Composite material for repairing concrete cracks by regulating and enhancing polyurea through few layers of hydrotalcite

Abstract

The invention discloses a composite material for repairing concrete cracks by regulating and enhancing polyurea through few-layer hydrotalcite, which comprises the following three steps: S1, adding hydrotalcite and a modifier into deionized water, heating to 70-85 DEG C, carrying out constant-temperature stirring reaction for 10-12 hours, after the reaction is finished, cooling, filtering and collecting solids, cleaning with deionized water, and then freeze-drying to obtain a composite material; further carrying out ball milling treatment to obtain modified few-layer hydrotalcite; s2, uniformly mixing the modified few-layer hydrotalcite with polyether polyol, and carrying out vacuum dehydration at the temperature of 100-160 DEG C for 1-3 hours; and S3, adding the dehydrated mixture into isocyanate, quickly and uniformly mixing, and then pouring the mixture into a mold for molding. By adding the modified few-layer hydrotalcite, the tensile strength of the polyurea composite material can be regulated and controlled between 20 MPa and 32 MPa, the tensile strength of the polyurea composite material is basically matched with the concrete while the interface bonding performance of the polyurea and the concrete is guaranteed, and the long-term use performance of the repaired concrete is improved.

Description

Technical Field

[0001] The invention relates to the technical field of composite materials, in particular to a composite material for repairing concrete cracks by regulating and strengthening polyurea with a few layers of hydrotalcite. Background Art

[0002] Concrete is widely used in civil engineering due to its advantages such as simple preparation method, low price, high compressive strength, good fire resistance, not easy to weather and low maintenance cost. In the process of concrete preparation, there are problems such as water-cement ratio, long concrete mixing and transportation time, non-standard formwork operation, unreasonable construction process, too fast construction speed, uneven vibration; and problems such as excessive load, insufficient curing time and inappropriate curing temperature during use may cause cracks in concrete. At present, the common concrete crack repair technologies mainly include concrete self-repair technology, polymer mortar repair technology, filling inorganic water-based cement sealing and anti-seepage agent technology and concrete surface coating flexible waterproof material technology. However, these technical methods have different defects: concrete self-repair technology has poor self-repair effect on cracks larger than 0.4mm, and too many fiber tubes or microcapsules will affect the macroscopic properties of the matrix. The polymer mortar scraping effect is not good, the construction efficiency is low, and the top and vertical surfaces flow seriously. The adhesion performance of inorganic water-based cement sealing and anti-seepage agent needs to be further improved. Ordinary flexible waterproof materials have the disadvantages of easy aging, short life and low strength. Therefore, it is particularly important to seek a concrete crack repair technology that is easy to construct, does not flow, has strong adhesion and good mechanical properties.

[0003] Polyurea technology is a new type of solvent-free, pollution-free green construction technology. It can form an overall dense, seamless, high-strength, high-elastic coating on any shape surface according to the construction environment. It is easy to construct, efficient and has excellent waterproof, anti-corrosion and aging resistance. However, the tensile strength of conventional polyurea is about 20Mpa, while the tensile strength of ordinary concrete is between 20-35Mpa, making it difficult for the tensile strength of polyurea to match the relevant properties of concrete, which is not conducive to long-term stability. Summary of the invention

[0004] Aiming at the problem that the existing polyurea material has low tensile strength and is difficult to match the tensile strength performance of concrete, the present invention provides a composite material for repairing concrete cracks by regulating and strengthening polyurea with a few layers of hydrotalcite.

[0005] The composite material for repairing concrete cracks by regulating and enhancing polyurea with a few layers of hydrotalcite provided by the present invention has the following preparation method:

[0006] S1. Add hydrotalcite and a modifier into deionized water, heat to 70-85°C, and react with constant temperature stirring for 10-12h. After the reaction is completed, cool, filter and collect the solid, wash with deionized water, and then freeze-dry, and further ball-mill. The hydrotalcite is peeled into a few layers by grinding to reduce its particle size, thereby obtaining a modified few-layer hydrotalcite.

[0007] The hydrotalcite is selected from any one of magnesium-aluminum hydrotalcite, nickel-aluminum hydrotalcite, nickel-iron hydrotalcite, magnesium-iron hydrotalcite and nickel-zinc hydrotalcite.

[0008] The modifier is selected from one of sodium lauryl sulfate, sodium stearate, and 2-carboxyethylphenylphosphinic acid.

[0009] S2. Evenly mix the modified few-layer hydrotalcite and the polyether polyol, and perform vacuum dehydration at a temperature of 100-160° C. for 1-3 hours to make the mixture anhydrous.

[0010] S3, adding the dehydrated mixture to isocyanate, quickly mixing at room temperature, the mixing time is controlled within 30s, and then pouring the mixture into a mold to be formed into a target composite material. In this step, the hydroxyl group on the few-layer hydrotalcite and the isocyanate can react chemically, fully ensuring the dispersion stability in the polyurea.

[0011] Preferably, the amount of the modifier is 10%-20% of the mass of the hydrotalcite.

[0012] Preferably, the mass ratio of the polyether polyol to the isocyanate is (0.9-1.3):1. The polyether polyol is selected from any one of polyoxypropylene glycol, polytetrahydrofuran diol, and tetrahydrofuran-oxypropylene copolymer glycol. The isocyanate is selected from any one of methyl isocyanate, toluene diisocyanate, diphenylmethane diisocyanate, and 1,6-hexamethylene diisocyanate.

[0013] Preferably, the amount of the modified few-layer hydrotalcite is 0.5%-2% of the total mass of the polyether polyol and the isocyanate.

[0014] Compared with the prior art, the present invention is beneficial in that:

[0015] (1) The polyurea composite material of the present invention is added with a few-layer hydrotalcite (LDH), which has a lamellar structure and contains a large number of hydroxyl groups on the lamellar structure; the lamellar structure is beneficial to improving the mechanical properties of the polyurea; the hydrotalcite is peeled into a few layers, so that its particle size becomes smaller and it is not easy to settle before spraying, thereby ensuring the dispersion and stability of the material; the hydroxyl groups on the few-layer hydrotalcite can react chemically with isocyanate, fully ensuring the dispersion stability in the polyurea; and finally, the tensile strength of the polyurea can be adjusted between 20 and 32 MPa, thereby ensuring the bonding performance of the interface between the polyurea and the concrete, and making the tensile strength basically consistent with that of the concrete, thereby improving the long-term performance of the repaired concrete.

[0016] (2) The polyurea composite material of the present invention can be used to quickly repair concrete cracks.

[0017] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. DETAILED DESCRIPTION

[0018] The preferred embodiments of the present invention are described below. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0019] Example 1

[0020] A composite material for repairing concrete cracks by regulating and enhancing polyurea with a few layers of hydrotalcite, the preparation method of which is as follows:

[0021] S1. Add 10 g of magnesium aluminum hydrotalcite and 10 g of sodium dodecyl sulfate into 100 ml of deionized water, heat to 80°C, and react with constant temperature stirring for 12 hours. After the reaction is completed, cool and filter to collect the solid. Wash the solid three times with deionized water and then freeze-dry. After drying, further ball milling is performed until the thickness of the hydrotalcite layer is less than 10 layers to obtain a modified few-layer magnesium aluminum hydrotalcite.

[0022] S2. 1.5 g of the modified few-layer magnesium aluminum hydrotalcite and 50 g of polyoxypropylene glycol were mixed evenly, and vacuum dehydrated at 150° C. for 2 h to make the mixture anhydrous.

[0023] S3. Add the dehydrated mixture to 50 g of toluene diisocyanate and mix quickly and evenly at room temperature. Preferably, use a degassing machine for mixing at 2000 rpm for 30 seconds. Then pour the mixture into a mold and wait for it to be formed to obtain the target composite material, referred to as composite material-1.5.

[0024] According to the above method, in step S2, the amount of modified few-layer magnesium aluminum hydrotalcite added is adjusted to 0g, 0.5g, 1.0g, and 2.0g, respectively, and the obtained materials are referred to as pure polyurea, composite material-0.5, composite material-1.0, and composite material-2.0, respectively.

[0025] According to the above method, step S1 is omitted, and in step S2, 1.5 g of unmodified magnesium aluminum hydrotalcite is directly mixed with polyoxypropylene glycol, and then step S3 is performed to obtain composite material-a.

[0026] The tensile strength and elongation at break of the six composite materials were tested according to GB / T 528-2009 standard. The test results are shown in Table 1.

[0027] Table 1. Test results of tensile strength and elongation at break of six composite materials

[0028] Composite Materials Tensile strength(MPa) Elongation at break Pure polyurea 21.0 325％ Composite material - 0.5 28.2 456％ Composite material-1 29.5 380％ Composite material - 1.5 31.5 355％ Composites-2.0 35.0 330％ Composite material-a 18.5 230％

[0029] It can be seen from the table that in the process of preparing polyurea materials, adding modified few-layer magnesium-aluminum hydrotalcite can significantly improve the tensile strength of polyurea materials to 28-35MPa, which matches the tensile strength of ordinary concrete. While ensuring the bonding performance of the interface between polyurea and concrete, its tensile strength is basically consistent with that of concrete, improving the long-term performance of concrete after repair. The tensile strength of pure polyurea without adding modified few-layer magnesium-aluminum hydrotalcite or the composite material obtained by adding unmodified magnesium-aluminum hydrotalcite is low and cannot meet the requirements of concrete; moreover, the tensile strength of the composite material-a obtained by adding unmodified magnesium-aluminum hydrotalcite is lower than that of pure polyurea, which shows that the addition of unmodified magnesium-aluminum hydrotalcite to polyurea materials will reduce the tensile strength of the composite material. It can also be seen from the data in the table that adding a small amount of modified few-layer magnesium-aluminum hydrotalcite can also improve the elongation at break of the composite material. When the amount of modified few-layer magnesium-aluminum hydrotalcite added continues to increase, it will have a counter-effect and reduce the elongation at break. Therefore, in actual use, it is necessary to comprehensively consider the tensile strength and elongation at break according to actual needs, and select the appropriate amount of modified few-layer hydrotalcite to achieve the purpose of regulating and enhancing polyurea to repair concrete cracks.

[0030] Example 2

[0031] A composite material for repairing concrete cracks by regulating and enhancing polyurea with a few layers of hydrotalcite, the preparation method of which is as follows:

[0032] S1. Add 10 g of nickel-iron hydrotalcite and 20 g of sodium stearate into 100 ml of deionized water, heat to 85° C., and react with constant temperature stirring for 10 h. After the reaction is completed, cool and filter to collect the solid. The solid is washed 3 times with deionized water and then freeze-dried. After drying, further ball milling is performed until the thickness of the hydrotalcite layer is less than 10 layers to obtain a modified few-layer nickel-iron hydrotalcite.

[0033] S2. Mix 1 g of the modified few-layer nickel-iron hydrotalcite and 50 g of polytetrahydrofuran diol evenly, and dehydrate under vacuum at 120° C. for 3 h to make the mixture anhydrous.

[0034] S3. Add the dehydrated mixture into 50 g of methyl isocyanate, mix with a degassing machine at room temperature at 2000 rpm for 30 seconds, and then pour the mixture into a mold for molding to obtain the target composite material.

[0035] According to GB / T 528-2009 standard, the tensile strength and elongation at break of the composite material are measured to be 29.5 MPa and 380% respectively.

[0036] Example 3

[0037] A composite material for repairing concrete cracks by regulating and enhancing polyurea with a few layers of hydrotalcite, the preparation method of which is as follows:

[0038] S1. Add 10 g of nickel-zinc hydrotalcite and 15 g of 2-carboxyethylphenylphosphinic acid into 100 ml of deionized water, heat to 75° C., and stir to react for 12 h at constant temperature. After the reaction is completed, cool and filter to collect the solid. Wash the solid three times with deionized water, then freeze-dry, and further ball-mill to obtain a modified few-layer nickel-iron hydrotalcite.

[0039] S2. Mix 2 g of the modified few-layer nickel-iron hydrotalcite and 50 g of tetrahydrofuran-propylene oxide copolymer glycol evenly, and dehydrate under vacuum at 150° C. for 1 h to make the mixture anhydrous.

[0040] S3. Add the dehydrated mixture to 50 g of 1,6-hexamethylene diisocyanate, mix with a degassing machine at room temperature at 2000 rpm for 30 seconds, then pour the mixture into a mold for molding to obtain the target composite material.

[0041] According to GB / T 528-2009 standard, the tensile strength and elongation at break of the composite material are measured to be 35.0 MPa and 330% respectively.

[0042] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A composite material for repairing concrete cracks by regulating and strengthening polyurea with a few layers of hydrotalcite, characterized in that: The preparation method is as follows: S1. Adding hydrotalcite and a modifier into deionized water, heating to 70-85° C., stirring and reacting at a constant temperature for 10-12 hours, cooling after the reaction, filtering and collecting solids, washing with deionized water, and then freeze-drying, further ball-milling to obtain a modified few-layer hydrotalcite; the modifier is selected from one of sodium dodecyl sulfate, sodium stearate, and 2-carboxyethylphenylphosphinic acid; S2, mixing the modified few-layer hydrotalcite and the polyether polyol uniformly, and vacuum dehydrating at a temperature of 100-160° C. for 1-3 hours to make the mixture anhydrous; S3. Add the dehydrated mixture to isocyanate, mix quickly and evenly at room temperature, and control the mixing time within 30 seconds. Then pour the mixture into a mold and wait for it to be formed to obtain the target composite material.

2. The composite material for repairing concrete cracks by regulating and enhancing polyurea with a few layers of hydrotalcite as claimed in claim 1, characterized in that: The hydrotalcite is selected from any one of magnesium-aluminum hydrotalcite, nickel-aluminum hydrotalcite, nickel-iron hydrotalcite, magnesium-iron hydrotalcite and nickel-zinc hydrotalcite.

3. The composite material for repairing concrete cracks by regulating and strengthening polyurea with a few layers of hydrotalcite as claimed in claim 2, characterized in that: The amount of the modifier is 10%-20% of the mass of the hydrotalcite.

4. The composite material for repairing concrete cracks by regulating and strengthening polyurea with a few layers of hydrotalcite as claimed in claim 3, characterized in that: The mass ratio of polyether polyol to isocyanate is (0.9-1.3):

1.

5. The composite material for repairing concrete cracks by regulating and strengthening polyurea with a few layers of hydrotalcite as claimed in claim 4, characterized in that: The amount of the modified few-layer hydrotalcite is 0.5%-2% of the total mass of the polyether polyol and the isocyanate.

6. The composite material for repairing concrete cracks by regulating and strengthening polyurea with a few layers of hydrotalcite as claimed in claim 4, characterized in that: The polyether polyol is selected from any one of polyoxypropylene glycol, polytetrahydrofuran glycol, and tetrahydrofuran-oxypropylene copolymer glycol.

7. The composite material for repairing concrete cracks by regulating and strengthening polyurea with a few layers of hydrotalcite as claimed in claim 4, characterized in that: The isocyanate is selected from any one of methyl isocyanate, toluene diisocyanate, diphenylmethane diisocyanate and hexamethylene diisocyanate.