JP2010100480A - Cement composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cement composition which has excellent fluidity and excellent construction property before hardening and which expresses high compressive strength and high static modulus of elasticity after hardening and which has a small shrinkage rate. <P>SOLUTION: The cement composition contains (A) cement, (B) fine powder having 5-25 m<SP>2</SP>/g BET specific surface area, (C) inorganic powder having 3,500-10,000 cm<SP>2</SP>/g Blaine specific surface area, (D) fine aggregate, (E) a water-reducing agent and water (F). The fine aggregate (D) is heavy-weight aggregate having ≥4 g/m<SP>3</SP>density in the saturated surface-dried condition. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a cement composition having good fluidity before curing, exhibiting a high compressive strength of about 200 N / mm ² after curing, small shrinkage, and large static elastic modulus.

Recently, cement composition capable of expressing a high compressive strength of about 200 N / mm ² have been proposed.
For example, it consists essentially of Portland cement, granular parts, pozzolanic reactive microparts, metal fibers, dispersions, optional admixtures and water, with the predominant amount of granular parts having a maximum particle size D of at most 800 μm, The dominant amount of metal fibers has an individual length l in the range of 4 mm to 20 mm, the ratio R of the average length L of the fibers to the maximum particle diameter D of the granular member is at least equal to 10, and the dominant amount A metal fiber concrete composition for molding a concrete member, characterized in that the amount of the metal fiber is such that the volume of the fiber is 1.0% to 4.0% of the volume of the concrete after curing. It has been proposed (Patent Document 1).
And (A) 100 parts by weight of cement having a specific surface area of 2500 to 5000 cm ² / g, (B) 10 to 40 parts by weight of fine particles having a BET specific surface area of 5 to 25 m ² / g, and (C) and 30000cm ² / g of the inorganic particles A10~50 parts, a hydraulic composition containing the inorganic particles B5~35 parts by weight (D) Blaine specific surface area 2500~5000cm ² / g, the inorganic particles a Has a Blaine specific surface area larger than that of the cement and the inorganic particles B, and the difference in Blaine specific surface area between the cement and the inorganic particles B is 100 cm ² / g or more. A hydraulic composition is proposed in which the total amount of particles B is 15 to 55 parts by weight with respect to 100 parts by weight of the cement (Patent Document 2).
Japanese National Patent Publication No. 9-500352 JP 2002-338323 A

In general, a cement composition excellent in compressive strength (specifically, mortar, concrete, etc.) has the following advantages.
(1) When building buildings on site, the thickness of the concrete layer can be reduced, reducing the amount of concrete placement, reducing labor, reducing costs, and increasing use space. Etc. can be achieved.
(2) When a precast member is manufactured, the thickness of the precast member can be reduced, so that the weight can be reduced, and transportation and construction are facilitated.
(3) Abrasion resistance and durability against neutralization and creep are improved.
(4) Since the static elastic modulus is large, stress loss is reduced when prestressed concrete is produced.
However, a cement composition that can express a compressive strength of about 200 N / mm ² generally has a problem that shrinkage increases due to a large amount of binder and a small water cement ratio. Here, it is conceivable to use a shrinkage reducing agent as a method of reducing the shrinkage of the cement composition. However, in this case, there is a problem that the strength development property of the cement composition is lowered and only a compressive strength of about 180 to 190 N / mm ² is obtained, and the static elastic modulus is also lowered.
The present invention has been made in view of the above background, has good fluidity before curing, exhibits high compressive strength of about 200 N / mm ² after curing, has low shrinkage, and is static elastic. An object is to provide a cement composition having a large coefficient.

As a result of intensive studies to solve the above problems, the present inventor can achieve the above object of the present invention by using a heavy aggregate having a surface dry density of 4 g / m ³ or more as a fine aggregate. The present invention has been completed by finding out what can be done.

That is, the present invention provides the following [1] to [3].
[1] (A) Cement, (B) Fine powder having a BET specific surface area of 5 to 25 m ² / g, (C) Inorganic powder having a Blaine specific surface area of 350,000 to 10,000 cm ² / g, (D) Fine aggregate, E) A cement composition containing a water reducing agent and (F) water, wherein the fine aggregate includes a heavy aggregate having a surface dry density of 4 g / m ³ or more. .
[2] (G) The cement composition according to the above [1], comprising metal fibers.
[3] The heavy aggregate contains at least one of FeO, Fe ₂ O ₃ , and metallic iron as a main constituent, and spherical particles out of all particles are 20% or more, and the nominal size is 0.15 mm. The cement composition according to the above [1] or [2], wherein the particles passing through the sieve are 10% to 20% by mass percentage of the total particles.

Since the cement composition of the present invention contains a heavy aggregate having a surface dry density of 4 g / m ³ or more as a fine aggregate, it has good fluidity before curing and excellent workability, and after curing, It exhibits a high compressive strength of about 200 N / mm ² and a high static elastic modulus of about 60 kN / mm ^2, and a shrinkage rate comparable to that when a shrinkage reducing agent is used can be obtained.

The cement composition of the present invention, (A) cement, (B) fine powder of BET specific surface area of 5~25m ² / g, (C) Blaine specific surface area of 3500~10000cm ² / g inorganic powder, (D) It contains fine aggregates containing heavy aggregates having a surface dry density of 4 g / m ³ or more, (E) water reducing agent and (F) water as essential components.
As the (A) cement, various Portland cements such as ordinary Portland cement, early-strength Portland cement, moderately hot Portland cement, and low heat Portland cement can be used. In the present invention, it is preferable to use moderately hot Portland cement or low heat Portland cement in view of fluidity of the cement composition, shrinkage reduction, and the like.

The fine powder (B) needs to have a BET specific surface area of 5 to 25 m ² / g, and preferably 7 to 15 m ² / g. When the BET specific surface area is less than 5 m ² / g, the strength and static elastic modulus after curing are lowered, and the denseness and impact resistance are inferior. On the other hand, when the BET specific surface area exceeds 25 m ² / g, the amount of water for obtaining a predetermined fluidity increases, the strength after curing, the static elastic modulus, and the like decrease.
Examples of the fine powder include silica fume, silica dust, fly ash, slag, volcanic ash, silica sol, precipitated silica, and limestone powder. In general, silica fume and silica dust have a BET specific surface area of 5 to 25 m ² / g and do not need to be pulverized, so are suitable as fine powders used in the present invention. Moreover, limestone powder is also suitable as the fine powder used in the present invention from the viewpoints of pulverizability and fluidity.
The blending amount of the fine powder is preferably 5 to 50 parts by mass and more preferably 10 to 40 parts by mass with respect to 100 parts by mass of cement. When the blending amount is less than 5 parts by mass, strength after curing, static elastic modulus, denseness, impact resistance, and the like may be lowered. On the other hand, when the blending amount exceeds 50 parts by mass, the amount of water for obtaining a predetermined fluidity increases, the strength after curing, the static elastic modulus and the like decrease.

(C) The inorganic powder is required to have a Blaine specific surface area of 3500 to 10000 cm ² / g, and preferably 4000 to 9000 cm ² / g. If the specific surface area of the brane is less than 3500 cm ² / g, the strength after curing, the static elastic modulus, the denseness, the impact resistance and the like are not preferable. On the other hand, if the Blaine specific surface area exceeds 10000 cm ² / g, the fluidity may decrease, or the strength after curing and the static elastic modulus may decrease. In this case, the cost also increases.
Examples of the inorganic powder include inorganic powders other than cement, such as slag, limestone powder, feldspar, mullite, alumina powder, quartz powder, fly ash, volcanic ash, silica sol, carbide powder, and nitride powder. Among these, slag, fly ash, limestone powder, and quartz powder are preferably used in terms of cost and quality stability after curing.
The blending amount of the inorganic powder is preferably 5 to 55 parts by mass and more preferably 10 to 50 parts by mass with respect to 100 parts by mass of cement. If the blending amount is out of the above range, fluidity, workability, strength after curing, denseness, impact resistance, etc. may decrease.

(D) The fine aggregate includes, as at least a part thereof, a heavy aggregate having a surface dry density of 4 g / m ³ or more (more preferably 4.5 g / m ³ or more). When the surface dry density of the heavy aggregate is less than 4 g / m ³ , the static elastic modulus after curing decreases, and the shrinkage rate also increases.
As a heavy aggregate having a surface dry density of 4 g / m ³ or more, (a) it contains at least one of FeO, Fe ₂ O ₃ , and metallic iron as main components, and spherical particles out of all particles are 20 % Aggregates, and the aggregate passing through a sieve having a nominal size of 0.15 mm is a heavy aggregate in which the percentage by mass is 10% to 20% of the total particles.

Weight aggregate (hereinafter referred to as "weight aggregate (a)") of the preferably used in the present invention (a) is, FeO as main constituents, Fe ₂ O _3, is intended to include at least one of metallic iron. Containing at least one of FeO, Fe ₂ O ₃ and metallic iron as a main constituent means containing iron in the form of such an oxide or metal, and there is no particular limitation on the content of iron in heavy aggregate However, it is preferable that Fe ₂ O ₃ is 65% by mass or more when the constituent elements are determined in terms of oxides by fluorescent X-ray analysis. When Fe ₂ O ₃ is less than 65% by mass when the constituent elements are determined in terms of oxide by fluorescent X-ray analysis, the aggregate dry density of the aggregate may be less than 4 g / m ³ , which is not preferable. More preferably, Fe ₂ O ₃ is 65% by mass or more when the constituent elements are calculated in terms of oxide by fluorescent X-ray analysis, and the surface dry density of the heavy aggregate at this time is 4.5 g / m ³ or more. Become.

  Since the heavy aggregate has a large density difference from the cement paste portion, the aggregate and the paste are easily separated at the time of placing. Therefore, fluidity needs to be ensured by the shape of the heavy aggregate. The heavy aggregate (a) used in the present invention contains 20% or more of spherical particles (hereinafter abbreviated as “spherical particles”) among all particles, so that it has high fluidity and is not separated from cement paste. Can be set. When the spherical particles are less than 20%, the aggregate and the paste may be separated at the time of placing, which is not preferable.

  In the heavy aggregate (a) used in the present invention, particles passing through a sieve having a nominal size of 0.15 mm are preferably 10% to 20% in terms of mass percentage of all particles. When the particles passing through a sieve with a nominal size of 0.15 mm are less than 10% by mass or more than 20% of the total particles, good fluidity cannot be obtained, or separation of aggregate and cement paste is not possible. It may occur and is not preferable.

In the heavy aggregate (a), it is preferable that particles passing through a sieve having a nominal size of 1.2 mm are 70% to 90% in terms of mass percentage of all particles. When the particles passing through a sieve with a nominal size of 1.2mm are less than 70% by mass or more than 90% of the total particles, good fluidity cannot be obtained, or the separation of aggregate and cement paste It may occur and is not preferable.
The heavy aggregate (a) is preferably obtained by mixing recycled materials generated in the steel making process.

In the steel slab cast by the continuous casting slab, inclusions such as Al are continuously deposited on the surface layer in the longitudinal direction of the steel slab by the molten steel injection flow into the mold. The hot scarf of recycled material generated in the process of melting and removing the surface inclusions in this steel slab contains FeO, Fe ₂ O ₃ and metallic iron as the main constituents, and the constituent elements are converted to oxides by fluorescent X-ray analysis. When Fe ₂ O ₃ is 80% by mass or more, the surface dry density is 4.8 g / m ³ or more. In addition, spherical particles occupy about 70%, and particles passing through a sieve with a nominal size of 0.15 mm are in the range of 10% to 20% by mass of the total particles, and used as heavy aggregate (a) as they are. Can do. However, the amount of the recycled material generated is not so large, and it is preferable to use it with other recycled materials. For example, of the converter dust for steelmaking, if it is coarse powder (coarse powder converter dust) screened at 50μm, if it is up to the volume ratio of coarse powder converter dust 30 to hot scarf 70, mixing can do. If the coarse powder converter dust is further mixed, the particles passing through the sieve having a nominal size of 0.15 mm exceed 20% in terms of the mass percentage of the total particles, so that good fluidity may not be obtained.

Granular pig iron separated from blast furnace granulated slag in the pulverization process is also composed of metallic iron and has a surface dry density of 4.8 g / m ³ or more, and contains nearly 50% of spherical particles. It is a recycled material that can be mixed and used. The hot scarf 70 can be mixed up to the volume ratio of the granular pig iron 30. When granular pig iron is further mixed, particles passing through a sieve having a nominal size of 0.15 mm are less than 10% in terms of mass percentage of the total particles, which is not preferable because good fluidity may not be obtained.

Mill scale recycling materials that occur in the rolling process of the steel also, FeO as main constituents, Fe ₂ O _3, comprising metallic iron, Fe ₂ O ₃ when calculated in terms of oxides by a constituent element X-ray fluorescence analysis Is 80% or more, and the surface dry density is 4.8 g / m ³ or more. Moreover, it shifts to the coarse grain side a little from a hot scarf, and has a particle size distribution close to crushed sand JIS. Moreover, the amount generated as recycled material is relatively large. However, since the particle shape is somewhat flat, fluidity tends to decrease when used as an aggregate, and aggregate and paste are easily separated when the amount of unit water or water reducing agent is excessively increased. . Therefore, the mill scale cannot be used alone as a heavy aggregate as it is. However, if the hot scarf 30 is mixed up to the volume ratio of the mill scale 70, it can be used as the heavy aggregate (a). If the mill scale is further mixed, the ratio of spherical particles is less than 20%, and it becomes difficult to ensure good fluidity.

  The “spherical particles” in the heavy aggregate (a) will be described. Spherical particles are particles that are literally nearly spherical. In the process of producing spherical particles, (1) when a solid is melted into a liquid state by heat and then cooled and solidified in the air, it becomes a shape close to a sphere with the smallest surface area per volume. (2) Non-spherical particles However, when the shape is almost spherical due to physical polishing, (3) the fine particles precipitated from the powder or the solution may be bonded to the periphery of the nucleus and grow into a nearly spherical shape. (2) In the case of (3), particles having a continuous shape from a spherical shape to a non-spherical shape are generated, but in the case of (1), particles having an intermediate shape are not generated.

  As described above, the hot scarf is a recycled material that is generated in the process of removing and removing the surface layer inclusions of the steel slab, and spherical particles are generated in the generation process (1). Coarse powder converter dust and granular pig iron also contain spherical particles, but the production process is considered to include not only (1) but also (2).

  The weight aggregate (a) used in the present invention is preferably 20% or more of “spherical particles” of all particles, and “spherical particles” having a strain unevenness degree of 3.3 or less described below are 20 of all particles. % Or more is more preferable.

Here, the “strain unevenness” is defined by the following equation.
[Strain unevenness] = [Perimeter of particle outline] / [Diameter of a perfect circle having the same area as the particle outline area]
That is, by visually observing a scanning electron microscope (SEM) image, particles that can be judged to be discoid or hemispherical from the shadow are excluded, and particles that are clearly close to a sphere are image-processed and analyzed. The image processing may be performed using general image processing software [for example, Adobe Photoshop (registered trademark of Adobe Systems Inc.)]. First, a contour-only figure is created by removing shadows from an image of particles close to a sphere, and the area of the figure and the perimeter of the outline are obtained. Approximates a figure shaped into a circle (assuming a circle of figure shaped the same area), we obtain the radius r from the area pi] r ² of the circle to determine the diameter as twice as large. The ratio of the circumference length to the diameter becomes smaller as the contour is closer to a circle, that is, as the particle is closer to a sphere, and becomes a value closer to the circumference ratio π. Incidentally, the spherical irregularity contained in the hot scarf has a strain irregularity of 3.2 or less.

  Moreover, when calculating | requiring the ratio of the spherical particle among all the particles, what is necessary is just to calculate the average by counting the number of all the particles and the number of spherical particles which appeared in the several SEM photograph. Assuming that the ratio is constant, only particles having a constant particle diameter, for example, 50 μm or more may be counted.

  On the other hand, the heavy aggregate (a) used in the present invention is separated from the mill scale generated in the steelmaking rolling process, the coarse fraction screened with a particle size of 50 μm in the steelmaking converter dust, and the granulated blast furnace slag. It can also be obtained by mixing at least two selected from the granular pig iron. The mill scale, the converter dust coarse particles, and the granular pig iron are all recycled materials that are generated in a larger amount than the hot scarf that is generated in the steel slab surface cutting process.

The mixing ratio of the mill scale, the converter dust coarse particles, and the granular pig iron is preferably 0 to 70%, 0 to 50%, and 0 to 60%, particularly 20 to 70%, respectively, in mass percentage. It is preferable that it is 20 to 50% and 0 to 40%.
If the mixing ratio of the mill scale exceeds 70% or the mixing ratio of the converter dust coarse particles exceeds 50%, good fluidity may not be obtained, which is not preferable. When the mixing ratio of the granular pig iron exceeds 60%, the aggregate and the cement paste may be separated, which is not preferable.
If the mixing ratio of the mill scale is less than 20%, the aggregate and the cement paste may be separated or good fluidity may not be obtained. When the mixing ratio of the converter dust coarse particles is less than 20% or the mixing ratio of the granular pig iron exceeds 40%, the aggregate and the cement paste may be separated.

(D) The fine aggregate preferably contains 50% by mass or more of the above heavy aggregate, more preferably 70% by mass or more, and particularly preferably 90% by mass or more. When the content ratio of the heavy aggregate in the fine aggregate is less than 50% by mass, the static elastic modulus after curing decreases, and the shrinkage rate also increases.
In addition, examples of the fine aggregate other than the heavy aggregate used as (D) the fine aggregate include river sand, land sand, sea sand, crushed sand, silica sand, and a mixture thereof.
In the case of fine aggregates other than heavy aggregates, the 85% mass cumulative particle size is preferably 2 mm or less in view of fluidity and workability of the cement composition, crack resistance after hardening, and the like. Furthermore, the maximum particle size is more preferably 2 mm or less, and the maximum particle size is particularly preferably 1.5 mm or less, from the viewpoint of separation resistance of the cement composition, strength development after curing, and the like.
Further, in the fine aggregate other than the heavy aggregate, the proportion of particles of less than 0.15 mm is preferably 5% by mass or less from the viewpoint of fluidity and workability of the cement composition.

  The blending amount of the fine aggregate is preferably 70 to 500 parts by mass, more preferably 100 to 350 parts by mass with respect to 100 parts by mass of cement. If the blending amount is out of the above range, the strength after curing, the static elastic modulus and the like are decreased, and the shrinkage rate is increased.

(E) As a water reducing agent, a lignin type, naphthalenesulfonic acid type, melamine type, polycarboxylic acid type water reducing agent, AE water reducing agent, high performance water reducing agent or high performance AE water reducing agent can be used. Among these, it is preferable to use a polycarboxylic acid-based high-performance water reducing agent or a high-performance AE water reducing agent. By blending a water reducing agent, the fluidity and workability of the cement composition, the denseness and strength after curing, and the like are improved.
The blending amount of the water reducing agent is preferably 0.1 to 4.0 parts by mass, more preferably 0.1 to 1.0 part by mass in terms of solid content with respect to 100 parts by mass of cement. When the blending amount is out of the above range, the fluidity is lowered, the strength after curing, the static elastic modulus and the like are lowered.

(F) As water, tap water etc. can be used.
In the present invention, the water / cement ratio is preferably 10 to 30% by mass, more preferably 15 to 25% by mass from the viewpoints of fluidity, workability, strength after curing, durability, denseness, impact resistance, and the like. preferable.

The cement composition of the present invention can contain (G) metal fiber from the viewpoint of increasing the bending strength and fracture energy after curing.
(G) Examples of metal fibers include steel fibers and amorphous fibers. Among them, steel fibers are excellent in strength, and are preferable from the viewpoint of cost and availability. The metal fiber preferably has a diameter of 0.01 to 1.0 mm and a length of 2 to 30 mm. If the diameter is less than 0.01 mm, the strength of the fiber itself is insufficient, and it is easy to break when subjected to tension. When the diameter exceeds 1.0 mm, the number of the same compounding amount decreases, and the effect of improving the bending strength and fracture energy decreases. If the length exceeds 30 mm, fiber balls are likely to occur during kneading. If the length is less than 2 mm, the effect of improving the bending strength and fracture energy decreases.
The compounding amount of the metal fibers is preferably less than 4% of the volume of the cement composition, more preferably less than 3%. When the blending amount of the metal fiber is increased, the unit water amount is increased in order to ensure the workability at the time of kneading, and the strength, denseness, impact resistance and the like after curing are decreased.
The compounding amount of the metal fiber is preferably 0.5% or more, more preferably 1% or more of the volume of the cement composition. If the blending amount of metal fibers is 0.5% or more, the effect of improving bending strength and fracture energy can be enhanced.

Further, the cement composition of the present invention can contain fibrous particles or flaky particles having an average particle size of 1 mm or less. Here, the particle size of the particle is the size of the maximum dimension (particularly, the length of the fibrous particle). By containing the fibrous particles or flaky particles, the toughness after curing can be increased. Moreover, when using a metal fiber, isolation | separation prevention of a metal fiber can also be aimed at.
Examples of fibrous particles include wollastonite, bauxite, mullite, and examples of flaky particles include mica flakes, talc flakes, vermiculite flakes, and alumina flakes.
The blending amount of the fibrous particles or flaky particles is preferably 35 parts by mass or less, more preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of cement, from the viewpoint of workability before curing and toughness after curing.
In addition, it is preferable to use a fibrous particle having a needle-like degree represented by a length / diameter ratio of 3 or more from the viewpoint of increasing toughness after curing.

In the present invention, the method for kneading the cement composition is not particularly limited.
Moreover, the apparatus used for kneading is not particularly limited, and a conventional mixer such as an omni mixer, a pan-type mixer, a biaxial kneading mixer, and a tilting mixer can be used.
The method of molding and curing the cement composition is not particularly limited, but considering the productivity and strength development of a hardened cementitious material obtained by curing the cement composition of the present invention, the following primary are shown: It is preferable to perform curing / secondary curing.
First, the kneaded cement composition is molded using a predetermined mold and subjected to primary curing. Here, the molding method is not particularly limited, and a conventional molding method such as casting can be employed. Examples of the primary curing include a method in which the cement composition kneaded in a mold is stored and left at 5 to 40 ° C. for a predetermined time (for example, about 3 to 48 hours). Demold after primary curing. Here, the compressive strength of the hardened cementitious body at the time of demolding is preferably 10 N / mm ² or more. If the compressive strength is less than 10 N / mm ^2, demolding is difficult.
After demolding, secondary curing is performed to produce a cementitious hardened body. Secondary curing includes steam curing at 75 to 95 ° C. for 10 to 48 hours.
In addition, the cement composition of this invention is normally manufactured as mortar.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.
[1. Material used)
The following materials were used.
(A) Cement: Low heat Portland cement (manufactured by Taiheiyo Cement)
(B) Fine powder; silica fume (BET specific surface area 10 m ² / g)
(C) Inorganic powder; quartz powder (Blaine specific surface area 7500 cm ² / g)
(D) Fine aggregate; (1) Heavy fine aggregate (surface dry density is 4.95 g / m ³ , particles containing Fe ₂ O ₃ and metallic iron as main components and passing through a sieve with a nominal size of 0.15 mm) 10% by mass, 82% by mass of particles passing through a sieve with a nominal size of 1.2mm, maximum particle size of 5mm, and 78% of spherical particles).
The heavy fine aggregate is a hot scarf.
(2) Silica sand (particle size 0.15-0.6mm)
(E) Water reducing agent; Polycarboxylic acid-based high-performance water reducing agent (F) Water; Tap water (G) Metal fiber; Steel fiber (diameter: 0.15mm, length: 15mm)
(H) Shrinkage reducing agent: n-butyl alcohol propylene oxide (average addition mole number 2) / ethylene oxide (average addition mole number 2) block adduct 100 parts by mass, iso-butyl alcohol propylene oxide adduct (average addition) Number of moles 50) Mixture with 0.5 parts by weight

[Example 1]
Low heat Portland cement 100 parts by mass, silica fume 32 parts by mass, quartz powder 30 parts by mass, heavy aggregate 215 parts by mass, water reducing agent 0.6 parts by mass (solid content conversion), water 22 parts by mass and steel fiber (in the cement composition) 2% of the total volume) was put into a biaxial kneader and kneaded to obtain a blend.
The flow value of the blend was measured in the method described in “JIS R 5201 (Cement physical test method) 11. Flow test” without performing 15 drop motions.
In addition, the compound was molded using a mold of φ50 × 100mm, left standing at 20 ° C for 48 hours (primary curing), demolded, and further steam-cured at 90 ° C for 48 hours (secondary curing) The compressive strength and the static elastic modulus were measured according to “JIS A 1108 (Method of testing compressive strength of concrete)” and “JIS A 1149 (Test method of static elastic modulus of concrete)”.
In addition, the mixture is poured into a 4 × 4 × 16 cm mold, left at 20 ° C. for 48 hours (primary curing), demolded, and further steam-cured at 90 ° C. for 48 hours (secondary curing). The bending strength was measured according to “JIS R 5201”.
In addition, the mixture is poured into a 10 × 10 × 40 cm mold, left to stand at 20 ° C. for 48 hours (primary curing), demolded, and further contracted after steam curing (secondary curing) at 90 ° C. for 48 hours. The rate was measured according to JCI-SAS2 “Methods for self-shrinkage and self-expansion of cement paste, mortar and concrete (draft)”.
As a result, the flow value was 270 mm, the compressive strength was 195 N / mm ² , the bending strength was 40 N / mm ² , the static elastic modulus was 60 kN / mm ² , and the shrinkage was 530 × 10 ⁻⁶ .

[Comparative Example 1]
Low heat Portland cement 100 parts by weight, silica fume 32 parts by weight, quartz powder 30 parts by weight, silica sand 105 parts by weight, water reducing agent 0.4 parts by weight (in terms of solid content), water 22 parts by weight and steel fibers (of the total volume in the cement composition) 2%) was put into a biaxial kneader and kneaded to obtain a blend.
The flow value, compressive strength, bending strength, static elastic modulus and shrinkage were measured in the same manner as in Example 1.
As a result, the flow value was 270 mm, the compressive strength was 210 N / mm ² , the bending strength was 40 N / mm ² , the static elastic modulus was 54 kN / mm ² , and the shrinkage was 850 × 10 ⁻⁶ .

[Comparative Example 2]
Low heat Portland cement 100 parts by mass, silica fume 32 parts by mass, quartz powder 30 parts by mass, silica sand 105 parts by mass, water reducing agent 0.4 parts by mass (solid content conversion), water 20 parts by mass, shrinkage reducing agent 2 parts by mass and steel fiber (cement 2% of the total volume in the composition) was put into a biaxial kneader and kneaded to obtain a blend.
The flow value, compressive strength, bending strength, static elastic modulus and shrinkage were measured in the same manner as in Example 1.
As a result, the flow value is 270 mm, compressive strength 190 N / mm ^2, bending strength of 39N / mm ^2, the static modulus of elasticity 50 kN / mm ^2, shrinkage rate was 510 × 10 ^-6.

From Example 1 and Comparative Examples 1 and 2, in Example 1 using heavy aggregate as a fine aggregate, excellent fluidity, high compressive strength of about 200 N / mm ² and high static of about 60 kN / mm ² are obtained. It can be seen that the elastic modulus is obtained. It can also be seen that the shrinkage rate is reduced to the same level as in Comparative Example 2 using the shrinkage reducing agent.

Claims (3)

(A) Cement, (B) Fine powder with a BET specific surface area of 5 to 25 m ² / g, (C) Inorganic powder with a Blaine specific surface area of 350,000 to 10,000 cm ² / g, (D) Fine aggregate, (E) Reduced water A cement composition comprising an agent and (F) water, wherein (D) the fine aggregate includes a heavy aggregate having a surface dry density of 4 g / m ³ or more.   The cement composition according to claim 1, comprising (G) a metal fiber. The heavy aggregate contains at least one of FeO, Fe ₂ O ₃ , and metallic iron as a main component, and spherical particles out of all particles pass through a sieve having a nominal size of 0.15 mm. The cement composition according to claim 1 or 2, wherein the particles to be produced are 10% to 20% by mass percentage of all particles.