Emulsified asphalt cold recycled mixture and preparation method thereof
By using emulsified asphalt cold regeneration mixture in the cold regeneration mixture, combining old material reducing agents of trihydroxymethylmethane and nanosilica sol and modified agents that trigger reactions in stages, the problems of low strength of cold regeneration mixture and insufficient utilization of old bitumen are solved, and the high strength and salt resistance of the mixture are significantly improved.
Patent Information
- Application Number
- CN202510036245.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-09
- Publication Date
- 2025-04-08
AI Technical Summary
The cold recycled mixture has a low strength, a long maintenance cycle, difficult to collect cores in the early stages, difficult to form, and insufficient utilization of old asphalt.
Emulsified asphalt cold regeneration mixture is used, including old materials, modifiers and old materials reducing agents, among which the old materials reducing agent is a mixture of trihydroxymethylmethane and nanosilica sol. The modifier is prepared by initiating reactions in stages to form a modifier with a hard core shell with high viscosity.
The stability, splitting strength, durability, cold resistance and water resistance of the recycled asphalt mixture are significantly improved, and the salt resistance is significantly improved.
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Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of road solid waste recycling and relates to an emulsified asphalt cold recycled mixture and a preparation method thereof. Background Art
[0002] With the rapid development of my country's social economy and urban construction, the transportation industry, such as roads, highways and bridges, has inevitably produced a large amount of waste from renewal, which has brought huge pressure on limited natural resources and environmental protection. Therefore, the resource utilization of waste is an important measure to achieve a sustainable and intensive society.
[0003] Cold recycling technology is a process that uses special cold recycling machinery at room temperature to continuously complete the milling and crushing of the old pavement structure layer including the surface layer and part of the base layer, add recycled materials, mix, spread, roll and other operations to re-form a structural layer with a certain bearing capacity. Compared with traditional asphalt pavement maintenance methods, asphalt pavement recycling can save a lot of raw materials such as asphalt, sand and gravel, save engineering investment, and is conducive to waste treatment and environmental protection, so it has significant economic and social benefits.
[0004] However, the strength of cold recycled mixture is low and the curing cycle is long, which leads to difficulties in early coring and difficult molding. At the same time, some new natural materials still need to be added to make up for the lack of grading and stability. Therefore, the strength of cold recycled mixture and the utilization rate of old asphalt need to be improved. Summary of the invention
[0005] The purpose of the present invention is to increase the strength of the cold recycled mixture and improve the utilization rate of the old asphalt. The present invention studies an emulsified asphalt cold recycled mixture and a preparation method thereof.
[0006] The technical solution adopted by the present invention provides an emulsified asphalt cold recycled mixture, the key point is that, measured by mass, the above-mentioned recycled mixture includes: 100 parts of old materials, 10 to 15 parts of modifiers, and 5 to 10 parts of old material reducing agents; the above-mentioned old materials include coarse aggregates, fine aggregates and recycled powder made from recycled old asphalt; the above-mentioned old material reducing agent is a mixture of trihydroxymethylmethane and nano-silica sol in a mass ratio of 8 to 10:1.
[0007] Specifically, the mass ratio of the above-mentioned coarse aggregate, fine aggregate and recycled powder is 1:0.9-1.1:0.2-0.3; the above-mentioned coarse aggregate and fine aggregate are milling materials of old asphalt; the above-mentioned recycled powder can be any one or a combination of flue ash, fly ash or rice husk ash.
[0008] Preferably, the particle size of the coarse aggregate is 6 mm to 15 mm, the particle size of the fine aggregate is 2 mm to 6 mm, and the particle size of the recycled powder is less than 200 meshes.
[0009] Furthermore, the preparation method of the above-mentioned modifier includes three steps, specifically: S1. Preparation of modifier A material: Add 0.3-0.4 parts of emulsifier and 4-5 parts of water, stir evenly; add 10-15 parts of base asphalt, 11-18 parts of acrylic acid, 3.5-10 parts of butyl acrylate, 0.2-0.4 parts of acrylamide and 0.2-0.5 parts of N-hydroxymethyl acrylamide, stir and let stand to obtain modifier A material; S2. Preparation of modifier B material: Add 0.3-0.4 parts of emulsifier and 4-5 parts of water and stir evenly; Then add 10-15 parts of base asphalt, 7-12 parts of acrylic acid, 5-10 parts of methyl methacrylate, 1-5 parts of isooctyl acrylate, 1.5-4 parts of butyl acrylate, 0.4-0.8 parts of acrylamide and 0.6-1.5 parts of N-hydroxymethyl acrylamide, stir and let stand to obtain modifier B material; S3. Preparation of modifier: Mixing 0.5 parts of an initiator and 1 to 2 parts of water to obtain an aqueous solution of the initiator; Add 10-15 parts of water and 0.2-0.4 parts of emulsifier into the reactor, heat it up, and after the temperature stabilizes, add 5% of modifier B and stir; The aqueous solution of the initiator, the remaining modifier B material and the modifier A material are added in three batches for reaction, and the reaction time is 3.5 h to 4.5 h. After the reaction is completed, the temperature is lowered to room temperature and the pH value is adjusted to neutral to obtain the modifier.
[0010] Specifically, the temperature increase in step S3 refers to a temperature increase to 90° C. to 100° C.
[0011] Furthermore, in step S3, the specific process of adding the aqueous solution of the initiator in three batches to carry out the reaction is: First, add an aqueous solution of 25% to 35% initiator by mass to start the reaction; After the reaction is stable for 10 min to 30 min, start to drop modifier B and an aqueous solution of 25% to 35% by mass of initiator, and react for 1.5 h to 2 h; Finally, add the aqueous solution of modifier A and the remaining initiator dropwise, and continue the reaction for 1.5 h to 2 h until the reaction is completed.
[0012] Most preferably, the emulsifier is allyl hydroxysulfonate, and the initiator is potassium persulfate or sodium persulfate.
[0013] A method for preparing an emulsified asphalt cold recycled mixture is used to prepare the above-mentioned recycled mixture. The key lies in stirring the mixture of coarse aggregate and fine aggregate in the old material while spraying the old material reducing agent. After the old material reducing agent is completely sprayed and stirred evenly, a cold recycled modifier and recycled powder are added, and stirring is performed while adding the materials to obtain a recycled asphalt mixture.
[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention uses a special reductant for old materials. Among them, trihydroxymethylmethane has low-temperature reducibility and can react with old materials without special heating. Nano silica sol can not only improve the adhesion between old materials and new materials in a liquid state, but also migrate with the evaporation of water to form a strong silicon-oxygen bond with the inorganic silicon in the mixture. Due to the strong rigidity of the silicon-oxygen bond, the strength and salt resistance of the product can be improved.
[0015] The asphalt modifier of the present invention adopts a special design, with modifier A material as the shell solution and modifier B material as the core solution, and the reaction is initiated in stages during the preparation process to prepare a modifier with a hard core but high shell viscosity, which reduces the use ratio of new materials and improves the utilization rate of old materials on the one hand, and improves the strength of the regenerated asphalt mixture on the other hand. This is because the isooctyl acrylate and methyl methacrylate introduced in the core solution have a larger molecular weight, a longer molecular chain, and a lower solubility in water, so that the hydrophobicity of isooctyl acrylate is better than that of butyl acrylate, which can help improve water resistance. At the same time, the mechanical strength of isooctyl acrylate is higher and has a higher Tg value than butyl acrylate, which can keep the modifier at a higher or lower temperature. Flexibility and adhesion, thereby showing better temperature resistance and cold resistance. N-hydroxymethyl acrylamide in the modifier designed by the present invention is a high-density cross-linking monomer that can make a linear emulsion cross-linked into a three-dimensional network structure, which not only greatly improves strength and water resistance, but also introduces polymerizable silane, so that the silicone structure is grafted on the molecular chain, which can give the product higher strength.
[0016] Therefore, the regenerated asphalt mixture sample of the present invention not only has significantly improved stability, splitting strength, durability, cold resistance and water resistance, but also has significantly improved salt resistance, which is manifested in that the reduction in the salt water Marshall residual stability and the salt water freeze-thaw splitting strength ratio can be maintained at about 10%. DETAILED DESCRIPTION
[0017] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0018] If no specific conditions are specified in the examples, the experiments can be carried out under conventional conditions; if no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased commercially. Embodiment 1 to Embodiment 3
[0019] In this embodiment, the modifier samples were prepared according to the following steps. The specific material ratios and parameters are shown in Tables 1 to 3: S1. Preparation of modifier A material: Add 0.3-0.4 parts of emulsifier allyl hydroxysulfonate and 4-5 parts of water, and stir evenly; add 10-15 parts of base asphalt, 11-18 parts of acrylic acid, 3.5-10 parts of butyl acrylate, 0.2-0.4 parts of acrylamide and 0.2-0.5 parts of N-hydroxymethyl acrylamide, stir and let stand for use to obtain modifier A material; S2. Preparation of modifier B material: Add 0.3-0.4 parts of emulsifier allyl hydroxysulfonate and 4-5 parts of water and stir evenly; Then add 10-15 parts of base asphalt, 7-12 parts of acrylic acid, 5-10 parts of methyl methacrylate, 1-5 parts of isooctyl acrylate, 1.5-4 parts of butyl acrylate, 0.4-0.8 parts of acrylamide and 0.6-1.5 parts of N-hydroxymethyl acrylamide, stir and let stand to obtain modifier B material; S3. Preparation of modifier: Mixing 0.5 parts of an initiator and 1 to 2 parts of water to obtain an aqueous solution of the initiator; Add 10-15 parts of water and 0.2-0.4 parts of emulsifier allyl hydroxysulfonate into the reactor, raise the temperature, and after the temperature stabilizes, add 5% of modifier B material and stir; The aqueous solution of the initiator was added in three batches to carry out the reaction, specifically: First, add an aqueous solution of 25% to 35% by mass of the initiator to start the reaction, i.e., add the aqueous solution of the initiator for the first time; After the reaction is stable for 10 min to 30 min, this stage of reaction is recorded as reaction time 1, and the remaining modifier B material and the aqueous solution of 25% to 35% by mass of the initiator are added dropwise, i.e., the initiator aqueous solution is added for the second time, and the reaction is carried out for 1.5 h to 2 h, and this stage of reaction is recorded as reaction time 2; Finally, add the modifier A material and the remaining initiator aqueous solution dropwise, i.e., add the initiator aqueous solution for the third time, and continue the reaction for 1.5 h to 2 h until the reaction is completed. This section of the reaction is recorded as reaction time 3, and the total reaction time is controlled at 3.5 h to 4.5 h; The temperature was lowered to room temperature, and the pH value was adjusted to neutral. Modifier samples 1 to 3 were obtained from Examples 1 to 3, respectively.
[0020] Table 1: Specific material dosage and process parameters of the modifier in step S1
[0021] Table 2: Specific material dosage and process parameters of modifier in step S2
[0022] Table 3: Specific material dosage and process parameters of the modifier in step S3 Embodiment 4 to Embodiment 7
[0023] In this embodiment, the emulsified asphalt cold recycled mixture is prepared according to the following steps. The specific material proportions and parameters are shown in Table 4: While stirring the mixture of coarse aggregate and fine aggregate in the old material, spray the old material reducing agent. After the old material reducing agent is completely sprayed and stirred evenly, add the cold regeneration modifier, recycled powder, and matrix emulsified asphalt. Stir while adding the materials. Example 4 to Example 7 respectively prepare recycled asphalt mixture samples 1 to 4.
[0024] Table 4: Material ratio of recycled asphalt mixture
[0025] Note: The particle size of the coarse aggregate in the above table is 6 mm to 15 mm, the particle size of the fine aggregate is 2 mm to 6 mm, and the particle size of the recycled powder is below 200 mesh, that is, 2 kg of material is randomly selected from the four corners of the aggregate pile or recycled powder that is evenly stirred and naturally stacked, and sieved. If the proportion of meeting the corresponding particle size requirements is more than 90%, it meets the particle size requirements of the present invention. According to this method, three parallel tests are carried out, and the materials used need to meet the particle size requirements of the present invention.
[0026] Among them, the average particle size of coarse aggregate and fine aggregate: each time, 10 aggregate samples are randomly selected from the 2kg sample for particle size testing, and the arithmetic mean is taken. Comparative Example 1
[0027] This comparative example is used to prepare the modifier, and the specific process is as follows: Add 0.7 parts of emulsifier allyl hydroxysulfonate to 9 parts of water and stir evenly; Add 25 parts of base asphalt, 25 parts of acrylic acid, 8.5 parts of butyl acrylate, 0.9 parts of acrylamide, 1.4 parts of N-hydroxymethyl acrylamide, 8 parts of methyl methacrylate and 3 parts of isooctyl acrylate, stir and let stand for use to obtain a modifier base material; Mixing 0.5 parts of an initiator and 1.5 parts of water to obtain an aqueous solution of the initiator; Add 12 parts of water and 0.3 parts of emulsifier allyl hydroxysulfonate into the reactor, heat to 95°C, and after the temperature stabilizes, add 5% of the modifier base and stir; The aqueous solution of the initiator was added in 2 batches to react, specifically: First, add an aqueous solution of 30% by mass of the initiator to start the reaction, i.e., the first addition of the aqueous solution of the initiator; After the reaction was stable for 20 min, the remaining modifier base and the remaining initiator aqueous solution were added dropwise and the reaction was continued for 4 h. The mixture was cooled to room temperature and the pH value was adjusted to neutral to prepare the modifier reference substance 1.
[0028] The modifier reference product 1 was used to prepare a regenerated asphalt mixture sample. Except for the different sources of the modifier, the amounts and proportions of other materials were the same as those in Example 4, and the regenerated asphalt mixture reference product 1 was prepared. Comparative Example 2
[0029] In this comparative example, the modifier is prepared. The specific process is the same as that of Example 1, except that in the preparation of S3, the initiator is not added in three batches, but is slowly added dropwise at one time, that is, 12 parts of water and 0.3 parts of emulsifier allyl hydroxysulfonate are added to the reactor, the temperature is raised to 95°C, and after the temperature is stabilized, all the modifier B material is added, the aqueous solution of the initiator and the modifier A material are added dropwise while stirring, and after all the materials are added dropwise, the mixture is stirred and reacted for 4 hours; The mixture was cooled to room temperature and the pH value was adjusted to neutral to prepare the modifier reference substance 2.
[0030] The modifier reference product 2 was used to prepare a regenerated asphalt mixture sample. Except for the different sources of the modifier, the amounts and proportions of other materials were the same as those in Example 4, and the regenerated asphalt mixture reference product 2 was prepared. Comparative Example 3
[0031] In this comparative example, no modifier is prepared, and modifier sample 1 is used to prepare the regenerated asphalt mixture. The specific preparation method is the same as Example 4, except that the old material reducing agent is not sprayed in this comparative example to prepare the regenerated asphalt mixture reference product 3. Comparative Example 4
[0032] In this comparative example, no modifier is prepared, and modifier sample 1 is used to prepare the regenerated asphalt mixture. The specific preparation method is the same as Example 4, except that the old material reducing agent sprayed in this comparative example is 8 parts of trihydroxymethylmethane, and nano-silica sol is not added to prepare the regenerated asphalt mixture reference product 4. Comparative Example 5
[0033] This comparative example adopts the existing formula to prepare the recycled asphalt mixture, specifically: 100 parts of old materials (the ratio of coarse aggregate to fine aggregate is 4:6), 8 parts of emulsified asphalt, 2 parts of an admixture consisting of carbon tetrachloride and anhydrous ethanol in a volume ratio of 4:6, 5 parts of water, 3 parts of cement, and 5 parts of mineral powder were stirred and mixed to prepare recycled asphalt mixture reference 5. Analysis and testing
[0034] Take the recycled asphalt mixture samples and reference materials respectively, and carry out paving construction according to the following steps: Step 1: Spreading: Spread the recycled asphalt mixture sample and the reference material using a paver, with a spreading speed of no more than 3m / min; Step 2: Rolling: Roll the mixture after paving in step 1 in sequence. Use a single steel wheel roller for the initial rolling, rolling twice; use a tire roller for the secondary rolling, rolling six times. The final rolling times are determined based on the compaction data of the sand filling method, and the compaction degree is not less than 99%; use a light tire roller for the final rolling, rolling twice to finish the surface; Step 3: Maintenance: Close the road surface for maintenance for 5 days; Step 4: Sampling and testing: Take cores and test the properties of the core samples. The results are shown in Table 3.
[0035] Test method: The test area belongs to a semi-arid and winter cold zone. The performance test of the mixture is carried out according to the "Test Procedure for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011) and the "Specification for Design of Asphalt Pavement" (JTG D50-2004). Among them, the Marshall residual stability of salt water and the freeze-thaw splitting strength of salt water are not recorded in the standard procedures. The Marshall residual stability of the salt water of the present invention is the residual stability after immersion in 10% salt water for 72 hours; the freeze-thaw splitting strength ratio of the salt water of the present invention is the residual strength ratio of the freeze-thaw splitting test after 9 salt-freezing cycles in the above-mentioned concentration of salt water.
[0036] Table 5: Performance test results of recycled asphalt mixture samples and reference products
[0037] As shown in Table 5, the regenerated asphalt mixture samples of the present invention not only have significantly improved stability, splitting strength, durability, cold resistance and water resistance, but also have significantly improved salt resistance, which is manifested in that the reduction in the salt water Marshall residual stability and the salt water freeze-thaw splitting strength ratio can be maintained at about 10%.
[0038] This is because the present invention adopts a special old material reducing agent, among which trihydroxymethylmethane has low-temperature reducing properties and can react with the old material without special heating. The nano-silica sol can not only improve the adhesion between the old material and the new material in the liquid state, but also migrate with the evaporation of water to form a strong silicon-oxygen bond with the inorganic silicon in the mixture. Due to the strong rigidity of the silicon-oxygen bond, the strength and salt resistance of the product can be improved.
[0039] The asphalt modifier of the present invention adopts a special design, with modifier A material as the shell solution and modifier B material as the core solution, and the reaction is initiated in stages during the preparation process to prepare a modifier with a hard core but high shell viscosity, which reduces the use ratio of new materials and improves the utilization rate of old materials on the one hand, and improves the strength of the regenerated asphalt mixture on the other hand. This is because the isooctyl acrylate and methyl methacrylate introduced in the core solution have a larger molecular weight, a longer molecular chain, and a lower solubility in water, so that the hydrophobicity of isooctyl acrylate is better than that of butyl acrylate, which can help improve water resistance. At the same time, the mechanical strength of isooctyl acrylate is higher and has a higher Tg value than butyl acrylate, which can keep the modifier at a higher or lower temperature. Flexibility and adhesion, thereby showing better temperature resistance. N-hydroxymethyl acrylamide in the modifier designed by the present invention is a high-density cross-linking monomer that can make a linear emulsion cross-linked into a three-dimensional network structure, which not only greatly improves strength and water resistance, but also introduces polymerizable silane, so that the silicone structure is grafted on the molecular chain, which can give the product higher strength.
[0040] Recycled asphalt mixture samples 1-2 changed the preparation method of the modifier respectively; recycled asphalt mixture samples 3-4 did not use the old material reducing agent or changed the composition of the old material reducing agent respectively, resulting in the strength, water resistance and salt resistance of the mixture being affected to varying degrees.
Claims
1. An emulsified asphalt cold recycled mixture, characterized in that: In terms of parts by mass, the recycled mixture includes: 100 parts of old materials, 10 to 15 parts of modifiers, and 5 to 10 parts of old material reducing agents; the old materials include coarse aggregates, fine aggregates and recycled powder made from recycled old asphalt; the old material reducing agent is a mixture of trihydroxymethylmethane and nano-silica sol in a mass ratio of 8 to 10:
1.
2. The emulsified asphalt cold recycled mixture according to claim 1, characterized in that: The mass ratio of the coarse aggregate, fine aggregate and recycled powder is 1:0.9-1.1:0.2-0.3; the coarse aggregate and fine aggregate are milling materials of old asphalt; the recycled powder can be any one or a combination of flue ash, fly ash or rice husk ash.
3. The emulsified asphalt cold recycled mixture according to claim 2, characterized in that: The particle size of the coarse aggregate is 6 mm to 15 mm, the particle size of the fine aggregate is 2 mm to 6 mm, and the particle size of the recycled powder is below 200 meshes.
4. The emulsified asphalt cold recycled mixture according to claim 1, characterized in that: The preparation method of the modifier comprises three steps, specifically: S1. Preparation of modifier A material: Add 0.3-0.4 parts of emulsifier and 4-5 parts of water, stir evenly; add 10-15 parts of base asphalt, 11-18 parts of acrylic acid, 3.5-10 parts of butyl acrylate, 0.2-0.4 parts of acrylamide and 0.2-0.5 parts of N-hydroxymethyl acrylamide, stir and let stand to obtain modifier A material; S2. Preparation of modifier B material: Add 0.3-0.4 parts of emulsifier and 4-5 parts of water and stir evenly; Then add 10-15 parts of base asphalt, 7-12 parts of acrylic acid, 5-10 parts of methyl methacrylate, 1-5 parts of isooctyl acrylate, 1.5-4 parts of butyl acrylate, 0.4-0.8 parts of acrylamide and 0.6-1.5 parts of N-hydroxymethyl acrylamide, stir and let stand to obtain modifier B material; S3. Preparation of modifier: Mixing 0.5 parts of an initiator and 1 to 2 parts of water to obtain an aqueous solution of the initiator; Add 10-15 parts of water and 0.2-0.4 parts of emulsifier into the reactor, raise the temperature, and after the temperature stabilizes, add 5% of modifier B and stir; The aqueous solution of the initiator, the remaining modifier B material and the modifier A material are added in three batches for reaction, and the reaction time is 3.5 h to 4.5 h. After the reaction is completed, the temperature is lowered to room temperature and the pH value is adjusted to neutral to obtain the modifier.
5. The emulsified asphalt cold recycled mixture according to claim 4, characterized in that: The temperature increase in step S3 refers to a temperature increase to 90°C to 100°C.
6. The emulsified asphalt cold recycled mixture according to claim 4, characterized in that: In step S3, the aqueous solution of the initiator is added in three batches to carry out the reaction. The specific process is: First, add an aqueous solution of 25% to 35% initiator by mass to start the reaction; After the reaction is stable for 10 min to 30 min, start to drop modifier B and an aqueous solution of 25% to 35% by mass of initiator, and react for 1.5 h to 2 h; Finally, add the modifier A and the remaining initiator aqueous solution dropwise, and continue the reaction for 1.5 h to 2 h until the reaction is completed.
7. The emulsified asphalt cold recycled mixture according to claim 4, characterized in that: The emulsifier is allyl hydroxysulfonate, and the initiator is any one of potassium persulfate or sodium persulfate.
8. A method for preparing an emulsified asphalt cold recycled mixture, for preparing the recycled mixture as claimed in any one of claims 1 to 7, characterized in that: While stirring the mixture of coarse aggregate and fine aggregate in the old material, spray the old material reducing agent. After the old material reducing agent is completely sprayed and stirred evenly, add the cold recycling modifier and recycling powder, and stir while adding the materials to obtain the recycled asphalt mixture.