JPH0648789A - Ultralow exotherm type b-type blast furnace cement - Google Patents

Abstract

PURPOSE:To provide the subject ultralow exotherm type cement capable of remarkably reducing the exotherm being accompanied with curing and of preventing reduction of durability of its cured concrete. CONSTITUTION:Cement is prepared by blending 15 to 30wt.% alite component with 50 to 75wt.% belite component, <=4wt.% C3A and 6 to 18wt.% C4AF an admixing gypsum with the resultant cement clinker. To 40 to 60wt.% the obtained cement, 60 to 40wt.% blast furnace slag powder is added, thus producing the objecting ultralow exotherm type B-type blast furnace cement.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultra-low heat generation type blast furnace type B cement suitable for use in mass concrete, especially large-scale concrete structures which require prevention or control of temperature cracking.

[0002]

2. Description of the Related Art In recent years, the size of concrete structures has been increasing due to the dramatic progress in concrete construction technology and structural analysis technology. In the construction of this large-scale concrete structure, so-called mass concrete structure, it is an important problem that temperature cracks occur due to heat generation due to progress of hardening of concrete. For this reason, the development of an ultra-low heat-generating cement that suppresses the calorific value lower than before and exhibits excellent strength development is under way. With such development, for example, a two-component ultra-low heat-generating cement obtained by adding blast furnace slag fine powder to Portland-based cement, or a fly ash mixed with the two-component ultra-low heat-generating cement 3
The component type ultra low heat generation cement is provided and put into practical use.

[0003]

[Problems to be Solved by the Invention] However, the above 2
In the case of one-component or three-component ultra-low heat-generating cement, it is necessary to adjust the mixing ratio of the base cement to 30 wt% or less in order to reduce the heat generation amount, and the heat generation amount can be greatly reduced. On the other hand, it has a new problem that the durability of concrete after hardening becomes low.
Therefore, when applied to concrete structures such as marine structures that require particularly durability, the surface of the concrete cannot be exposed and finished, and measures such as protecting the surface with permanent formwork etc. Must be taken.

The present invention has been made in view of the above problems, and can significantly reduce the amount of heat generated by curing.
Moreover, it is an object of the present invention to provide an ultra-low heat generation type blast furnace type B cement capable of suppressing deterioration of durability of concrete after hardening.

[0005]

The ultra-low heat generation type blast furnace type B cement of the present invention comprises an alite component of 15 to 30 wt%, a belite component of 50 to 75 wt% and a C ₃ A amount of 4 wt% or less,
Cement was prepared by adding and mixing gypsum to the cement clinker prepared so that the amount of C ₄ AF was 6 to 18 wt%, and the cement was prepared by containing 40 to 60 wt% of this cement and 60 to 40 wt% of blast furnace slag fine powder. It is characterized by becoming.

The present invention will be described in detail below. The ultra-low heat generation type blast furnace type B cement of the present invention is a cement mainly composed of belite within the range of the composition ratio of the main compounds, and the blast furnace slag fine powder is mixed in this cement by changing the mixing amount. However, a mixed cement that meets the specific surface area, compressive strength, and heat of hydration specifications of medium-heat Portland cement that has been conventionally used for mass concrete is prepared. After the concrete using the type B cement is hardened, the durability of the concrete using the blast furnace cement type B is improved.

Regarding the cement clinker as a base, among the main compounds of the cement clinker, C ₃ A, which has a large heat value of hydration, and alite are minimized, and those of belite and C ₄ AF, which have a relatively small heat value of hydration, are used. The composition ratio was increased. Among the main compounds, the alite component was set to 15 to 30 wt% because if it is less than 15 wt%, the expected early strength cannot be obtained, and if it exceeds 30 wt%, the reduction of the heat of hydration is sufficiently achieved. This is because it will not be possible. Moreover, the reason why the belite component is 50 to 75 wt% is that if it is less than 50 wt%, the composition ratio of alite is relatively increased and the heat value of hydration is increased.
This is because if the content exceeds wt%, the composition ratio of alite is relatively low, and the expected early strength cannot be obtained. The C ₃ A content is set to 4 wt% or less, because if it exceeds 4 wt%, the reduction of the heat value of hydration cannot be sufficiently achieved. Note that C ₃ A is generated in the manufacturing process of the clinker, and usually cannot be removed from the component composition. Further, the amount of C ₄ AF was set to 6 to 18 wt% according to the composition ratio of the above compound. Then, to the cement clinker thus prepared, an appropriate amount of gypsum powder, for example, 2 to 4 wt% is added and mixed to prepare cement.

With respect to the cement thus prepared,
This cement is 40-60wt%, and blast furnace slag fine powder is 6
The ultra low heat type blast furnace type B cement of the present invention was mixed by mixing so as to contain 0 to 40 wt%. The mixing ratio of the fine powder of the blast furnace slag and the cement (generally expressed as a weight percentage of the amount of the fine powder of blast furnace slag in the mixed cement, hereinafter referred to as the replacement ratio) is set to 60 to 40 wt% because the replacement ratio is 60 wt. This is because if the content exceeds 40%, the durability cannot be obtained like the conventional two-component and three-component super low heat-generating cement, and if it is less than 40 wt%, the specific surface area of the medium heat Portland cement (JIS R 5210) (2500 cm ² / g or more), compressive strength (3 days: 50 or more, 7 days 100 or more, 28 days: 230 or more, unit: kgf /
This is because the standard of cm ² ) and heat of hydration (7 days: 70 or less, 28 days: 83 or less, unit cal / g) cannot be satisfied.

[0009]

According to the ultra-low heat generation type blast furnace type B cement of the present invention, among the main compounds of the cement clinker, the composition ratio of C ₃ A and alite, which have a high heat value of hydration, is lowered and the composition ratio of belite is increased. As a result, the heat of hydration of the cement as a whole is suppressed, the drying shrinkage is small, and high chemical resistance is obtained. Further, the latent hydraulic property of the blast furnace slag fine powder suppresses the heat of hydration during the hardening process, and a dense hardened body can be obtained.

[0010]

EXAMPLES The present invention will be specifically described below with reference to examples. Table 1 shows the characteristics of the cement and the blast furnace slag fine powder used for the preparation of the ultra-low heat generation type blast furnace type B cement of the present invention.

[Table 1] As shown in Table 1, the cement used for preparation (hereinafter, this cement is referred to as belite cement) has a mineral composition of cement clinker, C ₃ S (alite) is 26.0 wt% and C ₂ S. (Belite) is 53.1 wt%, C ₃
A was adjusted to 2.6 wt% and C ₄ AF was adjusted to 13.0 wt%, and gypsum was mixed so that the SO ₃ amount was 2.0 wt%.
The fineness was 3500 cm ² / g in terms of Blaine specific surface area. On the other hand, the fineness of the blast furnace slag fine powder was 5500 cm ² / g in terms of Blaine specific surface area. When the strength development of the blast furnace slag fine powder was examined, the activity index was 62.0 in 3 days, 101 in 7 days, and 112 in 28 days. The substitution rate of the blast furnace slag fine powder for cement was 56%.

Table 2 shows the results of chemical analysis (JIS R 5202) of the ultra-low heat generation type blast furnace type B cement prepared by mixing the belite cement and the blast furnace slag shown in Table 1.

[Table 2]

Table 3 shows the results of a physical test (JIS R 5201) of the mortar obtained by preparing a mortar using the ultra-low heat generation type blast furnace type B cement. In addition, in the table,
For comparison, the test results for blast furnace cement type B (JIS R 5211) are also shown.

[Table 3] As shown in Table 3, in the mortar using the ultra-low heat generation type blast furnace type B cement of the present invention, although the setting start time and strength development were slightly delayed as compared with the mortar using the blast furnace cement type B cement, Regarding the Japanese heat, it was confirmed that the heat of hydration was largely suppressed to about 1/2 that of the mortar using blast furnace cement type B.

Table 4 shows that three types of concrete were obtained by using the ultra-low heat generation type blast furnace type B cement of the present invention and changing the water cement ratio, and the strength test (JIS A
1108 and JIS A 1113) were performed and the obtained results are shown in Table 4. As a comparison, similar to the mortar test,
The results of the concrete using the blast furnace cement type B are also shown in Table 4. Further, Table 5 shows the mixing ratio of concrete using each cement only for the mixing ratio of water cement ratio of 50%.

[Table 4]

[Table 5] From Table 4, as in the case of the mortar test, when the water-cement ratio was the same, the ultra-low heat generation type blast furnace type B cement of the present invention was used as compared with the concrete using the blast furnace cement type B. It was confirmed that the strength development of the concrete was slower. However, it has been found that with the ultra-low heat generation type blast furnace type B cement of the present invention, strength development equivalent to that of concrete using blast furnace cement type B can be obtained by lowering the water cement ratio.

FIG. 1 shows the results of an adiabatic temperature rise test of concrete using the super-low heat generation type blast furnace type B cement and the blast furnace cement type B of the present invention, respectively. The composition of the concrete used in the test was the same as that shown in Table 5 above. The casting temperature of the concrete was 20 ° C., and the measuring device used was a Sumitomo Cement company method. As can be seen in Fig. 1, the temperature of the concrete using blast furnace cement type B is 47.7 by the age of 3 days.
While the temperature rapidly rises up to 0 ° C, the temperature of the concrete using the ultra-low heat generation type blast furnace class B cement of the present invention rises gradually with the age, and at 10 days the age is 3
It was 3.8 ° C. Therefore, it was confirmed that the concrete using the ultra-low heat generation type blast furnace type B cement is less likely to undergo a rapid temperature change than the concrete using the blast furnace cement type B cement, and the calorific value is suppressed to a very low level. .

FIG. 2 shows the results of a drying shrinkage test (JIS A 1129) of concrete using the ultra-low heat generation type blast furnace type B cement and the blast furnace cement type B of the present invention, respectively. As shown in FIG. 2, the concrete using ultra-low heat generation type blast furnace cement B has a slightly larger shrinkage amount than the concrete using blast furnace cement type B, but is almost the same as the concrete using blast furnace cement type B. It was found to have equivalent durability.

FIG. 3 is a test for accelerating carbonation of concrete using the belite cement, the ultra-low heat-generating blast furnace type B cement of the present invention, the three-component ultra-low heat cement, and ordinary Portland cement (test conditions). : Test start date 91 days, set temperature 30 ° C., relative humidity 60%, carbon dioxide concentration 5% in nitrogen gas atmosphere). The mix of concrete using the ultra-low heat generation type blast furnace type B cement is the same as in Table 5 above, and the mix of other concrete is shown in Table 6.

[Table 6] As shown in Fig. 3, although the concrete using ultra-low heat generation type blast furnace type B cement is inferior to the concrete using ordinary Portland cement, it uses the three-component ultra-low heat cement currently in practical use. It was confirmed that an extremely excellent neutralization suppressing effect was obtained as compared with the concrete.

As described above, according to the ultra-low heat generation type blast furnace type B cement of the present invention, the belite cement and the blast furnace slag fine powder having the characteristics shown in Table 1 are mixed at a substitution rate of 56%. Belite has low exothermicity, low drying shrinkage, and chemical resistance. Due to latent hydraulicity of blast furnace slag fine powder, a dense cured product with low heat of hydration can be obtained. Therefore, it is possible to provide a concrete in which abrupt temperature change due to heat of hydration is suppressed, internal cracking due to temperature stress does not easily occur, and durability is superior to concrete using blast furnace cement type B.

[0018]

EFFECTS OF THE INVENTION The ultra-low heat generation type blast furnace type B cement of the present invention has the following effects. That is, lowering the high composition ratio of C ₃ A and the alite ones hydration heat of the main compounds of cement clinker, since enhanced composition ratio of belite is even suppressed low hydration heat value of the entire cement At the same time, the drying shrinkage after curing is small and high chemical resistance is obtained. Also,
Due to the latent hydraulic property of the blast furnace slag fine powder, the heat of hydration during the hardening process can be suppressed and a dense hardened product can be obtained. Therefore, the amount of heat generated during the curing process can be significantly reduced, and a cured concrete having excellent durability can be provided. Therefore, even when it is applied to a concrete structure requiring particularly durability, such as an offshore structure, it is not necessary to take measures such as protecting the surface with a permanent formwork, and the concrete surface is exposed. Can be a finish.

[Brief description of drawings]

FIG. 1 is a diagram showing adiabatic temperature rise test results of an ultra-low heat generation type blast furnace type B cement and a blast furnace cement type B of the present invention.

FIG. 2 is a diagram showing a result of the same dry shrinkage test.

FIG. 3 is a diagram showing a result of a neutralization accelerating test of concrete using the ultra-low heat generation type blast furnace type B cement, the belite cement, the three-component ultra-low heat generation cement, and the ordinary Portland cement of the present invention.

Front page continuation (72) Inventor Hideki Takemura, 585 Tomimachi, Funabashi, Chiba, Sumitomo Cement Corporation Central Research Laboratory (72) Inventor Akio Otsuka, 585, Tomimachi, Funabashi, Chiba Central Research Institute, Sumitomo Cement Co., Ltd.

Claims (1)

[Claims] 1. Alite component is 15 to 30 wt%, belite component is 50 to 75 wt%, C ₃ A content is 4 wt% or less, and C _{4 is}
A cement is prepared by adding and mixing gypsum to a cement clinker prepared so that the AF amount is 6 to 18 wt%. This cement contains 40 to 60 wt% and blast furnace slag fine powder contains 60 to 40 wt%. Low heat type blast furnace type B cement.