An ultra-sulfate concrete capable of curing sea sand chloride ions in situ and a preparation method thereof

Abstract

The application provides an ultra-sulphate concrete capable of curing chlorides in situ and a preparation method thereof, raw materials of the ultra-sulphate concrete include, in terms of weight fractions, granulated blast furnace slag 70-75 parts, desulfurization gypsum 15-18 parts, activated shell powder 8-12 parts, curing agent 1.5-3.0 parts, sodium aluminate 0.4-1.0 parts, nano-silicon dioxide 0.3-0.8 parts, graphene 0.01-0.05 parts, sea sand 120-150 parts, gravel 280-320 parts, water 40-45 parts and water reducing agent 0.3-0.6 parts; wherein, the sea sand is not subjected to desalination treatment; the application constructs a sodium aluminate-graphene-nano-silicon dioxide-activated shell powder-curing agent multi-site synergistic curing system, the curing rate of chlorides in the sea sand is more than 96%, and the diffusion of chlorides can be effectively inhibited, and the mechanical properties and use stability of the ultra-sulphate concrete are improved.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and more specifically, to a supersulfate concrete that can solidify chloride ions from sea sand in situ and its preparation method. Background Technology

[0002] The construction of major infrastructure projects such as cross-sea bridges, deep-water ports, artificial islands and reefs, coastal nuclear power plants, and coastal defense projects places extremely stringent requirements on high-durability, long-life, and low-carbon concrete. Sea sand, as a natural fine aggregate with vast reserves and low cost in coastal areas, is a key resource for alleviating the depletion of natural river sand and ensuring a stable supply of sand for engineering projects. However, chloride ions carried in sea sand are the primary factor inducing corrosion of steel reinforcement and structural deterioration in concrete. Chloride ions migrate to the surface of the steel reinforcement through concrete pores, forming an electrochemical corrosion circuit, leading to steel reinforcement cross-section reduction, rust expansion and cracking, and peeling of the protective layer, seriously threatening structural safety and long-term service performance.

[0003] Traditional sea sand utilization relies on water washing and desalination as its core technology. This not only consumes large amounts of freshwater resources but also generates high-salinity wastewater, easily leading to soil salinization and water pollution. Furthermore, water washing only removes chloride ions attached to the surface of the sea sand, having little effect on removing closed chloride ions within the pores and microcracks of the sand grains, posing a durability risk in engineering applications. While newer technologies such as electroosmosis, biological dechlorination, and electrochemical desalination have shown some effectiveness, they suffer from high equipment investment, long processing cycles, poor on-site adaptability, and difficulty in large-scale application, failing to meet the rapid construction needs of coastal projects. Therefore, achieving the safe direct utilization of sea sand without desalination, shifting from "passive dechlorination" to "in-situ chloride fixation," has become a core technological bottleneck that urgently needs to be overcome in the field of marine engineering building materials.

[0004] Meanwhile, my country's coastal aquaculture and seafood processing industries are massive, generating millions of tons of waste shells annually, mainly including oyster shells, scallop shells, and clam shells. The main component of these waste shells is calcium carbonate, which possesses a typical layered nanostructure, high specific surface area, and ion exchange potential, making it a promising biomass calcium-based solid waste for high-value utilization. However, currently, waste shells are generally simply landfilled or randomly piled up, with a resource utilization rate of less than 10%. This not only occupies a large amount of land but also easily rots, emits foul odors, and breeds microorganisms, forming "white pollution" along the coast. While existing technologies attempt to use shell powder as a concrete admixture, most are either unactivated or simply calcined, failing to fully utilize its multiple functions such as layered adsorption, lattice chlorine fixation, alkaline activation, and heterogeneous nucleation. The synergistic mechanism with the cementing system is unclear, the chlorine fixation effect is limited, and the strength improvement is not significant.

[0005] Supersulfate concrete uses granulated blast furnace slag, desulfurized gypsum, and other industrial solid wastes as main raw materials. It contains little or no clinker and has advantages such as low heat of hydration, strong resistance to chemical erosion, and extremely low carbon emissions, making it an ideal green cementitious system suitable for marine environments. However, traditional supersulfate concrete has significant shortcomings: the system has low alkalinity, resulting in weak chemical bonding ability with chloride ions; slow early strength development; loose matrix pore structure, leading to low resistance to chloride ion diffusion; and a lack of efficient synergistic chloride-fixing components, making it unsuitable for direct use in high-chloride sea sand concrete. Summary of the Invention

[0006] Based on the aforementioned technical problems in the existing technology, this invention provides a supersulfate concrete that can in-situ solidify chloride ions from sea sand. By constructing a multi-site synergistic solidification system of sodium aluminate-graphene-nano silica-activated shell powder-solvent, the various raw material components are synergistically coupled in multiple ways, including synergistic mechanism, synergistic structure, and synergistic interface. This allows sea sand to be directly applied to supersulfate concrete without desalination treatment, achieving a chloride ion solidification rate of over 95% in the sea sand and effectively inhibiting chloride ion diffusion. At the same time, it improves the mechanical properties and service stability of supersulfate concrete.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] A type of supersulfate concrete that can in-situ solidify chloride ions from sea sand, by weight, comprises the following raw materials: 70-75 parts granulated blast furnace slag, 15-18 parts desulfurized gypsum, 8-12 parts activated shell powder, 1.5-3.0 parts curing agent, 0.4-1.0 parts sodium aluminate, 0.3-0.8 parts nano silica, 0.01-0.05 parts graphene, 120-150 parts sea sand, 280-320 parts crushed stone, 40-45 parts water, and 0.3-0.6 parts water-reducing agent;

[0009] The sea sand was not desalinated; the curing agent included calcium aluminate powder and hydrotalcite.

[0010] In some embodiments, the sea sand has a chloride ion content of 0.06-0.12% and a fineness modulus of 2.3-3.0.

[0011] In some embodiments, the activated shell powder is obtained by washing, drying, calcining at 750-850°C, and then pulverizing waste shells; preferably, the calcined shells are pulverized to a mesh size of 200 or higher.

[0012] In some embodiments, the discarded shells include at least one of oyster shells, scallop shells, and clam shells.

[0013] In some embodiments, the crushed stone has a continuous gradation of 5-25mm, a crushing index of ≤8%, a needle-like or flaky texture of ≤15%, and a mud content of ≤0.5%.

[0014] In some embodiments, the mass ratio of the calcium aluminate powder to the hydrotalcite is (1-5):1.

[0015] In some embodiments, the granulated blast furnace slag has a specific surface area ≥ 450 m². 2 / kg, activity index ≥95%, vitreous content ≥85%.

[0016] In some embodiments, the nano-silica particles have a particle size of 10-50 nm and a specific surface area ≥150 m². 2 / kg.

[0017] In some embodiments, the graphene is 1-5 layers of graphene with a sheet diameter of 1-5 μm and a specific surface area ≥500 m². 2 / kg.

[0018] In some embodiments, the water-reducing agent is a polycarboxylate superplasticizer with a water reduction rate ≥25% and a chloride ion content ≤0.02%.

[0019] The water has a pH of 6.5-8.5 and a chloride ion content of ≤200mg / L.

[0020] The present invention also provides a method for preparing supersulfate concrete with in-situ curable chloride ions from sea sand according to any of the above embodiments, the method comprising the following steps:

[0021] S1. Mix and grind granulated blast furnace slag, desulfurized gypsum, and activated shell powder to a specific surface area ≥ 500 m². 2 / kg, to obtain cementitious material;

[0022] S2. Mix the curing agent, sodium aluminate, nano silica, graphene, water-reducing agent and water evenly to obtain the activation solution;

[0023] S3. Mix the cementitious material, sea sand, and crushed stone, then add the activating liquid and mix well to obtain the supersulfate cement concrete.

[0024] The present invention also provides the application of supersulfate concrete according to any of the above embodiments in marine engineering, ports, coastal buildings, cross-sea bridges, and island and reef engineering.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] The hypersulfate concrete provided by this invention constructs a multi-site synergistic curing system of sodium aluminate-graphene-nano silica-activated shell powder-curing agent through the proportioning of various raw materials. This system achieves multiple couplings of synergistic effects among the raw material components, mechanisms, structures, and interfaces. Sea sand can be directly applied to hypersulfate concrete without desalination treatment, achieving a chloride ion curing rate of over 96% in the sea sand and effectively inhibiting chloride ion diffusion. Simultaneously, it improves the mechanical properties and performance stability of the hypersulfate concrete. Specifically, sodium aluminate rapidly dissolves AlO₂. 2- , with Cl - In-situ generation of highly stable Friedel salts enables rapid solidification of chloride ions; continuous replenishment of aluminum source by calcium aluminate further generates Friedel salts and hydrated calcium aluminate, solidifying residual chloride ions through deep chemical precipitation and chloride fixation; interlayer anions of hydrotalcite react with Cl... - Quantitative exchange enables long-term stable storage; the highly active calcium phase in the activated shell adsorbs and dissolves chloride ions, while providing heterogeneous nucleation sites; the high specific surface area of ​​nano-SiO2 physically adsorbs and fills pores, cutting off chloride ion diffusion channels; graphene's two-dimensional barrier and multi-site adsorption form a tortuous barrier network, adsorbing chloride ions and inhibiting the electrochemical corrosion of steel bars. In addition, the hydration products of various cementing components co-precipitate and coat chloride: ettringite, CSH, and Friedel salt symbiotically interlock, firmly coating chloride ions inside the matrix.

[0027] In this invention, sodium aluminate increases the alkalinity of the system, accelerates the hydration of slag and shell powder, and improves early strength; nano-SiO2 particles are adsorbed on the surface of graphene, forming steric hindrance and inhibiting the aggregation of graphene sheets; graphene is uniformly dispersed in the matrix to form a nano-overlapping network, which undertakes stress transmission and crack resistance and toughening; finally, an interlocking spatial network structure of ettringite-Friedel salt-CSH-graphene is formed, with pore size concentrated in the harmless pore region below 20nm, and the thickness of the sea sand-slurry interface transition zone ≤20μm, achieving ultra-dense compaction and high structural stability.

[0028] The supersulfate concrete provided by this invention exhibits excellent comprehensive performance, with a chloride ion curing rate of over 95% for sea sand, a chloride ion diffusion coefficient of ≤0.44% at 28 days, a compressive strength of ≥57MPa at 28 days, and an electrical flux of ≤530C at 56 days. Attached Figure Description

[0029] Figure 1 The compressive strength test results are for the supersulfate concrete of Examples 1-7 and Comparative Examples 1-5;

[0030] Figure 2 The chloride ion curing rate of the supersulfate concrete in Examples 1-7 and Comparative Examples 1-5;

[0031] Figure 3Chloride ion diffusion coefficients of the supersulfate concrete in Examples 1-7 and Comparative Examples 1-5;

[0032] Figure 4 The 56-day electrical flux of the supersulfate concrete in Examples 1-7 and Comparative Examples 1-5 is given. Detailed Implementation

[0033] Numerous specific details are set forth in the following description to provide a full understanding of the invention. However, the invention can be practiced in many other ways different from those described herein, and similar modifications can be made by those skilled in the art without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0035] The parameters or preparation methods of some of the raw materials used in the following examples and comparative examples are as follows:

[0036] Activated shell powder: It is obtained by mixing oyster shells, scallop shells and clam shells in a mass ratio of 1:1:1, washing and drying them, then calcining them at 800℃ for 60 minutes, and finally grinding them to a fineness of 200 mesh or higher.

[0037] Unactivated shell powder: It is obtained by mixing oyster shells, scallop shells and clam shells in a mass ratio of 1:1:1, washing and drying them, and then grinding them to a fineness of 200 mesh or higher.

[0038] Sea sand: untreated sea sand with a chloride ion content of 0.06-0.12%, mud content ≤1.0%, and fineness modulus of 2.3-3.0;

[0039] Crushed stone: 5-25mm continuously graded granite crushed stone, with a crushing index ≤8%, needle-like and flaky particles ≤15%, and mud content ≤0.5%;

[0040] Granulated blast furnace slag: specific surface area ≥ 450 m² 2 / kg, 28d activity index ≥95%, vitreous content ≥85%;

[0041] Desulfurized gypsum: CaSO4·2H2O content ≥90%, moisture content ≤1.0%, fineness ≥80 mesh;

[0042] Curing agent: composed of calcium aluminate powder and hydrotalcite mixed in a mass ratio of 5:3;

[0043] Sodium aluminate: NaAlO2 purity ≥98%, active Al2O3 ≥40%, fineness ≥200 mesh;

[0044] Nano-silica: Particle size 10-50nm, specific surface area ≥150m² 2 / g, purity ≥98%;

[0045] Graphene: 1-5 layers of thin graphene, sheet diameter 1-5μm, specific surface area ≥500m² / g;

[0046] Water-reducing agent: a polycarboxylate high-efficiency water-reducing agent with a water reduction rate ≥25% and a chloride ion content ≤0.02%;

[0047] Water: pH 6.5-8.5, chloride ion content ≤200mg / L.

[0048] The standards and methods for testing mechanical properties and durability are as follows:

[0049] Compressive strength and flexural strength: in accordance with GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete";

[0050] Chloride ion curing rate: According to GB / T 50082-2009, curing rate = (total chlorine − free chlorine) / total chlorine × 100%;

[0051] Chloride ion diffusion coefficient: tested according to GB / T 50082-2009 using the RCM method;

[0052] Electrical flux: The electrical flux was measured over 6 hours according to ASTM C1202, and the specimen age was 56 days.

[0053] Example 1

[0054] A type of supersulfate concrete that can cure chloride ions in sea sand in situ comprises, by weight, 72 parts granulated blast furnace slag, 16 parts desulfurized gypsum, 10 parts activated shell powder, 2.0 parts curing agent, 0.6 parts sodium aluminate, 0.5 parts nano silica, 0.02 parts graphene, 135 parts undesalinated sea sand, 300 parts crushed stone, 42 parts water, and 0.4 parts polycarboxylate superplasticizer;

[0055] The specific steps of its preparation method are as follows:

[0056] 1) Mix activated shell powder, granulated blast furnace slag, and desulfurized gypsum according to the specified ratio, and ball mill for 15 minutes to obtain a cementitious material;

[0057] 2) Add sodium aluminate, curing agent, nano SiO2, graphene, and polycarboxylate superplasticizer to the mixing water, and stir at 800 r / min for 5 min using a high-speed stirrer to prepare a uniformly dispersed activation solution;

[0058] 3) Add the composite cementitious material, sea sand, and crushed stone into the concrete mixer and dry mix for 60 seconds;

[0059] 4) Add the activating solution and continue wet mixing for 120 seconds to obtain supersulfate concrete;

[0060] The supersulfate concrete was poured into a 100mm×100mm×100mm mold, compacted on a vibrating table, and the surface was smoothed. After being covered with a film and left to stand for 12 hours, the mold was removed and placed in a standard curing room with a temperature of (20±2)℃ and a relative humidity of ≥95% for curing until the specified age.

[0061] Example 2

[0062] The proportions, by weight, include 72 parts granulated blast furnace slag, 16 parts desulfurized gypsum, 10 parts activated shell powder, 2.0 parts curing agent, 0.8 parts sodium aluminate, 0.5 parts nano silica, 0.02 parts graphene, 135 parts undesalinated sea sand, 300 parts crushed stone, 42 parts water, and 0.4 parts polycarboxylate superplasticizer.

[0063] The preparation method, molding, and curing are exactly the same as those in Example 1.

[0064] Example 3

[0065] The proportions, by weight, include 72 parts granulated blast furnace slag, 16 parts desulfurized gypsum, 10 parts activated shell powder, 2.0 parts curing agent, 0.4 parts sodium aluminate, 0.5 parts nano silica, 0.02 parts graphene, 135 parts undesalinated sea sand, 300 parts crushed stone, 42 parts water, and 0.4 parts polycarboxylate superplasticizer.

[0066] The preparation method, molding, and curing are exactly the same as those in Example 1.

[0067] Example 4

[0068] The proportions, by weight, include 73 parts granulated blast furnace slag, 15 parts desulfurized gypsum, 9 parts activated shell powder, 1.8 parts curing agent, 0.6 parts sodium aluminate, 0.4 parts nano silica, 0.02 parts graphene, 130 parts undesalinated sea sand, 310 parts crushed stone, 40 parts water, and 0.5 parts polycarboxylate superplasticizer.

[0069] The preparation method, molding, and curing are exactly the same as those in Example 1.

[0070] Example 5

[0071] The proportions, by weight, include 70 parts granulated blast furnace slag, 17 parts desulfurized gypsum, 12 parts activated shell powder, 2.5 parts curing agent, 0.7 parts sodium aluminate, 0.6 parts nano silica, 0.02 parts graphene, 140 parts undesalinated sea sand, 290 parts crushed stone, 43 parts water, and 0.4 parts polycarboxylate superplasticizer.

[0072] The preparation method, molding, and curing are exactly the same as those in Example 1.

[0073] Example 6

[0074] The proportions, by weight, include 75 parts granulated blast furnace slag, 15 parts desulfurized gypsum, 10 parts activated shell powder, 2.2 parts curing agent, 0.6 parts sodium aluminate, 0.5 parts nano silica, 0.04 parts graphene, 135 parts undesalinated sea sand, 300 parts crushed stone, 42 parts water, and 0.4 parts polycarboxylate superplasticizer.

[0075] The preparation method, molding, and curing are exactly the same as those in Example 1.

[0076] Example 7

[0077] The proportions, by weight, include 71 parts granulated blast furnace slag, 16 parts desulfurized gypsum, 11 parts activated shell powder, 2.0 parts curing agent, 0.6 parts sodium aluminate, 0.5 parts nano silica, 0.02 parts graphene, 135 parts undesalinated sea sand, 300 parts crushed stone, 42 parts water, and 0.4 parts polycarboxylate superplasticizer.

[0078] The preparation method, molding, and curing are exactly the same as those in Example 1.

[0079] Comparative Example 1

[0080] The proportions, by weight, include 72 parts granulated blast furnace slag, 16 parts desulfurized gypsum, 10 parts activated shell powder, 2.0 parts curing agent, 135 parts undesalinated sea sand, 300 parts crushed stone, 42 parts water, and 0.4 parts polycarboxylate superplasticizer.

[0081] The specific steps of the preparation method are as follows:

[0082] 1) Mix activated shell powder, granulated blast furnace slag, and desulfurized gypsum according to the specified ratio, and ball mill for 15 minutes to obtain a cementitious material;

[0083] 2) Add the curing agent and polycarboxylate superplasticizer to the mixing water, and stir with a high-speed stirrer at 800 r / min for 5 min to prepare a uniformly dispersed activated liquid;

[0084] 3) Add the composite cementitious material, undesalinated sea sand, and crushed stone into the concrete mixer and dry mix for 60 seconds;

[0085] 4) Add the activating solution and continue wet mixing for 120 seconds to obtain supersulfate concrete;

[0086] The molding, vibration, and curing processes are the same as in Example 1.

[0087] Comparative Example 2

[0088] The proportions, by weight, include 72 parts granulated blast furnace slag, 16 parts desulfurized gypsum, 10 parts activated shell powder, 2.0 parts curing agent, 0.5 parts nano silica, 135 parts undesalinated sea sand, 300 parts crushed stone, 42 parts water, and 0.4 parts polycarboxylate superplasticizer.

[0089] The preparation method, molding, and curing are exactly the same as those in Example 1.

[0090] Comparative Example 3

[0091] The proportions, by weight, include 72 parts granulated blast furnace slag, 16 parts desulfurized gypsum, 10 parts activated shell powder, 2.0 parts curing agent, 0.02 parts graphene, 135 parts undesalinated sea sand, 300 parts crushed stone, 42 parts water, and 0.4 parts polycarboxylate superplasticizer.

[0092] Its preparation method, molding, and curing are exactly the same as those in Example 1.

[0093] Comparative Example 4

[0094] The mix proportions, by weight, include 350 parts of PO 42.5 ordinary Portland cement, 135 parts of undesalinated sea sand, 300 parts of crushed stone, 190 parts of mixing water, and 0.4 parts of polycarboxylate superplasticizer.

[0095] The specific steps of its preparation method are as follows:

[0096] 1) Add cement, undesalinated sea sand, and crushed stone to a forced concrete mixer in sequence and dry mix for 60 seconds to ensure that the aggregate and cementitious materials are evenly mixed.

[0097] 2) Add the pre-dissolved and well-stirred polycarboxylate superplasticizer aqueous solution, and continue wet mixing for 120 seconds until the freshly mixed concrete has a uniform color and meets the fluidity requirements;

[0098] The molding and curing processes are the same as those in Example 1.

[0099] Comparative Example 5: The seashells were used directly without calcination; all other aspects were the same as in Example 1.

[0100] The proportions, by weight, include 72 parts granulated blast furnace slag, 16 parts desulfurized gypsum, 10 parts unactivated shell powder (uncalcined), 2.0 parts composite chloride ion curing agent, 0.6 parts sodium aluminate, 0.5 parts nano silica, 0.02 parts graphene, 135 parts undesalinated sea sand, 300 parts crushed stone, 42 parts water, and 0.4 parts polycarboxylate superplasticizer.

[0101] Its preparation method, molding, and curing are exactly the same as those in Example 1.

[0102] The performance test results of specimens from Examples 1-7 and Comparative Examples 1-5 are shown in Table 1 and... Figures 1-4 As shown.

[0103] Table 1 Performance data test results of the examples and comparative examples

[0104]

[0105] As shown in Table 1 and Figure 1 As shown, the supersulfate concrete obtained by the scheme of the present invention has a 3-day compressive strength ≥26.5MPa, a 7-day compressive strength ≥41.9MPa, and a 28-day compressive strength ≥57.3MPa. The strength development is balanced, with a significant increase in early strength and a tendency for later strength to stabilize and continue to increase. Among them, Example 6 (0.04 parts of graphene) has a 28-day compressive strength of 60.2MPa, which is the optimal value, demonstrating the significant advantage of the synergistic enhancement of sodium aluminate, graphene, and nano-SiO2.

[0106] As shown in Table 1 and Figures 2-4 The supersulfate concrete obtained by the method of the present invention has a chloride ion curing rate of ≥95.8% and a chloride ion diffusion coefficient of ≤0.47×10⁻⁶ after 28 days. -12 m 2 / s, 56d electrical flux ≤568C, far exceeding the patent's preset targets (curing rate ≥95%, diffusion coefficient ≤0.5×10 -12 m 2 / s, electrical flux ≤600C); among which, Example 5 (0.7 parts sodium aluminate) has a diffusion coefficient as low as 0.40×10 -12 m 2 / s, Example 6 (0.04 parts graphene) has an electrical flux as low as 492C, which fully demonstrates that the synergistic effect of sodium aluminate, graphene and nano SiO2 can effectively block the chloride ion diffusion path and improve curing efficiency.

[0107] As the graphene content increased from 0.02 parts in Example 1 to 0.04 parts in Example 6, the 28-day compressive strength increased from 58.6 MPa to 60.2 MPa, and the chloride ion curing rate increased from 96.2% to 96.8%, while the electrical flux continued to decrease. This indicates that appropriately increasing the graphene content can further optimize the barrier properties, but excessive dosing can easily lead to agglomeration, and it needs to be controlled within the range of 0.01~0.05 parts. As the nano-SiO2 content increased from 0.5 parts in Example 1 to 0.8 parts in Example 5, the 28-day compressive strength first increased and then stabilized, while the chloride ion diffusion coefficient continued to decrease. This indicates that nano-SiO2 can effectively refine the pore structure and block chloride ion permeation channels, and the optimal dosing content is 0.5~0.7 parts. When the sodium aluminate content increased from 0.4 parts in Example 3 to 0.8 parts in Example 2, the chloride ion curing rate increased from 95.8%. The concentration was increased to 96.5%, proving that sodium aluminate, as an alkaline activator and aluminum source supplement, can significantly promote Friedel salt formation and enhance the chloride ion curing effect.

[0108] In summary, the key to the performance improvement of this invention lies in the synergistic effect of sodium aluminate, graphene, and nano-SiO2. Sodium aluminate increases the alkalinity of the system, replenishes the aluminum source, and promotes the formation of Friedel salt and the chemical precipitation of chloride ions; graphene constructs a two-dimensional barrier network to block chloride ion diffusion; and nano-SiO2 refines the pore structure and enhances the matrix density. These three components synergistically form a multiple chloride fixation mechanism of "alkaline activation-adsorption barrier-lattice solid solution," significantly improving the mechanical properties and impermeability of concrete.

[0109] Experimental data proves that this invention can directly use undesalinated sea sand without water washing and desalination, while realizing the high value of waste seashells and the large-scale utilization of industrial solid waste (slag, desulfurized gypsum). Combined with the synergistic modification of sodium aluminate, graphene, and nano-SiO2, it not only reduces costs but also improves the durability of concrete, making it fully adaptable to harsh marine environments and possessing extremely high engineering application value.

[0110] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0111] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A type of supersulfate concrete capable of in-situ curing chloride ions from sea sand, characterized in that, By weight, the raw materials include 70-75 parts granulated blast furnace slag, 15-18 parts desulfurized gypsum, 8-12 parts activated shell powder, 1.5-3.0 parts curing agent, 0.4-1.0 parts sodium aluminate, 0.3-0.8 parts nano silica, 0.01-0.05 parts graphene, 120-150 parts sea sand, 280-320 parts crushed stone, 40-45 parts water, and 0.3-0.6 parts water-reducing agent; The sea sand was not desalinated; the curing agent included calcium aluminate powder and hydrotalcite.

2. The supersulfate concrete with in-situ curable sea sand chloride ions according to claim 1, characterized in that, The sea sand has a chloride ion content of 0.06-0.12%, a fineness modulus of 2.3-3.0, and a mud content of ≤1.0%.

3. The supersulfate concrete with in-situ curable sea sand chloride ions according to claim 1, characterized in that, The activated shell powder is obtained by washing, drying, calcining at 750-850℃, and then pulverizing waste shells.

4. The supersulfate concrete with in-situ curable sea sand chloride ions according to claim 1, characterized in that, The crushed stone has a continuous gradation of 5-25mm, a crushing index of ≤8%, and a needle-like and flaky texture of ≤15%.

5. The supersulfate concrete with in-situ curable sea sand chloride ions according to claim 1, characterized in that, The mass ratio of calcium aluminate powder to hydrotalcite is (1-5):

1.

6. The supersulfate concrete with in-situ curable sea sand chloride ions according to claim 1, characterized in that, The granulated blast furnace slag has a specific surface area ≥450m². 2 / kg, activity index ≥95%, vitreous content ≥85%.

7. The supersulfate concrete with in-situ curable sea sand chloride ions according to claim 1, characterized in that, The nano-silica particles have a diameter of 10-50 nm and a specific surface area ≥150 m². 2 / kg.

8. The supersulfate concrete with in-situ curable sea sand chloride ions according to claim 1, characterized in that, The graphene is 1-5 layers of graphene with a sheet diameter of 1-5 μm and a specific surface area ≥500 m². 2 / kg.

9. The method for preparing supersulfate concrete with in-situ curable chloride ions from sea sand according to any one of claims 1-8, characterized in that, Includes the following steps: S1. Mix and grind granulated blast furnace slag, desulfurized gypsum, and activated shell powder to a specific surface area ≥ 500 m². 2 / kg, to obtain cementitious material; S2. Mix the curing agent, sodium aluminate, nano silica, graphene, water-reducing agent and water evenly to obtain the activation solution; S3. Mix the cementitious material, sea sand, and crushed stone, then add the activating liquid and mix well to obtain the supersulfate cement concrete.

10. The application of the supersulfate concrete according to any one of claims 1-8 in marine engineering, ports, coastal buildings, cross-sea bridges, and island and reef engineering.

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