A heat-shrinkable fiber mesh-reinforced long-span box arch C80 high-toughness concrete and its preparation method

Abstract

The present invention provides a heat-shrinkable fiber mesh-reinforced large-span box arch C80 high-toughness concrete and a preparation method thereof. Through the design of the material composition and structure, the present invention realizes the multi-scale toughening of the concrete for large-span reinforced concrete box arches: by optimizing the raw material composition and hydration process of the high-alumina cementitious material, the proportion of C-A-S-H gel in the cementitious paste is increased, realizing the toughening of C80 concrete materials at the nanoscale molecular level; by utilizing the characteristic that the heat-shrinkable fibers in the fiber-reinforcing material are subjected to molecular reconstruction due to the heat released by the hydration of the cementitious material and generate shrinkage, by adding heat-shrinkable fibers, uniform pre-compressive stress is applied inside the cementitious paste, and by adding CaCO3 whiskers, the toughening of C80 concrete materials at the micron scale is realized; by adding copper-plated straight steel fibers and multi-anchor steel fibers, the toughening of C80 concrete materials at the macro scale is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and particularly relates to a heat-shrinkable fiber mesh reinforced large-span box arch C80 high-toughness concrete and a preparation method thereof. Background Art

[0002] Traditional high-strength concrete has some inherent defects. For example: high brittleness: concrete is prone to brittle fracture when in tension, lacking sufficient ductility and toughness. Poor crack resistance: concrete is prone to generating cracks during use, especially in cases where the stress is concentrated (such as in cantilever construction) or the environmental change (such as large day-night temperature difference in mountainous areas) is significant. Traditional fiber-reinforced concrete usually only uses a single type of fiber, such as metal fiber, glass fiber, heat-shrinkable organic fiber, basalt fiber, etc. Although these single short-cut fibers can improve the toughness and crack resistance of concrete to a certain extent, due to the limited action mechanism and reinforcement effect of each fiber, it is difficult to meet the multiple requirements of modern engineering for high-performance concrete and ultra-high-performance concrete.

[0003] Based on the problems existing in the current fiber-reinforced concrete, it is necessary to improve it. Summary of the Invention

[0004] In view of this, the present invention provides a heat-shrinkable fiber mesh reinforced large-span box arch C80 high-toughness concrete and a preparation method thereof to solve or partially solve the problems existing in the prior art.

[0005] In a first aspect, the present invention provides a heat-shrinkable fiber mesh reinforced large-span box arch C80 high-toughness concrete, comprising the following raw materials: 580 - 640 kg / m of high-alumina cementitious material 3 、750 - 850 kg / m of fine aggregate 3 、950 - 1100 kg / m of high-strength coarse aggregate 3 、40 - 80 kg / m of fiber reinforcement material 3 、3 - 8 kg / m of heat-shrinkable fiber mesh 3 、9 - 11 kg / m of special viscosity-reducing and slump-keeping admixture 3 、140 - 160 kg / m of water 3 。

[0006] Preferably, the special viscosity-reducing and slump-keeping admixture comprises polycarboxylate superplasticizer mother liquor, air-entraining agent, retarder, boric acid, tetramethyl decyne diol foam controller, acrylic acid modified silicone defoamer and water;

[0007] The mass ratio of the polycarboxylate superplasticizer mother liquor, air-entraining agent, setting retarder, boric acid, tetramethyl decynediol foam control agent, acrylic acid-modified silicone defoamer and water is (52-56):(0.03-0.05):(1-2.5):(1.5-1.9):(0.05-0.2):(0.03-0.07):(33.65-35.15).

[0008] Preferably, the heat-shrinkable fiber mesh is a net structure woven from heat-shrinkable fibers, and the heat-shrinkable fibers include a heat-shrinkable core material and a heat-shrinkable skin material coated on the outer periphery of the heat-shrinkable core material;

[0009] The material of the heat-shrinkable skin material includes at least one of polyvinyl alcohol, polyethylene, and polyoxymethylene;

[0010] The molecular weight of the polyvinyl alcohol is 170,000-220,000;

[0011] The molecular weight of the polyethylene is 1,000,000-2,000,000;

[0012] The molecular weight of the polyoxymethylene is 20,000-30,000;

[0013] The material of the heat-shrinkable core material is polypropylene, and the molecular weight of the polypropylene is 6000-8000;

[0014] The tensile strength of the heat-shrinkable fiber is 500-1200 MPa, the elastic modulus is 7-35 GPa, the shrinkage rate is 0.5%-12%, and the response temperature is 30°C-100°C.

[0015] Preferably, the high-aluminum phase cementitious material includes a mixture of P·II 52.5 portland cement, P·II 42.5 high-iron phase sulphoaluminate cement, fly ash microspheres and silica fume;

[0016] The P·II 42.5 high-iron phase sulphoaluminate cement containing Q phase is P·II 42.5 high-iron phase sulphoaluminate cement containing Q phase;

[0017] The 28-day activity index of the fly ash microspheres is 109%, and the water demand ratio is 101%;

[0018] The mass content of SiO2 in the silica fume is ≥90%, the specific surface area is ≥20300m 2 / kg, and the 28-day activity index is ≥100%.

[0019] Preferably, the P·II 42.5 high-iron phase sulphoaluminate cement containing Q phase is prepared by the following method:

[0020] Mix fly ash, limestone, magnesite, and calcium sulfate to obtain a first mixture;

[0021] The first mixture is calcined at a heating rate of 5 - 10 °C / min to 1290 - 1350 °C and held for 40 - 45 min to obtain Q-phase calcium sulfoaluminate clinker;

[0022] Red mud, limestone, bauxite, and calcium sulfate are mixed to obtain a second mixture;

[0023] The second mixture is calcined at a heating rate of 5 - 10 °C / min to 1290 - 1350 °C and held for 40 - 45 min to obtain Calcium sulfoaluminate cement clinker;

[0024] The Q-phase calcium sulfoaluminate clinker, Calcium sulfoaluminate cement clinker are mixed to obtain Q-phase-rich P·II 42.5 high-iron-phase calcium sulfoaluminate cement clinker;

[0025] The Q-phase-rich P·II 42.5 high-iron-phase calcium sulfoaluminate cement clinker is mixed with dihydrate gypsum and then ground to a specific surface area of 330 - 350 m 2 / kg to obtain P·II 42.5 high-iron-phase calcium sulfoaluminate cement containing Q-phase.

[0026] Preferably, the fiber reinforcement material includes copper-plated straight steel fibers, multi-anchor steel fibers, heat-shrinkable fibers, and CaCO3 whiskers;

[0027] The mass ratio of the copper-plated straight steel fibers, multi-anchor steel fibers, heat-shrinkable fibers, and CaCO3 whiskers is (20 - 30):(20 - 30):(1 - 2):(10 - 15).

[0028] Preferably, the nominal length of the copper-plated straight steel fibers is 6 - 13 mm, the equivalent diameter is 0.20 ± 0.02 mm, the breaking strength is ≥2200 MPa, the elastic modulus is 190 - 230 GPa, and the tensile strength is 400 - 2100 MPa;

[0029] The nominal length of the multi-anchor steel fibers is 6 - 13 mm, the equivalent diameter is 0.18 ± 0.02 mm, the breaking strength is ≥1300 MPa, the elastic modulus is 220 - 240 GPa, and the tensile strength is 600 - 2200 MPa; the length of the heat-shrinkable fibers is 10 mm - 12 mm, the tensile strength is 500 - 1200 MPa, the elastic modulus is 7 - 35 GPa, the shrinkage rate is 0.5% - 12%, and the response temperature is 30 °C - 100 °C;

[0030] The nominal length of the CaCO3 whiskers is 10 - 20 μm, the elastic modulus is 410 - 710 GPa, and the tensile strength is 3000 - 6000 MPa.

[0031] Preferably, the mass ratio of fly ash, limestone, magnesite, and calcium sulfate is (60-70):(15-20):(5-10):(5-10);

[0032] The mass ratio of red mud, limestone, bauxite, and calcium sulfate is (40-45):(25-30):(20-25):(5-10);

[0033] The mass ratio of Q-phase calcium sulfoaluminate clinker, calcium sulfoaluminate cement clinker is (50-60):(40-50);

[0034] The mass of the dihydrate gypsum is 10-15% of the mass of the Q-phase-rich P·II 42.5 high-iron-phase calcium sulfoaluminate cement clinker;

[0035] The addition amount of P·II 52.5 portland cement is 350-355 kg / m 3 , the addition amount of P·II 42.5 calcium sulfoaluminate high-iron-phase cement is 150-155 kg / m 3 , the addition amount of fly ash microspheres is 80-90 kg / m 3 , silica fume 30-40 kg / m 3 .

[0036] Preferably, the fine aggregate is river sand, with an apparent density of 2560-2650 kg / m 3 , a fineness modulus of 2.8, and a water absorption rate ≤ 8%;

[0037] The high-strength coarse aggregate is a 5-16 mm continuously graded basalt ultra-high-strength coarse aggregate, with an apparent density of 2900-3000 kg / m 3 .

[0038] Second, the present invention also provides a method for preparing the heat-shrinkable fiber mesh-reinforced large-span box arch C80 high-toughness concrete as described above, including the following steps:

[0039] Mix the high-aluminum phase cementitious material, fine aggregate, and high-strength coarse aggregate and stir for 60-120 s, then add water and a viscosity-reducing and slump-retaining special admixture with a mass of 45-55%, and continue stirring; then add the fiber-reinforcing material, and after stirring, add the remaining viscosity-reducing and slump-retaining special admixture to obtain a mixture;

[0040] Fix the heat-shrinkable fiber mesh in the mold, and then place the mixture in the mold and vibrate to obtain the heat-shrinkable fiber mesh-reinforced large-span box arch C80 high-toughness concrete.

[0041] The heat-shrinkable fiber mesh-reinforced large-span box arch C80 high-toughness concrete and its preparation method of the present invention have the following beneficial effects compared with the prior art:

[0042] 1. The heat-shrinkable fiber mesh-reinforced long-span box arch C80 high-toughness concrete obtained by the present invention avoids the traditional concrete reinforcement technology that mainly relies on a single type of fiber reinforcement and cannot comprehensively improve the comprehensive performance of concrete. Among them, the heat-shrinkable fiber mesh can be effectively distributed and fixed inside the concrete matrix, effectively preventing the formation and expansion of cracks and improving the compressive strength of the concrete. The combination of multi-scale fibers (calcium carbonate whiskers, copper-plated straight steel fibers, multi-anchor steel fibers, heat-shrinkable fibers) and the three-dimensional fiber mesh enables the concrete to exhibit stronger tensile and flexural properties under tensile stress and bending stress. The three-dimensional fiber mesh forms a three-dimensional reinforcement network structure in the concrete, which can effectively disperse and resist external stresses, greatly improving the flexural toughness of high-performance concrete and being able to absorb more energy without damage. Moreover, the combination of the three-dimensional fiber mesh and the fiber reinforcement material improves the crack resistance and durability of the concrete, reducing the early shrinkage cracks and maintenance costs caused by environmental and load changes. By pre-placing the three-dimensional fiber mesh in the mold, the uniform distribution and fixation of the fiber mesh in the concrete are ensured, avoiding the uneven distribution of existing high-volume short-cut fibers in the concrete, resulting in unsatisfactory fiber reinforcement effects and the easy occurrence of fiber agglomeration during the construction process.

[0043] 2. The heat-shrinkable fiber mesh-reinforced long-span box arch C80 high-toughness concrete obtained by the present invention optimizes the raw material composition and hydration process of the high-aluminum phase cementitious material, increasing the proportion of C-A-S-H gel in the cementitious paste and achieving toughening of the C80 concrete material at the nano-scale molecular level; through the heat-shrinkage effect of the heat-shrinkable fibers, when the early hydration heat of high-strength concrete is too high, micro-precompressive stress is generated through shrinkage, reducing the early autogenous shrinkage of the concrete and improving the toughness of the concrete from the micro-nano scale; through the micro-scale effect of CaCO3 whiskers, the micro-cracks inside the concrete can be bridged, reducing the porosity of the concrete and improving the toughness of high-strength concrete from the micron scale; through the bridging effect of copper-plated straight steel fibers and multi-anchor steel fibers, the formation and expansion of internal cracks in the concrete are delayed, improving the toughness of high-strength concrete from the macroscopic millimeter scale.

[0044] 3. The apparent density of the heat-shrinkable fiber mesh-reinforced long-span box arch C80 high-toughness concrete obtained by the present invention is 2450 - 2650 kg / m 3 , and at the same time, the compressive strength grade can reach above C90. It has good workability, mechanical properties and durability, can effectively improve the flexural toughness, elastic modulus and volume stability of concrete components, and has important practical application value. Specific embodiments

[0045] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0046] It should be noted that the description order of the following embodiments does not limit the preferred order of the embodiments. In addition, in the description of the present application, the term "including" means "including but not limited to". The various embodiments of the present invention may exist in a range form; it should be understood that the description in a range form is only for convenience and brevity, and should not be construed as a rigid limitation on the scope of the present invention; therefore, it should be considered that the described range description has specifically disclosed all possible sub-ranges and single values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0047] The embodiment of the present application provides a heat-shrinkable fiber mesh-reinforced long-span box arch C80 high-toughness concrete, which includes the following raw materials: 580 - 640 kg / m of high-aluminum phase cementitious material 3 , 750 - 850 kg / m of fine aggregate 3 , 950 - 1100 kg / m of high-strength coarse aggregate 3 , 40 - 80 kg / m of fiber reinforcement material 3 , 3 - 8 kg / m of heat-shrinkable fiber mesh 3 , 9 - 11 kg / m of special viscosity-reducing and slump-keeping admixture 3 , 140 - 160 kg / m of water 3 .

[0048] The present invention realizes multi-scale toughening of concrete for long-span reinforced concrete box arches by designing the material composition and structure: by optimizing the raw material composition and hydration process of high-alumina cementitious materials, the proportion of C-A-S-H gel in the cementitious paste is increased to achieve toughening of C80 concrete materials at the nanoscale molecular level; using the characteristic that the heat-shrinkable fibers in the fiber-reinforced materials are reconstructed by the heat released during the hydration of the cementitious materials to generate shrinkage, by adding heat-shrinkable fibers, uniform pre-compressive stress is applied inside the cementitious paste, and by adding CaCO3 whiskers, toughening of C80 concrete materials at the micron scale is achieved; by adding copper-plated straight steel fibers and multi-anchor steel fibers, toughening of C80 concrete materials at the macroscopic scale is achieved; by adding a heat-shrinkable fiber mesh inside the steel bar protection layer of the long-span reinforced concrete box arch, the fiber mesh shrinks under the excitation of the hydration heat of the box arch concrete to further apply pre-compressive stress to the C80 concrete inside the steel bar protection layer, improving the toughness and crack resistance of the concrete. The application of micro-prestressing can effectively prevent the expansion of concrete cracks in the steel bar protection layer, thereby reducing the intrusion of moisture and harmful substances and preventing steel bar corrosion. Through high-alumina cementitious materials and special viscosity-reducing and slump-keeping admixtures, the workability of the concrete is optimized, and its fluidity and homogeneity are enhanced; in addition, by adjusting the proportion of alumina and gypsum in the high-alumina cementitious materials, the ettringite crystals generated are uniformly distributed in the C-S-H gel, and at the same time, the magnesium hydroxide formed by the hydration of Q phase and the ettringite formed by the further hydration of the hydration products of Q phase are used to compensate for the shrinkage of C80 concrete to achieve the volume stability design of C80 concrete. The high-toughness C80 concrete prepared by this technology can solve the problems of difficult pumping due to dense steel bars in long-span reinforced concrete box arches, easy shrinkage and cracking of high-strength concrete, and steel bar corrosion.

[0049] The present invention proposes fiber - reinforced materials and fiber mesh toughening technologies to improve the toughness of concrete; by using Mg(OH)₂ and ettringite generated from the hydration of Q - phase in sulphoaluminate high - iron - phase cement to compensate for shrinkage and cooperating with thermally - shrinking fibers to enhance the volume stability of concrete, thereby improving the crack - resistance performance of concrete; traditional fiber - reinforced concrete usually only uses a single type of fiber, such as metal fibers, glass fibers, thermally - shrinking fibers, basalt fibers, etc. Although these single - cut short fibers can improve the toughness and crack - resistance performance of concrete to a certain extent, due to the limited action mechanism and strengthening effect of each fiber, it is difficult to meet the multiple requirements of modern engineering for high - performance concrete and ultra - high - performance concrete. Multi - scale fiber - reinforced concrete uses different types and sizes of fibers in combination to exert the synergistic strengthening effect of various fibers, thereby significantly improving the comprehensive performance of concrete; specifically: Calcium carbonate whiskers, as micro - scale fibers, can bridge micro - cracks in concrete, improve the porosity of concrete, and enhance the compactness and crack - resistance performance of the matrix; steel fibers, as macro - scale fibers, have a bridging effect in concrete, enhancing the tensile strength and toughness index of the concrete matrix; thermally - shrinking fibers can expand or contract when the temperature changes, inducing the release of internal stress in concrete and reducing cracks caused by temperature stress. Introducing a thermally - shrinking fiber mesh into multi - scale fiber - reinforced concrete can further improve the toughness and crack - resistance performance of concrete; the three - dimensional fiber mesh has the following advantages: three - dimensional strengthening structure: the three - dimensional fiber mesh forms a three - dimensional network structure in concrete, providing multi - directional strengthening effects; uniform distribution: the three - dimensional fiber mesh can be evenly distributed in concrete, avoiding fiber aggregation and improving the overall performance of concrete; high durability: the organic fiber mesh is not easily corroded, avoiding the problem that steel bars in reinforced concrete are easily corroded.

[0050] The present invention regulates the mechanical properties and workability of concrete by adjusting the dosage of fly ash microspheres and the dosage of a special viscosity - reducing and slump - retaining admixture in high - alumina - phase cementitious materials, realizing the high - strength and high - fluidity design of concrete; the incorporation of fiber - reinforced materials and thermally - shrinking fiber meshes can improve the toughness of concrete at multiple scales such as macroscopic, millimeter, and micro - nanometer levels, realizing the high - toughness design of high - strength concrete; in addition, by using the temperature - rise and shrinkage characteristics of Mg(OH)₂, ettringite generated from the hydration of Q - phase in sulphoaluminate high - iron - phase cement and thermally - shrinking fibers, the shrinkage of concrete is reduced, and the volume stability and crack - resistance performance of concrete are enhanced. The thermally - shrinking fiber - mesh - reinforced large - span box arch C80 high - toughness concrete of the present invention has the characteristics of high strength, high toughness, high fluidity, and high durability, solving the problems of easy corrosion of steel bars in reinforced concrete and insufficient toughness of high - strength concrete, and having important practical application value.

[0051] In some embodiments, the special viscosity - reducing and slump - retaining admixture includes polycarboxylate superplasticizer mother liquor, air - entraining agent, retarder, boric acid, 2,4,7,9 - tetramethyl - 5 - decyn - 4,7 - diol foam controller, acrylic - modified silicone defoamer, and water;

[0052] The mass ratio of the polycarboxylate superplasticizer mother liquor, air-entraining agent, retarder, boric acid, tetramethyl decynediol foam control agent, acrylic acid-modified silicone defoaming agent and water is (52 - 56):(0.03 - 0.05):(1 - 2.5):(1.5 - 1.9):(0.05 - 0.2):(0.03 - 0.07):(33.65 - 35.15).

[0053] Specifically, the polycarboxylate superplasticizer mother liquor has a high water-reducing rate and is used to improve the fluidity and strength of concrete; the air-entraining agent is used to introduce microbubbles smaller than 100 μm to enhance workability; the retarder is used to extend the setting time of concrete and improve the slump retention effect; boric acid is used to improve the setting time of concrete and ensure the workability of fresh concrete; the tetramethyl decynediol foam control agent is used to stabilize the air content of concrete and reduce air loss during the pumping process of concrete; the acrylic acid-modified silicone defoaming agent is used to reduce the air content inside the concrete and control the air content at about 3%. Weigh each component of the above raw materials and use a high-speed stirring device to fully mix and homogenize each component, then we can obtain the special additive for viscosity reduction and slump retention.

[0054] In some embodiments, the heat-shrinkable fiber mesh is a mesh structure woven from heat-shrinkable fibers. The heat-shrinkable fibers include a heat-shrinkable core material and a heat-shrinkable skin material coated on the outer periphery of the heat-shrinkable core material;

[0055] The material of the heat-shrinkable skin material includes at least one of polyvinyl alcohol, polyethylene, and polyoxymethylene;

[0056] The molecular weight of polyvinyl alcohol is 170,000 - 220,000;

[0057] The molecular weight of polyethylene is 1,000,000 - 2,000,000;

[0058] The molecular weight of polyoxymethylene is 20,000 - 30,000;

[0059] The material of the heat-shrinkable core material is polypropylene, and the molecular weight of polypropylene is 6,000 - 8,000;

[0060] The tensile strength of the heat-shrinkable fiber is 500 - 1200 MPa, the elastic modulus is 7 - 35 GPa, the shrinkage rate is 0.5% - 12%, and the response temperature is 30°C - 100°C.

[0061] Specifically, in some embodiments, the preparation method of the heat-shrinkable fiber includes the following steps:

[0062] S1. Use two extruders to separately extrude the heat-shrinkable core material mixture and the heat-shrinkable skin material mixture into a die head with two cavities. Among them, the heat-shrinkable skin material enters the corresponding cavity for the skin material, and the heat-shrinkable core material enters the corresponding cavity for the core material. The materials in the two cavities converge at the position of the spinneret of the extruder. Among them, the spinneret has an inner ring and an outer ring. The inner ring of the spinneret is connected to the cavity of the core material, and the outer ring of the spinneret is connected to the cavity of the skin material. The two molten materials are extruded (molten extrusion) through the spinneret and stick together in the air, cooled by a cold water tank, and then drawn in hot water at 90-100 °C to form a composite fiber with a skin-core structure.

[0063] S2. Add the composite fiber obtained in step S1 to a silane coupling agent solution with a mass concentration of 1%-5% for modification for 10-20 min, and make surface indentations after drying to enhance its bonding performance with the concrete paste.

[0064] S3. Add the composite fiber obtained in step S2 to a modified polyvinyl alcohol solution added with an expansion component for coating modification, and dry it after taking it out to obtain the heat-shrinkable fiber.

[0065] Among them, for the heat-shrinkable skin material mixture, each raw material and its mass percentage are: 97% polyvinyl alcohol, 1.5% maleic anhydride grafted compatibilizer, 1.5% phthalate plasticizer; the extrusion pressure of the skin material cavity is 8 MPa, and the melting temperature is kept at 250 °C.

[0066] Among them, for the heat-shrinkable core material mixture, each raw material and its mass percentage are: 98% polypropylene, 2% rigidifying nucleating agent (composed of aluminum aromatic carboxylate and sodium benzoate in a mass ratio of 1:1); the melting temperature of the heat-shrinkable core material mixture is 200-280 °C; the extrusion pressure of the corresponding cavity is 7-10 MPa.

[0067] In the final extrusion section corresponding to the spinneret, the extrusion temperature of the two molten materials is kept at a temperature suitable for both materials, that is, 200-220 °C, and the extrusion pressure is 3-10 MPa.

[0068] In some embodiments, the coating modification temperature is room temperature static, and the time is 10-24 h.

[0069] In some embodiments, the expansion agent is composed of a calcium oxide expansion agent and a calcium sulfoaluminate expansion agent; preferably, the expansion agent is composed of a calcium oxide expansion agent and a calcium sulfoaluminate expansion agent compounded in a mass ratio of 1:40-50.

[0070] In some embodiments, the modified polyvinyl alcohol solution added with an expansion component is obtained by mixing a polyvinyl alcohol solution (6 wt%) and a liquid expansion agent evenly in a mass ratio of 7:3.

[0071] In some embodiments, a method for preparing a heat-shrinkable fiber web includes the following steps:

[0072] Weave the above-prepared heat-shrinkable fibers (with a length of 20 - 50 mm and a diameter of 20 - 100 microns) into a fiber web using a warp knitting machine. Set appropriate knitting speed and tension on the warp knitting machine to ensure the uniformity and stability of the fiber web. Arrange the fibers longitudinally and weave them according to a set grid size of 20 mm. The warp knitting process can ensure that the grid size of the fiber web is consistent and the arrangement is neat. Arrange the fibers transversely and weave them according to the set grid size. Use knitting equipment to weave the fibers into a web, and heat-treat the woven flat fiber web (the heat-setting temperature is 100 - 120 °C and the time is 10 - 20 minutes) to stabilize the size and shape of the fiber web. Thus, a two-dimensional heat-shrinkable fiber web is formed. Lay a two-dimensional fiber web flat on the workbench to ensure it is flat and wrinkle-free. Fold it once with a folding spacing of 20 mm, starting from one end and folding according to the spacing. When folding, form an upward fold angle and then fold it back down to form a wavy structure. The folding shape can be a wavy shape with alternating "mountain" and "valley" shapes. Use hot melt adhesive to fix at each fold angle to ensure the stable shape of the folded three-dimensional fiber web. After fixing each fold angle, perform additional heat treatment at the intersection between the wave peaks and wave valleys for fixation. Heat-treat the fixed wavy fiber web (temperature 110 ± 10 °C, time 12.5 ± 2.5 minutes) to ensure its shape and structure remain stable. Form an interlaced three-dimensional structure by cross-weaving multiple two-dimensional fiber web sheets together.

[0073] In some embodiments, the high-alumina cementitious material includes a mixture of P·II 52.5 Portland cement, P·II 42.5 high-iron phase sulphoaluminate cement, fly ash microspheres, and silica fume;

[0074] The P·II 42.5 high-iron phase sulphoaluminate cement is a P·II 42.5 high-iron phase sulphoaluminate cement containing Q phase;

[0075] The 28-day activity index of the fly ash microspheres is 109%, and the water demand ratio is 101%;

[0076] The mass content of SiO2 in the silica fume is ≥90%, the specific surface area is ≥20300 m 2 / kg, and the 28-day activity index is ≥100%.

[0077] The P·II 42.5 high-iron phase sulphoaluminate cement is a P·II high-iron phase sulphoaluminate cement containing Q phase, and the mineral composition calcined at 1290 - 1350 °C is 25% - 30% Q phase mineral (Ca 20 Al 26 Mg3Si3O 68 ), 40% - 45% Clinker containing minerals, 20%-25% C4AF minerals, 0%-5% C2S minerals and 10%-15% gypsum dihydrate is ground together to a specific surface area of 330-350 m 2 / kg for preparation.

[0078] In some embodiments, the P·II 42.5 high-iron phase sulphoaluminate cement containing Q phase is prepared by the following method:

[0079] S1. Mix fly ash, limestone, magnesite and calcium sulphate to obtain a first mixture;

[0080] S2. Heat the first mixture at a rate of 5-10 °C / min to 1290-1350 °C for calcination and keep it warm for 40-45 min to obtain Q-phase calcium sulphoaluminate clinker;

[0081] S3. Mix red mud, limestone, bauxite and calcium sulphate to obtain a second mixture;

[0082] S4. Heat the second mixture at a rate of 5-10 °C / min to 1290-1350 °C for calcination and keep it warm for 40-45 min to obtain Sulphoaluminate cement clinker;

[0083] S5. Mix the Q-phase calcium sulphoaluminate clinker and Sulphoaluminate cement clinker to obtain P·II 42.5 high-iron phase sulphoaluminate cement clinker rich in Q phase;

[0084] S6. Mix the P·II 42.5 high-iron phase sulphoaluminate cement clinker rich in Q phase with gypsum dihydrate and grind it to a specific surface area of 330-350 m 2 / kg to obtain the P·II 42.5 high-iron phase sulphoaluminate cement containing Q phase.

[0085] In some embodiments, the fiber reinforcement materials include copper-plated straight steel fibers, multi-anchor steel fibers, heat-shrinkable fibers and CaCO3 whiskers;

[0086] The mass ratio of copper-plated straight steel fibers, multi-anchor steel fibers, heat-shrinkable fibers and CaCO3 whiskers is (20-30):(20-30):(1-2):(10-15).

[0087] In some embodiments, the nominal length of the copper-plated straight steel fibers is 6-13 mm, the equivalent diameter is 0.20±0.02 mm, the breaking strength is ≥2200 MPa, the elastic modulus is 190-230 GPa, and the tensile strength is 400-2100 MPa;

[0088] The nominal length of the multi-anchor steel fiber is 6 - 13 mm, the equivalent diameter is 0.18 ± 0.02 mm, the fracture strength is ≥ 1300 MPa, the elastic modulus is 220 - 240 GPa, and the tensile strength is 600 - 2200 MPa;

[0089] The preparation method of the heat-shrinkable fiber is the same as above. The length of the heat-shrinkable fiber is 10 mm - 12 mm, the tensile strength is 500 - 1200 MPa, the elastic modulus is 7 - 35 GPa, the shrinkage rate is 0.5% - 12%, and the response temperature is 30°C - 100°C;

[0090] The nominal length of the CaCO3 whisker is 10 - 20 μm, the elastic modulus is 410 - 710 GPa, and the tensile strength is 3000 - 6000 MPa.

[0091] In some embodiments, the mass ratio of fly ash, limestone, magnesite, and calcium sulfate is (60 - 70):(15 - 20):(5 - 10):(5 - 10);

[0092] The mass ratio of red mud, limestone, bauxite, and calcium sulfate is (40 - 45):(25 - 30):(20 - 25):(5 - 10);

[0093] Q-phase calcium sulfoaluminate clinker, The mass ratio of calcium sulfoaluminate cement clinker is (50 - 60):(40 - 50);

[0094] The mass of dihydrate gypsum is 10 - 15% of the mass of rich Q-phase P·II 42.5 high-iron phase calcium sulfoaluminate cement clinker;

[0095] The addition amount of P·II 52.5 portland cement is 350 - 355 kg / m 3 , the addition amount of P·II 42.5 calcium sulfoaluminate high-iron phase cement is 150 - 155 kg / m 3 、the addition amount of fly ash beads is 80 - 90 kg / m 3 、the addition amount of silica fume is 30 - 40 kg / m 3 .

[0096] In some embodiments, the fine aggregate is river sand, the apparent density is 2560 - 2650 kg / m 3 , the fineness modulus is 2.8, and the water absorption rate ≤ 8%;

[0097] The high-strength coarse aggregate is 5 - 16 mm continuously graded basalt ultra-high-strength coarse aggregate, and the apparent density is 2900 - 3000 kg / m 3 .

[0098] Based on the same inventive concept, the present invention also provides a method for preparing the above-mentioned heat-shrinkable fiber mesh-reinforced long-span box arch C80 high-toughness concrete, comprising the following steps:

[0099] S1. Mix the high-alumina cementitious material, fine aggregate, and high-strength coarse aggregate, and stir for 60 - 120 s. Then add water and a viscosity-reducing and slump-retention special admixture with a mass percentage of 45 - 55%, and continue stirring. Then add the fiber reinforcement material, and after stirring, add the remaining viscosity-reducing and slump-retention special admixture to obtain a mixture.

[0100] S2. Fix the heat-shrinkable fiber mesh in the mold, and then place the mixture in the mold and vibrate it to obtain the heat-shrinkable fiber mesh-reinforced long-span box arch C80 high-toughness concrete.

[0101] In some embodiments, mix the high-alumina cementitious material, fine aggregate, and high-strength coarse aggregate, and stir for 60 - 120 s. Then add water and a part of the viscosity-reducing and slump-retention special admixture (45 - 55% of the viscosity-reducing and slump-retention special admixture), and continue stirring. Add the fiber reinforcement material, and after stirring for 30 s, add the remaining viscosity-reducing and slump-retention special admixture. Place the cut heat-shrinkable fiber mesh in a clean mold, heat the hot melt adhesive with a hot melt glue gun to an appropriate temperature, and apply the hot melt adhesive in dots on the peripheral side walls of the mold. Paste the edges of the three-dimensional fiber mesh on the side walls of the mold to make it immovable. Fix both ends of each fiber grid with hot melt adhesive to ensure its structural stability. Place the mixture in the mold and vibrate it to obtain the heat-shrinkable fiber mesh-reinforced long-span box arch C80 high-toughness concrete.

[0102] The principle of the present invention is:

[0103] 1. The heat-shrinkable fiber mesh-reinforced long-span box arch C80 high-toughness concrete obtained by the present invention avoids the traditional concrete reinforcement technology that mainly relies on a single type of fiber reinforcement and cannot comprehensively improve the comprehensive performance of concrete. The heat-shrinkable fiber mesh can be effectively distributed and fixed inside the concrete matrix, which can effectively prevent the formation and expansion of cracks and improve the compressive strength of the concrete. The combination of multi-scale fibers (calcium carbonate whiskers, copper-plated straight steel fibers, multi-anchor steel fibers, heat-shrinkable fibers) and three-dimensional fiber mesh enables the concrete to exhibit stronger tensile and flexural properties under tensile stress and bending stress. The three-dimensional fiber mesh forms a three-dimensional reinforcement network structure in the concrete, which can effectively disperse and resist external stresses, greatly improving the flexural toughness of high-performance concrete and being able to absorb more energy without damage. Moreover, the combination of the three-dimensional fiber mesh and fiber reinforcement materials improves the crack resistance and durability of the concrete, reducing the early shrinkage cracks and maintenance costs caused by environmental and load changes. By pre-placing the three-dimensional fiber mesh in the mold, the uniform distribution and fixation of the fiber mesh in the concrete are ensured, avoiding the uneven distribution of existing high-volume short-cut fibers in the concrete, resulting in unsatisfactory fiber reinforcement effects and the phenomenon of fiber agglomeration easily occurring during the construction process.

[0104] 2. The incorporation of the heat-shrinkable fiber mesh improves the problem of easy corrosion of steel bars. As an organic synthetic material, the heat-shrinkable fiber mesh itself has excellent corrosion resistance, especially in acid, alkali, and salt environments; high-toughness fiber concrete has extremely high crack resistance, can form a more dense structure, and usually has a smaller porosity, which can reduce the penetration of water and chloride ions, thereby further protecting the internal steel bars. Therefore, incorporating the heat-shrinkable fiber mesh in the steel bar concrete protective layer can effectively prevent the corrosion of steel bars.

[0105] 3. Utilize the "ball bearing effect" of fly ash microspheres in the high-alumina phase cementitious material and the polycarboxylate superplasticizer mother liquor in the special admixture for viscosity reduction and slump retention to synergistically regulate the viscosity of the concrete, optimize the workability of the fresh concrete, enable the concrete to fill the voids of the heat-shrinkable fiber mesh, improve the compactness of the concrete, and achieve the design of high fluidity, high toughness, and high durability of the concrete; utilize the Q phase in the sulphoaluminate high-iron phase cement to hydrate and generate magnesium hydroxide and ettringite; when the internal hydration heat of the concrete is too large in the early stage, the heat-shrinkable fibers generate micro-stresses by heating, and the two work together to reduce the early autogenous shrinkage and drying shrinkage of the concrete and improve the volume stability performance of high-strength concrete.

[0106] The apparent density of the heat-shrinkable fiber mesh-reinforced long-span box arch C80 high-toughness concrete obtained by the present invention is 2450 - 2650 kg / m 3, meanwhile, its compressive strength can reach over 90 MPa, and its flexural strength reaches over 10 MPa. It has good workability, mechanical properties, and durability, can effectively improve the flexural toughness, elastic modulus, and volume stability of concrete components, and has important practical application value.

[0107] The following further illustrates the heat-shrinkable fiber mesh-reinforced long-span box arch C80 high-toughness concrete and its preparation method of the present invention with specific embodiments. This part further explains the content of the present invention in combination with specific embodiments, but should not be construed as a limitation to the present invention. Unless otherwise specified, the technical means adopted in the embodiments are conventional means well-known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art.

[0108] In the following embodiments, the heat-shrinkable fiber mesh is obtained by weaving heat-shrinkable fibers. Among them, the preparation method of the heat-shrinkable fibers includes the following steps:

[0109] S1. Use two extruders to respectively extrude the heat-shrinkable core material mixture and the heat-shrinkable skin material mixture into a die head with two cavities. Among them, the heat-shrinkable skin material enters the corresponding skin cavity, and the heat-shrinkable core material enters the corresponding core cavity. The materials in the two cavities converge at the position of the spinneret plate of the extruder; among them, the spinneret plate has an inner ring and an outer ring. The inner ring of the spinneret plate is connected to the core cavity, and the outer ring of the spinneret plate is connected to the skin cavity. The two molten materials are extruded (molten extrusion) through the spinneret plate and stick together in the air, cooled by a cold water tank, and then drawn in 95 °C hot water to form a composite fiber with a skin-core structure;

[0110] S2. Add the composite fiber obtained in step S1 to a 3% (mass concentration) silane coupling agent (specifically octamethylcyclotetrasiloxane) solution for modification for 20 minutes, and make surface indentations after drying to enhance its bonding performance with the concrete paste;

[0111] S3. Add the composite fiber obtained in step S2 to a modified polyvinyl alcohol solution containing an expansion component for room-temperature static coating modification for 20 h, take it out and dry it to obtain the heat-shrinkable fiber; the modified polyvinyl alcohol solution containing an expansion component is obtained by mixing a polyvinyl alcohol solution (6 wt%) and an expansion agent in a mass ratio of 7:3. The expansion agent is composed of a calcium oxide expansion agent and a calcium sulfoaluminate expansion agent compounded in a mass ratio of 1:45;

[0112] Among them, for the heat-shrinkable skin material mixture, the raw materials and their mass percentages are: 97% polyvinyl alcohol, 1.5% maleic anhydride grafted compatibilizer (model provided by Dongguan Shenghao Plastic Raw Materials Co., Ltd., model PP-G-MAH), 1.5% phthalate plasticizer; the extrusion pressure of the skin cavity is 8 MPa, and the melting temperature is maintained at 250 °C;

[0113] The heat-shrinkable core material mixture, with each raw material and its mass percentage being: polypropylene 98%, rigidifying nucleating agent 2% (composed of aluminum aromatic carboxylate and sodium benzoate in a mass ratio of 1:1); the melting temperature adopted for the heat-shrinkable core material mixture is 210°C; the extrusion pressure corresponding to the cavity is 8 MPa;

[0114] In the last extrusion section corresponding to the spinneret, the extrusion temperatures of the two molten materials are maintained at a temperature suitable for both materials, that is, 215°C, and the extrusion pressure is 6 MPa;

[0115] The average diameter of the obtained core material fibers is 0.15 mm, and the thickness of the skin material fibers is 0.08 mm;

[0116] The length of the obtained heat-shrinkable fibers is 10 mm - 12 mm, the shrinkage rate is 0.5% - 12%, the response temperature is 30°C - 100°C, the tensile strength is 700 MPa, and the elastic modulus is 15.0 GPa.

[0117] Example 1

[0118] This example provides a heat-shrinkable fiber mesh-reinforced large-span box arch C80 high-toughness concrete, including the following raw materials: high-aluminum phase cementitious material 630 kg / m 3 、fine aggregate 805 kg / m 3 、high-strength coarse aggregate 1025 kg / m 3 、fiber-reinforcing material 63.5 kg / m 3 、heat-shrinkable fiber mesh 3 kg / m 3 、special viscosity-reducing and slump-retaining admixture 10.4 kg / m 3 、water 151 kg / m 3 ;

[0119] The special viscosity-reducing and slump-retaining admixture includes polycarboxylate superplasticizer mother liquor, air-entraining agent, retarder, boric acid, tetramethyl decyne diol foam control agent, acrylic acid-modified silicone defoaming agent and water;

[0120] The mass ratio of polycarboxylate superplasticizer mother liquor, air-entraining agent, retarder, boric acid, tetramethyl decyne diol foam control agent, acrylic acid-modified silicone defoaming agent and water is 54:0.04:2:1.7:0.1:0.05:34;

[0121] The polycarboxylate superplasticizer mother liquor is polycarboxylate high-adaptability superplasticizer mother liquor, produced by Jiangsu Sobute New Materials Co., Ltd.; the air-entraining agent is high-efficiency air-entraining agent for concrete, produced by Jiangsu Sobute New Materials Co., Ltd.; the retarder is The concrete retarder is produced by Jiangsu Sobute New Materials Co., Ltd.; boric acid is a white crystalline powder produced by Tianjin Beichen Fangzheng Reagent Factory; the tetramethyl decynediol foam control agent is produced by Jiangsu Sobute New Materials Co., Ltd.; the acrylic acid modified silicone defoamer is specifically type defoamer, produced by Jiangsu Sobute New Materials Co., Ltd.;

[0122] The high-alumina phase cementitious material includes a mixture of P·II 52.5 Portland cement (352.8 kg / m 3 ), P·II 42.5 sulfoaluminate high-iron phase cement (151.2 kg / m 3 ), fly ash microspheres (88.2 kg / m 3 ), and silica fume (37.8 kg / m 3 );

[0123] The P·II 42.5 sulfoaluminate high-iron phase cement is a P·II 42.5 high-iron phase sulfoaluminate cement containing Q phase;

[0124] The 28-day activity index of fly ash microspheres is 109%, and the water demand ratio is 101%;

[0125] The mass content of SiO2 in silica fume is ≥90%, the specific surface area is ≥20300 m 2 / kg, and the 28-day activity index is ≥100%.

[0126] The P·II 42.5 high-iron phase sulfoaluminate cement containing Q phase is prepared by the following method:

[0127] S1. Mix fly ash, limestone, magnesite, and calcium sulfate to obtain a first mixture; the mass ratio of fly ash, limestone, magnesite, and calcium sulfate is 60:20:5:10;

[0128] S2. Heat the first mixture to 1330°C at a rate of 5°C / min and keep it for 40 min to obtain Q-phase calcium sulfoaluminate clinker;

[0129] S2. Mix red mud, limestone, bauxite, and calcium sulfate to obtain a second mixture; the mass ratio of red mud, limestone, bauxite, and calcium sulfate is 45:25:25:5;

[0130] S3. Heat the second mixture to 1300°C at a rate of 5°C / min and keep it for 45 min to obtain sulfoaluminate cement clinker;

[0131] S4. Mix the Q-phase calcium sulfoaluminate clinker and the sulfoaluminate cement clinker in a mass ratio of 50:50 to obtain a Q-phase-rich P·II 42.5 high-iron phase sulfoaluminate cement clinker;

[0132] S5. After mixing the rich Q-phase P·II 42.5 high-iron sulfoaluminate cement clinker with gypsum dihydrate, grind it to a specific surface area of 340 m 2 / kg to obtain the P·II 42.5 high-iron sulfoaluminate cement containing Q-phase; the mass of gypsum dihydrate is 10% of the mass of the rich Q-phase P·II 42.5 high-iron sulfoaluminate cement clinker;

[0133] The fiber reinforcement materials include copper-plated straight steel fibers (26 kg / m 3 ), multi-anchor steel fibers (26 kg / m 3 ), heat-shrinkable fibers (1 kg / m 3 ), and CaCO3 whiskers (10.5 kg / m 3 );

[0134] The copper-plated straight steel fibers are produced by Wuhan Xintu Engineering New Materials Technology Co., Ltd., with a nominal length of 13 mm, an equivalent diameter of 0.20 ± 0.02 mm, a fracture strength ≥ 2200 MPa, an elastic modulus of 210 GPa, and a tensile strength of 1300 Mpa;

[0135] The multi-anchor steel fibers are produced by Wuhan Xintu Engineering New Materials Co., Ltd., with a nominal length of 13 mm, an equivalent diameter of 0.2 ± 0.02 mm, a fracture strength ≥ 1200 MPa, an elastic modulus of 220 GPa, and a tensile strength of 1400 Mpa;

[0136] The preparation method of the heat-shrinkable fibers is the same as above. The length of the heat-shrinkable fibers is 12 mm, the shrinkage rate is 0.5% - 12%, the response temperature is 30°C - 100°C, the tensile strength is 700 MPa, and the elastic modulus is 15.0 GPa;

[0137] The CaCO3 whiskers are produced by Chuangbo Products Co., Ltd., Lingshou County, Hebei Province, with a nominal length of 15 μm, an elastic modulus of 610 Gpa, and a tensile strength of 4500 Mpa;

[0138] The fine aggregate is river sand, with an apparent density of 2600 kg / m 3 , a fineness modulus of 2.8, and a water absorption rate ≤ 8%;

[0139] The high-strength coarse aggregate is 5 - 16 mm continuously graded basalt coarse aggregate, with a basalt coarse aggregate strength of 169 MPa, a crushing value of 10%, a needle and flake content ≤ 5%, and an apparent density of 3000 kg / m 3 .

[0140] The preparation method of the above heat-shrinkable fiber-reinforced large-span box arch C80 high-toughness concrete includes the following steps:

[0141] S1. Mix the high-alumina cementitious material, fine aggregate, and high-strength coarse aggregate, and stir for 100 s. Then add water and a viscosity-reducing and slump-retention special admixture with a mass of 50%, and continue stirring. Then add the fiber-reinforcing material, stir for 30 s, and then add the remaining viscosity-reducing and slump-retention special admixture to obtain a mixture.

[0142] S2. Fix the heat-shrinkable fiber mesh in the mold, and then place the mixture in the mold and vibrate it to obtain the heat-shrinkable fiber mesh-reinforced large-span box arch C80 high-toughness concrete.

[0143] Example 2

[0144] The heat-shrinkable fiber mesh-reinforced large-span box arch C80 high-toughness concrete provided by the embodiment of the present application is the same as that in Example 1, except that the addition amount of the heat-shrinkable fiber mesh is 4.5 kg / m 3 , and the rest are the same as those in Example 1.

[0145] Example 3

[0146] The heat-shrinkable fiber mesh-reinforced large-span box arch C80 high-toughness concrete provided by the embodiment of the present application is the same as that in Example 1, except that the addition amount of the heat-shrinkable fiber mesh is 6 kg / m 3 , and the rest are the same as those in Example 1.

[0147] Comparative Example 1

[0148] The C80 concrete provided by this comparative example is the same as that in Example 1, except that the heat-shrinkable fiber mesh is not added, and the rest are the same as those in Example 1.

[0149] Comparative Example 2

[0150] The C80 concrete provided by this comparative example is the same as that in Example 1, except that the addition amount of the heat-shrinkable fiber mesh is 6 kg / m 3 , and P·II 52.5 portland cement is used to replace the high-alumina cementitious material, and the rest are the same as those in Example 1.

[0151] Comparative Example 3

[0152] The C80 concrete provided by this comparative example is the same as that in Example 1, except that the addition amount of the heat-shrinkable fiber mesh is 6 kg / m 3 , and the CaCO3 whiskers are not added, and the rest are the same as those in Example 1.

[0153] Performance test

[0154] Test the performance of the heat-shrinkable fiber mesh-reinforced large-span box arch C80 high-toughness concrete in Examples 1 to 3 and the concrete in Comparative Examples 1 to 3. The results are shown in Table 1 below.

[0155] Table 1 - Performance of concrete in different examples and comparative examples

[0156]

[0157]

[0158] The above results show that the compressive strength of the heat-shrinkable fiber mesh reinforced large-span box arch C80 high-toughness concrete obtained by the present invention is above 90MPa, and the flexural strength is above 10MPa, and it has excellent working performance, mechanical properties and volume stability. In addition, by comparing Example 1 with Comparative Example 1, it is found that the addition of the heat-shrinkable fiber mesh can effectively improve the strength and toughness of the concrete; by comparing Example 3 with Comparative Example 3, it is found that the addition of calcium carbonate whiskers reduces the working performance of the concrete, but improves the toughness index and mechanical properties of the concrete; by comparing Example 3 with Comparative Example 2, sulphoaluminate high-iron phase cement can effectively improve the bending toughness and volume stability of the concrete, and the addition of sulphoaluminate high-iron phase cement can greatly reduce the 56d volume shrinkage of the concrete.

[0159] It can be understood that the technical features of the above-described embodiments can be arbitrarily combined. In order to make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0160] The above are only preferred embodiments of the present application, and only specifically describe the technical principles of the present application. These descriptions are only for explaining the principles of the present application and cannot be interpreted as limiting the scope of protection of the present application in any way. Based on the explanation here, any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application, and other specific implementation methods of the present application that can be associated with the technicians in this field without creative work, should be included in the scope of protection of the present application.

Claims

1. A heat-shrinkable fiber mesh-reinforced long-span box arch C80 high-toughness concrete, characterized in that, It includes the following raw materials: 580 - 640 kg / m of high - alumina phase cementitious material 3 , 750 - 850 kg / m of fine aggregate 3 , 950 - 1100 kg / m of high - strength coarse aggregate 3 , 40 - 80 kg / m of fiber - reinforced material 3 , 3 - 8 kg / m of heat - shrinkable fiber mesh 3 , 9 - 11 kg / m of special admixture for viscosity reduction and slump retention 3 , 140 - 160 kg / m of water 3 ; The high-aluminum phase cementitious material includes a mixture of P•II 52.5 Portland cement, P•II 42.5 sulfoaluminate high-iron phase cement, fly ash microspheres, and silica fume; The P•II 42.5 sulfoaluminate high-iron phase cement is P•II 42.5 high-iron phase sulfoaluminate cement containing Q phase; The P•II 42.5 high-iron phase sulfoaluminate cement containing Q phase is prepared by the following method: Mix fly ash, limestone, magnesite, and calcium sulfate to obtain a first mixture; Heat the first mixture at a rate of 5~10 °C / min to 1290~1350 °C, calcine it, and keep it warm for 40~45 min to obtain Q phase-calcium sulfoaluminate clinker; Mix red mud, limestone, bauxite, and calcium sulfate to obtain a second mixture; The second mixture is calcined at a heating rate of 5 - 10 °C / min to 1290 - 1350 °C and held for 40 - 45 min to obtain -C3S-C4AF sulphoaluminate cement clinker; Mix Q-phase calcium sulfoaluminate clinker with -C3S-C4AF sulfoaluminate cement clinker to obtain Q-phase-rich P•II 42.5 high-iron-phase sulfoaluminate cement clinker; After mixing the rich Q-phase P•II 42.5 high-iron sulfoaluminate cement clinker with gypsum dihydrate and grinding it to a specific surface area of 330 - 350 m 2 / kg, the P•II 42.5 high-iron sulfoaluminate cement containing Q-phase is obtained; The fiber reinforcement material includes copper-plated straight steel fibers, multi-anchor steel fibers, heat-shrinkable fibers, and CaCO3 whiskers; The mass ratio of the copper-plated straight steel fibers, multi-anchor steel fibers, heat-shrinkable fibers, and CaCO3 whiskers is (20-30):(20-30):(1-2):(10-15).

2. The heat-shrinkable fiber mesh-reinforced long-span box arch C80 high-toughness concrete according to claim 1, wherein, The special viscosity-reducing and slump-retention admixture includes polycarboxylate superplasticizer mother liquor, air-entraining agent, retarder, boric acid, 2,4,7,9-tetramethyl-5-decyne-4,7-diol foam control agent, acrylic acid-modified silicone defoamer, and water; The mass ratio of the polycarboxylate superplasticizer mother liquor, air-entraining agent, retarder, boric acid, 2,4,7,9-tetramethyl-5-decyne-4,7-diol foam control agent, acrylic acid-modified silicone defoamer, and water is (52~56):(0.03~0.05):(1~2.5):(1.5~1.9):(0.05~0.2):(0.03~0.07):(33.65~35.15).

3. The heat-shrinkable fiber mesh-reinforced long-span box arch C80 high-toughness concrete according to claim 1, wherein The heat-shrinkable fiber mesh is a net structure woven from heat-shrinkable fibers. The heat-shrinkable fibers include a heat-shrinkable core material and a heat-shrinkable skin material coated on the outer periphery of the heat-shrinkable core material; The material of the heat-shrinkable skin material includes at least one of polyvinyl alcohol, polyethylene, and polyoxymethylene; The molecular weight of the polyvinyl alcohol is 170,000~220,000; The molecular weight of the polyethylene is 1,000,000~2,000,000; The molecular weight of the polyoxymethylene is 20,000~30,000; The material of the heat-shrinkable core material is polypropylene, and the molecular weight of the polypropylene is 6000~8000; The tensile strength of the heat-shrinkable fibers is 500~1200 MPa, the elastic modulus is 7~35 GPa, the shrinkage rate is 0.5%~12%, and the response temperature is 30 °C~100 °C.

4. The heat-shrinkable fiber mesh-reinforced long-span box arch C80 high-toughness concrete according to claim 1, characterized in that The 28-day activity index of the fly ash microspheres is 109%, and the water demand ratio is 101%; The SiO2 mass content in the silica fume is ≥90%, the specific surface area is ≥20300 m 2 / kg, and the 28-day activity index is ≥100%.

5. The heat-shrinkable fiber mesh-reinforced long-span box arch C80 high-toughness concrete according to claim 1, wherein The nominal length of the copper-plated straight steel fibers is 6~13 mm, the equivalent diameter is 0.20±0.02 mm, the breaking strength is ≥2200 MPa, the elastic modulus is 190~230 GPa, and the tensile strength is 400~2100 MPa; The nominal length of the multi-anchor steel fibers is 6~13 mm, the equivalent diameter is 0.18±0.02 mm, the breaking strength is ≥1300 MPa, the elastic modulus is 220~240 GPa, and the tensile strength is 600~2200 MPa; The length of the heat-shrinkable fiber is 10 mm to 12 mm, the tensile strength is 500 - 1200 MPa, the elastic modulus is 7 - 35 GPa, the shrinkage rate is 0.5% - 12%, and the response temperature is 30°C - 100°C; The nominal length of the CaCO3 whisker is 10 - 20 μm, the elastic modulus is 410 - 710 GPa, and the tensile strength is 3000 - 6000 MPa.

6. The heat-shrinkable fiber mesh-reinforced long-span box arch C80 high-toughness concrete according to claim 1, wherein The mass ratio of the fly ash, limestone, magnesite, and calcium sulfate is (60 - 70):(15 - 20):(5 - 10):(5 - 10); The mass ratio of the red mud, limestone, bauxite, and calcium sulfate is (40 - 45):(25 - 30):(20 - 25):(5 - 10); The Q-phase-calcium sulfoaluminate clinker, -C3S-C4AF sulfoaluminate cement clinker has a mass ratio of (50~60):(40~50); The mass of the gypsum dihydrate is 10 - 15% of the mass of the rich-Q phase P•II 42.5 high-iron phase sulfoaluminate cement clinker; The addition amount of the P•II 52.5 portland cement is 350~355 kg / m 3 , the addition amount of the P•II 42.5 sulfoaluminate high-iron phase cement is 150~155 kg / m 3 , the addition amount of fly ash microspheres is 80~90 kg / m 3 , the addition amount of silica fume is 30~40 kg / m 3 .

7. The heat-shrinkable fiber mesh-reinforced long-span box arch C80 high-toughness concrete according to claim 1, characterized in that, The fine aggregate is river sand with an apparent density of 2560 - 2650 kg / m 3 , a fineness modulus of 2.8, and a water absorption rate ≤ 8%; The high-strength coarse aggregate is a continuously graded basalt ultra-high-strength coarse aggregate with a particle size of 5 - 16 mm, and the apparent density is 2900 - 3000 kg / m 3 .

8. A preparation method of heat-shrinkable fiber mesh-reinforced long-span box arch C80 high-toughness concrete as described in any one of claims 1 to 7, characterized in that, It includes the following steps: Mix the high-aluminum phase cementitious material, fine aggregate, and high-strength coarse aggregate and stir for 60 - 120 s, then add water and a special viscosity-reducing and slump-retention admixture with a mass of 45 - 55%, and continue stirring; then add the fiber reinforcement material, and after stirring, add the remaining special viscosity-reducing and slump-retention admixture to obtain a mixture; Fix the heat-shrinkable fiber mesh in the mold, and then place the mixture in the mold and vibrate to obtain the heat-shrinkable fiber mesh-reinforced long-span box arch C80 high-toughness concrete.

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