JP3500877B2 - Cement composition with reduced autogenous shrinkage and method for reducing autogenous shrinkage of cement - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention mainly civil engineering, in the field to use the cement architectural etc., of cement compositions and cement for reducing autogenous shrinkage caused by hydration of the cement A method for reducing self-shrinkage.

[0002]

BACKGROUND OF THE INVENTION One of the serious drawbacks of cement mortar and concrete is the cracking phenomenon. This crack not only impairs the aesthetics of the structure, but also reduces the strength of the structure, and in the long run, rainwater and air entering from the cracked part promote corrosion of the reinforcing bars and neutralization of concrete, Since it causes a significant decrease in the durability of the structure, investigations have been conducted on the cause of cracking and investigation of its cause.

Conventionally, as factors that cause cracking, it has been considered that drying shrinkage due to a decrease in volume accompanied by dissipation of water from concrete or mortar and adiabatic temperature rise caused by heat of hydration of cement in concrete. Proposals have been made to suppress cracking due to such factors.

For example, in order to suppress the rise in adiabatic temperature, a method of adding a hydration exothermic inhibitor has been proposed (JP-A-6-7).
2748), with respect to dry shrinkage, organic compound-based dry shrinkage reducing agents having a polyalkylene oxide skeleton, such as polyalkylene glycol and polyalkylene oxide ether, have been developed and are already on the market.

Recently, however, the importance of a factor called self-shrinkage has been pointed out in addition to the above-mentioned factors causing cracks (for example, Eiichi Tazawa, Cement Concrete, No. 565, pp 35-44. 19
94). Self-contraction is the entry and escape of water, temperature changes,
This is a macroscopic volume reduction that accompanies the progress of hydration of cement under conditions without carbonation, and the major difference from drying shrinkage is that there is no loss of water.

Although the existence of this self-shrinkage has been confirmed for a long time, its importance was not recognized so much because the degree of shrinkage was considered to be smaller than the dry shrinkage. Therefore, there are few studies, and the researches on the mechanism of development including self-shrinkage evaluation method have just started recently including the above-mentioned documents.

Recent studies have revealed that the denser the cement structure, the greater the self-shrinkage. This is the opposite of dry shrinkage. In order to increase the strength of concrete, densification of cement structure is an effective means, and development of high-performance water reducing agent and silica fume is
Although the cement ratio was made smaller to enable the densification of the cement structure, conversely, the self-shrinkage becomes so large that it cannot be ignored.

Recent studies on self-shrinkage have shown that the addition of the aforementioned dry shrinkage reducing agent also reduces self-shrinkage to some extent. However, the drying shrinkage-reducing agent has an effect of reducing self-shrinkage after the age of about 3 days, but the effect is small in the age before that.
Further, as described above, the dependence of the magnitude of shrinkage on the compactness of concrete is opposite in the tendency between dry shrinkage and self-shrinkage, that self-shrinkage cannot be suppressed by simply adding a dry shrinkage agent. Is shown.

There is also known a means for mechanically compensating for shrinkage by adding an expansive admixture regardless of the type of shrinkage, but in this method, contrary to the dry shrinkage agent, in the initial age Although the effect of canceling contraction including self-contraction is recognized, not only the contraction cannot be suppressed in the long term, but also expansion cracks may occur in the initial stage unless the expansion amount is adjusted properly.

In order to increase the strength of concrete, reduction of self-shrinkage is an unavoidable problem, but as a means therefor, it is effective in addition to insufficient addition of dry shrinkage agent or expansive admixture. There is no such thing.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention, the cement composition toward you reduce the self-shrinkage of cementitious materials such as concrete or mortar toward long from the initial method and autogenous shrinkage is reduced toward long from the initial To provide.

[0012]

The present invention SUMMARY OF] is cement alkylene oxide compound and particle size autogenous shrinkage during curing consisting of percarbonate <br/> Rushiu arm and cement 0.02~3.0μm is reduced compositions and relates to self-shrinkage reducing method of cement.

That is, the inventors made a self-shrinkage measuring device and studied the relationship between the self-shrinkage of cement paste and the hydration reaction for low-heat type cement and ordinary cement. That the combination of alkylene oxide compound and calcium carbonate fine powder having a certain particle size range shows an excellent self-shrinkage reducing effect of cement, and the concrete composition containing this agent shows significant self-shrinkage from the initial to long-term. The present invention has been found to provide a cured product having a reduced amount and solved the above-mentioned problems.
The present invention will be described in detail below.

[0014] Luer Ruki alkylene oxide compound put to the invention, wherein R ₁ OAR ₂ [wherein A is -CH ₂ CH ₂ O-or -CH ₂ CH (CH ₃₎ O- the monomer or a polymer A homopolymer of each monomer having a degree of 2 to 20 or a block or random copolymer of two monomers,
₁ is 1 to 3 carbon atoms such as hydrogen, methyl, ethyl and propyl
Represents a substituted phenyl group substituted at the 2- and / or 4-position with an alkyl group having 1 to 3 carbon atoms such as an alkyl group, a cyclohexyl group, a phenyl group or a methyl, ethyl, propyl group, etc., and R ₂ is H or methyl, ethyl. Represents an alkyl group having 1 to 3 carbon atoms such as propyl, etc.], and has a monomer or polymer of alkylene oxide as a basic skeleton, or a mixture of two or more thereof.

For example, polyalkylene glycol such as tetrapropylene glycol [A = (CH ₂ CH (CH ₃ ) O) ₄ , R ₁ , R ₂ = H], triethylene glycol monomethyl ether [A = (CH ₂ CH ₂ O) ₃ , R ₁ = C
H ₃ , R ₂ = H] and other polyalkylene glycol ethers, tetraethylene glycol tetrapropylene glycol monoethyl ether [A = (CH ₂ CH ₂ O) ₄ and (CH ₂ CH (CH ₃ ) O) ₄ copolymerization Object, R ₁ = C ₂ H ₅ ,
Examples thereof include ethers of block polymer such as R ₂ = H]. In addition, alkylene oxide-based chemicals commercially available as a drying shrinkage reducing agent can be suitably used as one kind or a mixture of two or more kinds, regardless of the kind.

On the other hand, the calcium carbonate fine powder used in the present invention is obtained by finely pulverizing a mineral mainly composed of calcium carbonate such as limestone or produced by reacting a calcium salt such as slaked lime with carbon dioxide gas. Therefore, what is called heavy calcium carbonate, light calcium carbonate, precipitated calcium carbonate, etc. are included. Although calcium carbonate is classified into calcite, vaterite and aragonite depending on the difference in crystal structure, calcium carbonate having any structure may be used.

The particle size of calcium carbonate affects the effect of reducing self-shrinkage. When the particle size is larger than 3.0 μm, sufficient self-shrinkage reducing effect is not exhibited, and 0.0
If the particle size is smaller than 2 μm, handling and kneading will be very difficult and not practical. Therefore, in the present invention, 0.02 to 3.0, preferably 0.7 to 2.2 μm
Use calcium carbonate.

[0018]

Further, with respect to base Susemento 100 parts by weight, the amount of the alkylene oxide compound is 0.5 to 1
0 parts by weight, and the amount of calcium carbonate having a particle size of 0.02 to 3.0 μm added is 10 to 30 parts by weight.

If the amount of the alkylene oxide compound added is less than 0.5 part by weight relative to 100 parts by weight of the base cement, a sufficient effect of reducing self-shrinkage cannot be obtained, and if it exceeds 10 parts by weight, not only the cost is increased but also the cement This is because the setting and hardening of the syrup may be delayed. on the other hand,
Grain size is 0.02 to 100 parts by weight of base cement
If the amount of calcium carbonate added to the amount of 3.0 μm is less than 10 parts by weight, a sufficient effect of reducing self-shrinkage cannot be obtained, and if it exceeds 30 parts by weight, the strength of the cured product may decrease, which is not preferable.

Examples of the base cement to which the present invention is applicable include various types of portland cement such as normal, early strength, moderate heat, low heat, and sulfate resistance, blast furnace cement, fly ash cement, and other mixed cements. .
Also, alumina gypsum added with various gypsum and awin type expansive material is also applicable.

[0022] In the present invention, calcium carbonate A Ruki alkylene oxide compound and is the particle diameter 0.02~3.0μm, if even are present simultaneously in the cement composition, method of adding the base cement additives It does not depend on the order at all. The alkylene oxide compound and calcium carbonate may be mixed in advance to form one agent, but
From the viewpoint of workability, the most preferable method is to add the respective components separately when kneading the base cement with water.

In addition, base cement and a
Ruylene oxide compound, particle size 0.02-3.0μ
m calcium carbonate and water, aggregates such as sand and gravel, water reducing agents, hardening accelerators, hardening retarders, reinforcing bar rust inhibitors, etc.
Addition of known additives does not cause any problems, and they can be used as materials for pastes, mortars and concretes according to conventionally known enforcement methods.

[0024]

DETAILED DESCRIPTION OF THE INVENTION

EXAMPLES The contents of the present invention will be specifically described below with reference to examples. Since self-shrinkage occurs in the cement paste portion, the effect of reducing self-shrinkage was evaluated with cement paste.

(1) Raw material cement used; ordinary Portland cement heavy calcium carbonate: average particle size 4.0, 2.9, 1.
1 μm 3 kinds of light calcium carbonate: average particle diameter 0.7 μm alkylene oxide compound: mixed polypropylene glycol having a molecular weight distribution of 100 to 800 [trade name:
"Hibidan", manufactured by Takemoto Yushi Co., Ltd.] was used.

(2) Kneading method The cement paste was kneaded by hand for 3 minutes in accordance with the setting test method of JIS R 5201 "Physical test method of cement". The water / powder ratio was 30% by weight.

(3) Method of measuring self-shrinkage strain The kneaded cement paste is 2 cm x 2 cm x 16c.
It was filled in the m frame and the gauge plugs were embedded on both sides of the cement paste. After sealing and curing for 1 day, the cement paste was taken out from the mold, and the whole cement paste was covered with a polyethylene film and then further covered with an aluminum film. The sample after wrapping is set in the shrinkage strain measuring device shown in Fig. 1, and the measurement start time and the distance between the gauge plugs embedded at both ends of the cement paste and the non-contact displacement sensor section at the specified age are measured to obtain the cement paste. The self-shrinkage strain of was calculated from the following equation. Kneading of cement paste, curing and measurement of self-shrinkage are all 20 ± 3
It was carried out in a constant temperature room at ℃.

Self-contraction strain = (L _t −L ₀ ) / L L ₀ : Distance between gauge plugs at both ends at the start of measurement and displacement sensor section (mm) L _t : Gauge plugs at both ends at age t and displacement Distance from sensor (mm) L: Length of test piece (= 160mm)

Examples 1 to 4 and Comparative Examples 1 to 5 Cement, alkylene oxide compound, addition amount of calcium carbonate, and particle size of calcium carbonate were changed as shown in Table 1, and the above (1) and (2) were changed. The cement paste was prepared by the method, and the self-shrinkage strain was measured by the method (3). The results are shown in FIG. 2, FIG. 3 and FIG.
Shown in.

[0030]

[Table 1]

FIG. 2 shows the effects of the combined use of an alkylene oxide compound included in the scope of the present invention and light calcium carbonate (Example 1), and the effect of not containing an alkylene oxide compound (Comparative Example 2). This is shown in comparison with the case where calcium is not contained (Comparative Example 3) and the case where neither alkylene oxide compound nor light calcium carbonate is contained (Comparative Example 1).

Addition of only light calcium carbonate (Comparative Example 2) shows a self-shrinkage reducing effect on the initial age, but 3
After the age of 30 days, the self-shrinkage sharply increases, and after 20 days of age, it does not differ from that of the alkylene oxide compound-free one. Further, in the case of adding only the alkylene oxide compound (Comparative Example 3), the effect of reducing the shrinkage of the initial age is smaller than that of light calcium carbonate, but the effect continues for a long time.

On the other hand, when the alkylene oxide compound and the light calcium carbonate coexist (Example 1), the effect of reducing self-shrinkage is greater than that when each is added alone, and the self-shrinkage of light calcium carbonate is reduced. Even after 20 days of age when the effect disappeared, the self-shrinkage reduction effect was greater than when only the alkylene oxide compound was added,
It is shown that the self-shrinkage reducing effect in the simultaneous addition of the alkylene oxide compound and the light calcium carbonate is not merely an additive effect.

FIG. 3 shows the influence of the calcium carbonate particle size. As the particle size of calcium carbonate increases, the effect of reducing self-shrinkage at the early age decreases, and the particle size is 4 μm.
In the case of calcium carbonate (Comparative Example 4), there is almost no difference from the case where only the alkylene oxide compound is added to the cement, and the effect of reducing the self-shrinkage at the initial age due to the addition of calcium carbonate is not recognized.

FIG. 4 shows the effect of the addition amount of calcium carbonate. When the addition amount of calcium carbonate to the cement is less than 10% (Comparative Example 5), only the alkylene oxide compound is added to the cement (Comparative Example 3). ), The effect of reducing the self-shrinkage in the early age by the addition of calcium carbonate is not recognized.

[0036]

EFFECTS OF THE INVENTION The cement composition of the present invention can reduce self-shrinkage of cement-based materials such as concrete and mortar from the initial to long-term without causing expansion, and thus can prevent cracking of the cured product during curing. Great effect.

[Brief description of drawings]

FIG. 1 shows an apparatus used for measuring self-shrinkage strain.

FIG. 2 is a diagram showing the effect of simultaneous addition of an alkylene oxide compound and calcium carbonate.

FIG. 3 is a diagram showing the influence of the average particle size of calcium carbonate.

FIG. 4 is a diagram showing the influence of the amount of calcium carbonate added.

[Explanation of symbols]

1 Aluminum plate 2 samples 3 sensors 4 micrometer

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Claims (2)

(57) [Claims] 1. To 100 parts by weight of base cement , 0.5 to 10 parts by weight of an alkylene oxide compound and 1 part of calcium carbonate having a particle size of 0.02 to 3.0 μm.
A cement composition with reduced self-shrinkage, added in an amount of 0 to 30 parts by weight. Respect 2. A base cement 100 parts by weight, 0.5 to 10 parts by weight of an alkylene oxide compound, and a particle diameter of the calcium carbonate 0.02～3.0Myuemu 1
0 to 30 to parts by weight added pressure, autogenous shrinkage reducing method of the cement.