Plant-mixed warm regenerated asphalt mixture and preparation method thereof

Abstract

A preparation method of a plant-mixed warm regenerated asphalt mixture, comprises the following steps: preparing a RAP material, a new aggregate, a mineral powder, a new asphalt and a regenerant with a total mass percentage of 100%; heating and stirring the RAP material, adding the regenerant, and continuing to heat and stir; placing the product in a development bin for development, wherein a development temperature is 40° C. to 150° C., and a development time is 0.5 h to 6 h; mixing, heating and stirring a product with the new aggregate; and after mixing and heating the product with the new asphalt, adding the mineral powder, and stirring to mold. Addition of the regenerated asphalt mixture in the development process improves the regeneration effect of the old asphalt, and pavement performances of the formed regenerated asphalt mixture can fully reach that of a hot-mixed asphalt mixture produced entirely with new materials.

Claims

1. A preparation method of a plant-mixed warm regenerated asphalt mixture, comprising the following steps of: (1) preparing a RAP material, an aggregate, a mineral powder, a new asphalt and a regenerant with a total mass percentage of 100%, wherein the aggregate is obtained by screening aggregates with four groups of particle sizes, the first group of particle sizes is less than 2.36 mm; the second group of particle sizes is 2.36 to 4.75 mm; the third group of particle sizes is more than 4.75 to 9.5 mm; and the fourth group of particle sizes is more than 9.5 to 16.0 mm; (2) heating and stirring the RAP material, adding the regenerant, and then continuing to heat and stir, wherein the regenerant comprises a density of 1.017 g/cm.sup.3 at 20° C.; a flash point of 259.5° C.; a kinematic viscosity of 60000 mm.sup.2/s at 60° C.; a water content (v/v) of 0.13%; an aromatic content (m) of 86.21%; a resin, asphaltene content (m) of 11.01%; and a furfural content of 0.11 mg/kg; (3) placing a product of step (2) in a development bin for development, wherein a development temperature is 40° C. to 150° C., and a development time is 0.5 h to 6 h; (4) mixing, heating and stirring a product of step (3) with the aggregate; and (5) mixing and heating a product of step (4) with the asphalt, adding the mineral powder, stirring, and placing a mixture comprising the asphalt and the mineral powder in a mold.

2. A preparation method of a plant-mixed warm regenerated asphalt mixture, comprising following steps of: (1) preparing an RAP material, an aggregate, a mineral powder, an asphalt and a regenerant with a total mass percentage of 100%, wherein the aggregate is obtained by screening aggregates with four groups of particle sizes, the first group of particle sizes is less than 2.36 mm; the second group of particle sizes is 2.36 to 4.75 mm; the third group of particle sizes is more than 4.75 to 9.5 mm; and the fourth group of particle sizes is more than 9.5 to 16.0 mm; (2) mixing and stirring the RAP material and the aggregate which are respectively heated; (3) adding the regenerant and the asphalt into a product of step (2), and mixing, heating and stirring, wherein the regenerant comprises a density of 1.017 g/cm.sup.3 at 20° C.; a flash point of 259.5° C.; a kinematic viscosity of 60000 mm.sup.2/s at 60° C.; a water content (v/v) of 0.13%; an aromatic content (m) of 86.21%; a resin, asphaltene content (m) of 11.01%; and a furfural content of 0.11 mg/kg; (4) adding the mineral powder into a product of step (3), and mixing and stirring; and (5) placing a product of step (4) in a development bin for development, and then taking out of the bin for molding, wherein a development temperature is 40° C. to 170° C., and a development time is 0.5 h to 6 h.

3. The preparation method of the plant-mixed warm regenerated asphalt mixture according to claim 1, wherein the development bin comprises a storage bin, and a stirrer and a heater arranged therein, a volume of the storage bin is 1 to 5000 tons, and a heating method of a heater is one of a heat-transfer oil, an electric heating, or flue discharges of an asphalt mixing plant.

4. The preparation method of the plant-mixed warm regenerated asphalt mixture according to claim 1, wherein the RAP material is 20 to 85%, the new aggregate is 10 to 70%, the mineral powder is 0.9 to 8%, the new asphalt is 0.5 to 5% and the regenerant is 0.21 to 0.5% by the mass percentage.

5. The preparation method of the plant-mixed warm regenerated asphalt mixture according to claim 1, wherein in step (2), a temperature of the heating of the RAP material is 70 to 160° C., and a time of the stirring is 5 to 10 s.

6. The preparation method of the plant-mixed warm regenerated asphalt mixture according to claim 1, wherein in step (2), after the regenerant is added, a temperature of the heating is 40 to 120° C., and a time of the stirring is 15 to 25 s.

7. The preparation method of the plant-mixed warm regenerated asphalt mixture according to claim 1, wherein in step (4), a temperature of the heating is 90 to 190° C., and a time of the stirring is 10 to 15 s.

8. The preparation method of the plant-mixed warm regenerated asphalt mixture according to claim 1, wherein in step (5), a temperature of the heating is 60 to 160° C., and a time of the stirring is 15 to 25 s.

9. The preparation method of the plant-mixed warm regenerated asphalt mixture according to claim 2, wherein in step (2), a temperature of the heating of the RAP material is 80 to 170° C., a temperature of the heating of the aggregate is 90 to 190° C., and a time of the stirring is 15 to 25 s.

10. The preparation method of the plant-mixed warm regenerated asphalt mixture according to claim 2, wherein in step (3), a temperature of the heating is 40 to 120° C., and a time of the stirring is 15 to 30 s.

11. The preparation method of the plant-mixed warm regenerated asphalt mixture according to claim 2, wherein in step (4), a time of the stirring is 10 to 20 s.

12. A plant-mixed warm regenerated asphalt mixture prepared by the preparation method of the plant-mixed warm regenerated asphalt mixture according to claim 1.

13. The preparation method of the plant-mixed warm regenerated asphalt mixture according to claim 2, wherein the development bin comprises a storage bin, and a stirrer and a heater arranged therein, a volume of the storage bin is 1 to 5000 tons, and a heating method of a heater is one of a heat-transfer oil, an electric heating, or flue discharges of an asphalt mixing plant.

14. The preparation method of the plant-mixed warm regenerated asphalt mixture according to claim 2, wherein the RAP material is 20 to 85%, the aggregate is 10 to 70%, the mineral powder is 0 to 8%, the asphalt is 0.5 to 5% and the regenerant is 0 to 0.5% by the mass percentage.

15. A plant-mixed warm regenerated asphalt mixture prepared by the preparation method of the plant-mixed warm regenerated asphalt mixture according to claim 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) The present invention will be further described hereinafter in details with reference to the technical solutions.

First Embodiment

(2) Laboratory test embodiment: old asphalt pavement crushed materials (RAP material) used in the test were materials with the same source and the same particle size specification. First, the separated and crushed RAP materials were sampled in a mixing plant, and then an asphalt content test was carried out according to T 0735 in “Test Methods of Asphalt and Asphalt Mixture for Highway Engineering” (JTG E20-2011). An oil-stone ratio of the RAP material was determined to be 4.51% by the test. The old materials in the RAP material obtained by the test were screened and the screening test results were shown in Table 1. An extraction test was carried out on the RAP materials by T 0726 in “Test Methods of Asphalt and Asphalt Mixture for Highway Engineering” (JTG E20-2011), and the old asphalt after the extraction test was recovered and detected by performance test. The detection results were shown in Table 2.

(3) TABLE-US-00001 TABLE 1 Gradation Test Results of Old Material in RAP Material Sieve pore 16 13.2 9.5 4.75 2.36 1.18 0.6 0.3 0.15 0.075 size (mm) Percent by 100 99.1 83.6 56.5 38.9 22.7 15.4 12.1 9.0 7.3 mass (%)

(4) TABLE-US-00002 TABLE 2 Performance Index Test Results of Old Asphalt in RAP Material Needle penetration Ductility Viscosity at 25° C. Softening at 15° C. at 60° C. (0.1 mm) point ° C. (cm) (mm.sup.2/s) 21.6 63.6 24.9 1290*10.sup.6

(5) Basalt was used as the new aggregate, and the new aggregate contained components with four groups of particle sizes, wherein the first group of particle sizes was 0 to 2.36 mm; the second group of particle sizes was 2.36 to 4.75 mm; the third group of particle sizes was 4.75 to 9.5 mm; and the fourth group of particle sizes was 9.5 to 16.0 mm. A screening test was carried out on the four groups of aggregates, and the results are shown in Table 3. A relative density test was carried out on the four groups of aggregates, and the results were shown in Table 4.

(6) TABLE-US-00003 TABLE 3 Screening Test Results of New Aggregate Sieve pore Mass percentage passing through the following sieve pores (%) size (mm) 16 13.2 9.5 4.75 2.36 1.18 0.6 0.3 0.15 0.075 Fourth group 100 88.1 16.5 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Third group 100 100 92.7 10.0 2.5 0.5 0.5 0.5 0.5 0.5 Second group 100 100 100 96.2 7.6 2.0 0.6 0.6 0.6 0.6 First group 100 100 100 100 82.6 53.5 35.6 24 18.8 12

(7) TABLE-US-00004 TABLE 4 Relative Density Test Results of New Aggregate First Second Third Fourth Particle size group group group group Relative density 2.810 2.853 2.871 2.885 of gross volume Relative apparent 2.943 2.961 2.953 2.960 density

(8) The screening results of limestone mineral powder were shown in Table 5, and the density was 2.720.

(9) TABLE-US-00005 TABLE 5 Screening Results of Mineral Powder Sieve pore size (mm) 0.6 0.3 0.15 0.075 Mass percentage 100.0 95.9 93.6 83.4 passing (%)

(10) Domestic No. 50 grade-A pavement petroleum asphalt was selected as the new asphalt, and the performance indexes were shown in Table 6.

(11) TABLE-US-00006 TABLE 6 Detection Indexes of AH-50 Pavement Petroleum Asphalt Kinematic Needle penetration Ductility viscosity at 25° C. Softening at 15° C. at 60° C. (0.1 mm) point ° C. (cm) (mm.sup.2/s) 52 53.5 Greater 425*10.sup.6 than 100

(12) WRA-1 regenerant produced by Jiangsu Tiannuo Road Materials Technology Co., Ltd., with a kinematic viscosity of 60000 mm.sup.2/s at 60° C. was used as the regenerant.

(13) Continuous dense gradation AC-13 was adopted in the plant-mixed warm regenerated asphalt mixture. According to the requirements of AC-13 synthetic gradation range in “Technical Specification for Construction of Highway Asphalt Pavement” JTG F40-2004, synthetic gradation was carried out on the RAP material, the new aggregates (four groups) and the limestone mineral powder. The synthetic gradation results were shown in Table 7.

(14) TABLE-US-00007 TABLE 7 AC-13 Synthetic Gradation of Plant-mixed Warm Regenerated Asphalt Mixture Sieve pore Mass percentage passing through the following sieve pores (%) size (mm) 16 13.2 9.5 4.75 2.36 1.18 0.6 0.3 0.15 0.075 AC-13 100 93.7 76.3 50.7 34.2 21.1 14.0 11.7 9.0 6.4

(15) The foregoing RAP material was mixed with the new aggregate, the mineral powder, the new asphalt and the regenerant, wherein the mass percentages of the RAP material and various newly added materials were as follows: 47.3% of the RAP material; 20.2% of the first group of new aggregates, 9.5% of the second group of new aggregates, 4.3% of the third group of new aggregates, and 14.9% of the fourth group of new aggregates (wherein, how many groups of single aggregates forming the new aggregates were determined according to the maximum stone particle size in the regenerated mixture, for example, the AC-13 asphalt mixture in this embodiment was formed by mixing four groups of single new aggregates); 0.9% of the mineral powder; 2.69% of the new asphalt; and 0.21% of the regenerant.

(16) The above RAP material was mixed with the new aggregate, the mineral powder, the new asphalt and the regenerant according to the preparation method of a preparation method of a plant-mixed warm regenerated asphalt mixture of the present invention, and the steps were as follows.

(17) (1) The RAP material was heated to 160° C., and then put into a mixing kettle to premix for 5 s.

(18) (2) The regenerant was heated to 120° C. and then put into the mixing kettle to mix with a product obtained in step (1) with a mixing time set to 20 s.

(19) (3) A product obtained in step (2) was taken out of the kettle, divided into 10 equal parts of samples (Y0, Y0.5, Y1, Y2, Y3, Y4, Y5, Y6, Y7, Y8) and stored in a special development bin at 150° C., wherein Y0 was developed for 0 h, Y0.5 was developed for 0.5 h, Y1 was developed for 1 h, Y2 was developed for 2 h, Y3 was developed for 3 h, Y4 was developed for 4 h, Y5 was developed for 5 h, Y6 was developed for 6 h, Y7 was developed for 7 h, and Y8 was developed for 8 h.

(20) (4) The new aggregate to 190° C., weighed and then put into the mixing kettle, and meanwhile, a product completely developed in step (3) was added into the mixing kettle, and the mixture was stirred for 10 s.

(21) (5) The AH-50 highway petroleum asphalt heated to 160° C. and the limestone mineral powder at room temperature were weighed, added into a product obtained in step (4), and then the mixture was stirred for 20 s.

(22) (6) 10 different samples obtained in step (5) were taken out of the kettle at 170° C. and molded into an asphalt mixture test piece, and then the pavement performances of the mixture were tested.

(23) For each sample obtained by the above preparation method of a plant-mixed warm regenerated asphalt mixture, the high-temperature performance (Marshall stability test, dynamic stability test), low-temperature performance (low-temperature bending test), water stability (Marshall residual stability test, freeze-thaw splitting test) and fatigue life (four-point bending fatigue life test) were evaluated after the test pieces were molded indoors. The test results were shown in Table 8, Table 9, Table 10 and Table 11 respectively.

(24) TABLE-US-00008 TABLE 8 High-temperature Performance Detection Results of Plant-mixed Warm Regenerated Asphalt Detection Plant-mixed warm regenerated asphalt mixture index Y0 Y0.5 Y1 Y2 Y3 Y4 Y5 Y6 Y7 Y8 Marshall 8.93 11.39 11.65 11.28 12.81 12.96 13.03 13.57 13.10 12.02 stability (KN) Dynamic 2822.6 3236.7 3517.1 3805.0 3991.5 4126.8 4285.9 4370.2 4280 3722 stability (times/mm) Remarks: Y0, Y0.5, Y1, Y2, Y3, Y4, Y5, Y6, Y7 and Y8 were the samples obtained after the plant-mixed warm regenerated asphalt mixture was developed at 150° C. for 0 h, 0.5 h, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h and 8 h respectively (the same below); it was stipulated in the “Technical Specification for Construction of Highway Asphalt Pavement” JTG F40-2004 (hereinafter referred to as the Specification) that the Marshall stability should be no less than 8 KN and the dynamic stability should be no less than 3000 times/mm.

(25) TABLE-US-00009 TABLE 9 Low-temperature Performance Detection Results of Plant-mixed Warm Regenerated Asphalt Mixture Detection Plant-mixed warm regenerated asphalt mixture index Y0 Y0.5 Y1 Y2 Y3 Y4 Y5 Y6 Y7 Y8 Maximum bending 2171.5 2514.2 2578.7 2681.3 2833.4 2957.0 3020.6 2917.2 2400.7 1954.3 strain at failure (με) Remarks: the test temperature was −10° C., and it was stipulated in the Specification that the maximum bending strain at failure should be no less than 2,300 με.

(26) TABLE-US-00010 TABLE 10 Water Stability Detection Results of Plant-mixed Warm Regenerated Asphalt Mixture Detection Plant-mixed warm regenerated asphalt mixture index Y0 Y0.5 Y1 Y2 Y3 Y4 Y5 Y6 Y7 Y8 Marshall residual 78.1 81.7 84.0 87.1 88.5 90.3 90.6 87.4 86.1 81.5 stability ratio (%) Freeze-thaw splitting 72.9 76.2 79.1 80.5 81.7 83.9 85.8 82.9 74.7 70.0 strength ratio (%) Remarks: it was stipulated in the Specification that the Marshall residual stability ratio should be no less than 80%, and the freeze-thaw splitting strength ratio should be no less than 75%.

(27) TABLE-US-00011 TABLE 11 Fatigue Life Detection Results of Plant-mixed Warm Regenerated Asphalt Mixture Detection Plant-mixed warm regenerated asphalt mixture index Y0 Y0.5 Y1 Y2 Y3 Y4 Y5 Y6 Y7 Y8 Four-point bending 4398 6251 6803 7493 9418 10160 11506 12231 7605 4602 fatigue life (times) Remarks: the test temperature was 15° C., the target strain was 600 με, the loading frequency was 10 HZ, and the test termination condition was 50%.

Second Embodiment

(28) Laboratory test embodiment: basically the same as the first embodiment, except that the development temperatures of the warm regenerated asphalt mixture in the embodiment were 20° C., 30° C., 40° C., 70° C., 100° C., 130° C., 150° C., 170° C. and 190° C. respectively; and the development time was 6 h. The high-temperature performance, low-temperature performance, water stability and fatigue life of the plant-mixed warm regenerated asphalt mixture were investigated respectively at the development temperatures and development time described in the embodiment. The test results were shown in Table 12, Table 13, Table 14 and Table 15.

(29) TABLE-US-00012 TABLE 12 High-temperature Performance Detection Results of Plant-mixed Warm Regenerated Asphalt Mixture Detection Plant-mixed warm regenerated asphalt mixture index 20° C. 30° C. 40° C. 70° C. 100° C. 130° C. 150° C. 170° C. 190° C. Marshall 8.12 8.29 10.71 11.10 12.83 13.36 14.57 14.50 13.10 stability (KN) Dynamic 2755.1 2901.7 3409.5 3622.6 3881.7 4063.3 4307.2 4003 3380 stability (times/mm) Remarks: the development time was 6 h (the same below); it was stipulated in the “Technical Specification for Construction of Highway Asphalt Pavement” JTG F40-2004 (hereinafter referred to as the Specification) that the Marshall stability should be no less than 8 KN and the dynamic stability should be no less than 3000 times/mm.

(30) TABLE-US-00013 TABLE 13 Low-temperature Performance Detection Results of Plant-mixed Warm Regenerated Asphalt Mixture Detection Plant-mixed warm regenerated asphalt mixture index 20° C. 30° C. 40° C. 70° C. 100° C. 130° C. 150° C. 170° C. 190° C. Maximum bending 1967.5 2118.4 2596.3 2715.8 2786.9 2844.0 2923.1 2409.5 1791.0 strain at failure (με) Remarks: the test temperature was −10° C., and it was stipulated in the Specification that the maximum bending strain at failure should be no less than 2,300 με.

(31) TABLE-US-00014 TABLE 14 Water Stability Detection Results of Plant-mixed Warm Regenerated Asphalt Mixture Detection Plant-mixed warm regenerated asphalt mixture index 20° C. 30° C. 40° C. 70° C. 100° C. 130° C. 150° C. 170° C. 190° C. Marshall residual 79.5 80.9 82.6 83.7 87.2 89.1 91.5 84.8 78.0 stability ratio (%) Freeze-thaw splitting 70.5 75.8 77.4 78.3 80.1 84.7 85.9 77.3 68.1 strength ratio (%) Remarks: it was stipulated in the Specification that the Marshall residual stability ratio should be no less than 80%, and the freeze-thaw splitting strength ratio should be no less than 75%.

(32) TABLE-US-00015 TABLE 15 Fatigue Life Detection Results of Plant-mixed Warm Regenerated Asphalt Mixture Detection Plant-mixed warm regenerated asphalt mixture index 20° C. 30° C. 40° C. 70° C. 100° C. 130° C. 150° C. 170° C. 190° C. Four-point bending 4722 6344 6690 7810 9022 9972 12991 8192 4100 fatigue life (times) Remarks: the test temperature was 15° C., the target strain was 600 με, the loading frequency was 10 Hz, and the test termination condition was 50%.

Third Embodiment

(33) Laboratory test embodiment: old asphalt pavement crushed materials (RAP material) used the test were materials with the same source and the same particle size specification. First, the separated and crushed RAP materials were sampled in a mixing plant, and then an asphalt content test was carried out according to T 0735 in “Test Methods Asphalt and Asphalt Mixture for Highway Engineering” (JTG E20-2011). An oil-stone ratio of the RAP material was determined to be 4.81% by the test. The old materials in the RAP material obtained by the test were screened and the screening test results were shown in Table 16. An extraction test was carried out on the RAP materials by T 0726 in “Test Methods of Asphalt and Asphalt Mixture for Highway Engineering” (JTG E20-2011), and the old asphalt after the extraction test was recovered and detected by performance test. The detection results were shown in Table 17.

(34) TABLE-US-00016 TABLE 16 Gradation Test Results of Old Material in RAP Material Sieve pore 16 13.2 9.5 4.75 2.36 1.18 0.6 0.3 0.15 0.075 size (mm) Percent by 100 99.7 89.5 57.3 40.2 23.9 16.4 13.7 10.3 7.6 mass (%)

(35) TABLE-US-00017 TABLE 17 Performance Index Test Results of Old Asphalt in RAP Material Needle penetration at Softening Ductility at Viscosity 25° C. (0.1 mm) point ° C. 15° C. (cm) 60° C. (mm.sup.2/s) 22.5 65.0 23.2 1250*10.sup.6

(36) Basalt was used as the new aggregate, and the new aggregate contained components with four groups of particle sizes, wherein the first group of particle sizes was 0 to 2.36 mm; the second group of particle sizes was 2.36 to 4.75 mm; the third group of particle sizes was 4.75 to 9.5 mm; and the fourth group of particle sizes was 9.5 to 16.0 mm. A screening test was carried out on the four groups of aggregates, and the results are shown in Table 18. A relative density test was carried out on the four groups of aggregates, and the results were shown in Table 19.

(37) TABLE-US-00018 TABLE 18 Screening Test Results of New Aggregate Sieve pore Mass percentage passing through the following sieve pores (%) size (mm) 16 13.2 9.5 4.75 2.36 1.18 0.6 0.3 0.15 0.075 Fourth group 100 88.1 16.5 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Third group 100 100 92.7 10.0 2.5 0.5 0.5 0.5 0.5 0.5 Second group 100 100 100 96.2 7.6 2.0 0.6 0.6 0.6 0.6 First group 100 100 100 100 82.6 53.5 35.6 24 18.8 12

(38) TABLE-US-00019 TABLE 19 Relative Density Test Results of New Aggregate First Second Third Fourth Particle size group group group group Relative density of 2.640 2.663 6.671 6.685 gross volume Relative apparent 2.713 2.721 2.713 2.720 density

(39) The screening results of the limestone mineral powder were shown in Table 20.

(40) TABLE-US-00020 TABLE 20 Screening Results of Mineral Powder Sieve pore size (mm) 0.6 0.3 0.15 0.075 Percent by mass (%) 100.0 98.2 96.0 87.0

(41) Domestic No. 70 grade-A pavement petroleum asphalt was selected as the new asphalt, and the performance indexes were shown in Table 21.

(42) TABLE-US-00021 TABLE 21 Detection Indexes of AH-70 Pavement Petroleum Asphalt Kinematic Needle penetration Ductility viscosity at 25° C. Softening at 15° C. at 60° C. (0.1 mm) point ° C. (cm) (mm.sup.2/s) 72 48.5 Greater 389*10.sup.6 than 100

(43) A domestic regenerant with a kinematic viscosity of 60000 mm.sup.2/s at 60° C. was used as the regenerant.

(44) Continuous dense gradation AC-13C was adopted in the plant-mixed warm regenerated asphalt mixture. According to the requirements of AC-13C synthetic gradation range in “Technical Specification for Construction of Highway Asphalt Pavement” JTG F40-2004, synthetic gradation was carried out on the RAP material, the new aggregates (four groups) and the limestone mineral powder. The synthetic gradation results were shown in Table 22.

(45) TABLE-US-00022 TABLE 22 AC-13C Synthetic Gradation of Plant-mixed Warm Regenerated Asphalt Mixture Sieve pore Mass percentage passing through the following sieve pores (%) size (mm) 16 13.2 9.5 4.75 2.36 1.18 0.6 0.3 0.15 0.075 AC-13C 100 93.9 77.5 51.3 35.0 21.7 15.0 11.8 9.2 6.7

(46) The foregoing RAP material was mixed with the new aggregate, the mineral powder, the new asphalt and the regenerant according to a preparation method of a plant-mixed warm regenerated asphalt mixture of the present invention, wherein the mass percentages of the RAP material and various newly added materials were as follows: 48.66% of the RAP material; 19.46% of the first group of new aggregates, 7.71% of the second group of new aggregates, 4.87% of the third group of new aggregates, and 15.57% of the fourth group of new aggregates; 0.97% of the mineral powder; 2.45% of the new asphalt; and 0.31% of the regenerant.

(47) The above RAP material was mixed with the new aggregate, the mineral powder, the new asphalt and the regenerant according to the preparation method of a preparation method of a plant-mixed warm regenerated asphalt mixture of the present invention, and the steps were as follows:

(48) (1) The RAP material was heated to 160° C., the new aggregate was heated to 180° C., and then the two were put into a mixing kettle to stir for 20 s.

(49) (2) The regenerant was heated to 100° C., the new asphalt was heated to 135° C., and then the two were put into the mixing kettle to mix with a product obtained in step (1) with a mixing time set to 25 s.

(50) (3) The weighed mineral powder was directly put into the mixing kettle without heating to mix with a product obtained in step (2) with a mixing time set to 10 s.

(51) (4) A product obtained in step (3) was taken out of the kettle, then divided into 10 equal parts of samples (Y0, Y0.5, Y1, Y2, Y3, Y4, Y5, Y6, Y7, Y8) and stored in a special development bin at 170° C., wherein Y0 was developed for 0 h, Y0.5 was developed for 0.5 h, Y1 was developed for 1 h, Y2 was developed for 2 h, Y3 was developed for 3 h, Y4 was developed for 4 h, Y5 was developed for 5 h, Y6 was developed for 6 h, Y7 was developed for 7 h, and Y8 was developed for 8 h.

(52) The completely developed mixture were taken out of the bin at 160° C. and molded into an asphalt mixture test piece at 160° C., and then the pavement performances of the mixture were tested

(53) For each sample obtained by the above preparation method of a plant-mixed warm regenerated asphalt mixture, the high-temperature performance (Marshall stability test, dynamic stability test), low-temperature performance (low-temperature bending test), water stability (Marshall residual stability test, freeze-thaw splitting test) and fatigue life (four-point bending fatigue life test) were evaluated respectively after the test pieces were molded indoors. The test results were shown in Table 23, Table 24, Table 25 and Table 26, respectively.

(54) TABLE-US-00023 TABLE 23 High-temperature Performance Detection Results of Plant-mixed Warm Regenerated Asphalt Mixture Detection Plant-mixed warm regenerated asphalt mixture index Y0 Y0.5 Y1 Y2 Y3 Y4 Y5 Y6 Y7 Y8 Marshall 7.64 8.78 9.91 11.70 12.03 13.38 13.71 13.00 11.92 9.08 stability (KN) Dynamic 2750.4 3216.2 3490.5 3753.0 3972.4 4200.9 4375.1 4219.8 3590.1 3016.5 stability (times/mm) Remarks: Y0, Y0.5, Y1, Y2, Y3, Y4, Y5, Y6, Y7 and Y8 were the samples obtained after the plant-mixed warm regenerated asphalt mixture was developed at 170° C. for 0 h, 0.5 h, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h and 8 h respectively (the same below); it was stipulated in the “Technical Specification for Construction of Highway Asphalt Pavement” JTG F40-2004 (hereinafter referred to as the Specification) that the Marshall stability should be no less than 8 KN and the dynamic stability should be no less than 3000 times/mm.

(55) TABLE-US-00024 TABLE 24 Low-temperature Performance Detection Results of Plant-mixed Warm Regenerated Asphalt Mixture Detection Plant-mixed warm regenerated asphalt mixture index Y0 Y0.5 Y1 Y2 Y3 Y4 Y5 Y6 Y7 Y8 Maximum bending 2158.2 2383.1 2509.5 2662.7 2818.9 2922.0 3000.4 2809.5 2290.8 1971.3 strain at failure (με) Remarks: the test temperature was −10° C., and it was stipulated in the Specification that the maximum bending strain at failure should be no less than 2,300 με.

(56) TABLE-US-00025 TABLE 25 Water Stability Detection Results of Plant-mixed Warm Regenerated Asphalt Mixture Detection Plant-mixed warm regenerated asphalt mixture index Y0 Y0.5 Y1 Y2 Y3 Y4 Y5 Y6 Y7 Y8 Marshall residual 77.9 81.5 83.6 86.0 88.4 89.7 90.5 91.7 85.2 80.2 stability ratio (%) Freeze-thaw splitting 73.0 75.4 77.7 79.8 80.1 83.9 85.0 87.7 80.6 76.1 strength ratio (%) Remarks: it was stipulated in the Specification that the Marshall residual stability ratio should be no less than 80%, and the freeze-thaw splitting strength ratio should be no less than 75%.

(57) TABLE-US-00026 TABLE 26 Fatigue Life Detection Results of Plant-mixed Warm Regenerated Asphalt Mixture Detection Plant-mixed warm regenerated asphalt mixture index Y0 Y0.5 Y1 Y2 Y3 Y4 Y5 Y6 Y7 Y8 Four-point bending 4890 5722 6605 7903 9986 10565 11286 13077 7109 3980 fatigue life (times) Remarks: the test temperature was 15° C., the target strain was 600 με, the loading frequency was 10 Hz, and the test termination condition was 50%.

Fourth Embodiment

(58) Laboratory test embodiment: basically the same as the third embodiment, except that the development temperatures of the warm regenerated asphalt mixture in the embodiment were 20° C., 30° C., 40° C., 70° C., 100° C., 130° C., 150° C., 170° C., 190° C. and 210° C. respectively; and the development time was 6 h. The high-temperature performance, low-temperature performance, water stability and fatigue life of the plant-mixed warm regenerated asphalt mixture were investigated respectively at the development temperatures and development time described in the embodiment. The test results were shown in Table 27, Table 28, Table 29 and Table 30.

(59) TABLE-US-00027 TABLE 27 High-temperature Performance Detection Results of Plant-mixed Warm Regenerated Asphalt Mixture Detection Plant-mixed warm regenerated asphalt mixture index 20° C. 30° C. 40° C. 70° C. 100° C. 130° C. 150° C. 170° C. 190° C. 210° C. Marshall 8.22 8.29 10.71 11.10 12.83 13.36 14.57 14.50 13.10 7.54 stability (KN) dynamic 2676.1 2815.9 3209.8 3446.3 3722.7 4178.3 4399.6 4420.0 3400 2876 stability (times/mm) Remarks: the development time was 6 h (the same below); it was stipulated in the “Technical Specification for Construction of Highway Asphalt Pavement” JTG F40-2004 (hereinafter referred to as the Specification) that the Marshall stability should be no less than 8 KN and the dynamic stability should be no less than 3000 times/mm.

(60) TABLE-US-00028 TABLE 28 Low-temperature Performance Detection Results of Plant-mixed Warm Regenerated Asphalt Mixture Detection Plant-mixed warm regenerated asphalt mixture index 20° C. 30° C. 40° C. 70° C. 100° C. 130° C. 150° C. 170° C. 190° C. 210° C. Maximum bending strain 1807.5 2307.1 2617.9 2790.3 2851.4 2922.0 2931.0 2807.0 2300.8 1623.9 at failure (με) Remarks: the test temperature was −10° C., and it was stipulated in the Specification that the maximum bending strain at failure should be no less than 2,300 με.

(61) TABLE-US-00029 TABLE 29 Water Stability Detection Results of Plant-mixed Warm Regenerated Asphalt Mixture Detection Plant-mixed warm regenerated asphalt mixture index 20° C. 30° C. 40° C. 70° C. 100° C. 130° C. 150° C. 170° C. 190° C. 210° C. Marshall residual 76.4 81.3 83.2 85.1 87.7 88.5 89.6 87.5 80.0 73.9 stability ratio (%) Freeze-thaw splitting 71.3 71.9 76.8 79.1 81.4 82.5 84.3 85.1 78.6 70.0 strength ratio (%) Remarks: it was stipulated in the Specification that the Marshall residual stability ratio should be no less than 80%, and the freeze-thaw splitting strength ratio should be no less than 75%.

(62) TABLE-US-00030 TABLE 30 Fatigue Life Detection Results of Plant-mixed Warm Regenerated Asphalt Mixture Detection Plant-mixed warm regenerated asphalt mixture index 20° C. 30° C. 40° C. 70° C. 100° C. 130° C. 150° C. 170° C. 190° C. 210° C. Four-point bending 4556 4890 6165 8105 8926 9741 12337 13022 9104 4663 fatigue life (times) Remarks: the test temperature was 15° C., the target strain was 600 με, the loading frequency was 10 Hz, and the test termination condition was 50%.

(63) From the pavement performance data of the plant-mixed warm regenerated asphalt mixtures obtained in the first and third embodiments, it can be seen that under the same development temperature, with the extension of the development time, the high-temperature performance of the mixture increases first and then decreases, when the development time is greater than 6 h, the high-temperature performance decreases rapidly, and when the development time is less than 0.5 h, the dynamic stability of the mixture rutting test does not meet the specification requirements; the low-temperature performance of the mixture increases first and then decreases, when the development time is less than 0.5 h, the maximum bending strain of the low-temperature bending test of the mixture does not meet the specification requirements, and the low-temperature performance decays rapidly after the development time is greater than 6 h; the water stability of the mixture increases first and then decreases, when the development time is less than 0.5 h, the water stability of the mixture cannot meet the specification requirements, when the development time is greater than 6 h, the water stability decreases rapidly; and the fatigue life of the mixture increases first and then decreases, when the development time is greater than 6 h, the four-point bending fatigue life decreases rapidly.

(64) With reference to the above test results, it can indicate that the development process of the recycled regenerated asphalt mixture significantly increases the opportunities for mutual permeation, fusion and organic binding between the new asphalt and the old asphalt, enables the new asphalt and the regenerant to fully exert renascence and reconstruction functions in the recycled asphalt pavement material (RAP material), and improves the recycling effect of the old asphalt, and pavement performances of the recycled regenerated asphalt mixture formed can fully reach that of a hot-mixed asphalt mixture produced entirely with new materials. Particularly, the low-temperature crack resistance, water damage resistance and fatigue life of the hot-mixed asphalt mixture are significantly better than that of the recycled regenerated asphalt mixture produced by the conventional technologies. However, with the increase of the development time to a certain extent, the hot warm recycled regenerated asphalt mixture is under a high temperature status for a long time, while the aging of the recycled regenerated asphalt binder therein is accelerated again, the aromatic components and saturated phenol in the asphalt will volatilize, the asphalt become hard and brittle, the viscosity of the asphalt will decrease and the flexibility of the asphalt will decrease, so that the low-temperature performance, water stability and fatigue life of the mixture reduce greatly and quickly, and the high-temperature performance begin to decrease obviously. Therefore, the development process of the hot warm recycled regenerated asphalt mixture has a specific time limit.

(65) From the pavement performance data of the plant-mixed warm regenerated asphalt mixtures obtained in the second and fourth embodiments, it can be seen that under the same development time, with the increase of the development temperature, the high-temperature performance, low-temperature performance, water stability and fatigue life of the mixture increase first and then decrease. When the temperature is low, the opportunity degrees for mutual permeation, fusion and organic binding between the new asphalt and the old asphalt are slow when the temperature are slow, so that the renascence and reconstruction functions of the new asphalt and the regenerant in the recycled asphalt pavement material (RAP material) are decreased, and the recycling effect of the old asphalt is poor; therefore, the comprehensive pavement performances of the mixture cannot reach that of a hot-mixed asphalt mixture produced entirely with new materials. However, with the increase of the development temperature, the aging of the regenerated asphalt binder in the warm regenerated asphalt mixture is accelerated, the light components such as aromatic components and saturated phenol in the asphalt volatilize, the asphalt become hard and brittle, the viscosity of the asphalt reduce and the flexibility of the asphalt decrease, so that the high-temperature performance, the low-temperature performance, the water stability and the fatigue life of the mixture decrease greatly and quickly. Therefore, the development process of the warm regenerated asphalt mixture has a specific temperature limit.

(66) According to the above test data, the optimal development temperature of the plant-mixed warm regenerated asphalt mixture prepared by the method of first heating and then mixing according to the present invention is 150° C. and the optimal development time is 5 h; and the optimal development temperature of the plant-mixed warm regenerated asphalt mixture prepared by the method of first mixing and then heating according to the present invention is 150° C. and the optimal development time is 6 h.