KR101631276B1

KR101631276B1 - Manufacturing method of recycled aggregates using bauxite residue

Info

Publication number: KR101631276B1
Application number: KR1020160010436A
Authority: KR
Inventors: 김용규
Original assignee: 조은산업주식회사; 김용규
Priority date: 2016-01-28
Filing date: 2016-01-28
Publication date: 2016-06-16

Abstract

The present invention relates to a manufacturing method of a recycled aggregate using residual bauxite, which manufactures a hard artificial aggregate that can exhibit a fixed level of strength via a process of solidifying a mixture composed of residual bauxite which is industrial waste and making the mixture into an aggregate. Accordingly, the recycled aggregate is used for multiple purposes such as a drain material or the like during a soft soil improvement process so the use of cement and environmental loads can be reduced. The purpose of the present invention is to manufacture the recycled aggregate comprising residual bauxite, cement, and an additive composed of a solidifying agent and an inorganic binder. The manufacturing method of the recycled aggregate using residual bauxite comprises the following steps: (a) drying residual bauxite; (b) mixing the dried residual bauxite and cement in the mass ratio of 4:1, mixing the mixed residual bauxite and cement and 1.5 wt% of an additive with respect to the weight of the cement to obtain a mixture, and agitating the mixture for at least one minute; (c) supplying the mixture to a pan of a pan-type molding machine with a grade of 45-55° at a constant rate, and also rotating the pan at a first speed of 35-45 rpm while adding water to the mixture at a constant rate through a nozzle so that the water-to-binder (W/B) ratio by weight becomes 0.2, thereby mixing the mixture and the water; and (d) rotating the pan at a second speed which is 1.5 times the first speed for at least 20 minutes to mold an aggregate, and putting one coating material among a rubber-based resin and an inorganic coating material into the pan to apply the coating material to the surface of the aggregate.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for manufacturing recycled aggregates using bauxite residues,

The present invention relates to a method for producing a hard synthetic artificial aggregate capable of manifesting a predetermined strength through solidification and aggregation of a mixture containing bauxite residues as an industrial waste, And a method for manufacturing recycled aggregate using bauxite residues that can reduce the environmental load.

The bauxite residues are solid industrial wastes generated as a by-product in the Bayer process for producing aluminum hydroxide and alumina from bauxite, and many studies have been conducted on the disposal or recycling of bauxite residues at home and abroad.

Conventional bauxite residues depended largely on marine dumping until 2008, but since then, the amount of bauxite residue has been mostly disposed of as a simple embankment embankment. However, bauxite residues are strongly alkaline slurries with a pH of 10 to 12.5, which can lead to serious environmental pollution in large landfills due to the specificity of the mineralogical composition.

Therefore, it is necessary to establish a new method for disposing a large amount of bauxite residue in a more economical and environmentally friendly manner.

On the other hand, aggregates that are widely used in various construction and civil engineering works are essential factors that influence the quantity and quality of the construction. However, due to the lack of natural aggregate and the degradation of ecosystem occurring in the process of collecting the aggregate, And other artificial aggregates.

And as local governments have decided not to collect sand, the supply of fine aggregate is also rapidly deteriorating.

In order to recycle the steelmaking by-products, the method disclosed in Japanese Patent Application Laid-Open No. 10-2010-0099494 entitled " Method for producing artificial lightweight aggregate using cold and hot sludge "discloses an artificial lightweight aggregate produced by mixing cold and hot sludge with clay at a certain ratio Technology has been proposed.

However, according to the above-mentioned technology, the steel sludge is oxidized by the air or moisture over time, so that the outer surface of the building or the like using the artificial aggregate may be contaminated, and the resulting green matter may be introduced into the sewer, have. Also, since the specific gravity is high, it is not suitable for use as a building aggregate, and harmful substances are generated in the course of expanding steel sludge, which is unsuitable for construction of residential structures.

In addition to this, studies on artificial aggregates using industrial byproducts have also been conducted on room temperature curing type non-plastic artificial aggregates, which have relatively low manufacturing costs.

However, conventional researches are limited to concrete secondary products, and there is insufficient verification for utilization as ground drainage or aggregate.

In addition, existing artificial aggregates contain a large amount of cement, which results in a low unit cost, low economic efficiency, and an enormous amount of carbon dioxide, which is not environmentally friendly.

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a method for manufacturing recycled aggregate using bauxite residues which can reduce the processing cost and environmental load by effectively recycling bauxite residues.

The present invention provides a method of manufacturing recycled aggregate using economical bauxite residues by minimizing the use of cement in the production of artificial aggregate.

The present invention relates to a recycled aggregate material using bauxite residues capable of supplying artificial aggregates applicable to various fields such as soft ground improvement, drainage material, concrete product, or clay soil through securing sufficient particle size, water permeability and shear strength performance. And to provide a manufacturing method thereof.

According to a preferred embodiment of the present invention, there is provided a method for producing recycled aggregate comprising bauxite residues, cement and additives as well as fire-fighting and inorganic binders, comprising the steps of: (a) drying bauxite residues; (b) mixing the dried bauxite residue with cement at a mass ratio of 4: 1 and mixing the additive with 1.5 wt% of cement for at least 1 minute; (c) The mixture was supplied to a pan of a fan-type molding machine having a slope of 45 to 55 degrees at a constant rate, and water was added thereto at a constant ratio through a nozzle so that the water binding ratio (W / B, weight ratio) Rotating and mixing at a first speed of 35 to 45 rpm; And (d) rotating the fan at a second speed of 1.5 times the first speed for at least 20 minutes to form an aggregate, wherein the coating material, either a rubber-based resin or an inorganic coating material, is applied to the aggregate surface; The present invention provides a method for manufacturing recycled aggregate using bauxite residues.

delete

The present invention has the following effects.

First, a mixture composed of bauxite residues, cement and additives is stirred and rotated in a fan of a fan-type molding machine to solidify and aggregate the mixture to form artificial aggregates having a predetermined strength. Therefore, alternative use of artificial aggregate can reduce the amount of natural aggregate and reduce the disposal cost and environmental burden of the industrial waste by not throwing it into the ocean or embedding it in the embankment.

Second, artificial aggregates of high quality can be manufactured by recycling bauxite residues that are unlikely to be contaminated with heavy metals and other harmful substances. Therefore, the pollution problem caused by the recycling of industrial waste can be prevented.

Third, the use of artificial aggregate can minimize cement usage because it contains a large amount of bauxite residues. Therefore, the use of cement is economical and environmentally friendly.

Fourthly, the aggregate produced by the present invention has an appropriate particle size, satisfies the satisfactory permeability, shear strength and compressive strength, and thus can be used for soft ground improvement, drainage material, or clay soil, It can be widely used for replacing fine aggregate.

1 is a perspective view showing a fan-type molding machine;
2 is a photograph showing a recycled aggregate produced by the present invention.
3 is an enlarged photograph of the recycled aggregate of FIG. 2;
4 is a graph showing the internal friction angle of an artificial aggregate produced by the present invention.
5 is a photograph showing a recycled aggregate having a surface coated with blast furnace slag cement.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings and preferred embodiments.

FIG. 1 is a perspective view showing a fan type molding machine, FIG. 2 is a photograph showing a recycled aggregate manufactured by the present invention, and FIG. 3 is an enlarged photograph of the recycled aggregate of FIG.

And FIG. 4 is a graph showing the internal friction angle of the artificial aggregate manufactured by the present invention.

The method for producing recycled aggregate using bauxite residue according to the present invention is for producing recycled aggregate comprising bauxite residues, cement and additives as well as fire-fighting and inorganic binders.

The present invention aims at producing recycled aggregate containing no harmful substances as a substitute aggregate by recycling bauxite residues as industrial waste. Furthermore, it can be used as a drainage material for improving the soft ground used in the landfill area in various civil engineering works by satisfying sufficient particle size, permeability and shear strength characteristics and securing an appropriate compressive strength. In case of manufacturing concrete products, And an artificial aggregate usable as a substitute for fine aggregate. Therefore, it is expected that the use of cement will be reduced and economic efficiency and environmental pollution can be reduced.

In the present invention, step (a) is carried out to dry the bauxite residue.

The bauxite residue is a particulate insoluble residue generated as a by-product in the Bayer process to produce aluminum hydroxide and alumina from bauxite.

The bauxite residue mainly contains SiO ₂ , Al ₂ O ₃ and Fe ₂ O ₃ , and CaO, K ₂ O, Na ₂ O, TiO ₂ , MnO, P ₂ O ₅ And the like.

The bauxite residue is a strongly alkaline slurry having a pH of 10 to 15 and has an average particle size of 10 탆 or less and a specific surface area of 10 to 25 m 2 / g, and is porous and contains moisture of 45% or more.

The bauxite residue is dried at room temperature or hot air to sufficiently remove moisture.

Next, (b) the dried bauxite residue and the cement are mixed in a mass ratio of 4: 1, and the mixture of the additive and 1.5% by weight of the cement is stirred for 1 minute or more.

The above-mentioned cement can be used as a powdered Portland cement by adding an appropriate amount of gypsum and crushing aid to a Portland cement clinker.

The additive may be a high fire or inorganic binder, and a high temperature may be an ash as a byproduct of the papermaking process, and harmful substances such as lead, copper, arsenic, and mercury may be used according to the waste process test standard.

The inorganic binder may be a ferric chloride-based inorganic binder.

The inorganic binder is used as a curing accelerator for cement, and serves to increase the strength and increase the viscosity.

That is, it is possible to increase the density of the cured product by forming the needle-like crystals during curing according to the mixing of the inorganic binder, thereby improving the water resistance and strength.

In the step (b), stirring of the mixture is preferably performed for 1 minute or more so that the materials can be evenly mixed.

In the step (b), the cement and the dried bauxite residue may have a mass ratio of 1: 4, and the additive may include 1.5 wt% of the cement.

That is, in the step (b), it can be constituted by a mass ratio of dried bauxite residues: cement: additive = 4: 1: 0.015.

This is the case where the aggregate compressive strength is the maximum, and the compressive strength at 28 days is the largest when the mass ratio of cement (C) and binder (B), that is, C / B is 0.2.

Here, the mass of the binder (B) is the sum of the bauxite residues and the mass of the cement. And the mass of the additive is a sum of the mass of the binder and the mass of the inorganic binder.

(C) The mixture is supplied to the fan 11 of the fan type molding machine 1 having a slope of 45 to 55 degrees at a predetermined ratio, and at the same time, a water binding ratio (W / B, weight ratio) of 0.2 (D) rotating the fan (11) at a second speed that is 1.5 times the first speed for at least 20 minutes, while mixing the water at a predetermined rate to mix the fan (11) at a first speed of 35 to 45 rpm To form an aggregate, and a coating material such as a rubber-based resin or an inorganic coating material is applied to the fan 11 to be applied to the aggregate surface.

In the step (c), the water binding ratio (W / B, weight ratio) is preferably 0.2.

1, the fan-type molding machine 1 includes a fan 11 which is rotated by a driving unit and inclined at a predetermined angle, a charging unit 12 for charging the mixture, and a nozzle 13 for charging water, .

(C) a step of solidifying a mixture obtained by mixing cement and an additive in a bauxite residue, while solidifying the mixture, and (d) converting the solidified mixture into an aggregate by forming a predetermined strength to form an aggregate, Can be completed.

That is, the artificial aggregate is formed through solidification of the mixture and aggregation.

In other words, a mixture of bauxite residues, cement and additives in the fan type molding machine 1 is subjected to nucleation, transformation, lamination, and rolling, and then granulated into an aggregate having an appropriate particle size.

The nucleation step is a step in which the core of the aggregate grows as the particles constituting the mixture rotate together as the fan 11 of the fan-type molding machine 1 rotates.

And the transition step is a step in which the small particles are joined to each other to grow into larger particles while helping the transition of the particles by the rotation of the fan 11 of the fan type molding machine 1 after the nucleation step.

After the nucleation and transfer steps are performed as described above, after the laminating step in which the laminar particles are adhered on the core of the particles and the laminar particles are grown into larger particles, the rolling operation by the rotation inside the fan 11 A rolling step is performed in which the particles are denuded through.

The laminating step and the rolling step are a step of repeating the process of solidifying the particles solidified by the inclination of the fan 11 while the particles are rotating together with the rotation of the fan 11, through which the hard aggregate is formed .

The aggregate produced can be confirmed through FIG. 2 and FIG. 3. As can be seen from the various test results below, it can be used as a substitute aggregate in various applications such as for construction, soft soil improvement, drainage, Do.

Hazardous materials analysis of artificial aggregate

First, the analysis of harmful materials on the artificial aggregate produced through the present invention showed that it is suitable for the 2014 waste test standard (Table 1).

Test Items unit Results Reference value lead Mg / L 0.14 3.0 or less Copper Mg / L Non-detection 3.0 or less arsenic Mg / L Non-detection Not more than 1.5 Mercury Mg / L Non-detection 0.005 or less cadmium Mg / L Non-detection 0.3 or less draft Mg / L Non-detection 1.0 or less Hexavalent chromium Mg / L Non-detection Not more than 1.5 Organic phosphorus Mg / L Non-detection 1.0 or less Oil component % 0.3 5 or less PCE Mg / L Non-detection 0.3 TCE Mg / L Non-detection 0.1

Physical properties of artificial aggregate

As a result of the particle size distribution of the artificial aggregate, the size of the aggregate was 5 mm ~ 19.5 mm, and the maximum particle size was 19.5 mm but mostly less than 16 mm. In addition, the specification No. shown in the specification. 200 sieve (0.075 mm) Passed amount 15% or less Completely satisfies the criteria. There is no less than 200 cells, and it meets specification standard. It is more than 4.75㎜ of coarse aggregate and is suitable as coarse aggregate.

Permeability of artificial aggregate

Water permeability test (KS F 2322) was carried out to evaluate permeability of artificial aggregate.

Specification for performing multiple functions based on permeability coefficient is ^{k = 1.0 × 10 -3 ㎝ /} sec or more, the test results the permeability of the artificial aggregate is 6.49 × 10 ^-1 ㎝ / sec shown in permeability is known to very high there was. As a result, it is possible to fully utilize artificial aggregate as a ground drainage material.

Shear Strength Properties of Artificial Aggregate

A large direct shear test was carried out to determine whether the artificial aggregate is adequately supported by horizontal drainage or vertical drainage.

As a result of the test, it can be seen that the internal friction angle Φ is 40.91 ° from the slope of the normal stress and shear stress, as can be seen from FIG.

As can be seen from Table 2, this is an appropriate level because it is within the range of 36 ~ 42 ° which is representative of the friction angle of the neutral to dense sandy soil.

As a result, the artificial aggregate exhibits sufficient shear resistance, so that it can be fully utilized as an aggregate for ground drainage.

Classification
Inclination angle
Friction angle The final angle of friction angle
Shear strength of shear Neutral to dense state Compact state Angle of repose
(Degree) slope
(Vertical: horizontal) Φ (degrees) tan Φ Φ _p (degrees) tan 陸_p Φ _p (degrees) tan 陸_p Silt
(Non-fired) 26-30 1: 2
1: 1.75 26-30 0.488
0.577 28 ~ 32 0.532
0.625 30 to 34 0.577
0.675 Uniform uniformity 26-30 1: 2
1: 1.75 26-30 0.488
0.577 30 to 34 0.577
0.675 32 to 36
0.675
0.729 Sand with good granulation 30 to 34 1: 1.75
1: 1.5 30 to 34 0.577
0.675 34 to 40 0.675
0.839 38 to 46 0.839
1.030 Sand and gravel 32 to 36 1: 1.6
1: 1.4 32 to 36 0.625
0.726 36 ~ 42 0.726
0.900 40 to 48 0.900
1.110

Compressive strength test of artificial aggregate

The 28 day compressive strength of artificial aggregate was 42.8MPa, which was equal to or higher than that of ordinary cement mortar without recycled aggregate. Therefore, it can be used by replacing artificial aggregate with recycled concrete product.

Review of applicability of clay soil

If the step (d) is omitted, only the solidification step of step (c) is performed.

In order to evaluate the applicability of the soil for embankment, the firing index and the California bearing ratio (CBR) were measured.

As a result, the plasticity index was NP (non - plastic) and the modified CBR was 32.5. Therefore, artificial aggregate can be used as clay soil.

The slope of the fan 11 of the fan-type molding machine 1 may be in the range of 45 to 55 degrees.

If the inclination of the fan 11, that is, the angle between the ground and the bottom of the fan 11 is less than 45 °, the free fall motion of the mixture in the fan 11 is reduced, and the particles are hardly solidified uniformly. As a result, it is difficult to obtain aggregates of homogeneous quality and the strength is lowered because the material is not dense because the rolling step is not properly performed.

If the inclination of the fan 11 exceeds 55 °, the free fall speed is accelerated due to the weight of the mixture, and the stacking step is not properly performed. Therefore, aggregates of sufficient size can not be formed.

The first speed of step (c) is 35 to 45 rpm when the inclination of the fan 11 of the fan type molding machine 1 is in the range of 45 to 55 degrees and the second speed of the step (d) 1.5 times the speed.

The step (c) is a step of solidifying the mixture. In order to sufficiently contact with water, the speed of the fan 11 should not be excessively high. When the slope of the fan 11 is in the range of 45 to 55, The speed is the optimal solidification speed.

Since the step (d) is a step of aggregating the solidified mixture, it is necessary to sufficiently contact the particles and to allow the core of the aggregate to pass through the transition, lamination, and rolling steps It is preferable that the rotation speed is 1.5 times faster than the first speed.

If the rotational speed of the fan 11 is less than the above range in the step (d), as the particle size increases, the mobility of the particles deteriorates.

On the other hand, when the rotational speed of the fan 11 is in the above range, the particles are only rotated without free fall in the fan 11, and the transfer step is not properly performed.

In the step (d), the fan 11 is preferably rotated for 20 minutes or more so that sufficient lamination and rolling can be performed.

Particularly, in consideration of the time required for the aggregate production, it is preferable to perform the rotation of the fan 11 within the range of 20 to 25 minutes in the step (d), and the rotation of the fan 11 for more than 25 minutes, It can be said that it is pointless because the anger is completed.

5 is a photograph showing a recycled aggregate having a surface coated with blast furnace slag cement.

In the step (d), the coating material may be applied to the fan 11 to be coated on the aggregate surface.

As shown in FIG. 5, a coating material such as a rubber-based resin, a blast furnace slag cement, and an inorganic coating material can be applied to the surface of an aggregate as shown in FIG. 5, to change the functionality such as an absorption rate and an elution acidity of the aggregate.

1: Fan molder
11: Fans
12:
13: Nozzle

Claims

For the production of recycled aggregates comprising bauxite residues, cements and additives as fire retardants and inorganic binders,
(a) drying the bauxite residue;
(b) mixing the dried bauxite residue with cement at a mass ratio of 4: 1 and mixing the additive with 1.5 wt% of cement for at least 1 minute;
(c) The mixture is supplied to the fan 11 of the fan-type molding machine 1 having a slope of 45 to 55 degrees at a predetermined ratio and at the same time the water binding ratio (W / B, weight ratio) is 0.2 through the nozzle 13 Rotating the fan (11) at a first speed of 35 to 45 rpm while mixing water at a certain rate; And
(d) rotating the fan (11) at a second speed of 1.5 times the first speed for at least 20 minutes to form an aggregate, wherein a coating material such as a rubber resin or an inorganic coating material is introduced into the pan (11) ; The method for manufacturing recycled aggregate using bauxite residues according to claim 1,

delete