed in an environment of 0.3 m / sec, immersed in an aqueous solution in a bath up to 1 cm, and 14 days later, the occurrence of white sinter was visually observed. The determination of the degree of occurrence of white sinter is based on the following criteria.

◎ No white fluff was observed 〇 Slightly white coloring around or around the center of the test piece △ White crystal growth on the peripheral area of the test piece × Table 1 shows the white pearl white crystal growth results.

2) Neutralization acceleration test Using the same admixture as used in the test in 1) above, changing the usage ratio in the same manner as in 1), and adding to ordinary Portland cement, river sand / cement weight ratio 1, gravel / Kneaded at a ratio of river sand weight ratio of 1.5 and water / cement weight ratio of 0.6 to obtain 10
cm × 10 cm × 20 cm rectangular parallelepiped specimen is molded at 20 ℃ × 90%
After culturing at RH for 1 week, it was dried at 20 ° C x 50% RH for 2 weeks. These specimens are 40 ℃ × 50% OH, carbon dioxide concentration 10%
It was left in the tank for 1 month.

After one month, remove each specimen from the tank, cut the specimen, and spray a 1% concentration phenolphthalein solution (ethyl alcohol) on the cross section to neutralize the depth (non-colored depth). Was measured.

The measurement results are shown in Table 1.

3) Dry shrinkage test Using the same admixture as used in 1) above, the usage ratio was changed in the same manner as in 1) and added to ordinary Portland cement to give a river sand / cement weight ratio of 1, gravel / river sand weight ratio of 1 , Water / cement weight ratio of 0.6, JIS
The test was carried out according to A 1129 "Method for testing length change of mortar and concrete".

The measurement was carried out after the lapse of 3 months.

The measurement results are shown in Table 1.

4) Rust accelerating test Using the same admixture as used in 1) above, the usage ratio was changed as in 1) and added to 50 parts by weight of ordinary Portland cement, and sea sand (NaCl conversion 0.2 100% by weight) was mixed and kneaded at a water / cement weight ratio of 0.5. A mild steel rod that has been thoroughly polished and degreased with acetone (4
φ × 100 mm) was placed in the center of the mold to pour the above kneaded product into a 4 × 4 × 160 mm rectangular parallelepiped concrete specimen.

This specimen was cured at 20 ℃ × 60% RH for 1 week, then 40 ℃ × 90
It was left in a thermo-hygrostat of% RH for 3 months, the specimen was broken, and the degree of rusting of the internal rebar was visually observed.

Judgment of the degree of rusting of reinforcing bars is based on the following criteria.

⊚: No rusting observed ◯: Almost no rusting △: Slight rusting ×: Significant rusting The results are shown in Table 1.

In addition, in Table 1 and the subsequent tables, "use amount" indicates parts by weight relative to 100 parts by weight of cement, and the use amount of the water-soluble amino resin is an amount as a dry solid content.

Comparative Example 1 Instead of the water-soluble amino resin, the following non-water-soluble amino resin in which the terminal methylol group was butyl etherified was used as described in Table 2 (Sample Nos. 43 to 45), and the same as in Example 1. The tests 1) to 4) were performed.

The results are shown in Table 2.

x: Water-insoluble urea resin (water-soluble urea resin a used in Example 1 butyl etherified) y: Water-insoluble melamine resin (water-soluble melamine resin b used in Example 1 was butyl etherified) Comparative Example 2 In addition, a higher fatty acid metal salt was used alone (Sample Nos. 46 and 4).
7) Or use nonionic surfactant alone (Sample No.48)
.About.50), and the tests 1) to 4) described above were conducted in the same manner as in Example 1. The results are shown in Table 2.

Table 2 also shows the results when only the cement formulation was used (plain) without using any admixture.

As is clear from Tables 1 and 2, when an appropriate amount of the water-soluble amino resin is used, white sinter, neutralization and rusting of reinforcing bars are prevented or suppressed, and the water-soluble amino resin and higher fatty acid metal are used. When an appropriate amount of each of salt and at least one kind of nonionic surfactant is used, white sinter, neutralization, drying shrinkage,
It can be seen that the rusting of the reinforcing bar is effectively prevented or suppressed in a composite manner.

Example 2 Separately using the sample Nos. 3, 14, 15 and 32 in Table 1, JIS-A
A water absorption test was conducted according to 1401. The results are shown in Table 3.

For comparison, sample No. 1 in Table 1 and sample N in Table 2
The results of o.51 (plain) are also shown in Table 3.

As is clear from Table 3, when a water-soluble amino resin is added (Sample No. 3), waterproofness is also imparted, and when the water-soluble amino resin is used in combination with a higher fatty acid metal salt or a nonionic surfactant ( It can be seen that the water resistance is further improved with sample Nos. 14, 15, 32).

Claims (3)

[Claims] 1. A method for improving the quality of a mortar, a mortar formed from concrete, and a concrete structure, characterized in that a water-soluble amino resin is added during kneading of the mortar and concrete. How to improve quality. 2. A method for improving the quality of a mortar, a mortar formed from concrete, and a concrete structure, comprising at least a water-soluble amino resin, a higher fatty acid metal salt and a nonionic surfactant when kneading the mortar and concrete. A method for improving the quality of a mortar and a concrete structure, which comprises blending one kind of mortar. 3. Containing 100 parts by weight of (a) a water-soluble amino resin (as a dry solid content), and (b) 5 to 25 parts by weight of a higher fatty acid metal salt and / or 1 to 20 parts by weight of a nonionic surfactant. An admixture for mortar and concrete.