• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The present invention discloses a method for preparing capsules with an attapulgite/calcium alginate composite wall for asphalt self-healing, including the following steps: preparing an industrial-grade sodium alginate solution; adding attapulgite, and subjecting the resulting mixture to high-speed shearing for even dispersion to give a mixture of sodium alginate and attapulgite; adding an asphaltrecycling agent and a surfactant to the obtained mixture of sodium alginate and attapulgite, and subjecting the resulting mixture to high-speed shearing for even dispersion to give a blend; adding the obtained blend dropwise to a calcium chloride solution, and stirring the resulting mixture to form wet capsules; and filtering out, washing and drying the wet capsules to give capsules with an attapulgite/calcium alginate composite wall for asphalt self-healing. The rod-like channel structure of attapulgite itself provides storage space for the asphaltrecycling agent, which allows the capsules with a composite wall for asphalt self- healing to release a significantly-lower amount of asphalt-recycling agent during drying shrinkage than the capsules with a calcium alginate wall for asphalt selfhealing, and have higher content of asphalt-recycling agent inside, resulting in longer functioning period during service.
    公开号:NL2026510A
    申请号:NL2026510
    申请日:2020-09-21
    公开日:2021-04-19
    发明作者:Liu Quantao；Bao Shiwen；Wu Shaopeng；Yuan Miao；Xie Jun；Chen Meizhu
    申请人:Univ Wuhan Tech；
    IPC主号:
    专利说明:

    METHOD FOR PREPARING CAPSULES WITH ATTAPULGITE/CALCIUM ALGINATE COMPOSITE WALL FOR ASPHALT SELF-HEALING
    TECHNICAL FIELD The present invention belongs to the technical field of materials, and specifically, designs a method for preparing capsules with an attapulgite/calcium alginate composite wall for asphalt self-healing.
    BACKGROUND Adding capsules to asphalt concrete to improve the healing performance of the pavement and extend the service life of the pavement has been widely recognized by researchers. The capsule for asphalt self-healing prepared by encapsulating asphalt-recycling agent with calcium alginate can gradually release the asphalt-recycling agent in the chamber due to elastic contraction under the cyclic loading without being broken, which is expected to solve the aging and cracking problem of asphalt pavement. However, the capsule with a calcium alginate wall for asphalt self-healing has disadvantages, such as low strength, early release of the asphalt-recycling agent during the drying shrinkage process, and low encapsulation efficiency of the asphalt-recycling agent, making the capsule hardly meet the requirements of application.
    SUMMARY The present invention is intended to provide capsules with an attapulgite/calcium alginate composite wall for asphalt self-healing and a preparation method thereof. The capsule has a controllable strength, releases a very small amount of asphalt-recycling agent during the drying shrinkage process, and can significantly improve the self-healing performance of asphalt concrete under traffic loading.
    In order to achieve the above objectives, the following technical solutions are adopted.
    The present invention provides a method for preparing capsules with an attapulgite/calcium alginate composite wall for asphalt self-healing, including the following steps: (1) preparing an industrial-grade sodium alginate solution with a concentration of 1 wi% to 8 wt®%; adding attapulgite at an amount 0.5% to 3.5% of the mass of the sodium alginate solution; and subjecting the resulting mixture to high-speed shearing for even dispersion to give a mixture of sodium alginate and attapulgite; {2) adding an asphalt-recycling agent and a surfactant to the obtained mixture of sodium alginate and attapulgite, and subjecting the resulting mixture to high-speed shearing for even dispersion to give a blend, where, the asphalt- recycling agent has a volume accounting for 5% to 30% of the volume of the sodium alginate solution, and the surfactant has a volume accounting for 2% to 8% of the volume of the asphalt-recycling agent; {3) adding the obtained blend dropwise to a 1 wt®% to 3 wt®% calcium chloride solution, and stirring the resulting mixture at 50°C to 55°C for 6 h to 12 h to form wet capsules; and (4) filtering out the wet capsules, then washing the capsules with deionized water, and removing water in the capsules by drying to give capsules with an attapulgite/calcium alginate composite wall for asphalt self-healing.
    According to the above solution, the asphalt-recycling agent is a common commercially-available asphalt-recycling agent.
    According to the above solution, the surfactant is Tween 80.
    According to the above solution, the high-speed shearing for dispersion described in step 2 and step 3 is conducted for 8 min to 15 min at a shearing rate of 2,000 rpm to 5,000 rpm.
    According to the above solution, the drying in step (4) is conducted as follows: forced-air drying in an oven at 40°C to 60°C for 4 h to 8 h, or air drying at room temperature for 48 h to 72 h.
    Attapulgite is a kind of clay with large reserves in China, low price and availability, which has excellent colloidal properties and can be evenly dispersed in a solution. Attapulgite is a prominent thickening and reinforcing material, and has a microstructure of rod-like channels, which provides space for storing substances.
    The capsules with an attapulgite/calcium alginate composite wall for asphalt self- healing prepared in the present invention can avoid the problem of early release of the asphalt-recycling agent, and the strength of the capsules can be independently adjusted by controlling the content of attapulgite. In addition, the present invention can also provide a new way for high-value utilization of attapulgite.
    Beneficial effects of the present invention are as follows:
    1. Attapulgite, as a thickening material, can increase the viscosity of an industrial-grade sodium alginate solution, and as a reinforcing material, can be used at varying amounts to adjust the strength of capsules, thereby effectively solving the problem that capsules for asphalt self-healing prepared from industrial- grade sodium alginate have low strength and cannot meet the requirements of application.
    2. The rod-like channel structure of attapulgite itself provides storage space for the asphalt-recycling agent, which allows the capsules with an attapulgite/calcium alginate composite wall for asphalt self-healing to release a significantly-lower amount of asphalt-recycling agent during drying shrinkage than the capsules with a calcium alginate wall for asphalt self-healing, and have higher content of asphalt-recycling agent inside, resulting in longer functioning period during service.
    3. The capsules with an attapulgite/calcium alginate composite wall for asphalt self-healing prepared by the method can enhance the healing performance of asphalt concrete, prolong the service life of a pavement, and save the maintenance cost.
    4. Attapulgite, with large output in China, is cheap and easily available, resulting in the reduction of the preparation cost of capsules for asphalt self- healing.
    5. The utilization of attapulgite is greatly restricted in China, and the present invention develops a new way for high-value utilization of this mineral.
    BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic diagram for the step of adding the blend dropwise to the calcium chloride solution according to a specific embodiment of the present invention; and FIG. 2 shows the appearance and size (with a diameter of 1 mm to 2 mm) of the capsules prepared in Example 3 of the present invention.
    DETAILED DESCRIPTION The technical solution of the present invention is further explained below through examples, but the claimed scope of the present invention is not limited thereto.
    Example 1 Four types of capsules with an attapulgite/calcium alginate composite wall for asphalt self-healing were prepared. Four 1.875 wt% industrial-grade sodium alginate solutions were prepared, each of 400 mi; then 0g, 4 g, 8 g and 12 g of attapulgite were added to the above solutions separately, where the attapulgite had a fineness of 325 mesh; and the resulting mixtures were separately subjected to high-speed shearing for 10 min in a shear, with a shearing rate of 4,000 rpm. 40 ml of asphalt-recycling agent and 2 mi of Tween 80 (surfactant) were added to each of the mixtures, and the resulting mixtures were separately subjected to high-speed shearing for 10 min in a shear, with a shearing rate of 4,000 rpm. The obtained mixtures were numbered as A1, A2, A3 and A4 in sequence. Then the viscosity was tested for the four different mixtures using a dynamic shear rheometer. The test was conducted at 25°C and a shearing rate of 0.1 s to 1,000 st. The test result for viscosity was as follows: A1 < A2 < A3 < A4. lt indicates that attapulgite has a thickening effect on the sodium alginate solution. Calcium chloride solutions with a concentration of 2.5 wt% were prepared; then the sheared blends were separately added dropwise to the calcium chloride solutions; and the resulting mixtures reacted for 8 h to form four different types of wet capsules. The wet capsules were air-dried for 72 h at room temperature to give four different types of capsules. The schematic diagram for the step of adding the blend dropwise to the calcium chloride solution is shown in FIG. 1.
    As measured, the four types of capsules have compressive strengths of 9.6 N, 11.8 N, 14.3 N and 16.6 N, respectively. It can be seen that the compressive strength of the capsule increases as the content of attapulgite increases.
    Thermogravimetric analysis (TGA) test was conducted with reference to the method for measuring the capsule-core content of the self-healing capsule (CN201811140923.1). The results show that the four types of capsules have asphalt-recycling agent contents of 56.3%, 60.1%, 67.3% and 75.1%, respectively.
    Asphalt was extracted from a mixed and compacted asphalt mixture for Fourier-transform infrared spectroscopy (FTIR) test. The area was calculated for the absorption peak of C-O at 1,745 cm’ (the characteristic peak for asphalt- recycling agent, where there was no absorption peak for asphalt), and referring to a standard spectrum, the release amount and the release rate were determined for the asphalt-recycling agent in the compacted capsules (see Construction and Building Materials, 2019, 211: 298-307 for specific methods). The results show that the four types of capsules, in the mixed and compacted asphalt mixture, exhibit release rates of 9.1%, 4.2%, 2.3% and 0.4%, respectively.
    It is proved that the addition of attapulgite increases the strength of the capsule and the content of asphalt-recycling agent, and reduces the early release of asphalt-recycling agent. 5 Example 2 Two types of capsules with an attapulgite/calcium alginate composite wall for asphalt self-healing were prepared. 400 g of 2.5 wt% sodium alginate solution was prepared, then 16 g (accounting for 4% of the mass of the sodium alginate solution) of attapulgite was added, and the resulting mixture was labelled as A1. 400 g of 1.25 wt% sodium alginate solution was prepared, then 1.5 g (accounting for 0.375% of the mass of the sodium alginate solution) of attapulgite was added, and the resulting mixture was labelled as B1. The resulting mixtures were separately subjected to high-speed shearing for 10 min in a shear, with a shearing rate of 4,000 rpm. 40 mi of sunflower oil (asphalt-recycling agent) and 2 ml of Tween 80 (surfactant) were added to each of the mixtures, and the resulting mixtures were separately subjected to high-speed shearing for 10 min in a shear, with a shearing rate of 4,000 rpm.
    The emulsions, made from At and B1 respectively, were separately added dropwise to a calcium chloride solution with a concentration of 2 wt%, and it was found that the emulsion made from B1 was unable to form capsules due to its too-low viscosity.
    The capsules formed by the emulsion made from A1 have a strength of 28 N after dried, which is so high that it is difficult to release the asphalt-recycling agent during fatigue loading.
    The capsules were added to asphalt concrete, and it was found that the capsules exhibited no significant reinforcement on the healing performance of the asphalt concrete.
    Example 3 Calcium alginate capsules were prepared. 200 g of 1 wt% industrial-grade sodium alginate solution was prepared, then 20 mi of asphalt-recycling agent and 1 ml of Tween 80 were added, and the resulting mixture was subjected to shearing.
    The resulting emulsion was dropped, and it was found that droplets flowed out linearly and were unable to form capsules due to low viscosity.
    Using attapulgite to increase the viscosity of the emulsion can effectively solve this problem. 200 g of 1 wi% industrial-grade sodium alginate solution was prepared, then 6 g (accounting for 3% of the mass of the sodium alginate solution) of attapulgite was added, and the resulting mixture was subjected to shearing; and then the same volumes of asphalt-recycling agent and Tween 80 were added, and the resulting mixture was subjected to shearing. It was found that the emulsion exhibited an increased viscosity and was able to form capsules. The prepared capsules have a strength of 12 N, which meets the technical requirements of asphalt concrete construction. The capsules prepared in this example have appearance shown in FIG. 2. Example 4 Two types of calcium alginate capsules were prepared. Two 1.875 wt% sodium alginate solutions were prepared, each of 400 mi; then 0 g and 12 g of attapulgite were added to the above solutions separately; and the resulting mixtures were separately subjected to high-speed shearing for 10 min in a shear, with a shearing rate of 3,500 rpm. 40 mi of sunflower oil (asphalt-recycling agent) and 2 ml of Tween 80 (surfactant) were added to each of the mixtures, and the resulting mixtures were separately subjected to high-speed shearing for 10 min in a shear, with a shearing rate of 4,000 rpm. The obtained capsules were dried in an oven at 45°C for 6 h. Then the dried capsules were added to an asphalt mixture (at an amount of 0.5 wt%), and an asphalt mixture without capsules was prepared as a control group. Then three point bending test, fatigue loading test (inducing the release of the asphalt-recycling agent), and three point bending test were conducted in sequence on a trabecular specimen prepared from the asphalt mixture to test the strength recovery rate for the healed trabecular specimen. The fatigue loading test was conducted under the following conditions: temperature: 20°C; loading intensity: 0.7 MPa; and the number of loading: 30,000. The healing rates (strength recovery rates) of the trabeculae with capsules were determined as
    60.3% and 71.3%, respectively, and the healing rate of the trabecula without capsules was determined as 45%. It shows that the asphalt-recycling agent released from the capsule improves the healing performance of the asphalt mixture, and the attapulgite enhances the effect of the calcium alginate capsule on the healing performance of asphalt.
    权利要求:
    Claims (5)
    [1]
    A method for manufacturing capsules having an attapulgite / calcium alginate composite wall for self-healing asphalt, comprising the steps of: (1) preparing an industrial grade sodium alginate solution at a concentration of 1 wt% to 8 wt% ,; adding attapulgite in an amount of 0.5% to 3.5% by weight of the sodium alginate solution; and subjecting the resulting mixture to high speed mixing to obtain a homogeneous dispersion of a mixture of sodium alginate and attapulgite; (2) adding an asphalt processing agent and a surfactant to the resulting mixture of sodium alginate and attapulgite, and subjecting the resulting mixture to a high speed mixing to obtain a homogeneous dispersion of a mixture in which the asphalt processing agent has a volume has from 5% to 30% of the volume of the sodium alginate solution, and the surfactant has a volume of 2% to 8% of the volume of the asphalt processing agent; (3) adding the resulting mixture dropwise to a 1 wt% to 3 wt% calcium chloride solution, and stirring the resulting mixture at 50 ° C to 55 ° C for 6 to 12 hours to form wet capsules; and (4) filtering out the wet capsules, then washing the capsules with deionized water, and removing water in the capsules by drying to obtain capsules having an attapulgite / calcium alginate composite wall for self-healing asphalt.
    [2]
    A method according to claim 1 for producing capsules having an attapulgite / calcium alginate composite wall for self-healing asphalt, wherein the asphalt processor is a conventional commercially available asphalt processor.
    [3]
    A method according to claim 1 for producing capsules having an attapulgite / calcium alginate composite wall for self-healing asphalt, wherein the surfactant is Tween 80.
    [4]
    A method according to claim 1, for manufacturing capsules having an attapulgite / calcium alginate composite wall for self-healing asphalt, wherein the high speed mixing to obtain a dispersion in step (2) and step (3) is carried out for 8 to 8 days. 15 minutes, at a mixing speed of 2000 to 5000 rpm.
    [5]
    A method according to claim 1, for producing capsules having an attapulgite / calcium alginate composite wall for self-healing asphalt, wherein the drying in step (4) is carried out as follows: air-forced drying in an oven at 40 ° C to 60 ° C for 4 to 8 hours, or air drying at room temperature for 48 to 72 hours.
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    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
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