Compression strength enhancer for blast furnace granulated slag

Abstract

To provide a compressive strength enhancing agent which can enhance compressive strength exhibited when a granulated blast furnace slag is cured by adding the agent to the granulated blast furnace slag.SOLUTION: A compressive strength enhancing agent to a granulated blast furnace slag is composed of an alkali stimulant, gypsum and an accelerator, wherein a content of the gypsum is 30.0 mass% or more in terms of SO3, and a content of the accelerator is 10.0 mass% or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure relates to a compressive strength enhancer for granulated blast furnace slag. [Background technology]

[0002] In recent years, with increasing demands for measures against global warming, there is a need to reduce CO2 emissions in cement production. As a method to reduce CO2 emissions, a method of replacing a portion of cement clinker, which has a large CO2 emission rate during preparation, with an admixture is being widely investigated. Among the admixtures, steel slag, such as blast furnace slag, is expected to enhance the long-term strength of concrete and improve its salt shielding effect. Therefore, research is underway on cement that uses steel slag as an admixture and increases its mixing ratio.

[0003] Blast furnace cement, in which a portion of the cement clinker is replaced with blast furnace slag such as granulated blast furnace slag (BFS), is classified according to the replacement ratio. JIS R 5211:2019 specifies blast furnace cement type B, where the amount of blast furnace slag exceeds 30% by mass but is 60% by mass or less, and blast furnace cement type C, where the amount exceeds 60% by mass but is 70% by mass or less. However, currently, there are no regulations for cement where the amount of blast furnace slag exceeds 70% by mass.

[0004] From the perspective of reducing CO2 emissions as described above, research has also been conducted on cement compositions with an even higher proportion of blast furnace slag than blast furnace cement type C (for example, Non-Patent Literature 1). Non-Patent Literature 1 confirms that the cement composition hardens when the cement clinker content is 1% by mass. However, this content needs to be strictly controlled, and it has been shown that if the cement clinker content is 4-5% by mass, the hardening reaction of the cement composition does not proceed, and the compressive strength decreases drastically. Specifically, 55 N / mm² when the cement clinker content is 1% by mass. 2 Depending on the strength, the amount of cement clinker mixed can vary from 1% by mass to 10 N / mm². 2It has been confirmed that fluctuations can occur over a wide range, such as decreasing to an intensity of less than a certain level.

[0005] Generally, the accuracy of measurements in the preparation of cement compositions at an industrial level is said to be at most 1-2 mass%, and as mentioned above, controlling the amount of cement clinker to 1 mass is not practical, making it difficult to commercialize cement compositions with an extremely large amount of blast furnace slag. In practice, it is common knowledge in our industry that it is appropriate to adjust the amount of cement clinker to 30 mass or more, as specified in JIS standards. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Tokyo Institute of Technology et al., "ECM Cement," a low-carbon cement capable of reducing energy consumption and CO2 emissions by more than 60%, Figure 6, [online], May 2017, NEDO Commercialization Document, [Retrieved January 4, 2022], Internet<URL:https: / / www.nedo.go.jp / hyoukabu / articles / 201705ecm / index.html> [Overview of the project] [Problems that the invention aims to solve]

[0007] A technology that can produce hydraulic compositions that exhibit stable quality even under industrial-level weighing accuracy, by suppressing large deviations from or below expected values ​​in the compressive strength of a hydraulic composition when hardened due to minute differences in the cement clinker content (for example, in the range of 5% by mass or less) would be useful.

[0008] The present disclosure aims to provide a compressive strength enhancer that, when added to granulated blast furnace slag, can increase the compressive strength exhibited when the granulated blast furnace slag hardens. [Means for solving the problem]

[0009] The present inventors have found that a composition containing predetermined amounts of gypsum and an accelerator, combined with an alkaline stimulant, is effective in increasing the compressive strength when granulated blast furnace slag hardens, and that a remarkable effect is obtained in a region where the total amount of alkaline stimulant in the hydraulic composition obtained by adding the above composition to granulated blast furnace slag is 5% by mass or less. This disclosure is based on this novel finding.

[0010] One aspect of this disclosure provides a compressive strength enhancer for granulated blast furnace slag, comprising an alkaline stimulant, gypsum, and an accelerator, wherein the gypsum content is 30.0% by mass or more in terms of SO3, and the accelerator content is 10.0% by mass or more.

[0011] The above-mentioned compressive strength enhancer can increase the compressive strength of granulated blast furnace slag when it hardens, by adding it to the granulated blast furnace slag. The above-mentioned compressive strength enhancer is also useful because, by using the above-mentioned enhancer which is pre-mixed with an alkaline stimulant, gypsum, and accelerator, it is possible to improve the compressive strength of granulated blast furnace slag without being constrained by weighing accuracy.

[0012] The alkali stimulant content may be 15.0% by mass or less. When the alkali stimulant content is within the above range, the alkali stimulant content relative to the total amount is low when added to granulated blast furnace slag, resulting in so-called low cement. However, even in this case, sufficient compressive strength can be expected.

[0013] The above-mentioned compressive strength enhancer may be used by adding it in an amount of 25.0 parts by mass or less per 100 parts by mass of granulated blast furnace slag. [Effects of the Invention]

[0014] According to this disclosure, a compressive strength enhancer can be provided that, when added to granulated blast furnace slag, can increase the compressive strength that develops when the granulated blast furnace slag hardens. [Modes for carrying out the invention]

[0015] Hereinafter, embodiments of the present disclosure will be described. However, the following embodiments are examples for explaining the present disclosure and are not intended to limit the present disclosure to the following content. In the following description, when it is described as "X to Y" (X and Y are arbitrary numbers), unless otherwise specified, it means "X or more and Y or less".

[0016] Unless otherwise specified, the materials exemplified in this specification can be used alone or in combination of two or more. The content of each component in the composition means the total amount of the plurality of substances present in the composition when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified.

[0017] [Compressive Strength Enhancer] One embodiment of the compressive strength enhancer for hydraulic slag consists of an alkali activator, gypsum, and an accelerator. In the above compressive strength enhancer, the content of the above gypsum is 30.0% by mass or more in terms of SO3, and the content of the above accelerator is 10.0% by mass or more. The compressive strength enhancer according to the present disclosure can improve the compressive strength of a hardened body (for example, a mortar hardened body) obtained by the reaction of blast furnace slag with water or the like by adding it to blast furnace slag. The compressive strength exhibited by blending and hardening the compressive strength enhancer according to the present disclosure with blast furnace slag can exhibit a strength enhanced compared to the compressive strength exhibited by mixing blast furnace slag and an alkali activator.

[0018] The alkali activator can start the hydration reaction and promote the hardening reaction by stimulating the glass structure of blast furnace slag. The alkali activator may contain at least one selected from the group consisting of Portland cement clinker, slaked lime, and quicklime, may be any one of Portland cement clinker, slaked lime, and quicklime, and may be Portland cement clinker. In addition, when there is no alkali activator, blast furnace slag does not react with water.

[0019] Portland cement clinker can use Portland cement clinker used for preparing various Portland cements specified in JIS R 5210:2003 "Portland Cement". Examples of the various Portland cements include ordinary Portland cement, early-strength Portland cement, medium-heat Portland cement, and low-heat Portland cement, etc. The Portland cement clinker may be a Portland cement clinker used for preparing ordinary Portland cement and early-strength Portland cement.

[0020] The mineral composition of Portland cement clinker can be calculated by the Bogue formula. Here, the Bogue formula is a formula widely used as a formula for calculating the content rate of main minerals in Portland cement clinker from the content ratio of chemical composition. By using the Bogue formula shown below, the contents of tricalcium silicate (3CaO·SiO2, denoted as C3S) and dicalcium silicate (2CaO·SiO2, denoted as C2S) and tricalcium aluminate (3CaO·Al2O3, denoted as C3A) in Portland cement clinker can be calculated. In the following formula, "%" means "mass %". The chemical formula represents the content ratio (mass %) of each compound shown by the chemical analysis value according to JIS R 5204:2019 "Fluorescent X-ray Analysis Method for Cement".

[0021] <Bogue formula> C3S [%]=(4.07×CaO [%])-(7.60×SiO2 [%])-(6.72×Al2O3 [%])-(1.43×Fe2O3 [%])-(2.85×SO3 [%]) C2S [%]=(2.87×SiO2 [%])-(0.754×C3S [%]) C3A [%]=(2.65×Al2O3 [%])-(1.69×Fe2O3 [%]) C4AF [%]=3.04×Fe2O3 [%]

[0022] The amount of C3A in Portland cement clinker is preferably 0.5 to 11.0% by mass, more preferably 0.5 to 10.5% by mass, still more preferably 0.5 to 10.0% by mass, and particularly preferably 0.5 to 9.5% by mass. When the amount of C3A in Portland cement clinker is within the above range, it is possible to further reduce the amount of gypsum in the compressive strength enhancer, so that the hydration reaction can be suppressed and the hydration reaction of blast furnace slag can be more fully exerted.

[0023] The fineness of Portland cement clinker may be adjusted from the viewpoint of further improving the performance of the hydration reaction when added to blast furnace slag. The lower limit value of the Blaine specific surface area of Portland cement clinker is, for example, 2800 cm 2 / g or more, or 3000 cm 2 / g or more. By setting the lower limit value of the Blaine specific surface area of Portland cement clinker within the above range, the hydration reaction with blast furnace slag can be further promoted. The upper limit value of the Blaine specific surface area of Portland cement clinker is, for example, 10000 cm 2 / g or less, 5000 cm 2 / g or less, 4000 cm 2 / g or less, or 3500 cm 2 / g or less. By setting the upper limit value of the Blaine specific surface area of Portland cement clinker within the above range, the manufacturing cost of the compressive strength enhancer can be reduced, and the CO2 emissions in the production of Portland cement clinker can be further reduced. The Blaine specific surface area of Portland cement clinker may be adjusted within the above range, for example, 2800 to 10000 cm 2 / g, 3000 to 5000 cm 2 / g, 3000 to 4000 cm 2 / g, or 3000 to 3500 cm 2 / g.

[0024] <The upper limit of the alkali stimulant content in the above compressive strength enhancer may be, for example, 15.0% by mass or less, 10.0% by mass or less, 8.0% by mass or less, or 6.0% by mass or less. When the alkali stimulant content is within the above range, the alkali stimulant content relative to the total amount is small when added to granulated blast furnace slag, resulting in so-called low cement, but even in this case, sufficient compressive strength can be expected. The lower limit of the alkali stimulant content in the above compressive strength enhancer may be, for example, 0.5% by mass or more, 2.0% by mass or more, 3.5% by mass or more, or 5.0% by mass or more. When the lower limit of the alkali stimulant content is within the above range, it is possible to prevent the granulated blast furnace slag from remaining unreacted due to insufficient alkali stimulation and to ensure more sufficient reactivity. The alkali stimulant content in the above compressive strength enhancer may be adjusted within the above range, for example, 0.5 to 15.0% by mass.

[0025] In this specification, the content of the alkali stimulant refers to the value determined by the method described below. Since the detection method differs for the alkali stimulants, Portland cement clinker, slaked lime, and quicklime, the content of the alkali stimulant is determined by performing the following three measurements and calculating their total amounts. First, the content of Portland cement clinker among the alkali stimulants is determined. Specifically, X-ray diffraction measurement is performed on the compressive strength enhancer, and the total amount of alite, belite, aluminate phase, and ferrite phase obtained by quantifying each crystalline phase in the compressive strength enhancer using the Rietveld analysis method is taken as the content of Portland cement clinker. Next, the content of slaked lime among the alkali stimulants is determined. The weight loss of 1 g of the compressive strength enhancer is measured by thermogravimetric differential thermal analysis (TG-DTA), and the weight loss value around 450-500°C is calculated as the amount of H2O due to the thermal decomposition reaction. The value obtained by converting the above weight loss value back to slaked lime (Ca(OH)2) using the respective molecular weights is taken as the content of slaked lime. Finally, the content of quicklime (CaO) among the alkaline stimulants is determined as follows: CaO is calculated using the Rietveld analysis method described above, and the quicklime content is obtained by subtracting the content of slaked lime (Ca(OH)2), which was determined by thermogravimetric differential thermal analysis (TG-DTA) and converted to quicklime (CaO) equivalent, from the calculated value. The content of the alkaline stimulant is determined by summing the contents of Portland cement clinker, slaked lime, and quicklime calculated as described above.

[0026] Gypsum can be used to enhance initial strength by generating ettringite at the start of hydration of blast furnace granulated slag. Examples of gypsum that can be used include dihydrate gypsum, hemihydrate gypsum, and anhydrous gypsum. The gypsum may also be gypsum obtained by recycling waste gypsum board. The gypsum may contain at least one selected from the group consisting of dihydrate gypsum and hemihydrate gypsum, or it may be one selected from the group consisting of dihydrate gypsum and hemihydrate gypsum.

[0027] The gypsum content in the above compressive strength enhancer is 30.0% by mass or more, in terms of SO3. The lower limit of the gypsum content in the above compressive strength enhancer may be, for example, 31.0% by mass or more, 32.0% by mass or more, 33.0% by mass or more, 34.0% by mass or more, or 35.0% by mass or more, in terms of SO3. By having the lower limit of the gypsum content within the above range, the compressive strength enhancing effect on granulated blast furnace slag can be further improved. The upper limit of the gypsum content in the above compressive strength enhancer may be, for example, 43.0% by mass or less, 41.0% by mass or less, 39.0% by mass or less, or 37.0% by mass or less, in terms of SO3. By having the upper limit of the gypsum content within the above range, even when a small amount of the compressive strength enhancer is added to granulated blast furnace slag, the fluctuation in compressive strength can be kept small in relation to the amount of accelerator blended in a predetermined amount, and a more sufficient compressive strength enhancing effect can be obtained. The gypsum content in the above compressive strength enhancer may be adjusted within the range described above, and may be, for example, 30.0 to 43.0% by mass in terms of SO3.

[0028] In this specification, the gypsum content refers to the total amount of gypsum components directly incorporated into the compressive strength enhancer, in addition to the gypsum equivalent components that may be contained in the alkaline stimulant and accelerator. In this specification, the gypsum content refers to the value determined by the method described below. Specifically, the gypsum content shall be measured in accordance with the SO3 analysis method specified in JIS R 5202:2015 "Chemical Analysis Methods for Cement".

[0029] Accelerators are compounds that accelerate the reaction of granulated blast furnace slag and increase its initial strength.

[0030] The accelerator may contain at least one selected from the group consisting of alkali metal salts and alkaline earth metal salts. By including alkali metal salts or alkaline earth metal salts in the accelerator, the reactivity when a compressive strength enhancer is added to granulated blast furnace slag can be further improved. Examples of alkali metals may be sodium and potassium, and examples of alkaline earth metals may be magnesium and calcium. From the viewpoint of promoting hydrate formation and improving compressive strength, it is preferable, and more preferable, for the alkaline earth metal to contain calcium. When the compressive strength enhancer contains a calcium salt as an accelerator, it is possible to further reduce the content of the alkali stimulant, and the compressive strength enhancing effect when added to granulated blast furnace slag can be further improved. Generally, in hydraulic compositions in which a portion of cement clinker is replaced with granulated blast furnace slag, it is believed that calcium hydroxide (Ca(OH)2) leached from the cement clinker contributes to accelerating the hardening reaction of the granulated blast furnace slag. By including a predetermined amount of calcium salt as an accelerator, it is possible to expect a sufficient acceleration effect on the hardening reaction of the granulated blast furnace slag even when the content of alkaline stimulants such as the aforementioned cement clinker is reduced.

[0031] The accelerator may contain a salt having a monovalent anion, and may also contain a calcium salt. The accelerator may contain at least one selected from the group consisting of nitrites, nitrates, and chlorides. Including nitrite in the accelerator can further improve its effect as a compressive strength enhancer. Furthermore, including nitrite in the accelerator can reduce the amount of heat generated by hydration when adding a compressive strength enhancer to granulated blast furnace slag and hardening it.

[0032] More specifically, accelerators include calcium nitrite, calcium nitrate, calcium chloride, calcium hydroxide, sodium nitrite, potassium nitrite, sodium nitrate, potassium nitrate, sodium chloride, and potassium chloride. Among the compounds mentioned above, the accelerator preferably contains an alkali metal nitrite, more preferably calcium nitrite, and even more preferably calcium nitrite.

[0033] The lower limit of the accelerator content in the above compressive strength enhancer may be, for example, 10.0% by mass or more, 10.5% by mass or more, or 11.0% by mass or more. By having the lower limit of the accelerator content within the above range, the initial strength development of granulated blast furnace slag can be further improved. The upper limit of the accelerator content in the above compressive strength enhancer may be, for example, 35.0% by mass or less, 30.0% by mass or less, 25.0% by mass or less, or 20.0% by mass or less. By having the upper limit of the accelerator content within the above range, the reaction-accelerating effect of granulated blast furnace slag can be more fully exhibited. The accelerator content in the above compressive strength enhancer may be adjusted within the above range, for example, 10.0 to 35.0% by mass.

[0034] In this specification, the accelerator content is determined by performing X-ray diffraction measurements on the powdered composition to be measured and then using the Rietveld analysis method. However, when preparing a hydraulic composition oneself, the accelerator content will be equal to the amount added, and therefore the above analysis is not required.

[0035] The above-mentioned compressive strength enhancer is used by adding it to granulated blast furnace slag. The above-mentioned compressive strength enhancer may be added in an amount of 25.0 parts by mass or less per 100 parts by mass of granulated blast furnace slag. The upper limit of the amount of the above-mentioned compressive strength enhancer added may be, for example, 24.5 parts by mass or less, 24.0 parts by mass or less, 23.5 parts by mass or less, 23.0 parts by mass or less, 22.5 parts by mass or less, 22.0 parts by mass or less, or 21.5 parts by mass or less per 100 parts by mass of granulated blast furnace slag. By keeping the upper limit of the amount of the above-mentioned compressive strength enhancer added within the above range, a greater effect on increasing the initial strength and long-term strength of the granulated blast furnace slag can be expected. The lower limit of the amount of the above-mentioned compressive strength enhancer added may be, for example, 18.0 parts by mass or more, 18.5 parts by mass or more, 19.0 parts by mass or more, or 20.0 parts by mass or more per 100 parts by mass of granulated blast furnace slag. By ensuring that the lower limit of the amount of the compressive strength enhancer is within the above range, the compressive strength of the granulated blast furnace slag can be further increased. The amount of the compressive strength enhancer added may be adjusted within the above range, and may be, for example, 18.0 to 25.0 parts by mass per 100 parts by mass of granulated blast furnace slag.

[0036] The granulated blast furnace slag to which the compressive strength enhancer is applied is not particularly limited; for example, commercially available products may be used, or slag equivalent to granulated blast furnace slag may be prepared and used in-house.

[0037] The upper limit of the aluminum oxide content (also referred to as Al2O3 content) in granulated blast furnace slag may be, for example, 14.5% by mass or less, or 14.3% by mass or less. Having the Al2O3 content in granulated blast furnace slag within this range helps to further suppress the long-term decrease in strength development of the hardened material when the compressive strength enhancer according to this disclosure is added and hardened. The lower limit of the Al2O3 content in granulated blast furnace slag may be, for example, 10.0% by mass or more, 11.0% by mass or more, 12.0% by mass or more, or 13.0% by mass or more. Having the lower limit of the Al2O3 content in granulated blast furnace slag within this range allows the latent hydraulic properties of the granulated blast furnace slag to be more fully exhibited. Latent hydraulic properties refer to the characteristic of initiating a hydration reaction by adding an alkaline stimulant. The amount of Al2O3 in the granulated blast furnace slag may be adjusted within the above range, for example, 10.0 to 14.5 mass%, 12.0 to 14.5 mass%, or 13.0 to 14.5 mass%.

[0038] The lower limit of the silicon dioxide content (also expressed as SiO2 content) in granulated blast furnace slag may be, for example, 30.0% by mass or more, 33.0% by mass or more, 34.0% by mass or more, 34.5% by mass or more, or 35.0% by mass or more. By keeping the lower limit of the SiO2 content of granulated blast furnace slag within the above range, a decrease in initial and long-term strength development can be suppressed. The upper limit of the SiO2 content of granulated blast furnace slag may be, for example, 40.0% by mass or less, 38.0% by mass or less, 36.5% by mass or less, or 35.5% by mass or less. By keeping the upper limit of the SiO2 content of granulated blast furnace slag within the above range, a decrease in initial strength development can be suppressed. The SiO2 content of granulated blast furnace slag may be adjusted within the above range, for example, 33.0 to 40.0% by mass, or 34.0 to 35.5% by mass.

[0039] The lower limit of the calcium oxide content (also referred to as CaO content) in granulated blast furnace slag may be, for example, 35.0% by mass or more, 38.5% by mass or more, or 40.0% by mass or more. Having the lower limit of the CaO content in granulated blast furnace slag within the above range can further improve initial strength development. The upper limit of the CaO content in granulated blast furnace slag may be, for example, 45.0% by mass or less, 43.5% by mass or less, 43.0% by mass or less, 42.5% by mass or less, 42.0% by mass or less, or 41.5% by mass or less. Having the upper limit of the CaO content in granulated blast furnace slag within the above range can suppress long-term deterioration of strength development. The CaO content in granulated blast furnace slag may be adjusted within the above range, for example, 38.5 to 45.0% by mass, or 40.0 to 42.5% by mass.

[0040] The lower limit of the magnesium oxide content (also referred to as MgO content) in granulated blast furnace slag may be, for example, 4.0% by mass or more, 5.0% by mass or more, 5.5% by mass or more, 6.0% by mass or more, or 7.0% by mass or more. By keeping the lower limit of the MgO content of granulated blast furnace slag within the above range, a decrease in initial and long-term strength development can be suppressed. The upper limit of the MgO content of granulated blast furnace slag may be, for example, 10.0% by mass or less, 9.0% by mass or less, less than 7.5% by mass, less than 7.4% by mass, less than 7.2% by mass, or less than 7.1% by mass. By keeping the upper limit of the MgO content of granulated blast furnace slag within the above range, a decrease in initial strength development can be suppressed. The MgO content of granulated blast furnace slag may be adjusted within the above range, for example, 4.0 to 10.0% by mass, or 6.0% by mass or more and less than 7.4% by mass.

[0041] The granulated blast furnace slag may also contain other components such as sulfur trioxide (SO3), sodium oxide (NaO2), potassium oxide (K2O), and titanium oxide (TiO2).

[0042] In this specification, the chemical composition of granulated blast furnace slag refers to the value measured in accordance with the description in JIS R 5202:2015 "Methods for Chemical Analysis of Cement".

[0043] The reactivity of granulated blast furnace slag is evaluated using an index called basicity, which is expressed as the value of (CaO + MgO + Al2O3) / SiO2 (the ratio of the total content of calcium oxide, magnesium oxide, and aluminum oxide to the silicon dioxide content in the granulated blast furnace slag). Granulated blast furnace slag can be used with high basicity or low basicity.

[0044] As for granulated blast furnace slag, a wide range of types with a basicity of, for example, 1.60 to 1.95 can be used. Granulated blast furnace slag with a basicity of less than 1.75 is generally considered to be low-grade slag with low basicity and low reactivity, but it can be used because it can be hardened to exhibit sufficient compressive strength by adding the compressive strength enhancer according to this disclosure.

[0045] The upper limit of the basicity of granulated blast furnace slag may be, for example, 1.95 or less, less than 1.95, less than 1.90, less than 1.85, or less than 1.80. The lower limit of the basicity of granulated blast furnace slag with relatively good reactivity may be, for example, greater than 1.75, or 1.78 or greater. Having the lower limit of basicity within the above range makes it easier to improve the initial strength of the hardened body when the compressive strength enhancer according to this disclosure is added and hardened. The basicity of granulated blast furnace slag can be adjusted within the above range, for example, 1.75 to 1.95, or 1.75 or more and less than 1.80, etc.

[0046] The basicity in this specification is a value measured in accordance with the description in JIS A 6206:2013 "Fine Powder of Blast Furnace Slag for Concrete," and specifically refers to the value of (CaO+MgO+Al2O3) / SiO2 (the ratio of the total content of calcium oxide, magnesium oxide, and aluminum oxide to the content of silicon dioxide).

[0047] The Blaine specific surface area of ​​granulated blast furnace slag is, for example, 2500 to 10000 cm². 2 / g, 2500~8000cm 2 / g, 2500~6000cm 2 / g, 2500~5000cm 2 / g, 3000~5000cm 2 / g, 4000~5000cm 2 / g, or 4000-4500cm 2 / g is acceptable.

[0048] In this specification, "Blaine specific surface area" refers to the value measured in accordance with the method described in JIS R 5201:2015 "Physical Testing Methods for Cement".

[0049] [Method for producing a hydraulic composition] The above-mentioned compressive strength enhancers can be suitably used in the preparation of hydraulic compositions that can exhibit excellent compressive strength. One embodiment of the method for producing a hydraulic composition includes the step of adding the above-mentioned compressive strength enhancer to 100 parts by mass of granulated blast furnace slag in an amount of 25.0 parts by mass or less.

[0050] The addition of blast furnace granulated slag and the above-mentioned compressive strength enhancer may be carried out using a mixer such as a pan mixer, a tilting drum mixer, and a ribbon mixer, or by mixing and grinding using a pulverizer such as a ball mill, a vertical roller mill, and a roller press, or by grinding each of the various components separately and then mixing them in a mixer such as a mechanical mixer.

[0051] [Method for producing a mortar composition or concrete composition] The above-mentioned compressive strength enhancer can also be suitably used in the preparation of mortar compositions and concrete compositions. In other words, one embodiment of a method for producing a mortar composition or concrete composition includes a step (mixing step) of adding aggregate, admixtures and water to a mixture containing granulated blast furnace slag and a compressive strength enhancer, wherein the amount of the compressive strength enhancer in the mixture is at most 25.0 parts by mass or less per 100 parts by mass of granulated blast furnace slag.

[0052] For example, fine aggregate and coarse aggregate can be used. Fine aggregate alone may be used, or both fine and coarse aggregate may be used.

[0053] Fine aggregate can be any fine aggregate specified in JIS A 5005:2020 "Crushed stone and crushed sand for concrete". Examples of fine aggregate include river sand, land sand, sea sand, crushed sand, silica sand, copper slag fine aggregate, and electric furnace oxidized slag fine aggregate. When using fine aggregate, the amount used may be, for example, 50 to 500 parts by mass, 100 to 300 parts by mass, or 200 to 250 parts by mass per 100 parts by mass of the above-mentioned mixture.

[0054] For coarse aggregate, you can use coarse aggregate as specified in JIS A 5005:2020 "Crushed stone and crushed sand for concrete". Examples of coarse aggregate include gravel and crushed stone. When using coarse aggregate, the amount used may be, for example, 50 to 500 parts by mass, 100 to 300 parts by mass, or 200 to 250 parts by mass per 100 parts by mass of the above-mentioned mixture.

[0055] Fine aggregate and coarse aggregate can be used in combination, in which case the total amount of fine aggregate and coarse aggregate used may be 100 to 300 parts by mass, or 200 to 250 parts by mass, per 100 parts by mass of the above-mentioned mixture.

[0056] Examples of admixtures include air-entraining agents, water-reducing agents, high-performance water-reducing agents, high-performance air-entraining agents, fluidizing agents, defoaming agents, shrinkage-reducing agents, setting accelerators, setting retarders, and thickeners. The amount of admixture used may be, for example, 0.01 to 2 parts by mass per 100 parts by mass of the above-mentioned mixture.

[0057] Examples of water include tap water, distilled water, and deionized water. The amount of water used may be 20 to 100 parts by mass, or 40 to 70 parts by mass, per 100 parts by mass of the above-mentioned mixture.

[0058] In the above mixing process, in addition to aggregate, admixture, and water, clay minerals such as limestone, fly ash, and silica fume may also be added. In this case, the amount of clay minerals added may be, for example, 0.01 to 2.00 parts by mass per 100 parts by mass of the above mixture.

[0059] Although several embodiments have been described above, this disclosure is not limited in any way to the embodiments described above. Furthermore, the descriptions of the embodiments described above are applicable to each other. [Examples]

[0060] The contents of this disclosure will be described in more detail below with reference to examples, comparative examples, and reference examples. However, this disclosure is not limited to the examples described below.

[0061] [Raw materials for compressive strength enhancers, etc.] The following materials were used as raw materials for the compressive strength enhancer.

[0062] (Cement clinker) For the cement clinker used, we used the cement clinker commonly used in the preparation of ordinary Portland cement. In Table 1, ordinary Portland cement clinker is referred to simply as "clinker." The chemical composition of the cement clinker was measured in accordance with the description in JIS R 5202:2015 "Methods for Chemical Analysis of Cement." The results are shown in Table 1.

[0063] (plaster) The gypsum used was excreted dihydrate gypsum, a by-product of coal-fired power plants, and anhydrous gypsum used as a reagent. In Table 1, excreted dihydrate gypsum is referred to as dihydrate gypsum. The chemical composition of the gypsum was measured in accordance with JIS R 5202:2015 "Methods for Chemical Analysis of Cement". The results are shown in Table 1.

[0064] (Promoting agent) An inorganic accelerator was used as the accelerator. Specifically, calcium nitrite monohydrate manufactured by Kishida Chemical Co., Ltd. was used.

[0065] (Blast furnace granulated slag) For the granulated blast furnace slag, we used blast furnace slag fine powder without gypsum additive. The chemical composition of the blast furnace slag fine powder was measured in accordance with the description in JIS R 5202:2015 "Methods for Chemical Analysis of Cement". The results are shown in Table 1.

[0066] [Table 1]

[0067] In Table 1, the C / S ratio refers to the value of (CaO content) / (SiO2 content). Furthermore, the ignition loss (also expressed as ig.loss) in Table 1 is the value measured at a heating temperature of 700°C, in accordance with the method described in "5. Method for determining ignition loss" of JIS R 5202:2010, specifically in "5. Cases other than blast furnace cement and blast furnace slag."

[0068] (Example 1) A compressive strength enhancer was prepared by weighing and mixing the following components: ordinary Portland cement at 15.0% by mass, gypsum dihydrate at 75.0% by mass, and calcium nitrite as an accelerator at 10.0% by mass. The gypsum content in the prepared compressive strength enhancer was 34.2% by mass in terms of SO3.

[0069] (Example 2) A compressive strength enhancer was prepared in the same manner as in Example 1, except that the formulation was modified so that the contents of ordinary Portland cement, gypsum dihydrate, and calcium nitrite were as shown in Table 2. The gypsum content in the prepared compressive strength enhancer was 38.0% by mass in terms of SO3.

[0070] (Comparative Examples 1-3) A compressive strength enhancer was prepared in the same manner as in Example 1, except that calcium nitrite was omitted and the formulation was modified so that the content of ordinary Portland cement and dihydrate gypsum were as shown in Table 2. The gypsum content (SO3 equivalent) in the prepared compressive strength enhancer is shown in Table 2.

[0071] (Comparative Examples 4-6) A compressive strength enhancer was prepared in the same manner as in Example 1, except that the formulation was modified so that the contents of ordinary Portland cement, gypsum dihydrate, and calcium nitrite were as shown in Table 2. The gypsum content (SO3 equivalent) in the prepared compressive strength enhancer is shown in Table 2.

[0072] (Reference example) A compressive strength enhancer was prepared in the same manner as in Example 1, except that calcium nitrite was omitted and the formulation was modified so that the contents of ordinary Portland cement and dihydrate gypsum were as shown in Table 2. The gypsum content in the prepared compressive strength enhancer was 2.0% by mass in terms of SO3.

[0073] <Evaluation of compressible strength enhancers> The compressive strength enhancing effect was evaluated for each of the compressive strength enhancers prepared in Examples 1-2 and Comparative Examples 1-6. The results are shown in Table 2.

[0074] [Measurement of compressive strength] First, a hydraulic composition was prepared by adding a compressive strength enhancer to 100 parts by mass of blast furnace granulated slag according to the amounts shown in Table 2. The obtained hydraulic composition was then prepared. A mortar composition was prepared by adding fine aggregate and water to the hydraulic composition prepared as described above. The composition of the mortar composition was 100 parts by mass of hydraulic composition, 200 parts by mass of sand (standard sand / manufactured by the Cement Association) as fine aggregate, and 50 parts by mass of water. The compressive strength of the obtained mortar composition was measured at 7 and 28 days of age according to the method described later. The above-mentioned mortar composition was adjusted so that the ratio of hydraulic composition:sand:water was 100:300:50 (by mass ratio, according to the description in JIS R 5201:2015 "Physical Test Methods for Cement").

[0075] Mortar hardened bodies were prepared using each of the obtained mortar compositions. First, the above mortar compositions were mixed as mortar in a constant temperature chamber at 20°C and filled into a mold measuring 4cm × 4cm × 16cm (prepared in accordance with the description in JIS R 5201:2015 "Physical Test Methods for Cement"). The mold was stored in a humidity chamber and cured for 24 hours. After 24 hours of curing, the mold was removed to obtain a hardened mortar body. The obtained hardened mortar body was cured in water for 7 days (age 7 days) in a constant temperature chamber at 20°C. The hardened mortar body after water curing was used as a test specimen, and the compressive strength of the hardened mortar body at 7 days was measured. Similarly, the obtained hardened mortar body was cured in water for 28 days (age 28 days) in a constant temperature chamber at 20°C, and the compressive strength of the hardened mortar body at 28 days was measured. The compressive strength was measured in accordance with the description in JIS R 5201:1992 "Physical Testing Methods for Cement".

[0076] [Table 2] [Industrial applicability]

[0077] The present disclosure aims to provide a compressive strength enhancer that, when added to granulated blast furnace slag, can increase the compressive strength exhibited when the granulated blast furnace slag hardens.

Claims

1. It consists of cement clinker, gypsum, and accelerator, The cement clinker content is 5.0% by mass or more and 15.0% by mass or less. The gypsum content is SO ３ In terms of conversion, it is between 30.0% by mass and 39.0% by mass. The aforementioned accelerator is calcium nitrite, A compressive strength enhancer for granulated blast furnace slag, wherein the content of the aforementioned accelerator is 10.0% by mass or more and 11.1% by mass or less.

2. The compressive strength enhancer according to claim 1, which is used by adding it in an amount of 25.0 parts by mass or less per 100 parts by mass of granulated blast furnace slag.

Images