Hydraulic composition

Abstract

To provide a hydraulic composition that is made to improve initial strength development when substituting blast furnace slag for a part of cement.SOLUTION: The present invention relates to a hydraulic composition that consists of Portland cement, blast furnace slag, crystalline layered sodium silicate, has the Portland cement of 30 pts.mass or more and less than 40 pts.mass, the blast furnace slag of over 60 pts.mass and 70 pts.mass or less (where, a total of the Portland cement and the blast furnace slag is 100 pts.mass), and the crystalline layered sodium silicate of over 0 mass% and 12 mass% or less per a whole composition.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a hydraulic composition comprising Portland cement, blast furnace slag, and crystalline layered sodium silicate. Specifically, it relates to a hydraulic composition for improving the early strength development of a hydraulic composition containing blast furnace slag. More specifically, it relates to a hydraulic composition for improving the early strength development by using crystalline layered sodium silicate in a hydraulic composition containing blast furnace slag.

Background Art

[0002] In connection with recent global environmental problems, the effective utilization of waste, by-products, etc. has become an important issue. Taking advantage of the characteristics of the cement industry and cement manufacturing facilities, it is effective from the viewpoint of enabling safe and large-scale disposal to effectively utilize or process waste as raw materials or fuels during cement production.

[0003] The cement industry, which is a mass production and mass consumption industry, is considered important to effectively utilize or process waste as raw materials or fuels during cement production and to manufacture cement efficiently with resource and energy savings.

[0004] On the other hand, from the viewpoint of global warming, the cement industry is positioned as an industry with a large CO2 emissions. The CO2 emitted in the cement industry is due to the decarbonation of limestone, which is a clinker raw material, during the cement manufacturing stage. For CO2 reduction in the cement industry, blended cement with a reduced amount of clinker is considered effective. As one of the blending components of such blended cement, there is blast furnace cement blended with blast furnace slag.

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

[0006] However, when blast furnace slag is used as a cement admixture to replace a part of cement, there is a problem that the initial strength decreases compared to the case of using cement alone. (Non-Patent Documents 1, 2) Therefore, the present invention provides a hydraulic composition that improves the development of initial strength when blast furnace slag is used to replace a part of cement. [Means for Solving the Problems]

[0007] The present inventors conducted intensive research to solve the above problems. As a result, it was found that crystalline layered sodium silicate acts as a stimulant for extracting the latent hydraulicity of blast furnace slag, and attention was paid to this fact.

[0008] As a result, it was found that Na2O contained in crystalline layered sodium silicate enhances the latent hydraulicity of blast furnace slag, and SiO2 reacts with cement to generate hydrates, thereby increasing the initial strength, and the present invention was completed.

[0009] Examples of the use of the hydraulic composition include mortar, fresh concrete, and factory secondary products. When water glass or powdered silica (sodium silicate), which is generally known as a quick-setting agent, is added to fresh concrete, the alkali concentration rapidly increases and causes a quick-setting action, resulting in a significant deterioration in workability from the viewpoints of fluidity and viscosity. However, it was found that crystalline layered sodium silicate has a gentle increase in alkali concentration during dissolution, so that in addition to improving the development of initial strength, fluidity can also be ensured.

[0010] That is, the present invention is composed of Portland cement, blast furnace slag, and crystalline layered sodium silicate, with the Portland cement being 30 parts by mass or more and less than 40 parts by mass, the blast furnace slag exceeding 60 parts by mass and being 70 parts by mass or less (provided that the total of the Portland cement and the blast furnace slag is 100 parts by mass), and the crystalline layered sodium silicate being more than 0% by mass and 12% by mass or less per total composition, which is a hydraulic composition.

[0011] In the above hydraulic composition, the crystalline layered sodium silicate is represented by the following formula (1) Na x H (2-x) ySi2O5·zH2O (1) (wherein x is a number greater than 0 and 2 or less, y is 1 ± 0.1, and z is a number greater than 0 and 5 or less) It preferably has a chemical composition represented by this.

Advantages of the Invention

[0012] According to the present invention, even when the blast furnace slag is substituted for a part of the cement in the hydraulic composition of the present invention, it is possible to improve the expression of the initial strength (compressive strength at 1-day age) without reducing the fluidity.

Embodiments for Carrying Out the Invention

[0013] The hydraulic composition of the present invention is composed of Portland cement, blast furnace slag, and crystalline layered sodium silicate, with the Portland cement being 30 parts by mass or more and less than 40 parts by mass, the blast furnace slag exceeding 60 parts by mass and being 70 parts by mass or less (provided that the total of the Portland cement and the blast furnace slag is 100 parts by mass), and the crystalline layered sodium silicate being more than 0% by mass and 12% by mass or less per total composition. As described above, when the blast furnace slag is substituted for a part of the cement, there is an influence that the initial strength decreases compared to the case of using cement alone. Therefore, in the present invention, crystalline layered sodium silicate is added to eliminate this influence.

[0014] As the Portland cement used in the present invention, known Portland cement defined by JIS standards is adopted. Specifically, those satisfying JIS R 5210 "Portland Cement" are applicable, and various Portland cements such as ordinary, early strength, super early strength, moderate heat, low heat, sulfate resistant, etc. can be mentioned.

[0015] As the blast furnace slag used in the present invention, known blast furnace slag as a cement admixture can be used. Specifically, it can be used without limitation as long as it is the one obtained by pulverizing the blast furnace slag by-produced as a by-product from an ironworks. The fineness of the blast furnace slag may be within the generally used range, and it is preferably adjusted to 3000 - 8000 cm 2 / g.

[0016] In the present invention, the usage amounts of Portland cement and blast furnace slag cement are such that, with the total amount of Portland cement and blast furnace slag being 100 parts by mass, the usage amount of Portland cement is 30 parts by mass or more and less than 40 parts by mass, and the usage amount of blast furnace slag is more than 60 parts by mass and 70 parts by mass or less. When the Portland cement contains blast furnace slag as a minor admixture defined in 5.3 (Minor admixture components) of JIS R 5210, that amount is included in the amount of the above-mentioned blast furnace slag.

[0017] Instead of using Portland cement and blast furnace slag respectively, a blended cement composed of Portland cement and blast furnace slag may be used. As the blended cement composed of Portland cement and blast furnace slag, known blast furnace cement type C defined by JIS R 5211 can be adopted.

[0018] In the present invention, crystalline sodium silicate is contained in an amount of more than 0% by mass and 12% by mass or less per hydraulic composition. By adding crystalline sodium silicate within the above range, the initial strength when a part of the blast furnace slag replaces the cement can be increased (the expression of the initial strength is improved) without reducing the fluidity.

[0019] When using general sodium silicates typified by water glass or powdered silica, although the effect of increasing the initial strength can be obtained, since these are amorphous, their solubility in water is relatively high. For example, when used in fresh concrete, the alkali concentration in the fresh concrete is significantly increased and the fluidity is reduced. In addition, since they react rapidly with cement and gel, the fluidity is also greatly reduced, significantly affecting the workability.

[0020] When the addition amount of crystalline layered sodium silicate exceeds 12% by mass, although the effect of increasing the initial strength can be obtained, since the amount of alkali increases, a predetermined fluidity cannot be obtained and the workability deteriorates. From the viewpoint of the effect of increasing the initial strength, the addition amount of crystalline layered sodium silicate is preferably 0.9% by mass or more, more preferably 2% by mass or more per hydraulic composition. When the addition amount of crystalline layered sodium silicate is 2% by mass or more, for example, it is also possible to make the compressive strength ratio compared to the compressive strength at the age of 1 day without adding crystalline layered sodium silicate 120% or more.

[0021] The crystalline layered sodium silicate is sodium silicate having an orthorhombic or monoclinic crystal form and a layered structure.

[0022] Such crystalline layered sodium silicate is specifically kenyaite represented by Na2Si 22 O 45 ·xH2O, magadiite represented by Na2Si 14 O 29 ·xH2O, iilaite represented by Na2Si8O 17 and those having a composition formula such as Na2Si2O5.

[0023] Among these, in terms of the gentle increase in alkali concentration during dissolution, the following formula (1) Na x H (2-x) ySi2O5·zH2O (1) (In the formula, x is a number greater than 0 and less than or equal to 2, y is 1 ± 0.1, and z is a number greater than 0 and less than or equal to 5) The crystalline layered sodium silicate represented by is preferably used.

[0024] In addition, the crystalline layered sodium silicate represented by the formula (1) may contain metal elements such as Na, K, Mg, Ca, and Al as long as it does not affect the effects of the present invention. The mixing amount of these elements is preferably 0.005 mol or less per 1 mol of Na.

[0025] The crystalline layered sodium silicate represented by the formula (1) reacts with water and dissolves after undergoing a crystal phase change to kanemite (NaHSi2O5·3H2O). Therefore, it takes time to dissolve, and it is presumed that the increase in the alkali concentration becomes gradual.

[0026] The crystalline layered sodium silicate represented by the formula (1) is industrially available. Specifically, "Prefeed" (Na2Si2O5) manufactured by Tokuyama Corporation, etc. can be mentioned. The crystalline layered sodium silicate exists in the form of powder or granules, and its particle size is 10 to 100 μm, preferably 30 to 80 μm.

[0027] The hydraulic composition of the present invention can be produced by mixing each component of Portland cement, blast furnace slag, and crystalline layered sodium silicate. There is no particular limitation on the mixing order of each component. As a preferable method for producing the hydraulic composition of the present invention, a method of simultaneously mixing Portland cement, blast furnace slag, and crystalline layered sodium silicate all at once can be mentioned. The hydraulic composition of the present invention may be prepared by mixing each component in advance to form a hydraulic composition and using it as needed, or by mixing each component at the time of use to form a hydraulic composition and using it. For example, when mixing at the time of use, as the mixer, a mixer used when kneading paste, mortar, and fresh concrete can be used without limitation. Specifically, a pan-type mixer, a forced twin-shaft mixer, etc. can be mentioned. In addition, as described above, a mixed cement composed of Portland cement and blast furnace slag may be used as the Portland cement and blast furnace slag.

[0028] The hydraulic composition of the present invention can be used in the same manner as Portland cement. Specifically, it is used in the form of paste, mortar, and concrete, and the water-to-powder ratio of water and the hydraulic composition is not particularly limited as long as it is within the generally used range, and is usually 25% or more and 70% or less. When used in the form of mortar or concrete, fine aggregates and coarse aggregates usually used in the production of mortar and concrete, that is, river sand, land sand, crushed sand, etc., and river gravel, mountain gravel, crushed stone, etc. can be used. Also, within the range that does not inhibit the effects of the present invention, known admixtures such as AE water reducing agents, high-performance water reducing agents, high-performance AE water reducing agents, air content regulators, etc. may be used.

Examples

[0029] Hereinafter, the present invention will be described more specifically by way of examples, but the present invention is not limited to these examples. Also, not all combinations of features described in the examples are essential for the solution means of the present invention.

[0030] (1) Formulation The formulation is shown in Table 1. Cement, blast furnace slag, and crystalline sodium layered silicate were blended at the ratios shown in Table 1 to prepare the hydraulic composition in the present invention. In this example, in order to evaluate the above-mentioned hydraulic composition, water, fine aggregate, and coarse aggregate were blended into the prepared hydraulic composition to make concrete.

[0031] Tap water was used as water. As the cement, ordinary Portland cement (density 3.16 g / cm 3 , fineness 3270 cm 2 / g) conforming to JIS R 5210 (Portland cement) was used. As the blast furnace slag, that with a density of 2.91 g / cm 3 and a fineness of 4000 cm 2 / g conforming to JIS A 6206 (ground granulated blast furnace slag for concrete) was used. As the fine aggregate, crushed sand (density 2.64 g / cm 3 ) and hill sand (density 2.58 g / cm 3Using the mixed sand of 3 ), hard sandstone crushed stone (maximum size 20 mm, density 2.70 g / cm 3 ), which conforms to JIS A 5005 (Crushed Stone and Crushed Sand for Concrete), was used as the coarse aggregate. As the crystalline layered sodium silicate, crystalline layered sodium silicate having a chemical composition represented by Na2Si2O5 (Tokuyama Corporation's "Prefeed", density 2.43 g / cm 3 ), abbreviation: LS) was used. Also, for comparison, powdered diatomaceous earth (density 2.50 g / cm

[0032]

[0033] <Reference Example 1> Only blast furnace cement type C in which blast furnace slag is 65 parts by mass in a total of 100 parts by mass of cement and blast furnace slag is used, and it is a hydraulic composition containing no sodium silicate.

[0034] <Examples 1 to 4> Blast furnace slag was 65 parts by mass in a total of 100 parts by mass of cement and blast furnace slag, and crystalline layered sodium silicate was added at 1, 3, 5, and 10% by mass per hydraulic composition.

[0035] <Comparative Example 1> Blast furnace slag was 65 parts by mass in a total of 100 parts by mass of cement and blast furnace slag, and crystalline layered sodium silicate was added at 20% by mass per hydraulic composition.

[0036] <Comparative Example 2> Blast furnace slag was 65 parts by mass in a total of 100 parts by mass of cement and blast furnace slag, and powdered diatomaceous earth was added at 5% by mass per hydraulic composition.

[0037]

Table 1

[0038] ​ *1 Water - powder ratio (%) = (Water (kg) / Hydraulic composition (kg)) × 100 *2 Blast furnace slag (parts by mass) = (Blast furnace slag (kg) / [Cement (kg) + Blast furnace slag (kg)]) × 100 *3 Sodium silicate (%) = (Sodium silicate (kg) / Hydraulic composition (kg)) × 100

[0039] (2) Measurement of slump In accordance with JIS A 1101:2020 "Test method for slump of concrete", the slump immediately after mixing was measured. Taking the standard as 18.0 ± 1.5 cm, when the slump is large, it means high fluidity, and when it is small, it means reduced fluidity. It is a physical property value serving as a guideline for workability. The obtained results are shown in Table 2.

[0040] (3) Measurement of 1 - day strength In accordance with JIS A 1108:2018 "Test method for compressive strength of concrete", the compressive strength at 1 - day age was measured. The size of the specimen was Φ100×200 mm. The obtained results are shown in Table 2.

[0041]

Table 2

[0042] In Examples 1 to 4, compared with Reference Example 1, the 1 - day strength increased, and the slump also showed values within a predetermined range. From these, it can be seen that the hydraulic composition of the present invention containing crystalline layered sodium silicate in an amount exceeding 0% by mass and not exceeding 12% by mass per hydraulic composition can obtain the effect of increasing the initial strength without reducing the fluidity.

[0043] In Comparative Example 1, due to the large addition amount of crystalline layered sodium silicate, the fluidity decreased, making mixing difficult and the evaluation impossible.

[0044] In Comparative Example 2, although the one-day strength exceeded that of Reference Example 1, a predetermined slump value could not be obtained. When using ordinary sodium silicate (powdered diatomaceous earth) instead of crystalline layered sodium silicate, it was found that the fluidity decreased and the workability deteriorated.

Claims

1. A hydraulic composition comprising Portland cement, blast furnace slag, and crystalline sodium layered silicate, wherein the Portland cement is 30 parts by mass or more and less than 40 parts by mass, the blast furnace slag is more than 60 parts by mass and 70 parts by mass or less (provided that the total of the Portland cement and the blast furnace slag is 100 parts by mass), and the crystalline sodium layered silicate is more than 0% by mass and 12% by mass or less per total composition.

2. The crystalline sodium layered silicate according to claim 1, having a chemical composition represented by the following formula (1): Na ｘ H （２－ｘ） ySi ２ O ５ ·zH ２ O (1) (In the formula, x is a number greater than 0 and 2 or less, y is 1 ± 0.1, and z is a number greater than 0 and 5 or less) The hydraulic composition according to claim 1, characterized in that it has a chemical composition represented by the formula.

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