JP6414657B2 - Ultra low shrinkage concrete - Google Patents

Description

  The present invention relates to ultra-low shrinkage concrete having excellent drying shrinkage performance.

As is well known, it is inevitable that the concrete shrinks in the process of gradually drying after curing, and the drying shrinkage rate is 6 × 10 ⁻⁴ to 10 × 10 at the age of 6 months in general concrete. ^-4 (600 × 10 ^{−6 to} 1000 × 10 ⁻⁶ or 600 μ to 1000 μ in the conventional notation of drying shrinkage strain).

  As a result of such drying shrinkage, hardened concrete may crack, but in recent years there has been a strict demand for high durability and further quality improvements for concrete structures. Compared to the above, it is said that it is necessary to prevent the generation of fine cracks as much as possible. For that purpose, it is indispensable to sufficiently suppress the generation of cracks due to drying shrinkage.

Therefore, for example, as shown in Non-Patent Document 1, development of ultra-low-shrinkage concrete that can sufficiently reduce drying shrinkage is also in progress.
FIG. 2 shows an outline of the ultra-low shrinkage concrete shown in Non-Patent Document 1, and the material shown in (a) is kneaded with the blending shown in (b), so that the material shown in (c). It is disclosed that the drying shrinkage strain at the age of 6 months can be about 200 × 10 ^{−6 to} 500 × 10 ⁻⁶ .

Inagaki et al., "Study on cracking suppression effect of dry shrinkage 200μ class ultra low shrinkage concrete (Part 1. Fundamental properties of ultra low shrinkage concrete)", Annual Meeting of Architectural Institute of Japan (Hokuriku), September 2010, p.917-918.

The ultra-low shrinkage concrete shown in Non-Patent Document 1 above is characterized by using limestone as a coarse aggregate and using a shrinkage reducing agent, a high-performance AE water reducing agent and dihydrate gypsum as an admixture, In any case, the drying shrinkage strain is about 200μ class (about 200 × 10 ⁻⁶ . The current notation of drying shrinkage is about 2 × 10 ⁻⁴ ). Therefore, there is a limit to the crack suppression effect.

  In view of the above circumstances, the present invention provides an effective and suitable ultra-low shrinkage concrete that has a further excellent shrinkage shrinkage performance compared to the ultra-low shrinkage concrete shown in Non-Patent Document 1 and can further improve the crack suppression effect. The purpose is to do.

  In order to achieve the above object, the invention according to claim 1 is prepared using cement, coarse aggregate, fine aggregate, and water as main materials, and has a drying shrinkage ratio of 1.5 × 10 −4 at the age of 6 months. Ultra-low shrinkage concrete, which uses only limestone as a raw material for the coarse aggregate and the fine aggregate, and is mixed with an admixture having a viscosity of 10 to 200 mPa · s (20 ° C.). The material water ratio is 1.54 to 3.33.

Invention of Claim 2 is the ultra-low shrinkage concrete of Claim 1 , Comprising: The high purity limestone whose CaO component is 50% or more was used as said limestone, It is characterized by the above-mentioned.

According to a third aspect of the invention, a ultra-low shrinkage concrete according to claim 1 or 2, characterized in that a 10 to 30 kg / m3 in solid unit amount of the admixture.

The invention according to claim 4 is the ultra-low shrinkage concrete according to any one of claims 1 to 3 , wherein Portland cement is used as the cement, and normal cement or moderately heated cement or It is characterized by using low heat cement.

Invention of Claim 5 is the ultra-low shrinkage concrete of any one of Claims 1-4 , Comprising: The expansion | swelling material was mix | blended, It is characterized by the above-mentioned.

The ultra-low-shrinkage concrete of the present invention uses limestone as a raw material for both coarse aggregate and fine aggregate, and blends an admixture with a viscosity of 10 to 200 mPa · s (20 ° C.), resulting in a binder water ratio of 1. .54 to 3.33, so that the drying shrinkage performance is improved without impairing the original performance of concrete, including the separability of fresh concrete, and the dry shrinkage rate is 1.5 × 10 ⁻⁴ or less. It is possible to realize ultra-low shrinkage concrete having excellent dry shrinkage performance.
The ultra-low-shrinkage concrete of the present invention uses limestone as a raw material for both the coarse aggregate and the fine aggregate, and blends an admixture so that the concrete plastic viscosity is 10 to 200 Pa · s, and the binder water Since the ratio is 1.54 to 3.33, it is possible to realize an ultra-low shrinkage concrete having an unprecedented excellent dry shrinkage performance with a dry shrinkage ratio of 1.5 × 10 ⁻⁴ or less.

It is a figure which shows the ultra-low-shrinkage concrete by 1st Embodiment of this invention, and shows a use material, preparation, and a drying shrinkage rate test result. An example of the conventional ultra-low shrinkage concrete is a figure which shows a use material, a mixing | blending, and a drying shrinkage rate test result. The ultra-low-shrinkage concrete by 2nd Embodiment of this invention is shown, and is a figure which shows a use material and mixing | blending. (A), (b) is a figure which shows the relationship between the amount of thickeners of an admixture, and a viscosity. The test level of the plastic viscosity test of fresh concrete is shown. (A)-(c) shows the test level of a drying shrinkage rate test. It is a figure which shows the relationship between binder water ratio (B / W) and the plastic viscosity of fresh concrete. It is a figure which shows the drying shrinkage rate test result of the test body from which a water binder ratio and unit water amount differ. It is a figure which shows the drying shrinkage rate test result of the test body from which an expanding material kind and its quantity differ. It is a figure which shows the drying shrinkage rate test result of the test body from which a shrinkage | contraction reducing agent kind and its quantity differ. It is a figure which shows the drying shrinkage rate test result of the test body when not considering the case where the initial effect of an expansion material is considered.

FIG. 1 shows materials used for the ultra-low shrinkage concrete according to the first embodiment of the present invention, its composition, and its drying shrinkage characteristics.
The ultra-low shrinkage concrete of the first embodiment is prepared using cement, coarse aggregate, fine aggregate and water as main materials in the same manner as normal concrete, but the dry shrinkage ratio is 1.5 × 10 ^{−. In} order to make it ⁴ or less, as shown in (a), limestone is used as a raw material for both coarse and fine aggregates, and an admixture with a viscosity at 20 ° C. of 10 to 200 mPa · s (20 ° C.) is blended In particular, various shrinkage reducing agents, in particular, shrinkage reducing agents mainly composed of special polyoxyalkylene glycol are used as the admixture.

Since limestone as coarse aggregate itself is a raw material that hardly shrinks, it is well known to use limestone as coarse aggregate as shown in Non-Patent Document 1.
In addition, the use of limestone as a fine aggregate as well as coarse aggregate has been studied in the past. However, simply using limestone as a fine aggregate significantly reduces the separability of fresh concrete, and the concrete itself. Therefore, even when using limestone as coarse aggregate as shown in Non-Patent Document 1, it is necessary to use ordinary pile sand as fine aggregate. Conventionally common.

In the first embodiment, limestone is used not only for coarse aggregates but also for fine aggregates in order to further reduce the drying shrinkage rate than ultra-low shrinkage concrete shown in Non-Patent Document 1, and in that case A special admixture as described above is blended to prevent a decrease in separability.
That is, the ultra-low-shrinkage concrete according to the first embodiment uses limestone as a fine aggregate and a viscosity of 10 to avoid a decrease in separability when the drying shrinkage rate is improved by using limestone as a fine aggregate. It is an organic combination with an admixture of 200 mPa · s (20 ° C.), whereby the viscosity of fresh concrete is moderately improved to maintain separability.

Based on the above configuration, the ultra-low-shrinkage concrete according to the first embodiment has improved drying shrinkage performance without impairing the original performance of the concrete, including separability, and thus has a dry shrinkage ratio of 1.5 × 10 ^{− The} present invention was the first to realize an ultra-low shrinkage concrete having excellent dry shrinkage performance of ⁴ or less (150 × 10 ⁻⁶ (150 μm or less in accordance with the notation in Non-Patent Document 1)). is there.

  When preparing the ultra-low shrinkage concrete according to the first embodiment, as described above, limestone is used as both the coarse aggregate and the fine aggregate, and the admixture has a viscosity of 10 to 200 mPa · s (20 ° C.). As long as the material is used, the specific materials and blending are arbitrary, and the optimum blending design may be performed each time considering the concrete application to be constructed, required performance and other conditions. For example, it is preferable to use the material shown in FIG. 1A to obtain the composition shown in FIG.

That is, it is preferable to use Portland cement as cement, and non-Portland cement such as silica cement, fly ash cement, blast furnace cement and the like is not preferable.
Ordinary cement can also be used as Portland cement, but it is particularly preferable to use moderately hot cement or low heat cement that can suppress heat of hydration. It is optimal because it can improve the rate.

  When the purity of limestone as coarse aggregate and fine aggregate is low, the improvement effect may be somewhat impaired, so the CaO (calcium carbonate) component is at least 50% or more, preferably 55% or more. It is preferable to use pure limestone.

The admixture material is not limited to a shrinkage reducing agent mainly composed of a special polyoxyalkylene glycol, but may be any one including various shrinkage reducing agents and thickening agents as long as the viscosity is 10 to 200 mPa · s (20 ° C.). It is possible to adopt the admixture material.
Furthermore, it is also preferable to use various expansion materials, particularly lime-based, ettringite-based, or lime-ettringite-based expansion materials.

About blending, as shown in FIG. 1 (b), the water binder ratio (W / B) is 30 to 65%, the unit water amount is 175 kg / m ³ or less, and the unit coarse aggregate amount is 900 to 1100 kg / m ^3. The unit amount of the admixture is preferably 10 to ³⁰ kg / m ³ in terms of solid content, and when an expander is used, the unit amount is preferably 10 to ³⁰ kg / m ³ .

FIG.1 (c) shows the drying shrinkage test result with respect to the ultra-low shrinkage concrete of this invention by the said mixing | blending, and shows one of the drying shrinkage test results in the nonpatent literature 1 shown in FIG.2 (c) as a comparative example. Part (results for samples No. 55-20 and No. 47-20 for which the best results are obtained) are shown in FIG.
As shown in FIG. 1C, the conventional 200 μ class ultra-low shrinkage concrete shown in Non-Patent Document 1 has 2 × 10 ⁻⁴ (200 μ) even when the dry shrinkage rate at the age of 6 months is the best. On the other hand, the ultra-low shrinkage concrete of the present invention has an excellent dry shrinkage performance of 100 μ class if it is slightly over 1 × 10 ⁻⁴ , and the present invention has a dry shrinkage rate of It was confirmed that the intended purpose of realizing ultra-low shrinkage concrete of 1.5 × 10 ⁻⁴ or less could be sufficiently achieved.

Next, FIG. 3 to FIG. 10 show the materials used for the ultra-low-shrinkage concrete according to the second embodiment of the present invention, its preparation, and its drying shrinkage characteristics.
The ultra-low-shrinkage concrete according to the second embodiment is prepared using cement, coarse aggregate, fine aggregate, and water as main materials in the same manner as the ultra-low-shrinkage concrete of the first embodiment, and has a dry shrinkage ratio of 1.5 ×. Limestone is used as a raw material for coarse aggregate and fine aggregate so as to be 10 ⁻⁴ or less.
And in 1st Embodiment, although the admixture whose viscosity in 20 degreeC is 50-200 mPa * s is mix | blended, in 2nd Embodiment, the plastic viscosity of fresh concrete is set to 10-200 Pa * s. Contains admixtures.
In the second embodiment, the materials other than the admixture are the same as those in the first embodiment, and the description of the materials other than the admixture is omitted.

  When preparing the ultra-low shrinkage concrete according to the second embodiment, limestone is used as the coarse aggregate and the fine aggregate as in the first embodiment, and the plastic viscosity of the fresh concrete is 10 to 200 Pa · s. As long as the admixture is blended, the specific materials used and blending are arbitrary, and the optimum blending design is performed each time considering the concrete application, required performance and other conditions. However, if one specific example is given, for example, it is preferable to use the material shown in FIG.

As shown in FIG. 3, a shrinkage reducing agent and a thickening agent are used as the admixture.
Examples of the shrinkage reducing agent include alkylene oxide adducts of lower alcohols, copolymers of low molecular weight ethylene oxide and propylene oxide, special polyoxyalkylene glycols, and the like as main components.
Examples of the thickener include powdered water-soluble cellulose ether, alkylammonium salt, alkylallylsulfonate, and the like.
The material used as the admixture may be other than the above.

Here, the thickener is used together with the shrinkage reducing agent when the desired viscosity of the fresh concrete cannot be obtained when only the shrinkage reducing agent is used as the admixture, and the plastic viscosity of the fresh concrete is adjusted to 10 to 10. Used for 200 Pa · s.
In the second embodiment, only the shrinkage reducing agent, or the shrinkage reducing agent and the thickening agent are used as admixtures, and the plastic viscosity of the fresh concrete is set to 10 to 200 Pa · s.

Here, regarding the admixture, the relationship between the amount of thickener mixed in the shrinkage reducing agent and its viscosity will be described.
The viscosity of the admixture was measured using a B-type viscometer. The viscosity of the admixture is preferably 10 to 200 mPa · s (20 ° C.).
As shown in FIG. 4 (a), when the shrinkage reducing agent of the admixture is an alkylene oxide adduct of a lower alcohol (solid content: 12 kg / con · m ³ ), if a thickener is used, the mixing amount is reduced. It can be seen that the viscosity increases proportionally.
As shown in FIG. 4B, when the shrinkage reducing agent of the admixture is a copolymer with low molecular weight ethylene oxide (solid content: 12 kg / con · m ³ ), a thickener is used. It can be seen that the viscosity increases proportionally with the mixing amount.

As described above, when the admixture used is a lower alcohol alkylene oxide adduct or a low-molecular-weight copolymer of ethylene oxide and propylene oxide as a shrinkage reducing agent, a thickener (water-soluble) is used. In the case of using a special polyoxyalkylene glycol as a main component as a shrinkage reducing agent, it is preferable to use only a shrinkage reducing agent without mixing a thickener.
And in mix | blending concrete, the shrinkage | contraction reducing agent (solid content) mixing amount shall be 10-30 kg / m < ³ >, and the mixing amount of a thickener shall be 0-0.6 kg / m < ³ >.

  Here, when preparing the cement paste, compared with the conventional method in which a thickener is added to the cement and mixed, and then a mixture of water and a shrinkage reducing agent is added and mixed. The method of mixing and mixing the mixture of the shrinkage reducing agent and the thickening agent afterwards increases the degree of concrete kneading and prepares a homogeneous cement paste in a short time. I was able to confirm.

5 and 6 show the test level of the dry shrinkage test for the ultra-low shrinkage concrete according to the second embodiment. FIG. 5 shows, as level A, the type of shrinkage reducing agent, the water binder ratio, and the unit amounts of various materials for testing the plastic viscosity of fresh concrete. FIG. 6A shows the dry shrinkage rate (water binder ratio and unit water amount) as level B, FIG. 6B shows the dry shrinkage rate (expansion material type and amount) as level C , and FIG. ) Shows, as level D, the water binder ratio for testing the drying shrinkage rate (kind and amount of shrinkage reducing agent), and unit amounts of various materials.
In FIGS. 5 and 6, (1) of the expansion material is lime-based, (3) is a lime-ettringite-based expansion material, and (1) of the shrinkage reducing agent is an alkylene oxide adduct of a lower alcohol as a main component. (2) shows a main component of a copolymer of low molecular weight ethylene oxide and propylene oxide, and (3) shows a main component of a special polyoxyalkylene glycol.
Moreover, in this embodiment, drying is started on the material age 7th.

From FIG. 7, it was confirmed that the plastic viscosity of fresh concrete was 10 to 200 (Pa · s) in the range of the binder water ratio of 1.54 to 3.33 (water binder ratio of 65 to 30%). .
And from FIG. 8 thru | or 10, it has confirmed that the test body with a water binder ratio of 65-30% became 1.5 * 10 < ^-4 > or less in the drying shrinkage rate in material age 6 months.
Thereby, also in the second embodiment, it is confirmed that the intended purpose of realizing ultra-low-shrinkage concrete having a drying shrinkage rate of 1.5 × 10 ⁻⁴ or less at the age of 6 months can be sufficiently achieved. did it.

It is known that the expansion material exerts its effect before the drying period (age 0 to 7 days), so that the effect on the drying shrinkage of the concrete during the drying period (after 7 days of age) is minor. Yes.
However, since the effect of the expanding material before the drying period is −1 × 10 ⁻⁴ or more in terms of drying shrinkage, considering the effect of the expanding material, as shown in FIG. An ultra-low shrinkage concrete having a rate corresponding to 0.5 × 10 ⁻⁴ or less can be realized.
In addition, when the plastic viscosity of fresh concrete is outside the range of 10 to 200 (Pa · s), separation occurs, so that it does not hold as concrete, and the drying shrinkage at 6 months of age is 1.5 ×. It was found to exceed 10 ⁻⁴ .

Claims (5)

Cement, coarse aggregate, fine aggregate, and water are prepared as main materials, and the ultra-low shrinkage concrete has a dry shrinkage rate of 1.5 × 10 −4 or less at the age of 6 months,
While using only limestone as a raw material of the coarse aggregate and the fine aggregate, an admixture having a viscosity of 10 to 200 mPa · s (20 ° C.) is blended, and a binder water ratio is 1.54 to 3.33. Ultra-low shrinkage concrete characterized by The ultra-low shrinkage concrete according to claim 1 ,
An ultra-low shrinkage concrete characterized in that a high-purity limestone having a CaO component of 50% or more is used as the limestone. The ultra-low shrinkage concrete according to claim 1 or 2 ,
An ultra-low shrinkage concrete characterized in that a unit amount of the admixture is 10 to 30 kg / m 3 in terms of solid content. The ultra-low shrinkage concrete according to any one of claims 1 to 3 ,
An ultra-low shrinkage concrete characterized in that Portland cement is used as the cement, and ordinary, medium-heated or low heat cement is used as the Portland cement. The ultra-low shrinkage concrete according to any one of claims 1 to 4 ,
Ultra-low shrinkage concrete characterized by blending expansion material.

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