High-strength corrosion-resistant marine mass concrete and preparation method thereof

Abstract

The application discloses high-strength corrosion-resistant marine mass concrete, which comprises 0.5-50 kg / m 3 of temperature shrinkage induced anti-cracking fiber and 50-800 kg / m 3 of pre-wetted internal curing aggregate; the temperature shrinkage induced anti-cracking fiber has a shrinkage rate of no less than 0.5%, a thermal excitation shrinkage temperature of 30-100 DEG C, and comprises thermal shrinkage composite fiber composed of thermal shrinkage core material and outer thermal shrinkage skin material, and a water-soluble modified polyvinyl alcohol layer further coated on the surface of the thermal shrinkage composite fiber; the water-soluble modified polyvinyl alcohol layer comprises polyvinyl alcohol and expansion component. The temperature shrinkage induced anti-cracking fiber with shrinkage compensation function and the internal curing aggregate with high micro-fine interconnected pore structure are simultaneously introduced into the high-strength marine mass concrete above C50, the microstructure of the high-strength marine mass concrete is synergistically controlled, and the mechanical property, anti-cracking property and anti-chloride salt erosion property of the high-strength marine mass concrete are improved, so that the technical difficulties of crack control and anti-chloride salt erosion of the high-strength marine mass concrete are effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a high-strength marine engineering large-volume concrete and its preparation method. Background Technology

[0002] With the advancement of the development plan for long-span cross-sea bridge projects, in addition to the application of C30-C45 medium-low strength marine engineering mass concrete, key structural parts require the use of C50 and above high strength marine engineering mass concrete (such as C55 solid sections of bridge piers and towers, C60-C70 continuous rigid frame prestressed box girders, C80 main arch rings of arch bridges, and C100 steel-concrete composite sections, etc.), and this application is becoming increasingly widespread. For the currently widely used C30-C50 bridge marine engineering mass concrete, mix proportion optimization measures are usually adopted, such as using low-heat cement or reducing cement content, adding large amounts of mineral admixtures and retarders, and incorporating crack-controlling functional materials such as shrinkage reducers, expansion agents or hydration heat inhibitors, as well as temperature control measures such as reducing the pouring temperature and laying cooling water pipes, thereby achieving a better crack control effect. However, as the strength grade of concrete increases to C50 and above, the difficulty of crack control increases. Once large-volume concrete in marine engineering cracks, chloride ions in seawater can easily penetrate into the reinforcing steel through the cracks, leading to steel corrosion, concrete expansion and spalling, and structural damage. This affects the load-bearing capacity and durability of the concrete structure, endangers the normal operation of the bridge structure, and brings significant safety hazards and high maintenance costs, thus restricting the large-scale construction of long-span cross-sea bridges.

[0003] Studies have found that introducing fibers and internal curing materials into large-volume marine concrete is one of the two effective ways to improve its crack resistance. Foreign countries were the first to add polypropylene fibers and steel fibers to large-volume concrete to improve its crack resistance. However, polypropylene fibers have a low modulus, poor dispersibility at high dosages, and affect the pumpability of the concrete. Ordinary steel fibers pose a risk of corrosion in marine engineering and increase construction costs. Furthermore, both commonly used fibers and concrete are thermally expandable and contractile materials; for example, steel fibers have a larger coefficient of thermal expansion than concrete. During the heating stage of large-volume concrete, the inconsistent thermal expansion between the steel fibers and the cementitious paste in the concrete easily leads to tension in the cementitious paste at the interface, causing micro-cracks at the interface. During the cooling stage, the shrinkage of the fibers further promotes crack development.

[0004] Incorporating internal curing materials can reduce concrete shrinkage. Currently, lightweight aggregates and superabsorbent polymers (SAPs) are commonly used internal curing materials for concrete; compared to lightweight aggregates, SAPs have better desorption capabilities. However, when SAPs release moisture, they leave pores in the dense cement matrix, thereby reducing the mechanical properties and durability of the concrete, making them unsuitable for high-strength marine engineering mass concrete. Ordinary lightweight aggregates reduce the mechanical properties of concrete, and their water release mechanism during the heating and cooling stages of mass concrete is closely related to their pore structure and the external temperature and humidity. During the heating process of high-strength marine engineering mass concrete, the heating rate is relatively fast, and the maximum internal temperature can reach 70-90℃. Lightweight aggregates release moisture rapidly at high temperatures, leading to an increase in the porosity of the cementitious paste around the lightweight aggregates and a relative decrease in moisture release during the cooling process of the mass concrete, thus reducing their internal curing effect. Summary of the Invention

[0005] The main objective of this invention is to address the problems and shortcomings of existing technologies by providing a high-strength, corrosion-resistant marine mass concrete. This invention simultaneously introduces thermally activated shrinkage fibers and internally cured aggregates with highly interconnected micropore structures into high-strength marine mass concrete with a strength of C50 or higher. This synergistically regulates the microstructure and enhances the crack resistance and chloride erosion resistance of the concrete, effectively solving the technical challenges of crack control and chloride erosion resistance in high-strength marine mass concrete.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A high-strength marine engineering large-volume concrete, including admixtures with a dosage of 0.5–50 kg / m³ 3 Heat-induced shrinkage fibers and 50–800 kg / m 3 The pre-wetted internal curing aggregate; the shrinkage rate of the heat-activated shrinkage fiber is ≥0.5%, and its shrinkage temperature is 30~100℃.

[0008] In the above scheme, the thermo-shrinkable crack-resistant fiber includes a thermo-shrinkable composite fiber composed of a thermo-shrinkable core material and an outer thermo-shrinkable sheath material, and a water-soluble modified polyvinyl alcohol layer further coating its surface; wherein the water-soluble modified polyvinyl alcohol layer contains polyvinyl alcohol and an expansion component.

[0009] In the above scheme, the main raw materials of the heat-shrinkable core material are one or more of polyester, polypropylene, and polyamide, wherein the molecular weight of polyester is 20,000 to 30,000, the molecular weight of polypropylene is 6,000 to 8,000, and the molecular weight of nylon is 20,000 to 30,000. Its shrinkage rate is 5% to 15%, its response temperature is 40 to 100℃, its tensile strength is 300 to 500 MPa, and its elastic modulus is 3 to 12 GPa. The main raw materials of the heat-shrinkable skin material are one or more of polyvinyl alcohol, ultra-high modulus polyethylene, and polyoxymethylene, wherein the molecular weight of polyvinyl alcohol is 170,000 to 220,000, the molecular weight of polyethylene is 1,000,000 to 2,000,000, and the molecular weight of polyoxymethylene is 20,000 to 30,000. Its tensile strength is 500 to 1200 MPa, and its elastic modulus is 7 to 35 GPa. Its shrinkage rate is 0.5% to 2%, its response temperature is 30 to 100℃, its strength is 500 to 1200 MPa, its elastic modulus is 7 to 35 GPa, and its shrinkage rate is 0.5% to 2%.

[0010] In the above scheme, the raw materials of the heat shrinkable core material also include a stiffening nucleating agent, the content of which (accounting for the total raw material mass, the same below) is 1 to 5 wt%; the raw materials of the heat shrinkable leather also include a plasticizer and a compatibilizer, wherein the content of the plasticizer (accounting for the total raw material mass) is 1 to 5 wt%, and the content of the compatibilizer is 1 to 3 wt%.

[0011] In the above scheme, the compatibilizer includes one or more of maleic anhydride grafted compatibilizer and imide modified polypropylene resin; the plasticizer includes one or more of phthalate, aliphatic diester, fatty acid ester, polyphenol ester, polyol ester, epoxy hydrocarbon, and alkyl sulfonate.

[0012] In the above scheme, the stiffening nucleating agent includes one or more of dibenzyl sorbitol, aluminum aluminum aromatic carboxylate, and sodium benzoate.

[0013] In the above scheme, the thermo-shrinkable crack-resistant fiber is obtained by surface modification of heat-shrinkable composite fiber with silicon solution or silane coupling agent solution, surface indentation after drying, coating modification with modified polyvinyl alcohol solution containing expansion component, and drying after removal.

[0014] In the above scheme, the modified polyvinyl alcohol solution is composed of a polyvinyl alcohol solution and a liquid expanding agent; wherein, the liquid expanding agent is mainly composed of an expanding component, a shrinkage reducing component, a stabilizing and dispersing component, and water.

[0015] In the above scheme, the concentration of the polyvinyl alcohol solution (aqueous solution) is 4-10 wt%, and the viscosity is 20.5-24.5 Pa·s.

[0016] In the above scheme, the components and their amounts in the liquid swelling agent include: 60-150 parts of swelling component, 20-60 parts of shrinkage component, 10-70 parts of stabilizing and dispersing component, and 600-1000 parts of water.

[0017] In the above scheme, the expansion component is composed of anhydrous aluminum sulfate and gypsum, wherein the mass ratio of anhydrous aluminum sulfate to gypsum is 1:(0.66~1.5); the shrinkage reduction component is one or more of amphiphilic diethylene glycol monobutyl ether and dipropylene glycol; and the stabilizing and dispersing component is cationic polyacrylamide.

[0018] In the above scheme, the mass ratio of the polyvinyl alcohol solution to the liquid expanding agent is 1:(0.4~0.9).

[0019] In the above scheme, the specific preparation steps of the thermo-shrinkage induced crack-resistant fiber include:

[0020] 1) Two extruders are used to extrude the heat-shrinkable core material and heat-shrinkable sheath material into a die with two cavities. The heat-shrinkable sheath material enters the cavity corresponding to the sheath material, and the heat-shrinkable core material enters the cavity corresponding to the core material. The materials in the two cavities meet at the position of the spinneret of the extruder. The spinneret has an inner ring and an outer ring. The inner ring of the spinneret connects to the cavity of the core material, and the outer ring of the spinneret connects to the cavity of the sheath material. The two molten materials are extruded through the spinneret (melt extrusion) and bonded together in the air. They are then cooled by a cold water tank and drawn into fibers in hot water at 90-100℃ to form a composite fiber with a core-sheath structure.

[0021] 2) The composite fibers obtained in step 1) are modified by adding silicon solution or silane coupling agent solution, and after drying, the surface is indented to increase the bonding performance with concrete paste.

[0022] 3) The composite fiber obtained in step 2 is added to a modified polyvinyl alcohol solution with added expansion components for coating modification. After removal, it is dried to obtain the temperature shrinkage induced crack-resistant fiber.

[0023] In the above scheme, the coating modification temperature is room temperature and the time is 10-24 hours.

[0024] In the above scheme, the silane coupling agent can be selected from γ-aminopropyltriethoxysilane (KH550), γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560), γ-(β-aminoethyl)aminopropyltrimethoxysilane (KH792), γ-methacryloyloxypropyltrimethoxysilane (KH570), or a mixture thereof; the silane coupling agent can play the role of connecting organic polymers and hydration products.

[0025] Preferably, the silane coupling agent is composed of γ-aminopropyltriethoxysilane, γ-(β-aminoethyl)aminopropyltrimethoxysilane and γ-methacryloyloxypropyltrimethoxysilane.

[0026] In the above scheme, the solvent used for the silane coupling agent solution is an aqueous alcohol solution (ethanol concentration of 80-95 vol%), and the concentration of the silane coupling agent is 0.1-10 wt%.

[0027] In the above scheme, the organosilicon oil is amino silicone oil or dimethyl silicone oil (such as commercially available 201 dimethyl silicone oil, etc.), with a concentration greater than 90%.

[0028] In the above scheme, the modification conditions adopted are standing at room temperature for 1 to 2 hours.

[0029] The preparation method of the thermo-shrinkage induced crack-resistant fiber in the above scheme includes the following steps:

[0030] 1) Two extruders are used to extrude the heat-shrinkable core material mixture and the heat-shrinkable leather material mixture into a die with two cavities. The heat-shrinkable leather material enters the corresponding leather material cavity, and the heat-shrinkable core material enters the corresponding core material cavity. The materials in the two cavities meet at the position of the spinneret of the extruder. The spinneret has an inner ring and an outer ring. The inner ring of the spinneret connects to the core material cavity, and the outer ring of the spinneret connects to the leather material cavity. The two molten materials are extruded through the spinneret (melt extrusion) and bonded together in the air. They are then cooled by a cold water tank and drawn into fibers in hot water at 90-100℃ to form a composite fiber with a core-sheath structure.

[0031] 2) The composite fibers obtained in step 1) are modified by adding silicon solution or silane coupling agent solution, and after drying, the surface is indented to increase the bonding performance with concrete paste.

[0032] 3) The composite fiber obtained in step 2 is added to a modified polyvinyl alcohol solution with added expansion components for coating modification. After removal, it is dried to obtain the temperature shrinkage induced crack-resistant fiber.

[0033] In the above scheme, the melting temperature of the heat-shrinkable core material mixture corresponding to the cavity is 200-280℃; the extrusion pressure is 7-10MPa.

[0034] In the above scheme, the melting temperature of the heat-shrinkable leather mixture corresponding to the cavity is 150-220℃; the extrusion pressure is 3-10MPa.

[0035] In the above scheme, in the final extrusion section corresponding to the spinneret, the melting temperature of the mixture of the two molten states is adjusted to 200-220℃, and the extrusion pressure is 3-10MPa.

[0036] In the above scheme, the shrinkage temperature of the thermo-shrinkage induced crack-resistant fiber is 30-100℃, the compressive strength is greater than 800MPa, the elastic modulus is greater than 10Gpa, the interface shrinkage stress with cement paste is greater than 30MPa, and the creep coefficient is less than 0.5.

[0037] Furthermore, the core of the thermo-shrinkage induced crack-resistant fiber has a diameter of 0.01–0.15 mm, a skin material thickness of 0.01–0.1 mm, and a length of 6–25 mm, and the thickness of the water-soluble modified polyvinyl alcohol layer is 0.01–0.02 mm.

[0038] In the above scheme, the particle size of the pre-wetted internal curing aggregate is 0-10 mm, and the apparent density is less than 1.35 g·cm³. -3 It has a water absorption rate greater than 10%, an open porosity greater than 30%, a compressive strength greater than 45.0 MPa, a cylindrical compressive strength greater than 6.0 MPa, and micro-fine interconnected pores with a size of 0.01 to 100 nm account for more than 50% of the total porosity.

[0039] In the above scheme, the preparation method of the internal curing aggregate includes the following steps:

[0040] 1) Weigh and mix the ingredients according to the formula (accurate to 0.01g). Each component and its weight percentage include: 40-50 parts phosphogypsum, 5-10 parts sodium hydroxide, 10-20 parts fly ash, 10-20 parts mineral powder, and 5-10 parts cement clinker.

[0041] 2) After the weighed raw materials are mixed by dry ball milling, they are passed through a 300-mesh sieve to obtain mixed powder. Then, water accounting for 10-15 wt% of the mixed powder is added, granulated and aged, dried, and then fired at 1200-1300℃ to obtain the internally cured lightweight aggregate. The fired lightweight aggregate is then screened to determine the particle size to be used.

[0042] The firing process described above is as follows: First, the temperature is raised to 890–910°C at a rate of 4–5°C / min, and then held at 190–210°C, 390–410°C, 590–610°C, and 790–810°C for 0.5–0.6 hours respectively. Then, the temperature is raised to the final firing temperature at a rate of 3–4°C / min (lower than the first step's heating rate) and held for 1.5–2.5 hours. Finally, the temperature is lowered to room temperature at a rate of 8–10°C / min.

[0043] Furthermore, in the high-strength marine mass concrete based on thermo-shrinkage induced crack-resistant fibers and internally cured aggregates, the components and their contents include: cement 250-450 kg / m³. 3 fly ash 50-150 kg / m³ 3 Mineral powder 50-150 kg / m³ 3Silica fume 0~150kg / m 3 Sand 300~1000kg / m 3 Crushed stone 800-1200 kg / m³ 3 Water 140-160 kg / m³ 3 Additive 4-10 kg / m³ 3 Shrinkage-induced crack-resistant fiber 0.5~50kg / m 3 Pre-wet curing aggregate: 50-800 kg / m³ 3 .

[0044] In the above scheme, the admixture is a polycarboxylate high-performance water-reducing agent with a water reduction rate of 20-30% and a shrinkage rate of no more than 100%.

[0045] Preferably, under severe chloride salt corrosion environments, the high-strength marine large-volume concrete can be further modified with hydrophilic micro-internal curing fibers, with a dosage of 0.1–5 kg / m³. 3 .

[0046] In the above scheme, the modified hydrophilic micro-internal curing fiber is obtained by soaking the hydrophilic micro-internal curing fiber in a concrete anti-erosion inhibitor and then drying it.

[0047] In the above scheme, the adsorption capacity of concrete anti-erosion inhibitor in the modified hydrophilic micro-internal curing fiber is 1-30 kg / m³. 3 .

[0048] In the above scheme, the hydrophilic micro-innervate protective fiber can be selected from submicron cellulose fiber or lignin fiber, etc., with a diameter of 100nm to 1.0μm and a length of 6 to 20mm.

[0049] In the above scheme, the concrete anti-erosion inhibitor is a type II concrete anti-erosion inhibitor, which contains hydrophobic groups that can react with Ca in the concrete pore solution. 2+ Complexes form water-insoluble crystalline products that clog capillary pores; the hydrophilic ends of the hydrophilic groups within the complex interact with the Ca in the pore solution. 2+ Complexation occurs, forming crystals insoluble in water and salt solutions. These crystals block capillary pores, resulting in a denser gel structure. The hydrophobic ends enhance the gel's hydrophobicity and inhibit chloride ion transport within the gel.

[0050] The above-mentioned method for preparing high-strength marine mass concrete based on thermo-shrinkage induced crack-resistant fibers and internally cured aggregates includes the following steps:

[0051] 1) Weigh each raw material according to the concrete mix proportion; concrete raw materials include cementitious materials, sand and gravel aggregates, internal curing aggregates, admixtures, thermal shrinkage-inducing crack-resistant fibers, and water;

[0052] 2) Soak the internal curing aggregate in water until it is saturated to obtain saturated pre-wetted internal curing aggregate. Add the pre-wetted internal curing aggregate, binder (cement, fly ash, mineral powder, silica fume), and sand and gravel aggregate (sand, crushed stone) to a concrete mixer and mix evenly. Then add water and admixtures and mix evenly. Finally, add thermo-shrinkage induced crack-resistant fibers evenly and mix evenly.

[0053] 3) After the obtained mixture is molded, vibrated and shaped, the surface is covered with a waterproof film for film curing. After the film is removed, the mold is removed and standard curing or heat curing is carried out to obtain the high-strength marine large-volume concrete.

[0054] In the above scheme, the standard temperature for standard maintenance is 20±2℃, and the standard relative humidity is above 95%.

[0055] In the above scheme, the heating and curing temperature is 40-90℃.

[0056] Furthermore, the heating and curing process employs hot water or steam curing, with a heating rate of 10–15°C / h, a constant temperature of 40–90°C, a curing time of 12–48h, and a cooling rate of 10–15°C / h.

[0057] The high-strength marine engineering mass concrete prepared according to the above scheme has a 28-day compressive strength of 60–100 MPa; a 28-day splitting tensile strength of 6–12 MPa; a 28-day shrinkage rate of less than 200 microstrain; a 28-day electrical flux of less than 500C; and a 28-day chloride ion diffusion coefficient of less than 3.0*10. -12 m 2 / s, the concrete crack resistance grade reaches level V.

[0058] The principle of this invention is as follows:

[0059] This invention introduces both temperature-shrinkage-induced crack-resistant fibers with shrinkage compensation function and highly fine interconnected pore-forming aggregates into high-strength marine mass concrete with a strength of C50 or higher. This synergistically regulates the microstructure and improves the crack resistance and chloride erosion resistance of the concrete, effectively solving the technical challenges of crack control and chloride erosion resistance in high-strength marine mass concrete.

[0060] 1) Synergistically improve the crack resistance of concrete; utilize the thermally activated shrinkage effect of high-modulus, shrinkage-inducing crack-resistant fibers and their bonding coupling effect with the cementitious paste interface to apply three-dimensional micro-prestress to concrete, thereby improving the tensile strength and toughness of concrete, and simultaneously enhancing the mechanical properties of the arch shell structure at the interface between the internally cured aggregate and the cementitious paste; combined with the in-situ shrinkage compensation performance of the expansion agent, it can effectively improve the fiber-reinforced toughening and crack resistance of large-volume concrete; utilize the internally cured aggregate to inhibit concrete shrinkage, reducing the loss of micro-prestress caused by concrete shrinkage and creep; the internally cured aggregate and cementitious paste interface form an arch shell structure to disperse internal stress; the thermal insulation effect of porous internally cured aggregate can reduce the temperature difference between the inner and outer surfaces of concrete, further improving crack resistance, etc.

[0061] 2) Synergistically improve the chloride salt erosion resistance of concrete: The three-dimensional micro prestress applied by thermo-shrinkage induced crack-resistant fibers improves the original defects of cementitious grout; the interface between internally cured aggregate and cementitious grout forms an arch shell structure, improving its interface microstructure; at the same time, the three-dimensional micro prestress and internal curing synergistically improve the microstructure of the interface between fibers, concrete aggregates and internally cured aggregates and cementitious grout.

[0062] Furthermore, to address the severe chloride-salt corrosion environment, hydrophilic micro-internal curing fibers that adsorb concrete anti-erosion inhibitors are introduced. These introduced hydrophilic micro-internal curing fibers (submicron-level cellulose fibers) have an internal curing effect on high-strength marine large-volume concrete slurry, regulating its microstructure to disperse and transfer internal stress, inducing and regulating the microstructure of the slurry, and toughening and improving the crack resistance of high-strength marine large-volume concrete at the microscale. When mixed with surface-modified thermo-shrinkage-induced crack-resistant fibers, they can synergistically further improve the crack resistance of high-strength marine large-volume concrete at multiple scales from "micro-fine-macro". The introduced concrete anti-erosion inhibitors contain both hydrophilic and hydrophobic groups; the hydrophilic ends interact with the Ca in the pore solution. 2+ Complexation forms crystals insoluble in water and salt solutions, blocking capillary pores and making the cement paste structure dense, reducing concrete drying shrinkage. On the other hand, spherical ultrafine interconnected pore high-strength internally cured aggregates and hydrophilic micro-internal curing fibers can offset the adverse effects of concrete anti-erosion inhibitors on the self-shrinkage of high-strength large-volume concrete. The hydrophobic end enhances the hydrophobicity of the paste and inhibits the transport of corrosive ions in the cement paste, thereby improving the chloride erosion resistance and crack resistance of high-strength marine large-volume concrete.

[0063] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0064] 1) This invention introduces thermo-shrinkage induced crack-resistant fibers and highly fine interconnected pore-forming aggregates into high-strength marine large-volume concrete with a strength of C50 or higher. This synergistically regulates the microstructure and improves the crack resistance and chloride ion corrosion resistance of the concrete, effectively solving the technical challenges of crack control and chloride ion corrosion resistance in high-strength marine large-volume concrete. In particular, the further introduction of hydrophilic micro-internal curing fibers (submicron-grade cellulose fibers and concrete corrosion inhibitors) can further effectively improve the crack resistance and chloride ion corrosion resistance of high-strength marine large-volume concrete, making it suitable for harsh chloride ion corrosion environments.

[0065] 2) This invention utilizes the multi-scale internal curing effect of internal curing aggregates and hydrophilic micro internal curing fibers, combined with the three-dimensional micro pre-stressing and toughening effect of thermo-shrinkage induced crack-resistant fibers, which can comprehensively reduce the amount of cementitious materials and cement used in high-strength, high-volume concrete, while significantly improving its crack resistance and chloride salt erosion resistance.

[0066] 3) The preparation method involved in this invention is relatively simple, and the resulting high-strength, high-volume concrete can effectively take into account good mechanical properties, crack resistance and chloride salt corrosion resistance, and is suitable for widespread application. Detailed Implementation

[0067] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0068] In the following examples, the main raw material of the core material used is polyester, which is provided by Shanghai Fengmeite Plastics Co., Ltd. Its molecular weight is 25,000, the maximum shrinkage rate is 15%, the response temperature can be designed (40~100℃), the tensile strength is 400MPa, and the elastic modulus is 12.0GPa.

[0069] The main raw material of the leather is polyoxymethylene, provided by Yunnan Yuntianhua Group Co., Ltd., with a molecular weight of 28,000, a shrinkage rate of 2%, a designable response temperature (40-100℃), a tensile strength of 800MPa, and an elastic modulus of 20.5GP.

[0070] The expanding component used in the liquid expanding agent is a mixture of anhydrous aluminum sulfate and gypsum in a 1:1 mass ratio; the shrinkage reducing component is amphiphilic diethylene glycol monobutyl ether provided by Jiangsu Bote New Materials Co., Ltd.; and the stabilizing and dispersing component is cationic polyacrylamide provided by Henan Hongchang Chemical Co., Ltd., with a molecular weight of 9.8 million.

[0071] The cement used was P·O42.5 cement supplied by Huaxin Cement Co., Ltd.; the fly ash was supplied by Wuhan Yangluo Power Plant, with a water requirement ratio of less than 100% and a loss on ignition of less than 5%; the mineral powder used was S95 grade mineral powder supplied by Wuxin New Building Materials, with a specific surface area of ​​420 m².2 / kg; the sand used is manufactured sand provided by a stone crushing plant in Wuhan, with a fineness modulus of 3.2, an MB value of 1.2, and a stone powder content of 7.0%; the crushed stone is 5-20mm continuously graded limestone crushed stone provided by a stone crushing plant in Wuhan; the admixture used is polycarboxylate high-performance water-reducing agent provided by Wuhan Subo New Building Materials Co., Ltd., with a water reduction rate of 28% and a 28-day shrinkage rate of 105%.

[0072] The submicron-sized cellulose fibers used were provided by Changzhou Bochao Engineering Materials Co., Ltd., with an equivalent diameter of 10μm, a tensile strength of 800MPa, and an average length of 6mm; the concrete anti-erosion inhibitor was a Type II anti-erosion inhibitor provided by Jiangsu Bote New Materials Co., Ltd. -TIA concrete erosion inhibitor).

[0073] The preparation steps of the internal curing aggregate are as follows: Weigh and mix the following ingredients according to the formula: 50% phosphogypsum, 10% sodium hydroxide, 15% fly ash, 15% mineral powder, and 10% cement clinker (accurate to 0.01g). After dry ball milling for 24 hours, pass the mixture through a 300-mesh sieve to obtain a mixed powder. Then, add 10-15 wt% deionized water for granulation and aging for 48 hours. Next, prepare cubic green bodies with dimensions of 5mm × 5mm × 5mm using a semi-dry pressing process, and prepare spherical green bodies using a fully automatic pelletizing machine. After drying at 100-105℃ for 48 hours, then... Cubic and spherical preforms were placed in a resistance muffle furnace and fired at 1250℃ to prepare lightweight aggregate. The specific firing steps were as follows: first, the aggregate was heated to 900℃ at a rate of 5℃ / min and held for 0.6h, followed by holding at 200℃, 400℃, 600℃, and 800℃ for 0.6h each; then, the temperature was increased to the firing temperature at a rate of 3℃ / min and held for 2h; finally, the aggregate was cooled to room temperature at a rate of 8℃ / min. The fired lightweight aggregate was then sieved to determine the usable particle size (0–2.36mm). The apparent density was measured to be 1.32 g / cm³. 3 It has a water absorption rate of 18.0%, an open porosity of 38.5%, a compressive strength of 49.0 MPa, a cylindrical compressive strength of 6.5 MPa, and micro-interconnected pores with a size of 0.01–100 nm account for 55% of the total porosity.

[0074] Examples 1-2

[0075] A high-strength, corrosion-resistant, large-volume marine concrete, the preparation method of which includes the following steps:

[0076] 1) Raw material weighing, the raw materials and their usage are as follows: cement 315kg / m³ 3 fly ash 95kg / m³ 3 Mineral powder 60kg / m 3 Silica fume 20kg / m 3350kg / m³ of sand 3 1098 kg / m³ of crushed stone 3 150kg / m³ of water 3 Additive 5.5 kg / m 3 2.5kg / m² thermo-shrinkage induced crack-resistant fiber 3 Pre-wet curing aggregate 200kg / m³ 3 ;

[0077] The preparation steps of the thermo-shrinkage induced crack-resistant fiber include:

[0078] The heat-shrinkable induced crack-resistant fiber is produced using two extruders. Polyester-based heat-shrinkable core material mixture and polyoxymethylene-based heat-shrinkable sheath material mixture are extruded into a die with two cavities. The heat-shrinkable sheath material mixture enters the cavity corresponding to the sheath material, and the heat-shrinkable core material mixture enters the cavity corresponding to the core material. The materials in the two cavities converge at the position of the extruder spinneret. The spinneret has an inner ring and an outer ring. The inner ring of the spinneret connects to the cavity of the core material, and the outer ring connects to the cavity of the sheath material. The two molten materials are extruded through the spinneret and bonded together in the air. The fibers are then cooled in a cold water tank and drawn into fibers in hot water at 90–100°C to form a composite fiber with a core-sheath structure. The average diameter of the core fiber 1 is 0.15 mm, and the thickness of the sheath fiber 2 is 0.05–0.1 mm.

[0079] The polyoxymethylene-based heat-shrinkable core material mixture consists of 97.5 wt% polyoxymethylene, 1.5 wt% maleic anhydride graft compatibilizer (provided by Dongguan Shenghao Plastic Raw Materials Co., Ltd., model PP-G-MAH), and 1 wt% phthalate plasticizer; the extrusion pressure is 8 MPa, and the melt temperature is maintained at 250℃. The polyester-based heat-shrinkable core material mixture consists of 98 wt% polyester and 2 wt% stiffening nucleating agent (composed of dibenzyl sorbitol and sodium benzoate in a 1:1 mass ratio); the extrusion pressure is 6 MPa, and the melt temperature is maintained at 210℃. In the final extrusion section corresponding to the spinneret, the extrusion temperature of the two molten materials is adjusted to 220℃, and the extrusion pressure is 7 MPa. The two materials are bonded together in the air, cooled by a cold water tank, and then drawn into fibers in hot water at 90-100℃ to form a composite fiber with a core-sheath structure. The average diameter of the core fiber 1 is 0.15 mm, and the thickness of the sheath fiber 2 is 0.05-0.1 mm.

[0080] The obtained composite fiber with a core-sheath structure was added to a coating bath. The liquid in the coating bath was a commercially available modified KH570 silane coupling agent solution (the solvent used was an alcohol-water solution with an ethanol concentration of 5 vol% and a silane coupling agent concentration of 10 wt%). After drying (100-105℃, 24-48h), surface indentation treatment was performed.

[0081] Simultaneously, the obtained indented composite fiber was added to a modified polyvinyl alcohol solution with added expansion components for coating modification (time was 24h). The concentration of the modified polyvinyl alcohol solution used was 5%, which was obtained by uniformly mixing polyvinyl alcohol solution and liquid expansion agent at a mass ratio of 7:3. After coating modification, the fiber was dried for 48h to obtain the temperature shrinkage induced crack-resistant fiber. Its average diameter was 0.2mm and its average length was 12mm.

[0082] After the water-soluble film on the surface of the obtained thermo-shrinkage induced crack-resistant fiber dissolves, the expansion components can undergo an expansion reaction with the concrete. The free expansion rate of the expansion agent in a closed environment is 0.02%. The bond strength between the core fiber and the concrete is greater than 20 MPa. The shrinkage rate of the obtained composite core fiber is 0.5-12%, the response temperature is 30-100℃, the tensile strength is 700 MPa, and the elastic modulus is 15.0 GPa.

[0083] 2) Soak the internal curing aggregate in water until it is saturated to obtain saturated pre-wetted internal curing aggregate. Add the saturated pre-wetted internal curing aggregate, cementitious materials (cement, fly ash, mineral powder), and aggregates (sand, crushed stone) to a concrete mixer and mix evenly. Then add water and water-reducing agent and mix evenly. Finally, add thermo-shrinkage induced crack-resistant fiber evenly and mix evenly to obtain the mixture.

[0084] 3) After the obtained mixture is molded, vibrated and shaped, the surface is covered with a waterproof film for film curing. After the film is removed, hot water curing (Example 1) or standard curing (Example 2) is performed to obtain the high-strength marine large-volume concrete.

[0085] The standard maintenance conditions are: 20℃±1℃, relative humidity greater than 90%, and maintenance until 28 days of age;

[0086] The hot water curing conditions are as follows: After the concrete is poured and formed, it is cured in a standard curing environment for 24 hours, then placed in a water bath and heated to 90℃ at a rate of 10℃ / h for 12 hours. Then it is cooled to 20℃ at a rate of 20℃ / h, and finally cured in a standard curing environment for 28 days.

[0087] Examples 3-4

[0088] A high-strength, corrosion-resistant, large-volume marine concrete is prepared using a method largely the same as in Example 1, except that the formulation conditions used are: cement 315 kg / m³. 3 fly ash 95kg / m³ 3 Mineral powder 60kg / m 3 Silica fume 20kg / m 3 350kg / m³ of sand 3 1098 kg / m³ of crushed stone 3 150kg / m³ of water3 Additive 5.5 kg / m 3 2.5kg / m² thermo-shrinkage induced crack-resistant fiber 3 Pre-wet curing aggregate 200kg / m³ 3 Modified hydrophilic micro-innervated fiber 0.5kg / m 3 Example 3 uses hot water curing for concrete, while Example 4 uses standard curing.

[0089] The preparation method of the modified hydrophilic micro-internal curing fiber includes: immersing dried submicron cellulose fibers in a concrete anti-erosion inhibitor for 48 hours, then removing and air-drying them naturally until they are saturated and surface-dry (no visible anti-erosion inhibitor solution is visible on the fiber surface); the adsorption capacity of the concrete anti-erosion inhibitor in the obtained modified hydrophilic micro-internal curing fiber is 30 kg / m³. 3 .

[0090] Comparative Example 1

[0091] A high-strength marine engineering large-volume concrete is prepared using a method largely the same as in Example 1, except that the formulation conditions used are: cement 315 kg / m³. 3 fly ash 95kg / m³ 3 Mineral powder 60kg / m 3 Silica fume 20kg / m 3 702 kg / m³ of sand 3 1098 kg / m³ of crushed stone 3 150kg / m³ of water 3 Additive 5.5 kg / m 3 .

[0092] Comparative Example 2

[0093] A high-strength marine engineering large-volume concrete is prepared using a method largely the same as in Example 1, except that the formulation conditions used are: cement 315 kg / m³. 3 fly ash 95kg / m³ 3 Mineral powder 60kg / m 3 Silica fume 20kg / m 3 350kg / m³ of sand 3 1098 kg / m³ of crushed stone 3 150kg / m³ of water 3 Additive 5.5 kg / m 3 Ordinary polypropylene fiber (non-heat shrinkable) 0.9kg / m 3 Pre-wet curing aggregate 200kg / m³ 3The non-heat-shrinkable ordinary polypropylene fiber (polypropylene molecular weight of 8800) used was provided by Shandong Xinfuman Chemical Technology Co., Ltd., with an equivalent diameter of 50μm, tensile strength of 400MPa, elastic modulus of 3GPa, and average fiber length of 12mm.

[0094] Comparative Example 3

[0095] A high-strength marine engineering large-volume concrete is prepared using a method largely the same as in Example 1, except that the formulation conditions used are: cement 315 kg / m³. 3 fly ash 95kg / m³ 3 Mineral powder 60kg / m 3 Silica fume 20kg / m 3 350kg / m³ of sand 3 1098 kg / m³ of crushed stone 3 150kg / m³ of water 3 Additive 5.5 kg / m 3 Ordinary heat-shrinkable polyester fiber 2.5kg / m 3 Pre-wet curing aggregate 200kg / m³ 3 The ordinary heat-shrinkable polyester fiber used was provided by Sinopec Yizheng Chemical Fiber Co., Ltd., with a density of 920 kg / m³. 3 Tensile breaking strength is 80 MPa, initial shrinkage temperature is 80℃, shrinkage rate at 80℃ is 1%, and shrinkage rate in boiling water is 8%.

[0096] Comparative Example 4

[0097] A high-strength marine engineering large-volume concrete is prepared using a method largely the same as in Example 1, except that the formulation conditions used are: cement 315 kg / m³. 3 fly ash 95kg / m³ 3 Mineral powder 60kg / m 3 Silica fume 20kg / m 3 350kg / m³ of sand 3 1098 kg / m³ of crushed stone 3 Water 135kg / m 3 Additive 5.5 kg / m 3 Ordinary heat-shrinkable polyester fiber (same as comparative example 3) 2.5 kg / m 3 Pre-wet curing aggregate 200kg / m³ 3 Add 20 kg / m³ of concrete anti-erosion inhibitor 3 .

[0098] Comparative Example 5

[0099] A high-strength, corrosion-resistant, large-volume marine concrete is prepared using a method largely the same as in Example 3, except that the formulation conditions used are: cement 315 kg / m³. 3 fly ash 95kg / m³ 3 Mineral powder 60kg / m 3 Silica fume 20kg / m 3 Sand 850kg / m 3 1098 kg / m³ of crushed stone 3 150kg / m³ of water 3 Additive 5.5 kg / m 3 2.5kg / m² thermo-shrinkage induced crack-resistant fiber 3 Modified hydrophilic micro-innervated fiber 0.5kg / m 3 .

[0100] Comparative Example 6

[0101] A high-strength, corrosion-resistant, large-volume marine concrete is prepared using a method largely the same as in Example 3, except that the formulation conditions used are: cement 315 kg / m³. 3 fly ash 95kg / m³ 3 Mineral powder 60kg / m 3 Silica fume 20kg / m 3 350kg / m³ of sand 3 1098 kg / m³ of crushed stone 3 150kg / m³ of water 3 Additive 5.5 kg / m 3 Pre-wet curing aggregate 200kg / m³ 3 Modified hydrophilic micro-innervated fiber 0.5kg / m 3 .

[0102] Comparative Example 7

[0103] A high-strength, corrosion-resistant, large-volume marine concrete is prepared using a method largely the same as in Example 1, except that the formulation conditions used are: cement 315 kg / m³. 3 fly ash 95kg / m³ 3 Mineral powder 60kg / m 3 Silica fume 20kg / m 3 Sand 850kg / m 3 1098 kg / m³ of crushed stone 3 150kg / m³ of water 3 Additive 5.5 kg / m 3 2.5kg / m² thermo-shrinkage induced crack-resistant fiber 3 .

[0104] Comparative Example 8

[0105] A high-strength marine engineering large-volume concrete is prepared using a method largely the same as in Example 1, except that the formulation conditions used are: cement 315 kg / m³. 3 fly ash 95kg / m³ 3 Mineral powder 60kg / m 3 Silica fume 20kg / m 3 350kg / m³ of sand 3 1098 kg / m³ of crushed stone 3 150kg / m³ of water 3 Additive 5.5 kg / m 3 Heat-shrinkable composite fiber 2.5kg / m 3 Pre-wet curing aggregate 200kg / m³ 3 Add 20 kg / m³ of concrete anti-erosion inhibitor 3 External expansion agent 35kg / m 3 The heat-shrinkable composite fiber is basically the same as that in Example 1, except that it is not coated with a modified polyvinyl alcohol solution containing an expansion component. The expansion agent is a type II expansion agent provided by Wuhan Sanyuan Special Materials Co., Ltd.

[0106] The performance test results of C55 high-strength, high-volume concrete obtained in Examples 1-6 and Comparative Examples 1-8 are shown in Table 1.

[0107] Table 1. Performance test results of C55 high-strength, high-volume concrete obtained in Examples 1-4 and Comparative Examples 1-8.

[0108]

[0109] In Table 1, the working performance of each embodiment and comparative example is basically the same, and will not be described in detail here.

[0110] The test results above show that under thermally activated curing, the compressive strength and splitting tensile strength of the aggregate with thermal shrinkage-induced crack-resistant fibers and highly micro-fine interconnected pores described in this invention are higher, and the volume stability is better, which can synergistically improve its crack resistance and chloride erosion resistance. The addition of submicron-sized cellulose fibers that adsorb corrosion ion inhibitors can further enhance the chloride erosion resistance and crack resistance of concrete.

[0111] The addition of thermally expanding and contracting polypropylene fibers, commonly used to improve the crack resistance of concrete, can only improve the splitting tensile strength of concrete to a limited extent, with a crack resistance grade of L-III. Moreover, its dispersibility is generally poor, and it cannot improve the concrete's resistance to chloride salt corrosion. The use of ordinary thermally expanding and contracting polypropylene fibers mixed with internal curing aggregates can reduce concrete shrinkage to a certain extent and slightly improve the splitting tensile strength of concrete, with a crack resistance grade of L-III. However, it cannot improve the concrete's resistance to chloride salt corrosion.

[0112] As can be further seen from Comparative Examples 5 and 7, compared with the scheme of incorporating ordinary heat-shrinkable polyester fibers or thermo-shrinkable crack-resistant fibers without expansion components and externally adding commercially available expansion agents, the thermo-shrinkable crack-resistant fibers described in this invention have better volume stability (with micro-expansion properties) and can significantly improve crack resistance after being incorporated into concrete.

[0113] Incorporating heat-shrinkable polyester fibers can improve the splitting tensile strength of concrete, achieving a crack resistance grade of L-III, but its dispersibility is generally poor, and it does not improve the concrete's resistance to chloride erosion. Mixing heat-shrinkable polyester fibers with pre-wetted internal curing aggregates can reduce concrete shrinkage to some extent and slightly improve the splitting tensile strength, achieving a crack resistance grade of L-IV, but it does not improve the concrete's resistance to chloride erosion. Mixing heat-shrinkable polyester fibers, internal curing aggregates, and concrete anti-erosion inhibitors can reduce concrete shrinkage to some extent and improve the concrete's resistance to chloride erosion, slightly improving the splitting tensile strength, but the crack resistance grade remains at L-IV, and further improvement in crack resistance is needed. However, incorporating the temperature-shrinkage-induced crack-resistant fibers and highly micro-fine interconnected internal curing aggregates described in this invention results in higher compressive strength and splitting tensile strength, and better volume stability (28-day shrinkage less than 200*10). -6 This can synergistically improve its crack resistance (crack resistance level reaches LV) and chloride salt corrosion resistance (28-day electrical flux less than 700C). Incorporating submicron-sized cellulose fibers, which adsorb corrosion ion inhibitors, can further enhance the chloride salt corrosion resistance and crack resistance of concrete.

[0114] The above embodiments are merely illustrative examples and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations; therefore, any obvious variations or modifications derived therefrom remain within the scope of protection of this invention.

Claims

1. A high-strength, corrosion-resistant, large-volume marine concrete, characterized in that, The components and their contents include: cement 250~450kg / m³ 3 fly ash 50~150kg / m³ 3 Mineral powder 50~150kg / m 3 Silica fume 0~150kg / m 3 Sand 500~1000kg / m 3 Crushed stone 800~1200kg / m 3 Water 140~160kg / m 3 Admixture 4~10kg / m 3 Temperature shrinkage induced crack-resistant fiber 0.5~50kg / m 3 Pre-wet curing aggregate: 50~800 kg / m³ 3 The shrinkage rate of the heat-shrinkable induced crack-resistant fiber is ≥0.5%, and its heat-induced shrinkage temperature is 30~100℃. The heat-shrinkable induced crack-resistant fiber comprises a heat-shrinkable composite fiber consisting of a heat-shrinkable core material and an outer heat-shrinkable sheath material, and a water-soluble modified polyvinyl alcohol layer further coated on the surface of the heat-shrinkable composite fiber; wherein the water-soluble modified polyvinyl alcohol layer contains polyvinyl alcohol and an expansion component; the main raw material of the heat-shrinkable core material is one or more of polyester, polypropylene, and polyamide, wherein the molecular weight of polyester is 20,000 to 30,000, the molecular weight of polypropylene is 6,000 to 8,000, and the molecular weight of polyamide is 20,000 to 30,000; the shrinkage rate of the heat-shrinkable core material is 5% to 15%, the response temperature is 40 to 100°C, and the tensile strength is 300 to 500 kcal / kg. The heat-shrinkable material has a tensile strength of 500-1200 MPa and an elastic modulus of 7-35 GPa; a shrinkage rate of 0.5-2% and a response temperature of 30-100℃; the main raw materials of the heat-shrinkable material are polyvinyl alcohol, ultra-high modulus polyethylene, and polyoxymethylene, wherein the molecular weight of polyvinyl alcohol is 170,000-220,000, the molecular weight of ultra-high modulus polyethylene is 1,000,000-2,000,000, and the molecular weight of polyoxymethylene is 20,000-30,000; the heat-shrinkable core material also includes a stiffening nucleating agent; the heat-shrinkable material also includes a plasticizer and a compatibilizer. The preparation method of the internal curing aggregate includes the following steps: 1) Weigh and mix the raw materials according to the formula composition. The components and their weight percentages are as follows: 40-50 parts of phosphogypsum, 5-10 parts of sodium hydroxide, 10-20 parts of fly ash, 10-20 parts of mineral powder, and 5-10 parts of cement clinker; 2) After the weighed raw materials are mixed by dry ball milling, the mixture is passed through a 300-mesh sieve to obtain a mixed powder. Then, water accounting for 10-15 wt% of the mixed powder is added, and the mixture is granulated, aged, dried, and then fired at 1200-1300℃ to obtain the internal curing aggregate. The fired internal curing aggregate is then screened to determine the particle size for use.

2. The high-strength, corrosion-resistant, large-volume marine concrete according to claim 1, characterized in that, The thermo-shrinkable crack-resistant fiber is obtained by surface modification of heat-shrinkable composite fiber with silane coupling agent solution, surface indentation after drying, coating modification with modified polyvinyl alcohol solution containing expansion component, and drying after removal. The modified polyvinyl alcohol solution is composed of a polyvinyl alcohol solution and a liquid expanding agent.

3. The high-strength, corrosion-resistant, large-volume marine concrete according to claim 1, characterized in that, The pre-wetted internal curing aggregate has a particle size of 0-10 mm and an apparent density of less than 1.35 g·cm³. -3 It has a water absorption rate greater than 10%, an open porosity greater than 30%, a compressive strength greater than 45.0 MPa, a cylindrical compressive strength greater than 6.0 MPa, and a porosity of more than 50% of the total porosity consisting of micro-fine interconnected pores with a size of 0.01~100 nm.

4. The high-strength, corrosion-resistant, large-volume marine concrete according to claim 1, characterized in that, In the high-strength corrosion-resistant marine large-volume concrete, modified hydrophilic micro-internal curing fibers are further introduced; the modified hydrophilic micro-internal curing fibers are obtained by soaking hydrophilic micro-internal curing fibers in concrete anti-erosion inhibitors and then drying them.

5. The high-strength, corrosion-resistant, large-volume marine concrete according to claim 4, characterized in that, The hydrophilic micro-innervate fiber is a submicron-grade cellulose fiber or lignin fiber.

6. The method for preparing high-strength, corrosion-resistant, large-volume marine concrete according to any one of claims 1 to 5, characterized in that, Includes the following steps: 1) Weigh each raw material according to the concrete mix proportion; Concrete raw materials include cement, fly ash, mineral powder, silica fume, sand, crushed stone, internal curing aggregate, admixtures, thermal shrinkage induced crack-resistant fibers, and water; 2) The internal curing aggregate is saturated with water to obtain pre-wet internal curing aggregate; the pre-wet internal curing aggregate, cement, fly ash, mineral powder, silica fume, sand and crushed stone are premixed evenly, then water and admixtures are added and mixed evenly, then thermal shrinkage-induced crack-resistant fibers are added and mixed evenly. 3) After the obtained mixture is molded, vibrated and shaped, it is cured with a film. After demolding, it is cured with standard curing or heat curing to obtain the high-strength corrosion-resistant marine large-volume concrete.

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