KR100956161B1 - The process of manufacture with a high quality of aggregate of circulation using the process water of sulfuric acid and the tirturation device of low speedy solution - Google Patents

Abstract

The present invention relates to a method for manufacturing circulating aggregate using waste concrete. After crushing waste concrete in construction waste, sulfuric acid is used in the process water to wash the aggregate to remove the lime component attached to the aggregate. The present invention relates to a method for producing circulating aggregate by using a low speed wet grinding device to increase the removal.

The present invention is to remove the foreign matter from the waste concrete and then crushing to a predetermined size;

Adding sulfuric acid to the process water for washing the pulverized aggregate and reacting the process water to pH 6 or less;

Including the process water of the pH 6 or less into the slow wet grinding device to react with the washing of the aggregate.

Circulating aggregate, sulfuric acid, waste concrete, process water

Description

The process of manufacture with a high quality of aggregate of circulation using the process water of sulfuric acid and the tirturation device of low speedy solution}

The present invention relates to a method for producing circulating aggregate using waste concrete. After crushing waste concrete in building wastes, sulfuric acid is used in the process water to wash the aggregates to remove the lime components attached to the aggregates. In order to increase the removal of the present invention relates to a method for producing a high quality recycled aggregate using a low speed wet grinding device.

Building waste generally refers to waste building materials that are generated when dismantling various buildings. Mostly, the construction waste is mainly made of reinforcing steel and cement blocks, such as waste concrete, waste wood, and waste plastics. These construction wastes are usually incinerated according to legal procedures, and non-combustible wastes such as waste concrete are crushed and recycled to road substrates, but the recycling scope cannot be recycled to concrete aggregates.

However, even though construction waste is legally recycled, it cannot be used as concrete aggregate. Therefore, aggregate is collected from the sea for supply of aggregate in the state where the aggregate of natural construction supplies is almost exhausted. It is destroying the natural environment by destroying the acid to destroy the waste and produce the crushed aggregate, which is a big problem nowadays.

However, such circulating aggregates have a problem that the factors such as density and water absorption are lower in quality than natural aggregates and crushed aggregates to be used as concrete aggregates.

Therefore, various methods for producing such recycled aggregates have been developed, and these methods can be classified into two types, a wet treatment method and a dry treatment method.

It is the most widely used dry treatment method. After removing impurities such as iron and plastics contained in waste concrete, the waste concrete mass is crushed by compression crushing or lot mill, ball mill, tube mill, etc. It consists of a process of sorting, separating or removing sludge using wind power.

Korean Utility Model Registration No. 387254 relates to a dry fine powder separator for the production of circulating aggregates of construction wastes. The fine powder, which is a fine powder that does not act as aggregates generated in the crushing process by crushing and sorting construction wastes, It describes about separating by dryness. The dry treatment method is not suitable to be used alone as a concrete aggregate produced by circulating aggregate products due to low peeling and classification efficiency, it is recommended to use 20% mixed with natural aggregate or crushed aggregate.

The wet treatment method is to crush waste concrete to a certain size, and then to crush the mortar on the surface of the aggregate in the wet state by using one of these types such as tube mill, drum type peeler, rod mill, ball mill, etc. It is a method of classifying sludge and fine aggregate by treating with water. This method has a greater effect of peeling and classification than the dry treatment method, but the circulating aggregate product produced by the wet method is better aggregate than the circulating aggregate produced by the dry method, but is not suitable to be used alone as a concrete aggregate. It is recommended to mix 30% with crushed aggregate.

Patent Publication No. 2001-0035288 discloses contacting recycled aggregates using waste concrete with acidic water, and describes patents for reacting recycled aggregates and acidic water, not for the production process of recycled aggregates. Although the method suggests that it is applicable to the production of high quality aggregates, it is described that a production time of 120 hours or more is required to make high quality. However, this patent differs in that the production time of high quality aggregates is dramatically shortened to within 10 minutes by continuously proceeding the reaction with acid and removing the reaction product by means of a slow-wetting grinding device, which is a production process facility.

The recycled aggregates produced in the above patents are limited to 30% replacement rate of recycled aggregates because they cannot produce the concrete structural recycled aggregates proposed in the recycled aggregates quality standard even though the quality is better than the existing ones.

An object of the present invention is to use a low-speed wet grinding device to crush aggregates in the circulating aggregates pulverized by dry treatment or wet treatment to effectively remove the lime components in the cement components attached to the aggregate surface. It is to provide a method for producing high-quality recycled aggregates by adding sulfuric acid to water, washing and reacting.

In order to achieve the above object, the present invention focuses on the fact that the lime component is contained in the cement component adhering to the surface of the aggregate crushed from the waste concrete. A high quality recycled aggregate was prepared using a grinding device.

The present invention can provide a circulating aggregate in which the lime component of the cement component is removed through a chemical reaction with sulfuric acid as compared to the conventional method by a physical method such as a dry method or a wet method.

In addition, the recycled aggregates are not used as fill aggregates and aggregates for road foundations, but can be preserved by reusing them as concrete aggregates.

The present invention is to remove the foreign matter such as reinforcing steel, plastic, wood from the waste concrete and then crushing it to a certain size;

Removing sludge (powder) by dry treatment or wet treatment of the pulverized concrete pulverized product;

Adding sulfuric acid to the process water for washing the pulverized aggregate, acidifying it to pH 6 or less of the washing water, maintaining the state, and adding the sulfuric acid to a slow wet grinding device to react with lime on the surface of the aggregate;

Separating the reaction product from the aggregate by reacting the aggregate with the surface of the aggregate by a slow wet grinding device;

Repeating the reaction of the aggregate and the wash water and the removal of the reactant on the aggregate surface in the grinding device

It is to provide a high-quality recycled aggregate manufacturing method using a low-speed wet grinding device using a sulfuric acid containing as a process water;

Waste concrete is a waste that is discarded after mixing cement, aggregate and water, and using it as a building material to solidify it in its natural state to maintain the structure.

Therefore, the waste concrete is a material in which the main components are aggregates (natural aggregates, crushed aggregates) and cements hardened by water react with water. Most of the hardened material is lime hydroxide, but as time passes, it reacts with carbon dioxide in the air, and some of it is converted into carbonate.

Lime hydroxide or lime carbonate is almost insoluble in water, so even if it is pulverized by dry method or wet method, lime hydroxide or carbonate remains as adhered to the aggregate, resulting in low density, high absorption rate Since it cannot be the same as aggregate, it is difficult to recycle the concrete aggregate again.

Therefore, in order to recycle to concrete aggregates, aggregates without lime hydroxide or carbonate in the crushed aggregates must be manufactured to be recycled to concrete aggregates.

Acid was used to remove lime hydroxide or lime carbonate adhering to the recycled aggregates pulverized by dry and wet methods.

Representative acids include hydrochloric acid and sulfuric acid, of which sulfuric acid reacts with lime to form gypsum. Gypsum is insoluble in water and is reacted with the components of old mortar or lime in cement paste, which are attached to the aggregate surface. By using this reaction, sulfuric acid water is dried on the surface of the aggregate in the crushing unit, and the spray is wet when it is wet to react with the lime component of the aggregate, and the product after the reaction is separated and removed from the aggregate. It is supposed to keep things done.

The present invention utilizes chemical reactions such as the lime components of cement and sulfuric acid in Schemes 1 and 2.

Scheme 1

CaCO ₃ + H ₂ SO ₄ ---- → CaSO ₄ + CO ₂ + H ₂ O

Scheme 2

Ca (OH) ₂ + H ₂ SO ₄ ---- → CaSO ₄ + 2H ₂ O

As in the reaction schemes 1 and 2, the lime component reacts with gypsum, carbon dioxide, and water. Carbon dioxide is released into the air, and gypsum is not soluble in water, so it is precipitated in water and is easy to separate from aggregate.

Hereinafter, specific configurations will be described in detail through the preferred embodiments of the present invention.

Example 1

1. Experiment plan and method

end. Experiment plan

The circulating fine aggregate has a large amount of gumortar component, which is composed mainly of calcium hydroxide (Ca (OH) ₂ ). As a result, when it comes into contact with process water, the process water is changed to strong alkaline water at pH 12-13, and the process water is converted into designated waste.When this process water is used in the production process, aggregate cleaning power is also lowered, resulting in low quality recycled aggregates. Cause.

Therefore, this experiment was conducted to examine the conditions for effectively separating the gumortar in the circulating aggregate. The four levels with good crushing efficiency were selected to compare acidic water with process water and natural water as process water.

This experimental plan is shown in [Table 1], and sulfuric acid was used to convert process water into acidic water. The overall experimental conditions were the same as the previous experiment. The measurement items were measured for each weight change, density, absorption rate, performance rate, and granulation rate. The pH and temperature changes of process water due to the use of sulfuric acid water, X-ray diffraction analysis (XRD) and chemical composition analysis (XRF) were used. The reaction product was reviewed.

[Table 1] Experimental Design

division Experimental factor Metric Natural water Sulfuric acid Aggregate: steel balls (weight ratio) Aggregate: process water (weight ratio) Time (min) A One 8: 1 1: 0.5 5 Physical properties Chemical properties   Density Absorption Rate Performance Rate Assembly Rate pH and Temperature   XRD XRF N 2 1: 1.0 5 C 3 2: 1 1: 0.5 5 D 4 1: 1.0 5

I. Material used

1) aggregate

The aggregates used in this experiment were recycled fine aggregates produced by Cheonan G, Chungnam, Korea. The physical properties of the materials are shown in [Table 2].

[Table 2] Physical Properties of Recycled Aggregate

sample Density (g / cm 3) Absorption rate (%) Assembly rate (FM) % Of performance Unit weight (kg / ㎥) Token Feudality Circular aggregate 2.42 2.27 6.56 3.40 59.6 1443

2) process water

The process water used for the experiment was generally used for tap water used by recycling aggregate producers, and the sulfuric acid water was mixed with sulfuric acid in the same process water.

3) sulfuric acid

Sulfuric acid was used as a product of L company with a specific gravity of 1.84 and a odorless, clear, colorless light yellow with a purity of 98%.

All. Experiment method

In this experiment, as shown in [Fig. 2] and [Fig. 3], the aggregate was added to the blending type mixer, and the process water was added to each ratio, and the grinding time was the same as 5 minutes.

la. Metric

Physical properties were measured to investigate the characteristics of aggregate after grinding, and pH and temperature changes of process water due to sulfuric acid were observed. In addition, X-ray diffraction analysis (XRD) and chemical conversion analysis (XRF) were used to examine what materials were formed after the reaction of sulfuric acid and cement paste contained in aggregate.

2 Experiment Results

end. Density and Absorption Rate

[Table 3] shows the density and water absorption rate when sulfuric acid water is used as the process water. [Fig. 4] and [FIG. 5] show the density and water absorption rate of the aggregate when using natural water and sulfuric acid water as the process water. Is a comparison. In terms of density and water absorption according to each condition, the more steel balls, the lower the number of processes used, the higher the density and the lower the water absorption rate. Especially, when the sulfuric acid water was used, the aggregate quality was improved.

[Table 3] Density and Absorption Rate

division Density (g / cm 3) Absorption rate (%) Surface Drying Saturation Never dry B 2.42 2.27 6.56 A 2.48 2.38 3.01 N 2.58 2.51 2.35 C 2.57 2.52 2.63 D 2.56 2.52 2.50

I. Weight change

As a result of the grinding test for each condition, the grinding efficiency was higher as more steel balls were used during grinding, fewer processes were used, and the grinding time was longer. As shown in FIGS. 6 and 7, the grinding efficiency increased when sulfuric acid water was used as the process water when crushed under the same conditions. In addition, 2.5mm aggregates decreased about 5 times compared to raw aggregates, while 1.2mm or less increased about 4 times. Particularly, fines increased about 7 times.

All. Performance rate

8 shows the performance rate as the quality of the aggregates improves the performance rate. In general, the smaller the aggregate size and the smaller the assembly rate (FM) value, the higher the performance rate. As shown in the weight change, the grinding action is active, and the aggregate rate increases as the aggregate becomes finer.

la. pH and temperature changes

[Table 4] and [FIG. 9] show changes in pH and temperature in the milling mill when milling with sulfuric acid water. When the first circulating aggregate aggregate is immersed in the process water, calcium hydroxide (Ca (OH) ₂ ), a cement hydration product, reacts with H2O among the gumortar constituents contained in the circulating aggregate aggregate. The strong alkaline water is changed to the above. However, when sulfuric acid is added to this environment, calcium hydroxide (Ca (OH) ₂ ) reacts with sulfuric acid (H ₂ SO ₄ ) to produce gypsum (CaSO ₄ ) and water (H ₂ O). The pH is lowered and the reaction with sulfuric acid causes an exothermic reaction to raise the temperature inside the mill.

[Table 4] Crusher inside, pH, temperature change

division pH Temperature (℃) start End start End One 10.24 5.80 18.6 21.5 2 10.20 6.60 20.2 23.3 3 10.58 6.88 20.2 23.4 4 10.24 6.25 19.3 22.0

Example 2 Wet Process

2-1 Review of grinding efficiency when process water is input

 -Tilt of grinding device: 1.8 °

 -Grinding media role: coarse aggregate (same proportion as aggregate)

 2-2. Experiment result

2.1 Supplying wash water from input of aggregate to final discharge

First aggregate discharge time 5 minutes 30 seconds Final discharge time 18 minutes Wash water supply time 15 minutes Amount of wash water required 506.5 kg

As the washing water was supplied from the aggregate input to the discharge, the initial discharge time was 5 minutes and 30 seconds, the final discharge time was 18 minutes, and the washing water was supplied for 15 minutes. As a result of the experiment, when the aggregate and the washing water were supplied at the same time, there was no rapid discharge of the aggregate by the washing water, and the washing water also did not drain quickly. The discharge was simultaneously carried out with the aggregate sufficiently submerged in the wash water.

However, because the amount of washing water added was too large, the residual particles were submerged in water and discharged in a sludge state, and the necessity of adjusting the amount of washing was found.

2.2 Supplying wash water from the input of aggregate to the end of input of aggregate

First aggregate discharge time 6 minutes Final discharge time Not measurable Wash water supply time 1 minute 30 seconds Amount of wash water required 50.6 kg

The initial discharge time was 6 minutes, but the final discharge time could not be measured. Experimental results Similar to the experimental results in 2.1, there was no rapid discharge of aggregate by washing water, and the washing water also did not drain quickly. However, the washing water and the particles used were converted into the sludge state in which the kneading machine had a considerable amount of time, and the sticking of the grinding blade and the wall occurred. As a result, a separation phenomenon in which only thick aggregates of 2.5 mm or more were discharged occurred, and final discharge time could not be measured because aggregates of 2.5 mm or less were not discharged.

Therefore, it is necessary to estimate the amount of washing that can prevent the phenomenon of sticking to the wall of the grinding machine and the wing due to the sludge generated by combining the washing water and the residual particles.

2.3 Supplying wash water up to 5 minutes after the end of aggregate

First aggregate discharge time 5 minutes 50 seconds Final discharge time 21 minutes Wash water supply time 6 minutes Amount of wash water required 202.6 kg

After the end of the aggregate input, the washing water was supplied for 5 minutes, and the initial discharge time was 5 minutes and 50 seconds, and the final discharge time was 21 minutes. As a result of the experiment, the rapid discharge phenomenon similar to the above experiment result and the drainage phenomenon in a short time by the washing water alone did not occur. In addition, the drooping phenomenon caused by excessive washing water was also reduced, and in particular, no sticking phenomenon occurred due to the combination of residual particles and water less than 2.5 mm.

The present invention is to add a sulfuric acid in order to remove the lime components attached to the circulating aggregate using waste concrete and to produce a high-quality circulating aggregate using a slow wet grinding device.

1 is a process chart applied to the present invention

2 is a block diagram of an experimental method of the present invention

3 is an exemplary view of an experimental process of the present invention.

Figure 4 is a graph of density change according to the number of steps used in the present invention

5 is a graph of change in water absorption according to the number of used processes of the present invention.

6 is a graph showing the aggregate size and the weight change amount of each particle of the present invention

7 is a graph showing the aggregate size and weight share of each particle of the present invention

Figure 8 is a graph of the change in the performance rate of the present invention

9 is a graph showing the change in the performance rate of the present invention.

Claims (2)

Removing the foreign matter from the waste concrete and pulverizing it to a predetermined size; Dry or wet treatment of the pulverized concrete pulverized material to remove sludge; Injecting the sludge-removed circulating aggregate and sulfuric acid water into the process water, and adding acidic water as the process water to the low-speed wet grinding device to cause a reaction on the surface of the circulating aggregate; Separating the by-product generated by the reaction with the aggregate, repeating the reaction with the acid continuously: Washing the pulverized product generated by the repetition with water to produce a circulating aggregate; and using a slow wet type grinding apparatus using sulfuric acid as process water, the density of not less than 2.5 g / cm 3 and an absorption rate of less than 3%. High quality recycled aggregate manufacturing method. The method of claim 1, In the step of reacting on the surface of the circulating aggregate, sulfuric acid water is introduced into the process water at a pH of 6 or less, and high-quality circulating aggregate using a slow wet grinding device using sulfuric acid, which may use waste sulfuric acid, as the process water instead of sulfuric acid water. Manufacturing method.

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