Chlorine salt corrosion resistant asphalt concrete and preparation method thereof

Abstract

The invention discloses a chlorine salt corrosion resistant asphalt concrete, which is prepared from the following components in parts by weight: 5 to 7 parts of asphalt, 85 to 90 parts of aggregate, 6 to 7 parts of mineral powder and 0.2 to 1 part of chlorine salt reaction type self-repairing capsule, mixing and shearing sodium alginate with the concentration of 2wt%-6wt%, a repairing agent and Tween 80 to form emulsion; dropwise adding the emulsion into 2-6wt% of calcium chloride solution at the temperature of 50-55 DEG C to form a wet capsule; and separating the wet capsule, and drying to obtain the chlorine salt reaction type self-repairing capsule. On the basis of enhancing the chlorine salt aging resistance of the asphalt and the adhesion of the asphalt and the aggregate, the chlorine salt reaction type self-repairing capsule is used for repairing microcracks in time, so that the aged asphalt is regenerated in situ, a chlorine salt corrosion channel is blocked, the structure and the performance of the asphalt concrete are recovered, and the chlorine salt aging resistant asphalt concrete is prepared. The chlorine salt corrosion resistance of the asphalt concrete is enhanced, and the service life of the asphalt pavement is prolonged.

Description

Technical Field

[0001] The present invention belongs to the technical field of building materials, and particularly relates to a bituminous concrete resistant to chloride salt corrosion and a preparation method thereof. Background Art

[0002] In chloride salt environments such as deicing salts, coastal salt mists, rich salts in salt lakes, and saline soils, bituminous pavements generally suffer from performance degradation and pavement structure damage caused by chloride salt erosion, greatly shortening the service life of bituminous pavements and increasing their maintenance costs. Therefore, how to enhance the chloride salt corrosion resistance of bituminous concrete has important practical significance.

[0003] Existing research has found that the main mechanisms of performance degradation and structure damage of asphalt and asphalt mixtures in chloride salt environments are as follows: after chloride salts penetrate into the material interior through pores, cracks, etc., they can produce an "emulsifying effect" with asphalt, accelerating asphalt aging and stripping, and reducing the adhesion between asphalt and aggregates; they can also accelerate the destruction of the internal structure of bituminous concrete through high-temperature crystallization expansion and low-temperature freezing expansion. Therefore, in order to enhance the chloride salt corrosion resistance of bituminous concrete, on the one hand, asphalt with good chloride salt aging resistance and aggregate types with strong adhesion to asphalt can be used to enhance the chloride salt aging resistance of asphalt and the adhesion performance between asphalt and aggregates; on the other hand, timely repair of microcracks in bituminous concrete, blocking the chloride salt infiltration channels, preventing the infiltration of chloride salts and the resulting expansion, and at the same time enabling in-situ regeneration of chloride salt-aged asphalt to restore the performance of asphalt mixtures is the technical key to inhibiting the damage of chloride salts to the structure, composition, and performance degradation of bituminous concrete.

[0004] At present, although researchers have conducted a large number of studies on the chloride salt erosion damage of asphalt and asphalt mixtures, and found that the type of asphalt is the main factor affecting its chloride salt corrosion resistance, the chloride salt corrosion resistance of crumb rubber modified asphalt is the best, followed by SBS modified asphalt, and the chloride salt corrosion resistance of matrix asphalt is the worst; the type of aggregate is the main factor affecting the adhesion between asphalt and aggregates, the chloride salt corrosion resistance of limestone is the best, followed by basalt, and granite is the worst. However, there is still a lack of methods for timely blocking the chloride salt corrosion channels, reducing the chloride salt corrosion intensity, repairing microcracks, enabling in-situ regeneration of chloride salt-aged asphalt, and restoring the performance of bituminous concrete, thereby enhancing the chloride salt corrosion resistance of bituminous concrete. Summary of the Invention

[0005] Aiming at the above problems, the purpose of the present invention is to provide a bituminous concrete resistant to chloride salt corrosion and a preparation method thereof. On the basis of enhancing the chloride salt aging resistance of asphalt and the adhesion between asphalt and aggregates, by means of chloride salt reaction-type self-healing capsules, timely repair microcracks, enable in-situ regeneration of aged asphalt, block the chloride salt corrosion channels, restore the structure and performance of bituminous concrete, prepare bituminous concrete resistant to chloride salt aging, enhance the chloride salt corrosion resistance of bituminous concrete, and extend the service life of bituminous pavements.

[0006] To achieve the above object, the following technical solutions are adopted:

[0007] An asphalt concrete resistant to chloride salt corrosion, comprising asphalt, aggregates, mineral powder and chloride salt reaction-type self-healing capsules; by weight, the asphalt is 5-7 parts, the aggregates are 85-90 parts, the mineral powder is 6-7 parts, and the chloride salt reaction-type self-healing capsules are 0.2-1 part; the wall material of the chloride salt reaction-type self-healing capsules is calcium alginate, and the core material is a repair agent.

[0008] According to the above solution, the preparation method of the chloride salt reaction-type self-healing capsules comprises the following steps:

[0009] Mix and shear sodium alginate with a concentration of 2wt%-6wt%, a repair agent and Tween 80 to form an emulsion; drop the emulsion into a calcium chloride solution with a concentration of 2wt%-6wt% and a temperature of 50°C-55°C to form wet capsules; separate and dry the wet capsules to obtain chloride salt reaction-type self-healing capsules.

[0010] According to the above solution, the repair agent is bio-oil or waste engine oil. In an optimized solution, the bio-oil is sunflower oil.

[0011] According to the above solution, the mass ratio of sodium alginate to the repair agent in the emulsion is (0.2-0.6):1.

[0012] According to the above solution, the average particle size of the chloride salt reaction-type self-healing capsules is 1-2mm.

[0013] According to the above solution, the asphalt is rubber powder modified asphalt or SBS modified asphalt or a mixture of the two, the asphalt-aggregate ratio is 3%-7%, and the matrix asphalt used for the modified asphalt is 70# asphalt; the rubber powder used for the rubber powder modified asphalt is 30 mesh-80 mesh, and the dosage is 10wt%-25wt%; the SBS dosage in the SBS modified asphalt is 3wt%-8wt%.

[0014] According to the above solution, the aggregates are limestone or basalt aggregates, and the gradation is any one or more of AC, SMA, and OGFC.

[0015] According to the above solution, the mineral powder is limestone powder.

[0016] The preparation method of the above asphalt concrete resistant to chloride salt corrosion comprises the following steps:

[0017] Heat the aggregates to 190°C-220°C, mix and stir with asphalt at 160°C-170°C for 80s-90s; then add mineral powder and chloride salt reaction-type self-healing capsules and stir for 80s-90s; obtain asphalt concrete resistant to chloride salt corrosion through a forming process.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] The chloride salt reaction type self-healing capsule is prepared by the sharp orifice-solidification method based on the ion exchange principle, that is, an emulsion formed by an alginate solution and a repair agent is dropped into a calcium chloride solution to form a chloride salt reaction type self-healing capsule with a multi-chamber structure. The chloride salt reaction type self-healing capsule is a calcium alginate capsule rich in amino or carboxyl chloride affinity functional groups, and the core material is various industrial asphalt regenerants such as bio-oil, waste engine oil, and aromatic oil. And this capsule has a multi-chamber structure, has the characteristic of a high repair agent content, and its average particle size is 1-2 mm.

[0020] In the SBS modified asphalt, the styrene rigid segments of SBS form a physical cross-linking network, enhancing the hydrophobicity of the asphalt and reducing water penetration. In the crumb rubber modified asphalt, the long-chain hydrocarbon structure and sulfide products of the rubber can adsorb chloride ions and inhibit their migration; the sulfides in the rubber can form complexes with metal ions, interfering with the crystallization process and reducing the formation of large-sized crystals. The elastic phase of SBS and the high elasticity of the rubber can absorb the salt crystallization expansion stress, prevent the propagation of microcracks, thereby reducing the risk of chloride salt damage; at the same time, by using crumb rubber modified asphalt and SBS modified asphalt, through the triple effects of a hydrophobic barrier, elastic energy dissipation and crystallization regulation, the chloride salt erosion resistance of the asphalt can be significantly improved.

[0021] The modified asphalt adopted in the present invention has the ability to effectively resist the diffusion of chloride salts, but it cannot prevent the rapid spread of chloride salts deep into the asphalt concrete due to cracks. After the outer shell of the calcium alginate capsule encounters chloride salt erosion, the dense calcium alginate salt in the outer shell undergoes ion exchange with sodium chloride to generate water-soluble sodium alginate, causing the outer shell to quickly soften, achieving the effect of releasing the regenerant, and the repair effect of the capsule on cracks effectively solves the problem of the spread of chloride salts deep into the cracks of asphalt concrete. In addition, the modified asphalt itself has stronger cohesion, and the modified asphalt has better adhesion to the aggregate. Under the action of the release-in-situ regeneration of the regenerant in the capsule, the cohesion and adhesion are further improved, effectively resisting the damage of chloride salt erosion to the cohesion of the asphalt and the asphalt-aggregate interface.

[0022] Using crumb rubber modified asphalt, SBS modified asphalt with strong chloride salt corrosion resistance, and limestone and basalt aggregates to prepare asphalt concrete can significantly reduce the emulsification effect of chloride salts on the asphalt and the damage to the adhesion interface between the asphalt and the aggregate, and improve the chloride salt corrosion resistance of the asphalt concrete. On this basis, by incorporating the chloride salt reaction type self-healing capsule, the repair agent can be released in time after the concrete is damaged by chloride salt erosion, repair microcracks, block the chloride salt corrosion channels, reduce the chloride salt corrosion intensity, and at the same time can regenerate the aged asphalt in-situ, restore the road performance of the asphalt concrete, and extend the service life of the asphalt concrete in the chloride salt corrosion environment. Brief Description of the Drawings

[0023] Figure 1 : AC-13 gradation curve.

[0024] Figure 2 : SMA-13 gradation curve. Specific implementation mode

[0025] The following embodiments further illustrate the technical solutions of the present invention, but do not limit the protection scope of the present invention.

[0026] The specific implementation mode provides an asphalt concrete resistant to chloride salt corrosion. By weight, the asphalt is 5-7 parts, the aggregate is 85-90 parts, the mineral powder is 6-7 parts, and the chloride salt reaction type self-healing capsule is 0.2-1 part. Heat the aggregate to 190°C - 220°C, mix and stir it with asphalt at 160°C - 170°C for 80s - 90s; then add the mineral powder and the chloride salt reaction type self-healing capsule and stir for 80s - 90s; obtain the asphalt concrete resistant to chloride salt corrosion through the forming process.

[0027] Example 1

[0028] Preparation of chloride salt reaction type self-healing capsule: The capsule uses a 3wt% calcium alginate solution, the core of the capsule is sunflower seed oil repair agent, the mass ratio of sodium alginate to sunflower seed oil is 3:7, and the mass of Tween 80 accounts for 5% of the mass of the repair agent. And the emulsion is sheared at 5000rmp / min for 30min and then dropped into a 5wt% calcium chloride solution to form calcium alginate capsules.

[0029] Preparation of crumb rubber modified asphalt: Pour 70# base asphalt into a tank and heat it to a flowing state. When the temperature reaches 160°C, add 40-mesh to 80-mesh rubber powder accounting for 10% of the mass of the asphalt, and use a high-speed stirrer to stir and disperse at 3000rad / min for 60min, keeping the temperature stable during the stirring process; after the stirring is completed, keep it warm and develop at 160°C for 2h to promote the full swelling of the rubber powder and the physical and chemical reaction with the asphalt. During this period, low-speed stirring (rotation speed ≤ 500rad / min) can be used to maintain the uniformity of the system, and finally, stable-performance rubber asphalt is prepared.

[0030] Preparation of asphalt concrete resistant to chloride salt corrosion: 7 parts of crumb rubber modified asphalt; 86 parts of aggregate, using limestone, with a gradation of AC-13 (the gradation curve is shown in the appendix Figure 1 shown); 6 parts of mineral powder, using limestone mineral powder; the dosage of chloride salt reaction type self-healing capsule is 0.4 part.

[0031] This embodiment also provides a base asphalt concrete for comparison. 7 parts of 70# base asphalt with an oil-stone ratio of 5%; 86 parts of aggregate, using limestone, with a gradation of AC-13 (the gradation curve is shown in the appendix Figure 1 shown); 6 parts of mineral powder, using limestone mineral powder.

[0032] This embodiment also provides a kind of rubber asphalt concrete for comparison, including 7 parts of crumb rubber modified asphalt; 86 parts of aggregate, using limestone with the grading of AC-13 (the grading curve is shown in the appendix Figure 1 as shown); 6 parts of mineral powder, using limestone powder.

[0033] This embodiment also provides a kind of capsule asphalt concrete added for comparison, including 7 parts of 70# base asphalt with an asphalt-aggregate ratio of 5%; 86 parts of aggregate, using limestone with the grading of AC-13 (the grading curve is shown in the appendix Figure 1 as shown); 6 parts of mineral powder, using limestone powder; and the dosage of chloride salt reaction type self-healing capsule is 0.4 part.

[0034] This embodiment studied the changes in the road performance of the obtained base asphalt, rubber asphalt concrete, capsule asphalt concrete and chloride salt resistant rubber asphalt concrete in terms of salt erosion. The salt erosion treatment method is salt freeze-thaw cycle, and the salt freeze-thaw cycle process is as follows: (1) At 25°C, place the specimen in 10wt% sodium chloride for vacuum water retention for 15 minutes, and then soak it in 10wt% sodium chloride for half an hour; (2) Put the specimen into a plastic bag, add 10 ml of 10wt% sodium chloride solution and place it in a constant temperature freezer at -20°C for freezing for 12 hours; (3) Take out the specimen and place it in a constant temperature water bath at 60°C for 12 hours. This is one freeze-thaw cycle, and a total of 14 freeze-thaw cycles are carried out. The test results are shown in Table 1.

[0035] Use a Marshall compactor to form standard Marshall specimens and a wheel roller to roll them into slab specimens. And use 10wt% sodium chloride solution to conduct salt freeze-thaw cycle treatment on the two kinds of specimens, and then conduct Marshall stability test, freeze-thaw splitting test, abrasion test and rutting test respectively.

[0036] Table 1

[0037]

[0038]

[0039] When there is no salt freeze-thaw cycle, the Marshall stability, residual stability, TSR, anti-stripping ability, and dynamic stability of the four types of concrete are, from largest to smallest, chloride-resistant rubber asphalt concrete, rubber asphalt concrete, capsule asphalt concrete, and matrix asphalt concrete, and the same pattern also appears after the salt freeze-thaw cycle. This shows that rubber asphalt is superior to matrix asphalt in terms of road performance. After the incorporation of chloride reaction-type self-healing capsules, the asphalt concrete is easier to be compacted, the void ratio decreases, resulting in an improvement in road performance. At the same time, the stability of matrix asphalt concrete, rubber asphalt concrete, capsule asphalt concrete, and chloride-resistant rubber asphalt concrete decreases by 19.13%, 16.32%, 17.61%, and 8.81% respectively before and after the salt freeze-thaw cycle, and the dynamic stability decreases by 24.14%, 19.16%, 19.69%, and 9.2% respectively, and the stripping loss increases by 30.01%, 20.91%, 23.11%, and 5.98% respectively. This indicates that the chloride reaction-type capsules release sunflower oil under the salt freeze-thaw cycle, repair the microcracks generated by salt crystallization and water freeze-thaw, block the chloride corrosion channels, reduce the chloride corrosion intensity, and at the same time can in-situ regenerate the aged asphalt and restore the road performance of the asphalt concrete.

[0040] Example 2

[0041] Preparation of chloride reaction-type self-healing capsules: The capsules are made of a 4wt% calcium alginate solution, and the core is a sunflower oil repair agent. The mass ratio of sodium alginate to sunflower oil is 1:4, and the mass of Tween 80 accounts for 5% of the mass of the repair agent. And the emulsion is dropped into a 5wt% calcium chloride solution to form calcium alginate capsules after shearing at 5000 rmp / min for 30 min.

[0042] Preparation of SBS modified asphalt: Pour 70# matrix asphalt with an asphalt-aggregate ratio of 6% into a tank and heat it to a flowing state. When the temperature reaches 180°C, add 4% of the SBS modifier based on the mass of the asphalt, and use a mechanical stirrer to stir and swell at 400 rad / min for 30 min. Add 0.5% of the sulfurization stabilizing agent based on the mass of the asphalt 5 min before the end of the stirring and swelling. High-speed shear at 180°C and 5000 rad / min for 30 min, and finally stir and develop at a low speed at 180°C for 30 min to obtain uniform and stable SBS modified asphalt.

[0043] Preparation of SBS modified asphalt concrete: Use 5 parts of the SBS modified asphalt obtained in this example; 90 parts of aggregate, using limestone, with a grading of SMA (the grading curve is shown in the appendix Figure 2 shown); 7 parts of mineral powder, using limestone mineral powder; 0.8 parts of chloride reaction-type self-healing capsules.

[0044] Mix the crumb rubber modified asphalt obtained in Example 1 and the SBS modified asphalt obtained in this example evenly according to a volume ratio of 1:1 to obtain a composite modified asphalt.

[0045] Preparation of the composite modified asphalt concrete: 5 parts of the composite modified asphalt obtained in this example are used; 90 parts of aggregate, limestone is used, and the gradation is SMA (the gradation curve is shown in the appendix Figure 2 as shown); 7 parts of mineral powder, limestone mineral powder is used; 0.8 part of the chloride salt reaction type self-healing capsule.

[0046] This example also studied the changes in the road performance of the obtained SBS modified asphalt concrete and composite modified asphalt concrete in terms of salt erosion, and the results are shown in Table 2.

[0047] Table 2

[0048]

[0049] In terms of water stability, it can be seen from the Marshall stability, residual stability, TSR, and flushing loss in the table that the ability of the composite modified asphalt concrete to resist the damage of salt freeze-thaw cycles is significantly improved compared with the SBS modified asphalt concrete. This is because during the salt freeze-thaw cycle, the repair agent released by the chloride salt reaction type capsule can improve the interfacial performance between the asphalt and the aggregate, prevent the asphalt from peeling off caused by the intrusion of moisture and the crystallization expansion of brine, so as to maintain a high water stability. At the same time, the dynamic stability of the composite modified asphalt concrete after salt freeze-thaw cycles is 9962 times / mm, and the decrease amplitude is 5.47%. The dynamic stability of the ordinary crumb rubber modified asphalt concrete is 7343 times / mm, and the decrease amplitude is 16.66%. It is proved that the rubber particles can fill the voids in the network structure formed by SBS, enhance the cohesion of the asphalt, and under the action of load, the elasticity of the rubber can absorb part of the energy and reduce the flow deformation of the asphalt, thus improving the dynamic stability. At the same time, during the salt freeze-thaw cycle, the sunflower oil repair agent released by the capsule can repair some cracks generated by salt erosion, resulting in the improvement of the dynamic stability.

Claims

1. A chloride-resistant asphalt concrete, characterized in that It includes asphalt, aggregate, mineral powder and chloride-reactive self-repairing capsules; in terms of weight, the asphalt is 5 to 7 parts, the aggregate is 85 to 90 parts, the mineral powder is 6 to 7 parts, and the chloride-reactive self-repairing capsules are 0.2 to 1 part; the wall material of the chloride-reactive self-repairing capsules is calcium alginate, and the core material is a repair agent.

2. The asphalt concrete resistant to chloride corrosion as claimed in claim 1, characterized in that The preparation method of the chloride-reactive self-repairing capsule comprises the following steps: Sodium alginate, a repair agent and Tween 80 with a concentration of 2wt%-6wt% are mixed and sheared to form an emulsion; the emulsion is dropped into a 2wt%-6wt% calcium chloride solution at a temperature of 50°C-55°C to form wet capsules; the wet capsules are separated and dried to obtain chloride-reactive self-repairing capsules.

3. The asphalt concrete resistant to chloride corrosion as claimed in claim 2, characterized in that The repairing agent is biological oil or waste engine oil.

4. The asphalt concrete resistant to chloride corrosion as claimed in claim 2, characterized in that The mass ratio of sodium alginate to the repair agent in the emulsion is (0.2-0.6):

1.

5. The asphalt concrete resistant to chloride corrosion as claimed in claim 1, characterized in that The average particle size of the chloride-reactive self-repairing capsules is 1-2 mm.

6. The asphalt concrete resistant to chloride corrosion as claimed in claim 1, characterized in that The asphalt is rubber powder modified asphalt or SBS modified asphalt or a mixture of the two, with an oil-stone ratio of 3%-7%, and the base asphalt used in the modified asphalt is 70# asphalt.

7. The asphalt concrete resistant to chloride corrosion as claimed in claim 6, characterized in that The rubber powder modified asphalt adopts rubber powder with a mesh size of 30-80 and a content of 10wt%-25wt%.

8. The asphalt concrete resistant to chloride corrosion as claimed in claim 6, characterized in that The SBS content in the SBS modified asphalt is 3wt%-8wt%.

9. The asphalt concrete resistant to chloride corrosion as claimed in claim 1, characterized in that The aggregate is limestone or basalt aggregate, and the gradation is any one or more of AC, SMA, and OGFC; the mineral powder is limestone mineral powder.

10. The method for preparing the chloride-resistant asphalt concrete according to any one of claims 1 to 9, characterized in that The following steps are involved: The aggregate is heated to 190-220°C, mixed with asphalt at 160-170°C and stirred for 80-90 seconds; then mineral powder and chloride-reactive self-repairing capsules are added and stirred for 80-90 seconds; after a molding process, chloride-corrosion-resistant asphalt concrete is obtained.

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