A method for determining the mix proportion of solid waste-based recycled asphalt mixture

Abstract

This invention belongs to the field of solid waste resource recycling technology, and in particular, a method for determining the proportion of solid waste-based recycled asphalt mixtures. The invention includes the following steps: S1, preparing solid waste-based recycled asphalt mixtures; S2, measuring the specific surface area of ​​the sample and calculating the porosity of the steel slag asphalt mixture and the amount of old asphalt mixture with a particle size ≤4.75mm; S3, calculating the amount of newly added asphalt in the solid waste-based recycled asphalt mixture based on the thickness of the asphalt film formed on the surface of steel slag particles with a particle size ≤4.75mm after the asphalt in the old asphalt mixture with a particle size ≤4.75mm is transferred to the surface.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource recycling technology, and particularly relates to a method for determining the proportion of solid waste-based recycled asphalt mixture. Background Technology

[0002] Steel slag is an industrial solid waste, the slag discharged from steelmaking. Extensive testing and engineering practice have proven that steel slag can replace natural aggregates in various structural layers, particularly suitable for heavy-duty traffic sections requiring rutting resistance. On the other hand, the total length of highways in operation nationwide is 5.35 million kilometers, of which asphalt pavement accounts for 68%. Due to various harsh conditions during their service life, these pavements generally develop various problems after about 5 years, requiring minor maintenance, and major repairs after about 10 years. Simultaneously, with the gradual increase in traffic volume, large-scale highways face the need for modification and expansion, generating a large amount of used asphalt mixture. Failure to utilize this would be a huge waste. Preparing solid waste-based recycled asphalt mixtures from steel slag and used asphalt mixtures provides an effective way to utilize these resources, representing a technology that integrates environmental protection, green practices, and low carbon emissions.

[0003] Road recycling technology refers to the process of remixing old asphalt pavement that needs repair or is abandoned with recycling agents, new asphalt, and new aggregates in a certain proportion to form a new mixture for use. In road recycling technology, the portion of the old asphalt mixture with a particle size greater than 4.75mm can generally be used as aggregate. Old asphalt mixtures with a particle size ≤4.75mm have a high old asphalt content and high recycling value. However, the amount and effect of old asphalt transfer in old asphalt mixtures with a particle size ≤4.75mm are uncertain, and the interaction between the newly added asphalt and the old asphalt is unclear, leading to significant variability in the performance of recycled asphalt mixtures, thus limiting their application.

[0004] Therefore, there is an urgent need for a method to determine the mix proportions of solid waste-based recycled asphalt mixtures to solve the above problems. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, this invention provides a method for determining the mix proportion of solid waste-based recycled asphalt mixtures. This invention effectively controls the amount of newly added asphalt and the amount of old asphalt mixture with a particle size ≤4.75mm, ensuring that the solid waste-based recycled asphalt mixture has good road performance.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for determining the mix proportion of a solid waste-based recycled asphalt mixture includes the following steps:

[0008] S1. Prepare solid waste-based recycled asphalt mixture, which includes steel slag with particle sizes of 4.75-9.5mm and 9.5-16mm, old asphalt mixture with particle size ≤4.75mm, and newly added asphalt; and extract the old asphalt mixture with particle size ≤4.75mm to determine the particle size composition and asphalt content of the aggregate in the old asphalt mixture.

[0009] S2. Measure the specific surface area of ​​the sample and calculate the porosity of the steel slag asphalt mixture. According to the volumetric filling theory, the old asphalt mixture with a particle size ≤4.75mm and some newly added asphalt fill the voids formed by the steel slag after the asphalt is coated with particles of 4.75~9.5mm and 9.5~16mm. The remaining voids are the porosity of the solid waste-based recycled asphalt mixture. Calculate the amount of old asphalt mixture with a particle size ≤4.75mm.

[0010] S3. Based on the thickness of the asphalt film formed on the surface of steel slag in old asphalt mixtures with a particle size ≤ 4.75mm, calculate the amount of newly added asphalt in the recycled asphalt mixture based on solid waste. The calculation formula is as follows:

[0011] + ;

[0012] In the formula:

[0013] P a - The amount of newly added asphalt in solid waste-based recycled asphalt mixture, %

[0014] μ - Optimal bitumen film thickness, μm;

[0015] μ aj - The thickness of the asphalt film on the surface of the steel slag after mixing old asphalt mixture with a particle size ≤ 4.75 mm with steel slag, in μm;

[0016] P c - Steel slag content in solid waste-based recycled asphalt mixture, %

[0017] ρ a - Density of asphalt, g / cm³ 3 ;

[0018] Specific surface area (m²) of steel slag with a particle size of SA1-4.75~9.5mm. 2 / kg;

[0019] The percentage of steel slag with a particle size of L1-4.75~9.5mm, %

[0020] Specific surface area of ​​SA2-9.5~16mm particle size steel slag, m² 2 / kg;

[0021] P j- Percentage of used asphalt mixture in solid waste-based recycled asphalt mixture, %

[0022] μ j - Average asphalt film thickness on aggregate surface in old asphalt mixtures, μm;

[0023] SA j -Specific surface area of ​​aggregates in old asphalt mixtures with a particle size ≤ 4.75 mm, in m² 2 / kg.

[0024] Preferably, the method for determining the specific surface area of ​​the sample is as follows: Take a sample of ≥500g, soak it in water for 24h, filter it, pour it into an iron cup, place absorbent paper at the bottom of the iron cup and separate it with filter paper at the top, put it in a centrifuge and rotate it for 2~3min, weigh the sample mass; put it in an oven to dry, weigh the dried sample mass, and calculate the specific surface area of ​​the sample based on the thickness of the water film on the sample surface and the volume of adsorbed water.

[0025] Preferably, the formula for calculating the specific surface area of ​​the sample is:

[0026] ;

[0027] In the formula:

[0028] SA - Specific surface area of ​​the sample, m² / kg;

[0029] m s - Mass of the sample after immersion in water and centrifugation, in g;

[0030] m g - Sample mass after drying, g;

[0031] μ s -Water film thickness, μm;

[0032] ρ s - The density of water, g / cm³;

[0033] m k -Sample mass at the time of sampling, in grams.

[0034] Preferably, the method for determining the void ratio of steel slag asphalt mixture is as follows: Based on engineering experience and relevant specifications, determine the proportion of steel slag with particle sizes of 4.75–9.5 mm and 9.5–16 mm. According to the asphalt film-forming theory, asphalt can coat steel slag with particle sizes of 4.75–9.5 mm and 9.5–16 mm at the optimal asphalt film thickness. Calculate the amount of asphalt coated with steel slag based on the specific surface area of ​​the steel slag and the thickness of the asphalt film. Prepare Marshall specimens based on the proportion of steel slag with particle sizes of 4.75–9.5 mm and 9.5–16 mm and the amount of asphalt, and calculate the void ratio of the steel slag asphalt mixture.

[0035] Preferably, the formula for calculating the void ratio of steel slag asphalt mixture is:

[0036] ;

[0037] ;

[0038] ;

[0039] In the formula:

[0040] L a - Asphalt dosage when coating steel slag with the optimal asphalt film thickness, %

[0041] μ - Optimal bitumen film thickness, μm;

[0042] ρ a - Density of asphalt, g / cm³;

[0043] Specific surface area of ​​steel slag with a particle size of SA1-4.75~9.5mm, m² / kg;

[0044] The percentage of steel slag with a particle size of L1-4.75~9.5mm, %

[0045] Specific surface area of ​​SA2-9.5~16mm particle size steel slag, m² / kg;

[0046] ρ h - Maximum theoretical density of steel slag asphalt mixture, g / cm³;

[0047] Density of steel slag with a particle size of ρ1-4.75~9.5mm, g / cm³;

[0048] Density of steel slag with a particle size of ρ2-9.5~16mm, g / cm³;

[0049] VC-steel slag asphalt mixture porosity, %

[0050] ρ m - Bulk density of steel slag asphalt mixture, g / cm³;

[0051] The preferred formula for calculating the amount of old asphalt mixture with a particle size ≤ 4.75mm is:

[0052] ;

[0053] ;

[0054] ;

[0055] + =100;

[0056] In the formula:

[0057] SA j -Specific surface area of ​​aggregates in old asphalt mixtures with a particle size ≤ 4.75 mm, in m² 2 / kg;

[0058] a-Passing rate of aggregates in old asphalt mixtures with a particle size ≤ 4.75mm through a 4.75mm sieve;

[0059] b - The passing rate of aggregates in old asphalt mixtures with a particle size ≤ 4.75 mm through a 2.36 mm sieve;

[0060] c - Passing rate of aggregates in old asphalt mixtures with a particle size ≤ 4.75 mm through a 1.18 mm sieve;

[0061] The passing rate of aggregates in old asphalt mixtures with a particle size ≤ 4.75 mm through a 0.6 mm sieve.

[0062] The passing rate of aggregates in old asphalt mixtures with a particle size ≤ 4.75 mm through a 0.3 mm sieve.

[0063] f - Passing rate of aggregates in old asphalt mixtures with a particle size ≤ 4.75 mm through a 0.15 mm sieve;

[0064] g - The passing rate of aggregates in old asphalt mixtures with a particle size ≤ 4.75 mm through a 0.075 mm sieve;

[0065] μ j - Average asphalt film thickness on aggregate surface in old asphalt mixtures with particle size ≤ 4.75 mm, in μm;

[0066] P aj - Asphalt-aggregate ratio in old asphalt mixtures with particle size ≤ 4.75mm, %

[0067] SA j -Specific surface area of ​​aggregates in old asphalt mixtures with a particle size ≤ 4.75 mm, in m² 2 / kg;

[0068] ρ a - Density of asphalt, g / cm³ 3 ;

[0069] P j - The percentage of recycled asphalt mixture with a particle size ≤4.75mm in the solid waste-based recycled asphalt mixture, %

[0070] μ - Optimal bitumen film thickness, μm;

[0071] P c - Steel slag content in solid waste-based recycled asphalt mixture, %

[0072] ρ j - Density of old asphalt mixture with particle size ≤ 4.75mm, g / cm³ 3 ;

[0073] ρ c - Bulk density of steel slag asphalt mixture after compaction, g / cm³ 3 ;

[0074] VC-steel slag asphalt mixture porosity, %

[0075] VV-solid waste-based recycled asphalt mixture design void ratio, %.

[0076] Preferably, the old asphalt mixture with a particle size ≤4.75mm has a moisture content ≤2.0%, wherein the old asphalt is old SBS modified asphalt; and the newly added asphalt is SBS modified asphalt.

[0077] Preferably, the water film thickness is 8-12 μm; the optimal asphalt film thickness is 13-16 μm.

[0078] The preferred formula for calculating the thickness of the asphalt film on the surface of the steel slag after mixing old asphalt mixture with a particle size ≤4.75mm is as follows:

[0079]

[0080] In the formula:

[0081] μ aj - The thickness of the asphalt film on the surface of the steel slag after mixing old asphalt mixture with a particle size ≤ 4.75 mm with steel slag, in μm;

[0082] P acj - The asphalt content of the old asphalt mixture with a particle size ≤4.75mm after mixing with steel slag, %

[0083] m j - The mass of old asphalt mixture in the mixture of old asphalt mixture with steel slag after mixing with particle size ≤4.75mm, in g;

[0084] m1 - The mass of steel slag with a particle size of 4.75 to 9.5 mm in the mixture of old asphalt mixture with a particle size ≤ 4.75 mm and steel slag, in g;

[0085] The mass (g) of steel slag with a particle size of 9.5–16 mm in the mixture of old asphalt mixture with a particle size ≤ 4.75 mm and steel slag.

[0086] Preferably, the design void ratio of the solid waste-based recycled asphalt mixture is 3-6%.

[0087] The advantages of this invention are:

[0088] (1) The present invention adopts the principle of volume filling, with asphalt coating steel slag to form a matrix skeleton. The old asphalt mixture with a particle size ≤4.75mm interacts with the new asphalt and fills the skeleton voids. By controlling the mixing ratio of old asphalt mixture and steel slag through volume parameters, the skeleton of solid waste-based asphalt mixture is ensured to have a dense structure and to give full play to the maximum value of old asphalt mixture, thus achieving controllable performance.

[0089] (2) The present invention accurately calculates the amount of new asphalt added and the blending ratio of old asphalt mixture with a particle size ≤4.75mm, so that the interaction effect of the newly added asphalt, steel slag and old asphalt mixture with a particle size ≤4.75mm reaches the optimal state, ensuring that the solid waste-based recycled asphalt mixture has good road performance.

[0090] (3) During the mixing process of old asphalt mixture and steel slag, the old asphalt is partially transferred to the surface of steel slag to form an asphalt film. Considering the thickness of the asphalt film on the surface of steel slag and old asphalt mixture after transfer, the aggregate in steel slag and old asphalt mixture reaches the optimal asphalt film thickness, thereby providing a scientific and effective method for calculating the amount of new asphalt added in solid waste-based recycled asphalt mixture, thus effectively exerting the bonding effect of new and old asphalt, which is conducive to the interaction between raw materials and exerts better performance.

[0091] (4) Based on the mixing ratio of steel slag and old asphalt mixture in solid waste-based recycled asphalt mixture, the present invention uses a certain test method to accurately determine the thickness of old asphalt film transferred from old asphalt mixture to steel slag surface, thereby ensuring the accuracy of the calculation of the amount of new asphalt added during the production process of solid waste-based recycled asphalt mixture and ensuring material performance. Detailed Implementation

[0092] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0093] A method for determining the mix proportion of a solid waste-based recycled asphalt mixture includes the following steps:

[0094] Solid waste-based recycled asphalt mixtures include steel slag with particle sizes of 4.75–9.5 mm and 9.5–16 mm, used asphalt mixtures with particle sizes ≤4.75 mm, and newly added asphalt. The results of testing the steel slag raw materials are shown in Table 1 below:

[0095] Table 1. Steel slag test results

[0096]

[0097] Extraction was performed on old asphalt mixtures with a particle size ≤ 4.75 mm to determine the particle size distribution and asphalt content of the aggregates. The sieving results and raw material test results after extraction are shown in Table 2-3 below:

[0098] Table 2. Sieving results of old asphalt mixture after extraction

[0099]

[0100] Table 3 Test Results of Raw Materials for Old Asphalt Mixture

[0101]

[0102] Based on relevant specifications and engineering experience, steel slag with particle sizes of 4.75–9.5 mm and 9.5–16 mm adopts a skeleton structure. According to the SMA13 gradation requirements, the proportion of steel slag with each particle size is determined, and the results are shown in Table 4 below.

[0103] Table 4 Results of steel slag gradation

[0104]

[0105] Take steel slag samples and weigh them as shown in Table 5 below:

[0106] Table 5 Sample quality

[0107]

[0108] The specific surface area of ​​each sample was determined using the following method: ≥500g of sample was soaked in water for 24 hours, filtered, and then poured into an iron cup. The bottom of the iron cup was lined with absorbent paper, and the top was separated by filter paper. The cup was then placed in a centrifuge and centrifuged for 3 minutes. The mass of the sample was then measured. The mass of each sample after centrifugation was determined using the same method. The mass of each sample after centrifugation is shown in Table 6 below.

[0109] Table 6. Mass after immersion in water and centrifugation

[0110]

[0111] After drying in an oven, the masses of each sample are shown in Table 7 below:

[0112] Table 7. Drying quality

[0113]

[0114] The water film thickness was 10 μm. Based on the water film thickness and the volume of adsorbed water on the sample surface, the specific surface area of ​​each sample was calculated using the following formula, and the results are shown in Table 8:

[0115] ;

[0116] Table 8 Specific Surface Area of ​​Materials

[0117]

[0118] Based on the theory of asphalt film formation, steel slag is coated with asphalt at the optimal asphalt film thickness. The amount of asphalt coated with steel slag is calculated by combining the specific surface area of ​​the steel slag and the asphalt film thickness. According to the proportion of steel slag of various particle sizes and the amount of asphalt used, the optimal asphalt film thickness is taken as 14 μm. Marshall specimens were prepared, and their bulk density was determined to be 2.45 g / cm³. 3 The void ratio of steel slag asphalt mixture is calculated according to the following formula.

[0119]

[0120] = 3.13

[0121]

[0122] According to the volumetric filling theory, old asphalt mixture with a particle size ≤4.75mm fills the voids formed by asphalt-coated steel slag, and the remaining voids are 4.0% of the void ratio of solid waste-based asphalt mixture. The amount of old asphalt mixture with a particle size ≤4.75mm is calculated according to the following formula.

[0123] = 8.12

[0124] = 8.13

[0125]

[0126] + =100

[0127] Calculated =13.4%, =86.6%.

[0128] Based on the calculated blending ratios of steel slag of various particle sizes and old asphalt mixture with a particle size ≤4.75mm, a 4500kg mixture sample was prepared. 1558kg of steel slag with a particle size of 4.75–9.5mm and 2338kg of steel slag with a particle size of 9.5–16mm were heated to 190℃, and 603kg of old asphalt mixture with a particle size ≤4.75mm was heated to 120℃. The mixture was poured into a mixing pot and stirred for 1.2 minutes. After cooling, the steel slag with particle sizes of 4.75–9.5mm and 9.5–16mm was manually sieved and removed. The remaining material was extracted, and its asphalt content was determined to be 4.1%. The thickness of the asphalt film on the surface of the steel slag after mixing the steel slag with particle sizes of 4.75–9.5mm, 9.5–16mm, and old asphalt mixture with a particle size ≤4.75mm was calculated using the following formula.

[0129] =1.27

[0130] Based on the asphalt transfer rate in old asphalt mixtures with a particle size ≤ 4.75mm, the amount of newly added asphalt in old asphalt mixtures with a particle size ≤ 4.75mm is calculated according to the following formula.

[0131] + =4.42

[0132] Based on the above design results, the following components were prepared: 34.64% steel slag with a particle size of 4.75–9.5 mm, 51.96% steel slag with a particle size of 9.5–16 mm, 13.4% old asphalt mixture with a particle size ≤4.75 mm, and 4.42% newly added SBS modified asphalt. The results of various properties of the prepared solid waste-based recycled asphalt mixture are shown in Table 9.

[0133] Table 9

[0134]

[0135] As shown in Table 9, the solid waste-based recycled asphalt mixture prepared by the method of the present invention meets all the technical requirements.

[0136] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of 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 method for determining the mix proportion of solid waste-based recycled asphalt mixture, characterized in that, Includes the following steps: S1. Prepare solid waste-based recycled asphalt mixture, which includes steel slag with particle sizes of 4.75-9.5mm and 9.5-16mm, old asphalt mixture with particle size ≤4.75mm, and newly added asphalt; and extract the old asphalt mixture with particle size ≤4.75mm to determine the particle size composition and asphalt content of the aggregate in the old asphalt mixture. S2. Measure the specific surface area of ​​the sample and calculate the porosity of the steel slag asphalt mixture. According to the volumetric filling theory, the old asphalt mixture with a particle size ≤4.75mm and some newly added asphalt fill the voids formed by the steel slag after the asphalt is coated with particles of 4.75~9.5mm and 9.5~16mm. The remaining voids are the porosity of the solid waste-based recycled asphalt mixture. Calculate the amount of old asphalt mixture with a particle size ≤4.75mm. S3. Based on the thickness of the asphalt film formed on the surface of steel slag in old asphalt mixtures with a particle size ≤ 4.75mm, calculate the amount of newly added asphalt in the recycled asphalt mixture based on solid waste. The calculation formula is as follows: + ； In the formula: P a - The amount of newly added asphalt in solid waste-based recycled asphalt mixture, % μ - Optimal bitumen film thickness, μm; μ aj - The thickness of the asphalt film on the surface of the steel slag after mixing old asphalt mixture with a particle size ≤ 4.75 mm with steel slag, in μm; P c - Steel slag content in solid waste-based recycled asphalt mixture, % ρ a - Density of asphalt, g / cm³ 3 ; Specific surface area of ​​SA1-4.75~9.5mm particle size steel slag, m² 2 / kg; The percentage of steel slag with a particle size of L1-4.75~9.5mm, % Specific surface area of ​​SA2-9.5~16mm particle size steel slag, m² 2 / kg; P j - Percentage of used asphalt mixture in solid waste-based recycled asphalt mixture, % μ j - Average asphalt film thickness on aggregate surface in old asphalt mixtures, μm; SA j -Specific surface area of ​​aggregates in old asphalt mixtures with a particle size ≤ 4.75 mm, in m² 2 / kg.

2. The method for determining the mix proportion of solid waste-based recycled asphalt mixture according to claim 1, characterized in that, The method for determining the specific surface area of ​​a sample is as follows: Take a sample of ≥500g, soak it in water for 24 hours, filter it, pour it into an iron cup, place absorbent paper at the bottom of the iron cup and separate it with filter paper at the top, put it in a centrifuge and rotate it for 2~3 minutes, and weigh the sample mass; after drying in an oven, weigh the dried sample mass, and calculate the specific surface area of ​​the sample based on the thickness of the water film on the sample surface and the volume of adsorbed water.

3. The method for determining the mix proportion of solid waste-based recycled asphalt mixture according to claim 2, characterized in that, The formula for calculating the specific surface area of ​​a sample is: ； In the formula: SA - Specific surface area of ​​the sample, m² / kg; m s - Mass of the sample after immersion in water and centrifugation, in g; m g - Sample mass after drying, g; μ s -Water film thickness, μm; ρ s - The density of water, g / cm³; m k -Sample mass at the time of sampling, in grams.

4. A method for determining the mix proportion of a solid waste-based recycled asphalt mixture according to claim 2 or 3, characterized in that, The method for determining the void ratio of steel slag asphalt mixture is as follows: Based on engineering experience and relevant specifications, determine the proportion of steel slag with particle sizes of 4.75–9.5 mm and 9.5–16 mm. According to the asphalt film-forming theory, asphalt can coat steel slag with particle sizes of 4.75–9.5 mm and 9.5–16 mm at the optimal asphalt film thickness. Calculate the amount of asphalt coated with steel slag based on the specific surface area of ​​the steel slag and the asphalt film thickness. Prepare Marshall specimens based on the proportion of steel slag with particle sizes of 4.75–9.5 mm and 9.5–16 mm and the amount of asphalt, and calculate the void ratio of the steel slag asphalt mixture.

5. The method for determining the mix proportion of solid waste-based recycled asphalt mixture according to claim 4, characterized in that, The formula for calculating the void ratio of steel slag asphalt mixture is: ； ； ； In the formula: L a - Asphalt dosage when coating steel slag with the optimal asphalt film thickness, % μ - Optimal bitumen film thickness, μm; ρ a - Density of asphalt, g / cm³; Specific surface area of ​​steel slag with a particle size of SA1-4.75~9.5mm, m² / kg; The percentage of steel slag with a particle size of L1-4.75~9.5mm, % Specific surface area of ​​SA2-9.5~16mm particle size steel slag, m² / kg; ρ h - Maximum theoretical density of steel slag asphalt mixture, g / cm³; Density of steel slag with a particle size of ρ1-4.75~9.5mm, g / cm³; Density of steel slag with a particle size of ρ2-9.5~16mm, g / cm³; VC-steel slag asphalt mixture porosity, % ρ m - Bulk density of steel slag asphalt mixture, g / cm³.

6. The method for determining the mix proportion of solid waste-based recycled asphalt mixture according to claim 1, characterized in that, The formula for calculating the amount of old asphalt mixture with a particle size ≤ 4.75mm is as follows: ； ； ； + =100； In the formula: SA j -Specific surface area of ​​aggregates in old asphalt mixtures with a particle size ≤ 4.75 mm, in m² 2 / kg; a-Passing rate of aggregates in old asphalt mixtures with a particle size ≤ 4.75mm through a 4.75mm sieve; b - The passing rate of aggregates in old asphalt mixtures with a particle size ≤ 4.75 mm through a 2.36 mm sieve; c - Passing rate of aggregates in old asphalt mixtures with a particle size ≤ 4.75 mm through a 1.18 mm sieve; The passing rate of aggregates in old asphalt mixtures with a particle size ≤ 4.75 mm through a 0.6 mm sieve. The passing rate of aggregates in old asphalt mixtures with a particle size ≤ 4.75 mm through a 0.3 mm sieve. f - Passing rate of aggregates in old asphalt mixtures with a particle size ≤ 4.75 mm through a 0.15 mm sieve; g - The passing rate of aggregates in old asphalt mixtures with a particle size ≤ 4.75 mm through a 0.075 mm sieve; μ j - Average asphalt film thickness on aggregate surface in old asphalt mixtures with particle size ≤ 4.75 mm, in μm; P aj - Asphalt-aggregate ratio in old asphalt mixtures with particle size ≤ 4.75mm, % ρ a - Density of asphalt, g / cm³ 3 ; P j - The percentage of recycled asphalt mixture with a particle size ≤4.75mm in the solid waste-based recycled asphalt mixture, % μ - Optimal bitumen film thickness, μm; P c - Steel slag content in solid waste-based recycled asphalt mixture, % ρ j - Density of old asphalt mixture with particle size ≤ 4.75mm, g / cm³ 3 ; ρ c - Bulk density of steel slag asphalt mixture after compaction, g / cm³ 3 ; VC-steel slag asphalt mixture porosity, % VV-solid waste-based recycled asphalt mixture design void ratio, %.

7. The method for determining the mix proportion of solid waste-based recycled asphalt mixture according to claim 1, characterized in that: The old asphalt mixture with a particle size ≤4.75mm has a moisture content ≤2.0%, wherein the old asphalt is old SBS modified asphalt; the newly added asphalt is SBS modified asphalt.

8. The method for determining the mix proportion of solid waste-based recycled asphalt mixture according to claim 2, characterized in that: The thickness of the water film is 8-12 μm; the optimal thickness of the asphalt film is 13-16 μm.

9. The method for determining the mix proportion of solid waste-based recycled asphalt mixture according to claim 1, characterized in that, The formula for calculating the thickness of the asphalt film on the surface of the steel slag after mixing old asphalt mixture with a particle size ≤4.75mm is as follows: In the formula: μ aj - The thickness of the asphalt film on the surface of the steel slag after mixing old asphalt mixture with a particle size ≤ 4.75 mm with steel slag, in μm; P acj - The asphalt content of the old asphalt mixture with a particle size ≤4.75mm after mixing with steel slag, % m j - The mass of old asphalt mixture in the mixture of old asphalt mixture with steel slag after mixing with particle size ≤4.75mm, in g; m1 - The mass of steel slag with a particle size of 4.75 to 9.5 mm in the mixture of old asphalt mixture with a particle size ≤ 4.75 mm and steel slag, in g; The mass (g) of steel slag with a particle size of 9.5–16 mm in the mixture of old asphalt mixture with a particle size ≤ 4.75 mm and steel slag.

10. The method for determining the mix proportion of solid waste-based recycled asphalt mixture according to claim 1, characterized in that: The designed porosity of the solid waste-based recycled asphalt mixture is 3-6%.

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