Preparation and application of river stone and tailing ore composite concrete

Abstract

The invention provides preparation and application of river stone and tailing ore composite concrete. The preparation method comprises the following steps: (1) respectively washing river stone and tailing ore with water, drying and removing impurities; (2) 100 parts of cement, 20 to 30 parts of an admixture, 180 to 220 parts of river stone, 80 to 120 parts of tailings, 1.5 to 2.5 parts of an additive and 35 to 45 parts of water; the admixture is formed by mixing fly ash and slag powder according to the mass ratio of 1: 1; the additive is a polycarboxylic acid type high-efficiency water reducing agent; (3) firstly, the river stones and the tailings are subjected to dry mixing for 2-3 min, then the cement and the admixture are added and subjected to dry mixing for 3-4 min, then 60%-70% of water is added and stirred for 4-5 min, finally, the admixture and the remaining water are added, and high-speed stirring is conducted for 5-6 min; and (4) pouring and vibrating the stirred concrete mixture, and performing standard curing for 28 days to obtain a composite concrete finished product. Through reasonable grading of the river stones and the tailings, the void ratio of the composite aggregate is effectively reduced, so that the compactness of the concrete is remarkably improved, and the compressive strength and the breaking strength of the finished concrete are effectively improved.

Description

Technical Field

[0001] This application relates to the field of building materials technology, specifically to the preparation and application of a composite concrete made from river stone and tailings. Background Technology

[0002] Concrete is one of the most widely used materials in construction projects. Its main raw materials include cement, aggregates, water, and admixtures. Among them, aggregates account for as much as 60%-80% of concrete. Traditional aggregates mostly use natural river sand and stones. However, long-term over-exploitation of natural sand and gravel will lead to environmental problems such as river ecological damage and soil erosion. Moreover, as natural sand and gravel resources become increasingly depleted, their prices continue to rise, increasing the production cost of concrete.

[0003] On the other hand, a large amount of tailings are generated during the mining process. According to statistics, my country's annual tailings discharge exceeds 1 billion tons. The large amount of tailings piled up not only occupies land resources, but may also cause heavy metal ion leakage due to rainwater erosion, polluting the soil and groundwater and causing serious environmental hazards. At present, the recycling and utilization of tailings are mostly concentrated in low value-added fields, such as landfill and road subbase, which fail to give full play to their material potential and the resource utilization rate is low.

[0004] While some existing technologies use single tailings or single river stones as aggregates to prepare concrete, single tailings aggregate concrete suffers from problems such as low strength and high shrinkage, making it difficult to meet the requirements of high-strength projects. Single river stone aggregate concrete, on the other hand, faces the dilemma of resource shortage and high cost. Therefore, developing a composite concrete preparation method that rationally combines river stones and tailings to improve concrete performance and achieve high-value utilization of tailings has become an urgent problem to be solved in the field of building materials. Summary of the Invention

[0005] In view of the above-mentioned defects or deficiencies in the prior art, it is desirable to provide a method for the preparation and application of composite concrete made from river stone and tailings.

[0006] This application provides a method for preparing and applying composite concrete made from river stone and tailings, comprising the following steps: (1) Raw material pretreatment: The river stone and tailings are washed, dried and cleaned of impurities respectively, and then set aside for use; the particle size of the river stone is 5-20 mm and the particle size of the tailings is 2-10 mm. (2) Weigh the following raw materials by weight: 100 parts cement, 20-30 parts admixture, 180-220 parts river stone, 80-120 parts tailings, 1.5-2.5 parts additive, and 35-45 parts water; the admixture is a mixture of fly ash and slag powder in a mass ratio of 1:1; the additive is a polycarboxylate-based high-efficiency water-reducing agent. (3) Mixing and stirring: First, dry mix the river stone and tailings for 2-3 minutes, then add cement and admixtures and dry mix for 3-4 minutes, then add 60%-70% water and stir for 4-5 minutes, and finally add the admixture and the remaining water and stir at high speed for 5-6 minutes. (4) Pouring and curing: After the mixed concrete mixture is poured and vibrated, it is cured for 28 days to obtain the finished composite concrete product.

[0007] Furthermore, In step (1), the drying temperature of the river stone and tailings is 180-200℃, and the moisture content after drying is ≤1%; the tailings are iron tailings, copper tailings or limestone tailings, and metal impurities are removed by magnetic separation, with an impurity removal rate ≥95%.

[0008] Furthermore, In step (2), the mass ratio of river stone to tailings is 1.8-2.2:1; the cement is 42.5 grade ordinary Portland cement; the fly ash is grade II or above; the slag powder is grade S95; and the water reduction rate of the polycarboxylate superplasticizer is ≥25%.

[0009] Furthermore, In step (3), the high-speed mixer has a rotation speed of ≥1500 r / min, and the slump of the concrete mixture after mixing is 180-220 mm.

[0010] Furthermore, In step (4), the vibration is performed using a vibrator with a frequency of ≥50Hz and a vibration time of 2-3 minutes; the standard curing conditions are a temperature of 20±2℃ and a relative humidity of ≥90%, and the mold is removed after curing for 1-2 days, and curing continues for 28 days after demolding.

[0011] Furthermore, The composite concrete has a 28-day compressive strength of 45-55 MPa and a flexural strength of 5-6 MPa.

[0012] The application of the preparation of river stone and tailings composite concrete according to claim 6 in the field of building construction.

[0013] The advantages and positive effects of this application are: This technical solution effectively reduces the porosity of composite aggregates through the reasonable gradation of river stone and tailings, thereby significantly improving the density of concrete. As a result, the compressive strength and flexural strength of the finished concrete are effectively improved. At the same time, the preparation process of this application does not require special equipment and can be scaled up by relying on existing concrete mixing plant production lines. It is easy to operate and promote. Detailed Implementation

[0014] To enable those skilled in the art to better understand the technical solution of this application, this application is described in detail below. The description in this section is merely exemplary and explanatory, and should not be construed as limiting the scope of protection of this application.

[0015] This embodiment provides a preparation and application of composite concrete made from river stone and tailings, including the following steps: (1) Raw material pretreatment: the river stone and tailings are washed, dried and cleaned of impurities respectively, and set aside for later use; the particle size of the river stone is 5-20 mm, and the particle size of the tailings is 2-10 mm; (2) Weigh the raw materials by mass: 100 parts cement, 20-30 parts admixture, 180-220 parts river stone, 80-120 parts tailings, 1.5-2.5 parts admixture, and 35-45 parts water; the admixture The material is a mixture of fly ash and slag powder in a mass ratio of 1:1; the admixture is a polycarboxylate-based high-efficiency water-reducing agent; (3) Mixing and stirring: first, dry mix the river stone and tailings for 2-3 minutes, then add cement and admixtures and dry mix for 3-4 minutes, then add 60%-70% water and stir for 4-5 minutes, and finally add the admixture and the remaining water and stir at high speed for 5-6 minutes; (4) Pouring and curing: after pouring and vibrating the mixed concrete mixture, cure it according to standard for 28 days to obtain the composite concrete finished product.

[0016] In this embodiment, the raw material pretreatment is as follows: natural river stones with a particle size of 5-20mm and tailings with a particle size of 2-10mm are selected and washed with high-pressure water guns to remove mud and dust adhering to the surface; then the washed river stones and tailings are placed in a drying oven, and finally the dead branches and weeds in the river stones and large impurities in the tailings are removed by manual screening for later use. In this embodiment, the raw materials are weighed as follows: 100 kg of 42.5 grade ordinary Portland cement, 25 kg of admixture, 200 kg of pretreated river stone, 100 kg of tailings, 2.0 kg of polycarboxylate-based high-efficiency water-reducing agent, and 40 kg of tap water are weighed according to the following mass percentages. In this embodiment, the mixing process is as follows: River stones and tailings are added to a forced mixer and dry-mixed for 2.5 minutes to ensure that the two aggregates are initially mixed evenly; then cement and admixtures are added and dry-mixed for another 3.5 minutes to ensure that the cementitious materials and aggregates are in full contact; then 28 kg (70% of the total water volume) of tap water is added and mixed for 4.5 minutes to form a preliminary homogeneous concrete mixture; finally, water-reducing agent and the remaining 12 kg of tap water are added and mixed at a high speed of 1600 r / min for 5.5 minutes. The slump is measured to be 200 mm, which meets the construction requirements. In a preferred embodiment, in step (1), the drying temperature of the river stone and tailings is 180-200℃, and the moisture content after drying is ≤1%; the tailings are iron tailings, copper tailings or limestone tailings, and metal impurities are removed by magnetic separation, with an impurity removal rate ≥95%.

[0017] In this embodiment, river stone and copper tailings were processed separately. After washing, they were placed in a drying oven and dried at 200°C for 20 minutes until the moisture content was 0.8%. A magnetic field strength of 12000 Gs was used to remove metallic impurities from the copper tailings.

[0018] In a preferred embodiment, in step (2), the mass ratio of river stone to tailings is 1.8-2.2:1; the cement is 42.5 grade ordinary Portland cement; the fly ash is grade II or above; the slag powder is grade S95; and the water reduction rate of the polycarboxylate superplasticizer is ≥25%.

[0019] In this embodiment, the admixture is a 1:1 mixture of Grade II fly ash and Grade S95 slag powder; the mass ratio of river stone to tailings is 1.8:1; and the water reduction rate of the polycarboxylate-based high-efficiency water-reducing agent is 26%.

[0020] In a preferred embodiment, in step (3), the high-speed mixing speed is ≥1500r / min, and the slump of the concrete mixture after mixing is 180-220mm.

[0021] In this embodiment, the high-speed mixer rotates at 1600 r / min; the slump of the concrete mixture after mixing is 200 mm.

[0022] In a preferred embodiment, in step (4), the vibration is performed using a vibrator with a frequency of ≥50Hz and a vibration time of 2-3 minutes; the standard curing conditions are a temperature of 20±2℃ and a relative humidity of ≥90%, and the mold is removed after curing for 1-2 days, and curing continues for 28 days after demolding.

[0023] In this embodiment, after the concrete mixture is poured into the test mold, it is vibrated with 50Hz and 60Hz vibrators for 2min and 3min respectively. Then it is placed in a standard curing room (temperature 20±2℃, relative humidity 90%) and cured for 1d and 2d respectively before demolding and continuing to cure for 28d.

[0024] Performance testing: The 28-day compressive strength of concrete vibrated at 50Hz for 2 minutes is 47MPa, and that of concrete vibrated at 60Hz for 3 minutes is 53MPa; the surface flatness deviation of concrete after demolding time of 1 day and 2 days is ≤2mm, with no chipped edges or corners.

[0025] In a preferred embodiment, the preparation of composite concrete made from river stone and tailings is applied in the field of building construction.

[0026] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. The above descriptions are only preferred embodiments of this application. It should be noted that due to the limitations of textual expression, while there are objectively infinite specific structures, those skilled in the art can make several improvements, modifications, or changes without departing from the principles of this invention, and can also combine the above technical features in an appropriate manner. These improvements, modifications, changes, or combinations, or the direct application of the inventive concept and technical solution to other situations without modification, should all be considered within the scope of protection of this application.

Claims

1. A method for preparing composite concrete made from river stone and tailings, characterized in that, Includes the following steps: (1) Raw material pretreatment: The river stone and tailings are washed, dried and cleaned of impurities respectively, and then set aside for use; the particle size of the river stone is 5-20 mm and the particle size of the tailings is 2-10 mm. (2) Weigh the following raw materials by weight: 100 parts cement, 20-30 parts admixture, 180-220 parts river stone, 80-120 parts tailings, 1.5-2.5 parts additive, and 35-45 parts water; the admixture is a mixture of fly ash and slag powder in a mass ratio of 1:1; the additive is a polycarboxylate-based high-efficiency water-reducing agent. (3) Mixing and stirring: First, dry mix the river stone and tailings for 2-3 minutes, then add cement and admixtures and dry mix for 3-4 minutes, then add 60%-70% water and stir for 4-5 minutes, and finally add the admixture and the remaining water and stir at high speed for 5-6 minutes. (4) Pouring and curing: After the mixed concrete mixture is poured and vibrated, it is cured for 28 days to obtain the finished composite concrete product.

2. The preparation of composite concrete made from river stone and tailings as described in claim 1, characterized in that, In step (1), the drying temperature of the river stone and tailings is 180-200℃, and the moisture content after drying is ≤1%; the tailings are iron tailings, copper tailings or limestone tailings, and metal impurities are removed by magnetic separation, with an impurity removal rate ≥95%.

3. The preparation of composite concrete made from river stone and tailings as described in claim 1, characterized in that, In step (2), the mass ratio of river stone to tailings is 1.8-2.2:1; the cement is 42.5 grade ordinary Portland cement; the fly ash is grade II or above; the slag powder is grade S95; and the water reduction rate of the polycarboxylate superplasticizer is ≥25%.

4. The preparation of composite concrete made from river stone and tailings as described in claim 1, characterized in that, In step (3), the high-speed mixer has a rotation speed of ≥1500 r / min, and the slump of the concrete mixture after mixing is 180-220 mm.

5. The preparation of composite concrete made from river stone and tailings as described in claim 1, characterized in that, In step (4), the vibration is performed using a vibrator with a frequency of ≥50Hz and a vibration time of 2-3 minutes; the standard curing conditions are a temperature of 20±2℃ and a relative humidity of ≥90%, and the mold is removed after curing for 1-2 days, and curing continues for 28 days after demolding.

6. The preparation of composite concrete of river stone and tailings according to any one of claims 1-5, characterized in that, The composite concrete has a 28-day compressive strength of 45-55 MPa and a flexural strength of 5-6 MPa.

7. The application of the preparation of river stone and tailings composite concrete according to claim 6 in the field of building construction.