JP2005350305A - Cement admixture and cement composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cement admixture and a cement composition which are used in the field of cement or concrete and can suppress the occurrence of crack as much as possible in high strength concrete under a steam curing condition and a normal curing condition. <P>SOLUTION: The cement admixture consists essentially of 100 pts.wt. II type anhydrous gypsum, 20-300 pts.wt. silica fume and 20-300 pts.wt. blast furnace slag powder 1-10% of which has ≥90 μm particle diameter, or consists essentially of 100 pts.wt. II type anhydrous gypsum, 20-300 pts.wt. silica fume, 20-300 pts.wt. blast furnace slag powder 1-10% of which has ≥90 μm particle diameter and 10-100 pts.wt. expansive admixture material. The cement composition comprises 6-50 pts.wt. cement mixture and 100 pts.wt. cement. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a cement admixture and a cement composition containing the same.

Conventionally, as a method for obtaining high strength under steam curing conditions and normal curing conditions, there is a method using a cement admixture in which type II anhydrous gypsum, silica fume and fine powder of blast furnace slag having a particle size of 12 μm or less is 60% or more. Are known.
Type II anhydrous gypsum has been used as a cement or concrete admixture in order to reduce shrinkage and increase the strength of concrete. Silica fume is used to ensure the fluidity of concrete at high strength and low water cement ratio. Use of blast furnace slag fine powder with particles of 12 μm or less of 60% or more provides higher strength than when using type II anhydrous gypsum and silica fume alone, and is excellent in durability, in particular, chloride ion penetration resistance. A concrete compact is obtained.
On the other hand, it is known that it is preferable that the blast furnace slag has a smaller fineness to reduce self-shrinkage and temperature rise.
JP-A-2-302349

In recent years, new crack cases that cannot be explained only by temperature cracks and drying shrinkage cracks have become apparent. In general, high-strength concrete is used at a low water cement ratio, and the self-shrinkage increases as the water-cement ratio decreases, and self-shrinkage is particularly noticeable in ultra-high-strength concrete of 80 N / mm ² or more. The phenomenon that the self-shrinkage increases becomes more prominent as the blast furnace slag fine powder becomes finer. In addition, the finer the blast furnace slag fine powder, the higher the temperature dependency in hydration, and the temperature of concrete rises and the risk of cracking due to temperature stress increases. Silica fume is one of the materials that increase the self-shrinkage, but it is difficult to obtain a flowable ultra-high strength concrete without using silica fume, so it must be used. On the other hand, type II anhydrous gypsum is known to have an effect of reducing self-shrinkage. However, such a conventional technique has a problem that it is difficult to secure ultra-high strength concrete that secures high fluidity and has low self-shrinkage.

  Therefore, an object of the present invention is to more economically add admixtures and cement compositions used in the field of cement and concrete that suppress the occurrence of cracks as much as possible in high-strength concrete under steam curing conditions and normal curing conditions. It is to provide.

The inventors of the present invention have paid attention to an admixture composed of coarse slag, type II anhydrous gypsum, silica fume, and an expanding material, which has not been studied so far. The present invention has been found to be effective in reducing self-shrinkage and temperature rise of high-strength concrete.
That is, the object of the present invention is, as described in claim 1, 100 parts by weight of type II anhydrous gypsum, 20 to 300 parts by weight of silica fume, and 20 to 300 parts by weight of blast furnace slag powder having 1 to 10% of particles of 90 μm or more. And a cement composition consisting of 6 to 50 parts by weight of this admixture and 100 parts by weight of cement.
Further, the object of the present invention is to provide 100 parts by weight of type II anhydrous gypsum, 20 to 300 parts by weight of silica fume, and 20 to 300 parts by weight of blast furnace slag powder containing 1 to 10% of particles of 90 μm or more. The cement admixture mainly composed of 10 parts by weight and 100 parts by weight of the expansion material and 6 to 50 parts by weight of the admixture according to claim 1 or 2 and 100 parts by weight of cement as claimed in claim 3. Part of the cement composition.

According to the present invention, it is possible to reduce the risk of occurrence of cracks in concrete due to temperature stress, self-shrinkage, drying shrinkage, and the like as much as possible. The admixture and the cement composition of the present invention use coarse slag containing 1 to 10% of particles of 90 μm or more, which greatly contributes to the reduction of carbon dioxide gas as well as the reduction of power during pulverization.

The slag of the present invention is characterized in that the particle size of 90 μm or more is 1 to 10%. A slag containing 10% or more particles of 90 μm or more is not preferable because it adversely affects strength development. In addition, slag having a particle size of 90 μm or more and 1% or less is not preferable because the effect of reducing the adiabatic temperature rise of concrete is reduced, and hydration shrinkage of a binder composed of Portland cement, slag and type II anhydrous gypsum. The effect of reducing the accompanying self-shrinkage of the concrete is reduced. High-strength concrete amount unit cement is greater than 1000 kg / m ³ and normal concrete from 700 kg / m3, to raise the temperature in the concrete is the heat of hydration of cement, blast furnace slag hydration 90μm or more becomes active Even if blast furnace slag powder having 1 to 10% of particles is used, there is no problem in developing the strength of high-strength concrete. In addition, hydration reaction of blast furnace slag becomes active if it is cured with steam at 40 ° C. or higher even under steam curing conditions, and there is no problem in strength development even if blast furnace slag powder containing 1 to 10% of particles of 90 μm or more is used.

Type II anhydrous gypsum includes natural anhydrous gypsum, hydrofluoric acid anhydrous gypsum, natural dihydrate gypsum, byproduct dihydrate gypsum, or type II anhydrous gypsum produced by baking dihydrate gypsum recovered from waste gypsum board. In the present invention, any type II anhydrous gypsum containing 90% or more of type II anhydrous gypsum can be used. Although fineness is not particularly limited, 8000 cm ² / g, from 3000 Blaine specific surface area is preferably 6000 cm ² / g to 4000.
Type II anhydrous gypsum functions to improve the initial strength of concrete and suppress the increase in heat insulation temperature, and also contributes to the reduction of self-shrinkage and drying shrinkage by producing ettringite by reacting with C3A in Portland cement. In addition, the present invention is that the blast furnace slag used in the present invention is coarser than the conventional blast furnace slag, so the hydration reaction rate is slow and the initial strength expression is reduced. It is based on material design that can be compensated by densification.

  Silica fume is not particularly limited, but those defined in JIS A 6207 are preferred.

  Commercially available expandable materials include, for example, “N-Expan”, “Hyperexpanse” from Taiheiyo Material Co., Ltd. and “CSA” from Electrochemical Industry Co., Ltd., but the expandable materials are those defined in JIS A 6202. There is no particular limitation. These expanding materials contain free CaO and CaSO4, and some contain Irwin minerals (C4A3SO3). These ratios are changed according to the purpose of use, but basically, the expansion due to the hydration of CaO and the expansion due to the formation of ettringite are utilized. In the present invention, the purpose of using these expansion materials is to reduce self-shrinkage, and does not expect expansion to introduce chemical prestressed. Therefore, with respect to 100 parts by weight of type II anhydrous gypsum, 20 to 300 parts by weight of silica fume, 20 to 300 parts by weight of blast furnace slag powder having 1 to 10% of particles of 90 μm or more, and 10 to 100 parts by weight of the expansion material, The ratio of the expansion material was lowered.

  Portland cement includes early strong, normal, moderate heat, low heat, and eco-cement, and any Portland cement can be used in the present invention.

The amount of the cement admixture of the present invention mainly composed of type II anhydrous gypsum, silica fume and blast furnace slag powder and the amount of the cement admixture of the present invention mainly composed of type II anhydrous gypsum, silica fume, blast furnace slag powder and expansion material are The amount is preferably 6 to 50 parts by weight per 100 parts by weight of cement. In particular, it is more preferable to use 2 to 10 parts by weight of each component of type II anhydrous gypsum, silica fume and blast furnace slag powder with respect to 100 parts by weight of cement.
If the amount of type II anhydrous gypsum, silica fume, and blast furnace slag powder is less than 2 parts by weight, the effect of improving strength development and durability is reduced. Moreover, when each exceeds 10 weight part, since the calcium hydroxide in concrete will be lose | eliminated and not only neutralization but a rusting of the PC steel rod of a prestressed molded object may be anxious, it is unpreferable.
More preferably, the expansion material is used in an amount of 1 to 5 parts by weight with respect to 100 parts by weight of cement. When the expansion material is less than 1 part by weight, the effect of reducing self-shrinkage is small, and depending on the type of expansion material used, even 5 parts by weight is the expansion side and the strength is reduced.

In producing a cement molded body using the cement admixture of the present invention, chemical admixtures such as a water reducing agent, an AE water reducing agent, an accelerator and a retarder can be used in combination as necessary. In particular, the use of a water reducing agent is preferable, and among the water reducing agents, the use of a high performance water reducing agent is more preferable.
High-performance water reducing agents are mainly composed of naphthalene sulfonic acid formaldehyde condensate salt, melanin sulfonic acid formaldehyde condensate salt, lignin sulfonate and polycarboxylate, and the type is not particularly limited. Polycarboxylates are preferred for high strength concrete used at the cement ratio.
The amount of the high-performance water reducing agent used is not particularly limited, but is preferably 0.5 to 2 parts by weight with respect to 100 parts by weight of cement in terms of solid content.

When kneading mortar / concrete by blending cement admixture of the present invention with cement, sand, gravel, appropriate amount of water and water reducing agent, the cement admixture of the present invention may be mixed with cement in advance as a cement composition. Alternatively, the cement admixture or each component may be mixed separately into the mixer directly at the time of kneading, and further dispersed in water and mixed in the form of a slurry. Moreover, admixtures, such as an expansion | swelling material, can be used as needed.
The kneading method is not particularly limited, and a method usually carried out with mortar / concrete can be used. However, in the case of high-strength concrete having a W / C ratio of about 25% or less, mortar is mixed, Thereafter, a method of adding coarse aggregate and kneading is preferable.

The molding method of high-strength concrete produced using the cement admixture and cement composition of the present invention includes centrifugal force molding, press molding, extrusion molding, papermaking, vibration molding, and vibration molding to form centrifugal force molding, casting biometer, etc. The law can be used.
Moreover, when carrying out normal pressure steam curing of a concrete molded object, it is important to carry out in the range whose atmospheric temperature in a curing tank or a curing sheet is 40-60 degreeC. Curing at an ambient temperature exceeding 60 ° C. is not preferable because the temperature inside the concrete becomes a high temperature of 60 ° C. or more and adversely affects the strength development. That is, it is preferable to manage the concrete so that the internal temperature of the concrete is 80 ° C. or lower, preferably about 60 ° C.
Examples of the high-strength concrete molded body molded as described above include centrifugal piles such as concrete piles, balls, fume pipes, steel pipe composite piles and steel pipe linings, box culverts, segments, concrete sleepers, sheet piles, bridge piers, and the like. Examples include precast molded bodies including prestressed concrete such as bridge girders.

  Using a cement admixture and a cement composition of the present invention, a ready-mixed concrete specified in JIS A 5308 is used to produce ready-mixed concrete for high strength using sand, gravel, an appropriate amount of water and a water reducing agent. It is possible to produce a high-strength concrete structure. For high-strength concrete with a W / C ratio of 25% or less, mix the cement with the cement admixture of the present invention or the cement composition of the present invention, sand, mortar with an appropriate amount of water and water reducing agent, and then add gravel. The method of kneading concrete is preferable.

Examples and Comparative Examples will be described below. Concrete materials used in the Examples and Comparative Examples are as follows.
Ordinary portland cement symbol N specific surface area of 3200 cm ² / g Density 3.14 Pacific Ocean Co. Low heat portland cement symbol L specific surface area of 3400 cm ² / g Density 3.22 Pacific Ocean Co. blast furnace slag symbol BS28 specific surface area of 2800 cm ² / g Density 2.92 90Myu sieve residue 3.1%
Symbol BS39 Specific surface area 3870cm ² / g Density 2.92 90μ Flue residue 0.3%
Symbol BS62 Specific surface area 6230cm ² / g Density 2.92 90μ Flue residue 0.0%
Symbol BS82 Specific surface area 8240cm ² / g Density 2.92 90μ Flue residue 0.0%
Natural anhydrous gypsum Symbol AG Specific surface area 4320cm ² / g Density 2.91
Silica Fume Symbol SF Density 2.24 Norwegian Expandable Material Symbol EX Density 3.20 Pacific Materials “N-Expan”
Fine aggregate Symbol S Density 2.63 Crushed sand coarse aggregate from Hatsutsuki-cho, Otsuki City Symbol G Density 2.63 Maximum dimension 20mm Crushed stone high-performance water reducing agent from Hatsukari-cho, Otsuki City Symbol AE Polycarboxylic acid ether type POZORIS SP8HU
Water symbol W Tap water

  The composition of the cement compositions used in the concrete tests of the examples and comparative examples are shown in Table 1 of FIG. 1 using symbols.

  The concrete formulations of the examples and comparative examples are listed in Table 2 in FIG. 2 using symbols.

  The properties and compressive strength (standard underwater curing) of fresh concrete were measured, and the results are shown in Table 3 of FIG.

  According to the results in Table 3, the fresh properties of the concrete were comparable with the cement composition. The strength of one day of 20 ° C. standard water curing of Examples No. 4 and 6 according to the present invention is slightly lower than that of No. 1, 2, and 3 of the comparative example, but the strength equivalent to that of the comparative example is 28 days. It is. In the system including the expansion material of Example NO6, the strength of the material age is increased per day.

  The self-shrinkage test of concrete was carried out according to the “Test method for self-shrinkage and self-expansion of cement paste, mortar and concrete (draft)” (JCI-1996) by the JCI Self-Shrinkage Research Committee. This test is a self-shrinkage test at 20 ° C. The results are shown in Table 4 in FIG.

  From the results of Table 4, the larger the fineness of the blast furnace slag powder, the greater the self-shrinkage. In the example using the blast furnace slag powder with large particles, the self-shrinkage was equal to or less than that of the low heat Portland cement-silica fume cement composition, which is considered to have a small self-shrinkage. It became clear that self-shrinkage could be reduced by using slag with large particles of blast furnace slag powder. Furthermore, it has become clear that self-shrinkage can be further reduced by using an expanding material.

  The specimen was placed in a simple thermal insulation tank made of expanded polystyrene having a thickness of 20 cm, the compressive strength in the simple thermal insulation curing and the temperature at the center of the specimen were measured, and the results are shown in Table 5 of FIG. Table 5 also shows the results of curing with 60 ° C. warm water.

By placing the specimen in a simple insulated tank made of expanded polystyrene, a high temperature rise due to high hydration heat generation is reproduced due to the high powder amount of high-strength concrete. Among them, the maximum temperature of the example was 39 ° C., which was lower than that of the comparative example. This indicates that blast furnace slag powder with large particles has a small hydration exotherm. In Example NO6 using the expanding material, the maximum temperature was about 1 ° C. higher than that in Example NO4.
Under the conditions of curing in a simple heat insulation tank made of expanded polystyrene or 60 ° C. warm water curing, the strengths of the 7-day ages of Examples Nos. 4 and 6 using blast furnace slag powder with large particles were equal to or higher than those of the comparative example.

  Place the specimen in a simple thermal insulation tank made of expanded polystyrene with a thickness of 20cm, and test the self-shrinkage of concrete by the JCI Self-Shrinking Research Committee "Self-shrinkage and self-expansion test method for cement paste, mortar and concrete (draft)" ( JCI-1996). The results are shown in Table 6 of FIG.

The self-shrinkage in the simple heat insulating state showed a shrinkage amount of 4 times or more compared with the self-shrinkage at 20 ° C. This is because the initial hydration was promoted because of a high temperature history in the initial stage.
Even when subjected to a high temperature history, the examples using the blast furnace slag powder with large particles showed less self-shrinkage than the low heat Portland cement-silica fume cement composition, which is considered to have a low self-shrinkage. In high-strength concrete subjected to a high temperature history, it was found that the use of slag with large particles of blast furnace slag powder was more effective in reducing self-shrinkage. Furthermore, it has become clear that self-shrinkage can be further reduced by using an expanding material.

Chart showing the composition of cement compositions used in the concrete tests of the examples and comparative examples Chart showing the mix of concrete in Examples and Comparative Examples using symbols Chart showing measurement results of properties and compressive strength (standard underwater curing) of fresh concrete Chart showing concrete self-shrinkage test results at 20 ° C Chart showing measurement results of compressive strength and temperature at the center of the specimen with simple heat insulation and 60 ° C warm water Chart showing concrete self-shrinkage test results in simple thermal insulation curing

Claims (3)

  A cement admixture mainly composed of 100 parts by weight of type II anhydrous gypsum, 20 to 300 parts by weight of silica fume, and 20 to 300 parts by weight of blast furnace slag powder containing 1 to 10% of particles of 90 μm or more.   Cement mainly composed of 100 parts by weight of type II anhydrous gypsum, 20 to 300 parts by weight of silica fume, 20 to 300 parts by weight of blast furnace slag powder containing 1 to 10% of particles of 90 μm or more, and 10 to 100 parts by weight of an expanding material Admixture.   A cement composition mainly comprising 100 parts by weight of cement and 6 to 50 parts by weight of the cement admixture according to claim 1 or 2.

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