JPH04320488A - Soil conditioner containing powdery collapsed slag - Google Patents

Abstract

PURPOSE:To obtain a soil conditioner excellent in strength at low costs by incorporating respectively given amounts of water-granulated blast furnace slag powder and gypsum in a specific powdery collapsed slag. CONSTITUTION:The title conditioner is prepared by mixing 10-30 pts.wt. of a water-granulated blast furnace slag powdery having a particle size of preferably 3,000-5,000cm<2>/g in terms of the Blaine value of specific surface area and 10-30 pts.wt. of gypsum (e.g. gypsum from flue gas desurfurization) with 100 pts.wt. of a powdery collapsed slag which contains 10wt.% or more of free lime and has a basicity of 5 or more and a particle size of 1,000-3,000cm<2>/g in terms of the Blaine value.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inexpensive ground improvement material using pulverized collapsed slag.

0002

[Prior Art] Ground improvement agents are chemicals that are injected into the ground, for example, to strengthen or dry soft ground, and due to their nature, they are applied over a fairly wide area.
Used in large quantities. Therefore, there is a need for a raw material that can be stably supplied in large quantities and is inexpensive. Particularly in the current situation where user needs for steel types have become more severe, C
There is a tendency to increase the amount of a source used. Therefore, f-CaO (free lime) in converter slag is also on the increase.
In particular, those containing 10% or more of f-CaO 2 will disintegrate into powder and become dust if stored in a factory yard.

0003

[Problems to be Solved by the Invention] As described above, the pulverized and disintegrated slag undergoes a pulverized and disintegrated phenomenon and becomes powdery, and the resulting dust scattering causes environmental deterioration in steel works. The effective use of pulverized and collapsed slag has been awaited in order to reduce steelmaking costs, but most of the technological developments to date have focused solely on technologies to prevent pulverization of high basicity slag. No attempt has been made to actively utilize the pulverized disintegrated slag itself. Therefore, the first object of the present invention is to establish a method for effectively utilizing pulverized collapsed slag.

[0004] Therefore, it is found that pulverized collapsed slag is produced as a by-product in large quantities and is discharged as a landfill material, so it is very inexpensive. Moreover, since it is currently being used as a landfill material, it is unlikely that it will have any negative effects on the soil. Therefore, a second object of the present invention is to provide an inexpensive ground improvement material that effectively utilizes pulverized collapsed slag.

[0005]

[Means for solving the problem] By the way, converter slag, which is produced as a by-product in converter steelmaking, similar to pulverized collapsed slag, contains about 10% or less of free lime, and is obtained in the form of lumps. It has been used as a soil improvement material by taking advantage of its properties, and its technology is disclosed in Japanese Patent Application Laid-open No. 53-84311 and No. 5.
This is as disclosed in No. 6-41916 and Japanese Unexamined Patent Publication No. 2-43281. That is, in JP-A No. 53-84311, a ground improvement material consisting of converter slag with an average particle size of about 0.1 to 5 mm, gypsum, and quicklime (the ratio of quicklime is about half) is
In JP-A-56-41916, the average particle size is 100 μm.
A soil improvement material containing converter slag, granulated slag, and a small amount of Portland cement is disclosed. Furthermore, in JP-A No. 2-43281, 10 to 40 parts by weight of fine water granulated slag powder and 10 parts by weight of gypsum to 100 parts of fine converter slag with a specific surface area Blaine value of 1000 to 5000 cm2/g. Discloses a soil improvement material blended in a proportion of ~40 parts.

[0006] All converter slags contain 10% or less of free lime and are obtained in the form of lumps. Therefore, all of the various ground improvement materials that have been made using converter slag use pulverized lumpy converter slag containing 5 to 10% free lime. Powdered disintegrated slag differs not only in its composition but also in its form, and has never been treated as an equivalent in the industry. Therefore, we investigated the reason why converter slag has been used as a ground improvement material in the past, and found that although converter slag alone has low strength, it can be improved by adding gypsum and granulated slag as additives. It generates a compound and causes strength development.

[0007] This is because 2CaFe2O3 in converter slag
(C2F) reacts with gypsum, and Etrin guide (3Ca
Free CaO in converter slag reacts with SiO2 in granulated slag powder to form CaO-SiO2-H2 system (C-S-H system) hydrate. It is said to be used to form On the other hand, since pulverized collapsed slag contains a large amount of free CaO, when gypsum or granulated slag powder is added to it, more Etrin guide and C-
Generates S-H type hydrate.

[0008] Furthermore, since the powdered and collapsed slag is a fine powder, and furthermore, CaO is in the form of Ca(OH)2,
The alkali stimulation effect on fine water granulated slag powder, which has a large amount of Ca++ ions eluted and has a large effect on strength development, is much greater than on normal slag.

[0009] Therefore, the strength obtained using this pulverized collapsed slag far exceeds the strength obtained using ordinary converter slag, and it is considered to be an extremely excellent ground improvement material. understood. Here, the present invention applies blast furnace water to 100 parts by weight of pulverized disintegrated slag that contains 10% by weight or more of free lime, has a basicity of 5 or more, and has a particle size of 1000 to 3000 cm2/g in Blaine value of specific surface area. This is a ground improvement material characterized by containing 10 to 30 parts by weight of crushed powder and 10 to 30 parts by weight of gypsum. The above-mentioned pulverized collapsed slag is a highly basic slag containing 10% or more of free CaO2, and is completely different from normal converter slag in terms of its mineral composition, which contains a large amount of Ca(OH)2 inside the slag. be.

0010

[Operation] The present invention will be explained in detail below. The pulverized and collapsed slag used in the present invention is a slag that is obtained by naturally pulverizing and collapsing high basicity slag containing a large amount of CaO among the slags produced during so-called converter refining. . Since high chloride slag contains a large amount of f-CaO, there is a large amount of a mineral phase called C3S (3CaO.SiO2). This C3S becomes fine crystals by rapid cooling (water cooling), and its reactivity increases. Furthermore, this C3S reacts with water and converts half of the lime content into C3S.
Released as a(OH)2.

[0011] Therefore, one of the causes of the pulverization and disintegration of slag is considered to be the volumetric expansion of Ca(OH)2. Therefore, since this powdered collapsed slag contains abundant CaO 2 phase, it is more reactive than ordinary converter slag and can be said to be highly applicable as a ground improvement material. Tables 1 and 2 show a comparison of typical compositions of normal converter slag and pulverized collapsed slag.

0012

[Table 1]

[0013]

[Table 2]

As is clear from this, the powdered collapsed slag is a highly basic slag containing more than 10% by weight of free CaO, whereas ordinary converter slag contains less than 10% of free CaO. C generated by hydration of CaO
a(OH)2 phase in a large amount, and T. CaO/Si
It is a by-product of converter steelmaking with a basicity expressed by O2 of 5 or more. Such pulverized disintegrated slag is usually obtained in a fine powder state with a specific surface area Blaine value in the range of 1000 to 3000 cm2/g, so no particular pulverization treatment is required, but if desired, it may be pulverized with a ball mill. This grinding and measuring operation is repeated until the Blaine value becomes 1000 cm2/g or more.

The larger the specific surface area of the pulverized collapsed slag, the higher its reactivity, which is advantageous in achieving the required strength as a soil improvement material, but the time it takes to grind to increase the specific surface area increases manufacturing costs. becomes high. In addition, when examining the influence of the specific surface area of pulverized collapsed slag on the strength of the ground improvement material, the Blaine value was 3000 cm2/g.
It was found that the strength of the obtained soil improvement material reached a plateau when the value exceeded 1000, and that no dramatic improvement in strength could be expected by increasing the specific surface area of the converter slag any further. Therefore, in order to satisfy the purpose of the present invention, which is to achieve high performance as a ground improvement material and to reduce cost, the particle size of the pulverized collapsed slag is set to a Blaine value of 1000 to 3000 cm.
Adjust to a range of 2/g. Preferably 2000-3
000cm2/g is good.

Further, in the present invention, pulverized blast furnace powder is used, and there are no particular restrictions on this powder as long as it is slag obtained by rapidly cooling and pulverizing blast furnace slag, which is produced as a by-product during so-called blast furnace refining. Brain value 3000~50
It is preferable to use a fine powder of about 0.00 cm2/g. In the present invention, as an additive, 10 to 30 parts by weight of blast furnace granulated powder is added to 100 parts by weight of the above-mentioned pulverized disintegrated slag.
parts by weight, and 10 to 30 parts by weight of gypsum.

The gypsum used in the present invention is α
Type and β-type hemihydrate gypsum may be used, but further cost reduction is expected if flue gas desulfurization gypsum, which is obtained by air oxidation of calcium sulfite recovered from flue gas desulfurization, is used. can.

[0018] To determine the mixing ratio of pulverized blast furnace pulverized powder and gypsum to the powdered collapsed slag, experiments were conducted on various mixing ratios, and the performance (strength) when used as a ground improvement material and the increase in the amount of these additives were determined. This decision was made in consideration of the associated manufacturing costs. That is, when the pulverized collapsed slag is 100 parts by weight, the amounts of granulated blast furnace pulverized powder and gypsum added are each 1 part by weight.
It has been found that if the amount is less than 0 parts by weight, the minimum strength required as a soil improvement material cannot be obtained. In addition, the amount of each of these added to 100 parts by weight of powdered disintegrated slag is 3
Even if the amount is more than 0 parts by weight, the strength as a soil improvement material does not change much, so when considering economic efficiency, 30 parts by weight or less is appropriate. More preferably, powdered collapsed slag 1
The amount of pulverized blast furnace powder to be added is preferably 20 to 30 parts by weight, and the amount of gypsum to be added is preferably 15 to 30 parts by weight.

[0019] The composition of the present invention consists of powdered collapsed slag having a Blaine value of 1000 to 3000 cm2/g, and pulverized blast furnace pulverized powder having a specific surface area of about 3000 to 5000 cm2/g, which has been specially adjusted in particle size. It is obtained by mixing gypsum and gypsum in a predetermined ratio. Alternatively, first mix powdered disintegrated slag and gypsum in a predetermined ratio,
A mixture with a Blaine value of 1000 to 3000 cm2/g obtained by crushing with a ball mill etc.
It can also be obtained by adding pulverized blast furnace pulverized powder of about 0 to 5000 cm2/g at a predetermined ratio and mixing the whole. EXAMPLES Hereinafter, the present invention will be explained in detail with reference to examples, but the scope of the present invention is not limited by the following examples.

[0020]

[Example] Pulverized blast furnace slag powder and gypsum were added to pulverized collapsed slag whose composition is shown in Table 1 to prepare a ground improvement material. For mixing, the pulverized collapsed slag was pulverized to the particle size shown in Table 3, and then granulated blast furnace granulated powder and gypsum, which also had the particle size shown in Table 3, were added and mixed well to obtain a ground improvement material. A mortar obtained by mixing this with water and sand was tested for strength. 5 parts by weight of granulated blast furnace slag powder per 100 parts of pulverized collapsed slag;
10, 20, 30 parts and gypsum were added in proportions of 5, 10, 20, 30 parts. The composition and particle size of each component were as follows. The mortar was cured in humid air at 20C until the third day of age, and in water at 20C after the fourth day. The composition of the created mortar was water: ground improvement material: sand = 1:2:3.

[0021]

[Table 3]

Mortar Test Results (1) Effect of Mixing Ratio on Compressive Strength In FIG. 1, the results of the compressive strength test are shown by the solid line. As can be seen from this figure, the compressive strength increases as the pulverized blast furnace slag powder and gypsum (referred to as additives) increase, but when each additive exceeds 20%, the degree of increase slows down, and the amount of additive increases. There will no longer be an increase in compressive strength commensurate with the cost increase associated with the increase in quantity. If 10% of each additive is added, the manufacturing cost will be lower, but it will not be possible to secure the required strength as a soil improvement material. For comparison, JP-A-2-43281 uses normal converter slag instead of pulverized collapsed slag.
Similar test results for the ground improvement material disclosed in the publication are shown in broken lines in FIG. According to the present invention, the compressive strength is improved by approximately 30% or more in all cases.

(2) Effect of particle size on compressive strength Figure 2
Compressive strength after 28 days curing of mortar (see sample code C in Figure 1) prepared by adding 20 parts of pulverized blast furnace slag powder and 20 parts of gypsum to 100 parts of pulverized collapsed slag. The relationship between this and the particle size of the pulverized disintegrated slag used is shown below. As can be seen from this figure, the higher the Blaine value (that is, the finer the powder), the higher the compressive strength, but the value reaches a plateau at 3000 to 4000 cm2/g. Further, if the Blaine value is less than 1000 cm2/g, the required compressive strength will not be achieved. Therefore, taking into consideration the crushing cost and the required compressive strength to increase the Blaine value, the particle size of the pulverized collapsed slag should be 1000 to 3000 cm2/g in Blaine value.
It is preferable that

Next, ordinary converter slag and pulverized collapsed slag were used to compare the effects of free CaO contained therein. According to the present invention, as described above, gypsum and granulated blast furnace powder are added to the pulverized collapsed slag containing a large amount of free CaO to generate ethrin guide and C-S-H hydrate. In particular, for the production of C-S-H type hydrates, Ca(OH)2 in the powdered slag acts as an alkaline stimulant, brings out the latent hydraulic properties of the granulated blast furnace powder, and causes it to coagulate and harden.

[0025] Therefore, the compressive strength of mortar using pulverized collapsed slag containing a large amount of free CaO is greater than that of mortar using ordinary converter slag.

FIG. 3 shows a comparison of the compressive strengths when using normal converter slag and when using pulverized collapsed slag. Here, the strength of normal converter slag is
This is the strength of slag seen in No. 1, and the strength of pulverized collapsed slag is 20% by weight of granulated blast furnace slag and gypsum, respectively.
% composition of mortar. As can be seen from FIG. 3, the compressive strength of the 7-day strength and 28-day strength of the specimens using powdered collapsed slag containing more free CaO 2 is greater than that of the specimens using normal converter slag.

[0027]

[Effect of the invention] By using fine particles of highly basic powdered collapsed slag (containing free CaO of 10% or more) and adding granulated blast furnace slag and gypsum as additives in a certain range of ratios, it is possible to It is possible to provide a ground improvement material that is less expensive to manufacture than when converter slag is used and that satisfies the required strength.

[Brief explanation of drawings]

FIG. 1 is a graph showing the results of an example in comparison with a conventional example.

FIG. 2 is a graph summarizing the results of Examples.

FIG. 3 is a graph showing a comparison between the example and the conventional example.

Claims (1)

[Claims] Claim 1: Contains 10% by weight or more of free lime, has a basicity of 5 or more, and has a particle size of 100 in Blaine value of specific surface area.
Powdered disintegration slag of 0 to 3000cm2/g 10
A ground improvement material comprising 10 to 30 parts by weight of granulated blast furnace powder and 10 to 30 parts by weight of gypsum.