JP2021130570A - Cement composition, method of producing the same, and mortar - Google Patents

Abstract

To provide a cement composition exhibiting resistance to separation of materials in the form of mortar, excellent in flow property and a serviceable life, exhibiting small drying shrinkage when hardened, and excellent in capability of developing strength.SOLUTION: The cement composition comprises cement, a pozzolan material, a blowing material, a shrinkage reducer, a thickener, and fine aggregate. The thickener has viscosity at 20°C of 100 to 5000 mPa s in the form of 2 mass% aqueous solution, with the content of the shrinkage reducer being 1 to 10 pts.mass and the content of the pozzolan material being 3 to 38 pts.mass, relative to 100 pts.mass of the cement.SELECTED DRAWING: None

Description

The present invention relates to a cement composition, a method for producing the same, and a mortar.

Cement-based grout mortar with high fluidity is widely used in the construction or repair of civil engineering structures and building structures, or in the installation of machines. In recent years, high durability has been required for civil engineering structures and building structures, and the grout mortar used has high fluidity and workability, as well as crack suppression due to drying shrinkage, strength development, and salt shielding properties. , Various properties such as neutralization measures are emphasized.

Conventionally, such a material contains a swelling material, a re-emulsifying powder resin, an aggregate, a fibrous material, a shrinkage reducing agent, a water reducing agent, and a defoaming agent, and has excellent fluidity and durability, and has a cross section of concrete. Known polymer cement compositions (see Patent Document 1) that can be suitably used for repair and repair applications, and polymer cement grout materials (see Patent Document 2) that have a high fluidity of 6 to 10 seconds in a J14 funnel flow time. There is.

Japanese Patent No. 4439957 Japanese Patent No. 5335176

By the way, as a grout mortar, fluidity and pot life are required, and a grout mortar having a small amount of curing shrinkage and excellent strength development is required. Furthermore, since it is used for pumping, it is resistant to material separation. Is also required. However, it has been difficult to achieve both such performance.

Therefore, an object of the present invention is to provide a cement composition which has material separation resistance as a mortar, is excellent in fluidity and pot life, has small drying shrinkage during curing, and is also excellent in strength development. And.

As a result of diligent studies on the above problems, the present inventors have material separation resistance as a mortar by adjusting the content of a shrinkage reducing agent and a pozzolan substance by using a thickener having a specific viscosity. It has been found that a cement composition having excellent fluidity and pot life, small drying shrinkage during curing, and excellent strength development can be obtained.

That is, the present invention is the following [1] to [9].
[1] Includes cement, pozzolan material, swelling material, shrinkage reducing agent, thickener and fine aggregate.
The thickener has a viscosity of 2% by mass aqueous solution at 20 ° C. and is 100 to 5000 mPa · s.
A cement composition having a shrinkage reducing agent content of 1 to 10 parts by mass and a pozzolan substance content of 3 to 38 parts by mass with respect to 100 parts by mass of cement.
[2] The cement composition according to [1], further comprising a re-emulsified powder resin.
[3] The cement composition according to [1] or [2], further comprising a water reducing agent.
[4] The cement composition according to any one of [1] to [3], which further contains a foaming agent.
[5] The cement composition according to any one of [1] to [4], wherein the coarse grain ratio of the fine aggregate is 2.0 to 3.6.
[6] The cement composition according to any one of [1] to [5], wherein the shrinkage reducing agent is a liquid shrinkage reducing agent, or a powder shrinkage reducing agent and a liquid shrinkage reducing agent.
[7] The cement composition according to [6], wherein the surface is coated with a liquid shrinkage reducing agent.
[8] The method for producing a cement composition according to [6] or [7], wherein the liquid shrinkage reducing agent is sprayed on the entire premix material mixed with the powder component other than the liquid shrinkage reducing agent.
[9] A mortar containing the cement composition according to any one of [1] to [7] and water, wherein the content of water is 35 to 60 parts by mass with respect to 100 parts by mass of cement.

According to the present invention, it is possible to provide a cement composition which has material separation resistance as a mortar, is excellent in fluidity and pot life, has small drying shrinkage during curing, and is also excellent in strength development. ..

Hereinafter, one embodiment of the present invention will be described in detail.

The cement composition of this embodiment contains a cement, a pozzolanic substance, a swelling material, a shrinkage reducing agent, a thickener and a fine aggregate.

Various cements can be used, such as ordinary, early-strength, ultra-fast-strength, low-heat, and moderate-heat, various Portland cements, and various mixed cements in which blast furnace slag, fly ash, or silica fumes are mixed with these Portland cements. Examples include filler cement mixed with fine powder of blast furnace slow-cooled slag such as limestone powder, and environment-friendly cement (eco-cement) produced from various industrial wastes as the main raw material. One type of cement may be used alone, or two or more types may be used in combination. The cement preferably has a relatively small degree of powder from the viewpoint of easily imparting high fluidity, and ordinary Portland cement or early-strength Portland cement is preferable.

Examples of the pozzolan material include various fly ash described in JIS A 6201: 2015, silica fume described in JIS A 6207: 2016, slag powder, amorphous aluminosilicate and the like. One type of pozzolan substance may be used alone, or two or more types may be used in combination.

The content of the pozzolanate is 3 to 38 parts by mass with respect to 100 parts by mass of cement. If the content of the pozzolanic substance is out of the above range, the material separation resistance, fluidity and pot life will decrease. From the viewpoint of further improving the material separation resistance and durability, the content of the pozzolanate is preferably 4 to 35 parts by mass, more preferably 6 to 30 parts by mass with respect to 100 parts by mass of cement. preferable.

The expansion material may be any expansion material as long as it is a JIS-compliant expansion material (JIS A 6202: 2008) generally used as an expansion material for concrete. Examples of the expansion material include an expansion material containing free quicklime as a main component (quicklime-based expansion material), an expansion material containing Irwin as a main component (ettringite-based expansion material), and a composite expansion material of free quicklime and an ettringite-producing substance. Can be mentioned. As the expansion material, one type may be used alone, or two or more types may be used in combination. It is preferable to use an expansion material having a brain specific surface area of 2000 to 6000 cm ^{2 / g.}

The content of the expansive material is preferably 2 to 8 parts by mass, more preferably 2.5 to 7 parts by mass, and further preferably 3 to 6 parts by mass with respect to 100 parts by mass of cement. .. When the content of the expanding material is within the above range, the denseness of the cured product is further improved, and the strength development and durability tend to be excellent.

As the shrinkage reducing agent, for example, a polyoxyalkylene compound, a polyether compound, an alkylene oxide compound, or the like can be used. Specific examples of the shrinkage reducing agent include polyoxyethylene / alkylallyl ether, polypropylene glycol, triethylene glycol, lower alcohol alkylene oxide adduct, glycol ether / amino alcohol derivative, polyether, polyoxyalkylene glycol, and ethylene oxide methanol addition. Examples thereof include ethylene oxide / propylene oxide polymers, phenyl / ethylene oxide polymers, cycloalkylene / ethylene oxide polymers, and dimethylamine / ethylene oxide polymers. One type of shrinkage reducing agent may be used alone, or two or more types may be used in combination.
The shrinkage reducing agent can be either a liquid shrinkage reducing agent or a powder shrinkage reducing agent, and can be used in combination. As the shrinkage reducing agent, a liquid shrinkage reducing agent is preferable from the viewpoint of further reducing dust.

The content of the shrinkage reducing agent is 1 to 10 parts by mass with respect to 100 parts by mass of cement. If the content of the shrinkage reducing agent is out of the above range, the material separation resistance is lowered or drying shrinkage occurs. From the viewpoint of further reducing drying shrinkage, the content of the shrinkage reducing agent is preferably 1.5 to 9.5 parts by mass and 2 to 9 parts by mass with respect to 100 parts by mass of cement. More preferred. When the shrinkage reducing agent is a liquid, its content shall be converted by the amount of the active ingredient.

The thickener is not particularly limited, and examples thereof include a cellulosic thickener, an acrylic thickener, and a guar gum thickener. As the thickener, a cellulosic thickener is particularly preferable. Examples of the cellulosic thickener include carboxymethyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose.

As the thickener, one having a viscosity of a 2% by mass aqueous solution at 20 ° C. of 100 to 5000 mPa · s is used. If the viscosity of the thickener is out of the above range, the kneadability of the grout is lowered, the fluidity and the holding time cannot be secured, and the material separation resistance is also lowered. From the viewpoint of ensuring better fluidity, holding time, and material separation resistance, the viscosity of the thickener is preferably 150 to 4500 mPa · s, more preferably 200 to 3000 mPa · s. It is more preferably 200 to 2500 mPa · s. In the present specification, the viscosity of the thickener is measured by measuring an aqueous solution of the thickener prepared so as to be 2% by mass using a single cylindrical rotary viscometer (B type) in an environment of 20 ° C. It is the value that was set. As the rotary viscometer, a commonly used one can be used. For example, an inner cylinder rotary viscometer and an outer cylinder rotary viscometer can be used.

The content of the thickener is not particularly limited, but is preferably 0.01 to 0.3 parts by mass, and 0.02 to 0.25 parts by mass in terms of solid content with respect to 100 parts by mass of cement. Is more preferable, and 0.03 to 0.2 parts by mass is further preferable. When the content of the thickener is within the above range, it is easy to secure good fluidity.

The fine aggregate is not particularly limited, and examples thereof include river sand, silica sand, crushed sand, cold water stone, limestone sand, and slag aggregate. Among these, it is preferable to use silica sand as the fine aggregate from the viewpoint of further excellent strength development at the time of spraying. As the fine aggregate, one type may be used alone, or two or more types may be used in combination.

The particle size of the fine aggregate is preferably particles having a particle size of 5 mm or less, preferably a coarse grain ratio (FM) of 2.0 to 3.6, and more preferably 2.8 to 3.2. .. When the coarse grain ratio of the fine aggregate is within the above range, the fluidity and material separation resistance are further excellent.

The content of the fine aggregate is preferably 150 to 280 parts by mass, more preferably 170 to 260 parts by mass, and further preferably 180 to 240 parts by mass with respect to 100 parts by mass of cement. When the content of the fine aggregate is within the above range, it is easy to secure good fluidity and pot life.

The cement composition of the present embodiment can further contain a re-emulsified powder resin, and can further improve the adhesiveness to a skeleton such as an RC structure. The re-emulsified powder resin is not particularly limited as long as it is a polymer that can be used for polymer cement in terms of composition. Examples of the re-emulsified powder resin include re-emulsified powder resins specified in JIS A 6203: 2015. Specifically, acrylic copolymers, vinyl acetate copolymers, and styrene-butadiene copolymers are used. Examples thereof include polymers, vinyl acetate / vinyl versaticate copolymers, ethylene / vinyl acetate copolymers, vinyl acetate / vinyl versaticate / acrylic acid ester-based copolymers and the like. As the re-emulsified powder resin, one type may be used alone, or two or more types may be used in combination. Among the re-emulsified powder resins, an acrylic copolymer is preferable from the viewpoint of further excellent water resistance.

The content of the re-emulsified powder resin is preferably 2 to 15 parts by mass and more preferably 3 to 10 parts by mass with respect to 100 parts by mass of cement from the viewpoint of further excellent adhesion. It is more preferably 4 to 9 parts by mass.

The low-shrinkage, high-fluidity cement composition of the present embodiment preferably further contains a water-reducing agent from the viewpoint of reducing the unit water amount and suppressing drying shrinkage. The water reducing agent is not particularly limited, but it is preferable to use a polycarboxylic acid system (polycarboxylic acid polymer, polycarboxylic acid polymer compound and crosslinked polymer, etc.) from the viewpoint of maintaining high fluidity for a long time. In addition, as other water reducing agents, naphthalene-based and melamine-based (melamine sulfonic acid and modified lignin, modified methylose melamine condensate and water-soluble special polymer, etc.) are used as long as the effects of the present invention are not impaired. You may use it. One type of water reducing agent may be used alone, or two or more types may be used in combination.

The content of the water reducing agent is preferably 0.1 to 2 parts by mass in terms of solid content with respect to 100 parts by mass of cement from the viewpoint of easily reducing the unit water amount, and is 0.15 to 1.7 parts by mass. It is more preferably parts, and even more preferably 0.2 to 1.3 parts by mass.

The low-shrinkage, high-fluidity cement composition of the present embodiment preferably further contains a foaming agent from the viewpoint of imparting non-shrinkage. The type of foaming agent is not limited, and specifically, any substance that generates gas after kneading with water may be used. Examples of the foaming agent include powders of amphoteric metals such as aluminum and zinc, and peroxide substances. Among the foaming agents, aluminum powder is preferable because it is easy to obtain a swelling action.

The content of the foaming agent is preferably 0.0001 to 0.08 parts by mass, more preferably 0.0002 to 0.03 parts by mass, and 0.0003 to 0 parts by mass with respect to 100 parts by mass of cement. It is more preferably 0.01 parts by mass. When the content of the foaming agent is within the above range, sufficient expandability can be easily obtained, and integration with the structure can be easily achieved.

In addition to the above components, the low shrinkage and high fluidity cement composition of the present invention can be added with other materials used for mortar and concrete as long as the effects of the present invention are not impaired. Other materials include, for example, fibers, Glauber's salt, gypsum, stone powder, slag powder, inorganic fillers, defoamers, accelerators, retarders and the like. Other materials may be used alone or in combination of two or more.

The method for premixing the cement composition is not particularly limited, but for example, a ribbon mixer or paddle mixer that has a relatively small shearing action and mainly mixes the dispersing action and the diffusing action by scraping with a paddle or a blade. Etc. can be mixed. For mixing, all the raw materials may be mixed, weighed and put into the mixing mixer and then kneaded. If the shrinkage reducing agent is a liquid, all the raw materials other than the liquid shrinkage reducing agent are mixed, weighed and put into the mixing mixer. After that, the liquid shrinkage reducing agent may be sprayed while mixing using a liquid sprayer and dispersed throughout the premix material. From the viewpoint of further reducing the generation of dust when the premix material is kneaded with water, a method of spraying the liquid shrinkage reducing agent on the entire premix material is preferable.
This makes it possible to obtain a cement composition whose surface is coated with a liquid shrinkage reducing agent.

The cement composition of the present embodiment can be prepared as a mortar by mixing with water, and the content of the water may be appropriately adjusted according to the intended use. The water content is preferably 35 to 60 parts by mass, more preferably 36 to 57 parts by mass, and even more preferably 37 to 55 parts by mass with respect to 100 parts by mass of cement. When the water content is within the above range, it is easy to secure fluidity and material separation resistance, and the strength development tends to be good.

The cement composition and cement mortar of the present embodiment are excellent in material separation resistance, fluidity and pot life, have small drying shrinkage during curing, and have good strength development. Therefore, the cement composition and mortar of the present embodiment can also be used as repair / reinforcing materials for concrete structures, steel / concrete composite structures, and the like. The method of using the cement composition and mortar of the present embodiment can be appropriately selected. For example, by increasing or decreasing the water ratio and adjusting the fluidity, in addition to the pouring method into the mold, the spraying method and the recess can be used. You can select the plastering method for filling with a trowel.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto.

The materials used in the examples are as follows.
Cement: Ordinary Portland cement Pozzolan substance: A mixture of fly ash (JIS type II) and amorphous aluminosilicate compound (mass of fly ash: mass of amorphous aluminosilicate compound = 3: 2)
Expansion material: Lime-based expansion material Liquid shrinkage reducing agent: Lower alcohol alkylene oxide adduct Powder shrinkage reducing agent: Lower alcohol alkylene oxide adduct thickener A: Water-soluble cellulose ether (20 ° C., viscosity of 2% by mass aqueous solution) : 307 mPa · s)
Thickener B: Water-soluble cellulose ether (viscosity of 2% by mass aqueous solution at 20 ° C.: 4140 mPa · s)
Thickener B: Water-soluble cellulose ether (viscosity of 2% by mass aqueous solution at 20 ° C.: 30740 mPa · s)
Water reducing agent A: Polycarboxylic acid-based high-performance water reducing agent Water reducing agent B: Naphthalene sulfonic acid-based water reducing agent Re-emulsifying powder Resin: Acrylic copolymer resin Foaming agent: Aluminum powder Fine aggregate: Silica sand adjusted product (coarse grain ratio 2. The particle size was adjusted to 6 to 3.6)

[Experimental Example 1]
<Manufacturing of cement composition>
Materials other than the liquid shrinkage reducing agent were mixed at the blending ratios shown in Table 1 and charged into a Henschel mixer, and the liquid shrinkage reducing agent was sprayed while mixing to produce a cement composition. As the shrinkage reducing agent, a powdery one and a liquid one were used in equal amounts.

<Manufacturing of mortar>
The prepared cement composition and water were kneaded with a high-speed hand mixer for 90 seconds to prepare a mortar. The proportion of water is as shown in Table 1.

<Evaluation of mortar>
The fluidity, fluidity retention time, and material separation resistance of the prepared mortar (Products 1 to 6 of the present invention and Reference products 2 to 5) in the fresh properties were measured and evaluated. Each evaluation test method is shown below.
〔Liquidity〕
The cement paste container (flow cone) of JIS R5201-1997 "Physical test method for cement" was filled with mortar, and the table flow value after the container was pulled up was measured.
[Workability retention time]
As for the workability holding time, the fluidity 90 minutes after kneading was confirmed by the table flow value of the above test. Those having a table flow value of 200 mm or more were judged to be good, and those having a table flow value of less than 200 mm were judged to be unacceptable.
[Material separation resistance]
Material separation resistance was confirmed by the presence or absence of aggregate separation and the presence or absence of bleeding.
For aggregate separation, when the mortar after kneading in the container is checked by putting a hand, the mortar is not uniform and the tactile sensation of fine aggregate is recognized on the bottom surface of the container. The case where the tactile sensation of the fine aggregate was not observed on the bottom surface of the container was defined as no aggregate separation.
The bleeding was in accordance with JIS A 1123: 2011, and it was confirmed whether or not bleeding occurred in the mortar 2 hours after kneading, and some bleeding occurred and some did not.
From these results, it was judged that "none" was good and "yes" was not possible.

Table 2 shows the evaluation results of the fresh properties. In each of the examples of the present invention, it was confirmed that the flow value immediately after kneading had high fluidity of 270 mm or more, and the flow value after 90 minutes also maintained 200 mm or more. In addition, it was shown that it had excellent material separation resistance without the occurrence of aggregate separation and bleeding.

[Experimental Example 2]
<Evaluation of curing properties of mortar>
The drying shrinkage and compressive strength of the prepared mortar (Products 1 to 6 of the present invention, Reference products 1 and 6) in the curability property were measured and evaluated. Each evaluation test method is shown below.
[Dry shrinkage]
Using a specimen molded into a 4 × 4 × 16 cm steel mold with a gauge plug, the dimensional change rate was measured according to NEXCO cross-section repair mortar: test method 432. After 48 hours from molding, the cured specimen was demolded and cured in a constant temperature and humidity chamber set at a temperature of 23 ± 3 ° C. and a humidity of 50 ± 5 ° C.
[Compressive strength]
Compressive strength was measured for a 28-day-old specimen in accordance with JIS R5201: 1997 "Physical test method for cement". For curing, the cured specimen was removed 48 hours after molding, and aerial curing was performed in a laboratory at 20 ° C. and RH 60% until the age of 28 days.

Table 3 shows the evaluation results of the curability property. In the specimens of the examples, the dimensional change rate was 500 × ^10-6 or less at 91 days of age, and good low shrinkage was confirmed. In addition, it was confirmed that the compressive strength of the specimens of the examples was 50 N / mm ^{2 or more at the age of 28 days.}

[Experimental Example 3]
In the cement compositions of the products 1 to 3 of the present invention in Table 1, a material in which 0.03 part by mass of a foaming agent is externally added to 100 parts by mass of cement is used as a material other than the liquid shrinkage reducing agent as in Experimental Example 1. Was mixed and put into a Henschel mixer, and a liquid shrinkage reducing agent was sprayed while mixing to produce a cement composition. Using the prepared cement composition, 45 parts by mass of water was added to 100 parts by mass of cement and kneaded with a high-speed hand mixer for 90 seconds to prepare a mortar.

In order to evaluate the non-shrinkability of the prepared mortar, the initial expansion rate was measured. The evaluation test method is shown below.
[Initial expansion coefficient test]
The initial expansion coefficient was measured according to JSCE-F-533 “PC grout bleeding rate and expansion coefficient test method”.

The test results are shown in Table 4. All of the specimens of the examples had an expansion / contraction rate of +0.5 to 1.2% on the expansion side on the day of age, and showed good non-contraction.

Claims (9)

Contains cement, pozzolan material, swelling material, shrinkage reducing agent, thickener and fine aggregate,
The thickener has a viscosity of a 2% by mass aqueous solution at 20 ° C. and is 100 to 5000 mPa · s.
A cement composition having a shrinkage reducing agent content of 1 to 10 parts by mass and a pozzolan substance content of 3 to 38 parts by mass with respect to 100 parts by mass of cement. The cement composition according to claim 1, further comprising a re-emulsified powder resin. The cement composition according to claim 1 or 2, further comprising a water reducing agent. The cement composition according to any one of claims 1 to 3, further comprising a foaming agent. The cement composition according to any one of claims 1 to 4, wherein the coarse grain ratio of the fine aggregate is 2.0 to 3.6. The cement composition according to any one of claims 1 to 5, wherein the shrinkage reducing agent is a liquid shrinkage reducing agent, or a powder shrinkage reducing agent and a liquid shrinkage reducing agent. The cement composition according to claim 6, wherein the surface is coated with the liquid shrinkage reducing agent. The method for producing a cement composition according to claim 6 or 7, wherein the liquid shrinkage reducing agent is sprayed on the entire premix material mixed with the powder component other than the liquid shrinkage reducing agent. Contains the cement composition and water according to any one of claims 1 to 7.
A mortar having a water content of 35 to 60 parts by mass with respect to 100 parts by mass of the cement.