Quick-setting hydrogel curing sand as well as preparation method and application thereof

Abstract

The invention provides quick-setting hydrogel curing sand as well as a preparation method and application thereof, and belongs to the technical field of engineering materials. A system of tetrahydroxy diboron and potassium persulfate is utilized to initiate copolymerization of methacrylic acid, methacrylamide and acrylamide to form hydrogel, and the hydrogel and building sand are further prepared to obtain the high-performance quick-setting hydrogel cured sand. The hydrogel cured sand can be rapidly cured within a short time and has excellent mechanical properties. A novel green solution is provided for infrastructure maintenance and wartime defense engineering, and a scientific basis is provided for replacement of traditional quick-setting cement.

Description

Technical Field

[0001] The present invention belongs to the technical field of engineering materials, and particularly relates to a rapid-setting hydrogel solidified sand, a preparation method thereof, and uses thereof. Background Art

[0002] Emergency repair materials play an irreplaceable and important role in modern infrastructure maintenance. In key projects such as municipal roads, airport runways, bridges, and military facilities, traffic loads, natural disasters, and emergencies may cause damage and aging problems at any time. Timely repair of these facilities is the core requirement for ensuring normal operation and public safety.

[0003] Currently, rapid-setting cement (especially double-fast cement) is the most widely used traditional emergency repair material. With its characteristics of high early strength and fast curing speed, rapid-setting cement is widely used in repair tasks such as roads, runways, and bridges, and has played an important role especially in quickly repairing bunkers and bridges during wartime. Therefore, developing new emergency repair materials that are environmentally friendly, low-carbon, and highly adaptable has become the core technical requirement for current infrastructure maintenance and wartime defense projects.

[0004] In recent years, many materials to replace rapid-setting cement have been proposed to improve emergency repair efficiency and reduce the environmental burden. In emergency repair projects, the types of cement usually selected are as follows: ordinary Portland cement, rapid-hardening Portland cement, rapid-hardening high-strength cement, and waterproof Portland cement. Ordinary Portland cement is a common cement with low cost but low strength. In emergency repair projects, ordinary Portland cement is generally not preferentially selected. Rapid-hardening Portland cement has the characteristic of rapid hardening and can quickly solidify the repaired part, being suitable for emergency repair situations. Rapid-hardening high-strength cement has the characteristics of rapid hardening and high strength, being suitable for projects that need to be quickly put into use. Waterproof Portland cement has excellent waterproof performance and can be preferentially selected in emergency repair projects that require waterproofing. However, the rapid-setting cement prepared from these materials has significant deficiencies in terms of performance and environmental friendliness. Its production process requires high-temperature calcination, which not only consumes a large amount of energy but also contributes approximately 8% of the global carbon emissions. In extreme environments, the adaptability of rapid-setting cement construction is limited. Especially under low-temperature or high-humidity conditions in winter, its curing performance and final strength are not satisfactory.

[0005] The literature (DOI: 10.1021 / acs.chemmater.8b05262) discloses a hydrogel prepared from methacrylic acid and methacrylamide, but its mechanical properties are poor and need to be further improved. Summary of the Invention

[0006] The purpose of the present invention is to provide a rapid-setting hydrogel solidified sand, a preparation method thereof, and uses thereof.

[0007] The present invention provides a hydrogel precursor solution, which is composed of acrylamide monomers, acrylic acid monomers, crosslinking agents, catalysts, initiators and water. Among them, the acrylamide monomers are methacrylamide and acrylamide;

[0008] The ratio of methacrylamide, acrylamide, acrylic acid monomer, crosslinking agent, catalyst, initiator and water is 1-6M: 0-8M: 5-12M: 0-0.1M: 0.05-1M: 0.01-1M: 10-40 ml.

[0009] Further, the ratio of methacrylamide, acrylamide, acrylic acid monomer, crosslinking agent, catalyst, initiator and water is 1.96M: 0-8M: 7.75M: 0.004M: 0.07M: 0.03M: 15 ml; preferably 1.96M: 5.63M: 7.75M: 0.004M: 0.07M: 0.03M: 15 ml.

[0010] The unit "M" represents "mol / L".

[0011] Further, the acrylic acid monomer is methacrylic acid; the crosslinking agent is N,N'-methylenebisacrylamide; the catalyst is a boron-containing hydroxy compound, preferably tetraboron dihydroxide; the initiator is a persulfate, preferably potassium persulfate.

[0012] "Boron-containing hydroxy compound" means that its molecular structure contains both boron (B) element and hydroxy (-OH) group. The characteristic of such compounds is that boron atoms are directly or indirectly bonded to hydroxy groups to form a specific chemical structure.

[0013] The present invention also provides a method for preparing the above hydrogel precursor solution. The method includes the following steps: mixing methacrylamide, acrylic acid monomer, crosslinking agent, catalyst and water, and then adding acrylamide and initiator to obtain the hydrogel precursor solution.

[0014] The present invention also provides a hydrogel, which is a product obtained by gelation of the above hydrogel precursor solution.

[0015] The present invention also provides a hydrogel-cured sand precursor solution, which is composed of the above hydrogel precursor solution and construction sand. Among them, the mass ratio of the hydrogel precursor solution to the construction sand is 0.1-0.5: 1.

[0016] Further, the mass ratio of the hydrogel precursor solution to the construction sand is 0.287: 1.

[0017] The present invention also provides a hydrogel-cured sand, which is a product obtained by curing the above hydrogel-cured sand precursor solution.

[0018] The present invention also provides the uses of the above hydrogel precursor solution, the above hydrogel, the above hydrogel-cured sand precursor solution, and the above hydrogel-cured sand in the preparation of emergency repair materials.

[0019] Further, the material is a material in a road, an airport runway, a bridge or a military facility.

[0020] The present invention uses a system of THDB (tetrahydroxy diboron) and potassium persulfate (KPS) to initiate the terpolymerization of MAAc (methacrylic acid), MAAm (methacrylamide) and AM (acrylamide), and a hydrogel with a tensile strength of up to 15 MPa and excellent anti-swelling performance can be prepared within a short time (20 minutes). By optimizing the hydrogel formula, the preferred ratio shown in Example 1 was screened out.

[0021] The present invention uses MAAc, MAAm and AM to copolymerize to form a polymer network, and introduces THDB to induce rapid gelation under various environmental conditions. The hydrogel is further prepared with construction sand to obtain a high-strength, tough and rapid-setting hydrogel-cured sand to replace cement materials. The hydrogel-cured sand can simultaneously solve the problem that it is difficult to rapidly and quantitatively prepare hydrogels with high mechanical properties and anti-swelling properties. The hydrogel-cured sand can be rapidly cured within a short time and has excellent mechanical properties. The present invention provides a new green solution for infrastructure maintenance and wartime defense projects, and provides a scientific basis for the replacement of traditional rapid-setting cement.

[0022] Compared with the hydrogel prepared in the literature (DOI: 10.1021 / acs.chemmater.8b05262), the curing time of the hydrogel prepared in the present invention is shortened from several hours to about twenty minutes, meeting the requirements of emergency repair; at the same time, its mechanical properties are significantly improved, its Young's modulus can reach more than 300 MPa, and its toughness can reach 25 MJ / m 3 Above; while the Young's modulus of the hydrogel in the literature is only 2.3 - 217.3 MPa, and the toughness is only 2.9 - 23.5 kJ / m 2 . The innovation of the present invention lies in that the rapid gelation process induced by THDB drives the hydrogel to form a unique inhomogeneous network structure and microphase separation structure, which is beneficial to improving the mechanical properties and anti-swelling properties of the hydrogel.

[0023] Obviously, based on the above content of the present invention, according to the common general knowledge and conventional means in the art, without departing from the above basic technical idea of the present invention, various other forms of modifications, substitutions or changes can also be made.

[0024] The following is a further detailed description of the above content of the present invention in the form of specific embodiments. However, this should not be construed as limiting the scope of the above subject matter of the present invention to the following embodiments. Any technology implemented based on the above content of the present invention falls within the scope of the present invention. Brief Description of the Drawings

[0025] Figure 1 It is a schematic diagram for preparing a hydrogel solidified sand column.

[0026] Figure 2 It is the influence of different contents of acrylamide (AM) on the gelation time.

[0027] Figure 3 It is the test result of the mechanical properties of the hydrogel: (a) the influence of different contents of AM on the stress; (b) the influence of different contents of AM on the tensile strength and Young's modulus.

[0028] Figure 4 It is the test result of the mechanical properties of the hydrogel-solidified sand: (a) the influence of different contents of AM on the curing time and compressive strength; (b) the influence of different contents of AM on the stress and compressive strength. Detailed Description of the Invention

[0029] The raw materials and equipment used in the present invention are all known products, obtained by purchasing commercially available products.

[0030] Example 1. Preparation of a quick-setting hydrogel precursor solution and a quick-setting hydrogel

[0031] 1.96 M of methacrylamide (MAAm), 7.75 M of methacrylic acid (MAAc), 0.004 M of cross-linking agent N,N'-methylenebisacrylamide (MBA), and 0.07 M of tetrahydroxy diboron (THDB) were dissolved in 15 g (i.e., 15 ml) of deionized water to obtain a precursor solution without acrylamide (AM); 0.94 M of AM and 0.03 M of potassium persulfate (KPS) were added to the solution to prepare a quick-setting hydrogel precursor solution containing 0.94 M of AM. After further gelation, the corresponding quick-setting hydrogel can be obtained.

[0032] Example 2. Preparation of a quick-setting hydrogel precursor solution and a quick-setting hydrogel

[0033] Referring to the method of Example 1, the difference is only that 0.94 M of AM is replaced by 0 M to prepare a quick-setting hydrogel precursor solution containing 0 M of AM. After further gelation, the corresponding quick-setting hydrogel can be obtained.

[0034] Example 3. Preparation of a quick-setting hydrogel precursor solution and a quick-setting hydrogel

[0035] Referring to the method of Reference Example 1, the difference is only that 0.94 M AM is replaced with 1.88 M to prepare a quick-setting hydrogel precursor solution containing 1.88 M AM. After further gelation, the corresponding quick-setting hydrogel can be obtained.

[0036] Example 4. Preparation of a quick-setting hydrogel precursor solution and a quick-setting hydrogel

[0037] Referring to the method of Reference Example 1, the difference is only that 0.94 M AM is replaced with 2.81 M to prepare a quick-setting hydrogel precursor solution containing 2.81 M AM. After further gelation, the corresponding quick-setting hydrogel can be obtained.

[0038] Example 5. Preparation of a quick-setting hydrogel precursor solution and a quick-setting hydrogel

[0039] Referring to the method of Reference Example 1, the difference is only that 0.94 M AM is replaced with 3.75 M to prepare a quick-setting hydrogel precursor solution containing 3.75 M AM. After further gelation, the corresponding quick-setting hydrogel can be obtained.

[0040] Example 6. Preparation of a quick-setting hydrogel precursor solution and a quick-setting hydrogel

[0041] Referring to the method of Reference Example 1, the difference is only that 0.94 M AM is replaced with 4.69 M to prepare a quick-setting hydrogel precursor solution containing 4.69 M AM. After further gelation, the corresponding quick-setting hydrogel can be obtained.

[0042] Example 7. Preparation of a quick-setting hydrogel precursor solution and a quick-setting hydrogel

[0043] Referring to the method of Reference Example 1, the difference is only that 0.94 M AM is replaced with 5.63 M to prepare a quick-setting hydrogel precursor solution containing 5.63 M AM. After further gelation, the corresponding quick-setting hydrogel can be obtained.

[0044] Example 8. Preparation of a quick-setting hydrogel precursor solution and a quick-setting hydrogel

[0045] Referring to the method of Reference Example 1, the difference is only that 0.94 M AM is replaced with 6.57 M to prepare a quick-setting hydrogel precursor solution containing 6.57 M AM. After further gelation, the corresponding quick-setting hydrogel can be obtained.

[0046] Example 9. Preparation of a hydrogel-cured sand precursor solution and hydrogel-cured sand

[0047] The quick-setting hydrogel precursor solution prepared in Example 1 was thoroughly mixed with standard sand at a mass ratio of 0.287:1 to obtain a hydrogel-cured sand precursor solution. The hydrogel-cured sand precursor solution was rapidly transferred into a silica gel mold and cured to form a hydrogel-cured sand column with a diameter of 40 mm and a height of about 50 mm ( Figure 1 ), denoted as M1.

[0048] Example 10. Preparation of hydrogel-cured sand precursor solution and hydrogel-cured sand

[0049] Referring to the method of Example 9, the difference is only that the quick-setting hydrogel solution prepared in Example 1 was replaced with the quick-setting hydrogel solution prepared in Example 2 to obtain a hydrogel-cured sand precursor solution. A hydrogel-cured sand column was prepared from the hydrogel-cured sand precursor solution, denoted as M0.

[0050] Example 11. Preparation of hydrogel-cured sand precursor solution and hydrogel-cured sand

[0051] Referring to the method of Example 9, the difference is only that the quick-setting hydrogel solution prepared in Example 1 was replaced with the quick-setting hydrogel solution prepared in Example 3 to obtain a hydrogel-cured sand precursor solution. A hydrogel-cured sand column was prepared from the hydrogel-cured sand precursor solution, denoted as M2.

[0052] Example 12. Preparation of hydrogel-cured sand precursor solution and hydrogel-cured sand

[0053] Referring to the method of Example 9, the difference is only that the quick-setting hydrogel solution prepared in Example 1 was replaced with the quick-setting hydrogel solution prepared in Example 4 to obtain a hydrogel-cured sand precursor solution. A hydrogel-cured sand column was prepared from the hydrogel-cured sand precursor solution, denoted as M3.

[0054] Example 13. Preparation of hydrogel-cured sand precursor solution and hydrogel-cured sand

[0055] Referring to the method of Example 9, the difference is only that the quick-setting hydrogel solution prepared in Example 1 was replaced with the quick-setting hydrogel solution prepared in Example 5 to obtain a hydrogel-cured sand precursor solution. A hydrogel-cured sand column was prepared from the hydrogel-cured sand precursor solution, denoted as M4.

[0056] Example 14. Preparation of hydrogel-cured sand precursor solution and hydrogel-cured sand

[0057] Referring to the method of Example 9, the difference is only that the quick-setting hydrogel solution prepared in Example 1 was replaced with the quick-setting hydrogel solution prepared in Example 6 to obtain a hydrogel-cured sand precursor solution. A hydrogel-cured sand column was prepared from the hydrogel-cured sand precursor solution, denoted as M5.

[0058] Example 15, Preparation of Hydrogel-Cured Sand Precursor Solution and Hydrogel-Cured Sand

[0059] Referring to the method of Reference Example 9, the difference is only that the quick-setting hydrogel solution prepared in Example 1 is replaced with the quick-setting hydrogel solution prepared in Example 7 to obtain the hydrogel-cured sand precursor solution. The hydrogel-cured sand precursor solution is used to prepare a hydrogel-cured sand column, denoted as M6.

[0060] Example 16, Preparation of Hydrogel-Cured Sand Precursor Solution and Hydrogel-Cured Sand

[0061] Referring to the method of Reference Example 9, the difference is only that the quick-setting hydrogel solution prepared in Example 1 is replaced with the quick-setting hydrogel solution prepared in Example 8 to obtain the hydrogel-cured sand precursor solution. The hydrogel-cured sand precursor solution is used to prepare a hydrogel-cured sand column, denoted as M7.

[0062] The beneficial effects of the present invention are demonstrated by the following experimental examples.

[0063] Experimental Example 1, Performance Testing of Quick-Setting Hydrogel and Hydrogel-Cured Sand

[0064] 1. Experimental Method

[0065] 1) Performance Testing of Quick-Setting Hydrogel

[0066] The performance of the quick-setting hydrogel precursor solutions and quick-setting hydrogels prepared in Examples 1 to 8 was tested.

[0067] (1) Determination of Gelation Time of Hydrogel: The Fishe method for determining the gelation time of epoxy resin matrix was used to test the gelation time of the hydrogel. Pour 35 mL of the precursor solution containing the initiator (i.e., the prepared hydrogel solution) into a glass dish with a diameter of 9 cm. Use a glass rod to measure the time required for the precursor solution to reach the wire-drawing state, and define this time as the gelation time. All tests were carried out under the condition of 25 °C. In order to make the gelation more intuitive, the small bottle inversion method was used for demonstration.

[0068] (2) Determination of Mechanical Properties of Hydrogel: The tensile properties of the hydrogel were tested using an Instron 5567 universal testing machine (USA). (1) Tensile Property Testing: The hydrogel sample was prepared into a dumbbell shape (length 20 mm, width 4 mm, thickness 1 mm). The tensile stress-strain curve was obtained by stretching the sample at a speed of 100 mm / min until it broke.

[0069] 2) Performance Testing of Hydrogel-Cured Sand

[0070] The performance of the hydrogel-cured sands prepared in Examples 9 to 13 was tested.

[0071] (1) Determination of the curing time of hydrogel-cured sand: Pour the well-mixed hydrogel-cured sand into a silicone mold and start timing immediately. Stop timing when its surface becomes hard and does not draw. Define this period as the curing time of the hydrogel-cured sand.

[0072] (2) Determination of the mechanical properties of hydrogel-cured sand: Compress the hydrogel-cured sand sample at a speed of 5 mm / min until the strain reaches 20% and then stop the test to obtain the compressive stress-strain curve of the hydrogel-cured sand.

[0073] 2. Experimental results

[0074] (1) Performance test of the fast-setting hydrogel

[0075] Fix the contents of MAAc, MAAm and THDB, and study the effect of the content of AM on the rapid gelation of the hydrogel. The results ( Figure 2 ) show that within the AM content range of 0 - 6.57 M, the hydrogel can gel within 20 min. When the AM content of the hydrogel increases from 0 M to 1.88 M, the Young's modulus of the hydrogel increases and reaches a peak at 1.88 M of AM content. As the AM content continues to increase, the Young's modulus of the hydrogel decreases; when the AM content of the hydrogel increases from 0 M to 2.81 M, the tensile strength of the hydrogel increases. When the AM content of the hydrogel is 3.75 M, the tensile strength of the hydrogel decreases compared with that at 2.81 M. When the AM content continues to increase to 4.69 M or 5.63 M, the tensile strength of the hydrogel increases compared with that at 2.81 M, but when it increases to 6.57 M, the tensile strength of the hydrogel decreases compared with that at 4.69 M. The above results indicate that the AM content will significantly affect the hydrogel network structure and thus the mechanical properties ( Figure 3 a, b).

[0076] (2) Performance test of the hydrogel-cured sand

[0077] This invention explores the influence of hydrogels with different AM dosages on the curing time and mechanical properties of sand when replacing cement materials. The results ( Figure 4 a) show that as the amount of AM increases, the curing time increases, and the curing time gradually increases from 4 min to 17 min; the compressive strength first increases and then decreases. When the AM dosage is 0.94 M, the compressive strength can reach up to 8.07 MPa ( Figure 4 b).

[0078] Based on the above results, when the hydrogel replaces the cement material to cure sand, it has a relatively fast curing time and the best mechanical properties at an AM content of 0.94 M.

[0079] In summary, the present invention provides a rapid-setting hydrogel solidified sand, a preparation method thereof, and uses thereof. The present invention uses a system of tetrahydroxy diboron and potassium persulfate to initiate the copolymerization of methacrylic acid, methacrylamide, and acrylamide to form a hydrogel, and further prepares a high-performance rapid-setting hydrogel solidified sand with construction sand. The hydrogel solidified sand can be rapidly solidified in a short time and has excellent mechanical properties. The present invention provides a new green solution for infrastructure maintenance and wartime defense projects, and provides a scientific basis for the replacement of traditional rapid-setting cement.

Claims

1. A hydrogel precursor solution, characterized in that: It consists of acrylamide monomer, acrylic acid monomer, crosslinking agent, catalyst, initiator and water, wherein the acrylamide monomer is methacrylamide and acrylamide; The ratio of the methacrylamide, acrylamide, acrylic acid monomer, crosslinking agent, catalyst, initiator and water is 1-6M: 0-8M: 5-12M: 0-0.1M: 0.05-1M: 0.01-1M: 10-40ml.

2. The hydrogel precursor solution according to claim 1, characterized in that The ratio of methacrylamide, acrylamide, acrylic acid monomer, crosslinking agent, catalyst, initiator and water is 1.96M: 0-8M: 7.75M: 0.004M: 0.07M: 0.03M: 15ml; preferably 1.96M: 5.63M: 7.75M: 0.004M: 0.07M: 0.03M: 15ml.

3. The hydrogel precursor solution according to claim 1, characterized in that The acrylic monomer is methacrylic acid; the crosslinking agent is N,N'-methylenebisacrylamide; the catalyst is a boron-containing hydroxy compound, preferably tetrahydroxydiboron; and the initiator is a persulfate, preferably potassium persulfate.

4. A method for preparing the hydrogel precursor solution according to any one of claims 1 to 3, characterized in that: The method comprises the following steps: mixing methacrylamide, acrylic acid monomer, crosslinking agent, catalyst and water, and then adding acrylamide and initiator to obtain a hydrogel precursor solution.

5. A hydrogel, characterized in that: It is a product obtained by gelling the hydrogel precursor solution described in any one of claims 1 to 3.

6. A hydrogel-cured sand precursor solution, characterized in that: It consists of the hydrogel precursor solution according to any one of claims 1 to 3 and building sand, wherein the mass ratio of the hydrogel precursor solution to the building sand is 0.1 to 0.5:

1.

7. The hydrogel-cured sand precursor solution according to claim 6, characterized in that: The mass ratio of the hydrogel precursor solution to the building sand is 0.287:

1.

8. A hydrogel-cured sand, characterized in that: It is a product obtained by solidifying the hydrogel solidified sand precursor solution as described in any one of claims 6 to 7.

9. Use of the hydrogel precursor solution according to any one of claims 1 to 3, the hydrogel according to claim 5, the hydrogel-cured sand precursor solution according to any one of claims 6 to 7, and the hydrogel-cured sand according to claim 8 in preparing emergency repair materials.

10. The use according to claim 9, characterized in that The material is that found in roads, airport runways, bridges or military installations.

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