JPS6291449A - Dry shrinkage reducing agent for cement mixture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" Generally, mixtures of cement and water, such as concrete mortars and grouts, exhibit a volume reduction as they harden and dry. This is a phenomenon called "drying shrinkage" and is the main cause of cracking in concrete walls and floor slabs.

These cracks not only cause a decline in the functionality and rigidity of the structure, but also cause water and air to penetrate into the concrete through the cracks, promoting neutralization of the concrete and rusting the reinforcing steel inside. This accelerates this and significantly impairs the durability of the structure.

The present invention reduces "drying shrinkage" that causes cracking of concrete, mortar, or similar cement I/mixtures by a factor of 11, and reduces drying shrinkage for cement mixtures as a material that does not cause a decrease in the strength of cement mixtures. This is related to drugs.

"Prior art" As a general countermeasure against cracks caused by drying shrinkage, on the premise that shrinkage is avoided,
tl! 1, and make the cracks appear in this part,
Prevent it from occurring in other parts. Amount i) Extra reinforcing bars are installed in advance at locations where cracks are likely to occur, and these reinforcing bars keep cracks i+ small. Although the following measures have been taken, none of these measures has been able to completely control cracks.

Also, the idea is that it will offset the "shrinkage".

Attempts have been made to prevent drying shrinkage cracking by adding an expanding agent to concrete, etc., but the expansion phenomenon of concrete, etc. ends very early in the hardening period of cement. It does not follow drying shrinkage over a long period of time (there is also a tendency to do so).

For example, it is difficult to determine the appropriate amount of addition of 44 to reduce drying shrinkage, and cracking has not yet been completely prevented.

Based on the history of conventional technology, it has been found that in order to prevent drying shrinkage cracks in concrete, etc., it is most certain and most effective to reduce the drying shrinkage itself by about 1. It's becoming clear.

From this point of view, for example, published patent publication U.S. 56-
0372511. A drying shrinkage reducing agent for cement has been developed as shown in Japanese Patent Publication No. 56-037259.

In addition, in the patent application filed in August 1982, 1 of the amount of cement was
We have discovered a compound that exhibits the effect of reducing drying shrinkage when added at around 50%.

"The problem that the invention attempts to solve" However, in the former case of the reducing agent mentioned above.

Practical -1l unless the amount added is around 4% of the amount of cement
This has the disadvantage that it is extremely expensive because the same effect cannot be obtained, and when the latter is added to the cement mixture, the strength of the cement mixture decreases by 3 to 12%.

``Means for solving problems'' and ``effects'' The present invention is
This was done in consideration of the circumstances mentioned above.

As a result of tests using new compounds, with extremely small amounts of use,
Greatly reduces drying shrinkage of concrete etc.

At the same time, it was possible to prevent the drying shrinkage cracks that occur in concrete at a low cost without causing a decrease in the strength of the cement mixture.

In other words, the present inventors et al.

General formula [wherein, R1 represents a hydrogen atom or an alkyl group having 5 to 12 carbon atoms, R2 represents an alkyl group having 5 to 12 carbon atoms, X represents -Ctl 2 C1l 20-, Y
represents -CH2C1l (C1l 3 ) O- and 2m
is a number from 0 to 4.

n is 0 or a number from 1 to 10, and m+n is from 1 to 10
is a number with . X and Y are arranged in any order. Of course, it refers to single adducts and polymers of ethylene oxide or propylene oxide, block polymers, or random polymers. ] can be added in extremely small amounts without causing a decrease in strength.

It has been found that this method is extremely effective in reducing cement drying shrinkage.

In formula (1) of 011, the alkyl group having 5 to 12 carbon atoms in R1 and R2 includes pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, F-decyl group. etc.

However, it is not limited to these alkyl groups.

X and Y are ethylene oxide, propylene oxide alone (single adducts and polymers, or ethylene oxide).

It consists of a block or random polymer of M-propylene, and 1 X and Y are arranged in any order.

The compound represented by general formula (1) is as described above.

It is a compound obtained by adding ethylene oxide or propylene oxide to phenol or mono- and di-alkylphenol, and as an alkylene oxide, this compound can be used with other oxides such as butylene oxide, styrene oxide, and alkylene oxide having 2 to B carbon atoms. They may be co-added to an extent that does not impair performance, and such compounds are also included within the scope of the present invention.

In addition, ethylene oxide (1 additive) of alkylphenol as an admixture for cement, which has been conventionally used, is usually made by adding 5 to 30 moles of ethylene oxide to 1 mole of alkylphenol having 8 to 10 carbon atoms. Since these compounds have surface active functions such as dispersibility, wettability, and chlorine properties, they are used as air entraining agents for cement, dispersants for cement, and the like. However, such an ethylene oxide adduct of alkylphenol has almost no function as a drying shrinkage reducing agent for cement.

In general formula (11), even if R1 and R2 are hydrogen groups or alkyl groups having 1 to 4 carbon atoms, the effect of reducing drying shrinkage of the cement mixture is exhibited, but the strength of the cement mixture decreases by about 10%. Although this decrease in strength does not fundamentally impede its function as a drying shrinkage reducer, additional cement is required to compensate for this decrease in strength. This is not desirable.

In general (1), when 2 m exceeds 5, the surfactant function becomes strong, and not only the effect of reducing drying shrinkage is not exhibited, but also the strength of the cement mixture containing it is significantly reduced.

On the other hand, in the general formula (]), R1 is a hydrogen group or an alkyl group having 4J carbon atoms of 5 to 12, R2
is an alkyl group having 5 to 12 carbon atoms, and 1m is 0 to
4, and n is 0 or a number from 1 to 10.

When m4-n is a number between 1 and 10, it has the function of greatly reducing the drying shrinkage of the cement mixture, and the strength of the cement mixture is also lower than that without additives. It has the feature of being able to move in one direction.

The method for adding the shrinkage reducing agent of the present invention to concrete, etc. is 1.
It may be added to the kneading water in advance like a normal admixture.
It may be added to concrete etc. that have been mixed once. It may also be added after the concrete arrives at the site using a truck mixer. Which addition method to adopt may be determined depending on the type of shrinkage reducing agent, the conditions of the structure, etc.

The shrinkage reducing agent of the present invention is not limited by the type of cement, type of cement, admixture used in combination, and admixture (A material).

That is, as for the type of cement, commonly available commercially available cements such as ordinary cement, early strength cement, moderate heat cement, A-furnace cement, and fly ash cement can be used. In addition, part of it can be replaced with fly ash, granulated slag powder, siliceous mixture, etc., and the purpose of the present invention may be advantageously achieved by this replacement.

In addition, water reducing agents and air entraining agents for concrete.

It can also be used in combination with an expanding agent and other known admixtures for concrete or mortar.

When applying the present invention to an actual structure.

It is also possible to limit the use to areas where cracks are expected to occur due to drying shrinkage, which may increase economic efficiency.

"Example" The present invention will be explained below based on two examples.

By actual lid ↓ Mortars with and without the addition of various shrinkage reducing agents of the present invention and polyoxyalkylenes and alkylphenyl ethers other than the present invention, respectively, at 1 and 4% by weight based on the cement (water-cement ratio 60%, Cement sand settling 0.5. The sand is Toyoura standard sand) JIS A 11
Drying shrinkage was measured by the comparator method of No. 29.

The curing method was also certified as JISJ 1129. In addition, compressive strength tests were conducted on specimens with a diameter of 5 cm and a height of 1Q cm that had been subjected to standard water curing at 7 and 28 days of age.

The test results are shown in the diagram in Figure 1.

Example 2 = The drying shrinkage rate of concrete with and without the addition of the shrinkage reducing agent of Example 1 at 1% and 4% by weight based on the cement, respectively, was measured in the same manner as in Example 1.

Further, a compressive strength test similar to that in Example 1 was conducted on a specimen having a diameter of 10 cm and a height of 20 cm.

The mixing ratio is shown in the table below, and the test results are shown in the chart in Figure 2. -10= figure.

As is clear from the above results, drying shrinkage No. 11 of the mortar and concrete No. 11 to which the invention product 1 was added showed significantly lower drying shrinkage than that of the mortar without the addition of I.
The F shrinkage strength is 7 (11°) compared to 1) of jHj j5 addition.
It shows a value of 11.

"Effects of the Invention 1 As described above, the present invention reduces the drying shrinkage of cement mixtures such as mortar, concrete, etc. to 111% with an extremely small amount of use, and prevents cracks caused by shrinkage. It has become clear that the cement mixture has an excellent effect of not reducing the strength of the cement mixture at all.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are charts showing the test results of the product of the present invention and the comparative product.

Claims (1)

[Claims] General formula ▲ Numerical formula, chemical formula, table, etc. , X represents -CH_2CH_2O-, Y represents -CH_2CH(CH_3)O-, m is a number from 0 to 4, n is a number from 0 or 1 to 10, and m+n is from 1 to
It is a number with 10. X and Y are arranged in any order. That is, it indicates a single adduct or polymer of ethylene oxide or propylene oxide, a block polymer, or a random polymer. 1. A drying shrinkage reducing agent for cement mixtures, which comprises as a main component one or more of the compounds represented by the following.