JP2014162716A - Concrete composition and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a concrete composition that can reduce the contraction of concrete, that is also small in slump loss, and that can impart a high crack resistance and to provide a method for producing the same.SOLUTION: Methods for producing: (1) a concrete composition that contains an aggregate formed by subjecting portland cement clinker to carbonation treatment, and a shrinkage-reducing agent, (2) a concrete composition of (1) in which COcontent in the aggregate is 2% or more, (3) a concrete composition of (1) or (2) in which the aggregate is coarse aggregate of 5 to 40 mm and/or fine aggregate of below 5 mm, and (4) a concrete composition that is formed by blending a shrinkage reducing agent into an aggregate formed by comminuting portland cement clinker and subjecting the same to carbonation while immersing in water.

Description

  The present invention mainly relates to a concrete composition used in the field of civil engineering / architecture and a method for producing the same.

  In recent years, with regard to the durability of concrete, there has been a great deal of interest not only by concrete engineers but also by the general public. In relation to the durability of concrete, cracking of concrete is regarded as a problem. Concrete cracks are caused by concrete shrinkage. For this reason, research on reducing shrinkage of concrete has been actively conducted.

Examples of a method for reducing the shrinkage of concrete include a method of applying an expansion material and a shrinkage reducing agent. However, since these admixtures and admixtures are used in a small amount, they are greatly affected by cement and aggregate, which have a large unit usage in concrete.
Therefore, a method of first reducing the shrinkage of the base concrete itself before mixing the admixture or admixture is also desired.

  Among the constituent materials of concrete, the amount of aggregate used is the largest. It is known that the shrinkage of concrete also depends greatly on the properties of the aggregate. For this reason, proposal of the aggregate which makes shrinkage | contraction of concrete small is also awaited.

  On the other hand, research using cement clinker as an aggregate is also being conducted. There are also reports on research using cement clinker as a coarse aggregate (Non-patent Documents 1 to 4) and properties of mortar using cement clinker as a fine aggregate (Non-patent Document 5).

  However, the concrete using the conventional Portland cement clinker as an aggregate has no problem in strength characteristics, but has problems in shrinkage characteristics and fluidity. The shrinkage of concrete using Portland cement clinker aggregate is larger than that of concrete using general natural aggregate and its fluidity is worse, so it cannot be actively used in the concrete field.

In view of the above problems, the inventors of the present invention have found that, originally, an aggregate obtained by modifying a Portland cement clinker having a larger shrinkage than natural aggregate with CO ₂ can be improved, and fluidity can be improved. The present inventors have found that a concrete composition blended in combination with a shrinkage reducing agent exhibits high crack resistance and has completed the present invention.

Suzukawa Kenji, Abe Mitsufumi, Kawakami Masafumi: An experiment on strength properties of concrete using cement clinker as coarse aggregate, Abstracts of Annual Conference of Japan Society of Civil Engineers, Vol. 5, Vol. 45, pp. 420-421, 1990 Tsujimura Shinya, Suzukawa Kenji, Kawakami Masafumi: About the influence of cement clinker as coarse aggregate on the compressive toughness of concrete, Abstracts of Annual Conference of Japan Society of Civil Engineers, Part 5, Vol. 45, pp. 422-423, 1990 Isao Tanaka, Nobuo Suzuki: Research on easy-to-recycle concrete using clinker as aggregate, Summary of Academic Lectures of Architectural Institute of Japan, A-1, Materials Construction, pp. 1497-1498, 1995 Hojo Yasuhide, Obana Hiroshi, Takahashi Akira: Aggregate properties of eco-cement clinker, Japan Road Conference Proceedings, Vol. 24, General C, pp. 472-473, 2001 Makio Yamashita, Haruki Miura, Hissunori Tanaka, Kenichi Shimosaka: Properties of mortar with cement clinker as a fine aggregate, Ube Mitsubishi Cement Research Report, No. 5, pp. 56-64, 2004

  Provided is a concrete composition in which shrinkage of concrete can be reduced, slump loss is small, and high crack resistance is obtained.

That is, the present invention is (1) a concrete composition containing an aggregate obtained by carbonating Portland cement clinker and a shrinkage reducing agent, and (2) the CO ₂ content of the aggregate is 2% or more. (1) Concrete composition, (3) Aggregate is 5-40 mm coarse aggregate and / or fine aggregate below 5 mm (1) or (2) concrete composition, (4) Portland cement A method for producing a concrete composition in which a shrinkage reducing agent is blended with an aggregate obtained by pulverizing a clinker and soaking it in water.

  By employing the concrete composition and the method for producing the same according to the present invention, shrinkage of the concrete can be reduced and high crack resistance can be obtained. Moreover, since fluidity | liquidity is also improved, there exists an effect of being excellent also in workability | operativity.

Hereinafter, the present invention will be described in detail.
The concrete referred to in the present invention is mortar or concrete.
Further, parts and percentages in the present invention are based on mass unless otherwise specified.

  Examples of the Portland cement clinker used in the present invention include ordinary cement clinker, early strong cement clinker, low heat cement clinker, medium heat heat cement clinker, eco cement clinker and the like. Of these, from the viewpoint of reducing shrinkage, it is preferable to select a normal cement clinker, a low heat cement clinker, or a medium heat heat cement clinker.

As one of the clinker also _{minerals, 3CaO · SiO 2 (C 3} S for short) and 2CaO · _SiO 2 Calcium silicate represented by _{(C 2} S _{abbreviated), 4CaO · Al 2 O 3} · Fe 2 O 3 (C ₄ abbreviated as AF) and calcium aluminate represented by 3CaO.Al ₂ O ₃ (abbreviated as C ₃ A). The content of each mineral is calculated by the Borg formula from the result of chemical analysis according to JIS R 5202 or JIS R 5204.

  In the present invention, Portland cement clinker is used as coarse aggregate or fine aggregate. The coarse aggregate can be used in a size of 5 to 40 mm. The fine aggregate can be used in a size of 5 mm below. In the present invention, coarse aggregates and fine aggregates can be used alone or in combination.

In the present invention, the Portland cement clinker aggregate is carbonized. At this time, carbonation is performed until the CO ₂ content is 2% or more. When the CO ₂ content is less than 2%, the shrinkage reduction effect is not sufficient. It is also not desirable from the viewpoint of CO ₂ reduction.

Although the manufacturing method of the aggregate of this invention is not specifically limited, Usually, it is desirable to prepare in the following procedures.
(1) A coarse aggregate and a fine aggregate are prepared by pulverizing Portland cement clinker.
(2) Next, carbonation is performed until the CO ₂ content becomes 2% or more.
If this procedure is reversed, that is, if the aggregate of Portland cement clinker is first carbonized and then pulverized to prepare coarse aggregate or fine aggregate, sufficient shrinkage reduction effect and fluidity retention effect can be obtained. It may not be possible.

  In carrying out the carbonation treatment, it is preferable to carry out carbonation while immersing the coarse aggregate or fine aggregate of Portland cement clinker in water. Specific examples include, for example, a method in which coarse and fine aggregates of Portland cement clinker are placed in a water tank and carbon dioxide gas is blown into the tank, or coarse and fine aggregates of Portland cement clinker are piled up. For example, a method of moistening with watering and applying carbon dioxide gas can be used.

  Carbon dioxide gas can be high purity carbon dioxide, but it is desirable to use exhaust gas generated from a cement factory. Alternatively, exhaust gas discharged from steelworks, electric power industry, biomass boilers, incinerators, and other industries can be applied.

The carbon dioxide gas concentration is not particularly limited, but it is sufficient if it is about 5% by volume to 20% by volume. The temperature is not particularly limited, but is preferably in the range of 20 ° C to 60 ° C.

The shrinkage reducing agent according to the present invention is not particularly limited, and any one can be used.
The main components are roughly classified into lower alcohol alkylene oxide adduct systems, alcohol systems, glycol ether / amino alcohol derivative systems, polyether systems, and low molecular weight alkylene oxide copolymer systems.
Shrinkage reducing agents are commercially available from various companies, and representative examples thereof include, for example, “Eskard” manufactured by Denki Kagaku Kogyo, “Hibiguard” and “Shrink Guard” manufactured by Floric, “Hibidan” manufactured by Takemoto Yushi Co., Ltd. Examples include "Tetragard" manufactured by Taiheiyo Cement.

The amount of the shrinkage reducing agent is not particularly ^{limited, 1kg / m 3 ~10kg / m} 3 is preferred. If it is less than 1 kg / m ³ , the crack suppression effect may not be sufficiently obtained,
If it exceeds 10 kg / m ³ , strength management may be difficult.

  As the cement used in the present invention, various portland cements such as normal, early strength, super early strength, low heat, and moderate heat, various mixed cements in which blast furnace slag, fly ash and silica are mixed with these portland cements, municipal waste Waste-use cement (eco-cement) manufactured using incineration ash, sewage sludge incineration ash, etc., and various filler cements mixed with limestone fine powder or blast furnace slow-cooled slag fine powder, etc. Species or two or more can be used.

  In the present invention, blast furnace granulated slag fine powder, limestone fine powder, fly ash, silica fume, and other admixtures, setting modifier, quick hardening material, water reducing agent, AE water reducing agent, high performance water reducing agent, high performance AE water reducing agent, Defoamers, thickeners, rust inhibitors, antifreeze agents, expanding materials, polymers, fibrous materials such as steel fibers, vinylon fibers and carbon fibers, clay minerals such as bentonite, and anion exchangers such as hydrotalcite, etc. In the range that does not substantially impede the purpose of the present invention, one or more of the group consisting of known additives used in ordinary cement materials, fine aggregates, coarse aggregates, and the like Can be used together.

"Experiment 1"
The shrinkage behavior and crack resistance of concrete were investigated. The following coarse aggregate of 5 to 40 mm and fine aggregate below 5 mm were used, and the unit cement amount was 330 kg / m ³ and the shrinkage reducing agent was 4 kg / m ³ . Concrete having a unit water amount of 175 kg / m ³ , s / a = 43%, and an air amount of 4.5 ± 1.5% was prepared. Using this concrete, the length change rate was measured, the shrinkage behavior was compared, and the crack resistance was also examined.

<Materials used>
Cement: Ordinary Portland cement, commercially available.
Shrinkage reducing agent A: “SK GUARD” manufactured by Denki Kagaku Kogyo Co., Ltd., a low molecular weight alkylene oxide copolymer system.
Aggregate A: Silica-based coarse aggregate and fine aggregate, true specific gravity 2.65.
Aggregate B: limestone coarse aggregate and fine aggregate, true specific gravity 2.71.
Aggregate C: Rough aggregate and fine aggregate of ordinary cement clinker: C ₃ S 58.1%, C ₂ S 18.7%, C ₄ AF 10.0%, C _{3 A} 10.2%. CO ₂ content of 0.3%. Those that have not been carbonized. Grind to 5-40mm and 5mm below.
Aggregate D: Rough aggregate and fine aggregate of ordinary cement clinker: C ₃ S 58.1%, C ₂ S 18.7%, C ₄ AF 10.0%, C _{3 A} 10.2%. CO ₂ content 3.0%. What was pulverized to 5-40 mm and 5 mm below and then carbonized while being immersed in water. Using the exhaust gas of CO ₂ concentration of 10% by volume of cement factories as carbon dioxide.
Aggregate E: Eco-cement clinker coarse aggregate and fine aggregate: C ₃ S 64.9%, C ₂ S 5.0%, C ₄ AF 12.7%, C _{3 A} 13.3%. CO ₂ content 3.0%. What was pulverized to 5-40 mm and 5 mm below and then carbonized while being immersed in water. Using the exhaust gas of CO ₂ concentration of 10% by volume of cement factories as carbon dioxide.
Aggregate F: Coarse and fine aggregate of low heat cement clinker: C ₃ S 28.0%, C ₂ S 58.2%, C ₄ AF 1.5%, C _{3 A} 10.5%. CO ₂ content 3.0%. What was pulverized to 5-40 mm and 5 mm below and then carbonized while being immersed in water. Using the exhaust gas of the CO ₂ concentration of 10% by volume of cement factories as carbon dioxide.
Aggregate G: Coarse and fine aggregate of medium heat cement clinker: C ₃ S 43.0%, C ₂ S 39.0%, C ₄ AF 9.0%, C _{3 A} 7.0%. CO ₂ content 3.0%. What was pulverized to 5-40 mm and 5 mm below and then carbonized while being immersed in water. Using the exhaust gas of CO ₂ concentration of 10% by volume of cement factories as carbon dioxide.
Aggregate H: Coarse aggregate and fine aggregate of early strong cement clinker: C ₃ S 71.2%, C ₂ S 7.2%, C ₄ AF 10.0%, C _{3 A} 8.7%. CO ₂ content 3.0%. What was pulverized to 5-40 mm and 5 mm below and then carbonized while being immersed in water. Using the exhaust gas of CO ₂ concentration of 10% by volume of cement factories as carbon dioxide.
Aggregate I: Coarse aggregate and fine aggregate of intermediate heat cement clinker: C ₃ S 43.0%, C ₂ S 39.0%, C ₄ AF 9.0%, C _{3 A} 7.0%. CO ₂ content 2.0%. What was pulverized to 5-40 mm and 5 mm below and then carbonized while being immersed in water. Using the exhaust gas of CO ₂ concentration of 10% by volume of cement factories as carbon dioxide.
Aggregate J: Coarse and fine aggregate of medium heat cement clinker: C ₃ S 43.0%, C ₂ S 39.0%, C ₄ AF 9.0%, C _{3 A} 7.0%. CO ₂ content 5.0%. What was pulverized to 5-40 mm and 5 mm below and then carbonized while being immersed in water. Using the exhaust gas of CO ₂ concentration of 10% by volume of cement factories as carbon dioxide.

<Measurement method>
Drying shrinkage: The length change rate of 91 days of age was measured and evaluated according to JIS A 6202 (B).
Crack observation: A deck slab having a thickness of 100 mm and an area of 50 m ² was formed. A deck slab is a composite of concrete cast on corrugated steel sheets. Sheet curing was performed until age 5 days, and then the sheet was removed. The occurrence of cracks was observed at 91 days of age. When ² cracks occurred per 1 m ² , it was evaluated as x, when 1 or 2 cracks were generated, and when no crack was generated, it was evaluated as ◯.
Slump loss: Kneaded at 18 cm ± 1.0 cm, measured slump after 90 minutes, and defined the difference from immediately after kneading as slump loss. However, the kneaded concrete was allowed to stand, and after 90 minutes, it was kneaded with a scoop before measurement.

Table 1 shows that when the concrete composition of the present invention is used, the drying shrinkage is small and the crack resistance is high. It can also be seen that the slump loss is small. On the other hand, using ordinary cement clinker aggregates that have not been carbonized causes more shrinkage and slump loss than quartzite and limestone aggregates.

"Experimental example 2"
The same procedure as in Experimental Example 1 was conducted except that aggregate D was used and the type and amount of shrinkage reducing agent were changed as shown in Table 2. The results are shown in Table 2.

<Materials used>
Shrinkage reducing agent b: “Higarard” manufactured by Floric, glycol ether / amino alcohol derivative-based shrinkage reducing agent c: “Tetragard” manufactured by Taiheiyo Cement, an alkylene oxide adduct system of lower alcohol.

Table 2 shows that when the concrete composition of the present invention is used, the drying shrinkage is small and the crack resistance is high. It can also be seen that the slump loss is small. On the other hand, if a shrinkage reducing agent is not blended, many cracks are generated in structures that are easily cracked, such as deck slab concrete.

  By using the concrete composition of the present invention and the method for producing the same, shrinkage of the concrete can be reduced, slump loss can be reduced, and high crack resistance can be obtained, so that it can be widely used in the civil engineering and construction fields.

Claims (4)

A concrete composition containing an aggregate obtained by carbonating Portland cement clinker and a shrinkage reducing agent. The concrete composition according to claim 1, wherein the aggregate has a CO ₂ content of 2% or more. The concrete composition according to claim 1 or 2, wherein the aggregate is a coarse aggregate of 5 to 40 mm and / or a fine aggregate below 5 mm. A method for producing a concrete composition, comprising combining a shrinkage reducing agent with an aggregate obtained by pulverizing Portland cement clinker and soaking in water while being carbonated.