Hydraulic composition and production method of hydraulic composition

Abstract

To provide a hydraulic composition that can restrain contraction strain as much as possible, and a production method of the hydraulic composition.SOLUTION: A hydraulic composition according to the present invention is the hydraulic composition containing normal Portland cement, blast furnace slag, water, fine aggregates, gypsum, and calcium carbonate, and a content of the calcium carbonate is 15 to 60 mass% of a content of the gypsum (gypsum dihydrate conversion amount). In the hydraulic composition according to the present invention, preferably, the content of the calcium carbonate is 1.25 to 12.0 pts.mass to the sum of 100 pts.mass of the normal Portland cement and the blast furnace slag, and the content of the gypsum (gypsum dihydrate conversion amount) is 5.0 to 8.0 pts.mass to the sum of 100 pts.mass of the normal portland cement and the blast furnace slag.SELECTED DRAWING: Figure 5B

Description

Technical Field

[0001] The present invention relates to a hydraulic composition containing blast furnace slag and a method for producing the hydraulic composition.

Background Art

[0002] Conventionally, in order to reduce CO2 emissions, instead of reducing cement, blast furnace cement containing blast furnace slag has been used. Concrete using this blast furnace cement (especially blast furnace cement type B with a blast furnace slag content exceeding 30% by mass) has a tendency for the shrinkage strain to increase significantly due to a high-temperature history compared to the case of using ordinary Portland cement, and it is known that cracking is likely to occur. Therefore, as in Patent Document 1, technologies for suppressing the occurrence of cracking have been proposed for blast furnace cement.

[0003] Specifically, in Patent Document 1, a hydraulic composition characterized by comprising 98 to 75% by weight of granulated blast furnace slag having a Blaine specific surface area of 1500 to 3600 cm 2 / g and 2 to 25% by weight of anhydrous gypsum is disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As described above, although the increase in shrinkage strain due to a high-temperature history in concrete using blast furnace cement type B is regarded as a problem, in mass concrete, which usually occupies the majority of materials for civil engineering structures, the temperature rise due to the heat of hydration is inevitable. Therefore, the increase in shrinkage strain due to a high-temperature history when using blast furnace cement type B can be said to be an inevitable and important problem. Therefore, the inventors considered that further enhancement was necessary for the shrinkage strain suppression effect regarding Blast Furnace Cement Type B from the prior art including Patent Document 1 and the like.

[0006] Accordingly, an object of the present invention is to provide a hydraulic composition capable of suppressing shrinkage strain as much as possible and a method for producing the hydraulic composition.

Means for Solving the Problems

[0007] The above problems can be solved by the following means. The hydraulic composition according to the present invention is a hydraulic composition containing ordinary Portland cement, blast furnace slag, water, fine aggregate, gypsum, and calcium carbonate, wherein the content of the calcium carbonate is 15 to 60% by mass of the content of the gypsum (in terms of dihydrate gypsum). According to the present invention, since it contains gypsum and calcium carbonate and the content of calcium carbonate is a predetermined mass ratio with respect to the content of gypsum, shrinkage strain (specifically, drying shrinkage strain due to high temperature history) can be suppressed more than in the prior art. In the hydraulic composition according to the present invention, the content of the calcium carbonate is preferably 1.25 to 12.0 parts by mass with respect to 100 parts by mass in total of the ordinary Portland cement and the blast furnace slag, and the content of the gypsum (in terms of dihydrate gypsum) is preferably 5.0 to 8.0 parts by mass with respect to 100 parts by mass in total of the ordinary Portland cement and the blast furnace slag. Further, in the hydraulic composition according to the present invention, the total of the content of the calcium carbonate and the content of the gypsum (in terms of dihydrate gypsum) is preferably 6.25 to 20.0 parts by mass with respect to 100 parts by mass in total of the ordinary Portland cement and the blast furnace slag. Further, in the hydraulic composition according to the present invention, the calcium carbonate is preferably fine limestone powder. According to the present invention, the shrinkage strain suppression effect can be more surely exhibited. The manufacturing method of the hydraulic composition according to the present invention is a manufacturing method for manufacturing a hydraulic composition by mixing water, fine aggregate, additive, and chemical admixture with respect to blast furnace cement type B, wherein the additive contains gypsum and calcium carbonate, and the additive is mixed with the blast furnace cement type B such that the content of calcium carbonate in the hydraulic composition is 15 to 60% by mass of the content of gypsum (in terms of dihydrate gypsum) in the hydraulic composition. According to the present invention, by using an additive containing gypsum and calcium carbonate and setting the content of calcium carbonate to a predetermined mass ratio with respect to the content of gypsum, it is possible to manufacture a hydraulic composition in which the shrinkage strain can be suppressed more than in the prior art. Further, according to the present invention, an additive containing gypsum and calcium carbonate may be added to the blast furnace cement type B supplied from a cement silo or the like. Therefore, the entire inside of the cement silo is not occupied by the hydraulic composition of the present invention. In addition, according to the present invention, since the amount of the additive added to the blast furnace cement type B is not large, problems in transporting the additive to the plant (such as an increase in the amount of transportation and transportation cost) do not occur.

Effects of the Invention

[0008] The hydraulic composition according to the present invention can suppress shrinkage strain as much as possible. The manufacturing method of the hydraulic composition according to the present invention can manufacture a hydraulic composition that can suppress shrinkage strain as much as possible.

Brief Description of the Drawings

[0009]

Figure 1A

Figure 1B

Figure 2A

Figure 2B

Figure 3A

Figure 3B

Figure 4A

Figure 4B

Figure 5A

Figure 5B

Figure 6A

Figure 6B

[0010] Hereinafter, the hydraulic composition according to the present embodiment and the method for manufacturing the hydraulic composition will be described. [Hydraulic Composition] The hydraulic composition according to this embodiment is a composition containing ordinary Portland cement, blast furnace slag, water, fine aggregate, gypsum, and calcium carbonate. And the content of calcium carbonate in the hydraulic composition according to this embodiment is a predetermined mass ratio with respect to the content of gypsum (in terms of the amount of dihydrate gypsum). Hereinafter, each component will be described in detail.

[0011] (Ordinary Portland Cement) Ordinary Portland cement is a general cement and conforms to the provisions of JIS R5210:2009. The content of ordinary Portland cement in the hydraulic composition is, for example, 150 kg / m 3 or more, 200 kg / m 3 or more, 250 kg / m 3 or more, 280 kg / m 3 or more, and 500 kg / m 3 or less, 450 kg / m 3 or less, 400 kg / m 3 or less, 350 kg / m 3 or less.

[0012] (Blast Furnace Slag) Blast furnace slag (ground granulated blast furnace slag) is obtained by drying and pulverizing granulated blast furnace slag, or adding gypsum thereto, and is defined in JIS A6206:2013. The content of blast furnace slag in the hydraulic composition is, for example, 100 kg / m 3 or more, 150 kg / m 3 or more, 170 kg / m 3 or more, 180 kg / m 3 or more, and 350 kg / m 3 or less, 300 kg / m 3 or less, 250 kg / m 3 or less, 200 kg / m 3 or less. Note that the content of blast furnace slag is preferably more than 30% by mass and not more than 60% by mass of the total amount of ordinary Portland cement and blast furnace slag (the content of blast furnace slag is more than 30% by mass and not more than 60% by mass). In this case, it becomes a binder equivalent to Type B blast furnace cement.

[0013] (Gypsum) Gypsum is a mineral mainly composed of calcium sulfate, and examples include anhydrous gypsum (CaSO4, molecular weight: 136.14), dihydrate gypsum (CaSO4·2H2O, molecular weight: 172.17), hemihydrate gypsum (CaSO4·1 / 2H2O, molecular weight: 145.15), etc. The content of gypsum (in terms of dihydrate gypsum) is preferably 3.0 to 10.0 parts by mass, more preferably 5.0 to 8.0 parts by mass, based on 100 parts by mass in total of ordinary Portland cement and blast furnace slag. By setting the content of gypsum within a predetermined range, the effect of suppressing shrinkage strain based on gypsum can be sufficiently exerted. Note that the "content of gypsum (in terms of dihydrate gypsum)" in this specification is a value obtained by converting the content of gypsum in the hydraulic composition into the content of dihydrate gypsum, and it can be converted based on the molecular weight of the contained gypsum and the molecular weight of dihydrate gypsum. For example, in the case of a hydraulic composition where the content of anhydrous gypsum is X kg / m 3 the content of gypsum (in terms of dihydrate gypsum) can be calculated as X×172.17 (molecular weight of dihydrate gypsum) / 136.14 (molecular weight of anhydrous gypsum). Also, since the "content of gypsum" in this specification refers to the content in the hydraulic composition, for example, if gypsum is contained in ordinary Portland cement or blast furnace slag, of course, it is the amount including these gypsums (that is, the total amount of gypsum contained in the hydraulic composition).

[0014] (Calcium carbonate) Calcium carbonate is a carbonate of calcium represented by the chemical formula CaCO3. It is preferable that the calcium carbonate is fine limestone powder (natural calcium carbonate), which is heavy calcium carbonate (CaCO3) obtained by pulverizing and classifying limestone. However, light calcium carbonate (synthetic calcium carbonate), which is calcium carbonate obtained by precipitating fine crystals through a chemical reaction (including calcium carbonate produced by recovering CO2), may also be used. The inventors of the present invention have found that by setting the mass ratio of calcium carbonate to the above-mentioned gypsum content (in terms of the equivalent amount of dihydrate gypsum) within a predetermined range, the "effect of suppressing shrinkage strain due to high-temperature history (specifically, drying shrinkage strain)" is exhibited, and thus the present invention has been created. The content of calcium carbonate in the hydraulic composition is preferably 15% or more, more preferably 20% or more, and still more preferably 25% or more of the gypsum content (in terms of the equivalent amount of dihydrate gypsum). By setting the content of calcium carbonate to a predetermined value or more, the shrinkage strain due to high-temperature history can be suppressed. The content of calcium carbonate in the hydraulic composition is preferably 60% or less, more preferably 55% or less, and still more preferably 50% or less of the gypsum content (in terms of the equivalent amount of dihydrate gypsum). By setting the content of calcium carbonate to a predetermined value or less, it is possible to avoid a situation where the effect of suppressing shrinkage strain conversely decreases. Also, the content of calcium carbonate in the hydraulic composition is preferably 0.5 to 15.0 parts by mass, more preferably 1.25 to 12.0 parts by mass, based on 100 parts by mass in total of ordinary Portland cement and blast furnace slag. By setting the content of calcium carbonate within a predetermined range, the above-mentioned effect of suppressing shrinkage strain can be firmly exhibited.

[0015] (Content of gypsum and calcium carbonate) The total content of calcium carbonate and the content of gypsum (in terms of dihydrate gypsum) in the hydraulic composition is preferably 3.5 to 25.0 parts by mass, more preferably 6.25 to 20.0 parts by mass, based on 100 parts by mass in total of ordinary Portland cement and blast furnace slag. By setting the total content of calcium carbonate and gypsum within a predetermined range, the above-described shrinkage strain suppressing effect can be firmly exhibited.

[0016] (Fine aggregate) Examples of the fine aggregate include mountain sand, lime crushed sand, river sand, sea sand, crushed sand, silica sand, lime sand, etc., and it complies with JISA5005:2020. The content of ordinary fine aggregate in the fine aggregate is, for example, 800 kg / m 3 or more, 1000 kg / m 3 or more, 1200 kg / m 3 or more, and 1800 kg / m 3 or less, 1600 kg / m 3 or less, 1400 kg / m 3 or less.

[0017] (Water) The water content in the hydraulic composition is, for example, 150 kg / m 3 or more, 180 kg / m 3 or more, 200 kg / m 3 or more, 250 kg / m 3 or more, and 350 kg / m 3 or less, 300 kg / m 3 or less. Note that the water in the hydraulic composition is not particularly limited, and tap water, sludge water, etc. can be used.

[0018] (Others) The hydraulic composition according to the present embodiment may appropriately contain conventionally known materials (chemical admixtures, coarse aggregates, etc.) used in general cement, mortar, and concrete, as long as the desired effects of the present invention are not inhibited. Examples of the chemical admixture include AE agent, high-performance water reducer, water reducer, AE water reducer, high-performance AE water reducer, fluidizing agent, etc. specified in JIS A6204:2011. Examples of the coarse aggregate include mountain gravel, river gravel, sea gravel, etc., which comply with JIS A5005:2020.

[0019] [Method for producing hydraulic composition] The method for producing a hydraulic composition according to this embodiment is a production method in which water, fine aggregate, additive (including gypsum and calcium carbonate), and chemical admixture are mixed with blast furnace cement type B to produce a hydraulic composition. Note that blast furnace cement type B is specified in JIS R5211:2019. Specifically, considering the content of gypsum in blast furnace cement type B, etc., the blending ratio of gypsum and calcium carbonate in the additive and the addition amount of the additive are calculated so that the content of gypsum and the content of calcium carbonate in the finally obtained hydraulic composition fall within the above-mentioned ranges. Then, a hydraulic composition is produced by adding and mixing an additive, etc. to the blast furnace cement type B supplied from a cement silo or the like.

Examples

[0020] (Specimen) The composition of the hydraulic composition used for the specimen (mortar) is as shown in Table 1, and the materials shown in Table 2 were used. Although the ordinary Portland cement used contained gypsum, the "gypsum content (in terms of dihydrate gypsum)" shown in the table is a value considering the amount of gypsum in the ordinary Portland cement.

[0021]

Table 1

[0022]

Table 2

[0023] (Test content: Measurement of drying shrinkage strain) The measurement of drying shrinkage strain was carried out in accordance with JIS A1129-2. Specifically, it was as follows. The dimensions of the prepared specimens were 40×40×160 mm, and the number of specimens was 3 for each. First, the specimens were sealed and cured until the age of 14 days (using wrap and plastic bags, temperature conditions: 3 conditions shown below). In addition, two contact chips were attached to the specimens at the timing when the age of the specimens reached 7 days. Slight drying was allowed during the attachment operation of the contact chips. Next, the base length L between the contact chips was measured at the age of 14 days, and then drying was started. The length Ld between the contact chips was measured at drying ages of 0, 1, 2, 4, 8, and 13 weeks. Then, based on the base length L and the length Ld measured at each drying age, the drying shrinkage strain (ε = (Ld - L) / L) was calculated for each of the 3 specimens, and then the average value was calculated. Note that the temperature conditions for sealed curing were the three conditions of 'constant temperature of 20°C' (appropriately indicated as 'in the case of 20°C', etc.), 'the kneading temperature is 20°C, the maximum temperature reached at the age of 1 - 2 days is 40°C, and the temperature at the age of 7 days is 20°C' (appropriately indicated as 'in the case of 40°C', etc.), and 'the kneading temperature is 20°C, the maximum temperature reached at the age of 1 - 2 days is 60°C, and the temperature at the age of 7 days is 20°C' (appropriately indicated as 'in the case of 60°C', etc.).

[0024] (Discussion of results: When the temperature curing condition is 20°C) Figure 1A is a line graph showing the shrinkage strain (drying ages of 0, 1, 2, 4, 8, 13 weeks) of Specimens 1 - 6 when the temperature curing condition (temperature condition in sealed curing) is 20°C. Figure 1B is a bar graph focusing on the results at the drying age of 4 weeks from the results of Figure 1A. Figure 2A is a line graph showing the shrinkage strain (drying ages of 0, 1, 2, 4, 8, 13 weeks) of Specimens 1, 2, 7 - 11 when the temperature curing condition is 20°C. Figure 2B is a bar graph that focuses on the results of the specimen at 4 weeks of dry material age among the results of Figure 2A. Note that the numerical values after the specimen numbers in the figure (e.g., 4.5%:0%) indicate that the former value is the gypsum content and the latter value is the content of fine limestone powder. As is clear from comparing the results of Figure 1A and Figure 2A, and the results of Figure 1B and Figure 2B respectively, it was confirmed that in an environment of 20°C, the greater the gypsum content, the more the drying shrinkage strain is suppressed. However, it was also confirmed that in a 20°C environment, the content of fine limestone powder (calcium carbonate) has little effect on the drying shrinkage strain.

[0025] (Discussion of results: When the temperature curing condition is 40°C) Figure 3A is a line graph showing the shrinkage strains (dry material ages 0, 1, 2, 4, 8, 13 weeks) of Specimens 1 to 6 when the temperature curing condition is 40°C. Figure 3B is a bar graph that focuses on the results of the specimen at 4 weeks of dry material age among the results of Figure 3A. Figure 4A is a line graph showing the shrinkage strains (dry material ages 0, 1, 2, 4, 8, 13 weeks) of Specimens 1, 2, 7 to 11 when the temperature curing condition is 40°C. Figure 4B is a bar graph that focuses on the results of the specimen at 4 weeks of dry material age among the results of Figure 4A. As is clear from comparing the results of Figure 3A and Figure 4A, and the results of Figure 3B and Figure 4B respectively, it was confirmed that in an environment of 40°C, the greater the gypsum content, the more the drying shrinkage strain is suppressed. Based on the results of Figure 3B, it was also confirmed that in a 40°C environment, when the content of fine limestone powder (calcium carbonate) is in a mass ratio of 15 - 60% of the gypsum content (in terms of hydrated gypsum), especially in a mass ratio of 25 - 50%, the drying shrinkage strain can be more effectively suppressed. Also, based on the results in Fig. 4B, when the temperature is 40°C and the content of gypsum (in terms of hydrated gypsum) is 8.0 parts by mass with respect to a total of 100 parts by mass of ordinary Portland cement and blast furnace slag, it was confirmed that the content of fine limestone powder (calcium carbonate) has little effect on the dry shrinkage strain, and there is no adverse effect even if the content of fine limestone powder (calcium carbonate) increases.

[0026] (Discussion of Results: When the Temperature Curing Condition is 60°C) Fig. 5A is a line graph showing the shrinkage strain (dry ages 0, 1, 2, 4, 8, 13 weeks) of Specimens 1 to 6 when the temperature curing condition is 60°C. Fig. 5B is a bar graph focusing on the results at a dry age of 4 weeks among the results in Fig. 5A. Fig. 6A is a line graph showing the shrinkage strain (dry ages 0, 1, 2, 4, 8, 13 weeks) of Specimens 1, 2, 7 to 11 when the temperature curing condition is 60°C. Fig. 6B is a bar graph focusing on the results at a dry age of 4 weeks among the results in Fig. 6A. As is clear from comparing the results of Fig. 5A and Fig. 6A, and the results of Fig. 5B and Fig. 6B respectively, it was confirmed that in an environment of 60°C, a higher content of gypsum suppresses the dry shrinkage strain. Based on the results of Fig. 5B and 6B, it was also confirmed that in a 60°C environment, when the content of fine limestone powder (calcium carbonate) is in a mass ratio of 15 - 60%, particularly 25 - 50%, of the content of gypsum (in terms of hydrated gypsum), the dry shrinkage strain can be more effectively suppressed.

[0027] From these results, it was confirmed that according to the present invention, the shrinkage strain at high temperature history (40°C or higher, particularly 60°C or higher) can be more effectively suppressed. Also, from these results, it was confirmed that according to the present invention, since the addition amount of additives (including gypsum and calcium carbonate) with respect to the amount of cement is not large, problems in transporting the additives to the plant (such as an increase in the amount of transportation and transportation cost) do not occur.

Claims

1. A hydraulic composition comprising ordinary Portland cement, blast furnace slag, water, fine aggregate, gypsum, and calcium carbonate, wherein the content of the calcium carbonate is 15 to 60% by mass of the content of the gypsum (in terms of hydrated gypsum), characterized by the hydraulic composition.

2. The content of the calcium carbonate is 1.25 to 12.0 parts by mass with respect to 100 parts by mass in total of the ordinary Portland cement and the blast furnace slag, and the content of the gypsum (in terms of hydrated gypsum) is 5.0 to 8.0 parts by mass with respect to 100 parts by mass in total of the ordinary Portland cement and the blast furnace slag, characterized by the hydraulic composition according to Claim 1.

3. The total of the content of the calcium carbonate and the content of the gypsum (in terms of hydrated gypsum) is 6.25 to 20.0 parts by mass with respect to 100 parts by mass in total of the ordinary Portland cement and the blast furnace slag, characterized by the hydraulic composition according to Claim 1 or Claim 2.

4. The calcium carbonate is fine limestone powder, characterized by the hydraulic composition according to Claim 1 or Claim 2.

5. A production method for producing a hydraulic composition by mixing water, fine aggregate, an additive, and a chemical admixture with blast furnace cement type B, wherein the additive contains gypsum and calcium carbonate, and the additive is mixed with the blast furnace cement type B such that the content of the calcium carbonate in the hydraulic composition is 15 to 60% by mass of the content of the gypsum (in terms of hydrated gypsum) in the hydraulic composition, characterized by the production method of the hydraulic composition.

Images