JP2018184329A - High fluidity concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly fluid concrete in which the amount of unit cement is suppressed. A highly fluid concrete containing cement, water, an aggregate, a thickener, and a high-performance AE water-reducing agent, wherein the thickener is made of a water-soluble cellulose ether, and the high-performance AE water-reducing agent is used. The agent has a water reduction rate of 18% or more, a water-cement ratio of 47.5% or more and 65% or less, and a slump flow of 35 cm or more and 75 cm or less as specified in JIS A 6204. [Selection diagram] None

Description

  The present invention relates to concrete with high fluidity.

  Highly fluid concrete obtained by adding an admixture to commonly used concrete (ordinary concrete) is known. High fluidity concrete includes what are called high fluidity concrete and medium fluidity concrete obtained by adding an admixture (water reducing agent) in a different composition from ordinary concrete.

  Since the high fluidity concrete has a high fluidity of a slump flow of about 50 to 70 cm, the concrete itself can pass through the gaps of the reinforcing bar structure and can be uniformly filled to every corner of the formwork. Therefore, since the compacting work at the time of concrete construction (work which gives vibration by the vibrator to the concrete poured into the mold) can be omitted, the workability is remarkably improved.

  Moreover, since the medium fluidity concrete has a high fluidity of about slump flow 35 to 50 cm, the fluidity and the filling property to the reinforcing bar structure are higher than that of ordinary concrete, and the compacting operation can be simplified.

JP 2012-116671 A

  However, high fluid concrete and medium fluid concrete need to increase the unit cement amount (powder amount) more than ordinary concrete in order to ensure material separation resistance commensurate with high fluidity.

For example, the unit cement amount of ordinary concrete used in the general civil engineering field is 300 kg / m ³ or less, whereas high fluid concrete requires a unit cement amount of 500 kg / m ³ or more, for example.

Moreover, a one-pack type high-performance AE water reducing agent containing a thickening component is known as an admixture. However, even when such a high-performance AE water reducing agent is added, the unit cement amount is 400 kg / m ³ or more for high fluid concrete, and the unit cement amount is 350 kg / m ³ or more for medium fluid concrete. .

  That is, the conventional high-fluidity concrete and medium-fluidity concrete have a large unit cement amount, and thus the ratio of the unit water amount to the unit cement amount (water cement ratio) becomes small. Moreover, when the amount of unit cement increases, the hydration calorific value of cement increases, and cracks and the like are likely to occur when the concrete is hardened. Furthermore, the material cost of concrete increases due to the increase in the amount of unit cement.

  An object of this invention is to provide the concrete with high fluidity | liquidity which suppressed the amount of unit cement.

To achieve the above object, the present invention provides a highly flowable concrete containing cement, water, aggregate, thickener, and high-performance AE water reducing agent, wherein the thickener is a water-soluble cellulose ether. The high-performance AE water reducing agent has a water reduction rate of 18% or more as defined in JIS A 6204, a water cement ratio of 47.5% or more and 65% or less, and a slump flow of 35 cm or more and 75 cm or less. is there.
Further, the highly fluid concrete of the present invention has a filling height of 30 cm or more (obstruction: rank 2) as defined in the 2012 Standard Specification for Concrete [Construction], the slump flow is 55 cm or more and 75 cm or less, and It is preferable that the high flow concrete has a flow arrival time of 500 mm for 3 to 15 seconds.
Alternatively, the high fluidity concrete of the present invention has a filling height of 28 cm or more (obstruction: rank 3) defined by the East, Middle and West Japan Expressway Tunnel Construction Management Guidelines, and the slump flow is 35 cm or more and 50 cm. The following medium fluidity concrete is preferable.
Moreover, it is preferable that the unit water amount of the water is 185 kg or less per 1 m ³ of the highly fluid concrete.

  According to the highly fluid concrete of the present invention, the unit cement amount can be suppressed.

== Embodiment ==
This embodiment relates to concrete with high fluidity containing cement, water, aggregate, thickener, and high-performance AE water reducing agent. In the present embodiment, high fluidity concrete includes high fluidity concrete (self-filling concrete) and medium fluidity concrete.

  High fluidity concrete is concrete having a filling height of 30 cm or more (obstruction: rank 2) as defined in the 2012 Standard Specification for Concrete (Construction), and a slump flow of 55 cm or more and 75 cm or less. In addition, the high fluidity concrete has a 500 mm flow arrival time of 3-15 seconds as defined in the 2012 Standard Specification for Concrete [Construction], and the bleeding rate based on JIS A 1123 is equal to or less than that of ordinary concrete. It is preferable. The high-fluid concrete is used for a structure adopting a reinforced concrete structure (RC structure), for example.

  On the other hand, medium-fluid concrete refers to concrete having a filling height of 28 cm or more (obstruction: rank 3) specified in the East, Middle and West Japan Highway Tunnel Construction Management Guidelines and a slump flow of 35 cm to 50 cm. . Moreover, it is preferable that the medium fluidity concrete has a bleeding rate based on JIS A 1123 equal to or less than that of ordinary concrete. Medium fluidity concrete is used, for example, as tunnel lining concrete.

[Cement, water, aggregate]
As the cement, water, and aggregate, various materials used in normal concrete production can be used.

  The cement is, for example, Portland cement (ordinary Portland cement, early-strength Portland cement, moderately hot Portland cement, etc.) or mixed cement (blast furnace cement, fly ash cement, etc.). The water is, for example, tap water or “water other than tap water” shown in JIS A5308.

The water cement ratio in the highly fluid concrete according to the present embodiment is 47.5% or more and 65% or less. For example, when the unit water amount in concrete with high fluidity is 175 kg per m ^{3 of} concrete, the unit cement amount in concrete with high fluidity is about 269 kg to about 368 kg per m ^{3 of} concrete.

The unit water amount per 1 m ^{3 of} concrete is preferably 175 kg or less in the civil engineering field, and 185 kg or less is preferable in the construction field.

  Aggregates include coarse aggregates and fine aggregates.

The coarse aggregate is crushed stone, river gravel, mountain gravel, land gravel and the like. The fine aggregate is land sand, river sand, mountain sand, quartz sand, crushed sand and the like. The unit amount of the coarse aggregate with respect to concrete with high fluidity according to the present embodiment is preferably 700 kg to 1100 kg per 1 m ³ of concrete. The unit amount of fine aggregate with respect to concrete with high fluidity according to the present embodiment is preferably 700 kg to 1100 kg per 1 m ³ of concrete. In addition, in the concrete standard specification [construction edition] established in 2012, the standard for the minimum amount of cement when using aggregate with a coarse aggregate size of 40 mm is 250 kg / m ³ or more. The standard of the minimum cement amount when using the material is 270 kg / m ³ or more.

[Thickener]
A thickener is used to increase the viscosity of highly fluid concrete and suppress material separation. The addition amount of the thickener is preferably 15 to 250 g per 1 m ³ of concrete. The thickener which concerns on this embodiment consists of water-soluble cellulose ether.

  The water-soluble cellulose ether is nonionic, and is capable of suppressing material separation of concrete with high fluidity, improving durability by reducing bleeding, and reducing variation in strength and quality. Alkyl cellulose, hydroxyalkyl cellulose, Hydroxyalkyl alkyl cellulose is preferred.

  As the alkyl cellulose, DS is preferably 1.0-2.2, more preferably 1.2-2.0 methylcellulose, and DS is preferably 1.0-2.2, more preferably 1.2-2. 0.0 ethylcellulose and the like. As the hydroxyalkylalkyl cellulose, DS is preferably 1.0 to 2.2, more preferably 1.2 to 2.0, MS is preferably 0.05 to 0.6, more preferably 0.10 to 0. .5 hydroxyethyl methylcellulose, DS is preferably 1.0-2.2, more preferably 1.2-2.0, MS is preferably 0.05-0.6, more preferably 0.10-0 .5 hydroxypropyl methylcellulose, DS is preferably 1.0-2.2, more preferably 1.2-2.0, MS is preferably 0.05-0.6, more preferably 0.10-0 .5 hydroxyethyl ethyl cellulose.

  Here, DS represents the degree of substitution (degree of substitution) and is the number of alkoxy groups present per glucose ring unit of cellulose. MS represents the number of moles of substitution (molar substitution), and per cellulose glucose ring unit. Is the average number of moles of hydroxyalkoxy groups added to.

  As a method for measuring the degree of substitution of the alkyl group and the number of moles of substitution of the hydroxyalkyl group, it is determined by converting values that can be measured by the substitution degree analysis method for hypromellose (hydroxypropylmethylcellulose) described in the 17th revised Japanese Pharmacopeia. Can do.

  The aqueous solution viscosity of 2% by mass or 1% by mass of the water-soluble cellulose ether is preferably 30 (2% by mass) to 30 (2% by mass) at 20 rpm in a BH viscometer from the viewpoint of giving a predetermined viscosity to concrete. 1,000 (1% by mass) mPa · s, more preferably 80 (2% by mass) to 25,000 (1% by mass) mPa · s, and even more preferably 350 (2% by mass) to 20,000 mPa · s (1 Mass%). The viscosity of the water-soluble cellulose ether was measured with a 2% by mass aqueous solution at 50,000 mPa · s or less, and with a 1% by mass aqueous solution when the viscosity was higher than that.

  The addition amount of the water-soluble cellulose ether is preferably 0.01 to 20% by mass, more preferably 0.05 to 10% by mass, and further preferably 0.1 to 5% by mass with respect to the high-performance AE water reducing agent. is there.

[High-performance AE water reducing agent]
A high performance AE water reducing agent is used to disperse cement particles, increase the fluidity of concrete, and maintain the slump flow. As the high-performance AE water reducing agent, a known one can be used, and preferably a liquid polycarboxylic acid-based water reducing agent. The high-performance AE water reducing agent according to the present embodiment has a water reduction rate (hereinafter sometimes referred to as “water reduction rate”) defined by JIS A 6204 of 18% or more.

  The amount of the high-performance AE water reducing agent added is preferably 0.5 to 2.5% by weight of the unit cement amount.

[Other admixtures]
The highly fluid concrete according to the present embodiment may contain a general AE water reducing agent or an air amount adjusting agent (AE agent or antifoaming agent) as an admixture. The air amount adjusting agent is used for securing a predetermined amount of air to concrete having high fluidity and obtaining durability of the concrete. As the antifoaming agent, oxyalkylene type, silicone type, alcohol type, mineral oil type, fatty acid type, fatty acid ester type and the like are used. In addition, the concrete having high fluidity may contain a drying shrinkage reducing agent or an expansion material.

[Manufacturing method of highly fluid concrete]
The highly fluid concrete according to the present embodiment can be manufactured according to the same manufacturing method as that of general concrete.

  For example, concrete with high fluidity can be produced by first kneading the aggregate and cement first, then adding an admixture (thickener, high-performance AE water reducing agent, etc.) and water, and further kneading. Concrete with high fluidity can be produced in advance as ready-mixed concrete, or can be produced immediately before use at an actual site.

  The thickener and the high-performance AE water reducing agent may be mixed in advance. Or after manufacturing the base concrete into which other than the admixture is added, the admixture may be added and kneaded at an appropriate timing.

  The amount of cement, water, aggregate, thickener, and high-performance AE water reducing agent should be adjusted as appropriate within the range where high fluidity concrete satisfying the definition of high fluidity concrete and medium fluidity concrete can be obtained. Is possible. However, the water cement ratio in the highly fluid concrete according to the present embodiment is adjusted to be 47.5% or more and 65% or less.

== Example ==
[Materials used]
Table 1 shows the materials used in the examples or comparative examples.

In all the examples and all the comparative examples, as the cement (C), ordinary Portland cement (density 3.16 g / cm ³ ) manufactured by Taiheiyo Cement was used. For fine aggregate (S), land sand from Kisarazu City, Chiba Prefecture (surface dry density 2.61 g / cm ³ , water absorption 1.80%, coarse grain rate 2.46, actual rate 66.0%) is used. It was. Coarse aggregate (G) is crushed stone from Ome-shi, Tokyo (category: crushed stone 2005, surface dry density 2.65 g / cm ³ , water absorption 0.75%, coarse particle rate 6.62, actual rate 59.7. %) Was used. Water (W) was tap water (density 1.00 g / cm ³ ).

  On the other hand, as the admixture, an AE water reducing agent (WR), a high performance AE water reducing agent (SP), an air amount adjusting agent (AE agent: AE), and a thickener (VMA1 or VMA2) were appropriately used.

  Specifically, the AE water reducing agent (WR) is a master pozzolith (registered trademark) No. 1 manufactured by BASF Japan. 70 was used. As the high-performance AE water reducing agent, Master Grenium (registered trademark) SP-8SV (water reduction rate: 18%. SP) manufactured by BASF Japan Ltd. was used. As the air amount adjusting agent (AE agent: AE), Master Air 775S manufactured by BASF Japan Ltd. was used.

  As the thickeners (VMA1 and VMA2), an agent manufactured by Shin-Etsu Chemical Co., Ltd. was used. VMA1 is hydroxypropylmethylcellulose (HPMC), DS: 1.7, MS: 0.14, and a 1 mass% aqueous solution viscosity at 20 ° C. is 5,100 mPa · s at 20 rpm of a BH viscometer. VMA2 is hydroxyethyl methylcellulose (HEMC), DS: 1.4, MS: 0.31, and a 1 mass% aqueous solution viscosity at 20 ° C. is 15,400 mPa · s at 20 rpm of a BH viscometer.

[Composition of materials used]
Table 2 shows the composition of the materials used in the examples and comparative examples.

  Examples 1-5 differ in water cement ratio (W / C). The water cement ratio of Example 1 is 65.0%, the water cement ratio of Example 2 is 60.0%, the water cement ratio of Example 3 is 48.6%, and Examples 4 and The water cement ratio of Example 5 is 47.5%.

Furthermore, Examples 4 and 5 differ from Examples 1 to 3 in unit water amount. Example 4 unit water is 185 kg / ^{m 3,} Example 5 unit water is 165 kg / ^{m 3.}

Examples 6-9 differ in the addition amount of a thickener. Example 6 is an example in which 20 g of thickener was added per 1 m ^{3 of} concrete. Example 7 is an example in which 40 g of thickener was added per 1 m ^{3 of} concrete. Example 8 is an example in which 80 g of thickener was added per 1 m ^{3 of} concrete. Example 9 is an example in which 120 g of thickener was added per 1 m ^{3 of} concrete.

  Examples 10 and 11 are examples using thickeners of a different type from the other examples. Example 10 uses VMA2 (hydroxyethylmethylcellulose) as a thickener.

  In Examples 11 to 13, the water cement ratio (W / C) is changed on the assumption of the slump flow range (35 cm to 50 cm) of the medium fluidized concrete. The water cement ratio of Example 11 is 65.0%, the water cement ratio of Example 12 is 60.0%, and the water cement ratio of Example 13 is 55.0%.

  The concrete obtained by the blending of Comparative Example 1 is a concrete (ordinary concrete) to which a thickener and a high-performance AE water reducing agent are not added.

  Comparative Examples 2 to 4 are concrete to which no thickener is added. Comparative Examples 2-4 differ in water cement ratio (W / C). The water cement ratio of Comparative Example 2 is 55.0%, the water cement ratio of Comparative Example 3 is 46.1%, and the water cement ratio of Comparative Example 4 is 35.0%.

  The target slump flow (slump flow after kneading after 5 minutes, cm) is 65 ± 10 cm in Examples 1 to 11, 42.5 ± 7.5 cm in Examples 12 to 14, and 12 in Comparative Example 1. It is ± 2.5 cm, and in Comparative Examples 2 to 4, it is 65 ± 10 cm.

[Production of concrete]
Concretes were prepared by kneading the materials shown in Table 2 together. The manufacturing method is the same in all examples and comparative examples. For kneading, a forced biaxial kneading mixer with a nominal capacity of 60 L was used. The amount of kneading was 40 L per batch. First, aggregate and cement were put into a mixer and kneaded for 10 seconds, and then admixture and water were added and kneaded for 90 seconds to prepare concrete.

[Measurement of concrete]
With respect to the produced concrete, filling height (cm), slump flow (cm), 500 mm flow arrival time (seconds, excluding Examples 11 to 13 and Comparative Example 1), and bleeding rate (%) were measured. In addition, in each Example and the comparative example, it mix | blended and designed so that the air content might be 4.5 +/- 1.5% (range of the general air content of concrete).

  With respect to filling height, slump flow, and 500 mm flow arrival time, Examples 1 to 10 and Comparative Examples 1 to 4 were measured based on the provisions of the 2012 Standard Specification for Concrete [Construction]. Moreover, about the filling height and slump flow, Examples 11-13 measured based on the prescription | regulation of the east / middle / west Japan highway tunnel construction management point. In addition, about filling height, Examples 1-10 and Comparative Examples 1-4 are "failure: rank 2", and Examples 11-13 are "failure: rank 3".

  The bleeding rate was measured based on JIS A 1123.

[Measured value, judgment result]
Table 3 shows a determination result obtained by determining whether or not the produced concrete satisfies a predetermined condition based on the measurement value and the measurement value. Each measured value is a concrete value sampled at the time when 5 minutes have passed since the kneading.

  The determination results shown in Table 3 were made by (1) visual determination of the fresh state and (2) determination of whether the required performance of the highly fluid concrete shown in Table 4 is satisfied.

  (1) In the visual judgment of the fresh state, the state where the cement and the aggregate are uniformly distributed without separation and the appropriate material separation resistance is considered to be secured is “◯”. Is partly distributed in the center of the concrete, and the state where the water can be confirmed to bleed (bleeding) on the outer periphery and surface of the concrete is marked with “△”, and the material separation between the cement and the aggregate is remarkable, clearly the material The state in which it was determined that the separation resistance could not be secured was determined as “x”.

  (2) When judging whether or not the required performance of concrete with high fluidity shown in Table 4 is satisfied, the case where all the required performance is satisfied is set to “◯ (pass)”, and any one of the required performance is not satisfied Was judged as “× (failed)”.

  The required performance of the high-fluidity concrete shown in Table 4 is “filling height: 30 cm or more (obstruction: rank 2)”, “slump flow: 65 ± 10 cm ”and“ 500 mm flow arrival time: 3 to 15 seconds ”. Moreover, in this example, it was prescribed | regulated that the bleeding rate is equivalent to or lower than that of ordinary concrete (Comparative Example 1) as the required performance of the high fluidity concrete.

  In addition, the required performance of the medium-fluid concrete shown in Table 4 is “filling height: 28cm or more (obstacle: rank 3)”, “slump” as stipulated in the East, Middle and West Japan Highway Tunnel Construction Management Guidelines. Flow: 42.5 ± 7.5 cm ”. Moreover, in this example, it was prescribed | regulated that the bleeding rate is equivalent to or lower than normal concrete (comparative example 1) as the required performance of the medium fluidized concrete.

  It was judged that the concrete whose determination result of said (1) and (2) is "(acceptable)" is the target high fluidity concrete or medium fluidity concrete.

  As is clear from the results of Examples 1 to 5 and Comparative Examples 1 to 4, in the formulations of Examples 1 to 5, the water cement ratio is a large value of 47.5 to 65.0%. Even high fluidity concrete was obtained.

  On the other hand, also by the blending of Comparative Example 4, it was possible to obtain a concrete in which both of the determination results of (1) and (2) passed. However, in Comparative Example 4, the water cement ratio was as small as 35.0%.

That is, in the formulations of Examples 1 to 5, the unit cement amount can be reduced (about 269 to about 389 kg / m ³ ), while in the formulation of Comparative Example 4, the unit cement amount increases (500 kg / m ³ ). Became clear. As is clear from the results of Comparative Examples 2 and 3, in the blends of Comparative Examples 2 and 3, the higher the water-cement ratio (the smaller the unit cement amount), (1) and (2) The judgment result becomes worse.

Further, as is clear from the results of Examples 1 to 5, the required performance as high fluidity concrete is satisfied at least in the range of unit water amount of 165 to 185 kg / m ³ . Moreover, as is clear from the results of Examples 6 to 9, the thickener is effective when added at least 20 g to 120 g per 1 m ^{3 of} concrete. Further, as is clear from the results of Example 10, the special thickener is not limited to a specific agent as long as it is a cellulose ether alone.

Further, as is clear from the results of Examples 11 to 13, the required performance as medium fluidity concrete is satisfied at least in the range of unit water amount of 164 to 175 kg / m ³ .

  As described above, as apparent from the results of Examples 1 to 10, the amount of unit cement was suppressed by using a thickener composed of a water-soluble cellulose ether and a high-performance AE water reducing agent having a water reduction rate of 18% or more. It became clear that high fluidity concrete was obtained.

  Moreover, as is clear from the results of Examples 11 to 13, by adjusting the addition amount of the thickener and the high-performance AE water reducing agent described in the above embodiment, a medium-fluid concrete with a reduced unit cement amount is obtained. It became clear that

  The above-described embodiments, examples and comparative examples are presented as examples and do not limit the scope of the invention. The above configurations can be implemented in appropriate combination, and various omissions, replacements, and changes can be made without departing from the scope of the invention. The above-described embodiments and modifications thereof are included in the invention described in the claims and equivalents thereof in the same manner as included in the scope and spirit of the invention.

Claims (4)

A highly flowable concrete containing cement, water, aggregate, thickener, and high performance AE water reducing agent,
The thickener comprises a water-soluble cellulose ether,
The high-performance AE water reducing agent has a water reduction rate defined in JIS A 6204 of 18% or more,
The water-cement ratio is 47.5% or more and 65% or less,
Highly fluid concrete with a slump flow of 35 cm to 75 cm.   The high-fluidity concrete has a filling height of 30 cm or more (obstruction: rank 2) as defined in the 2012 Standard Specification for Concrete (Construction), the slump flow is 55 cm to 75 cm, and a 500 mm flow arrival time. The high-fluidity concrete according to claim 1, wherein the high-fluidity concrete is 3 to 15 seconds.   The high-fluidity concrete has a filling height of 28 cm or more (obstruction: rank 3) specified by the East, Middle and West Japan Expressway Tunnel Construction Management Guidelines, and the slump flow is 35 to 50 cm. The concrete with high fluidity according to claim 1, wherein the concrete is concrete. 4. The highly fluid concrete according to claim 1, wherein a unit water amount of the water is 185 kg or less per 1 m ³ of the highly fluid concrete.