JP6564674B2 - Cement composition and hardened cement body - Google Patents

Description

  The present invention relates to a cement composition and a hardened cement body.

  Conventionally, steelmaking slag has been used as a concrete material. Steelmaking slag is produced when steel is produced by refining hot metal, scrap, etc., and is roughly classified into converter slag and electric furnace slag depending on the type of refining furnace. In addition to these, the steelmaking slag includes hot metal pretreatment slag, secondary refining slag, and the like.

  Hot metal pretreatment slag is a general term for slag that is produced when hot metal is desulfurized, desiliconized, dephosphorized, etc. as a pretreatment before charging the hot metal into the converter. The generated slag is called desulfurization slag, desiliconization slag, dephosphorization slag or the like.

  On the other hand, molten steel produced from converters may be subjected to refining treatment (secondary refining) such as desulfurization, dephosphorization, degassing, etc. Secondary refining slag is a generic term for slag produced at that time is there.

  However, although such secondary refining slag is less generated than converter slag and electric furnace slag, in recent years, the amount of generation has increased as the quality requirements for steel materials have increased. Effective utilization of secondary refining slag is required.

Therefore, a technique for effectively using secondary refining slag has been proposed.
For example, a steelmaking slag hardened body produced by kneading SiO ₂ having a potential hydraulic property such as pozzolanic reactivity, a secondary refining slag, and water and forming the mixture under a predetermined pressure has been proposed. According to such a steelmaking slag hardened body, it is conventionally considered that it is not suitable as an aggregate because the viscosity of the mortar becomes too high when used as an aggregate of a concrete material as compared with a converter slag or an electric furnace slag. The secondary refining slag can be used as a hardened body, thereby enabling effective use of the secondary refining slag.

Japanese Patent No. 3687444

  However, in the technique of the above-mentioned Patent Document 1, although it is possible to use the secondary refining slag itself, it is necessary to form a compression molded body. It is hard to say that it is used effectively.

  On the other hand, if the secondary refining slag can be used as a concrete material, the secondary refining slag can be used more effectively.

  In view of the above circumstances, an object of the present invention is to provide a cement composition capable of sufficiently effectively using secondary refining slag as a concrete material, and a cement hardened body obtained by curing the cement composition.

In order to solve the above-mentioned problems, the present inventors have conducted intensive research as follows.
General secondary refining slag tends to be insufficiently stirred due to the structure of the refining vessel. As a result, after cooling, high strength and low strength portions are mixed, or unreacted free lime remains. Therefore, the quality is often non-uniform compared to converter slag and electric furnace slag.
For this reason, when secondary refining slag was used as an aggregate of concrete material, it turned out that the function as this aggregate is not fully exhibited, for example, there exists a danger that a hardened object will carry out abnormal expansion.
In addition, the particle size of the secondary smelting slag is relatively small (the particle size distribution is biased toward the fine powder side), which reduces the yield even when used as an aggregate, and increases the viscosity of the cement composition. Therefore, it is considered that problems such as inferior workability such as a trowel finish and a large water absorption rate cause a change in slump over time and a shortened pot life.

  On the other hand, in order to secure the pot life, it is conceivable to use a high-performance AE water reducing agent in combination. However, as described above, since the secondary refining slag has a small particle size, it is easy to adsorb the high-performance AE water reducing agent. Therefore, when the high-performance AE water reducing agent is used in combination with the secondary refining slag, the amount of the high-performance AE water reducing agent increases, resulting in an uneconomical composition. Moreover, when the usage-amount of a high performance AE water reducing agent increases, it will be thought that the intensity | strength expression of concrete becomes late by that much.

  Therefore, when the present inventors conducted further research based on the above findings, when using secondary refining slag in combination with sand, when these were used as fine aggregate, the iron finish of the obtained cement composition As a result, it is possible to sufficiently increase the strength of the obtained concrete hardened body while ensuring sufficient workability, such as secondary properties, which makes it possible to use secondary refining slag as a concrete material. It has been found that the next refining slag can be used effectively enough, and the present invention has been completed.

That is, the cement composition according to the present invention is
Containing cement, fine aggregate and water,
The fine aggregate contains secondary refining slag and sand.

According to such a configuration, the secondary refining slag is contained as fine aggregate together with sand, so that the fresh properties of the cement composition are sufficient, and the strength of the cured body obtained by curing the cement composition is sufficient. Therefore, it can be used as an aggregate.
Therefore, secondary refining slag can be sufficiently effectively used as a concrete material.

In the cement composition having the above structure,
When the fine aggregate is 100 parts by volume, it is preferable to contain 20 to 25 parts by volume of the secondary refining slag.

According to such a configuration, the strength of the cured product obtained by hardening the cement composition by making the fresh property of the cement composition more satisfactory by containing 0.1 to 25 parts by volume of the secondary refining slag. Can be further increased sufficiently, so that it can be used as an aggregate.
Therefore, secondary refining slag can be more effectively used as a concrete material.

The hardened cement body of the present invention is
The cement composition is cured.

  According to this configuration, the secondary refining slag can be sufficiently effectively used as described above.

  ADVANTAGE OF THE INVENTION According to this invention, the cement composition which can fully utilize effectively secondary refining slag as a concrete material, and the cement hardening body which hardens this are provided.

Graph showing the relationship between the cement water ratio and the bending strength in the cured body produced in the example Graph showing bending strength and compressive strength in the cured body produced in the examples

  Hereinafter, embodiments of the cement composition and the hardened cement body according to the present invention will be described.

  The cement composition of this embodiment contains cement, fine aggregate, and water, and the fine aggregate contains secondary refining slag and sand.

A conventionally well-known cement is mentioned as said cement. Examples of such cement include Portland cement described in JIS R 5210. Of these, early-strength Portland cement is preferable in consideration of securing early strength.
For example, the blending amount of the cement is preferably 12 to 32 parts by mass, and more preferably 13 to 26 parts by mass with respect to 100 parts by mass of the entire cement composition.
When the blending amount of the cement is 12 to 32 parts by mass, there is an advantage that a hardened cement body can be manufactured, in which the surface finish by the trowel at the time of construction becomes better and the early strength development can be further secured.

The fine aggregate contains secondary refining slag and sand.
In the present embodiment, the fine aggregate is an aggregate that passes through all of the 10 mm mesh sieve specified in JIS A 0203: 2014 and passes through the 5 mm mesh sieve by 85 mass% or more.

The secondary refining slag is slag that is generated when refining treatment (secondary refining) such as desulfurization, dephosphorization, and degassing is performed on molten steel discharged from a converter or the like.
Absolute dry density of secondary refining slag is preferably ^{2.0~3.0g / m 3, 2.2~2.6g / m} 3 and more preferably.
Table dry density of secondary refining slag is preferably ^{2.0~3.5g / m 3, 2.3~3.0g / m} 3 and more preferably.
The water absorption of the secondary refining slag is preferably 0 to 12% by mass, and more preferably 0 to 10% by mass.
0-15 mass% is preferable and, as for the fine particle amount of secondary refining slag, 0-10 mass% is more preferable.
2-5 are preferable and, as for the coarse grain ratio of secondary refining slag, 2-4 are more preferable.

The sand is not particularly limited as long as it is sand used as a fine aggregate. Examples of such sand include sand derived from natural products such as river sand, land sand, mountain sand, sea sand, crushed sand, limestone crushed sand, sand derived from slag such as blast furnace slag, electric furnace oxidation slag, ferronickel slag and copper slag. Can be mentioned.
The sand preferably satisfies the quality shown in JIS A 5308 Annex A: 2014 “Aggregates for ready-mixed concrete”.
When the sand is the above-mentioned type of sand that satisfies the above-mentioned quality, even when secondary refining slag with a relatively large amount of fine particles is used, it is easier to adjust the particle size of the fine aggregate as a whole, and the fluidity And there is an advantage that it is easy to obtain a cement composition having a good surface finish with a trowel.

The cement composition preferably contains 0.1 to 25 parts by volume of secondary refining slag with respect to 100 parts by volume of sand, and more preferably 10 to 25 parts by volume.
By containing the secondary refining slag in an amount of 0.1 to 25 parts by volume, the fresh properties of the cement composition are further improved, and the strength of the cured product obtained by curing the cement composition is further sufficiently increased. Since it can be increased, it can be used as an aggregate.
Therefore, secondary refining slag can be more effectively used as a concrete material.

The cement composition preferably contains 2 to 10 parts by mass, more preferably 2 to 9 parts by mass of the sand with respect to 100 parts by mass of the cement composition as a whole.
By containing 23 to 35 parts by mass of sand, there is an advantage that it is easy to obtain a cement composition with better fluidity and surface finish by a trowel.

The amount of water added to the cement composition is, for example, preferably 10 to 60 (cement water ratio 10 to 1.7), more preferably 30 to 45 (cement water ratio 3). .3 to 2.2).
When the water-cement ratio is 10 to 60, there is an advantage that a kneaded product that has better surface finish by a trowel and can further secure early strength development can be produced.

  The cement composition may contain additives other than those described above. For example, coarse aggregate, high-performance AE water reducing agent, high-performance water reducing agent, air amount adjusting agent, fluidizing agent, curing accelerator, expansion material and the like may be contained.

For example, when the cement composition contains coarse aggregate, the coarse aggregate includes coarse aggregate such as river gravel, land gravel, mountain gravel, sea gravel, crushed stone, lime crushed stone, blast furnace slag, electric furnace Examples include coarse aggregates such as oxidized slag. Moreover, it is preferable that these coarse aggregates satisfy the quality shown in JIS A 5308 Annex A: 2014 “Aggregates for ready-mixed concrete”. The above-mentioned type of coarse aggregate satisfying the above-mentioned quality, and even with a cement composition using secondary smelting slag with a large amount of fine particles, the proportion of fine particles in the whole aggregate is not greatly increased, and workability is improved. There is an advantage that it is easy to obtain a good cement composition.
Moreover, the compounding quantity of a coarse aggregate becomes like this. Preferably it is 32-54 mass parts with respect to 100 mass parts of the whole cement composition, More preferably, it can be 37-50 mass parts.

For example, when the cement composition contains a high-performance AE water reducing agent, examples of the high-performance AE water reducing agent include polycarboxylic acid ether compounds, polycarboxylic acid copolymers, and methacrylic acid polymers. Of these, polycarboxylic acid ether compounds and polycarboxylic acid copolymers are preferred.
Moreover, the compounding quantity of a high performance AE water reducing agent can be 0.1-4 mass parts preferably with respect to 100 mass parts of cement, More preferably, it can be 0.5-2.0 mass parts.

For example, when the cement composition contains an air amount adjusting agent, examples of the air amount adjusting agent include alkyl ether anionic surfactants and nonionic surfactants.
Moreover, the compounding amount of the air amount adjusting agent is preferably 0.0005 to 1 part by mass, and more preferably 0.001 to 0.006 part by mass with respect to 100 parts by mass of cement.

The slump value or the slump flow value of the cement composition is preferably a slump value of 6.5 to 21 cm or a slump flow value of 25 to 60 cm at the time of unloading at a construction site. More preferably, it is 5 to 18 cm, or the slump flow value is 30 to 50 cm. Moreover, it is preferable to satisfy both the slump value or the slump flow value.
The slump value is a value measured according to JIS A 1101: 2014 (a concrete slump test method). Moreover, a slump flow value is a value measured by the method described in the Example mentioned later.
Since the slump value when unloading is 6.5 to 21 cm, or the slump flow is 25 to 60 cm, it is possible to secure better workability without further separation of the concrete. There is an advantage that the property becomes higher.
In order to bring the slump value or slump flow value at the time of unloading into the above range, it is preferable that the slump value is 6.5 to 26 cm or the slump flow value is 25 to 75 cm immediately after manufacture. It is preferable that it is 6.5-23 cm or a slump flow value is 30-65 cm.
More preferably, the slump value or the slump flow value of the cement composition is reduced by 0 to 5 cm in terms of the slump value and 0 to 15 cm in terms of the slump flow value after standing for 60 minutes after kneading.
As described above, the decrease amount of the slump value after 60 minutes from the kneading is 0 to 5 cm, or the decrease amount of the slump flow value is 0 to 15 cm, so that the transportation time from the manufacturing site to the construction site is 60 minutes. Even when necessary, there is an advantage that a cement composition with easy consistency management can be obtained.

  The cement composition can be produced by kneading the cement, the fine aggregate, water, and other additives as necessary.

According to the cement composition of the present embodiment, the secondary refining slag is contained as fine aggregate together with sand, so that the fresh properties of the cement composition are sufficient, and the hardening is performed by hardening the cement composition. Since the strength of the body can be sufficiently increased, it can be used as an aggregate.
Therefore, secondary refining slag can be sufficiently effectively used as a concrete material.

The hardened cement body of the present embodiment is formed by hardening the cement composition.
As described above, this hardened cement body is produced by kneading cement, coarse aggregate, water, and, if necessary, other additives, then placing and hardening.
According to the cement hardened body of the present embodiment, the secondary refining slag can be sufficiently effectively used as described above.

  The cement composition and the hardened cement body of the present embodiment are preferably for road pavement.

  The cement composition and cement hardened body of the present embodiment are as described above, but the present invention is not particularly limited to the above embodiment.

  EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.

  The physical properties of the aggregate are measured as described below, and a cement composition is prepared using the aggregate. Further, the cement composition is cast and cured to produce a cured cement body. Evaluated.

(1) Material used As a cement, early strong Portland cement (density 3.14 g / cm ³ ) was used.
As the admixture, a high-performance AE water reducing agent (polycarboxylic acid ether compound) and an air amount adjusting agent (alkyl ether anionic surfactant) were used.
As aggregates, as shown in Table 1, coarse aggregates and fine aggregates were used. Blast furnace slag was used as the coarse aggregate, and land sand and secondary refining slag generated in the steelworks were used as the fine aggregate.

(2) Aggregate physical test The aggregate was subjected to a quality test in accordance with JIS A 5308 Annex A: 2014.
Further, the absolute dry density and the surface dry density were measured in accordance with JIS A 1109: 2006 (fine aggregate density and water absorption test method) and JIS A 1110 (coarse aggregate density and water absorption test method).
Further, the coarse grain ratio was measured according to JIS A 1102: 2014 (Aggregate screening test method).
The results are shown in Table 1. Table 1 also shows the quality standard values of sand described in JIS A 5308 Annex A: 2014.
As shown in Table 1, the secondary smelting slag was slightly smaller in dry density and remarkably large in water absorption and fine particle amount than the quality standard of sand described in JIS A 5308 Annex A: 2014. .

(3) Preparation of cement composition and evaluation of fresh properties In a thermostatic chamber at room temperature of 20 ° C., the above cement, aggregate, and water are put into a forced biaxial mixer with the composition shown in Table 2 and kneaded. Mixing was done. After kneading, the kneaded product is allowed to stand. Immediately after kneading and after 60 minutes from the kneading (standing), the slump flow value of the kneaded product (shown as SF in Table 4), and kneading. The amount of air in the product (shown as Air in Table 4) was measured.
Moreover, in order to investigate the influence exerted on the characteristics of the kneaded material by using the secondary refining slag, as shown in Table 3, the mixing ratio (volume ratio) of the secondary refining slag to the fine aggregate was changed. The above kneading and the following measurements were performed.

The target fresh property of the cement composition is that the slump flow value is within a range of 40 ± 7.5 cm and the air amount is within a range of 4.5 ± 1.5% after 60 minutes from the kneading, and The time-dependent change in the slump flow (the value obtained by subtracting the slump flow value after 60 minutes from the immediately following slump flow value) was 15 cm or less. Further, no separation occurred in the kneaded product, and the viscosity of the cement composition was low. Viscosity is an index for evaluating workability.
The slump flow value was measured based on JIS A 1150: 2007 (concrete slump flow test method).
The amount of air was measured in accordance with JIS A 1128: 2005 (test method by pressure of air amount of fresh concrete-air chamber pressure method).
The separation state was judged by visually confirming whether coarse aggregates were concentrated locally, or whether cement paste or moisture rose toward the upper surface of the concrete over time. And when said phenomenon was not confirmed, it represented as "(circle)" that separation did not arise in a kneaded material, and when said phenomenon was confirmed, it represented as "x" that separation occurred.
The viscosity was judged by visually checking whether the cement paste on the surface was pulled or not when the surface of the cement composition was leveled using a gold trowel. The case where the cement paste was not pulled with a gold trowel was shown as “good” as “good”, and the case where the cement paste was pulled with a gold trowel was shown as “bad” as bad.
The results are shown in Table 4.

As shown in Table 4, when secondary refining slag in an amount exceeding 25% by volume was used in the fine aggregate, the viscosity of the cement composition increased, and the change over time (decrease) in the slump flow value increased. . This is thought to be due to the large amount of fine particles of secondary refining slag.
Further, in order to obtain a target slump flow value of 40 ± 7.5 cm after 60 minutes of kneading, it is necessary to increase the high-performance AE water reducing agent. It was expected that it would be difficult to secure a strength of 3.5 N / mm ² , and it was thought that the composition would be uneconomical.
In this way, when the high-performance AE water reducing agent is set near the standard usage amount (cement mass × 0.9 mass%), the amount of secondary refining slag in the fine aggregate is required to satisfy the target fresh properties. It was found that the upper limit of 25% by volume is preferable.
Therefore, the following study was performed using the slag 20 as a fine aggregate, and compared with the case where the land sand 100 was used.

(4) Examination of cement water ratio in cement composition In the formulation of Table 5, a cement composition was prepared in the same manner as described above, and in accordance with JIS A 1132: 2014 (How to make a specimen for strength test of concrete) A 10 × 10 × 40 cm prismatic cured body was produced. As above, the slump flow value and the amount of air are measured for the cement composition, the bending strength is measured for the hardened body, and the relationship between the cement water ratio and the fresh properties of the cement composition and the bending strength of the hardened body. I investigated.
The bending strength was measured according to JIS A 1106: 2006 (Concrete bending strength test method).
The results are shown in Table 5. Moreover, the relationship between cement water ratio and bending strength is shown in FIG.

From the approximate expression shown in FIG. 1, in order to obtain a bending strength of 3.5 N / mm ² at an age of 24 hours, the water-cement ratio is 35.7% for land sand 100 and 35.8% for slag 20; Was found to be roughly the same value.
In consideration of environmental conditions and material variations, the test construction was carried out as follows with a blend of 35% water cement ratio in both land sand 100 and slag 20.

(5) Test construction using secondary refining slag as fine aggregate In the composition shown in Table 6, a cement composition was prepared using land sand 100 and slag 20, and the obtained cement composition was 80 m ² each of 4 m × extension 20 mm was casted, spread, and cured while curing using a film curing agent to perform road construction and test construction. In addition, the pavement configuration was a surface layer cured body of 30 cm and an upper road bed of 50 cm, and driving joints were installed at intervals of 5 m.
The land composition 100 and the cement composition using the slag 20 were all as good in workability from preparation to spreading. In both constructions, the cast thickness was as large as 30 cm, and the viscosity of the cement composition was relatively low with respect to the thickness. did.

A cement composition was prepared in the same manner as above with the formulation shown in Table 6, and the fresh properties of the cement composition at the time of shipment (immediately after completion of the adjustment) and at the time of unloading (here, 30 minutes after the completion of preparation) Measured in the same manner as above. The results are shown in Table 7.
Moreover, the hardening body was produced like the above using each cement composition, and the bending strength of the hardening body was measured like the above. Moreover, the compressive strength was measured.
The compressive strength was measured in accordance with JIS A 1108: 2006 (Concrete compressive strength test method).
The results are shown in FIG.

As shown in Table 7, both the land sand 100 and the slag 20 obtained results satisfying the target fresh properties. In addition, there was no difference in the change over time in the fresh properties between the two formulations.
As shown in FIG. 2, the bending strength of the slag 20 tended to be lower than that of the land sand 100, but a result satisfying the target bending strength of 3.5 N / mm ² at a material age of 24 hours was obtained. It was.
In the above test construction, curing was performed using only the film curing agent without using a sheet or the like, but no cracks were confirmed on the next day of construction, and it was confirmed that the cured body was in a healthy state.

As described above, as a fine aggregate, it was found that even when a part of land sand was replaced with secondary refining slag, construction was possible in the same manner as when not replacing (all land sand). Further, it was found that the bending strength of the cured body with a material age of 24 hours tended to become slightly smaller by substituting with secondary refining slag, but satisfied the target strength.
Thus, it was found that the secondary refining slag can be effectively used as a concrete material by containing the secondary refining slag and sand.

Claims (2)

Containing cement, fine aggregate, coarse aggregate, and water,
The fine aggregate is a cement composition comprising secondary smelting slag and sand ,
The amount of the coarse aggregate is 32 to 54 parts by mass when the entire cement composition is 100 parts by mass,
A cement composition comprising 20 to 25 parts by volume of the secondary refining slag when the fine aggregate is 100 parts by volume . A hardened cement body obtained by curing the cement composition according to claim 1 .