Rpcs reinforcing agent and preparation method thereof, rpc reinforcing asphalt mixture and preparation method thereof

Abstract

The application discloses a RPC reinforcing agent and a preparation method thereof, a RPC reinforced asphalt mixture and a preparation method thereof, and belongs to the technical field of road engineering materials. The RPC reinforcing agent takes "regenerated PE-SBS-rubber powder" as a ternary core component, is matched with a compatibilizer, a filler, a flow aid and other auxiliaries, forms a "high polymer alloy" structure, is divided into three products (RPC-I type, RPC-II type and RPC-III type) according to traffic scenes, and the specifications, functions and ratios of the components are determined according to actual application environment conditions and design requirements, so that the grading dynamic optimization of the asphalt mixture is realized, and multi-scale stress dispersion is realized. The RPC reinforced asphalt mixture provided by the application can realize the effects of high-temperature anti-rutting, low-temperature anti-cracking and water damage resistance, and the dynamic stability of RPC-III type asphalt mixture at 60 DEG C is more than 14000 times / mm.

Description

Technical Field

[0001] This invention belongs to the field of road engineering materials technology, specifically relating to an RPC reinforcing agent and its preparation method, and an RPC-reinforced asphalt mixture and its preparation method. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Asphalt pavement has become the mainstream choice for road construction worldwide due to its advantages such as low driving noise, convenient maintenance, and strong adaptability. However, under the influence of heavy traffic and extreme climates (such as high temperature and severe cold), asphalt pavement is prone to diseases such as high temperature rutting, low temperature cracking, and water damage. These problems seriously shorten the service life of the pavement (the service life of traditional pavement is only 5-7 years) and significantly increase the maintenance cost throughout the entire cycle.

[0004] Current research on anti-rutting technology for asphalt pavement mainly focuses on four types of anti-rutting agents, but they all have significant defects: (1) Natural rock asphalt modified type: good high-temperature stability, but high low-temperature brittleness, which cannot meet the needs of cold regions; (2) Rubber modified type: good elastic recovery ability, but poor rubber particle dispersion, and requires complex wet process, which requires modification of existing mixing equipment, resulting in high promotion costs; (3) Plastic-based modified type: strong anti-rutting ability, but insufficient low-temperature crack resistance (low-temperature bending strain ≤2000με), which makes it difficult to meet the dual requirements of "high-temperature anti-rutting - low-temperature crack resistance"; (4) Dual composite type: slightly better comprehensive performance, but dynamic stability is only about 6000 times / mm, which cannot meet the requirement of ≥10000 times / mm for heavy-load road sections, and it relies on imported raw materials, which is costly (the cost of imported product mixtures increases by 42 yuan / ton, far exceeding the industry target of ≤30 yuan / ton). At the same time, the bonding force of rubber-plastic composite interface is weak and the stress is unevenly dispersed, which further restricts the performance.

[0005] In addition, existing technologies face the challenge of a “triple imbalance”: First, there is a performance imbalance, as a single modified material cannot simultaneously meet the comprehensive performance requirements of high-temperature rutting resistance, low-temperature crack resistance, and water damage resistance; second, there is an economic imbalance, as the high-end market is monopolized by imported products, and the cost of domestic products fluctuates greatly, resulting in high maintenance costs throughout the entire life cycle; and finally, there is a process imbalance, as traditional wet processes require modification of mixing equipment, have poor compatibility, and have low solid waste utilization rates (failure to utilize recycled PE and waste tire rubber powder on a large scale).

[0006] Therefore, there is an urgent need to develop a composite modified mixture that combines high performance, low cost, and greenness. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide an RPC reinforcing agent and its preparation method, as well as an RPC-reinforced asphalt mixture and its preparation method. The prepared RPC reinforcing agent is used in asphalt pavement to prepare asphalt mixtures, making them suitable for ordinary traffic sections, urban arterial roads, and heavy traffic sections. It can achieve long-life pavement construction under complex working conditions such as high temperature, severe cold, and heavy rain, and solve the core problems of traditional asphalt pavement such as high temperature rutting, low temperature cracking, and water damage.

[0008] This invention aims to overcome the shortcomings of existing asphalt pavement modification materials and preparation processes, and solve the following core technical problems:

[0009] 1. Solved the problem of balancing performance: Existing anti-rutting agents cannot simultaneously meet the comprehensive requirements of "high-temperature rutting resistance (dynamic stability ≥10000 cycles / mm), low-temperature crack resistance (low-temperature flexural strain ≥2500με), and water loss resistance (freeze-thaw splitting strength ratio ≥80%)", especially in heavy-load and cold-weather road sections where their applicability is poor. The RPC-reinforced asphalt mixture prepared by this invention can effectively achieve the effects of high-temperature rutting resistance, low-temperature crack resistance, and water loss resistance.

[0010] 2. This invention solves the problem of poor interfacial compatibility: In traditional rubber-plastic composite modified materials, the interfacial bonding force among plastics, rubber, and asphalt is weak, resulting in uneven stress distribution and problems such as segregation and aging. The RPC-reinforced asphalt mixture prepared by this invention can be well dispersed uniformly.

[0011] 3. This invention resolves the contradiction between process and cost: Traditional wet processes require modification of existing mixing equipment, resulting in high barriers to entry; they also have a high dependence on imported raw materials, increasing the cost of the mixture by over 30 yuan / ton, and have low solid waste utilization rates, failing to meet green and low-carbon requirements. This invention is applicable to existing mixing equipment without modification; furthermore, it achieves cost reduction, such as increasing the cost of RPC-I type mixture materials by only 25-30 yuan / ton, extending road surface life to 10-12 years (compared to 5-7 years for traditional roads), and reducing total maintenance costs by 37.4%.

[0012] 4. Solves the problem of insufficient scenario adaptability: Existing products lack hierarchical design and cannot dynamically match performance according to traffic load (ordinary road sections, main roads, heavy-load road sections), resulting in "performance overkill" or "performance underkill". This invention achieves dynamic optimization design, which can be adjusted according to needs.

[0013] To achieve the above objectives, the technical solution of the present invention is as follows:

[0014] In a first aspect, the present invention provides an RPC reinforcing agent, the RPC reinforcing agent comprising: 45-65 parts of recycled PE, 0-25 parts of PP, 0-50 parts of styrene-butadiene-styrene block copolymer (SBS), 0-30 parts of rubber powder, and 5-15 parts of additives;

[0015] The additives include compatibilizers, fillers, and flow aids, with a mass ratio of (40~50):(15~20):(30~40);

[0016] The compatibilizer is maleic anhydride-grafted PE;

[0017] The filler is heavy calcium carbonate;

[0018] The gliding agent is polyethylene wax.

[0019] The RPC enhancers include RPC-I, RPC-II, and RPC-III;

[0020] The RPC-I type is prepared from the following raw materials in parts by weight: 55-65 parts recycled PE, 0 parts PP, 0 parts SBS, 20-30 parts rubber powder, and 5-15 parts additives;

[0021] The RPC-II type is prepared from the following raw materials in parts by weight: 50-60 parts recycled PE, 15-25 parts PP, 0 parts SBS, 0 parts rubber powder, and 5-15 parts additives;

[0022] The RPC-III type is prepared from the following raw materials in parts by weight: 45-55 parts recycled PE, 0 parts PP, 40-50 parts SBS, 0 parts rubber powder, and 5-15 parts additives.

[0023] It should be noted that RPC reinforcing agent refers to RPC asphalt pavement reinforcing material, where R: rubber; P: high molecular polymers PE and PP; C: rubber-plastic composite, dynamically blended combination.

[0024] Preferably, the RPC-I type is prepared from the following raw materials in parts by weight: 58-62 parts recycled PE, 0 parts PP, 0 parts SBS, 23-27 parts rubber powder, and 7-11 parts additives;

[0025] The RPC-II type is prepared from the following raw materials in parts by weight: 53-57 parts recycled PE, 18-22 parts PP, 0 parts SBS, 0 parts rubber powder, and 7-11 parts additives.

[0026] The RPC-III type is prepared from the following raw materials in parts by weight: 48-52 parts recycled PE, 0 parts PP, 43-47 parts SBS, 0 parts rubber powder, and 8-12 parts additives.

[0027] More preferably, the RPC-I type is prepared from the following raw materials in parts by weight: 59-61 parts recycled PE, 0 parts PP, 0 parts SBS, 24-26 parts rubber powder, and 8-10 parts additives;

[0028] The RPC-II type is prepared from the following raw materials in parts by weight: 54-56 parts recycled PE, 19-21 parts PP, 0 parts SBS, 0 parts rubber powder, and 8-10 parts additives;

[0029] The RPC-III type is prepared from the following raw materials in parts by weight: 49-51 parts recycled PE, 0 parts PP, 44-46 parts SBS, 0 parts rubber powder, and 9-11 parts additives.

[0030] In one or more embodiments, the additives include a compatibilizer, a filler, and a flow aid, with a mass ratio of (44~47):(17~19):(35~37), most preferably 46:18:36.

[0031] In one or more embodiments, the recycled PE is recycled HDPE material with a density of 0.8~1.2 g / cm³. 3 The melt flow rate is 1.4~1.8 g / 10 min, such as recycled HDPE from South Korea, with a density of 0.935 g / cm³. 3 The melt flow rate is 1.6 g / 10 min. Recycled PE is used to construct a rigid framework, improving high-temperature stability.

[0032] In one or more embodiments, SBS (styrene-butadiene-styrene block copolymer) has an elongation at break of 1000-1100%, such as Ningbo Changhong CH301, which has an elongation at break of 1073%. SBS can form an elastic network, improving low-temperature crack resistance.

[0033] In one or more embodiments, the particle size of the adhesive powder is 40-60 mesh, and the specific surface area is 10-20 m². 2 / g. For example, finely ground waste tire particles have a specific surface area of ​​12m². 2 / g, with a rough and porous surface. The rubber powder acts as a toughening filler, enhancing physical adsorption with asphalt.

[0034] In one or more embodiments, the compatibilizer is maleic anhydride-grafted PE with a grafting rate of 1-2%. For example, Changzhou Huazhiyuan maleic anhydride-grafted PE has a grafting rate of 1.2%. The compatibilizer can reduce interfacial tension (by 38%) and optimize the bonding force between rubber and plastic.

[0035] In one or more embodiments, the filler is heavy calcium carbonate with a purity ≥95%, whiteness ≥90%, and particle size ≤20μm. For example, a purity of 96% and a whiteness of 93%. The filler can fill the voids in the rubber-plastic phase, increasing the internal friction angle of the mixture to 35°.

[0036] In one or more embodiments, the flow aid is polyethylene wax, specifically polyethylene wax type W1111, with a melting point of 100-110°C (preferably 105°C), viscosity of 10-600 (CPS 140°C), and density of 0.93-0.98 g / cm³. 3 It has a softening point of 90~120℃, a maximum hardness of 3~8, and a penetration of 1~4. Polyethylene wax type W1111 can be produced in Thailand.

[0037] Flow aids can reduce melt viscosity and shorten aggregate adhesion time to 3 seconds.

[0038] Secondly, the present invention provides a method for preparing the above-mentioned RPC enhancer, comprising the following steps:

[0039] The dried recycled PE, SBS, rubber powder, and additives are placed in a screw extruder for extrusion, and then water-cooled and pelletized.

[0040] Preferably, the screw extruder includes a twin-screw extruder.

[0041] Preferably, the recycled PE, SBS, and rubber powder are dried to a moisture content of ≤0.1% to avoid air bubbles during granulation.

[0042] Preferably, the screw extruder is equipped with three temperature zones: a feeding zone of 110~130℃, a melting zone of 170~190℃, and a homogenization zone of 160~180℃. The screw speed is 200~400 r / min, and the kneading blocks are arranged in a "forward-reverse" staggered pattern (with a shear strength of up to 2000 Pa) to promote the formation of an interpenetrating network structure between PE and SBS (scanning electron microscopy shows an interface blurring degree of ≥70%). More preferably, the feeding zone is 115~125℃ to ensure stable solid material conveying; the melting zone is 175~185℃ to promote full plasticization of the rubber and plastic materials; and the homogenization zone is 165~175℃ to stabilize material flowability.

[0043] Preferably, water-cooled pelletizing is used. After the extruded material is cooled in a water-cooling tank at 20~25℃, it is cut into cylindrical particles with a particle size of 2~4 mm by a pelletizer, and the particle density is controlled to be 0.93~0.98 g / cm³. 3 Bulk density 0.65 g / cm³ 3 Surface roughening treatment (surface energy increased to 45 mN / m, contact angle with asphalt ≤30°) enhances interfacial wetting ability.

[0044] Thirdly, the present invention provides the application of the above-mentioned RPC reinforcing agent in asphalt pavement.

[0045] Fourthly, the present invention provides an RPC-reinforced asphalt mixture, which is composed of the aforementioned RPC reinforcing agent, mixture, and asphalt.

[0046] The mixture includes aggregates and / or fillers, and the fillers include mineral powder and / or cement.

[0047] The aggregate includes coarse aggregate and fine aggregate. The coarse aggregate is crushed stone, and the fine aggregate is manufactured sand. The coarse aggregate is aggregate with a size ≥4.75mm and ≤25mm. The fine aggregate is aggregate <4.75mm.

[0048] The asphalt is Grade A 70# asphalt, which comes from Shandong Expressway Materials Group Co., Ltd., and its performance indicators are shown in Table 1.

[0049] There are no restrictions on mineral powder, as long as it meets the specifications.

[0050] The cement used must be ordinary Portland cement or slag Portland cement of grade 32.5 or above. Considering the construction technical conditions, the initial setting time must be greater than 2 hours.

[0051] In RPC-reinforced asphalt mixtures, the asphalt content is 4-5%, with the optimal value being 4.12%.

[0052] The dosage of RPC reinforcing agent is 0.3~0.5% of the total mass of RPC-reinforced asphalt mixture, 0.3~0.31% for RPC-I type, 0.35~0.36% for RPC-II type, and 0.4~0.41% for RPC-III type. Preferably, it is 0.3% for RPC-I type, 0.35% for RPC-II type, and 0.4% for RPC-III type.

[0053] In one or more embodiments, the mixture comprises three types: suspended dense gradation, balanced skeleton dense gradation, and strongly interlocked skeleton dense gradation.

[0054] In the suspended dense gradation, the porosity is 4.5~4.7%, and the mass ratio of (18~22mm):(11~18mm):(6~11mm):(3~6mm):(0~3mm):mineral powder is (14~16):(23~25):(22~24):(7~9):(26~28):(2~4). Preferably, in the suspended dense formulation, the porosity is 4.6%, and the mass ratio of (18~22mm):(11~18mm):(6~11mm):(3~6mm):(0~3mm):mineral powder is (14.5~15.5):(23.5~24.5):(22.5~23.5):(7.5~8.5):(26.5~27.5):(2.5~3.5). The optimal suspended dense formulation has a porosity of 4.6% and a mass ratio of (18~22mm):(11~18mm):(6~11mm):(3~6mm):(0~3mm):mineral powder of 15:24:23:8:27:3.

[0055] In a balanced skeleton dense gradation, the porosity is 3.7~4.3%, and the mass ratio of mineral powder to cement is (10~12):(32~34):(23.5~25.5):(4~6):(22~24):(1~3):(0.5~2.5). Preferably, in a balanced skeleton dense gradation, the porosity is 4%, and the mass ratio of mineral powder to cement is (10.5~11.5):(32.5~33.5):(24~25):(4.5~5.5):(22.5~23.5):(1.5~2.5):(1~2). The optimal balanced skeleton dense gradation has a porosity of 4% and a mass ratio of (18~22mm):(11~18mm):(6~11mm):(3~6mm):(0~3mm):mineral powder:cement to 11:33:24.5:5:23:2:1.5.

[0056] In a densely packed, strongly interlocked skeleton, the porosity is 2.8-3.2%, and the mass ratio of particles smaller than 19mm:16mm:13.2mm:9.5mm:4.75mm:2.36mm:1.18mm:0.6mm:0.3mm:0.15mm:0.075mm is (4-6):(16.5-18.5):(7-9):(14-16):(13.5-15.5):(11-13):(8-10):(4.5-6.5):(3-5):(2-4):(0.5-2.5):(4-6). Preferably, in the dense gradation of the strongly interlocked skeleton, the porosity is 3%, and the mass ratio of 19mm:16mm:13.2mm:9.5mm:4.75mm:2.36mm:1.18mm:0.6mm:0.3mm:0.15mm:0.075mm:0.075mm or less is (4.5~5.5):(17~18):(7.5~8.5):(14.5~15.5):(14~15):(11.5~12.5):(8.5~9.5):(5~6):(3.5~4.5):(2.5~3.5):(1~2):(4.5~5.5). The most preferred dense gradation of the strongly interlocked skeleton, with a porosity of 3%, has a mass ratio of 5:17.5:8:15:14.5:12:9:5.5:4:3:1.5:5:5.5:4:3:1.5:5.

[0057] Among them, 18~22mm, 11~18mm, 6~11mm, 3~6mm, and 0~3mm refer to the size of the screen openings of the vibrating screen of the mixing equipment before the aggregates are dry-mixed.

[0058] Among them, 19mm, 16mm, 13.2mm, 9.5mm, 4.75mm, 2.36mm, 1.18mm, 0.6mm, 0.3mm, 0.15mm, 0.075mm, and below refer to the standard sieve aperture size after the aggregate is dry-mixed and then screened again.

[0059] The gradation type is selected based on traffic load to achieve dynamic control of aggregate gradation. Combined with different RPC reinforcing agents, dynamic optimization of asphalt mixture gradation and multi-scale stress dispersion are achieved. Three types of RPC reinforcing agents are combined with three types of mixture gradations, resulting in nine possible combinations. Specifically, for example... Figure 2As shown, RPC-reinforced asphalt mixtures include the following nine combinations of compatibility: suspension-dense gradation is compatible with RPC-I, RPC-II, and RPC-III reinforcing agents respectively; balanced skeleton-dense gradation is compatible with RPC-I, RPC-II, and RPC-III reinforcing agents respectively; and strong interlocking skeleton-dense gradation is compatible with RPC-I, RPC-II, and RPC-III reinforcing agents respectively.

[0060] To achieve better technical results, the following preferred adaptation method can be selected:

[0061] Dynamic control of aggregate gradation: The gradation type is selected according to the traffic load. For ordinary road sections (design traffic volume ≤ 1000 vehicles / day), the suspended dense gradation is preferred; for urban arterial roads (design traffic volume 5000~10000 vehicles / day), the balanced skeleton dense gradation is preferred; and for heavy-load road sections (design traffic volume > 10000 vehicles / day), the strongly interlocked skeleton dense gradation is preferred.

[0062] Dynamic control of RPC reinforcing agents: RPC-I type is preferably adapted to a suspended dense gradation for use on ordinary road sections (traffic volume ≤ 1000 vehicles / day); RPC-II type is preferably adapted to a balanced skeleton dense gradation for use on urban arterial roads (traffic volume 5000~10000 vehicles / day); RPC-III type is preferably adapted to a strongly interlocked skeleton dense gradation for use on heavy-load road sections (design traffic volume > 10000 vehicles / day).

[0063] The three-level product performance provided by this invention are as follows: For the RPC-I type, when adapted to a suspended dense-gradation configuration and suitable for ordinary road sections (traffic volume ≤ 1000 vehicles / day), the dynamic stability is 6000~8000 cycles / mm (6000 ≤ RPC-I type dynamic stability < 8000), suitable for light traffic volumes (design axle load < 1 million cycles). For the RPC-II type, when adapted to a balanced skeleton dense-gradation configuration and suitable for urban arterial roads (traffic volume 5000~10000 vehicles / day), the dynamic stability is 8000~14000 cycles / mm (8000 ≤ RPC-II type dynamic stability < 14000), suitable for medium traffic volumes (design axle load 1 million~5 million cycles). When the RPC-III type is adapted to a densely graded, strongly interlocked frame and is suitable for heavy-load road sections (design traffic volume > 10,000 vehicles / day, axle load ≥ 100kN), its dynamic stability is ≥ 14,000 cycles / mm (preferably dynamic stability can reach 16,000 cycles / mm), its low-temperature bending strain is 2798με, its freeze-thaw splitting strength ratio is 89%, and it is suitable for heavy traffic volumes (design axle load > 5 million cycles).

[0064] Fifthly, the present invention provides a method for preparing the above-mentioned RPC-reinforced asphalt mixture, comprising the following steps:

[0065] The aggregates in the mixture are first heated and then dry-mixed according to the preset proportions.

[0066] The mixture is prepared by wet mixing of the asphalt, heated asphalt, and RPC reinforcing agent.

[0067] This involves temperature-controlled mixing, which regulates the discharge temperature of RPC-reinforced asphalt mixtures by controlling the heating temperatures of asphalt and aggregates.

[0068] Depending on the gradation type, mineral powder and cement may be selectively added to the mixture.

[0069] The aggregates also need to be screened.

[0070] Furthermore, the coarse and fine aggregates are heated, and the resulting hot material is screened by vibrating screens (3*3mm, 6*6mm, 11*11mm, 18*18mm, 22*22mm square hole screens) and stored in six hot material bins (bin #1 0-3mm, bin #2 3-6mm, bin #3 6-11mm, bin #4 11-18mm, bin #5 18-22mm).

[0071] If a dense gradation with a strong interlocking skeleton is used, the dry-mixed aggregates need to be screened to obtain aggregates with screening sizes of 19 mm, 16 mm, 13.2 mm, 9.5 mm, 4.75 mm, 2.36 mm, 1.18 mm, 0.6 mm, 0.3 mm, 0.15 mm, 0.075 mm, and below.

[0072] The asphalt heating temperature is 145±5℃, the aggregate heating temperature is 160~180℃, the dry mixing time is 3~8 seconds (to ensure that the RPC particles are evenly coated with the aggregate), the wet mixing time is 35~40 seconds (to avoid asphalt aging or mixture segregation), and the discharge temperature is controlled at 150~160℃ (the mixture should not have white spots or clumping).

[0073] In this invention, such as Figure 3As shown, the main components of RPC reinforcing agent are rubber powder, PE, and PP, which are added to the mixture through dry mixing and direct addition. This not only improves the performance of the asphalt mastic but also strengthens the asphalt mixture skeleton, specifically by significantly increasing the internal friction angle and cohesion of the mixture. Under the high temperature during the mixing process with aggregates, the rubber-plastic composite particles gradually soften to a plastic state. Simultaneously subjected to the shearing and extrusion of the aggregates, they are firmly and evenly embedded in the mixture under the adhesion of the asphalt, acting as reinforcement and filling voids. This effectively resists the dynamic water pressure generated by water erosion, enhancing the toughness of the asphalt mixture. After melting and deformation, the rubber-plastic composite particles adhere to the aggregate surface and bond with the fine aggregates, forming a stable composite structure with larger volume and higher strength, resulting in higher strength of the mixture skeleton and less rutting at high temperatures. It also enhances the bonding ability between the asphalt film and aggregates, and between aggregates themselves, allowing the mixture to withstand greater loads at low temperatures without cracking.

[0074] PE polymer modifiers can resist excessive deformation, but a high fatigue threshold is required to resist crack propagation under cyclic loading. PE polymers can significantly resist excessive deformation but do not increase the fatigue threshold. Rubber-plastic composites can amplify the fatigue threshold through the synergistic effect of polymers, PE particles, aggregates, and their inter-particle adhesion. Multi-scale stress dispersion is achieved through the polymer and then through the particles, thereby enhancing the fatigue threshold of the rubber and preventing crack initiation.

[0075] One or more of the above technical solutions have the following advantages or beneficial effects:

[0076] The RPC reinforcing agent provided by this invention uses "recycled PE-SBS-rubber powder" as the ternary core components, combined with compatibilizers, fillers, flow aids, and other additives to form a "polymer alloy" structure. In this invention, based on the rubber-plastic composite mechanism, the interfacial forces between rubber and plastic are enhanced through the selection of appropriate modifiers (SBS), optimization of components and proportions, and process control. Using a dry-mix direct-injection process, the RPC asphalt pavement reinforcing agent is mixed with asphalt and aggregates. Through multiple effects such as surface thickening, reinforcement, filling, and elastic recovery, the reinforcing agent significantly improves the high-temperature stability of the asphalt mixture and enhances its water stability and low-temperature crack resistance.

[0077] Based on actual application environment conditions and design requirements, three RPC reinforcing agents were developed through raw material control and component and ratio optimization: RPC-I (PE recycled material / rubber powder composite RPC reinforcing agent), RPC-II (PE recycled material / PP composite RPC reinforcing agent), and RPC-III (PE / SBS composite RPC reinforcing agent). Furthermore, by selecting the gradation type according to traffic load, dynamic control of aggregate gradation was achieved. Combined with different RPC reinforcing agents, dynamic optimization of asphalt mixture gradation and multi-scale stress dispersion were realized.

[0078] RPC series asphalt pavement reinforcing agents offer numerous advantages, enhancing the road performance of asphalt mixtures. All three series of reinforcing agents meet technical requirements and can be used as needed; road performance test results provide a basis for practical applications. High dynamic stability: The manufactured asphalt mixtures achieve a dynamic stability of up to 14,000 cycles / mm, meeting the needs of special scenarios such as heavy traffic. Excellent comprehensive performance: A "rubber-plastic composite, combining rigidity and flexibility," integrating PE polymers and a high fatigue threshold, it possesses excellent high-temperature deformation resistance, good low-temperature crack resistance, and water damage resistance. Convenient and economical construction: Utilizing a dry construction method, it is highly adaptable, convenient, and efficient, requiring no modification to existing processes and equipment. The RPC series reinforcing agents also feature good melt flow and anisotropy, good rutting resistance, and good crack resistance, achieving effects such as high-temperature rutting resistance, low-temperature crack resistance, and melt flow and workability. The research and application of RPC asphalt pavement reinforcing agents provide an effective solution to the problem of rutting damage in asphalt pavements, suitable for various types of asphalt mixtures and heavy-load traffic sections. Attached Figure Description

[0079] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0080] Figure 1 This is a diagram showing the dispersion effect of the RPC-reinforced asphalt mixture prepared in Example 10 of the present invention;

[0081] Figure 2 This is a dynamic optimization diagram of the gradation of three RPC reinforcing agents and three mixture gradations in asphalt mixtures in this invention;

[0082] Figure 3 The diagram shows the mechanism of rubber-plastic composite action and the structure of the "polymer alloy" in this invention; (a) is a schematic diagram of the local micro-connection in (b), (b) is a schematic diagram of the "polymer alloy" structure, and (c) shows the crack propagation under different stresses. Detailed Implementation

[0083] In this invention, unless otherwise specified, all other test materials and instruments are conventional test materials in the field and can be purchased through commercial channels.

[0084] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0085] Table 1 Summary of Test Results for Grade 70#A Road Petroleum Asphalt

[0086]

[0087] The mixture formula is as follows:

[0088] The first type of gradation, the suspended dense gradation, has a porosity of 4.6%. The mixture includes aggregates and mineral powder, with a mass ratio of (18~22mm):(11~18mm):(6~11mm):(3~6mm):(0~3mm):mineral powder of 15:24:23:8:27:3.

[0089] The second type of gradation, the balanced skeleton dense gradation, has a porosity of 4%. The mixture includes aggregates, mineral powder and cement, with a mass ratio of (18~22mm):(11~18mm):(6~11mm):(3~6mm):(0~3mm):mineral powder:cement of 11:33:24.5:5:23:2:1.5.

[0090] Among them, 18~22mm, 11~18mm, 6~11mm, 3~6mm, and 0~3mm refer to the size of the screen openings of the vibrating screen of the mixing equipment before the aggregates are dry-mixed.

[0091] The third type of gradation, the dense gradation of the strongly interlocked skeleton, has a porosity of 3%. The mixture includes aggregates with a mass ratio of less than 19mm:16mm:13.2mm:9.5mm:4.75mm:2.36mm:1.18mm:0.6mm:0.3mm:0.15mm:0.075mm:0.075mm, which is 5:17.5:8:15:14.5:12:9:5.5:4:3:1.5:5.

[0092] Among them, 19mm, 16mm, 13.2mm, 9.5mm, 4.75mm, 2.36mm, 1.18mm, 0.6mm, 0.3mm, 0.15mm, 0.075mm, and below refer to the standard sieve aperture size after the aggregate is dry-mixed and then screened again.

[0093] Recycled PE: Recycled HDPE material from South Korea, density 0.935 g / cm³ 3 The melt flow rate is 1.6 g / 10 min.

[0094] SBS: Ningbo Changhong CH301 type, styrene-butadiene-styrene block copolymer, elongation at break 1073%.

[0095] Rubber powder: 40-60 mesh waste tire finely ground particles, specific surface area 12m² 2 / g, with a rough and porous surface.

[0096] Compatibilizer: Changzhou Huazhiyuan maleic anhydride grafted PE, grafting rate 1.2%.

[0097] Filler: Heavy calcium carbonate, purity 96%, whiteness 93%, particle size ≤20μm.

[0098] Glide aid: W1111 type polyethylene wax from Thailand, melting point 105℃, viscosity 10~600 (CPS 140℃), density 0.93~0.98 g / cm³ 3 Softening point 90~120℃, maximum hardness 3~8, penetration 1~4.

[0099] Example 1

[0100] The entire production process of RPC series reinforced asphalt mixtures is divided into RPC reinforcing agent processing and manufacturing, and mixture production. This invention employs a two-step method of "RPC reinforcing agent prefabrication + dry direct mixing," with the specific steps as follows:

[0101] Step 1: Pre-processing of RPC reinforcing agent (twin-screw extrusion granulation)

[0102] According to the RPC series reinforcing agent formulation, using a twin-screw extruder, the raw materials undergo melting, homogenization, screw extrusion, cooling, shearing granulation, and bagging to produce the RPC series reinforcing agents. Specifically:

[0103] Raw material pretreatment: Dry the recycled PE, PP, SBS, adhesive powder and additives to a moisture content of ≤0.1% to avoid air bubbles during granulation;

[0104] Twin-screw extrusion control: A KH-150 twin-screw extruder is used, with three temperature settings: feeding section 120℃ (ensuring stable solid material conveying), melting section 180℃ (promoting full plasticization of rubber and plastic materials), and homogenization section 170℃ (stabilizing material flowability). The screw speed is 300 r / min, and the kneading blocks are arranged in a "forward-reverse" staggered pattern (shear strength reaches 2000 Pa), promoting the formation of an interpenetrating network structure between PE and SBS (scanning electron microscopy shows that the phase interface blurring degree is ≥70%).

[0105] Water-cooled pelletizing: After the extruded material is cooled in a water-cooling tank at 20~25℃, it is cut into cylindrical particles with a particle size of 2~4mm by a pelletizer, and the particle density is controlled at 0.93~0.98g / cm³. 3 Bulk density 0.65 g / cm³ 3 Surface roughening treatment (surface energy increased to 45mN / m, contact angle with asphalt ≤30°) enhances interfacial wetting ability.

[0106] Step 2: Dry direct-injection preparation of RPC-reinforced asphalt mixture (compatible with existing mixing equipment)

[0107] Production and preparation of reinforced asphalt mixture: Following the RPC series reinforced asphalt mixture mix design, asphalt mixing equipment is used. Coarse and fine aggregates are added to the cold aggregate bins using a loader, and then conveyed to the heating drum by a conveyor belt. The aggregates are heated to 170℃, and the hot aggregates are lifted to the top of the mixing plant by an elevator. They are then screened by vibrating screens (3*3mm, 6*6mm, 11*11mm, 18*18mm, 22*22mm square hole screens) and stored in six hot aggregate bins (Bin #1: 0-3mm, Bin #2: 3-6mm, Bin #3: 6-11mm). The material is weighed and added to the mixing pot according to a preset ratio via computer control. Dry mixing (5-8 seconds) is then performed, followed by the addition of mineral powder, cement, asphalt (heated to 145±5℃), and reinforcing agent (weighed and added to the mixing pot by the feeder). After mixing, wet mixing is performed for 35-40 seconds. The discharge temperature is controlled at 150-160℃. The RPC series reinforced asphalt mixture is then produced and loaded into insulated transport vehicles for shipment. Mineral powder and cement are selectively added depending on the gradation type.

[0108] Because the RPC-III formulation has high requirements, it needs to be controlled according to the gradation after mixing, and the production setting ratio needs to be adjusted according to the laboratory sieve gradation after mixing. Therefore, if RPC-III type reinforcing agent is used to adapt to the dense gradation of the strong interlocking skeleton, the aggregate needs to be screened after dry mixing. By screening the dry-mixed aggregate to obtain aggregates with sieve sizes of less than 19mm, 16mm, 13.2mm, 9.5mm, 4.75mm, 2.36mm, 1.18mm, 0.6mm, 0.3mm, 0.15mm, 0.075mm, and 0.075mm, respectively, the aggregates are then mixed with other components according to the gradation ratio.

[0109] Dynamic control of aggregate gradation: Selecting the gradation type based on traffic load.

[0110] Heavy-load road sections (design traffic volume > 10,000 vehicles / day): adopt a strong interlocking skeleton dense gradation, with coarse aggregate of 4.75mm and above accounting for 45%, 0.075mm sieve passing rate of 8~10%, and increase the internal friction angle to 38%;

[0111] Ordinary road sections (design traffic volume ≤ 1000 vehicles / day): adopt suspended dense gradation, with fine aggregates below 2.36mm accounting for 20%~40% to ensure construction workability;

[0112] Urban main roads (designed traffic volume of 5,000-10,000 vehicles / day): adopt a balanced and dense skeleton, and add 1-2% cement filler, maintain the ratio of mineral powder and cement at 3.5%, control the proportion of 4.75mm aggregate at 5-5.5%, and control the porosity at 4%±0.3%.

[0113] Intelligent dry feeding: The FM-5000 intelligent feeding machine (weighing accuracy ±0.05%, single-pot feeding time ≤3 seconds) is used. RPC enhancer (RPC-I type 0.3%, RPC-II type 0.35%, RPC-III type 0.4%) is added at a ratio of 0.3-0.5% of the total mass of the mixture, without the need to modify the existing mixing equipment;

[0114] Temperature-controlled mixing: A J4000 intermittent asphalt mixing plant (asphalt content 4.12%) is used, and the temperature is controlled by a PID algorithm: asphalt heating temperature 145±5℃, aggregate heating temperature 160~180℃, dry mixing time 5~8 seconds (to ensure that RPC particles are evenly coated with aggregates), wet mixing time 35~40 seconds (to avoid asphalt aging or mixture segregation), and discharge temperature controlled at 150~160℃ (to prevent white spots and clumping in the mixture).

[0115] Dynamic performance correction: The amount of RPC added is adjusted in real time based on the rutting factor (G / sinδ) and asphalt viscosity: when the rutting factor at 60℃ is <1.0kPa, the amount added is increased by 0.05% until G / sinδ ≥2.2kPa; when the kinematic viscosity of the base asphalt at 135℃ is >3Pa·s, the amount added is reduced by 0.05% to avoid excessively high construction viscosity.

[0116] The RPC reinforcing agent provided by this invention uses "recycled PE-SBS-rubber powder" as the ternary core components, combined with compatibilizers, fillers, flow aids, and other additives to form a "polymer alloy" structure. It is divided into three product types (RPC-I, RPC-II, and RPC-III) according to traffic scenarios. The specifications, functions, and proportions of each component are shown in Table 2 below. Performance verification tests were conducted using a conventional suspended dense AC class asphalt mixture gradation (specifically, the first gradation). The additives in Table 2 include compatibilizers, fillers, and flow aids, with a mass ratio of 46:18:36.

[0117] Table 2 Comparison of Mechanical and Physical Properties of Test Formulation Samples

[0118]

[0119] As shown in Table 2, when the amount of rubber powder is greater than 10%, the reinforcing agent is difficult to melt; when the amount of PE is greater than 60%, the melted reinforcing agent agglomerates severely and forms mud balls; when no additives are added or the added additives are not properly matched, the reinforcing agent is not evenly dispersed when the asphalt mixture is mixed for 10 seconds.

[0120] The dispersion effect of the RPC-reinforced asphalt mixture prepared according to the proportions in Example 10, as shown in Table 2, is as follows: Figure 1 As shown.

[0121] The dynamic stability test method shall be performed in accordance with the "T0719 Rutting Test of Asphalt Mixture" in the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011).

[0122] The elongation at break was determined using the low-temperature tensile test method for asphalt mixtures in the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011).

[0123] The test method for low-temperature crack resistance (-10℃ low-temperature bending) shall be performed in accordance with "T0715 Low-temperature bending test of asphalt mixture" in the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011).

[0124] The test method for water damage resistance (freeze-thaw splitting strength ratio TSR) shall be performed in accordance with "T0729 Freeze-thaw Splitting Test of Asphalt Mixture" in the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011).

[0125] Table 3 Comparison of Main Formula Combinations

[0126]

[0127] Level 3 product performance:

[0128] When the RPC-I type is suitable for suspended dense-gradation road sections (traffic volume ≤ 1000 vehicles / day), its dynamic stability is 6000~8000 cycles / mm, and it is suitable for light traffic volumes (design axle cycles < 1 million cycles). Its elongation at break is 32~33%, its low-temperature crack resistance (-10℃ low-temperature bending) is 2900~3000με, and its freeze-thaw splitting strength ratio (TSR) is 88~88.2%.

[0129] The RPC-II type, with its balanced, densely graded frame, is suitable for urban arterial roads (traffic volume 5000~10000 vehicles / day), exhibiting a dynamic stability of 8000~14000 cycles / mm. It is also suitable for medium traffic volumes (design axle cycles 1 million~5 million). Its elongation at break is 28~29%, its low-temperature crack resistance (-10℃ low-temperature bending) is 2800~2850 με, and its freeze-thaw splitting strength ratio (TSR) is 88.3~88.5%.

[0130] When the RPC-III type is adapted to a densely graded, strongly interlocked skeleton and is suitable for heavy-load road sections (axle load ≥100kN), its dynamic stability is ≥14000 cycles / mm, its low-temperature bending strain is 2700~2800με, its freeze-thaw splitting strength ratio is 88.5~89.5%, and it is suitable for heavy traffic volumes (design axle load >5 million cycles).

[0131] The RPC rubber-plastic composite modified compound prepared by this invention has been experimentally verified to have core performance indicators that far exceed those of traditional materials and industry standards:

[0132] High-temperature rutting resistance: The dynamic stability of RPC-III type asphalt mixture at 60℃ reaches more than 14,000 cycles / mm, far exceeding the traditional SBS modified mixture (4,000~6,000 cycles / mm) and industry standard requirements (≥2,800 cycles / mm).

[0133] Low-temperature crack resistance: The bending strain of RPC-III type asphalt mixture at -10℃ reaches 2798με, which is 40% higher than that of traditional SBS modified mixture, and meets the requirement of ≥2500με in extremely cold regions.

[0134] Water damage resistance: The freeze-thaw splitting strength ratio (TSR) of RPC-III type asphalt mixture reaches 89%, which is higher than the industry standard requirement of ≥80%;

[0135] Economic benefits: The material cost of RPC-I type mixture increases by only 25-30 yuan / ton, while extending the pavement life to 10-12 years (compared to 5-7 years for traditional pavements), and reducing the total maintenance cost by 37.4%.

[0136] Greenness: The utilization rate of solid waste (recycled PE, waste tire rubber powder) exceeds 60%, the asphalt consumption is reduced by 18% throughout the entire life cycle, and the fuel consumption is reduced by 12%.

[0137] Table 4 Comparison and Analysis of Technical Performance at Home and Abroad

[0138]

[0139] The RPC-I type reinforced mixture, RPC-I type reinforced mixture, and RPC-I type reinforced mixture in Table 4 correspond to the formulations of Example 10, Example 13, and Example 14 in Table 3, respectively.

[0140] Compared with traditional SBS modified asphalt mixtures, French FR material mixtures, and domestically produced NRP material asphalt mixtures, the RPC-type reinforced asphalt mixture provided by this invention has superior technical performance.

[0141] Table 5 Recommended Application Scenarios for RPC Enhancers

[0142]

[0143] Based on the material properties of the RPC reinforcing agent series and the positioning of two application scenarios (prevention and treatment of common road surface defects), two engineering practice applications were selected, which achieved the predicted level in the laboratory and will be further promoted and applied in the future. As shown in Table 5.

[0144] RPC-I possesses rutting resistance and improved fatigue resistance, enhancing aggregate adhesion and stabilizing asphalt mixtures. It can be widely used in asphalt concrete pavements to improve the performance of asphalt pavements.

[0145] The RPC-II boasts excellent dynamic stability, tensile strength, yield strength, and fatigue resistance, offering high driving comfort. It can be widely used on urban main roads, long downhill sections, and urban road intersections.

[0146] RPC-III, with added styrene, possesses excellent dynamic stability and crack resistance. It can be used in urban heavy-duty slow-moving road sections, bus bays, long downhill sections overlapping with road intersections, bridge approach slopes and intersection turning sections, heavy-duty bridge sections with high vibration loads, tunnel sections connecting with urban roads, and can also be used for the prevention of surface asphalt pavement defects on national and provincial highways with high traffic volume of heavy vehicles. It can also be used for the treatment of rutting defects in vehicle stop line areas on national and provincial highways and urban main roads with severe rutting defects, providing both prevention and treatment.

[0147] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An RPC enhancer, characterized in that, The RPC reinforcing agent is RPC-III type, which is prepared from the following raw materials in parts by weight: 45-55 parts recycled PE, 0 parts PP, 40-50 parts styrene-butadiene-styrene block copolymer, 0 parts rubber powder, and 5-15 parts additives. The additives include compatibilizers, fillers, and flow aids, with a mass ratio of (40~50):(15~20):(30~40); The compatibilizer is maleic anhydride-grafted PE; The filler is heavy calcium carbonate; The gliding agent is polyethylene wax; The preparation method of RPC reinforcing agent includes the following steps: placing dried recycled PE, styrene-butadiene-styrene block copolymer and additives into a screw extruder for extrusion, and then water-cooling and pelletizing.

2. The RPC enhancer according to claim 1, characterized in that, Recycled PE is a type of recycled HDPE material with a density of 0.8~1.2 g / cm³. 3 Melt flow rate 1.4~1.8 g / 10 min; The elongation at break of styrene-butadiene-styrene block copolymers is 1000~1100%; The grafting rate of maleic anhydride onto PE is 1-2%; The purity of heavy calcium carbonate is ≥95%, the whiteness is ≥90%, and the particle size is ≤20μm; The viscosity of polyethylene wax is 10~600 CPS.

3. A method for preparing the RPC enhancer according to any one of claims 1 to 2, characterized in that, Includes the following steps: The dried recycled PE, styrene-butadiene-styrene block copolymer, and additives are placed in a screw extruder for extrusion, and then water-cooled and pelletized.

4. The preparation method according to claim 3, characterized in that, Screw extruders include twin-screw extruders; Recycled PE and styrene-butadiene-styrene block copolymer were dried to a moisture content of ≤0.1%; The screw extruder is set with three temperature zones: feeding zone 110~130℃, melting zone 170~190℃, and homogenization zone 160~180℃, and screw speed 200~400r / min; Water-cooled pelletizing is used. After the extruded material is cooled in a water-cooling tank at 20~25℃, it is cut into particles with a diameter of 2~4mm.

5. The application of the RPC reinforcing agent according to any one of claims 1 to 2 or the RPC reinforcing agent obtained by the preparation method according to claim 3 or 4 in asphalt pavement.

6. An RPC-reinforced asphalt mixture, characterized in that, It uses the RPC reinforcing agent described in any one of claims 1 to 2 or the RPC reinforcing agent obtained by the preparation method described in claim 3 or 4, and the RPC-reinforced asphalt mixture is composed of RPC reinforcing agent, mixture and asphalt; The mixture includes aggregates and / or fillers, and the fillers include mineral powder and / or cement; The mixture includes three types: suspended dense gradation, balanced skeleton dense gradation, and strongly interlocked skeleton dense gradation. In the suspended dense gradation, the porosity is 4.5~4.7%, and the mass ratio of (18~22mm):(11~18mm):(6~11mm):(3~6mm):(0~3mm):mineral powder is (14~16):(23~25):(22~24):(7~9):(26~28):(2~4). In the balanced skeleton dense gradation, the porosity is 3.7~4.3%, and the mass ratio of mineral powder to cement is (10~12):(32~34):(23.5~25.5):(4~6):(22~24):(1~3):(0.5~2.5). In the dense gradation of the strongly interlocked skeleton, the porosity is 2.8~3.2%, and the mass ratio of 19mm:16mm:13.2mm:9.5mm:4.75mm:2.36mm:1.18mm:0.6mm:0.3mm:0.15mm:0.075mm:0.075mm or less is (4~6):(16.5~18.5):(7~9):(14~16):(13.5~15.5):(11~13):(8~10):(4.5~6.5):(3~5):(2~4):(0.5~2.5):(4~6); 18~22mm, 11~18mm, 6~11mm, 3~6mm, and 0~3mm refer to the dimensions of the aggregates before dry mixing. The following measurements (19mm, 16mm, 13.2mm, 9.5mm, 4.75mm, 2.36mm, 1.18mm, 0.6mm, 0.3mm, 0.15mm, 0.075mm, 0.075mm) refer to the aggregate size after dry mixing.

7. The RPC-reinforced asphalt mixture according to claim 6, characterized in that, The cement used is ordinary Portland cement or slag Portland cement of grade 32.5 or above; The asphalt is Grade A 70# asphalt; In RPC-reinforced asphalt mixtures, the asphalt content is 4-5%; The dosage of RPC reinforcing agent is 0.3~0.5% of the total mass of RPC-reinforced asphalt mixture.

8. A method for preparing RPC-reinforced asphalt mixture according to claim 6 or 7, characterized in that, Includes the following steps: The aggregates in the mixture are first heated and then dry-mixed according to the preset ratio; The mixture is prepared by wet mixing of the asphalt, heated asphalt, and RPC reinforcing agent.

9. The preparation method according to claim 8, characterized in that, Select the gradation type according to traffic load: ordinary road sections with a design traffic volume of ≤1000 vehicles / day are suitable for suspended dense gradation; urban arterial roads with a design traffic volume of 5000~10000 vehicles / day are suitable for balanced skeleton dense gradation; and heavy-load road sections with a design traffic volume of >10000 vehicles / day are suitable for strong interlocking skeleton dense gradation. The asphalt heating temperature is 145±5℃, the aggregate heating temperature is 160~180℃, the dry mixing time is 3~8 seconds, the wet mixing time is 35~40 seconds, and the discharge temperature is controlled at 150~160℃.

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