A Mix Proportion Design Method for Dense-graded Elastic Pavement Paving Mixture

Abstract

The present invention relates to a mix proportion design method for a dense-graded elastic pavement paving mixture, comprising: mixing rubber particles with different particle size ranges according to different mass ratios and then conducting a compaction density test to determine the minimum skeleton void ratio and the optimal mass ratio; uniformly stirring the filler and the polymer binder according to different powder-binder ratios respectively to obtain several groups of binders; calculating the mass ratios of rubber aggregate, polymer binder and filler in the mixtures with different powder-binder ratios; uniformly mixing the rubber particles with the optimal aggregate gradation with each group of binders respectively to obtain several groups of elastic pavement paving mixtures; respectively filling the several groups of elastic pavement paving mixtures into test molds, ramming them and then curing and forming them to obtain several groups of specimens of elastic pavement paving mixtures; testing the void ratios of the several groups of specimens of elastic pavement paving mixtures, and determining the optimal powder-binder ratio of the filler and the polymer binder according to the void ratios. This method effectively guides the preparation of specimens of elastic pavement paving mixtures.

Description

Technical Field

[0001] The present invention belongs to the technical field of road engineering materials, and particularly relates to a method for designing the mix proportion of a dense-graded elastic pavement paving mixture. Background Art

[0002] An elastic pavement is a new type of pavement mainly composed of waste tire rubber particles, polymer binders, and stones. It has excellent noise reduction performance and environmental protection characteristics. Due to its low modulus, it is often used as a functional wearing course of the pavement.

[0003] The pavement mixture prepared with waste rubber particles as aggregates has the advantages of strong elastic recovery ability, light weight, and low cost, but it also has the problem of difficult mixture forming. In order to ensure the mixture strength while obtaining good elasticity and noise reduction performance, the current rubber aggregate pavements are mostly prepared by traditional gradation design and forming methods. The prepared rubber aggregate pavement mixtures are mostly open-graded porous structures, and the rubber particle content is small, resulting in large voids in the mixture. The large void structure reduces the contact points between the aggregates, reducing the overall bearing capacity and structural stiffness of the rubber aggregate pavement. Under the action of vehicle loads, larger relative displacements are more likely to occur between the rubber particles, leading to structural loosening and crack propagation. At the same time, the large void structure will cause moisture to penetrate into the pavement interior, accelerating the aging of the binder and reducing the adhesion between the rubber particles and the binder, thereby further weakening the durability of the pavement.

[0004] Therefore, the rubber aggregate pavement mixtures prepared by traditional gradation design and forming methods have problems such as unqualified compaction degree and loose mixture, resulting in insufficient pavement durability and seriously affecting the popularization and application of the rubber aggregate pavement mixtures. Summary of the Invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a method for designing the mix proportion of a dense-graded elastic pavement paving mixture. The technical problems to be solved by the present invention are realized through the following technical solutions:

[0006] The embodiment of the present invention provides a method for designing the mix proportion of a dense-graded elastic pavement paving mixture, including the steps of:

[0007] S1. Mix rubber particles in different particle size ranges according to different mass ratios and conduct a compacted density test to determine the minimum skeleton void ratio and the optimal mass ratio between rubber particles in different particle size ranges, and obtain the optimal aggregate gradation of rubber particles in different particle size ranges;

[0008] S2. Stir the filler and the polymer binder evenly according to different powder-binder ratios to obtain several groups of binders;

[0009] S3. Using the main aggregate filling method, calculate the mass ratios of rubber aggregate, polymer binder, and filler in mixtures with different powder-binder ratios according to the fact that the sum of the volumes of the binder, filler, and the volume occupied by the target air void ratio of the mixture is equal to the void volume of the aggregate skeleton, where the void volume of the aggregate skeleton is obtained from the minimum skeleton void ratio;

[0010] S4. Mix the rubber particles with the optimal aggregate gradation and each group of the binder evenly according to the mass ratios to obtain several groups of elastic pavement paving mixtures;

[0011] S5. Fill the several groups of elastic pavement paving mixtures into test molds respectively, tamp them, and then cure and form them to obtain several groups of specimens of elastic pavement paving mixtures;

[0012] S6. Test the air void ratios of the several groups of specimens of elastic pavement paving mixtures, and determine the optimal powder-binder ratio of the filler and the polymer binder according to the air void ratios.

[0013] In an embodiment of the present invention, the particle size range of the rubber particles includes at least two of 9.5 - 4.75 mm, 4.75 - 2.36 mm, and 2.36 - 1.18 mm.

[0014] In an embodiment of the present invention, step S1 includes:

[0015] Adopting the step-by-step filling method, mixing rubber particles in the first particle size range and rubber particles in the second particle size range in different mass ratios, then conducting a tamping density test to determine the minimum skeleton void ratio and the optimal mass ratio of the rubber particles in the first particle size range and the rubber particles in the second particle size range;

[0016] Mix the mixed rubber particles and rubber particles in the third particle size range in different mass ratios, then conduct a tamping density test to determine the minimum skeleton void ratio and the optimal mass ratio of the mixed rubber particles and the rubber particles in the third particle size range, and obtain the optimal aggregate gradation of the rubber particles in the first particle size range, the rubber particles in the second particle size range, and the rubber particles in the third particle size range; wherein, the mixed rubber particles are obtained by mixing the rubber particles in the first particle size range and the rubber particles in the second particle size range according to the optimal mass ratio.

[0017] In an embodiment of the present invention, step S2 includes:

[0018] Dry the filler by heating until its weight remains constant, and cool the dried filler to room temperature;

[0019] Stir the cooled filler and the polymer binder evenly according to different powder-binder ratios to obtain several groups of binders.

[0020] In one embodiment of the present invention, the filler includes one or more of mineral powder and rubber powder;

[0021] The polymer binder includes a thermosetting polymer with a curing time greater than 30 min.

[0022] In one embodiment of the present invention, the viscosity of the binder is 2 Pa·s to 30 Pa·s.

[0023] In one embodiment of the present invention, the mass ratio of the rubber aggregate, the filler, and the polymer binder satisfies the relationship:

[0024] q c +q p +q a = 100;

[0025]

[0026] wherein, q c is the percentage of the rubber aggregate dosage, q p is the percentage of the filler dosage, q a is the percentage of the binder dosage, ρ c is the compacted density of the rubber aggregate, ρ p is the density of the filler, ρ a is the density of the binder, VCA DRC is the minimum skeleton void ratio of the rubber aggregate, V v is the target void ratio of the mixture.

[0027] In one embodiment of the present invention, the target void ratio of the mixture is 3% to 6%.

[0028] In one embodiment of the present invention, step S5 includes:

[0029] Gradually load each group of the elastic pavement paving mixture into the test mold, insert a tamping tool along the perimeter of the test mold several times, insert it several times in the middle of the test mold, and level the surface of the elastic pavement paving mixture. Then, compress the elastic pavement paving mixture to the preset specimen height with a counterweight, and statically cure it at the preset temperature and humidity until the elastic pavement paving mixture cures to obtain an elastic pavement paving mixture specimen.

[0030] In one embodiment of the present invention, the calculation formula for the void ratio is:

[0031]

[0032] wherein, VV is the void ratio, γ f is the bulk relative density of the elastic pavement paving mixture, γ t is the maximum theoretical relative density of the elastic pavement paving mixture.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] The mix design method of the present invention uses rubber particles as the main aggregate. First, the optimal aggregate gradation of rubber particles in different particle size ranges is determined. Then, the mass ratios of rubber aggregate, polymer binder, and filler are determined by the main aggregate filling method combined with volume parameters. Considering the resilience of rubber particles, the mixture is tamped and then cured and formed to determine the optimal powder-binder ratio of the filler and polymer binder, making the dense-graded elastic pavement paving design with rubber particles as the main aggregate follow certain rules, effectively guiding the preparation of elastic pavement paving mixture specimens, avoiding the problems of unqualified compaction degree and looseness of specimens caused by traditional design and forming methods, ensuring the uniformity of the mixture and the accurate achievement of the target void ratio. Compared with open-graded elastic pavement paving materials, it effectively improves the pavement durability and water stability, enriches the structural forms of elastic pavement materials, and is conducive to the further promotion of elastic pavement paving. Description of the Drawings

[0035] Figure 1 It is a schematic flow chart of a mix design method for a dense-graded elastic pavement paving mixture provided by an embodiment of the present invention. Detailed Embodiments

[0036] The following further describes the present invention in detail with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0037] Please refer to Figure 1 , Figure 1 It is a schematic flow chart of a mix design method for a dense-graded elastic pavement paving mixture provided by an embodiment of the present invention. The design method includes the following steps:

[0038] S1. Mix rubber particles in different particle size ranges in different mass ratios and conduct a compaction density test to determine the minimum skeleton void ratio and the optimal mass ratio between rubber particles in different particle size ranges, and obtain the optimal aggregate gradation of rubber particles in different particle size ranges.

[0039] Specifically, the step-by-step filling method is adopted. First, rubber particles in the first particle size range and rubber particles in the second particle size range are mixed in different mass ratios and then subjected to a tamped density test to determine the minimum skeleton void ratio and the optimal mass ratio of the rubber particles in the first particle size range and the rubber particles in the second particle size range. The minimum skeleton void ratio and the optimal mass ratio can be used as the optimal aggregate gradation of the rubber particles in the first particle size range and the rubber particles in the second particle size range. Then, mixed rubber particles are obtained by mixing rubber particles in the first particle size range and rubber particles in the second particle size range according to the optimal mass ratio. The mixed rubber particles and rubber particles in the third particle size range are mixed in different mass ratios and then subjected to a tamped density test to determine the minimum skeleton void ratio and the optimal mass ratio of the mixed rubber particles and the rubber particles in the third particle size range, so as to obtain the optimal aggregate gradation of the rubber particles in the first particle size range, the rubber particles in the second particle size range, and the rubber particles in the third particle size range.

[0040] Specifically, the particle size range of the rubber particles includes at least two of 9.5 - 4.75 mm, 4.75 - 2.36 mm, and 2.36 - 1.18 mm.

[0041] Exemplarily, first, rubber particles with a particle size range of 9.5 - 4.75 mm and 4.75 - 2.36 mm are subjected to a tamped density test according to mass ratios of 9:1, 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, 2:8. Each test can determine the natural packing density, tamped density, natural void ratio, and tamped void ratio at the current mass ratio. By comparing the tamped void ratios of all mass ratios, the minimum tamped void ratio and its mass ratio are used as the minimum skeleton void ratio and the optimal mass ratio of the rubber particles with a particle size range of 9.5 - 4.75 mm and 4.75 - 2.36 mm. Then, the rubber particles with a particle size range of 9.5 - 4.75 mm and 4.75 - 2.36 mm are mixed according to the optimal mass ratio to obtain mixed rubber particles. The mixed rubber particles and rubber particles with a particle size range of 2.36 - 1.18 mm are subjected to a tamped density test according to mass ratios of 10:0.6, 10:1.2, 10:1.8, 10:2.4, 10:3, 10:3.6, 10:4.2, 10:4.8. The natural packing density, tamped density, natural void ratio, and tamped void ratio at each mass ratio are determined. By comparing the tamped void ratios of all mass ratios, the minimum tamped void ratio and its mass ratio are used as the minimum skeleton void ratio and the optimal mass ratio of the mixed rubber particles and the rubber particles with a particle size range of 2.36 - 1.18 mm, so as to obtain the optimal aggregate gradation of the rubber particles with a particle size range of 9.5 - 4.75 mm, 4.75 - 2.36 mm, and 2.36 - 1.18 mm.

[0042] S2. Stir the filler and the polymer binder evenly according to different powder-to-binder ratios to obtain several groups of binders.

[0043] Specifically, the filler is dried by heating until its weight remains constant, and the dried filler is cooled to room temperature. The cooled filler and the polymer binder are respectively stirred evenly according to different powder-to-binder ratios to obtain several groups of binders; for example, a stirring device is used to stir evenly 3 to 4 groups of fillers with different powder-to-rubber ratios and the polymer binder to obtain 3 to 4 groups of binders.

[0044] Specifically, the filler includes one or more of mineral powder and rubber powder. Among them, the mineral powder includes limestone powder, cement powder, silica powder, cement active powder, etc.; the rubber powder includes tire rubber powder and rubber powder made from other non-tire rubbers.

[0045] Specifically, the polymer binder includes thermosetting polymers with a curing time greater than 30 min, including epoxy resin-based thermosetting polymers, phenolic resin-based thermosetting polymers, unsaturated polyester resin-based thermosetting polymers, polyurethane-based thermosetting polymers, etc. Taking epoxy resin-based thermosetting polymers as an example, its main components include thermosetting epoxy resin and curing agent. Among them, the thermosetting epoxy resin includes epoxy resin cured at low temperature, epoxy resin cured at medium temperature, and epoxy resin cured at high temperature. Among them, the curing temperature of the epoxy resin cured at low temperature is -10 to 30 °C, and aliphatic amines (such as ethylenediamine), modified amine curing agents, etc. can be used, and the curing time is usually 24 to 48 h; the curing temperature of the epoxy resin cured at medium temperature is 50 to 100 °C, and imidazole or anhydride curing agents (such as phthalic anhydride) can be used, and the curing time is 1 to 4 h; the curing temperature of the epoxy resin cured at high temperature is 100 to 180 °C, and aromatic amines (such as DDM) or dicyandiamide curing agents can be used, and the curing time is 30 min to 2 h.

[0046] Furthermore, to ensure workability during construction, the viscosity of the binder obtained by mixing the filler and the polymer binder should be maintained at 2 Pa·s to 30 Pa·s.

[0047] S3. Using the main aggregate filling method, according to the sum of the volume of the binder, the volume of the filler, and the volume occupied by the target void ratio of the mixture being equal to the void volume of the aggregate skeleton, calculate the mass ratio of rubber aggregate, polymer binder, and filler in the mixture with different powder-to-binder ratios, where the void volume of the aggregate skeleton is calculated from the minimum skeleton void ratio.

[0048] Specifically, based on the main aggregate filling method (CAVF method) for the composition design of asphalt mixtures, the minimum skeleton void ratio between rubber particles with different particle size ranges in step S1 is converted into the minimum skeleton void volume of aggregates, so that the sum of the binder volume, filler volume, and the volume occupied by the target air voids of the mixture is equal to the minimum skeleton void volume of aggregates, and the mass ratios of rubber aggregates, polymer binders, and fillers in mixtures with different powder-binder ratios are calculated. Among them, the target air voids of the mixture refer to the target air voids of the dense-graded elastic pavement paving material obtained by mixing rubber aggregates, polymer binders, and fillers, and the value is 3% - 6%.

[0049] Specifically, the mass ratios of rubber aggregates, fillers, and polymer binders satisfy the relationship:

[0050] q c +q p +q a = 100;

[0051]

[0052] Among them, q c is the percentage of rubber aggregate dosage (%), q p is the percentage of filler dosage (%), q a is the percentage of binder dosage (%), ρ c is the compacted density of rubber aggregates (g / cm 3 ), ρ p is the density of fillers (g / cm 3 ), ρ a is the density of binders (g / cm 3 ), VCA DRC is the minimum skeleton void ratio of rubber aggregates (%), V v is the target air voids of the mixture (%).

[0053] S4. Mix the rubber particles with the best aggregate gradation and each group of binders evenly according to the mass ratio to obtain several groups of elastic pavement paving mixtures.

[0054] Specifically, dry the rubber particles with the best aggregate gradation until the weight is constant, and after cooling the rubber particles to room temperature, use a mixing device to mix the rubber particles with 3 - 4 groups of binders with different powder-binder ratios evenly to obtain 3 - 4 groups of mixed elastic pavement paving mixtures.

[0055] S5. Pour several groups of elastic pavement paving mixtures into test molds respectively, tamp them, and then cure and form them to obtain several groups of elastic pavement paving mixture specimens.

[0056] Specifically, each group of elastic pavement paving mixture is loaded into the test mold in batches. The test mold can be cylindrical or square. Then, based on the interlocking filling principle and fully considering the resilience of rubber particles, use a bayonet to insert and tamp along the periphery of the test mold several times, insert and tamp in the middle of the test mold several times, and level the surface of the elastic pavement paving mixture. After that, use a weight block to compress the elastic pavement paving mixture to the preset specimen height, and statically cure it at the preset temperature and humidity until the mixture solidifies to obtain an elastic pavement paving mixture specimen.

[0057] Furthermore, the total filling mass of the mixture is calculated based on the volume of the formed specimen.

[0058] Furthermore, the preset temperature and curing time of the static curing are determined by the curing conditions of the polymer binder. That is, when the polymer binder is a low-temperature curing epoxy resin, the preset temperature of the static curing is -10 to 30 °C, and the curing time is 24 to 48 h; when the polymer binder is a medium-temperature curing epoxy resin, the preset temperature of the static curing is 50 to 100 °C, and the curing time is 1 to 4 h; when the polymer binder is a high-temperature curing epoxy resin, the preset temperature of the static curing is 100 to 180 °C, and the curing time is 30 min to 2 h. The preset humidity of the static curing is controlled at 40 to 70%.

[0059] S6. Test the void ratios of several groups of elastic pavement paving mixture specimens, and determine the optimal powder-binder ratio of the filler and the polymer binder according to the void ratios.

[0060] Specifically, for the void ratio test, refer to T0705-2011 Compaction Bituminous Mixture Density Test (Table Dry Method) in the "Specifications for Highway Asphalt and Asphalt Mixture Tests" (JTG E20-2011) to measure the bulk relative density γ of the elastic pavement paving mixture specimen. f and the maximum theoretical relative density γ t , and calculate the void ratio VV using the following formula:

[0061]

[0062] where VV is the void ratio (%), γ f is the bulk relative density of the elastic pavement paving mixture (g / cm 3 ), and γ t is the maximum theoretical relative density of the elastic pavement paving mixture (g / cm 3 ).

[0063] Further, after determining the optimal powder-bitumen ratio of the filler and the polymer binder, the basic properties of the elastic pavement paving mixture specimens corresponding to the optimal powder-bitumen ratio are verified. The basic property tests refer to the "Test Procedures for Highway Asphalt and Asphalt Mixtures", and the elastic pavement paving mixture is subjected to immersion flushing loss test, rutting test and low-temperature bending test, and the immersion flushing loss rate, dynamic stability and maximum flexural tensile strain are used as the basis for evaluating the water stability, high-temperature stability and low-temperature crack resistance.

[0064] Further, according to the optimal aggregate gradation of rubber particles in different particle size ranges and the optimal powder-bitumen ratio of the filler and the polymer binder, the rubber particles, filler and polymer binder in different particle size ranges are mixed, and the mixture is rammed and then cured and formed to prepare a dense-graded elastic pavement paving mixture.

[0065] To facilitate the understanding of the present invention, the following examples are listed. Those skilled in the art should understand that the examples are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0066] Example 1: Purchase waste tire rubber particles produced by Company A and prepare a dense-graded elastic pavement paving mixture with a target void ratio of 3%.

[0067] S1. Rammed density tests are carried out on waste tire rubber particles in different particle size ranges after mixing them in different mass ratios. It is determined that when the mass ratio of rubber particles of 9.5 - 4.75 mm: 4.75 - 2.36 mm: 2.36 - 1.18 mm is 10:15:6, the minimum rubber skeleton void ratio is 38.34%.

[0068] Specifically, first, rammed density tests are carried out on rubber particles with particle size ranges of 9.5 - 4.75 mm and 4.75 - 2.36 mm according to mass ratios of 9:1, 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, 2:8. Each test can determine the natural bulk density, rammed density, natural void ratio and rammed void ratio under the current mass ratio, as shown in Table 1. It can be seen from Table 1 that when the mass ratio of rubber particles of 9.5 - 4.75 mm to 4.75 - 2.36 mm is 4:6, the rammed void ratio is the smallest. Therefore, the minimum skeleton void ratio of rubber particles of 9.5 - 4.75 mm and 4.75 - 2.36 mm is 41.25%, and the optimal mass ratio is 4:6.

[0069] Table 1

[0070]

[0071] Then, rubber particles with a particle size range of 9.5 - 4.75 mm and 4.75 - 2.36 mm are mixed in the optimal mass ratio of 4:6 to obtain mixed rubber particles. The mixed rubber particles and rubber particles with a particle size of 2.36 - 1.18 mm are subjected to a tamping density test at mass ratios of 10:0.6, 10:1.2, 10:1.8, 10:2.4, 10:3, 10:3.6, 10:4.2, and 10:4.8, that is, the rubber particles with particle sizes of 9.5 - 4.75 mm, 4.75 - 2.36 mm, and 2.36 - 1.18 mm are subjected to a tamping density test at mass ratios of 4:6:0.6, 4:6:1.2, 4:6:1.8, 4:6:2.4, 4:6:3, 4:6:3.6, 4:6:4.2, and 4:6:4.8. The natural bulk density, tamping density, natural void ratio, and tamping void ratio at each mass ratio are determined, as shown in Table 2. It can be seen from Table 2 that when the mass ratio of rubber particles with particle sizes of 9.5 - 4.75 mm, 4.75 - 2.36 mm, and 2.36 - 1.18 mm is 4:6:2.4, the tamping void ratio is the smallest. Therefore, the minimum skeleton clearance ratio of rubber particles with particle sizes of 9.5 - 4.75 mm, 4.75 - 2.36 mm, and 2.36 - 1.18 mm is 38.34%, and the optimal mass ratio is 4:6:2.4 (i.e., 10:15:6).

[0072] Table 2

[0073]

[0074] Therefore, it can be determined that the optimal mass ratio of rubber particles with particle sizes of 9.5 - 4.75 mm:4.75 - 2.36 mm:2.36 - 1.18 mm is 10:15:6, and the minimum skeleton clearance ratio is 38.34%.

[0075] S2. The limestone powder is dried by heating until its weight remains constant and then cooled to room temperature. Then, a stirring device is used to uniformly stir the limestone powder with powder - binder ratios of 0.8, 1.1, 1.4, and 1.7 with a low - temperature curing epoxy resin - based binder. The low - temperature curing epoxy resin - based binder is composed of a mercaptan curing agent and bisphenol A epoxy resin, obtaining 4 groups of binders with different powder - binder ratios. Among them, the viscosities of the 4 groups of binders are 2.2 Pa·s, 3.9 Pa·s, 9.7 Pa·s, and 29.3 Pa·s, respectively.

[0076] S3. Based on the main aggregate filling method (CAVF method) for asphalt mixture composition design, with a minimum rubber skeleton clearance ratio of 38.34%, a target void ratio of 3%, the density of limestone powder being 2.73 g / cm 3 , and the density of the binder being 1.14 g / cm 3Substitute into the mass ratio relationship of rubber aggregate, filler, and polymer binder, and calculate the amounts of rubber aggregate, polymer binder, and filler in the mixtures with powder-binder ratios of 0.8, 1.1, 1.4, and 1.7 respectively. The results are shown in Table 3.

[0077] Table 3

[0078]

[0079] S4. Dry the rubber particles with the optimal aggregate gradation until their weight remains constant. After cooling the rubber particles to room temperature, according to the mass ratios in Table 3, use a mixing device to uniformly mix the rubber particles with the binders of 4 different powder-binder ratios respectively to obtain 4 groups of mixed elastic pavement paving mixtures.

[0080] S5. Load each group of mixed elastic pavement paving mixtures into the test mold in 3 times and fix them with spacer blocks. Then, use an inserting tool to insert and tamp 15 times along the periphery of the steel cylinder of the test mold and 10 times in the middle of the test mold and level the surface of the mixture; finally, compress the mixture fixed by the test mold and spacer blocks to the required specimen height through a counterweight block and statically press it at 30°C for 24 h until the binder is completely cured to obtain elastic pavement paving mixture specimens.

[0081] S6. Test the void ratio of the elastic pavement paving mixture, and verify its water stability, high-temperature stability, and low-temperature crack resistance with reference to the "Test Procedures for Highway Asphalt and Asphalt Mixtures". The results are shown in Table 4.

[0082] Table 4

[0083]

[0084] It can be seen from Table 4 that the optimal powder-binder ratio of limestone powder and epoxy resin-based binder is 1.4. At this time, the void ratio of the mixture is the smallest, and its basic performance meets the requirements of the "Specifications for Design of Highway Asphalt Pavements" (JTG D50-2017) for pavement materials.

[0085] Example 2: Purchase waste tire rubber particles produced by Company B and prepare a dense-graded elastic pavement paving mixture with a target void ratio of 6%.

[0086] S1. Conduct a compaction density test on waste tire rubber particles in different particle size ranges after mixing them in different mass ratios. It is determined that when the mass ratio of rubber particles with particle sizes of 9.5 - 4.75 mm: 4.75 - 2.36 mm: 2.36 - 1.18 mm is 6:14:7, the minimum rubber skeleton void ratio is 36.24%.

[0087] S2. Dry the limestone powder by heating until its weight remains constant, then cool it to room temperature. Next, use a stirring device to evenly stir the limestone powder with powder-to-binder ratios of 0.8, 1.1, 1.4, and 1.7 with a low-temperature curing epoxy resin-based binder. The low-temperature curing epoxy resin-based binder is composed of a thiol curing agent and bisphenol A epoxy resin, obtaining 4 groups of binders with different powder-to-binder ratios. Among them, the viscosities of the 4 groups of binders are 2.2 Pa·s, 3.9 Pa·s, 9.7 Pa·s, and 29.3 Pa·s respectively.

[0088] S3. Based on the main aggregate filling method (CAVF method) for asphalt mixture composition design, with a minimum rubber skeleton void ratio of 36.24%, a target void ratio of 6%, and a limestone powder density of 2.73 g / cm 3 and a binder density of 1.14 g / cm 3 Substitute them into the mass ratio relationship formula of rubber aggregate, filler, and polymer binder, and calculate the amounts of rubber aggregate, polymer binder, and filler in the mixtures with powder-to-binder ratios of 0.8, 1.1, 1.4, and 1.7 respectively. The results are shown in Table 5.

[0089] Table 5

[0090]

[0091] S4. Dry the rubber particles with the best aggregate gradation until their weight remains constant. After cooling the rubber particles to room temperature, according to the mass ratios in Table 5, use a mixing device to evenly mix the rubber particles with the 4 groups of binders with different powder-to-binder ratios respectively, obtaining 4 groups of mixed elastic pavement paving mixtures.

[0092] S5. Pour the mixed elastic pavement paving mixture into the test mold in 3 times and fix it with a spacer block. Then, use a bayonet to insert and tamp 15 times along the periphery of the steel cylinder of the test mold and 10 times in the middle of the test mold and level the surface of the mixture. Finally, compress the mixture fixed with the test mold and spacer block to the required specimen height through a counterweight block and statically press it at 30°C for 24 h until the binder is completely cured, obtaining specimens of the elastic pavement paving mixture.

[0093] S6. Test the void ratio of the elastic pavement paving mixture, and verify its water stability, high-temperature stability, and low-temperature crack resistance with reference to the "Test Procedures for Highway Asphalt and Asphalt Mixtures". The results are shown in Table 6.

[0094] Table 6

[0095]

[0096] As can be seen from Table 6, the optimal powder-binder ratio of limestone powder to epoxy resin is 1.4. At this time, the void ratio of the mixture is the smallest, and its basic performance meets the requirements of the "Specifications for Highway Asphalt Pavement Design" (JTG D50-2017) for pavement materials.

[0097] Comparative Example 1: The remaining steps are the same as those in Example 1. In step S2, the powder-binder ratio of the filler limestone powder to the epoxy resin-based binder is 0.5, and the viscosity of the binder is 0.6 Pa·s, resulting in serious segregation during the mixing in S4 and the forming in S5, and it is impossible to form a uniform specimen.

[0098] Comparative Example 2: The remaining steps are the same as those in Example 1. In step S5, the Marshall compaction method is used to form the specimen. During the compaction process, the rubber aggregate undergoes compression and rebound, resulting in the void ratio of the mixture decreasing first and then increasing, so that part of the binder used to fill the void ratio is extruded, and the target void ratio cannot be achieved.

[0099] The mix design method of this embodiment uses rubber particles as the main aggregate in the gradation design. First, the optimal aggregate gradation of rubber particles in different particle size ranges is determined, and then the mass ratios of rubber aggregate, polymer binder, and filler are determined by using the main aggregate filling method combined with volume parameters. Based on the principle of interlocking and filling, the resilience of rubber particles is fully considered, and the mixture is tamped and then cured and formed, so as to determine the optimal powder-binder ratio of the filler and the polymer binder, making the dense-graded elastic pavement paving design with rubber particles as the main aggregate have rules to follow, effectively guiding the preparation of elastic pavement paving mixture specimens, avoiding the problems of unqualified compaction degree and looseness of specimens caused by traditional design and forming methods, ensuring the uniformity of the mixture and the accurate achievement of the target void ratio, effectively improving the pavement durability and water stability compared with open-graded elastic pavement paving materials, enriching the structural forms of elastic pavement materials, and being conducive to the further popularization of elastic pavement paving.

[0100] The above content is a further detailed description of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, which should all be regarded as belonging to the protection scope of the present invention.

Claims

1. A mix proportion design method for a densely graded elastic pavement paving mixture, characterized in that, Including the steps: S1. Mix rubber particles with different particle size ranges in different mass ratios and then conduct a compacted density test to determine the minimum skeleton void ratio and the optimal mass ratio between rubber particles with different particle size ranges, and obtain the optimal aggregate gradation of rubber particles with different particle size ranges; the particle size ranges of the rubber particles include at least two of 9.5 - 4.75 mm, 4.75 - 2.36 mm, and 2.36 - 1.18 mm; S2. Stir the filler and the polymer binder evenly according to different powder - binder ratios respectively to obtain several groups of binders; S3. Using the main - aggregate filling method, calculate the mass ratios of rubber aggregate, polymer binder, and filler in mixtures with different powder - binder ratios according to the fact that the sum of the volume of the binder, the volume of the filler, and the volume occupied by the target void ratio of the mixture is equal to the aggregate skeleton void volume, where the aggregate skeleton void volume is calculated from the minimum skeleton void ratio; the mass ratios of the rubber aggregate, the filler, and the polymer binder satisfy the relationship: q c +q p +q a = 100; where q c is the percentage of rubber aggregate dosage, q p is the percentage of filler dosage, q a is the percentage of binder dosage, ρ c is the compacted density of rubber aggregate, ρ p is the density of filler, ρ a is the density of binder, VCA DRC is the minimum skeleton void ratio of rubber aggregate, V v is the target void ratio of the mixture; S4. Mix the rubber particles with the optimal aggregate gradation and each group of the binders evenly according to the mass ratios to obtain several groups of elastic pavement paving mixtures; S5. Put each group of the elastic pavement paving mixtures into test molds, tamp them, and then carry out curing and forming to obtain several groups of elastic pavement paving mixture specimens; S6. Test the void ratios of the several groups of elastic pavement paving mixture specimens, and determine the optimal powder - binder ratio of the filler and the polymer binder according to the void ratios.

2. The mix proportion design method of the dense-graded elastic pavement paving mixture according to claim 1, characterized in that, Step S1 includes: Adopting the step - by - step filling method, mix rubber particles in the first particle size range and rubber particles in the second particle size range in different mass ratios and then conduct a compacted density test to determine the minimum skeleton void ratio and the optimal mass ratio between the rubber particles in the first particle size range and the rubber particles in the second particle size range; Mix the mixed rubber particles and rubber particles in the third particle size range in different mass ratios and then conduct a compacted density test to determine the minimum skeleton void ratio and the optimal mass ratio between the mixed rubber particles and the rubber particles in the third particle size range, and obtain the optimal aggregate gradation of rubber particles in the first particle size range, rubber particles in the second particle size range, and rubber particles in the third particle size range; wherein, the mixed rubber particles are obtained by mixing rubber particles in the first particle size range and rubber particles in the second particle size range according to the optimal mass ratio.

3. The mix proportion design method of the dense-graded elastic pavement paving mixture according to claim 1, characterized in that, Step S2 includes: Dry the filler by heating until its weight remains constant, and cool the dried filler to room temperature; Mix the cooled filler and the polymer binder evenly according to different powder - binder ratios respectively to obtain several groups of binders.

4. The mix proportion design method of the dense-graded elastic pavement paving mixture according to claim 1, characterized in that, The filler includes one or more of mineral powder and rubber powder; The polymer binder includes a thermosetting polymer with a curing time greater than 30 min.

5. The mix proportion design method of the dense-graded elastic pavement paving mixture according to claim 1, characterized in that, The viscosity of the binder is 2 Pa·s - 30 Pa·s.

6. The mix proportion design method of the dense-graded elastic pavement paving mixture according to claim 1, wherein The target void ratio of the mixture is 3% - 6%.

7. The mix proportion design method of the dense-graded elastic pavement paving mixture according to claim 1, characterized in that, Step S5 includes: Each group of the elastic pavement paving mixture is loaded into the test mold in batches, and a bayonet is used to tamp along the periphery of the test mold for several times, tamp in the middle of the test mold for several times and level the surface of the elastic pavement paving mixture. Then, a counterweight is used to compress the elastic pavement paving mixture to a preset specimen height, and static pressure curing is carried out at a preset temperature and a preset humidity until the elastic pavement paving mixture is cured, so as to obtain an elastic pavement paving mixture specimen.

8. The mix proportion design method of the dense-graded elastic pavement paving mixture according to claim 1, wherein The calculation formula for the void ratio is as follows: Among them, VV is the void ratio, and γ f is the bulk relative density of the elastic pavement paving mixture, and γ t is the maximum theoretical relative density of the elastic pavement paving mixture.

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