Anti-ion erosion self-repairing marine concrete and preparation method thereof

Abstract

This invention discloses a self-healing marine concrete resistant to ion erosion and its preparation method. The concrete comprises the following components by weight: 100 parts cement, 120-280 parts fine aggregate, 220-350 parts coarse aggregate, 30-40 parts water, 2-4 parts ZnAl-NO3 layered double hydroxide, 0.5-1 part disodium fumarate, 0-10 parts metakaolin, and 0.5-1 part water-reducing agent. The use of ZnAl-NO3 layered double hydroxide in this invention can effectively adsorb corrosive anions such as Cl- that enter the concrete. ‑ and SO4 2‑ These ions prevent further damage to concrete. On the other hand, using disodium fumarate can impart self-healing ability to concrete cracks by using corrosive cations such as Mg... 2+ It transforms into precipitate to repair cracks, achieving a dual defense against corrosive ions.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a self-healing marine concrete resistant to ion erosion and its preparation method. Background Technology

[0002] Concrete, as a commonly used building material, plays an irreplaceable role in infrastructure projects. Currently, with the continuous expansion of China's marine construction industry, concrete is widely used in large-scale marine engineering projects such as cross-sea bridges and port terminals. However, concrete is a heterogeneous multiphase mixture material with high brittleness and low tensile strength. Coupled with the complex and harsh service environment of coastal areas, concrete is highly susceptible to cracking. Cracks provide channels for moisture penetration, allowing harmful ions from the ocean, such as magnesium, to seep in. 2+ Cl - and SO4 2- As water seeps into the concrete, it accelerates the corrosion of the reinforcing steel and surface spalling, thereby exacerbating the deterioration of concrete performance and seriously affecting the load-bearing capacity and stability of concrete buildings in coastal areas.

[0003] To improve the resistance of marine concrete to ion attack, existing technologies mainly focus on reducing the porosity and increasing the density of concrete by controlling the water-cement ratio, adding air-entraining agents, and mineral admixtures, thereby inhibiting the entry of harmful ions into the concrete. However, concrete is a porous material, and while these methods can alleviate the damage caused by corrosive ions to concrete to some extent, corrosive ions can still enter the concrete through microcracks and enlarged pores during its service life. Therefore, these methods cannot truly solve the problem of marine concrete being damaged by corrosive ions. Summary of the Invention

[0004] In view of the above-mentioned shortcomings of the existing technology, the purpose of the present invention is to provide an anti-ionic erosion self-healing marine concrete and its preparation method, so as to solve the problem that in the service of marine concrete, corrosive ions can still enter the concrete through cracked microcracks and enlarged pores, which makes it impossible to fundamentally solve the problem of marine concrete being damaged by corrosive ions.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A self-healing marine concrete resistant to ion erosion, comprising the following components by weight:

[0007] The composition is as follows: 100 parts cement, 120-280 parts fine aggregate, 220-350 parts coarse aggregate, 30-40 parts water, 2-4 parts ZnAl-NO3 layered double hydroxide, 0.5-1 part disodium fumarate, 0-10 parts metakaolin, and 0.5-1 part water-reducing agent.

[0008] Preferably, the ZnAl-NO3 layered double hydroxide is prepared by the following method:

[0009] Step 1: According to the weight parts, weigh out 30-35 parts of Zn(NO3)2·6H2O, 20-25 parts of Al(NO3)3·9H2O, 20-25 parts of NaNO3, and 15-20 parts of NaOH.

[0010] Step 2: Dissolve Zn(NO3)2·6H2O, Al(NO3)3·9H2O, NaNO3, and NaOH in CO2-free water;

[0011] Step 3: Prepare a sodium hydroxide solution using de-CO2 water, and pour the sodium hydroxide solution into the mixed solution obtained in Step 2 under a nitrogen protective atmosphere. Stir vigorously and adjust the pH value to 8 to obtain a slurry.

[0012] Step 4: Crystallize the slurry obtained in Step 3 at 65-75℃ for 24 hours, filter, and wash the solid obtained by filtration with de-CO2 water until neutral, dry and grind to obtain the ZnAl-NO3 layered double hydroxide.

[0013] Preferably, the cement is PO42.5 or PO52.5 silicate cement.

[0014] Preferably, the fine aggregate is natural river sand or manufactured sand.

[0015] Preferably, the coarse aggregate is continuously graded crushed stone with a diameter of 5-31.5 mm.

[0016] Preferably, the water-reducing agent is a polycarboxylate superplasticizer.

[0017] The present invention also provides a method for the above-mentioned self-healing marine concrete resistant to ion erosion, characterized in that it specifically includes the following steps:

[0018] (1) Weigh out 100 parts of cement, 120-280 parts of fine aggregate, 220-350 parts of coarse aggregate, 30-40 parts of water, 2-4 parts of ZnAl-NO3 layered double hydroxide, 0.5-1 parts of disodium fumarate, 0-10 parts of metakaolin, and 0.5-1 parts of water-reducing agent according to the weight of each raw material.

[0019] (2) Weigh the cement, fine aggregate, coarse aggregate and metakaolin into the mixer and mix for 1 to 3 minutes. Then add water, ZnAl-NO3 layered double hydroxide, disodium fumarate and water-reducing agent and continue to mix for 1 to 3 minutes to make it evenly mixed. The anti-ion erosion self-healing marine concrete is thus obtained.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. This invention simultaneously incorporates ZnAl-NO3 layered double hydroxide and disodium fumarate into concrete: when the marine concrete is not cracked, the corrosive ion Cl... - and SO4 2- It will enter the interior of the concrete through the pores, due to Cl - and SO4 2- Diffusion into the ZnAl-NO3 layered double hydroxide has low interlayer resistance, Cl - and SO4 2- Will and the NO3 between layers - Ion exchange occurs, thereby immobilizing Cl in the ZnAl-NO3 layered double hydroxide. - and SO4 2- To prevent corrosive anions from damaging concrete; disodium fumarate can effectively complex Mg2+ that has entered the concrete. 2+ This forms an unstable magnesium complex, which can further react with Ca(OH)₂ in the concrete to form Mg(OH)₂ precipitate, filling the pores of the concrete, increasing its density, and effectively solidifying the corrosive cations that have entered the concrete. When marine concrete is damaged by loads and other factors, resulting in microcracks, the ZnAl-NO₃ layered double hydroxide can still prevent Cl₂ from entering the concrete through the cracks. - and SO4 2- Fixation; disodium fumarate can fix Mg that has entered the concrete at the crack. 2+ Complexation, through crystallization and precipitation reaction, transforms it into Mg(OH)2, which is insoluble and water-resistant, and solidifies it at the crack, thereby gradually repairing the cracks in the concrete, improving the durability of the concrete, and ultimately continuously reducing the size of the cracks, thus achieving self-healing of marine concrete.

[0022] 2. The use of ZnAl-NO3 layered double hydroxide in this invention can effectively adsorb corrosive anions such as Cl that have entered concrete. - and SO4 2- These ions prevent further damage to concrete. On the other hand, using disodium fumarate can impart self-healing ability to concrete cracks by using corrosive cations such as Mg... 2+ It transforms into precipitate to repair cracks, achieving a dual defense against corrosive ions.

[0023] 3. The present invention also improves the compactness of concrete by adding metakaolin to fill the pores inside the concrete, thereby further reducing the damage caused to the concrete by the penetration of corrosive ions.

[0024] 4. The self-healing marine concrete resistant to ion erosion described in this invention has excellent resistance to ion erosion, which can significantly improve the service life of concrete in coastal areas and has a promising application prospect. Attached Figure Description

[0025] Figure 1 The diagram shows the mass loss of Example 1 and Comparative Example 1 during the seawater dry-wet cycle.

[0026] Figure 2 The graph shows the compressive strength loss rate of Example 1 and Comparative Example 1 during the seawater dry-wet cycle.

[0027] Figure 3 The graph shows the increase in total porosity of Example 1 and Comparative Example 1 during the seawater dry-wet cycle.

[0028] Figure 4 The diagram shows the crack width changes during the seawater wet-dry cycle process in Example 1 and Comparative Example 1. Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the present invention are within the scope of protection of the present invention.

[0030] Unless otherwise specified in the specific circumstances, the numerical ranges listed herein include upper and lower limits, as well as all integers and fractions within that range, but are not limited to the specific values ​​listed when the range is defined.

[0031] I. A self-healing marine concrete resistant to ion erosion

[0032] The concrete comprises the following components by weight:

[0033] The composition is as follows: 100 parts cement, 120-280 parts fine aggregate, 220-350 parts coarse aggregate, 30-40 parts water, 2-4 parts ZnAl-NO3 layered double hydroxide, 0.5-1 part disodium fumarate, 0-10 parts metakaolin, and 0.5-1 part water-reducing agent.

[0034] This invention, after studying existing technologies, finds that current methods for improving the resistance of marine concrete to ion corrosion primarily focus on reducing the porosity and increasing the density of the concrete, thereby preventing harmful ions from entering and corroding it. However, micro-cracks inevitably appear in marine concrete during service, which does not truly solve the problem of damage caused by corrosive ions. This invention addresses the issue from two aspects. First, when marine concrete is not cracked, this invention attempts to adsorb and fix corrosive anions that have entered the concrete, preventing them from eroding the concrete. While increasing the concrete's density, it also effectively solidifies corrosive cations already present, preventing their erosion and further filling any remaining pores. Second, when marine concrete has already developed cracks, this invention aims to prevent corrosive ions from corroding the concrete through the cracks, while also repairing the cracks to prevent their expansion, thus fundamentally solving the problem of damage caused by corrosive ions to marine concrete.

[0035] This invention has discovered that the simultaneous use of ZnAl-NO3 layered double hydroxides and disodium fumarate effectively achieves the aforementioned conceptual design. When marine concrete is not cracked, the interlayer exchange capacity of the ZnAl-NO3 layered double hydroxides can effectively remove corrosive anions (Cl-) that have entered the concrete interior from the pores. - and SO4 2- Effective adsorption and fixation, thereby exchanging NO3 between layers. - To prevent corrosive anions from damaging concrete; disodium fumarate can effectively complex Mg2+ that has entered the concrete. 2+ This forms an unstable magnesium complex, which then crystallizes with Ca(OH)₂ in the concrete to generate Mg(OH)₂ precipitate, filling the pores of the concrete, increasing its density, and further effectively solidifying the corrosive cations that have entered the concrete, thus improving the durability of marine concrete. When marine concrete develops microcracks due to load or other reasons, the ZnAl-NO₃ layered double hydroxide can still retain the Cl₂ that has entered the concrete through the cracks. - and SO4 2- Adsorption and fixation; disodium fumarate can adsorb and fix Mg that has entered the concrete through cracks. 2+ The complex is formed by crystallization and precipitation, transforming it into insoluble, water-resistant Mg(OH)₂, which is then solidified at the cracks, thereby repairing the concrete cracks and improving its durability. The use of ZnAl-NO₃ layered double hydroxides in this invention can effectively adsorb and fix corrosive anions such as Cl₂ that have entered the concrete. - and SO4 2-These ions prevent damage to concrete. On the other hand, using disodium fumarate can impart self-healing ability to concrete cracks by using corrosive cations such as Mg... 2+ It is converted into a precipitate to repair cracks, achieving a dual defense against corrosive ions. However, if only ZnAl-NO3 layered double hydroxide is used, although it can adsorb and fix corrosive anions, corrosive cations can still penetrate into the concrete through pores and cracks to corrode it; while if only disodium fumarate is used, although it can complex corrosive cations such as Mg... 2+ It transforms into precipitates that fill and repair the pores and cracks in the concrete, preventing them from entering the concrete interior. However, corrosive anions can still enter the concrete through the pores and cracks that are not fully filled and not fully repaired, continuously eroding the concrete.

[0036] In some embodiments, the ZnAl-NO3 layered double hydroxide is prepared by the following method:

[0037] Step 1: According to the weight parts, weigh out 30-35 parts of Zn(NO3)2·6H2O, 20-25 parts of Al(NO3)3·9H2O, 20-25 parts of NaNO3, and 15-20 parts of NaOH.

[0038] Step 2: Dissolve Zn(NO3)2·6H2O, Al(NO3)3·9H2O, NaNO3, and NaOH in CO2-free water;

[0039] Step 3: Prepare a sodium hydroxide solution using de-CO2 water, and pour the sodium hydroxide solution into the mixed solution obtained in Step 2 under a nitrogen protective atmosphere. Stir vigorously and adjust the pH value to 8 to obtain a slurry.

[0040] Step 4: The slurry obtained in Step 3 is crystallized at 65-75℃ for 24 hours, filtered, and the solid obtained by filtration is washed with CO2-removed water until neutral. It is then dried and ground to obtain the ZnAl-NO3 layered double hydroxide. The amount of ZnAl-NO3 layered double hydroxide used is 2-4 parts by weight. Too little ZnAl-NO3 layered double hydroxide will not fully exert its intended function, making it difficult to effectively adsorb and solidify the corrosive anions in concrete. Too much ZnAl-NO3 will reduce the fluidity of the concrete and cause excessive microscopic defects inside the concrete. Therefore, the amount of ZnAl-NO3 layered double hydroxide can be 2 parts, 3 parts, 4 parts, etc., as well as all ranges and sub-ranges between these values. It should be understood that, in the embodiments, any of the above ranges can be combined with any other range.

[0041] In some embodiments, the amount of disodium fumarate used is 0.5 to 1 part by weight. Disodium fumarate can effectively complex Mg that has entered the concrete. 2+ This process forms an unstable magnesium complex, which then crystallizes with Ca(OH)₂ in the concrete to form Mg(OH)₂ precipitate. This precipitate fills the pores in the concrete, increasing its density and effectively solidifying any corrosive cations that have entered the concrete. When marine concrete develops microcracks, the concrete described in this invention is used to repair these cracks. The aforementioned process is also performed during the repair process, further repairing the cracks and enabling the concrete to self-heal, thereby improving its durability. However, if the amount of disodium fumarate is too low, insufficient magnesium complex will be formed, preventing the formation of enough Mg(OH)₂ precipitate to fill the pores and repair the cracks in time. This allows corrosive ions to enter the concrete from the pores and cracks and cause corrosion. If the amount is too high, it will interfere with the cement hydration reaction, leading to a decrease in concrete strength. Therefore, the amount of disodium fumarate can be 0.5 parts, 0.8 parts, 1.0 parts, etc., as well as all ranges and sub-ranges between these values. It should be understood that, in the embodiments, any of the above ranges can be combined with any other range.

[0042] In some implementations, the metakaolin content is 0-10 parts by weight. The addition of metakaolin is to further fill the pores in the concrete formed by the incorporation of ZnAl-NO3 layered double hydroxide and disodium fumarate, thereby improving the concrete's density and reducing the damage caused by the penetration of corrosive ions. However, adding only ZnAl-NO3 layered double hydroxide and disodium fumarate without metakaolin does not hinder the excellent anti-corrosion properties and self-healing advantages of these two components in the concrete; it only slightly reduces the concrete's anti-corrosion performance, which remains excellent compared to using only ZnAl-NO3 layered double hydroxide or disodium fumarate. If either ZnAl-NO3 layered double hydroxide or disodium fumarate is used in combination with metakaolin, the concrete may not be able to completely resist the damage to its internal structure caused by corrosive ions. Excessive metakaolin content can affect the flowability of the concrete, thereby reducing its early strength. Therefore, the amount of metakaolin used can be 0 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, etc., as well as all ranges and sub-ranges between the above values. It should be understood that, in the implementation plan, any of the above ranges can be combined with any other range.

[0043] In some embodiments, the cement is PO42.5 or PO52.5 ordinary Portland cement. In actual use, the proportions can be adjusted according to the amount of cement used. For example, when the weight of cement is increased to 200 parts, the proportions of other components can be increased accordingly.

[0044] In some embodiments, the fine aggregate is natural river sand or manufactured sand. The amount of fine aggregate, calculated by weight, is 120–280 parts. Too little fine aggregate will reduce the density of the concrete, thereby decreasing its durability and impermeability; too much will increase the viscosity of the concrete, leading to insufficient fluidity, making mixing and vibration more difficult, and hindering rapid pouring. Therefore, the amount of fine aggregate can be 120 parts, 150 parts, 200 parts, 250 parts, 280 parts, etc., as well as all ranges and sub-ranges between these values. It should be understood that, in the embodiments, any of the above ranges can be combined with any other range.

[0045] In some embodiments, the coarse aggregate is continuously graded crushed stone of 5–31.5 mm. Calculated by weight, the coarse aggregate is 220–350 parts. Too little coarse aggregate will result in an excessively high proportion of cement paste in the concrete, increasing the likelihood of shrinkage and cracking. Too much coarse aggregate will result in insufficient cement paste in the concrete, thus affecting its setting and hardening. Therefore, the amount of coarse aggregate can be 220 parts, 250 parts, 300 parts, 350 parts, etc., as well as all ranges and sub-ranges between these values. It should be understood that, in embodiments, any of the above ranges can be combined with any other range.

[0046] Preferably, the water-reducing agent is a polycarboxylate superplasticizer. The water-reducing agent is used in amounts of 0.5 to 1 part by weight. Too little water-reducing agent will fail to effectively improve the fluidity of the concrete or achieve the expected water-reducing effect, while too much will cause excessive fluidity in the concrete, leading to segregation and bleeding, affecting the uniformity and overall structural strength of the concrete. Therefore, the amount of water-reducing agent can be 0.5 parts, 0.8 parts, 1.0 parts, etc., as well as all ranges and sub-ranges between these values. It should be understood that, in the embodiments, any of the above ranges can be combined with any other range.

[0047] II. A method for preparing self-healing marine concrete resistant to ion erosion.

[0048] (1) Weigh out 100 parts of cement, 120-280 parts of fine aggregate, 220-350 parts of coarse aggregate, 30-40 parts of water, 2-4 parts of ZnAl-NO3 layered double hydroxide, 0.5-1 parts of disodium fumarate, 0-10 parts of metakaolin, and 0.5-1 parts of water-reducing agent according to the weight of each raw material.

[0049] (2) Weigh the cement, fine aggregate, coarse aggregate and metakaolin into the mixer and mix for 1 to 3 minutes. Then add water, ZnAl-NO3 layered double hydroxide, disodium fumarate and water-reducing agent and continue to mix for 1 to 3 minutes to make it evenly mixed. The anti-ion erosion self-healing marine concrete is thus obtained.

[0050] III. Examples and Comparative Examples

[0051] The preparation process of the ZnAl-NO3 layered double hydroxide used in the embodiments of the present invention is as follows (in parts by weight): Weigh 35 parts Zn(NO3)2·6H2O, 22 parts Al(NO3)3·9H2O, 22 parts NaNO3, and 20 parts NaOH; [The process is described in the original text, but the provided text is incomplete and requires further context.]

[0052] 6H2O, Al(NO3)3·9H2O and NaNO3 are mixed and dissolved in deionized water after CO2 removal, and placed in a 500ml four-necked flask. NaOH is dissolved in deionized water after CO2 removal. Under N2 protection, the alkaline solution is slowly added dropwise to the zinc-aluminum solution while stirring vigorously. The pH is adjusted to 8, and the slurry is crystallized at 70℃ for 24h. After filtration, the solution is washed with deionized water after CO2 removal until neutral, dried, and ground to obtain ZnAl-NO3 layered double hydroxide.

[0053] Example 1

[0054] (1) Weigh out the following raw materials according to the required weight proportions: 100 parts of PO42.5 ordinary Portland cement, 150 parts of natural river sand, 300 parts of 5-31.5mm continuously graded crushed stone, 8 parts of metakaolin, 35 parts of water, 2 parts of ZnAl-NO3 layered double hydroxide, 0.5 parts of disodium fumarate, and 0.8 parts of polycarboxylate superplasticizer.

[0055] (2) Weigh out PO42.5 ordinary silicate cement, natural river sand, crushed stone and metakaolin and add them to the mixer and stir for 1 minute. Then add water, ZnAl-NO3 layered double hydroxide, disodium fumarate and polycarboxylate superplasticizer and continue to stir for 2 minutes to make it evenly mixed. This will give you anti-ion erosion self-healing marine concrete.

[0056] The self-healing marine concrete resistant to ion erosion prepared in this embodiment was poured into a 100mm×100mm×100mm mold. After 24 hours, it was demolded, and the concrete specimens were cured in a standard curing room for 28 days. Then, a seawater wet-dry cycle test was conducted based on the actual service environment in the coastal area: the concrete was first placed in a drying oven and dried at (60±5)℃ until its mass remained constant. It was then cooled indoors for 20 minutes, and then placed in a constant-temperature water bath or tank containing seawater solution, with the water level 30mm above the top surface of the specimen, for 8 hours. It was then placed back in the drying oven and kept at (60±5)℃ for 8 hours, constituting one wet-dry cycle. The performance of the concrete prepared in Example 1 after 0, 50, and 100 seawater wet-dry cycles was tested.

[0057] Compared with the self-healing marine concrete resistant to ion erosion before seawater wet-dry cycles, the concrete mass loss rate after 50 and 100 seawater wet-dry cycles was 1.91% and 4.66%, respectively; the compressive strength loss rate was 5.44% and 10.38%, respectively; and the total porosity increase rate was 2.37% and 6.15%, respectively.

[0058] Self-healing marine concrete resistant to ion erosion was prepared according to the method in Example 1. After curing for 28 days, cracks were created through a splitting crack test, followed by seawater wet-dry cycles. The crack width changes after 0, 50, and 100 seawater wet-dry cycles were then tested. Experimental observation showed that a crack with a width of 0.28 mm became 0 mm after 50 seawater wet-dry cycles, a crack with a width of 0.48 mm became 0.11 mm after 50 cycles, and a crack with a width of 0.48 mm became 0 mm after 100 cycles. This demonstrates that the self-healing marine concrete resistant to ion erosion described in Example 1 can effectively repair cracks after seawater wet-dry cycles. Furthermore, the repaired concrete retains sufficient strength, thus achieving self-healing properties in the marine concrete.

[0059] Comparative Example 1

[0060] This example is an adjustment based on Example 1, except that metakaolin, ZnAl-NO3 layered double hydroxide, and disodium fumarate were not added. All other steps and component dosages are identical to Example 1. Ordinary cement concrete was prepared according to the operating procedures of Example 1, and the curing and wet-dry cycle experiments were also conducted in the same manner as in Example 1.

[0061] Compared with ordinary concrete specimens before seawater wet-dry cycling, the mass loss rates of ordinary concrete after 50 and 100 seawater wet-dry cycles were 5.32% and 8.21%, respectively; the compressive strength loss rates were 9.12% and 17.07%, respectively; and the total porosity growth rates were 7.24% and 15.43%, respectively. Compared with Comparative Example 1, the ion-resistant self-healing marine concrete prepared in Example 1 showed significantly lower mass loss rates, compressive strength loss rates, and total porosity growth rates after seawater wet-dry cycling experiments than ordinary concrete, demonstrating excellent resistance to ion erosion.

[0062] Ordinary cement concrete was prepared according to the operating steps of Example 1. After curing for 28 days, cracks were created through a splitting crack test, followed by seawater wet-dry cycles. The crack width of the ordinary cement concrete was then tested after 0, 50, and 100 seawater wet-dry cycles. Experimental observations showed that a crack with a width of 0.24 mm became 0.20 mm after 50 seawater wet-dry cycles and 0.15 mm after 100 cycles; a crack with a width of 0.37 mm became 0.35 mm after 50 cycles and 0.30 mm after 100 cycles. Compared with Comparative Example 1, the ion-resistant self-healing marine concrete prepared in Example 1 exhibited a significantly higher self-healing ability during seawater wet-dry cycles than ordinary concrete, demonstrating excellent self-healing capabilities.

[0063] Example 2

[0064] (1) Weigh out 100 parts of PO52.5 ordinary silicate cement, 180 parts of natural river sand, 320 parts of 5-31.5mm continuously graded crushed stone, 10 parts of metakaolin, 40 parts of water, 4 parts of ZnAl-NO3 layered double hydroxide, 1 part of disodium fumarate, and 1 part of polycarboxylate superplasticizer according to the required weight parts of each raw material.

[0065] (2) Anti-ion erosion self-healing marine concrete was prepared according to the method in Example 1, and subjected to seawater wet-dry cycles. The performance of the anti-ion erosion self-healing marine concrete after 0, 100, and 200 seawater wet-dry cycles was then tested. Compared with the anti-ion erosion self-healing marine concrete before seawater wet-dry cycles, the concrete mass loss rates after 100 and 200 seawater wet-dry cycles were 4.08% and 6.77%, respectively; the compressive strength loss rates were 8.64% and 14.97%, respectively; and the total porosity increase rates were 5.23% and 9.14%, respectively.

[0066] Self-healing marine concrete resistant to ion erosion was prepared according to the method in Example 1. After curing for 28 days, cracks were created through a splitting crack test, followed by seawater wet-dry cycles. The crack width changes were then tested after 0, 100, and 200 seawater wet-dry cycles. Experimental observations showed that a crack with a width of 0.34 mm became 0 mm after 100 seawater wet-dry cycles, a crack with a width of 0.55 mm became 0.17 mm after 100 seawater wet-dry cycles, and a crack with a width of 200 mm became 0 mm after 200 seawater wet-dry cycles.

[0067] Comparative Example 2

[0068] Based on Example 2, adjustments were made to Comparative Example 2, the difference being that metakaolin, ZnAl-NO3 layered double hydroxide, and disodium fumarate were not added. Other steps and component dosages were completely consistent with Example 2; ordinary cement concrete was prepared according to the operating steps of Example 1, and the curing and wet-dry cycle experiments were also the same as in Example 1. Compared with the ordinary concrete specimens before seawater wet-dry cycles, the mass loss rates of the ordinary concrete after 100 and 200 seawater wet-dry cycles were 7.92% and 10.18%, respectively; the compressive strength loss rates were 15.13% and 18.91%, respectively; and the total porosity growth rates were 14.54% and 20.82%, respectively. Compared with Comparative Example 2, the ion-resistant self-healing marine concrete prepared in Example 2 showed significantly lower mass loss rates, compressive strength loss rates, and total porosity growth rates after seawater wet-dry cycles, demonstrating excellent resistance to ion erosion.

[0069] Ordinary cement concrete was prepared according to the operating steps of Example 1. After curing for 28 days, cracks were created through a splitting crack test, followed by seawater wet-dry cycles. The crack width of the ordinary cement concrete was then tested after 0, 100, and 200 seawater wet-dry cycles. Experimental observations showed that a crack with a width of 0.26 mm decreased to 0.13 mm after 100 seawater wet-dry cycles and to 0.06 mm after 200 cycles; a crack with a width of 0.41 mm decreased to 0.32 mm after 100 cycles and to 0.24 mm after 200 cycles. Compared with Comparative Example 2, the ion-resistant self-healing marine concrete prepared in Example 2 exhibited significantly greater self-healing ability during seawater wet-dry cycles than ordinary concrete, demonstrating excellent self-healing capabilities.

[0070] Example 3

[0071] The following adjustments were made based on Example 1, the difference being that: 100 parts of PO42.5 ordinary silicate cement, 120 parts of natural river sand, 220 parts of 5-31.5mm continuously graded crushed stone, 5 parts of metakaolin, 30 parts of water, 2 parts of ZnAl-NO3 layered double hydroxide, 0.5 parts of disodium fumarate, and 0.5 parts of polycarboxylate superplasticizer were weighed according to the required weight parts of each raw material.

[0072] Self-healing marine concrete resistant to ion erosion was prepared according to the method in Example 1 and subjected to seawater wet-dry cycles. The performance of the self-healing marine concrete after 0, 100, and 200 seawater wet-dry cycles was then tested. Compared with the self-healing marine concrete before seawater wet-dry cycles, the concrete mass loss rates after 50 and 100 seawater wet-dry cycles were 2.12% and 4.91%, respectively; the compressive strength loss rates were 5.84% and 10.61%, respectively; and the total porosity increase rates were 2.44% and 6.37%, respectively.

[0073] Self-healing marine concrete resistant to ion erosion was prepared according to the method in Example 1. After curing for 28 days, cracks were created through a splitting crack test, followed by seawater wet-dry cycles. The crack width of the self-healing marine concrete was then tested after 0, 100, and 200 seawater wet-dry cycles. Experimental observations showed that a crack with a width of 0.30 mm became 0 mm after 50 seawater wet-dry cycles, a crack with a width of 0.45 mm became 0.09 mm after 50 seawater wet-dry cycles, and a crack with a width of 1.45 mm became 0 mm after 50 seawater wet-dry cycles and 0 mm after 100 seawater wet-dry cycles.

[0074] Example 4

[0075] The following adjustments were made based on Example 1, the difference being that: 100 parts of PO42.5 ordinary silicate cement, 280 parts of natural river sand, 350 parts of 5-31.5mm continuously graded crushed stone, 10 parts of metakaolin, 40 parts of water, 4 parts of ZnAl-NO3 layered double hydroxide, 1 part of disodium fumarate, and 1 part of polycarboxylate superplasticizer were weighed according to the required weight parts of each raw material.

[0076] Self-healing marine concrete resistant to ion erosion was prepared according to the method in Example 1 and subjected to seawater wet-dry cycles. The performance of the self-healing marine concrete after 0, 100, and 200 seawater wet-dry cycles was then tested. Compared with the self-healing marine concrete before seawater wet-dry cycles, the concrete mass loss rates after 50 and 100 seawater wet-dry cycles were 4.17% and 6.92%, respectively; the compressive strength loss rates were 8.89% and 15.13%, respectively; and the total porosity increase rates were 5.37% and 9.31%, respectively.

[0077] Self-healing marine concrete resistant to ion erosion was prepared according to the method in Example 1. After curing for 28 days, cracks were created through a splitting crack test, followed by seawater wet-dry cycles. The crack width of the self-healing marine concrete was then tested after 0, 100, and 200 seawater wet-dry cycles. Experimental observations showed that a crack with a width of 0.31 mm became 0 mm after 100 seawater wet-dry cycles, a crack with a width of 0.52 mm became 0.21 mm after 100 seawater wet-dry cycles, and a crack with a width of 200 mm became 0 mm after 200 seawater wet-dry cycles.

[0078] Comparative Example 3

[0079] The modification is based on Example 1, but differs in that ZnAl-NO3 layered double hydroxide is not added.

[0080] Cement concrete was prepared according to the operating steps of Example 1, and the curing and wet-dry cycle experiments were also conducted in the same manner as in Example 1. Compared with the cement concrete before the seawater wet-dry cycle, the concrete mass loss rate after 50 and 100 seawater wet-dry cycles was 3.49% and 6.16%, respectively; the compressive strength loss rate was 7.19% and 14.54%, respectively; and the total porosity increase rate was 5.44% and 10.87%, respectively. Compared with Example 1, Comparative Example 3 showed a very significant increase in concrete mass loss rate, compressive strength loss rate, and total porosity increase rate. This indicates that the absence of ZnAl-NO3 layered double hydroxides means that corrosive anions can still enter the concrete through unfilled pores and unrepaired cracks, continuously eroding the concrete. This makes the total porosity increase rate of this comparative example significantly higher than that of other examples, making it easier for corrosive anions to enter the concrete. In the long run, the corrosion resistance of this comparative example is significantly inferior to that of other examples. However, compared with Comparative Example 1, the erosion resistance of concrete has been significantly improved, but the improvement is not substantial.

[0081] Cement concrete was prepared according to the method in Example 1. After curing for 28 days, cracks were created through a splitting crack test, followed by seawater wet-dry cycles. The crack width of the self-healing marine concrete with resistance to ion erosion was then tested after 0, 100, and 200 seawater wet-dry cycles. Experimental observations showed that a crack with a width of 0.29 mm became 0 mm after 50 seawater wet-dry cycles, a crack with a width of 0.41 mm became 0.10 mm after 50 cycles, and a crack became 0 mm after 100 cycles. Compared to Example 1, Comparative Example 3, although lacking ZnAl-NO3 layered double hydroxide, contained disodium fumarate, which gave the concrete of Comparative Example 3 a certain degree of self-healing ability, but not anti-erosion effect. Compared to Comparative Example 1, the self-healing ability was significantly improved.

[0082] Comparative Example 4

[0083] This is an adjustment based on Example 1, the difference being that disodium fumarate was not added.

[0084] Cement concrete was prepared according to the operating steps of Example 1, and the curing and wet-dry cycle experiments were also conducted in the same manner as in Example 1. Compared with the self-healing marine concrete resistant to ion erosion before seawater wet-dry cycles, the concrete mass loss rates after 50 and 100 seawater wet-dry cycles were 3.78% and 6.54%, respectively; the compressive strength loss rates were 7.33% and 15.22%, respectively; and the total porosity increase rates were 6.23% and 11.29%, respectively. It is evident that the total porosity increase rate was significantly higher without the addition of disodium fumarate, indicating a significant decrease in concrete density. Although ZnAl-NO3 layered double hydroxides alone can fix the corrosive anions entering the concrete, the decreased concrete density means that even with the use of metakaolin to fill the pores, the effect is significantly less than that of using disodium fumarate and ZnAl-NO3 layered double hydroxides in combination. From a long-term perspective, the corrosion resistance of this comparative example is still inferior to that of other examples.

[0085] Cement concrete was prepared according to the method in Example 1. After curing for 28 days, cracks were created through a splitting crack test, followed by seawater wet-dry cycles. The crack width of the self-healing marine concrete with ionic erosion resistance was then tested after 0, 100, and 200 seawater wet-dry cycles. Experimental observations showed that a crack with a width of 0.26 mm decreased to 0.20 mm after 50 seawater wet-dry cycles and to 0.13 mm after 100 cycles; a crack with a width of 0.43 mm decreased to 0.39 mm after 50 cycles and to 0.28 mm after 100 cycles. Compared to Example 1, the absence of disodium fumarate not only affected the self-healing ability of Comparative Example 4 but also significantly reduced its erosion resistance. This indicates that disodium fumarate not only provides self-healing properties but also, in combination with ZnAl-NO3 layered double hydroxides, further enhances the erosion resistance of the concrete.

[0086] Example 5

[0087] The method is an adjustment based on Example 1, the difference being that metakaolin is not added.

[0088] Cement concrete was prepared according to the operating steps of Example 1, and the curing and wet-dry cycle experiments were also conducted in the same manner as in Example 1. Compared with the self-healing marine concrete resistant to ion erosion before seawater wet-dry cycles, the concrete mass loss rates after 50 and 100 seawater wet-dry cycles were 2.21% and 4.98%, respectively; the compressive strength loss rates were 5.91% and 10.77%, respectively; and the total porosity increase rates were 2.56% and 6.41%, respectively. Compared with Example 1, the erosion resistance of Example 5 was somewhat affected, but it can be seen that the impact was not very significant, and it still exhibited excellent erosion resistance.

[0089] Cement concrete was prepared according to the method in Example 1. After curing for 28 days, cracks were created by splitting crack test, followed by seawater wet-dry cycles. The crack width of the self-healing marine concrete resistant to ion erosion was then tested after 0, 100, and 200 seawater wet-dry cycles. Experimental observations showed that a crack with a width of 0.33 mm became 0 mm after 50 seawater wet-dry cycles, a crack with a width of 0.47 mm became 0.12 mm after 50 seawater wet-dry cycles, and a crack with a width of 1.47 mm became 0 mm after 50 seawater wet-dry cycles and 0 mm after 100 seawater wet-dry cycles.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A self-healing marine concrete resistant to ion erosion, characterized in that, The concrete comprises the following components by weight: The composition includes 100 parts cement, 120-280 parts fine aggregate, 220-350 parts coarse aggregate, 30-40 parts water, 2-4 parts ZnAl-NO3 layered double hydroxide, 0.5-1 part disodium fumarate, 5-10 parts metakaolin, and 0.5-1 part water-reducing agent; the cement is PO42.5 or PO52.5 silicate cement.

2. The self-healing marine concrete resistant to ion erosion according to claim 1, characterized in that, The ZnAl-NO3 layered double hydroxide was prepared by the following method: Step 1: Calculate by weight and weigh out 30-35 parts of Zn(NO3)2•6H2O, 20-25 parts of Al(NO3)3•9H2O, 20-25 parts of NaNO3, and 15-20 parts of NaOH. Step 2: Dissolve Zn(NO3)2•6H2O, Al(NO3)3•9H2O, NaNO3 and NaOH in CO2-free water; Step 3: Prepare a sodium hydroxide solution using de-CO2 water, and pour the sodium hydroxide solution into the mixed solution obtained in Step 2 under a nitrogen protective atmosphere. Stir vigorously and adjust the pH value to 8 to obtain a slurry. Step 4: Crystallize the slurry obtained in Step 3 at 65~75℃ for 24h, filter and wash the solid obtained by filtration with de-CO2 water until neutral, dry and grind to obtain the ZnAl-NO3 layered double hydroxide.

3. The self-healing marine concrete resistant to ion erosion according to claim 1, characterized in that, The fine aggregate is natural river sand or manufactured sand.

4. The self-healing marine concrete resistant to ion erosion according to claim 1, characterized in that, The coarse aggregate is continuously graded crushed stone with a diameter of 5~31.5mm.

5. The self-healing marine concrete resistant to ion erosion according to claim 1, characterized in that, The water-reducing agent is a polycarboxylate superplasticizer.

6. A method for preparing the ion-resistant self-healing marine concrete according to any one of claims 1 to 5, characterized in that, Specifically, the steps include the following: (1) Weigh out 100 parts of cement, 120-280 parts of fine aggregate, 220-350 parts of coarse aggregate, 30-40 parts of water, 2-4 parts of ZnAl-NO3 layered double hydroxide, 0.5-1 parts of disodium fumarate, 5-10 parts of metakaolin, and 0.5-1 parts of water-reducing agent according to the weight of each raw material; (2) Add the weighed cement, fine aggregate, coarse aggregate and metakaolin to the mixer and stir for 1 to 3 minutes. Then add water, ZnAl-NO3 layered double hydroxide, disodium fumarate and water-reducing agent and continue stirring for 1 to 3 minutes to make it evenly mixed. The anti-ion erosion self-healing marine concrete is then obtained.

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