JPH02160647A - Method for improving quality of mortar or concrete structure and admixture - Google Patents

Abstract

PURPOSE:To prevent mortar, etc., from whitening and improve durability thereof by blending a water-soluble amino resin in kneading the mortar or concrete. CONSTITUTION:A water-soluble amino resin is blended with one or more of metal salts of higher fatty acids and nonionic surfactants in kneading mortar or concrete. A water-soluble resin in a prepolymer stage consisting essentially of dimers or trimers obtained by reacting an amino compound, such as melamine or urea, or amide compound with aldehydes, such as formaldehyde, is used as the water-soluble resin. A resin free of methylol groups is especially preferred. For example, an admixture consisting of 100 pts.wt. water-soluble amino resin (expressed in terms of dry solid), 5-25 pts.wt. metal salt of a higher fatty acid and/or 1-20 pts.wt. nonionic surfactant is blended with mortar, etc. A secondary product, such as the mortar, can be prevented from whitening and suppression of neutralization in structures, such as the mortar, reduction in dry shrinkage and rust prevention of reinforcing bars can be carried out by the above- mentioned method.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to mortar, a method for improving the quality of concrete structures, and mortar and concrete admixtures used in the method. More specifically, the present invention aims to prevent efflorescence of mortar and concrete secondary products, suppress carbonation of mortar and concrete structures, reduce drying shrinkage, and prevent rust of reinforcing bars. Concerning how to improve durability.

Conventional technologyIn general, cement mixtures such as mortar and concrete are
As it hardens and dries, it exposes various fatal flaws. For example, efflorescence generated on the surface of a hardened cement compound has adverse effects such as impairing the appearance of buildings and causing peeling and discoloration of finishing materials such as tiles and paints. Although various methods for preventing efflorescence have been proposed in the past, a method for preventing efflorescence that is sufficiently effective has not yet been developed.

One of the reasons why it is difficult to prevent efflorescence is that efflorescence usually occurs due to two causes. That is, as described in JP-A-60-16843, one of the causes of efflorescence is that calcium hydroxide present inside the hardened body is carbonated on the surface of the hardened body and becomes calcium carbonate, resulting in crystal growth. Another cause is that alkali metals and sulfate radicals are eluted onto the surface of the cured product, become alkali metal sulfates, and grow as crystals. Therefore, even if an anti-efflorescence agent is capable of preventing efflorescence due to one cause, it may not be able to prevent efflorescence due to the other cause, and therefore, complete prevention of efflorescence cannot be achieved.

Next, regarding the durability of concrete structures, the lifespan of reinforced concrete structures has traditionally been 50 to 60 years.
It is thought to be about 20 years old. The reason for this is the phenomenon that carbonation from the surface of the concrete progresses to the inside of the concrete due to carbon dioxide gas, and when this neutralized region reaches the position of the reinforcing bars, the reinforcing bars rust and the reinforced concrete members lose their strength. This is due to

Cement mixtures also decrease in volume as they harden and dry, and this drying shrinkage causes cracks in concrete structures and the like. These cracks reduce the strength of concrete structures, allow carbon dioxide to penetrate into the interior through the cracks, promote carbonation of the concrete, and cause rusting of reinforcing bars, which significantly reduces the durability of concrete structures. let Conventional countermeasures against such carbonation and cracking include: 1) reducing the water/cement ratio of the cement mixture; 2) applying a finishing material with excellent airtightness, such as paint, to the concrete surface; Such methods have been used. However, when the water/cement ratio is reduced, workability is significantly impaired, and the heat generated by curing increases, resulting in cracking. Further, even if the use of finishing materials such as the above-mentioned paints is effective in the short term, there are problems with the durability of the finishing materials themselves. Therefore, neither of the above methods 1) and 2) can be said to be satisfactory.

Another factor that reduces the durability of concrete structures is corrosion of reinforcing bars in concrete due to iron-corrosive chlorides. More specifically, corrosion of reinforcing bars is caused by the increasing use of sea sand in recent years and the penetration of iron-corrosive chlorides carried by sea breezes into concrete structures along the coast. As a countermeasure,
Additives that accelerate initial hardening and additives that enhance watertightness have been proposed in the past, but these are not always satisfactory (particularly when the content of corrosive chlorides in iron JK in aggregate sand is converted to NaC1). If the amount is 0.01% by weight or more, no particularly suitable rust preventive has been found.

Problems to be Solved by the Invention The purpose of the present invention is to provide a method for improving the above-mentioned disadvantages inherent in mortar and concrete structures, preventing efflorescence, and providing mortar and concrete structures with excellent durability. do.

Means to solve problems The present inventor has conducted extensive research in order to solve the above problems.

As a result, it was found that the water-soluble amino resin is effective not only in preventing efflorescence caused by the above two causes, but also in suppressing carbonation and preventing rust on reinforcing bars.

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

That is, the present invention provides a method for improving the quality of mortar and concrete structures formed from mortar and concrete, which is characterized in that a water-soluble amino resin is blended during mixing of the mortar and concrete. It provides a method to improve the quality of

Furthermore, the present invention provides a method for improving the quality of mortar and concrete structures formed from mortar and concrete, in which a water-soluble amino resin, a higher fatty acid metal salt, and a nonionic surfactant are mixed together during kneading of mortar and concrete. The present invention also provides a method for improving the quality of mortar and concrete structures, characterized by blending at least one of them.

According to the present invention, when the above-mentioned 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 effects are enhanced by using the water-soluble amino resin and at least one of a higher fatty acid metal salt and a nonionic surfactant in appropriate amounts.

More specifically, when the above-mentioned water-soluble amino resin and higher fatty acid metal salt are used together, the efflorescence-preventing effect and the neutralization-inhibiting effect are enhanced.

When the above-mentioned water-soluble amino resin and nonionic surfactant are used in combination, the efflorescence-preventing effect, neutralization-inhibiting effect, and drying shrinkage-inhibiting effect are enhanced, and when both are used together in specific amounts, the efflorescence-preventing effect, It exhibits remarkable effects in all of its neutralization inhibiting action, drying shrinkage inhibiting action, and reinforcing steel rust prevention action.

When the above-mentioned water-soluble amino resin, higher fatty acid metal salt, and nonionic surfactant are used, all of the efflorescence prevention effect, neutralization suppression effect, drying shrinkage suppression effect, and reinforcing steel rust prevention effect can be achieved at least partially. When these three are used in specific ways, they have an anti-efflorescence effect, a neutralization suppressing effect,
It exhibits remarkable effects in both drying shrinkage suppressing action and reinforcing steel rust prevention action.

The water-soluble amino resin used in the present invention includes:
It is a dimer obtained by the reaction of an amino compound or amide compound such as melamine or urea with an aldehyde such as formaldehyde, or a water-soluble resin at the prepolymer stage mainly composed of a dimer, and can be used in a wide range of applications as long as it is water-soluble. Those within this range are included, and those free of methylol groups are particularly preferred. Amino resins that are water-insoluble due to etherification of methylol groups or the like cannot sufficiently exhibit the desired quality improvement effect. In the present invention, among the above-mentioned water-soluble amino resins, water-soluble urea resins, melamine resins, urea/melamine resins, etc. can be particularly preferably used. Such urea resin is
The ratio of formaldehyde to 1 mole of urea is about 1 to 2.5 moles, especially about 1.5 to 2 moles, and the ratio of melamine resin is about 1.5 to 3.5 moles of formaldehyde to 1 mole of melamine.
Water-soluble resins obtained by methylolation and condensation reactions are more preferable at a ratio of about 5 moles, particularly about 2 to 3 moles, respectively, and urea/melamine resins are mixtures of such specific urea resins and melamine resins. Or, it is more preferable that it is a co-condensate. 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, when used alone, the water-soluble amino resin is used in an amount of about 0.4 to 1.5 parts by weight, preferably about 0.5 to 1.0 parts by weight, based on 100 parts by weight of cement.

If the amount is less than 0.4 parts by weight, the effect will be insufficient;
When the amount exceeds 5 parts by weight, hardening is sometimes inhibited, and there is a tendency to inhibit the rust prevention effect of reinforcing bars.

As mentioned above, in the present invention, the water-soluble amino resin and at least one of a higher fatty acid metal salt and a nonionic surfactant are used.
The action of the water-soluble amino resin can be enhanced by using it in combination with seeds.

Various types of higher fatty acid metal salts can be used, but
Alkali metal salts or alkaline earth metal salts of higher saturated or unsaturated monocarboxylic acids having 6 to 24 carbon atoms are preferably used. In particular, alkaline earth metal salts of higher saturated monocarboxylic acids having 9 to 21 carbon atoms are inexpensive and more preferred 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, etc. can be particularly preferably used.

Various types of nonionic surfactants can be used, but typically, the following general formula % formula % (1) [wherein R is an alkyl group having 6 to 22 carbon atoms or a substituent having 1 to 1 carbon atoms] It represents a phenyl group which may have 16 alkyl groups or a halogen atom, and n is an integer of 4 to 30. ] or general formula % formula % (3) [wherein R1 represents an alkyl group having 6 to 22 carbon atoms, m
is an integer from 4 to 30. ] or the general formula [wherein R2 represents an alkyl group having 6 to 22 carbon atoms, R3
represents a hydrogen atom or a 2-hydroxyethyl group. Preferably, the one represented by .

The above higher fatty acid metal salts or nonionic surfactants alone do not exhibit any of the effects of preventing efflorescence, suppressing neutralization, reducing drying shrinkage, and preventing rust from reinforcing steel, and do not work together with the water-soluble amino resin. When used in combination, it enhances the efflorescence prevention effect, neutralization suppression effect, and drying shrinkage reduction effect of the water-soluble amino resin.

Therefore, when used in combination, the water-soluble amino resin may be used in a smaller amount than when used alone, and generally has a dry solid content of 0.2 to 100 parts by weight per 100 parts by weight of cement.
It is sufficient to use about 1.5 parts by weight, preferably about 0.3 to 1.0 parts by weight. When used in combination with the above water-soluble amino resin, the higher fatty acid metal salt is generally about 0.02 to 0.1 part by weight, preferably 0 parts by weight, based on 100 parts by weight of cement.
．． The nonionic surfactant is generally used in an amount of 0.03 to 0.088 parts by weight per 100 parts by weight of cement.
04 to 0.088 parts by weight, preferably 0.005 to 0.088 parts by weight
About 0.055 parts by weight is used.

When 0.2 to 1.5 parts by weight of the water-soluble amino resin (calculated as dry solid content) and 0.02 to 0.1 parts by weight of higher fatty acid metal salt are used in combination with 100 parts of cement, the water-soluble The anti-efflorescence and neutralization-inhibiting effects of the amino resin are enhanced. If the amount of higher fatty acid metal salt used is less than 0.02 part by weight, the effect of enhancing the efflorescence prevention effect and neutralization suppressing effect will be small, and if it exceeds 0.1 part by weight, efflorescence will be more likely to occur. There is a tendency to

When about 0.2 to 1.5 parts by weight of the above-mentioned water-soluble amino resin (calculated as dry solid content) and about 0.004 to 0.08 parts by weight of a nonionic surfactant are used together with 100 parts by weight of cement, The efflorescence prevention effect, neutralization suppression effect, and drying shrinkage suppression effect are enhanced. No amount of nonionic surfactant used
．． If it is less than 0.04 parts by weight, the effect of enhancing the neutralization suppressing effect and drying shrinkage suppressing effect is small, and if it exceeds 0.08 part by weight, the effect of enhancing the effect of preventing efflorescence and the suppressing effect of carbonation tends to be small. arise.

For 100 parts by weight of cement, about 0.2 to 1.5 parts by weight of the water-soluble amino resin (calculated as dry solid content), about 0.02 to 0.1 parts by weight of higher fatty acid metal salts, and nonionic surfactant. When about 0.004 to 0.08 parts by weight is used, all of the efflorescence-preventing effect, neutralization-inhibiting effect, drying shrinkage-inhibiting effect, and rust-preventing effect on reinforcing bars are at least partially enhanced.

In order to obtain remarkable effects in all aspects of preventing efflorescence, suppressing carbonation, drying shrinkage, and preventing rust of reinforcing bars, cement 1.
0.3 to 1.0 parts by weight of the above water-soluble amino resin.
Either use about 0 parts by weight (in terms of dry solid content) and about 0.005 to 0.03 parts by weight of a nonionic surfactant, or use 0 parts by weight of the above water-soluble amino resin per 100 parts by weight of cement. When using about .3 to 1.0 parts by weight (in terms of dry solid content), about 0.03 to 0.1 parts by weight of higher fatty acid metal salts, and about 0.005 to 0.03 parts by weight of nonionic surfactants, good.

Furthermore, according to the present invention, in addition to improving the efflorescence prevention effect, carbonation suppression effect, drying shrinkage suppression effect, and rust prevention effect of reinforcing bars, the waterproofness of mortar and concrete structures is also improved. do.

Cement that is subject to the efflorescence prevention method of the present invention includes:
Commonly used cements can be used without particular limitation, such as Portland cement, alumina cement, fly ash cement, blast furnace cement, and silica cement.

When a water-soluble amino resin and at least one of a higher fatty acid metal salt and a nonionic surfactant are used together, these may be added to the cement mixture separately or mixed in advance to achieve the desired quality. It may be added as a composition. When creating a composition that meets the desired quality, the composition can be determined appropriately in light of the amount used, but in general, higher fatty acid metal is added to 100 parts of water-soluble amino resin (as dry solid content). About 5 to 25 parts by weight of salt, preferably about 7.5 to 20 parts by weight, and/or about 1 to 20 parts by weight of nonionic surfactant, preferably 1.5 to 7 parts by weight.
．． It is desirable that the composition contains about 5 parts by weight.

Therefore, the present invention comprises (a) 100 parts by weight of a water-soluble amino resin (as dry solids) 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. The present invention also provides mortar and concrete admixtures characterized by containing.

According to the present invention, the above-mentioned water-soluble amino resin alone or the above-mentioned water-soluble amino resin and at least one of the above-mentioned higher fatty acid metal salt and nonionic surfactant are blended into a cement composition such as mortar or concrete to form a homogeneous mixture. When this is poured into formwork and then hardened to produce walls and floors of buildings, bridges, and other mortar and concrete structures, the quality of such structures is improved as described above. Furthermore, efflorescence and carbonation can also be prevented or suppressed by applying or spraying the uniform mixture onto the surface of an already completed mortar or concrete structure.

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

Example 1 (1) Mixed H material The water-soluble amino resin used in this example is as follows.

a: Water-soluble urea resin (product name "Igetalime" series manufactured by Sumitomo Bakelite ■, formaldehyde 1.7 per mole of urea)
b: Water-soluble melamine resin (produced by Sumitomo Bakelite ■ under the product name "Igetalime J series", where 1 mole of melamine contains 2 formaldehyde)
．． C: Water-soluble urea melamine resin (3=7 (weight ratio) mixture of the above water-soluble urea resin a and the above water-soluble melamine resin S), and higher fatty acid metal salt The following was used.

■Calcium nistearate ■: Calcium palmitate The following nonionic surfactants were used.

■: CH3 (CH2) +5COO (CH2CH20
)s H■: Cl1a (C1l 2 ) a C
0NIICH2CI+2011 (2) Test method 1) Using a water-soluble amino resin, higher fatty acid metal salt, and/or nonionic surfactant with a rating higher than the efflorescence acceleration test, and changing the usage ratio as shown in Table 1 below, ordinary Portland cement was used. added to the
Gravel/river sand weight ratio: 3 (using Toyoura standard sand), water/cement weight ratio: 0. 7 mortar, 1010X10X10
Formed into a cement mortar prismatic body, 20℃ x 90%R
After curing in humid air for 24 hours in H, the mold was demolded.

Next, these cement mortar prismatic bodies are longitudinally divided into two
It was cut to a width of cm to obtain a cut piece of 1010 x 10 x 2.

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 an efflorescence test.

Separately, an aqueous solution containing 2% sodium sulfate and excess calcium hydroxide was placed in a bathtub, and the oil was floated to prevent carbonation. This bathtub is 7℃ x 55%RH, wind speed is 0.
．． 2-0. The test piece was placed in an environment of 3 ml for 1 sec, and immersed in an aqueous solution in a bathtub up to 1 CI11. After 14 days, the appearance of efflorescence was visually observed. The degree of efflorescence occurrence is determined based on the following criteria.

◎ No efflorescence observed O Slight white coloring on the periphery or center of the test piece △ Crystal growth of efflorescence on the periphery of the test piece X The results of crystal growth of efflorescence on the entire surface are shown in Table 1.

2) Accelerated carbonation test Using the same admixture as in the test conducted in 1) above, and changing the proportions used in 1), it was added to ordinary Portland cement, with a river sand/cement weight ratio of 1, gravel/ The mixture was mixed with a river sand weight ratio of 1.5 and a water/cement weight ratio of 0.6, formed into a rectangular parallelepiped specimen of 10 cm x 1 Q cm x 20 cm, and cured at 20°C x 90% RH for one week.
It was dried for 2 weeks at 50% RH. These specimens were placed in a tank at 40° C., 50% RH, and 10% carbon dioxide gas concentration, and left for one month.

After one month, each specimen was removed from the tank, the specimen was cut, and a 1% concentration phenolphthalein solution (ethyl alcohol) was sprayed on the cross section to determine the neutralization depth (uncolored depth). was measured.

The measurement results are shown in Table 1.

3) Drying shrinkage test Using the same admixture as in the test conducted in 1) above, and changing the proportions used in 1), they were added to ordinary Portland cement, and the river sand/cement weight ratio was 1, and the gravel/river sand weight ratio was 1. , mixed at a water/cement weight ratio of 0.6, J
The test was conducted in accordance with IS A 1129 "Length change test method for mortar and concrete".

Measurements were taken after 3 months had elapsed.

The measurement results are shown in Table 1.

4) Rust acceleration test Using the same admixture as in the test conducted in 1) above, the proportions used were changed in the same way as in 1), and 50 parts of ordinary Portland cement was added to 50 parts of normal Portland cement. .0
2% by weight) was mixed and kneaded at a water/cement weight ratio of 0.5. A well-polished and acetone-degreased mild steel rod (4 φ x 100 mm) was placed in the center of the mold, and the above kneaded material was poured into it to form a rectangular parallelepiped concrete specimen measuring 4 x 4 x 160 mm.

After culturing this specimen for one week at 20°C x 60% RH,
Leave it in a constant temperature and humidity container at 0°C x 90% RH for 3 months.
The specimen was broken and the degree of rust on the internal reinforcing bars was visually observed.

The degree of rust on reinforcing bars is judged based on the following criteria.

◎No second-shot rust observed ○: Almost no rust observed Δ: Slight rusting X: Significant rusting The results are shown in Table 1.

In Table 1 and the subsequent tables, "amount used" indicates parts by weight based on 100 parts by weight of cement, and the amount of water-soluble amino resin used is 2 as dry solid content.

Comparative Example 1 In place of the water-soluble amino resin, the following water-insoluble amino 1 resin obtained by converting the terminal methylol group to butyl ether was used as shown in Table 2 (
Sample No. 43-45) was used as described in Example 1.
Tests 1) to 4) above were conducted in the same manner as above.

The results are shown in Table 2.

X: Water-insoluble urea resin (butyl etherified water-soluble urea resin a used in Example 1) y: Water-insoluble melamine resin (butyl etherified water-soluble melamine resin used in Example 1) Comparative Example 2 In addition, higher fatty acid metal salt was used alone in sample No. 4.
6.47), or using a nonionic surfactant alone (sample No. 48 to 50) and performing 1) in the same manner as in Example 1.
Tests 4) to 4) were conducted. The results are shown in Table 2.

Table 2 also shows the results when only the cement mixture was used without using any admixtures (blane).

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

Example 2 Separately, a water absorption test was conducted according to JIS-A1401 using sample Nos. 3, 14, 15, and 32 in Table 1.

The results are shown in Table 3.

For comparison, the results of sample No. 1 in Table 1 and sample No. 51 (plain) in Table 2 are also listed in Table 3.

As is clear from Table 3, when a water-soluble amino resin is added (sample No. 3), waterproof properties are also imparted, and when a water-soluble amino resin is used in combination with a higher fatty acid metal salt or a nonionic surfactant ( Sample No. 14.15.32), it can be seen that the waterproofness is further improved.

(that's all) Procedures Shinbo Seisho (self-motivated) Display of incidents 1999 Patent Application No. 139486 name of invention mortar, concrete structures Quality improvement methods and admixtures person who makes corrections Relationship to the incident: Patent applicant Melbab Co., Ltd.

Claims (3)

[Claims] (1) In a method for improving the quality of mortar and concrete structures formed from mortar and concrete, the quality of mortar and concrete structures is improved by blending a water-soluble amino resin when mixing the mortar and concrete. How to improve. (2) In a method for improving the quality of mortar and concrete structures formed from mortar and concrete, at least one of a water-soluble amino resin, a higher fatty acid metal salt, and a nonionic surfactant is added during kneading of the mortar and concrete. A method for improving the quality of mortar and concrete structures, characterized by blending with. (3) a) Water-soluble amino resin (as dry solid content) 10
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.