Preparation method of warm-mixing regenerated SMA asphalt mixture

Abstract

The invention discloses a preparation method of a warm-mixing regenerated SMA asphalt mixture, which comprises the following steps: 1) flexibly separating recycled old materials into old materials with particle sizes of more than two grades to obtain the old materials; 2) heating the SBS modified asphalt to 135-145 DEG C, adding a composite warm mixing agent, and stirring for 20-30 minutes to obtain warm mixed modified asphalt; 3) heating the new aggregate and the mineral powder to 135-145 DEG C by adopting a heat radiation heating mode; 4) performing two-stage activation on the old material, adding the new aggregate and the wood fiber, performing dry stirring for 20-30 seconds, adding the warm-mixed modified asphalt, performing stirring for 20-30 seconds, finally adding the mineral powder, performing stirring for 20-30 seconds, and controlling the discharging temperature to be 130-140 DEG C; the two-stage activation step of the old material comprises the following steps: drying the old material for 40-90 minutes at the temperature of 70-80 DEG C; then heating to 120-130 DEG C, adding porous powder quartz powder, and keeping the temperature for 20-30 minutes; according to the invention, the recycled old material is utilized, the asphalt content of the SMA concrete is reduced, and the new aggregate is used, so that the effects of reducing cost and improving efficiency are achieved; the mixing temperature is reduced, the environmental protection property is improved, and the energy consumption is reduced; and a regenerant is not needed, so that the stability and low temperature resistance of the pavement are improved.

Description

Technical Field

[0001] The present invention relates to a preparation method of warm mix recycled SMA asphalt mixture, belonging to the technical field of pavement environmental protection and energy-saving materials. Background Art

[0002] SMA asphalt mastic mixture is a kind of asphalt surface mixture that is widely recognized (used more) internationally at present, with strong anti-deformation ability and good durability. Due to the good interlock of coarse aggregates, the mixture has very good high-temperature rutting resistance. At the same time, due to the bonding effect of asphalt mastic, the low-temperature deformation performance and water stability are also greatly improved. The gap-graded aggregate forms large pores on the surface, with large texture depth and good skid resistance. At the same time, the void ratio of the mixture is very small, and the anti-aging performance and durability are very good, thus comprehensively improving the road performance of asphalt mixture, and it is commonly used in high-grade pavements such as expressways and national highways.

[0003] However, SMA asphalt mastic mixture still has many disadvantages, such as:

[0004] 1. High cost: The cost of SMA asphalt mixture is high, and it is generally only used in expressways;

[0005] 2. Poor environmental protection and energy-saving performance: The heating temperature of traditional SMA reaches 175 - 185 °C, with large energy consumption and emissions;

[0006] 3. Poor low-temperature performance;

[0007] 4. Need to use a rejuvenator, otherwise the road surface is easy to disperse and the flying loss is large;

[0008] On the other hand, the total mileage of highways in China has reached 5.2 million kilometers, and it is entering the era of highway maintenance and major repairs. It is estimated that only for the major repairs of arterial highways in China, 160 million tons of asphalt mixture recycled materials are generated every year. How to dispose of these old materials has become an urgent problem to be solved in the highway industry. Summary of the Invention

[0009] The present invention provides a preparation method of warm mix recycled SMA asphalt mixture, which reduces the asphalt content of SMA concrete and the use of new aggregates through the utilization of recycled materials, achieving the effect of cost reduction and efficiency improvement; reduces the mixing temperature, improves environmental protection, and saves energy consumption; and does not need to use a rejuvenator, improving the stability and low-temperature resistance of the road surface.

[0010] To solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0011] A preparation method of warm mix recycled SMA asphalt mixture, comprising the following steps:

[0012] 1) Flexibly separate the recycled materials into two or more particle sizes to obtain recycled materials;

[0013] 2) Heat the SBS modified asphalt to 135 - 145 °C, add the composite warm mix agent, and stir for 20 - 30 min to obtain the warm mix modified asphalt;

[0014] 3) Using the thermal radiation heating method, heat the new aggregate and mineral powder to 135 - 145 °C;

[0015] 4) After two - stage activation of the old material, add the new aggregate and wood fiber and dry - mix for 20 - 30 s, then add the warm mix modified asphalt and mix for 20 - 30 s, and finally add the mineral powder and mix for 20 - 30 s. Control the discharge temperature at 130 - 140 °C;

[0016] The two - stage activation steps of the old material include: drying the old material at 70 - 80 °C for 40 - 90 min to remove surface moisture and volatile components; then heating up to 120 - 130 °C, adding porous powder quartz powder and mixing evenly, keeping warm for 20 - 30 min, and releasing the light components in the old asphalt through adsorption to restore fluidity.

[0017] The mixture obtained in this application has no phenomenon of white and flower materials or agglomeration.

[0018] The above two - stage activation steps of the old material can effectively release the internal stress of the old material and improve the fusion degree of new and old asphalt; using infrared spectroscopy to measure the carbonyl index, the change rate of the carbonyl index after two - stage activation is ≥95%.

[0019] This application is for plant - mix hot recycling.

[0020] In the raw materials of the above warm mix recycled SMA asphalt mixture: the mass ratio of new aggregate : mineral powder : old material is (50 - 60) : (5 - 10) : (30 - 45); the mass dosage of SBS modified asphalt is 4.5% - 5.5% of the sum of the masses of new aggregate and mineral powder; the mass dosage of the composite warm mix agent is 0.3% - 0.6% of the mass of SBS modified asphalt; the mass dosage of wood fiber is 0.2% - 0.4% of the mass of SBS modified asphalt; the mass dosage of porous powder quartz powder is 0.2 - 0.3% of the mass of the old material.

[0021] The above new aggregate serves as the main skeleton structure; the composite warm mix agent can reduce the mixing temperature, activate the old asphalt, and improve the properties such as the stability and low - temperature resistance of the mixture; the wood fiber enhances the crack resistance.

[0022] In the above step 2), the composition of the composite warm mix agent is: ethylene bisoleamide (EBO) 40 - 60%, alkylphenol polyoxyethylene ether 2 - 5%, polyoxyethylene fatty acid ester 2 - 5%, lignosulfonate 30 - 50%, graphene oxide 0.5 - 1.5%, thioester 2 - 5% and nano - silica 3 - 8%, and the percentages are mass percentages, and the sum of the masses of each component is 100%.

[0023] The warm mix additive with the specific composition synergizes with porous silica powder to achieve efficient activation of old asphalt under warm mix conditions of 130-140 °C, while achieving efficient low-temperature viscosity reduction (viscosity reduction up to 40%), reducing the construction temperature during the production process, and reducing energy consumption and waste emissions.

[0024] The inventors found in experiments that ethylene bisoleamide (EBO) synergizes with alkylphenol polyoxyethylene ether and alkylphenol polyoxyethylene ether to reduce the interfacial tension between asphalt and aggregates, enabling asphalt to better coat the aggregates, thereby achieving good uniformity and adhesion at a lower mixing temperature, contributing to good workability of the mixture at a lower construction temperature, being easy to stir, spread, and compact, improving construction efficiency and quality. At the same time, it can also increase the dispersibility of each component, make the combination of asphalt and aggregates more compact, improve the overall performance of the mixture, improve the low-temperature performance of the mixture, and enhance the water stability and durability of the mixture. The sulfur atom of thioester can undergo an addition reaction with the unsaturated bonds in asphalt and a substitution reaction with the active hydrogen atoms in asphalt to form a stable cross-linked structure, thereby improving the stability and aging resistance of the mixture; at the same time, graphene oxide and nano-silica form a three-dimensional network structure to play a role in nano-reinforcement, inhibiting the low-temperature embrittlement of asphalt. At the same time, the graphene oxide sheet structure consumes stress through interfacial friction, and lignosulfonate binds to asphalt components through hydrogen bonds to improve low-temperature ductility. And there is an obvious positive promotion effect among the components. While reducing the mixing temperature and operation ease, it also promotes a significant improvement in the performance of the mixture, improves adaptability, and is applicable not only to areas with higher temperatures but also to extremely cold areas.

[0025] The above-mentioned lignosulfonate is preferably sodium lignosulfonate. The thioester is preferably dilauryl thiodipropionate.

[0026] To improve the durability of the mixture, in the above step 2), the warm mix additive further includes 2,6-di-tert-butyl-4-methylphenol (BHT) 0.3-0.5%, and the percentage is by mass, and the sum of the masses of each component is 100%. In this way, it can synergize with other components to delay asphalt aging.

[0027] In the above step 2), the preparation method of the composite warm mix additive is: mixing each material in proportion and grinding to D50≤5μm to form a homogeneous powder.

[0028] To improve the uniformity of the materials, in the above step 2), the stirring speed is 4000-5000 rpm.

[0029] In the above step 1), the recycled old materials are flexibly separated into two particle sizes of 10-15 mm and 0-5 mm with a mass ratio of 5:1, which is convenient for controlling the SMA gradation.

[0030] In step 3) above, the new aggregate is basalt.

[0031] In step 3) above, the grading of the new aggregate is 10 - 15 mm aggregate : 5 - 10 mm aggregate : 0 - 3 mm aggregate = (24 - 26) : (31 - 33) : (4 - 6). The aforementioned ratio is by mass. It can be considered that 5 - 10 includes 5 but not 10, 10 - 15 includes 10 and also 15, 0 - 3 includes 0 and also 3. For the remaining ranges that do not involve common endpoints, they are considered to include the endpoints.

[0032] To further ensure the stability of the mixture, the grading of the above new aggregate, mineral powder and old material, in terms of the mass percentage passing through the square-hole sieve, is as follows: the mineral material passing through the 16 mm square-hole sieve is 100%, the mineral material passing through the 13.2 mm square-hole sieve is 93.4 - 95.0%, the mineral material passing through the 9.5 mm square-hole sieve is 62.5 - 67.5%, the mineral material passing through the 4.75 mm square-hole sieve is 27.0 - 27.7%, the mineral material passing through the 2.36 mm square-hole sieve is 20.5 - 23.1%, the mineral material passing through the 1.18 mm square-hole sieve is 18.7 - 19.0%, the mineral material passing through the 0.6 mm square-hole sieve is 15.1 - 16.0%, the mineral material passing through the 0.3 mm square-hole sieve is 12.3 - 13.0%, the mineral material passing through the 0.15 mm square-hole sieve is 10.6 - 12.0%, and the mineral material passing through the 0.075 mm square-hole sieve is 9.1 - 10.0%.

[0033] Unless otherwise specified in this application, all % are mass percentages.

[0034] Through material innovation and process breakthrough, this application has achieved a balance between low-temperature performance and engineering practicability, and has carried out pilot tests and pavement tests, achieving the expected results.

[0035] For the technologies not mentioned in the present invention, reference is made to the prior art.

[0036] The present invention provides a method for preparing warm mix recycled SMA asphalt mixture. By recycling and using old materials, it reduces the asphalt content of SMA concrete and the use of new aggregates, achieving the effect of cost reduction and efficiency improvement; it reduces the mixing temperature, improves environmental protection, and saves energy consumption; and it does not require a recycling agent, improving the stability and low-temperature resistance of the road surface, and can be used in severe cold areas of -40°C and heavy traffic roads. Brief Description of the Drawings

[0037] Figure 1 It is the grading diagram in Embodiment 1 of the present invention;

[0038] Figure 2 It is the first on-site paving and compaction photo in Embodiment 1 of the present invention;

[0039] Figure 3 It is the second on-site paving and compaction photo in Embodiment 1 of the present invention;

[0040] Figure 4 This is the first pavement performance test photo in Embodiment 1 of the present invention;

[0041] Figure 5 This is the second pavement performance test photo in Embodiment 1 of the present invention; Detailed implementation manners

[0042] To better understand the present invention, the content of the present invention will be further clarified below in conjunction with embodiments. However, the content of the present invention is not limited to the following embodiments.

[0043] Embodiment 1

[0044] The recycled old materials are flexibly separated into three particle size grades as shown in Table 1, and extraction tests are respectively carried out to analyze the asphalt content, and the results are shown in Table 1.

[0045] Table 1 Analysis of old material separation

[0046]

[0047] The first row in the table is the aperture of the square-hole sieve, with the unit of mm. The data in the column where the aperture of each square-hole sieve is located is the passing rate of each grade of old material through the corresponding aperture, with the unit of %.

[0048] Table 2 Gradation of new aggregates and mineral powder

[0049]

[0050]

[0051] The first row in the table is the aperture of the square-hole sieve, with the unit of mm. The data in the column where the aperture of each square-hole sieve is located is the passing rate of each grade of mineral material through the corresponding aperture, with the unit of %.

[0052] Table 3 Gradation of warm-mix recycled SMA asphalt mixture

[0053]

[0054] The first row in the table is the aperture of the square-hole sieve, with the unit of mm. The data in the column where the aperture of each square-hole sieve is located is the passing rate of each grade of mineral material through the corresponding aperture, with the unit of %. The unit of the second column ratio is %, which is the mass ratio.

[0055] A preparation method of warm-mix recycled SMA asphalt mixture includes the following steps:

[0056] 1) Heat the SBS modified asphalt to 135 - 145 °C, add the composite warm-mix agent, and stir at 5000 rpm for 30 min to obtain warm-mix modified asphalt;

[0057] 2) Adopt the thermal radiation heating method to heat the new aggregate and mineral powder to 135 - 145 °C;

[0058] 3) After two - stage activation of the old material, add the new aggregate and wood fiber and dry - mix for 30 s, then add the warm - mix modified asphalt and mix for 30 s, and finally add the mineral powder and mix for 30 s. Control the discharge temperature at 130 - 140 °C;

[0059] The two - stage activation steps of the old material include: drying the old material at a temperature of 70 - 80 °C for 1 h to remove surface moisture and volatile components; then raising the temperature to 120 - 130 °C, adding porous powder quartz powder and mixing evenly, keeping warm for 30 min, releasing the light components in the old asphalt through adsorption to restore fluidity, and using infrared spectroscopy to measure the carbonyl index. The change rate of the carbonyl index after two - stage activation is ≥95%.

[0060] The mass ratio of the new aggregate: mineral powder: old material is 62:8:30; the mass dosage of SBS modified asphalt is 4.7% of the sum of the masses of the new aggregate and mineral powder; the mass dosage of the composite warm - mix agent is 0.5% of the mass of SBS modified asphalt; the mass dosage of wood fiber is 0.3% of the mass of SBS modified asphalt; the mass dosage of porous powder quartz powder is 0.3% of the mass of the old material.

[0061] Composition of the composite warm - mix agent: ethylene bisoleamide (EBO) 50%, nonylphenol polyoxyethylene (10) ether (TX - 10) 2.5%, polysorbate - 80 2.5%, sodium lignosulfonate (CMN, Shanghai Nazhifu Chemical Co., Ltd.) 35%, graphene oxide (LGtO1111, Angxing New Carbon Materials Changzhou Co., Ltd.) 1.5%, dilauryl thiodipropionate 3% and nano - silica (ZL - 330, Shandong Zhonglian Chemical Co., Ltd.) 5%, 2,6 - di - tert - butyl - 4 - methylphenol (BHT) 0.5%. The preparation method of the composite warm - mix agent is: mix each material in proportion and grind to D50 ≤ 5 μm to form a homogeneous powder.

[0062] The SBS modified asphalt is SBS modified asphalt I - D provided by Sinopec. The new aggregate is made of basalt, and the mineral powder is ground from limestone, both provided by Liuan Gongxin Road Materials Co., Ltd. The wood fiber is MZS - 1 type wood fiber provided by Zhenjiang Daoyi Material Technology Co., Ltd. The porous powder quartz powder is provided by Donghai County Fucai Mineral Products Co., Ltd., with an average pore diameter of 8 nm.

[0063] The obtained mixture has no phenomenon of white or flower material and agglomeration.

[0064] Make Marshall specimens (diameter 101.6 mm, height 63.5 mm) and rut - board specimens (300 mm×300 mm×50 mm) at the same discharge, compaction, forming and other temperatures. Detect the performance of the mixture such as stability and rut, and the results are shown in Table 4.

[0065] Mixture transportation and paving: The prepared warm mix recycled SMA asphalt mixture is transported to the construction site with heat preservation measures. During transportation, the temperature of the mixture should not be lower than 120 °C. During paving, the temperature of the paver screed should not be lower than 100 °C, and the paving speed should be controlled at 3 m / min.

[0066] Mixture compaction: Compaction is carried out using a steel wheel roller and a rubber wheel roller. Compaction should be completed when the mixture temperature is not lower than 80 °C. The initial compaction is carried out by the steel wheel roller with static pressure for 2 passes, the re-compaction is carried out by the steel wheel roller with vibratory compaction for 4 passes, and the final compaction is carried out by the rubber wheel roller with static pressure for 2 passes to ensure that the pavement smoothness and compaction degree meet the requirements. Figure 2-5 Photos of on-site paving, compaction and testing.

[0067] Comparative Example 1

[0068] The difference from Example 1 is that: ethylene bisoleate is omitted; in order to improve comparability and ensure that the proportions of other materials remain unchanged as much as possible, ethylene bisoleate is replaced by nonylphenol polyoxyethylene (10) ether (TX-10), that is, the dosage of nonylphenol polyoxyethylene (10) ether (TX-10) is 52.5%, and the rest refer to Example 1.

[0069] Comparative Example 2

[0070] The difference from Example 1 is that: nonylphenol polyoxyethylene (10) ether (TX-10) is omitted; in order to improve comparability and ensure that the proportions of other materials remain unchanged as much as possible, the dosage of polysorbate-80 is increased to 5%, and the rest refer to Example 1.

[0071] Comparative Example 3

[0072] The difference from Example 1 is that: polysorbate-80 is omitted; in order to improve comparability and ensure that the proportions of other materials remain unchanged as much as possible, the dosage of nonylphenol polyoxyethylene (10) ether (TX-10) is increased to 5%, and the rest refer to Example 1.

[0073] Comparative Example 4

[0074] The difference from Example 1 is that: sodium lignosulfonate is omitted; in order to improve comparability and ensure that the proportions of other materials remain unchanged as much as possible, the dosage of ethylene bisoleate is increased to 85%, and the rest refer to Example 1.

[0075] Comparative Example 5

[0076] The difference from Example 1 is that: graphene oxide is omitted; in order to improve comparability and ensure that the proportions of other materials remain unchanged as much as possible, the dosage of nano-silica is increased to 6.5%, and the rest refer to Example 1.

[0077] Comparative Example 6

[0078] The difference from Example 1 is that nano-silica is omitted; in order to improve comparability and ensure that the proportions of other materials remain unchanged as much as possible, the dosage of graphene oxide is increased to 6.5%, and the rest refers to Example 1.

[0079] Comparative Example 7

[0080] The difference from Example 1 is that dilauryl thiodipropionate is omitted; in order to improve comparability and ensure that the proportions of other materials remain unchanged as much as possible, the dosage of ethylene bisoleamide is increased to 53%, and the rest refers to Example 1.

[0081] Example 2

[0082] The difference from Example 1 is that the mass ratio of new aggregate: mineral powder: old material is 52:8:40, and the rest refers to Example 1.

[0083] Performance table of the mixtures obtained in each example in Table 4

[0084]

[0085]

Claims

1. A preparation method of warm mix recycled SMA asphalt mixture, characterized in that: It includes the following steps: 1) Separating the recycled waste materials into two or more particle size grades to obtain waste materials; 2) Heating the SBS modified asphalt to 135 - 145 °C, adding a composite warm mix additive, and stirring for 20 - 30 min to obtain warm mix modified asphalt; 3) Using a thermal radiation heating method to heat the new aggregate and mineral powder to 135 - 145 °C; 4) After two - stage activation of the waste materials, adding the new aggregate and wood fiber and dry - mixing for 20 - 30 s, adding the warm mix modified asphalt and mixing for 20 - 30 s, and finally adding the mineral powder and mixing for 20 - 30 s, with the discharge temperature controlled at 130 - 140 °C; The two - stage activation steps of the waste materials include: drying the waste materials at a temperature of 70 - 80 °C for 40 - 90 min; then raising the temperature to 120 - 130 °C, adding porous silica powder, and keeping warm for 20 - 30 min.

2. The preparation method of the warm mix recycled SMA asphalt mixture according to claim 1, wherein: In the raw materials of the warm mix recycled SMA asphalt mixture: the mass ratio of new aggregate: mineral powder: waste material is (50 - 60):(5 - 10):(30 - 45); the mass dosage of SBS modified asphalt is 4.5% - 5.5% of the sum of the masses of the new aggregate and mineral powder; the mass dosage of the composite warm mix additive is 0.3% - 0.6% of the mass of the SBS modified asphalt; the mass dosage of wood fiber is 0.2% - 0.4% of the mass of the SBS modified asphalt; the mass dosage of porous silica powder is 0.2 - 0.3% of the mass of the waste material.

3. The preparation method of the warm mix recycled SMA asphalt mixture according to claim 1 or 2, characterized in that: In step 2), the composite warm mix additive is composed of: ethylene bisoleamide 40 - 60%, alkylphenol polyoxyethylene ether 2 - 5%, polyoxyethylene fatty acid ester 2 - 5%, lignosulfonate 30 - 50%, graphene oxide 0.5 - 1.5%, thioester 2 - 5%, and nano - silica 3 - 8%, and the percentages are mass percentages, and the sum of the masses of each component is 100%.

4. The preparation method of the warm mix recycled SMA asphalt mixture according to claim 3, characterized in that: In step 2), the warm mix additive also includes 2,6 - di - tert - butyl - 4 - methylphenol 0.3 - 0.5%, and the percentages are mass percentages, and the sum of the masses of each component is 100%.

5. The preparation method of the warm mix recycled SMA asphalt mixture according to claim 3, characterized in that: In step 2), the preparation method of the composite warm mix additive is: mixing each material in proportion and grinding to D50 ≤ 5 μm to form a homogeneous powder.

6. The preparation method of the warm mix recycled SMA asphalt mixture according to claim 1 or 2, characterized in that: In step 2), the stirring speed is 4000 - 5000 rpm.

7. The preparation method of the warm mix recycled SMA asphalt mixture according to claim 1 or 2, characterized in that: In step 1), the recycled waste materials are flexibly separated into two particle size grades of 10 - 15 mm and 0 - 5 mm with a mass ratio of 5:

1.

8. The preparation method of the warm mix recycled SMA asphalt mixture according to claim 1 or 2, characterized in that: In step 3), the new aggregate is basalt.

9. The preparation method of the warm mix recycled SMA asphalt mixture according to claim 1 or 2, characterized in that: In step 3), the gradation of the new aggregate is 10 - 15 mm aggregate: 5 - 10 mm aggregate: 0 - 3 mm aggregate = (24 - 26):(31 - 33):(4 - 6), and the aforementioned ratio is a mass ratio.

10. The preparation method of the warm mix recycled SMA asphalt mixture according to claim 1 or 2, characterized in that: The new aggregate, mineral powder and old material gradations, expressed as the mass percentage passing through the square-hole sieve, are as follows: the mineral material passing through the 16-mm square-hole sieve is 100%, the mineral material passing through the 13.2-mm square-hole sieve is 93.4 - 95.0%, the mineral material passing through the 9.5-mm square-hole sieve is 62.5 - 67.5%, the mineral material passing through the 4.75-mm square-hole sieve is 27.0 - 27.7%, the mineral material passing through the 2.36-mm square-hole sieve is 20.5 - 23.1%, the mineral material passing through the 1.18-mm square-hole sieve is 18.7 - 19.0%, the mineral material passing through the 0.6-mm square-hole sieve is 15.1 - 16.0%, the mineral material passing through the 0.3-mm square-hole sieve is 12.3 - 13.0%, the mineral material passing through the 0.15-mm square-hole sieve is 10.6 - 12.0%, and the mineral material passing through the 0.075-mm square-hole sieve is 9.1 - 10.0%.

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