Low-temperature-resistant self-heating regenerative asphalt mixture and preparation method thereof

Abstract

The application discloses a low-temperature-resistant self-heating recycled asphalt mixture and a preparation method thereof, and relates to the field of recycled asphalt.The low-temperature-resistant self-heating recycled asphalt mixture comprises the following raw materials in parts by weight: recycled asphalt old material 60-80 parts; polyurethane modified asphalt 7-12 parts; aggregate 25-33 parts; bio-based recycling agent 5-9 parts; warm-mixing agent 1-4 parts; quicklime 3-6 parts; self-heating microcapsule 4-8 parts; tannic acid modified bamboo fiber 1-3 parts; wherein the self-heating microcapsule is a microcapsule with metal powder and paraffin phase change material as a capsule core, and gelatin and sodium alginate as a capsule material; and the bio-based recycling agent is selected from one or more of the following: waste soybean oil, tung oil, lubricating oil and waste engine oil.The recycled asphalt mixture of the application does not need to be heated by external equipment during mixing, and has good low-temperature crack resistance and water damage resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of regenerated asphalt, in particular to a low-temperature-resistant self-heating regenerated asphalt mixture and a preparation method thereof. BACKGROUND

[0002] Asphalt pavement refers to various types of pavements paved with road asphalt materials mixed in mineral materials, and is one of the most widely used high-grade pavements in current road construction. The asphalt structure layer of the asphalt pavement itself belongs to the category of flexible pavement. With the aging of asphalt due to factors such as oxygen, light, and water, the asphalt gradually loses its cementing ability and ductility, causing the binder to gradually harden and become brittle, so that most asphalt pavements are prone to rutting, water damage, and other pavement diseases during use.

[0003] In order to realize the resource utilization of waste pavement and asphalt materials, asphalt regeneration technology has been developed. The regeneration of asphalt refers to adding appropriate oil in the developed network structure of asphalt to supplement the oil lost in the aging process of asphalt and improve the low-temperature crack resistance of asphalt. Regenerated asphalt mixture is a pavement material reprocessed from recycled old asphalt pavement materials by adding a regenerating agent or new aggregate.

[0004] In the preparation of regenerated asphalt mixture, hot mixing is usually selected, which means that external heating equipment is often needed to heat the mixture, and the internal temperature of the mixture is raised to achieve mixing and compaction. When facing a cold environment with low temperature and high humidity, the mixture loses heat quickly, making it difficult to compact the mixture at this time, which is not conducive to paving, and the low-temperature crack resistance and water damage resistance of the generated regenerated asphalt mixture are poor. SUMMARY

[0005] In order to make the regenerated asphalt mixture not need to rely on external equipment for heating during mixing, and have good low-temperature crack resistance and water damage resistance, the present application provides a low-temperature-resistant self-heating regenerated asphalt mixture and a preparation method thereof.

[0006] The low-temperature-resistant self-heating regenerated asphalt mixture and the preparation method thereof provided by the present application adopt the following technical scheme:

[0007] In a first aspect, the present application discloses a low-temperature-resistant self-heating regenerated asphalt mixture, which comprises the following raw materials by weight:

[0008] 60-80 parts of recycled asphalt old material;

[0009] 7-12 parts of polyurethane modified asphalt;

[0010] 25-33 parts of aggregate;

[0011] 5-9 parts of bio-based regenerating agent;

[0012] Warm agent 1-4 parts;

[0013] Quicklime 3-6 parts;

[0014] Self-heating microcapsule 4-8 parts;

[0015] Tannic acid modified bamboo fiber 1-3 parts;

[0016] The self-heating microcapsule is a microcapsule with metal powder and paraffin phase change material as the capsule core and gelatin and sodium alginate as the capsule material;

[0017] The bio-based regenerant is selected from one or more of waste soybean oil, tung oil, lubricating oil and waste engine oil.

[0018] In the above technical solution, the bio-based regenerant is used to regenerate the recycled asphalt old material, the light oil component is supplemented to soften the recycled asphalt old material, the agglomerated aged asphalt glue is dispersed, the mixing with the newly added polyurethane modified asphalt is promoted, the low temperature performance and fatigue resistance are improved, the tannic acid modified bamboo fiber is added to the recycled asphalt old material as a filler to supplement the high temperature anti-rutting performance of the recycled asphalt mixture. The polyurethane modified asphalt is used as new asphalt, the isocyanate active group is introduced to crosslink with the hydroxyl group in the recycled asphalt old material, aggregate and other components, the adhesion between the asphalt and the aggregate is increased, and the strength and crack resistance of the recycled asphalt mixture are excellent. The addition of the warm agent can reduce the mixing temperature required during construction, the addition of quicklime and self-heating microcapsules enables self-heating during mixing without the aid of external equipment. The reaction of quicklime and water releases heat, the self-heating microcapsules continuously emit heat and maintain for a long time, so that temperature compensation is achieved in a low temperature and high humidity environment, facilitating the mixing of the recycled asphalt mixture. In addition, quicklime and self-heating microcapsules can absorb moisture from the environment to react, which is beneficial to improving the water resistance of the recycled asphalt mixture. The recycled asphalt mixture prepared by the raw materials of the present application has excellent high temperature anti-rutting performance, low temperature crack resistance and water resistance, and can be mixed and paved in a low temperature and high humidity environment.

[0019] Preferably, the polyurethane modified asphalt comprises the following raw materials by weight:

[0020] A component: natural rubber 7-10 parts; castor oil polyol 15-18 parts;

[0021] Hydrogenated terpene resin 14-17 parts; bio-based plasticizer 28-32 parts;

[0022] Natural asphalt 4-7 parts;

[0023] B component: bio-based plasticizer 9-13 parts; hexamethylene diisocyanate 3-6 parts;

[0024] Hydrogenated diphenylmethane diisocyanate 9-12 parts.

[0025] Through the above technical scheme, the polyurethane modified asphalt is selected, the polyurethane molecular chain is introduced into the asphalt, the asphalt has better water resistance, crack resistance and aging resistance, the natural rubber is added in the raw material to form a three-dimensional network structure by swelling and crosslinking, the bio-based plasticizer is added to improve the flexibility of the natural asphalt, and the hydrogenated terpene resin is added to improve the compatibility of the natural asphalt and the polyurethane system, so that the crosslinking degree of the prepared polyurethane modified asphalt is increased, and the high-temperature performance and low-temperature crack resistance are improved.

[0026] Preferably, the self-heating microcapsule is prepared by the following method:

[0027] The paraffin is heated to melt at 60-70℃, the metal powder is added and stirred uniformly to form a slurry, and the mass ratio of paraffin and metal powder is 1:(1.2-1.7);

[0028] The gelatin and deionized water are stirred and dissolved under heating at 60-65℃ in a water bath, and then cooled to 35-40℃, and then the sodium alginate deionized water solution is added to form a mixed solution, and the mass ratio of gelatin and sodium alginate is (2.2-2.8):1;

[0029] The slurry is slowly added to the mixed solution, high-speed shearing emulsification is carried out for 10-15min to form a stable emulsion, the emulsion is added to the calcium chloride solution, stirring and crosslinking are carried out for 5-10min, and then the glutaraldehyde solution is added, the temperature is raised to 40-45℃, and stirring is carried out, after the reaction is completed, centrifugation is carried out, the lower layer powder is taken out for washing, and after freeze-drying, the self-heating microcapsule is obtained.

[0030] Through the above technical scheme, the paraffin phase change material and metal powder are selected as the capsule core, the metal powder releases heat quickly by contacting oxygen and moisture, and the temperature during mixing is increased, and the paraffin phase change material can absorb heat to store heat, and then the latent heat is used to compensate the temperature and realize long-acting temperature control; the capsule material is selected to be gelatin and sodium alginate, the gelatin can be triggered at low temperature, the sodium alginate can enhance the mechanical strength of the shell material, and the cooperation of the two can delay the penetration of water and control the reaction rate of the metal powder; so that the heating rate of the self-heating microcapsule is controllable, and the temperature required for the mixing of the mixture in a low-temperature environment is provided.

[0031] Preferably, the bio-based regenerant is a mixture of waste soybean oil, modified cardanol surfactant and dioctyl phthalate with a mass ratio of (60-80):(22-27):(6-11), wherein the modified cardanol surfactant is prepared by the following steps:

[0032] The cashew phenol is heated to 30-40℃ in a reaction kettle, concentrated sulfuric acid is added while stirring, the molar ratio of cashew phenol to concentrated sulfuric acid is 1:(0.2-0.5), the temperature is kept and the reaction is carried out for 0.5-1h to obtain an intermediate product and cool to 25-30℃;

[0033] Sodium hydroxide is added to the intermediate product while stirring, and the addition is stopped when the pH of the solution is 8.5-9.5 to obtain a modified cashew phenol surfactant.

[0034] By the above technical scheme, the light oil in the waste soybean oil is used to supplement the recycled asphalt old material, the asphaltene is dissolved and dispersed by physical blending, the modified cashew phenol surfactant is used to disperse the agglomerated asphalt, and dioctyl phthalate is used as a plasticizer to restore the flexibility of the recycled asphalt old material and reduce the viscosity. Thus, the performance of the recycled asphalt old material is restored by the regeneration of the regenerant, and the low temperature performance and fatigue performance of the asphalt are significantly improved.

[0035] Preferably, the tannic acid modified bamboo fiber is prepared by the following method:

[0036] The bamboo fiber is washed with deionized water and dried in an oven at 60-65℃ for 6-8h, a tannic acid solution with a mass fraction of 10-15% is prepared, the bamboo fiber is added to the tannic acid solution and stirred for 40-60min under a magnetic stirrer, then it is left to stand for 2-3h to allow the tannic acid to fully wrap the bamboo fiber, during which the stirring is repeated for 10-15min every half hour to improve the wrapping degree, after the end, the modified bamboo fiber is taken out, washed and dried in an oven at 60-65℃ for 8-9h to obtain the tannic acid modified bamboo fiber.

[0037] By the above technical scheme, the stable adhesion of tannic acid on the surface of bamboo fiber is realized by hydrogen bonding, the adhesion of bamboo fiber and asphalt interface is improved, and the modified bamboo fiber is used as a filler to enhance the recycled asphalt old material and improve the high temperature anti-rutting performance of the recycled asphalt mixture.

[0038] Preferably, the bio-based plasticizer is selected from one or more of 1,2-cyclohexane dicarboxylic acid diethylene glycol ester, diacetyl epoxidized vegetable oil acid glyceride, and sebacate.

[0039] Preferably, the aggregate includes the following particle size of mineral aggregate:

[0040] 9.5-13.2mm mineral aggregate 38-43%, 4.75-9.5mm mineral aggregate 30-35%, 2.36-4.75mm mineral aggregate 11-16%, and mineral aggregate below 2.36mm 7-11%.

[0041] Preferably, the warm mix agent is selected from one or more of Aspha-min, RH-WMA, and Rediset.

[0042] In a second aspect, the application discloses a preparation method of a low-temperature-resistant self-heating recycled asphalt mixture, which comprises the following steps:

[0043] The recycled asphalt waste, the tannic acid modified bamboo fiber and the bio-based recycling agent are mixed, and after stirring for 3-5 min, the quicklime is added and stirred uniformly, the self-heating microcapsules and the aggregate are added, and the polyurethane modified asphalt and the warm mix agent are added, and the mixture is stirred for 15-20 min, to obtain the low-temperature-resistant self-heating recycled asphalt mixture.

[0044] Through the above technical scheme, the temperature during mixing is increased by the self-heating of the quicklime and the self-heating microcapsules, so that the mixing and paving of the recycled asphalt mixture are realized, the compaction degree is high, and the prepared recycled asphalt mixture has excellent performance.

[0045] In summary, the application has the following beneficial effects:

[0046] In the recycled asphalt mixture, the recycled asphalt waste is regenerated by using the bio-based recycling agent, the recycled asphalt waste is softened by supplementing light oil, and the agglomerated aged asphalt colloidal particles are dispersed, so that the mixing with the newly added polyurethane modified asphalt is promoted, the low-temperature performance and the fatigue resistance are improved, and the tannic acid modified bamboo fiber is added to the recycled asphalt waste as a filler to supplement the high-temperature rutting resistance of the recycled asphalt mixture. The polyurethane modified asphalt is used as new asphalt, the isocyanate active groups are introduced to crosslink with the hydroxyl groups in the recycled asphalt waste, the aggregate and other components, the bonding between the asphalt and the aggregate is increased, and the strength and the crack resistance of the recycled asphalt mixture are excellent. The addition of the warm mix agent can reduce the mixing temperature required during construction, and the addition of the quicklime and the self-heating microcapsules can realize self-heating during mixing without the aid of external equipment. The temperature during mixing is increased by the reaction between the quicklime and water, and the self-heating microcapsules continuously emit heat and maintain for a long time, so that the temperature compensation is realized in a low-temperature and high-humidity environment, the mixing of the recycled asphalt mixture is facilitated, and in addition, the quicklime and the self-heating microcapsules can absorb water from the environment to react, which is beneficial to improving the water damage resistance of the recycled asphalt mixture. The recycled asphalt mixture prepared by the raw materials of the application has excellent high-temperature rutting resistance, low-temperature crack resistance and water damage resistance, and can realize mixing and paving in a low-temperature and high-humidity environment. DETAILED DESCRIPTION

[0047] The recycled asphalt waste is selected from the milled material produced by raking the waste asphalt pavement by using a heated milling machine;

[0048] The aggregate is selected from a mixture of basalt and diabase, and is configured by the following particle size of the mineral aggregate: 9.5-13.2mm mineral aggregate 42%, 4.75-9.5mm mineral aggregate 34%, 2.36-4.75mm mineral aggregate 15%, and mineral aggregate below 2.36mm 9%;

[0049] The natural asphalt is selected from No. 90 base asphalt.

[0050] The application is further described in detail below in combination with Examples 1-6 and Comparative Examples 1-2.

[0051] Preparation Example 1

[0052] The preparation of the polyurethane modified asphalt includes the following raw materials:

[0053] Component A: natural rubber 7 parts; castor oil polyol 15 parts;

[0054] Hydrogenated terpene resin 14 parts;

[0055] Bio-based plasticizer 28 parts, selected from 1,2-cyclohexane dicarboxylic acid diethylene glycol ester;

[0056] Natural asphalt 4 parts;

[0057] Component B: bio-based plasticizer 9 parts, selected from diacetyl epoxy vegetable oil acid glyceride;

[0058] Hexamethylene diisocyanate 3 parts;

[0059] Hydrogenated diphenyl methane diisocyanate 9 parts.

[0060] Preparation Example 2

[0061] The preparation of the polyurethane modified asphalt includes the following raw materials:

[0062] Component A: natural rubber 10 parts; castor oil polyol 18 parts;

[0063] Hydrogenated terpene resin 17 parts;

[0064] Bio-based plasticizer 32 parts, selected from 1,2-cyclohexane dicarboxylic acid diethylene glycol ester;

[0065] Natural asphalt 7 parts;

[0066] Component B: bio-based plasticizer 13 parts, selected from diacetyl epoxy vegetable oil acid glyceride;

[0067] Hexamethylene diisocyanate 6 parts;

[0068] Hydrogenated diphenyl methane diisocyanate 12 parts.

[0069] Preparation Example 3

[0070] Preparation of polyurethane modified asphalt, comprising the following raw materials:

[0071] Component A: natural rubber 8 parts; castor oil polyol 17 parts;

[0072] Hydrogenated terpene resin 15 parts;

[0073] Bio-based plasticizer 30 parts, selected from 1,2-cyclohexane diethylene glycol dicarboxylate;

[0074] Natural asphalt 6 parts;

[0075] Component B: bio-based plasticizer 11 parts, selected from diacetyl glycerol epoxidized vegetable oil acid;

[0076] Hexamethylene diisocyanate 4 parts;

[0077] Hydrogenated diphenyl methane diisocyanate 10 parts.

[0078] Preparation Example 4

[0079] Preparation method of self-heating microcapsules, comprising the following steps:

[0080] The paraffin is heated to melt at 60℃, metal powder is added and stirred uniformly to form a slurry, the metal powder is specifically selected from iron powder, and the mass ratio of paraffin to metal powder is 1:1.2;

[0081] The gelatin and a certain amount of deionized water are stirred and dissolved under heating at 60℃ in a water bath, then cooled to 35℃, and then a sodium alginate deionized water solution is added to form a mixed solution, the mass ratio of gelatin to sodium alginate is 2.2:1;

[0082] The slurry is slowly added to the mixed solution, high-speed shearing emulsification is performed for 10min to form a stable emulsion, the emulsion is added to a 0.5mol / L calcium chloride solution, stirred and crosslinked for 5min, then a 10% mass fraction of pentanediol solution is added, the temperature is raised to 40℃ and stirred to react, after the reaction is completed, centrifugation is performed, the lower layer powder is taken out for washing, and after freeze-drying, self-heating microcapsules are obtained.

[0083] Preparation Example 5

[0084] Preparation method of self-heating microcapsules, comprising the following steps:

[0085] The paraffin is heated to melt at 70℃, metal powder is added and stirred uniformly to form a slurry, the metal powder is specifically selected from a mixture of iron powder and magnesium powder, and the mass ratio of paraffin to metal powder is 1:1.7;

[0086] The gelatin and a certain amount of deionized water are stirred and dissolved under heating at 65℃ in a water bath, then cooled to 40℃, and then a sodium alginate deionized water solution is added to form a mixed solution, the mass ratio of gelatin to sodium alginate is 2.8:1;

[0087] The slurry is slowly added to the mixed solution, high-speed shearing emulsification is performed for 15 min to form a stable emulsion, the emulsion is added to a 0.5 mol / L calcium chloride solution, stirring and crosslinking are performed for 10 min, a 10% by mass pentanediol solution is then added, and stirring is performed at 45°C until the reaction is completed. After the reaction is completed, centrifugation is performed, the lower layer powder is taken out, and washing, freeze-drying are performed to obtain the self-heating microcapsules.

[0088] Preparation Example 6

[0089] A preparation method of tannic acid modified bamboo fiber includes the following steps:

[0090] The bamboo fiber is washed with deionized water and dried in an oven at 60°C for 6 h. A 10% by mass tannic acid solution is prepared, the bamboo fiber is added to the tannic acid solution, and stirring is performed under a magnetic stirrer for 40 min. Then, the tannic acid is allowed to fully wrap the bamboo fiber by standing for 2 h, and the wrapping degree is improved by stirring again for 10 min every half hour during the period. After the end, the modified bamboo fiber is taken out, washed, and dried in an oven at 60°C for 8 h to obtain the tannic acid modified bamboo fiber.

[0091] Preparation Example 7

[0092] A preparation method of tannic acid modified bamboo fiber includes the following steps:

[0093] The bamboo fiber is washed with deionized water and dried in an oven at 65°C for 8 h. A 15% by mass tannic acid solution is prepared, the bamboo fiber is added to the tannic acid solution, and stirring is performed under a magnetic stirrer for 60 min. Then, the tannic acid is allowed to fully wrap the bamboo fiber by standing for 3 h, and the wrapping degree is improved by stirring again for 15 min every half hour during the period. After the end, the modified bamboo fiber is taken out, washed, and dried in an oven at 65°C for 9 h to obtain the tannic acid modified bamboo fiber.

[0094] Example 1

[0095] The low-temperature-resistant self-heating recycled asphalt mixture includes the following raw materials:

[0096] The recycled asphalt old material is 60 parts;

[0097] The polyurethane modified asphalt is 7 parts, and the polyurethane modified asphalt prepared in Preparation Example 1 is selected;

[0098] The aggregate is 25 parts;

[0099] The bio-based regenerant is 5 parts, and the waste soybean oil is specifically selected;

[0100] The warm-mixing agent is 1 part, and the warm-mixing agent Aspha-min is specifically selected;

[0101] The quicklime is 3 parts;

[0102] Self-heating microcapsules 4 parts, specifically self-heating microcapsules prepared in Preparation Example 4 are selected.

[0103] Tannic acid modified bamboo fiber 1 part, specifically tannic acid modified bamboo fiber prepared in Preparation Example 6 is selected.

[0104] The low-temperature-resistant self-heating recycled asphalt mixture is prepared by the following steps:

[0105] The recycled asphalt old material, the tannic acid modified bamboo fiber and the bio-based recycling agent are mixed, stirred for 3 min, and then the quicklime is added and stirred uniformly, the self-heating microcapsules and the aggregate are added and uniformly mixed, the polyurethane modified asphalt and the warm-mixing agent are added and stirred for 15 min, to obtain the low-temperature-resistant self-heating recycled asphalt mixture.

[0106] Examples 2-4

[0107] Examples 2-4 and Example 1 are different in that the raw material ratio and the stirring time in the recycled asphalt mixture are different, as shown in Table 1.

[0108] Table 1

[0109] Sample Example 2 Example 3 Example 4 Reclaimed asphalt 80 70 70 Polyurethane modified asphalt 12, Preparation Example 2 9, Preparation Example 3 9, Preparation Example 2 Aggregate 33 29 29 Bio-based rejuvenator 9, Waste engine oil 6, Tung oil 6, Lubricating oil Warm mix agent 4, Warm mix agent RH-WMA 3, Warm mix agent Rediset 3, Warm mix agent RH-WMA Quicklime 6 5 5 Self-heating microcapsule 8, Preparation Example 5 7, Preparation Example 4 7, Preparation Example 5 Tannin-modified bamboo fiber 3, Preparation Example 7 2, Preparation Example 7 2, Preparation Example 6 First mixing time 5 4 4 Second mixing time 20 17 17

[0110] Example 5

[0111] This example and Example 1 are different in that the bio-based recycling agent in the recycled asphalt mixture is different.

[0112] The bio-based recycling agent in this example is a mixture of waste soybean oil, modified cardanol surfactant and dioctyl phthalate in a mass ratio of 60:22:6, wherein the modified cardanol is prepared by the following steps:

[0113] The cardanol is placed in a reaction kettle and heated to 30℃, and concentrated sulfuric acid is added while stirring, the molar ratio of cardanol to concentrated sulfuric acid is 1:0.2, the temperature is maintained and reacted for 0.5h, to obtain an intermediate product and cool to 25℃;

[0114] Sodium hydroxide is added to the intermediate product while stirring, until the solution pH is 8.5-9.5, to stop adding, to obtain the modified cardanol surfactant.

[0115] Example 6

[0116] This example and Example 1 are different in that the bio-based recycling agent in the recycled asphalt mixture is different.

[0117] The bio-based recycling agent in this example is a mixture of waste soybean oil, modified cardanol surfactant and dioctyl phthalate in a mass ratio of 80:27:11, wherein the modified cardanol is prepared by the following steps:

[0118] The cardanol was placed in a reaction kettle and heated to 40℃, concentrated sulfuric acid was added while stirring, the molar ratio of cardanol to concentrated sulfuric acid was 1:0.5, the temperature was maintained and reacted for 1h, to obtain an intermediate product and cooled to 30℃;

[0119] Sodium hydroxide was added to the intermediate product while stirring, until the pH of the solution was 8.5-9.5, to stop adding, to obtain a modified cardanol surfactant.

[0120] Comparative Example 1

[0121] The difference between this comparative example and Example 1 is that the raw materials in the recycled asphalt mixture are different, in this comparative example, the same weight part of No. 90 base asphalt is used instead of polyurethane modified asphalt.

[0122] The other raw materials and preparation methods of the recycled asphalt mixture are the same as those of Example 1.

[0123] Comparative Example 2

[0124] The difference between this comparative example and Example 1 is that the raw materials in the recycled asphalt mixture are different, in this comparative example, no tannic acid modified bamboo fiber is added.

[0125] The other raw materials and preparation methods of the recycled asphalt mixture are the same as those of Example 1.

[0126] The low-temperature self-heating recycled asphalt mixtures prepared in Examples 1-6 and Comparative Examples 1-2 were tested for the following properties, according to JTG E20-2011 “Highway Engineering Asphalt and Asphalt Mixture Test Procedures”, and the test results were recorded in Table 2.

[0127] Rutting test: Rutting test was used to evaluate the high-temperature stability of the recycled asphalt mixture. A full-automatic asphalt mixture rutting test machine was selected, the wheel pressure was 0.7 MPa, the test temperature was 60℃, and the loading time was 1h.

[0128] Low-temperature bending test: Low-temperature bending test was used to evaluate the low-temperature crack resistance of the recycled asphalt mixture. A universal testing machine was selected, the test temperature was -10℃, and a concentrated load was applied to the middle part of the recycled asphalt mixture beam at a rate of 50mm / min until fracture failure.

[0129] Soaked Marshall test: Soaked Marshall test was used to test the water resistance (water stability) of the asphalt mixture. Cylindrical test pieces with a diameter of 101.6mm and a height of 63.5mm were prepared, and the asphalt mixture Marshall test was carried out after 0.5h and 48h in a constant temperature water tank at 60℃, respectively, the test loading rate was 50mm / min, the soaked residual stability MS0 was used as the evaluation index, and the calculation method was shown in formula (1).

[0130] MS0 = MS1 / MS x 100% (1)

[0131] In the formula: MS0 is the residual stability of the test piece after immersion; MS1 is the Marshall stability of the test piece after immersion for 48h, kN; MS is the Marshall stability of the test piece, kN.

[0132] Table 2

[0133] Sample Dynamic stability (times / mm) Maximum bending tensile strain (με) Immersion residual stability (%) Example 1 4387 3128.2 88.2 Example 2 4413 3140.6 87.9 Example 3 4366 3116.8 88.6 Example 4 4375 3132.9 88.3 Example 5 4169 3401.4 89.6 Example 6 4147 3389.2 89.4 Comparative Example 1 3874 2762.5 84.7 Comparative Example 2 3509 2975.1 88.0

[0134] According to the data in Table 2, the dynamic stability of the recycled asphalt mixture prepared in the application is higher than the requirement of 2800 times / mm, the high-temperature anti-rutting performance meets the use requirements in summer hot areas; the maximum bending tensile strain is all greater than or equal to 3000με, the low-temperature anti-cracking performance meets the use requirements in winter cold areas; the residual stability after immersion is all higher than the requirement of 85%, and the water stability meets the use requirements of high-grade asphalt pavement.

[0135] In the recycled asphalt mixture prepared in the application, by adding quicklime and self-heating microcapsules, the temperature of the recycled asphalt mixture can be automatically raised during mixing in a low-temperature and high-humidity environment, so that external heating equipment is not needed, construction is convenient, and the mixing performance of the recycled asphalt mixture is better.

[0136] According to the comparison between Examples 5-6 and Example 1, by selecting a fixed combination of the recycling agent, selecting a specific mass of waste soybean oil, a modified cardanol surfactant and dioctyl phthalate, the recycling agent prepared by mixing can further disperse the asphalt colloidal group, improve the miscibility and uniformity of new asphalt and recycled asphalt waste, and improve the contact area and interfacial bonding strength of recycled asphalt waste and aggregate, so that the performance of recycled asphalt waste is restored, and the low-temperature anti-cracking performance and water damage resistance of the recycled asphalt mixture are improved. When the agglomeration degree of the recycled asphalt waste is reduced, the flexibility of the recycled asphalt waste is improved, so that compared with hardened asphalt after aging, the high-temperature anti-rutting performance is reduced to a certain extent, but under the premise of adding tannin-modified bamboo fiber to compensate for the high-temperature performance, the high-temperature performance of the recycled asphalt mixture still meets the requirements.

[0137] Compared with Example 1, the polyurethane modified asphalt and tannin modified bamboo fiber in the raw materials of the recycled asphalt mixture of Comparative Example 1 and Comparative Example 2 are changed, and the performance is reduced to a certain extent. The selection of new asphalt in the application does not use matrix asphalt, but uses polyurethane modified asphalt mixed with recycled asphalt old materials. Compared with matrix asphalt, the water resistance and internal crosslinking degree of the polyurethane modified asphalt are improved, the high temperature performance, crack resistance and water resistance are improved by forming a polymer network structure, thereby improving the performance of the entire recycled asphalt mixture. The tannin modified bamboo fiber enhances the recycled asphalt old material through the filler, mainly used to compensate for the high temperature anti-rutting performance.

[0138] The specific embodiment is only an explanation of the application, and is not a limitation of the application. Those skilled in the art can make modifications to the specific embodiment without creative contribution after reading the specification, but as long as it is within the scope of the claims of the application, it is protected by the patent law.

Claims

1. A low-temperature resistant, self-heating recycled asphalt mixture, characterized in that: Including the following parts by weight of raw materials: Recycle 60-80 portions of old asphalt; 7-12 parts of polyurethane-modified bitumen; 25-33 parts of aggregate; 5-9 parts of bio-based regenerator; 1-4 parts of warm mixing agent; 3-6 parts quicklime; 4-8 portions of self-heating microcapsules; 1-3 parts of tannic acid-modified bamboo fiber; The self-heating microcapsule is a microcapsule with a mixture of metal powder and paraffin phase change material as the core and a mixture of gelatin and sodium alginate as the encapsulation material. The bio-based regenerant is a mixture of waste soybean oil, modified cashew nut shell surfactant, and dioctyl phthalate in a mass ratio of (60-80):(22-27):(6-11), wherein the modified cashew nut shell surfactant is prepared according to the following steps: Cashew phenol is placed in a reaction vessel and heated to 30-40℃. While stirring, concentrated sulfuric acid is added. The molar ratio of cashew phenol to concentrated sulfuric acid is 1:(0.2-0.5). The temperature is maintained and the reaction is carried out for 0.5-1h to obtain the intermediate product, which is then cooled to 25-30℃. Sodium hydroxide was added to the intermediate product while stirring until the pH of the solution reached 8.5-9.5, at which point the addition was stopped to obtain the modified cashew phenol surfactant.

2. The low-temperature resistant self-heating recycled asphalt mixture according to claim 1, characterized in that: The polyurethane-modified asphalt comprises the following raw materials in parts by weight: Component A: 7-10 parts natural rubber; 15-18 parts castor oil polyol; 14-17 parts hydrogenated terpene resin; 28-32 parts bio-based plasticizer; 4-7 parts natural asphalt; Component B: 9-13 parts of bio-based plasticizer; 3-6 parts of hexamethylene diisocyanate; 9-12 parts of hydrogenated diphenylmethane diisocyanate.

3. The low-temperature resistant self-heating recycled asphalt mixture according to claim 1, characterized in that: Self-heating microcapsules were prepared by the following method: The paraffin wax is heated to 60-70℃ and melted. Metal powder is added and stirred evenly to form a slurry. The mass ratio of paraffin wax to metal powder is 1:(1.2-1.7). Gelatin and deionized water are heated in a water bath at 60-65℃ and stirred until dissolved. Then, after cooling to 35-40℃, a deionized aqueous solution of sodium alginate is added to form a mixture. The mass ratio of gelatin to sodium alginate is (2.2-2.8):

1. The slurry was slowly added to the mixture and emulsified by high-speed shearing for 10-15 minutes to form a stable emulsion. The emulsion was then added to a calcium chloride solution and stirred for crosslinking for 5-10 minutes. Glutaraldehyde solution was then added and the temperature was raised to 40-45℃ and stirred to react. After the reaction was completed, the mixture was centrifuged, and the lower layer of powder was washed and freeze-dried to obtain self-heating microcapsules.

4. The low-temperature resistant self-heating recycled asphalt mixture according to claim 1, characterized in that: Tannic acid-modified bamboo fiber was prepared by the following method: Bamboo fiber is thoroughly washed with deionized water and dried in an oven at 60-65℃ for 6-8 hours. A tannic acid solution with a mass fraction of 10-15% is prepared. The bamboo fiber is added to the tannic acid solution and stirred in a magnetic stirrer for 40-60 minutes. Then, it is allowed to stand for 2-3 hours to allow the tannic acid to fully coat the bamboo fiber. During this period, the mixture is stirred again for 10-15 minutes every half hour to improve the degree of coating. After the process is completed, the modified bamboo fiber is removed, washed, and dried in an oven at 60-65℃ for 8-9 hours to obtain tannic acid modified bamboo fiber.

5. The low-temperature resistant self-heating recycled asphalt mixture according to claim 2, characterized in that: The bio-based plasticizer is selected from one or more of diethylene glycol 1,2-cyclohexanedicarboxylate, diacetylepoxy glyceryl vegetable oil, and sebacic acid ester.

6. The low-temperature resistant self-heating recycled asphalt mixture according to claim 1, characterized in that: The aggregate is composed of minerals with the following particle sizes: 5-13.2mm ore: 38-43%; 4.75-9.5mm ore: 30-35%; 2.36-4.75mm ore: 11-16%; ore smaller than 2.36mm: 7-11%.

7. The low-temperature resistant self-heating recycled asphalt mixture according to claim 1, characterized in that: The warm mixing agent is selected from one or more of the following: Aspha-min, RH-WMA, and Rediset.

8. A method for preparing a low-temperature resistant, self-heating recycled asphalt mixture according to any one of claims 1-7, characterized in that, Includes the following steps: Mix recycled asphalt, tannic acid-modified bamboo fiber, and bio-based regenerator. After stirring for 3-5 minutes, add quicklime and stir evenly. Add self-heating microcapsules and aggregates, and continue to mix evenly. Add polyurethane-modified asphalt and warm mix agent, and stir for 15-20 minutes to obtain a low-temperature resistant self-heating recycled asphalt mixture.