KR20210144250A - Flowable Fill - Google Patents

Abstract

The present invention relates to liquefied stabilized soil for filling and, more specifically, includes 30 to 70% by weight of ferronickel slag, 5 to 30% by weight of in situ soil, 5 to 10% by weight of cementitious solidifying material, and 10 to 30% by weight of coal ash. According to the liquefied stabilized soil for filling of the present invention, by recycling and using ferronickel slag and in situ soil as the main raw material of the liquefied stabilized soil for filling, the liquefied stabilized soil for filling has the same level of fluidity and compressive strength of the existing liquefied stabilized soil for filling, while the waste of resources can be significantly reduced, and pollution to the soil can be minimized. In addition, since the liquefied stabilized soil for filling of the present invention contains waste tire rubber powder, it is possible to suppress cracks caused by drying shrinkage that occur during the curing period after construction.

Description

Fluidized soil for filling {Flowable Fill}

The present invention relates to fluidized soil for filling, which can minimize resource waste and environmental pollution by recycling waste resources.

In general, in the excavation and restoration work of civil engineering works, after installing a pipeline or an underground facility, backfilling is performed. The traditional backfill method consists of compacting sand or on-site soil. In order to minimize the traffic flow and inconvenience to nearby residents, when performing excavation and restoration work, the construction is usually started at midnight and completed around 6 am. guidelines are set. However, the traditional backfill method is difficult to compact parts such as the lower part of the pipe or small gaps, and it is difficult to perform high-quality construction due to insufficient construction time, which may cause damage to underground structures. If the soil compaction is insufficient in this way, dents and cracks of roads, subsidence around structures, subsidence of backfilling of abutments, etc. occur, and thus safety problems and economic damage continue to increase.

In order to compensate for this problem, recently, a construction method using fluidized soil for filling with fluidity is also being used. The fluidized soil for filling is made by applying the concept of low-strength concrete to geotechnical engineering, and is composed of solidifying material, soil, water, fly ash and admixture, etc. Whereas the existing covering material obtains appropriate density and strength through compaction, fluidized soil for filling has flow characteristics and the characteristic that strength develops over time. Fluidized soil for filling has the following advantages when used as a filling material for various structures. It has fluidity before curing, so it can be easily poured with a chute, conveyor, pump or bucket depending on the shape of the structure or the location of the space. can be blended, and the required strength can be obtained by controlling the amount of the solidifying material to be blended. In addition, it does not create gaps during pouring, and it is hardened enough to exclude long-term settlement, so that erosion by drift water and seepage water does not occur, and it is effective in preventing cavitation of the ground due to erosion. Fluidized soil for filling with these advantages can be used for underground pipelines such as water and gas, backfilling of electric power and communication facilities buried underground, backfilling or filling a narrow space between underground structures and the ground, and structures such as retaining walls, abutments, and culverts. Backfilling and covering work where voltage work is difficult. Filling of gaps in the slab lower surface of structures due to ground subsidence, filling of cavities under road pavement that cause road surface depression, backfilling of complex cavities such as abandoned mines, and filling in water where compaction is impossible used

However, most of the existing fluidized soil for filling uses quicklime and cement as main raw materials, and the solidified mixture is used as a filling material and then landfilled. There is a problem of wasting resources.

In addition, the existing fluidized soil for filling has a problem of generating secondary environmental pollution due to quicklime, which is the main raw material of the existing solidification material manufactured through the firing process, and carbon dioxide generated during the cement firing process.

Therefore, there is a need to develop an eco-friendly fluidized soil for filling that can significantly reduce waste of resources and minimize soil contamination while having the fluidity and compressive strength of the existing fluidized soil for filling at the same level.

Patent Document 1: Korean Patent Registration No. 10-0256021 Patent Document 2: Korean Patent Registration No. 10-0279171

The present invention is to overcome the above problems, and while having the fluidity and compressive strength of the existing fluidized soil for filling at the same level, it is possible to significantly reduce the waste of resources and to minimize pollution to the soil. Its purpose is to provide fluidized soil for filling.

The problem to be solved by the present invention is not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by those of ordinary skill in the art to which the present invention belongs from the following description. will be.

The present invention for solving the above problems relates to fluidized soil for filling, and more specifically, 30 to 70% by weight of ferronickel slag, 5 to 30% by weight of in-situ soil, 5 to 10% by weight of cementitious solidifying material, and coal ash 10 to 30% by weight.

According to the fluidizing soil for filling of the present invention, by recycling and using ferronickel slag and on-site generated soil as main raw materials for fluidizing soil for filling, the fluidity and compressive strength of the existing fluidized soil for filling are at the same level, while Waste can be significantly reduced, and there is an effect that can minimize soil contamination.

In addition, since the fluidized soil for filling of the present invention contains coal ash, cracking due to drying shrinkage can be minimized, and thus, it has high watertightness and has the effect of preventing the spread of soil contamination.

Since the present invention can apply various transformations and can have various embodiments, specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention. In describing the present invention, if it is determined that a detailed description of a related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present application, terms such as “comprise” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof.

Terms such as first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another.

The present invention relates to fluidized soil for filling, and more specifically, it is characterized in that it is prepared by mixing ferronickel slag, on-site soil, cement-based solidifying material, coal ash and water.

In the present invention, the ferronickel slag refers to slag that is produced as a by-product of manufacturing ferronickel, a stainless raw material, and is generated every year around the world by 1.8 million tons. . Since the ferronickel slag has a spherical shape, when used as an aggregate, the ferronickel slag has excellent fluidity due to the ball bearing effect, and can reduce the amount of water used, thereby exhibiting high strength and reducing the shrinkage stress. In addition, the ferro-nickel slag 2MgO crystalline o SiO ₂ and MgO o comprises a crystal phase of SiO ₂ or, 2MgO o SiO ₂ and MgO o It consists of a crystal phase of SiO ₂ do not have a hydraulic (hardenability), used as a sand substitute can In the present invention, the ferronickel slag preferably has a particle size of 0.01 to 5 mm. This is that when the particle size of the ferronickel slag is less than 0.01 mm, the increase in permeability of the fluidized soil is insignificant, whereas the production and quality control of the ferronickel slag aggregate has a problem that becomes too difficult, and when it exceeds 5 mm, fluidization when pouring the filler material This is because soil permeability is excessively reduced, and problems may occur in filling voids in the ground.

The fluidized soil for filling according to the present invention can replace existing aggregates such as quicklime, gravel, and sand by recycling and using industrial waste ferronickel slag as the main aggregate, thereby minimizing the waste of resources, eco-friendly, and manufacturing cost can be reduced.

In the present invention, the content of the ferronickel slag is not particularly limited, but is preferably 30 to 70% by weight based on the weight of the fluidized soil for the entire filling, which is the fluidity of the fluidized soil when the content of the ferronickel slag is less than 30% by weight When the content of the ferronickel slag exceeds 70% by weight, the internal friction angle is disadvantageous due to the monotonous filling material properties, and the filling material by the pozzolan reaction of the coal ash industrial by-products mixed together- This is because it can cause problems in long-term stable strength expression by lowering the distribution of bonding force at the interface between binders.

In the present invention, the site-generated soil is an aggregate, meaning that bedrock and large stones are removed from the soil generated at the construction site. It is preferable that the content is 5 to 30% by weight, which has a problem in that it does not have sufficient durability when the content of the on-site soil is less than 5% by weight, and when it exceeds 30% by weight, the fluidity is excessively reduced and the workability is deteriorated because there is

Fluidized soil for filling according to the present invention can minimize waste of resources and reduce manufacturing cost by using in-situ soil generated in the field as the main aggregate, and it is more durable when only ferronickel slag is used. can be further strengthened.

In the present invention, the cement-based solidifying material strengthens the bonding force between aggregates, so that even if the buried pipe is damaged, it can suppress the loss by fluid, and also reduce the permeability coefficient of the fluidized soil for filling, thereby preventing penetration into the fluidized soil for filling the underground wastewater. can be effectively suppressed. The cement-based solidifying material may be a cement such as ordinary Portland cement, medium heat portland cement, crude steel portland cement, low heat Portland cement, or mixed cement, or a mixture of gypsum or lime with the cement.

In the present invention, the content of the cement-based solidifying material is not particularly limited, but is preferably 5 to 10% by weight relative to the total weight of the fluidized soil for filling. The watertightness is too low, so it is difficult to express the performance of the fluidized soil, and there is a problem in that durability is reduced due to the internal penetration of contaminants. This is because problems that may interfere with usability such as excavation and excavation may occur.

In the present invention, the coal ash includes bottom ash and fly ash, and provides bonding strength with the cement solidifying material contained in the fluidized soil for filling, thereby contributing to the long-term strength performance expression after the curing period after construction. In addition to this, the coal ash in the present invention serves to seal the transition section between the aggregate and the binder to prevent the spread of soil contamination due to contaminants, pipe leakage, etc., and to improve watertightness by minimizing cracks caused by drying shrinkage. Although the content of is not particularly limited, it is preferably 10 to 30% by weight based on the weight of the fluidized soil for filling, which is the long-term strength performance of the coal ash when the content of the coal ash is less than 10% by weight based on the weight of the fluidized soil for filling. This expression is not sufficient, there is a problem that the spread of soil contamination cannot be sufficiently prevented, and when it exceeds 30% by weight, it causes a decrease in early compressive strength and there is a problem of strength expression such as an increase in the number of mixing.

In the present invention, the water content of the water is preferably 30 to 40% by weight.

According to the fluidizing soil for filling of the present invention, by recycling and using ferronickel slag and on-site generated soil as main raw materials for fluidizing soil for filling, the fluidity and compressive strength of the existing fluidized soil for filling are at the same level, while There is an advantage in that waste can be significantly reduced and pollution to the soil can be minimized.

In addition, since the fluidized soil for filling of the present invention contains coal ash, cracks due to drying shrinkage can be minimized, and thus, it has high watertightness and can prevent the spread of soil contamination.

Hereinafter, the present invention will be described by way of examples. The following examples are merely examples for explaining the present invention, and the scope of the present invention is not limited thereby.

Example

A dry mixture was prepared by mixing ferronickel slag, field-generated soil, ordinary Portland cement, and coal ash powder in the amounts shown in Table 1 below, followed by stirring using a stirrer. After adding water in the amount shown in Table 1 to the dry mixture, the mixture was stirred using a stirrer to prepare fluidized soil for filling according to the present invention.

ferronickel slag
(weight%) on-site soil
(weight%) usually portland
cement
(weight%) coal ash
powder
(weight%) water content
(weight%) Example 1 30 30 10 30 30 Example 2 50 15 10 25 33 Example 3 60 18 5 17 37 Example 4 70 15 5 10 40

comparative example

A dry mixture was prepared by mixing 50% by weight of ferronickel slag, 40% by weight of in-situ soil, and 10% by weight of ordinary Portland cement, followed by stirring using a stirrer. After adding water to the dry mixture to a water content of 33% by weight, the mixture was stirred using a stirrer to prepare fluidized soil for filling.

test example

1. Fluidity test

In order to check the fluidity of the fluidized soil samples for filling prepared in Examples 1 to 4, a fluidity test was performed according to the ASTM D 6103 method prescribed by the ACI committee 229. A cylinder having a diameter of 75 mm and a height of 150 mm is placed on a non-absorbent plate having a width of 600 mm and a length of 600 mm, and after filling the cylinder with the fluidized soil samples for filling of Examples 1 to 4 without compaction, the cylinder is vertically raised. The direction perpendicular to the largest direction of the flow diameter of the sample was measured, and the average value of the two diameters was used as the flow value. The minimum value of the fluidity of the fluidized soil for filling was set to a flow of 200 mm by referring to the high flow criteria set by the ACI, and the test results are as shown in Table 2 below.

flow value
(mm) Example 1 201 Example 2 203 Example 3 204 Example 4 202

In Table 2, it can be seen that all of Examples 1 to 4 according to the present invention have sufficient fluidity.

2. Compressive strength test

For the test of uniaxial compressive strength, the filling fluidized soil prepared in Examples 1 to 4 was filled in a mold for uniaxial compressive strength test with a diameter of 10 cm and a height of 20 cm, and then compaction was not performed. After filling, curing at room temperature for 1 day, demolding, air-drying up to 7 days of age, and testing each of them for uniaxial compressive strength. For the compression of the specimen, a strain control method in which compression is applied at a constant speed in the axial direction is used, and the load rate is maintained at 1%/min so that compression of 0.5 to 2% of the height of the specimen occurs for 1 minute, and the axial load is measured at each constant rate of strain. While the test was conducted until the destruction of the specimen occurred. The test results for uniaxial compressive strength are shown in Table 3 below.

Uniaxial compressive strength
(MPa) Example 1 1.31 Example 2 1.00 Example 3 0.86 Example 4 0.77

It can be seen from Table 3 that all of Examples 1 to 4 according to the present invention have sufficient compressive strength.

3. Soil Pollution Degree Test

In order to test the soil contamination level for the fluidized soil samples for filling of Examples 1 to 4, soil contamination level analysis was performed according to the soil contamination concern standard and the soil contamination countermeasure standard according to the Waste Management Act, and the test results are shown in Table 4 below. as shown.

pollutant soil contamination
Criterion of Concern Example 1 Example 2 Example 3 Example 4 cadmium 12 - - - - copper 200 6.9 6.4 6.6 7.1 arsenic 20 - - - - Mercury 16 - - - - lead 400 4.95 4.92 5.03 5.02 hexavalent chromium 12 8.8 8.5 9.2 8.9 zinc 800 19.5 19.3 18.6 19.1 nickel 160 17.3 20.2 25.3 31.4 fluoride 800 - - - - organophosphorus compounds 30 - - - - polychlorinated biphenyl
(Polychlorinated biphenyls) 12 - - - - draft 120 - - - - phenol 20 - - - - - Benzene ㅇ Toluene ㅇ Ethylbelzen ㅇ Xylene

- Total Petroleum Hydrocarbons (TPH) 80


2000 - - - - trichlorethylene
(TCE) 40 - - - - tetrachlorethylene
(PCE) 24 - - - -

As can be seen in Table 4, the fluidized soil for filling according to the present invention has a lower value than the reference value of soil contamination, indicating that the possibility of soil contamination is low.

4. Dry shrinkage test

The drying shrinkage of the fluidized soil samples for filling of Examples 1 to 4 and the fluidized soil samples for filling prepared according to Comparative Examples were measured according to KS F 2424 (Test method for length change of concrete), and the test results are shown in Table 5 below as shown in

division Example 1 Example 2 Example 3 Example 4 comparative example Length change rate (%) 0.013 0.013 0.009 0.007 0.15

As can be seen in Table 5, it can be confirmed that the fluidized soil for filling of Examples 1 to 4 according to the present invention has a reduction in shrinkage by reducing the rate of change in length compared to the fluidizing soil for filling prepared according to the comparative example, Accordingly, it can be seen that cracks due to drying shrinkage can be minimized.

As described above, those skilled in the art to which the present invention pertains will understand that the present invention may be embodied in other specific forms without changing the technical spirit or essential characteristics thereof. The scope of the present invention is indicated by the claims to be described later rather than the above detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts are interpreted as being included in the scope of the present invention. should be

Claims (2)

30 to 70% by weight of ferronickel slag, 5 to 30% by weight of in situ soil, 5 to 10% by weight of cementitious solidifying material, and 10 to 30% by weight of coal ash, and fluidized soil for filling having a water content of 30 to 40% by weight.
The method of claim 1,
The ferronickel slag is fluidized soil for filling, characterized in that the particle size is 0.01 to 5 mm.