KR20120110241A - Light weight aggregate - Google Patents

Abstract

PURPOSE: A light weight aggregate using coal debris and waste molding sand and a method of manufacture thereof are provided to show high intensity with light weight by using industrial waste of coal tailing and waste molding sand as main raw materials. CONSTITUTION: A light weight aggregate using coal debris and waste molding sand comprises the following steps: kneading 10-30% of coal tailing, 20-30% of waste molding sand, and 50-60% of clay with water; molding the kneaded mixture into a spherical shape having the diameter of 10-15mm and drying thereof; and sintering the dried molded product at 1100-1200 deg. Celsius for 15-25 minutes in a kiln. The coal tailing is pulverized into the particle size of 30-50 meshes. The mixing ratio of the waste molding sand to clay is 2-3:1. The inner temperature of the kiln is maintained at 1200 deg. Celsius. [Reference numerals] (AA) Compressive strength (Kg/cm^2); (BB) Sintering time(min); (CC) Practical example 1; (DD) Practical example 2; (EE) Practical example 3; (FF) Practical example 4; (GG) Practical example 5; (HH) Practical example 6; (II) Practical example 7; (JJ) Practical example 8; (KK) Practical example 9; (LL) Practical example 10

Description

Light aggregate and its manufacturing method using coal waste rock and waste foundry sand {light weight aggregate}

The present invention relates to a method for producing a lightweight aggregate having high strength as a light weight and industrial aggregates, such as waste foundry sand and coal waste-rock as a main raw material and its light aggregate.

Patent

The present invention does not require expensive additives by using only industrial waste and clay such as coal waste-rock and waste foundry sand.

In addition, the high-pressure molding process is not required at the time of manufacturing, so it is a lightweight bone that can greatly reduce the production cost

It is an object to provide a method for preparing ash.

Sour, 50 to 60% (w / w) clay is kneaded with an appropriate amount of water and molded into a sphere of diameter 10 to 15 mm.

After drying, the method was baked in a kiln at a temperature of 1100 to 1200 ° C. for 15 to 25 minutes.

A matching lightweight aggregate was produced.

Coal waste-rock and foundry sand have use as aggregate for building materials.

1 is a specific gravity change of the firing time of the present invention.
2 is a change in absorption rate according to firing time of the present invention.
3 is a change in compressive strength according to firing time of the present invention.

The present invention relates to a method for producing light weight aggregates having high strength as light weights and industrial lightweight wastes such as waste foundry sand and coal waste-rock as main raw materials, and light weight aggregates thereof.

In recent years, as the domestic construction industry has grown, the shortage of supply and demand for building materials has gradually reached a serious situation. Among the building materials, the shortage of concrete aggregates used in large-scale construction works is getting worse. In addition, stable supply and demand of aggregates is more difficult due to the limitation of collecting aggregates in order to preserve nature.

In order to solve the shortage of aggregate supply and demand, researches on how to recycle industrial waste have been actively conducted in recent years.

Industrial waste is a by-product of the rapid progress of industrialization.In contrast to the quantitative increase, facilities and resources for their disposal are inadequate, and problems such as natural environmental pollution caused by various industrial wastes have already been revealed. have.

As one of the industrial wastes causing such serious damage, the waste foundry sand used in the present invention is a kind of industrial waste generated in the casting process and contains heavy metals, which may be directly connected to the causes of various pollutions.

In addition, coal waste-rock is an industrial waste that is generated when coal is mined, and it penetrates into the strata with rainwater due to neglect in coal mine areas, contaminates groundwater, and causes rain and sediment during rainy weather to damage nearby forests or in open air in severe cases. Not only water pollution, but also farmland, damage crops.

In order to solve this problem, landfilling is sometimes carried out. However, since coal mines are located in the mountains, it is difficult to transport them for landfilling. Therefore, landfills around coal mines are generally not used. In order to secure a site for reclamation, there is a problem of damaging the natural environment such as forestry.

The present invention is to provide a lightweight aggregate having a high strength by using industrial waste, such as waste foundry sand and coal waste-rock as a main material as the main material as described above.

As a related art related to the production of lightweight aggregate, a technique is known in which a cement mortar is coated on the surface of the expanded styrene particles for curing, or a clay is coated on the surface of the expanded styrene particles for firing. However, the above-described technology was able to achieve the purpose of reducing the weight of the aggregate itself. However, when producing the material required for the building using the manufactured aggregate, the compressive strength of the manufactured building material is remarkably low, which makes it difficult to use as a general building material. There was this. Known techniques for the production of aggregates using industrial wastes include a method of manufacturing a lightweight ceramic body through a high pressure molding process and a high temperature firing process of a sample made of coal ash as a basic material. Korean Patent Publication No. 93-5252 Introduced from While the above technique has the advantage of recycling waste resources using coal ash as industrial waste, not only sodium hydroxide should be added to increase the strength of the aggregate, but also aluminum powder or sodium hydrogencarbonate to show the lightness. Since a relatively expensive additive is required, the production cost is increased, and a high pressure of 10 to 70 kg / cm 2 is required at the time of molding the sample, which causes a problem in manufacturing process. The present invention solves the problems of the prior art as described above, and by using only industrial waste and clay such as coal waste-rock and waste foundry sand, not only expensive additives are required, but also high-pressure molding process is not required at the time of production, thereby reducing production costs. It is an object of the present invention to provide a method for manufacturing lightweight aggregate that can greatly reduce. In the present invention, 10 to 30% (w / w) of coal waste crushed to a particle size of 30 to 50 mesh, 20 to 30% (w / w) of waste casting sand, and 50 to 60% (w / w) of clay are mixed To prepare a solid mixture, add an appropriate amount of water and knead it to form a spherical shape of 10 to 15mm and then dry it sufficiently, and then set the firing time to 15 to 25 minutes in a firing furnace at a temperature of 1100 to 1200 ° C. As a method of firing, a lightweight aggregate was produced in accordance with the above object.

Clay, coal waste-rock and waste foundry sand used in the present invention all contain a large amount of SiO2. In particular, in the case of waste foundry, water glass (sodium silicate) is used as a binder as a builder, and the content of silicon dioxide (SiO 2) is 91.7% (w / w) as shown in Table 1 below. The content of sodium oxide (Na2O) and potassium oxide (K2O) is

Since there are more or less configurations, when they are fired at a high temperature, they form a highly viscous glass phase.

The coal waste-rock used in the present invention generates bubbles in the aggregate during high temperature firing to lighten the aggregate and insulate, insulate, etc.

It shows the effect of the chemical composition is shown in Table 2 below.

Among the components shown in Table 2, the other is the amount of ignition loss occurring during ignition and is determined to be reduced by the generation of carbon dioxide (CO) by oxidation of carbon, and with this, the coal waste-rock used in the present invention is 6.2%. (W / w) FeO is included, so when high-temperature firing, oxygen (O) gas is generated by dissociation of FeO, and the generated oxygen (O) promotes oxidation of carbon powder to To be generated. In addition, when the clay has a high temperature property, carbonates such as calcium carbonate (CaCO) and magnesium carbonate (MgCO) in clay are decomposed, but organic matters are burned to generate carbon dioxide (CO), thereby forming pores in the aggregate. will be. Therefore, when the composition ratio of coal waste-rock, waste foundry sand, and clay is calcined at a high temperature of the composition of the present invention as described above, carbon dioxide (CO) generated from coal waste-rock and clay and air present in the gaps in the sample are formed on the highly viscous glass.

As the gas pressure is increased by the foaming, the foaming is carried out, which results in low specific gravity and light weight after firing. In the case of firing the composition of the present invention having such a foaming mechanism, the firing conditions such as the congestion ratio, firing temperature, firing time, firing rate, etc. between the composition materials are greatly influenced by physical properties such as specific gravity, absorption rate or compressive strength of aggregate after firing. Get involved. Absorption rate of the light weight aggregate according to the present invention depends on the change in the mixing ratio of the clay and the waste foundry sand used in the manufacture, if the mixing ratio of the waste foundry sand is relatively higher than the clay, the water absorption is improved by lowering the absorption rate of the aggregate, If the mixing ratio of the waste foundry sand becomes less than that of the clay, the absorption rate becomes higher. However, if the mixing ratio of waste foundry sand is increased to increase the absorption rate, there is a problem that the compressive strength is lowered. Therefore, it is important to determine an appropriate mixing ratio of clay and waste foundry sand in order to show the appropriate absorption rate and compressive strength of lightweight aggregate. Since the heavy metal material is contained, there is a problem that the heavy metal material is dissolved and dissolved in the absorbed moisture when water is absorbed in the light weight aggregate manufactured by using the same. The meaning of wool is very important not only in terms of water resistance, such as resistance to freezing and thawing, but also in terms of pollution prevention. As a result of this study, the ratio of clay to waste foundry sand is 2 to 3: 1. Is the most suitable

Could know. In addition, if the firing temperature at the time of firing is higher than 1200 ℃, the production cost required for high-temperature firing is not only high, but excessive foaming occurs in the aggregate, resulting in poor surface condition of the aggregate after firing. Since the glass nitriding is difficult to be made and the sintering state is poor, the firing temperature during firing is preferably 1100 to 1200 ° C, more preferably 1200 ° C. Determination of the firing time within the firing temperature range greatly affects the specific gravity and compressive strength of the light weight aggregate, and when the firing time is 15 minutes or less, uneven sintering proceeds without foaming phenomenon. If the specific gravity is rapidly increased, the compressive strength is lowered, and it is maintained for more than 25 minutes, the sintering proceeds rapidly as the foaming action in the aggregate ends, and the structure in the aggregate becomes dense, and the molecular motion of the generated carbon dioxide becomes active. As the gas (CO) escapes, the specific gravity is increased and the aggregate is not lightened, and the specific gravity required for long-term high temperature maintenance is excessive, which acts as an increase factor of the production cost, so the firing time is preferably 15 to 25 minutes. 20 minutes is more preferred. Determination of the firing time within the firing temperature range greatly affects the specific gravity and compressive strength of the light weight aggregate, and when the firing time is 15 minutes or less, uneven sintering proceeds without foaming phenomenon. If the specific gravity is rapidly increased, the compressive strength is lowered, and it is maintained for more than 25 minutes, the sintering proceeds rapidly as the foaming action in the aggregate ends, and the structure in the aggregate becomes dense, and the molecular motion of the generated carbon dioxide becomes active. As the gas (CO) escapes, the specific gravity is increased and the aggregate is not lightened, and the specific gravity required for long-term high temperature maintenance is excessive, which acts as an increase factor of the production cost, so the firing time is preferably 15 to 25 minutes. 20 minutes is more preferred. In the case of using a tubular furnace as a firing furnace, the length of the tubular furnace is different depending on the firing time. For example, when the length is 600 mm, the maximum injection speed is 24 mm / min and the minimum injection speed is 600 mm. Should be 40mm / min. Hereinafter, the present invention will be described in more detail with reference to Examples and Experimental Examples.

Example 1

5 kg of waste foundry sand, 15 kg of coal pulverized sand and 40 kg of clay, and an appropriate amount of water are mixed and kneaded, and the finished mixture is formed into a spherical sample having a diameter of 13 mm, and then maintained in a drying chamber at a temperature of 80 ° C. for 24 hours. Maintained. After drying the sample, use a tubular electric furnace (hereinafter referred to as tubular furnace) having an internal diameter of 60 mm and a length of 600 mm.

After maintaining the temperature of 1100 ℃ and heat treatment by dividing the injection rate of 60mm / min, 40mm / min, 30mm / min, 24mm / min, 20mm / min respectively to produce lightweight aggregate, and then measured specific gravity, compressive strength and absorption rate It was.

[Example 2]

A lightweight aggregate was prepared in the same composition and method as in Example 1, but after the lightweight aggregate was prepared at a firing temperature of 1200 ° C. in the tubular furnace, specific gravity, compressive strength, and water absorption were measured.

[Example 3]

In the same manner as in Example 1, but in the composition of the amount of waste foundry sand 10kg, the amount of coal waste-rock is 10kg, the amount of clay to 30kg after producing lightweight aggregate, specific gravity, compressive strength and Absorption rate was measured.

Example 4

A lightweight aggregate was prepared in the same composition and method as in Example 3, but after the lightweight aggregate was prepared at a firing temperature of 1200 ° C. in the tubular furnace, specific gravity, compressive strength, and water absorption were measured.

[Example 5]

In the same manner as in Example 1, but in the composition of the amount of waste foundry sand 15kg, the amount of coal waste-rock 5kg, the amount of clay to 30kg after producing lightweight aggregate, specific gravity, compressive strength and Absorption rate was measured.

[Example 6]

A lightweight aggregate was prepared in the same composition and method as Example 5, but after the lightweight aggregate was prepared at a firing temperature of 1200 ° C. in the tubular furnace, specific gravity, compressive strength, and water absorption were measured.

[Example 7]

In the same manner as in Example 1, but in the composition, the amount of waste foundry sand to 10kg, the amount of coal waste-rock to 15kg, the amount of clay to 25kg to prepare a lightweight material, specific gravity, compressive strength and Absorption rate was measured.

[Example 8]

A lightweight aggregate was prepared in the same composition and method as in Example 7, but after the lightweight aggregate was prepared at a firing temperature of 1200 ° C. in the tubular furnace, specific gravity, compressive strength, and water absorption were measured.

[Example 9]

In the same manner as in Example 1, but in the composition of the amount of waste foundry sand 5kg, the amount of coal waste-rock to 10kg, the amount of clay to 35kg after producing the light till aggregate, specific gravity, compressive strength and Absorption rate was measured.

[Example 10]

A lightweight aggregate was prepared in the same composition and method as in Example 9, but after the lightweight aggregate was manufactured at a firing temperature of 1200 ° C. in the tubular furnace, specific gravity, compressive strength, and water absorption were measured.

Specific gravity test method

Gram weight (ms) and apparent weight (mw) of samples in water in the surface dry saturated water state of lightweight aggregates according to the present invention according to the specific gravity test method of structural lightweight coarse aggregates specified in KS F 2533. After measuring in units and substituting the following formula, the surface specific gravity (Ds) was calculated, and the result is shown in FIG.

Compressive Strength Test

The spherical sample was measured at a cross head speed of 0.5 mm / min under displacement control using a MTS 810. U.S.A universal testing machine, and the results are shown in FIG.

Absorption rate test method

The apparent weight (md) of the sample after drying of the lightweight aggregate according to the present invention was measured in grams (g) by the specific gravity test method of the structural lightweight coarse aggregate determined in KS F 2533, and the surface measured in the specific gravity test. After substituting the sample weight (ms) in the dry saturated water state to the following formula, the water absorption rate (Q) was calculated, and the result is shown in FIG.

1 is a graph showing the specific gravity measurement results according to the firing time change of the light weight aggregates manufactured in the sealing 1 to 10, when the firing temperature is 1100 ℃ is represented by a solid line and when the firing temperature is 1200 ℃ as a dotted line Indicated.

From FIG. 1, when the firing time is 20 minutes, the specific gravity of the light weight aggregate manufactured from each example is the lowest value, and the specific gravity is rapidly increased when the firing time is less than 15 minutes or more than 25 minutes. It can be seen that.

This means that if the firing time is 15 minutes or less, the specific gravity of the aggregate is rapidly increased due to uneven sintering in the state of no foaming phenomenon. If the firing time is 25 minutes or more, the sintering is rapidly completed after the foaming action in the aggregate is finished. As the tissue in the aggregate becomes dense, the weight of the aggregate increases.

In addition, when the light weight aggregate composition according to the present invention has the same composition, it can be seen that the heat treatment at 1200 ° C. shows a very low specific gravity as a whole when the firing temperature at the time of firing is 1100 ° C.

2 is a graph showing the results of measuring the compressive strength according to the change in firing time of the lightweight aggregates prepared in Examples 1 to 10. As in FIG. 1, when the firing temperature is 1100 ° C., the firing temperature is represented by a solid line. Is 1200 ° C. In FIG. 2, when the firing time is 20 minutes, the compressive strength of the grain aggregate prepared from each example is the highest and the firing time is less than 15 minutes. Or if it exceeds 25 minutes it can be seen that the compressive strength is sharply lowered.

In addition, when the light weight aggregate composition according to the present invention has the same composition, the compressive strength is generally higher when the heat treatment is performed at 1200 ° C. than when the firing temperature at the time of firing is 1100 ° C., in particular, in the case of Example 4 It can be seen that the compressive strength is higher than 20 kg / ㎠ or more than 3, this result means that the sintered state at 1200 ℃ is better than 1100 ℃. 3 is a graph showing the results of absorbance measurement according to the firing time change of the light weight aggregates prepared in Examples 1 to 10, and as shown in FIGS. 1 and 2 when the firing temperature is 1100 ° C. In the case where the firing temperature is 1200 ℃, it is indicated by the dotted line. In the case of the absorption rate of the light weight aggregate shown in FIG. 3, it can be seen that, unlike the specific gravity and compressive strength measurement results, the firing time decreases continuously, which increases the firing time. It is thought that the cause is that the sintering continues at the end and the structure in the aggregate becomes dense.

When considering only the absorption rate of the light weight aggregate according to the above results, it is preferable to maintain a long heat treatment time during manufacture, but as shown in FIGS. 1 and 2, the specific gravity rapidly increases and compresses after 25 minutes or more. In addition to the problem of sharply decreasing the strength, the production cost required to maintain a high temperature of 1100 to 1200 ℃ for a long time is excessively taken, in consideration of this, the firing time for manufacturing lightweight aggregate is 15 to 25 minutes is the most suitable.

In addition, the light weights prepared in Examples 3 and 4, in which the mixing ratio of clay and feju sand is 3: 1, and Examples 5 and 6, in which the mixing ratio is 2.5: 1, and in Examples 7, 8, in which the mixing ratio is 2: 1. Absorption rate of the aggregate is lower than the absorption rate of the light weight aggregates prepared in Examples 1 and 2, in which the mixing ratio of clay and waste molding sand is 6: 1 and Examples 9 and 10, in which the mixing ratio is 7: 1, over the entire firing time. Particularly, when the firing temperature is 1100 ° C., the absorption rate of Example 5 having a mixing ratio of 7: 1 is 13% or more, which is a big difference from the absorption rate of other examples. When the firing temperature is 1200 ° C., the mixing ratio is shown. Since the absorption rate of Example 2, which is 6: 1, is much larger than that of the other examples, the mixing ratio of clay and waste molding sand is 2 to 3: 1 considering the correlation with the absorption rate and the recycling ability of the waste casting sand. It can be seen that it is the most appropriate. As can be seen from the test results, the present invention provides a method for producing a lightweight aggregate that can express high strength as light weight using only coal waste-rock and waste foundry sand and clay which are industrial wastes without using any expensive additives. By doing so, it is possible to solve the problem of industrial waste disposal, increase the utilization of waste resources, and at the same time, solve the problems of insufficient aggregate supply and demand caused by the rapid development of the construction industry.

Patent

Claims (1)

Claim 1
10 to 30% (w / w), 20 to 30% (w / w) of waste foundry sand, pulverized to a particle size of 30 to 50 mesh in the method of manufacturing lightweight aggregate using coal waste and clay, 50 To 60% (w / w) of clay by kneading with an appropriate amount of water, molded into a sphere having a diameter of 10 to 15 mm and dried, and then firing for 15 to 25 minutes in a firing furnace at a temperature of 1100 to 1200 ° C. Method of manufacturing lightweight aggregate.
Claim 2
The method for producing lightweight aggregate according to claim 1, wherein the mixing ratio of clay and waste foundry sand is 2 to 3: 1.
Claim 3
The method for producing lightweight aggregate according to claim 1 or 2, wherein the temperature in the kiln is maintained at 1200 ° C.

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