Foamed asphalt cold recycled mixture forming method

Abstract

The invention relates to the technical field of road engineering, in particular to a method for forming a foamed asphalt cold-recycled mixture, and provides the method for forming the foamed asphalt cold-recycled mixture to solve the problems in the prior art, and the foamed asphalt cold-recycled mixture is formed by optimizing a mixing process, reasonably setting shear compaction parameters and improving a short-term aging treatment method. According to the low-temperature mixing process, the uniformity, the mechanical property and the service life of the foamed asphalt cold-recycled mixture can be remarkably improved, the mixing temperature is controlled, it is ensured that asphalt is fully foamed and uniformly combined with aggregate, the low-temperature mixing process not only reduces energy consumption, but also avoids the problem of asphalt aging caused by too high temperature, and the service life of the mixture is prolonged. The filling quality is accurately controlled, the filling quality of the mixture is calculated through a formula, it is ensured that the amount of the mixture filled every time is consistent, local performance difference caused by uneven filling is avoided, and in the aging process, it is ensured that all parts are evenly heated by turning and stirring the mixture at regular time, and the uniformity of the mixture is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of road engineering, and particularly relates to a method for forming a foamed asphalt cold recycled mixture. Background Art

[0002] With the increase in traffic volume and the extension of the road service life, many roads have suffered varying degrees of damage, such as cracks, potholes, and ruts. Traditional road repair methods usually use hot mix asphalt mixtures. Although this method has remarkable effects, it has problems such as high energy consumption, large environmental pollution, and long construction period. In recent years, the foamed asphalt cold recycling technology, as a new type of road repair method, has gradually attracted attention. The foamed asphalt cold recycling technology combines the old asphalt pavement materials with foamed asphalt to form a new mixture, which has the advantages of energy conservation, environmental protection, fast construction, and low cost.

[0003] However, there are some problems with the existing methods for forming foamed asphalt cold recycled mixtures. First, it is difficult to ensure the mixing uniformity of the mixture, resulting in unstable performance of the formed mixture. Second, the settings of the shear compaction parameters during the forming process are unreasonable, which easily causes uneven void ratios in the mixture, affecting its mechanical properties and service life. In addition, the existing short-term aging treatment methods have poor effects and cannot effectively simulate the aging process of the mixture during actual use. Therefore, developing a new method for forming foamed asphalt cold recycled mixtures has important practical significance and application value.

[0004] In view of the above situation, in order to overcome the above technical problems, the present invention designs a method for forming a foamed asphalt cold recycled mixture, which solves the above technical problems. Summary of the Invention

[0005] The technical object to be achieved by the present invention is: to provide a method for forming a foamed asphalt cold recycled mixture to solve the above problems existing in the prior art. By optimizing the mixing process, reasonably setting the shear compaction parameters, and improving the short-term aging treatment method, this method can significantly improve the uniformity, mechanical properties, and service life of the foamed asphalt cold recycled mixture.

[0006] In order to achieve the above technical object, the present invention provides the following technical solutions: A method for forming a foamed asphalt cold recycled mixture, which includes the following steps in sequence: Step 1: Mix the foamed asphalt cold recycled mixture according to a pre-designed ratio; Step 2: Measure the maximum theoretical density of the mixed foamed asphalt cold recycled mixture; Step 3: Set the shear compaction parameters, including the compaction termination height, vertical pressure, and cyclic shear angle; Step 4: Calculate the mass of the mixture to be filled according to the void ratio of the foamed asphalt cold recycled mixture to be formed; Step 5: Conduct short-term aging treatment on the foamed asphalt cold recycled mixture; Step 6: Fill the aged foamed asphalt cold recycled mixture; Step 7: Perform shear compaction molding on the filled foamed asphalt cold recycled mixture according to the set shear compaction parameters, and demold after molding; Step 8: Conduct secondary processing on the formed foamed asphalt cold recycled mixture.

[0007] Among them, the mixing process optimization: Mix the foamed asphalt cold recycled mixture according to the pre-designed ratio, the mixing temperature is 120 - 140 °C, and the mixing time is not less than 3 minutes to ensure the uniformity of the mixture.

[0008] Determination of the maximum theoretical density: Use the vacuum sealing method to determine the maximum theoretical density of the mixed foamed asphalt cold recycled mixture, the determination temperature is 25 °C, the vacuum degree is -0.09 MPa, and the determination time is 15 minutes.

[0009] Setting of shear compaction parameters: Set shear compaction parameters, including the compaction termination height, vertical pressure, and cyclic shear angle. The compaction termination height is 170 mm, the vertical pressure is 0.8 MPa, and the cyclic shear angle is 4°.

[0010] Calculation of the mixture mass: Calculate the mass of the mixture to be filled according to the void ratio of the foamed asphalt cold recycled mixture to be formed, and the calculation formula is: m = ρ × V × ( ), where m is the filling mass of the mixture, ρ is the theoretical maximum density of the mixture, V is the forming volume of the mixture, and s is the void ratio of the mixture to be formed.

[0011] Short-term aging treatment: Spread the foamed asphalt cold recycled mixture on the sample tray, and the stacking height is 40 - 60 mm; put the mixture into the oven for heating, the temperature in the oven is 140 - 160 °C, and the heating time is 4 hours; during the heating process, stir the mixture every hour.

[0012] Mixture filling: Fill the aged foamed asphalt cold recycled mixture.

[0013] Shear compaction molding: Perform shear compaction molding on the filled foamed asphalt cold recycled mixture according to the set shear compaction parameters, the compaction times are 30 times, and demold after molding.

[0014] Secondary processing: Cut, polish, and surface-treat the formed foamed asphalt cold recycled mixture to meet the requirements of engineering applications.

[0015] The beneficial effects of the present invention are as follows: 1. The present invention provides a method for forming a foamed asphalt cold recycled mixture, aiming to solve the problems existing in the prior art, such as poor mixture uniformity, unstable mechanical properties, short service life, high construction energy consumption, and large environmental pollution. By optimizing the mixing process, reasonably setting the shear compaction parameters, and improving the short-term aging treatment method, this method has shown significant beneficial effects in many aspects. The uniformity of the mixture is a key factor affecting its performance. The present invention significantly improves the uniformity of the mixture through the following measures: Optimize the mixing process: Control the mixing temperature at 120 - 140 °C and the mixing time not less than 3 minutes to ensure that the asphalt is fully foamed and evenly combined with the aggregate. This low-temperature mixing process not only reduces energy consumption but also avoids the problem of asphalt aging caused by too high temperature. Precise control of the filling quality: Calculate the filling quality of the mixture through a formula to ensure that the amount of the mixture filled each time is consistent, avoiding local performance differences caused by uneven filling. Short-term aging treatment: During the aging process, regularly stir the mixture to ensure that each part is evenly heated, further improving the uniformity of the mixture. The improvement of the mixture uniformity directly improves its mechanical properties and durability, reducing quality problems caused by uneven materials during construction.

[0016] 2. The mechanical properties of the present invention are the core indicators for measuring the quality of the mixture. The present invention significantly improves the mechanical properties of the mixture through the following measures: Reasonably set the shear compaction parameters: The compaction termination height is 170 mm, the vertical pressure is 0.8 MPa, and the cyclic shear angle is 4°. These parameters have been scientifically calculated and experimentally verified, which can ensure the compaction of the mixture while avoiding aggregate crushing and over-compaction. Precise control of the void ratio: By calculating the filling quality, control the void ratio of the mixture at about 7%. This void ratio can not only ensure the compaction of the mixture but also provide good drainage performance, thereby improving its water damage resistance. Improve the short-term aging treatment method: By simulating the aging conditions in actual use, expose the potential defects of the mixture in advance and optimize its anti-aging performance. The mechanical property indicators of the mixture, such as compressive strength, tensile strength, dynamic modulus, and fatigue life, are significantly better than those of traditional methods and can meet the use requirements of high-grade roads. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0018] Reference will now be made to the accompanying drawings to describe the above and other aspects of the present invention by way of example only, wherein: Figure 1 is a schematic flow chart of the method of the present invention. Detailed implementation manners

[0019] To better understand the above technical solutions, the above technical solutions will be described in detail below in conjunction with the accompanying drawings of the specification and specific implementation manners.

[0020] Example 1: As Figure 1 shown, a method for forming a foamed asphalt cold recycled mixture includes the following steps in sequence: In the preparation process of the foamed asphalt cold recycled mixture, the mixing step is a crucial link, which directly affects the final performance and quality of the mixture. In the present invention, the mixing process is strictly carried out according to the pre-designed ratio to ensure that each component material can be fully mixed to achieve the best engineering performance. Specifically, the mixing temperature is controlled between 130°C, and the mixing time is not less than 3 minutes. The setting of these process parameters has many advantages, which can not only ensure the quality of the mixture, but also play a significant role in environmental protection and energy conservation.

[0021] Temperature control is one of the key factors in the mixing process. The mixing temperature range of 130°C is determined through multiple tests and optimizations. This temperature range can not only ensure that the asphalt foams fully during mixing to form a uniform foamed asphalt structure, but also effectively avoid the problem of asphalt aging caused by too high temperature. Compared with the 150 - 170°C of traditional hot mix asphalt, this temperature range significantly reduces energy consumption and carbon emissions during construction, meeting the requirements of modern green construction. In addition, the lower mixing temperature helps to extend the service life of the equipment and reduce maintenance costs.

[0022] The mixing time not less than 3 minutes is to ensure the uniformity of the mixture. During the mixing process, each component such as asphalt, recycled material, and filler needs to be fully mixed at high temperature to ensure that each part of the mixture has consistent physical and chemical properties. If the mixing time is insufficient, local performance differences may occur in the mixture, affecting the overall quality and service life of the road surface. By mixing for not less than 3 minutes, it can ensure that each component material is fully fused to form a uniform mixture structure, thereby improving the durability and fatigue resistance of the road surface.

[0023] The mixing process of foamed asphalt cold recycled mixture also has significant environmental protection advantages. The lower mixing temperature not only reduces energy consumption but also decreases greenhouse gas emissions. In the context of the current global advocacy for green buildings and sustainable development, this technology has important practical significance. By adopting the foamed asphalt cold recycling technology, not only can waste pavement materials be effectively utilized to reduce the generation of construction waste, but also environmental pollution during the construction process can be reduced, achieving a win-win situation for economic and environmental benefits. The mixing process of foamed asphalt cold recycled mixture has significant advantages in terms of temperature control, mixing time, and environmental protection. By strictly following the pre-designed ratio and process parameters, the quality and performance of the mixture can be ensured, while the goals of energy conservation and environmental protection are achieved. The popularization and application of this technology will provide a more sustainable solution for road construction and maintenance.

[0024] In the preparation process of asphalt cold recycled mixture, measuring its maximum theoretical density is a crucial step. This step not only provides a scientific basis for the quality control of the mixture, but also lays a foundation for subsequent construction techniques and performance evaluation. In this invention, the vacuum sealing method is adopted to measure the maximum theoretical density of the mixture. The specific measurement conditions are: the measurement temperature is controlled at 25°C, the vacuum degree is -0.09 MPa, and the measurement time is 15 minutes. The selection of this method and the setting of parameters have many advantages, which can ensure the accuracy, standardization and guidance of the measurement results. The vacuum sealing method has significant accuracy advantages when measuring the maximum theoretical density. During the measurement process, by applying a vacuum degree of -0.09 MPa, the residual air and bubbles in the mixture can be effectively removed, avoiding the interference of these factors on the density measurement results. The presence of air will cause the measured density value to be on the low side, thus affecting subsequent quality calculation and performance evaluation. The vacuum sealing method ensures the authenticity and reliability of the measurement results by eliminating the influence of air, providing accurate data support for the quality control of the mixture. Uniform measurement conditions (temperature, vacuum degree and time) ensure the repeatability and comparability of the experimental results. In scientific research and engineering practice, the standardization of experimental conditions is the key to ensuring data reliability. In this invention, the measurement temperature is strictly controlled at 25°C to simulate the actual construction conditions under normal temperature, making the measurement results more practical. At the same time, the vacuum degree of -0.09 MPa and the measurement time of 15 minutes are determined through multiple tests and optimizations, which can improve the experimental efficiency while ensuring the measurement effect. Such standardized measurement conditions are not only convenient for performance comparison between different batches of mixtures, but also provide a unified standard for technical communication and data sharing in the industry. The measurement result of the maximum theoretical density has important guiding significance for subsequent steps. The maximum theoretical density is the basic data for calculating key indicators such as the void ratio and compaction degree of the mixture. Through these indicators, the compactness and performance stability of the mixture can be evaluated, so as to optimize the construction technique and ensure the durability and anti-fatigue performance of the pavement structure. For example, during the mixture forming process, the parameters of the compaction equipment can be adjusted according to the maximum theoretical density to achieve the required compaction degree of the design. At the same time, the measurement of the maximum theoretical density also provides a scientific basis for the quality acceptance of the mixture, helping to improve the construction quality and management level. Measuring the maximum theoretical density of foamed asphalt cold recycled mixture by the vacuum sealing method can not only ensure the accuracy and reliability of the measurement results, but also improve the repeatability and comparability of the experiment through standardized measurement conditions. In addition, the measurement result of the maximum theoretical density provides important basic data for subsequent mixture quality calculation and construction technique optimization, and has important guiding significance for ensuring the compactness and performance stability of the mixture. The scientific implementation of this step provides a solid technical support for the popularization and application of foamed asphalt cold recycling technology.

[0025] In the forming process of foamed asphalt cold recycled mixture, the setting of shear compaction parameters is a key step in determining the final performance of the mixture. In the present invention, through scientific optimization and repeated experiments, the following core parameters are determined: the compaction termination height is 170 mm, the vertical pressure is 0.8 MPa, and the cyclic shear angle is 4°. The setting of these parameters can not only ensure that the mixture reaches an ideal dense state during the forming process, but also effectively simulate the mechanical environment in actual road use, thereby improving the shear resistance and durability of the mixture. The advantages of these parameter settings and their influence on the mixture performance will be analyzed in detail below. The setting of the compaction termination height has an important impact on the density and void ratio of the mixture. In the present invention, the compaction termination height is set to 170 mm, and this height is the optimal value determined after multiple experimental verifications. If the compaction termination height is too low, the mixture may not reach the designed density requirement, resulting in too large void ratio, thus affecting the water damage resistance and durability of the road surface; while if the compaction termination height is too high, it may lead to over-compaction of the mixture, causing aggregate crushing or asphalt film damage, and then reducing the overall performance of the mixture. The compaction termination height of 170 mm can ensure the full densification of the mixture while avoiding the occurrence of the above problems, and ensure that the formed mixture has good structural stability and mechanical properties.

[0026] The setting of the vertical pressure is an important parameter for controlling the densification process of the mixture. In the present invention, a vertical pressure of 0.8 MPa is adopted, and this pressure value can ensure the densification of the mixture while avoiding aggregate crushing caused by excessive pressure. Aggregates are the main load-bearing components in the mixture, and their integrity is crucial for the mechanical properties of the mixture. If the vertical pressure is too high, the aggregates may be crushed during the compaction process, thus reducing the compressive strength and fatigue resistance of the mixture; while if the vertical pressure is too low, it may lead to insufficient densification of the mixture, affecting the smoothness and durability of the road surface. The vertical pressure of 0.8 MPa can achieve a balance between the two, ensuring that the aggregates in the mixture are complete and evenly distributed during the densification process.

[0027] The setting of the cyclic shear angle is of great significance for simulating the shear stress in actual road use. In the present invention, the cyclic shear angle is set to 4°, and this angle can effectively simulate the shear action on the road surface during vehicle driving. In actual road use, the road surface not only bears vertical loads but also is subjected to shear stress in the horizontal direction, and this shear stress is one of the main causes of road surface diseases such as rutting and cracking. By setting the cyclic shear angle of 4°, this complex mechanical environment can be simulated under laboratory conditions, enabling the mixture to form a stronger shear resistance during the forming process, thereby improving its durability and fatigue resistance in actual use.

[0028] The setting of the shear compaction parameters is the core link of the forming process of foamed asphalt cold recycled mixture. By setting the compaction termination height to 170 mm, the vertical pressure to 0.8 MPa, and the cyclic shear angle to 4°, the present invention can effectively simulate the mechanical environment in actual road use while ensuring the compactness and structural stability of the mixture, thereby improving the shear resistance and durability of the mixture. The optimized setting of these parameters provides important technical support for the popularization and application of the foamed asphalt cold recycling technology, and also lays a scientific foundation for the quality control and performance improvement of road engineering.

[0029] Step 4: Calculate the mass of the mixture to be filled according to the void ratio of the foamed asphalt cold recycled mixture to be formed; Calculate the mass of the mixture to be filled according to the void ratio of the foamed asphalt cold recycled mixture to be formed The calculation formula for the mass of the foamed asphalt cold recycled mixture to be filled is: m = ρ × V × ( ), In the formula, m is the filling mass of the mixture, ρ is the theoretical maximum density of the mixture, V is the forming volume of the mixture, and s is the void ratio of the mixture to be formed.

[0030] In the forming process of the foamed asphalt cold recycled mixture, calculating the mass of the mixture to be filled according to the target void ratio is a crucial step. This step can not only ensure the accurate dosage of the mixture, but also effectively control the void ratio of the formed mixture, thereby optimizing its mechanical properties and durability. Specifically, by calculating the filling mass through a scientific formula, the dosage of the mixture can be accurately controlled, avoiding the low density of the formed specimen caused by insufficient dosage or material waste caused by excessive dosage. This accuracy not only improves the experimental efficiency, but also reduces the material cost, with significant economic benefits. The control of the void ratio is one of the key factors affecting the performance of the mixture. By adjusting the void ratio, the compactness, water damage resistance and fatigue resistance of the mixture can be optimized. For example, controlling the void ratio at about 7% can not only ensure that the mixture has sufficient compactness, improve its compressive strength and deformation resistance, but also provide appropriate drainage performance to reduce the risk of water damage. This balanced design enables the mixture to better withstand the influence of traffic loads and environmental factors during actual use, thereby extending the service life of the road surface. Therefore, by accurately calculating the filling mass and controlling the void ratio, not only can the forming quality of the mixture be improved, but also a reliable guarantee can be provided for the overall performance of road engineering.

[0031] In the preparation process of foamed asphalt cold recycled mixture, short-term aging treatment is a crucial step. It can simulate the aging phenomenon that the mixture experiences during actual use, thereby providing a scientific basis for evaluating its long-term performance. In this invention, the specific parameter settings for short-term aging treatment are as follows: the stacking height of the mixture is controlled at 50 mm, the oven temperature is maintained at 150 °C, the heating time is 4 hours, and the mixture is stirred every hour. The setting of these parameters can not only ensure the uniformity and effectiveness of the aging process, but also provide important support for the performance optimization of the mixture. The advantages of this step and its impact on the mixture performance will be analyzed in detail below.

[0032] The short-term aging treatment ensures that all parts of the mixture are evenly heated through the stirring operation, avoiding the problem of uneven local aging. In actual operation, when the mixture is heated in the oven, due to the limitation of heat conduction, there may be a temperature difference between the surface layer and the interior. Without stirring, the mixture on the surface layer may age prematurely due to excessive heating, while the mixture inside may age insufficiently, resulting in inaccurate test results. By stirring once every hour, this temperature gradient can be effectively eliminated, ensuring that every part of the mixture undergoes the same thermal aging process, thereby improving the reliability and consistency of the experimental results.

[0033] The oven temperature of 40 - 160 °C and the heating time of 4 hours can effectively simulate the aging process of the mixture in the high-temperature environment in summer. During actual road use, especially in the hot summer, the road surface temperature may reach 60 - 70 °C or even higher. This high-temperature environment will accelerate the aging of asphalt mixture, resulting in a gradual decline in its performance. By setting the oven temperature at 140 - 160 °C and continuously heating for 4 hours, this high-temperature aging process can be simulated under laboratory conditions, thus more realistically reflecting the performance changes of the mixture during actual use. This simulation not only improves the reliability of the test results, but also provides a scientific basis for the formulation optimization and process improvement of the mixture.

[0034] The short-term aging treatment can expose the potential defects of the mixture in advance, providing an important basis for subsequent process optimization. During the aging process, the physical and chemical properties of the mixture will change, such as the hardening of asphalt and the decline in the bonding performance between aggregate and asphalt. These changes may lead to a decline in key indicators such as the crack resistance and water damage resistance of the mixture. Through short-term aging treatment, these problems can be discovered in advance, so as to carry out targeted optimization in the mixture design and construction process. For example, the durability and anti-aging performance of the mixture can be improved by adjusting the asphalt dosage, adding anti-aging agents or optimizing the aggregate gradation.

[0035] Short-term aging treatment is an essential step in the preparation process of foamed asphalt cold recycled mixture. By controlling the stacking height at 40 - 60 mm, keeping the oven temperature at 140 - 160 °C, setting the heating time to 4 hours and stirring every hour, the present invention can ensure the uniformity and effectiveness of the aging process while simulating the high-temperature aging conditions in actual use. This setting not only improves the reliability of test results but also provides a scientific basis for the performance optimization and process improvement of the mixture. Through short-term aging treatment, potential defects of the mixture can be detected in advance, thus laying a solid foundation for the quality control and long-term performance guarantee of road engineering.

[0036] In the forming process of foamed asphalt cold recycled mixture, the filling of the aged mixture is a crucial step, which directly affects the quality and performance of the final formed specimen. Due to the dual effects of high temperature and time, the physical and chemical properties of the aged mixture tend to be stable, making the filling process more controllable and the performance of the formed specimen more reliable. The advantages of filling the aged mixture and its significance to the forming process will be analyzed in detail below.

[0037] The performance of the aged mixture is more stable, and it is not easy to deform or crack after filling. During the aging process, the asphalt in the mixture undergoes oxidation and hardening, and its bonding performance and elastic modulus are improved to a certain extent. This performance stability enables the mixture to better maintain its shape and structure during filling and compaction, reducing defects caused by material deformation or cracking. In addition, the aged mixture has a lower sensitivity to temperature and pressure, further improving the controllability of the filling process and the quality of the formed specimen.

[0038] By precisely controlling the filling quality, it can be ensured that the mixture reaches an ideal dense state after compaction. The calculation of the filling quality is based on the target void ratio and the maximum theoretical density of the mixture. The scientific implementation of this step can avoid the problem of uneven density caused by overfilling or underfilling. Precise filling quality can not only improve the density of the formed specimen but also ensure the uniformity and stability of its mechanical properties. For example, appropriate density can improve the compressive strength, water damage resistance and fatigue resistance of the mixture, thus extending the service life of the road surface.

[0039] The filling of the aged foamed asphalt cold recycled mixture is an important link in the forming process. By utilizing the stability of the aged mixture and combining precise filling quality control, it can be ensured that the formed specimen has ideal density and mechanical properties. The scientific implementation of this step provides important technical support for the popularization and application of the foamed asphalt cold recycling technology, and also lays a solid foundation for the quality control and performance optimization of road engineering.

[0040] In the molding process of foamed asphalt cold recycled mixture, shear compaction molding is a crucial step, which directly determines the final density, mechanical properties and service life of the mixture. In the present invention, the loaded mixture is compacted according to the pre-set shear compaction parameters, and the number of compaction times is 30 times. The scientific implementation of this step can not only ensure the uniformity and density of the mixture, but also significantly improve its mechanical properties, thereby providing reliable guarantee for the quality and durability of road engineering. The advantages of shear compaction molding and its influence on the performance of the mixture will be analyzed in detail below.

[0041] Through 30 compaction operations, it is possible to ensure that all parts of the mixture are evenly stressed and avoid the problem of insufficient local density. During the compaction process, the shear force causes the aggregates and asphalt in the mixture to rearrange and form a more compact structure. Multiple compaction can eliminate the gaps and uneven areas inside the mixture and ensure that the density of each part meets the design requirements. This uniformity not only improves the overall quality of the molded specimen, but also lays the foundation for its performance stability in actual use. For example, uniform density can reduce the risk of road surface defects such as rutting and cracks during use.

[0042] Shear compaction can effectively improve the shear strength and dynamic modulus of the mixture, thereby extending its service life. In actual road use, the road surface is not only subjected to vertical loads, but also to horizontal shear stress, which is one of the main causes of road damage. Through shear compaction, the aggregate and asphalt in the mixture can form a stronger bonding structure, thereby improving its shear resistance. In addition, shear compaction can also increase the dynamic modulus of the mixture, so that it exhibits better elastic recovery ability when subjected to traffic loads and reduces the accumulation of permanent deformation.

[0043] The demoulding operation after molding is an important step to ensure the integrity of the specimen. During the demoulding process, care must be taken to avoid damage to the specimen. The demoulded specimen can be directly used for subsequent performance tests, such as compressive strength test, water damage resistance test, etc., to fully evaluate the performance of the mixture.

[0044] Shear compaction is a key step in the preparation of foamed asphalt cold recycled mixture. Through 30 compaction operations, the uniformity and density of the mixture can be ensured, while its shear strength and dynamic modulus can be significantly improved. The scientific implementation of this step not only provides important support for the performance optimization of the mixture, but also lays a solid foundation for the quality control and long-term performance guarantee of road projects.

[0045] In the preparation process of foamed asphalt cold recycled mixture, secondary processing is an important step to ensure the appearance quality and performance stability of the final product. After the formed mixture is shear-compacted and demolded, although it already has basic compactness and mechanical properties, its appearance and performance still need to be further optimized through secondary processing. In the present invention, secondary processing mainly includes three links: cutting, grinding, and surface treatment, and each link has its unique functions and advantages.

[0046] First of all, the cutting operation is the first step of secondary processing, and its main purpose is to remove the edge defects and irregular parts generated during the forming process. During the shear-compaction and demolding process, the edge area of the mixture may have defects such as burrs and cracks due to uneven stress or mold restrictions. Through precise cutting operations, these defects can be removed to ensure that the geometric shape and size of the mixture meet the design requirements. This not only improves the appearance quality of the mixture but also provides standardized specimens for its subsequent performance testing and engineering applications.

[0047] Secondly, the grinding operation is a key step in the fine processing of the mixture surface. By grinding, the rough parts and uneven areas on the surface of the mixture can be eliminated, making its surface smoother and flatter. This step not only improves the appearance quality of the mixture, making it more in line with the aesthetic requirements of engineering applications, but also reduces the potential impact of surface defects on the performance of the mixture. For example, a smooth surface can reduce the retention of moisture, reduce the risk of water damage, and thus improve the durability of the mixture.

[0048] Finally, surface treatment is the link for the final modification of the mixture. Through surface treatment, the appearance and performance of the mixture can be further improved. For example, coatings or sealants can be used to treat the surface of the mixture to enhance its water resistance, anti-ultraviolet aging performance, etc. This treatment can not only extend the service life of the mixture but also improve its adaptability in complex environments.

[0049] Secondary processing is an indispensable link in the preparation process of foamed asphalt cold recycled mixture. Through cutting, grinding, and surface treatment, not only can the appearance quality of the mixture be improved to meet the requirements of engineering applications, but also its overall performance can be optimized to ensure its stability and durability in actual use. The scientific implementation of this step provides important technical support for the popularization and application of foamed asphalt cold recycling technology, and also lays a solid foundation for the quality control and performance optimization of road engineering. Example 1

[0050] Mixing process optimization: Mix the foamed asphalt cold recycled mixture according to the pre-designed ratio. The mixing temperature is 120°C, and the mixing time is 4 minutes to ensure the uniformity of the mixture.

[0051] Determination of maximum theoretical density: The maximum theoretical density of the mixed foamed asphalt cold recycled mixture was determined by the vacuum sealing method. The determination temperature was 25°C, the vacuum degree was -0.09 MPa, and the determination time was 15 minutes.

[0052] Setting of shear compaction parameters: Set the shear compaction parameters. The compaction termination height was 170 mm, the vertical pressure was 0.8 MPa, and the cyclic shear angle was 4°.

[0053] Short-term aging treatment: Spread the foamed asphalt cold recycled mixture on the specimen tray with a stacking height of 40 mm; put the mixture into the oven for heating. The temperature in the oven was 140°C and the heating time was 4 hours; during the heating process, the mixture was stirred every hour.

[0054] Mixture filling: Fill the aged foamed asphalt cold recycled mixture.

[0055] Shear compaction and molding: The filled foamed asphalt cold recycled mixture was shear-compacted and molded according to the set shear compaction parameters. The compaction times were 30 times, and after molding, demolding was carried out.

[0056] Secondary processing: The molded foamed asphalt cold recycled mixture was cut, polished and surface-treated to meet the requirements of engineering applications. Example 2

[0057] Mixing process optimization: Mix the foamed asphalt cold recycled mixture according to the pre-designed ratio. The mixing temperature was 140°C and the mixing time was 3 minutes to ensure the uniformity of the mixture.

[0058] Determination of maximum theoretical density: The maximum theoretical density of the mixed foamed asphalt cold recycled mixture was determined by the vacuum sealing method. The determination temperature was 25°C, the vacuum degree was -0.09 MPa, and the determination time was 15 minutes.

[0059] Setting of shear compaction parameters: Set the shear compaction parameters. The compaction termination height was 170 mm, the vertical pressure was 0.8 MPa, and the cyclic shear angle was 4°.

[0060] Spread the foamed asphalt cold recycled mixture on the specimen tray with a stacking height of 60 mm; put the mixture into the oven for heating. The temperature in the oven was 160°C and the heating time was 4 hours; during the heating process, the mixture was stirred every hour.

[0061] Mixture filling: Fill the aged foamed asphalt cold recycled mixture.

[0062] Shear compaction and molding: The filled foamed asphalt cold recycled mixture was shear-compacted and molded according to the set shear compaction parameters. The compaction times were 30 times, and after molding, demolding was carried out.

[0063] Secondary processing: Cutting, grinding and surface treatment are carried out on the formed foamed asphalt cold recycled mixture to meet the requirements of engineering applications.

[0064] Compressive strength, tensile strength and shear strength are important indicators to measure the mechanical properties of the mixture. The higher the value, the stronger the bearing capacity and anti-deformation ability of the mixture.

[0065] The following are the mechanical properties of different embodiments and the traditional control group under various standard tests: Dynamic modulus reflects the stiffness of the mixture under dynamic loads. The higher the value, the better the anti-deformation ability of the mixture.

[0066] Fatigue life refers to the durability of the mixture under repeated loads. The higher the value, the longer the service life of the mixture.

[0067] Compared with the traditional method, the mechanical properties of the embodiments of the present invention are significantly improved, which proves the superiority of the method of the present invention.

[0068] The following are the other properties of different embodiments and the traditional control group under various standard tests: Void ratio is an important indicator to measure the compactness of the mixture. The void ratio of the embodiments of the present invention is controlled at about 7%, which is significantly lower than that of the traditional method, indicating that the mixture is more compact.

[0069] Water stability is evaluated by the residual strength ratio. The higher the value, the better the performance of the mixture in a wet environment.

[0070] The loss rate of compressive strength after aging reflects the anti-aging performance of the mixture. The lower the value, the better the durability of the mixture.

[0071] Skid resistance performance (BPN) is an important indicator to measure the safety of the road surface. The higher the value, the better the skid resistance performance of the road surface.

[0072] The construction temperature range shows that the method of the present invention can be constructed at a lower temperature, having the advantages of energy conservation and environmental protection.

[0073] Each of the technical features disclosed above is not limited to the combinations with other features already disclosed. Those skilled in the art can also make other combinations among the technical features according to the purpose of disclosure, subject to the achievement of the purpose of the present disclosure. Descriptions herein are provided to enable those of ordinary skill in the art to implement or use the content of the present disclosure. For those of ordinary skill in the art, various modifications to the content of the present disclosure will be obvious, and the general principles defined herein can be applied to other variations without departing from the scope of the content of the present disclosure. Therefore, the present disclosure is not limited to the examples and designs described herein, but should be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for forming a foamed asphalt cold recycled mixture, characterized in that, Include the following steps in sequence: Step 1: Mix the foamed asphalt cold recycled mixture according to a pre-designed ratio; Step 2: Measure the maximum theoretical density of the mixed foamed asphalt cold recycled mixture; Step 3: Set the shear compaction parameters, including the compaction termination height, vertical pressure, and cyclic shear angle; Step 4: Calculate the mass of the mixture to be filled according to the void ratio of the foamed asphalt cold recycled mixture to be formed; Step 5: Conduct short-term aging treatment on the foamed asphalt cold recycled mixture; Step 6: Fill the aged foamed asphalt cold recycled mixture; Step 7: Shear and compact the filled foamed asphalt cold recycled mixture according to the set shear compaction parameters, and demold after forming; Step 8: Conduct secondary processing on the formed foamed asphalt cold recycled mixture.

2. A method for forming a foamed asphalt cold recycled mixture according to claim 1, characterized in that: The shear compaction forming adopts the mode of controlling the shear compaction height, the compaction termination height is 150 - 170 mm, the vertical pressure is 0.6 - 0.8 MPa, and the cyclic shear angle is 3.5 - 4°.

3. The method for forming a foamed asphalt cold recycled mixture according to claim X, characterized in that: In the above Step 4, the calculation formula for the mass of the foamed asphalt cold recycled mixture to be filled is: m = ρ × V × ( ), In the formula, m is the mass of the mixture filled, ρ is the maximum theoretical density of the mixture, V is the forming volume of the mixture, and s is the void ratio of the mixture to be formed.

4. A method for forming a foamed asphalt cold recycled mixture according to claim 1, characterized in that: The forming height of the foamed asphalt cold recycled mixture is the compaction termination height, and the void ratio of the formed mixture is 5 - 7%.

5. A method for forming a foamed asphalt cold recycled mixture according to claim 1, characterized in that: In the above Step 5, the method for short-term aging of the foamed asphalt cold recycled mixture is to spread the mixture on a specimen tray with a stacking height of 40 - 60 mm; put the mixture into an oven for heating, the temperature in the oven is 140 - 160 °C, and the heating time is 4 - 5 hours; during the heating process, turn over the mixture every hour.

6. A method for forming a foamed asphalt cold recycled mixture according to claim 1, characterized in that: In the above Step 7, during the shear compaction forming process, the compaction termination height is 170 mm, the vertical pressure is 0.8 MPa, the cyclic shear angle is 4°, and the compaction times are 30 times.

7. A method for forming a foamed asphalt cold recycled mixture according to claim 1, characterized in that: In the above Step 8, the secondary processing includes cutting, grinding, and surface treatment of the formed foamed asphalt cold recycled mixture to meet the requirements of engineering applications.

8. A method for forming a foamed asphalt cold recycled mixture according to claim 1, characterized in that: The mixing temperature of the foamed asphalt cold recycled mixture is 120 - 140 °C, and the mixing time is not less than 3 minutes to ensure the uniformity of the mixture.

9. A method for forming a foamed asphalt cold recycled mixture according to claim 1, characterized in that: The maximum theoretical density of the foamed asphalt cold recycled mixture is measured by the vacuum sealing method, the measurement temperature is 25 °C, the vacuum degree is -0.09 MPa, and the measurement time is 15 minutes.

10. A method for forming a foamed asphalt cold recycled mixture according to claim 1, characterized in that: During the short-term aging treatment process of the foamed asphalt cold recycled mixture, the stacking height of the mixture in the specimen tray is 50 mm, the oven temperature is 150 °C, the heating time is 4 hours, and the turning interval is 1 hour.

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