Toughened composite modified discontinuous semi-open graded GATB-25 asphalt mixture and preparation method thereof

Abstract

The invention provides a toughened composite modified discontinuous semi-open graded GATB-25 asphalt mixture, which is prepared from G type rubber and plastic composite modified asphalt and discontinuous semi-open graded GATB-25 aggregate, and the G type rubber and plastic composite modified asphalt uniformly wraps the discontinuous semi-open graded GATB-25 aggregate; the G-type rubber-plastic composite modified asphalt comprises asphalt, rubber powder and PE particles, the mass ratio of the rubber powder to the PE particles is 3: 1-5: 1, and the total mixing amount of the rubber powder and the PE particles is 18-22% of the weight of the asphalt; and the mass percentages of the discontinuous semi-open graded GATB-25 aggregate passing through a 9.5 mm sieve pore, a 4.75 mm sieve pore and a 2.36 mm sieve pore are respectively 20%-45%, 18%-26% and 14%-22%. The invention also provides a preparation method thereof. The toughened composite modified discontinuous semi-open graded GATB-25 asphalt mixture disclosed by the invention can be balanced in high and low temperature performance, and is excellent in fatigue resistance and strong in water damage resistance and shear resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of road engineering materials, and more specifically, to the technical field of asphalt mixtures, and particularly refers to a toughened composite modified discontinuous semi-open graded GATB-25 asphalt mixture and a preparation method thereof. Background Art

[0002] Road engineering materials refer to the materials used for constructing and maintaining roads. Asphalt mixture is a commonly used material in road engineering. It is composed of asphalt and mineral additives, and has good water resistance, durability and wear resistance. Asphalt mixture is suitable for various roads, such as highways, urban roads and rural roads. Using asphalt mixture can improve the bearing capacity and durability of roads and extend the service life of roads.

[0003] In traditional semi-rigid base asphalt pavements, the asphalt lower layer needs to undertake multiple functions such as dispersing the upper load, suppressing the expansion of base reflective cracks, and resisting flexural fatigue stress. The currently widely used unmodified dense graded ATB-25 mixture has the following defects:

[0004] Insufficient fatigue resistance: The continuous gradation results in a loose coarse aggregate interlocking structure and uneven distribution of asphalt mortar, and fatigue cracks are likely to occur under long-term load action;

[0005] Imbalance between high-temperature performance and low-temperature performance: Although SBS modified asphalt can improve high-temperature stability, its low-temperature ductility is limited, and the cost is high (about 300 yuan per ton more than ordinary asphalt);

[0006] Limitations of single modifiers: Rubber modified asphalt has excellent crack resistance but poor high-temperature deformation resistance, and plastic modified asphalt has prominent high-temperature performance but significant low-temperature brittleness, and cannot meet the comprehensive performance requirements under complex climate conditions;

[0007] Unreasonable gradation design: The traditional dense gradation has a low void ratio (5% - 7%) and a high asphalt saturation (>65%), resulting in weak shear deformation resistance and a high risk of water damage.

[0008] In the prior art, the Chinese invention patent application CN201810205850.3 proposed a mixture solution using SBS modified asphalt combined with fiber reinforcement. Although the crack resistance was improved, the addition of fibers led to complex construction technology and a sharp increase in cost. Others tried to compound and modify waste rubber and plastic, but did not solve the problems of gradation optimization and the synergistic effect of binders, resulting in limited improvement in fatigue resistance in actual projects.

[0009] Therefore, there is an urgent need for an asphalt mixture solution that can balance high and low temperature performance, has excellent fatigue resistance, strong water damage resistance and shear resistance. Summary of the Invention

[0010] In order to overcome the above-mentioned disadvantages in the prior art, an object of the present invention is to provide a toughened composite modified discontinuous semi-open graded GATB-25 asphalt mixture, which can balance the high and low temperature performance, has excellent anti-fatigue performance, strong water damage resistance and shear resistance, and is suitable for large-scale popularization and application.

[0011] Another object of the present invention is to provide a preparation method of a toughened composite modified discontinuous semi-open graded GATB-25 asphalt mixture, which is simple to prepare. The toughened composite modified discontinuous semi-open graded GATB-25 asphalt mixture prepared therefrom can balance the high and low temperature performance, has excellent anti-fatigue performance, strong water damage resistance and shear resistance, and is suitable for large-scale popularization and application.

[0012] To achieve the above object, in the first aspect of the present invention, a toughened composite modified discontinuous semi-open graded GATB-25 asphalt mixture is provided, which is characterized in that it includes G-type rubber-plastic composite modified asphalt and discontinuous semi-open graded GATB-25 aggregates, and the G-type rubber-plastic composite modified asphalt uniformly coats the discontinuous semi-open graded GATB-25 aggregates;

[0013] Among them, the G-type rubber-plastic composite modified asphalt includes asphalt, rubber powder and PE particles, the mass ratio of the rubber powder to the PE particles is 3:1 to 5:1, and the total dosage of the rubber powder and the PE particles is 18% to 22% by weight of the asphalt;

[0014] The mass percentage of the discontinuous semi-open graded GATB-25 aggregates passing through the 9.5 mm sieve hole is 20% to 45%, the mass percentage of the discontinuous semi-open graded GATB-25 aggregates passing through the 4.75 mm sieve hole is 18% to 26%, and the mass percentage of the discontinuous semi-open graded GATB-25 aggregates passing through the 2.36 mm sieve hole is 14% to 22%.

[0015] Preferably, the asphalt-aggregate ratio of the G-type rubber-plastic composite modified asphalt and the discontinuous semi-open graded GATB-25 aggregates is 5.6%.

[0016] Preferably, the rubber powder is waste tire rubber powder.

[0017] Preferably, the PE particles are recycled polyethylene particles.

[0018] Preferably, the mass percentage of the discontinuous semi-open graded GATB-25 aggregates passing through the 9.5 mm sieve hole is 31.9%, the mass percentage of the discontinuous semi-open graded GATB-25 aggregates passing through the 4.75 mm sieve hole is 24.2%, and the mass percentage of the discontinuous semi-open graded GATB-25 aggregates passing through the 2.36 mm sieve hole is 18.2%.

[0019] Preferably, the discontinuous semi-open-graded GATB-25 aggregate comprises 11% by weight of gravel sized 25 mm to 31.5 mm, 36% by weight of gravel sized 15 mm to 25 mm, 32% by weight of gravel sized 5 mm to 15 mm, 2% by weight of gravel sized 3 mm to 5 mm, 16% by weight of stone dust sized 0 mm to 3 mm, and 3% by weight of mineral powder not greater than 0.3 mm.

[0020] In a second aspect of the present invention, there is provided a method for preparing the toughened composite modified discontinuous semi-open-graded GATB-25 asphalt mixture as described above, characterized by comprising the following steps:

[0021] (1) Heating the discontinuous semi-open-graded GATB-25 aggregate to remove surface moisture;

[0022] (2) After heating the G-type composite modified asphalt, adding it to the discontinuous semi-open-graded GATB-25 aggregate;

[0023] (3) Stirring to uniformly coat the discontinuous semi-open-graded GATB-25 aggregate with the G-type composite modified asphalt to obtain the toughened composite modified discontinuous semi-open-graded GATB-25 asphalt mixture.

[0024] Preferably, in the step (1), the heating temperature reaches 180°C to 190°C; in the step (2), the heating temperature reaches 160°C to 170°C; in the step (3), the stirring is carried out by a forced mixer, and the stirring time is 90 seconds to 120 seconds.

[0025] Preferably, the G-type rubber-plastic composite modified asphalt is prepared by the following method:

[0026] (A) After heating the asphalt, adding the rubber powder and stirring to fully swell the rubber powder;

[0027] (B) Then adding the PE particles and raising the temperature, followed by high-speed shearing to form a homogeneous colloid, namely the G-type rubber-plastic composite modified asphalt.

[0028] More preferably, in the step (A), the heating temperature reaches 160°C to 180°C, and the stirring time is 30 minutes; in the step (B), the temperature rise reaches 180°C to 190°C, the high-speed shearing speed is 3000 r / min to 4000 r / min, and the high-speed shearing time is 1 hour.

[0029] The beneficial effects of the present invention are as follows:

[0030] 1. The toughened composite modified gap-graded GATB-25 asphalt mixture of the present invention comprises G-type rubber-plastic composite modified asphalt and gap-graded GATB-25 aggregate, and the G-type rubber-plastic composite modified asphalt uniformly coats the gap-graded GATB-25 aggregate; wherein, the G-type rubber-plastic composite modified asphalt comprises asphalt, rubber powder and PE particles, the mass ratio of the rubber powder to the PE particles is 3:1 to 5:1, and the total dosage of the rubber powder and the PE particles is 18% to 22% by weight of the asphalt; the mass percentage of the gap-graded GATB-25 aggregate passing through the 9.5 mm sieve hole is 20% to 45%, the mass percentage of the gap-graded GATB-25 aggregate passing through the 4.75 mm sieve hole is 18% to 26%, and the mass percentage of the gap-graded GATB-25 aggregate passing through the 2.36 mm sieve hole is 14% to 22%. Therefore, it can balance the high and low temperature performances, has excellent anti-fatigue performance, strong water damage resistance and shear resistance, and is suitable for large-scale popularization and application.

[0031] 2. The preparation method of the toughened composite modified gap-graded GATB-25 asphalt mixture of the present invention comprises the following steps: (1) heating the gap-graded GATB-25 aggregate to remove surface moisture; (2) heating the G-type composite modified asphalt and adding it to the gap-graded GATB-25 aggregate; (3) stirring to make the G-type composite modified asphalt uniformly coat the gap-graded GATB-25 aggregate to obtain the toughened composite modified gap-graded GATB-25 asphalt mixture. Therefore, its preparation is simple, and the toughened composite modified gap-graded GATB-25 asphalt mixture prepared therefrom can balance the high and low temperature performances, has excellent anti-fatigue performance, strong water damage resistance and shear resistance, and is suitable for large-scale popularization and application.

[0032] These and other objects, features and advantages of the present invention are fully embodied by the following detailed description and claims, and can be realized by the means, devices and their combinations specifically pointed out in the appended claims. Brief Description of the Drawings

[0033] Figure 1 is a three-dimensional schematic diagram of the composite form of rubber particles (black) and PE network (gray) in Example 1, used to explain the elastic recovery and high temperature stability mechanism, wherein the rubber particles are marked with thick black arrows and the PE network is marked with thin black arrows.

[0034] Figure 2 is a comparison chart of the grading curve of the gap-graded GATB-25 aggregate in Example 1 and the grading requirement range. Through the sieve hole passing rate curve, the grading break characteristics in the 4.75 mm - 9.5 mm interval are highlighted, where 1 is the grading upper limit, 2 is the grading lower limit, 3 is the grading median value, and 4 is the grading curve of the gap-graded GATB-25 aggregate in Example 1. Detailed implementation mode

[0035] In order to solve the following problems of existing asphalt mixtures: 1. Insufficient anti-fatigue performance: Traditional mixtures are prone to fatigue cracks under long-term cyclic loads, shortening the service life of the road surface; 2. Imbalance between high and low temperature performance: Single modified asphalt is difficult to meet the requirements of high temperature rutting resistance and low temperature cracking resistance at the same time; 3. Limited economy: The cost of SBS modified asphalt and fiber reinforcement technology is high and it is difficult to promote on a large scale; 4. Defects in gradation structure: The internal stress distribution of dense gradation mixtures is uneven, and the resistance to water damage and shear is insufficient. Through in-depth and extensive research, the inventor proposes a toughened composite modified discontinuous semi-open gradation GATB-25 asphalt mixture, which can balance high and low temperature performance, has excellent anti-fatigue performance, and strong resistance to water damage and shear.

[0036] The toughened composite modified discontinuous semi-open gradation GATB-25 asphalt mixture of the present invention includes G-type rubber-plastic composite modified asphalt and discontinuous semi-open gradation GATB-25 aggregate, and the G-type rubber-plastic composite modified asphalt uniformly coats the discontinuous semi-open gradation GATB-25 aggregate;

[0037] Among them, the G-type rubber-plastic composite modified asphalt includes asphalt, rubber powder and PE particles, the mass ratio of the rubber powder to the PE particles is 3:1 to 5:1, and the total dosage of the rubber powder and the PE particles is 18% to 22% by weight of the asphalt;

[0038] The mass percentage of the discontinuous semi-open gradation GATB-25 aggregate passing through the 9.5 mm sieve hole is 20% to 45%, the mass percentage of the discontinuous semi-open gradation GATB-25 aggregate passing through the 4.75 mm sieve hole is 18% to 26%, and the mass percentage of the discontinuous semi-open gradation GATB-25 aggregate passing through the 2.36 mm sieve hole is 14% to 22%.

[0039] The asphalt-aggregate ratio of the G-type rubber-plastic composite modified asphalt and the discontinuous semi-open gradation GATB-25 aggregate can be determined as needed. Preferably, the asphalt-aggregate ratio of the G-type rubber-plastic composite modified asphalt and the discontinuous semi-open gradation GATB-25 aggregate is 5.6%.

[0040] The rubber powder can be any suitable rubber powder. Preferably, the rubber powder is waste tire rubber powder.

[0041] The particle size of the rubber powder can be determined as needed. Preferably, the particle size of the rubber powder is 80 mesh to 120 mesh.

[0042] The PE particles can be any suitable PE particles. Preferably, the PE particles are recycled polyethylene particles.

[0043] The mass percentage of the discontinuous semi-open graded GATB-25 aggregate passing through the 9.5 mm sieve opening, the mass percentage of the discontinuous semi-open graded GATB-25 aggregate passing through the 4.75 mm sieve opening, and the mass percentage of the discontinuous semi-open graded GATB-25 aggregate passing through the 2.36 mm sieve opening can be determined as needed. Preferably, the mass percentage of the discontinuous semi-open graded GATB-25 aggregate passing through the 9.5 mm sieve opening is 31.9%, the mass percentage of the discontinuous semi-open graded GATB-25 aggregate passing through the 4.75 mm sieve opening is 24.2%, and the mass percentage of the discontinuous semi-open graded GATB-25 aggregate passing through the 2.36 mm sieve opening is 18.2%.

[0044] The discontinuous semi-open graded GATB-25 aggregate can have any suitable composition. More preferably, the discontinuous semi-open graded GATB-25 aggregate includes 11% by weight of crushed stones of 25 mm - 31.5 mm, 36% by weight of crushed stones of 15 mm - 25 mm, 32% by weight of crushed stones of 5 mm - 15 mm, 2% by weight of crushed stones of 3 mm - 5 mm, 16% by weight of stone chips of 0 mm - 3 mm, and 3% by weight of mineral powder not greater than 0.3 mm.

[0045] The present invention also provides a method for preparing the toughened composite modified discontinuous semi-open graded GATB-25 asphalt mixture as described above, comprising the following steps:

[0046] (1) Heating the discontinuous semi-open graded GATB-25 aggregate to remove surface moisture;

[0047] (2) After heating the G-type composite modified asphalt, adding it to the discontinuous semi-open graded GATB-25 aggregate;

[0048] (3) Stirring to make the G-type composite modified asphalt uniformly coat the discontinuous semi-open graded GATB-25 aggregate to obtain the toughened composite modified discontinuous semi-open graded GATB-25 asphalt mixture.

[0049] In the step (1), the temperature reached by heating can be determined as needed. Preferably, in the step (1), the temperature reached by heating is 180°C - 190°C.

[0050] In the step (2), the temperature reached by heating can be determined as needed. Preferably, in the step (2), the temperature reached by heating is 160°C - 170°C.

[0051] In step (3), the stirring can be carried out by any suitable equipment, and the stirring time can be determined as needed. Preferably, in step (3), the stirring is carried out by a forced mixer, and the stirring time is 90 seconds to 120 seconds.

[0052] The G-type rubber-plastic composite modified asphalt can be prepared by any suitable method. Preferably, the G-type rubber-plastic composite modified asphalt is prepared by the following method:

[0053] (A) Heat the asphalt and then add the rubber powder for stirring to fully swell the rubber powder;

[0054] (B) Then add the PE particles and raise the temperature, and then carry out high-speed shearing to form a homogeneous colloid, that is, the G-type rubber-plastic composite modified asphalt.

[0055] In step (A), the temperature reached by heating and the stirring time can be determined as needed. More preferably, in step (A), the temperature reached by heating is 160°C to 180°C, and the stirring time is 30 minutes.

[0056] In step (B), the temperature reached by heating, the speed of high-speed shearing, and the time of high-speed shearing can be determined as needed. More preferably, in step (B), the temperature reached by heating is 180°C to 190°C, the speed of high-speed shearing is 3000 r / min to 4000 r / min, and the time of high-speed shearing is 1 hour.

[0057] In order to more clearly understand the technical content of the present invention, the following specific examples are given for detailed description.

[0058] The experimental methods without specific conditions in the following examples are usually determined according to national standards. If there is no corresponding national standard, they are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0059] Unless otherwise defined or stated, all professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to the described content can be applied to the method of the present invention.

[0060] Example 1 Toughened Composite Modified Gap-graded GATB-25 Asphalt Mixture I

[0061] 1. Preparation of G-type rubber-plastic composite modified asphalt:

[0062] Raw material selection: The rubber powder is waste tire rubber powder (particle size 80 - 120 mesh) (Shanghai Huanxun Environmental Protection Technology Co., Ltd., waste tire rubber powder, particle size 80 - 120 mesh), and the PE particles are recycled polyethylene particles (Shanghai Suyuan Renewable Resources Co., Ltd., recycled polyethylene particles, model PE-HD-01). The mass ratio of the two is controlled at 3:1 and used as the composite modifier.

[0063] Modification process: Heat the matrix asphalt (Sinopec Shanghai Petrochemical Co., Ltd., 70# A-grade road petroleum asphalt) to 170°C, add the rubber powder and stir for 30 minutes to fully swell the rubber.

[0064] Add the PE particles and raise the temperature to 185°C, and perform high-speed shearing (4000 r / min) for 1 hour to form a homogeneous colloid.

[0065] The total dosage of the rubber powder and PE particles is controlled at 18% by weight of the asphalt, so that the Brookfield viscosity at 180°C ≥ 1.0 Pa·s to ensure the fluidity during high-temperature construction.

[0066] 2. Gap-graded semi-open-graded GATB-25 aggregate (see Table 1 below):

[0067] Raw material selection: 25 mm - 31.5 mm crushed stone (11% by weight), 15 mm - 25 mm crushed stone (36% by weight), 5 mm - 15 mm crushed stone (32% by weight), 3 mm - 5 mm crushed stone (2% by weight), 0 mm - 3 mm stone chips (16% by weight), mineral powder not greater than 0.3 mm (Zhejiang Jinhua Dongyang Mineral Powder Factory, limestone mineral powder) (3% by weight). The crushed stone is limestone purchased from Huizhou Stone Material Factory, Huangshan City, Anhui Province.

[0068] Fully mix the above raw materials to obtain gap-graded semi-open-graded GATB-25 aggregate. The passing rate of the gradation: 31.9% by weight for the 9.5 mm sieve hole, 24.2% by weight for the 4.75 mm sieve hole, and 18.2% by weight for the 2.36 mm sieve hole.

[0069] Table 1 GATB-25 Design Gradation and Combined Gradation

[0070]

[0071]

[0072] 3. Preparation process of toughened composite modified gap-graded semi-open-graded GATB-25 asphalt mixture I

[0073] 3.1 Aggregate pretreatment:

[0074] Heat the gap-graded semi-open-graded GATB-25 aggregate to 185°C to remove the surface moisture.

[0075] 3.2 Asphalt mixing:

[0076] Heat the G-type rubber-plastic composite modified asphalt to 165 °C and add it to the aggregate at an asphalt-aggregate ratio of 5.6%.

[0077] The forced mixer is stirred for 105 seconds to ensure that the asphalt evenly coats the aggregate, obtaining the toughened composite modified gap-graded GATB-25 asphalt mixture I.

[0078] 4. Molding and compaction:

[0079] The toughened composite modified gap-graded GATB-25 asphalt mixture I is molded into specimens using a rotary compactor (SGC) with 60 compaction times to simulate the actual pavement compaction conditions.

[0080] The final compaction temperature is 130 °C to avoid excessive aging of the asphalt binder.

[0081] Example 2 Toughened Composite Modified Gap-Graded GATB-25 Asphalt Mixture II

[0082] 1. Preparation of G-type rubber-plastic composite modified asphalt:

[0083] Raw material selection: The rubber powder uses waste tire rubber powder (particle size 80 - 120 mesh) (same as Example 1), and the PE particles use recycled polyethylene particles (same as Example 1). The mass ratio of the two is controlled at 4:1 as the composite modifier.

[0084] Modification process: Heat the base asphalt (same as Example 1) to 180 °C, add the rubber powder and stir for 30 minutes to fully swell the rubber.

[0085] Add the PE particles and raise the temperature to 190 °C, and perform high-speed shearing (3500 r / min) for 1 hour to form a homogeneous colloid.

[0086] The total dosage of the rubber powder and PE particles is controlled at 22% by weight of the asphalt, so that the Brookfield viscosity at 180 °C ≥ 1.0 Pa·s to ensure the workability during high-temperature construction.

[0087] 2. Gap-graded GATB-25 aggregate (see Table 2 below):

[0088] Raw material selection: 25 mm - 31.5 mm crushed stone (8% by weight), 15 mm - 25 mm crushed stone (25% by weight), 5 mm - 15 mm crushed stone (25% by weight), 3 mm - 5 mm crushed stone (5% by weight), 0 mm - 3 mm stone chips (32% by weight), mineral powder not greater than 0.3 mm (same as Example 1) (5% by weight). The source of the crushed stone is the same as that in Example 1.

[0089] The above raw materials are fully mixed to obtain discontinuous semi-open graded GATB-25 aggregate, with the gradation pass rate as follows: 9.5 mm sieve hole 44.7% by weight, 4.75 mm sieve hole 25.1% by weight, 2.36 mm sieve hole 21.8% by weight.

[0090] Table 2 Design gradation and composite gradation of GATB-25

[0091]

[0092] 3. Preparation process of toughened composite modified discontinuous semi-open graded GATB-25 asphalt mixture I

[0093] 3.1 Aggregate pretreatment:

[0094] The discontinuous semi-open graded GATB-25 aggregate was heated to 190°C to remove surface moisture;

[0095] 3.2 Asphalt mixing:

[0096] Heat G-type rubber-plastic composite modified asphalt to 160°C and add it to the aggregate at a 5.6% asphalt-to-stone ratio;

[0097] The forced mixer was stirred for 90 seconds to ensure that the asphalt evenly coated the aggregates to obtain the toughened composite modified discontinuous semi-open graded GATB-25 asphalt mixture I;

[0098] 4. Molding and compaction:

[0099] The toughened composite modified discontinuous semi-open graded GATB-25 asphalt mixture I was formed into specimens using a rotary compactor (SGC) and compacted 75 times to simulate the actual pavement compaction conditions.

[0100] The final pressing temperature is 135℃ to avoid excessive aging of the asphalt binder.

[0101] Example 3 Toughened composite modified discontinuous semi-open gradation GATB-25 asphalt mixture III

[0102] 1. Preparation of G-type rubber-plastic composite modified asphalt:

[0103] Raw material selection: Rubber powder uses waste tire rubber powder (particle size 80-120 mesh) (same as Example 1), and PE particles use recycled polyethylene particles (same as Example 1), and the mass ratio of the two is controlled at 5:1 as a composite modifier.

[0104] Modification process: Heat the base asphalt (same as in Example 1) to 160°C, add rubber powder and stir for 30 minutes to allow the rubber to fully swell;

[0105] Add PE particles and heat to 180°C, and high-speed shear (3000r / min) for 1 hour to form a homogeneous colloid;

[0106] The total dosage of rubber powder and PE particles is controlled at 20% by weight of the asphalt, so that the Brookfield viscosity at 180 °C ≥ 1.0 Pa·s to ensure the workability during high-temperature construction.

[0107] 2. Gap-graded semi-open-graded GATB-25 aggregates (see Table 3 below):

[0108] Raw material selection: 25 mm - 31.5 mm crushed stones (15% by weight), 15 mm - 25 mm crushed stones (40% by weight), 5 mm - 15 mm crushed stones (33% by weight), 3 mm - 5 mm crushed stones (5% by weight), 0 mm - 3 mm stone dust (5% by weight), mineral powder not larger than 0.3 mm (same as in Example 1) (2% by weight). The source of the crushed stones is the same as in Example 1.

[0109] Mix the above raw materials fully to obtain gap-graded semi-open-graded GATB-25 aggregates. The passing rate of the gradation: 20.3% by weight for the 9.5 mm sieve hole, 18.1% by weight for the 4.75 mm sieve hole, and 14.5% by weight for the 2.36 mm sieve hole.

[0110] Table 3 GATB-25 Design Gradation and Synthetic Gradation

[0111]

[0112]

[0113] 3. Preparation process of toughened composite modified gap-graded semi-open-graded GATB-25 asphalt mixture I

[0114] 3.1 Aggregate pretreatment:

[0115] Heat the gap-graded semi-open-graded GATB-25 aggregates to 180 °C to remove the surface moisture;

[0116] 3.2 Asphalt mixing:

[0117] Heat the G-type rubber-plastic composite modified asphalt to 170 °C and add it to the aggregates at an asphalt-aggregate ratio of 5.6%;

[0118] Stir with a forced mixer for 120 seconds to ensure that the asphalt uniformly coats the aggregates and obtain toughened composite modified gap-graded semi-open-graded GATB-25 asphalt mixture I;

[0119] 4. Molding and compaction:

[0120] Use a rotary compactor (SGC) to mold specimens from the toughened composite modified gap-graded semi-open-graded GATB-25 asphalt mixture I, with 50 compaction times to simulate the actual pavement compaction condition;

[0121] The final compaction temperature is 140 °C to avoid excessive aging of the asphalt binder.

[0122] Comparative Example 1: SBS Modified GATB-25

[0123] Using the discontinuous semi-open graded ATB-25 aggregate prepared in Example 1, 4.6% by weight of SBS modified asphalt (Shanghai Petrochemical Asphalt Co., Ltd., SBS I-D modified asphalt) and 0.3% by weight of lignin fiber (Zhejiang Jinsen Fiber New Materials Co., Ltd., lignin fiber, model KS-LF-02) were added during asphalt mixing, instead of adding G-type rubber-plastic composite modified asphalt, to obtain SBS modified GATB-25. Then, the specimens were formed using the forming and compaction methods of Example 1.

[0124] Comparative Example 2: ATB-25 Mixture

[0125] Using the discontinuous semi-open graded ATB-25 aggregate prepared in Example 1, 3.6% by weight of 70# asphalt (Zhenhai No. 70 asphalt) was added during asphalt mixing, instead of adding G-type rubber-plastic composite modified asphalt, to obtain ATB-25 mixture. Then, the specimens were formed using the forming and compaction methods of Example 1.

[0126] Performance Test

[0127] The specimens of Examples 1 to 3 and Comparative Examples 1 to 2 were tested for dynamic stability, fatigue life and other indicators according to the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20). The comparison test results of various physical parameters and related performance indicators are shown in Table 4. All tests were carried out in accordance with the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20): such as the Cantabro abrasion test: T 0733-2011 "Cantabro Abrasion Test for Asphalt Mixtures", uniaxial penetration test: T 0718-2011 "Uniaxial Penetration Strength Test for Asphalt Mixtures", dynamic stability test: T 0719-2011 "Wheel Tracking Test for Asphalt Mixtures", fatigue life test: T 0736-2011 "Four-Point Bending Fatigue Test for Asphalt Mixtures".

[0128] Table 4 Test Results of Volumes and Properties of Different Types of Asphalt Mixtures

[0129]

[0130] It can be seen from the test results in Table 4 that the following remarkable advantages are achieved by using the present invention:

[0131] 1. Breakthrough in anti-fatigue performance:

[0132] The four-point bending beam test shows that at a strain level of 400 με, the fatigue life reaches 441,000 times (only 23,000 times for ordinary ATB-25), an increase of nearly 20 times;

[0133] The high-elastic binder and the skeleton structure act synergistically to disperse stress concentration and delay crack propagation.

[0134] 2. Excellent high-temperature stability:

[0135] The dynamic stability (8 cm template) reaches 3320 times / mm, far exceeding the specification requirement of 3000 times / mm;

[0136] The PE modified component forms a three-dimensional network structure to resist high-temperature shear deformation.

[0137] 3. Improvement in comprehensive durability:

[0138] The immersion residual stability ratio is 90.1%, and the Kentucky fly-away loss is only 5.4%. The water damage resistance performance is better than that of traditional materials;

[0139] The uniaxial penetration strength is 2.6 MPa (the specification requirement is 0.7 - 1.2 MPa), and the shear resistance ability is significantly enhanced.

[0140] 4. Win-win in economy and environmental protection:

[0141] The utilization rate of waste rubber powder reaches 30%, and the cost per ton of mixture only increases by 135 yuan, saving 25% - 30% compared with the SBS modification scheme;

[0142] Reduce the landfill volume of plastic and rubber waste, meeting the construction requirements of the "waste-free city".

[0143] 5. Wide construction adaptability:

[0144] The gap grading improves the workability of the mixture during construction, and the compaction energy consumption is reduced by 15% - 20%;

[0145] The viscosity of the binder is moderate, and the paving temperature can be controlled at 150°C - 160°C, reducing energy consumption and greenhouse gas emissions.

[0146] Therefore, the present invention conducts collaborative design from two dimensions of binder modification and gradation optimization:

[0147] (1) Innovative design of the binder

[0148] Adopt G-type rubber-plastic composite modified asphalt

[0149] # Material characteristics:

[0150] Use rubber powder and polyethylene (PE) particles as composite modifiers to composite modify asphalt;

[0151] # Performance advantages:

[0152] The rubber component endows the binder with a high elastic recovery rate (95%), improving the crack resistance;

[0153] The PE component enhances the high-temperature viscoelasticity through physical crosslinking, and the dynamic stability is increased by 15% - 20% compared with SBS modified asphalt;

[0154] The waste utilization rate reaches 30%, and the cost is reduced by 25% - 30% compared with SBS modified asphalt.

[0155] (2) Gradation optimization design

[0156] Use discontinuous semi-open graded GATB-25 aggregate

[0157] # Gradation characteristics:

[0158] Set a gradation break at the key sieve holes (4.75mm - 9.5mm) to reduce the proportion of intermediate-sized aggregate;

[0159] The proportion of coarse aggregate (>4.75mm) is 74 - 82%, forming a framework interlocking structure;

[0160] The proportion of fine aggregate (<2.36mm) is 14% - 22%, filling the framework gaps and enhancing the compaction;

[0161] # Design parameters:

[0162] The target void ratio is 8% - 10% (higher than the 5% - 7% of traditional ATB-25), improving the shear deformation resistance ability;

[0163] The voids in mineral aggregate (VMA) is 18% - 20%, and the asphalt saturation (VFA) is 45% - 55%, balancing durability and water damage resistance ability.

[0164] Thus, through optimizing the binder formula and gradation structure design, the present invention significantly improves the anti-fatigue cracking performance, water damage resistance performance and high-temperature stability of the asphalt pavement, while taking into account economy and environmental protection, and is especially suitable for the lower layer structure of heavy-duty traffic roads, rainy areas and high-grade highways that need to serve for a long time.

[0165] In summary, the toughened composite modified discontinuous semi-open graded GATB-25 asphalt mixture of the present invention can balance the high and low temperature performances, has excellent anti-fatigue performance, strong water damage resistance and anti-shear ability, and is suitable for large-scale popularization and application.

[0166] In this specification, the present invention has been described with reference to its specific embodiments. However, it is obvious that various modifications and transformations can still be made without departing from the spirit and scope of the present invention. Therefore, the specification should be regarded as illustrative rather than restrictive.

Claims

1. A toughened composite modified discontinuous semi-open graded GATB-25 asphalt mixture, characterized in that, It includes G-type rubber-plastic composite modified asphalt and gap-graded GATB-25 aggregate, and the G-type rubber-plastic composite modified asphalt evenly coats the gap-graded GATB-25 aggregate; Among them, the G-type rubber-plastic composite modified asphalt includes asphalt, rubber powder and PE particles. The mass ratio of the rubber powder to the PE particles is 3:1 to 5:1, and the total dosage of the rubber powder and the PE particles is 18% to 22% by weight of the asphalt; The mass percentage of the gap-graded GATB-25 aggregate passing through the 9.5 mm sieve hole is 20% to 45%, the mass percentage of the gap-graded GATB-25 aggregate passing through the 4.75 mm sieve hole is 18% to 26%, and the mass percentage of the gap-graded GATB-25 aggregate passing through the 2.36 mm sieve hole is 14% to 22%.

2. The toughened composite modified discontinuous semi-open graded GATB-25 asphalt mixture according to claim 1, wherein The asphalt-aggregate ratio of the G-type rubber-plastic composite modified asphalt and the gap-graded GATB-25 aggregate is 5.6%.

3. The toughened composite modified discontinuous semi-open graded GATB-25 asphalt mixture according to claim 1, characterized in that, The rubber powder is waste tire rubber powder.

4. The toughened composite modified discontinuous semi-open graded GATB-25 asphalt mixture according to claim 1, wherein, The PE particles are recycled polyethylene particles.

5. The toughened composite modified discontinuous semi-open graded GATB-25 asphalt mixture according to claim 1, wherein, The mass percentage of the gap-graded GATB-25 aggregate passing through the 9.5 mm sieve hole is 31.9%, the mass percentage of the gap-graded GATB-25 aggregate passing through the 4.75 mm sieve hole is 24.2%, and the mass percentage of the gap-graded GATB-25 aggregate passing through the 2.36 mm sieve hole is 18.2%.

6. The toughened composite modified discontinuous semi-open graded GATB-25 asphalt mixture according to claim 5, wherein, The gap-graded GATB-25 aggregate includes 11% by weight of 25 mm - 31.5 mm crushed stones, 36% by weight of 15 mm - 25 mm crushed stones, 32% by weight of 5 mm - 15 mm crushed stones, 2% by weight of 3 mm - 5 mm crushed stones, 16% by weight of 0 mm - 3 mm stone chips, and 3% by weight of mineral powder not greater than 0.3 mm.

7. A preparation method of a toughened composite modified discontinuous semi-open graded GATB-25 asphalt mixture according to claim 1, characterized in that, It includes the following steps: (1) Heat the gap-graded GATB-25 aggregate to remove surface moisture; (2) After heating the G-type composite modified asphalt, add it to the gap-graded GATB-25 aggregate; (3) Stir to make the G-type composite modified asphalt evenly coat the gap-graded GATB-25 aggregate to obtain the toughened composite modified gap-graded GATB-25 asphalt mixture.

8. The preparation method of the toughened composite modified discontinuous semi-open graded GATB-25 asphalt mixture according to claim 7, characterized in that, In the step (1), the heating temperature reaches 180°C to 190°C; in the step (2), the heating temperature reaches 160°C to 170°C; in the step (3), the stirring is carried out by a forced mixer, and the stirring time is 90 seconds to 120 seconds.

9. The preparation method of the toughened composite modified discontinuous semi-open graded GATB-25 asphalt mixture according to claim 7, characterized in that, The G-type rubber-plastic composite modified asphalt is prepared by the following method: (A) Heat the asphalt and then add the rubber powder and stir to make the rubber powder fully swell; (B) Then add the PE particles and raise the temperature, and then carry out high-speed shearing to form a homogeneous colloid, that is, the G-type rubber-plastic composite modified asphalt.

10. The preparation method of the toughened composite modified discontinuous semi-open graded GATB-25 asphalt mixture according to claim 9, characterized in that, In the step (A), the temperature reached by heating is 160°C to 180°C, and the stirring time is 30 minutes; in the step (B), the temperature reached by heating up is 180°C to 190°C, the speed of high-speed shearing is 3000 r / min to 4000 r / min, and the time of high-speed shearing is 1 hour.

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