Modified asphalt preparation process for accelerating asphalt swelling

Abstract

The invention relates to a modified asphalt preparation process for accelerating the swelling rate of SBS in asphalt by adding dibenzoyl peroxide (BPO) and dibenzoylmethane (BPA). According to the method, a certain proportion of BPO and BPA are added in the preparation process of SBS modified asphalt, an SBS network structure is destroyed under the action of free radicals generated by BPO, absorption of the SBS to light components of matrix asphalt is enhanced, meanwhile, excessive free radicals are captured by BPA, and performance degradation caused by excessive crosslinking is avoided, so that the swelling rate of SBS is remarkably increased, and the swelling time is shortened to 150 minutes. According to the process, the shear viscosity change is measured through a standard viscometer, so that the improvement of the swelling efficiency is verified, the shear viscosity amplification of a system added with BPO and BPA is improved by about 39% compared with that of a system without an agent, the swelling rate is improved to 2.37 times, and finally, the modified asphalt shows excellent high and low temperature performance and anti-aging performance. The method is simple in process, efficient and suitable for the rapid preparation requirement in asphalt pavement construction.

Description

Technical Field

[0001] The invention relates to the technical field of road engineering materials, and in particular to a process for preparing modified asphalt for accelerating asphalt swelling. Background Art

[0002] In the wet process of preparing modified asphalt, swelling refers to the process by which modifiers such as styrene-butadiene-styrene block copolymer (SBS) absorb light components from the base asphalt, causing the asphalt to expand. The mechanism primarily involves the following: the modifier (e.g., rubber powder and high-molecular-weight polymers like SBS) absorbs the light components in the base asphalt, gradually expanding its molecular chains and increasing its volume, thus causing the asphalt to expand. During this process, the polar groups of the modifier adsorb aromatic and saturated hydrocarbon components from the asphalt. The modifier molecules then interact with the light components in the asphalt through intermolecular interactions, such as hydrogen bonding and van der Waals forces, causing the modifier to gradually disperse and form an expanded network structure. This network structure enhances the viscoelasticity of the asphalt, giving the modified asphalt improved high-temperature resistance and deformation resistance. The swelling process essentially involves the modifier and the components of the asphalt base reaching thermodynamic equilibrium, ultimately forming a relatively stable system. This system exhibits high viscosity at room temperature, helping to alleviate stratification and sedimentation issues in the modified asphalt.

[0003] During the preparation of SBS-modified asphalt, the modifier is first thoroughly dispersed into the base asphalt through methods such as high-speed shearing, stirring, or ultrasonic dispersion. The SBS modifier gradually absorbs the lighter components in the asphalt, causing its molecular chains to unfold and form an expanded structure. This stage may be accompanied by slight dissolution and intermolecular interactions, and the swollen particles begin to form a network structure. Due to the longer molecular chains of the SBS modifier, absorption and expansion take longer, with the entire swelling process taking approximately 3 to 5 hours to complete.

[0004] Because SBS swells slowly in asphalt, it requires prolonged shearing and mixing to achieve the desired modification effect, increasing energy consumption and impacting production efficiency. Traditional swelling accelerators, such as dioctyl phthalate (DOP), only indirectly increase the swelling rate by reducing asphalt viscosity, but their effect is slow. Swelling efficiency is affected by plasticizer volatilization and thermal aging, making it difficult to maintain over time. Plasticizer residues impair high-temperature performance, and their effectiveness depends primarily on the dosage. Excessive addition can easily lead to "overswelling" of the modifier, ultimately weakening the asphalt's overall performance. Therefore, improving the swelling efficiency of SBS modifiers while maintaining the performance of the modified asphalt remains a pressing technical challenge. Summary of the Invention

[0005] The present invention provides a modified asphalt preparation process for accelerating asphalt swelling, the purpose of which is to provide a method for accelerating the swelling of SBS in asphalt by utilizing the synergistic effect of dibenzoyl peroxide (BPO) and dibenzoylmethane (BPA). The method can achieve efficient swelling in a relatively short time and significantly improve the high and low temperature performance and anti-aging performance of the modified asphalt.

[0006] The purpose of the present invention is achieved through the following technical solutions: A process for preparing modified asphalt for accelerating asphalt swelling, wherein the main raw materials include base asphalt, SBS modifier, BPO, BPA and environmentally friendly aromatic oil, and the preparation process comprises the following steps: (1) preparing asphalt mortar: heating the base asphalt to 160-180° C., adding the SBS modifier under shearing conditions, shearing and stirring to uniformly disperse the base asphalt, and obtaining asphalt mortar; (2) Adding swelling accelerator: Add BPO and BPA under shear conditions and maintain the temperature at around 180°C; (3) Shearing and swelling: Mixing at 2000-3000 rpm for 30-60 minutes, adding environmentally friendly aromatic oil, the asphalt swells and develops during this process; (IV) Finished product collection: After completion of swelling and shearing, the modified asphalt finished product is obtained.

[0007] In some embodiments, the SBS modifier is an SBS thermoplastic elastomer.

[0008] In some embodiments, the amount of BPO added is 0.1-0.5%, preferably 0.4%, of the weight of the modified asphalt. As an initiator, BPO promotes the crosslinking of SBS molecular chains through free radical reactions, thereby improving the swelling rate and high-temperature performance of the asphalt.

[0009] In some embodiments, the BPA is added in an amount of 0.1-0.3%, preferably 0.3%, of the weight of the modified asphalt. As a stabilizer and cosolvent, it synergizes with BPO to reduce the risk of oxidation caused by excessive free radicals while enhancing the compatibility and anti-aging ability of the asphalt.

[0010] In some embodiments, the environmentally friendly aromatic oil refers to an aromatic hydrocarbon solvent that has been treated to reduce harmful substances and meets environmental standards. It has low volatile organic compound (VOC) emissions and significantly reduced levels of harmful aromatic compounds (such as benzene, toluene, and xylene). Its primary components are low-boiling aromatic hydrocarbons and a small amount of saturated hydrocarbons. The environmentally friendly aromatic oil is added at a level of 2% by weight of the modified asphalt. This can further enhance the swelling efficiency of the SBS and the asphalt's low-temperature flexibility.

[0011] The modified asphalt is obtained by the above preparation process.

[0012] In some embodiments, the modified asphalt has a needle penetration of 78 dmm at 25°C and an elongation of 18 cm at -10°C.

[0013] In some embodiments, the modified asphalt has a softening point of 58.5-64.5°C, a low-temperature ductility of 20-22 cm at -10°C, an RTFOT softening point increment of 4.0-6.5°C, and a PAV ductility reduction rate of 10-15%.

[0014] In some embodiments, the shear viscosity of the modified asphalt is 3.9 Pa·s.

[0015] Beneficial Effects: Through the synergistic effect of BPO and BPA, the present invention enables the SBS modifier to rapidly absorb lightweight components in asphalt, improving its compatibility with the base asphalt. Furthermore, by controlling the dosage of BPO and BPA, the asphalt's high-temperature performance is enhanced while also improving its low-temperature flexibility and aging resistance. This invention also allows for the complete swelling of SBS in a relatively short time, reducing production costs.

[0016] The present invention uses BPO as a free radical initiator, promoting the opening and moderate crosslinking of SBS molecular chains, thereby increasing its swelling rate in asphalt. BPA and BPO also work synergistically to inhibit excessive free radical reactions, preventing accelerated asphalt oxidation and performance degradation. By regulating free radical concentration, the present invention effectively inhibits asphalt aging and extends its service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0018] Figure 1 The molecular structure of BPO; Figure 2 The molecular structure of BPA; Figure 3 This is a diagram showing the shear viscosity change of modified asphalt according to a preferred embodiment of the present invention; Figure 4 This is a diagram of the swelling rate constant of the modified asphalt according to a preferred embodiment of the present invention; Figure 5 The figure is a flow chart of the modified asphalt preparation process according to a preferred embodiment of the present invention.

[0019] Specific embodiment In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments.

[0020] Example 1 The base asphalt is 100 parts, with a needle penetration of 90 dmm (25°C) and a softening point of 48°C; 4 parts of SBS modifier, linear styrene-butadiene-styrene (SBS) thermoplastic elastomer, styrene content of 30%; 0.3 parts of BPO was selected as a free radical initiator; 0.2 parts of BPA was selected as a free radical stabilizer; 3 parts of environmentally friendly aromatic oil is selected to further improve the compatibility of SBS with the asphalt matrix.

[0021] Step (1) preparing asphalt mortar: heating the base asphalt to 160°C to allow it to fully flow and remain uniform; maintaining the base asphalt at 160°C and stirring for 10 minutes to remove impurities and bubbles; slowly adding the SBS thermoplastic elastomer to the heated base asphalt; continuing stirring for 15 minutes to uniformly disperse the SBS in the asphalt.

[0022] Step (2): gradually add BPO and BPA while stirring; ensure uniform dispersion during addition to avoid excessive local concentration leading to overreaction.

[0023] In step (3), a high shear mixer is used with a shear speed set at 2500 rpm for continuous shear mixing for 40 minutes; the temperature is maintained at 180°C during the shearing process to ensure efficient swelling and chemical reactions; after the shearing is completed, environmentally friendly aromatic oil is added; and stirring is continued for another 10 minutes to ensure full compatibility between the modifier and the asphalt.

[0024] Step (4) collect the modified asphalt finished product for future use or direct use in performance testing. Using a needle penetrometer, a ring-ball softening point meter, and a ductility meter, the modified asphalt parameters are shown in Table 1 below: Table 1 Modified asphalt test parameters The above tests clearly demonstrate that BPO releases free radicals, weakening the physical crosslinks between SBS molecules and promoting their absorption of lighter asphalt components. BPA captures excess free radicals, inhibiting excessive oxidation and ensuring a smooth swelling process. The synergistic effect of BPO and BPA improves the swelling efficiency of SBS while avoiding performance degradation caused by increased oxidation. The aromatic oil further enhances the compatibility between asphalt and SBS, improving low-temperature ductility.

[0025] Example 2 In order to explore the effects of different BPO and BPA dosages on the performance of modified asphalt, the following experiments were designed to compare the modification effects under different ratios.

[0026] BPO dosage: set to 0.2%, 0.3%, 0.4%, 0.5% (mass fraction, relative to the total mass of modified asphalt).

[0027] BPA dosage: set to 0.1%, 0.2%, 0.3%, 0.4% (mass fraction, relative to the total mass of modified asphalt).

[0028] The modified asphalt was prepared according to the process described in Example 1, with emphasis on maintaining consistent temperature and shear conditions.

[0029] The modified asphalt parameters tested using a ring-ball softening point tester, ductility tester, rotating film aging tester, and pressure aging tester are shown in the following table: Table 2 Test parameters of modified asphalt in Example 2 Through the above tests, it can be found that the softening point increases with the increase of BPO and BPA dosage, especially when BPO is 0.4% and BPA is 0.3%, the softening point reaches 64°C, indicating that the viscosity of the system is enhanced; the low-temperature ductility improves with the increase of BPO and BPA dosage, but the ductility decreases slightly when BPO exceeds 0.4%, which is due to the weakening of the plastic effect of the system; the synergistic effect of BPA effectively prevents the adverse effects of excessive free radical reactions on low-temperature performance.

[0030] The RTFOT test showed that the optimization of the BPO and BPA dosage significantly reduced the softening point increment, indicating that the thermal oxidative aging resistance of the modified asphalt was enhanced; in the PAV test, the ductility reduction rate decreased significantly with the increase of BPA dosage, indicating that the antioxidant effect of BPA can effectively alleviate the long-term aging effects.

[0031] Therefore, in this experiment, the performance of modified asphalt is optimal when the BPO dosage is 0.4% and the BPA dosage is 0.3%.

[0032] Example 3 In order to quantitatively evaluate the accelerating effect of BPO and BPA in the swelling process of SBS modified asphalt, a standard viscometer was used to measure the change in viscosity with time until the swelling ended (viscosity stabilized).

[0033] The same materials and procedures as in Example 1 were used for the experiment, along with a control group without BPO or BPA. The same temperature and shear conditions were maintained. Shear viscosity was measured every 30 minutes at 150°C using a standard viscometer. Testing continued until the shear viscosity stabilized, indicating complete swelling.

[0034] After testing, the modified asphalt parameters are shown in the following table: Table 3 Swelling time viscosity determination The experimental results show that the shear viscosity of the conventional process tends to be stable after 210 minutes and the swelling rate is slow; the new modified process using BPO and BPA reaches a stable viscosity in 150 minutes, and the swelling time is shortened by 40% compared with the process without additives.

[0035] The addition of BPO and BPA resulted in a more rapid increase in the system's shear viscosity. Within the first 45 minutes, the viscosity of the system increased by 1.9 Pa·s, 2.1 times the conventional process (0.9 Pa·s). The addition of BPO and BPA significantly increased the swelling rate of SBS, while the viscosity stability value increased by 39% compared to the untreated system, indicating a more uniform and stable swelling of the system.

[0036] The swelling rate constant of the system prepared using the new modification process of BPO and BPA is 0.0076 Pa·s / min, and the swelling rate constant of the system with the addition of BPO and BPA is 0.018 Pa·s / min, which is 2.37 times that of the conventional process.

[0037] This indicates that BPO releases free radicals that promote the disintegration of the SBS network, enabling it to absorb lighter asphalt components more rapidly; BPA stabilizes free radicals, preventing excessive cross-linking and ensuring a smooth swelling process. The synergistic effect of the two significantly shortens swelling time while improving the system's final performance. Changes in shear viscosity indicate that the additive promotes the initial stages of swelling while ensuring a higher and more stable final viscosity. Using a standard viscometer to measure viscosity changes is an effective means of evaluating swelling rates, providing a scientific basis for optimizing the preparation process of SBS-modified asphalt.

[0038] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

Claims

1. A process for preparing modified asphalt that accelerates asphalt swelling, wherein the main raw materials include base asphalt, SBS modifier, BPO, BPA, and environmentally friendly aromatic oil, and the preparation process comprises the following steps: (1) preparing asphalt mortar: heating the base asphalt to 160-180° C., adding the SBS modifier under shearing conditions, shearing and stirring to uniformly disperse the base asphalt, and obtaining asphalt mortar; (2) Adding swelling accelerator: Add BPO and BPA under shear conditions and maintain the temperature at around 180°C; (3) Shearing and swelling: Mixing at 2000-3000 rpm for 30-60 minutes, adding environmentally friendly aromatic oil, the asphalt swells and develops during this process; (IV) Finished product collection: After swelling and shearing, the modified asphalt finished product is obtained.

2. The process for preparing modified asphalt for accelerating asphalt swelling according to claim 1, wherein: The SBS modifier is an SBS thermoplastic elastomer.

3. The process for preparing modified asphalt for accelerating asphalt swelling according to claim 1, wherein: The added amount of BPO is 0.1-0.5% of the weight of the modified asphalt.

4. The process for preparing modified asphalt for accelerating asphalt swelling according to claim 3, wherein: The added amount of BPO is 0.4% of the weight of the modified asphalt.

5. The process for preparing modified asphalt for accelerating asphalt swelling according to claim 1, wherein: The amount of BPA added is 0.1-0.3% of the weight of the modified asphalt.

6. The process for preparing modified asphalt for accelerating asphalt swelling according to claim 5, wherein: The amount of BPA added is 0.3% by weight of the modified asphalt.

7. The process for preparing modified asphalt for accelerating asphalt swelling according to claim 1, wherein: The added amount of the environmentally friendly aromatic oil is 2% of the weight of the modified asphalt.

8. Modified asphalt obtained by the modified asphalt preparation process for accelerating asphalt swelling according to any one of claims 1 to 7.

9. The modified asphalt according to claim 8, wherein The modified asphalt has a softening point of 58.5-64.5°C, a low-temperature ductility of 20-22 cm at -10°C, an RTFOT softening point increment of 4.0-6.5°C, and a PAV ductility reduction rate of 10-15%.

10. The modified asphalt according to claim 8, wherein The shear viscosity of the modified asphalt is 3.9 Pa·s.

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