JP3369053B2 - Dry shrinkage crack reduction method for mortar or concrete - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method of reducing dry shrinkage cracks of mortar and concrete.

[0002]

2. Description of the Related Art Conventionally, as a method of reducing dry shrinkage cracks that occur in mortar and concrete, coating with a film curing agent, mixing with an AE water reducing agent or an inorganic expansive admixture, or shrinkage mainly containing lower alcohol Attempts have been made to incorporate a reducing agent.

[0003]

The film curing agent is applied mainly for the purpose of preventing excessive dissipation of water from the surface of the mortar and concrete during curing. Since it takes a lot of trouble to apply and the application site is limited, it has not been widely spread.

Further, the AE water reducing agent reduces the amount of unit water for obtaining desired workability by suppressing the agglomeration of cement particles, and the water reduction rate is 3 to 8% (without air entrainment) or 12%. Although it is about 16% (with air entrainment), there is a limit to the suppression of shrinkage due to drying only by reducing the water / cement ratio.

Further, the use of the expansion admixture and the shrinkage reducing agent may have an unexpected adverse effect on the concrete depending on the amount of the admixture, and the amount used is limited, and only the effect within the limited range can be expected. There wasn't.

By the way, various attempts have been made to strengthen mortar, mortar obtained by adding reinforcing fibers to concrete, and cement composition. However, the affinity between these fibers and cement particles is low, and the fiber-matrix matrix has a low affinity. Peeling occurs on the surface, the reinforcing effect is insufficient, and the surface smoothness is impaired by the exposure of the fiber to the surface, so it has not been put to practical use.

On the other hand, the inventors of the present invention have a high water content as a material for ensuring water retention in mortar and concrete.
As a result of various studies on materials that have a high affinity for the matrix of mortar and concrete and can even ensure sufficient water retention of the matrix, the fine fibrous cellulose has a high water content and sufficient alkali resistance. I found it expensive.

The present invention has been made based on the above-mentioned attention, and improves the affinity of the fine fibrous cellulose for the matrix in addition to the water retention property of the fine fibrous cellulose. An object of the present invention is to provide a method for preventing drying shrinkage of mortar or concrete, which can be uniformly kneaded into the mortar and thereby prevent drying shrinkage of mortar or concrete.

[0009]

To achieve the above object, the present invention relates to a matrix of fine fibrous cellulose by adding both fine fibrous cellulose and a shrinkage reducing agent during the production of mortar or concrete. The affinity was ensured, and the water retention component consisting of fine fibrous cellulose was dispersed in the matrix by uniform kneading. Therefore, the mortar in which this is dispersed and the concrete itself are prevented from being dried, and dimensional changes and cracks due to shrinkage are also prevented.

The fine fibrous cellulosic fibers can be obtained by subjecting cellulose suspended in water to high shearing force and high impacting force to highly disintegrate and miniaturize the cellulose fibrils. The cellulose is various natural fibers such as wood fibers (wood pulp such as conifers and hardwoods), seed hair fibers (cottons such as linters, bombax cotton, kapok, etc.), gin skin fibers (hemp, flax, jute). , Ramie, kozo, mitsumata, etc.), leaf fiber (manila hemp, etc.) and the like. Preferred celluloses include wood pulp, linter pulp and the like.

The aspect ratio of the fine fibrous cellulose fibers is, for example, 250 to 15,000, preferably 500.
It is about 10,000, more preferably about 500 to 8,000. The fiber diameter of the fine fibrous cellulose fibers is, for example, an average fiber diameter of 3 μm or less (for example, 0.01 to
3 μm), preferably 2 μm or less (for example, 0.01 to 2)
μm), more preferably 0.01 to 1.5 μm or less (for example, 0.01 to 1 μm), and often has an average fiber diameter of 0.1 to 1.5 μm.

The fiber length of the fine fibrous cellulose fibers is, for example, 5 to 3,000 μm, preferably 500 to 1,5.
00 μm, more preferably 100 to 1,000 μm
(Preferably 200 to 1,000 μm) and an average fiber length of 300 to 1,000 μm (for example, 500 to 9).
In many cases, it is about 00 μm.

Since fine fibrous cellulose fibers are highly miniaturized, they have a large specific surface area, and when applied to a base material, they are useful for greatly improving the adhesion to the base material and the adhesion to the top coat or finishing material. Is. The specific surface area of the fine fibrous cellulose fibers is, for example, 50 to 300 m ² /
g, preferably 100 to 300 m ² / g, more preferably 150 to 250 ² / g approximately.

The fine fibrous cellulosic fibers are available from Daicel Chemical Industries, Ltd. under the trade name "Cerish".

The shrinkage reducing agent used in the present invention includes:
A shrinkage reducing agent comprising an amide compound and / or a modified amide compound disclosed in Japanese Patent Application No. 54-110902, or a general formula RO (AO) nH ... (whose main part is disclosed in Japanese Patent Application No. 54-110903). 1) (wherein R is an alkyl group having 1 to 7 carbon atoms or a cycloalkyl group having 5 to 6 carbon atoms, A is one or two kinds of alkylene groups having 2 to 3 carbon atoms, and n is a number of 1 to 10) And one or more types of shrinkage-reducing agents consisting of the compound represented by

Examples of the former are mono- or polyamide compounds having an amino group in a known molecule obtained by reacting at least one of polymerized fatty acid and monobasic acid with polyamines. The above-mentioned mono- or polyamide compound is usually semi-solid to liquid, and its total amine value is usually 80 to 700, preferably 2
It is 00-400. The mono- or polyamide resin may be the same as that used as the epoxy resin curing agent, and unreacted polyamines may remain in these mono- or polyamide compounds.

As the modified amide compound, at least one of polymerized fatty acid and monobasic acid, polyamines and a modifier such as a monoepoxy compound, a vinyl compound having an electron-withdrawing group (acrylonitrile, acrylic ester, etc.), a ketone compound ( Proportion of amino groups remaining in the molecule of methyl ethyl ketone, methyl isobutyl ketone, diacetone acrylamide, etc., aldehyde compounds (formalin, acetaldehyde, furfuryl aldehyde, etc.) and methylol compounds (methylol / phenol, methylol / melamine) The modified mono- or polyamide compounds obtained by reacting with Of these, preferred are polymerized fatty acids and monobasic acids, at least one of which is a polyamine and a monoepoxy compound as a modifier, or a modified mono- or polyamide compound obtained by using a vinyl compound having an electron-withdrawing group ( For example, Japanese Patent Publication No. 51-23560
And those disclosed in Japanese Examined Patent Publication No. 52-5554). The modified mono- or polyamide compound is usually a semi-solid to liquid compound, and the total amine value thereof is usually 80 to 700, preferably 200 to 400.

Further, as the latter, R in the general formula (1) is an alkyl group having 1 to 7 carbon atoms or a cycloalkyl group having 5 to 6 carbon atoms. Examples of such groups include a methyl group, an ethyl group, a normal propyl group,
Examples thereof include an isopropyl group, a normal butyl group, an isobutyl group, a normal ventil group, an isopentyl group, a cyclopentyl group, a cyclohexyl group, a normal hexyl group, an isohexyl group, a normal hebutyl group, and an isohebutyl group. Considering the cement shrinkage reducing effect of these, an alkyl group having 1 to 5 carbon atoms or a cyclohexyl group, particularly a butyl group is preferable. A is an alkylene group having 2 to 3 carbon atoms, and examples thereof include an ethylene group and / or a propylene group. Further, n (the number of moles of alkylene oxide added) is 1 to 10.

Further, in the present invention, the chemical admixture 100
It is desirable to add 0.5 to 5 parts by weight of fine fibrous cellulose to each part. The reason for this is that the amount of the chemical admixture added to the mortar and concrete is determined by the specifications, so if it is less than 0.5 parts by weight,
This is because the necessary amount as a water-retaining component is insufficient, the desired effect of preventing dry shrinkage and cracking cannot be obtained, and in the case where the amount exceeds 5 parts by weight, problems such as a decrease in workability occur.

Therefore, the present invention is limited to the above range, more preferably 0.5 to 5 parts by weight.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Next, specific examples of the present invention will be described.

Example: Water 7 parts by weight Cement 16 parts by weight Fine sand 33 parts by weight Gravel 44 parts by weight A high performance shrinkage reducing agent was added in an amount of 0.32 parts by weight to a concrete composition. To this high performance shrinkage reducing agent, 5 parts by weight of fine fibrous cellulose was previously added and mixed with 100 parts of this, and this was added at the same time when concrete was kneaded. As a high-performance shrinkage reducing agent, the product name of Tetra Guard A manufactured by Nippon Cement Co., Ltd.
S20 "was used. In addition, as the fine fibrous cellulose, trade name “Serisch KY-100S, KY-110S” manufactured by Daicel Chemical Co., Ltd., which is processed from natural plant fibers.
Was used.

After kneading, the mixture was poured into a mold for a specimen, and allowed to cure for 91 days in an atmosphere of 20 ° C. and 65% RH.

Comparative Example A 0.32 part by weight of a high-performance shrinkage reducing agent alone was added to a concrete composition having the same specifications as in Example 1 above, and the mixture was poured into a mold and mixed under the same conditions as in Example 1. I left it to cure.

<< Comparison Results >> The changes in the surface condition of the concrete specimens obtained in Example 1 and Comparative Example with respect to the age are visually observed, and the changes in the material strength and the length thereof are measured. The results shown were obtained.

[0026]

[Table 1] However, ⊚ indicates that the surface is good, ○ indicates that the surface is slightly good, and Δ indicates that there are fine cracks.

Therefore, from the results of this table, the product of the present invention has a significantly smaller degree of dry shrinkage and cracking than the conventional product having the general composition, and the material strength is higher than that of the conventional product.
It was also confirmed that it was kept almost constant.

Example 2 Premixed mortar 70 parts by weight Water 19 parts by weight Polymer dispersion 11 parts by weight High performance shrinkage reducing agent 0.4 parts by weight In a mortar composition composed of 0.4 parts by weight of fine fibrous cellulose. Parts by weight were added at the same time when the mortar was mixed. As premix mortar, Nippon Cement Co., Ltd.'s trade name "Asano KSM # 30", as polymer dispersion, Daicel Chemical Industries' trade name "Cevian" (solid content 40%), high performance shrinkage reduction. As the agent, trade name "Tetraguard AS20" of Nippon Cement Co., Ltd., and as fine fibrous cellulose,
The product name “Cerish” manufactured by Daicel Chemical Industries, Ltd. was used.

Comparative Example A mortar composition having the same specifications as in the above-mentioned Example 2 was kneaded and mixed into a mortar in which fine fibrous cellulose was not added, and then the mixture was poured into a mold to obtain Example 2.
It was left to cure under the same conditions as above.

<< Comparison Results >> The changes in the surface condition of the mortar specimens obtained in Example 2 and Comparative Examples with respect to the age are visually observed, and the changes in the material strength and length thereof are measured. The results shown were obtained.

[0031]

[Table 2] However, ⊚ indicates that the surface is good, ○ indicates that the surface is slightly good, and Δ indicates that there are fine cracks.

Therefore, from the results shown in this table, the product of the present invention has a significantly lower degree of dry shrinkage cracking than the conventional product of the general composition, and the material strength is higher than that of the conventional product, and is kept almost constant. Was confirmed.

[0033]

As described above, according to the present invention, there is an advantage that the drying of mortar and concrete can be suppressed, and the shrinkage and cracking caused by the drying can be reduced. In addition, the fine fibrous cellulose kneaded has high alkali resistance and has an advantage that the reinforcing effect of the fibers can be improved.

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Eiji Sawada 1-2-23 Kiyosumi, Koto-ku, Tokyo Inside Central Research Institute, Japan Cement Co., Ltd. (72) Inventor Masao Kawahara 1-10-4 Minamidai, Kawagoe City, Saitama Prefecture Stock Company Shock Beton Japan (72) Inventor Takeshi Kawaji 4-640 Shimoseido, Kiyose City, Tokyo Inside Obayashi Technical Research Institute Co., Ltd. (72) Inventor Yuji Saito 4-640 Shimoseido, Kiyose City, Tokyo Obayashi Corporation Inside the Technical Research Institute (72) Yoshimasa Hayashi 4-640 Shimo-Seido, Kiyose-shi, Tokyo Obayashi Corporation Research Institute (72) Inventor Haruka Ogawa 4-640 Shimo-Seido, Kiyose-shi, Tokyo Incorporated Company Obayashi Technical Research In-house (72) Inventor, Ichifusa Mitani 4-640 Shimo-Seido, Kiyose-shi, Tokyo In-house Obayashi Technical Research Institute (56) Documents JP-A-3-285855 (JP, A) JP-A-8-40758 (JP, A) JP-A-3-50144 (JP, A) JP-A-5-229859 (JP, A) JP-A-56- 37258 (JP, A) JP 56-37259 (JP, A) JP 60-171262 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C04B ^7/ 00-32 / 02

Claims (4)

(57) [Claims] 1. A method for reducing dry shrinkage cracks of mortar or concrete, which comprises adding both fine fibrous cellulose and a shrinkage reducing agent during the production of mortar or concrete. 2. The shrinkage reducing agent is a shrinkage reducing agent comprising an amide compound and / or a modified amide compound, or a general formula RO (AO) nH (wherein R is an alkyl group having 1 to 7 carbon atoms or a carbon atom). A cycloalkyl group having 5 to 6 carbon atoms, A is one or two alkylene groups having 2 to 3 carbon atoms, and n is 1 to 1
The method for reducing dry shrinkage cracks of mortar or concrete according to claim 1, which is one or more kinds of shrinkage reducing agents consisting of a compound represented by the following formula. 3. Reduction of dry shrinkage cracks of mortar or concrete according to claim 1, wherein 0.5 to 5 parts by weight of fine fibrous cellulose is added to 100 parts by weight of the shrinkage reducing agent. Method. 4. The fine fibrous cellulose is mixed in advance with the shrinkage reducing agent or the remaining kneading water, or a mixture of the shrinkage reducing agent and the remaining kneading water. 4. The method for reducing dry shrinkage cracks of mortar or concrete according to any one of 3 above.