hydraulic materials

Abstract

To provide a hydraulic material that makes it possible to produce mortar and concrete having high initial strength even when the usage ratio of Portland cement is reduced and blast furnace slag powder is used.SOLUTION: A hydraulic material contains Portland cement, blast furnace slag powder and a stimulant. In the hydraulic material, the content of the blast furnace slag powder is more than 30% and 60% or less. The stimulant contains calcium nitrite and / or magnesium chloride. The molar number of chloride contained in the hydraulic material is preferably smaller than twice the molar number of aluminum oxide contained in the hydraulic material.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a hydraulic material that can be used as a material for mortar and concrete. [Background technology]

[0002] Portland cement is the main material used for mortar and concrete. A cement firing process is required to produce Portland cement. The cement firing process emits a large amount of carbon dioxide. Therefore, from the perspective of reducing carbon dioxide emissions, it is desirable to reduce the proportion of Portland cement used as a material for mortar and concrete.

[0003] Therefore, it is conceivable to reduce the proportion of Portland cement used as a material for mortar and concrete and use blast furnace slag powder, sodium silicate, and aluminum sulfate as described in the following Patent Document 1. However, doing so would result in a decrease in the initial strength of mortar and concrete produced without high-temperature curing such as steam curing, compared to when mortar and concrete are produced using Portland cement without using blast furnace slag powder. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-183338 Summary of the Invention [Problem to be solved by the invention]

[0005] As a result of various studies into this issue, the inventors have discovered that by using a specific stimulant together with powdered blast furnace slag, it is possible to produce mortar and concrete with high early strength even when cured at room temperature, i.e., 20° C. The present invention was made based on this discovery, and aims to provide a hydraulic material that can be used to produce mortar and concrete with high early strength even when using powdered blast furnace slag with a reduced proportion of Portland cement. [Means for solving the problem]

[0006] The hydraulic material according to the first aspect of the present invention contains Portland cement, blast furnace slag powder, and a stimulant. The content of the blast furnace slag powder in the hydraulic material is more than 30% and not more than 60%. The stimulant contains calcium nitrite and / or magnesium chloride.

[0007] According to the first aspect of the present invention, it is possible to produce mortar and concrete having higher early strength than hydraulic materials made of Portland cement and blast furnace slag powder without containing any stimulant when cured in an environment at a temperature of 20° C. Furthermore, according to the first aspect, since the content of blast furnace slag powder in the hydraulic material exceeds 30%, the content of Portland cement is correspondingly lower, thereby reducing carbon dioxide emissions from the manufacturing process of the hydraulic material.

[0008] In the hydraulic material according to the second aspect of the present invention, the number of moles of chloride contained in the hydraulic material is less than twice the number of moles of aluminum oxide contained in the hydraulic material.

[0009] According to the second aspect of the present invention, when mixing a hydraulic material, aggregate, and water, it is possible to cause many of the chloride ions contained in the hydraulic material to react with aluminum oxide. This allows for the formation of sparingly soluble complex salts (e.g., Friedel's salt, 3CaO·Al2O3·CaCl2·10H2O) in the mortar and concrete produced by this mixing. This reduces the amount of soluble chloride ions contained in the mortar and concrete, which adversely affect the corrosion of rebar. This in turn inhibits the corrosion of rebar placed in the mortar and concrete. [Effects of the Invention]

[0010] As described above, according to the present invention, mortar and concrete having high early strength can be produced using a hydraulic material containing blast furnace slag powder. DETAILED DESCRIPTION OF THE INVENTION

[0011] A hydraulic material according to one embodiment of the present invention will be described. The hydraulic material according to this embodiment is intended for producing mortar or concrete by mixing the hydraulic material with aggregate and water. The hydraulic material contains Portland cement, blast furnace slag powder, and a stimulant. The blast furnace slag powder content in the hydraulic material is greater than 30% and less than or equal to 60%. The stimulant content in the hydraulic material is preferably 1.5% to 6.5%. Calcium nitrite or magnesium chloride, or a mixture of calcium nitrite and magnesium chloride, is used as the stimulant.

[0012] In order to prevent corrosion of reinforcing bars placed in the mortar or concrete, it is preferable that the number of moles of chloride contained in the hydraulic material is less than twice the number of moles of aluminum oxide contained in the hydraulic material.

[0013] Next, examples 1 to 3 of a hydraulic material according to one embodiment of the present invention and comparative examples 1 to 7 will be described. In all examples and comparative examples, 450 g of hydraulic material, 1350 g of fine aggregate, and 225 g of water were mixed in a Hobart mixer in accordance with JIS R 5201 "Physical Testing Methods for Cement" to prepare a mixture.

[0014] In all examples and comparative examples, the kneaded mixture was molded using a steel mold with internal dimensions of 4 × 4 × 16 cm and left to stand for 24 hours in a room at a temperature of 20°C and a relative humidity of 60%. The molded mixture was then removed from the mold and sealed and cured in a room at 20°C until the material age reached 3 days or 7 days. Mortar was thus obtained. The compressive strength of this mortar was measured in accordance with JIS R 5201 "Physical Testing Methods for Cement."

[0015] Table 1 shows the composition of the hydraulic material in all Examples and Comparative Examples. As shown in Table 1, in Comparative Example 1, blast furnace cement alone was used as the hydraulic material. In Comparative Examples 2 to 7 and Examples 1 to 3, a mixture of 95% blast furnace cement and 5% stimulant was used as the hydraulic material. However, in Example 3, a mixture of 2.5% calcium nitrite and 2.5% magnesium chloride was used as the stimulant. The blast furnace cement is a mixture of Portland cement and blast furnace slag powder. In Table 1, the blast furnace slag powder content refers to the content of the blast furnace slag powder contained in the blast furnace cement in the hydraulic material. The hydraulic materials in all Examples and Comparative Examples correspond to blast furnace cement type B because the blast furnace slag powder content in these hydraulic materials is more than 30% and not more than 60%.

[0016] [Table 1]

[0017] The chemical compositions of the blast furnace slag cements used in all the examples and comparative examples are shown in Table 2.

[0018] [Table 2]

[0019] Table 3 shows the relationship between the type of stimulant, 3-day strength, and 7-day strength for all examples and comparative examples. In Table 3, the "3-day strength" column indicates the compressive strength of the mortar when the mortar is 3 days old. The "7-day strength" column indicates the compressive strength of the mortar when the mortar is 7 days old. As mentioned above, no stimulant was used in Comparative Example 1, and therefore, in Table 3, the "Type of stimulant" column for Comparative Example 1 is marked as "No addition."

[0020] [Table 3]

[0021] As shown in Table 3, in Examples 1 to 3, the use of the stimulant resulted in greater 3-day and 7-day strengths than in Comparative Example 1. On the other hand, in Comparative Examples 2 to 7, the use of the stimulant resulted in a lower 7-day strength than in Comparative Example 1. Furthermore, in Comparative Examples 3 to 7, the use of the stimulant resulted in a lower 3-day strength than in Comparative Example 1.

[0022] From the above, the following conclusion can be drawn from all of the Examples and Comparative Examples shown in Table 3. In a hydraulic material containing Portland cement, blast furnace slag powder, and a stimulant, if the content of blast furnace slag powder in this hydraulic material is more than 30% and not more than 60%, and calcium nitrite and / or magnesium chloride are contained as the stimulant, it is possible to produce mortar with higher early strength than when this hydraulic material does not contain a stimulant.

[0023] Table 4 shows the moles of aluminum oxide and chloride contained in the hydraulic material in Example 2. As shown in Table 4, in Example 2, the moles of chloride contained in the hydraulic material is less than twice the moles of aluminum oxide contained in the hydraulic material. Therefore, in Example 2, it is believed that by mixing the hydraulic material, the fine aggregate, and the water, much of the chloride contained in the hydraulic material reacted with aluminum oxide. As a result, in Example 2, the amount of soluble chloride ions in the mortar is small, which is believed to be able to suppress corrosion of the reinforcing steel placed in the mortar.

[0024] [Table 4]

[0025] As described above, according to the above-described embodiment, it is possible to produce mortar and concrete with higher early strength than hydraulic materials made of Portland cement and blast furnace slag powder without containing a stimulant. Furthermore, according to the above-described embodiment, since the content of blast furnace slag powder in the hydraulic material exceeds 30%, the content of Portland cement is correspondingly lower, thereby reducing carbon dioxide emissions from the manufacturing process of the hydraulic material.

[0026] Furthermore, in the above embodiment, if the number of moles of chloride contained in the hydraulic material is less than twice the number of moles of aluminum oxide contained in the hydraulic material, when the hydraulic material, aggregate, and water are mixed, many of the chloride ions contained in the hydraulic material can react with the aluminum oxide to form a sparingly soluble complex salt. This reduces the amount of soluble chloride ions in the mortar and concrete produced by this mixing. This reduces corrosion of the reinforcing steel bars installed in the mortar and concrete.

[0027] Furthermore, according to the above-described embodiment, the mortar and concrete obtained by curing at 20°C can develop high early strength. This eliminates the need for autoclave curing, steam curing, or heat curing to develop early strength in the mortar and concrete. In other words, it is possible to save energy required for curing to obtain the mortar and concrete.

Claims

[Claim 1] A hydraulic material comprising Portland cement, blast furnace slag powder and a stimulant, The content of the blast furnace slag powder in the hydraulic material is more than 30% and not more than 60%; The content of the stimulant in the hydraulic material is 1.5% or more and 6.5% or less, A hydraulic material characterized in that the stimulant is a mixture of calcium nitrite and magnesium chloride.

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