An improved microbial synergistic concrete repair material and its preparation method

Abstract

The present application provides an improved microbial synergistic concrete repair material, which is composed of two parts of concrete slurry: a microbial synergistic repair high-bonding concrete slurry and a salt-resistant dense concrete slurry. The microbial synergistic repair high-bonding concrete slurry is composed of: 40-50wt.% modified magnesium phosphate cement, 1.5-2.5wt.% ternary copolymer polyacrylamide, 20-30wt.% quartz sand with a fineness modulus of 2.5-2.7, 4-8wt.% ultrafine steel fiber with a cross-sectional area of ​​less than or equal to 0.01mm2, 0.1-0.5wt.% denitrifying bacteria spores, 0.01-0.2wt.% nutrients, and the balance is water. The salt-resistant dense concrete slurry is composed of 40-45 wt.% modified magnesium phosphate cement, 0.3-0.7 wt.% ternary copolymer polyacrylamide, 15-20 wt.% coarse aggregate, 10-15 wt.% fine aggregate, 5-10 wt.% ordinary steel fiber, 0.1-0.5 wt.% water reducer, and the balance is water. By combining these two concrete ingredients, a stable and excellent repair effect can be achieved.

Description

Technical Field

[0001] The present application belongs to the field of concrete, and specifically relates to an improved microbial synergistic concrete repair material for use in marine environments and a preparation method thereof. Background Art

[0002] As we all know, the marine environment is quite different from the terrestrial environment, primarily due to the presence of large amounts of salt and marine microorganisms in seawater. While the main factors contributing to concrete failure on land are oxygen erosion and external impact, in the marine environment, the primary factors contributing to concrete failure are chloride ion attack, marine microbial attack, seawater pressure, and periodic tidal impact.

[0003] Therefore, when designing concrete for land use and marine use, researchers approach the design from completely different perspectives to ensure that the concrete is suitable for the respective environments. Similarly, when researching repair materials for land-based and marine-based concrete, different failure causes and usage environments must be considered.

[0004] A research team at Tongji University has proposed a self-repairing material for concrete cracks that uses microbial synergistic mineralization. This material, which uses both aerobic and anaerobic microorganisms, can effectively repair concrete cracks. However, concrete in offshore environments is constantly exposed to low oxygen levels, preventing aerobic microorganisms from fully functioning. Therefore, this solution is not suitable for offshore environments.

[0005] Currently, there is no comprehensive research on marine concrete repair materials, and repair materials used for terrestrial concrete are typically used. However, when used to repair marine concrete, these terrestrial concrete repair materials suffer from poor repair effectiveness, unstable performance, and short lifespan. Therefore, this application aims to provide a seawater-resistant concrete repair material and a method for its preparation. Summary of the Invention

[0006] In order to fill the relative gap in concrete repair materials specifically for use in marine engineering environments, the present application provides a seawater-resistant concrete repair material and a preparation method thereof that are particularly suitable for use in marine engineering environments. The material can effectively repair partially failed concrete in marine engineering environments with good repair effects, stable performance and long service life.

[0007] An improved microbial synergistic concrete repair material is composed of two parts of concrete slurry, namely microbial synergistic repair high-bonding concrete slurry and salt-resistant dense concrete slurry;

[0008] Among them, the composition of the microbial synergistic repairable high-bonding concrete slurry is:

[0009]

[0010] Among them, the composition of salt-resistant dense concrete slurry is:

[0011]

[0012]

[0013] Among them, the microbial synergistic repairable high-bonding concrete slurry is used to directly repair the failed parts of the concrete and continuously repair the cracks in the failed parts of the concrete. The salt-resistant dense concrete slurry is used to enhance the strength and life of the repaired concrete.

[0014] Furthermore, the nutrient is a mixture of potassium nitrate and potassium sodium tartrate in a mass ratio of 3:2.

[0015] Furthermore, the modified magnesium phosphate cement is composed of: magnesium oxide: potassium dihydrogen phosphate: aluminum silicate: EDTA-2Na in a mass ratio of (20-30): (20-25): (4-8): (1-5).

[0016] Furthermore, the ternary copolymer polyacrylamide is a ternary copolymer polyacrylamide of acrylamide, acrylic acid, and allyl-A-D-galactopyranoside.

[0017] Furthermore, the acrylamide, acrylic acid, and allyl-A-D-galactopyranoside ternary copolymerized polyacrylamide preferably has a structure as shown in (I),

[0018] (I)

[0019] Wherein, in formula (I), x:y:z=(50-70):(15-25):(15-25).

[0020] Furthermore, in the microbial synergistic repairing high-bonding concrete slurry, the content of the ternary copolymer polyacrylamide is preferably 2-2.5 wt.%.

[0021] Furthermore, the ordinary steel fiber refers to a steel fiber with a cross-sectional area between 0.1 mm 2 -4mm 2 of steel fiber.

[0022] In the microbial synergistic repair high-bonding concrete slurry, considering that the application environment is a seawater environment, a low-oxygen or anaerobic state, and there will be some internal cracks in the failed parts of the concrete, the present application uses spores of denitrifying bacteria that can undergo mineralization reactions in a low-temperature anaerobic environment. The growth of the spores of denitrifying bacteria in a low-temperature anaerobic environment is utilized to continuously repair cracks deep inside the concrete and increase the strength of the concrete.

[0023] Furthermore, considering the seawater environment, the addition of a relatively high content of ternary copolymer polyacrylamide can increase the viscosity of the concrete while maintaining low turbidity, reducing its expansion, making repair work in seawater environments relatively easy. This means that relatively small amounts of concrete can be used to quickly repair specific failure sites. Microorganisms can then work together with the high-bonding concrete slurry to specifically repair the failure site and areas with microcracks. If the ternary copolymer polyacrylamide content is less than 1.5 wt.%, the expansion is too high, making it unsuitable for rapid repair of concrete in marine environments.

[0024] In addition, the inventors discovered during their previous research that ternary copolymer polyacrylamide has good water absorption. The more it is incorporated into concrete, the stronger its water absorption. When it is incorporated too much, more water is not discharged during molding. This water evaporates during the mortar hardening process, causing certain micropores, which manifests as an increase in the content of harmful pores and multiple harmful pores in the microscopic morphology, and then a decrease in compressive strength in the macroscopic view. However, in the concrete repair material used in the marine environment of this application, the microbial synergistic repair high-bonding concrete slurry is used to directly repair the concrete failure site. Its outer surface is also surface-repaired with a salt-tolerant dense concrete slurry, and no coarse aggregate is used. Therefore, the formation of a large number of harmful pores and multiple harmful pores in the repair layer is almost non-existent. Therefore, 1.5-2.5wt.% of ternary copolymer polyacrylamide is more suitable, and is no longer limited to the 1.5wt.% upper limit of addition in traditional concrete. More preferably, the content of ternary copolymer polyacrylamide in the microbial synergistic repair high-bonding concrete slurry is preferably 2-2.5wt.%.

[0025] At the same time, the role of the microbial synergistic repair high-bonding concrete slurry is to quickly repair the parts that need to be repaired and serve as an intermediate layer to receive the external salt-resistant and antibacterial concrete layer. No coarse aggregate is added to its composition. However, this will reduce the strength of the intermediate layer. To this end, the present application adds a cross-sectional area of ​​​​less than or equal to 0.01mm to the microbial synergistic repair high-bonding concrete slurry. 2 Ultrafine steel fibers. General steel fibers have excellent tensile strength and can be used to improve the compressive strength, tensile strength, flexural strength, impact strength, toughness, impact toughness and other properties of concrete. The cross-sectional area S1 used in this application is less than or equal to 0.01mm 2 The steel fibers not only improve the strength of concrete, but also effectively increase the density of the middle layer of concrete, thereby increasing the stability and service life of the repaired concrete. When the cross-sectional area of ​​the steel fibers is too large, the density of the concrete will decrease as the cross-sectional area increases.

[0026] Salt-tolerant dense concrete slurry is used to repair the entire concrete surface and improve the strength and life of the entire concrete surface. Therefore, compared with microbial synergistic repair high-bonding concrete slurry, the expansion of concrete made from salt-tolerant dense concrete slurry needs to be appropriately increased, and it is also necessary to maintain a relatively high viscosity and low turbidity. Therefore, it is necessary to control the content of ternary copolymer polyacrylamide within the range of 0.4-0.8wt.%. If the content of ternary copolymer polyacrylamide is too high, especially above 1.2wt.%, the expansion of concrete will decrease significantly, which will affect the strength of concrete.

[0027] Furthermore, salt-tolerant dense concrete slurry requires both fine and coarse aggregates to maintain the concrete's basic strength. Furthermore, conventional steel fibers should be added to improve the concrete's compressive, tensile, flexural, impact, and toughness properties, leveraging their superior tensile and compressive strengths. Furthermore, considering cost, conventional steel fibers are sufficient.

[0028] The modified magnesium phosphate cement used in this application is made from magnesium oxide, potassium dihydrogen phosphate, silicon oxide, aluminum oxide, and EDTA-2Na in appropriate proportions. EDTA-2Na is suitable for use in marine environments and can appropriately extend the setting time of magnesium phosphate cement in marine construction environments. Aluminum silicate can react with potassium dihydrogen phosphate and magnesium oxide to form various stable products, such as magnesium aluminum phosphate and magnesium aluminum silicate, improving the concrete's salt resistance, water resistance, and strength. DETAILED DESCRIPTION

[0029] The specific solutions of this application will be described in detail below.

[0030] Preparation Example 1

[0031] A method for preparing polyacrylamide for underwater non-dispersible concrete comprises the following steps:

[0032] 1) Weigh 42.65 g (about 0.6 mol) of acrylamide, 14.41 g (about 0.2 mol) of acrylic acid, and 44.04 g (about 0.2 mol) of allyl-A-D-galactopyranoside, and dissolve them in 404.4 g of deionized water to obtain an aqueous solution with a total mass concentration of 20 wt.%;

[0033] 2) adding 0.17 g of urea (approximately 0.4 wt.% of acrylamide), 0.085 g of EDTA-2Na (approximately 0.2 wt.% of acrylamide), and 0.17 g of sodium formate (approximately 0.4 wt.% of acrylamide) to the aqueous solution in sequence, and stirring uniformly at room temperature;

[0034] 3) Adjust the pH to 8 with NaOH solution, and then introduce nitrogen to deoxygenate for 28 minutes;

[0035] 4) Add 0.26 g of azobisisobutylimidazoline hydrochloride (approximately 0.6 wt.% of acrylamide) and seal the container and heat at 20° C. for 4 hours;

[0036] 5) Add 0.26 g of ammonium persulfate (approximately 0.6 wt.% of acrylamide) and seal the container and heat at 35° C. for 5 hours;

[0037] 6) The obtained colloidal product is taken out, dried and crushed to obtain powdered polyacrylamide, which is recorded as M1.

[0038] The product M1 of Example 1 was subjected to infrared spectroscopy (IR) and quantitative 13C spectrum determination.

[0039] In the IR spectrum, the stretching vibration peak of the carbonyl group (C=O) in the amide group appears at 1656 cm -1 The stretching vibration peak of the primary amide (-NH2) in the amide group appears at 3348 cm -1 The stretching vibration peak of secondary amide (-NH) is at 3178cm -1 The stretching vibration peak of -CN is at 1119cm -1 1405cm -1 and 1549cm -1 The absorption peaks at 2918 cm-1 are the symmetric and antisymmetric stretching vibration peaks of the carboxyl group (-COO-). The characteristic absorption peak of the methylene group (-CH2) in the skeleton is at 2918 cm-1. -1 1316cm -1 The peak at is caused by the stretching vibration of the methine (-CH).

[0040] Quantitative 13C spectrometry revealed characteristic peaks for the pyranose rings C1-C6 at 61.02-102.77 ppm. The integrated area of ​​the characteristic peaks revealed an x:y:z ratio of approximately 3:1:1. Viscometry revealed a viscosity-average molecular weight (Mv) of 14.83 million, with a monomer conversion rate exceeding 99.9%. This confirms that the polyacrylamide prepared in this example has the structure shown in Formula (I).

[0041]

[0042] And the x:y:z is 3:1:1.

[0043] Preparation Example 2

[0044] The modified magnesium phosphate cement is prepared according to the mass ratio of magnesium oxide: potassium dihydrogen phosphate: aluminum silicate: EDTA-2Na of 30 kg: 25 kg: 6 kg: 3 kg.

[0045] Example 1

[0046] An improved microbial synergistic concrete repair material is composed of two parts of concrete slurry, namely microbial synergistic repair high-bonding concrete slurry and salt-resistant dense concrete slurry;

[0047] Among them, the composition of the microbial synergistic repairable high-bonding concrete slurry is:

[0048]

[0049]

[0050] Among them, the composition of salt-resistant dense concrete slurry is:

[0051]

[0052] Example 2

[0053] An improved microbial synergistic concrete repair material is composed of two parts of concrete slurry, namely microbial synergistic repair high-bonding concrete slurry and salt-resistant dense concrete slurry;

[0054] Among them, the composition of the microbial synergistic repairable high-bonding concrete slurry is:

[0055]

[0056]

[0057] Among them, the composition of salt-resistant dense concrete slurry is:

[0058]

[0059] Example 3

[0060] An improved microbial synergistic concrete repair material is composed of two parts of concrete slurry, namely microbial synergistic repair high-bonding concrete slurry and salt-resistant dense concrete slurry;

[0061] Among them, the composition of the microbial synergistic repairable high-bonding concrete slurry is:

[0062]

[0063]

[0064] Among them, the composition of salt-resistant dense concrete slurry is:

[0065]

[0066] Comparative Example

[0067] In order to verify and compare the excellent performance and effect of an improved microbial synergistic concrete repair material of the present application, the following comparative examples are set for comparison.

[0068] Comparative Example 1

[0069] The salt-resistant dense concrete slurry in Example 1 is directly used as a repair material for repairing concrete structures in marine environments, and the microbial synergistic repair high-bonding concrete slurry is omitted.

[0070] Comparative Example 2

[0071] The microbial synergistic repairing high-bonding concrete slurry in Example 1 is directly used as a repair material for repairing concrete structures in marine environments, and the salt-resistant dense concrete slurry is omitted.

[0072] Comparative Example 3

[0073] The content of ternary copolymerized polyacrylamide in the microbial synergistic repairing high-bonding concrete slurry of Example 1 was reduced to 0.6 wt.%, while the rest remained unchanged.

[0074] Comparative Example 4

[0075] The content of ternary copolymerized polyacrylamide in the salt-resistant dense concrete slurry of Example 1 was increased to 2 wt.%, while the rest remained unchanged.

[0076] Comparative Example 5

[0077] The ultrafine steel fibers in the microbial synergistic repairable high-bonding concrete slurry of Example 1 were replaced with ordinary steel fibers of corresponding content.

[0078] Comparative Example 6

[0079] The spores of the denitrifying bacteria and the corresponding nutrient solution in Example 1 were omitted.

[0080] The concrete repair materials of Examples 1-3 and Comparative Examples 1-6 were respectively used to repair concrete in a simulated marine environment, and then performance tests were performed.

[0081] The repair method is as follows: first, remove the defective parts of the failed parts of the concrete in the simulated marine environment, then apply the microbial synergistic repair high-bonding concrete slurry to the cleaned area to be repaired, and then apply the salt-resistant dense concrete slurry to the surface of the concrete slurry made by the microbial synergistic repair high-bonding concrete slurry.

[0082] The tested properties include 28-day compressive strength, bonding strength between the repair structure and the repair matrix, and resistance to chloride ion penetration.

[0083] Chloride ion penetration resistance was assessed using the DC coulometric method, following the test method outlined in the "Standard for Electrical Evaluation of Chloride Ion Permeability of Concrete." The specimens were vacuum-saturated with water, and the current flowing through them was then measured at 60V DC voltage every 30 minutes for 6 hours. Permeability was graded from best to worst as "impermeable," "very low," "low," "medium," and "high." See Table 1 for detailed test results.

[0084] Table 1 Performance test results

[0085]

[0086] The performance test results in Table 1 indicate that the seawater-resistant concrete repair material of this application, when used to repair concrete structures in a simulated marine environment, achieves excellent compressive and bonding strengths, along with extremely low resistance to chloride ion penetration, by first removing defects from failed concrete sites in a simulated marine environment, then applying a microbially synergistically repairable, high-bonding concrete slurry to the cleaned area to be repaired, and then applying a salt-resistant, dense concrete slurry to the surface of the resulting concrete slurry.

Claims

1. An improved microbial synergistic concrete repair material, consisting of two parts of concrete slurry: a microbial synergistic repairable high-bonding concrete slurry and a salt-tolerant dense concrete slurry; in, The composition of microbial synergistic repairable high-bonding concrete slurry is: The balance is water; Among them, the composition of salt-resistant dense concrete slurry is: The balance is water; The modified magnesium phosphate cement is composed of: magnesium oxide: potassium dihydrogen phosphate: aluminum silicate: EDTA-2Na in a mass ratio of (20-30): (20-25): (4-8): (1-5); The ternary copolymerized polyacrylamide is a ternary copolymerized polyacrylamide of acrylamide, acrylic acid, and allyl-A-D-galactopyranoside, and has a structure as shown in (I). Wherein, in formula (I), x:y:z=(50-70):(15-25):(15-25).

2. The improved microbial synergistic concrete repair material according to claim 1, characterized in that: The nutrient is a mixture of potassium nitrate and potassium sodium tartrate in a mass ratio of 3:

2.

3. The improved microbial synergistic concrete repair material according to claim 1, characterized in that: In the microbial synergistic repairing high-bonding concrete slurry, the content of the ternary copolymer polyacrylamide is preferably 2-2.5 wt.%.

4. The improved microbial synergistic concrete repair material according to claim 1, characterized in that: The ordinary steel fiber refers to a steel fiber with a cross-sectional area of ​​0.1 mm 2 -4mm 2 of steel fiber.

Images