Cold recycled asphalt mixture based on light base oil regenerant

Abstract

The invention provides a cold recycled asphalt mixture based on a light base oil regenerant, and belongs to the technical field of recycled asphalt, the oil regenerant is composed of the following components by weight: 70-80 parts of light base oil, 12-17 parts of a plasticizer, 6-8 parts of a penetrant, and 2-4 parts of an anti-aging agent. A thermogravimetric analysis test shows that the prepared regenerant has relatively high aromatic content and relatively low asphaltene content, and can adjust the balance of components in asphalt, so that the missing components in the aged asphalt are supplemented to reach the degree of matching with new asphalt; on the basis of strength, the optimal mixing amount of the regenerant is determined through an asphalt mixture splitting test and a compression test, and when the mixing amount of the light base oil regenerant is 0.6%, the mechanical strength improvement effect is optimal; the high-temperature stability and the low-temperature crack resistance of the recycled asphalt mixture are reduced due to the increase of the mixing amount of the recycled asphalt mixture, but the recycled asphalt mixture still meets the requirements of regeneration specifications.

Description

Technical Field

[0001] The invention relates to the technical field of recycled asphalt, and in particular to a cold recycled asphalt mixture based on a light base oil regeneration agent. Background Art

[0002] After large-scale highway construction, highway traffic has become the most widely covered and most populous mode of transportation in my country. The main task of highway traffic development has transitioned from the road construction era to the maintenance era. The recycling of old asphalt pavement materials can ease resource pressure, protect the environment and reduce construction costs, which is in line with the national strategic goals of carbon peak and carbon neutrality. The old asphalt pavement regeneration technology can be divided into cold regeneration and hot regeneration according to the mixing and construction temperature of the recycled mixture. The cold regeneration construction process is carried out at room temperature, which saves energy consumption for heating and mixing materials compared with hot regeneration technology, and has little pollution to the environment. At present, foamed asphalt, emulsified asphalt and cement are often used as binders in engineering, but there are problems such as low early strength of the recycled pavement, slow strength development, unstable quality, and poor water stability and fatigue performance of the mixture obtained after regeneration. It can only meet the requirements of the pavement base or subbase, and the use of the old asphalt mixture is limited to aggregate, among which the aged asphalt basically does not play its due value. Therefore, it is necessary to design a recycled asphalt mixture. Summary of the invention

[0003] The purpose of the present invention is to provide a cold regenerated asphalt mixture based on a light base oil regeneration agent to solve the technical problems of low early strength, slow strength development, unstable quality of existing regenerated pavements, and poor water stability and fatigue performance of the mixture obtained after regeneration.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0005] The regeneration agent based on light base oil is composed of the following components in parts by weight: 70-80 parts of light base oil, 12-17 parts of plasticizer, 6-8 parts of penetrant, and 2-4 parts of anti-aging agent.

[0006] Furthermore, it is composed of the following components in parts by weight: 75 parts of light base oil, 15 parts of plasticizer, 7 parts of penetrant, and 3 parts of anti-aging agent.

[0007] The preparation method of the light base oil regeneration agent comprises the following steps: (1) heating the light base oil to 75°C; (2) sequentially adding a penetrant and a plasticizer, stirring for 25 minutes at a stirring rate of 350 r / min; (3) heating the mixture to 120°C, adding an anti-aging agent and shearing and mixing the mixture evenly at a shearing time of 20 minutes and a shearing rate of 2000 r / min; and (4) cooling the mixture naturally to obtain the light base oil regeneration agent.

[0008] The cold recycled asphalt mixture based on light base oil regeneration agent is composed of recycled asphalt mixture, new aggregate mixture, cement and regeneration agent. Taking the sum of the recycled asphalt mixture, the new aggregate mixture and cement as 100%, the recycled asphalt mixture accounts for 55-62%, the new aggregate mixture accounts for 36.5-43.5% and the cement accounts for 1-2%. Among them, the recycled asphalt mixture includes aged asphalt in the recycled material and aggregate of the recycled material, and the ratio of aged asphalt in the recycled material to aggregate of the recycled material is 2.1-2.4:48-52. The new aggregate mixture includes newly added aggregate and newly added emulsified asphalt, and the ratio of newly added aggregate to newly added emulsified asphalt is 4.1-4.6:93-107. The amount of regeneration agent is 0.4-0.7% of the amount of aged asphalt in the recycled material.

[0009] The present invention has the following beneficial effects due to the adoption of the above technical solution:

[0010] (1) The present invention has found through thermogravimetric analysis that the prepared regeneration agent has a higher aromatic content and a lower asphaltene content, which can adjust the balance of components in asphalt and supplement the missing components in aged asphalt to a degree matching that of new asphalt. Adding an appropriate amount of light base oil regeneration agent can improve the splitting strength and compressive strength of cold regenerated asphalt mixture. When the regeneration agent dosage is 0.6%, the mechanical strength improvement effect reaches the best. With the increase of the dosage of recycled materials in the asphalt mixture, the high temperature stability and low temperature crack resistance of the regenerated mixture are reduced, but can still meet the requirements of the specification.

[0011] (2) The regeneration agent is used to dilute and dissolve aged asphalt to improve the utilization rate of aged asphalt. The optimal dosage of the regeneration agent is determined based on strength through asphalt mixture splitting test and compression test. The effect of light base oil regeneration agent on the performance of cold recycled asphalt mixture is studied based on road performance, providing data support for the promotion and application of asphalt cold recycling technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is the gradation curve diagram of the recycled mixture of the present invention;

[0013] Figure 2 This is a test result diagram of the regeneration agent and the four components of asphalt of the present invention;

[0014] Figure 3 is a graph of splitting strength of regenerated asphalt mixtures with different regeneration agent dosages of the present invention;

[0015] Figure 4 It is a compressive strength diagram of the regenerated asphalt mixture with different regeneration agent dosages of the present invention. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and preferred embodiments. However, it should be noted that many details listed in the specification are only for the purpose of enabling the reader to have a thorough understanding of one or more aspects of the present invention, and these aspects of the present invention can be implemented even without these specific details.

[0017] 1 Raw materials and tests

[0018] 1.1 Asphalt mixture

[0019] The old asphalt mixture was taken from the road surface of a trunk road in Nanning, Guangxi. The road has been in use for 8 years, and the original road surface has serious defects such as rutting, cracking, and block cracks. The moisture content of the old asphalt mixture measured by the drying method is 0.6%, and the oil-stone ratio of the old asphalt mixture measured by the Absen recycled asphalt method is 4.6%. The gradation of the old asphalt mixture obtained by weighing by the screening method is shown in Table 1.

[0020] Table 1 Gradation of old asphalt mixture

[0021]

[0022] According to the screening results in Table 1, the gradation design of the recycled mixture adopts the medium-grained gradation of the "Technical Specifications for Highway Asphalt Pavement Regeneration" (JTG / T 5521-2019). When the milling material gradation does not meet the engineering gradation requirements, limestone aggregate is added. The test uses slow-cracking cationic emulsified asphalt and slag silicate cement with a dosage of 1.5%. The technical indicators of limestone aggregate, emulsified asphalt, cement and mineral powder all meet the requirements of the specification. The optimized gradation curve is shown in the figure below: Figure 1 shown.

[0023] 1.2 Regeneration agent

[0024] 1.2.1 Preparation of regeneration agent

[0025] The main components of the regeneration agent used in the study include light base oil, plasticizer, penetrant and anti-aging agent, among which the light base oil is environmentally friendly rubber oil, the plasticizer is epoxy fatty acid methyl ester, the penetrant is an environmentally friendly penetrant with a high aromatic content provided by the market, and the anti-aging agent is organic modified nano-montmorillonite. The light base oil in the regeneration agent is rich in aromatics and has a strong ability to dissolve asphaltene; the plasticizer can be inserted into the polymer molecular chain, weaken the interaction force of the asphalt molecular chain, increase the mobility of the asphalt molecular chain, and thus improve the low-temperature ductility of the aged asphalt; the penetrant increases the penetration effect of the regeneration agent, so that the regeneration agent can be integrated with the aged asphalt on the surface of the stone during the mixing process, which can improve the regeneration performance of the asphalt regeneration agent and be used for the regeneration of waste asphalt.

[0026] The preparation method of the regeneration agent is as follows: (1) heating the light base oil to 75°C; (2) adding the penetrant and plasticizer in sequence, stirring for 25 minutes, and the stirring rate is 350r / min; (3) heating the mixture to 120°C, adding the anti-aging agent and shearing and mixing evenly, the shearing time is 20 minutes, and the shearing rate is 2000r / min; (4) cooling naturally to obtain the light base oil regeneration agent. The performance indicators of the regeneration agent are shown in Table 2.

[0027] Table 2 Regeneration agent performance indicators

[0028]

[0029] 1.2.2 Study on the performance of regeneration agent

[0030] The main manifestation of asphalt aging is the reduction of light components such as saturated and aromatic components and the increase of colloid and asphalt. High-quality regeneration agent has a high aromatic content, which can supplement the missing light components in aged asphalt, making the content of the four components of regenerated asphalt close to that of new asphalt. The study fully mixed the regeneration agent with the aged asphalt prepared by laboratory simulation, with the regeneration agent dosage of 6%. The asphalt was analyzed by thermogravimetric analysis, and the results are as follows Figure 2 shown.

[0031] Depend on Figure 2 It can be seen that the regeneration agent used in the study has a higher aromatic content and a lower asphaltene content. Compared with the old asphalt, the saturated and aromatic content of the regenerated asphalt is increased, the colloid and asphaltene content is reduced, and the content of the four components of the regenerated asphalt is close to that of the new asphalt, indicating that this regeneration agent can adjust the balance of the four components of asphalt, so that the missing components in the aged asphalt can be supplemented to a level that matches the new asphalt.

[0032] 2 Determine the optimal dosage of regeneration agent

[0033] 2.1 Splitting test

[0034] The Marshall test was used to determine that the asphalt content of the recycled asphalt mixture was 4.3%, and the light base oil regeneration agent content was 0%, 0.2%, 0.4%, 0.6%, 0.8%, and 1.0%. The asphalt mixture specimens with a diameter of 101.6 mm and a height of 63.5 mm were formed by the Marshall standard compaction method. According to the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering", the asphalt mixture splitting test was used to determine the mechanical properties of the asphalt mixture at 15°C and a loading rate of 50 mm / min when it was split or in the elastic stage. The test results are shown in Figure 3 .

[0035] from Figure 3It can be seen that the splitting strength of asphalt mixture increases first and then decreases with the increase of the light base oil regeneration agent dosage. When the dosage is 0.6%, the splitting strength reaches the extreme value, which is 26.7% higher than the splitting strength of the mixture without light base oil regeneration agent. The addition of light base oil regeneration agent increases the viscosity of asphalt on the one hand, giving the asphalt mixture a greater viscous resistance, and on the other hand, it increases the bonding force between asphalt and aggregate, improves the shear performance of the asphalt mixture, and increases the splitting strength.

[0036] 2.2 Uniaxial compression test

[0037] The asphalt mixture specimens with the light base oil regeneration agent content of 0%, 0.2%, 0.4%, 0.6%, 0.8% and 1.0% were subjected to uniaxial compression test. The specimen size was a cylinder with a diameter of 100mm and a height of 100mm. The test temperature was 20℃ and the loading rate was 2mm / min. The compressive strength of the asphalt mixture was determined by uniaxial compression test. The test results are shown in Figure 4 .

[0038] from Figure 4 It can be seen that when the dosage of light base oil regeneration agent is 0.6%, the compressive strength reaches the extreme value, and the splitting strength of the mixture without light base oil regeneration agent is increased by 15.4%, indicating that the addition of an appropriate amount of light base oil regeneration agent also improves the compressive strength performance of the asphalt mixture; and as the dosage of light base oil regeneration agent continues to increase, the compressive strength of the asphalt mixture decreases rapidly, even lower than that without light base oil regeneration agent. Analysis shows that this is mainly because when the dosage of the regeneration agent is small, the aged asphalt is diluted and dissolved, and the viscosity of the asphalt increases. As the dosage of the regeneration agent increases, the light base oil and penetrant in the regeneration agent seriously dilute the aged asphalt wrapped around the aggregate, the cohesion of the mixture decreases, and the compressive strength of the asphalt mixture decreases.

[0039] Based on the above mechanical test results, the optimal dosage of the regeneration agent is determined to be 0.6% based on the strength of the asphalt mixture.

[0040] 3. Road performance of cold recycled asphalt mixture

[0041] 3.1 High temperature stability

[0042] In this paper, rutting tests were conducted on cold recycled asphalt mixtures with 60%, 70%, 80%, 90% and 100% recycled material content in asphalt mixtures to study the influence of different recycled material content in asphalt mixtures on the high temperature performance of cold recycled asphalt mixtures. The results are shown in Table 3.

[0043] Table 3 Rutting test results of different asphalt mixture recycled material dosage

[0044]

[0045]

[0046] As can be seen from Table 3, the dynamic stability of cold recycled asphalt mixture gradually decreases with the increase of recycled material content in asphalt mixture. When the recycled material content in asphalt mixture is 60%, the maximum dynamic stability is 6100 times / mm. When the recycled material content in asphalt mixture is 100%, the minimum dynamic stability is 3010 times / mm, and the dynamic stability is reduced by 1 times. This is mainly because when the recycled material content in asphalt mixture is small, the emulsified asphalt and cement in the cold recycled asphalt mixture play a major role, and the dynamic stability of the mixture is high. With the increase of recycled material content in asphalt mixture, the content of aged asphalt in cold recycled asphalt mixture increases. At the test temperature of 60℃, the light oil of the regeneration agent softens the recycled asphalt and the demulsified aged asphalt. During the rutting test, the softening effect is more obvious after repeated rolling by the load wheel, resulting in a significant decrease in the dynamic stability of the mixture.

[0047] 3.2 Low temperature crack resistance

[0048] In this paper, small beam bending tests were conducted on cold recycled asphalt mixtures with 60%, 70%, 80%, 90% and 100% recycled material content in asphalt mixtures to study the effect of the amount of recycled material in asphalt mixtures on the low-temperature crack resistance of cold recycled asphalt mixtures. The results are shown in Table 4.

[0049] Table 4 Results of low-temperature beam bending tests with different amounts of recycled asphalt mixtures

[0050]

[0051] It can be seen from Table 4 that the flexural strain of cold recycled asphalt mixture gradually decreases with the increase of the amount of recycled material in the asphalt mixture. Because the content of aged asphalt increases while increasing the amount of recycled material in the asphalt mixture, the asphalt mixture exhibits high brittleness and low toughness, and its low-temperature performance decreases.

[0052] Based on the problem of low utilization rate of aged asphalt in the cold regeneration technology commonly used in engineering, a light base oil regeneration agent was prepared, and relevant performance research was carried out to provide technical support for engineering applications. The main conclusions are as follows: (1) Through thermogravimetric analysis tests, it was found that the prepared regeneration agent has a high aromatic content and a low asphaltene content. It can adjust the balance of components in asphalt and supplement the missing components in aged asphalt to a level that matches that of new asphalt. (2) The addition of an appropriate amount of light base oil regeneration agent can improve the splitting strength and compressive strength of cold recycled asphalt mixtures. When the regeneration agent dosage is 0.6%, the mechanical strength improvement effect is optimal. (3) With the increase in the amount of recycled material in the asphalt mixture, the high temperature stability and low temperature crack resistance of the recycled mixture are reduced, but it can still meet the requirements of the specification.

[0053] The amount of regeneration agent is based on the content of aged asphalt, which is 0.6% of the amount of aged asphalt in the old mixture. The oil-to-aggregate ratio in the old asphalt mixture is 4.6%, that is, asphalt: aggregate is 4.6:100. The oil-to-aggregate ratio of the recycled asphalt mixture is 4.3%, that is, asphalt: aggregate is 4.3:100. The amount of newly added cement is based on the mass of the recycled asphalt mixture, which is 1.5% of the mass of the recycled asphalt mixture.

[0054] Through thermogravimetric analysis tests, it was found that the prepared regeneration agent has a higher aromatic content and a lower asphalt content, which can adjust the balance of components in asphalt and supplement the missing components in aged asphalt to a level matching that of new asphalt; the optimal dosage of the regeneration agent was determined based on strength through asphalt mixture splitting tests and compression tests. When the dosage of light base oil regeneration agent was 0.6%, the mechanical strength improvement effect was optimal; the increase in the dosage of recycled materials in the asphalt mixture resulted in a decrease in the high temperature stability and low temperature crack resistance of the recycled asphalt mixture, but it still met the regeneration specification requirements.

[0055] The regeneration agent is used to dilute and dissolve aged asphalt to improve the utilization rate of aged asphalt. The optimal dosage of the regeneration agent is determined based on strength through asphalt mixture splitting test and compression test. The effect of light base oil regeneration agent on the performance of cold recycled asphalt mixture is studied based on road performance, providing data support for the promotion and application of asphalt cold recycling technology.

[0056] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A light base oil based regeneration agent characterized by: The invention is composed of the following components in parts by weight: 70-80 parts of light base oil, 12-17 parts of plasticizer, 6-8 parts of penetrant and 2-4 parts of anti-aging agent.

2. The light base oil-based regeneration agent according to claim 2, characterized in that: The invention is composed of the following components in parts by weight: 75 parts of light base oil, 15 parts of plasticizer, 7 parts of penetrant and 3 parts of anti-aging agent.

3. The method for preparing a light base oil-based regeneration agent according to claim 1, characterized in that: (1) Heat the light base oil to 75°C; (2) Add the penetrant and plasticizer in sequence, stir for 25 minutes, and the stirring rate is 350r / min; (3) Heat the mixture to 120°C, add the anti-aging agent and shear mix evenly, the shear time is 20 minutes, and the shear rate is 2000r / min; (4) Cool naturally to obtain the light base oil regeneration agent.

4. The cold regenerated asphalt mixture based on light base oil regeneration agent according to claim 1, characterized in that: It is composed of recycled asphalt mixture, new aggregate mixture, cement and regeneration agent. Taking the sum of the recycled asphalt mixture, the new aggregate mixture and cement as 100%, the recycled asphalt mixture accounts for 55-62%, the new aggregate mixture accounts for 36.5-43.5% and the cement accounts for 1-2%. Among them, the recycled asphalt mixture includes aged asphalt in the recycled material and aggregate of the recycled material, and the ratio of aged asphalt in the recycled material to aggregate of the recycled material is 2.1-2.4:48-52. The new aggregate mixture includes newly added aggregate and newly added emulsified asphalt, and the ratio of newly added aggregate to newly added emulsified asphalt is 4.1-4.6:93-107. The amount of the regeneration agent is 0.4-0.7% of the amount of aged asphalt in the recycled material.

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