A warm-mix type in-place hot recycled asphalt mixture modifier and a preparation method thereof

Abstract

The application discloses a warm-mixing in-place hot recycling asphalt mixture modifier and a preparation method thereof. The modifier comprises: 90# base asphalt, coumarone-indene resin, waste rubber powder, linear 30 / 70 type SBS, 4,4'-dithiodimorpholine, butyl propionate, poly-alpha-olefin, N-(2-hydroxyethyl)dodecylamide, cocamide propyl betaine and composite release agent. The modifier can reduce the use amount of new asphalt and recycling agent to a certain extent, significantly improve the performance of the recycled pavement and solve the problems of poor low-temperature performance and poor water damage resistance of the recycled pavement. In addition, some additives contained in the modifier have certain surface-active warm-mixing agent characteristics, thereby reducing the mixing temperature and improving the compaction degree of the in-place hot recycling mixture.

Description

Technical Field

[0001] This invention belongs to the field of in-situ thermal recycling technology, specifically relating to a warm-mix in-situ thermal recycling asphalt mixture modifier and its preparation method. Background Technology

[0002] Asphalt pavement is the most common type of road surface in highway transportation, accounting for approximately 80% of my country's expressways due to its high driving comfort and durability. With decades of highway construction and development in my country, many highways have been in operation for decades. As their service life increases, under the combined effects of sunlight, oxidation, rainwater erosion, and traffic loads, the asphalt pavement binder gradually ages, leading to various road defects such as cracking, rutting, potholes, and loosening, necessitating extensive maintenance. Current maintenance solutions generally involve milling and repaving the old pavement or adding an overlay. Milling the old pavement inevitably generates a large amount of waste asphalt mixture. Currently, the main method for disposing of milled asphalt mixture is dumping, which occupies a large amount of arable land, pollutes the surrounding ecological environment, and represents a significant waste of resources. Compared to traditional milling and repaving maintenance techniques, hot recycling pavement can reduce the generation of solid waste such as waste asphalt mixture while also achieving the effect of functional regeneration of the asphalt pavement.

[0003] Hot recycling technology is currently the most widely used asphalt pavement recycling method in the world. It involves heating the reclaimed RAP, then correcting the gradation, adding recycling agents, and supplementing with new asphalt to bring the recycled material to the required specifications for pavement applications.

[0004] Current research in the field of in-situ thermal recycling remains focused on recycling agents. The market offers a wide variety of recycling agents, most of which are composed of low-viscosity, light oils such as waste engine oil and waste lubricating oil, blended with modifiers and anti-aging agents. These recycling agents generally suffer from low cost-effectiveness, rudimentary production processes, inability to effectively guarantee quality, and secondary environmental pollution. Furthermore, in-situ thermal recycling of SBS modified asphalt pavements, rubber asphalt pavements, and high-performance road sections, the performance of the recycled pavement shows a significant decline compared to the original pavement. Currently, the recycling agents added in in-situ thermal recycling projects primarily reduce viscosity and improve the performance of the recycled asphalt, failing to achieve the same performance as the original pavement, especially after multiple thermal recycling cycles, where performance degradation becomes more pronounced. Many current recycling agents have limited functionality, generally only reducing the viscosity of aged asphalt and improving the mixing performance of waste mixtures, with limited improvement on other properties of asphalt mixtures.

[0005] How to effectively improve the performance of in-situ thermally recycled pavement, while maintaining a high level of pavement performance during multiple recycling processes, is a pressing problem that needs to be solved in the field of in-situ thermal recycling. Summary of the Invention

[0006] To effectively overcome the problem that the performance of in-situ hot recycled pavement deteriorates significantly compared to the original pavement, and this performance degradation becomes even more severe with each recycling cycle, this invention develops a warm-mix in-situ hot recycled asphalt mixture modifier and its preparation method. This modifier not only reduces the amount of new asphalt and recycling agent required to a certain extent, but also significantly improves multiple properties of recycled pavement.

[0007] The warm-mix in-situ thermally recycled asphalt mixture modifier includes: 90# base asphalt, coumarone-indene resin, waste rubber powder, linear 30 / 70 type SBS, 4,4'-dithiodimorpholine, butyl propionate, polyalphaolefin, N-(2-hydroxyethyl)dodecylamide, cocamidopropyl betaine, and composite release agent.

[0008] The softening point of the coumarone-indene resin is not lower than 80-100℃.

[0009] The waste rubber powder needs to be preheated to 80-100℃, and the specifications are radial tire rubber powder with a mesh size of 60-80 mesh.

[0010] The polyalphaolefin type is one or more of PAO8, PAO9, PAO10 and PAO25.

[0011] The composite isolating agent is composed of 10-20 wt% palmitamide propyl dimethylamine lactate, 20-25 wt% sodium di(2-ethylhexyl) succinate sulfonate and 55-70 wt% talc.

[0012] The preparation method of the warm-mix in-situ thermal recycled asphalt mixture modifier includes the following steps:

[0013] 1) Weigh 100 parts by weight of 90# base petroleum asphalt and add it to the development tank. Purge with nitrogen and stir at 500 rpm for 5 minutes at 230-250℃. Add 40-50 parts by weight of coumarone-indene resin and continue stirring for 10 minutes. Then add 100-150 parts by weight of waste rubber powder in batches. After the addition is complete, stir at 1000-2000 rpm for 60-90 minutes at 230-250℃.

[0014] 2) Weigh 20-30% of the mass of 90# base petroleum asphalt and add linear 30 / 70 type SBS to the above-mentioned development tank. Maintain the reaction temperature at 230-250℃ and stir the reaction at 1000-2000 rpm for 30 min under nitrogen protection.

[0015] 3) Pump the product obtained in step 2) into the reaction tank using a high-viscosity asphalt pump. At the same time, add 0.3-0.5% of 4,4'-dithiodimorpholine by weight of waste rubber powder. Maintain the reaction tank temperature at 230-250℃, adjust the shear rate to 6000-8000rpm, purge with nitrogen for protection, increase the reaction tank pressure to 3-5MPa, and stir the reaction for 30-60min.

[0016] 4) Purge with nitrogen to maintain a pressure of 3-5 MPa, lower the reaction temperature to 200℃±10℃, adjust the shear rate to 1000-2000 rpm, and add 5-10% by weight of waste rubber powder, 3-5% of polyα-olefin, 3-5% of N-(2-hydroxyethyl)dodecylamide, and 2-3% of cocamidopropyl betaine to the reaction vessel. React for 20-30 min.

[0017] 5) The material is conveyed to the twin-screw extruder through the discharge port of the reaction tank. The heating temperature of the twin-screw extruder is maintained at 130-150℃. The material is extruded into 2-3mm granules through the twin-screw extruder. The temperature of the granules is reduced to 50-80℃ by the air-cooling device at the discharge port of the twin-screw extruder, and the granules are uniformly coated with the composite release agent.

[0018] The exhaust pipe of the development tank is connected to the inlet pipe of the reaction tank, the exhaust pipe of the reaction tank is connected to spray tower 1, and spray tower 1 is connected to spray tower 2. The spray liquid of spray tower 1 is a 2-5% NaOH aqueous solution, and the spray liquid of spray tower 2 is a 2-5% H2SO4 aqueous solution. The exhaust gas discharged from the reaction tank passes through spray tower 1 and spray tower 2, is dehydrated by a dryer, and then passes through a regenerative thermal oxidizer to remove the remaining VOCs in the exhaust gas before being discharged after meeting the standards.

[0019] The advantages of this invention are:

[0020] 1. Due to the increase in asphalt modulus caused by the aging of recycled asphalt mixtures, the high-temperature performance of recycled asphalt mixtures is generally better than that of original asphalt pavements. However, the aging of asphalt leads to a severe decline in the water loss resistance and low-temperature crack resistance of recycled asphalt pavements, which in turn causes diseases such as network cracking in old pavements. The warm-mix in-situ hot recycled asphalt mixture modifier prepared in this invention adds coumarone-indene resin, waste rubber powder, linear 30 / 70 type SBS and other modifiers, which can effectively improve the high-temperature performance of in-situ hot recycled mixtures and greatly improve the low-temperature performance of the mixture, thereby solving the problem of poor low-temperature performance and water loss resistance of current recycled pavements.

[0021] 2. The butyl propionate contained in the warm-mix in-situ thermal recycled asphalt mixture modifier prepared by this invention can effectively dissolve modifiers such as SBS and waste rubber powder, making them evenly dispersed. At the same time, the excellent viscosity-temperature properties of polyalphaolefins ensure that the modifier maintains a suitable viscosity when added to the recycled mixture. In addition, the excellent solubility of butyl propionate reduces the viscosity of aged asphalt in the recycled asphalt mixture, thereby reducing the amount of recycling agent required after adding the modifier prepared by this invention. Furthermore, the asphalt contained in this modifier also reduces the amount of newly added asphalt to a certain extent.

[0022] 3. The N-(2-hydroxyethyl)dodecylamide, cocamidopropyl betaine, palmitamide propyl dimethylamine lactate and sodium di(2-ethylhexyl)succinate sulfonate contained in the warm-mix in-situ thermally recycled asphalt mixture modifier prepared by this invention have excellent hydrophilic and oleophilic properties and certain surfactant-type warm-mix agent characteristics, thereby achieving the effect of reducing the mixing temperature and solving the problem of insufficient compaction caused by the low material temperature of in-situ thermally recycled mixtures;

[0023] 4. In the warm-mix in-situ thermal recycling asphalt mixture modifier prepared by this invention, 4,4'-dithiodimorpholine undergoes local vulcanization crosslinking with waste rubber powder and SBS at high temperatures, allowing the modifier to maintain a certain degree of three-dimensional network structure. This structure helps to improve the crack resistance and water loss resistance of the modified mixture. At the same time, the general in-situ thermal recycling mixing temperature is not lower than 150℃. At this temperature, butyl propionate begins to volatilize and vaporize, thereby destroying the continuous structure of the asphalt mixture, reducing the viscosity of the asphalt, and also playing a certain role in reducing viscosity through warm mixing. Furthermore, after the butyl propionate volatilizes, the remaining modifier has an increased polymer content. When the recycled pavement returns to normal temperature, the remaining modifier components fully exert their excellent high and low temperature performance. Detailed Implementation

[0024] To better understand this invention, the following embodiments further illustrate its content; however, the invention is not limited to these embodiments. If the experiments and construction based on this invention do not involve creative improvements or labor by the construction personnel, then these embodiments also fall within the scope of protection of this invention.

[0025] All test values ​​in these embodiments are from laboratory conditions. To better compare with the performance of conventional in-situ hot recycled pavement, the indicators tested in this experiment are compared with the performance of existing conventional in-situ hot recycled mixtures. Asphalt aging was simulated using PVA to mimic the aging process of asphalt in in-situ hot recycled pavement. Since in-situ hot recycling causes minimal damage to the original pavement aggregate mix, the aggregates involved in the embodiments of this invention were prepared according to AC-13 aggregate mix design, and the asphalt-aggregate ratio was determined based on different modifier addition amounts. The performance of the mixture prepared with the optimal asphalt-aggregate ratio was compared. The mixing temperature was determined based on the Marshall specimen compaction degree; the lowest mixing temperature at which the compaction degree met 96% was the mixing temperature of the embodiments. No new asphalt or recycling agent was added in embodiments 1-3, recycling agent and new asphalt were added in embodiment 4, and no modifier was added in embodiment 5. The modification effect of the modifier was evaluated by comparing it with embodiment 4.

[0026] Example 1:

[0027] The preparation method of warm-mix in-situ thermal recycled asphalt mixture modifier includes the following steps:

[0028] 1) Weigh 100 parts of base petroleum asphalt and add it to the development tank. Protect it with nitrogen gas and stir at 500 rpm for 5 minutes at 230°C. Add 40 parts of coumarone-indene resin and continue stirring for 10 minutes. Then add 100 parts of 80-mesh radial tire waste rubber powder (preheated to 100°C) in batches. After the addition is complete, stir at 2000 rpm for 90 minutes at 230°C.

[0029] 2) Weigh 30% of the mass of asphalt and add linear 30 / 70 type SBS to the above-mentioned development tank. Maintain the reaction temperature at 230℃ and stir at 2000 rpm for 30 min under nitrogen protection.

[0030] 3) Pump the product obtained in 2) into the reaction tank using a high viscosity asphalt pump, and add 0.5% of 4,4'-dithiodimorpholine by weight of waste rubber powder. Maintain the temperature of the reaction tank at 230℃, adjust the shear rate to 6000rpm, purge with nitrogen for protection, increase the pressure of the reaction tank to 3MPa, and stir for 30min.

[0031] 4) Purge with nitrogen to maintain a pressure of 3 MPa, lower the reaction temperature to 200℃±10℃, adjust the shear rate to 2000 rpm, and add 10% butyl propionate, 3% PAO25, 3% N-(2-hydroxyethyl) dodecylamide and 2% cocamidopropyl betaine by weight of total adhesive powder to the reaction vessel, and react for 30 min.

[0032] 5) The material is conveyed to the twin-screw extruder through the discharge port of the reaction tank. The heating temperature of the twin-screw extruder is maintained at 130℃. The material is extruded into 2mm granules through the twin-screw extruder. The temperature of the granules is reduced to no more than 70℃ through the air cooling device at the discharge port of the twin-screw extruder. After cooling, the granules are uniformly coated with a composite release agent (10% palmitamide propyl dimethylamine lactate, 20% sodium di(2-ethylhexyl) succinate sulfonate and 70% talc).

[0033] The exhaust pipe of the development tank is connected to the inlet pipe of the reaction tank, and the exhaust pipe of the reaction tank is connected to spray tower 1. Spray tower 1 is connected to spray tower 2. The spray liquid of spray tower 1 is a 2% NaOH aqueous solution, and the spray liquid of spray tower 2 is a 2% H2SO4 aqueous solution. The exhaust gas discharged from the reaction tank passes through spray tower 1 and spray tower 2, is dehydrated by a dryer, and then passes through a regenerative thermal oxidizer to remove the remaining VOCs in the exhaust gas before being discharged in compliance with emission standards.

[0034] The prepared modifier was used in AC-13 asphalt mixture tests at an addition rate of 2% of the aggregate. The optimal asphalt-aggregate ratio was determined to be 4.1 (PVA aged asphalt), the mixing temperature was 145℃, and the performance of the mixture was tested.

[0035] Example 2:

[0036] The modifier preparation process was the same as in Example 1, with a modifier addition amount of 4%, an optimal asphalt-aggregate ratio of 2.4 (PVA aged asphalt), a mixing temperature of 140℃, and the performance of the mixture was tested.

[0037] Example 3:

[0038] The preparation method of warm-mix in-situ thermal recycled asphalt mixture modifier includes the following steps:

[0039] 1) Weigh 100 parts of base petroleum asphalt and add it to the development tank. Protect it with nitrogen gas and stir at 500 rpm for 5 minutes at 250°C. Add 50 parts of coumarone-indene resin and continue stirring for 10 minutes. Then add 150 parts of 60-mesh radial tire waste rubber powder in batches. After the addition is complete, stir at 2000 rpm for 60 minutes at 250°C.

[0040] 2) Weigh 20% of the mass of asphalt and add linear 30 / 70 type SBS to the above-mentioned development tank. Maintain the reaction temperature at 250℃ and stir at 2000 rpm for 30 min under nitrogen protection.

[0041] 3) Pump the product obtained in 2) into the reaction tank using a high viscosity asphalt pump, and add 0.3% of 4,4'-dithiodimorpholine by weight of waste rubber powder. Maintain the temperature of the reaction tank at 250℃, adjust the shear rate to 8000rpm, purge with nitrogen for protection, increase the pressure of the reaction tank to 5MPa, and stir for 60min.

[0042] 4) Purge with nitrogen to maintain a pressure of 5 MPa, lower the reaction temperature to 200℃±10℃, adjust the shear rate to 1000 rpm, add 5% butyl propionate, 5% PAO10, 5% N-(2-hydroxyethyl) dodecylamide and 2% cocamidopropyl betaine by mass of total rubber powder to the reaction vessel, and prepare a warm-mix in-situ hot recycled asphalt mixture modifier after reacting for 20 min.

[0043] 5) The warm-mix in-situ thermally recycled asphalt mixture modifier is conveyed to the twin-screw extruder through the discharge port of the reaction tank. The heating temperature of the twin-screw extruder is maintained at 150℃. The environmentally friendly warm-mix waste rubber powder-based asphalt mixture modifier is formed into 3mm warm-mix in-situ thermally recycled asphalt mixture modifier particles through the twin-screw extruder discharge port air cooling device to reduce the particle temperature to no more than 80℃. After cooling, the warm-mix in-situ thermally recycled asphalt mixture modifier particles are uniformly coated with a composite release agent (20% palmitamide propyl dimethylamine lactate, 25% sodium di(2-ethylhexyl) succinate sulfonate and 55% talc).

[0044] The exhaust pipe of the development tank is connected to the inlet pipe of the reaction tank, and the exhaust pipe of the reaction tank is connected to spray tower 1. Spray tower 1 is connected to spray tower 2. The spray liquid in spray tower 1 is a 5% NaOH aqueous solution, and the spray liquid in spray tower 2 is a 5% H2SO4 aqueous solution. The exhaust gas discharged from the reaction tank passes through spray tower 1 and spray tower 2, is dehydrated by a dryer, and then passes through a regenerative thermal oxidizer to remove the remaining pollutants and VOCs before being discharged after meeting the emission standards.

[0045] The prepared modifier was used in AC-13 asphalt mixture tests at an addition rate of 3% of the aggregate. The optimal asphalt-aggregate ratio was determined to be 4.1 (PVA aged asphalt). The mixing temperature was 145℃, and the performance of the mixture was tested.

[0046] Example 4:

[0047] The modifier was prepared in the same way as in Example 3. The prepared modifier was used in the AC-13 asphalt mixture test. The amount added was 3% of the aggregate. The optimal asphalt-aggregate ratio was determined to be 4.1 (3.1% of PVA aged asphalt and 1% of unaged 70# base asphalt). The amount of regenerator added was 1.5% of the mixture amount. The mixing temperature was 145℃. The performance of the mixture was tested.

[0048] Example 5:

[0049] Without adding modifiers, the optimal asphalt-aggregate ratio was determined to be 4.9 (of which 3.9% was PVA-aged asphalt and 1% was unaged 70# base asphalt). The amount of recycling agent added was 1.5% of the mixture weight. The mixing temperature was selected as 165℃, and the performance of the mixture was tested.

[0050] The performance tests are shown in the table below, and the test methods refer to relevant standards.

[0051] The performance is as follows:

[0052]

[0053]

Claims

1. A method for preparing a warm-mix in-situ thermally recycled asphalt mixture modifier, characterized in that, The modifier comprises: 90# base asphalt, coumarone-indene resin, waste rubber powder, linear 30 / 70 type SBS, 4,4'-dithiodimorpholine, butyl propionate, polyalphaolefin, N-(2-hydroxyethyl)dodecylamide, cocamidopropyl betaine, and a composite release agent; the coumarone-indene resin has a softening point of not less than 80-100℃; the composite release agent is composed of 10-20wt% palmitamide propyl dimethylamine lactate, 20-25wt% sodium di(2-ethylhexyl)succinate sulfonate, and 55-70wt% talc. The preparation method includes the following steps: 1) Weigh 100 parts by weight of 90# base petroleum asphalt and add it to the development tank. Purge with nitrogen and stir at 500 rpm for 5 minutes at 230-250℃. Add 40-50 parts by weight of coumarone-indene resin and continue stirring for 10 minutes. Then add 100-150 parts by weight of waste rubber powder in batches. After the addition is complete, stir at 1000-2000 rpm for 60-90 minutes at 230-250℃. 2) Weigh 20-30% of the mass of 90# base petroleum asphalt and add linear 30 / 70 type SBS to the above-mentioned development tank. Maintain the reaction temperature at 230-250℃ and stir the reaction at 1000-2000 rpm for 30 minutes under nitrogen protection. 3) Pump the product obtained in step 2) into the reaction tank using a high-viscosity asphalt pump. At the same time, add 0.3-0.5% of 4,4'-dithiodimorpholine by weight of waste rubber powder. Maintain the temperature of the reaction tank at 230-250℃, adjust the shear rate to 6000-8000 rpm, purge with nitrogen for protection, increase the pressure of the reaction tank to 3-5 MPa, and stir the reaction for 30-60 minutes. 4) Purge with nitrogen to maintain a pressure of 3-5 MPa, lower the reaction temperature to 200℃±10℃, adjust the shear rate to 1000-2000 rpm, and add 5-10% by weight of waste rubber powder, 3-5% of polyalphaolefin, 3-5% of N-(2-hydroxyethyl)dodecylamide, and 2-3% of cocamidopropyl betaine to the reaction vessel. React for 20-30 min. 5) The material is conveyed to the twin-screw extruder through the discharge port of the reaction tank. The heating temperature of the twin-screw extruder is maintained at 130-150℃. The material is extruded into 2-3mm granules through the twin-screw extruder. The temperature of the granules is reduced to 50-80℃ by the air-cooling device at the discharge port of the twin-screw extruder, and the granules are uniformly coated with the composite release agent.

2. The preparation method according to claim 1, characterized in that, The waste rubber powder needs to be preheated to 80-100℃, and the specifications are radial tire rubber powder with a mesh size of 60-80 mesh.

3. The preparation method according to claim 1, characterized in that, The polyalphaolefin type is one or more of PAO8, PAO9, PAO10 and PAO25.

4. The preparation method according to claim 1, characterized in that, The exhaust pipe of the development tank is connected to the inlet pipe of the reaction tank, the exhaust pipe of the reaction tank is connected to spray tower 1, and spray tower 1 is connected to spray tower 2. The spray liquid of spray tower 1 is a 2-5% NaOH aqueous solution, and the spray liquid of spray tower 2 is a 2-5% H2SO4 aqueous solution. The exhaust gas discharged from the reaction tank passes through spray tower 1 and spray tower 2, is dehydrated by a dryer, and then passes through a regenerative thermal oxidizer to remove the remaining VOCs in the exhaust gas before being discharged after meeting the standards.

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