Hot-mix recycled asphalt mixture with modified reinforcing agent and process for making

Abstract

The application discloses a hot-mixing recycled asphalt mixture containing a modified reinforcing agent and a preparation process, and belongs to the field of asphalt materials. The hot-mixing recycled asphalt mixture containing the modified reinforcing agent comprises the following components in terms of weight parts: 35-56 parts of asphalt mixture recycling material, 1-10 parts of the modified reinforcing agent, 130-210 parts of aggregate, and 6-9 parts of soft asphalt. The modified reinforcing agent is prepared by free radical polymerization reaction of ethenylized mineral powder, styrene, alpha-olefin and alkenyl isocyanate with a mass ratio of (50-100):(2-4):(2-4):(1-3). The application solves the problem of dispersibility of the mineral powder, enhances the cohesive force between the aged asphalt and the soft asphalt, omits the addition of a recycling agent, and strengthens the performance of the recycled asphalt mixture.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of asphalt materials, and particularly relates to hot-mixed reclaimed asphalt mixture containing modified reinforcing agent and a preparation process. BACKGROUND

[0002] Asphalt pavement is the main form of high-grade pavement in China, and has the advantages of good flatness, low noise, convenient construction, easy maintenance and the like. At present, the asphalt pavement mileage accounts for more than 90% of the total high-grade pavement mileage in China. According to the design service life and actual service effect of the asphalt pavement, the early built highways are seriously damaged, and most of them have entered the period of major and medium repair. Therefore, the highway management department faces the arduous task of reconstruction and a large amount of disposal pressure of reclaimed asphalt pavement (RAP). Since the quantity of early asphalt mixture recycling material is not large and the asphalt recycling technology is not mature, the highway management department often adopts the ways of direct disposal landfill or use in low-grade pavement and high-grade pavement base for disposal. In this way, on the one hand, the waste accumulation will occupy a large area of land and cause great damage and pollution to the surrounding environment; on the other hand, these ways will cause serious resource waste, greatly increase the mining intensity of new mineral materials and the amount of new asphalt, and increase the cost.

[0003] The colloidal structure of asphalt is closely related to the technical properties of asphalt. It is found that the process of asphalt aging is mainly the process of change of chemical components. With the aging of asphalt, asphaltene increases, aromatic fraction decreases, and colloid decreases, thereby leading to the decrease of penetration, the increase of softening point, and the decrease of ductility. Generally, the process of asphalt recycling is to add a recycling agent to the aged asphalt to adjust the relative content change of chemical components of the asphalt due to aging, so as to restore the service performance of the asphalt. However, it is also found that although all recycling agents have a softening effect on aged asphalt, only a few can activate the physical and chemical properties of the aged asphalt, that is, although the recycling agent makes the aged asphalt can be used again, since the recycling asphalt is oxidized during the service life, more carbonyl and sulfoxide groups are generated, and the change of groups is not large after the recycling by the recycling agent, so the various physical and chemical properties of the asphalt pavement material mixed with the recycling asphalt are obviously decreased.

[0004] On the other hand, the mineral powder is generally added in the asphalt mixture as a filler, and the appropriate high-quality mineral powder fills the mineral aggregate voids, which can reduce the void ratio of the mixture, improve the compactness of the mixture, and improve the strength, stability and adhesion of the mixture, thus enhancing the ability of the asphalt mixture to resist external destructive forces, thereby increasing the service life of the road. However, as an inorganic powder, the mineral powder generally has the following characteristics: large specific surface area and high surface energy, which makes it prone to agglomeration in the composite material and difficult to disperse uniformly, and its adding effect cannot be fully exerted. The hydrophilic and oleophobic nature of the surface of the inorganic powder makes it difficult to be compatible with the organic system, and it agglomerates in the matrix material due to its high surface energy, and it is difficult to disperse uniformly, and its function cannot be fully exerted. SUMMARY

[0005] In order to overcome the shortcomings of the prior art, the present application provides a hot-mixed recycled asphalt mixture containing a modified reinforcing agent and a preparation process.

[0006] The hot-mixed recycled asphalt mixture containing a modified reinforcing agent provided by the present application comprises the following components: 35-56 parts of asphalt mixture recycling material, 1-10 parts of modified reinforcing agent, 130-210 parts of aggregate, and 6-9 parts of soft asphalt. The modified reinforcing agent is prepared by free radical polymerization of ethylenated mineral powder, styrene, alpha-olefin and alkenyl isocyanate with a mass ratio of (50-100):(2-4):(2-4):(1-3).

[0007] Preferably, the ethylenated mineral powder is prepared by surface modification of the mineral powder with a vinyl silane coupling agent.

[0008] Preferably, the preparation method of the ethylenated mineral powder is as follows: weigh the mineral powder and calcine it at 300-500℃ for 1-4h, mix the vinyl silane coupling agent with an ethanol solution, adjust the pH to 4-5 by adding acetic acid, stir, add the mineral powder to the stirrer while spraying the silane coupling agent solution, continue stirring for 10-60min after the spraying is completed, and then dry again at 30-60℃ to obtain the ethylenated mineral powder.

[0009] Preferably, the mass ratio of the vinyl silane coupling agent to the mineral powder is (2-5):100.

[0010] Preferably, the alpha-olefin is selected from alpha-olefins with a carbon chain length of 6-18 carbon atoms.

[0011] Further preferably, the alpha-olefin is selected from at least one of 1-hexene, 1-octene and 1-octadecene.

[0012] Preferably, the alkenyl isocyanate is selected from at least one of 3-isocyanate propylene or isocyanate ethyl acrylate.

[0013] Preferably, the vinyl silane coupling agent is at least one of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, vinylmethyldimethoxysilane, and vinyltriisopropoxysilane.

[0014] Preferably, the soft pitch is pitch with a penetration of 90-110.

[0015] Preferably, the conditions of the radical polymerization reaction are anhydrous and anaerobic atmosphere, azobisisobutyronitrile as initiator, and heating and stirring for 12-24 hours at 60-80°C.

[0016] Preferably, the specific conditions of the radical polymerization reaction are: dispersing the dehydrated vinylated mineral powder, styrene, alpha-olefin, and azobisisobutyronitrile in dehydrated tetrahydrofuran under nitrogen atmosphere, stirring and dispersing, purging with nitrogen for 10-60 min, then heating to 60-80°C and stirring for 6-12 hours, adding alkenyl isocyanate and continuing the reaction for 6-12 hours, cooling after the reaction, filtering, washing the solid with dehydrated toluene and dehydrated tetrahydrofuran respectively, vacuum drying to constant weight, quickly discharging after cooling and packaging in aluminum foil bags to obtain the modified reinforcing agent.

[0017] Another object of the present application is to protect a preparation process of hot-mixed recycled asphalt mixture containing a modified reinforcing agent, comprising the following steps:

[0018] (1) Analysis of asphalt mixture recycling material composition: extracting the asphalt mixture recycling material, determining the asphalt content, screening the old aggregate after centrifugal extraction, and analyzing the screening grading results;

[0019] (2) Pre-treatment preheating: grading and screening the aggregate and mineral powder according to the old aggregate screening grading results of step S1 and design requirements; heating the asphalt mixture recycling material to 130-150°C, heating the aggregate to 160-180°C, and heating the asphalt to 145-165°C to remove moisture;

[0020] (3) Mixing: adding the preheated asphalt to the asphalt mixture recycling material and stirring for 80-100 s, then adding the aggregate and the modified reinforcing agent and continuing to stir for 80-150 s.

[0021] Still another object of the present application is to protect the application of the hot-mixed recycled asphalt mixture containing the modified reinforcing agent in road engineering.

[0022] Advantages

[0023] The present application provides a modified reinforcing agent hot-mixed recycled asphalt mixture and a preparation process, which has the following beneficial effects: on the one hand, the soft asphalt containing a high content of soft components is mixed with the asphalt mixture recycling material to perform hot-mixed recycling, the aged asphalt particles are softened, and the recycling of the asphalt mixture recycling material is realized, but at this time, due to the addition of the aged asphalt, the physicochemical properties of the hot-mixed recycled asphalt mixture will be affected. Therefore, the comb-shaped polymer modified mineral powder is added to the hot-mixed recycled asphalt mixture as a reinforcing agent, the comb-shaped polymer on the surface of the mineral powder has a phenyl group, a long carbon chain and an isocyanate group, the phenyl group is combined with the aromatic group in the asphalt through a π-π bond, the compatibility and cohesion between the mineral powder and the asphalt are improved, the long carbon chain provides hydrophobicity and flexibility, the crystallinity of the surface modification group is reduced, and the isocyanate group (-NCO) can react with the active hydrogen-containing groups such as carbonyl and sulfoxide in the aged asphalt, the aged asphalt molecules are re-crosslinked to form a chemical crosslinking network, and the physicochemical properties are improved. At the same time, the interfacial bonding strength between the mineral powder and the asphalt is also significantly improved, the proportion of free asphalt is reduced, the cohesion between the aged asphalt and the soft asphalt is enhanced on the basis of solving the problem of dispersion of the mineral powder, the addition of the recycling agent is omitted, and the performance of the recycled asphalt mixture is improved. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The infrared spectra of the mineral powder and the modified reinforcing agent. DETAILED DESCRIPTION

[0025] The following is a more detailed description of the specific implementation method of the present application, which is intended to illustrate the concept and characteristics of the present application, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made in accordance with the spirit and essence of the present application shall be covered within the protection scope of the present application.

[0026] In the examples, the experimental methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used can be obtained from commercial channels unless otherwise specified.

[0027] The raw materials and equipment used in the examples and comparative examples are described as follows:

[0028] Asphalt mixture recycling material: based on the Guangming Expressway pavement repair project, the asphalt mixture recycling material collected from the Guangming Expressway pavement repair project (Tanlang Interchange-Gaocun Interchange) east of the Foshan Tanlang Interchange and ending at the Gaocun Interchange section of the upper layer of the Foshan Gaoming District Genghe Town after milling;

[0029] Mineral powder: S95 mineral powder, purchased from Dongguan Lihui Mineral Products Co., Ltd.;

[0030] Vinyl silane coupling agent: vinyl triethoxysilane, commercially available;

[0031] Alpha-olefin 1: 1-octadecene, commercially available;

[0032] Alpha-olefin 2: 1-hexene, commercially available;

[0033] Alkenyl isocyanate 1: 3-isocyanatopropene, commercially available;

[0034] Alkenyl isocyanate 2: isocyanate ethyl acrylate, commercially available;

[0035] Modified reinforcing agent 1: self-made, the preparation method is as follows: 100 parts by weight of mineral powder is calcined at 400℃ for 2h, 2 parts by weight of vinyl silane coupling agent is mixed with 100 parts by weight of ethanol solution (volume concentration 95%) to form a solution, acetic acid is added to adjust the pH to 4-5, stirring for 1h, the mineral powder is added into the blender while spraying the silane coupling agent solution, after the spraying is completed, continue to stir for 60min, then dry again at 60℃, and the vinylized mineral powder is obtained;

[0036] In a nitrogen atmosphere, 50 parts by weight of the dehydrated vinylized mineral powder, 2 parts by weight of styrene, 4 parts by weight of 1-octadecene, and 0.2 parts by weight of azobisisobutyronitrile are dispersed in 30 parts by weight of dehydrated tetrahydrofuran, stirred and dispersed, purged with nitrogen for 30min, then heated to 70℃ with a stirring rate of 300rpm, reacted for 12 hours, 3 parts by weight of 3-isocyanatopropene is added, and the reaction continues for 12 hours, after the reaction is completed, the temperature is lowered, filtered, and the solid is washed with dehydrated toluene and dehydrated tetrahydrofuran three times respectively, vacuum dried at 60℃ to constant weight, after cooling, quickly discharged and packaged in aluminum foil bags, and the modified reinforcing agent 1 is obtained.

[0037] The mineral powder and the modified reinforcing agent are respectively subjected to Fourier transform infrared spectroscopy determination: KBr tabletting method is used to prepare the sample, KBr (analytical pure) is dried, usually dried in an oven at 120℃ for 4 hours, then placed in a desiccator to cool for standby; the agate mortar and grinding rod are cleaned and dried with alcohol cotton, the potassium bromide is ground into powder, then the mineral powder and the modified reinforcing agent sample are respectively ground until they are completely mixed, and finally the tablet press is pressed into shape (transparent sheet) for infrared spectrum test, and the test results are shown in Figure 1 It can be seen that the stretching vibration absorption peak of hydroxyl-OH at 3621cm -1 of the modified reinforcing agent is weaker than that of the mineral powder, which is because the silicon hydroxyl after hydrolysis of the silane coupling agent is condensed with the hydroxyl on the surface of the mineral powder to form a silicon-oxygen-silicon bond, and the absorption peak of Si-O-Si is detected at 818cm -1 In addition, the methylene CH2alkane symmetric stretching vibration and anti-symmetric stretching vibration peaks are detected at 2871cm -1 and 2913cm -1The characteristic peak of isocyanate group NCO was detected, but the characteristic peak of styrene benzene ring skeleton was not detected due to the strong anti-symmetrical stretching vibration of the mineral powder itself at 1430 cm -1 The characteristic peak of isocyanate group NCO was detected, but the characteristic peak of styrene benzene ring skeleton was not detected due to the strong anti-symmetrical stretching vibration of the mineral powder itself at 1430 cm

[0038] Modified reinforcing agent 2: self-made, the difference between the preparation method and modified reinforcing agent 1 is that 1-octadecene carbon is replaced by 1-hexene;

[0039] Modified reinforcing agent 3: self-made, the difference between the preparation method and modified reinforcing agent 1 is that 3-isocyanate propylene is replaced by isocyanate ethyl acrylate;

[0040] Modified reinforcing agent 4: self-made, the difference between the preparation method and modified reinforcing agent 1 is that the addition amount of styrene is 4 parts by weight, and the addition amount of 1-octadecene carbon is 2 parts by weight;

[0041] Modified reinforcing agent 5: self-made, the difference between the preparation method and modified reinforcing agent 1 is that the addition amount of 3-isocyanate propylene is 1 part by weight;

[0042] Modified reinforcing agent 6: self-made, the difference between the preparation method and modified reinforcing agent 1 is that 3-isocyanate propylene is not added;

[0043] Modified reinforcing agent 7: self-made, the difference between the preparation method and modified reinforcing agent 1 is that 1-octadecene carbon is not added;

[0044] Modified reinforcing agent 8: self-made, the difference between the preparation method and modified reinforcing agent 1 is that styrene is not added;

[0045] Soft asphalt 1: meets the index requirements in “Highway Asphalt Pavement Construction Technical Specification” (JTG F40-2004), and the asphalt is No. 90 heavy traffic asphalt;

[0046] Soft asphalt 2: meets the index requirements in “Highway Asphalt Pavement Construction Technical Specification” (JTG F40-2004), and the asphalt is No. 110 heavy traffic asphalt;

[0047] Soft asphalt 3: meets the index requirements in “Highway Asphalt Pavement Construction Technical Specification” (JTG F40-2004), and the asphalt is No. 70 heavy traffic asphalt;

[0048] Coarse aggregate: granite, 10-30 mm, from Guangdong Xijiang along the line;

[0049] Machine-made sand: from Guangdong Xijiang along the line;

[0050] Unless otherwise specified, the component raw materials used in the embodiments and comparative examples of the present application are all commercially available raw materials, and the component raw materials used in each parallel experiment are all the same.

[0051] Examples and Comparative Examples

[0052] Asphalt mixture recycling material component analysis: 5 groups of asphalt mixture recycling materials were extracted and separated with trichloroethylene as the solvent to determine the asphalt content. The old aggregate after centrifugal extraction was sieved, and the sieving gradation results were analyzed. The results are shown in Table 1.

[0053] Pre-treatment preheating: according to the old aggregate sieving gradation results of step S1, the aggregate and mineral powder were graded and sieved according to the design requirements. The results are shown in Tables 2 and 3. The asphalt mixture recycling material was heated to 140℃, the aggregate was heated to 170℃, and the asphalt was heated to 155℃ to remove moisture.

[0054] Mixing: the preheated asphalt was added to the asphalt mixture recycling material and stirred for 100s, then the aggregate and the modified reinforcing agent were added and continued to stir for 120s.

[0055] Table 1 Oil-stone ratio of asphalt mixture recycling material

[0056]

[0057] Table 2 Gradation of old aggregate

[0058] Mesh size (mm) 19 16 13.2 9.5 4.75 2.36 1.18 0.6 0.3 0.15 0.075 Pass rate 100 100 95.2 61.3 44.5 35.6 16.6 8.3 15.9 5.9 3.6

[0059] As can be seen from Table 2, the recycled coarse aggregate has a small particle size due to long-term compaction, and needs to be mixed with coarse aggregate of large particle size and machine-made sand to meet the gradation requirements. The aggregate gradation after mixing is shown in Table 3.

[0060] Table 3 Aggregate gradation after mixing

[0061] Mesh size (mm) 19 16 13.2 9.5 4.75 2.36 1.18 0.6 0.3 0.15 0.075 Pass rate 100 90.6 71.2 60.7 40.1 31.9 20.1 16.0 10.9 8.6 5.5

[0062] The ratio of the hot-mixed recycled asphalt mixture of the examples and the comparative examples is shown in Table 4:

[0063] Table 4 Ratio of hot-mixed recycled asphalt mixture of examples and comparative examples (parts by weight)

[0064]

[0065]

[0066]

[0067] The hot-mixed recycled asphalt mixture prepared in the examples and the comparative examples was tested for the following properties, and the results are shown in Table 5, which are as follows:

[0068] (1)Penetration: Reference JTG E20-2011 "Highway Engineering Asphalt and Asphalt Mixture Test Procedures" T0604-2011 "Asphalt Penetration Test" to test hot mix recycled asphalt mixture; test conditions: temperature 25℃, load 100g, penetration time 5s;

[0069] (2) Marshall stability: Reference JTG E20-2011 "Highway Engineering Asphalt and Asphalt Mixture Test Procedures" T0709-2011 "Asphalt Mixture Marshall Stability Test" to test hot mix recycled asphalt mixture;

[0070] (3) Freeze-thaw splitting performance: Reference JTG E20-2011 "Highway Engineering Asphalt and Asphalt Mixture Test Procedures" T0729-2000 "Asphalt Mixture Freeze-thaw Splitting Test" to test hot mix recycled asphalt mixture;

[0071] (4) Rutting test: Reference JTG E20-2011 "Highway Engineering Asphalt and Asphalt Mixture Test Procedures" T0719-2011 "Asphalt Mixture Rutting Test" to test hot mix recycled asphalt mixture, test temperature 60℃, wheel pressure 0.7MPa.

[0072] Table 5 Performance test of hot mix recycled asphalt mixture

[0073]

[0074]

[0075] From the results of the examples and comparative examples, it can be seen that the modified reinforcing agent obtained by using styrene, long-chain olefin and isocyanate modified mineral powder improves the dispersibility of the mineral powder, and the active isocyanate groups therein can cross-link the active hydrogen-containing groups such as carbonyl and sulfoxide of aged asphalt, thereby increasing the interfacial cohesive force between new asphalt, aged asphalt and mineral powder.

[0076] From Examples 1, 3 and 4, it can be seen that since no other recycling agent is added in the present application, soft asphalt with high penetration is needed to melt and depolymerize the aged asphalt. When the penetration is low, the aged asphalt that is not completely depolymerized will have a negative impact on the low-temperature crack resistance and Marshall stability of the mixture through mechanisms such as brittle enhancement, adhesion deterioration and uneven dispersion; but when the penetration is too high, it will affect the high-temperature stability of the asphalt mixture, thereby affecting the rutting resistance.

[0077] From Examples 2 and 5, it can be seen that short-chain hexene modified mineral powder will reduce the molecular chain entanglement between the surface modification groups, thereby reducing the flexibility of the surface modification groups and slightly reducing the compatibility with asphalt.

[0078] From the examples 2, 6, 8 and the comparative example 2, it can be seen that the isocyanate acrylate and the isocyanate acryl have strong cross-linking ability, and too little or no isocyanate acryl in the surface modification group will have a significant impact on the physicochemical properties of the hot-mixed reclaimed asphalt.

[0079] The preferred embodiments of the application disclosed above are only used to help explain the application. The preferred embodiments do not describe all the details and limit the application to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of the specification. The specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the application, so that those skilled in the art can well understand and utilize the application. The application is limited only by the claims and their full scope and equivalents.

Claims

1. Hot mix recycled asphalt mixture containing a modified reinforcing agent, characterized in that, By weight, including the following components: asphalt mixture recycling 35~56 parts, modified reinforcing agent 1~10 parts, aggregate 130~210 parts, soft pitch 6~9 parts, the modified reinforcing agent is prepared by free radical polymerization of ethylenic mineral powder, styrene, alpha-olefin and alkenyl isocyanate with mass ratio of (50~100):(2~4):(2~4):(1~3), and the alpha-olefin is selected from alpha-olefin with carbon chain length of 6~18 carbon atoms.

2. The hot mix recycled asphalt mixture containing a modified enhancer of claim 1, wherein, The ethylenic mineral powder is prepared by surface modification of mineral powder with vinyl silane coupling agent.

3. The hot mix recycled asphalt mixture containing a modified enhancer of claim 1, wherein, The alpha-olefin is selected from at least one of 1-hexene, 1-octene and 1-octadecene.

4. The hot mix recycled asphalt mixture containing a modifying enhancer of claim 1, wherein, The alkenyl isocyanate is selected from at least one of 3-isocyanate propylene or isocyanate ethyl acrylate.

5. The hot mix recycled asphalt mixture containing a modifying enhancer as recited in claim 2, wherein, The vinyl silane coupling agent is at least one of vinyl trimethoxysilane, vinyl triethoxysilane, vinyl tri(2-methoxyethoxy)silane, vinyl methyl dimethoxysilane and vinyl triisopropoxysilane.

6. The hot mix recycled asphalt mixture containing a modifying enhancer of claim 1, wherein, The soft pitch is pitch with penetration of 90~110.

7. The hot mix recycled asphalt mixture containing a modifying enhancer of claim 1, wherein, The conditions of the free radical polymerization reaction are anhydrous and anaerobic atmosphere, azobisisobutyronitrile as initiator and heating and stirring for 12~24 hours at 60~80℃.

8. The process for preparing a hot mix recycled asphalt mixture containing a modifying enhancer as claimed in any one of claims 1 to 7, wherein, Including the following steps: (1) Component analysis of asphalt mixture recycling: extract the asphalt mixture recycling, determine the asphalt content, sieve the old aggregate after centrifugal extraction, and analyze the sieve grading results; (2) Pre-treatment preheating: according to the old aggregate sieve grading results of step S1, grade the aggregate and mineral powder according to the design requirements, sieve, heat the asphalt mixture recycling to 130~150℃, heat the aggregate to 160-180℃, and heat the asphalt to 145~165℃, remove the moisture; (3) Mixing: add the preheated asphalt to the asphalt mixture recycling and stir for 80~100 s, then add the aggregate and the modified reinforcing agent and continue to stir for 80~150 s.

9. Application of the hot-mixed recycled asphalt mixture containing modified reinforcing agent according to any one of claims 1~7 in road engineering.

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