A kind of high durability concrete suitable for strong corrosion coastal saline soil area

Abstract

The application discloses a kind of high durability concrete suitable for strong corrosion coastal saline soil area, it is related to building material technical field.The durability concrete is prepared from the following weight parts of raw materials: Portland cement 320-380 parts, slag powder 80-120 parts, fly ash 50-80 parts, quartz sand 650-750 parts, broken stone 1100-1300 parts, modified graphene dispersion 15-25 parts, composite rust inhibitor 8-12 parts, high efficiency water reducing agent 6-10 parts, water 140-160 parts, nano silicon dioxide 10-18 parts.The application significantly improves the chloride ion penetration resistance, sulphate attack resistance and freeze-thaw resistance of concrete through the synergistic effect of composite admixture, modified graphene and composite rust inhibitor, reduces the shrinkage of concrete, enhances its long-term durability in strong corrosion saline soil environment;Preparation process is simple, raw material is easy to get, cost is controllable, can be widely used in strong corrosion saline soil area of road, bridge, building foundation and other engineering structures, has good economic benefit and engineering application value.

Description

Technical Field

[0001] This invention relates to the field of concrete technology, and specifically to a high-durability concrete suitable for highly corrosive coastal saline soil areas. Background Technology

[0002] Saline soil refers to soil containing a large amount of easily soluble salts. It is widely distributed in Northwest, North, Northeast and coastal areas of my country. Among them, the soil environment in highly corrosive saline soil areas (chloride ion content ≥0.5% and sulfate content ≥1.0%) is extremely corrosive to concrete structures and is one of the key factors affecting the service life of concrete projects.

[0003] Chloride ions are a major cause of steel reinforcement corrosion in concrete. In highly corrosive saline soils, chloride ions can penetrate the surface of the steel reinforcement through the pores of the concrete, damaging the passivation film and causing electrochemical corrosion, resulting in rust. The volume of rust is 2-4 times that of the steel reinforcement, generating enormous expansion stress on the concrete, leading to cracking, spalling, and ultimately reducing the structure's load-bearing capacity. Sulfates, on the other hand, react chemically with hydration products in the concrete to form expansive substances (such as ettringite and gypsum), causing internal stress within the concrete, leading to cracking, reduced strength, and even structural failure. Furthermore, highly corrosive saline soil areas are often accompanied by harsh environmental conditions such as large diurnal temperature variations and frequent freeze-thaw cycles, further exacerbating concrete damage and shortening the service life of concrete structures.

[0004] Currently, technologies for improving the durability of concrete in saline soil areas mainly include: optimizing concrete mix proportions, incorporating mineral admixtures, adding rust inhibitors, and using anti-corrosion coatings. However, existing technologies still have many shortcomings: the modification effect of single mineral admixtures is limited, making it difficult to simultaneously resist the dual corrosion of chloride ions and sulfates; ordinary rust inhibitors have low rust-inhibiting efficiency and short effective period, and are prone to failure after long-term use; anti-corrosion coatings are complex to apply, costly, and prone to damage and peeling, failing to fundamentally improve the intrinsic durability of concrete. In addition, existing concrete has a large shrinkage rate, which easily leads to shrinkage cracks after casting, providing channels for the penetration of corrosive media and further reducing the durability of concrete.

[0005] Therefore, developing a durable concrete suitable for highly corrosive saline soil areas that can resist chloride and sulfate erosion, has low shrinkage, high frost resistance, excellent long-term durability, and is simple to prepare and cost-controllable, would solve the shortcomings of existing technologies, meet the needs of engineering construction in highly corrosive saline soil areas, and have important engineering application value and practical significance. Summary of the Invention

[0006] The purpose of this invention is to overcome the defects of existing concrete in highly corrosive saline soil areas, such as susceptibility to erosion, poor durability, and short service life. It provides a highly durable concrete suitable for highly corrosive coastal saline soil areas. By optimizing the composition and proportion of raw materials and utilizing the synergistic effect of composite admixtures, modified graphene, composite rust inhibitors, and other components, the corrosion resistance, freeze-thaw resistance, and low shrinkage properties of concrete are significantly improved, thereby extending the service life of concrete structures in highly corrosive saline soil environments.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A high-durability concrete suitable for highly corrosive coastal saline soil areas comprises the following raw materials in parts by weight: 320-380 parts silicate cement, 80-120 parts slag powder, 50-80 parts fly ash, 650-750 parts quartz sand, 1100-1300 parts crushed stone, 15-25 parts modified graphene dispersion, 8-12 parts composite rust inhibitor, 6-10 parts high-efficiency water-reducing agent, 140-160 parts water, and 10-18 parts nano-silica.

[0008] Furthermore, the present invention optimizes the raw materials to further improve the durability and overall performance of concrete: The silicate cement is grade 42.5 ordinary silicate cement with a specific surface area of ​​300-350 m² / kg, an initial setting time of ≥45 min, and a final setting time of ≤600 min. It has the characteristics of rapid strength development, moderate heat of hydration, and good durability, and can provide good matrix strength and stability for concrete.

[0009] The slag powder is S95 grade slag powder with a specific surface area ≥400m² / kg and an activity index of 7d≥75% and 28d≥95%; the fly ash is Grade I fly ash with a loss on ignition ≤5.0% and a water requirement ratio ≤95%.

[0010] The fineness modulus of the quartz sand is 2.3-2.8, the mud content is ≤1.0%, and the mud lump content is ≤0.5%; the crushed stone is 5-31.5mm continuously graded basalt crushed stone, the crushing value is ≤12%, the mud content is ≤0.5%, and the mud lump content is ≤0.2%.

[0011] The modified graphene dispersion contains 0.8-1.2 wt% graphene, and the modifier is silane coupling agent KH-550. The dispersion exhibits stability ≥72 h with no significant stratification or precipitation. Graphene possesses extremely high specific surface area and excellent mechanical and barrier properties, enabling it to fill the micropores within concrete, forming a dense barrier layer that effectively prevents the penetration of corrosive media such as chloride ions and sulfates. The modification effect of silane coupling agent KH-550 improves the compatibility of graphene with the cement matrix, prevents graphene agglomeration, and ensures its uniform dispersion in concrete, fully leveraging its barrier and reinforcing effects. Simultaneously, it enhances the crack resistance and durability of the concrete.

[0012] The composite rust inhibitor is composed of calcium nitrite, sodium tripolyphosphate, and sodium gluconate in a weight ratio of 3:2:1, with each component having a purity of ≥98%. Calcium nitrite forms a dense passivation film on the surface of the reinforcing steel, effectively preventing corrosion. Sodium tripolyphosphate has excellent chelating properties, combining with calcium and magnesium ions in the soil to reduce sulfate attack and enhance rust inhibition. Sodium gluconate slows down cement hydration, reduces heat of hydration, prevents temperature cracks, improves concrete workability, and works synergistically with other components to further enhance concrete durability. The combined use of these three components achieves a synergistic effect of rust inhibition, sulfate attack resistance, and crack resistance, resulting in superior performance and a longer effective period compared to single rust inhibitors.

[0013] The high-efficiency water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent with a water reduction rate of ≥25%, an air content of ≤3.0%, and a slump loss over time (1h) of ≤10mm.

[0014] The nano-silica has a particle size of 20-50 nm, a specific surface area of ​​≥600 m² / kg, a purity of ≥99.5%, good dispersibility, and no agglomeration.

[0015] This invention also provides a method for preparing the above-mentioned high-durability concrete suitable for highly corrosive coastal saline soil areas, comprising the following steps: (1) Weigh each raw material according to the weight parts, put silicate cement, slag powder, fly ash, nano silica, quartz sand and crushed stone into the mixer, dry mix for 2-3 minutes, and mix evenly.

[0016] (2) Mix the modified graphene dispersion, composite rust inhibitor, high-efficiency water-reducing agent and water evenly to prepare a mixed solution.

[0017] (3) Slowly add the mixed solution into the mixer and mix with the dry material for 4-6 minutes to make a uniform concrete mixture.

[0018] (4) Pour the concrete mixture into shape, vibrate and compact it, and then cure it for 7 days at 20±2℃ and relative humidity ≥90%, and then transfer it to natural curing for 28 days to obtain the final product.

[0019] This invention also provides the application of the aforementioned high-durability concrete suitable for highly corrosive coastal saline soil areas. The concrete is used in engineering structures such as roads, bridges, building foundations, culverts, and slope protection in these areas, where the highly corrosive saline soil has a chloride ion content ≥0.5% and a sulfate content ≥1.0%. The concrete of this invention exhibits excellent resistance to chloride ion penetration, sulfate attack, freeze-thaw resistance, and low shrinkage, enabling it to adapt to the harsh environment of highly corrosive saline soil areas, extending the service life of engineering structures, reducing maintenance costs, and demonstrating broad engineering application prospects.

[0020] Beneficial effects

[0021] Compared with the prior art, the present invention has the following advantages: 1. This invention significantly improves the corrosion resistance of concrete through the synergistic effect of composite admixtures (slag powder + fly ash), modified graphene, composite rust inhibitors, and nano-silica. It can effectively resist the dual erosion of chloride ions and sulfates in highly corrosive saline soils, reducing the occurrence of steel corrosion and concrete cracking and spalling. At the same time, the optimized raw material ratio and preparation process give the concrete good density and pore structure, further reducing the penetration ability of corrosive media and improving the long-term durability of concrete.

[0022] 2. This invention uses a polycarboxylate-based high-efficiency water-reducing agent, combined with the effects of composite admixtures and nano-silica, to effectively reduce the water consumption and water-cement ratio of concrete, reduce the shrinkage rate of concrete, improve the crack resistance of concrete, prevent shrinkage cracks from providing a penetration channel for corrosive media, and further ensure the durability of concrete; at the same time, the concrete has good workability, small slump loss over time, facilitates construction and pouring, and can improve construction efficiency and project quality.

[0023] 3. The composite rust inhibitor of the present invention is composed of calcium nitrite, sodium tripolyphosphate and sodium gluconate, which achieves synergistic effects of rust inhibition, sulfate corrosion resistance and crack resistance. It has high rust inhibition efficiency and long effective period, and can protect the steel bars in concrete for a long time and avoid the damage of steel bar corrosion to concrete structure. Compared with single rust inhibitors, it has a wider range of applications and is more suitable for the harsh environment of highly corrosive saline soil areas.

[0024] 4. The modified graphene dispersion of the present invention is modified with silane coupling agent KH-550, resulting in uniform graphene dispersion and good compatibility with the cement matrix. It can fully exert its barrier and reinforcing effects, further refine the pore structure of concrete, and improve the strength and impermeability of concrete. The synergistic effect of nano-silica and composite admixtures promotes the full hydration reaction of cement, improves the density and strength of concrete, and achieves simultaneous improvement of concrete strength and durability.

[0025] 5. The raw materials used in this invention are all readily available conventional raw materials on the market. The preparation process is simple, requiring no additional complex production equipment, and the cost is controllable. Compared with existing anti-corrosion concrete, the production cost is reduced by 8%-15%, which facilitates large-scale industrial production and engineering applications. At the same time, the various properties of the concrete meet the requirements for use in engineering structures in highly corrosive saline soil areas, which can significantly extend the service life of engineering structures, reduce engineering maintenance costs, and have good economic benefits, social benefits, and engineering application value. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. The described embodiments are only some preferred embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Unless otherwise specified, the experimental methods used in the embodiments are conventional or common methods in the art, and the materials and reagents used are commercially available unless otherwise specified.

[0028] The raw materials used in the examples and comparative examples are described below: Portland cement: Grade 42.5 ordinary Portland cement, specific surface area 320m² / kg, initial setting time 55min, final setting time 520min; Slag powder: S95 grade, specific surface area 420m² / kg, activity index 7d=78%, 28d=98%; Fly ash: Grade I, loss on ignition 4.2%, water requirement ratio 92%; Quartz sand: fineness modulus 2.5, mud content 0.8%, mud lump content 0.3%; Crushed stone: 5-31.5mm continuously graded basalt crushed stone, crushing value 10%, mud content 0.3%, mud lump content 0.1%; Modified graphene dispersion: graphene content 1.0wt%, modifier is silane coupling agent KH-550, stability 72h, no stratification or precipitation; Composite rust inhibitor: Calcium nitrite, sodium tripolyphosphate, and sodium gluconate are compounded in a weight ratio of 3:2:1, and all have a purity of 98.5%. High-efficiency water-reducing agent: polycarboxylate-based, water reduction rate 28%, air content 2.5%, slump loss over time (1h) 8mm; Nano silica: particle size 30nm, specific surface area 650m² / kg, purity 99.6%, good dispersibility; Water: Ordinary tap water.

[0029] Example 1

[0030] A high-durability concrete suitable for highly corrosive coastal saline soil areas is prepared from the following raw materials in parts by weight: 320 parts silicate cement, 80 parts slag powder, 50 parts fly ash, 650 parts quartz sand, 1100 parts crushed stone, 15 parts modified graphene dispersion, 8 parts composite rust inhibitor, 6 parts high-efficiency water-reducing agent, 140 parts water, and 10 parts nano silica.

[0031] Preparation method: (1) Weigh each raw material according to the weight parts, put silicate cement, slag powder, fly ash, nano silica, quartz sand and crushed stone into the mixer, dry mix for 2 minutes, and mix evenly; (2) Mix modified graphene dispersion, composite rust inhibitor, high-efficiency water-reducing agent and water evenly to make a mixed solution; (3) Slowly add the mixed solution into the mixer, mix with dry materials for 4 minutes to make a uniform concrete mixture; (4) Pour the concrete mixture into shape, vibrate and compact it, cure it for 7 days under the conditions of 20±2℃ and relative humidity ≥90%, and then transfer it to natural curing for 28 days to obtain the final product.

[0032] Example 2

[0033] A high-durability concrete suitable for highly corrosive coastal saline soil areas is prepared from the following raw materials in parts by weight: 350 parts silicate cement, 100 parts slag powder, 65 parts fly ash, 700 parts quartz sand, 1200 parts crushed stone, 20 parts modified graphene dispersion, 10 parts composite rust inhibitor, 8 parts high-efficiency water-reducing agent, 150 parts water, and 14 parts nano silica.

[0034] Preparation method: (1) Weigh each raw material according to the weight parts, put silicate cement, slag powder, fly ash, nano silica, quartz sand and crushed stone into the mixer, dry mix for 2.5 min, mix evenly; (2) Mix modified graphene dispersion, composite rust inhibitor, high-efficiency water-reducing agent with water evenly to make a mixed solution; (3) Slowly add the mixed solution into the mixer, mix with dry materials for 5 min, and make a uniform concrete mixture; (4) Pour the concrete mixture into shape, vibrate and compact it, cure it for 7 days at 20±2℃ and relative humidity ≥90%, and then transfer it to natural curing for 28 days to obtain the final product.

[0035] Example 3

[0036] A high-durability concrete suitable for highly corrosive coastal saline soil areas is prepared from the following raw materials in parts by weight: 380 parts silicate cement, 120 parts slag powder, 80 parts fly ash, 750 parts quartz sand, 1300 parts crushed stone, 25 parts modified graphene dispersion, 12 parts composite rust inhibitor, 10 parts high-efficiency water-reducing agent, 160 parts water, and 18 parts nano silica.

[0037] Preparation method: (1) Weigh each raw material according to the weight parts, put silicate cement, slag powder, fly ash, nano silica, quartz sand and crushed stone into the mixer, dry mix for 3 minutes, and mix evenly; (2) Mix modified graphene dispersion, composite rust inhibitor, high-efficiency water-reducing agent and water evenly to make a mixed solution; (3) Slowly add the mixed solution into the mixer, mix with dry materials for 6 minutes to make a uniform concrete mixture; (4) Pour the concrete mixture into shape, vibrate and compact it, cure it for 7 days under the conditions of 20±2℃ and relative humidity ≥90%, and then transfer it to natural curing for 28 days to obtain the final product.

[0038] Example 4

[0039] A high-durability concrete suitable for highly corrosive coastal saline soil areas is prepared from the following raw materials in parts by weight: 330 parts silicate cement, 90 parts slag powder, 55 parts fly ash, 670 parts quartz sand, 1150 parts crushed stone, 17 parts modified graphene dispersion, 9 parts composite rust inhibitor, 7 parts high-efficiency water-reducing agent, 145 parts water, and 12 parts nano silica.

[0040] The preparation method is the same as in Example 2.

[0041] Example 5

[0042] A high-durability concrete suitable for highly corrosive coastal saline soil areas is prepared from the following raw materials in parts by weight: 370 parts silicate cement, 110 parts slag powder, 75 parts fly ash, 730 parts quartz sand, 1250 parts crushed stone, 23 parts modified graphene dispersion, 11 parts composite rust inhibitor, 9 parts high-efficiency water-reducing agent, 155 parts water, and 16 parts nano silica.

[0043] The preparation method is the same as in Example 2.

[0044] Comparative Example Comparative Example 1 A type of concrete, compared with Example 2, without the addition of modified graphene dispersion, with all other raw materials and weight parts and preparation methods being the same as in Example 2.

[0045] Comparative Example 2 A type of concrete, compared with Example 2, without the addition of composite rust inhibitor, with the remaining raw materials and weight parts, and preparation method being the same as in Example 2.

[0046] Comparative Example 3 A type of concrete, compared with Example 2, without the addition of nano-silica, but with the same raw materials, weight parts, and preparation method as Example 2.

[0047] Comparative Example 4 A type of concrete, compared with Example 2, in which the composite admixture (slag powder + fly ash) is replaced with an equal amount of silicate cement, and the remaining raw materials, weight parts, and preparation methods are the same as in Example 2.

[0048] Comparative Example 5 A type of concrete, compared with Example 2, wherein the modified graphene dispersion is replaced with an equal amount of ordinary graphene dispersion (not modified with silane coupling agent KH-550), and the remaining raw materials, weight parts, and preparation methods are the same as in Example 2.

[0049] Technical effect verification test Experimental Objective The durability and comprehensive performance of the durable concrete prepared in Examples 1-5 and the concrete prepared in Comparative Examples 1-5 in a highly corrosive saline soil environment were verified. The compressive strength, chloride ion penetration resistance, sulfate attack resistance, freeze-thaw resistance and shrinkage rate of the concrete were tested in particular. The influence of each component on the concrete performance was analyzed to clarify the technical effect of the present invention.

[0050] Test sample Concrete samples prepared in Examples 1-5 and Comparative Examples 1-5 were used to prepare standard test specimens. The following specimens were used: compressive strength specimens were 150mm × 150mm × 150mm cubes; chloride ion penetration resistance specimens were Φ100mm × 50mm cylinders; sulfate attack resistance specimens were 100mm × 100mm × 100mm cubes; freeze-thaw resistance specimens were 100mm × 100mm × 400mm prisms; and shrinkage rate specimens were 100mm × 100mm × 515mm prisms. Three specimens were selected for each performance test, and the average value was taken as the test result.

[0051] Test methods 1. Compressive strength test: The test was conducted in accordance with the "Standard for Test Methods of Mechanical Properties of Concrete" (GB / T50081-2019), and the compressive strength of concrete at 7d and 28d was tested respectively.

[0052] 2. Chloride ion penetration resistance test: The rapid chloride ion migration method (RCM method) in "Test Method for Chloride Ion Penetration of Concrete" (GB / T50082-2009) was used to test the chloride ion migration coefficient of concrete after 28 days. The smaller the migration coefficient, the better the chloride ion penetration resistance of the concrete.

[0053] 3. Test for resistance to sulfate attack: The test was conducted according to the "Test Method for Resistance to Sulfate Attack of Concrete" (GB / T50082-2009). The specimens were immersed in a 5% sodium sulfate solution for 180 days. The strength loss rate and mass loss rate of the specimens were then tested. The smaller the strength loss rate and mass loss rate, the better the resistance to sulfate attack of the concrete.

[0054] 4. Freeze-thaw resistance test: The test is conducted according to the rapid freezing method in "Test Method for Freeze-thaw Resistance of Concrete" (GB / T50082-2009). The strength loss rate and relative dynamic elastic modulus of concrete after 300 freeze-thaw cycles are tested. The smaller the strength loss rate and the larger the relative dynamic elastic modulus, the better the freeze-thaw resistance of the concrete.

[0055] 5. Shrinkage rate test: The test shall be conducted in accordance with the "Test Method for Shrinkage of Concrete" (GB / T50082-2009). The drying shrinkage rate of concrete after 28 days shall be tested. The smaller the shrinkage rate, the better the crack resistance of the concrete.

[0056] Table 1. Performance test results of concrete in each embodiment and comparative example.

[0057] Analysis of Experimental Results As can be seen from the test results in Table 1, the durable concrete prepared in Examples 1-5 of this invention has better performance in all aspects than the concrete prepared in Comparative Examples 1-5. The specific analysis is as follows: 1. Compressive Strength Analysis: The 7-day compressive strength of the concrete in Examples 1-5 was 38.6-42.3 MPa, and the 28-day compressive strength was 56.8-62.5 MPa, both significantly higher than those of the comparative examples (7-day compressive strength 34.5-37.1 MPa, 28-day compressive strength 50.7-54.9 MPa). Among them, Example 2 had the highest compressive strength, reaching 42.3 MPa at 7 days and 62.5 MPa at 28 days, indicating that the raw material ratio and preparation process of the present invention can effectively improve the strength of concrete. Comparative analysis shows that the absence of modified graphene dispersion (Comparative Example 1), composite rust inhibitor (Comparative Example 2), and nano-silica (Comparative Example 3), or the replacement of composite admixture (Comparative Example 4) and the use of unmodified graphene dispersion (Comparative Example 5), all lead to a decrease in concrete strength. This is because there is a synergistic reinforcing effect among the components: the composite admixture undergoes a secondary hydration reaction with cement hydration products, improving the matrix strength; modified graphene and nano-silica fill pores, refine the structure, and further enhance the density and strength of concrete; the composite rust inhibitor improves the workability of concrete, prevents cracking, and ensures strength development.

[0058] 2. Chloride ion penetration resistance analysis: The chloride ion migration coefficient of the concrete in Examples 1-5 after 28 days was 1.8-2.3 × 10⁻⁶. -12 m² / s, far lower than the comparative proportions (3.9-5.2×10). -12 The concentration of chloride ions in the concrete (m² / s) indicates that the concrete of this invention has excellent resistance to chloride ion penetration. Among them, Example 2 has the lowest chloride ion migration coefficient, at only 1.8 × 10⁻⁶. -12 The m² / s indicates that the synergistic effect of modified graphene dispersion, nano-silica, and composite admixtures can effectively refine the pore structure of concrete, forming a dense barrier layer to prevent chloride ion penetration. Comparative Example 1, without modified graphene dispersion, has a relatively loose pore structure and a significantly increased chloride ion migration coefficient. In Comparative Example 4, after replacing the composite admixture, the secondary hydration reaction is insufficient, the porosity increases, and the chloride ion penetration resistance significantly decreases. In Comparative Example 5, using unmodified graphene dispersion, graphene agglomerates, failing to fully exert its barrier effect, and the chloride ion penetration resistance also significantly deteriorates.

[0059] 3. Analysis of Sulfate Erosion Resistance: The concrete in Examples 1-5 showed a strength loss rate of only 2.5-3.2% and a mass loss rate of only 0.3-0.4% after 180 days of sulfate erosion, far lower than the comparative examples (strength loss rate 6.5-8.3%, mass loss rate 0.9-1.3%), indicating that the concrete of this invention has extremely strong sulfate erosion resistance. Sodium tripolyphosphate in the composite rust inhibitor can chelate calcium and magnesium ions in the soil, reducing the occurrence of sulfate erosion reactions; the composite admixture can consume free Ca(OH)2, reducing the content of reactants; the dense structure formed by modified graphene and nano-silica prevents sulfate solution penetration. The synergistic effect of these three components significantly improves sulfate erosion resistance. Comparative Example 2, without the addition of the composite rust inhibitor, showed a significant increase in strength and mass loss rates, indicating that the composite rust inhibitor plays a crucial role in sulfate erosion resistance; Comparative Examples 1, 3, 4, and 5 also showed a significant decrease in sulfate erosion resistance due to the lack of corresponding components or poor component performance.

[0060] 4. Freeze-thaw resistance analysis: After 300 freeze-thaw cycles, the concrete in Examples 1-5 showed a strength loss rate of only 4.5-5.8% and a relative dynamic elastic modulus of 88.6-91.2%, both superior to the comparative examples (strength loss rate 8.6-11.2%, relative dynamic elastic modulus 74.8-81.2%), indicating that the concrete of the present invention has good freeze-thaw resistance. The uniform fine air bubbles introduced by the polycarboxylate-based high-efficiency water-reducing agent can buffer the expansion stress generated by freeze-thaw cycles; the high density of the concrete reduces the water content in the internal pores, reducing freeze-thaw damage; modified graphene and nano-silica enhance the toughness of the concrete, preventing crack propagation, thereby improving freeze-thaw resistance. The comparative examples, due to insufficient concrete density and poor toughness, showed a significantly higher strength loss rate and a significantly lower relative dynamic elastic modulus after freeze-thaw cycles.

[0061] 5. Shrinkage analysis: The 28-day drying shrinkage rate of the concrete in Examples 1-5 was 352 × 10⁻⁶. -6 -385×10 -6 This is lower than the ratios of each pair (428×10). -6 -475×10 -6 This indicates that the concrete of the present invention has good crack resistance. The composite admixture and nano-silica can slow down the cement hydration rate, reduce the heat of hydration, and prevent temperature cracks; modified graphene can inhibit the drying shrinkage of concrete and improve its toughness; sodium gluconate in the composite rust inhibitor can improve the workability of concrete and reduce the formation of shrinkage cracks. The synergistic effect of the components effectively reduces the shrinkage rate of concrete. The comparative examples, lacking the corresponding components, showed a significantly higher shrinkage rate, making them prone to shrinkage cracks, providing channels for corrosive media penetration, and further reducing the durability of the concrete.

[0062] In summary, this invention, by optimizing the composition and proportion of raw materials and utilizing the synergistic effect of each component, produces durable concrete with advantages such as high strength, high resistance to chloride ion penetration, high resistance to sulfate attack, good freeze-thaw resistance, and low shrinkage. It can effectively adapt to the harsh environment of highly corrosive saline soil areas, significantly extend the service life of concrete structures, and solve the technical problem of poor durability of concrete in highly corrosive saline soil areas in the prior art. It has good engineering application value and promotion prospects.

[0063] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A high-durability concrete suitable for highly corrosive coastal saline soil areas, characterized in that, The raw materials include the following parts by weight: 320-380 parts silicate cement, 80-120 parts slag powder, 50-80 parts fly ash, 650-750 parts quartz sand, 1100-1300 parts crushed stone, 15-25 parts modified graphene dispersion, 8-12 parts composite rust inhibitor, 6-10 parts high-efficiency water-reducing agent, 140-160 parts water, and 10-18 parts nano silica.

2. The high-durability concrete according to claim 1, characterized in that, The silicate cement is grade 42.5 ordinary silicate cement with a specific surface area of ​​300-350 m² / kg, an initial setting time of ≥45 min, and a final setting time of ≤600 min.

3. The high-durability concrete according to claim 1, characterized in that, The slag powder is S95 grade slag powder with a specific surface area ≥400m² / kg and an activity index of 7d≥75% and 28d≥95%; the fly ash is Grade I fly ash with a loss on ignition ≤5.0% and a water requirement ratio ≤95%.

4. The high-durability concrete according to claim 1, characterized in that, The fineness modulus of the quartz sand is 2.3-2.8, the mud content is ≤1.0%, and the mud lump content is ≤0.5%; the crushed stone is 5-31.5mm continuously graded basalt crushed stone, the crushing value is ≤12%, the mud content is ≤0.5%, and the mud lump content is ≤0.2%.

5. The high-durability concrete according to claim 1, characterized in that, The modified graphene dispersion contains 0.8-1.2 wt% graphene, the modifier is silane coupling agent KH-550, the dispersion has a stability of ≥72 h, and there is no obvious stratification or precipitation.

6. The high-durability concrete according to claim 1, characterized in that, The composite rust inhibitor is composed of calcium nitrite, sodium tripolyphosphate, and sodium gluconate in a weight ratio of 3:2:1, and all have a purity of ≥98%.

7. The high-durability concrete according to claim 1, characterized in that, The high-efficiency water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent.

8. The high-durability concrete according to claim 1, characterized in that, The particle size of the nano-silica is 20-50 nm.

9. A method for preparing high-durability concrete as described in any one of claims 1-8, characterized in that, The process includes the following steps: (1) Weigh each raw material by weight, and put silicate cement, slag powder, fly ash, nano silica, quartz sand and crushed stone into a mixer and dry mix for 2-3 minutes until they are evenly mixed; (2) Mix the modified graphene dispersion, composite rust inhibitor, high-efficiency water-reducing agent and water evenly to make a mixed solution; (3) Slowly add the mixed solution into the mixer and mix with the dry material for 4-6 minutes to make a uniform concrete mixture.

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