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 60%. The stimulant contains one or more of calcium nitrite, calcium chloride, magnesium carbonate and magnesium chloride. The stimulant may contain two or more of calcium nitrite, calcium chloride, magnesium carbonate, magnesium chloride and sodium thiosulfate. 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 comprises Portland cement, blast furnace slag powder, and a stimulant, the blast furnace slag powder content of which is greater than 60%, and the stimulant comprises one or more of calcium nitrite, calcium chloride, magnesium carbonate, and magnesium chloride.

[0007] The stimulant may also include two or more of calcium nitrite, calcium chloride, magnesium carbonate, magnesium chloride, and sodium thiosulfate.

[0008] 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 60%, the content of Portland cement is correspondingly lower, thereby reducing carbon dioxide emissions from the manufacturing process of the hydraulic material.

[0009] 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.

[0010] 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]

[0011] 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

[0012] 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 exceeds 60%. The stimulant content in the hydraulic material is preferably 1.5% or more and 6.5% or less.

[0013] The stimulant may be one or more of calcium nitrite, calcium chloride, magnesium carbonate, and magnesium chloride, or two or more of each of the above four compounds and sodium thiosulfate.

[0014] 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.

[0015] Next, Examples A1 to A4 and B1 to B6 of a hydraulic material according to one embodiment of the present invention and Comparative Examples A1 to A5 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 kneaded mixture.

[0016] 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."

[0017] In Comparative Example A1, Example A1, Example A4, and Example B4, the flow values ​​of the kneaded mixture were measured by a flow test 0 minutes, 15 minutes, and 30 minutes after the start of mixing 450 g of the hydraulic material, 1350 g of fine aggregate, and 225 g of water. The flow test was conducted in accordance with JIS R 5201 "Physical Testing Methods for Cement." The flow values ​​measured 15 minutes and 30 minutes after the start of mixing were measured after the mixture was mixed with a spoon for 15 seconds before the flow test.

[0018] For Examples A1, A4, and B4, the flow value ratios were calculated after 0, 15, and 30 minutes, respectively. These flow value ratios are the percentages of the flow value of Example A1, A4, or B4 relative to the flow value of Comparative Example A1 after a predetermined time has elapsed since the start of mixing.

[0019] Table 1 shows the composition of the hydraulic material in all examples and comparative examples. As shown in Table 1, in Comparative Example A1, a mixture of 52.6% blast furnace cement and 47.4% additional blast furnace slag powder was used as the hydraulic material. In the other comparative examples and all examples, a mixture of 50% blast furnace cement, 45% additional blast furnace slag powder, and 5% stimulant was used as the hydraulic material. Note that the blast furnace cement is a mixture of Portland cement and blast furnace slag powder. In Table 1, the total content of blast furnace slag powder refers to the total content of the blast furnace slag powder and the additional 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 C because the total content of the blast furnace slag powder in these hydraulic materials exceeds 60%.

[0020] [Table 1]

[0021] Table 2 shows the chemical compositions of the blast furnace cement and the additional blast furnace slag powder used in all the examples and comparative examples.

[0022] [Table 2]

[0023] Table 3 shows the relationship between the type of stimulant, 3-day strength, and 7-day strength for Comparative Examples A1 to A5 and Examples A1 to A4. 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 A1, and therefore, in Table 3, the "type of stimulant" column for Comparative Example A1 is marked "no addition."

[0024] [Table 3]

[0025] As shown in Table 3, in Examples A1 to A4, the use of the stimulant resulted in greater 3-day and 7-day strengths than in Comparative Example A1. On the other hand, in Comparative Examples A2 to A5, the use of the stimulant resulted in a smaller 7-day strength than in Comparative Example A1. Furthermore, in Comparative Examples A3 to A5, the use of the stimulant resulted in a smaller 3-day strength than in Comparative Example A1.

[0026] Table 4 shows the relationship between the type of stimulant and the 3-day and 7-day strengths in Comparative Example A1 and Examples B1 to B6. The definitions of 3-day and 7-day strengths in Table 4 are the same as those in Table 3. Examples B1 to B6 differ from Comparative Examples A2 to A5 and Examples A1 to A4 in that 2.5% each of the two compounds shown in Table 4 was used as the stimulant.

[0027] [Table 4]

[0028] As shown in Table 4, in Examples B1 to B6, the use of the stimulant resulted in greater 3-day strength and 7-day strength than in Comparative Example A1.

[0029] Table 5 shows the flow value ratios for Examples A1, A4, and B4 at 0, 15, and 30 minutes after the start of mixing. As shown in Table 5, in Examples A1, A4, and B4, the flow value ratios exceeded 100% at 0, 15, and 30 minutes after the start of mixing, i.e., exceeded the flow value in Comparative Example A1.

[0030] [Table 5]

[0031] From the above, the following conclusion can be drawn from Examples A1 to A4 and Comparative Examples A1 to A5 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 exceeds 60% and the stimulant contains one or more of calcium nitrite, calcium chloride, magnesium carbonate, and magnesium chloride, it is possible to produce mortar with higher early strength than when the hydraulic material does not contain a stimulant.

[0032] Furthermore, the following conclusion can be drawn from Examples B1 to B6 and Comparative Example A1 shown in Table 4. Even if this hydraulic material contains two or more of the above-mentioned calcium nitrite, calcium chloride, magnesium carbonate, magnesium chloride, and sodium thiosulfate as the stimulant, it is possible to produce mortar with higher early strength than when this hydraulic material does not contain a stimulant.

[0033] Furthermore, the following conclusion can be drawn from Examples A1, A4, and B4 shown in Table 5: When the hydraulic material contains calcium nitrite or magnesium chloride, or a mixture of calcium nitrite and magnesium chloride as the stimulant, a mortar with higher fluidity can be produced compared to when the hydraulic material does not contain a stimulant.

[0034] Table 6 shows the moles of aluminum oxide and chloride contained in the hydraulic material of Example A4. As shown in Table 6, in Example A4, 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 A4, 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, the amount of soluble chloride ions in the mortar in Example A4 is small, which is believed to be able to suppress corrosion of the reinforcing steel placed in the mortar.

[0035] [Table 6]

[0036] 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 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 60%, the content of Portland cement is correspondingly lower, thereby reducing carbon dioxide emissions from the manufacturing process of the hydraulic material.

[0037] 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.

[0038] Furthermore, in the above embodiment, when calcium nitrite or magnesium chloride, or a mixture of calcium nitrite and magnesium chloride, is used as a stimulant, mortar and concrete having higher fluidity can be produced compared to when no stimulant is used.

[0039] 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 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 magnesium chloride and calcium nitrite.

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