Warm mix asphalt mixture and design method thereof

Abstract

The invention discloses a warm mix asphalt mixture and a design method thereof, and belongs to the field of road engineering. In the warm mix asphalt mixture, the cementing material comprises emulsified asphalt and newly added hot asphalt, the water content of the cementing material is 1-10%, and the discharging temperature of the warm mix asphalt mixture is 110-140 DEG C. When the mixture is designed, the performance of the cementing material and the performance of the mixture can meet the design requirements by adjusting the mixing amount of the emulsified asphalt and the newly added hot asphalt. Compared with the prior art, the warm mix asphalt mixture disclosed by the invention is low in cost, the milling material mixing amount of the regenerated mixture is greatly increased (the milling material mixing amount is up to 100%), the pavement performance of the mixture is excellent, and the warm mix asphalt mixture has extremely high popularization and application values.

Description

Technical Field

[0001] The invention relates to the field of road engineering, and specifically provides a warm mix asphalt mixture and a design method thereof. Background Art

[0002] Compared with traditional hot mix, warm mix asphalt mixture can reduce the construction temperature by nearly 20-30℃, greatly reducing the energy consumption and pollutant emissions generated by the construction project, and has extremely high environmental value. Currently, warm mix asphalt can be used for virgin mixture and recycled mixture. Its common processes include mechanical foaming warm mix technology and warm mix technology with warm mix agent addition:

[0003] (1) Mechanical foaming warm mix technology

[0004] Through mechanical foaming equipment, hot asphalt is prepared into foamed asphalt under certain processes, and the warm mix characteristics of foamed asphalt are used to prepare asphalt mixtures. This technology is mature. However, the foaming effect of modified asphalt is not good, and the foaming equipment is installed separately, which is relatively expensive, limiting its further application and limited application scope; and when applied to recycled asphalt mixtures, the milling material content is mostly below 50%, which limits further improvement;

[0005] (2) Warm mix technology with warm mix agent

[0006] Warm mix technology, that is, adding warm mix agent to asphalt mixture. There are many types of warm mix agents in this technology. Common warm mix agents include wax-containing type, zeolite, surfactant type, etc. When used for recycled asphalt mixture, in addition to adding warm mix agent, regeneration agent also needs to be added. At present, the technical threshold of warm mix agent and regeneration agent is relatively high. Construction units do not have independent production capabilities, and most of them are purchased from the market, and the price is relatively expensive. This seriously limits the enthusiasm of relevant units to carry out warm mix technology construction. In addition. Warm mix agent often leads to the attenuation of certain performance indicators, which seriously limits the application and development of warm mix recycled asphalt mixture in my country. Summary of the invention

[0007] The present invention aims at solving the above-mentioned deficiencies of the prior art and provides a warm mix asphalt mixture.

[0008] The technical solution adopted by the present invention to solve the technical problem is: a warm-mix asphalt mixture, including a binder, wherein the binder includes emulsified asphalt, newly added hot asphalt,

[0009] The water content of the binder is 1-10%.

[0010] The discharge temperature of the warm mix asphalt mixture is 110-140°C.

[0011] The newly added hot asphalt can be any type of road petroleum asphalt, such as No. 70 road petroleum asphalt, No. 50 road petroleum asphalt, No. 30 road petroleum asphalt, No. 90 road petroleum asphalt, SBS modified asphalt, rubber modified asphalt or other polymer modified asphalt.

[0012] The emulsified asphalt may be any type of emulsified asphalt for roads, such as cationic emulsified asphalt, nonionic emulsified asphalt, modified emulsified asphalt, etc. Preferably, the solid content of the emulsified asphalt is not less than 45%.

[0013] When no milling material is added to the warm mix asphalt mixture, the binder is composed of emulsified asphalt and newly added hot asphalt, and its water content is preferably 2-6%; the discharge temperature of the warm mix asphalt mixture is preferably 110-130°C, and particularly preferably 120-130°C.

[0014] When milling material is added to warm mix asphalt mixture, the binder is composed of emulsified asphalt, newly added hot asphalt, and old asphalt from milling material. The moisture content of the binder is preferably 3-9%, and particularly preferably 4-8%; the discharge temperature of the warm mix asphalt mixture is 120-140°C, and particularly preferably 120-130°C.

[0015] The present application provides a design method for warm mix asphalt mixture, which is characterized by adjusting the dosage of emulsified asphalt and newly added hot asphalt; or

[0016] By adjusting the amount of emulsified asphalt, newly added hot asphalt and milling material,

[0017] The moisture content of the binder reaches 1-10%, the discharge temperature of the warm mix asphalt mixture reaches 110-140°C, and the performance of the binder and the mixture meets the design requirements. The solid content of the emulsified asphalt is not less than 45%.

[0018] In some embodiments, particularly when the warm mix asphalt mixture is not mixed with milled material, the design method of the warm mix asphalt mixture includes:

[0019] S1. Design of moisture content of binder

[0020] The amount of emulsified asphalt in the binder and the amount of newly added hot asphalt are preset so that the moisture content of the binder is 1-5%, and the solid content of the emulsified asphalt is not less than 45%;

[0021] S2. Binder performance test

[0022] Perform a performance test on the binder. If the test result meets the requirements, proceed to step S3; if the test result does not meet the requirements, return to step S1;

[0023] S3. Mixture discharge temperature design

[0024] Calculate the discharge temperature of the mixed material. If the discharge temperature is 110-140°C, proceed to step S4; otherwise, return to step S1;

[0025] S4. Mixture performance verification

[0026] The mixture is formed and subjected to performance verification test. If the test results meet the requirements, the design is completed; if the test results do not meet the requirements, return to step S1.

[0027] In some embodiments, particularly when milled material is added to the warm mix asphalt mixture, the design method of the warm mix asphalt mixture includes:

[0028] S1. Design of moisture content of binder

[0029] The amount of emulsified asphalt, newly added asphalt and milling material in the binder is preset so that the moisture content of the binder is 2-10%, and the mixture meets the grading requirements, and the solid content of the emulsified asphalt is not less than 45%;

[0030] S2. Binder performance test

[0031] Perform a performance test on the binder. If the test result meets the requirements, proceed to step S3; if the test result does not meet the requirements, return to step S1;

[0032] S3. Mixture discharge temperature design

[0033] Calculate the discharge temperature of the mixed material. If the discharge temperature is 120-140°C, proceed to step S4; otherwise, return to step S1;

[0034] S4. Mixture performance verification

[0035] The mixture is formed and subjected to performance verification test. If the test results meet the requirements, the design is completed; if the test results do not meet the requirements, return to step S1.

[0036] In some embodiments, when the binder is subjected to performance testing in step S2, the testing items include penetration test, softening point test, and ductility test.

[0037] In some embodiments, when the binder is tested for performance in step S2, the test items also include wax content test, flash point test, solubility test, thin film heating test, etc.

[0038] In some embodiments, when the performance of the binder is tested in step S2, the test items also include a dynamic shear test and a 60°C complex modulus test on the old asphalt.

[0039] In some embodiments, when the performance verification test is performed on the mixture in step S4, the test items include a rutting test dynamic stability test, a freeze-thaw splitting test residual strength ratio test, and a low-temperature bending test failure strain test.

[0040] In some embodiments, when the performance verification test is performed on the mixture in step S4, the test items include dynamic modulus test and fatigue life test.

[0041] The applicant has found through extensive research that when cold (emulsified asphalt) and hot asphalt are compounded to meet certain configuration requirements, they can demonstrate extremely excellent working characteristics, have significant warm mix characteristics, greatly improve construction and workability, and significantly reduce energy consumption and emissions. Compared with the prior art, the warm mix asphalt mixture and its design method of the present invention have the following outstanding beneficial effects:

[0042] (1) The materials are easy to obtain and inexpensive. Emulsified asphalt is used for cold asphalt, and traditional common asphalt can be used for hot asphalt. The current emulsified asphalt process is extremely mature and widely used. Construction mixing stations generally have emulsified asphalt equipment, which can be produced and applied at any time and has a low cost. This solves the current high cost of warm mix (recycling);

[0043] (ii) Achieve medium-temperature mixing, high warm-mixing efficiency. The cold and hot compounding process greatly reduces the construction temperature of asphalt mixture, reducing the construction temperature by 20-40°C and the minimum rolling temperature to 80°C, achieving medium-temperature construction effect, which is significantly improved compared with conventional warm-mixing technology;

[0044] (III) When applied to recycled asphalt mixture, warm mixing and recycling are integrated. Under the cold and hot compounding process, no warm mixing agent or recycling agent needs to be added in the production process, which greatly increases the amount of milling material in the recycled mixture, and can increase the amount of milling material to 100%. Under the same performance level, the cost can be reduced by nearly 80%, which is extremely cost-effective; the performance and quality of the mixture are balanced, and the energy consumption during the construction process is low. It solves the technical and production problems of high energy consumption and uneven performance when using large-volume recycled (fully recycled) mixtures. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Attached Figure 1 The figure is a flow chart of the mixture design method of the present invention. DETAILED DESCRIPTION

[0046] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0047] The warm-mix asphalt mixture in each embodiment of the present application uses cold asphalt (emulsified asphalt) and newly added hot asphalt as a binder, or uses cold asphalt (emulsified asphalt), newly added hot asphalt and old asphalt from milling materials as a binder.

[0048] As attached Figure 1 As shown in the figure, when designing the mixture, by adjusting the dosage of emulsified asphalt and newly added hot asphalt; or by adjusting the dosage of emulsified asphalt, newly added hot asphalt and milling material, the moisture content of the binder reaches 1-10%, the discharge temperature of the warm mix asphalt mixture reaches 110-140°C, and the performance of the binder and the mixture meet the design requirements.

[0049] [Example 1]

[0050] Raw warm mix design

[0051] The warm mix asphalt mixture gradation of this embodiment adopts AC-20 type. The common oil-stone ratio of this type of asphalt mixture is 4.8%. The emulsified asphalt used is cationic ordinary emulsified asphalt, which is prepared by emulsifying No. 70 road petroleum asphalt. The solid content of the emulsified asphalt is 50% (water content is 50%); the newly added hot asphalt is No. 70 road petroleum asphalt.

[0052] The design process of the original warm mix asphalt mixture in this embodiment is as follows:

[0053] (1) Moisture content design

[0054] Taking the common asphalt-to-stone ratio of 4.8% in AC-20 asphalt mixture as a reference, the dosage of the two types of asphalt was preset and the moisture content of the binder was calculated. The results are shown in Table 1-1.

[0055] Table 1-1 Moisture content design

[0056]

[0057] (2) Test of residual evaporation performance of blends

[0058] According to the proportions in Table 1-1, the emulsified asphalt and the newly added asphalt are evenly mixed. The residual evaporation performance of the mixture is tested in accordance with the "Test Procedures for Asphalt and Asphalt Mixtures for Highway Engineering" (JTG E20). The results are shown in Table 1-2.

[0059] Table 1-2 Performance test of residual evaporation of blends

[0060]

[0061]

[0062] Note: If the test results do not meet the requirements, return to step (1) to adjust the proportion of emulsified asphalt and newly added asphalt until they meet the requirements.

[0063] (3) Mixture discharge temperature design

[0064] According to the proportion of each material, the discharge temperature of the mixture is calculated through its specific heat capacity, initial temperature parameters, etc. The results are shown in Table 1-3.

[0065] Table 1-3 Mixture discharge temperature design

[0066]

[0067] Note: ① When calculating, the latent heat of vaporization is 2257.2 kJ / kg, and the latent heat of vaporization and the specific heat of the material are both the average values ​​of the current common materials; ② The amount of asphalt used in the temperature design process is the amount of common asphalt used in the proposed grading, which is AC-20 in this case, and the asphalt-to-stone ratio is 4.8%; ③ The heating temperatures of aggregates, asphalt, etc. are all the commonly used temperatures in the current process.

[0068] After calculation, the discharge temperature of the mixture is expected to be 125℃, which meets the design requirements.

[0069] (4) Mixture performance verification

[0070] The asphalt mixture was molded and the performance verification test was carried out according to the method described in the JTG E20 asphalt mixture test process. During the mixture test, the heating temperature design stage of various materials was the same. The performance verification results are shown in Table 1-4, and all met the requirements.

[0071] Table 1-4 Mixture performance verification

[0072]

[0073] (5) Economic and energy consumption comparison

[0074] Table 1-5 Comparison of economy and energy consumption

[0075] project unit This embodiment Hot asphalt binder Savings ratio (%) Energy consumption kJ / ton 92727.6 117209.9 20.9 Material prices Yuan / ton 236.9 236.3 -0.3

[0076] From the comparison data of mixture performance and economic energy consumption in Tables 1-4 and 1-5, it can be seen that although the raw material price of the mixture of this embodiment is slightly increased (0.6 yuan / ton), the unit energy consumption is greatly reduced by 20.9%. The energy consumption cost of conventional asphalt mixture combustion is about 35 yuan / ton, that is, the unit energy consumption price of this technology saves 7.3 yuan / ton compared with conventional mixture; at the same time, various road performance can meet the technical index requirements. In addition, compared with conventional warm mix technology, this technology reduces the price by nearly 8-10 yuan / ton.

[0077] (6) Comparison of rolling effects

[0078] Table 1-6 Comparison of rolling effects

[0079]

[0080]

[0081] It can be seen from Table 1-6 that under the rolling condition of 80°C, the compaction degree of this embodiment still reaches 98%, which meets the compaction requirements. However, the compaction degree of conventional hot asphalt mixture is only 94%, which obviously does not meet the technical requirement of achieving a compaction degree of more than 98% on site.

[0082] [Example 2]

[0083] Design of warm mix with large amount of recycled materials

[0084] The warm mix asphalt mixture of this embodiment adopts EME-16 type gradation, and the common asphalt-to-stone ratio of this type of asphalt mixture is 5.3%. The emulsified asphalt used is cationic common emulsified asphalt, which is prepared by emulsifying No. 70 road petroleum asphalt, and the solid content of the emulsified asphalt is 50%; the newly added hot asphalt is No. 70 road petroleum asphalt. The amount of milling material is 65% (accounting for 100% of the total mass of milling material and new aggregate), of which the content of old asphalt in the milling material is 4.4%.

[0085] The design process of the recycled warm mix asphalt mixture in this embodiment is as follows:

[0086] (1) Moisture content design

[0087] Taking the common oil-stone ratio of 5.3% of EME-16 asphalt mixture as a reference, according to the amount of milling material and the content of old asphalt in the milling material, the amount of emulsified asphalt and newly added asphalt is preset and the moisture content of the binder is calculated. The results are shown in Table 2-1-1.

[0088] Table 2-1-1 Moisture content design

[0089]

[0090] According to the proportion of new aggregate and milled material, gradation is configured to verify whether the gradation meets the corresponding specifications and design requirements. See Table 2-1-2, Table 2-1-3 and Table 2-1-4 for details.

[0091] Table 2-1-2 New aggregate screening data

[0092]

[0093] Table 2-1-3 Screening data of milling material extraction test

[0094]

[0095] Table 2-1-4 Synthetic gradation data

[0096]

[0097] It has been verified that the gradation composition meets the EME-16 gradation composition requirements.

[0098] (2) Binder performance test

[0099] According to the proportions in Table 2-1-1, the residual evaporation performance of the mixture of cold and hot asphalt was tested. The results are shown in Table 2-2-1. The dynamic shear test 60℃ complex modulus test was carried out on the old asphalt of the milling material (according to the JTG E20 dynamic shear test method). The results are shown in Table 2-2-2.

[0100] Table 2-2-1 Performance test of residual evaporation of hot and cold asphalt blends

[0101]

[0102] Table 2-2-2 Test of old asphalt performance

[0103]

[0104] Note: If the test results do not meet the requirements, return to step (1) to adjust the emulsified asphalt, the proportion of newly added asphalt, the amount of milling material, etc. until they meet the requirements.

[0105] (3) Mixture discharge temperature design

[0106] According to the proportion of each material, the discharge temperature of the mixture is calculated through its specific heat capacity, initial temperature parameters, etc. The results are shown in Table 2-3.

[0107] Table 2-3 Mixture discharge temperature design

[0108]

[0109] Note: ① When calculating, the latent heat of vaporization is 2257.2 kJ / kg, and the data of its and the specific heat capacity of materials are all based on the average values ​​of current common materials; ② The amount of asphalt used in the temperature design process is the amount of common asphalt with the planned grade, which is EME-20 this time, with an asphalt-to-stone ratio of 5.2%; ③ The heating temperatures of milling materials, aggregates, asphalt, etc. are all the temperatures commonly used in mixing plants in current processes.

[0110] After calculation, the discharge temperature of the mixture is expected to be 124℃, which meets the design requirements.

[0111] (4) Mixture performance verification

[0112] The asphalt mixture was molded according to the method described in the JTG E20 asphalt mixture test process and the performance verification test was carried out. During the mixture test, the heating temperature design stage of various materials was the same. The performance verification results are shown in Table 2-4, and all met the requirements.

[0113] Table 2-4 Mixture performance verification

[0114]

[0115] Note: According to the conventional recycling design method (such as JTG F40 design method), at this milling material dosage, the mixture is not mixed evenly, and white material is prone to occur, and the low temperature and water stability are low.

[0116] (5) Economic and energy consumption comparison

[0117] Table 2-5 Comparison of economy and energy consumption

[0118]

[0119]

[0120] As shown in Tables 2-5, the technology of the present invention reduces energy consumption by 17.6% and 14.1% respectively compared with conventional primary and conventional renewable energy, and reduces prices by 44.8% and 22.7% respectively, with significant economic and environmental benefits.

[0121] [Example 3]

[0122] Fully recycled warm mix design

[0123] The warm mix gradation of this embodiment adopts EME-20 type, and the common asphalt-to-stone ratio of this type of asphalt mixture is 5.4%. The emulsified asphalt used is a cationic modified emulsified asphalt, which is prepared by emulsifying SBS modified asphalt, and the solid content of the emulsified asphalt is 65%; the newly added hot asphalt is SBS modified asphalt. The amount of milling material added this time is 100% (accounting for the percentage of milling material and new aggregate), of which the content of old asphalt in the milling material is 4.4% (accounting for the percentage of milling material).

[0124] The design process of the recycled warm mix asphalt mixture in this embodiment is as follows:

[0125] (1) Moisture content design

[0126] Taking the common oil-stone ratio of 5.4% of EME-20 asphalt mixture as a reference, according to the content of old asphalt in the milling material, the dosage of emulsified asphalt and newly added asphalt is preset and the moisture content of the binder is calculated. The results are shown in Table 3-1-1.

[0127] Table 3-1-1 Moisture content design

[0128]

[0129] According to the composition of the milling material, verify whether the synthetic grading meets the corresponding specifications and design requirements, see Table 3-1-2 for details.

[0130] Table 3-1-2 Composition and gradation of milling material extraction and screening

[0131]

[0132] It has been verified that the gradation composition meets the EME-20 gradation composition requirements.

[0133] (2) Binder performance test

[0134] According to the proportions in Table 3-1-1, the residual evaporation performance of the cold and hot asphalt mixture was tested. The results are shown in Table 3-2-1. The dynamic shear test 60℃ complex modulus test was carried out on the old asphalt of the milling material (according to the JTG E20 dynamic shear test method), and the results are shown in Table 3-2-2.

[0135] Table 3-2-1 Performance test of residual evaporation of hot and cold asphalt mixture

[0136]

[0137]

[0138] Table 3-2-2 Inspection of old asphalt

[0139]

[0140] Note: When the test results do not meet the requirements, the addition ratio of emulsified asphalt and newly added asphalt can be adjusted until it is qualified.

[0141] (3) Mixture discharge temperature design

[0142] According to the proportion of each material, the discharge temperature of the mixture is calculated through its specific heat capacity, initial temperature parameters, etc. The results are shown in Table 3-3.

[0143] Table 3-3 Mixed material discharge temperature design

[0144]

[0145] Note: ① When calculating, the latent heat of vaporization is 2257.2 kJ / kg, and the latent heat of vaporization and the specific heat of materials are both the average values ​​of common materials currently used; ② The amount of asphalt used in the temperature design process is the amount of common asphalt used in the proposed grading, which is EME-16 this time, with an asphalt-to-stone ratio of 5.4%; ③ The heating temperatures of aggregates, asphalt, etc. are all the commonly used temperatures in the current process.

[0146] After calculation, the discharge temperature of the mixture is expected to be 121°C, which meets the design requirements.

[0147] (4) Mixture performance verification

[0148] The molding was carried out according to the method described in the JTG E20 asphalt mixture test process, and the performance verification test was carried out. During the mixture test, the heating temperature design stage of various materials was the same. The performance verification results are shown in Table 3-4, all of which met the requirements and had excellent performance.

[0149] Table 3-4 Mixture performance verification

[0150]

[0151] Note: According to the conventional recycling design method (such as JTG F40 design method), at this dosage, the mixture is loose and the comprehensive road performance of the mixture is extremely poor.

[0152] (5) Economic and energy consumption comparison

[0153] Table 3-5 Comparison of economy and energy consumption

[0154]

[0155] As shown in Tables 3-5, the technology of the present invention reduces energy consumption by 29.3% and 19.4% respectively compared with conventional primary and conventional renewable energy, and reduces prices by 70.4% and 58.6% respectively, with significant economic and environmental benefits.

Claims

1. A warm mix asphalt mixture, comprising a binder, characterized in that: The binder includes emulsified asphalt and newly added hot asphalt. The water content of the binder is 1-10%. The discharge temperature of the warm mix asphalt mixture is 110-140°C.

2. The warm mix asphalt mixture according to claim 1, characterized in that: The binder is composed of emulsified asphalt and newly added hot asphalt. The moisture content of the binder is 2-6%.

3. The warm mix asphalt mixture according to claim 1, characterized in that: The binder is composed of emulsified asphalt, newly added hot asphalt, and old asphalt from milling materials. The moisture content of the binder is 3-9%, and the discharge temperature of the warm mix asphalt mixture is 120-140°C.

4. The warm mix asphalt mixture according to claim 1, 2 or 3, characterized in that: The solid content of emulsified asphalt shall not be less than 45%.

5. A method for designing warm mix asphalt mixture, characterized in that: By adjusting the amount of emulsified asphalt and newly added hot asphalt; or By adjusting the amount of emulsified asphalt, newly added hot asphalt and milling material, The moisture content of the binder reaches 1-10%, the discharge temperature of the warm mix asphalt mixture reaches 110-140°C, and the performance of the binder and the mixture meets the design requirements. The solid content of the emulsified asphalt is not less than 45%.

6. The method for designing warm mix asphalt according to claim 5, characterized in that: include: S1. Design of moisture content of binder The amount of emulsified asphalt in the binder and the amount of newly added hot asphalt are preset so that the moisture content of the binder reaches 1-5%, and the solid content of the emulsified asphalt is not less than 45%; S2. Binder performance test Perform a performance test on the binder. If the test result meets the requirements, proceed to step S3; if the test result does not meet the requirements, return to step S1; S3. Mixture discharge temperature design Calculate the discharge temperature of the mixed material. If the discharge temperature is 110-140°C, proceed to step S4; otherwise, return to step S1; S4. Mixture performance verification The mixture is formed and subjected to performance verification test. If the test results meet the requirements, the design is completed; if the test results do not meet the requirements, return to step S1.

7. The method for designing warm mix asphalt according to claim 5, characterized in that: include: S1. Design of moisture content of binder The amount of emulsified asphalt, newly added asphalt and milling material in the binder is preset so that the moisture content of the binder reaches 2-10%, and the mixture meets the grading requirements, and the solid content of the emulsified asphalt is not less than 45%; S2. Binder performance test Perform a performance test on the binder. If the test result meets the requirements, proceed to step S3; if the test result does not meet the requirements, return to step S1; S3. Mixture discharge temperature design Calculate the discharge temperature of the mixed material. If the discharge temperature is 120-140°C, proceed to step S4; otherwise, return to step S1; S4. Mixture performance verification The mixture is formed and subjected to performance verification test. If the test results meet the requirements, the design is completed; if the test results do not meet the requirements, return to step S1.

8. The method for designing warm mix asphalt mixture according to claim 6 or 7, characterized in that: In step S2, the binder is subjected to a performance test, and the test items include a needle penetration test, a softening point test, and a ductility test.

9. The method for designing warm mix asphalt mixture according to claim 8, characterized in that: The performance test of the binder as described in step S2 includes a dynamic shear test and a 60°C complex modulus test on the old asphalt.

10. The method for designing warm mix asphalt mixture according to claim 6 or 7, characterized in that: The performance verification test of the mixture as described in step S4 includes the following test items: dynamic stability test of rutting test, residual strength ratio test of freeze-thaw splitting test, and failure strain test of low temperature bending test.

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