Coal gangue pervious concrete as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of resource utilization of building materials and solid wastes, and discloses coal gangue pervious concrete as well as a preparation method and application thereof. The pervious concrete is prepared by taking sandstone coal gangue as aggregate and fly ash as an admixture, matching cement, a water reducing agent and water through an optimized proportion and process. Aggregate grading is controlled through secondary crushing and screening, stirring is conducted through a secondary feeding method or a cement-coated stone method, and a finished product is prepared through inserting and tamping forming and standard curing. The concrete has good water permeability, compressive strength and porosity, can be widely applied to projects such as mine road hardening, slope treatment and sponge city construction, and realizes efficient resource utilization of mine solid wastes.

Description

Technical Field

[0001] This invention relates to the field of building materials and solid waste resource utilization technology, and in particular to a permeable concrete made from coal gangue, its preparation method and application. Background Technology

[0002] Permeable concrete, as a porous ecological building material, allows rainwater to infiltrate rapidly due to its continuous pore structure. It plays an important role in replenishing groundwater, alleviating urban flooding, and reducing the urban heat island effect, and has been widely used in municipal roads, plaza paving, and other fields. Traditional permeable concrete usually uses high-quality aggregates such as natural granite and basalt, which not only consumes a lot of natural resources but also leads to high building material costs.

[0003] Coal gangue is a solid waste generated during coal mining and washing. Large-scale open-air stockpiling of coal gangue not only occupies valuable land resources but also causes air and water pollution through dust and leaching, and can even trigger geological disasters such as landslides and spontaneous combustion, becoming a key issue restricting the green development of the coal industry. Current utilization methods for coal gangue mainly include brick making, backfilling, and power generation, but these suffer from low utilization efficiency and low added value.

[0004] Sandstone coal gangue (commonly known as "white gangue") is mainly composed of silicon dioxide and aluminum oxide, and its physical and mechanical properties are similar to those of natural stone, making it a potential aggregate for concrete. However, existing technologies for permeable coal gangue concrete face the following technical bottlenecks: First, unreasonable control of the gradation of coal gangue aggregates leads to poor connectivity of the concrete's pore structure, making it difficult to balance permeability and mechanical strength; second, improper water-cement ratio design easily results in problems such as weak bonding between aggregates and cementitious materials and insufficient strength; third, the preparation process lacks targeted optimization, failing to fully utilize the performance advantages of coal gangue aggregates. Therefore, this invention proposes a high-performance, process-feasible permeable coal gangue concrete, which is of great significance for realizing solid waste resource utilization and ecological environmental protection. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a permeable concrete with coal gangue as the main aggregate, so as to realize the high-value resource utilization of mining solid waste.

[0006] Another objective of this invention is to provide a method for preparing the above-mentioned permeable concrete from coal gangue, which is simple in process and easy to operate and control.

[0007] Another object of the present invention is to provide the application of the above-mentioned permeable concrete made from coal gangue.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A permeable concrete made from coal gangue, comprising coal gangue aggregate, cement, fly ash, water-reducing agent, and water; wherein the coal gangue aggregate is aggregate obtained by crushing and screening sandstone coal gangue, with a particle size ranging from 4.75 mm to 26.5 mm; and the permeable concrete has a water-cement ratio of 0.26 to 0.32 and a designed porosity of 15% to 25%.

[0010] Furthermore, the coal gangue aggregate is sandstone coal gangue with a particle size range of 4.75mm-26.5mm.

[0011] Furthermore, the particle size range of the coal gangue aggregate is 9.5mm-16mm.

[0012] Furthermore, the cement is PO 42.5 ordinary Portland cement.

[0013] Furthermore, the water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent, and the dosage is 0.5% to 1% of the mass of the cementitious material.

[0014] A method for preparing permeable concrete made from coal gangue includes the following steps:

[0015] (1) Raw material pretreatment: The sandstone coal gangue is first crushed by a crusher, then crushed again by a jaw crusher, and then screened by a standard sieve to obtain coal gangue aggregate with the required particle size.

[0016] (2) Batching and mixing: Weigh out coal gangue aggregate, cement, fly ash, water-reducing agent and water according to the design ratio, and use a forced mixer to mix until the mixture is uniform and forms a mixture.

[0017] (3) Molding: The mixture is poured into the mold in batches and compacted by tamping. Each layer is tamped 16 to 20 times and the surface is smoothed.

[0018] (4) Curing: After molding, let stand for 24 hours to remove the mold, and place the specimen under standard curing conditions for curing until the specified age.

[0019] Furthermore, the mixing in step (2) adopts a two-stage feeding method or a cement-coated stone method; wherein, the specific operation of the two-stage feeding method is as follows: first, the coal gangue aggregate is mixed with some water for 1 to 2 minutes, then cement, fly ash and water-reducing agent are added, and the remaining water is added and the mixing continues for 3 to 5 minutes.

[0020] Furthermore, the test mold mentioned in step (3) is a 100mm×100mm×100mm cube test mold, and the mixture is loaded in 3 batches.

[0021] Furthermore, the standard curing conditions described in step (4) are: temperature 20±2℃, relative humidity not less than 95%.

[0022] Application of a permeable coal gangue concrete in mining area road hardening, mine slope treatment, or sponge city construction projects.

[0023] The beneficial effects of this invention are as follows:

[0024] (1) Solid waste utilization, environmental protection and economy: Coal gangue completely replaces natural aggregates, effectively consumes a large amount of mine solid waste, reduces the production cost of permeable concrete, and solves the environmental problems caused by coal gangue stockpiling, which meets the requirements of green and sustainable development.

[0025] (2) Performance synergistic optimization: Through reasonable particle size distribution, water-cement ratio and porosity design, the prepared coal gangue permeable concrete maintains good permeability while having high compressive strength (7-day compressive strength can reach more than 33.2 MPa), which can meet the mechanical requirements of various engineering applications.

[0026] (3) Simple and feasible process: The preparation process does not require special equipment and can be scaled up using conventional concrete production processes, which is convenient for engineering promotion and application.

[0027] (4) Significant ecological and environmental benefits: When applied to sponge city construction, it can effectively intercept rainwater, replenish groundwater, and alleviate urban flooding; when applied to mining areas, it can improve the regional ecological environment and promote mine revegetation. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the overall technical roadmap of the present invention;

[0030] Figure 2 This is a diagram showing the feeding sequence for the cement-coated stone method. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0032] A type of permeable concrete made from coal gangue, with the following material selection:

[0033] Coal gangue aggregate: Sandstone coal gangue is selected, and after secondary crushing and standard sieving, the particle size is controlled between 4.75mm and 26.5mm, preferably 9.5mm to 16mm. Aggregates within this particle size range can form continuous and interconnected pores, taking into account both permeability and skeletal support.

[0034] Cementitious materials: PO 42.5 ordinary Portland cement and fly ash are mixed at a mass ratio of 8:2. The addition of fly ash can improve the workability of cementitious materials, reduce the heat of hydration, and improve the interfacial bonding strength.

[0035] Water-reducing agent: Polycarboxylate-based high-efficiency water-reducing agent with a water reduction rate of ≥30%. The dosage is 0.5% to 1% of the mass of cementitious materials. It can effectively reduce the water-cement ratio and improve the density and strength of concrete.

[0036] Water-cement ratio: 0.26 to 0.32. This range ensures that the cementitious material is fully hydrated while avoiding pore blockage or strength reduction due to excessive moisture.

[0037] Design porosity: 15%–25%, adjusted according to the application scenario. 15%–20% is preferred for mining area roads, and 20%–25% is preferred for sponge city paving.

[0038] Preparation method:

[0039] (1) Raw material pretreatment: After removing impurities from sandstone and coal gangue, the material is put into a jaw crusher for initial crushing, then crushed a second time by an impact crusher, and screened by a standard sieve to select aggregates with a particle size of 4.75mm to 26.5mm for later use.

[0040] (2) Batching and Mixing: Weigh out the coal gangue aggregate, cement, fly ash, water-reducing agent, and water according to the designed proportions. Use a forced mixer, and a two-stage feeding method is recommended: first add the coal gangue aggregate and 50% water, and mix for 1-2 minutes to moisten the surface of the aggregate; then add the cement, fly ash, and water-reducing agent, add the remaining water, and continue mixing for 3-5 minutes until the mixture is uniform and free of lumps. If the cement-coated aggregate method is used, the feeding sequence is: aggregate → cement → dry mix for 2 minutes → add water and water-reducing agent → wet mix for 4 minutes.

[0041] (3) Molding: The mixture is poured into a 100mm×100mm×100mm cube mold in three layers. After each layer is poured, it is tamped 16 to 20 times with a tamping rod to ensure uniform density. Finally, the surface is smoothed with a trowel.

[0042] (4) Curing: After molding, stand at room temperature for 24 hours, then demold and place the specimen in a standard curing room (temperature 20±2℃, relative humidity ≥95%) for 7 days and 28 days until the design strength is reached.

[0043] This permeable concrete made from coal gangue can be directly applied to: ① hardening of roads in mining areas (industrial squares, transportation access roads); ② slope treatment in mines (ecological protection, drainage systems); ③ sponge city construction (sidewalks, non-motorized vehicle lanes, square paving); ④ permeable paving projects such as parking lots and parks.

[0044] Example 1

[0045] 1. Raw material preparation:

[0046] Coal gangue aggregate: Sandstone coal gangue, after crushing and screening, has a particle size of 9.5mm~16mm and a bulk density of 1650kg / m³. 3 ;

[0047] Cement: PO 42.5 ordinary Portland cement, 3-day compressive strength 24.5 MPa;

[0048] Fly ash: Grade II fly ash, water requirement ratio 95%;

[0049] Water-reducing agent: Polycarboxylate-based high-efficiency water-reducing agent, water reduction rate 30%;

[0050] Water: tap water.

[0051] 2. Mix design:

[0052] Cementitious material dosage: 400 kg / m 3 (Cement:Fly ash = 8:2);

[0053] Coal gangue aggregate consumption: 1450 kg / m³ 3 ;

[0054] Water-cement ratio: 0.30

[0055] Water-reducing agent dosage: 1% (percentage of cementitious material mass);

[0056] Design porosity: 20%.

[0057] 3. Preparation process:

[0058] a. Weigh each raw material according to the above key parameters.

[0059] b. A forced single-shaft concrete mixer is used, and mixing is carried out using a two-stage feeding method.

[0060] c. Pour the mixture into a 100mm×100mm×100mm cubic mold in three batches, tamping each layer 16-20 times, and finally smooth the surface.

[0061] d. After molding, let stand for 24 hours, then demold.

[0062] e. Place the demolded specimens in a standard curing room (temperature 20±1℃, relative humidity above 95%) and cure for 7 days and 28 days.

[0063] 4. Performance Testing:

[0064] 7-day compressive strength: 33.2 MPa;

[0065] 28-day compressive strength: 41.5 MPa;

[0066] Permeability coefficient: 2.3 mm / s;

[0067] Actual porosity: 19.8%.

[0068] Example 2

[0069] The difference from Example 1 is as follows:

[0070] Coal gangue aggregate particle size: 4.75mm~9.5mm;

[0071] Design porosity: 15%;

[0072] Water-reducing agent dosage: 1%

[0073] Water-cement ratio: 0.30

[0074] Coal gangue aggregate consumption: 1520 kg / m³ 3 .

[0075] Performance test results:

[0076] 7-day compressive strength: 44.8 MPa;

[0077] 28-day compressive strength: 52.3 MPa;

[0078] Permeability coefficient: 1.8 mm / s;

[0079] Actual porosity: 14.7%.

[0080] The following table shows the experimental results for each group:

[0081] Table 1. Proportions and Results of the Trial Experiment

[0082]

[0083] Table 2 Levels of Influencing Factors in the Experiment

[0084] Factor Level Aggregate particle size Water-to-glue ratio Design porosity 1 4.75~9.5mm 0.26 15％ 2 9.5~16mm 0.28 20％ 3 16~19mm 0.30 25％ 4 19~26.5mm 0.32 -

[0085] Application Examples

[0086] The permeable concrete made from coal gangue prepared in Example 1 was applied to a road hardening project in an industrial square of a coal mine, covering an area of ​​5000㎡ with a pavement thickness of 120mm. During construction, a paver was used for paving, and a vibrator was used for compaction. After 28 days of curing, performance tests were conducted: pavement smoothness deviation ≤5mm, 28-day compressive strength 40.8MPa, and permeability coefficient 2.1mm / s. After 6 months of use and observation, the pavement showed no cracks or settlement, no water accumulation during rainfall, and good rainwater infiltration, achieving the dual goals of large-scale utilization of coal gangue and improvement of the mining area environment.

[0087] In summary, this invention successfully applies coal gangue to permeable concrete, producing a high-performance green building material product, and providing an effective technical solution for the disposal and comprehensive utilization of mine solid waste.

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A permeable concrete made from coal gangue, characterized in that: The raw materials include coal gangue aggregate, cement, fly ash, water-reducing agent, and water; the coal gangue aggregate is aggregate obtained by crushing and screening sandstone coal gangue, with a particle size range of 4.75mm to 26.5mm; the water-cement ratio of the permeable concrete is 0.26 to 0.32, and the designed porosity is 15% to 25%.

2. The permeable concrete made from coal gangue according to claim 1, characterized in that, The coal gangue aggregate is sandstone coal gangue with a particle size range of 4.75mm-26.5mm.

3. The permeable coal gangue concrete according to claim 2, characterized in that, The particle size range of the coal gangue aggregate is 9.5mm-16mm.

4. The permeable coal gangue concrete according to claim 1, characterized in that, The cement is PO 42.5 ordinary Portland cement.

5. The permeable coal gangue concrete according to claim 1, characterized in that, The water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent, and the dosage is 0.5% to 1% of the mass of the cementitious material.

6. A method for preparing permeable coal gangue concrete as described in any one of claims 1 to 5, characterized in that, Includes the following steps: (1) Raw material pretreatment: The sandstone coal gangue is first crushed by a crusher, then crushed again by a jaw crusher, and then screened by a standard sieve to obtain coal gangue aggregate with the required particle size. (2) Batching and mixing: Weigh out coal gangue aggregate, cement, fly ash, water-reducing agent and water according to the design ratio, and use a forced mixer to mix until the mixture is uniform and forms a mixture. (3) Molding: The mixture is poured into the mold in batches and compacted by tamping. Each layer is tamped 16 to 20 times and the surface is smoothed. (4) Curing: After molding, let stand for 24 hours to remove the mold, and place the specimen under standard curing conditions for curing until the specified age.

7. The preparation method according to claim 6, characterized in that, The mixing in step (2) adopts a two-stage feeding method or a cement-coated stone method; the specific operation of the two-stage feeding method is as follows: first, mix the coal gangue aggregate with some water for 1 to 2 minutes, then add cement, fly ash and water-reducing agent, add the remaining water and continue mixing for 3 to 5 minutes.

8. The preparation method according to claim 5, characterized in that, The test mold mentioned in step (3) is a 100mm×100mm×100mm cube test mold, and the mixture is loaded in 3 batches.

9. The preparation method according to claim 5, characterized in that, The standard curing conditions described in step (4) are: temperature 20±2℃, relative humidity not less than 95%.

10. The application of permeable coal gangue concrete as described in any one of claims 1 to 5 in mining area road hardening, mine slope treatment, or sponge city construction projects.

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