Secondary screening and dehydration device and method for concrete system

Abstract

The present invention relates to a secondary screening and dehydration device and method for a concrete system, the device comprises a material tank and a secondary screening machine connected in sequence, the secondary screening machine comprises a fixed grid screen for screening out discarded materials > 150 mm, a mechanical vibration screen group for screening aggregates of 20 mm to 150 mm, and a dehydration screen for screening aggregates < 20 mm, the mechanical vibration screen group and the dehydration screen are respectively connected to a mixing plant through a belt conveyor. The device can fully utilize fine aggregates of small particle size, effectively avoiding excessive moisture content caused by washing of fine aggregates.

Description

Technical Field

[0001] The invention belongs to the technical field of civil engineering concrete, and in particular relates to a secondary screening and dehydration device and method for a concrete system. Background Art

[0002] The large-scale hydropower projects that have been built and are under construction at home and abroad have a huge demand for cast-in-place concrete, and the concrete production capacity has become the main controlling factor for the construction progress, quality and investment. In most current engineering applications, a secondary screening system for sand and gravel aggregates is set up in the concrete production process. According to the industry specifications formulated by relevant national departments, fine aggregates less than 5mm (accounting for about 6% to 8% of the total amount of sand and gravel aggregates) that are sieved out through secondary screening are not allowed to be directly used in concrete mixing, and are usually treated as waste. This has become an industry consensus.

[0003] The current flow diagram of the secondary screening device of the concrete system is usually as follows: Figure 1 As shown, the crushed stone aggregate is stored in a material tank 100, and the aggregate is screened by a secondary screening machine 200 at any time. The screened 5mm-150mm aggregate can directly enter the mixing plant 400 for concrete production, and then be transported to the construction site by a concrete transport vehicle 500, while the remaining fine aggregate less than 5mm is directly discarded into the abandoned material field 300. Discarding the fine aggregate less than 5mm in the secondary screening not only causes a waste of resources, but also shows that the quality control of the finished aggregate is too conservative. In addition, the sand and gravel are broken due to falling, collision and other reasons during the storage and transportation process, and the fine aggregate with a particle size of less than 5mm and the stone powder with a very small particle size are easily "coated" on the surface of the fine aggregate, resulting in an excessively high moisture content (greater than 15%) during the flushing process, which restricts the use of fine aggregate. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems existing in the prior art and provide a secondary screening and dehydration device for a concrete system, which can utilize small-size fine aggregates and avoid excessively high moisture content of the fine aggregates.

[0005] The secondary screening and dehydration device of the concrete system of the present invention comprises a material tank and a secondary screening machine connected in sequence, wherein the secondary screening machine comprises a fixed grid screen for screening out discarded materials >150 mm, a mechanical vibrating screen group for screening aggregates of 20 mm to 150 mm, and a dehydrating screen for screening aggregates <20 mm, wherein the mechanical vibrating screen group and the dehydrating screen are respectively connected to a mixing plant via a belt conveyor.

[0006] Furthermore, the mechanical vibrating screen group is, in order of screening, a first vibrating screen for obtaining 80mm-150mm aggregate, a second vibrating screen for obtaining 40mm-80mm aggregate, and a third vibrating screen for obtaining 20mm-40mm aggregate; the aggregates obtained by the first vibrating screen, the second vibrating screen and the third vibrating screen are respectively transported to the mixing plant through a belt conveyor.

[0007] The concrete secondary screening method of the present invention uses the aforementioned concrete system secondary screening and dehydration device, and comprises the following steps:

[0008] (1) Storing crushed stone aggregate in a material tank;

[0009] (2) The crushed stone aggregate in the material tank is placed in a secondary screening machine for screening. The 20mm to 150mm aggregate obtained by the mechanical vibrating screen group is transported to the mixing plant through a belt conveyor for concrete production;

[0010] (3) Rinse the remaining <20mm aggregate, and after dehydration through the dehydration screen, the <20mm aggregate is directly transported to the mixing plant through a belt conveyor.

[0011] Furthermore, the 20mm-150mm aggregate is screened in sequence into 80mm-150mm aggregate, 40mm-80mm aggregate and 20mm-40mm aggregate in the mechanical vibration screen group, and transported to the mixing plant respectively through the belt conveyor.

[0012] Furthermore, in step (3), the moisture content of the aggregate <20 mm after dehydration through the dehydration screen is less than 6.5%.

[0013] Beneficial effects of the present invention:

[0014] The secondary screening and dehydration device for the concrete system of the present invention cancels the 5mm aperture vibrating screen in the original secondary screening machine of the concrete system and replaces the 5mm aperture vibrating screen with a dehydration screen, thereby solving the problem of excessively high moisture content of aggregates with a particle size less than 20mm caused by flushing. The aggregates with a particle size less than 20mm can directly enter the mixing plant to produce concrete after being processed.

[0015] The secondary screening method of the concrete system of the present invention can use all the fine aggregates less than 5 mm produced by the original concrete system in the production of concrete. By controlling the amount of fine aggregate-sand in the concrete to ensure that the concrete mix ratio meets the specification requirements, the amount of engineering aggregate can be saved by about 6% to 8%, with obvious economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the process of a secondary screening device for a concrete system in the prior art;

[0017] Figure 2 It is a structural schematic diagram of the secondary screening and dehydration device of the concrete system of the present invention;

[0018] Figure 3 It is a schematic diagram of the process of the secondary screening and dehydration device of the concrete system of the present invention;

[0019] In the figure: a material tank 100; a secondary screening machine 200; a fixed grid screen 210; a mechanical vibration screen group 220; an 80 mm vibration screen 221; a 40 mm vibration screen 222; a 20 mm vibration screen 223; a dewatering screen 230; an existing secondary screening machine 200'; a waste material yard 300; a mixing plant 400; and a transport vehicle 500. DETAILED DESCRIPTION

[0020] The implementation of the present invention will be described in detail below with reference to the accompanying drawings, but they do not constitute a limitation of the present invention and are merely examples.

[0021] like Figure 2-3 The secondary screening and dehydration device of the concrete system shown in the figure comprises a material tank 100 and a secondary screening machine 200 which are connected in sequence; the secondary screening machine 200 comprises, from top to bottom, a fixed grid screen 210, a mechanical vibration screen group 220 and a dehydration screen 230. The fixed screen 210 screens out aggregates with a particle size greater than 150 mm and turns them into waste materials.

[0022] The mechanical vibration screen group 220 consists of a first vibration screen 221 with a pore size of 80 mm, a second vibration screen 222 with a pore size of 40 mm, and a third vibration screen 223 with a pore size of 20 mm. Aggregates with a particle size of 80 mm to 150 mm can be obtained on the first vibrating screen 221, and the aggregates are directly transported to the mixing plant 400 through a belt conveyor. Aggregates with a particle size less than 80 mm pass through the first vibrating screen 221 and fall into the second vibrating screen 222 for screening. Aggregates with a particle size of 40 mm to 80 mm obtained on the second vibrating screen 222 are transported to the mixing plant 400 through a belt conveyor. Aggregates with a particle size less than 40 mm continue to descend and pass through the third vibrating screen 223. Aggregates with a particle size of 20 mm to 40 mm are obtained and transported to the mixing plant 400 through a belt conveyor. The remaining aggregates with a particle size less than 20 mm can also be directly transported to the mixing plant 400 through a belt conveyor after being dehydrated by the dehydration screen 230 and mixed with the coarse aggregate separated before, so as to ensure that the concrete mix ratio meets the specification requirements.

[0023] The use of this device includes the following steps:

[0024] The first step is to store the crushed stone aggregate in the material tank 100;

[0025] In the second step, the crushed stone aggregate is screened by the improved secondary screening machine 200, and the discarded material >150mm, the aggregate of 80mm-150mm, the aggregate of 40mm-80mm and the aggregate of 20mm-40mm are screened out respectively, and each batch of aggregate is transported to the mixing plant 400 by the belt conveyor;

[0026] In the third step, the remaining <20 mm aggregate is washed and then dehydrated through the dehydration screen 230, and the obtained <20 mm aggregate is transported to the mixing plant 400 through a belt conveyor;

[0027] In the fourth step, the prepared concrete is transported to the construction site by the transport vehicle 500.

[0028] After testing, the moisture content of the obtained aggregate <20mm was 6.23%.

[0029] In order to more clearly illustrate the advantages of the improved concrete system secondary screening and dehydration method and device of the present invention compared with the original concrete system secondary screening method and device, the benefits generated by its application in a large-scale water conservancy project are estimated. The water conservancy project uses a total of 3.143 million m3 of concrete, and the fine aggregate less than 5 mm is about 148,000 tons. The economic benefits generated are as follows:

[0030] (1) Waste slag fee: the labor, material and machinery costs required to clean up waste materials with a size less than 5 mm. The unit price of waste slag is 15.72 yuan / t. A total of 148,000 tons of sand can be reused, and a total waste slag fee of 2.3266 million yuan can be saved.

[0031] (2) The material cost of finished sand equal to the amount of discarded materials was saved, which was about 148,000 tons. According to the contract unit price of RMB 33.88 per ton, the cost of finished sand was saved by about RMB 5,014,200.

[0032] The total cost savings were approximately RMB 7.3408 million.

[0033] Statistics of benefits generated

[0034] Savings Project Waste management costs Finished sand cost total Amount (ten thousand yuan) 232.66 501.42 734.08

Claims

1. The secondary screening and dehydration device of the concrete system is characterized by: The invention comprises a material tank (100) and a secondary screening machine (200) connected in sequence, wherein the secondary screening machine comprises a fixed grating (210) for screening out discarded materials with a diameter greater than 150 mm, a mechanical vibration screen group (220) for screening aggregates with a diameter between 20 mm and 150 mm, and a dewatering screen (230) for screening aggregates with a diameter less than 20 mm, wherein the mechanical vibration screen group (220) and the dewatering screen (230) are respectively connected to a mixing plant (400) via a belt conveyor.

2. The secondary screening and dehydration device for concrete system according to claim 1, characterized in that: The mechanical vibration screen group (220) comprises, in order of screening, a first vibration screen (221) for obtaining aggregates of 80 mm to 150 mm, a second vibration screen (222) for obtaining aggregates of 40 mm to 80 mm, and a third vibration screen (223) for obtaining aggregates of 20 mm to 40 mm; the aggregates obtained by the first vibration screen (221), the second vibration screen (222) and the third vibration screen (223) are respectively transported to a mixing plant via a belt conveyor.

3. The secondary screening and dehydration method of the concrete system is characterized by: The use of the secondary screening and dehydration device for a concrete system according to claim 1 comprises the following steps: (1) Storing crushed stone aggregate in a material tank (100); (2) The crushed stone aggregate in the material tank (100) is placed in a secondary screening machine (200) for screening, and the 20 mm to 150 mm aggregate obtained by the mechanical vibration screen group (220) is transported to the mixing plant (400) through a belt conveyor for concrete production; (3) The remaining <20 mm aggregate is washed and dehydrated by the dehydration screen (230). The <20 mm aggregate is directly transported to the mixing plant (400) via a belt conveyor.

4. The method for secondary screening and dehydration of concrete system according to claim 3, characterized in that: The 20 mm to 150 mm aggregate is screened in sequence in the mechanical vibration screen group (220) into 80 mm to 150 mm aggregate, 40 mm to 80 mm aggregate and 20 mm to 40 mm aggregate, and transported to the mixing plant (400) respectively through a belt conveyor.

5. The method for secondary screening and dehydration of concrete system according to claim 3, characterized in that: In step (3), the moisture content of the aggregate <20 mm after dehydration by the dehydration screen (230) is less than 6.5%.

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