Emulsified asphalt early-strength, high-toughness in-place cold recycled mixture and preparation method therefor

Abstract

An emulsified asphalt early-strength, high-toughness in-place cold recycled mixture, and a preparation method therefor. The preparation method comprises the following steps: S1, determining an optimal mixing moisture content S of a reclaimed asphalt; S2, determining an evaporative residue content of a high-viscosity modified emulsified asphalt; S3, determining the amounts of the reclaimed asphalt, water, the high-viscosity modified emulsified asphalt, and an early-strength organic demulsifier; S4, sequentially adding water, the high-viscosity modified emulsified asphalt and the early-strength organic demulsifier into the reclaimed asphalt, and mixing. The optimal total water amount of the emulsified asphalt early-strength high-toughness in-place cold recycled mixture is the product of the mass of the reclaimed asphalt and the optimal mixing moisture content S. This method produces a cold recycled asphalt mixture with rapid early strength formation and high initial strength, resolving the issues in conventional engineering of the utilization rate of reclaimed asphalt being low, and a prepared cold recycled mixture exhibiting slow early strength development and insufficient initial strength.

Description

A high-early-strength, high-toughness emulsified asphalt in-situ cold recycled mixture and its preparation method

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 202411177552.X, filed on August 26, 2024, entitled "An Emulsified Asphalt Early Strength High Toughness In-situ Cold Recycled Mixture and Its Preparation Method", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to the field of asphalt mixture technology, and in particular to an emulsified asphalt early-strength, high-toughness in-situ cold recycled mixture and its preparation method. Background Technology

[0004] The utilization rate of recycled asphalt has always been a challenge in traditional road engineering. With increasing environmental awareness and growing calls for resource recycling, how to efficiently utilize recycled asphalt to reduce reliance on new materials and lessen the environmental burden has become a hot topic in industry research.

[0005] Traditional methods for processing recycled asphalt mainly involve cold recycling technology. While this method achieves material recycling to some extent, the insufficient initial strength of cold recycled materials severely affects the quality of road construction, making it difficult to widely promote recycled asphalt in engineering applications. Summary of the Invention

[0006] The purpose of this invention is to propose a method for preparing emulsified asphalt early-strength and high-toughness in-situ cold recycled mixture, which can produce a cold recycled asphalt mixture with fast early strength formation and high initial strength. This solves the problem that the utilization rate of asphalt recycled material in traditional engineering is low, and the cold recycled mixture prepared by cold recycling generally has the problems of slow early strength formation and insufficient initial strength.

[0007] Another objective of this invention is to propose an emulsified asphalt early-strength and high-toughness in-situ cold recycled mixture, which has rapid early strength formation and high initial strength, thus solving the problem of slow early strength formation and insufficient initial strength in recycled asphalt materials.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] A method for preparing an emulsified asphalt early-strength, high-toughness in-situ cold recycled mixture includes the following steps:

[0010] S1. Determine the optimal mixing moisture content S of the recycled asphalt;

[0011] S2. Determine the evaporation residue content of high-viscosity modified emulsified asphalt;

[0012] S3. Determine the dosage of recycled asphalt, water, high-viscosity modified emulsified asphalt, and early-strength organic demulsifier;

[0013] S4. Water, high-viscosity modified emulsified asphalt, and early-strength organic demulsifier are added sequentially to the asphalt recycled material and mixed to prepare an emulsified asphalt early-strength high-toughness in-situ cold recycling mixture.

[0014] The optimal total water content of the emulsified asphalt early-strength, high-toughness in-situ cold recycled mixture is the product of the mass of the recycled asphalt and the optimal mixing moisture content S.

[0015] Furthermore, the early-strength organic demulsifier is one or more of polyacrylamide, acrylic acid, and acrylamide copolymer.

[0016] Furthermore, the molecular weight of the early-strength organic demulsifier is 1000-10000.

[0017] Furthermore, the high-viscosity modified emulsified asphalt has a PG grade ≥ PG82, an elastic recovery of ≥ 98% at 25℃, a composite shear modulus G* ≥ 10 kPa at 60℃, a dynamic viscosity of ≥ 30,000 Pa·s at 60℃, a G* / sinδ of the evaporation residue ≥ 2.2 kPa, and a critical temperature ≥ 82℃.

[0018] Furthermore, the high-viscosity modified emulsified asphalt contains an SBS modifier, and the mass content of the modifier is ≥3%.

[0019] Furthermore, the method for determining the optimal mixing moisture content in S1 includes the following steps:

[0020] 1) Weigh the asphalt recycling material as m2 and the container as m1;

[0021] 2) Add 0.5% water by mass to the asphalt recycling material and mix for 20-60 seconds. The total weight of the weighing container, asphalt recycling material and water is m3.

[0022] 3) Tilt the beaker until the mouth is facing down, pour out the asphalt recycling material inside, weigh the container and the water-containing asphalt recycling material residue together, and record the weight as m4;

[0023] 4) Calculate the residual rate X of asphalt recycled material at the corresponding moisture content. l :

[0024] X l = (m4-m1) / (m3-m1)*100%;

[0025] Repeat the above operation, record the segregation residual rate of asphalt recycled material at different moisture contents, and plot the moisture content-segregation residual rate curve. The moisture content corresponding to the peak point of the segregation residual rate in the curve is the optimum moisture content S.

[0026] Furthermore, the weight ratio of the total water content of the early-strength organic demulsifier and the emulsified asphalt early-strength high-toughness in-situ cold recycled mixture is 1:(20-100):.

[0027] Furthermore, step S3 specifically involves, by weight, 100 parts of recycled asphalt, 0.1-10 parts of water, 3-10 parts of high-viscosity modified emulsified asphalt, and 0.01-3 parts of early-strength organic demulsifier.

[0028] Furthermore, the specific steps of S4 include the following:

[0029] S41. Mix the asphalt mixture and water thoroughly for 20-40 seconds;

[0030] S42. Add the high-viscosity modified emulsified asphalt to the mixture in S41 and mix thoroughly for 30-50 seconds.

[0031] S43. Add an early-strength organic demulsifier to the mixture in S42 and mix thoroughly for 20-40 seconds to prepare an emulsified asphalt early-strength high-toughness in-situ cold recycled mixture.

[0032] An emulsified asphalt early-strength, high-toughness in-situ cold-recycled mixture is prepared by a method for preparing an emulsified asphalt early-strength, high-toughness in-situ cold-recycled mixture.

[0033] Compared with the prior art, the technical solution proposed in this invention can have the following beneficial effects:

[0034] 1. In this scheme, the total water content of the emulsified asphalt early strength and high toughness in-situ cold recycled mixture is limited to the product of the mass of the asphalt recycled material and the optimum mixing moisture content S, which ensures that the high viscosity modified emulsified asphalt can better adhere to its surface during the mixing process of the asphalt recycled material, thereby improving the early strength of the asphalt mixture.

[0035] 2. The early-strength organic demulsifier is one or more of polyacrylamide, acrylic acid, and acrylamide copolymers. Acrylic acid contains hydrophilic carboxyl groups, while acrylamide and polyacrylamide both contain hydrophilic amide groups. These properties endow the early-strength organic demulsifier obtained by polymerizing propylene-based organic compounds with good hydrophilicity, promoting water consumption in high-viscosity modified emulsified asphalt, breaking the stable emulsion structure in the high-viscosity modified emulsified asphalt, and further enabling the high-viscosity modified emulsified asphalt to rapidly demulsify and form strength, thereby increasing the speed of early strength formation. Furthermore, during the later curing process, the early-strength organic demulsifier can better form a continuous film structure with the recycled asphalt, further enhancing the continuity and stability of the structure at the microscale, thus ensuring the initial strength of the asphalt mixture in this scheme. Detailed Implementation

[0036] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0037] This invention provides a method for preparing emulsified asphalt early-strength, high-toughness in-situ cold recycled mixture, comprising the following steps:

[0038] S1. Determine the optimal mixing moisture content S of the recycled asphalt;

[0039] S2. Determine the evaporation residue content of high-viscosity modified emulsified asphalt;

[0040] S3. Determine the dosage of recycled asphalt, water, high-viscosity modified emulsified asphalt, and early-strength organic demulsifier;

[0041] S4. Water, high-viscosity modified emulsified asphalt, and early-strength organic demulsifier are added sequentially to the asphalt recycled material and mixed to prepare an emulsified asphalt early-strength high-toughness in-situ cold recycling mixture.

[0042] The optimal total water content of the emulsified asphalt early-strength, high-toughness in-situ cold recycled mixture is the product of the mass of the recycled asphalt and the optimal mixing moisture content S.

[0043] Currently, the utilization rate of recycled asphalt in engineering projects is low. Cold recycled asphalt mixtures prepared by cold recycling generally suffer from slow early strength formation and insufficient initial strength. To address these issues, this technical solution proposes a method for preparing emulsified asphalt early-strength, high-toughness in-situ cold recycled asphalt mixtures. This method can produce cold recycled asphalt mixtures with rapid early strength formation and high initial strength.

[0044] Before use, recycled asphalt requires pretreatment through milling and gradation. After pretreatment, the surface porosity of recycled asphalt is larger than that of conventional new aggregate, resulting in lower hygroscopicity and severely affecting the demulsification effect of high-viscosity modified emulsified asphalt. Therefore, in this solution, the recycled asphalt needs to be wetted with water.

[0045] To avoid excessive total water content in the asphalt mixture, this scheme first determines the water content by considering the evaporation residue content in the high-viscosity modified emulsified asphalt and the optimum mixing moisture content of the recycled asphalt. This ensures that the total water content of the early-strength, high-toughness in-situ cold recycled asphalt mixture in this scheme is the product of the mass of the recycled asphalt and the optimum mixing moisture content S. This allows the recycled asphalt to better adhere to the surface of the high-viscosity modified emulsified asphalt during the mixing process, thereby improving the early strength of the asphalt mixture.

[0046] High-viscosity modified emulsified asphalt adheres to the surface of recycled asphalt at room temperature, forming an asphalt film that wraps and bonds the recycled asphalt, thus binding the asphalt mixture into a whole. This ensures that the asphalt mixture has good early strength and excellent viscoelastic properties, further improving the early strength of the asphalt mixture and thus enhancing its road performance.

[0047] Traditional cold-recycled asphalt mixtures contain cement, which can increase the early strength formation of the mixture to some extent, but significantly reduces its fatigue performance and low-temperature crack resistance. Therefore, this solution uses an early-strength organic demulsifier to replace inorganic materials such as cement, with the weight percentage of the early-strength organic demulsifier ranging from 0.01 to 3 parts. When the addition amount of the early-strength organic demulsifier exceeds 3 parts, the high-viscosity modified emulsified asphalt demulsifies rapidly, causing it to demulsify between the asphalt recycled material before fully coating the aggregate. This results in poor aggregate bonding, leading to significant failure of the adhesive interface between the high-viscosity modified emulsified asphalt and the asphalt recycled material, which also affects the early strength of the asphalt mixture and results in insufficient road performance. This solution not only achieves emission reduction but also eliminates the negative impact of cement on toughness and low-temperature performance by using an organic binder system.

[0048] Furthermore, the early-strength organic demulsifier is one or more of polyacrylamide, acrylic acid, and acrylamide copolymer.

[0049] This method does not use cement-based materials as an external admixture to promote the demulsification of emulsified asphalt. At low dosages, cement-based admixtures do not have a significant effect on the rapid formation of early strength in emulsified asphalt. The presence of emulsified asphalt will inhibit cement hydration to some extent, which is not beneficial to the early strength formation of recycled asphalt mixtures.

[0050] Acrylic acid contains hydrophilic carboxyl groups, while acrylamide and polyacrylamide both contain hydrophilic amide groups. These properties impart good hydrophilicity to the early-strength organic demulsifier obtained by polymerizing propylene-based organic compounds, promoting water consumption in high-viscosity modified emulsified asphalt, breaking down the stable emulsion structure, and further accelerating the demulsification and strength formation of the high-viscosity modified emulsified asphalt, thus increasing the speed of early strength formation. Furthermore, during the later curing process, the early-strength organic demulsifier can better form a continuous film structure with the recycled asphalt, further enhancing the continuity and stability of the structure at the microscale, thereby ensuring the initial strength of the asphalt mixture in this solution.

[0051] The early-strength organic demulsifier has a molecular weight of 1000-10000.

[0052] It is worth noting that the polyacrylamide, acrylic acid, and acrylamide copolymer in this solution are all commercially available products. By combining one or more of them, an early-strength organic demulsifier with a molecular weight of 1000-1000 can be obtained.

[0053] When the molecular weight is below 1000, the early-strength organic demulsifier raw material has a low degree of polymerization, and the dosage needs to be increased to achieve the specified demulsification effect. However, excessive dosage will further affect the porosity and strength level of the mixture in the later stage. When the molecular weight is above 10000, the early-strength organic demulsifier raw material has a high degree of polymerization, and its dosage is low. It is difficult to disperse evenly in the interior of the recycled mixture during the mixing process, thereby affecting the strength level of the mixture.

[0054] The high-viscosity modified emulsified asphalt has a PG grade ≥ PG82, an elastic recovery of ≥ 98% at 25℃, a composite shear modulus G* ≥ 10 kPa at 60℃, a dynamic viscosity of ≥ 30,000 Pa·s at 60℃, an evaporation residue G* / sinδ ≥ 2.2 kPa, and a critical temperature ≥ 82℃.

[0055] Dynamic viscosity is an important indicator for measuring the flow properties of asphalt at a certain temperature. High viscosity can improve the asphalt's resistance to deformation and water damage, and also help improve its workability during construction. In a preferred embodiment of this technical solution, a dynamic viscosity of ≥30,000 Pa·s at 60℃ can ensure the high-temperature stability, water damage resistance, and adhesion to recycled asphalt mixtures of the asphalt mixture.

[0056] The PG grade of high-viscosity modified emulsified asphalt should not be lower than PG82, with an elastic recovery of ≥98% at 25℃, a composite shear modulus G* ≥10KPa at 60℃, a dynamic viscosity of ≥30,000 Pa·s at 60℃, a G* / sinδ of evaporation residue ≥2.2kPa, and a critical temperature ≥82℃. This will further improve the early strength and early forming speed of asphalt mixtures, and further improve their road performance.

[0057] The high-viscosity modified emulsified asphalt contains SBS modifier, and the mass content of the modifier is ≥3%.

[0058] In one embodiment of this technical solution, the modifier for high-viscosity modified emulsified asphalt is generally preferably a star-shaped SBS modifier. The addition of SBS modifier can significantly increase the softening point and dynamic viscosity of asphalt. Star-shaped SBS modified asphalt not only adheres to the surface of recycled asphalt at room temperature, forming an asphalt film to encapsulate and bond the recycled asphalt, thus binding the asphalt mixture into a cohesive whole and ensuring good early strength, but it also possesses excellent viscoelastic properties, further improving the early strength of the asphalt mixture and thereby enhancing its road performance.

[0059] Furthermore, the addition amount of SBS modifier, calculated as a percentage by mass, is ≥3%. When the SBS modifier content reaches 3% or more, it can significantly improve the softening point and dynamic viscosity of asphalt mixtures. A modifier content of 3% or more can provide sufficient viscosity and fluidity for high-viscosity modified emulsified asphalt, facilitating paving and bonding with recycled asphalt, and meeting the requirements for workability.

[0060] Moreover, increasing the modifier dosage can significantly improve the durability properties of asphalt mixtures, such as fatigue resistance, resistance to reflective cracking, and resistance to water damage.

[0061] The method for determining the optimal mixing moisture content in S1 includes the following steps:

[0062] 1) Weigh the asphalt recycling material as m2 and the container as m1;

[0063] 2) Add 0.5% water by mass to the asphalt recycling material and mix for 20-60 seconds. The total weight of the weighing container, asphalt recycling material and water is m3.

[0064] 3) Tilt the beaker until the mouth is facing down, pour out the asphalt recycling material inside, weigh the container and the water-containing asphalt recycling material residue together, and record the weight as m4;

[0065] 4) Calculate the residual rate X of asphalt recycled material at the corresponding moisture content. l :

[0066] X l = (m4-m1) / (m3-m1)*100%;

[0067] Repeat the above operation, record the segregation residual rate of asphalt recycled material at different moisture contents, and plot the moisture content-segregation residual rate curve. The moisture content corresponding to the peak point of the segregation residual rate in the curve is the optimum moisture content S.

[0068] Because recycled asphalt has large surface pores and low hygroscopicity after milling and gradation, it is difficult for high-viscosity modified emulsified asphalt to be evenly distributed in the recycled asphalt, thus seriously affecting the demulsification effect of the high-viscosity modified emulsified asphalt. Therefore, the optimal mixing moisture content of the asphalt mixture is designed to determine the water content in this scheme. An appropriate water content can ensure that the surface of the recycled asphalt is wet, has good coating performance with the high-viscosity modified emulsified asphalt, and can also prevent the pre-demulsification of the high-viscosity emulsified asphalt during mixing, thereby improving the early strength and compaction performance of the asphalt mixture.

[0069] In this diagram, moisture content is plotted on the x-axis, and residual segregation rate on the y-axis, with moisture content varying in 0.5% increments. A moisture content-residual segregation rate curve is generated based on the residual segregation rates obtained from the above operations. The water content corresponding to the peak point of the residual segregation rate on this curve is the optimum mixing moisture content. Since this scheme does not specify the moisture content of the recycled asphalt itself, the optimum mixing moisture content varies for different types of recycled asphalt.

[0070] The weight ratio of the total water content of the early-strength organic demulsifier and the emulsified asphalt early-strength high-toughness in-situ cold recycled mixture is between 1:20 and 1:100.

[0071] This scheme limits the water consumption level in the high-viscosity modified emulsified asphalt to between 50% and 80% during the demulsification process. This allows some of the high-viscosity modified emulsified asphalt to demulsify under the action of the early-strength agent, ensuring the early strength of the asphalt mixture. Additionally, some of the high-viscosity modified emulsified asphalt can act as a lubricant between recycled asphalt materials in the undemulsified state, helping to improve compaction performance.

[0072] Therefore, based on the total water content in the asphalt mixture, the evaporation residue content of the high-viscosity modified emulsified asphalt, and the water consumption, since the weight ratio of the early-strength organic demulsifier to the total water content of the asphalt mixture is 1:(20-100), the amount of early-strength organic demulsifier to be added can be determined.

[0073] This scheme limits the weight ratio of early-strength organic demulsifier to the total water content of the asphalt mixture, ensuring the demulsification effect of high-viscosity modified emulsified asphalt. It ensures that the early-strength organic demulsifier can form strong hydrogen bonds with the water in the high-viscosity modified emulsified asphalt, causing the high-viscosity modified emulsified asphalt to demulsify and form a continuous and complete asphalt film on the surface of the recycled asphalt. This allows the asphalt mixture to bond and form a cohesive whole, ensuring the early strength of the asphalt mixture.

[0074] Step S3 specifically involves calculating by weight parts: 100 parts of recycled asphalt, 0.1-10 parts of water, 3-10 parts of high-viscosity modified emulsified asphalt, and 0.01-3 parts of early-strength organic demulsifier.

[0075] Determining the water content and asphalt recycling amount in this scheme can ensure that the surface of the asphalt recycling material is wet, has good coating performance with high viscosity modified emulsified asphalt, and can also prevent the high viscosity emulsified asphalt from pre-demulsifying during the mixing process, thereby improving the early strength and compaction performance of the asphalt mixture.

[0076] High-viscosity modified emulsified asphalt encapsulates and bonds recycled asphalt, forming a whole asphalt mixture, ensuring its early strength, and improving the performance of the asphalt mixture.

[0077] This solution uses an early-strength organic demulsifier to replace inorganic materials such as cement, with the weight percentage of the early-strength organic demulsifier ranging from 0.01 to 3 parts. When the addition amount of the early-strength organic demulsifier exceeds 3 parts, the high-viscosity modified emulsified asphalt demulsifies too quickly, causing it to demulsify between the asphalt recycled material before fully coating the aggregate. This results in poor aggregate bonding, leading to significant failure of the adhesive interface between the high-viscosity modified emulsified asphalt and the asphalt recycled material, which in turn affects the early strength of the asphalt mixture and leads to insufficient road performance. This solution not only achieves emission reduction but also eliminates the negative impact of cement on toughness and low-temperature performance by using an organic binder system.

[0078] The specific steps of S4 include the following:

[0079] S41. Mix the asphalt mixture and water thoroughly for 20-40 seconds;

[0080] S42. Add the high-viscosity modified emulsified asphalt to the mixture in S41 and mix thoroughly for 30-50 seconds.

[0081] S43. Add an early-strength organic demulsifier to the mixture in S42 and mix thoroughly for 20-40 seconds to prepare an emulsified asphalt early-strength high-toughness in-situ cold recycled mixture.

[0082] First, water is added to the recycled asphalt and stirred to achieve good wetting of the asphalt mixture surface. At this point, the recycled asphalt has not yet reached its optimal mixing moisture content. Then, high-viscosity modified emulsified asphalt is added and stirred. A small portion of the water in the high-viscosity emulsified asphalt is further absorbed by the recycled asphalt, bringing its moisture content to the optimal mixing moisture content. Simultaneously, the high-viscosity modified emulsified asphalt coats and bonds the recycled asphalt, ensuring the early strength of the asphalt mixture. Next, an early-strength organic demulsifier is added and stirred. The early-strength organic demulsifier reacts with and consumes some of the water in the high-viscosity emulsified asphalt, causing the high-viscosity modified emulsified asphalt to undergo quantitative demulsification, forming a continuous and complete asphalt film on the surface of the recycled asphalt. This ensures the early strength of the asphalt mixture and achieves rapid early strength formation during the mixing process.

[0083] The mixing time setting in S4 ensures a more uniform distribution of components, which helps to guarantee the relevant properties of the asphalt mixture.

[0084] An emulsified asphalt early-strength, high-toughness in-situ cold-recycled mixture is prepared by a method for preparing an emulsified asphalt early-strength, high-toughness in-situ cold-recycled mixture.

[0085] Currently, the utilization rate of recycled asphalt in engineering projects is low. Cold recycled mixtures prepared using cold recycling methods generally suffer from slow early strength development and insufficient initial strength. To address these issues, this technical solution utilizes an emulsified asphalt early-strength, high-toughness in-situ cold recycled mixture, which exhibits rapid early strength development and high initial strength, thus resolving the problems of slow early strength development and insufficient initial strength associated with recycled asphalt.

[0086] The present invention will be further illustrated below with reference to embodiments and comparative examples.

[0087] Examples 1-3

[0088] Prepare the raw materials according to the corresponding materials listed in Table 2 below, and prepare the early strength and high toughness in-situ cold recycled mixtures of Examples 1-3 according to the process parameters listed in Table 2 and the following steps.

[0089] S1. Determine the optimal mixing moisture content of recycled asphalt;

[0090] S2. Determine the evaporation residue content of high-viscosity modified emulsified asphalt;

[0091] S3. Determine the dosage of recycled asphalt, water, high-viscosity modified emulsified asphalt, and early-strength organic demulsifier;

[0092] S4. Water, high-viscosity modified emulsified asphalt, and early-strength organic demulsifier are added sequentially to the asphalt recycled material and mixed to prepare an emulsified asphalt early-strength high-toughness in-situ cold recycling mixture.

[0093] The mixture consists of 100 parts recycled asphalt, 0.1-10 parts water, 3-10 parts high-viscosity modified emulsified asphalt, and 0.01-3 parts early-strength organic demulsifier.

[0094] The early-strength organic demulsifier is one or more of polyacrylamide, acrylic acid, and acrylamide copolymer. The molecular weight of the early-strength organic demulsifier is 1000-10000.

[0095] The high-viscosity modified emulsified asphalt should have a PG grade of no less than PG82, an elastic recovery of no less than 98% at 25℃, a composite shear modulus G* of no less than 10 kPa at 60℃, a dynamic viscosity of ≥30,000 Pa·s at 60℃, a G* / sinδ of evaporation residue ≥2.2 kPa, and a critical temperature ≥82℃. The high-viscosity modified emulsified asphalt includes an SBS modifier, with a modifier content of ≥3% by mass.

[0096] The weight ratio of the early-strength organic demulsifier to the total water content of the asphalt mixture is 1:(20-100).

[0097] The specific steps of S1 are as follows:

[0098] S11, The mass of the recycled asphalt material is m2, and the mass of the container is m1;

[0099] S12. Add 0.5% water by mass to the asphalt recycling material and mix for 20-60 seconds. The total weight of the weighing vessel, asphalt recycling material, and water is m3.

[0100] S13. Quickly tilt the beaker until the mouth of the beaker is facing down, pour out the asphalt recycling material contained inside, weigh the combined mass of the container and the asphalt recycling material residue containing water, and record it as m4.

[0101] S14. Calculate the segregation residual rate X of recycled asphalt with a moisture content of 5%. l X l = (m4-m1) / (m3-m1)*100%;

[0102] Repeat the above operation, record the segregation residual rate of asphalt recycled material at different moisture contents, and plot the moisture content-segregation residual rate curve. The moisture content corresponding to the peak point of the segregation residual rate in the curve is the optimum moisture content.

[0103] The specific steps for S2 refer to the T0651-1993 test for the evaporation residue content of emulsified asphalt as described in (JTG E20-2011). This test involves weighing a 300g ± 1g emulsified asphalt sample and evaporating it until all the water has evaporated, obtaining the evaporation residue of the emulsified asphalt. The specific calculation formula is as follows: Evaporation residue content = Mass of evaporation residue of emulsified asphalt / Mass of emulsified asphalt * 100%.

[0104] The specific steps for S4 are as follows:

[0105] S41. Mix the asphalt mixture and water thoroughly for 20-40 seconds;

[0106] S42. Add the high-viscosity modified emulsified asphalt to the mixture in S41 and mix thoroughly for 30-50 seconds.

[0107] S43. Add an early-strength organic demulsifier to the mixture in S42 and mix thoroughly for 20-40 seconds to prepare an emulsified asphalt early-strength high-toughness in-situ cold recycled mixture.

[0108] The recycled asphalt material is a uniform aggregate obtained after milling, and its gradation range is shown in Table 1.

[0109] Table 1. Gradation range of asphalt mixtures

[0110] Table 2 Raw material composition and process parameters

[0111] Comparative Example 1

[0112] S1. Mix 100 parts of recycled asphalt and 2.8 parts of water thoroughly for 20 seconds. The optimal mixing moisture content of the recycled asphalt is 4.5%.

[0113] S2. Add 5.0 parts of commercially available conventional cationic medium-crack modified emulsified asphalt with an evaporation residue content of 60% to the mixture in step one, and mix thoroughly for 30 seconds.

[0114] S3. Add 1.5 parts of PO32.5 cement to the mixture in step two and mix thoroughly for 20 seconds to obtain a cement-emulsified asphalt in-situ cold recycled mixture.

[0115] Comparative Example 2

[0116] S1. Mix 100 parts of recycled asphalt with 2 parts of water for 20 seconds. The optimal mixing moisture content of the recycled asphalt is 4.5%.

[0117] S2. Add 5.0 parts of commercially available conventional cationic medium-crack modified emulsified asphalt with an evaporation residue content of 60% to the mixture in step one, and mix thoroughly for 30 seconds.

[0118] S3. Add 0.8 parts of PO32.5 cement to the mixture in step two and mix thoroughly for 20 seconds to obtain a cement-emulsified asphalt in-situ cold recycled mixture.

[0119] The asphalt mixtures prepared in Examples 1-3 and Comparative Examples 1-2 were molded into Marshall specimens according to the method in "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011 T0702), and compacted on both sides 50 times. After molding, no curing was required, and the specimens were demolded. Then, the early 15°C splitting tensile strength of the emulsified asphalt cold recycled mixture was determined according to the method in "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011 T0716), and the results are summarized in Table 3.

[0120] Table 3. Early-stage splitting strength of asphalt mixtures at 15°C

[0121] The asphalt mixtures prepared in Examples 1-3 and Comparative Examples 1-2 were molded into Marshall specimens according to the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011 T0702). Each specimen was compacted 50 times on both sides, cured in a 60℃ constant temperature oven for 48 hours, and then compacted 25 times on both sides. The splitting tensile strength and wet-dry splitting ratio of the emulsified asphalt cold recycled mixture were determined according to the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011 T0716), and the results are summarized in Table 3.

[0122] Table 4 Comparison of splitting tensile strength and wet / dry splitting ratio of asphalt mixtures after curing at 15℃

[0123] The asphalt mixtures prepared in Examples 1-3 and Comparative Examples 1-2 were molded into 5cm thick rutting slab specimens according to the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011 T0719) without curing. To simulate the effect of nighttime traffic opening, dynamic stability was tested at 25℃ (uncured). Immediately after mixing, 5cm thick rutting slab specimens were molded according to the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011 T0719) and cured in a 60℃ constant temperature oven for 48 hours. Afterward, they were re-compacted 12 times to simulate the supplementary compaction effect after traffic opening. The dynamic stability measured before and after curing is summarized in Table 5.

[0124] Table 5 Comparison of dynamic stability of asphalt mixtures before and after curing

[0125] As can be seen from the performance test results in Tables 3, 4, and 5, the emulsified asphalt early-strength, high-toughness in-situ cold recycled mixture prepared by this technical solution has a better molding effect and better early and later strength. Specifically, the early 15℃ splitting strength is higher than that of the cement-emulsified asphalt cold recycled mixture. After curing, the 15℃ splitting strength and wet-dry splitting ratio of Example 1 both meet the requirements of the "Technical Specification for Recycling Asphalt Pavement of Highways" (JTG / T 5521-2019) for surface layers with heavy or higher traffic load levels, which stipulates a 15℃ splitting strength ≥ 0.60 MPa and a wet-dry splitting strength ratio ≥ 80%.

[0126] In addition, the emulsified asphalt early-strength and high-toughness in-situ cold recycled mixture prepared by this technical solution also has good early-stage resistance to rutting deformation and resistance to rutting deformation after curing.

[0127] In Comparative Example 1, although the material could be formed early, the hydration reaction between cement and water took a long time, resulting in insufficient demulsification of the emulsified asphalt. Despite a high cement content, the curing time at room temperature was short, leading to slow strength development. After curing at 60℃, the strength was higher than that measured under normal temperature curing due to the accelerated cement hydration process and increased demulsification of the emulsified asphalt. However, the excessive cement content affected the uniform distribution within the material, and some emulsified asphalt was over-demulsified, preventing the formation of a continuous asphalt film within the internal structure, thus creating weak interfaces in the material's stress distribution. Furthermore, the use of conventional emulsified asphalt limited strength development.

[0128] In Comparative Example 2, due to the shorter early curing time and lower cement content, the material was difficult to form in the early stages. The internal emulsified asphalt had not yet broken down to form sufficient bond strength, and the cement hydration was insufficient. After curing at 60℃, the cement content was lower than in Comparative Example 1, and the splitting strength at 15℃ was even lower. At the same time, the strength development was limited by the use of conventional emulsified asphalt.

[0129] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of the invention and should not be construed as limiting the scope of protection of the invention in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of the invention without inventive effort, and these embodiments will all fall within the scope of protection of the present invention.

Claims

1. A method for preparing an emulsified asphalt early-strength, high-toughness in-situ cold recycled mixture, characterized in that, Includes the following steps: S1. Determine the optimal mixing moisture content S of the recycled asphalt; S2. Determine the evaporation residue content of high-viscosity modified emulsified asphalt; S3. Determine the dosage of recycled asphalt, water, high-viscosity modified emulsified asphalt, and early-strength organic demulsifier; S4. Water, high-viscosity modified emulsified asphalt, and early-strength organic demulsifier are added sequentially to the asphalt recycled material and mixed to prepare an emulsified asphalt early-strength high-toughness in-situ cold recycling mixture. The optimal total water content of the emulsified asphalt early-strength, high-toughness in-situ cold recycled mixture is the product of the mass of the recycled asphalt and the optimal mixing moisture content S.

2. The method for preparing an emulsified asphalt early-strength, high-toughness in-situ cold recycled mixture according to claim 1, characterized in that, The early-strength organic demulsifier is one or more of polyacrylamide, acrylic acid and acrylamide copolymer.

3. The method for preparing an emulsified asphalt early-strength, high-toughness in-situ cold recycled mixture according to claim 1, characterized in that, The early-strength organic demulsifier has a molecular weight of 1000-10000.

4. The method for preparing an emulsified asphalt early-strength, high-toughness in-situ cold recycled mixture according to claim 1, characterized in that, The high-viscosity modified emulsified asphalt has a PG grade ≥ PG82, an elastic recovery of ≥ 98% at 25℃, a composite shear modulus G* ≥ 10 kPa at 60℃, a dynamic viscosity of ≥ 30,000 Pa·s at 60℃, an evaporation residue G* / sinδ ≥ 2.2 kPa, and a critical temperature ≥ 82℃.

5. The method for preparing an emulsified asphalt early-strength, high-toughness in-situ cold recycled mixture according to claim 1, characterized in that, The high-viscosity modified emulsified asphalt contains SBS modifier, and the mass content of the modifier is ≥3%.

6. The method for preparing an emulsified asphalt early-strength, high-toughness in-situ cold recycled mixture according to claim 1, characterized in that, The method for determining the optimal mixing moisture content in S1 includes the following steps: 1) Weigh the asphalt recycling material as m2 and the container as m1; 2) Add 0.5% water by mass to the asphalt recycling material and mix for 20-60 seconds. The total weight of the weighing container, asphalt recycling material and water is m3. 3) Tilt the beaker until the mouth is facing down, pour out the asphalt recycling material inside, weigh the container and the water-containing asphalt recycling material residue together, and record the weight as m4; 4) Calculate the residual rate X of asphalt recycled material at the corresponding moisture content. l : X l =(m4-m1) / (m3-m1)*100%; Repeat the above operation, record the segregation residual rate of asphalt recycled material at different moisture contents, and plot the moisture content-segregation residual rate curve. The moisture content corresponding to the peak point of the segregation residual rate in the curve is the optimum moisture content S.

7. The method for preparing an emulsified asphalt early-strength, high-toughness in-situ cold recycled mixture according to claim 1, characterized in that, The weight ratio of the total water content of the early-strength organic demulsifier and the emulsified asphalt early-strength high-toughness in-situ cold recycled mixture is 1:(20-100).

8. The method for preparing an emulsified asphalt early-strength, high-toughness in-situ cold recycled mixture according to claim 1, characterized in that, Step S3 specifically involves calculating by weight parts: 100 parts of recycled asphalt, 0.1-10 parts of water, 3-10 parts of high-viscosity modified emulsified asphalt, and 0.01-3 parts of early-strength organic demulsifier.

9. The method for preparing an emulsified asphalt early-strength, high-toughness in-situ cold recycled mixture according to claim 1, characterized in that, The specific steps of S4 include the following: S41. Mix the asphalt mixture and water thoroughly for 20-40 seconds; S42. Add the high-viscosity modified emulsified asphalt to the mixture in S41 and mix thoroughly for 30-50 seconds. S43. Add an early-strength organic demulsifier to the mixture in S42 and mix thoroughly for 20-40 seconds to prepare an emulsified asphalt early-strength high-toughness in-situ cold recycled mixture.

10. An emulsified asphalt early-strength, high-toughness, in-situ cold-recycled mixture, characterized in that, It is prepared by the preparation method of the emulsified asphalt early strength high toughness in-situ cold recycled mixture according to any one of claims 1-9.

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