A cement concrete crack multiple self-healing benzene and propylene emulsion microcapsule assembly and a preparation method thereof

Abstract

The present application relates to a kind of cement concrete crack multiple self-healing with styrene-acrylic emulsion microcapsule assembly and its preparation method, first, the present application adopts the polyethylene terephthalate with higher melting point to be covered with styrene-acrylic emulsion, and be made into small particle size microcapsule, then by the lower melting point of mineral wax / beeswax composite wall material, small particle size microcapsule and styrene-acrylic emulsion are covered to form microcapsule assembly.The present application adds styrene-acrylic emulsion microcapsule assembly into concrete, when the first microcrack of concrete occurs, under the stress of crack tip, the outer layer of microcapsule assembly capsule wall breaks, and styrene-acrylic emulsion diffuses into concrete crack, and is reacted into film to make crack healing.Small particle size microcapsule is discharged with styrene-acrylic emulsion when the outer layer of assembly capsule wall breaks, and is dispersed in concrete.When the crack in concrete occurs again, small particle size microcapsule in crack breaks and then self-heals crack, so that the multiple self-healing of concrete crack is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concrete, in particular to a styrene-acrylic emulsion microcapsule assembly for multiple self-healing of cement concrete cracks and a preparation method thereof. BACKGROUND

[0002] As a most commonly used building construction material, concrete has been widely used in the fields of building, highway, bridge, hydraulic engineering, marine engineering, etc. However, due to its brittleness and relatively low tensile strength, micro-cracks will inevitably occur when it is subjected to load or deformation (temperature and humidity change, shrinkage and expansion, uneven settlement, etc.), which will further expand and develop into a continuous network structure crack, aggravate the penetration of harmful substances such as chloride ions, and accelerate the destruction of the concrete structure, thus reducing its durability.

[0003] Microcapsule technology has been used to heal cracks in concrete. By adding microcapsules containing liquid healing agent to the concrete during mixing, when micro-cracks occur in the concrete during later service, the microcapsules will break under the stress at the crack tip, allowing the healing agent inside the microcapsules to flow into the crack and react with the curing agent to heal the crack. However, the existing microcapsule wall has high strength, which makes it difficult to break and release the healing agent under the stress at the crack tip, and the healing agent is released only once after the wall breaks, which can only heal the crack once and cannot protect the internal structure of the concrete for a long time, limiting the application of microcapsules in the field of concrete self-healing. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a styrene-acrylic emulsion microcapsule assembly for multiple self-healing of cement concrete cracks and a preparation method thereof.

[0005] The technical solution of the present application to solve the above technical problems is as follows:

[0006] A styrene-acrylic emulsion microcapsule assembly for multiple self-healing of cement concrete cracks, small particle size microcapsules are prepared by using polyethylene terephthalate with a high melting point as the capsule wall and styrene-acrylic emulsion as the core material repair agent; and the small particle size microcapsules and styrene-acrylic emulsion are coated with a mixture of mineral wax and beeswax with a lower melting point to obtain the microcapsule assembly for multiple self-healing of cement-based material cracks.

[0007] Further, the raw materials include the following components in parts by weight: 20-65 parts of mineral wax, 20-65 parts of beeswax, 20-65 parts of polyethylene terephthalate, and 70-160 parts of styrene-acrylic emulsion.

[0008] Further, the solid content of the styrene-acrylic emulsion is 40-50%.

[0009] Further, the melting point of the beeswax is 55-75℃, and the melting point of the mineral wax is 60-80℃.

[0010] Further, the melting point of the polyethylene terephthalate is 240-260℃.

[0011] A preparation method of a polyacrylate emulsion microcapsule assembly for multiple self-healing of cement concrete cracks comprises the following steps:

[0012] Step 1, 20-65 parts by weight of polyethylene terephthalate is heated to 300-320℃ and stirred for 20-30 min; 35-80 parts by weight of polyacrylate emulsion is added, the temperature is kept at 300-320℃, and slow stirring is continued for 30-40 min to obtain a polyethylene terephthalate coated polyacrylate emulsion mixture;

[0013] Step 2, stop heating and accelerate stirring, and full-fluorine tributylamine is added to the mixture obtained in the previous step to obtain a microcapsule suspension;

[0014] Step 3, the suspension is dispersed by ultrasonic wave for 15-30 min, and then the microcapsules separated by filtration are dried in an oven for more than 48 h to obtain polyethylene terephthalate coated polyacrylate emulsion microcapsules;

[0015] Step 4, 20-65 parts by weight of mineral wax and 20-65 parts by weight of beeswax are heated to 110-120℃, and stirred for 15-20 min, then 35-80 parts by weight of polyacrylate emulsion is added, the temperature is kept at 110-120℃, and stirring is continued for 25-30 min; all the microcapsules obtained in step 3 are added, and stirring is continued for 40-60 min to mix the mixture uniformly;

[0016] Step 5, stop heating and accelerate stirring, and full-fluorine tributylamine is added to the mixture in the previous step to obtain a microcapsule assembly suspension;

[0017] Step 6, the suspension obtained in the previous step is dispersed by ultrasonic wave, and then the cement concrete crack multiple self-healing polyacrylate emulsion microcapsule assembly is obtained after filtration and drying.

[0018] Further, the ultrasonic wave frequency is 60 kHz, and the ultrasonic time is 15-30 min.

[0019] The beneficial effects of the present application are:

[0020] (1) The present application uses styrene-acrylic emulsion as core material, polyethylene terephthalate as capsule wall to prepare small particle size microcapsules, and uses mineral wax / beeswax composite wall material, small particle size microcapsules and styrene-acrylic emulsion as core material to prepare microcapsule assemblies. When the concrete is first cracked by temperature stress or external force, the stress at the crack tip causes the mineral wax / beeswax composite capsule wall to break, releasing the internal small particle size microcapsules and polymer emulsion, which heals the crack. When the concrete cracks again, the small particle size microcapsules break, and the polymer emulsion flows out, healing the crack again, giving the concrete the ability to heal multiple times, greatly extending the service life of the concrete.

[0021] (2) The present application uses styrene-acrylic emulsion as core material to prepare microcapsules, which can react and heal cracks at room temperature without the use of curing agents. At the same time, the polymer emulsion has good room temperature fluidity, and when the microcapsule wall breaks, the polymer emulsion is more easily diffused into the crack and polymerized into a film to repair the crack in time. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 Figure (a) is a picture before repair, and figure (b) is a picture after repair.

[0023] Figure 2 Figure (a) is a picture before repair, and figure (b) is a picture after repair. DETAILED DESCRIPTION

[0024] The principles and characteristics of the present application are described below in conjunction with the accompanying drawings, which are used only to explain the present application and are not intended to limit the scope of the present application.

[0025] Example 1

[0026] A cement concrete crack multiple self-healing styrene-acrylic emulsion microcapsule assembly is prepared by the following method:

[0027] (1) 20 parts of polyethylene terephthalate and 80 parts of styrene-acrylic emulsion are weighed according to the required weight of each raw material;

[0028] (2) 20 parts of polyethylene terephthalate are heated to 310℃, and stirred at 300rpm for 30min; 80 parts of styrene-acrylic emulsion is added, the temperature is kept at 310℃, and slow stirring is carried out for 30min to make the mixture uniform, obtaining a polyethylene terephthalate coated styrene-acrylic emulsion mixture;

[0029] (3) stop heating, and add perfluorotributylamine to the mixture under rapid stirring at 1000 rpm to rapidly reduce the temperature of the mixture, to obtain a suspension containing polyethylene terephthalate-coated styrene-acrylic emulsion microcapsules;

[0030] (4) the suspension is dispersed by ultrasonic wave for 30 min, and then filtered, and the separated microcapsules are dried in an oven at 50°C for 48 h to obtain the polyethylene terephthalate-coated styrene-acrylic emulsion microcapsules;

[0031] (5) 20 parts of mineral wax, 20 parts of beeswax, 40 parts of styrene-acrylic emulsion and 20 parts of small-particle-size microcapsules are weighed by weight fraction;

[0032] (6) 20 parts of mineral wax and 20 parts of beeswax are heated to 120°C, and stirred at a speed of 300 rpm for 15 min; 40 parts of styrene-acrylic emulsion is added, and the temperature is kept at 120°C, and stirred slowly for 25 min; 20 parts of small-particle-size microcapsules obtained in step (4) is added, and the stirring is continued for 60 min;

[0033] (7) stop heating, and add perfluorotributylamine to the mixture of step (6) under rapid stirring at 1000 rpm to rapidly reduce the temperature of the mixture, to obtain a suspension of microcapsule assemblies;

[0034] (8) the suspension is dispersed by ultrasonic wave at a frequency of 60 kHz for 30 min, and then filtered, and the separated microcapsules are dried in an oven at 50°C for 48 h to obtain the styrene-acrylic emulsion microcapsule assemblies for multiple self-healing of cement concrete cracks.

[0035] The average particle size, sealing performance and micromechanics of the prepared styrene-acrylic emulsion microcapsule assemblies for multiple self-healing of cement concrete cracks are tested, and the results are shown in Table 1. The results in Table 1 show that the average particle size of the prepared styrene-acrylic emulsion microcapsule assemblies for multiple self-healing of cement concrete cracks is small, the mass loss rate within 30 days is low, and the elastic modulus and hardness are good.

[0036] Table 1: Microcapsule assemblies prepared in Example 1

[0037]

[0038] Self-healing experiments are carried out on cement concrete doped with the microcapsule assemblies prepared in Example 1:

[0039] 1) Preparation, molding and curing of self-healing concrete: The microcapsule mixture prepared above was added to the concrete (3.5% of the cement content) to obtain self-healing concrete, which was poured into a 100 mm x 100 mm x 100 mm mold, vibrated and leveled, demolded after 24 hours, and moved to a curing room, and taken out after 56 days, and placed at room temperature for 14 days;

[0040] 2) Crack pre-preparation and self-healing: The surface of the test piece was made to have microcracks by the splitting test method, and the test piece was immediately removed, the initial crack width was measured, and the width of the crack was tested after 7 days at room temperature. Figure 1 It is shown that the crack with a width of 0.26 mm can be self-repaired after adding the microcapsule assembly prepared in Example 1.

[0041] 3) The concrete test piece was again subjected to crack pre-preparation (refer to the above steps), and the test piece was immediately removed when the surface had microcracks, the crack width was measured, and the width of the crack was tested after 7 days at room temperature. Figure 2 It is shown that the secondary crack with a width of 0.21 mm can be self-repaired after adding the microcapsule assembly prepared in Example 1.

[0042] Example 2

[0043] A styrene-acrylic emulsion microcapsule assembly for multiple self-healing of cement concrete cracks was prepared by the following method:

[0044] The preparation method of the microcapsule assembly is the same as that of Example 1, except that:

[0045] (1) 50 parts of polyethylene terephthalate and 50 parts of styrene-acrylic emulsion were weighed according to the required weight fraction of each raw material to prepare small-diameter microcapsules;

[0046] (2) 30 parts of mineral wax, 30 parts of beeswax, 30 parts of styrene-acrylic emulsion, and 10 parts of small-diameter microcapsules were weighed according to the required weight fraction of each raw material to prepare the microcapsule assembly.

[0047] The average particle size, sealing performance and micromechanical properties of the styrene-acrylic emulsion microcapsule assembly for multiple self-healing of cement concrete cracks prepared above were tested, and the results are shown in Table 2. The results in Table 2 show that the styrene-acrylic emulsion microcapsule assembly for multiple self-healing of cement concrete cracks prepared in this example has small average particle size, low mass loss rate within 30 days, and good elastic modulus and hardness.

[0048] Table 2 Microcapsule assembly prepared in Example 2

[0049]

[0050] Example 3

[0051] A styrene-acrylic emulsion microcapsule assembly for multiple self-healing of cement concrete cracks is prepared by the following method:

[0052] The preparation method of the microcapsule assembly is the same as in Example 1, except that:

[0053] (1) 30 parts of polyethylene terephthalate and 70 parts of styrene-acrylic emulsion are weighed according to the required weight fraction of each raw material to prepare small-diameter microcapsules;

[0054] (2) 25 parts of mineral wax, 35 parts of beeswax, 10 parts of styrene-acrylic emulsion, and 30 parts of small-diameter microcapsules are weighed according to the required weight fraction of each raw material to prepare the microcapsule assembly.

[0055] The average particle size, sealing performance, and micromechanical properties of the styrene-acrylic emulsion microcapsule assembly for multiple self-healing of cement concrete cracks prepared above are tested, and the results are shown in Table 3. The results in Table 3 show that the styrene-acrylic emulsion microcapsule assembly for multiple self-healing of cement concrete cracks prepared in this example has small average particle size, low mass loss rate within 30 days, and good elastic modulus and hardness.

[0056] Table 3 Microcapsule assembly prepared in Example 3

[0057]

[0058] Example 4

[0059] A styrene-acrylic emulsion microcapsule assembly for multiple self-healing of cement concrete cracks is prepared by the following method:

[0060] The preparation method of the microcapsule assembly is the same as in Example 1, except that:

[0061] (1) 35 parts of polyethylene terephthalate and 65 parts of styrene-acrylic emulsion are weighed according to the required weight fraction of each raw material to prepare small-diameter microcapsules;

[0062] (2) 35 parts of mineral wax, 25 parts of beeswax, 20 parts of styrene-acrylic emulsion, and 20 parts of small-diameter microcapsules are weighed according to the required weight fraction of each raw material to prepare the microcapsule assembly.

[0063] The average particle size, sealing performance, and micromechanical properties of the styrene-acrylic emulsion microcapsule assembly for multiple self-healing of cement concrete cracks prepared above are tested, and the results are shown in Table 4. The results in Table 4 show that the styrene-acrylic emulsion microcapsule assembly for multiple self-healing of cement concrete cracks prepared in this example has small average particle size, low mass loss rate within 30 days, and good elastic modulus and hardness.

[0064] Table 4 Microcapsule assembly prepared in Example 4

[0065]

[0066] Example 5

[0067] A styrene-acrylic emulsion microcapsule assembly for repeated self-healing of cracks in cement concrete was prepared by the following method:

[0068] The preparation method of the microcapsule assembly is the same as in Example 1, except that:

[0069] (1) Weigh 65 parts of polyethylene terephthalate and 35 parts of styrene-acrylic emulsion according to the required weight of each raw material to prepare small particle size microcapsules.

[0070] (2) Weigh out 45 parts of mineral wax, 45 parts of beeswax, 5 parts of styrene-acrylic emulsion and 5 parts of small-diameter microcapsules according to the required weight of each raw material to prepare microcapsule assemblies.

[0071] The average particle size, sealing performance, and micromechanical properties of the styrene-acrylic emulsion microcapsule assembly for repeated self-healing of cement concrete cracks prepared above were tested, and the results are listed in Table 5. Table 5 shows that the styrene-acrylic emulsion microcapsule assembly for repeated self-healing of cement concrete cracks prepared in this embodiment has a small average particle size, low mass loss rate within 30 days, and good elastic modulus and hardness.

[0072] Table 5. Microcapsule assemblies prepared in Example 5

[0073]

[0074] The above embodiments are merely illustrative examples and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a styrene-acrylic emulsion microcapsule assembly for repeated self-healing of cement concrete cracks, characterized in that, Includes the following steps: Step 1: Heat 20-65 parts by weight of polyethylene terephthalate to 300-320℃ and stir for 20-30 minutes; add 35-80 parts by weight of styrene-acrylic emulsion, maintain the temperature at 300-320℃, and continue stirring slowly for 30-40 minutes to obtain a polyethylene terephthalate-coated styrene-acrylic emulsion mixture; the melting point of the polyethylene terephthalate is 240-260℃; Step 2: Stop heating, accelerate stirring, and add perfluorotributylamine to the mixture obtained in the previous step to obtain a suspension of microcapsules; Step 3: Disperse the suspension with ultrasound for 15-30 minutes, then dry the filtered microcapsules in an oven for more than 48 hours to obtain polyethylene terephthalate-coated styrene-acrylic emulsion microcapsules. Step 4: Heat 20-65 parts by weight of mineral wax and 20-65 parts by weight of beeswax to 110-120℃, stir for 15-20 minutes, then add 35-80 parts by weight of styrene-acrylic emulsion, maintain the temperature at 110-120℃, and continue stirring for 25-30 minutes; add all the microcapsules obtained in Step 3, and continue stirring for 40-60 minutes to ensure the mixture is homogeneous; the melting point of the beeswax is 55-75℃, and the melting point of the mineral wax is 60-80℃; Step 5: Stop heating, accelerate stirring, and add perfluorotributylamine to the mixture from the previous step to obtain a suspension of the microcapsule assembly; Step 6: The suspension obtained in the previous step is subjected to ultrasonic dispersion treatment, and then filtered, separated and dried to obtain a styrene-acrylic emulsion microcapsule assembly for multiple self-healing of cement concrete cracks.

2. The method for preparing the styrene-acrylic emulsion microcapsule assembly for repeated self-healing of cement concrete cracks according to claim 1, characterized in that, The ultrasonic frequency is 60kHz, and the ultrasonic time is 15-30min.

3. The method for preparing the styrene-acrylic emulsion microcapsule assembly for repeated self-healing of cement concrete cracks according to claim 1, characterized in that, The solid content of the styrene-acrylic emulsion is 40-50%.

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