Maritime work concrete with salt corrosion resistance and self-repairing function and preparation method thereof

Abstract

The invention provides marine concrete with salt corrosion resistance and self-repairing and a preparation method thereof.The marine concrete is prepared from, by weight, 190-210 parts of cement, 91-100 parts of a natural mineral activating group, 10-15 parts of a composite corrosion inhibitor, 30-35 parts of an exciting agent, 3-6 parts of a high-efficiency water reducing agent, 4-8 parts of a polyamide / polyether sulfone copolymer and 20-25 parts of microcapsules; the preparation method comprises the following steps: preparing the composite corrosion inhibitor and the microcapsule; mixing the cement, the natural mineral activating group, the composite corrosion inhibitor, the exciting agent and the high-efficiency water reducing agent, adding the treated polypropylene fibers and the microcapsules, reacting and curing. According to the invention, the long-acting protection and self-repairing functions of the marine concrete in a high-salt environment are realized by utilizing the cooperation of multiple physical and chemical mechanisms of various formula materials.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete, and particularly to a marine concrete with anti-salt corrosion and self-healing functions and a preparation method thereof. Background Art

[0002] Marine engineering concrete, as the core material for infrastructure such as cross-sea bridges, port terminals, and offshore drilling platforms, is exposed to harsh environments of high salinity, high humidity, splash impact, and chloride ion penetration for a long time. Reinforcement corrosion and concrete deterioration caused by chloride ion erosion have become the "number one killer" of the service life of marine engineering structures. According to statistics, nearly 40% of marine structures globally fail prematurely due to salt corrosion damage, resulting in annual economic losses in the tens of billions. At the same time, the lack of self-healing ability after concrete cracking leads to continuous accumulation of damage, forming a vicious cycle of "penetration - corrosion - cracking - accelerated penetration", further shortening the project life. Existing anti-salt corrosion technologies mainly rely on high-performance concrete (HPC) systems, which improve density by reducing the water-binder ratio and adding mineral admixtures (such as fly ash, silica fume), or use epoxy-coated steel bars for passive protection. However: HPC requires an ultra-low water-binder ratio (<0.35) to ensure density, but has poor construction fluidity and is difficult to pump, especially in large-volume concrete projects, it is prone to temperature cracks, which instead exacerbate chloride ion penetration; although fly ash can improve the pore structure, its pozzolanic activity depends on late alkali activation, and the early-stage impermeability improvement is limited, and the diffusion of chloride ions in nanoscale pores is still difficult to block; organic coatings are prone to aging and peeling under tidal cycles and ultraviolet radiation, forming "local accelerated corrosion channels", and it is difficult to repair in situ after the coating is damaged. For the problem of concrete cracking, existing self-healing technologies are mainly divided into two categories: encapsulating repair agents such as epoxy resin in urea-formaldehyde resin microcapsules, and releasing the repair agent when cracks occur. However, the microcapsules are easily damaged during the mixing process, and the capsule shells will degrade rapidly due to chloride ion erosion in the marine environment, resulting in attenuation of the repair efficiency; using microorganisms such as Bacillus alkalophilus to induce calcium carbonate precipitation. However, the high salinity of the marine environment will inhibit the activity of bacteria, and the mineralization process depends on oxygen and moisture conditions, and the repair efficiency is significantly reduced in wet-dry alternating areas such as the splash zone. More critically, existing self-healing technologies mostly target single damage modes (such as microcracks), while concrete in the marine environment often faces complex damage caused by the coupling action of salt corrosion - freeze-thaw - load, and a single repair mechanism is difficult to cope with complex working conditions.

[0003] In summary, there is an urgent need in the market for a marine concrete with anti-salt corrosion and self-healing functions and a preparation method thereof, which can not only reduce longitudinal cracks, lower chloride ion content, but also avoid the crumbling of the core concrete leading to local collapse. Summary of the Invention

[0004] The present invention provides a marine concrete with anti-salt corrosion and self-healing functions and a preparation method thereof to solve the problems raised in the above background art.

[0005] To solve the above technical problems, the present invention discloses a marine concrete with anti-salt corrosion and self-healing properties, which comprises the following components: cement, natural mineral activator, composite corrosion inhibitor, activator, high-range water reducer, polyamide / polyethersulfone copolymer, and microcapsules.

[0006] Furthermore, by weight, it comprises the following components: 190 - 210 parts of cement, 91 - 100 parts of natural mineral activator, 10 - 15 parts of composite corrosion inhibitor, 30 - 35 parts of activator, 3 - 6 parts of high-range water reducer, 4 - 8 parts of polyamide / polyethersulfone copolymer, and 20 - 25 parts of microcapsules.

[0007] Furthermore, the preparation method of the composite corrosion inhibitor comprises: by weight, dispersing 1 part of nano-Al2O3 and 1 part of coal tar pitch carbon powder in an ethanol solution at a solid-liquid ratio of 1:15, subjecting it to ultrasonic treatment, adding SO4 2- modified graphene oxide, and stirring and vacuum drying.

[0008] Furthermore, the preparation method of the microcapsules comprises: using tetradecanol as the core material and titanium dioxide as the shell material, reacting at a weight ratio of 4:1 under the conditions of pH = 8.5 and 50 °C.

[0009] Furthermore, the activator is composed of Na2SiO3 and NaOH, and the modulus is 1.2.

[0010] Furthermore, the polyamide / polyethersulfone copolymer is a fiber treated by plasma, with a length of 12 mm, and is treated by plasma at a power of 50 W in an Ar atmosphere.

[0011] Furthermore, the natural mineral activator is composed of 45% metakaolin, 30% limestone powder, and 25% natural volcanic ash by mass percentage.

[0012] Furthermore, the high-range water reducer is a polycarboxylic acid-lignosulfonic acid complex.

[0013] Furthermore, the preparation method of the marine concrete with anti-salt corrosion and self-healing properties comprises:

[0014] S1: Prepare the composite corrosion inhibitor;

[0015] S2: Prepare the microcapsules;

[0016] S3: Mixing: Mix cement, natural mineral activator, composite corrosion inhibitor, activator, and high-range water reducer, stir at 60 rpm for 2 hours, add treated polypropylene fibers and microcapsules, and stir for 4 hours to obtain a mixture;

[0017] S4: Curing treatment: Heat the mixture to 50°C at a rate of 0.5°C / min within 2 hours, keep it warm for 24 hours, and then cool it naturally to room temperature over 10 hours.

[0018] Furthermore, the application of the marine concrete in the caissons of cross-sea bridges, port breakwaters, and the foundation engineering of offshore oil platforms.

[0019] Compared with the prior art, the present invention provides a marine concrete with anti-salt corrosion and self-healing properties and its preparation method, having the following beneficial effects:

[0020] 1. Through the synergy of multi-scale materials (nano-micro-millimeter) and multiple mechanisms (physical barrier - chemical bonding - intelligent response), the present invention realizes the long-term protection and self-healing functions of marine concrete in a high-salt environment. The composite corrosion inhibitor, natural mineral activation group, and activator are used synergistically to improve the anti-salt corrosion ability; the microcapsules and the polyethersulfone-g-polyamide block copolymer with a hydrogen bond cross-linking network function are used synergistically to improve the self-healing performance; finally, the gradient heating curing promotes the full cross-linking of the geopolymer network, activates the bonding at the interface between the microcapsules and the matrix, and pre-distributes the repair agent to the potential defect areas;

[0021] 2. Tidal, diurnal, and seasonal temperature differences cause periodic changes in the surface temperature of concrete structures (e.g., the daily temperature difference in the Yellow Sea area reaches 10 - 15 °C). The microcapsules of this application utilize the transformation of tetradecanol from solid to liquid when the temperature > 25 °C, with a volume expansion of about 12%, squeezing the shell layer to generate microcracks and release the pre-encapsulated repair agent. When the temperature < 25 °C, tetradecanol solidifies and shrinks, and the shell layer cracks close, preventing external corrosive media from invading. It precisely matches the seawater temperature fluctuation range and has a strong self-healing ability. The phase change-driven release of the repair agent can repair cracks ≤ 0.3 mm. When microcracks occur in concrete, the stress concentration at the crack tip leads to a local temperature rise (the frictional heat generation effect can increase the temperature in the crack area by 3 - 5 °C), forming a temperature gradient signal. Only the microcapsules in the damaged area trigger a phase change due to the local temperature rise and release the encapsulated repair agent (such as sodium silicate precursor), while the microcapsules in the intact area remain intact, avoiding ineffective consumption. The repair agent diffuses along the crack network and reacts with Ca(OH)2 in the concrete to generate C-S-H gel, achieving 3D self-healing of millimeter-scale cracks (≤ 0.3 mm); the phase change material buffers the temperature stress during the heat absorption / exotherm process, and using the thermal buffering effect, synergistically enhances the effect with the repair agent to jointly reduce the generation of microcracks caused by the difference in the thermal expansion coefficient of concrete; in addition, the microcapsules are also excellent Cl- penetration inhibitors because the TiO2 shell layer itself can adsorb Cl- (adsorption capacity ≈ 15 mg / g), combined with the CaCO3 precipitate generated by the repair agent, comprehensively reducing the Cl- penetration rate by ≥ 80%; the essential relationship between the temperature-sensitive phase change mechanism and the self-healing function is a closed-loop response system of "environmental signal perception - damage-targeted repair - performance dynamic recovery". By converting the inherent temperature fluctuations in the marine environment into a repair driving force, it realizes "zero-energy consumption" adaptive maintenance;

[0022] 3. The released repair agent (such as sodium silicate) not only fills the cracks but also forms a FeSiO3 passivation film on the surface of the steel bars, and synergistically with the composite corrosion inhibitor (containing SO4 2- modified graphene oxide) reduces the Cl - penetration rate, and the mineral activation group replaces 60% of the cement, reducing CO2 emissions by 45%, having good low-carbon benefits. Detailed implementation manners

[0023] The following describes the preferred embodiments of the present invention. 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.

[0024] In addition, in the present invention, descriptions such as "first", "second", etc. are for descriptive purposes only, and do not particularly refer to the meaning of order or sequence, nor are they used to limit the present invention. They are merely used to distinguish components or operations described with the same technical terms, and should not be construed as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions and technical features between various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0025] Unless otherwise specified, the examples and comparative examples are parallel tests with the same components, component contents, preparation steps, and preparation parameters. The experimental methods in the following examples are all conventional methods unless otherwise specified; the test materials used in the following examples are all analytical reagents (A.R.) and are all purchased from commercial channels.

[0026] Nano-Al2O3 was purchased from Zhejiang Manli Nano Technology Co., Ltd., model: ML-AlO3-Y20 (γ-phase nano-aluminum oxide, 20 nm); coal tar pitch carbon powder was purchased from Hebei Weixiang Chemical Technology Co., Ltd.; SO4 2- Modified graphene oxide was purchased from Shandong Jincheng Graphene Technology Co., Ltd., model: G205 sulfonated graphene; titanium dioxide was purchased from Shanghai Jianghu Titanium White Chemical Products Co., Ltd., model: T1966 titanium dioxide for chemical fibers; cement was purchased from Jiyuan Zhonglian Cement Co., Ltd.; metakaolin was purchased from Gongyi Jiahong Refractory Materials, model 325 - 4000 mesh activated metakaolin; limestone powder was purchased from Xinfu Mineral Products Processing Factory in Lingshou County; natural pozzolan was purchased from Shijiazhuang Tourmaline Mineral Products, with SiO2 content ≥ 70%; liquid sodium silicate was purchased from Hubei Xingyinhe Chemical Industry, modulus 3.3, concentration 40%; sodium hydroxide was purchased from Hubei Zhonglong Kangsheng Fine Chemicals, ≥ 98% flaky solid; high-range water reducer was purchased from Jiangsu Nihigh Technology Co., Ltd.; polypropylene fiber was FiberForce 12.

[0027] The preparation method of the activator Na2SiO3-NaOH is to dissolve 1 part of flaky NaOH in 2 parts of deionized water to obtain a NaOH solution, and stir and mix 10 parts of sodium silicate solution with 1.5 parts of NaOH solution to obtain the activator Na2SiO3-NaOH with a modulus of 1.2.

[0028] Example 1

[0029] S1. Preparation of composite corrosion inhibitor: Ultrasonically disperse nano-Al2O3 (particle size 20 nm) and coal tar pitch carbon powder (D50 = 3 μm) in an ethanol solution (solid-liquid ratio 1:15) (40 kHz, power 500 W) for 30 minutes; add SO4 2- modified graphene oxide, and magnetically stir at 600 rpm at room temperature for 2 hours, and then set aside after vacuum drying.

[0030] S2. Preparation of microcapsules: Using the interfacial polymerization method, the weight ratio of tetradecanol to titanium dioxide (thickness 200 nm) is 4:1, react at pH = 8.5 and 50 °C for 6 hours, and control the particle size to 60 μm.

[0031] S3. Mixing: Put 200 parts by weight of cement (C3A < 8%) and 96 parts by weight of natural mineral activation group (45% metakaolin, 30% limestone powder and 25% natural pozzolan), add 12 parts by weight of composite corrosion inhibitor, 32 parts by weight of activator (Na2SiO3-NaOH, modulus 1.2) and 4 parts by weight of high-performance water reducer (polycarboxylic acid-lignosulfonic acid complex), stir at 60 rpm for 2 hours, add 6 parts by weight of 12 mm long polypropylene fibers after plasma surface treatment with a power of 50 W in an Ar atmosphere, reduce the stirring speed to 20 rpm, and add 22.5 parts by weight of microcapsules and stir for 4 hours.

[0032] S4. Curing: After molding, raise the temperature from room temperature to 50 °C (rate 0.5 °C / min) in 2 hours, keep it at 50 °C for 24 hours, and then naturally cool to room temperature in 10 hours to obtain a marine concrete with anti-salt corrosion and self-repairing properties.

[0033] Example 2

[0034] S3. Mixing: Put 190 parts by weight of cement (C3A < 8%) and 91 parts by weight of natural mineral activation group (45% metakaolin, 30% limestone powder and 25% natural pozzolan), add 10 parts by weight of composite corrosion inhibitor, 30 parts by weight of activator (Na2SiO3-NaOH, modulus 1.2) and 3 parts by weight of high-performance water reducer (polycarboxylic acid-lignosulfonic acid complex), stir at 60 rpm for 2 hours, add 4 parts by weight of 12 mm long polypropylene fibers after plasma surface treatment with a power of 50 W in an Ar atmosphere, reduce the stirring speed to 20 rpm, and add 20 parts by weight of microcapsules and stir for 3 hours.

[0035] Example 3

[0036] S3. Mixing: Add 210 parts by weight of cement (C3A < 8%) and 100 parts by weight of natural mineral activation group (45% metakaolin, 30% limestone powder, and 25% natural volcanic ash), then add 15 parts by weight of compound corrosion inhibitor, 35 parts by weight of activator (Na2SiO3 - NaOH, modulus 1.2), and 6 parts by weight of high - efficiency water - reducing agent (polycarboxylic acid - lignosulfonic acid complex). Stir at 60 rpm for 2 hours, add 8 parts by weight of polypropylene fibers with a length of 12 mm after plasma surface treatment under an Ar atmosphere with a power of 50 W. Reduce the stirring speed to 20 rpm, and then add 25 parts by weight of microcapsules and stir for 6 hours.

[0037] The temperature sensors used in the S4 curing step in the above - mentioned embodiments are PT100 platinum resistors, and 3 PT100 platinum resistors (center, surface layer, middle layer) are buried per cubic meter of concrete; the humidity sensors are capacitive humidity probes, which are arranged at the same positions as the temperature sensors; the data acquisition instrument used is HIOKI LR8450, which supports wireless transmission and the sampling frequency is ≥ 1 time / minute; the environmental control equipment includes a steam generator ELMO TE - 1000, electric blankets, and an automatic spraying system.

[0038] The S4 curing step in the above - mentioned embodiments: After the concrete is cast and formed, cover it with a plastic film, start the sensors to record the initial temperature and humidity, set the target temperature to 25 °C and the humidity to 95%. If the humidity < 95%, turn on the steam generator for 5 minutes to make the humidity in the film reach the standard. When heating up, heat in zones through electric blankets. If the center temperature < 50 °C and the heating rate > 0.5 °C / min, then pause heating. If the difference between the surface layer temperature and the center temperature > 5 °C, then reduce the power of the surface layer electric blanket by 50%; if the humidity < 90%, then start the steam generator and the spraying system. If the humidity > 97%, then briefly uncover the film for ventilation for 30 s. When the temperature ≥ 23 °C, detect the phase change of microcapsules (endothermic peak of liquid tetradecanol) through an infrared thermal imager FLIRA655sc, capture the local temperature drop points caused by the endothermic absorption of microcapsules, define all regions with T ≥ 1 °C as activated microcapsules. The number of activated microcapsules is the number N2 of low - temperature points with T ≥ 1 °C. The total number of microcapsules N1 is 22.5 parts by weight of microcapsules, which is converted to 4.2×10 5 pieces / m 3 , Ensure that the self - repair function activation rate ≥ 90%. If the activation rate < 90%, then extend the heat - preservation time at 50 °C for 12 hours.

[0039] Simulate the marine environment by soaking in 3.5% NaCl solution + wet-dry cycling (ASTM D1141). During curing, dynamically adjust the humidity and temperature through the internal temperature and relative humidity monitoring system of the concrete to ensure that the self-healing function activation rate of the marine concrete with anti-salt corrosion and self-healing is ≥90%. After 1 year, the compressive strength retention rate of the marine concrete is 86%, and the weight loss rate of steel bar corrosion is 0.05%.

[0040] Comparative Example 1

[0041] It is different from Example 1 in that it lacks the composite corrosion inhibitor in equal weight parts, and the others are the same.

[0042] Comparative Example 2

[0043] It is different from Example 1 in that it lacks the microcapsules in equal weight parts, and the others are the same.

[0044] Comparative Example 3

[0045] It is different from Example 1 in that it lacks the activator in equal weight parts, and the others are the same.

[0046] Comparative Example 4

[0047] It is different from Example 1 in that it lacks the polypropylene fibers after plasma surface treatment in equal weight parts, and the others are the same.

[0048] Comparative Example 5

[0049] It is different from Example 1 in that the polypropylene fibers lack plasma surface treatment, and the others are the same.

[0050] Comparative Example 6

[0051] It is different from Example 1 in that it lacks the microcapsules in weight parts, and the others are the same.

[0052] Performance Test

[0053] Conduct compressive strength, chloride ion diffusion, and salt spray tests on the concrete prepared in the examples and comparative examples. The compressive strength is measured according to the ISO 679 standard. Prepare 40mm×40mm×160mm specimens. The chloride ion permeability test refers to ASTM C1202, with a voltage of 60V and a test duration of 90 days. The specimen thickness is 50mm; Salt spray accelerated corrosion experiment: Place the concrete specimens in a salt spray chamber (5% NaCl, 35°C) for cyclic corrosion for 90 days, and measure the corrosion current density; Crack self-healing test: Precast cracks with a width of 0.2mm and observe the self-healing situation under a microscope for 90 days. The results are shown in Table 1.

[0054] Table 1

[0055]

[0056]

[0057] As can be seen from Table 1, the strength of the example is > 38.2 MPa. In Comparative Example 3, the lack of an activator led to insufficient mineral activation and a sharp drop in strength; in Comparative Example 1, the lack of the nano-filling effect of the composite corrosion inhibitor increased the porosity and caused a decrease in strength; in Comparative Example 2, the lack of microcapsules reduced the repair efficiency; in Comparative Example 5, the untreated fibers led to weak interfacial bonding and a 27% decrease in the release efficiency of the repair agent; in Comparative Example 1, the lack of the composite corrosion inhibitor caused a 325% surge in the Cl- diffusion coefficient; in Comparative Example 3, the lack of an activator led to incomplete pozzolanic reaction and the highest value of Cl- penetration; in Comparative Example 1, the lack of a corrosion inhibitor increased the corrosion current by 15 times. According to the ISO 14064 standard, the carbon emissions of cement (ordinary Portland cement of grade 42.5, carbon emission factor 0.82 kg CO2 / kg) and the mineral activation group (0.15 kg CO2 / kg) were calculated. The carbon emissions of Example 1 were 195 kg / m 3 , while the carbon emissions of traditional C40 concrete (320 kg cement / m 3 ) were 262 kg / m 3 . Therefore, the carbon emissions of Example 1 were significantly reduced.

[0058] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. If these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these changes and modifications.

Claims

1. An offshore concrete with anti-salt corrosion and self-healing properties, characterized in that, It includes the following components: cement, natural mineral activator, composite corrosion inhibitor, activator, high-range water reducer, polyamide / polyethersulfone copolymer and microcapsules.

2. The marine concrete with anti-salt corrosion and self-healing according to claim 1, characterized in that, By weight, it includes the following components: 190 - 210 parts of cement, 91 - 100 parts of natural mineral activator, 10 - 15 parts of composite corrosion inhibitor, 30 - 35 parts of activator, 3 - 6 parts of high-range water reducer, 4 - 8 parts of polyamide / polyethersulfone copolymer and 20 - 25 parts of microcapsules.

3. The marine concrete with anti-salt corrosion and self-healing according to claim 1, characterized in that, The preparation method of the composite corrosion inhibitor includes: by weight, dispersing 1 part of nano-Al2O3 and 1 part of coal tar pitch carbon powder in an ethanol solution at a solid-liquid ratio of 1:15, subjecting to ultrasonic treatment, and adding SO4 2 -modified graphene oxide, stirring and drying under vacuum.

4. The marine concrete with salt corrosion resistance and self - repair according to claim 1, characterized in that, The preparation method of the microcapsules includes: using tetradecanol as the core material and titanium dioxide as the shell material, reacting at a weight ratio of 4:1 under the conditions of pH = 8.5 and 50 °C.

5. The marine concrete with anti-salt corrosion and self-healing according to claim 1, characterized in that, The activator consists of Na2SiO3 and NaOH, with a modulus of 1.

2.

6. The marine concrete with anti-salt corrosion and self-healing according to claim 1, characterized in that, The polyamide / polyethersulfone copolymer is a fiber treated by plasma, with a length of 12 mm, and plasma treatment is carried out at a power of 50 W in an Ar atmosphere.

7. The marine concrete with anti-salt corrosion and self-repairing according to claim 1, characterized in that The natural mineral activator consists of 45% metakaolin, 30% limestone powder and 25% natural volcanic ash by mass percentage.

8. The marine concrete with salt corrosion resistance and self - repair according to claim 1, wherein The high-range water reducer is a polycarboxylic acid - lignosulfonic acid complex.

9. The marine concrete with salt erosion resistance and self-healing according to claim 1, characterized in that, The preparation method of the marine concrete with salt corrosion resistance and self - repair ability includes: S1: Prepare the composite corrosion inhibitor; S2: Prepare the microcapsules; S3: Mixing: Mix cement, natural mineral activator, composite corrosion inhibitor, activator and high-range water reducer, stir at 60 rpm for 2 hours, add treated polypropylene fibers and microcapsules, and stir for 4 hours to obtain a mixture; S4: Curing treatment: Heat the mixture to 50 °C at a rate of 0.5 °C / min within 2 hours, keep it warm for 24 hours, and then cool it naturally to room temperature in 10 hours.

10. The marine concrete with anti-salt corrosion and self-healing according to claim 1, characterized in that, The application of the marine concrete in the caissons of cross - sea bridges, port breakwaters and the foundation engineering of offshore oil platforms.

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