Red mud pervious concrete double-layer pavement structure as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of road engineering materials and pavement structures, and discloses a red mud pervious concrete double-layer pavement structure as well as preparation and application thereof. The pavement structure comprises a red mud pervious concrete layer (1) and a red mud pervious concrete layer (2) from top to bottom, the thickness ratio of the red mud pervious concrete layer (1) to the red mud pervious concrete layer (2) is (30-50): (70-150). The graded aggregate of the concrete layer (1) is a double-graded aggregate with the particle size of 2.36-4.75 mm: 4.75-9.5 mm according to the mass ratio of (50-100%): (50-0%), and the graded aggregate of the concrete layer (2) is a single-graded aggregate with the particle size of 4.75-9.5 mm. The red mud pervious concrete double-layer pavement structure disclosed by the invention has better mechanical property and water permeability, and compared with a common pervious concrete pavement, the red mud pervious concrete double-layer pavement structure has excellent anti-blocking performance, purification performance and sound absorption and noise reduction performance.

Description

Technical Field

[0001] The invention belongs to the technical field of road engineering material preparation and pavement structure, and particularly relates to a red mud permeable concrete double-layer pavement structure and a preparation method and application thereof. Background Art

[0002] Cu in road surface runoff from rainfall and road washing 2+ , Pb 2+ The content of heavy metal ion pollutants is high. At present, most of the road surface runoff in China is directly discharged into the ecosystem or urban drainage system through the road surface. The degradation rate of these heavy metal ion pollutants is very slow or even difficult to degrade, which leads to the continuous accumulation of these pollutants, causing serious damage to the ecosystem and posing a serious threat to human health through the water cycle and food chain. At the same time, most roads are adjacent to lakes, rivers and farmland. The accumulation of pollutants may cause water pollution, deterioration of water quality, and affect the growth of crops.

[0003] Permeable concrete pavement has been widely used in the construction of sponge cities. However, during the service life of permeable pavement, dirt, sand and gravel carried in the runoff will enter the concrete, causing blockage of the pores inside the concrete and reducing the permeability of the pavement structure.

[0004] Red mud is a solid waste generated by the aluminum industry when producing alumina. Studies have found that the surface of red mud is highly active and exhibits a certain adsorption capacity. It can remove impurities and pollutants such as heavy metal ions in sewage through physical and chemical adsorption mechanisms, thereby achieving the effect of purifying water quality and treating waste with waste. Summary of the invention

[0005] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide an ecological double-layer permeable pavement structure based on red mud permeable concrete. The pavement structure has good mechanical properties, water permeability, sound absorption and noise reduction performance, water purification performance and anti-clogging performance.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned ecological double-layer permeable pavement structure based on red mud permeable concrete.

[0007] Another object of the present invention is to provide an application of the above-mentioned ecological double-layer permeable pavement structure based on red mud permeable concrete.

[0008] The purpose of the present invention is achieved through the following solutions:

[0009] A red mud permeable concrete double-layer pavement structure, the pavement structure comprising from top to bottom: a red mud permeable concrete layer (1) and a red mud permeable concrete layer (2); the thickness ratio of the red mud permeable concrete layer (1) to the red mud permeable concrete layer (2) is (30-50):(70-150).

[0010] Preferably, the thickness of the red mud permeable concrete layer (1) is (30-50) mm; the thickness of the red mud permeable concrete layer (2) is (70-150) mm.

[0011] The red mud permeable concrete layer (1) and the red mud permeable concrete layer (2) both comprise the following raw materials: graded aggregate, cementitious material, water, water reducing agent and water repellent, wherein the cementitious material comprises cement and red mud, and the graded aggregate is diabase aggregate, but the particle sizes of the graded aggregate in the two concrete layers are different, specifically as follows: the concrete layer (1) is a small-pore and small-particle red mud permeable concrete layer, the graded aggregate is a double-graded aggregate with a mass ratio of particle size 2.36-4.75 mm:4.75-9.5 mm=(50%-100%):(50%-0%), and the designed porosity of the concrete layer (1) is 15%-21%; the concrete layer (2) is a large-pore and large-particle red mud permeable concrete layer, the graded aggregate is a single-graded aggregate with a particle size of 4.75-9.5 mm, and the designed porosity of the concrete layer (2) is 18%-24%.

[0012] Preferably, the concrete layer (1) is a small-pore and small-particle red mud permeable concrete layer, and the graded aggregate is a double-graded aggregate with a mass ratio of particle size 2.36-4.75 mm:4.75-9.5 mm=(50%-70%):(50%-30%).

[0013] Preferably, the designed porosity of the concrete layer (2) is greater than the designed porosity of the concrete layer (1), preferably 3% greater.

[0014] The cement in the red mud permeable concrete layer (1) is general-purpose silicate cement with a strength of not less than 52.5; the red mud is Bayer red mud, which is dried at 105°C and fully ground in a grinder before use to make its particle size less than 0.075mm; the water reducer is a polycarboxylic acid high-efficiency water reducer; and the water repellent is a sodium methyl silicate organic silicon water repellent. The mass ratio of cement to red mud is (80-90): (10-20). The mass ratio of the graded aggregate to the cementitious material is 1: (0.25-0.35); the amount of water used satisfies the water-cement ratio of 0.28-0.35; the amount of the water reducer and the water repellent is 0.1%-0.3% of the mass of the cementitious material.

[0015] The red mud permeable concrete layer (1) is prepared by the following method:

[0016] M11: Add all the aggregates of the red mud permeable concrete layer (1) and 40% to 60% of water into a mixer and stir for 30 to 40 seconds to fully wet the surface of the aggregates;

[0017] M12: Add 40% to 60% of cement, 40% to 60% of red mud and 40% to 60% of the remaining water, and stir for 50 to 70 seconds;

[0018] M13: Add the remaining cement, the remaining red mud, the remaining water and all the water reducers and water repellents, and stir for 110 to 130 seconds.

[0019] The cement in the red mud permeable concrete layer (2) is general-purpose silicate cement with a strength of not less than 52.5; the red mud is Bayer red mud, which is dried at 105°C and fully ground in a grinder before use to make its particle size less than 0.075mm; the water reducer is a polycarboxylic acid high-efficiency water reducer; and the water repellent is a methyl sodium silicate organic silicon water repellent. The mass ratio of cement to red mud is (80-90): (10-20). The mass ratio of the graded aggregate to the cementitious material is 1: (0.25-0.35); the amount of water used satisfies the water-cement ratio of 0.28-0.35; the amount of the water reducer and the water repellent is 0.1%-0.3% of the mass of the cementitious material.

[0020] The red mud permeable concrete layer (2) is prepared by the following method:

[0021] M21: Add all the aggregates of the red mud permeable concrete layer (2) and 40% to 60% of water into a mixer and stir for 30 to 40 seconds to fully wet the surface of the aggregates;

[0022] M22: Add 40% to 60% of cement, 40% to 60% of red mud and 40% to 60% of the remaining water, and stir for 50 to 70 seconds;

[0023] M23: Add the remaining cement, remaining red mud, remaining water and all water reducers and water repellents, and stir for 110 to 130 seconds.

[0024] A method for preparing the above-mentioned red mud permeable concrete double-layer pavement structure, wherein the red mud permeable concrete layer (1) and the red mud permeable concrete layer (2) are formed by a "wet joint" construction process, and the time interval between the "wet joint" of the upper and lower layers is 15 to 25 minutes, specifically comprising the following steps:

[0025] The raw materials are mixed evenly according to steps M21-M23, and then molded in a mold to obtain a red mud permeable concrete layer (2). 15 to 25 minutes after the red mud permeable concrete layer (2) is molded, the mixture mixed evenly according to steps M11-M13 is loaded into the test mold on which the red mud permeable concrete layer (2) has been molded to obtain a red mud permeable concrete layer (1), which is then left to stand, thereby obtaining a red mud permeable concrete double-layer pavement structure.

[0026] The molding refers to molding in a mold by manual tamping, which specifically includes the following steps: the mixed mixture is loaded into the mold in layers by manual tamping, and each layer is tamped 25 to 35 times from the edge to the center in the same direction with a tamping rod, and the top surface is properly compacted with a hammer, and finally, the excess mixture around the mold is removed with a spatula and the surface is filled;

[0027] The standing still refers to leaving the molded specimen to stand still indoors for 24 hours.

[0028] The composite pavement structure should preferably adopt an automated paving method to ensure the construction quality. Therefore, the materials used for the red mud permeable concrete layer (1) and the red mud permeable concrete layer (2) should have good construction and workability, no slurry overflow when compacted, and be suitable for fast and large-area paving.

[0029] The removed specimens are moved to a standard curing room for curing to the corresponding age. The mechanical properties of the permeable concrete specimens are tested in accordance with the "Testing Code for Cement and Cement Concrete for Highway Engineering" (JTG 3420-2020); the permeability of the permeable concrete specimens is tested in accordance with the "Technical Code for Permeable Cement Concrete Pavement" (CJJ / T135-2009).

[0030] The ecological double-layer red mud permeable concrete pavement can purify heavy metal ions (such as Cu 2+ , Pb 2+ ), the heavy metal ion purification rate was tested through indoor tests using permeable specimens.

[0031] Red mud is a solid waste generated by the aluminum industry when producing alumina. Red mud can purify runoff sewage through different adsorption mechanisms such as surface complexation adsorption, electrostatic attraction and chemical precipitation. In an alkaline environment, it can effectively adsorb Cu 2+ , Pb 2+ Using red mud to replace part of cement can effectively improve the adsorption and purification effect of permeable concrete pavement on heavy metal ions.

[0032] The double-layer permeable concrete can absorb and reduce the noise generated by tires and roads. The standing wave tube is used to test the sound absorption coefficient of permeable concrete to 100-1600Hz spectrum sound waves. The double-layer permeable concrete has excellent anti-clogging performance. The durability of the permeability of the double-layer permeable concrete is tested through indoor clogging-cleaning tests.

[0033] Silicone water repellent can form a hydrophobic film on the inner wall of the pores of permeable concrete, significantly improving the permeability of the permeable concrete. Therefore, while ensuring that the permeable concrete has a large permeability coefficient, a relatively dense permeable concrete can be formed to improve its mechanical properties.

[0034] The present invention replaces part of the cement with red mud and mixes it into the permeable concrete. The double-layer pavement structure design is adopted. On the basis of ensuring the permeability of the permeable concrete, the mechanical properties, anti-clogging properties, purification properties and sound absorption and noise reduction properties of the permeable concrete pavement are synergistically improved; the purification and adsorption properties of red mud are brought into play to achieve the effect of purifying runoff sewage and treating waste with waste, providing a new way to achieve large-scale disposal of red mud; the double-layer structure is adopted to improve the anti-clogging performance of the permeable pavement, improve the durability of the permeability of the permeable pavement, and extend the effective service life of the permeable concrete pavement. The test results show that the double-layer pavement structure of red mud permeable concrete of the present invention has good mechanical properties and permeability. Compared with ordinary permeable concrete pavements, it has excellent anti-clogging performance, purification performance and sound absorption and noise reduction performance.

[0035] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0036] 1) The red mud used in the present invention is a solid waste generated by the aluminum industry when producing alumina. my country has a large production of alumina, and its production and red mud emissions rank first in the world. However, red mud is mostly directly piled up and landfilled. Long-term stacking not only occupies land resources, but also causes environmental pollution. Using red mud to replace part of the cementitious material reduces the cost of permeable concrete, realizes the utilization of solid waste, and improves the purification performance of permeable concrete.

[0037] 2) The red mud permeable concrete double-layer pavement structure of the present invention has higher mechanical properties and water permeability.

[0038] 3) Compared with ordinary permeable concrete pavement, the double-layer red mud permeable concrete pavement structure of the present invention has excellent anti-clogging performance, and the permeability and durability of the permeable pavement are significantly improved.

[0039] 4) Compared with ordinary permeable concrete pavement, the double-layer red mud permeable concrete pavement structure of the present invention has a higher heavy metal ion purification rate and better sound absorption and noise reduction performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a comparison chart of the mechanical properties of double-layer red mud permeable concrete and single-layer red mud permeable concrete (S1, S2) of Example 1 (D1), Example 2 (D2) and Example 3 (D3) of the present invention.

[0041] Figure 2 It is a comparison chart of the water permeability of double-layer red mud permeable concrete and single-layer red mud permeable concrete (S1, S2) of Example 1 (D1), Example 2 (D2) and Example 3 (D3) of the present invention.

[0042] Figure 3 It is a comparison chart of water purification performance of double-layer red mud permeable concrete of Example 1 (D1), Example 2 (D2) and Example 3 (D3) of the present invention and single-layer red mud permeable concrete (S1, S2).

[0043] Figure 4 It is a comparison chart of the anti-clogging performance of double-layer red mud permeable concrete and single-layer red mud permeable concrete (S1, S2) of Example 1 (D1), Example 2 (D2) and Example 3 (D3) of the present invention.

[0044] Figure 5 It is a comparison chart of the sound absorption and noise reduction performance of double-layer red mud permeable concrete and single-layer red mud permeable concrete (S1, S2) of Example 1 (D1), Example 2 (D2) and Example 3 (D3) of the present invention. DETAILED DESCRIPTION

[0045] The present invention is further described in detail below in conjunction with the examples and drawings, but the embodiments of the present invention are not limited thereto. If specific conditions are not specified in the examples, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0046] Example 1 (double-layer permeable concrete D1):

[0047] The raw materials used in this embodiment are as follows:

[0048] Cement: PⅡ52.5 silicate cement, density 3.10g / cm 3 ;

[0049] Red mud: Red mud produced by the Bayer process in Pingguo, Guangxi, with a density of 2.95g / cm 3 The main mineral components of red mud are calcite, hematite, gibbsite, etc.

[0050] Water: City tap water, in compliance with the "Standard for Water Use in Concrete" (JGJ63-2006);

[0051] Water reducing agent: polycarboxylic acid high efficiency water reducing agent;

[0052] Water repellent: Sodium methyl silicate silicone water repellent;

[0053] Aggregate: multi-grade diabase;

[0054] The aggregate of the red mud permeable concrete layer (1) is double-graded aggregate (particle size 2.36-4.75 mm by mass: particle size 4.75-9.5 mm by mass = 7:3), and the designed porosity is 15%; the aggregate of the red mud permeable concrete layer (2) is single-graded aggregate (particle size 4.75-9.5 mm by mass), and the designed porosity is 18%. The thickness of the red mud permeable concrete layer (1) and the thickness of the red mud permeable concrete layer (2) are 30 mm and 70 mm respectively. The mass ratio of cement to red mud in the red mud permeable concrete layer (1) and the red mud permeable concrete layer (2) is 85%:15%; the water-cement ratio is 0.3; the amount of water reducer is 0.3% of the mass of cementitious material; and the amount of effective active ingredient of water repellent is 0.1% of the mass of cementitious material.

[0055] According to the Technical Specification for Permeable Cement Concrete Pavement (CJJ / T 135-2009), red mud permeable concrete is prepared. The specific preparation and application steps are as follows:

[0056] 1) drying the red mud in an oven at 105° C. and grinding it with a grinder, wherein the particle size of the red mud particles after grinding is less than 0.075 mm;

[0057] 2) Add all the aggregates and 50% of the water into a mixer and stir for 30 seconds to fully wet the surface of the aggregates;

[0058] 3) Add 50% of cement, 50% of red mud and 50% of the remaining water and stir for 60 seconds;

[0059] 4) Add all the remaining cement, red mud, water, and all the water reducers and water repellents, and stir for 120 seconds;

[0060] 5) The mixed mixture is loaded into the mold in layers by manual tamping. Each layer is tamped 30 times in the same direction from the edge to the center with a tamping rod, and the top surface is properly compacted with a hammer. Finally, the excess mixture around the mold is removed with a spatula and the surface is filled to obtain a formed red mud permeable concrete layer (2);

[0061] 6) 20 minutes after the red mud permeable concrete layer (2) is formed, the red mud permeable concrete layer (1) is directly inserted and rammed on the upper part of the red mud permeable concrete layer (2) according to steps 1) to 5);

[0062] 7) After the double-layer red mud permeable concrete specimen is formed, a film is covered on the surface of the specimen, placed indoors for 24 hours and then demolded. After demolding, it is moved to a standard curing room and cured to 28 days.

[0063] Embodiment 2 (double-layer permeable concrete D2):

[0064] The raw materials used in this embodiment are as follows:

[0065] Cement: PⅡ52.5 silicate cement, density 3.10g / cm 3 ;

[0066] Red mud: Red mud produced by the Bayer process in Pingguo, Guangxi, with a density of 2.95g / cm 3 The main mineral components of red mud are calcite, hematite, gibbsite, etc.

[0067] Water: City tap water; in accordance with the "Standard for Water Use in Concrete" (JGJ63-2006);

[0068] Water reducer: high efficiency polycarboxylate water reducer;

[0069] Water repellent: Sodium methyl silicate silicone water repellent;

[0070] Aggregate: multi-grade diabase;

[0071] The aggregate of the red mud permeable concrete layer (1) is double-graded aggregate (particle size 2.36-4.75 mm mass: 4.75-9.5 mm mass = 1:1), and its designed porosity is 18%; the aggregate of the red mud permeable concrete layer (2) is single-graded aggregate (particle size 4.75-9.5 mm), and its designed porosity is 21%. The thickness of the red mud permeable concrete layer (1) and the thickness of the red mud permeable concrete layer (2) are 30 mm and 70 mm respectively. In the raw materials of the red mud permeable concrete layer (1) and the red mud permeable concrete layer (2), the mass ratio of cement to red mud is 85%:15%; the water-cement ratio is 0.3; the amount of water reducer is 0.3% of the mass of cementitious material; and the amount of effective active ingredient of water repellent is 0.1% of the mass of cementitious material.

[0072] According to the Technical Specification for Permeable Cement Concrete Pavement (CJJ / T 135-2009), red mud permeable concrete is prepared. The specific preparation and application steps are as follows:

[0073] 1) drying the red mud in an oven at 105° C. and grinding it with a grinder, wherein the particle size of the red mud particles after grinding is less than 0.075 mm;

[0074] 2) Add all the aggregates and 50% of the water into a mixer and stir for 30 seconds to fully wet the surface of the aggregates;

[0075] 3) Add 50% of cement, 50% of red mud and 50% of the remaining water and stir for 60 seconds;

[0076] 4) Add all the remaining cement, red mud, water, and all the water reducers and water repellents, and stir for 120 seconds;

[0077] 5) The mixed mixture is loaded into the mold in layers by manual tamping. Each layer is tamped 30 times in the same direction from the edge to the center with a tamping rod, and the top surface is properly compacted with a hammer. Finally, the excess mixture around the mold is removed with a spatula and the surface is filled to obtain a formed red mud permeable concrete layer (2);

[0078] 6) 20 minutes after the red mud permeable concrete layer (2) is formed, the red mud permeable concrete layer (1) is directly inserted and rammed on the upper part of the red mud permeable concrete layer (2) according to steps 1) to 5);

[0079] 7) After the double-layer red mud permeable concrete specimen is formed, a film is covered on the surface of the specimen, placed indoors for 24 hours and then demolded. After demolding, it is moved to a standard curing room and cured to 28 days.

[0080] Embodiment 3 (double-layer permeable concrete D3):

[0081] The raw materials used in this embodiment are as follows:

[0082] Cement: PⅡ52.5 silicate cement, density 3.10g / cm 3 ;

[0083] Red mud: Red mud produced by the Bayer process in Pingguo, Guangxi, with a density of 2.95g / cm 3 The main mineral components of red mud are calcite, hematite, gibbsite, etc.

[0084] Water: City tap water; in accordance with the "Standard for Water Use in Concrete" (JGJ63-2006);

[0085] Water reducer: high efficiency polycarboxylate water reducer;

[0086] Water repellent: Sodium methyl silicate silicone water repellent;

[0087] Aggregate: multi-grade diabase;

[0088] The aggregate of the red mud permeable concrete layer (1) is single-graded (particle size 2.36-4.75 mm), and its designed porosity is 18%; the aggregate of the red mud permeable concrete layer (2) is single-graded (particle size 4.75-9.5 mm), and its designed porosity is 21%. The thickness of the red mud permeable concrete layer (1) and the thickness of the red mud permeable concrete layer (2) are 30 mm and 70 mm respectively. In the raw materials of the red mud permeable concrete layer (1) and the red mud permeable concrete layer (2), the mass ratio of cement to red mud is 85%:15%; the water-cement ratio is 0.3; the amount of water reducer is 0.3% of the mass of cementitious materials; and the amount of effective active ingredients of water repellent is 0.1% of the mass of cementitious materials.

[0089] According to the Technical Specification for Permeable Cement Concrete Pavement (CJJ / T 135-2009), red mud permeable concrete is prepared. The specific preparation and application steps are as follows:

[0090] 1) drying the red mud in an oven at 105° C. and grinding it with a grinder, wherein the particle size of the red mud particles after grinding is less than 0.075 mm;

[0091] 2) Add all the aggregates and 50% of the water into a mixer and stir for 30 seconds to fully wet the surface of the aggregates;

[0092] 3) Add 50% of cement, 50% of red mud and 50% of the remaining water and stir for 60 seconds;

[0093] 4) Add all the remaining cement, red mud, water, and all the water reducers and water repellents, and stir for 120 seconds;

[0094] 5) The mixed mixture is loaded into the mold in layers by manual tamping. Each layer is tamped 30 times in the same direction from the edge to the center with a tamping rod, and the top surface is properly compacted with a hammer. Finally, the excess mixture around the mold is removed with a spatula and the surface is filled to obtain a formed red mud permeable concrete layer (2);

[0095] 6) 20 minutes after the red mud permeable concrete layer (2) is formed, the red mud permeable concrete layer (1) is directly inserted and rammed on the upper part of the red mud permeable concrete layer (2) according to steps 1) to 5);

[0096] 7) After the double-layer red mud permeable concrete specimen is formed, a film is covered on the surface of the specimen, placed indoors for 24 hours and then demolded. After demolding, it is moved to a standard curing room and cured to 28 days.

[0097] Comparative example (single-layer red mud permeable concrete S1, S2)

[0098] In order to highlight the performance advantages of the double-layer red mud permeable concrete pavement structure, single-layer red mud permeable concrete (S1 and S2) of the same thickness were used for comparison.

[0099] Single-layer red mud permeable concrete S1 and S2 both use single-grade aggregate (particle size 4.75-9.5mm), the mass ratio of cement to red mud is 85%:15%, and the thickness is 100mm. The water-cement ratio is 0.3, the amount of water reducer is 0.3% of the mass of cementitious materials, and the amount of effective active ingredients of water repellent is 0.1% of the mass of cementitious materials. The designed porosity of single-layer red mud permeable concrete S1 and S2 is 18% and 21% respectively.

[0100] The gradation and design porosity of the single-layer red mud permeable concrete S1 are the same as those of the lower layer of the double-layer permeable concrete D1.

[0101] The gradation and design porosity of the single-layer red mud permeable concrete S2 are the same as the gradation and design porosity of the lower layer of the double-layer permeable concrete D2 and D3, respectively.

[0102] According to the Technical Specification for Permeable Cement Concrete Pavement (CJJ / T 135-2009), red mud permeable concrete is prepared. The specific preparation and application steps of single-layer red mud permeable concrete S1 and S2 are as follows:

[0103] 1) drying the red mud in an oven at 105° C. and grinding it with a grinder, wherein the particle size of the red mud particles after grinding is less than 0.075 mm;

[0104] 2) Add all the aggregates and 50% of the water into a mixer and stir for 30 seconds to fully wet the surface of the aggregates;

[0105] 3) Add 50% of cement, 50% of red mud and 50% of the remaining water and stir for 60 seconds;

[0106] 4) Add all the remaining cement, red mud, water, and all the water reducers and water repellents, and stir for 120 seconds;

[0107] 5) The mixed mixture is loaded into the mold in layers by manual tamping method. Each layer is tamped 30 times in the same direction from the edge to the center with a tamping rod, and the top surface is properly compacted with a hammer. Finally, the excess mixture around the mold is removed with a spatula and the surface is filled to obtain a formed red mud permeable concrete;

[0108] 6) After the red mud permeable concrete specimens are formed, a film is covered on the surface of the specimens, placed indoors for 24 hours, and then demolded. After demolding, they are moved to a standard curing room and cured to 28 days.

[0109] Based on the study of surface runoff sewage in Guangzhou, various heavy metal ions (Cu 2+ or Pb 2+ ) concentration of 1.5 mg / L aqueous solution. 2+ , Pb2+ 1L of runoff sewage passes through a cubic permeable concrete specimen with a side length of 100mm, and the filtrate is collected. The purification rate of red mud permeable concrete for each pollutant is calculated by dividing the difference in pollutant concentration before and after purification by the initial concentration of each pollutant.

[0110] For the above Cu 2+ , Pb 2+ The contaminated liquid was CuCl 2 、PbCl 2 The solution was prepared, and the concentration of each metal ion in the solution before and after purification was detected by atomic absorption spectrophotometer.

[0111] The 28d compressive strength and 28d flexural strength of permeable concrete specimens were tested in accordance with the "Test Code for Cement and Cement Concrete for Highway Engineering" (JTG 3420-2020).

[0112] The permeability coefficient of permeable concrete specimens was tested in accordance with the Technical Specification for Permeable Cement Concrete Pavement (CJJ / T 135-2009).

[0113] Fully graded sand is used as the plugging material, and the mass ratio of its particle size composition is (1.18-2.36) mm: (0.6-1.18) mm: (0.3-0.6) mm: (0.15-0.3) mm = 30%: 35%: 25%: 10%. An indoor plugging-cleaning test is carried out to test the anti-blocking performance of permeable concrete.

[0114] The indoor blockage-cleaning test steps are as follows:

[0115] (1) Determination of the initial permeability coefficient k of red mud permeable concrete specimens 0 ;

[0116] (2) Collect the blockage particles on the road surface and estimate the blockage mass m of the specimen area in one year. Place the specimen in the device for testing the water permeability coefficient, and evenly spread the prepared blockage on the surface of the specimen. The amount of each spreading is the same mass m of full-graded sand. Turn on the shower to inject water into the test device. To avoid the blockage from agglomerating, use a glass rod to stir appropriately during the process. After the water circulates for 120 seconds, one blockage test is completed;

[0117] (3) Repeat step (2) 8 times to complete 8 continuous blocking tests so that the specimen is fully blocked;

[0118] (4) After the 8 continuous blockage tests, the specimen was rinsed with a high-pressure water gun. The specific cleaning method is: keep the muzzle of the high-pressure water gun 20 cm away from the surface of the specimen, tilt the muzzle so that the water flow is about 60 degrees to the surface of the specimen, continue to rinse for 1 minute, test the water permeability coefficient of the cleaned specimen, and complete one blockage-cleaning test.

[0119] (5) Repeat steps (2), (3), and (4) 6 times, for a total of 6 plugging-cleaning cycle tests.

[0120] The permeability coefficient recovery rate ε of permeable concrete is defined to represent the recovery effect of the permeability coefficient of permeable concrete after being washed by a high-pressure water gun. The calculation formula is as shown in formula (1).

[0121]

[0122] Where: ε i ——Recovery rate of water permeability coefficient of the ith plugging-cleaning test (%);

[0123] k i ——Water permeability coefficient after the ith clogging-cleaning test (mm / s);

[0124] k 0 ——Initial water permeability coefficient (mm / s).

[0125] A standing wave tube was used to carry out the noise reduction test of permeable concrete specimens. The test steps were based on the national standard "Measurement of Sound Absorption Coefficient and Acoustic Impedance in Acoustic Impedance Tubes" (GB / T 18696.2-2002) to test the sound absorption and noise reduction performance of permeable concrete.

[0126] From the comparison of the test results of double-layer permeable concrete and single-layer permeable concrete,

[0127] (1) The compressive strength and flexural strength of the double-layer permeable concrete D1 prepared by the method provided by the present invention are 31.6MPa and 4.78MPa, respectively, which are 3.61% and 4.60% higher than those of the single-layer permeable concrete S1 with the same porosity and gradation in the lower layer; the compressive strength and flexural strength of the double-layer permeable concrete D2 and D3 are 28.2MPa, 4.08MPa, 26.6MPa, 4.01MPa, respectively, which are 11.46%, 3.03%, 5.14%, 1.26% higher than those of the single-layer permeable concrete S2 with the same porosity and gradation in the lower layer. The double-layer permeable concrete D1 meets the strength requirements of C30 concrete, and the double-layer permeable concretes D2 and D3 meet the strength requirements of C25 concrete, indicating that the double-layer permeable concrete of the present invention has good mechanical properties.

[0128] (2) The water permeability coefficient of the double-layer permeable concrete D1 prepared by the method provided by the present invention is 4.08 mm / s, which is 26.09% lower than that of the single-layer permeable concrete S1 with the same porosity and gradation in the lower layer; the water permeability coefficients of the double-layer permeable concrete D2 and D3 are 6.01 and 6.29 mm / s respectively, which are 38.30% and 35.42% lower than that of the single-layer permeable concrete S2 with the same porosity and gradation in the lower layer. This is due to the reduction of the porosity of the upper material of the double-layer permeable concrete and the use of small-size aggregate gradation. However, the water permeability coefficients of the double-layer permeable concrete D1, D2, and D3 of the present invention far exceed the requirement of the permeability coefficient value of permeable concrete greater than 0.5 mm / s stipulated in the specification, indicating that the double-layer permeable concrete of the present invention has good water permeability.

[0129] (3) Cu of double-layer permeable concrete D1 prepared by the method provided by the present invention 2+ , Pb 2+ The purification rates were 85.32% and 92.37% respectively, which were 14.97% and 11.38% higher than those of the single-layer permeable concrete S1 with the same porosity and gradation in the lower layer. The Cu 2+ , Pb 2+ The purification rates are 78.79%, 90.44%, 74.52% and 84.73% respectively; compared with the single-layer permeable concrete S2 with the same porosity and gradation in the lower layer, they are increased by 25.04%, 23.84%, 18.27% and 16.02% respectively. This shows that the double-layer permeable concrete of the present invention has good performance in purifying heavy metal ions.

[0130] (4) The average value of the six permeability coefficient recovery rates obtained from the six plugging-cleaning tests of the double-layer permeable concrete D1 prepared by the method provided by the present invention is 48.53%, which is 9.37% higher than that of the single-layer permeable concrete S1 with the same porosity and gradation of the lower layer. The average values ​​of the six permeability coefficient recovery rates obtained from the six plugging-cleaning tests of the double-layer permeable concrete D2 and D3 are 56.88% and 56.12%, respectively; compared with the single-layer permeable concrete S2 with the same porosity and gradation of the lower layer, they are 11.94% and 11.18% higher, respectively. This shows that the double-layer permeable concrete of the present invention has good anti-blockage durability.

[0131] (5) The peak value of the sound absorption coefficient of the double-layer permeable concrete D1 prepared by the method provided by the present invention is 0.789, which appears at a frequency of 700 Hz. The peak value of the sound absorption coefficient of the single-layer permeable concrete S1 with the same porosity and gradation as the lower layer is 0.643, which appears at a frequency of 900 Hz. The peak values ​​of the sound absorption coefficients of the double-layer permeable concretes D2 and D3 are 0.771 and 0.731, respectively, both appear at a frequency of 800 Hz. The peak value of the sound absorption coefficient of the single-layer permeable concrete S2 with the same porosity and gradation as the lower layer is 0.67, which appears at a frequency of 1000 Hz. This indicates that the peak value of the sound absorption coefficient of the double-layer permeable concrete of the present invention moves to the frequency range of 600 to 800 Hz, and a "peak left shift" phenomenon occurs, and the sound absorption coefficient of the double-layer permeable concrete at a frequency of 1600 Hz shows another peak. Compared with single-layer permeable concrete, double-layer permeable concrete has a larger sound absorption coefficient in the frequency range of 600-800Hz and 1400-1600Hz, and there are two obvious sound absorption coefficient peaks, which can effectively absorb medium-low frequency and medium-high frequency noise and have better sound absorption and noise reduction performance.

[0132] In summary, while ensuring good permeability, the ecological double-layer red mud permeable concrete has excellent mechanical properties, purification performance, anti-clogging performance and sound absorption and noise reduction performance compared with single-layer permeable concrete.

[0133] Compared with double-layer permeable concrete D2 and D3, D2 is preferred. The mechanical properties, purification performance, anti-clogging performance and sound absorption and noise reduction performance of the double-layer permeable concrete D2 with double-graded aggregate (particle size 2.36-4.75mm mass: 4.75-9.5mm mass = 1:1) in the upper layer are better than those of the double-layer permeable concrete D3 with single-graded aggregate (particle size 2.36-4.75mm) in the upper layer, and are also better than those of the single-layer permeable concrete S2 with single-graded aggregate (particle size 4.75-9.5mm). The permeability coefficient of the double-layer permeable concrete D2 reaches 6.01mm / s, which has excellent permeability.

[0134] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A red mud permeable concrete double-layer pavement structure, characterized in that: The pavement structure comprises, from top to bottom: a red mud permeable concrete layer (1) and a red mud permeable concrete layer (2); The red mud permeable concrete layer (1) and the red mud permeable concrete layer (2) both comprise the following raw materials: graded aggregate, cementitious material, water, water reducing agent and water repellent, wherein the cementitious material comprises cement and red mud; The graded aggregate of the red mud permeable concrete layer (1) is a double-graded aggregate with a mass ratio of particle size 2.36-4.75 mm:4.75-9.5 mm=(50%-100%):(50%-0%), and the graded aggregate of the red mud permeable concrete layer (2) is a single-graded aggregate with a particle size of 4.75-9.5 mm.

2. The red mud permeable concrete double-layer pavement structure according to claim 1 is characterized in that: The graded aggregate of the concrete layer (1) is a double-graded aggregate with a mass ratio of particle size 2.36-4.75 mm:4.75-9.5 mm=(50%-70%):(50%-30%).

3. The red mud permeable concrete double-layer pavement structure according to claim 1 is characterized in that: The designed porosity of the red mud permeable concrete layer (1) is 15% to 21%; the designed porosity of the red mud permeable concrete layer (2) is 18% to 24%.

4. The red mud permeable concrete double-layer pavement structure according to claim 1 is characterized in that: The designed porosity of the concrete layer (2) is greater than the designed porosity of the concrete layer (1).

5. The red mud permeable concrete double-layer pavement structure according to claim 1 is characterized in that: The cement in the red mud permeable concrete layer (1) is general-purpose silicate cement with a strength of not less than 52.5; the red mud is Bayer red mud; the graded aggregates are all diabase aggregates; the water reducer is a polycarboxylic acid high-efficiency water reducer; the water repellent is a sodium methyl silicate organic silicon water repellent; the mass ratio of cement to red mud is (80-90):(10-20); the mass ratio of the graded aggregate to the cementitious material is 1:(0.25-0.35); the amount of water used satisfies a water-cement ratio of 0.28-0.35; the amount of the water reducer and the water repellent is 0.1%-0.3% of the mass of the cementitious material; The cement in the red mud permeable concrete layer (2) is general silicate cement with a strength of not less than 52.5; the red mud is Bayer red mud; the graded aggregates are all diabase aggregates; the water reducer is a polycarboxylic acid high-efficiency water reducer; the water repellent is a sodium methyl silicate organic silicon water repellent; the mass ratio of cement to red mud is (80-90):(10-20); the mass ratio of the graded aggregate to the cementitious material is 1:(0.25-0.35); the amount of water used satisfies a water-cement ratio of 0.28-0.35; the amount of the water reducer and the water repellent is 0.1%-0.3% of the mass of the cementitious material.

6. The red mud permeable concrete double-layer pavement structure according to claim 1 is characterized in that: The thickness ratio of the red mud permeable concrete layer (1) to the red mud permeable concrete layer (2) is (30-50):(70-150).

7. A method for preparing a double-layer red mud permeable concrete pavement structure according to any one of claims 1 to 6, characterized in that: The red mud permeable concrete layer (1) is prepared by the following method: M11: Add all the aggregates and 40% to 60% of water into the mixer and mix for 30 to 40 seconds to make the surface of the aggregates fully wet; M12: Add 40% to 60% of cement, 40% to 60% of red mud and 40% to 60% of the remaining water, and stir for 50 to 70 seconds; M13: Add the remaining cement, the remaining red mud, the remaining water, and all the water reducers and water repellents, and stir for 110 to 130 seconds; The red mud permeable concrete layer (2) is prepared by the following method: M21: Add all the aggregates and 40% to 60% of water into the mixer and mix for 30 to 40 seconds to fully wet the surface of the aggregates; M22: Add 40% to 60% of cement, 40% to 60% of red mud and 40% to 60% of the remaining water, and stir for 50 to 70 seconds; M23: Add the remaining cement, remaining red mud, remaining water, and all water reducers and water repellents, and stir for 110 to 130 seconds; The red mud permeable concrete layer (1) and the red mud permeable concrete layer (2) are formed by a "wet joint" construction process, and the time interval between the "wet joint" of the upper and lower layers is 15 to 25 minutes.

8. The method for preparing a double-layer red mud permeable concrete pavement structure according to claim 7, characterized in that The specific steps include: The raw materials are mixed evenly according to steps M21-M23, and then molded in a mold to obtain a red mud permeable concrete layer (2). 15 to 25 minutes after the red mud permeable concrete layer (2) is molded, the mixture mixed evenly according to steps M11-M13 is loaded into the test mold on which the red mud permeable concrete layer (2) has been molded to obtain a red mud permeable concrete layer (1), which is then left to stand, thereby obtaining a red mud permeable concrete double-layer pavement structure.

9. The method for preparing a double-layer red mud permeable concrete pavement structure according to claim 7, characterized in that The specific steps include: The molding refers to molding in a mold by manual tamping, which specifically includes the following steps: the mixed mixture is loaded into the mold in layers by manual tamping, and each layer is tamped 25 to 35 times from the edge to the center in the same direction with a tamping rod, and the top surface is properly compacted with a hammer, and finally, the excess mixture around the mold is removed with a spatula and the surface is filled; The said standing still means that the formed test piece is left standing still indoors for 24 hours.

10. Application of the red mud permeable concrete double-layer pavement structure according to any one of claims 1 to 6 in permeable pavement.

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