Warm-mix asphalt mixture based on a warm-mixing agent and a method for producing the same

Abstract

The application provides a warm-mixing agent based asphalt mastic stone chip mixture and a preparation method, and relates to the technical field of road engineering materials, and the preparation method comprises the following steps: heating warm-mixing asphalt to a mixing temperature of 145±5 DEG C; heating coarse aggregate and fine aggregate to 3-5 DEG C higher than the mixing temperature respectively; mixing the heated aggregate, mineral powder and fiber with the warm-mixing asphalt at the mixing temperature; and using a Marshall compactor to perform double-side compaction forming with a compaction number of 75±5 times, wherein the application realizes the unification of energy saving and emission reduction and high performance by the synergistic effect of a specific mixing temperature and a compaction number, the construction temperature is reduced by 20-30 DEG C, the prepared SMA mixture has excellent high-temperature stability and low-temperature crack resistance, and is suitable for high-grade highway, airport runway and other engineering.

Description

Technical Field

[0001] This invention relates to the field of road engineering materials technology, and in particular to an asphalt mastic aggregate based on a warm mix additive and its preparation method. Background Technology

[0002] Stone matrix asphalt (SMA) mixture is a pavement material formed by the interlocking of coarse aggregate skeleton and the binding of rich asphalt mastic. It has excellent road performance properties such as high temperature rutting resistance, low temperature crack resistance, water damage resistance and wear resistance, and has been widely used in engineering fields such as high-grade highways, airport runways, bridge deck paving and heavy traffic roads.

[0003] Traditional SMA (Stone Mold Asphalt) mixtures are constructed using the hot-mix process, with mixing temperatures typically not lower than 160℃ and compaction temperatures maintained above 150℃. However, excessively high construction temperatures bring a series of technical problems: First, energy consumption is enormous, with approximately 1-1.5 kg of fuel oil consumed per ton of hot-mix SMA mixture, and large amounts of carbon dioxide, harmful smoke, and asphalt fumes emitted. Second, the high-temperature environment accelerates the thermo-oxidative aging of the asphalt binder, leading to asphalt embrittlement and affecting the long-term durability of the mixture and the service life of the pavement. Third, the hot-mix process is significantly affected by the construction season and environment; compaction quality is difficult to guarantee in low-temperature or humid environments, limiting the construction window.

[0004] To overcome the aforementioned shortcomings of hot-mix asphalt mixtures, warm-mix asphalt (WMA) technology emerged. WMA technology reduces the viscosity of asphalt at construction temperatures through physical or chemical methods, enabling the mixture to achieve good mixing and compaction even at temperatures 20–50°C lower than hot-mix temperatures. Currently, mainstream WMA technologies include organic additive methods, surfactant methods, and foamed asphalt methods. While these technologies can reduce construction temperatures to some extent, applying them to SMA mixtures, which are highly sensitive to gradation and binder properties, presents complex performance control challenges.

[0005] Existing research indicates that process parameters such as warm mix additive dosage, mixing temperature, and compaction work (number of compaction passes) significantly affect the volumetric parameters (void ratio, aggregate interstitial ratio, etc.) and mechanical properties (high-temperature stability, low-temperature crack resistance) of SMA mixtures. However, existing technologies lack systematic optimization in selecting process parameters for warm mix SMA mixtures, especially the typical SMA-13 ​​gradation. On the one hand, excessively low mixing temperatures or insufficient compaction work can lead to inadequate compaction and excessively high void ratios, thereby weakening its resistance to water damage and fatigue. On the other hand, excessively high mixing temperatures or excessively high compaction work may disrupt the interlocking structure of the coarse aggregate skeleton, reducing high-temperature rutting resistance and diminishing the energy-saving advantages of warm mix technology. More critically, existing technologies generally fail to reveal the synergistic effect between mixing temperature and number of compaction passes, leading to the frequent use of empirical values ​​or simple application of hot mix SMA process parameters in practical engineering. This makes it difficult to balance high-temperature and low-temperature performance, limiting the widespread application of warm mix SMA technology.

[0006] Therefore, how to provide a warm-mix SMA preparation method for SMA-13 ​​gradation that can balance the reduction of construction temperature and the maintenance of road performance, and clearly give the combination of mixing temperature and compaction number with synergistic effect, forming a quality control process that can be directly referenced in engineering, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide an asphalt mastic aggregate based on warm mix additive and its preparation method.

[0008] This invention is achieved through the following technical solution: A method for preparing asphalt mastic aggregate based on warm mix additive includes the following steps: The warm-mix asphalt is heated to a mixing temperature of 145±5℃; The coarse and fine aggregates are heated separately to a temperature 3-5°C higher than the mixing temperature. Heated coarse aggregate, heated fine aggregate, mineral powder and fiber are mixed with warm-mix asphalt heated to the mixing temperature to obtain a warm-mix mixture. The warm-mixed material was compacted on both sides using a Marshall compactor with 75±5 compaction cycles.

[0009] According to the above technical solution, preferably, the mixing temperature is 145°C and the number of compactions is 75.

[0010] According to the above technical solution, preferably, the warm mix asphalt comprises base asphalt and a warm mix agent accounting for 0.4% to 0.6% of the mass of the base asphalt, wherein the warm mix agent is a surfactant-type warm mix agent, and the base asphalt is heavy traffic road petroleum asphalt AH-70#.

[0011] According to the above technical solution, preferably, the fiber is basalt fiber, the basalt fiber accounts for 0.3%~0.5% of the total mass of the mixture, and the length of the basalt fiber is 10-14mm and the diameter is 15±2μm.

[0012] According to the above technical solution, preferably, the aggregate gradation is SMA-13; the mixing step is as follows: first, the heated coarse aggregate, heated fine aggregate, mineral powder and fiber are dry-mixed, and then warm-mix asphalt heated to the mixing temperature is added for wet mixing.

[0013] This invention also discloses an asphalt mastic aggregate mixture based on a warm mix additive, comprising the following raw materials by mass: Asphalt binder: 5.5~6.0 parts; Aggregate: 84-85 parts; Mineral powder: 9-10 parts; Fiber stabilizer: 0.3~0.5 parts; The aggregate has an SMA-13 ​​gradation and is further subdivided by particle size into the following mass fractions: 3.0-4.0 parts of 13.2mm particle size, 30.0-33.0 parts of 9.6mm particle size, 34.0-36.0 parts of 4.75mm particle size, 4.0-5.0 parts of 2.36mm particle size, 2.0-3.0 parts of 1.18mm particle size, 2.0-3.0 parts of 0.6mm particle size, 1.0-2.0 parts of 0.3mm particle size, 0.5-1.5 parts of 0.15mm particle size, and 2.0-3.0 parts of 0.075mm particle size.

[0014] According to the above technical solution, preferably, it comprises the following raw materials by mass: The asphalt binder content is 5.83 parts; The aggregate consisted of 84.38 parts. The mineral powder content was 9.39 parts. The fiber stabilizer is 0.4 parts; The aggregate has an SMA-13 ​​gradation and is further subdivided by particle size into the following mass fractions: 3.47 parts for 13.2mm particle size, 31.69 parts for 9.6mm particle size, 35.16 parts for 4.75mm particle size, 4.69 parts for 2.36mm particle size, 2.34 parts for 1.18mm particle size, 2.34 parts for 0.6mm particle size, 1.41 parts for 0.3mm particle size, 0.94 parts for 0.15mm particle size, and 2.34 parts for 0.075mm particle size.

[0015] According to the above technical solution, preferably, the asphalt binder comprises base asphalt and a warm mix agent accounting for 0.4% to 0.6% of the mass of the base asphalt, wherein the warm mix agent is a surfactant-type warm mix agent, and the base asphalt is heavy traffic road petroleum asphalt AH-70#.

[0016] According to the above technical solution, preferably, the fiber stabilizer is basalt fiber, the basalt fiber accounts for 0.3%~0.5% of the total mass of the mixture, and the length of the basalt fiber is 10-14mm and the diameter is 15±2μm.

[0017] The beneficial effects of this invention are: (1) By adding a surfactant-type warm mix agent, this invention effectively reduces the viscosity of asphalt at the construction temperature, enabling SMA-13 ​​mixture to be mixed and compacted at a temperature significantly lower than that of traditional hot mix processes. The reduction in construction temperature directly reduces fuel consumption and greenhouse gas emissions, while significantly inhibiting the generation of asphalt fumes and harmful volatile substances, improving the construction working environment, and meeting the development requirements of green and low-carbon road materials; (2) Through extensive process screening, this invention has determined a specific combination of mixing temperature (145±5℃) and compaction frequency (75±5 times). This combination is not a simple addition of parameters, but rather a synergistic effect between the two: on the one hand, the appropriate mixing temperature ensures that the warm-mix asphalt fully coats the aggregates, while avoiding excessively high temperatures that cause thermo-oxidative aging of the asphalt binder; on the other hand, the optimized number of compaction times ensures that the mixture can still achieve sufficient compaction work at lower temperatures, forming a stable coarse aggregate skeleton interlocking structure. The above synergistic effect significantly improves the mixture's resistance to rutting at high temperatures and its resistance to cracking at low temperatures, overcoming the technical difficulty of existing warm-mix technologies in simultaneously achieving high and low temperature performance. (3) This invention, through a specific combination of process parameters, ensures that the volumetric indices of the warm-mix SMA-13 ​​mixture, such as void ratio, aggregate void ratio, and effective asphalt saturation, are all within a reasonable range. This indicates that even under reduced construction temperature conditions, the mixture can still form a good dense skeleton structure, the interlocking effect between coarse aggregates is fully utilized, and the asphalt mastic fills the skeleton voids fully and uniformly, thereby ensuring the durability, stability, and fatigue resistance of the pavement. (4) This invention provides an optimal combination of mixing temperature and number of compaction times for SMA-13 ​​gradation, supported by experimental data, forming a clear and quantifiable process guideline. This preparation method does not require major modifications to existing asphalt mixing and construction equipment; it only requires precise control of temperature and number of compaction times during the mixing process. It can be directly promoted and applied in existing production systems, and has the outstanding advantages of simple operation, low modification cost, and easy quality control. Attached Figure Description

[0018] Figure 1 A flowchart illustrating an embodiment of the present invention is shown; Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0020] In the description of the invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention.

[0021] As shown in the figure, the present invention provides a method for preparing asphalt mastic aggregate based on warm mix additive, comprising the following steps: The warm-mix asphalt is heated to a mixing temperature of 145±5℃; The coarse and fine aggregates are heated separately to a temperature 3-5°C higher than the mixing temperature. Heated coarse aggregate, heated fine aggregate, mineral powder and fiber are mixed with warm-mix asphalt heated to the mixing temperature to obtain a warm-mix mixture. The warm-mixed material was compacted on both sides using a Marshall compactor with 75±5 compaction cycles.

[0022] Optionally, in one possible implementation, the mixing temperature is 145°C and the number of compactions is 75.

[0023] Optionally, in one possible implementation, the warm mix asphalt comprises base asphalt and a warm mix agent comprising 0.4% to 0.6% of the mass of the base asphalt, wherein the warm mix agent is a surfactant-type warm mix agent, and the base asphalt is heavy traffic road petroleum asphalt AH-70#.

[0024] Optionally, in one possible implementation, the fiber is basalt fiber, which accounts for 0.3% to 0.5% of the total mass of the mixture, and the basalt fiber has a length of 10-14 mm and a diameter of 15±2 μm.

[0025] Optionally, in one possible implementation, the aggregate gradation is SMA-13; the mixing step specifically involves: first, dry mixing the heated coarse aggregate, heated fine aggregate, mineral powder and fiber, and then adding warm-mix asphalt heated to the mixing temperature for wet mixing.

[0026] This invention also discloses an asphalt mastic aggregate mixture based on a warm mix additive, comprising the following raw materials by mass: Asphalt binder: 5.5~6.0 parts; Aggregate: 84-85 parts; Mineral powder: 9-10 parts; Fiber stabilizer: 0.3~0.5 parts; The aggregate has an SMA-13 ​​gradation and is further subdivided by particle size into the following mass fractions: 3.0-4.0 parts of 13.2mm particle size, 30.0-33.0 parts of 9.6mm particle size, 34.0-36.0 parts of 4.75mm particle size, 4.0-5.0 parts of 2.36mm particle size, 2.0-3.0 parts of 1.18mm particle size, 2.0-3.0 parts of 0.6mm particle size, 1.0-2.0 parts of 0.3mm particle size, 0.5-1.5 parts of 0.15mm particle size, and 2.0-3.0 parts of 0.075mm particle size.

[0027] Optionally, in one possible implementation, the product comprises the following raw materials by weight: The asphalt binder content is 5.83 parts; The aggregate consisted of 84.38 parts. The mineral powder content was 9.39 parts. The fiber stabilizer is 0.4 parts; The aggregate has an SMA-13 ​​gradation and is further subdivided by particle size into the following mass fractions: 3.47 parts for 13.2mm particle size, 31.69 parts for 9.6mm particle size, 35.16 parts for 4.75mm particle size, 4.69 parts for 2.36mm particle size, 2.34 parts for 1.18mm particle size, 2.34 parts for 0.6mm particle size, 1.41 parts for 0.3mm particle size, 0.94 parts for 0.15mm particle size, and 2.34 parts for 0.075mm particle size.

[0028] Optionally, in one possible implementation, the asphalt binder comprises base asphalt and a warm mix agent comprising 0.4% to 0.6% of the mass of the base asphalt, wherein the warm mix agent is a surfactant-type warm mix agent, and the base asphalt is heavy traffic road petroleum asphalt AH-70#.

[0029] Optionally, in one possible implementation, the fiber stabilizer is basalt fiber, which accounts for 0.3% to 0.5% of the total mass of the mixture, and the basalt fiber has a length of 10-14 mm and a diameter of 15±2 μm.

[0030] Example 1 I. Raw Material Preparation (1) Asphalt binder: Heavy traffic road petroleum asphalt AH-70# is used as the base asphalt. The warm mix agent is a surfactant-type warm mix agent (such as Evotherm®), and the dosage is 0.5% of the mass of the base asphalt. The base asphalt is heated to 150-160℃, the warm mix agent is added, and then mechanically stirred to mix evenly to obtain warm mix asphalt, which is then kept warm for later use; (2) Aggregates and mineral powder: The coarse and fine aggregates are limestone crushed stone, and the composite gradation meets the requirements of SMA-13. The mineral powder is limestone mineral powder with a particle size of less than 0.075 mm; (3) Fiber stabilizer: Basalt fiber is used, with a length of 12mm (allowable range of 10-14mm), a diameter of 15±2μm, and a tensile strength of 3900MPa. The fiber content is 0.4% of the total mass of the mixture (allowable range of 0.3%-0.5%).

[0031] II. Preparation Method of Mixture S1: Heat the warm mix asphalt to the required mixing temperature (135±5℃, 145±5℃ or 155±5℃, depending on the example). S2: Heat the coarse aggregate and fine aggregate separately to a temperature 3-5°C higher than the mixing temperature (to prevent heat loss during mixing and operation), while the mineral powder and fiber are not heated separately; S3: The heated coarse aggregate, heated fine aggregate, mineral powder and fiber are put into the mixing pot and dry-mixed first; then warm-mix asphalt heated to the mixing temperature is added and wet-mixed at the mixing temperature to obtain a uniform warm-mix SMA mixture. S4: The above warm-mixed material is loaded into the mold at a specified temperature (usually the mixing temperature + 5℃), and double-sided compaction is performed using a Marshall compactor according to the set number of compaction times (50 or 75 times) to obtain a standard Marshall specimen or a specimen for performance testing.

[0032] III. Performance Testing and Calculation Methods; In accordance with the relevant provisions of the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20), the performance of the prepared warm-mix SMA-13 ​​mixture was tested, specifically including: determining the bulk relative density of the specimens using the surface-dry method, determining the theoretical maximum relative density using the vacuum method, and calculating the void ratio (VV), aggregate void ratio (VMA), and effective asphalt saturation (VFA) based on these results; determining the Marshall stability (MS) and flow value (FL) using a Marshall tester, and calculating the Marshall modulus (T=MS / FL); and determining the flexural tensile strength (R_B), maximum flexural tensile strain (ε_B), and flexural stiffness modulus (S_B) using a small beam bending tester at -10℃, with the specific calculation process based on the corresponding formulas in the specification.

[0033] IV. Examples and Performance Data; Table 1. High-Temperature Performance Test and Calculation Results of Warm Mixtures

[0034] in: Ma represents the dry mass of the specimen in air; mw represents the mass of the specimen in water; mf represents the surface dry mass of the specimen; VV represents porosity; VMA represents the void fraction of the mineral aggregate; VFA represents effective bitumen saturation; MS represents Marshall stability; FL represents the stream value; T represents the Marshall modulus, which is the ratio of MS to FL; γf represents the bulk relative density of the specimen; Among the mixing temperatures and compaction times mentioned above, the SMA-13 ​​warm mix achieved Marshall moduli of 3.99 KN / mm and 3.53 KN / mm under the combinations of 50-135℃ and 75-145℃, respectively, far exceeding the warm mix prepared by other combinations, demonstrating excellent resistance to deformation.

[0035] Example 2: S1: Same as Example 1; S2: Heat the three pre-made warm-mix asphalt portions to the required mixing temperatures (135±5℃, 145±5℃, 155±5℃). S3: Heat the three parts of coarse aggregate and fine aggregate separately to a temperature slightly higher than the mixing temperature, approximately 3-5°C higher, to prevent heat loss during operation; S4: The heated aggregate, mineral powder and fiber are put into the mixing pot for dry mixing. After the dry mixing is completed, the warm mix asphalt prepared in S2 at the corresponding mixing temperature is added and wet mixing is carried out at the respective mixing temperatures to obtain 3 uniform SMA-13 ​​warm mix mixtures. S5: The mixture obtained in S4 was used to make small beam specimens with dimensions of 250mm×30mm×50mm; S6: Perform beam bending test according to conventional methods; S7: Performance testing and calculations, results are shown in Table 2: Table 2. Low-temperature performance test and calculation results of warm-mixed asphalt.

[0036] The warm mix mixture can still be well compacted when mixed at a mixing temperature of 145℃, and its flexural tensile strength is... The bending stiffness modulus is It exhibits the most outstanding low-temperature crack resistance among different mixing temperatures, and its low-temperature bending tensile strain (3400με) is significantly higher than the standard requirement (≥2000με in winter temperature zone), demonstrating excellent low-temperature crack resistance.

[0037] The above embodiments and calculation results show that, as can be seen from Tables 1 and 2, although the 50 cycles -135℃ combination has a high Marshall modulus (3.99 KN / mm), its low-temperature bending tensile strain is only 1420 με, which cannot meet the requirement of not less than 2000 με in the winter temperature zone; while the 75 cycles -145℃ combination maintains a high Marshall modulus (3.53 KN / mm) and achieves a low-temperature bending tensile strain of 3400 με, realizing the synergistic optimization of high-temperature performance and low-temperature performance. This indicates that the 75 cycles -145℃ combination is the preferred technical solution of the present invention.

[0038] The optimized preparation method of SMA asphalt mixture based on warm mix agent provided by this invention can achieve synergistic optimization of mixture volume parameters and mechanical properties through precise process control. This significantly reduces the construction temperature while ensuring or even improving the high and low temperature performance of the pavement, and has broad engineering application prospects.

[0039] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing asphalt mastic aggregate based on warm mix additive, characterized in that, Includes the following steps: The warm-mix asphalt is heated to a mixing temperature of 145±5℃; The coarse and fine aggregates are heated separately to a temperature 3-5°C higher than the mixing temperature. Heated coarse aggregate, heated fine aggregate, mineral powder and fiber are mixed with warm-mix asphalt heated to the mixing temperature to obtain a warm-mix mixture. The warm-mixed material was compacted on both sides using a Marshall compactor with 75±5 compaction cycles.

2. The method for preparing asphalt mastic aggregate based on warm mix additive according to claim 1, characterized in that, The mixing temperature is 145°C, and the number of compactions is 75.

3. The method for preparing asphalt mastic aggregate based on warm mix additive according to claim 1, characterized in that, The warm mix asphalt comprises base asphalt and a warm mix agent comprising 0.4% to 0.6% of the mass of the base asphalt. The warm mix agent is a surfactant-type warm mix agent, and the base asphalt is heavy traffic road petroleum asphalt AH-70#.

4. The method for preparing asphalt mastic aggregate based on warm mix additive according to claim 1, characterized in that, The fiber is basalt fiber, which accounts for 0.3% to 0.5% of the total mass of the mixture, and the length of the basalt fiber is 10-14 mm and the diameter is 15±2 μm.

5. The method for preparing asphalt mastic aggregate based on warm mix additive according to claim 1, characterized in that, The aggregate gradation is SMA-13; the mixing steps are as follows: first, the heated coarse aggregate, heated fine aggregate, mineral powder and fiber are dry-mixed, and then warm-mix asphalt heated to the mixing temperature is added for wet mixing.

6. A warm-mix asphalt mastic aggregate mixture, characterized in that, By weight, it contains the following ingredients: Asphalt binder: 5.5~6.0 parts; Aggregate: 84-85 parts; Mineral powder: 9-10 parts; Fiber stabilizer: 0.3~0.5 parts; The aggregate is graded as SMA-13 ​​and further subdivided by particle size into the following parts by weight: 3.0-4.0 parts of 13.2mm particle size, 30.0-33.0 parts of 9.6mm particle size, 34.0-36.0 parts of 4.75mm particle size, 4.0-5.0 parts of 2.36mm particle size, 2.0-3.0 parts of 1.18mm particle size, 2.0-3.0 parts of 0.6mm particle size, 1.0-2.0 parts of 0.3mm particle size, 0.5-1.5 parts of 0.15mm particle size, and 2.0-3.0 parts of 0.075mm particle size.

7. The asphalt mastic aggregate based on warm mix additive according to claim 6, characterized in that, By weight, it contains the following ingredients: The asphalt binder content is 5.83 parts; The aggregate consisted of 84.38 parts; The mineral powder content was 9.39 parts. The fiber stabilizer is 0.4 parts; The aggregate is graded as SMA-13 ​​and further subdivided by particle size into the following parts by weight: 3.47 parts of 13.2 mm particle size, 31.69 parts of 9.6 mm particle size, 35.16 parts of 4.75 mm particle size, 4.69 parts of 2.36 mm particle size, 2.34 parts of 1.18 mm particle size, 2.34 parts of 0.6 mm particle size, 1.41 parts of 0.3 mm particle size, 0.94 parts of 0.15 mm particle size, and 2.34 parts of 0.075 mm particle size.

8. The asphalt mastic aggregate based on warm mix additive according to claim 6, characterized in that, The asphalt binder comprises base asphalt and a warm mix agent comprising 0.4% to 0.6% of the mass of the base asphalt. The warm mix agent is a surfactant-type warm mix agent, and the base asphalt is heavy traffic road petroleum asphalt AH-70#.

9. The asphalt mastic aggregate based on a warm mix additive according to claim 6, characterized in that, The fiber stabilizer is basalt fiber, which accounts for 0.3% to 0.5% of the total mass of the mixture, and the length of the basalt fiber is 10-14 mm and the diameter is 15±2 μm.

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