JPS5934302A - Road foundation material and construction of road foundation - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] and also includes its use.

The slag associated with electric furnace steelmaking includes oxidation stage slag (usually abbreviated as "oxidation slag") discharged at the end of the oxidation refining stage, and reduction stage slag (also referred to as "reduction slag") discharged upon completion of reduction refining. (abbreviated as "slag"), which is generated in a ratio of approximately 7:3 by weight.

In the past, attempts have been made to crush oxidized slag to an appropriate size and use it as aggregate for conocrete or as a roadbed material for asphalt pavement, with some success, but reduced slag has no other uses. It was only used as a landfill.

The biggest reason why reduced slag is not used is because it contains a large amount of dical silicate/rum 2CaO when it is generated.
- When SIO2 is cooled from high temperature to low temperature, it transforms from β phase to γ phase, and due to the volume expansion accompanying the transformation, it tends to collapse and become powder, which not only creates dust and is difficult to handle.
The reason is that it is not suitable for applications that require a certain particle size.

The present inventors conducted research with the intention of using the entire electric furnace slag, including not only oxidized slag but also reduced slag, and found that a mixture of both in a certain ratio can be used as a roadbed material, for example, under asphalt pavement. We have found that it is useful for roadbeds, and have established the optimum method for its use, resulting in the present invention.

The roadbed material using the electric furnace slag of the present invention is produced by crushing the oxidized slag and reduced slag discharged from electric furnace steelmaking into appropriate sizes as a roadbed material, and adjusting the particle size as necessary. Graph = 8 0-60%:
It is blended in a proportion of 20 to 40% (weight %).

Figure 1 shows the results of measuring the unconfined compressive strength of compacted mixtures of oxidized slag and reduced slag in various proportions and crushed oxidized slag alone.

As shown in the graph of FIG. 1, the mixture of oxidized slag and reduced slag has better results than the previously attempted use of oxidized slag alone. and.

The blending ratio of the two is preferably in the range of 80 to 60%:20 to 40% of oxidized slag:reduced slag, particularly around 70:30. As mentioned above, oxidized slag and reduced slag are generated in a ratio of approximately 7:3, so in order to utilize this as a roadbed material according to the present invention, it is sufficient to use the generated slag as it is.
It's extremely convenient.

The reason why good results can be obtained by using a combination of oxidized slag and reduced slag is not clear, but one reason is that the former has a moderately large particle size, while the latter is a relatively fine powder, and the particles in between, resulting in overall Another reason is that reduced slag has higher hydraulic properties than oxidized slag. A modified CBR test was conducted to compare the strength with natural crushed stone.

The results were good, as shown in FIG. It is unavoidable that oxidized slag and reduced slag contain some free lime, and if they are applied to the roadbed while containing this, volumetric expansion will occur later due to changes in CaO - Ca(OH)2. Asphalt pavement will cause cracks, so it must be thoroughly digested in advance.

As a countermeasure to this problem, we tried aging and obtained the results shown in Figure 3.

Oxidized slag and reduced slag are
It is preferable to use it after aging for at least 3 months under the action of water. If water is sprayed immediately after crushing the slag, water will flow through the slag, and the rest will proceed through the absorption of rainwater and moisture in the air.

Next, when applying the roadbed material composition of the present invention, in order to take advantage of the above-mentioned hydraulic properties of reduced slag and oxidized slag,
Adequate amounts of water should be given. Appropriate initial moisture content values vary somewhat depending on conditions such as particle size distribution as well as chemical composition of the slag, but experimental results for typical examples are shown in Figure 3. In other words, at a mixing ratio of oxidized slag:reduced slag = 80-60% = 20-40, if the initial moisture content is selected in the range of 6-10Li6, the uniaxial compressive strength required as a road base material (HMS) is '
2''9/c) A value exceeding 712 is obtained. From the figure, in the case of the optimal blending ratio of 70:30, the ratio is wider.

It can be seen that a wide range of initial moisture contents can be employed, and that by selecting the optimum initial moisture content, extremely high unconfined compressive strength can be obtained.

As long as the above-mentioned precautions are taken, the construction as a roadbed material can be carried out in accordance with conventional techniques.

The present invention completely utilizes electric furnace slag, which is composed of oxidized slag and reduced slag, in the generation ratio, and has the effect of killing two birds with one stone by treating waste and saving resources. The only steps necessary to obtain the roadbed material of the present invention are crushing, some particle size adjustment, and mixing, so no special equipment is required, energy consumption is small, and the cost is extremely low.

Roadbeds made using this material are strong enough for regular asphalt pavement and are highly practical.

EXAMPLE Oxidized slag and reduced slag were used in their original proportions, ie, 69%+31% (by weight). The chemical composition of each is as follows.

Oxidized slag Reduced slag CaO41,849,4 SiOz 20,2 28.2AA
2034.7 11.8 FeO22,80,8 Mri0 3.67,6 Mn5 5.9 0.2S
O,090,26 Oxidized slag and some lumps of reduced slag were crushed and sieved to a maximum diameter of 25 mm. The cumulative particle size distribution is as follows, and the MS-2
5. Meets particle size standards.

25m 100 95-10020
90.0 13 74.6 55-8510
66.8 5 52.3 30-652.5
39.3 20-50], 2 pharynx
30.6 0.6 21.1 0.4 19.0
10-300.3 17.0 0.15 10.9 0.074 6.4
2-10 A uniaxial compressive strength test according to JISA5015 was conducted on the above roadbed material. The results were as follows.

We conducted a modified CBR test based on the asphalt pavement guidelines, with an optimal water content ratio of 7.1% and unconfined compressive strength of 15 kg/Cm2.
The results are as follows.

Optimum water content ratio 6.2 coefficient Maximum dry density 2840'J/Cm3 corrected CBR value 114.0 coefficient

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between slag composition and unconfined compressive strength when electric furnace slag is used as a roadbed material. FIG. 2 is a graph showing the relationship between slag composition and modified CBR value. FIG. 3 is a graph showing how the water immersion expansion coefficient of electric furnace slag decreases due to aging. FIG. 4 is a graph showing the influence of initial moisture content on unconfined compressive strength when using the roadbed material of the present invention. Patent applicant Daido Steel Co., Ltd. Nippon Paido Co., Ltd. Maruta Kogyo Co., Ltd. Agent Patent attorney Sou Suga J. Okinokura Joya (°/,) Procedural Amendment September 24, 1980 Director General of the Patent Office Kazuo Wakasugi 1, Indication of the case 1982 Patent Application No. 144036 2, Name of the invention Roadbed material and roadbed construction method 3. Relationship with the case of the person making the amendment Patent applicant address 66, Hoshizaki-cho, Minami-ku, Nagoya, Aichi Prefecture Name (371) Daido Steel Co., Ltd. (2 others)
4. Agent Address: 15-14 Tsukiji 2-chome, Chuo-ku, Tokyo Column J3 of the detailed description of the invention in the specification and the name of the applicant at the end 6. Contents of the amendment (1) 4 from the bottom of page 9 of the specification The maximum dry density value "2840" in the row is corrected to r2.840J.

Claims (1)

[Scope of Claims] ill Oxidized slag and reduced slag discharged from electric furnace steelmaking are crushed into suitable sizes for use as roadbed material, and the particle size is adjusted as necessary to obtain a ratio of oxidized slag to reduced slag of 80 to 60%. : A roadbed material mixed in a proportion of 20 to 40 inches (% by weight). (2) The roadbed material according to claim 1, which is used after aging in which the reduced slag is left under the action of water for three months or more. (3) The oxidized slag and reduced slag discharged from electric furnace steelmaking are crushed into suitable sizes for use as roadbed material, and the P particle size is adjusted as necessary to obtain a ratio of oxidized slag: reduced slag -80 to 60%: 20. A roadbed construction method consisting of compacting a roadbed material mixed at a ratio of ~4ochi (wt%) at an initial moisture content of 6 to 10%.