High-thixotropy modified asphalt and preparation method thereof

Abstract

The invention relates to the technical field of road engineering materials, in particular to high-thixotropy modified asphalt and a preparation method thereof. The high-thixotropy modified asphalt is prepared from the following components in parts by weight: 85 parts of matrix asphalt, 3 to 6 parts of SBS (Styrene Butadiene Styrene) modifier, 5 to 8 parts of organobentonite and synthetic polymer wax, 1.5 to 2.5 parts of dispersing agent and 0.5 to 3.5 parts of coupling agent, the weight ratio of the organic bentonite to the synthetic polymer wax is (2-4): 1. According to the high-thixotropy modified asphalt, the organobentonite and the synthetic polymer wax are mainly adopted, the organobentonite and the synthetic polymer wax have a mutual synergistic effect, a dual-network thixotropic system is constructed, the asphalt is endowed with excellent thixotropy, in the thin overlay process, when the paving temperature is 165 DEG C, the viscosity of the asphalt is lower than 2.3 Pas, paving and rolling are facilitated, and the construction workability is improved; and during formal use, the asphalt can be self-repaired after being structurally damaged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of road engineering materials, in particular to a high thixotropic modified asphalt and a preparation method thereof, which is suitable for thin-layer overlay road maintenance engineering. BACKGROUND

[0002] The thin-layer overlay, a maintenance technology for asphalt pavement, can restore the anti-skid, waterproof and flatness performance of the road surface with an extremely thin thickness of 1.5-2 cm at one time, and can open traffic within a few hours after construction, thereby reducing the interference with road traffic to the minimum. Meanwhile, the thin-layer overlay directly meets the maintenance concept of green and low carbon by reducing the milling of old materials and saving stone asphalt. Therefore, the thin-layer overlay has become the "first choice" for preventive maintenance of asphalt pavement. However, the current thin-layer overlay technology has the following problems: first, in order to ensure the road performance, the high-viscosity high-elasticity or high-toughness asphalt is usually used for the thin-layer overlay technology due to the thin maintenance layer. However, the use of such asphalt makes it difficult for the pavement to self-repair after structural damage. Second, the use of high-viscosity high-elasticity or high-toughness asphalt has poor workability at a paving temperature of 165℃ due to its high viscosity.

[0003] In view of the above problems, there is an urgent need for a modified asphalt suitable for thin-layer overlay paving, which has strong self-repairing ability after structural damage during use, and is easy to compact at high temperature paving, thereby improving the workability. SUMMARY

[0004] To solve the above technical problems, the present application provides a high thixotropic modified asphalt and a preparation method thereof. The modified asphalt obtained by the technical scheme has low viscosity at high temperature paving during road maintenance, which is beneficial to paving and compaction, and improves the workability of construction. In addition, the modified asphalt has strong self-repairing ability after structural damage during use.

[0005] The present application provides a high thixotropic modified asphalt and a preparation method thereof, which adopts the following technical scheme: The present application provides a high thixotropic modified asphalt, which comprises the following components by weight: 85 parts of base asphalt, 3-6 parts of SBS modifier, 5-8 parts of organic bentonite and synthetic polymer wax, 1.5-2.5 parts of dispersant, and 0.5-3.5 parts of coupling agent; the weight ratio of the organic bentonite to the synthetic polymer wax is (2-4):1. The base asphalt has a penetration of 60-80 (0.1 mm).

[0006] Preferably, the SBS modifier has a star structure, a styrene content of 30%-35%, and a molecular weight of 140-300 thousand.

[0007] By adopting the technical scheme, the star type SBS modifier can provide higher adhesion and viscosity in rheological properties, and further improve the adhesion between the asphalt and the aggregate. Moreover, due to the characteristics of the molecular structure of the star type SBS modifier, a more stable network structure can be formed in the asphalt, so that the strength and waterproof ability of the asphalt mixture are significantly improved, and the durability is enhanced.

[0008] Preferably, the organic bentonite is a quaternary ammonium salt modified montmorillonite, and the interlayer spacing d 001 ≥1.9nm. When the interlayer spacing d 001 ≥1.9nm, the thixotropy of the asphalt is obviously enhanced.

[0009] Preferably, the synthetic polymer wax is polyamide wax or polyethylene wax, the polyamide wax is PA-8700 free activated solvent type polyamide wax powder, the amine value is ≤5mgKOH / g, and the molecular weight is 8000-12000; the amine value of the polyethylene wax is close to 0, and the molecular weight is 2000-4000. The synthetic polymer wax provides a shear thinning effect, and the low amine value (≤5mgKOH / g) is conducive to forming a stable, uniform and reversible thixotropic network in the asphalt.

[0010] By adopting the technical scheme, the organic bentonite and the SBS modifier network interpenetrate to form a more compact "elastic-viscous" dual-phase structure, the physical crosslinking points of the polyamide wax and the SBS flexible chain interpenetrate to form a more compact composite reversible network. The two are combined to build a dual-network thixotropic system.

[0011] Preferably, the dispersant is one of zinc stearate, oleamide, modified polyisobutylene succinimide and the like.

[0012] By adopting the technical scheme, because the dispersant mainly has a stabilizing effect, the hydrophobic alkyl chain of the zinc stearate adsorbs the asphaltene, and the polar carboxylic acid group is arranged in a directional manner to form steric hindrance, thereby preventing the modified agent from agglomerating.

[0013] Preferably, the coupling agent is one of γ-aminopropyl triethoxysilane (KH550), bisamino silane and 3-glycidyl ether propyl trimethoxysilane (KH-560). The coupling agent mainly has a coupling effect, and the dosage of the coupling agent has a significant influence on the viscosity of the asphalt, the thixotropic ring and the self-healing index.

[0014] By adopting the technical scheme, the γ-aminopropyl triethoxysilane is hydrolyzed to generate silanol, which is condensed with the hydroxyl group on the surface of the aggregate to form a-Si-O-Si- bond, and the amino group reacts with the carboxyl group of the asphalt, so that the adhesion between the asphalt and the aggregate is improved.

[0015] The second aspect of the present application provides a preparation method of high thixotropy modified asphalt, which comprises the following steps: Step one: heat the base pitch to 170-180℃ to melt; Step two: first, add organic bentonite and synthetic polymer wax to the melted base pitch obtained in step one at a temperature of 170-180℃, and shear at a high speed of 1500-2500 rpm for 25-35 minutes; then, first add SBS modifier at a temperature of 170-180℃, shear at a high speed of 4000-5000 rpm, and react for 45-60 minutes; then, add dispersant and coupling agent in sequence, shear at a high speed of 1200-2000 rpm, and react for 50-70 minutes; Step three: defoam at a temperature of 150-170℃ and a vacuum degree of -0.08~-0.1 MPa for 25-40 minutes, and cool to room temperature to obtain high thixotropic modified pitch.

[0016] Compared with the prior art, the application has the following beneficial effects: 1. The high thixotropic modified pitch has a viscosity of less than 2.3 Pa·s at a paving temperature of 165℃, the viscosity is reduced, the flowability of the pitch is improved, and the workability is improved.

[0017] 2. The high thixotropic modified pitch mainly forms a more compact “elastic-viscous” dual-phase structure through the synergistic effect of organic bentonite and polyamide wax, the hard segment molecular chain and the soft segment molecular chain of the organic bentonite form physical crosslinking points, and the physical crosslinking points of the polyamide wax and the SBS modifier network interpenetrate to form a more compact composite reversible network. The two are combined to build a dual-network thixotropic system, so that the pitch has a thixotropic ring area of greater than 600 Pa·s·rad⁻¹ and a healing index of greater than 0.9, and the pitch has excellent thixotropy and is more easily restored after structural damage. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The viscosity change curves of the modified pitches obtained in Example 1, Example 8, and Comparative Example 16 at different temperatures. DETAILED DESCRIPTION

[0019] The application will be further described in detail below in combination with specific embodiments. The following are preferred embodiments of the application, but do not limit the protection scope of the application, and all other embodiments obtained by equivalent changes made on the basis of the embodiments and principles of the application without creative labor, should be covered by the protection scope of the application.

[0020] The temperature during asphalt paving directly affects pavement quality. If the temperature is too low, the viscosity of the mixture increases, making compaction difficult and leading to porosity and looseness in the pavement. If the temperature is too high, it can cause wheel sticking, resulting in an uneven surface. Temperature adjustments are necessary at different stages of construction to ensure optimal paving results. The paving temperature for ordinary asphalt mixtures should be maintained at 135℃-150℃, while modified asphalt should be maintained at 150℃-165℃. This invention discloses a high-thixotropic modified asphalt that, during road maintenance at a paving temperature of 165℃, improves asphalt fluidity; the thixotropic ring area is greater than 500 Pa·s·rad⁻¹; the healing index is greater than 0.9; and a dual-network thixotropic system is constructed, making the asphalt more easily recoverable after structural damage. This material has broad application prospects in efficient, energy-saving, and durable thin-layer pavement overlay operations.

[0021] I. Preparation and related performance tests of each embodiment and comparative example The raw materials used in the following examples are as follows: Base bitumen: Penetration 60-80 (0.1 mm); SBS modifier: star-shaped structure, styrene content 30%-35%, molecular weight 140,000-300,000; (Sinopec Baling Petrochemical, model: YH-792E) Organic bentonite is quaternary ammonium salt modified montmorillonite, with a layer spacing of d. 001 ≥1.9 nm (Zhejiang Fenghong New Material Co., Ltd., Model: DK2); The synthetic polymer wax is a polyamide wax with an amine value ≤5mg KOH / g and a molecular weight of 8000~12000 (Zhejiang Fenghong New Material Co., Ltd., product model: PA-8700).

[0022] Dispersant: Zinc stearate (Guangzhou Huicai Pigment Co., Ltd., product model: Huicai HC-ZnSt asphalt grade zinc stearate); Coupling agent: γ-aminopropyltriethoxysilane (Shanghai Maclean Biochemical Technology Co., Ltd., product model: KH-550 silane coupling agent).

[0023] The performance testing method is as follows: Asphalt viscosity: JTG E20-2011 (T0625), Test Procedure for Asphalt and Asphalt Mixtures in Highway Engineering, Blockfield rotational viscometer method (T 0625). Softening point difference (°C): Separation test method (T0661-2011); Thixotropic ring area: Thixotropic ring area test method Using a dynamic shear rheometer (DSR), a continuous scan is performed on an asphalt sample at a constant temperature (e.g., 25 °C) by applying a shear rate from 0 linearly to a set maximum value (e.g., 100 s⁻¹) and then linearly back to 0, recording the shear stress-shear rate curve, forming a closed hysteresis loop; the loop area (in Pa·s⁻¹) is calculated by integration, and the larger the area, the stronger the thixotropy. The test needs to control the time of the ascending / descending segments to be symmetrical and ensure that the temperature is constant to ensure comparability.

[0024] Healing index: fatigue-healing-fatigue loading test In the formula: HI1 is the healing index, %; W is the dissipated energy, MJ / m 3 ; W b , W a are the cumulative dissipated energies before and after the healing of the asphalt mortar, MJ / m 3 .

[0025] Through the fatigue-healing-fatigue intermittent loading mode, the process of the asphalt pavement actually experiencing the cyclic load action and then experiencing the cyclic load action again during the intermittent period of the load is simulated. The test is usually tested by DSR time scanning. The parallel plate diameter is 8 mm, and the distance is 2 mm.

[0026] Basic test parameters of time scanning Example 1 A high thixotropy modified asphalt comprises the following raw materials by weight: 85 parts of base asphalt, 4 parts of SBS modifier, 4.875 parts of quaternary ammonium salt modified montmorillonite, 1.625 parts of polyamide wax (quaternary ammonium salt modified montmorillonite: polyamide wax = 3:1), 2 parts of dispersant, and 2.5 parts of coupling agent. The preparation method of the high thixotropy modified asphalt, comprising the following steps: Step one: heat the base asphalt to 180±5°C to melt; Step two: first, under the condition that the temperature is 180±5°C, add quaternary ammonium salt modified montmorillonite and polyamide wax to the molten base asphalt obtained in step one, and shear at a high speed of 1500±50 rpm for 30±5 minutes; then, under the condition that the temperature is 180±5°C, first add the SBS modifier, shear at a high speed of 4000-5000 rpm, and react for 45-60 minutes; then, add the dispersant and the coupling agent in turn, shear at a high speed of 1200±50 rpm, and react for 60±5 minutes; Step three: under the condition that the temperature is 160±5°C and the vacuum degree is -0.08~ -0.1 MPa, perform defoaming treatment for 30±5 minutes, and cool to room temperature to obtain the high thixotropy modified asphalt.

[0027] Examples 2 to 7 Different from Example 1, only the total amount of quaternary ammonium salt modified montmorillonite and polyamide wax (the ratio of the two is unchanged) is changed, and the content of other components is unchanged. The preparation method is the same as that of Example 1, and the preparation is carried out through the steps of base asphalt melting, high-speed shearing, vacuum degassing, etc.

[0028] Example 8 Fine-tune the content of each component: A high thixotropic modified asphalt, comprising the following raw materials by weight: 85 parts of base asphalt; 5 parts of SBS modifier; 4.5 parts of quaternary ammonium salt modified montmorillonite, 1.5 parts of polyamide wax (quaternary ammonium salt modified montmorillonite: polyamide wax = 3:1); 1.5 parts of dispersant; 2.5 parts of coupling agent; The preparation method is the same as that of Example 1, and the preparation is carried out through the steps of base asphalt melting, high-speed shearing, vacuum degassing, etc.

[0029] Examples 9 to 14 Different from Example 1, only the amount of SBS modifier is changed, and the content of other components is unchanged. The preparation method is the same as that of Example 1, and the preparation is carried out through the steps of base asphalt melting, high-speed shearing, vacuum degassing, etc.

[0030] Examples 15 to 16 Different from Example 1, only the amount of dispersant is changed, and the content of other components is unchanged. The preparation method is the same as that of Example 1, and the preparation is carried out through the steps of base asphalt melting, high-speed shearing, vacuum degassing, etc.

[0031] Examples 17 to 22 Different from Example 1, only the amount of coupling agent is changed, and the content of other components is unchanged. The preparation method is the same as that of Example 1, and the preparation is carried out through the steps of base asphalt melting, high-speed shearing, vacuum degassing, etc.

[0032] Examples 23 and 24 Different from Example 1, only the ratio of quaternary ammonium salt modified montmorillonite and polyamide wax is changed, and the content of other components is unchanged. The preparation method is the same as that of Example 1, and the preparation is carried out through the steps of base asphalt melting, high-speed shearing, vacuum degassing, etc.

[0033] Comparative Examples 1 to 4 Different from Example 1, the amount of quaternary ammonium salt modified montmorillonite and polyamide wax exceeds the protection range, and the content of other components is unchanged. The preparation method is the same as that of Example 1, and the preparation is carried out through the steps of base asphalt melting, high-speed shearing, vacuum degassing, etc.

[0034] The modified asphalts of Examples 1 to 7 and Comparative Examples 1 to 4 are tested for viscosity, thixotropic ring area and healing index, and the results are shown in Table 1: Table 1, modified asphalt test results of examples 1 to 7 and comparative examples 1 to 4 From the data in Table 1, if the weight amount of quaternary ammonium salt modified montmorillonite and polyamide wax is less than 5, the thixotropy of modified asphalt decreases. The viscosity of asphalt at 165℃ decreases to below 0.6 Pa·s; the viscosity of asphalt at 105℃ decreases to below 80 Pa·s; the thixotropic ring area decreases to below 450 Pa·s·rad⁻¹; the healing index decreases to below 0.7, and the overall performance approaches that of SBS modified asphalt. When the total amount of quaternary ammonium salt modified montmorillonite and polyamide wax is less than the range defined in the present application, the amount is insufficient to build a complete and stable three-dimensional network structure in the system. This structural defect results in a significant lack of high-temperature viscosity under static conditions, and after being subjected to shear, the network reconstruction ability (i.e. thixotropy) and self-healing performance of the material are both deteriorated.

[0035] If the weight amount of quaternary ammonium salt modified montmorillonite and polyamide wax is in the range of 5-8, the thixotropy of modified asphalt is enhanced, the viscosity of asphalt at 165℃ is below 2.3 Pa·s; the viscosity of asphalt at 105℃ is above 120 Pa·s; the thixotropic ring area increases to above 600 Pa·s·rad⁻¹; and the healing index always remains above 0.9. When the weight amount of quaternary ammonium salt modified montmorillonite and polyamide wax is 6.5 parts, the viscosity of asphalt at 165℃ is the lowest; the viscosity of asphalt at 105℃ is the highest; the thixotropic ring area is the largest, being 668.34 Pa·s·rad⁻¹; and the healing index is the largest, being 0.97. This is mainly because the quaternary ammonium salt modified montmorillonite and the star-shaped SBS modifier network interpenetrate, forming a dense "elastic-viscous" dual-phase structure, and the physical crosslinking points of polyamide wax and the SBS flexible chain interpenetrate, forming a more dense composite reversible network, which together build a dual-network thixotropic system.

[0036] If the weight amount of quaternary ammonium salt modified montmorillonite and polyamide wax is above 8, the viscosity of modified asphalt is excessively increased, but the self-healing performance is decreased. The viscosity of asphalt at 165℃ rises to above 5.5 Pa·s; the viscosity of asphalt at 105℃ rises to above 210 Pa·s; but the thixotropic ring area decreases to below 500 Pa·s·rad⁻¹; and the healing index decreases to below 0.3, and the overall performance approaches that of high-viscosity asphalt. When the amount of quaternary ammonium salt modified montmorillonite and polyamide wax exceeds the upper limit of the present application, the physical crosslinking points in the system are too dense, resulting in a rigid network structure that is too strong. This structure not only causes the high-temperature construction viscosity to exceed the acceptable range, but also severely weakens the thixotropy and self-healing performance of the material due to its poor elastic recovery ability.

[0037] Considering the influence of the viscosity of asphalt on construction and workability and the influence of thixotropy on self-repair of asphalt structure, the weight amount of quaternary ammonium salt modified montmorillonite and polyamide wax is preferably 5-8 parts, and the optimal value is 6.5 parts.

[0038] Comparative examples 5 to 8 Different from example 1, the amount of SBS modifier exceeds the protection range, and the content of the remaining components remains unchanged. The preparation method is the same as that of example 1, and the preparation is carried out through the steps of melting of base asphalt, high-speed shearing, vacuum degassing and the like.

[0039] The modified asphalt of examples 1 and 9 to 14 and comparative examples 5 to 8 is subjected to viscosity, thixotropic ring area and healing index tests, and the results are shown in table 2: Table 2, test results of modified asphalt of examples 1 and 9 to 14 and comparative examples 5 to 8 From the data in table 2, if the weight amount of SBS modifier is less than 3, the thixotropic performance of the modified asphalt is indirectly reduced. The viscosity of asphalt at 165℃ is reduced to below 0.3 Pa·s; the viscosity of asphalt at 105℃ is reduced to below 110 Pa·s; the thixotropic ring area is suddenly reduced to below 450 Pa·s·rad⁻¹; and the healing index is reduced to below 0.6. The overall performance approaches that of base asphalt. The amount of star-shaped SBS modifier is too low to have a sufficient stable network structure to interpenetrate with the organic bentonite, so that a more compact "elastic-viscous" dual-phase structure cannot be formed, and the physical crosslinking points of polyamide wax cannot be effectively interpenetrated, resulting in a reduction in the thixotropic performance of the whole system. At the same time, due to the instability of the network structure, the high-temperature viscosity of the material is too low, which is not conducive to paving.

[0040] If the weight amount of SBS modifier is in the range of 3-6, the viscosity of asphalt at 165℃ is below 2.0 Pa·s; the viscosity of asphalt at 105℃ is above 130 Pa·s; the thixotropic ring area is suddenly increased to above 600 Pa·s·rad⁻¹; and the healing index is always kept above 0.9. When the weight amount of SBS modifier is 4 parts, the viscosity of asphalt at 165℃ is the lowest; the viscosity of asphalt at 105℃ is the highest; the thixotropic ring area is the largest, being 668.34 Pa·s·rad⁻¹; and the healing index is the largest, being 0.97. The main reason is that the network structure of the star-shaped SBS modifier interpenetrates with the physical crosslinking points formed by the hard segment molecular chain and the soft segment molecular chain of the quaternary ammonium salt modified montmorillonite, forming a more compact "elastic-viscous" dual-phase structure; the SBS flexible chain also interpenetrates with the physical crosslinking points of polyamide wax, forming a more compact composite reversible network, and the two are combined to build a dual-network thixotropic system, which gives the asphalt excellent thixotropy and makes it easier to recover after the structure is damaged.

[0041] If the weight amount of SBS modifier is higher than 6 parts, the viscosity of modified asphalt is excessively increased, but the self-healing performance is decreased. The viscosity of asphalt at 165℃ is increased to more than 2.5 Pa·s; the viscosity of asphalt at 105℃ is increased to more than 160 Pa·s; the thixotropic ring area is suddenly decreased to less than 600 Pa·s·rad-1; the healing index is decreased to less than 0.4; and the overall performance is slowly close to that of high-viscosity asphalt. When the amount of star-shaped SBS modifier exceeds the upper limit of the present application, a rigid network with excessively high crosslinking density is formed. This structure not only significantly increases the high-temperature construction viscosity, which is not conducive to paving operation, but also severely limits the movement and reconstruction ability of molecular chains, resulting in significant decrease in the elasticity, thixotropy and self-healing performance of the system.

[0042] Considering the influence of asphalt viscosity on construction and workability and the influence of thixotropy on self-repairing of asphalt structure, the weight amount of SBS modifier is preferably 3-6 parts, and the best value is 4 parts.

[0043] Comparative Examples 9-12 Different from Example 1, the amount of dispersant exceeds the protection range, and the content of other components remains unchanged. The preparation method is the same as that of Example 1, and the preparation is carried out through the steps of melting of base asphalt, high-speed shearing, vacuum degassing and the like.

[0044] The modified asphalts of Examples 1 and 15-16 and Comparative Examples 9-12 are tested for softening point difference, thixotropic ring area and healing index, and the results are shown in Table 3: Table 3, test results of modified asphalts of Examples 1, 15 and 16 and Comparative Examples 9-12 As shown in Table 3, if the weight amount of dispersant is less than 1.5 parts, the unstable variability of asphalt is enhanced, the softening point difference is greater than 2.5℃, the thixotropic ring area is suddenly decreased to less than 450 Pa·s·rad-1, and the healing index is decreased to less than 0.7.

[0045] If the weight amount of dispersant is in the range of 1.5-2.5 parts, the unstable variability of asphalt is reduced and is in the normal range, the softening point difference is less than 2.5℃, which meets the requirements. When the weight amount of dispersant is 2 parts, the softening point difference of asphalt is the smallest, the thixotropic ring area is the largest, which is 668.34 Pa·s·rad-1, and the healing index is the largest, which is 0.97.

[0046] If the weight amount of dispersant is higher than 2.5 parts, excessive dispersant will cause sedimentation, resulting in decrease in the stability of modified asphalt system, the softening point difference is greater than 2.5℃, the thixotropic ring area is suddenly decreased to less than 500 Pa·s·rad-1, and the healing index is decreased to less than 0.75.

[0047] Considering the influence of viscosity on construction and workability and the influence of thixotropy on self-repairing of asphalt structure, the weight amount of dispersant is preferably 1.5-2.5 parts, and the optimal value is 2 parts.

[0048] Comparative Examples 13-15 Different from Example 1, the amount of coupling agent exceeds the protection range, and the content of the remaining components remains unchanged. The preparation method is the same as that of Example 1, and the preparation is carried out through the steps of melting of base asphalt, high-speed shearing, vacuum degassing and the like.

[0049] The modified asphalts of Examples 1 and 17-22 and Comparative Examples 13-15 are subjected to viscosity, thixotropic ring area and healing index tests, and the results are shown in Table 4: Table 4, test results of modified asphalts of Examples 1 and 17-22 and Comparative Examples 13-15 From the data in Table 4, if the weight amount of coupling agent is less than 0.5 parts, the dosage is too small, and the viscosity and self-healing performance of the modified asphalt are greatly reduced. The asphalt viscosity at 165℃ is reduced to below 0.5 Pa·s; the asphalt viscosity at 105℃ is reduced to below 65 Pa·s; the thixotropic ring area is suddenly reduced to below 450 Pa·s·rad⁻¹; the healing index is reduced to below 0.6, and the overall performance is close to that of base asphalt.

[0050] If the weight amount of coupling agent is in the range of 0.5-3.5 parts, the asphalt viscosity at 165℃ is below 2.0 Pa·s; the asphalt viscosity at 105℃ is above 130 Pa·s; the thixotropic ring area is suddenly increased to above 600 Pa·s·rad⁻¹; and the healing index is always kept above 0.9. When the weight amount of coupling agent is 2.5 parts, the asphalt viscosity at 165℃ is the lowest; the asphalt viscosity at 105℃ is the highest; the thixotropic ring area is the largest, being 668.34 Pa·s·rad⁻¹; and the healing index is the largest, being 0.97.

[0051] If the weight amount of coupling agent is more than 3.5 parts, the dosage is too large, the viscosity of the modified asphalt is increased, but the self-healing performance is reduced. The asphalt viscosity at 165℃ is increased to above 3.0 Pa·s; the asphalt viscosity at 105℃ is increased to above 200 Pa·s; the thixotropic ring area is suddenly reduced to below 500 Pa·s·rad⁻¹; and the healing index is reduced to below 0.3.

[0052] Considering the influence of viscosity on construction and workability and the influence of thixotropy on self-repairing of asphalt structure, the weight amount of coupling agent is preferably 0.5-3.5 parts, and the optimal value is 2.5 parts.

[0053] Comparative Example 16 Different from example 1, the quaternary ammonium salt modified montmorillonite and polyamide wax are replaced by high viscosity agent (PT-HVA), and the rest of the components remain unchanged: 85 parts of base asphalt, 4 parts of SBS modifier, 6.5 parts of high viscosity agent, 2 parts of dispersing agent, 2.5 parts of coupling agent; The preparation method is the same as that of example 1, and the modified asphalt is prepared through the steps of base asphalt melting, high-speed shearing, vacuum degassing, etc.

[0054] The modified asphalts obtained in example 1, example 8 and comparative example 16 are tested for viscosity, thixotropic ring area and healing index at different temperatures, and the results are shown in table 5 (as shown in Figure 1 ).

[0055] Table 5, test results of modified asphalts obtained in example 1, example 8 and comparative example 16 for viscosity, thixotropic ring area and healing index at different temperatures From the data in table 5, it can be seen that the high thixotropic modified asphalts prepared in examples 1 and 8 have low viscosity at paving temperature 165℃, which is convenient for paving and rolling, and has good workability; the thixotropic ring area is greater than 600 Pa·s·rad⁻¹, and the healing index is greater than 0.9, which builds a double network thixotropic system, and the asphalt is more easily restored after structural damage. Among them, the high thixotropic modified asphalt prepared according to the formulation of example 1 has a first damage dissipation energy of 45.17 Mj / m 3 , a second damage dissipation energy of 43.81 Mj / m 3 , and a healing index of 0.97. The high thixotropic modified asphalt prepared according to the formulation of example 8 has a first damage dissipation energy of 43.66 Mj / m 3 , a second damage dissipation energy of 40.60 Mj / m 3 , and a healing index of 0.93. The modified asphalt prepared according to the formulation of comparative example 16 has a first damage dissipation energy of 44.88 Mj / m 3 , a second damage dissipation energy of 14.36 Mj / m 3 , and a healing index of 0.32. The greater the dissipation energy, the better the fatigue performance of the asphalt, and the longer the fatigue life; the higher the healing index, the better the self-healing performance of the asphalt. (Healing index = second damage dissipation energy / first damage dissipation energy) Comparative example 16, compared with examples 1 and 8, uses high viscosity agent to replace quaternary ammonium salt modified montmorillonite and polyamide wax, so that the viscosity of the asphalt is high at paving temperature 165℃, which is not easy to pave and roll, and has poor workability; the thixotropy is low under normal use, and it is difficult to recover after structural damage.

[0056] Comparative examples 17 and 18 Different from example 1, the ratio of quaternary ammonium salt modified montmorillonite and polyamide wax exceeds the protection range, and the content of the remaining components is unchanged. The preparation method is the same as example 1, and the preparation is carried out through the steps of matrix asphalt melting, high-speed shearing, vacuum degassing and the like.

[0057] The modified asphalt of examples 1 and 23 and 24 and comparative examples 17 and 18 is subjected to viscosity, thixotropic ring area and healing index test, and the results are shown in table 6: Table 6, test results of modified asphalt of examples 1 and 23 and 24 and comparative examples 17 and 18 From the data in table 6, if the ratio of quaternary ammonium salt modified montmorillonite and polyamide wax is less than 2:1, the viscosity of asphalt at 165℃ rises to more than 6.0 Pa·s; the viscosity of asphalt at 105℃ decreases to less than 130 Pa·s; the thixotropic ring area decreases to less than 450 Pa·s·rad⁻¹; and the healing index decreases to less than 0.5.

[0058] If the ratio of quaternary ammonium salt modified montmorillonite and polyamide wax is in the range of (2-4):1, the viscosity of asphalt at 165℃ is less than 2.3 Pa·s; the viscosity of asphalt at 105℃ is higher than 130 Pa·s; the thixotropic ring area increases to more than 600 Pa·s·rad⁻¹; and the healing index always remains above 0.9. When the ratio of quaternary ammonium salt modified montmorillonite and polyamide wax is 3:1, the viscosity of asphalt at 165℃ is the lowest; the viscosity of asphalt at 105℃ is the highest; the thixotropic ring area is the largest, which is 668.34 Pa·s·rad⁻¹; and the healing index is the largest, which is 0.97.

[0059] If the ratio of quaternary ammonium salt modified montmorillonite and polyamide wax is higher than 4.0, the viscosity of asphalt at 165℃ rises to more than 5.0 Pa·s; the viscosity of asphalt at 105℃ decreases to less than 120 Pa·s; the thixotropic ring area decreases to less than 450 Pa·s·rad⁻¹; and the healing index decreases to less than 0.5.

[0060] Considering the influence of asphalt viscosity on construction and workability and the influence of thixotropy on asphalt structure self-repair, the ratio of quaternary ammonium salt modified montmorillonite and polyamide wax is preferably (2-4):1, and the best value is 3:1.

[0061] II. Application performance test The modified asphalt obtained according to the formulations of example 1, example 8 and comparative example 16 is used as raw material to prepare asphalt mixture, and the asphalt mixture with gradation of SMA-8 (DB37T 4852-2025) is prepared by using oil stone ratio of 6.3. While maintaining high thixotropy, the road performance is also improved to a certain extent, and the specific test results are shown in table 7.

[0062] Table 7, the road performance test results of the modified asphalt obtained in Example 1, Example 8, and Comparative Example 16 Note: The high-temperature stability of the asphalt mixture is measured by dynamic stability, the low-temperature stability is measured by the maximum bending tensile strain, and the crack resistance is measured by the fracture energy.

[0063] The above road performance parameter test methods are as follows: Dynamic stability: JTG E20-2011, T0719 rutting test; Maximum bending tensile strain: JTG E20-2011, T0715 low-temperature bending test; Fracture energy: JTG E20-2011 T0715 half-circle bending test.

[0064] According to the data analysis in Table 7, the asphalt mixture prepared by using the high-thixotropy modified asphalt as the raw material has certain improvement in the road performance while maintaining the high thixotropy, and the high-temperature stability, the low-temperature stability, and the crack resistance are all improved by more than 20% compared with the conventional high-viscosity asphalt mixture.

[0065] As can be seen above, in the thin-layer overlay process, when the paving temperature is 165℃, the viscosity of the asphalt is less than 2.3 Pa▪s, which is convenient for paving and rolling, and improves the workability; when in formal use, the asphalt can also be self-repaired after being structurally damaged, and has a wide application prospect in the efficient, energy-saving, and durable thin-layer overlay operation of the pavement.

[0066] The above is only a specific embodiment of the present application, but the technical features of the present application are not limited thereto. Any simple change, equivalent replacement or modification made on the basis of the present application to solve the basically same technical problem and realize the basically same technical effect is also covered in the protection scope of the present application.

Claims

1. A high thixotrope modified asphalt characterized by, The components include the following weight parts: 85 parts of base pitch, 3-6 parts of SBS modifier, 5-8 parts of organic bentonite and synthetic polymer wax, 1.5-2.5 parts of dispersant, and 0.5-3.5 parts of coupling agent; the weight ratio of the organic bentonite to the synthetic polymer wax is (2-4):1; the SBS modifier has a star structure and a styrene content of 30%-35%.

2. The high-tack modified asphalt of claim 1, wherein, The organic bentonite is a quaternary ammonium salt modified montmorillonite, with an interlayer spacing d 001 ≥ 1.9 nm.

3. The high-tan modified asphalt of claim 1, wherein, The synthetic polymer wax is polyamide wax or polyethylene wax, the amine value of the polyamide wax is ≤5 mg KOH / g, and the molecular weight is 8000-12000; the amine value of the polyethylene wax is close to 0, and the molecular weight is 2000-4000.

4. The high-tan modified asphalt of claim 1, wherein, The dispersant is one of zinc stearate, oleamide, and modified polyisobutylene succinimide.

5. The high-tan modified asphalt of claim 1, wherein, The coupling agent is one of γ-aminopropyl triethoxysilane, bisamino silane, and 3-glycidyl ether propyl trimethoxysilane.

6. A process for the preparation of a high-tan modified bitumen according to any one of claims 1 to 5, characterized in that, The method includes the following steps: Step one: heating the base pitch to 170-180°C for melting; Step two: first, under the condition of a temperature of 170-180°C, adding the organic bentonite and the synthetic polymer wax to the base pitch in a molten state obtained in step one, and shearing at a high speed of 1500-2500 rpm for 25-35 minutes; then, under the condition of a temperature of 170-180°C, first adding the SBS modifier, shearing at a high speed of 4000-5000 rpm, and reacting for 45-60 minutes; then, adding the dispersant and the coupling agent in sequence, shearing at a high speed of 1200-2000 rpm, and reacting for 50-70 minutes; Step three: under the condition of a temperature of 150-170°C and a vacuum degree of -0.08~-0.1 MPa, defoaming for 25-40 minutes, and cooling to room temperature to obtain the high thixotropy modified pitch.

Images