Sup25 asphalt mixture highly doped with RAP fine separation material and preparation method of sup25 asphalt mixture

Abstract

The invention belongs to the technical field of highway construction materials, and particularly relates to a sup25 asphalt mixture highly doped with RAP fine separation materials and a preparation method. According to the invention, oilstone fine separation is carried out on the RAP material of the original pavement under the action of physical collision, the RAP material is separated into five-grade materials of 16-25 mm, 10-16 mm, 5-10 mm, 3-5 mm and 0-3 mm, and the plant-mixed Sup-25 hot recycled asphalt mixture highly doped with the RAP fine separated material is obtained through the design of a sup25 plant-mixed hot mixture in which the five-grade fine separated material is used for replacing a new aggregate part by utilizing a plant-mixed hot recycling construction process. The recycled RAP material is fully utilized, the use value of the recycled RAP material is exerted, resources are saved, and the construction cost of highway engineering is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of highway construction materials, and particularly relates to a SUP25 asphalt mixture highly mixed with RAP fine material and a preparation method thereof. Background Art

[0002] As highway construction enters the era of comprehensive maintenance, my country produces nearly 200 million tons of recycled asphalt mixture (also known as recycled asphalt mixture, abbreviated as RAP) every year during major and medium maintenance. The efficient resource recycling of RAP has become a development trend in highway maintenance. In recent years, with the development of asphalt pavement regeneration technology, it is divided into hot recycled asphalt mixture, cold mix recycled asphalt mixture and warm mix recycled asphalt mixture according to the regeneration temperature. At present, hot recycled asphalt mixture is the most studied. At present, the RAP material (recycled asphalt mixture) in the factory-mixed hot recycled asphalt mixture is in the range of 10% to 30%, which is a relatively mature technology, and the content of more than 30% is considered high. my country's research on high-content factory-mixed hot recycled asphalt mixture is in its infancy. Given the complexity of RAP material itself, the current obstacles to increasing the content of RAP material mainly include technical standards, variability and road performance restrictions. Therefore, controlling the quality stability of RAP material is the key.

[0003] Superpave is a relatively new and extensive asphalt mixture design and analysis system. It is also a result of the US Strategic Highway Research Program (SHRP). Superpave asphalt mixture has many advantages. At present, the introduction and application of Superpave technology has become more common in my country, and more and more provinces have issued local standards. RAP is rich in aged asphalt, and the penetration of aged asphalt decreases, indicating that the material becomes harder and the asphalt viscosity increases, so its high temperature performance becomes better; and the softening point increases, the viscosity increases, and the thermal stability increases; applying RAP material to Sup structure can further enhance its superior high temperature stability.

[0004] Among the existing patents, most of the patents related to plant-mixed hot-recycled RAP use traditional RAP materials, such as "A high-dosage RAP plant-mixed AC-25 hot-recycled asphalt mixture and its preparation method" (CN202211583124.8), which uses waste oil as a regeneration agent, reducing the amount of new asphalt to a certain extent, but only uses conventionally separated RAP materials; "A mix ratio design method for plant-mixed hot-recycled asphalt mixture" (CN202010514745.5) determines the optimal RAP asphalt dosage by performance, but also only uses conventionally separated RAP materials; Or only part of the aggregate is used and no hot regeneration technology is used, such as "A RAP new fine aggregate fully recycled asphalt pavement functional layer material and preparation method thereof" (CN202210223987.8), which only uses 0-4.75mm RAP new fine aggregate, which is mixed with emulsified asphalt to improve the performance of cold recycled mixture; "A RAP new fine aggregate asphalt pavement functional layer paving material and preparation method thereof" (CN202310817927.3) also only uses RAP new fine aggregate, and the performance of cold recycled RAP mixture is worse than that of hot recycled mixture. The traditional RAP materials used in the above inventions have problems such as a large number of false particles and large variability, which have a great impact on the grading of asphalt mixtures and are prone to adversely affect the performance of green mixtures. Summary of the invention

[0005] In order to solve the above problems in the prior art, the present invention provides a sup25 asphalt mixture with a high content of RAP fine fraction, which comprises the following raw materials: RAP fine fraction, new aggregate, regeneration agent and new asphalt.

[0006] Furthermore, the content of the RAP fine fraction in the sup25 asphalt mixture is higher than 30%.

[0007] Furthermore, the RAP refined material is obtained as follows: the RAP material is finely separated from the oilstone to obtain five grades of materials of 16-25mm, 10-16mm, 5-10mm, 3-5mm, and 0-3mm, which are tested to meet the Superpave design requirements, and the 0-3mm grade material with an asphalt content of about 5-9% (preferably about 7%), the 3-5mm grade material with an asphalt content of ≤3%, and the refined material of 5mm or more with an asphalt content of ≤2% are selected as the required RAP refined material.

[0008] Furthermore, the new aggregate consists of 20-28 mm new coarse aggregate, 10-20 mm new coarse aggregate, 10-15 mm new coarse aggregate, 5-10 mm new coarse aggregate and 0-3 mm new fine aggregate.

[0009] Furthermore, the new aggregate is limestone.

[0010] Furthermore, the regeneration agent is a RA-75 model regeneration agent.

[0011] Furthermore, the new asphalt is ordinary road petroleum asphalt and SBS modified asphalt, such as No. 70 road petroleum asphalt, No. 90 road petroleum asphalt, ID type SBS modified asphalt, IC type SBS modified asphalt, preferably No. 70 road petroleum asphalt, No. 90 road petroleum asphalt, etc.

[0012] Furthermore, the sup25 asphalt mixture contains 40-80 parts of RAP refined material and 20-60 parts of new aggregate by weight, and the content of regeneration agent in the sup25 asphalt mixture is 10% of the asphalt content in the RAP refined material, and the content of new asphalt is the total asphalt required for the sup25 asphalt mixture minus the asphalt content in the RAP refined material.

[0013] Furthermore, the sup25 asphalt mixture contains 41 parts of RAP refined material and 59 parts of new aggregate by weight.

[0014] Furthermore, the sup25 asphalt mixture comprises 41 parts of RAP refined material, 59 parts of new aggregate, 0.15 parts of regeneration agent and 1.93-3.43 parts of new asphalt in parts by weight.

[0015] Furthermore, the RAP fine material comprises, by weight, 15 parts by weight of 0-3 mm stop material, 6 parts by weight of 3-5 mm stop material, and 10 parts by weight of fine materials of 5 mm and above.

[0016] Furthermore, the sup25 asphalt mixture comprises 80 parts of RAP fine aggregate, 16 parts of new coarse aggregate and 4 parts of new fine aggregate in parts by weight.

[0017] Furthermore, the sup25 asphalt mixture comprises, by weight, 80 parts of RAP refined material, 16 parts of new coarse aggregate, 0.15 parts of regeneration agent, 2.5 parts of new asphalt and 4 parts of new fine aggregate.

[0018] Furthermore, the RAP fine material comprises, by weight, 14.5 parts of 0-3 mm material, 16 parts of 3-5 mm material, 15 parts of 5-10 mm material, 18.5 parts of 10-16 mm material and 16 parts of 16-25 mm material.

[0019] Furthermore, the new aggregate comprises, by weight, 14-20 parts of 20-28 mm new coarse aggregate, 0-22 parts of 10-20 mm new coarse aggregate, 0-8.5 parts of 10-15 mm new coarse aggregate, 0-11.5 parts of 5-10 mm new coarse aggregate and 4-8 parts of 0-3 mm new fine aggregate.

[0020] Furthermore, the new aggregate comprises, by weight, 20 parts of 20-28 mm new coarse aggregate, 22 parts of 10-20 mm new coarse aggregate, 7 parts of 10-15 mm new coarse aggregate, 6 parts of 5-10 mm new coarse aggregate and 4 parts of 0-3 mm new fine aggregate.

[0021] Furthermore, the new aggregate comprises, by weight, 16 parts of 20-28 mm new coarse aggregate, 19 parts of 10-20 mm new coarse aggregate, 8 parts of 10-15 mm new coarse aggregate, 10 parts of 5-10 mm new coarse aggregate and 6 parts of 0-3 mm new fine aggregate.

[0022] Furthermore, the new aggregate comprises, by weight, 14 parts of 20-28 mm new coarse aggregate, 17 parts of 10-20 mm new coarse aggregate, 8.5 parts of 10-15 mm new coarse aggregate, 11.5 parts of 5-10 mm new coarse aggregate and 8 parts of 0-3 mm new fine aggregate.

[0023] Furthermore, the new aggregate consists of 20-28 mm new coarse aggregate.

[0024] The sup25 asphalt mixture with high RAP fine material as described herein can be prepared by those skilled in the art using conventional techniques according to actual conditions. For example, the raw materials of the sup25 asphalt mixture with high RAP fine material can be formed using a rotary compactor, a Marshall test method, etc.

[0025] Furthermore, the present invention also provides an exemplary method for preparing a sup25 asphalt mixture with a high content of RAP fine material as described herein, which comprises using a mixing plant to load RAP fine material above 3 mm together with new aggregate, heating it to 180°C using a low-position heating roller, and mixing it with unpreheated 0-3 mm grade fine material after fine metering through a vibrating screen, stirring for 60 seconds, and then adding new asphalt and regeneration agent preheated to 170°C at the same time, and mixing at 170°C for 120 seconds to obtain a sup25 asphalt mixture with a high content of RAP fine material.

[0026] Furthermore, the preheating temperature of RAP fine material above 3 mm can be 165-185°C.

[0027] Further, the preheating temperature of the new aggregate may be 165-185°C.

[0028] Further, the preheating temperature of the new asphalt may be 155-175°C.

[0029] Further, the mixing may be performed at 155-175°C.

[0030] Beneficial Effects of the Invention

[0031] The present invention aims to provide a sup25 asphalt mixture with a high content of RAP fine material, and has the following functions:

[0032] (1) Efficient use of large amounts of recycled asphalt mixture (RAP): Traditional RAP materials are generally classified and utilized by secondary crushing and screening methods, which contain a large number of agglomerated pseudo-particles, resulting in uncontrollable grading and large variability. The present invention uses a large-scale oilstone fine separation equipment to perform oilstone fine separation on RAP through physical collision, and separates conventional RAP into five grades of 16-25mm, 10-16mm, 5-10mm, 3-5mm, and 0-3mm (collectively referred to as RAP fine-graded materials), solving the problem of a large number of pseudo-particles and large variability in RAP materials, and obtaining RAP fine-graded materials with stable grading, which plays an important role in optimizing the grading in the pavement structure and improving the compactness and stability of the pavement. Among them, the oil-poor fine material (above 3mm) can be directly used as new aggregate for high-value application because of its stable grading and greatly reduced old asphalt content (oil content ≤3% or ≤2%). The oil-rich fine material (0-3mm) is rich in a large amount of old asphalt stripped off by collision (the oil content is generally around 5-9%), which can reduce the amount of new asphalt added to the recycled mixture.

[0033] (2) The present invention makes full use of the finely separated five-grade RAP fine material and replaces the new aggregate part with the five-grade fine material, thereby realizing the efficient utilization of the RAP fine material, reducing the consumption of non-renewable resources such as asphalt and stone, avoiding the environmental problems caused by the disposal of old materials, and reducing the cost of highway engineering.

[0034] (3) Increasing the dosage of RAP hot recycled mixture: The RAP fine material dosage designed by the present invention is 40-80%, which belongs to a high dosage (dosage greater than 30%) hot recycled asphalt mixture, and uses RA-75 regeneration agent with 10% of old asphalt, which reduces the use of asphalt and stone, etc., and effectively reduces the cost of highway engineering.

[0035] (4) Improving the high-temperature stability of asphalt pavement: The present invention obtains a high-mixed Sup-25 hot-regenerated asphalt mixture by comparing three fine formula designs and material combinations. The mixture can be used in the lower layer of the road to improve the high-temperature stability of the road and extend the service life of the road.

[0036] (5) The factory-mixed hot recycling construction process is adopted, which has mature technology, uniform mixing of the mixture, and stable and reliable recycling quality. It does not require on-site heating and can be constructed continuously and quickly, saving time and improving construction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Three experimental gradation curves in Section 4.1 of Example 1 of the present invention are shown.

[0038] Figure 2 A curve chart showing the relationship between volume index and asphalt dosage in Part 5 of Example 1 is shown.

[0039] Figure 3 The grading curve of Example 2 of the present invention is shown. DETAILED DESCRIPTION

[0040] The present invention is further described below with reference to specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0041] In the following embodiments, the sup25 asphalt mixture with a high content of RAP fine material is produced using a mixing plant, including loading RAP fine material above 3 mm together with new aggregate, heating it to 180°C using a low-position heating roller, and mixing it with unpreheated 0-3 mm grade fine material after fine metering through a vibrating screen, stirring for 60 seconds, and then adding new asphalt and regeneration agent preheated to 170°C at the same time, and mixing at 170°C for 120 seconds to obtain the sup25 asphalt mixture with a high content of RAP fine material.

[0042] Example 1: Gradation design and performance verification of sup25 asphalt mixture with high RAP fine material

[0043] 1. Acquisition of RAP fine materials and performance index testing

[0044] The RAP material of the original road surface is finely separated by using existing large-scale oil-stone fine separation equipment and physical collision to separate the oil-stone into five grades of materials: 16-25mm, 10-16mm, 5-10mm, 3-5mm, and 0-3mm; the asphalt content is tested according to the requirements of the "Test Procedures for Asphalt and Asphalt Mixtures for Highway Engineering" (JTG E20-2011), and T0725-2011 (rotary evaporator method) is commonly used, requiring that the asphalt content of refined materials above 5mm is ≤2%, the asphalt content of refined materials of 3-5mm is ≤3%, and the asphalt content of refined materials of 0-3mm is about 5-9%.

[0045] The five grades of finely separated materials, namely 16-25mm, 10-16mm, 5-10mm, 3-5mm and 0-3mm, were subjected to aggregate (milling material) density test (test results shown in Table 1), milling material test (test results shown in Table 2) and asphalt (including extracted recovered asphalt) test (test results shown in Table 3) according to Superpave design requirements.

[0046] Table 1: Aggregate (milling material) density test results

[0047]

[0048] *Note: The relative density of the milling material is obtained by sieving the mineral material extracted from the milling material through a 2.36mm sieve, dividing it into >2.36mm and <2.36mm, and testing their relative densities separately, and then obtaining the weighted average based on the 2.36mm pass rate.

[0049] Table 2: Milling material extraction test results

[0050]

[0051]

[0052] Table 3: Asphalt (including extracted and recovered asphalt) test results

[0053]

[0054] 2. Testing of new aggregate performance indicators

[0055] All new aggregates are limestone, and the material specifications are new coarse aggregate (20-28) mm, new coarse aggregate (10-20) mm, new coarse aggregate (10-15) mm, new coarse aggregate (5-10) mm, and new fine aggregate (0-3) mm. According to the Superpave design requirements, aggregate commonality tests (see Table 4) and aggregate density tests (see Table 5) were carried out on new aggregates and mineral powder.

[0056] Table 4: Aggregate commonality test results

[0057]

[0058] Table 5: Aggregate density test results

[0059]

[0060] 3. Regeneration agent performance index detection

[0061] The regeneration agent used is RA-75 model, and its content is 10% of the old asphalt. Its related indicators are shown in Table 6.

[0062] Table 6 Technical indicators of regeneration agent

[0063]

[0064]

[0065] 4. Grading design process

[0066] 4.1. Primary grading

[0067] According to the general method of Superpave design, when selecting the aggregate structure, firstly, three high-mixing gradations of coarse, medium and fine are selected (see Table 7), and the initial asphalt dosage of the three gradations is calculated according to the properties of the aggregate (density and water absorption), and then the test pieces are formed with the initial asphalt dosage. According to the test results, the asphalt dosage required for the asphalt mixtures of the three gradations when the void ratio is 4.0% and the corresponding other properties of the asphalt mixture are calculated, such as the mineral void ratio (VMA), saturation (VFA), the ratio of powder to effective asphalt (DP), the compaction degree of the initial rotation number (%Gmm@N ini Table 8 is a detailed table of the screening test results of various mineral materials, the proportion of each grade of the three debugging grade materials, and the mineral material passing rate of each sieve hole size of the three test gradings. Table 9 is a summary table of the estimated asphalt consumption. Figure 1 There are three test gradation curves.

[0068] Table 7: RAP fine material mixing ratio comparison table

[0069]

[0070]

[0071] Table 8 Ratio of each grade of test gradation and synthetic gradation

[0072]

[0073]

[0074]

[0075] Note: 1. The specifications of new coarse aggregate 1# are (20-28) mm, new coarse aggregate 2# are (10-20) mm, new coarse aggregate 3# are (10-15) mm, new coarse aggregate 4# are (5-10) mm, and new fine aggregate are 0-3 mm. 2. The specifications of RAP2# are (10-16) mm, RAP3# are (5-10) mm, RAP4# are (3-5) mm, and RAP5# are (0-3) mm.

[0076] Table 9 Summary of estimated asphalt consumption

[0077]

[0078]

[0079] In the table: G sb – Relative bulk density of graded aggregate; G sa – composite apparent relative density of graded aggregate; G se – effective relative density of graded aggregate; V ba– the volume of asphalt binder absorbed by the aggregate; V be – Volume of effective asphalt binder; W s –The mass of aggregate per cubic centimeter of mixture.

[0080] 4.2 Evaluation of test gradation

[0081] According to the estimated asphalt dosage of each gradation, it is planned to use 4.0% total asphalt dosage and use a rotary compactor to form the test piece. Since the asphalt dosage provided by the milling material is 1.49%, the amount of added asphalt this time is 2.51%, and the amount of regeneration agent is 0.15%. The unit pressure of the rotary compactor is set to 0.6MPa. The number of compaction times N selected in this design is 初始 =8 times, N 设计 =100 times, N 最大 = 160 times. According to the design standard of Superpave, the estimated oilstone ratio test piece is formed, and the number of rotary compaction is set at N 设计 =100 times, the rotary compaction test results of each grade with estimated asphalt dosage are summarized in Table 10; the volume property test results of three gradations are shown in Table 11; the evaluation table of the test results of estimated asphalt dosage of three gradations is shown in Table 12.

[0082] Table 10: Summary of the results of the three test gradations rotary compaction test

[0083]

[0084]

[0085] Note: The theoretical maximum relative density is subject to actual measurement.

[0086] Table 11: Test results of volume properties of three gradations

[0087]

[0088] Table 12: Evaluation table of test results of three gradation estimated asphalt dosage

[0089]

[0090]

[0091] Note: * indicates that when the gradation passes below the restricted area, the powder-to-glue ratio can be increased to 0.8-1.6.

[0092] According to the results in Table 12, it can be seen that the volume indicators of asphalt mixtures of gradations 1, 2, and 3 all meet the Superpave design requirements, and based on the design and use experience of Superpave, gradation 2 is selected as the design gradation.

[0093] 5. Select the asphalt-stone ratio for the design gradation

[0094] After the design gradation is determined, the asphalt dosage of the design gradation is 3.92% based on the test results in Table 11 and Table 12, and considering the transportation distance from the mixing plant to the on-site paving, the regeneration effect of Sup25 structural asphalt and the durability of the pavement. The asphalt dosage of 3.42%, 3.92%, 4.42%, and 4.92% (the amount of added asphalt is 1.93%, 2.43%, 2.93%, and 3.43%, respectively), and the regeneration agent dosage is 0.15% (accounting for the mass of the asphalt mixture) to conduct the test. The number of compaction times in the test is set at N 设计 (This time N 设计 =100 times).

[0095] Table 13: Summary of test results of four asphalt dosages for design gradations

[0096]

[0097]

[0098] Table 14: Volumetric properties of asphalt mixtures with four asphalt dosages

[0099]

[0100]

[0101] Note: * indicates that when the gradation passes below the restricted area, the powder-to-glue ratio can be increased to 0.8-1.6.

[0102] According to the volume properties of the four asphalt dosages of 3.42%, 3.92%, 4.42%, and 4.92% in Table 14, the asphalt dosage corresponding to the void ratio of 4.0% is 3.92% through the interpolation method. Considering the on-site construction effect and asphalt regeneration effect, the designed asphalt dosage is 3.92%. The relationship between VV, VMA, VFA, DP and asphalt-stone ratio is shown in Figure 2 .

[0103] 6. Maximum number of verifications

[0104] According to the asphalt dosage of 3.92% determined by the design gradation, the test piece was formed to verify that the asphalt dosage of 3.92% was set at the compaction times N. 最大 The corresponding volume property index (this time N 最大 =160 times), the test results are summarized in Table 15.

[0105] Table 15: Designed asphalt dosage verification test results

[0106]

[0107] Note: * indicates that when the gradation passes below the restricted area, the powder-to-glue ratio can be increased to 0.8-1.6.

[0108] 7. Design results

[0109] Through the analysis of the above test results, gradation 2 is the design gradation, and the mix ratio is new coarse aggregate 1#: 2#: 3#: 4#: new fine aggregate: RAP2#: RAP3#: RAP4#: RAP5# = 16.0: 19.0: 8.0: 10.0: 6.0: 10.0: 10.0: 6.0: 15.0. The corresponding asphalt mixture characteristics are as follows:

[0110] Table 16: Mixture volume properties

[0111] Asphalt mixture characteristics Design Results Superpave Standard Void ratio VV(%) 4.0 4.0 Mineral void ratio VMA (%) 12.37 ≥12.0 Saturation VFA (%) 67.74 65～75 Powder-rubber ratio DP 1.50 0.6～1.2* Initial times compaction degree (%) 82.88 ≤89 Maximum times compaction degree (%) 96.44 ≤98

[0112] Note: * indicates that when the gradation passes below the restricted area, the powder-binder ratio (DP) can increase to 0.8-1.6.

[0113] 8. Summary of the Marshall Test

[0114] The Sup25 hot recycled asphalt mixture obtained according to the Superpave design method was molded into specimens using the Marshall test method to obtain the corresponding Marshall index. The test results are summarized in Table 17.

[0115] Table 17: Technical index table of Sup25 hot recycled mixture Marshall test

[0116]

[0117]

[0118] 9. Asphalt mixture performance verification test

[0119] 9.1. Water stability test

[0120] In order to test the water damage resistance of Sup25 hot recycled asphalt mixture, the immersion Marshall test and freeze-thaw splitting test were carried out according to the design requirements. The test results are shown in Tables 18 and 19.

[0121] Table 18: Marshall stability test results after immersion

[0122]

[0123]

[0124] Table 19: Freeze-thaw splitting test results

[0125]

[0126] 9.2 High temperature stability test

[0127] Test conditions: The rutting test was carried out at 60±1℃ and 0.7±0.05MPa to test the high temperature stability of the hot recycled Sup25 asphalt mixture. The dynamic stability test results are shown in Table 19. From the data in Table 20, it can be seen that the high temperature stability of the three gradations all meet the requirements of the specification, and the dynamic stability times of the three gradations are significantly improved compared with the design specifications. This is mainly because the 0-3mm RAP fine material is rich in aged asphalt. Compared with the base asphalt, the aged asphalt has less aromatic and saturated components, which is manifested as a higher softening point and greater viscosity of the asphalt, resulting in an improvement in the high temperature stability of the asphalt mixture.

[0128] Table 20: Summary of rutting test results

[0129]

[0130]

[0131] 10. Design Conclusion

[0132] Through the mixture grading adjustment and related mixture performance tests, it is shown that the void ratio, mineral gap ratio, saturation, powder-rubber ratio, stability, residual stability, freeze-thaw splitting strength ratio, and dynamic stability of the hot-recycled Sup25 asphalt mixture using finely separated milling materials all meet the technical requirements of the relevant design documents. This asphalt mixture can be used in the lower layer of the road and can improve the high-temperature stability of the road. The designed asphalt dosage and mineral aggregate ratio are shown in Table 21 below.

[0133] Table 21: Designed asphalt dosage and mineral aggregate ratio

[0134]

[0135] Example 2: Gradation design and performance verification of sup25 asphalt mixture with 80% RAP fine material

[0136] 1. Acquisition of RAP fine materials and performance index testing

[0137] The RAP material of the original road surface is finely separated by using existing large-scale oil-stone fine separation equipment and physical collision to separate the oil-stone into five grades of materials: 16-25mm, 10-16mm, 5-10mm, 3-5mm, and 0-3mm; the asphalt content is tested according to the requirements of the "Test Procedures for Asphalt and Asphalt Mixtures for Highway Engineering" (JTG E20-2011), and T0725-2011 (rotary evaporator method) is commonly used, requiring that the asphalt content of refined materials above 5mm is ≤2%, the asphalt content of refined materials of 3-5mm is ≤3%, and the asphalt content of refined materials of 0-3mm is about 5-9%.

[0138] The five grades of finely separated materials, namely 16-25mm, 10-16mm, 5-10mm, 3-5mm and 0-3mm, were subjected to aggregate (milling material) density test (test results see Table 22) and milling material test (test results see Table 23) according to Superpave design requirements.

[0139] Table 22: Aggregate (milling material) density test results

[0140]

[0141] *Note: The relative density of the milling material is obtained by sieving the mineral material extracted from the milling material through a 2.36mm sieve, dividing it into >2.36mm and <2.36mm, and testing their relative densities separately, and then obtaining the weighted average based on the 2.36mm pass rate.

[0142] Table 23: Milling material extraction test results

[0143]

[0144]

[0145] 2. Testing of new aggregate performance indicators

[0146] The new aggregates are all limestone, with material specifications of 20-28mm, 10-20mm, 10-15mm, 5-10mm, and 0-3mm. According to the Superpave design requirements, the new aggregates and mineral powders were subjected to aggregate commonality tests (see Table 24) and aggregate density tests (see Table 25).

[0147] Table 24: Aggregate commonality test results

[0148]

[0149]

[0150] Table 25: Aggregate density test results

[0151]

[0152]

[0153] 3. Selection of new asphalt and testing of regeneration agent performance indicators

[0154] The new asphalt uses No. 90 ordinary road petroleum asphalt, and the regeneration agent uses RA-75 model, with a content of 10% of the old asphalt. The relevant indicators are shown in Table 26.

[0155] Table 26: Regeneration agent technical indicators

[0156]

[0157] 4. Summary of Marshall Test

[0158] Sup25 hot recycled asphalt mixture obtained according to the Superpave design method (designed asphalt dosage and mineral aggregate ratio are shown in Table 31 below, Figure 3 The test gradation curve designed for this purpose was used, and the specimens were formed using the Marshall test method to obtain the corresponding Marshall index. The test results are summarized in Table 6.

[0159] Table 27: Technical index table of Sup25 hot recycled mixture Marshall test

[0160] Test items Test results Require Compaction times (times) 75 times forward and reverse 75 times forward and reverse Relative density of Marsh hair volume 2.438 / Stability (kN) 10.46 ≮8 Flow value (0.1mm) 31.27 20～40 Void ratio (%) 4.37 4.0～6.0 Asphalt saturation (%) 68.43 60～70 Mineral void ratio VMA (%) 13.84 ≥12.0

[0161] 5. Asphalt mixture performance verification test

[0162] 5.1 Water stability test

[0163] In order to test the water damage resistance of Sup25 hot recycled asphalt mixture, the immersion Marshall test and freeze-thaw splitting test were carried out according to the design requirements. The test results are shown in Tables 28 and 29.

[0164] Table 28: Marshall stability test results after immersion

[0165]

[0166]

[0167] Table 29: Freeze-thaw splitting test results

[0168]

[0169] 5.2 High temperature stability test

[0170] Test conditions: The rutting test was carried out at 60±1℃ and 0.7±0.05MPa to test the high temperature stability of the hot recycled Sup25 asphalt mixture. The dynamic stability test results are shown in Table 30. The data in Table 30 show that the high temperature stability of the asphalt mixture meets the specification requirements, and the dynamic stability times are significantly improved compared with the design specifications. This is mainly because the 0-3mm RAP fine fraction is rich in aged asphalt. Compared with the base asphalt, the aged asphalt has less aromatic and saturated components, which is manifested as a higher softening point and greater viscosity of the asphalt, resulting in an improvement in the high temperature stability of the asphalt mixture.

[0171] Table 30: Summary of rutting test results

[0172]

[0173]

[0174] 6. Design conclusion

[0175] The relevant performance tests of the mixture show that the void ratio, mineral gap ratio, saturation, powder-rubber ratio, stability, residual stability, freeze-thaw splitting strength ratio, and dynamic stability of the hot-recycled Sup25 asphalt mixture using finely separated milling materials all meet the technical requirements of the relevant design documents. This asphalt mixture can be used in the lower layer of the road and can improve the high-temperature stability of the road. The designed asphalt dosage and mineral aggregate ratio are shown in Table 31 below.

[0176] Table 31: Designed asphalt dosage and mineral aggregate ratio

[0177]

[0178] Example 3

[0179] The RAP material is finely separated from the oilstone (the fine separation process is: the RAP fine material is separated to obtain five grades of material, which are screened in order of particle size from large to small, specifically including the primary screening process, the middle screening process, and the final screening process, wherein the primary screening process is: screening the 16-25mm material, the middle screening process includes screening the 10-16mm, 5-10mm, and 3-5mm materials in sequence, and the final screening process includes screening the 0-3mm material;) the following separation control system is used, which is suitable for any one of the primary screening process, the middle screening process, and the final screening process in the fine separation process, and the separation control system includes the following modules:

[0180] Monitoring module: obtain material separation data in real time;

[0181] Among them, separation data include regional screening flow rate;

[0182] In some embodiments, the carrying space of the material to be separated is divided into monitoring areas at equal intervals along the horizontal direction, and a collection area for collecting the screened and separated materials is provided in each monitoring area. A weight sensor is provided in the collection area, and the weight sensor weighs the separated materials in real time to obtain the weight of the separated materials per unit time in each collection area, and marks the screening flow rate of the area;

[0183] Analysis module: Based on the separation data, the material residual impact ratio and the material flow impact ratio are analyzed and obtained, and then the screening control coefficient is calculated from the material residual impact ratio and the material flow impact ratio;

[0184] In some embodiments, all regional screening flows are obtained, and all regional screening flows are analyzed to obtain the material remaining impact ratio and the material flow impact ratio, which are marked as BYs and BYl;

[0185] By formula The screening control coefficient XK is calculated, where a1 and a2 are weight ratio coefficients, a1+a2=1, a1 is 0.42, a2 ​​is 0.58, and the values ​​of a1 and a2 represent the influence of the residual material influence ratio and the material flow influence ratio on the screening control coefficient respectively;

[0186] First, specifically, the analysis process of the material residual impact ratio is:

[0187] Obtain all regional screening flows, calculate the sum of all regional screening flows, obtain the real-time total screening flow, calculate the sum of the real-time total screening flow during the screening working time, and obtain the material screening and separation weight value;

[0188] Obtain the total weight of the material before screening, calculate the difference between the total weight of the material before screening and the weight value of the material screening separation, and obtain the remaining weight of the material;

[0189] Calculate the ratio of the remaining weight of the material to the total weight of the material before screening to obtain the material remaining impact ratio;

[0190] Set the monitoring period, obtain the material remaining impact ratio within the end time of the monitoring period, and mark it as the material remaining impact ratio;

[0191] Second, specifically, the analysis process of the material flow rate influence ratio is:

[0192] Obtain all regional screening flows and process the data of each regional screening flow. The processing process is as follows:

[0193] Obtain the regional screening flow rates at adjacent times, make a difference between the regional screening flow rates at adjacent times, and take the absolute value to obtain the adjacent difference of the regional screening flow rates;

[0194] Compare the adjacent difference values ​​of the regional screening flow rates with the adjacent difference threshold value of the regional screening flow rates;

[0195] If the adjacent difference of the regional screening flow is greater than or equal to the adjacent difference threshold of the regional screening flow, a screening abnormality signal is generated;

[0196] If the adjacent difference of the regional screening flow is less than the adjacent difference threshold of the regional screening flow, a screening normal signal is generated;

[0197] The adjacent differences of the regional screening flow corresponding to the screening abnormal signal are calculated with the regional screening flow at the previous moment to obtain the material flow impact value;

[0198] Set the monitoring period, obtain all material flow impact values ​​within the monitoring period, and calculate the average to obtain the material flow impact ratio;

[0199] What needs to be explained is: Setting of monitoring cycle: obtaining the preset screening process time of each particle size material, and dividing the preset screening process time into multiple monitoring cycles according to equal time;

[0200] The control module obtains the screening vibration frequency within the monitoring period based on the screening control coefficient, and realizes variable frequency screening of RAP materials;

[0201] In some implementation schemes, a screening control coefficient is obtained, and a real-time screening vibration frequency is obtained during a monitoring period, and mean calculation is performed to obtain a mean screening vibration frequency;

[0202] The mean value of the screening vibration frequency is multiplied by the screening control coefficient to obtain the screening vibration frequency control value for the next monitoring period;

[0203] The technical solution of this embodiment is as follows: acquiring the separation data of the material in real time; based on the separation data, analyzing and obtaining the material residual influence ratio and the material flow influence ratio, and then calculating the screening control coefficient from the material residual influence ratio and the material flow influence ratio; based on the screening control coefficient, acquiring the screening vibration frequency within the monitoring period, and realizing variable frequency screening of the RAP material; the present invention uses the RAP material in the screening process, especially in the mixed material screening process, wherein during the screening work, the material of the corresponding particle size is reduced, which will make the remaining material easier to be screened out, and there is a large difference in the quality of the screened materials in adjacent time, which will effectively indicate that the screening effect is abnormal, that is, the vibration frequency provided in the current period cannot meet the screening of the remaining materials. Therefore, based on this, by performing online analysis of the separation data within the real-time monitoring period, variable frequency screening of the RAP material is realized, thereby effectively improving the screening process of the RAP material.

[0204] It should be noted that the preferred embodiments of the present invention are given in the specification of the present invention, but the present invention can be implemented in many different forms and is not limited to the embodiments described in this specification. These embodiments are not intended to be additional limitations on the content of the present invention. The purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive. In addition, the above-mentioned technical features continue to be combined with each other to form various embodiments not listed above, which are all considered to be within the scope of the present invention specification; further, for ordinary technicians in this field, they can be improved or transformed according to the above description, and all these improvements and transformations should belong to the protection scope of the claims attached to the present invention.

Claims

1. A sup25 asphalt mixture with a high content of RAP fine material, characterized in that: Contains the following raw materials: RAP fine fraction, new aggregate, regeneration agent and new asphalt; in: The amount of the RAP fine material in the sup25 asphalt mixture is higher than 30%. The RAP fine material is obtained as follows: fine separation of oilstone is performed on the RAP material to obtain five grades of materials of 16-25mm, 10-16mm, 5-10mm, 3-5mm and 0-3mm, which are tested to meet the Superpave design requirements, and the 0-3mm grade material with an asphalt content of 5-9%, the 3-5mm grade material with an asphalt content of ≤3%, and the fine material of 5mm or more with an asphalt content of ≤2% are selected as the required RAP fine material; The new aggregate consists of 20-28 mm new coarse aggregate, 10-20 mm new coarse aggregate, 10-15 mm new coarse aggregate, 5-10 mm new coarse aggregate and 0-3 mm new fine aggregate.

2. The sup25 asphalt mixture according to claim 1, characterized in that: The sup25 asphalt mixture contains 40-80 parts of RAP refined material and 20-60 parts of new aggregate by weight, and the content of regeneration agent in the sup25 asphalt mixture is 10% of the asphalt content in the RAP refined material, and the content of new asphalt is the total asphalt required for the sup25 asphalt mixture minus the asphalt content in the RAP refined material.

3. The sup25 asphalt mixture according to claim 2, characterized in that: The sup25 asphalt mixture contains 41 parts of RAP refined material and 59 parts of new aggregate by weight.

4. The sup25 asphalt mixture according to claim 3, characterized in that: The sup25 asphalt mixture comprises 41 parts of RAP fine fraction, 59 parts of new aggregate, 0.15 parts of regeneration agent and 1.93-3.43 parts of new asphalt in parts by weight.

5. The sup25 asphalt mixture according to claim 3 or 4, characterized in that: The RAP fine material comprises, by weight, 15 parts by weight of 0-3 mm stop material, 6 parts by weight of 3-5 mm stop material and 10 parts by weight of fine materials above 5 mm.

6. The sup25 asphalt mixture according to claim 2, characterized in that: The sup25 asphalt mixture comprises 80 parts of RAP fine aggregate, 16 parts of new coarse aggregate and 4 parts of new fine aggregate by weight.

7. The sup25 asphalt mixture according to claim 3, characterized in that: The sup25 asphalt mixture comprises 80 parts of RAP fine fraction, 16 parts of new coarse aggregate, 0.15 parts of regeneration agent, 2.5 parts of new asphalt and 4 parts of new fine aggregate by weight.

8. The sup25 asphalt mixture according to claim 6 or 7, characterized in that: The RAP fine material comprises, by weight, 14.5 parts of 0-3 mm material, 16 parts of 3-5 mm material, 15 parts of 5-10 mm material, 18.5 parts of 10-16 mm material and 16 parts of 16-25 mm material.

9. The sup25 asphalt mixture according to claim 1, characterized in that: The new aggregate comprises, by weight, 14-20 parts of 20-28 mm new coarse aggregate, 0-22 parts of 10-20 mm new coarse aggregate, 0-8.5 parts of 10-15 mm new coarse aggregate, 0-11.5 parts of 5-10 mm new coarse aggregate and 4-8 parts of 0-3 mm new fine aggregate.

10. A method for preparing a sup25 asphalt mixture with a high amount of RAP fine material according to any one of claims 1 to 9, characterized in that: The method includes using a mixing plant to load RAP fine materials with a size of 3 mm or larger together with new aggregates, heating them to 180°C using a low-position heating roller, and mixing them with unpreheated 0-3 mm fine materials after fine metering through a vibrating screen, stirring for 60 seconds, and then adding new asphalt and regeneration agent preheated to 170°C at the same time, mixing at 170°C for 120 seconds, and thus obtaining a sup25 asphalt mixture with a high content of RAP fine materials.

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