High-modulus recycled asphalt mortar based on oil-rich RAP fine material and preparation method of high-modulus recycled asphalt mortar

Abstract

The invention discloses high-modulus recycled asphalt mortar based on an oil-rich RAP fine material, and the high-modulus recycled asphalt mortar comprises the following components in percentage by mass: waste asphalt RAP fine material, new asphalt, limestone fine aggregate, limestone mineral powder, a high-modulus agent and a regenerant, the regenerant is prepared from the following components: unsaturated polyester resin, acrylate rubber and n-hexyl carbamate. The regenerated asphalt is regenerated and modified through the regenerant and the high modulus agent, the prepared regenerated asphalt has high bearing capacity and excellent anti-fatigue performance, the durability of the mixture is prolonged, and elastic deformation and rutting of an asphalt pavement under the vehicle load effect are effectively reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of recycled asphalt, and in particular relates to a high-modulus recycled asphalt mortar based on oil-rich RAP fine material and a preparation method thereof. Background Art

[0002] The efficient recycling of waste asphalt pavement (RAP) has become a key research topic in highway construction and maintenance. Asphalt pavement maintenance projects generate significant amounts of RAP annually, posing a significant challenge in efficiently disposing of this waste. RAP is an irregularly shaped, multiphase mixture of aged asphalt bonded to multiple aggregate particles, characterized by significant agglomeration. The addition of new asphalt and aggregate to regenerate RAP can easily lead to inadequate fusion of the old and new asphalt, resulting in poor regeneration of the aged asphalt.

[0003] RAP fines contain a large amount of aged asphalt. Long-term exposure to both vehicle loads and environmental factors has severely damaged its polar components, significantly reducing the asphalt's cohesiveness and adhesion. Specifically, asphalt aging primarily occurs during contact with the external environment, primarily driven by oxygen and temperature. From production to commissioning, asphalt begins to undergo varying degrees of thermal oxidative aging. It is generally believed that thermal oxidative aging can be divided into three stages: post-production transportation and storage; mixing, spreading, and compacting of asphalt and aggregate; and post-paving aging reactions due to temperature fluctuations, UV exposure, and other factors. Due to the high content and variability of aged asphalt in RAP fines, traditional factory-mix hot regeneration techniques are difficult to regenerate effectively and stably. The resulting asphalt pavement material exhibits poor skid resistance, wear resistance, fatigue resistance, and high-temperature resistance, and is susceptible to low-temperature cracking. Therefore, the development of high-modulus recycled asphalt mortars and preparation methods based on oil-rich RAP fines is crucial. Summary of the Invention

[0004] In order to address the deficiencies of the prior art, the purpose of the present invention is to provide a high-modulus regenerated asphalt mortar based on oil-rich RAP fine material and a preparation method. The regenerated asphalt is regenerated and modified by a regeneration agent and a high-modulus agent. The prepared regenerated asphalt has a strong bearing capacity and excellent fatigue resistance, which extends the durability of the mixture and effectively reduces the elastic deformation and rutting of the asphalt pavement under vehicle load.

[0005] In order to achieve the above objectives, the present invention adopts the following technical solutions:

[0006] A high-modulus recycled asphalt mortar based on oil-rich RAP fines comprises the following components: waste asphalt RAP fines, new asphalt, limestone fine aggregate, limestone mineral powder, a high-modulus agent and a regeneration agent, wherein the mass ratio of the components is 600-601:20.3-20.4:441.2-441.4:1.3-1.5:0.96-0.98:2.1-4.6, and the regeneration agent comprises the following components: unsaturated polyester resin, acrylic rubber and n-hexyl carbamate.

[0007] Preferably, the waste asphalt RAP fine material is screened into three parts with particle sizes of 2.36-4.75 mm, 1.18-2.36 mm, and 0.6-1.18 mm, respectively, of which the proportion of aged asphalt in the RAP material is 3.3-3.4%, 5.7-5.8%, and 7.4-7.5%, respectively.

[0008] Preferably, the aforementioned waste asphalt RAP fines account for 60% of the weight of the regenerated asphalt mortar, and the regeneration agent is 7.5% of the aged asphalt content.

[0009] Preferably, the sum of the masses of the aged asphalt and the new asphalt is 4.9% of the sum of the masses of the crushed old fine aggregate and the limestone fine aggregate.

[0010] Preferably, the content of the aforementioned unsaturated polyester resin is 4% to 8% of the sum of the mass of aged asphalt and new asphalt (total mass of asphalt), the amount of acrylic rubber accounts for 8% to 16% of the mass of the unsaturated polyester resin, and the amount of n-hexyl carbamate accounts for 1% to 3% of the mass of the unsaturated polyester resin.

[0011] Preferably, the aforementioned limestone fine aggregate is divided into particle sizes of 2.36-3 mm, 1.18-2.36 mm, 0.6-1.18 mm, 0.3-0.6 mm, 0.15-0.3 mm, and 0.075-0.15 mm.

[0012] The preparation method of high modulus recycled asphalt mortar comprises the following specific steps:

[0013] S1. First, add acrylate rubber to new asphalt, stir evenly, then add n-hexyl carbamate, react for a period of time, and then add unsaturated polyester resin to obtain modified asphalt after the reaction. When acrylate rubber is first added to new asphalt, the saturated carbon chain will not react with the components in the asphalt, and no by-products will be produced, which is relatively stable. After stirring evenly, n-hexyl carbamate is added to react with the phenolic resin in the asphalt to enhance the adhesion of the asphalt and improve the durability of the asphalt mixture. After stirring evenly, unsaturated polyester resin is added to enhance the fluidity and wettability of the asphalt, and polymerization reaction occurs with n-hexyl carbamate to accelerate the asphalt curing process. The carboxylic acid groups carried by the acrylate rubber can react with alkaline limestone to enhance the interfacial adhesion effect.

[0014] S2. First, stir the waste asphalt RAP fine material in a mixing pot for 1 to 2 minutes, add the high modulus agent and stir for 2 to 4 minutes, then add the modified asphalt and stir for 2 to 4 minutes to obtain a mixture;

[0015] S3. Add limestone fine aggregate and limestone mineral powder to the mixture, stir for 1 to 2 minutes at a temperature of 175 to 180°C, and obtain high modulus recycled asphalt mortar after mixing.

[0016] Preferably, before the reaction, the screened limestone fine aggregate, limestone mineral powder, waste asphalt RAP fine material and modified asphalt are placed in an oven for preheating respectively, the preheating temperature of the waste asphalt RAP fine material is 120-140°C, the preheating temperature of the limestone fine aggregate and limestone mineral powder is 170-200°C, and the preheating temperature of the modified asphalt is 165-175°C.

[0017] The principle of asphalt modification by regeneration agent:

[0018] The regeneration agent's composition differs, resulting in superior results compared to conventional regeneration agents. The carboxyl groups at the ends of the unsaturated polyester resin react with alkaline earth metal oxides and hydroxides contained in limestone, extending the molecular chain to form a complex. When heated, the complex exhibits excellent fluidity and enhances the workability of the asphalt. n-Hexyl carbamate can cross-link and modify the phenolic resin in petroleum asphalt. The resulting phenol-carbamate bonds form a three-dimensional cross-linked network that can break and reform under certain conditions (such as temperature fluctuations), imparting self-healing properties to the material. Amino groups react chemically with carbon-oxygen double bonds, slowing asphalt aging. Under alkaline conditions, the carbon-carbon double bonds in the unsaturated polyester resin and the carbon-oxygen double bonds in n-Hexyl carbamate undergo a Michael addition reaction, forming new C-C and C-O bonds, facilitating the formation of new polymers. Furthermore, acrylic rubber, as a saturated carbon chain, exhibits advantages such as heat resistance, aging resistance, and UV resistance.

[0019] R-COOH+Ca(OH)2→R-COOCa+Ca(OH)2

[0020] Among them, R-COOH represents the carboxyl group at the end of the unsaturated polyester resin, and Ca(OH)2 represents the alkaline earth metal oxides and hydroxides contained in the limestone.

[0021] R-CH=CH2+H2N-R'→R-CH(NH-R')-CH3

[0022] Wherein, R and R' are alkyl groups or aromatic groups, and the amino group (-NH2) can undergo addition reaction with the carbonyl group (C=O) to form an imine (C=N) and water (H2O).

[0023] CH2=CH-COO-+HO-CH2-CH2-CH2-NH-COO-

[0024] →CH2-CH(OH)-CH2-NH-COO-+CH2=CH-COO-

[0025] Among them, CH2=CH-COO represents the carbon-carbon double bond in unsaturated polyester resin, and HO-CH2-CH2-CH2-NH-COO- represents the carbon-oxygen double bond in n-hexyl carbamate.

[0026] The present invention is beneficial in that:

[0027] (1) The present invention regenerates and modifies the regenerated asphalt through a regeneration agent and a high modulus agent. The regeneration agent plays a role in restoring the elasticity and adhesion of aged asphalt and improving the aging resistance of asphalt. It can make the asphalt fully infiltrate the aggregate and has good dispersion and adhesion properties, thereby ensuring the uniformity of the asphalt mixture. The modified regenerated asphalt has good aging resistance, and good rebound can improve the compressive strength of the regenerated asphalt mixture. Under the action of the regeneration agent, the interface between the asphalt and the mineral material can be enhanced, which improves the adhesion between the asphalt and the aggregate and the mineral powder, reduces the fatigue damage of the mixture, and enables the regenerated asphalt mixture to have good resistance to low-temperature cracking and high-temperature stability. The high modulus agent can increase the modulus of the asphalt mortar and improve its anti-rutting performance.

[0028] (2) The regenerated asphalt prepared by the present invention has a strong bearing capacity and excellent fatigue resistance, which prolongs the durability of the mixture and effectively reduces the elastic deformation and rutting of the asphalt pavement under vehicle load, thereby generating ecological and economic benefits. DETAILED DESCRIPTION

[0029] The present invention is described in detail below with reference to specific embodiments.

[0030] Example 1

[0031] A method for preparing high modulus modified recycled asphalt mortar, comprising the following steps:

[0032] S1: Preparation process of modified asphalt:

[0033] (1) Weigh new asphalt, the amount of unsaturated polyester resin is 4% of the total mass of the asphalt, the amount of n-hexyl carbamate is 1% of the mass of the unsaturated polyester resin, and the amount of acrylic rubber is 8% of the mass of the unsaturated polyester resin;

[0034] (2) Adding acrylate rubber, n-hexyl carbamate, and unsaturated polyester resin into fresh asphalt in the order mentioned above, shearing them at 160°C using a high-speed shearing machine with a rotation speed of 1200 r / min, 1100 r / min, and 1400 r / min, respectively, with an interval of 10 minutes between each addition.

[0035] S2: Preparation process of high modulus modified recycled asphalt mortar:

[0036] (1) Weigh the sieved waste asphalt RAP fines with a particle size of 0-3 mm, limestone fine aggregate, and limestone mineral powder, and preheat them in an oven at 180°C until the mass change is negligible. The optimal oil-stone ratio is set at 4.1%. The gradation of the limestone fine aggregate is based on the HFM-20 shown in the Anhui Provincial Local Standard "Technical Specifications for the Design and Construction of High Fatigue Performance and High Modulus Asphalt Mixtures". The proportion of waste asphalt RAP fines added is selected to be 60%, and the amount of aged asphalt is 7%;

[0037] The limestone fine aggregate is screened, and the particle sizes after screening include 2.36-3mm, 1.18-2.36mm, 0.6-1.18mm, 0.3-0.6mm, 0.15-0.3mm, and 0.075-0.15mm. After screening, the weight ratios of the limestone fine aggregate and the limestone mineral powder are 141.0:88.2:14.7:10.6:98.7:88.1:1.3 respectively; the waste asphalt RAP fine material is screened into three parts. After screening, it can be mixed with new aggregate according to the target gradation and aged asphalt content. The particle sizes of the three parts are 2.36-4.75mm, 1.18-2.36mm, and 0.6-1.18mm, and the weight ratios are 227.7:137.3:173.2 respectively.

[0038] (2) The waste asphalt RAP fine material was stirred in a mixing pot for 1 min, the high modulus agent was added and stirred for 3 min, and then the modified asphalt was added. The weight of the modified asphalt was 4.4% of the total weight of the new and old asphalt, the weight of the high modulus agent was 2% of the total weight of the new and old asphalt, and the weight of the modified asphalt was 4.9% of the total weight of the aggregate. The difference between the weight of the modified asphalt and the aged asphalt contained in the waste asphalt RAP fine material was calculated as follows:

[0039] m 总 =m 新集料 +m 改性 +m RAP ;

[0040] m RAP =m 老化沥青 +m 旧集料 ;

[0041] (m 改性 +m老化沥青 ) / (m 新集料 +m 旧集料 )=4.9%;

[0042] m 改性 =4.9%m 新集料 -2.4% m RAP .

[0043] (3) After adding preheated new aggregate (aggregate except limestone mineral powder), stir for another 1 minute, stir for 3 minutes, and finally add limestone mineral powder to the mixing pot and mix for 3 minutes. During steps (2) and (3), the mixing pot temperature is maintained at 175-180°C to obtain high modulus recycled asphalt mortar.

[0044] Example 2

[0045] The specific difference between this embodiment and embodiment 1 is that the amount of unsaturated polyester resin used is 6% of the total mass of asphalt, the amount of n-hexyl carbamate used is 2% of the mass of the unsaturated polyester resin, and the amount of acrylic rubber used is 12% of the mass of the unsaturated polyester resin.

[0046] Example 3

[0047] The specific difference between this embodiment and embodiment 1 is that the amount of unsaturated polyester resin used is 8% of the total mass of asphalt, the amount of n-hexyl carbamate used is 3% of the mass of the unsaturated polyester resin, and the amount of acrylic rubber used is 16% of the mass of the unsaturated polyester resin.

[0048] Comparative Example 1

[0049] The specific difference between this comparative example and Example 3 is that the weight ratio of the mineral powder is changed to 40.3:22.4:3.7:14.6:13.7:3.6:0.6.

[0050] Comparative Example 2

[0051] The specific difference between this embodiment and embodiment 1 is: the process of preparing modified asphalt: weigh new asphalt, add 9.52% of the total mass of the asphalt common regeneration agent, and shear it at 160°C through a high-speed shearing machine with a rotation speed of 1200r / min.

[0052] Comparative Example 3

[0053] The specific difference between this comparative example and Example 1 is: the process of preparing modified asphalt: weighing new asphalt, adding unsaturated polyester resin, acrylic rubber and n-hexyl carbamate without distinguishing the order of addition, and stirring them uniformly to prepare modified asphalt.

[0054] Performance test: The high modulus modified recycled asphalt mortars prepared in Examples 1 to 3 and Comparative Examples 1 to 2 were tested for modulus, high and low temperature performance, and shear strength. The test methods were in accordance with the corresponding manufacturing methods and test methods in the "Technical Guide for Construction of High Modulus Asphalt Pavements for Highways" (TCHTS 10004-2018) and the "Test Procedure for Asphalt and Asphalt Mixtures for Highway Engineering" (JTG E20-2011). The test results are shown in the following table:

[0055] Table 1 Performance test of recycled asphalt mortar

[0056]

[0057] As shown in Table 1, the various properties of the asphalt mixtures prepared in Examples 1-3 meet the requirements of the China Highway and Transportation Society Group Standard TCHTS10004-2018, "Technical Guide for Construction of High-Modulus Asphalt Pavements for Highways," and all indicators are significantly higher than the standard technical requirements. Comparing the data in Example 1, it can be seen that compared to Example 3, the performance test results of the prepared specimens are not significantly affected, with minimal fluctuations, demonstrating that gradation variations within the gradation range of Example 3 are reasonable.

[0058] Compared to Example 1, Comparative Example 2 shows a decrease in performance despite an increased regeneration agent dosage. This demonstrates that simply increasing the regeneration agent dosage does not effectively improve the regeneration of aged asphalt, and that the regeneration agent dosage should be controlled within a range of approximately 4.4%. Compared to Example 3, Comparative Example 2 shows a significant decrease in the dynamic modulus, demonstrating that the regenerated modified asphalt mortar prepared by the present invention is superior to conventional regenerated asphalt mortar, exhibiting a good regeneration agent effect and a 15% improvement in low-temperature crack resistance. This demonstrates that the modified asphalt prepared by the present invention exhibits superior regeneration performance, and that the high-modulus modified asphalt mortar prepared using the gradation type designed by the present invention exhibits excellent high-temperature stability, rutting resistance, low-temperature crack resistance, and a high modulus.

[0059] The low-temperature crack resistance test results and dynamic modulus values ​​of Comparative Example 3 are similar to those of Comparative Example 2, demonstrating the importance of the order in which the regeneration agent components are added. The optimal stirring times for the unsaturated polyester resin, acrylic rubber, and n-hexyl carbamate differ. Adding the regeneration agent components at the same time results in poor fusion, preventing the chemical components from fully reacting, and resulting in poor low-temperature crack resistance and fatigue resistance. Therefore, the addition sequence specified in this invention should be followed. Compared to Example 3, the high-temperature stability of the prepared specimens did not change significantly, indicating that the order of addition in this invention affects the regeneration agent's fusion with aged asphalt, but has little effect on the specimen's high-temperature performance.

[0060] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any form, and any technical solutions obtained by equivalent replacement or equivalent transformation fall within the scope of protection of the present invention.

Claims

1. A high modulus recycled asphalt mortar based on oil-rich RAP fines, characterized in that: Includes the following components: The mass ratios of waste asphalt RAP fine material, new asphalt, limestone fine aggregate, limestone mineral powder, high modulus agent and regeneration agent are 600~601:20.3~20.4:441.2~441.4:1.3~1.5:0.96~0.98:2.1~4.6, respectively. The regeneration agent includes the following components: unsaturated polyester resin, acrylic rubber and n-hexyl carbamate.

2. A high modulus recycled asphalt mortar based on oil-rich RAP fines according to claim 1, characterized in that: The waste asphalt RAP fine material was sieved into three parts with particle sizes of 2.36~4.75mm, 1.18~2.36mm, and 0.6~1.18mm, of which the aged asphalt accounted for 3.3~3.4%, 5.7~5.8%, and 7.4~7.5%, respectively.

3. A high modulus recycled asphalt mortar based on oil-rich RAP fines according to claim 2, characterized in that: The waste asphalt RAP fines account for 60% of the weight of the regenerated asphalt mortar, and the regeneration agent is 7.5% of the aged asphalt content.

4. A high modulus recycled asphalt mortar based on oil-rich RAP fines according to claim 2, characterized in that: The sum of the masses of the aged asphalt and the new asphalt is 4.9% of the sum of the masses of the crushed old fine aggregate and the limestone fine aggregate.

5. The high modulus recycled asphalt mortar based on oil-rich RAP fines according to claim 2, characterized in that: The content of the unsaturated polyester resin is 4% to 8% of the sum of the mass of the aged asphalt and the new asphalt, the amount of the acrylic rubber is 8% to 16% of the mass of the unsaturated polyester resin, and the amount of the n-hexyl carbamate is 1% to 3% of the mass of the unsaturated polyester resin.

6. The high modulus recycled asphalt mortar based on oil-rich RAP fines according to claim 1, characterized in that: The limestone fine aggregate is divided into 2.36~3 mm, 1.18~2.36 mm, 0.6~1.18 mm, 0.3~0.6 mm, 0.15~0.3 mm, and 0.075~0.15 mm according to particle size.

7. The method for preparing high modulus regenerated asphalt mortar according to any one of claims 1 to 6, characterized in that: The specific steps include: S1. Adding a regeneration agent to new asphalt to obtain modified asphalt after reaction; S2. adding a high modulus agent and modified asphalt to the waste asphalt RAP fine material to obtain a mixture; S3. Add limestone fine aggregate and limestone mineral powder to the mixture, and mix to obtain high modulus recycled asphalt mortar.

8. The method for preparing high modulus regenerated asphalt mortar according to claim 7, characterized in that: The specific method of step S1 is: first add acrylate rubber to new asphalt, stir evenly, then add n-hexyl carbamate, react for a period of time, and then add unsaturated polyester resin.

9. The method for preparing high modulus regenerated asphalt mortar according to claim 7, characterized in that: Before the reaction, the screened limestone fine aggregate, limestone mineral powder, waste asphalt RAP fine material and modified asphalt were placed in an oven for preheating. The preheating temperature of waste asphalt RAP fine material was 120~140℃, the preheating temperature of limestone fine aggregate and limestone mineral powder was 170~200℃, and the preheating temperature of modified asphalt was 165~175℃.

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