Preparation method of recycled concrete

Abstract

The invention discloses a preparation method of recycled concrete, which comprises the following steps: carrying out pre-wetting treatment on waste concrete to enable the pre-wetting rate in the waste concrete to be greater than or equal to 70%, and taking the maximum water content of the waste concrete as the pre-wetting rate of 100%; after the surface of the pre-wetted waste concrete does not have obvious water stains, carrying out concrete crushing treatment, and then screening to obtain regenerated coarse aggregate; and mixing the recycled coarse aggregate with natural gravel and ingredients to obtain the recycled concrete. According to the preparation method, the dust amount in the production process can be reduced, meanwhile, the yield of the recycled coarse aggregate is effectively increased, the prepared recycled concrete can be used for concrete construction of on-site cushion layers, construction roads, temporary roads and the like, source reduction, process control and cyclic utilization of construction waste are achieved, and the purposes of green construction and resource saving are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of building material recycling, and in particular to a method for preparing recycled concrete. Background Art

[0002] In the past, the primary method for handling construction waste was to transport the waste concrete to the suburbs for storage or landfill, but this not only occupies land but also causes environmental pollution. Recycling waste concrete through the production of recycled concrete can alleviate the environmental pollution problems associated with its disposal. However, the existing process of producing recycled materials from waste concrete produces excessive dust, which seriously affects the health of construction workers. Furthermore, due to the limitations of the production method, the yield of recycled coarse aggregate obtained by crushing the waste concrete is limited.

[0003] In view of this, it is necessary to design a preparation method of recycled concrete to solve the above problems. Summary of the Invention

[0004] The object of the present invention is to provide a method for preparing recycled concrete which can reduce the amount of dust in the production process and effectively improve the yield of recycled coarse aggregate.

[0005] To achieve the above object of the invention, the present invention provides a method for preparing recycled concrete, comprising the following steps: S1. Pre-wetting the waste concrete so that the pre-wetting rate of the waste concrete is greater than or equal to 70%, wherein the maximum moisture content of the waste concrete is taken as 100% pre-wetting rate; S2, after the surface of the waste concrete that has been pre-wetted in step S1 has no obvious water stains, the concrete is crushed and then sieved to obtain recycled coarse aggregate; S3. The recycled coarse aggregate obtained in step S3 is mixed with natural crushed stone and ingredients to obtain recycled concrete.

[0006] As a further improvement of the present invention, in step S1, the waste concrete is pre-screened before the pre-wetting treatment.

[0007] As a further improvement of the present invention, in step S1, the waste concrete is pre-wetted by spraying. The spraying method can moisten the surface of the waste concrete and gradually absorb water, thereby better controlling the water absorption of the waste concrete and preventing excessive water absorption. The spraying method is relatively simple and takes up little space.

[0008] As a further improvement of the present invention, in step S2, a two-step crushing method is used to crush the concrete. The two-step crushing method can maximize the crushing efficiency and can more finely manage the particle size after crushing.

[0009] As a further improvement of the present invention, when performing the first crushing step, the particle size of the obtained crushed pieces is within the range of 200-300 mm.

[0010] As a further improvement of the present invention, a jaw crusher is used to crush the concrete.

[0011] As a further improvement of the present invention, the recycled coarse aggregate is crushed concrete with a particle size greater than 4.75 mm.

[0012] As a further improvement of the present invention, in step S2, a circular vibrating screen is used for screening.

[0013] As a further improvement of the present invention, in step S3, the mass proportion of natural crushed stone in the recycled concrete is greater than or equal to 15%.

[0014] As a further improvement of the present invention, in step S3, the ingredients include cement and sand and gravel.

[0015] The beneficial effects of the present invention are: 1. The present invention pre-wets the waste concrete to maintain a water content of over 70%, and then crushes the waste concrete after no obvious water stains are left on the surface. This reduces dust production and effectively increases the yield of recycled coarse aggregate. The process of crushing the pre-wetted waste concrete after no obvious water stains are left on the surface indicates that water has entered the internal pores of the waste concrete, allowing continued crushing. Furthermore, it prevents accumulation of water on the surface of the waste concrete, which could result in the formation of mud mixed with dust during crushing, thereby affecting the crushing effect of the waste concrete and causing the recycled coarse aggregate to contain excessive mud, thereby accelerating equipment wear, and the like.

[0016] 2. The present invention performs pre-wetting treatment before crushing the waste concrete, which can increase the yield of the obtained recycled coarse aggregate and fill the internal pores of the recycled coarse aggregate with water, thereby avoiding the absorption of mix moisture when subsequently used in concrete production, thereby improving the strength of the stone.

[0017] 3. By adding at least a certain amount of natural crushed stone, the present invention can utilize the characteristic that natural crushed stone has sharper edges and corners than recycled coarse aggregate to enhance the bonding force between cement, sand and gravel and other ingredients and recycled coarse aggregate, thereby avoiding the situation where the weak bonding force between recycled coarse aggregate and cement, sand and gravel and other ingredients makes it easy for the sidewalks made of recycled concrete to be damaged along the bonding surface when loaded, thereby restricting the strength of the concrete. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a flow chart for preparing recycled concrete in Example 1. DETAILED DESCRIPTION

[0019] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] It should also be noted here that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the solutions of the present invention are shown in the drawings, while other details that are not closely related to the present invention are omitted.

[0021] In addition, it should be noted that the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0022] Example 1 This embodiment provides a method for preparing recycled concrete, which is described using waste concrete from the broken pile heads of bored piles, and includes the following steps: S1. Pretreatment: First, use a hydraulic breaker to crush the pile head, breaking the large pile head into 500-1000mm blocks, and then perform pre-screening to remove concrete blocks containing steel bars and remove excess impurities; S2, pre-wetting the block, i.e., using a spraying method to make the pre-wetting rate in the block 70%; S3. After the pre-wetting waste concrete blocks have no obvious water stains on their surfaces, the concrete is crushed. The specific crushing operation is as follows: first, a jaw crusher with relatively large feed and discharge openings is used for primary crushing to obtain crushed blocks with a particle size within the range of 200-300 mm. Then, a jaw crusher with relatively small feed and discharge openings is used for secondary crushing of the crushed blocks to obtain aggregates. S4. Using a circular vibrating screen to perform grading and screening of aggregate to obtain recycled coarse aggregate with a particle size greater than 4.75 mm; S5. Mixing the recycled coarse aggregate with natural crushed stone, cement, and sand and gravel to obtain recycled concrete, wherein the mass proportion of natural crushed stone is 15%.

[0023] Example 2 This embodiment provides a method for preparing recycled concrete. Compared with Example 1, Example 2 only adjusts the pre-wetting rate of the block from 70% to 100% in step S2. The remaining steps are the same and will not be repeated here.

[0024] Comparative Example 1-2 Comparative Examples 1-2 respectively provide a method for preparing recycled concrete. Compared with Example 1, in Comparative Examples 1 and 2, only the pre-wetting rate of the block in step S2 is adjusted from 70% to 0 and 50%, respectively. The remaining steps are the same and will not be repeated here.

[0025] Comparative Example 3 Comparative Example 3 provides a method for preparing recycled concrete. Compared with Example 1, in Comparative Example 3, the mass proportion of natural crushed stone in step S5 is adjusted from 15% to 12%. The remaining steps are the same and will not be repeated here.

[0026] The crushed stones of different particle sizes obtained by screening in step S4 of Example 1-2 and Comparative Example 1-2 were subjected to weight-bearing to calculate the weight of the crushed stones in different particle size ranges after crushing as the crushing effect to calculate the aggregate yield, among which the particle size greater than 4.75 mm is recycled coarse aggregate, the particle size in the range of 0.15-4.75 mm is recycled fine aggregate, and the particle size less than 0.15 mm is powder. The statistical results are shown in Table 1.

[0027] Table 1 Proportions of different aggregates in Examples 1-2 and Comparative Examples 1-2

[0028] It can be seen from Table 1 that when the pre-wetting rate is above 70%, the coarse aggregate yield can reach more than 90%.

[0029] In addition, the powder proportions in Example 2 and Comparative Examples 1-2 are 4.5%, 6.29% and 8.59%, respectively, indicating that with the increase of the pre-wetting rate, after the water fully enters the waste concrete, the generation of dust can be greatly reduced during the crushing process. At the same time, the pre-wetting treatment can also achieve a good crushing optimization effect, effectively improving the yield of coarse aggregate.

[0030] Two temporary walkways were prepared using the recycled concrete obtained in Example 1 and Comparative Example 3. The compressive strength of the temporary walkway prepared from the recycled concrete in Example 1 was above 20 MPa, while the compressive strength of the temporary walkway prepared from the recycled concrete in Comparative Example 3 was less than 20 MPa. In addition, within a certain period of time, the surface of the temporary walkway prepared from the recycled concrete in Example 1 was intact, while some cracks appeared on the surface of the temporary walkway prepared from the recycled concrete in Comparative Example 3. This may be because the surface of the recycled coarse aggregate is relatively smooth, and the natural crushed stone has more angular edges than the recycled coarse aggregate. The addition clearly shows that the presence of natural crushed stone can enhance the bonding force between cement, sand and gravel and other ingredients and recycled coarse aggregate. Then, by adding a certain amount of natural crushed stone, it can be avoided that the bonding force between recycled coarse aggregate and cement, sand and gravel and other ingredients is weak, which makes the temporary access road prepared by recycled concrete prone to cracks and affects its service life. That is, when the mass proportion of natural crushed stone in recycled concrete is less than 15%, the bonding force between recycled coarse aggregate and cement, sand and gravel and other ingredients will be weak, affecting the strength of recycled concrete and the service life of facilities such as temporary access roads prepared by it.

[0031] The recycled concrete prepared by the preparation method of the present invention has a compressive strength of more than 20 MPa and can be used for facilities with relatively low compressive strength requirements such as landscapes, cushion layers, and temporary walkways, thereby realizing resource recycling.

[0032] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing recycled concrete, characterized in that: The following steps are involved: S1. Pre-wetting the waste concrete so that the pre-wetting rate of the waste concrete is greater than or equal to 70%, wherein the maximum moisture content of the waste concrete is taken as 100% pre-wetting rate; S2, after the surface of the waste concrete that has been pre-wetted in step S1 has no obvious water stains, the concrete is crushed and then sieved to obtain recycled coarse aggregate; S3. Mixing the recycled coarse aggregate obtained in step S3 with natural crushed stone and ingredients to obtain recycled concrete.

2. The method for preparing recycled concrete according to claim 1, wherein: In step S1, the waste concrete is pre-screened before the pre-wetting treatment.

3. The method for preparing recycled concrete according to claim 1, wherein: In step S1, the waste concrete is pre-wetted by spraying.

4. The method for preparing recycled concrete according to claim 1, wherein: In step S2, concrete crushing is performed by adopting a two-step crushing method.

5. The method for preparing recycled concrete according to claim 4, wherein: During the first crushing step, the particle size of the obtained crushed pieces is within the range of 200-300 mm.

6. The method for preparing recycled concrete according to claim 4, wherein: A jaw crusher is used to crush concrete.

7. The method for preparing recycled concrete according to claim 1, wherein: The recycled coarse aggregate is crushed concrete with a particle size greater than 4.75 mm.

8. The method for preparing recycled concrete according to claim 1, wherein: In step S2, a circular vibrating screen is used for screening.

9. The method for preparing recycled concrete according to claim 1, wherein: In step S3, the mass proportion of natural crushed stone in the recycled concrete is greater than or equal to 15%.

10. The method for preparing recycled concrete according to claim 1, wherein: In step S3, the ingredients include cement and sand and gravel.

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