JP2010013315A - Manufacturing method of civil engineering material using steel slag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for efficiently suppressing consolidation of a slag civil engineering material, especially a method for effectively using a particle-size regulated slag and a crusher-run steel slag as a steel slag for roads. <P>SOLUTION: One or two slags selected from a blast furnace slag and a steelmaking slag are immersed in free water containing carbonic acid to form an insoluble mineral facies on the slag surface. Specifically, a blast furnace slow cooling slag of ≤25 mm in particle size is subjected to an aging treatment so that the free CaO content in a sample slag obtained from a treated slag by a predetermined means becomes ≤0.45 mass% (for a blast furnace slow cooling slag), and ≤4.5 mass% (for a converter slag), and thereafter is immersed to be subjected to a carbonation treatment in a carbonic acid-containing free water (pH is 3.5 to 5.4) so that the carbonation ratio of a sample slag obtained from the treated slag by a predetermined means becomes ≥15%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to blast furnace slag (slow-cooled slag (hereinafter also referred to as “blast furnace decooled slag”), slag obtained from a blast furnace such as granulated slag) and steel slag (converter). The present invention relates to a method for producing a civil engineering material in which caking is suppressed using slag produced in a steelmaking process such as slag, hot metal pretreatment slag, and secondary refining slag.

Conventionally, blast furnace slag and steelmaking slag have been used as civil engineering materials.
Civil engineering materials using slag are advantageous in hydraulic properties for the purpose of forming a strong ground, and begin to consolidate after a few days after construction.

  However, a few days to several years after the construction, the construction site is dug up, the construction is newly buried, the planting is performed, or the dug up again after several decades There is also.

  In such a case, the consolidated civil engineering material, particularly the slag roadbed material, requires a large force for the excavation work, and further, the excavation work in the piping work or the like has a risk of causing damage to the existing objects.

Such a consolidation hardening phenomenon of slag civil engineering materials is considered to proceed by the following mechanism.
First, CaO on the slag surface dissolves in the surrounding water, and pH increase (pH 10-11) starts.
CaO + H ₂ O → Ca ²⁺ + 2OH ⁻
Due to this alkali stimulation, components such as vitreous silica on the surface of the slag are eluted.
SiO ₂ + OH ⁻ → SiO ₃ ²⁻ + H ₂ O

When the concentration of components such as calcium, silicon, and aluminum in the liquid phase near the slag particles rises to the precipitation conditions for various hydrated products, the formation of hydrates begins, and calcium silicate hydrate (CaO—SiO ₂ —H ₂ O gel) and ettringite (3CaO.Al ₂ O ₃ .3CaSO ₄ .32H ₂ O) and other hydrated mineral phases are generated, and the layer thickness is gradually increased, leading to consolidation hardening of particles. In addition, this hydrate formation reaction occurs not only in the liquid phase but also inside the particles near the surface of the slag.

As an invention for suppressing consolidation hardening of this slag roadbed material, for example, a method disclosed in Patent Document 1 is shown.
After adjusting the amount of water added so that the method shown in Patent Document 1 is less than the moisture value at which free water begins to exist and is in a range of 10% by mass less than the moisture value, A gas containing carbon dioxide gas and having a relative humidity of 75 to 100% is flowed to carbonize the slag, suppress the formation of a mineral phase that causes consolidation hardening on the outer periphery of the slag, and the slag particles are consolidated. It is intended to prevent this from happening.
Japanese Patent No. 3828977

However, Patent Document 1 of the above prior art has the following problems.
It is necessary to adjust the amount of water to be added so that the slag itself is less than the moisture value at which free water begins to be present and more than 10% by mass less than the moisture value. Moreover, it is said that a slag is carbonized by flowing a gas having a relative humidity of 75 to 100% containing carbon dioxide gas. However, how much the slag surface is carbonated and how much or more is carbonized in the outer periphery of the slag. It is not stipulated whether the mineral phase that causes consolidation hardening can be suppressed.

  Here, the object of the present invention is to solve such problems and to provide a production method capable of efficiently suppressing the consolidation of slag civil engineering materials, and in particular, grain size-adjusted steel slag and steel slag for roads of crusheran steel slag. It is an object of the present invention to provide a method that can be used effectively.

As a result of studying to solve the above problems, the present inventor has found that calcium silicate water can be obtained without changing the water around the slag to a high pH if the CaO on the surface of the blast furnace slag and the steelmaking slag can be changed to an insoluble mineral phase (CaCO ₃ ). It came to the idea that the caking hardening due to the formation of hydrates such as Japanese and ettringite can be suppressed.

That is, free water (carbonated water) containing carbon dioxide gas is brought into contact with the surface of the slag particles (specifically, immersion in carbonated water or spraying of carbonated water is exemplified), so that the slag side It was thought that CaCO ₃ eluted from each slag particle surface by the reaction (carbonation reaction) of Ca ions eluted from the water and CO ₂ dissolved in free water. Specifically, by carbonizing the surface of the slag to a certain extent or more, the elution of CaO from the surfaces of the blast furnace slag and the steelmaking slag can be suppressed, so that the pH increase is suppressed and the solidification and solidification of the civil engineering material is suppressed. Is done.

The present invention has been made based on the above findings, and the gist thereof is as follows.
(1) A method for producing a material for civil engineering, characterized in that one or two slags selected from blast furnace slag and steelmaking slag are immersed in free water containing carbonic acid.

  (2) A method for producing a civil engineering material produced by subjecting a blast furnace slow-cooled slag having a particle size of 25 mm or less to aging treatment, followed by further carbonation treatment, wherein the aging treatment and carbonation treatment are performed as follows. The manufacturing method of the material for civil engineering characterized by the above-mentioned.

(A) Aging treatment of blast furnace slow-cooled slag with a particle size of 25 mm or less, 1 kg of sample slag with a particle size of 0 to 25 mm after the aging treatment was randomly collected, and the whole was coarsely crushed and shrunk to a particle size of 5 mm or less 200 g collected from the sample slag having a particle size of 5 mm or less is pulverized and reduced to a particle size of 1 mm or less, and 50 g collected from the sample slag having a particle size of 1 mm or less is crushed to a particle size of 0.25 mm or less. The free CaO content contained in the collected 50 g of sample slag should be controlled to 0.45% or less by mass%.
(B) By the carbonation process which immerses the slag which carried out the said aging process in the free water which contained carbonic acid and was adjusted to pH 3.5-5.4, the particle size 0-25 mm after the carbonation process 1 kg of the sample slag was randomly sampled and coarsely crushed and reduced to a particle size of 5 mm or less. 200 g sampled from the sample slag having a particle size of 5 mm or less was crushed and reduced to a particle size of 1 mm or less. The carbonation rate of 50 g of sample slag collected by pulverizing 50 g of sample slag having a particle diameter of 1 mm or less to a particle size of 0.25 mm or less should be controlled to 15% or more.
Here, the carbonation rate is (slag free CaO mass concentration before carbonation treatment−slag free CaO mass concentration after carbonation treatment−slag free Ca (OH) ₂ mass concentration after carbonation treatment × 0.76) / (Slag free CaO mass concentration before carbonation treatment) × 100.

(3) A civil engineering material produced by the method described in (2) above is produced by aging treatment of converter slag having a mass% of 100 to 30% and a particle size of 25 mm or less, followed by further carbonation treatment. A method for producing a civil engineering material, comprising mixing 70% or less by mass of a civil engineering material produced by a method in which aging treatment and carbonation treatment are respectively performed as follows: .
(C) Aging of converter slag having a particle size of 25 mm or less, 1 kg of sample slag having a particle size of 0 to 25 mm after the aging treatment was randomly collected, and the whole was coarsely crushed and reduced to a particle size of 5 mm or less Then, 200 g collected from the sample slag having a particle size of 5 mm or less is crushed and reduced to a particle size of 1 mm or less, and 50 g collected from the sample slag having a particle size of 1 mm or less is crushed to a particle size of 0.25 mm or less and recovered. The content of free CaO contained in 50 g of sample slag thus obtained should be controlled to 4.5% or less by mass%.
(D) By the carbonation treatment in which the slag subjected to the aging treatment is immersed in free water containing carbonic acid and having a pH adjusted to 3.5 to 5.4, the particle size after the carbonation treatment is 0 to 25 mm. 1 kg of the sample slag was randomly sampled and coarsely crushed and reduced to a particle size of 5 mm or less. 200 g sampled from the sample slag having a particle size of 5 mm or less was crushed and reduced to a particle size of 1 mm or less. The carbonation rate of 50 g of sample slag collected by pulverizing 50 g of sample slag having a particle diameter of 1 mm or less to a particle size of 0.25 mm or less should be controlled to 15% or more.
Here, the carbonation rate is (slag free CaO mass concentration before carbonation treatment−slag free CaO mass concentration after carbonation treatment−slag free Ca (OH) ₂ mass concentration after carbonation treatment × 0.76) / (Slag free CaO mass concentration before carbonation treatment) × 100.

(4) The civil engineering material obtained by the carbonation treatment has a uniaxial compressive strength based on JIS A 5015 of 0.7 N / mm ² or less, and is obtained by eluting the civil engineering material based on JIS A 0058-1. The method for producing a civil engineering material as described in (2) or (3) above, wherein the pH of the test solution is 8.0 or less.

  The production method according to the present invention can efficiently suppress consolidation hardening in a slag civil engineering material containing blast furnace slag and / or steelmaking slag. For this reason, it is possible to use the obtained material effectively for road materials and civil engineering materials.

Moreover, since the surface of the slow-cooled slag and converter slag carbonized according to the present invention is covered with an insoluble mineral layer, CaO and Ca (OH) ₂ are eluted and the pH of groundwater and the pH of seawater There is no problem of raising Therefore, it can be used as an alternative raw material for various aggregates, roadbed materials, and natural sand.

Moreover, since carbon dioxide contained in the gas discharged from various factories in the steel works can be used as carbon dioxide used for the treatment, it is possible to suppress the emission of CO _{2 in} the gas to the atmosphere, and global warming It can also be positioned as one of the means for solving problems.

Hereinafter, the present invention will be described in detail.
In developing an efficient treatment method for suppressing consolidation hardening of slag civil engineering materials using blast furnace slag and / or steelmaking slag, the influence of carbonation on slag free CaO concentration was examined.

Here, the free CaO concentration is a concentration in which quick lime added in steel production remains undissolved in the slag, and specifically, the ratio of the residual CaO mass to the total slag mass (unit: mass%). Is defined as In the present invention, the free CaO concentration is controlled as follows: “Sample slag having a particle size of 0 to 25 mm is randomly sampled and 1 kg of the sample slag is roughly crushed and reduced to a particle size of 5 mm or less. 200 g is pulverized and reduced to a particle size of 1 mm or less, and 50 g sampled from the sample slag having a particle size of 1 mm or less is crushed to a particle size of 0.25 mm or less and recovered. This is because it was found that the free CaO concentration of the sample population can be managed by managing the sample slag in this particle size range. When this free CaO concentration is high, it reacts with water to become Ca (OH) ₂ , which causes the slag to expand and collapse. Therefore, the free CaO concentration contained in 50 g of sample slag obtained by applying the above method to the slag after aging treatment is 0.45 mass% or less (blast furnace decooling slag), 4.5 mass% or less ( A slag having a particle size of 25 mm or less may be aged so as to form a converter slag.

Aging treated slowly cooled blast furnace slag _{(CaO: 42%, SiO 2} : 33.8%, Al 2 O 3: 14.4%, MgO: 6.7% of the general blast furnace slow cooling slag) and Tenro Slag (a general converter slag of CaO: 44.3%, SiO ₂ : 13.8%, Al ₂ O ₃ : 1.5%, MgO: 6.4%) is converted into a gas containing carbon dioxide ( A fixed amount (gas pressure 4 kg / cm ² ) of carbon dioxide gas was flowed and immersed in free water (carbonated water) adjusted to 3.5 to 5.4, which is a general pH of carbonated water. .

  As a gas containing carbon dioxide used in the present invention, commercially available carbon dioxide or carbon dioxide mixed with air, commercially available nitrogen or argon gas was used in the laboratory. As for the treatment method, for example, it is efficient to use exhaust gas or carbonate discharged from various factories in the steelworks.

  If the carbon dioxide gas concentration in the carbon dioxide-containing gas is low, the carbonation effect decreases. However, the lower the carbon dioxide concentration, the higher the carbonation efficiency.

Arbitrary grains of blast furnace slow-cooled slag and converter slag that have been carbonized by immersion in free water (carbonated water) containing carbonic acid at pH 3.5 to 5.4 are embedded in the resin, and the cross section is As a result of observation, it was confirmed that CaCO ₃ was stabilized. Moreover, it is immersed in free water having a pH of 3.5 to 5.4, and the carbonation rate (= (slag free CaO concentration before carbonation treatment−free CaO concentration after carbonation treatment−free Ca (OH) after carbonation treatment) ) JIS K 0058 for the blast furnace slow-cooled slag and converter slag before and after the carbonation treatment was performed so that ₂ concentration) / (slag free CaO concentration before carbonation treatment) was 15.1%. -1 (Method for testing chemical substances of slags, Part 1: Dissolution test method) The pH of the obtained eluate was measured with the number of specimens being 3 in each case. The results are shown in FIGS. The free CaO concentration was measured by ethylene glycol extraction-atomic absorption spectrometry. In the present invention, the carbonation rate is controlled as follows: “1 kg of sample slag having a particle size of 0 to 25 mm is randomly sampled, and the whole is coarsely crushed and reduced to a particle size of 5 mm or less. 200 g collected from the above is pulverized and reduced to a particle size of 1 mm or less, and 50 g sampled from the sample slag having a particle size of 1 mm or less is crushed to a particle size of 0.25 mm or less and recovered. This is because it was found that the carbonation rate of the sample population can be managed by managing the sample slag in this particle size range.

  From this result, the carbonation treatment according to the present invention, that is, the slag after the aging treatment so that the carbonation rate of 50 g sample slag obtained by applying the above method to the slag after immersion is 15% or more. By performing the treatment of immersing in free water containing carbonic acid whose pH is adjusted to 3.5 to 5.4, the blast furnace slow cooling slag having a pH of 11.2 to 11.5 is changed to 6.0 to 7.1. It has been found that the converter slag at pH 12.4 to 12.6 decreases to 6.9 to 7.5.

FIG. 3 shows the results of evaluating the relationship between the carbonation rate and the compressive strength of various slags obtained by performing the carbonation treatment so as to obtain a plurality of carbonation rates including the case of 15.1%. Show. From this result, it was found that the compression strength of the slag after the treatment can be suppressed to 0.7 N / mm ² by performing the carbonic acid treatment according to the present invention.

As a result of the above, the water added by the method disclosed in Patent Document 1 is less than the moisture value at which free water begins to exist in the slag itself, and more than 10% by mass less than the moisture value. There is no need to adjust the amount, and the pH of the eluate from the slag is adjusted to 8.0 or less by simply contacting the carbonated water, which is free water containing carbon dioxide, that is, the CaO on the slag surface is adjusted to the insoluble mineral phase. It is possible to provide an efficient treatment method that suppresses formation of hydrates that contribute to consolidation hardening of slag such as calcium silicate hydrate and ettringite generated between slag particles in a high pH atmosphere by changing to (CaCO ₃ ). Was confirmed.

  30 kg of the blast furnace slow-cooled slag having the slag composition described above was subjected to atmospheric aging for 3 months so that the free CaO concentration contained was 0.45 mass% or less. For this free CaO, 1 kg of sample slag with a particle size of 0 to 25 mm was randomly collected, and all of them were coarsely crushed and reduced to a particle size of 5 mm or less, and 200 g sampled from the sample slag with a particle size of 5 mm or less 50 g sample slag which was pulverized and reduced to 1 mm or less and collected from this sample slag having a particle size of 1 mm or less was pulverized to a particle size of 0.25 mm or less, and the above-described ethylene glycol extraction-atomic absorption analysis method was used. It managed by measuring by.

  Note that this measurement management can be achieved by atmospheric aging for 3 months if it is a general blast furnace slow cooling slag having a particle size of 25 mm or less, so it is not necessary to measure each time. Further, the method of aging treatment is not limited to “atmospheric aging”. In short, it is sufficient to control the “contained free CaO concentration to 0.45% by mass or less”, so that it is exposed to a pressurized atmosphere or a water vapor atmosphere. An aging process may be used. Furthermore, the slag immediately before being subjected to the carbonation treatment after this can be used as it is, but, as a precaution, the period from the aging treatment to the carbonation treatment Is 3 months at the longest, and free CaO in the slag is substantially unchanged (rate of change ≦ 0.1%) with such a prolonged period.

  Further, 30 kg of converter slag having the above-mentioned slag composition was subjected to aging treatment (steam aging) for 72 hours in a steam atmosphere at 100 ° C. under atmospheric pressure, and the free CaO concentration contained was 4.5 mass%. It was as follows. This free CaO concentration is obtained by randomly collecting 1 kg of sample slag having a particle size of 0 to 25 mm, coarsely crushing and reducing the whole to a particle size of 5 mm or less, and 200 g sampled from the sample slag having a particle size of 5 mm or less. 50 g of sample slag which was pulverized and reduced to a diameter of 1 mm or less, collected from the sample slag having a particle diameter of 1 mm or less and pulverized to a particle diameter of 0.25 mm or less was recovered by the above-described ethylene glycol extraction-atomic absorption analysis. We managed by measuring by the method.

  In addition, this measurement management is normally achieved by steam aging for 72 hours if it is a converter slag having a general particle diameter of 25 mm or less, and therefore it is not necessary to measure each time. In addition, the method of aging treatment is not limited to “steam aging”, and in short, it is sufficient if the “contained free CaO concentration is 4.5 mass% or less”. Furthermore, the slag immediately before being subjected to the carbonation treatment after this can be used as it is, but for the sake of explanation, the period until the carbonation treatment after the aging treatment is as follows. Even if it is 3 months at the longest and a period of time has passed in the air atmosphere, the free CaO in the slag is between 0 and 4.5% by mass and is substantially unchanged (change rate ≦ 0.1%).

Carbonated water (free water, pH 3.5 to 5.4, obtained by continuously blowing carbon dioxide gas with a concentration of 20% at a gas pressure of 4 kg / cm ² into the blast furnace slow-cooled slag and converter slag after the completion of the aging treatment. It was immersed in a water temperature of 20 ° C.

  By changing the treatment time of this immersion treatment, the blast furnace slow cooling slag and converter slag adjusted to a carbonation rate of 15 and 16% were blended under the conditions shown in Table 1, and the uniaxial compressive strength test procedure (conforming to JIS A5015) Specimens were prepared according to the above. In addition, the immersion time for setting the carbonation rate to 15% was 5 minutes in the above carbonated water.

  A specimen used as a comparative example was prepared by blending a blast furnace slow-cooled slag and a converter slag adjusted to a carbonation rate of 12 and 14% under the conditions shown in Table 1 and preparing a specimen for uniaxial compressive strength (according to JIS A5015). ).

Table 2 shows the test results obtained by sealing the prepared specimen and curing it in a thermostatic chamber at a temperature of 20 ° C.
The specimen prepared according to the present invention was an agglomerate that was not consolidated with each other in any curing period and was separated by an external force that was lightly touched with a finger.

It is a graph which shows the pH change of the blast furnace cooling slag before and behind carbonation treatment. It is a graph which shows the pH change of the converter slag before and behind carbonation treatment. It is a graph which shows the relationship between the carbonation rate computed based on the measurement result in ethylene glycol extraction-atomic absorption spectrometry, and compressive strength.

Claims (4)

  A method for producing a civil engineering material, characterized in that one or two slags selected from blast furnace slag and steelmaking slag are immersed in free water containing carbonic acid. A method for producing a civil engineering material which is produced by aging a blast furnace slow-cooled slag having a particle size of 25 mm or less and then performing a carbonation treatment, wherein the aging treatment and the carbonation treatment are performed as follows. A method for producing civil engineering materials.
(A) Aging treatment of blast furnace slow-cooled slag with a particle size of 25 mm or less, 1 kg of sample slag with a particle size of 0 to 25 mm after the aging treatment was randomly collected, and the whole was coarsely crushed and shrunk to a particle size of 5 mm or less 200 g taken from the sample slag having a particle size of 5 mm or less is crushed and reduced to a particle size of 1 mm or less, and 50 g taken from the sample slag having a particle size of 1 mm or less is crushed to a particle size of 0.25 mm or less. The free CaO content contained in the collected 50 g of sample slag should be controlled to 0.45% or less by mass%.
(B) By the carbonation process which immerses the slag which carried out the said aging process in the free water which contained carbonic acid and was adjusted to pH 3.5-5.4, the particle size 0-25 mm after the carbonation process 1 kg of the sample slag was randomly collected and the whole was coarsely crushed and reduced to a particle size of 5 mm or less, and 200 g collected from the sample slag having a particle size of 5 mm or less was pulverized and reduced to a particle size of 1 mm or less. The carbonation rate of 50 g of sample slag collected by pulverizing 50 g of sample slag having a particle diameter of 1 mm or less to a particle size of 0.25 mm or less should be controlled to 15% or more.
Here, the carbonation rate is (slag free CaO mass concentration before carbonation treatment−slag free CaO mass concentration after carbonation treatment−slag free Ca (OH) ₂ mass concentration after carbonation treatment × 0.76) / (Slag free CaO mass concentration before carbonation treatment) × 100. Production of civil engineering materials produced by aging treatment of converter slag having a mass percentage of 100 to 30% and a particle size of 25 mm or less, followed by further carbonation treatment. A method for producing a civil engineering material, comprising blending 70% or less by mass of a civil engineering material produced by a method in which the aging treatment and carbonation treatment are respectively performed as follows.
(C) Aging of converter slag having a particle size of 25 mm or less, 1 kg of sample slag having a particle size of 0 to 25 mm after the aging treatment was randomly collected, and the whole was coarsely crushed and reduced to a particle size of 5 mm or less Then, 200 g collected from the sample slag having a particle size of 5 mm or less is crushed and reduced to a particle size of 1 mm or less, and 50 g collected from the sample slag having a particle size of 1 mm or less is crushed to a particle size of 0.25 mm or less and recovered. The content of free CaO contained in 50 g of sample slag thus obtained should be controlled to 4.5% or less by mass%.
(D) By the carbonation treatment in which the slag subjected to the aging treatment is immersed in free water containing carbonic acid and having a pH adjusted to 3.5 to 5.4, the particle size after the carbonation treatment is 0 to 25 mm. 1 kg of the sample slag was randomly sampled and coarsely crushed and reduced to a particle size of 5 mm or less. 200 g sampled from the sample slag having a particle size of 5 mm or less was crushed and reduced to a particle size of 1 mm or less. The carbonation rate of 50 g of sample slag collected by pulverizing 50 g of sample slag having a particle diameter of 1 mm or less to a particle size of 0.25 mm or less should be controlled to 15% or more.
Here, the carbonation rate is (slag free CaO mass concentration before carbonation treatment−slag free CaO mass concentration after carbonation treatment−slag free Ca (OH) ₂ mass concentration after carbonation treatment × 0.76) / (Slag free CaO mass concentration before carbonation treatment) × 100. The civil engineering material obtained by the carbonation treatment has a uniaxial compressive strength of 0.7 N / mm ² or less based on JIS A 5015, and is obtained by eluting the civil engineering material based on JIS A 0058-1. The method for producing a civil engineering material according to claim 2 or 3, wherein the pH of said material is 8.0 or less.

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