A method for optimizing design of mixture ratio of phase change asphalt mixture

Abstract

The application discloses a kind of phase change asphalt mixture mix proportion optimization design method, when phase change asphalt mixture mix proportion design, the influence of phase change material to asphalt mixture mineral aggregate gradation and optimum asphalt consumption is fully considered, by optimizing phase change asphalt mixture mix proportion design method, to improve the road performance and functionality of phase change asphalt mixture.Equivalent volume of phase change material of equal mass ratio different particle size replaces fine aggregate method is used for mixture gradation design, and the optimum asphalt content of phase change asphalt mixture containing phase change material is determined using improved Marshall design method, while ensuring the temperature regulating effect of phase change material, reduce the influence of phase change material physical properties on mixture road performance.The method effectively uses phase change material in asphalt mixture, so that phase change asphalt mixture has good temperature regulating effect, can improve the service level of phase change asphalt pavement, reduce road maintenance cost, reduce the consumption of natural resources, and the economic benefit is remarkable.

Description

Technical Field

[0001] This invention relates to a method for optimizing the mix design of asphalt mixtures by applying phase change materials. This method can determine the blending ratio of phase change materials in asphalt mixtures, determine the optimal asphalt content of phase change asphalt mixtures, and ensure that the phase change asphalt mixtures designed by this method meet the application technical requirements of asphalt pavements. Background Technology

[0002] Asphalt pavement boasts advantages such as convenient maintenance, low paving cost, and excellent paving effect, accounting for over 90% of high-grade pavements in my country. However, asphalt is a temperature-sensitive viscoelastic material, it faces negative impacts from temperature changes in practical engineering applications. Currently, the application of phase change materials (PCMs) in road engineering has a very broad prospect. Phase change temperature regulation technology is a widely used energy storage and temperature control technology in recent years. It utilizes the characteristic of PCMs to change their phase state with temperature changes within their phase change temperature range, absorbing or releasing latent heat of phase change while maintaining a stable temperature range to regulate the temperature of the material. However, compared with natural stone, the physical and mechanical properties of commonly used PCMs are inferior. PCMs have a large specific surface area, high water absorption, low density, and poor crush resistance. Studies suggest that incorporating PCMs into asphalt mixtures will worsen the road performance of the asphalt mixture, meaning that the performance of PCM asphalt mixtures is worse than that of asphalt mixtures using natural stone. The main reason for this is that the traditional Marshall design method for phase change asphalt mixtures does not adequately consider the characteristics of phase change materials (PCMs). It merely treats PCMs as admixtures added to asphalt mixtures, neglecting their impact on the gradation and asphalt-aggregate ratio of the asphalt mixture. Therefore, the design methodology needs to specifically consider the blending method and proportion of PCMs. Furthermore, the road performance of PCMs is affected by the amount of asphalt used, and common PCMs have a large specific surface area, enabling them to adsorb asphalt to a significant extent. Therefore, the method for determining the optimal asphalt content should be adjusted. Summary of the Invention

[0003] To address the aforementioned issues, this invention proposes a method for optimizing the mix design of phase change asphalt mixtures. Its purpose is to fully consider the impact of phase change materials (PCMs) on the aggregate gradation and optimal asphalt content of asphalt mixtures during mix design, thereby improving the road performance and functionality of PCMs. This invention employs a method of replacing fine aggregates with PCMs of equal mass ratios but different particle sizes in equal volumes for mix gradation design, and utilizes an improved Marshall design method to determine the optimal asphalt content in PCM-containing asphalt mixtures. This approach ensures the temperature-regulating effect of PCMs while reducing the impact of their physical properties on the road performance of the mixture. This method effectively utilizes PCMs in asphalt mixtures, resulting in PCMs with excellent temperature-regulating effects and road performance, improving the service level of PCM pavements, reducing road maintenance costs, lowering natural resource consumption, and demonstrating significant economic benefits.

[0004] The technical solution adopted in this invention is a method for optimizing the mix proportion of phase change asphalt mixtures, which applies phase change materials to asphalt mixtures. It mainly includes the following steps:

[0005] Step 1: Type of phase change material.

[0006] The phase change material should be a composite shaped phase change material, composed of a core sample and a carrier in a mass ratio of 92:8. The core sample is polyethylene glycol, and the carrier is expanded graphite. The particle size of the phase change material is less than 0.6 mm, falling into the category of fine aggregates.

[0007] Step 2: Gradation design of phase change asphalt mixture.

[0008] The design of phase change material blending adopts the idea of ​​replacing natural fine aggregate stone with the equal volume method:

[0009] First, based on the design documents or engineering requirements, the target optimal gradation J0 and the optimal asphalt content a0 of the asphalt mixture without phase change materials are determined by the traditional Marshall mix design method, and these are used as the basic aggregate gradation and basic asphalt content of the phase change asphalt mixture.

[0010] Based on the actual needs of using phase change materials (PCMs), combined with mixture design requirements and engineering experience, this invention determines five PCM blending ratio schemes, with PCM blending amounts of 20%, 40%, 60%, 80%, and 100% (percentage by mass of base asphalt). The PCMs are incorporated using a method of replacing fine aggregates with PCMs by equal volume. The PCMs replace 0.6mm, 0.3mm, 0.15mm, and 0.075mm fine aggregates in the gradation using an equal mass ratio replacement method.

[0011] The mass of fine aggregate for each replaced particle size is calculated using formula (1):

[0012]

[0013] In the formula:

[0014] m a —Mass of phase change material addition, in grams;

[0015] ρ a —Volume relative density of phase change materials, in g / cm³ 3 ;

[0016] m b —The mass of fine aggregate of a certain particle size that is being replaced, in grams;

[0017] ρ b —Volume relative density of fine aggregate, in g / cm³ 3 ;

[0018] Step 3: Determine the optimal amount of bitumen using the Marshall method.

[0019] (1) Select the asphalt used in the asphalt mixture according to the design requirements or specifications;

[0020] (2) A method for determining the optimal amount of asphalt is proposed:

[0021] An improved Marshall design method is adopted.

[0022] The specific method is as follows: First, keeping the basic aggregate gradation unchanged, the lowest 20% phase change material (PCM) content (as a percentage of asphalt mass) is used to replace the 0.6mm, 0.3mm, 0.15mm, and 0.075mm fine aggregates in the basic aggregate gradation using an equal volume method and equal mass ratio, forming the "phase change asphalt mixture" gradation J1. The specific method for determining its optimal asphalt content a1 is as follows: According to the Marshall test method, the optimal asphalt content a0 of the asphalt mixture without PCM is taken as the median value, and it is fluctuated up and down at intervals of ±0.5% and ±1.0%, forming a set of five test asphalt contents, and standard Marshall specimens are prepared. Furthermore, based on the results of the traditional Marshall test, the optimal asphalt content a1 of the PCM mixture with a 20% PCM replacement rate is determined by combining OAC1 and OAC2.

[0023] Then, keeping the basic aggregate gradation unchanged, 40% of the phase change material (PCM) was added (as a percentage of asphalt mass) to replace the fine aggregates of 0.6mm, 0.3mm, 0.15mm, and 0.075mm in the basic aggregate gradation using the equal volume method, forming the "phase change asphalt mixture" gradation J2, and determining its optimal asphalt content a2. The specific method is as follows: Following the Marshall test method, the optimal asphalt content a1 of the asphalt mixture with a 20% PCM addition was used as the median, and the values ​​were adjusted upwards and downwards at intervals of ±0.5% and ±1.0%, forming a set of five test asphalt contents, and standard Marshall specimens were prepared. Furthermore, the optimal asphalt content a2 of the phase change asphalt mixture with a 40% PCM replacement rate was determined by comprehensively considering the results of the traditional Marshall test.

[0024] Following this method, while keeping the basic aggregate gradation unchanged, 60%, 80%, and 100% of the phase change material (as a percentage of asphalt mass) were added to replace the fine aggregates of 0.6mm, 0.3mm, 0.15mm, and 0.075mm in the basic aggregate gradation in equal proportions by volumetric method, respectively, to form the "phase change asphalt mixture" gradations J3, J4, and J5.

[0025] The optimal asphalt content a3 of phase change asphalt mixture gradation J3 was determined according to the Marshall test method. The optimal asphalt content a2 of asphalt mixture with 40% phase change material admixture was taken as the median value, and it was fluctuated up and down at intervals of ±0.5% and ±1.0% to form a set of five test asphalt contents. Standard Marshall specimens were prepared, and the optimal asphalt content was determined by combining OAC1 and OAC2 based on the results of traditional Marshall test.

[0026] The optimal asphalt content a4 of phase change asphalt mixture gradation J4 was determined according to the Marshall test method. The optimal asphalt content a3 of asphalt mixture with 60% phase change material was taken as the median value, and it was fluctuated up and down at intervals of ±0.5% and ±1.0% to form a set of five test asphalt contents. Standard Marshall specimens were prepared, and the optimal asphalt content was determined by comprehensively considering the results of traditional Marshall tests.

[0027] The optimal asphalt content a5 of phase change asphalt mixture gradation J5 was determined according to the Marshall test method. The optimal asphalt content a4 of asphalt mixture with 80% phase change material was taken as the median value, and it was fluctuated up and down at intervals of ±0.5% and ±1.0% to form a set of five test asphalt contents. Standard Marshall specimens were prepared, and the optimal asphalt content was determined by comprehensively considering the results of traditional Marshall tests.

[0028] Step 4: Determine the optimal dosage of phase change material.

[0029] Indoor tests were conducted to evaluate the road performance of phase change asphalt mixtures with various phase change material (PCM) incorporations. Following the methods specified in the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTGE20-2011), indoor tests were performed on the high-temperature rutting resistance, low-temperature crack resistance, and water stability of PCM mixtures with designed PCM incorporations of 20%, 40%, 60%, 80%, and 100% (as a percentage of the base asphalt mass). The corresponding PCM incorporation amounts that meet the road performance specifications for asphalt mixtures were then selected. This invention defines the highest PCM incorporation amount that meets the road performance specifications for asphalt mixtures as the optimal PCM incorporation amount, thereby enabling the design of PCM mixtures that meet road performance requirements and have good temperature regulation effects.

[0030] This invention proposes a method for optimizing the mix design of phase change asphalt mixtures to reduce the impact of the physical properties of phase change materials (PCMs) on the road performance of asphalt mixtures. This method enables the mixture to achieve good temperature regulation while meeting road performance requirements. The method employs an equal-volume substitution of fine aggregates with PCMs of different particle sizes at equal mass ratios for gradation design. An improved Marshall design method is then used to determine the optimal asphalt content in the PCM-containing asphalt mixture, thereby reducing the influence of PCM physical properties on the road performance of the mixture. This method effectively utilizes PCMs in asphalt mixtures, resulting in PCM mixtures with excellent temperature regulation and road performance, improving road service levels, reducing road maintenance costs, and lowering natural resource consumption, thus yielding significant economic benefits. Attached Figure Description

[0031] Figure 1 : Screening results of mineral materials and mineral powder.

[0032] Figure 2 Three initial selection gradations. Detailed Implementation

[0033] The technical solution of the present invention will be further described below with reference to the following embodiments, but the present invention is not limited to the following embodiments.

[0034] Example 1:

[0035] Selection of Phase Change Material and Asphalt Mixture Type: A polyethylene glycol / expanded graphite composite shaped phase change material was selected as an admixture and incorporated into SMA-10 asphalt mixture. The mix proportion of this phase change asphalt mixture was optimized to prepare a phase change asphalt mixture that meets the requirements for road performance and temperature control. The selected polyethylene glycol / expanded graphite composite shaped phase change material has good shaped-forming effect and will not cause leakage of the phase change core material in the asphalt mixture due to the phase change of the phase change material. The particle size of the polyethylene glycol / expanded graphite composite phase change material is less than 0.6 mm, belonging to the category of fine aggregate. Some raw material information is shown in Table 1.

[0036] Table 1. Physical properties of some raw materials

[0037]

[0038] 1. Mix design of phase change asphalt mixture:

[0039] (1) Determination of the basic aggregate gradation and basic asphalt content of phase change asphalt mixture.

[0040] First, based on the design documents or engineering requirements, the target optimal gradation J0 and optimal asphalt content a0 of the SMA-10 asphalt mixture without phase change materials are determined using the traditional Marshall mix design method. These are then used as the basic aggregate gradation and basic asphalt content for the phase change asphalt mixture. The sieving results of SMA-10 aggregates and mineral powders are shown below. Figure 1 The three initial gradations are as follows: Figure 2 As shown.

[0041] The volumetric parameters of the Marshall specimens with the three gradations are shown in Table 2.

[0042] Table 2. Specimen volume parameters for three gradations

[0043]

[0044]

[0045] Through comparative analysis of the volumetric parameters of the three gradations of asphalt mixtures, gradation 3 was determined to be the optimal gradation. Its optimal asphalt content was determined using the traditional Marshall mix design test method. The relationship between asphalt content and void ratio, bulk density, stability, asphalt saturation, and flow value was plotted using OAC1 and OAC2, and the final optimal asphalt content was determined to be 6.5%.

[0046] The optimal gradation and optimal asphalt content determined in this way are used as the base aggregate gradation and base asphalt content of phase change asphalt mixture.

[0047] (2) Blending scheme for phase change materials.

[0048] Based on the actual needs of using phase change materials (PCMs), combined with mixture design requirements and engineering experience, five PCM blending ratio schemes were determined, with PCM blending amounts of 20%, 40%, 60%, 80%, and 100% (percentage of base asphalt mass). PCMs were incorporated using an equal-volume substitution method for fine aggregates. To reduce the impact of PCM particle size inhomogeneity on asphalt mixture gradation, PCMs were used to replace 0.6mm, 0.3mm, 0.15mm, and 0.075mm fine aggregates in the gradation using an equal-mass substitution method.

[0049] The mass of fine aggregate replaced by each phase change material dosage is calculated using formula (1). Before the specimen is mixed and formed, the fine aggregate is sieved to remove the corresponding mass of fine aggregate with the corresponding particle size, and then replaced by an equal volume of phase change material.

[0050] (3) Optimal asphalt content for phase change asphalt mixture.

[0051] Step 1: Select SBS modified asphalt as the asphalt binder for SMA-10 phase change asphalt mixture according to design requirements.

[0052] Step Two: Keeping the basic aggregate gradation unchanged, the lowest 20% phase change material (PCM) admixture (as a percentage of asphalt mass) is used to replace the 0.6mm, 0.3mm, 0.15mm, and 0.075mm fine aggregates in the basic aggregate gradation using the equal volume method and equal mass ratio, forming the "phase change asphalt mixture" gradation J1. Then, according to the Marshall test method, using the optimal asphalt content a0 of the asphalt mixture without PCM as the median value, and fluctuating it up and down at intervals of ±0.5% and ±1.0%, a set of five test asphalt contents is formed, and standard Marshall specimens are prepared. Then, using the traditional Marshall mix proportion test method, by plotting the relationship between asphalt content and void ratio, bulk density, stability, asphalt saturation, and flow value, the optimal asphalt content a1 of the "phase change asphalt mixture" gradation J1 is determined using OAC1 and OAC2.

[0053] Step 3: Keeping the basic aggregate gradation unchanged, replace the 0.6mm, 0.3mm, 0.15mm, and 0.075mm fine aggregates in the basic aggregate gradation with 40% phase change material (as a percentage of asphalt mass) using the equal volume method and equal mass ratio to form the "phase change asphalt mixture" gradation J2, and determine its optimal asphalt content a2. The specific method is as follows: According to the Marshall test method, take the optimal asphalt content a1 of the asphalt mixture with 20% phase change material as the median value, and fluctuate it up and down at intervals of ±0.5% and ±1.0% to form a set of five test asphalt contents. Using the traditional Marshall mix proportion test method, by plotting the relationship between asphalt content and void ratio, bulk density, stability, asphalt saturation, and flow value, use OAC1 and OAC2 to determine the optimal asphalt content a2 of the phase change asphalt mixture with a 40% phase change material replacement rate.

[0054] Step 4: While maintaining the basic aggregate gradation unchanged, 60% of the phase change material (PCM) is added (as a percentage of asphalt mass) to replace the fine aggregates of 0.6mm, 0.3mm, 0.15mm, and 0.075mm in the basic aggregate gradation using the equal volume method, forming the "phase change asphalt mixture" gradation J3. The optimal asphalt content a3 of the PCM mixture gradation J3 is determined according to the Marshall test method, using the optimal asphalt content a2 of the asphalt mixture with 40% PCM as the median value, and fluctuating within ±0.5% and ±1.0% intervals to form a set of five test asphalt contents. Standard Marshall specimens are prepared, and the optimal asphalt content is determined by comprehensively considering the results of traditional Marshall tests.

[0055] Step 5: While maintaining the basic aggregate gradation unchanged, 80% of the phase change material (PCM) is added (as a percentage of asphalt mass) to replace the fine aggregates of 0.6mm, 0.3mm, 0.15mm, and 0.075mm in the basic aggregate gradation using the equal volume method, forming the "phase change asphalt mixture" gradation J4. The optimal asphalt content a4 of the PCM mixture gradation J4 is determined according to the Marshall test method, using the optimal asphalt content a3 of the asphalt mixture with 60% PCM as the median value, and fluctuating within ±0.5% and ±1.0% intervals to form a set of five test asphalt contents. Standard Marshall specimens are prepared, and the optimal asphalt content is determined by comprehensively considering the results of traditional Marshall tests.

[0056] Step Six: While maintaining the basic aggregate gradation unchanged, replace the 0.6mm, 0.3mm, 0.15mm, and 0.075mm fine aggregates in the basic aggregate gradation with 100% phase change material (as a percentage of asphalt mass) using the equal volume method and equal mass ratio to form the "phase change asphalt mixture" gradation J5. The optimal asphalt content a5 of the phase change asphalt mixture gradation J5 is determined according to the Marshall test method, using the optimal asphalt content a4 of the asphalt mixture with 80% phase change material as the median value, and fluctuating up and down at intervals of ±0.5% and ±1.0%, forming a set of five test asphalt contents. Standard Marshall specimens are prepared, and the optimal asphalt content is determined by comprehensively considering the results of traditional Marshall tests.

[0057] (4) Determination of the optimal phase change material dosage.

[0058] Indoor tests were conducted to evaluate the road performance of phase change asphalt mixtures with various phase change material (PCM) incorporations. Following the methods specified in the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTGE20-2011), indoor tests were performed on the high-temperature rutting resistance, low-temperature crack resistance, and water stability of PCM mixtures with designed PCM incorporations of 20%, 40%, 60%, 80%, and 100% (as a percentage of the base asphalt mass). To improve the actual temperature control effect of PCM mixtures, this invention uses the highest PCM incorporation that meets the specified road performance requirements as the optimal PCM incorporation, thus enabling the design of PCM mixtures that meet the requirements.

Claims

1. A method for optimizing the mixture ratio of a phase change asphalt mixture, characterized in that: Comprising the following steps: Step one: phase change material type; The phase change material should be a composite shaped phase change material, which is composed of a core sample and a carrier in a mass ratio of 92:

8. The core sample is polyethylene glycol, and the carrier is expanded graphite. The particle size of the phase change material is less than 0.6 mm, which belongs to fine aggregate; Step two: phase change asphalt mixture gradation design; The phase change material is mixed by the equal volume method instead of natural fine aggregate stone: Through the Marshall mix proportion test method, the target optimal gradation J0 and the best asphalt content a0 of the asphalt mixture without adding phase change material are determined, which are used as the basis for the mineral aggregate gradation and the basis for the asphalt content of the phase change asphalt mixture; Step three: Marshall method to determine the best asphalt content; (1) Select the asphalt used in the asphalt mixture according to the design requirements or specification requirements; (2) The method for determining the asphalt content is proposed: Improved Marshall design method: First, keep the basis for the mineral aggregate gradation unchanged, and replace the fine aggregate of 0.6 mm, 0.3 mm, 0.15 mm and 0.075 mm in the basis for the mineral aggregate gradation with 20% phase change material by equal volume method, which is equal in mass ratio, to form "phase change asphalt mixture" gradation J1, and the best asphalt content a1 is determined as follows: According to the Marshall test method, the best asphalt content a0 of the asphalt mixture without adding phase change material is taken as the median value, and is floated up and down with an interval of ±0.5% and ±1.0% to form a group of five test asphalt contents, and standard Marshall test pieces are prepared; Through the Marshall test results, the asphalt content a1 of the phase change asphalt mixture under the replacement rate of 20% phase change material is determined by OAC1 and OAC2; Keep the basis for the mineral aggregate gradation unchanged, and replace the fine aggregate of 0.6 mm, 0.3 mm, 0.15 mm and 0.075 mm in the basis for the mineral aggregate gradation with 40% phase change material by equal volume method, which is equal in mass ratio, to form "phase change asphalt mixture" gradation J2, and determine its best asphalt content a2; The specific method is as follows: According to the Marshall test method, the best asphalt content a1 of the asphalt mixture with 20% phase change material is taken as the median value, and is floated up and down with an interval of ±0.5% and ±1.0% to form a group of five test asphalt contents, and standard Marshall test pieces are prepared; Through the Marshall test results, the best asphalt content a2 of the phase change asphalt mixture under the replacement rate of 40% phase change material is determined; Subsequently, according to this method, under the premise of keeping the basis for the mineral aggregate gradation unchanged, 60%, 80% and 100% phase change material is added by equal volume method, which is equal in mass ratio, to replace the fine aggregate of 0.6 mm, 0.3 mm, 0.15 mm and 0.075 mm in the basis for the mineral aggregate gradation, to form "phase change asphalt mixture" gradations J3, J4 and J5 in turn; Step four: best phase change material content determination; The road performance of the phase change asphalt mixture with different phase change material contents is tested indoors; the high-temperature rutting resistance, low-temperature cracking resistance and water stability of the phase change asphalt mixture with the designed 20%, 40%, 60%, 80% and 100% phase change material contents are tested indoors, and the corresponding phase change material contents of the phase change asphalt mixture meeting the requirements of the asphalt mixture road performance specification are screened out.

2. The method for optimizing the mixture ratio of a phase change asphalt mixture according to claim 1, characterized in that: According to the actual needs of using the phase change material, combining the mixture design requirements and engineering experience, the blending ratio scheme of the five phase change materials is determined, wherein the phase change material contents are 20%, 40%, 60%, 80% and 100% respectively, the phase change material is mixed by using the method of replacing the fine aggregate with equal volume; the phase change material replaces the fine aggregate with equal mass ratio in the gradation of 0.6mm, 0.3mm, 0.15mm and 0.075mm; The mass of the replaced fine aggregate of each particle size is calculated by formula (1): In the formula: m a — Phase change material addition mass, in g; p a Phase change material bulk volume relative density, g / cm 3 ; m b - the mass of the fine aggregate of the certain particle size that is replaced, in g; p b - fine aggregate apparent volume relative density, in g / cm3 3 .

3. The method for optimizing the mixture ratio of a phase change asphalt mixture according to claim 1, characterized in that: The optimal asphalt content a3 of the phase change asphalt mixture gradation J3 is determined according to the Marshall test method, the optimal asphalt content a2 of the asphalt mixture with 40% phase change material content is taken as the median value, and a group of five test asphalt contents are formed by floating up and down with an interval of ±0.5% and ±1.0%, the standard Marshall test pieces are prepared, and the optimal asphalt content is determined by the Marshall test results and the OAC1 and OAC2; The optimal asphalt content a4 of the phase change asphalt mixture gradation J4 is determined according to the Marshall test method, the optimal asphalt content a3 of the asphalt mixture with 60% phase change material content is taken as the median value, and a group of five test asphalt contents are formed by floating up and down with an interval of ±0.5% and ±1.0%, the standard Marshall test pieces are prepared, and the optimal asphalt content is determined by the Marshall test results; The optimal asphalt content a5 of the phase change asphalt mixture gradation J5 is determined according to the Marshall test method, the optimal asphalt content a4 of the asphalt mixture with 80% phase change material content is taken as the median value, and a group of five test asphalt contents are formed by floating up and down with an interval of ±0.5% and ±1.0%, the standard Marshall test pieces are prepared, and the optimal asphalt content is determined by the Marshall test results.

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