Ultra-high performance concrete gradient composite structure and preparation method thereof

Abstract

This application relates to a super high performance concrete gradient composite structure and a preparation method thereof, which sequentially include a first super high performance concrete layer, a connection layer, and a second super high performance concrete layer. Among them, the first super high performance concrete layer is a first super high performance concrete curing layer doped with steel fibers; the second super high performance concrete layer is a second super high performance concrete curing layer doped with coarse aggregates and polymer fibers; the connection layer, by mass, includes: 20-100 parts of steel fiber mesh, 5-30 parts of diatomite, 5-30 parts of gypsum, and 5-30 parts of silica sol. The super high performance concrete gradient composite structure prepared by this application not only gives full play to the performance advantages of the materials of each gradient layer, but also has good overall stability. When used in airport pavements, it not only has excellent service performance and durability, but also can greatly reduce the thickness of the pavement slab and the maintenance cost, achieving the coordinated improvement of long-term economic efficiency and social benefits.

Description

Technical Field

[0001] This application relates to the technical field of building materials, and particularly relates to an ultra-high performance concrete gradient composite structure and a preparation method thereof. Background Art

[0002] Since cement concrete pavements have the characteristics of high strength, good wear resistance and durability, and low maintenance cost compared with asphalt concrete pavements, more than 80% of civil and military airports in China use cement concrete pavements. However, with the rapid increase in the number of large / ultra-large aircraft and the passenger and cargo throughput at Chinese airports, the load and damage caused by the takeoff and landing of high-frequency and heavy-load aircraft to airport pavements are becoming increasingly severe. The service stability and lifespan of airport cement concrete pavements have both significantly decreased and shortened. The modern aviation industry has put forward higher performance requirements for airport cement concrete pavements.

[0003] Ultra-high performance concrete has ultra-high mechanical properties and durability, and can well meet the new requirements for the performance improvement of cement concrete pavements in modern airports. However, directly using ordinary ultra-high performance concrete to build airport pavements still faces many problems: 1) The self-shrinkage of ultra-high performance concrete is relatively large, and shrinkage micro-cracks are easily formed. Under the repeated impact of aircraft takeoff and landing, the crack propagation and penetration will be accelerated, resulting in structural damage; 2) The steel fibers in ultra-high performance concrete are easily exposed during the abrasion process of the aircraft wheels on the pavement surface, thereby causing damage to the aircraft tires and leading to potential safety hazards; 3) The material cost of ultra-high performance concrete is high, about 10 times that of ordinary concrete. The high construction cost greatly restricts its popularization and application in the field of airport pavements.

[0004] Based on this, developing an ultra-high performance concrete structure applicable to airport pavements, with impact resistance, high strength, and low cost, has important technical innovation and practical value. Summary of the Invention

[0005] The embodiments of this application provide an ultra-high performance concrete gradient composite structure and a preparation method thereof to solve the problems of low impact resistance, high cost, short service life, and short durability of ultra-high performance concrete in the related art.

[0006] The technical solutions provided by this application are specifically as follows:

[0007] In the first aspect, this application provides an ultra-high performance concrete gradient composite structure, which sequentially includes a first ultra-high performance concrete layer, a connection layer, and a second ultra-high performance concrete layer, wherein,

[0008] The first ultra-high performance concrete layer is a cured layer of first ultra-high performance concrete doped with steel fibers;

[0009] The second ultra-high performance concrete layer is a second ultra-high performance concrete curing layer doped with coarse aggregate and polymer fiber;

[0010] The connecting layer, by mass, comprises: 20-100 parts of steel fiber mesh, 5-30 parts of diatomite, 5-30 parts of gypsum, and 5-30 parts of silica sol.

[0011] In some embodiments, the cross-section of the connecting layer is in a W-shaped serrated form;

[0012] And / or, the surface of the second ultra-high performance concrete layer is provided with a pressed groove.

[0013] In some embodiments, the first ultra-high performance concrete, by mass, comprises:

[0014] 550-1000 parts of portland cement, 100-600 parts of mineral admixture, 500-1500 parts of sand aggregate, 2-10 parts of internal curing agent, 10-50 parts of expansive agent, 5-30 parts of shrinkage reducing agent, 10-50 parts of water reducing agent, 80-400 parts of steel fiber, and 160-220 parts of water.

[0015] In some embodiments, the second ultra-high performance concrete, by mass, comprises:

[0016] 550-1000 parts of portland cement, 100-600 parts of mineral admixture, 400-1000 parts of sand aggregate, 300-900 parts of coarse aggregate, 2-10 parts of internal curing agent, 10-50 parts of expansive agent, 5-30 parts of shrinkage reducing agent, 10-50 parts of water reducing agent, 20-80 parts of polymer fiber, 2-10 parts of modifier, and 160-220 parts of water.

[0017] Second, the present application also provides a preparation method of the above ultra-high performance concrete gradient composite structure, comprising the following steps:

[0018] Pour the first ultra-high performance concrete to form a first ultra-high performance concrete layer;

[0019] Mix diatomite and gypsum evenly, add water and stir to obtain a composite gypsum slurry;

[0020] Spray silica sol onto the surface of the steel fiber mesh to obtain a modified steel fiber mesh;

[0021] Spray the composite gypsum slurry onto the surface of the first ultra-high performance concrete layer, and then lay the modified steel fiber mesh onto the surface of the composite gypsum slurry to form a connecting layer;

[0022] Pour the second ultra-high performance concrete onto the surface of the connecting layer to form a second ultra-high performance concrete layer.

[0023] In some embodiments, the preparation method further includes the following steps for preparing the first ultra-high performance concrete:

[0024] Mix the expansive agent, shrinkage reducing agent and part of the water evenly, then add the internal curing agent, mix well, seal and stand still to obtain the standby material of the internal curing agent;

[0025] Mix the portland cement, mineral admixture, sand aggregate, water reducing agent and the remaining water until fluidized, and successively add the standby material of the internal curing agent and steel fibers, and stir to obtain the first ultra-high performance concrete.

[0026] In some embodiments, the preparation method further includes the following steps for preparing the second ultra-high performance concrete:

[0027] Mix the modifier, part of the mineral admixture, part of the portland cement and part of the water evenly to obtain a modified slurry;

[0028] Roll and imprint the modified slurry onto the surface of the polymer fiber to obtain a modified polymer fiber;

[0029] Mix the expansive agent, shrinkage reducing agent and part of the water evenly, then add the internal curing agent, mix well, seal and stand still to obtain the standby material of the internal curing agent;

[0030] Mix the remaining portland cement, remaining mineral admixture, coarse aggregate, sand aggregate, water reducing agent and the remaining water until fluidized, and successively add the standby material of the internal curing agent and the modified polymer fiber, and stir to obtain the second ultra-high performance concrete.

[0031] In some embodiments, before "pouring the second ultra-high performance concrete on the surface of the connection layer", it further includes:

[0032] Press the surface of the connection layer into a W-shaped serrated shape.

[0033] In some embodiments, after "pouring the second ultra-high performance concrete on the surface of the connection layer", it further includes:

[0034] Groove the surface of the second ultra-high performance concrete layer.

[0035] In some embodiments, the mass ratio of the total mass of diatomite and gypsum plaster to the mass of water in the composite gypsum slurry is (1 to 1.5):1;

[0036] And / or, the water-binder ratio of the modified slurry is 0.3 to 0.6.

[0037] The beneficial effects brought by the technical solution provided by this application include:

[0038] 1. The first ultra-high performance concrete layer doped with steel fibers provides good bearing capacity, anti-foundation deformation ability, fatigue resistance and durability for the pavement structure;

[0039] 2. The second ultra-high performance concrete layer is doped with coarse aggregates and polymer fibers. On the one hand, the coarse aggregates reduce the production cost. On the other hand, their high elastic modulus and high constrained deformation ability can significantly improve the impact abrasion resistance and crack resistance of the second ultra-high performance concrete layer. While enhancing the impact toughness of the ultra-high performance concrete, the high-strength polymer fibers can greatly reduce the damage of fiber erosion to the structure and the damage of fibers to the wheels, and reduce the material cost, providing good impact toughness, wear resistance, crack resistance, durability, economy and safety for the pavement structure.

[0040] 3. The steel fiber mesh increases the tensile strength of the interface between the connection layer and the ultra-high performance concrete on both sides through the interlocking effect, making the gradient structure have stronger integrity and stability. Silica sol is used for the modification of the steel fiber mesh to increase the bite and friction at the interface and improve the bonding strength between the steel fiber mesh and the ultra-high performance concrete matrix. Gypsum can delay the hydration of cement and thus delay the formation of the false set layer on the surface of the ultra-high performance concrete, preventing the formation of cold joints at the interface between the connection layer and the ultra-high performance concrete on both sides. Diatomite can improve the timeliness of the gypsum slurry and promote the secondary hydration of the interface, improving the interface bonding strength.

[0041] The design of the connection layer in this application effectively composes ultra-high performance concrete layers with different functions into a stable structure. While giving full play to the material performance advantages of each gradient layer, the overall stability is good. When used in airport pavements, it not only has excellent service performance and durability, but also can greatly reduce the thickness of the pavement slab and the maintenance cost, achieving the coordinated improvement of long-term economic efficiency and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0043] Figure 1 It is a schematic structural diagram of the ultra-high performance concrete gradient composite structure provided in Embodiment 1 of the present application;

[0044] Figure 2 It is a diagram of the early-age autogenous shrinkage change of the ultra-high performance concrete gradient composite structure provided in Embodiment 1 of the present application and Comparative Examples 2-3;

[0045] Figure 3 It is a tensile stress-strain curve diagram of the ultra-high performance concrete gradient composite structure provided in Embodiment 1 of the present application and Comparative Example 4;

[0046] Figure 4Schematic diagram of the ultra-high performance concrete gradient composite structure provided in Embodiment 2 of the present application;

[0047] Figure 5 Graph of early autogenous shrinkage change of the ultra-high performance concrete gradient composite structure provided in Embodiment 2 of the present application and Comparative Examples 6-7;

[0048] Figure 6 Tensile stress-strain curve graph of the ultra-high performance concrete gradient composite structure provided in Embodiment 2 of the present application and Comparative Example 8.

[0049] In the figure: 1. First ultra-high performance concrete layer; 2. Connection layer; 3. Second ultra-high performance concrete layer; 31. Groove. Detailed implementation manners

[0050] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are some, rather than all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the scope of protection of the present application.

[0051] As Figure 1 shown, in the first aspect, the embodiments of the present application provide an ultra-high performance concrete gradient composite structure, which sequentially includes a first ultra-high performance concrete layer 1, a connection layer 2, and a second ultra-high performance concrete layer 3, wherein,

[0052] The first ultra-high performance concrete layer 1 is a first ultra-high performance concrete solidified layer doped with steel fibers;

[0053] The second ultra-high performance concrete layer 3 is a second ultra-high performance concrete solidified layer doped with coarse aggregates and polymer fibers;

[0054] The connection layer, by mass, includes: 20-100 parts of steel fiber mesh, 5-30 parts of diatomaceous earth, 5-30 parts of gypsum, and 5-30 parts of silica sol.

[0055] The present application uses steel fiber-reinforced high-steady ultra-high performance concrete as the base layer of the pavement structure, which can provide good bearing capacity, anti-foundation deformation ability, fatigue resistance, and durability;

[0056] Using coarse aggregate and polymer fiber-reinforced high-steady ultra-high performance concrete as the top layer of the pavement structure provides good impact toughness, wear resistance, crack resistance, durability, economy, and safety for the pavement structure.

[0057] And the multi-dimensional modified connection layer provides good bonding performance for the base layer and the top layer of the pavement structure, enabling the gradient structure to have good integrity and stability. While overcoming the performance defects and deficiencies of ordinary ultra-high performance concrete airport pavements, through reasonable gradient design, the construction cost of ultra-high performance concrete airport pavements is greatly reduced, further promoting its practical engineering applications.

[0058] It should be noted that the steel fiber mesh is formed by weaving steel fibers. Further, the area of the steel fiber mesh is 20-100 cm 2 , and the mesh hole diameter is 6-12 mm.

[0059] Further, the diatomite is calcined diatomite, the calcination temperature of the calcined diatomite is ≥500 °C, and the average particle size is 5-30 μm;

[0060] Further, the gypsum plaster has a gypsum grade ≥80%, and the average particle size is 10-80 μm;

[0061] It should be noted that the gypsum grade of the gypsum plaster refers to the content of calcium sulfate dihydrate in the gypsum plaster;

[0062] Further, the silica sol is alkaline silica sol.

[0063] The action principle of the connection layer provided by this application includes:

[0064] The steel fiber mesh increases the tensile strength of the interface between the connection layer and the gradient ultra-high performance concrete through the interlocking effect, enabling the gradient structure to have stronger integrity and stability;

[0065] The silica sol is sprayed on the surface of the steel fiber mesh to modify the surface of the steel fiber mesh. Its highly active nano-silica component enables the steel fiber mesh to generate more adherent hydration products on the contact surface with the ultra-high performance concrete paste, increasing the bite and friction at the interface and enhancing the bonding strength between the steel fiber mesh and the ultra-high performance concrete matrix;

[0066] The gypsum plaster reacts with water to form calcium sulfate dihydrate, which quickly dissolves at the contact with the ultra-high performance concrete paste to form an ettringite coating, delaying the hydration of cement and thus delaying the formation of the false set layer on the surface of the ultra-high performance concrete, preventing the formation of cold joints at the interface between the connection layer and the gradient ultra-high performance concrete;

[0067] The water holding and releasing function of the porous structure of diatomite can continuously supply water to the gypsum slurry to prevent the gypsum slurry from losing water and hardening prematurely, improving the timeliness of the function of the gypsum slurry. At the same time, the calcined diatomite has pozzolanic activity, which can promote the secondary hydration of the ultra-high performance concrete paste at the interface, further enhancing the interface bonding strength.

[0068] In some embodiments, the cross-section of the connection layer 2 is in the shape of a W-shaped sawtooth;

[0069] And / or, the surface of the second ultra-high performance concrete layer 3 is provided with a pressed groove 31.

[0070] The cross-section of the connecting layer 2 is in a W-shaped serrated shape, which can increase the contact area and surface mechanical engagement force between the connecting layer and the ultra-high performance concrete layers on both sides, and further improve the bonding and tensile strength of the connecting layer;

[0071] The surface of the second ultra-high performance concrete layer 3 is provided with a pressed groove 31, which can ensure that the polymer fibers in the groove are not disturbed and pulled out, the structure in the groove is flat, and the stability is good.

[0072] In some embodiments, the first ultra-high performance concrete, by mass, includes:

[0073] 550-1000 parts of portland cement, 100-600 parts of mineral admixture, 500-1500 parts of sand aggregate, 2-10 parts of internal curing agent, 10-50 parts of expansive agent, 5-30 parts of shrinkage reducing agent, 10-50 parts of water reducing agent, 80-400 parts of steel fiber, 160-220 parts of water.

[0074] Further, the specific surface area of the portland cement ≥ 320 m 2 / kg;

[0075] The mineral admixture can adopt common mineral admixtures in the art, including but not limited to silica fume, fly ash, slag powder, etc. Further, the average particle size of the mineral admixture is 0.2-20 μm;

[0076] The sand aggregate can adopt common sand aggregates in the art, including but not limited to quartz sand, etc. Further, the average particle size of the sand aggregate ≤ 5 mm;

[0077] The internal curing agent is selected as a high water absorption resin powder internal curing agent. Further, the average particle size of the internal curing agent is 30-150 μm;

[0078] The expansive agent is selected as a calcium oxide liquid expansive agent;

[0079] The shrinkage reducing agent is selected as a polycarboxylic acid-based liquid shrinkage reducing agent;

[0080] The water reducing agent is selected as a polycarboxylic acid powder water reducing agent;

[0081] The steel fiber is selected as an end-hooked copper-plated steel fiber, with a length of 5-20 mm and a diameter of 0.15-0.35 mm.

[0082] The action principles of each component of the first ultra-high performance concrete provided by this application include:

[0083] As a storage carrier for water and liquid shrinkage-reducing functional components, the high water-absorbing resin internal curing agent has a slow-release effect. On the one hand, it plays an internal curing and shrinkage-reducing role. On the other hand, it continuously provides the water required for the expansion reaction of the expansion source in a timely manner to stimulate its continuous compensating shrinkage effect. Its powdery form can minimize its adverse effects on the mechanical properties and durability of ultra-high performance concrete.

[0084] The calcium oxide liquid expansive agent reacts to form expansive calcium hydroxide crystals to generate an expansion effect to compensate for the shrinkage of ultra-high performance concrete. Its liquid form can be adsorbed and slowly released by the internal curing agent to achieve an effective reaction in the extremely water-deficient environment inside the ultra-high performance concrete to form an expansion effect.

[0085] The polycarboxylate-based liquid shrinkage-reducing agent realizes its shrinkage-reducing effect by reducing the surface tension and shrinkage stress of the pore solution in ultra-high performance concrete. Its liquid form can be adsorbed and slowly released by the internal curing agent, thereby achieving a continuous shrinkage-reducing effect.

[0086] The end-hooked copper-plated steel fiber's end-hooked structure can increase the mechanical interlocking force between the steel fiber and the ultra-high performance concrete matrix to achieve high-efficiency toughening. Its thin and short form can effectively reduce its hook connection and overlap rate, achieve its good orientation and distribution, and thus improve the mechanical contribution efficiency of the steel fiber.

[0087] In some embodiments, the second ultra-high performance concrete, by mass, includes:

[0088] 550 - 1000 parts of portland cement, 100 - 600 parts of mineral admixture, 400 - 1000 parts of sand aggregate, 300 - 900 parts of coarse aggregate, 2 - 10 parts of internal curing agent, 10 - 50 parts of expansive agent, 5 - 30 parts of shrinkage-reducing agent, 10 - 50 parts of water-reducing agent, 20 - 80 parts of polymer fiber, 2 - 10 parts of modifier, and 160 - 220 parts of water.

[0089] Furthermore, the specific surface area of the portland cement ≥ 320 m 2 / kg;

[0090] The mineral admixture can adopt commonly used mineral admixtures in the art, including but not limited to silica fume, fly ash, slag powder, etc. Furthermore, the average particle size of the mineral admixture is 0.2 - 20 μm; the activity index ≥ 100%;

[0091] The sand aggregate can adopt commonly used sand aggregates in the art, including but not limited to quartz sand, etc. Furthermore, the average particle size of the sand aggregate ≤ 5 mm;

[0092] The coarse aggregate can adopt commonly used coarse aggregates in the art, including but not limited to crushed stone, etc. Furthermore, the average particle size of the coarse aggregate is 5 - 12 mm;

[0093] The internal curing agent is selected as a superabsorbent resin powder internal curing agent. Further, the average particle size of the internal curing agent is 30 to 150 μm;

[0094] The expansive agent is selected as a calcium oxide liquid expansive agent;

[0095] The shrinkage reducing agent is selected as a polycarboxylate-based liquid shrinkage reducing agent;

[0096] The water reducing agent is selected as a polycarboxylate powder water reducing agent;

[0097] The modifier is oligoethylene glycol;

[0098] The polymer fiber includes but is not limited to high-strength modified polyester fiber (FC fiber), high-strength modified polyvinyl alcohol fiber (PVA fiber), etc. Further, the tensile strength of the polymer fiber is ≥500 MPa, the elastic modulus is ≥8 GPa, the length is 12 to 40 mm, and the diameter is 0.1 to 1 mm.

[0099] For the second ultra-high performance concrete provided by this application, the action principles of each component include:

[0100] The superabsorbent resin internal curing agent serves as a storage carrier for water and liquid shrinkage reducing functional components. Its slow release effect plays an internal curing and shrinkage reducing role on the one hand, and on the other hand, it continuously provides the water required for the expansive reaction of the expansion source in a timely manner to stimulate its continuous compensated shrinkage effect. Its powder form can minimize its adverse effects on the mechanical properties and durability of ultra-high performance concrete;

[0101] The calcium oxide-based liquid expansive agent reacts to form expansive calcium hydroxide crystals to form an expansive effect to compensate for the shrinkage of ultra-high performance concrete. Its liquid form can be adsorbed and slowly released by the internal curing agent to achieve its effective reaction in the extremely water-deficient environment inside ultra-high performance concrete to form an expansive effect;

[0102] The polycarboxylate-based liquid shrinkage reducing agent realizes its shrinkage reducing effect by reducing the surface tension and shrinkage stress of the pore solution in ultra-high performance concrete. Its liquid form can be adsorbed and slowly released by the internal curing agent, thereby achieving a continuous shrinkage reducing effect;

[0103] On the one hand, the coarse aggregate reduces the material cost of ultra-high performance concrete, and on the other hand, its high elastic modulus and high constrained deformation ability can significantly improve the abrasion resistance and crack resistance of ultra-high performance concrete;

[0104] While enhancing the impact toughness of ultra-high performance concrete, the high-strength polymer coarse fiber can greatly reduce the damage of fiber erosion to the structure and the damage of fibers to the wheels, and reduce the material cost;

[0105] The oligoethylene glycol modifier enhances its hydrophilic property through the modification of the neat cement paste, and enhances the interfacial bonding force of the modified neat cement paste adhering to and wrapping the surface of the polymer fiber.

[0106] In a second aspect, the present application provides a method for preparing the ultra-high performance concrete gradient composite structure as described above, comprising the following steps:

[0107] 101: Pour the first ultra-high performance concrete to form the first ultra-high performance concrete layer 1;

[0108] 102: Mix diatomite and gypsum plaster evenly, add water and stir to obtain a composite gypsum slurry;

[0109] 103: Spray silica sol onto the surface of the steel fiber mesh to obtain a modified steel fiber mesh;

[0110] 104: Spray the composite gypsum slurry onto the surface of the first ultra-high performance concrete layer, and then lay the modified steel fiber mesh onto the surface of the composite gypsum slurry to form the connection layer 2;

[0111] 105: Pour the second ultra-high performance concrete onto the surface of the connection layer 2 to form the second ultra-high performance concrete layer 3.

[0112] In the preparation method provided by the present application, in step 102, gypsum plaster that inhibits the formation of the false set layer on the surface of ultra-high performance concrete and active diatomite with the function of water absorption and release are compounded to improve the timeliness of the retarding effect of the gypsum slurry and reserve sufficient working time for subsequent layered pouring;

[0113] In step 103, using the steel fiber mesh as the connection layer reinforcement structure can meet the requirements of the structural reinforcement process. Pretreating its surface by spraying silica sol can enhance its bonding strength with the ultra-high performance concrete matrix and the interfacial tensile strength of the connection layer;

[0114] In step 104, the prepared composite gypsum slurry is sprayed on the bare surface of the stabilized ultra-high performance concrete mixture. The composite gypsum slurry can effectively and continuously inhibit the formation of the false set layer and cold joints on the surface of the mixture, optimize the interfacial transition zone, and improve the interfacial bonding strength of the structure.

[0115] In a preferred embodiment, the operation time of step 102 ≤ 20 min.

[0116] In a preferred embodiment, the pouring interval time between the first ultra-high performance concrete and the second ultra-high performance concrete ≤ 45 min.

[0117] In some embodiments, the preparation method further comprises the following steps for preparing the first ultra-high performance concrete:

[0118] 101: Mix the expansion agent, shrinkage reducing agent and part of the water evenly, then add the internal curing agent, mix well, seal and stand still to obtain the internal curing agent stock;

[0119] 102: Mix the Portland cement, mineral admixture, sand aggregate, water reducer and remaining water until fluidized, and sequentially add the prepared internal curing agent stock and steel fibers, then stir to obtain the first ultra-high performance concrete.

[0120] In the above preparation method, in step 101, the expansive agent, shrinkage reducing agent and internal curing water are loaded by using the internal curing agent, so as to realize the coupling shrinkage reducing effect of the expansive agent compensating for shrinkage, the shrinkage reducing agent reducing the shrinkage stress, and the internal curing relieving the autogenous drying shrinkage to play an efficient and continuous role in the ultra-high performance concrete system, thereby reducing the shrinkage deformation of the ultra-high performance concrete.

[0121] Adopt a step-by-step feeding and mixing process. In the first step, mix the Portland cement, mineral admixture, sand aggregate, water reducer and water until fluidized. In the second step, add the prepared internal curing agent stock and steel fibers. The step-by-step feeding and mixing process can form a protective mixing of the fragile internal curing agent in the relatively flexible fluidized slurry, avoiding direct dry mixing and friction with the solid powder material or steel fibers, which may cause the internal curing agent to break and affect its loading function and shrinkage reducing effect.

[0122] In a preferred embodiment, in step 101, the sealing and standing time ≥ 6h.

[0123] The addition amount of water is 8 - 30 times the mass of the internal curing agent.

[0124] In some embodiments, the preparation method further includes the following steps for preparing the second ultra-high performance concrete:

[0125] 101: Mix the modifier, part of the mineral admixture, part of the Portland cement and part of the water evenly to obtain a modified slurry.

[0126] 102: Stamp the improved slurry onto the surface of the polymer fiber by a roller to obtain a modified polymer fiber.

[0127] 103: Mix the expansive agent, shrinkage reducing agent and part of the water evenly, then add the internal curing agent, mix well, seal and stand to obtain the internal curing agent stock.

[0128] 104: Mix the remaining Portland cement, remaining mineral admixture, coarse aggregate, sand aggregate, water reducer and remaining water until fluidized, and sequentially add the internal curing agent stock and the modified polymer fiber, then stir to obtain the second ultra-high performance concrete.

[0129] In the above preparation method, in steps 101 and 102, the cement paste is hydrophilized and highly activated by using the modifier and ultrafine mineral admixture to improve the adhesion between the paste and the polymer fiber, and the surface of the polymer fiber is subjected to pressure / hanging slurry treatment by roller stamping, which is beneficial to the discharge of air bubbles to reduce air sacs and further enhance the bonding force between the paste and the polymer fiber.

[0130] In Step 103, an internal curing agent is used to load an expansive agent, a shrinkage-reducing agent, and internal curing water, so as to enable the coupling shrinkage-reducing effects of the expansive agent compensating for shrinkage, the shrinkage-reducing agent reducing shrinkage stress, and the internal curing alleviating autogenous drying shrinkage to play efficiently and continuously in the ultra-high performance concrete system, thereby reducing the shrinkage deformation of the ultra-high performance concrete;

[0131] A step-by-step feeding and mixing process is adopted. In the first step, Portland cement, mineral admixture, coarse aggregate, sand aggregate, water reducer, and water are stirred until fluidized. In the second step, the prepared standby material of the internal curing agent and the modified polymer fiber are added. The step-by-step feeding and mixing process can, on the one hand, enable the fragile internal curing agent to form a protective mixing in the relatively flexible fluidized slurry, avoiding direct dry mixing and friction with solid powder materials, coarse aggregates, and polymer fibers, which may cause the internal curing agent to break and affect its loading function and shrinkage-reducing effect; on the other hand, it can also form a protective mixing for the modified slurry attached / wrapped on the surface of the polymer fiber, avoiding direct dry mixing and friction with solid powder materials and coarse aggregates, which may cause the attached / wrapped slurry to fall off and reduce the structural bonding performance.

[0132] In a preferred embodiment, in Step 103, the sealing and standing time ≥ 6h;

[0133] The addition amount of water is 8 - 30 times the mass of the internal curing agent.

[0134] In some embodiments, before "casting the second ultra-high performance concrete on the surface of the connection layer 2", it further includes:

[0135] Imprinting the surface of the connection layer 2 into a W-shaped serrated shape.

[0136] In some embodiments, after "applying the second ultra-high performance concrete on the surface of the connection layer 2", it further includes:

[0137] Grooving the surface of the second ultra-high performance concrete layer 3.

[0138] In a preferred embodiment, when the penetration resistance of the second ultra-high performance concrete layer 3 is 3 - 10 MPa, grooving is performed on the surface of the second ultra-high performance concrete layer 3.

[0139] In some embodiments, the mass ratio of the total mass of diatomite and gypsum in the composite gypsum slurry to the mass of water is (1 - 1.5):1;

[0140] And / or, the water-binder ratio of the modified slurry is 0.3 - 0.6.

[0141] Furthermore, the fluidity of the modified slurry ≥ 220 mm, and the initial setting time ≥ 60 min.

[0142] By optimizing the preparation solutions such as material functionalization and modification pretreatment, step-by-step feeding and stirring process, and interface activation coating enhancement, the preparation method of the ultra-high performance concrete gradient composite structure provided by this application has high controllability of each process, can well meet the on-site construction requirements, and has strong engineering promotion and application value.

[0143] The following further illustrates this application through specific embodiments.

[0144] Example 1

[0145] See Figure 1 , this Example 1 provides an ultra-high performance concrete gradient composite structure, including: the first ultra-high performance concrete layer 1, the connection layer 2, and the second ultra-high performance concrete layer 3, wherein the thickness ratio of the first ultra-high performance concrete layer 1 to the second ultra-high performance concrete layer 3 is 2:8.

[0146] 1) Raw material description:

[0147] Portland cement: Ordinary Portland cement (commercially available);

[0148] Mineral admixture: Silica fume (commercially available), fly ash (commercially available);

[0149] Sand aggregate: Quartz sand, continuous gradation 0 - 3mm (commercially available);

[0150] Coarse aggregate: Crushed stone, continuous gradation 5 - 8mm (commercially available);

[0151] Steel fiber: End-hooked copper-plated steel fiber, length 13mm, diameter 0.22mm (produced by Shanghai Beikaert Applied Materials Technology Co., Ltd.);

[0152] Polymer fiber: High-strength modified polyester fiber (FC fiber), length 28mm, diameter 0.6mm (produced by Tongkun Group Co., Ltd.);

[0153] Steel fiber mesh: Area 72cm 2 , pore diameter 8mm (produced by Anping Gaobo Wire Mesh Manufacturing Co., Ltd.);

[0154] Internal curing agent: High water-absorbing resin internal curing agent, average particle size 40 - 80μm (produced by Guangdong Longhu Technology Co., Ltd.);

[0155] Expansion agent: Calcium oxide liquid expansion agent (produced by Hubei Tongyuan Building Materials Co., Ltd.);

[0156] Shrinkage reducing agent: Polycarboxylate-based liquid shrinkage reducing agent (produced by Wuhan Sanyuan Special Building Materials Co., Ltd.);

[0157] Water reducing agent: Polycarboxylate powder water reducing agent (produced by Jiangsu Sobute New Materials Co., Ltd.);

[0158] Modifier: Oligoethylene glycol (produced by Shanghai Aladdin Biochemical Technology Co., Ltd.);

[0159] Silica sol: Alkaline silica sol (produced by Zhejiang Delixin Micro-Nano Technology Co., Ltd.);

[0160] Plaster of Paris: (produced by Shaoyang Jintuo Technology Development Co., Ltd.);

[0161] Diatomite: Calcined diatomite (produced by Guangdong Sendai Diatomite Materials Co., Ltd.).

[0162] 2) The preparation method includes the following steps:

[0163] Preparation of the first ultra-high performance concrete:

[0164] 101: By mass, mix 46 parts of expansive agent, 22 parts of shrinkage reducing agent, and 60 parts of water evenly. Add 6 parts of internal curing agent to the mixture, mix well, and seal and stand for 13 h to obtain the standby material of internal curing agent;

[0165] 102: By mass, stir 833 parts of portland cement, 171 parts of fly ash, 88 parts of silica fume, 1039 parts of quartz sand, 14 parts of water reducing agent, and 199 parts of water until fluidized. Then, successively add 74 parts of the standby material of internal curing agent prepared in step 101 and 202 parts of steel fiber, and stir evenly to obtain the first ultra-high performance concrete.

[0166] Preparation of the second ultra-high performance concrete:

[0167] 101: By mass, mix 46 parts of expansive agent, 22 parts of shrinkage reducing agent, and 60 parts of water evenly. Add 6 parts of internal curing agent to the mixture, mix well, and seal and stand for 13 h to obtain the standby material of internal curing agent;

[0168] 102: By mass, stir 4 parts of modifier, 3 parts of silica fume, 14 parts of cement, and 7 parts of water evenly to obtain a modified slurry. Press the modified slurry on the surface of 47 parts of flattened high-strength modified polyester fiber by roller imprinting to obtain modified FC fiber;

[0169] 103: By mass, stir 617 parts of portland cement, 106 parts of fly ash, 57 parts of silica fume, 552 parts of quartz sand, 734 parts of crushed stone, 13 parts of water reducing agent, and 162 parts of water until fluidized. Then, successively add 60 parts of the standby material of internal curing agent prepared in step 101 and the modified FC fiber prepared in step 102, and stir evenly to obtain the second ultra-high performance concrete.

[0170] Preparation of the connecting layer stock:

[0171] 101: By mass, mix 6 parts of diatomite, 9 parts of plaster of Paris, and 13 parts of water evenly to obtain a composite gypsum slurry;

[0172] 102: Spraying 9 parts of silica sol evenly on the surface of 47 parts of steel fiber mesh by mass to obtain a modified steel fiber mesh.

[0173] Preparation of gradient composite structure:

[0174] 101: Pour the first ultra-high performance concrete. After no obvious air bubbles escape from the surface of the first ultra-high performance concrete mixture, scrape off the surface layer, and spray the composite gypsum slurry onto the surface of the first ultra-high performance concrete to obtain a composite gypsum covering layer;

[0175] 102: Lay the modified steel fiber mesh flat on the composite gypsum covering layer, and then use a mold to imprint the surface into a W-shaped serrated shape to obtain a connecting layer;

[0176] 103: Pour the second ultra-high performance concrete on the surface of the connecting layer. After the second ultra-high performance concrete hardens until the penetration resistance reaches 5 MPa, perform grooving and roughening on its surface. After complete hardening and curing, obtain an ultra-high performance concrete gradient composite structure.

[0177] Comparative Example 1

[0178] This Comparative Example 1 provides a common C60 concrete, and the raw materials include portland cement, fly ash, quartz sand, crushed stone, water reducing agent and water.

[0179] Comparative Example 2

[0180] It includes most of the operation steps of Example 1, and the difference is only that:

[0181] The raw materials of the first ultra-high performance concrete do not include an expansive agent, a shrinkage reducing agent and an internal curing agent;

[0182] The preparation of the first ultra-high performance concrete does not perform the preparation of the standby material of the internal curing agent in step 101.

[0183] Comparative Example 3

[0184] It includes most of the operation steps of Example 1, and the difference is only that:

[0185] The raw materials of the first ultra-high performance concrete do not include an expansive agent, a shrinkage reducing agent and an internal curing agent;

[0186] And the preparation of the first ultra-high performance concrete does not perform the preparation of the standby material of the internal curing agent in step 101;

[0187] The raw materials of the second ultra-high performance concrete do not include a modifier;

[0188] And the preparation of the second ultra-high performance concrete does not perform the preparation of the modified FC fibers in step 102, and uses FC fibers to replace the modified FC fibers in step 103.

[0189] Comparative Example 4

[0190] It includes most of the operation steps of Example 1, and the difference is only that:

[0191] The preparation of the connection layer is not carried out.

[0192] Example 2

[0193] Refer to Figure 2 , this Example 2 provides a super high performance concrete gradient composite structure, including: a first super high performance concrete layer 1, a connection layer 2 and a second super high performance concrete layer 3, wherein, the thickness ratio of the first super high performance concrete layer 1 to the second super high performance concrete layer 3 is 5:5.

[0194] 1) Raw material description:

[0195] Portland cement: Ordinary Portland cement (commercially available);

[0196] Mineral admixture: Blast furnace slag powder (commercially available), fly ash (commercially available);

[0197] Sand aggregate: Quartz sand, continuous gradation 0 - 5mm (commercially available);

[0198] Coarse aggregate: Crushed stone, continuous gradation 5 - 10mm (commercially available);

[0199] Steel fiber: End - hooked copper - plated steel fiber, length 11mm, diameter 0.25mm (produced by Shanghai Bekaert Applied Materials Technology Co., Ltd.);

[0200] Polymer fiber: High - strength modified polyvinyl alcohol fiber (PVA fiber), length 30mm, diameter 0.8mm (produced by Shandong Senhong Engineering Materials Co., Ltd.);

[0201] Steel fiber mesh: Area 64cm 2 , pore diameter 9mm (produced by Anping Gaobo Wire Mesh Manufacturing Co., Ltd.);

[0202] Internal curing agent: High - water - absorbent resin internal curing agent, average particle size 50 - 100μm (produced by Guangdong Longhu Technology Co., Ltd.);

[0203] Expansion agent: Calcium oxide liquid expansion agent (produced by Hubei Tongyuan Building Materials Co., Ltd.);

[0204] Shrinkage - reducing agent: Polycarboxylate - based liquid shrinkage - reducing agent (produced by Wuhan Sanyuan Special Building Materials Co., Ltd.);

[0205] Water - reducing agent: Polycarboxylate powder water - reducing agent (produced by Jiangsu Sobute New Materials Co., Ltd.);

[0206] Modifier: Oligoethylene glycol (produced by Shanghai Aladdin Biochemical Technology Co., Ltd.);

[0207] Silica sol: Alkaline silica sol (produced by Zhejiang Delixin Micro-Nano Technology Co., Ltd.);

[0208] Plaster of Paris: (produced by Shaoyang Jintuo Technology Development Co., Ltd.);

[0209] Diatomaceous earth: Calcined diatomaceous earth (produced by Guangdong Sendai Diatomaceous Earth Materials Co., Ltd.).

[0210] 2) The preparation method includes the following steps:

[0211] Preparation of the first ultra-high performance concrete:

[0212] 101: By mass, mix 36 parts of expansive agent, 28 parts of shrinkage reducing agent, and 65 parts of water evenly. Add 5 parts of internal curing agent to the mixture, mix well, and seal and stand for 18 h to obtain the standby material of the internal curing agent;

[0213] 102: By mass, stir 779 parts of portland cement, 102 parts of fly ash, 89 parts of slag powder, 1126 parts of quartz sand, 17 parts of water reducing agent, and 203 parts of water until fluidized. Then, successively add 69 parts of the standby material of the internal curing agent prepared in step 101 and 252 parts of steel fiber, and stir evenly to obtain the first ultra-high performance concrete.

[0214] Preparation of the second ultra-high performance concrete:

[0215] 101: Mix 36 parts of expansive agent, 28 parts of shrinkage reducing agent, and 65 parts of water evenly. Add 5 parts of internal curing agent to the mixture, mix well, and seal and stand for 18 h to obtain the standby material of the internal curing agent;

[0216] 102: By mass, mix 5 parts of modifier, 4 parts of slag powder, 12 parts of cement, and 8 parts of water evenly to obtain a modified slurry. Press the modified slurry onto the surface of 55 parts of flattened high-strength modified polyvinyl alcohol fiber by roller imprinting to obtain modified PVA fiber;

[0217] 103: By mass, stir 626 parts of portland cement, 73 parts of fly ash, 89 parts of slag powder, 633 parts of quartz sand, 699 parts of crushed stone, 14 parts of water reducing agent, and 166 parts of water until fluidized. Then, successively add 65 parts of the standby material of the internal curing agent prepared in step 101 and the modified PVA fiber prepared in step 102, and stir evenly to obtain the second ultra-high performance concrete.

[0218] Preparation of the connecting layer stock:

[0219] 101: By mass, mix 5 parts of diatomaceous earth, 10 parts of plaster of Paris, and 12 parts of water evenly to obtain a composite plaster slurry;

[0220] 102: Spraying 8 parts of silica sol evenly on the surface of 39 parts of steel fiber mesh by mass to obtain a modified steel fiber mesh.

[0221] Preparation of gradient composite structure:

[0222] 101: Pour the first ultra-high performance concrete. After no obvious bubbles escape from the surface of the first ultra-high performance concrete mixture, scrape off the surface layer, and spray the composite gypsum slurry onto the surface of the first ultra-high performance concrete to obtain a composite gypsum covering layer;

[0223] 102: Lay the modified steel fiber mesh flat on the composite gypsum covering layer, and then use a mold to press the surface into a W-shaped serrated shape to obtain a connection layer;

[0224] 103: Pour the second ultra-high performance concrete on the surface of the connection layer. After the second ultra-high performance concrete hardens until the penetration resistance reaches 8 MPa, groove and roughen its surface. After complete hardening and curing, obtain an ultra-high performance concrete gradient composite structure.

[0225] Comparative Example 5

[0226] This Comparative Example 5 provides a common C60 concrete, and the raw materials include portland cement, fly ash, quartz sand, crushed stone, water reducing agent and water.

[0227] Comparative Example 6

[0228] It includes most of the operation steps of Example 2, and the difference is only that:

[0229] The raw materials of the first ultra-high performance concrete do not include an expansive agent, a shrinkage reducing agent and an internal curing agent;

[0230] The preparation of the first ultra-high performance concrete does not carry out the preparation of the internal curing agent reserve in step 101.

[0231] Comparative Example 7

[0232] It includes most of the operation steps of Example 2, and the difference is only that:

[0233] The raw materials of the first ultra-high performance concrete do not include an expansive agent, a shrinkage reducing agent and an internal curing agent;

[0234] And the preparation of the first ultra-high performance concrete does not carry out the preparation of the internal curing agent reserve in step 101;

[0235] The raw materials of the second ultra-high performance concrete do not include a modifier;

[0236] And the preparation of the second ultra-high performance concrete does not carry out the preparation of the modified PVA fiber in step 102, and directly uses PVA fiber to replace the modified PVA fiber in step 103..

[0237] Comparative Example 8

[0238] It includes most of the operation steps of Example 2, and the difference is only that:

[0239] The preparation of the connection layer is not carried out.

[0240] Performance Test

[0241] The following performance tests are carried out on the concrete structures prepared in Examples 1-2 and Comparative Examples 1-8:

[0242] (1) Mechanical properties: The compressive strength, flexural strength and elastic modulus of ultra-high performance concrete are tested according to the Standard Test Method for Mechanical Properties of Ordinary Concrete (GB / T 50081-2002);

[0243] (2) Interface properties and durability properties: The shrinkage properties, fracture properties, abrasion resistance, interface properties, chloride ion penetration resistance and frost resistance of ultra-high performance concrete are tested according to the Test Code for Hydraulic Concrete (SL / T 352-2020), and the test results are filled in Table 1.

[0244] Table 1

[0245]

[0246] Note: In the table, "S" represents an example, for example, "S1" represents "Example 1"; "D" represents a comparative example, for example, "D1" represents "Comparative Example 1".

[0247] It can be seen from the data in Table 1 that compared with the ordinary C60 concrete in Comparative Examples 1 and 5, the ultra-high performance concrete composite structures provided in Examples 1-2 of the present application have been greatly improved in terms of mechanical properties, volume stability, impact toughness, abrasion resistance and durability;

[0248] Combining the data of Example 1 and Comparative Example 2, and Example 2 and Comparative Example 6, it can be seen that through the internal curing technology, the base layers of Examples 1-2 have been improved to a certain extent in terms of mechanical properties and durability compared with ordinary ultra-high performance concrete. The volume stability has been improved by 85% and 86% respectively, the abrasion resistance strength has been improved by 30% and 31% respectively, and the cost has been reduced by 31% and 21% respectively;

[0249] From the data of Example 1 combined with Comparative Example 3, and Example 2 combined with Comparative Example 7, it can be seen that through the internal curing technology and fiber modification technology, the top surface layers of Examples 1-2 have significantly improved durability compared with ordinary coarse aggregate polymer fiber ultra-high performance concrete. The compressive strengths are increased by 14% and 23% respectively, the flexural strengths are increased by 62% and 85% respectively, the volume stabilities are increased by 80% and 83% respectively, the impact toughnesses are increased by 55% and 81% respectively, and the abrasion resistance strengths are increased by 13% and 15% respectively.

[0250] From the data of Example 1 combined with Comparative Example 4, and Example 2 combined with Comparative Example 8, it can be seen that by introducing a specially designed connection layer between the base layer and the top surface layer in this application, compared with ordinary gradient ultra-high performance concrete, its mechanical properties, volume stability, impact toughness, abrasion resistance performance, and durability have all been significantly improved. The interfacial tensile strengths are increased by 268% and 230% respectively, the flexural strengths are increased by 247% and 252% respectively, the shear strengths are increased by 294% and 263% respectively, and the structural stability has been greatly improved.

[0251] See Figure 2 as shown, Figure 2 The early-age autogenous shrinkage deformation diagrams of Example 1 and Comparative Examples 2-3 are shown. It can be seen from the figure that compared with Comparative Examples 2-3, the 7-day autogenous shrinkage of Example 1 is reduced by 90% and 86% respectively.

[0252] See Figure 3 as shown, Figure 3 The tensile stress-strain curves of Example 1 and Comparative Example 4 are shown. It can be seen from the figure that compared with Comparative Example 4, the interfacial tensile strength of Example 1 is increased by 268%.

[0253] See Figure 5 as shown, Figure 5 The early-age autogenous shrinkage deformation diagrams of Example 2 and Comparative Examples 6-7 are shown. It can be seen from the figure that compared with Comparative Examples 6-7, the 7-day autogenous shrinkage of Example 2 is reduced by 90% and 87% respectively.

[0254] See Figure 6 as shown, Figure 6 The tensile stress-strain curves of Example 2 and Comparative Example 8 are shown. It can be seen from the figure that compared with Comparative Example 8, the interfacial tensile strength of Example 2 is increased by 230%.

[0255] In summary, in terms of material optimization design of this application: at the low layer of ultra-high performance concrete, the co-compensated shrinkage technology of internal curing and expansion / shrinkage reduction components is used to significantly reduce the shrinkage of ultra-high performance concrete, improve its volume stability and crack resistance; at the top layer of ultra-high performance concrete, high-strength polymer fibers are used to replace steel fibers, and the mechanical properties and dimensions of the polymer fibers are optimized and modified to prepare high-strength and high impact toughness polymer fiber-reinforced ultra-high performance concrete; at the level of economic design of ultra-high performance concrete materials, coarse aggregates are reasonably introduced and their dosage and gradation are optimized to prepare low-cost and high abrasion-resistant coarse aggregate ultra-high performance concrete. In terms of structural optimization design: according to the force characteristics of different parts, the gradient design of the ultra-high performance concrete structure for airport pavements is carried out to further reduce its construction cost on the basis of ensuring the structural performance of the pavement; at the same time, the connection layer between different gradient layers of ultra-high performance concrete is strengthened to make the ultra-high performance concrete gradient structure for airport pavements have good integrity and stability;

[0256] The ultra-high performance concrete gradient composite structure and its preparation method provided by this application can greatly improve the mechanical properties, impact toughness, abrasion resistance, crack resistance and durability of airport pavements. At the same time, compared with the ordinary ultra-high performance concrete structure, it can not only improve its key performance, but also greatly reduce the economic cost.

[0257] It should be noted that in this application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variation thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the existence of additional identical elements in the process, method, article or device comprising the element.

[0258] The above are only specific embodiments of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application will not be limited to these embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A preparation method of a super high performance concrete gradient composite structure, the super high performance concrete gradient composite structure sequentially includes a first super high performance concrete layer (1), a connection layer (2) and a second super high performance concrete layer (3), wherein, the first super high performance concrete layer (1) is a cured layer of first super high performance concrete doped with steel fibers; the second super high performance concrete layer (3) is a cured layer of second super high performance concrete doped with coarse aggregates and polymer fibers; the connection layer (2), by mass, includes: 20 - 100 parts of steel fiber mesh, 5 - 30 parts of diatomite, 5 - 30 parts of gypsum, 5 - 30 parts of silica sol; the cross-section of the connection layer (2) is in a W-shaped serrated shape; and / or, the surface of the second super high performance concrete layer (3) is provided with grooves (31), and it is characterized in that it includes the following steps: Pour the first super high performance concrete to form the first super high performance concrete layer (1); Mix diatomite and gypsum evenly, add water and stir to obtain a composite gypsum slurry; Spray silica sol onto the surface of the steel fiber mesh to obtain a modified steel fiber mesh; Spray the composite gypsum slurry onto the surface of the first super high performance concrete layer (1), and then lay the modified steel fiber mesh onto the surface of the composite gypsum slurry to form the connection layer (2); Pour the second super high performance concrete onto the surface of the connection layer (2) to form the second super high performance concrete layer (3).

2. The preparation method of the super high performance concrete gradient composite structure as described in claim 1, characterized in that, the preparation method further includes the following steps for preparing the first super high performance concrete: Mix the expansive agent, shrinkage reducing agent and part of the water evenly, then add the internal curing agent, mix well, seal and stand still to obtain the internal curing agent standby material; Mix the portland cement, mineral admixture, sand aggregate, water reducing agent and the remaining water until fluidized, and sequentially add the internal curing agent standby material and steel fibers, and stir to obtain the first super high performance concrete.

3. The preparation method of the super high performance concrete gradient composite structure as described in claim 1, characterized in that, the preparation method further includes the following steps for preparing the second super high performance concrete: Mix the modifier, part of the mineral admixture, part of the portland cement and part of the water evenly to obtain a modified slurry; Roll and imprint the modified slurry onto the surface of the polymer fibers to obtain modified polymer fibers; Mix the expansive agent, shrinkage reducing agent and part of the water evenly, then add the internal curing agent, mix well, seal and stand still to obtain the internal curing agent standby material; Mix the remaining portland cement, remaining mineral admixture, coarse aggregate, sand aggregate, water reducing agent and the remaining water until fluidized, and sequentially add the internal curing agent standby material and the modified polymer fibers, and stir to obtain the second super high performance concrete.

4. The preparation method of the super high performance concrete gradient composite structure as described in claim 1, characterized in that, before "pouring the second super high performance concrete onto the surface of the connection layer (2)", it further includes: Press and imprint the surface of the connection layer (2) into a W-shaped serrated shape.

5. The preparation method of the super high performance concrete gradient composite structure as described in claim 1, characterized in that, After "casting the second ultra-high performance concrete on the surface of the connection layer (2)", it further includes: Grooving the surface of the second ultra-high performance concrete layer (3).

6. The preparation method of the ultra-high performance concrete gradient composite structure according to claim 3, characterized in that the mass ratio of the total mass of diatomite and gypsum in the composite gypsum slurry to the mass of water is (1 to 1.5):1; and / or, the water-binder ratio of the modified slurry is 0.3 to 0.

6.

7. The preparation method of the ultra-high performance concrete gradient composite structure according to claim 1, characterized in that the first ultra-high performance concrete, by mass, includes: 550 to 1000 parts of portland cement, 100 to 600 parts of mineral admixture, 500 to 1500 parts of sand aggregate, 2 to 10 parts of internal curing agent, 10 to 50 parts of expansive agent, 5 to 30 parts of shrinkage reducing agent, 10 to 50 parts of water reducing agent, 80 to 400 parts of steel fiber, 160 to 220 parts of water.

8. The preparation method of the ultra-high performance concrete gradient composite structure according to claim 1, characterized in that the second ultra-high performance concrete, by mass, includes: 550 to 1000 parts of portland cement, 100 to 600 parts of mineral admixture, 400 to 1000 parts of sand aggregate, 300 to 900 parts of coarse aggregate, 2 to 10 parts of internal curing agent, 10 to 50 parts of expansive agent, 5 to 30 parts of shrinkage reducing agent, 10 to 50 parts of water reducing agent, 20 to 80 parts of polymer fiber, 2 to 10 parts of modifier, 160 to 220 parts of water.

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