hydraulic components

Abstract

The present invention provides a hydraulic composition containing blast furnace slag fine powder and sodium silicate, which allows for a reduced amount of sodium silicate to be added while still exhibiting strength development properties. [Solution] The hydraulic composition consists of blast furnace slag fine powder and sodium silicate powder with a Na / Si molar ratio of 0.9 to 2.5, preferably with 2.0 to 20 parts by mass of sodium silicate powder per 100 parts by mass of blast furnace slag fine powder.

Description

Technical Field

[0001] The present invention relates to a hydraulic composition used for ground improvement materials and the like, which contains blast furnace slag fine powder and sodium silicate powder.

Background Art

[0002] As a base material for cement-based solidifying materials used as ground improvement materials, Portland cement or blast furnace cement is used.

[0003] The amount of CO2 emissions when firing 1 t of cement clinker is about 1.1 t derived from the firing of raw materials and fuels, and it is said to account for about 40% of the total CO2 emissions in the construction industry. Also, the amount of CO2 emissions due to the production of 1 t of Portland cement using cement clinker as a raw material is 807 kg.

[0004] Therefore, as an effort to realize a low-carbon society in the current construction industry, technological development is underway to reduce the CO2 emissions during the production of solidifying materials as much as possible by using materials that replace Portland cement or blast furnace cement as the binder of the solidifying materials.

[0005] Blast furnace slag fine powder is an industrial waste whose constituent components are similar to those of cement, and it has the characteristic of exhibiting hydraulicity by alkali stimulation. Therefore, by replacing cement with blast furnace slag fine powder, it is possible to enhance chemical resistance and seawater resistance, and to suppress CO2 emissions.

[0006] Also, a cement-free solidifying material that substitutes for cement-based solidifying materials and uses blast furnace slag fine powder and sodium orthosilicate as raw materials has been developed (Non-Patent Document 1).

Prior Art Documents

Non-Patent Documents

[0007]

Non-Patent Document 1

[0008] The ground improvement material described in Non-Patent Literature 1 consists of blast furnace slag powder and sodium orthosilicate. While the use of blast furnace slag powder instead of cement reduces CO2 emissions, further reductions in CO2 emissions are desired.

[0009] Therefore, the object of the present invention is to propose a hydraulic composition that can be used as a ground improvement material, etc., which further reduces CO2 emissions during manufacturing and exhibits strength development (hereinafter also simply referred to as strength development) equivalent to or greater than that of conventional ground improvement materials consisting of blast furnace slag fine powder and sodium orthosilicate. [Means for solving the problem]

[0010] The carbon dioxide emissions during the production of sodium silicate are 892 kg-CO2 / t, which is significantly higher than the 807 kg-CO2 / t emissions from Portland cement. Therefore, the inventors considered that it would be possible to further reduce CO2 emissions during production by reducing the amount of sodium orthosilicate added. As a result of diligent research, they discovered that the amount of sodium silicate added can be reduced by setting the Na / Si molar ratio of the sodium silicate powder used together with blast furnace slag fine powder to a specific range, leading to the completion of the present invention.

[0011] In other words, the present invention is a hydraulic composition characterized by containing blast furnace slag fine powder and sodium silicate powder with a Na / Si molar ratio of 0.9 to 2.5. Preferably, the composition contains 2.0 to 20 parts by mass of sodium silicate powder per 100 parts by mass of blast furnace slag fine powder. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a hydraulic composition that can be used as a ground improvement material, etc., which has strength development properties while reducing the amount of sodium silicate added compared to conventional materials. In line with the realization of a low-carbon society in recent years, it is possible to reduce carbon dioxide emissions compared to conventional ground improvement materials consisting of blast furnace slag fine powder and sodium orthosilicate. [Modes for carrying out the invention]

[0013] The hydraulic composition of the present invention contains blast furnace slag fine powder and sodium silicate powder having a Na / Si molar ratio of 0.9 to 2.5.

[0014] (Blast furnace slag fine powder) The blast furnace slag fine powder contained in the hydraulic composition of the present invention is a by-product of pig iron production and mainly consists of CaO, SiO2, Al2O3, and MgO. This blast furnace slag fine powder exhibits hydraulic properties upon alkaline stimulation, allowing for the production of a highly strong hardened body. The fineness of the blast furnace slag fine powder can be within a range commonly used, with a specific surface area of ​​3000-8000 cm² as measured by the Blaine air permeation method. 2 It is preferable that it be adjusted to / g.

[0015] (Sodium silicate) The sodium silicate contained in the hydraulic composition of the present invention is sodium silicate powder with a Na / Si molar ratio of 0.9 to 2.5. If the Na / Si molar ratio is less than 0.9, it is thought that it will induce rapid solidification of the blast furnace slag, making it difficult to use as a ground improvement material, for example, as uniform mixing with soil is not possible. If the Na / Si molar ratio is greater than 2.5, the strength development will be low. Within this range, the strength development is excellent, but a Na / Si molar ratio of 0.9 to 2.0 is more preferable, 0.9 to 1.5 is even more preferable, and 1.0 is particularly preferable because it exhibits excellent strength development even at low mixing ratios with blast furnace slag fine powder. Furthermore, a Na / Si molar ratio in the range of 1.0 to 2.5 is also suitable. Note that the sodium silicate needs to be in powder form to prevent rapid solidification due to the reaction of the blast furnace slag fine powder during construction. If the sodium silicate is liquid, the blast furnace slag fine powder will rapidly solidify when mixed with it.

[0016] From the viewpoint of strength development, the mixing ratio of blast furnace slag fine powder and sodium silicate powder constituting the hydraulic composition is preferably 2.0 to 20 parts by mass of sodium silicate powder per 100 parts by mass of blast furnace slag fine powder, and more preferably 5.0 to 10 parts by mass of sodium silicate powder.

[0017] Commonly available sodium silicate powders have Na / Si molar ratios of 1.0, 2.0, 3.0, and 4.0. In the hydraulic composition of the present invention, sodium silicate powder with a Na / Si molar ratio of 0.9 to 2.5 may be a single sodium silicate powder or different sodium silicate powders may be mixed to adjust the molar ratio as needed.

[0018] The hydraulic composition of the present invention may contain concrete admixtures such as limestone fine powder, fly ash, silica fume, and bentonite, as well as fluidizers, to the extent that they do not impair the effects of the present invention.

[0019] The hydraulic composition of the present invention can be produced by mixing blast furnace slag fine powder and sodium silicate powder with a Na / Si molar ratio of 0.9 to 2.5. For this mixing, any mixer capable of mixing powders can be used without limitation. For example, a mixer generally used for kneading mortar or concrete can be used. Specifically, a pan mixer, a forced double-shaft mixer, a tilting mixer, a mortar mixer, etc. can be mentioned. Also, a mixer equipped with a mechanism capable of shearing at high speed, such as a chopper, may be used for the purpose of homogeneous mixing and dispersion.

[0020] The hydraulic composition of the present invention is applicable to various ground improvements such as shallow improvement and deep improvement of soft ground, improvement of construction-generated soil, solidification treatment of sediment, etc. The hydraulic composition of the present invention can be used either by directly mixing it with soil as a powder or by dissolving the hydraulic composition in water to make a slurry for improvement. 3 For 1 m³ of soil, 30 to 600 kg of the hydraulic composition can be mixed, but from the aspects of uniform mixing and the cost of ground improvement, it is preferably 50 to 400 kg / m³. 3 The amount of water is preferably 50 to 100 parts by mass, and more preferably 50 to 70 parts by mass with respect to 100 parts by mass of the hydraulic composition. Also, since the hydraulic composition of the present invention can exhibit a predetermined strength, it can also be used for manufacturing structures like ordinary cement.

Examples

[0021] Hereinafter, specific examples will be given to explain the present invention in more detail. However, the present invention is not limited only to the following examples. Various modifications and application examples are also included in the present invention as long as the characteristics of the present invention are not significantly impaired.

[0022] (Raw materials) (1) Slag fine powder: 4000 blast furnace slag fine powder (powder fineness 3960 cm² / g) (conforming to JIS A 6201) 2 / g)(Conforming to JIS A 6201) (2) Sodium silicate powder · Sodium silicate powder with a Na / Si molar ratio of 1.0 (Na / Si molar ratio = 1.0, H2O = approximately 20% by mass, manufactured by Tokuyama Corporation), · Sodium silicate powder with a Na / Si molar ratio of 2.0 (Na / Si molar ratio = 2.0, H2O = 0% by mass, manufactured by Sigma-Aldrich), · Sodium silicate powder with a Na / Si molar ratio of 4.0 (Na / Si molar ratio = 4.0, H2O = approximately 20% by mass, manufactured by Nippon Chemical Industry Co., Ltd.) (3) Water: Ion-exchanged water

[0023] (Examples 1 - 8) Fine powder of blast furnace slag and sodium silicate powder with Na / Si molar ratios of 1.0 and 2.0 were weighed according to the formulation table in Table 1 below, and mixed uniformly with a whisk until a hydraulic composition was prepared.

[0024]

Table 1

[0025] [Mixing of the paste using the hydraulic composition] After adding the above hydraulic composition and a predetermined amount of water to a soil mixer and stirring for 60 seconds, the sample adhering to the side was scraped off, and then stirred again for 120 seconds to obtain a uniformly mixed paste. The W / P (mass ratio) was set to 0.5. The compressive strength of the specimens made from the obtained paste was measured, and the results are shown in Table 1.

[0026] (Comparative Examples 1 - 4) Comparative Examples 1 - 4 are conventional hydraulic compositions composed of fine powder of blast furnace slag and sodium silicate powder with a Na / Si molar ratio of 4.0. They were prepared in the same manner as Examples 1 - 4, except that sodium silicate powder with a Na / Si molar ratio of 4.0 was used. The W / P (mass ratio) was the same as that of Examples 1 - 8. The measurement results of the compressive strength are shown in Table 1.

[0027] [Compressive strength test] Pastes of the hydraulic compositions from Examples 1-8 and Comparative Examples 1-4 were poured into molds (2.0 cm wide x 2.0 cm long x 8.0 cm high), sealed and cured at 20°C, demolded after 3 days, and sealed and cured again at 20°C to prepare the test specimens. The compressive strength of the test specimens was measured after 28 days of age.

[0028] As shown in Table 1, Examples 1, 2, 3, and 4 had a Na / Si molar ratio of 1.0, while Examples 5, 6, 7, and 8 had a Na / Si molar ratio of 2.0. Compared to Comparative Examples 1, 2, 3, and 4, which had a Na / Si molar ratio of 4.0, the compressive strength was greater when using sodium silicate powder with a Na / Si molar ratio of 1.0 or 2.0, even with the same amount of added sodium silicate powder.

[0029] Furthermore, as shown in Examples 1 and 5, when sodium silicate powder with a Na / Si molar ratio of 1.0 is used, it exhibits superior strength development even at lower concentrations compared to when a powder with a molar ratio of 2.0 is used.

[0030] As shown in Table 1, for example, Example 2 and Comparative Example 3 have almost the same strength level. In this case, Example 2 uses 10 parts by mass of sodium silicate powder for every 100 parts by mass of blast furnace slag fine powder, while Comparative Example 3 uses 15 parts by mass. Considering the need to achieve a similar level of strength, the amount of sodium silicate required is less in Example 2. The carbon dioxide emissions from blast furnace slag are 26.5 kg-CO2 / t, and those from sodium silicate are 892 kg-CO2 / t. Therefore, as shown in Table 1, when 1 ton is produced as a hydraulic composition, the carbon dioxide emissions from Example 2 are 67.7 kg-CO2 / t, and those from Comparative Example 3 are 86.9 kg-CO2 / t, resulting in a 22% reduction.

Claims

1. A hydraulic composition characterized by containing blast furnace slag fine powder and sodium silicate powder with a Na / Si molar ratio of 0.9 to 2.

5.

2. The hydraulic composition according to claim 1, comprising 2.0 to 20 parts by mass of sodium silicate powder per 100 parts by mass of blast furnace slag fine powder.

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