A multi-scale toughened and compensated shrinkage C80 high crack-resistant self-compacting concrete and its preparation method

Abstract

The present invention provides a multi-scale toughening and shrinkage-compensating C80 high-crack-resistant self-compacting concrete and a preparation method thereof. The present invention uses low-shrinkage and crack-resistant composite cement to compensate for the shrinkage of C80 concrete, avoiding the disadvantage that general expansive agents are difficult to function due to the low water-cement ratio design of ordinary C80 concrete, and solving the problem that C80 concrete is prone to shrinkage and cracking. The present invention uses multi-scale hybrid fibers to strengthen toughness and crack resistance, and uses high-strength fine steel fibers, multi-anchor steel fibers, and temperature-shrinkage-induced organic fibers to improve the toughness of C80 concrete and its crack resistance in the heating / cooling stages on a macro scale; and uses CaCO3 and CaSO4 composite whiskers and nano-silica-modified water-based polyurethane to form a uniform three-dimensional toughening network inside the cementitious slurry, thereby improving the tensile strength and toughness of C80 concrete on a micron scale. This allows C80 concrete to have the characteristics of low shrinkage, high toughness, and high crack resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and in particular to a multi-scale toughening and shrinkage-compensating C80 high-crack-resistance self-compacting concrete and a preparation method thereof. Background Art

[0002] Western my country is home to many deep mountain gorges and turbulent rivers. Planned highways and railways have a high bridge-tunnel ratio, creating a significant demand for heavy-duty, high-pier, and long-span bridges. Reinforced concrete rigid-frame arch bridges combine the characteristics of both concrete-filled steel tubular (CFST) and steel-reinforced concrete (SRC), offering excellent stiffness and stability, making them highly competitive in the design of long-span bridges. However, they also suffer from numerous structural system transitions, complex structural forces, and long construction periods, making them unsuitable for bridge construction in complex mountainous areas.

[0003] Reinforced concrete box arches offer low construction costs, large spans, and high bearing capacity. Compared to reinforced concrete rigid frames, reinforced concrete box arches offer advantages such as ease of location, reduced equipment lifting requirements, and a shorter construction period. However, currently, reinforced concrete box arches are mostly cast using C50-C60 concrete, with wall thicknesses ranging from 50-120 cm. Due to their heavy weight, the span of a cantilevered cast-in-place basket is generally limited to 200 meters. Current research focuses on increasing the span of a cantilevered cast-in-place reinforced concrete box arch to address the challenges of difficult and dangerous construction.

[0004] Using C80 concrete to design and manufacture box walls not only improves the overall performance and service life of the structure, but also reduces wall thickness and deadweight, increases the span of the reinforced concrete box arch hanging basket, ensures project safety and reliability, and reduces maintenance and repair costs. However, current C80 concrete suffers from defects such as low compressive strength, low flexural strength, and low flexural toughness, necessitating improvements. Summary of the Invention

[0005] In view of this, the present invention proposes a multi-scale toughening and shrinkage-compensating C80 high-crack-resistant self-compacting concrete and a preparation method thereof to solve or partially solve the problems existing in the prior art.

[0006] In the first aspect, the present invention provides a multi-scale toughening and shrinkage compensating C80 high crack resistance self-compacting concrete, comprising the following raw materials: low shrinkage and crack resistance composite cement 400-500 kg / m 3 , viscosity-adjusting and reinforcing mineral admixture 150~200kg / m 3 , fine aggregate 680~800kg / m 3 , high-strength coarse aggregate 950~1100kg / m 3 , multi-scale mixed fiber 50~80kg / m 3, Nano-silica modified waterborne polyurethane emulsion 9~20kg / m 3 , high efficiency water reducing, slump retaining, foam stabilizing and viscosity regulating admixture 9~11kg / m 3 , water 140~160kg / m 3 ;

[0007] The low shrinkage and crack-resistant composite cement is prepared by compounding P·II 52.5 silicate cement and P·II 42.5 high-iron phase sulphoaluminate cement containing Q phase.

[0008] Preferably, the P·II 42.5 high iron phase sulphoaluminate cement containing Q phase is prepared by the following method:

[0009] Mixing fly ash, limestone, magnesite, and calcium sulfate to obtain a first mixture;

[0010] The first mixture is heated to 1290-1350° C. at a rate of 5-10° C. / min and calcined, and kept at this temperature for 40-45 minutes to obtain Q phase-calcium sulfoaluminate clinker;

[0011] Mixing red mud, limestone, bauxite, and calcium sulfate to obtain a second mixture;

[0012] The second mixed material is heated to 1290-1350°C at a rate of 5-10°C / min and calcined, and kept at this temperature for 40-45 minutes to obtain sulphoaluminate cement clinker;

[0013] Q phase - calcium sulphoaluminate clinker, Sulphoaluminate cement clinker was mixed to obtain Q-rich P·II 42.5 high iron phase sulphoaluminate cement clinker;

[0014] The Q-rich P·II 42.5 high iron phase sulphoaluminate cement clinker is mixed with dihydrate gypsum and ground to a specific surface area of 330-350m 2 / kg, that is, P·II 42.5 high iron phase sulphoaluminate cement containing Q phase is obtained.

[0015] Preferably, the multi-scale hybrid fibers are composed of high-strength fine straight steel fibers, multi-anchor steel fibers, temperature shrinkage-induced organic fibers, CaCO3 whiskers and CaSO4 whiskers;

[0016] The high-strength fine straight steel fiber has a nominal length of 6 to 13 mm, an equivalent diameter of 0.20 ± 0.02 mm, a breaking strength of ≥ 2200 MPa, an elastic modulus of 190 to 230 GPa, and a tensile strength of 400 to 2100 MPa;

[0017] The multi-anchor steel fiber has a nominal length of 6 to 13 mm, an equivalent diameter of 0.2 ± 0.02 mm, a breaking strength ≥ 1200 MPa, an elastic modulus of 210 to 230 GPa, and a tensile strength of 550 to 2150 MPa;

[0018] The temperature shrinkage-induced organic fiber has a tensile strength of 500-1200 MPa, an elastic modulus of 7-35 GPa, a shrinkage rate of 0.5%-12%, and a response temperature of 30°C-100°C;

[0019] The CaSO4 whiskers have a nominal length of 100 to 300 μm, an equivalent diameter of 1 to 3 μm, and an apparent density of 2.3 to 2.6 g / cm 3 ;

[0020] The CaCO3 whisker has a nominal length of 10 to 20 μm and an elastic modulus of 410 to 710 GPa.

[0021] Preferably, the mass ratio of the P·II 52.5 silicate cement to the P·II 42.5 high iron phase sulphoaluminate cement containing the Q phase is (60-70):(30-40);

[0022] The mass ratio of the fly ash, limestone, magnesite and calcium sulfate is (60-70):(15-20):(5-10):(5-10);

[0023] The mass ratio of the red mud, limestone, bauxite and calcium sulfate is (40-45):(25-30):(20-25):(5-10);

[0024] The Q phase - calcium sulphoaluminate clinker, The mass ratio of sulphoaluminate cement clinker is (50-60):(40-50);

[0025] The mass of the dihydrate gypsum is 10-15% of the mass of the Q-rich P·II 42.5 high-iron phase sulphoaluminate cement clinker;

[0026] The addition amount of the high-strength fine straight steel fiber is 20-30 kg / m 3 ;

[0027] The addition amount of the multi-anchor steel fiber is 20-30 kg / m 3 ;

[0028] The addition amount of the temperature shrinkage inducible organic fiber is 1-2 kg / m 3 ;

[0029] The amount of CaCO3 whiskers added is 5-8 kg / m 3

[0030] The amount of CaSO4 whiskers added is 5-8 kg / m 3 .

[0031] Preferably, the viscosity-adjusting and reinforcing mineral admixture comprises a mixture of fly ash microbeads and silica fume;

[0032] The amount of fly ash microbeads added is 75-100 kg / m 3 ;

[0033] The amount of silica fume added is 75-100 kg / m 3 ;

[0034] The fly ash microbeads have a 28-day activity index of 107% and a water requirement ratio of 101%;

[0035] The SiO2 mass content in the silica fume is ≥91%, and the specific surface area is ≥20100m 2 / kg, 28d activity index ≥101%.

[0036] Preferably, the preparation method of the nano-silica modified waterborne polyurethane emulsion is:

[0037] Adding nano-silicon dioxide into aqueous polyurethane emulsion, and uniformly dispersing the nano-silicon dioxide in the aqueous polyurethane emulsion by ultrasonic dispersion or high shear stirring, thereby obtaining nano-silicon dioxide modified aqueous polyurethane emulsion;

[0038] The nano-silicon dioxide has a particle size of 10 to 20 nm and a specific surface area of 200 to 400 m 2 / g, apparent density is 2.2~2.5g / cm 3 .

[0039] Preferably, the high-efficiency water-reducing, slump-preserving, foam-stabilizing and viscosity-adjusting admixture comprises a polycarboxylate water-reducing agent mother liquor, an air-entraining agent, boric acid, a tetramethyldecynediol foam control agent, a polyhydroxycarboxylate retarder and water;

[0040] Among them, the addition amount of polycarboxylate water-reducing agent mother liquor is 6.1~6.2kg / m 3 ;

[0041] The amount of air entraining agent added is 0.003~0.005kg / m 3 ;

[0042] The amount of boric acid added is 0.11~0.13kg / m 3 ;

[0043] The addition amount of tetramethyldecynediol foam control agent is 0.01~0.02kg / m 3 ;

[0044] The addition amount of polyhydroxycarboxylate retarder is 0.11~0.13kg / m 3 ;

[0045] The amount of water added is 3.5-3.7 kg / m 3 .

[0046] Preferably, the fine aggregate is river sand, and the apparent density of the fine aggregate is 2560-2650 kg / m 3 , the fineness modulus is 2.8.

[0047] Preferably, the high-strength coarse aggregate is 5-16 mm continuously graded basalt coarse aggregate, the basalt coarse aggregate has a strength of 169 MPa, a crushing value of 10%, a needle-like content ≤ 5%, and an apparent density of 2900-3000 kg / m 3 .

[0048] In a second aspect, the present invention further provides a method for preparing the multi-scale toughening and shrinkage compensating C80 high crack resistance self-compacting concrete, comprising the following steps:

[0049] Low shrinkage and crack-resistant composite cement, viscosity-adjusting and reinforcing mineral admixtures, fine aggregate, high-strength coarse aggregate and multi-scale mixed fibers are mixed and stirred, and then water, high-efficiency water-reducing and collapse-preserving, foam-stabilizing and viscosity-adjusting admixtures, and nano-silica modified waterborne polyurethane emulsion are added and stirred to obtain multi-scale toughening and shrinkage-compensating C80 high crack-resistant self-compacting concrete.

[0050] The multi-scale toughening and shrinkage-compensating C80 high-crack-resistance self-compacting concrete and its preparation method of the present invention have the following beneficial effects compared with the prior art:

[0051] 1. The present invention uses low-shrinkage, crack-resistant composite cement to compensate for the shrinkage of C80 concrete, avoiding the drawback that general expansive agents are difficult to function due to the low water-cement ratio design of ordinary C80 concrete, and solving the problem of C80 concrete's easy shrinkage and cracking. The present invention uses multi-scale hybrid fibers for toughening and crack resistance, and utilizes high-strength fine steel fibers, multi-anchor steel fibers, and temperature-shrinkage-induced organic fibers to improve the toughness of C80 concrete and its crack resistance during the heating and cooling stages on a macroscale. It also utilizes CaCO3 and CaSO4 composite whiskers and nano-silica-modified waterborne polyurethane to form a uniform three-dimensional toughening network within the cementitious slurry, improving the tensile strength and toughness of C80 concrete on a micrometer scale. This allows C80 concrete to possess the characteristics of low shrinkage, high toughness, and high crack resistance.

[0052] 2. The present invention adopts viscosity-adjusting and reinforcing mineral admixtures and high-efficiency water-reducing, slump-preserving, foam-stabilizing and viscosity-adjusting admixtures to improve the fluidity of concrete; by incorporating polycarboxylate water-reducing agent mother liquor and fly ash microbeads, the fluidity and workability of concrete are improved; by incorporating high-efficiency air-entraining agent and tetramethyldecynediol foam control agent, a large number of fine bubbles of 50 to 100 microns are introduced, achieving good fluidity, cohesiveness and long-term pumping stability of C80 concrete at a low water-binder ratio, thereby realizing the self-compacting design of C80 concrete. DETAILED DESCRIPTION

[0053] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0054] It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments. In addition, in the description of this application, the term "including" means "including but not limited to". Various embodiments of the present invention may be in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be understood as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values within the range. For example, the range description from 1 to 6 should be considered to have 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., as well as single numbers within the numbered ranges, such as 1, 2, 3, 4, 5 and 6, regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited numbers (fractions or integers) within the indicated range.

[0055] The embodiment of the present application provides a multi-scale toughening and shrinkage compensating C80 high crack resistance self-compacting concrete, including the following raw materials: low shrinkage and crack resistance composite cement 400-500 kg / m 3 , viscosity-adjusting and reinforcing mineral admixture 150~200kg / m 3 , fine aggregate 680~800kg / m 3 , high-strength coarse aggregate 950~1100kg / m 3 , multi-scale mixed fiber 50~80kg / m 3 , Nano-silica modified waterborne polyurethane emulsion 9~20kg / m 3 , high efficiency water reducing, slump retaining, foam stabilizing and viscosity regulating admixture 9~11kg / m 3 , water 140~160kg / m 3 ;

[0056] The low shrinkage and crack-resistant composite cement is prepared by compounding P·II 52.5 silicate cement and P·II 42.5 high iron phase sulphoaluminate cement containing Q phase.

[0057] The present invention aims to develop an organic-inorganic composite multi-scale toughening, shrinkage-compensating, C80 high-crack-resistance self-compacting concrete suitable for the construction of heavy-load, high-pier, and long-span bridges by rationally utilizing P·II 42.5 high-iron phase sulphoaluminate cement containing Q phase, nano-silica-modified waterborne polyurethane, multi-scale hybrid fibers, and high-efficiency water-reducing, slump-preserving, foam-stabilizing, and viscosity-regulating admixtures. The concrete is suitable for the construction of heavy-load, high-pier, and long-span bridges. The P·II high-iron phase sulphoaluminate cement containing Q phase is composed of minerals sintered at 1290-1350°C, with a Q phase mineral composition of 25%-30% (Ca 20 Al 26 Mg3Si3O 68 ), The clinker of mineral, 20%-25% C4AF mineral, 0%-5% C2S mineral and 10%-15% dihydrate gypsum are ground together to a specific surface area of 330-350m 2 The low shrinkage and crack-resistant composite cement has a 3-day compressive strength of 28.5 MPa and a 28-day compressive strength of 57.8 MPa, as well as a 3-day flexural strength of 6.8 MPa and a 28-day flexural strength of 8.9 MPa.

[0058] In some embodiments, P·II 42.5 high iron phase sulphoaluminate cement containing Q phase is prepared by the following method:

[0059] Mixing fly ash, limestone, magnesite, and calcium sulfate to obtain a first mixture;

[0060] The first mixture is heated to 1290-1350° C. at a rate of 5-10° C. / min and calcined, and kept at this temperature for 40-45 minutes to obtain Q phase-calcium sulfoaluminate clinker;

[0061] Mixing red mud, limestone, bauxite, and calcium sulfate to obtain a second mixture;

[0062] The second mixed material is heated to 1290-1350°C at a rate of 5-10°C / min and calcined, and kept at this temperature for 40-45 minutes to obtain sulphoaluminate cement clinker;

[0063] Q phase - calcium sulphoaluminate clinker, Sulphoaluminate cement clinker was mixed to obtain Q-rich P·II 42.5 high iron phase sulphoaluminate cement clinker;

[0064] The Q-rich P·II 42.5 high iron phase sulphoaluminate cement clinker is mixed with dihydrate gypsum and ground to a specific surface area of 330-350m2 / kg, that is, P·II 42.5 high iron phase sulphoaluminate cement containing Q phase is obtained.

[0065] The Q phase and C4AF mineral phase in the P·II 42.5 high-iron phase sulfoaluminate cement used in the present invention can synergistically regulate the microstructure of the composite cement hydration product C-(A)-SH gel to form a highly Al-doped C-(A)-SH gel, thereby improving the mechanical properties and toughness of the C-(A)-SH gel. At the same time, C4AF reacts with gypsum to generate needle-rod-shaped ettringite crystals that are uniformly distributed in the C-(A)-SH gel, forming ettringite microcrystals to toughen the C-(A)-SH gel, thereby significantly improving the strength and toughness of the composite cement hydrated gelled slurry. In addition, the Q phase in the high-iron phase sulfoaluminate cement is hydrated to form magnesium hydroxide and The mineral phase is hydrated to form ettringite. Expansive hydration products such as magnesium hydroxide and ettringite compensate for the shrinkage of C80 concrete and improve the crack resistance of concrete.

[0066] In some embodiments, the multi-scale hybrid fibers are composed of high-strength fine straight steel fibers, multi-anchor steel fibers, temperature-shrinkage-induced organic fibers, CaCO3 whiskers, and CaSO4 whiskers;

[0067] The nominal length of high-strength fine straight steel fiber is 6-13mm, the equivalent diameter is 0.20±0.02mm, the breaking strength is ≥2200MPa, the elastic modulus is 190-230GPa, and the tensile strength is 400-2100MPa;

[0068] The nominal length of the multi-anchor steel fiber is 6-13mm, the equivalent diameter is 0.2±0.02mm, the breaking strength is ≥1200MPa, the elastic modulus is 210-230GPa, and the tensile strength is 550-2150Mpa;

[0069] The temperature-shrinkage-induced organic fiber has a tensile strength of 500-1200 MPa, an elastic modulus of 7-35 GPa, a shrinkage rate of 0.5%-12%, and a response temperature of 30°C-100°C.

[0070] The nominal length of CaSO4 whiskers is 100-300 μm, the equivalent diameter is 1-3 μm, and the apparent density is 2.3-2.6 g / cm 3 ;

[0071] The nominal length of CaCO3 whiskers is 10-20 μm, and the elastic modulus is 410-710 GPa.

[0072] The present invention adopts multi-scale hybrid fiber toughening and crack resistance. By adding high-strength fine steel fibers and multi-anchor steel fibers into C80 concrete, stress is dispersed, micro cracks are bridged, and the toughness of C80 concrete is improved on a macro scale. By adding temperature-shrinkage-induced fibers, the pre-compressive stress generated on the cementitious slurry during hydration and heat release of the fiber molecules is reconstructed and shrinkage occurs during the hydration of the cementitious slurry. This partially or completely offsets the temperature difference stress inside and outside the concrete, thereby improving the crack resistance of the concrete during the heating / cooling stage. By adding CaCO3 and CaSO4 composite whiskers, more nucleation sites and additional SO4 are provided for the formation of ettringite. 2- , filling microcracks and micropores, improving the density and durability of concrete. By incorporating nano-silica modified waterborne polyurethane, a uniform three-dimensional toughening network is formed inside the cementitious slurry, strengthening the internal bonding force of the concrete, improving the stability of the overall structure, and improving the tensile strength and toughness of C80 concrete at the micro-nano scale.

[0073] In some embodiments, the mass ratio of P·II 52.5 silicate cement to P·II 42.5 high iron phase sulfoaluminate cement containing Q phase is (60-70):(30-40).

[0074] In some embodiments, the mass ratio of fly ash, limestone, magnesite, and calcium sulfate is (60-70):(15-20):(5-10):(5-10).

[0075] In some embodiments, the mass ratio of red mud, limestone, bauxite, and calcium sulfate is (40-45):(25-30):(20-25):(5-10).

[0076] In some embodiments, Q phase - calcium sulfoaluminate clinker, The mass ratio of sulphoaluminate cement clinker is (50-60):(40-50).

[0077] In some embodiments, the mass of the dihydrate gypsum is 10-15% of the mass of the Q-phase-rich P·II 42.5 high-iron phase sulphoaluminate cement clinker.

[0078] In some embodiments, the addition amount of high-strength fine straight steel fiber is 20-30 kg / m 3 .

[0079] In some embodiments, the amount of multi-anchor steel fiber added is 20-30 kg / m 3 .

[0080] In some embodiments, the amount of temperature shrinkage inducible organic fiber added is 1-2 kg / m 3 .

[0081] In some embodiments, the amount of CaCO3 whiskers added is 5-8 kg / m3 .

[0082] In some embodiments, the amount of CaSO4 whiskers added is 5-8 kg / m 3 .

[0083] In some embodiments, the viscosity-adjusting and reinforcing mineral admixture includes a mixture of fly ash microspheres and silica fume.

[0084] In some embodiments, the amount of fly ash microbeads added is 75-100 kg / m 3 .

[0085] In some embodiments, the amount of silica fume added is 75-100 kg / m 3 .

[0086] In some embodiments, the fly ash microspheres have a 28d activity index of 107% and a water requirement ratio of 101%.

[0087] In some embodiments, the SiO2 mass content in the silica fume is ≥91%, and the specific surface area is ≥20100m 2 / kg, 28d activity index ≥101%.

[0088] In some embodiments, the preparation method of nano-silica modified waterborne polyurethane emulsion is:

[0089] Adding nano-silicon dioxide into aqueous polyurethane emulsion, and uniformly dispersing the nano-silicon dioxide in the aqueous polyurethane emulsion by ultrasonic dispersion or high shear stirring, thereby obtaining nano-silicon dioxide modified aqueous polyurethane emulsion;

[0090] The particle size of nano-silicon dioxide is 10-20nm, and the specific surface area is 200-400m 2 / g, apparent density is 2.2~2.5g / cm 3 .

[0091] In some embodiments, the high-efficiency water-reducing, slump-preserving, foam-stabilizing and viscosity-adjusting admixture includes a polycarboxylate water-reducing agent mother liquor, an air-entraining agent, boric acid, a tetramethyldecynediol foam control agent, a polyhydroxycarboxylate retarder and water.

[0092] Specifically, the polycarboxylate water-reducing agent mother liquor has a water reduction rate of 30%-35% and a slump retention time of 2h-4h; the air-entraining agent introduces tiny bubbles, and the air content loss after standing for 1h is less than 1%; boric acid extends the initial setting time of concrete from 3h to 4h; and the polyhydroxycarboxylate retarder extends the initial setting time of concrete to 1h-4h.

[0093] In some embodiments, the amount of polycarboxylate water-reducing agent mother solution added is 6.1-6.2 kg / m 3 ;

[0094] The amount of air entraining agent added is 0.003~0.005kg / m 3 ;

[0095] The amount of boric acid added is 0.11~0.13kg / m 3 ;

[0096] The addition amount of tetramethyldecynediol foam control agent is 0.01~0.02kg / m 3 ;

[0097] The addition amount of polyhydroxycarboxylate retarder is 0.11~0.13kg / m 3 ;

[0098] The amount of water added is 3.5-3.7 kg / m 3 .

[0099] The present invention adopts viscosity-regulating and reinforcing mineral admixtures and high-efficiency water-reducing, slump-preserving, foam-stabilizing and viscosity-regulating admixtures to improve the fluidity of concrete; by adding polycarboxylate water-reducing agent mother liquor and fly ash microbeads, the fluidity and workability of concrete are improved; by adding high-efficiency air-entraining agent and tetramethyldecynediol foam control agent, a large number of fine bubbles of 50 to 100 microns are introduced, thereby achieving good fluidity, cohesiveness and long-term pumping stability of C80 concrete at a low water-binder ratio, thereby realizing the self-compacting design of C80 concrete.

[0100] In some embodiments, the fine aggregate is river sand, and the apparent density of the fine aggregate is 2560-2650 kg / m 3 , the fineness modulus is 2.8.

[0101] In some embodiments, the high-strength coarse aggregate is a basalt coarse aggregate with a continuous gradation of 5 to 16 mm, wherein the basalt coarse aggregate has a strength of 169 MPa, a crushing value of 10%, a needle-like content of ≤5%, and an apparent density of 2900 to 3000 kg / m 3 .

[0102] In some embodiments, a method for preparing temperature-shrinkage-induced organic fibers comprises the following steps:

[0103] S1. Two extruders are used to extrude the heat-shrinkable core material mixture and the heat-shrinkable skin material mixture into a die head with two cavities, wherein the heat-shrinkable skin material enters the cavity corresponding to the skin material, and the heat-shrinkable core material enters the cavity corresponding to the core material. The materials in the two cavities converge at the position of the extruder spinneret; wherein 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 (melt 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;

[0104] S2, adding 1%-5% (mass concentration) silane coupling agent solution to the composite fiber obtained in step S1 for modification for 10-20 minutes, drying, and then indenting the surface to enhance its bonding performance with the concrete paste;

[0105] S3, adding the composite fiber obtained in step S2 to a modified polyvinyl alcohol solution containing an expansion component for coating and modification, taking it out and drying it to obtain a temperature-shrinkage-induced organic fiber;

[0106] The heat shrinkable leather material mixture contains the following raw materials and their weight percentages: polyvinyl alcohol 97%, maleic anhydride grafted compatibilizer 1.5%, and phthalate plasticizer 1.5%. The extrusion pressure of the leather material cavity is 8 MPa, and the melt temperature is maintained at 250°C.

[0107] The heat shrinkable core material mixture comprises the following raw materials and their mass percentages: 98% polypropylene, 2% rigidity-enhancing nucleating agent (aluminum aromatic carboxylate and sodium benzoate in a mass ratio of 1:1); the heat shrinkable core material mixture has a melting temperature of 200-280°C; and the corresponding cavity extrusion pressure is 7-10 MPa;

[0108] In the final extrusion section corresponding to the spinneret, the extrusion temperature of the two molten materials is maintained at a temperature suitable for both materials, namely 200-220° C., and the extrusion pressure is 3-10 MPa.

[0109] In some embodiments, the coating modification temperature is room temperature and the time is 10 to 24 hours.

[0110] In some embodiments, the expansion agent is a compound of a calcium oxide expansion agent and a calcium sulfoaluminate expansion agent; preferably, the expansion agent is a compound of a calcium oxide expansion agent and a calcium sulfoaluminate expansion agent in a mass ratio of 1:40 to 50;

[0111] In some embodiments, the modified polyvinyl alcohol solution with the expansion component added is obtained by uniformly mixing a polyvinyl alcohol solution (6 wt %) and a liquid expansion agent in a mass ratio of 7:3.

[0112] Based on the same inventive concept, the present invention also provides a method for preparing the above-mentioned multi-scale toughening and shrinkage-compensating C80 high-crack-resistant self-compacting concrete, comprising the following steps:

[0113] Low shrinkage and crack-resistant composite cement, viscosity-adjusting and reinforcing mineral admixtures, fine aggregate, high-strength coarse aggregate and multi-scale mixed fibers are mixed and stirred, and then water, high-efficiency water-reducing and collapse-preserving, foam-stabilizing and viscosity-adjusting admixtures, and nano-silica modified waterborne polyurethane emulsion are added and stirred to obtain multi-scale toughening and shrinkage-compensating C80 high crack-resistant self-compacting concrete.

[0114] In some embodiments, low shrinkage and crack-resistant composite cement, viscosity-adjusting and reinforcing mineral admixtures, fine aggregate, high-strength coarse aggregate, and multi-scale mixed fibers are mixed and stirred for 60 to 120 seconds, and then water, high-efficiency water-reducing and collapse-preserving, foam-stabilizing and viscosity-adjusting admixtures, and nano-silica-modified waterborne polyurethane emulsion are added and stirred for 120 seconds to obtain multi-scale toughening and shrinkage-compensating C80 high-cracking-resistant self-compacting concrete.

[0115] The present invention adopts P II 42.5 high iron phase sulphoaluminate cement containing Q phase (25%-30% Q phase minerals, 40%-45% Minerals, 20%-25% C4AF minerals, 5%-10% dihydrate gypsum) are compounded with PII 52.5 silicate cement to form a low shrinkage and crack-resistant composite cement; the Q phase in the high iron phase sulphoaluminate cement is used to form a low shrinkage and crack-resistant composite cement. The C4AF mineral phase regulates the microstructure of C-(A)-SH gel to form calcium aluminate microcrystal-toughened C-(A)-SH gel, which compensates for shrinkage and enhances toughness; multi-scale hybrid fibers are used to enhance toughness and crack resistance. By adding high-strength fine steel fibers and multi-anchor steel fibers, stress is dispersed, microcracks are bridged, and the toughness of C80 concrete is improved on a macro scale; by adding temperature-shrinkage-induced fibers, their temperature-rise shrinkage characteristics are used to partially or completely offset the temperature difference stress inside and outside the concrete, thereby improving the crack resistance of concrete on a micro-meso scale; by adding CaCO3 and CaSO4 composite whiskers and nano-silica-modified water-based polyurethane, a uniform three-dimensional toughening network is formed inside the cementitious slurry, thereby improving the tensile strength and toughness of C80 concrete on a micron scale. By incorporating viscosity-adjusting and reinforcing mineral admixtures and highly efficient water-reducing, slump-preserving, and foam-stabilizing viscosity-adjusting admixtures, the viscosity of concrete is reduced and its fluidity is improved using fly ash microspheres, polycarboxylic acid high-efficiency water-reducing agents, and air-entraining agents. Silica fume is used to improve the encapsulation of fibers and aggregates, preventing them from sinking during vibration. By incorporating highly efficient air-entraining agents and tetramethyldecynediol foam control agents, a large number of tiny bubbles (50 to 100 micrometers) are introduced, achieving excellent fluidity, cohesiveness, and long-term pumping stability in C80 concrete at low water-binder ratios, thereby achieving a self-compacting design for C80 concrete. The organic-inorganic composite multi-scale toughening and shrinkage-compensating C80 high-crack-resistance self-compacting concrete of the present invention combines the characteristics of high strength, high toughness, self-compacting, and high crack resistance, solving the problem of insufficient tensile strength and easy shrinkage cracking of concrete during the construction of long-span concrete box arch bridges using hanging baskets, and has important practical application value.

[0116] The present invention uses low-shrinkage, crack-resistant composite cement to compensate for shrinkage in C80 concrete, avoiding the drawback of general expansive agents being difficult to function due to the low water-cement ratio of ordinary C80 concrete, and solving the problem of C80 concrete being prone to shrinkage and cracking. The present invention uses multi-scale hybrid fibers for toughening and crack resistance, utilizing high-strength fine steel fibers, multi-anchor steel fibers, and temperature-shrinkage-induced organic fibers to improve the toughness of C80 concrete and its crack resistance during the heating and cooling stages on a macroscale. Furthermore, CaCO3 and CaSO4 composite whiskers and nano-silica-modified waterborne polyurethane are used to form a uniform three-dimensional toughening network within the cementitious slurry, improving the tensile strength and toughness of C80 concrete on a micrometer scale. This allows C80 concrete to possess the characteristics of low shrinkage, high toughness, and high crack resistance.

[0117] The following further illustrates the multi-scale toughening, shrinkage-compensating, C80, high-crack-resistance, self-compacting concrete and its preparation method of the present invention using specific examples. This section further illustrates the present invention in conjunction with specific examples, but should not be construed as limiting the present invention. Unless otherwise specified, the technical means employed in the examples are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment employed in the present invention are conventional reagents, methods, and equipment in the art.

[0118] The preparation method of the temperature shrinkage-induced organic fiber in the following embodiment includes the following steps:

[0119] S1. Using two extruders, the heat-shrinkable core material mixture and the heat-shrinkable skin material mixture are respectively extruded into a die head with two cavities, wherein the heat-shrinkable skin material enters the cavity corresponding to the skin material, and the heat-shrinkable core material enters the cavity corresponding to the core material. The materials in the two cavities converge at the position of the extruder spinneret; wherein 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 (melt extrusion) through the spinneret, 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;

[0120] S2. Adding a 3% (mass concentration) silane coupling agent (specifically octamethylcyclotetrasiloxane) solution to the composite fiber obtained in step S1 for modification for 20 minutes, drying, and then indenting the surface to enhance its bonding performance with the concrete paste;

[0121] S3. Adding the composite fiber obtained in step S2 to a modified polyvinyl alcohol solution containing an expansion component, performing coating modification at room temperature for 20 hours, and then drying the composite fiber to obtain a temperature-shrinkage-induced organic fiber. The modified polyvinyl alcohol solution containing an expansion component is obtained by uniformly mixing a polyvinyl alcohol solution (6 wt%) and an expansion agent in a mass ratio of 7:3, wherein the expansion agent is a composite of a calcium oxide expansion agent and a calcium sulfoaluminate expansion agent in a mass ratio of 1:45.

[0122] The heat shrinkable leather material mixture contains the following raw materials and their weight percentages: polyvinyl alcohol 97%, maleic anhydride grafted compatibilizer (model PP-G-MAH, provided by Dongguan Shenghao Plastic Materials Co., Ltd.), and phthalate plasticizer 1.5%. The extrusion pressure of the leather material cavity is 8 MPa, and the melt temperature is maintained at 250°C.

[0123] The heat shrinkable core material mixture, the raw materials and their weight percentages are: 98% polypropylene, 2% rigidity nucleating agent (aluminum aromatic carboxylate and sodium benzoate in a mass ratio of 1:1); the melt temperature of the heat shrinkable core material mixture is 210°C; the extrusion pressure of the corresponding cavity is 8MPa;

[0124] In the final extrusion section corresponding to the spinneret, the extrusion temperature of the two molten materials is maintained at a temperature suitable for both materials, i.e., 215°C, and the extrusion pressure is 6 MPa;

[0125] The average diameter of the core fiber obtained was 0.15 mm, and the thickness of the skin fiber was 0.08 mm;

[0126] The obtained temperature-shrinkage-induced organic fiber has a length of 10 mm to 12 mm, a shrinkage rate of 0.5% to 12%, a response temperature of 30° C. to 100° C., a tensile strength of 700 MPa, and an elastic modulus of 15.0 GPa.

[0127] Example 1

[0128] This embodiment provides a multi-scale toughening and shrinkage compensating C80 high crack resistance self-compacting concrete, including the following raw materials: low shrinkage and crack resistance composite cement 450kg / m 3 , viscosity-adjusting and reinforcing mineral admixture 150kg / m 3 , fine aggregate 708kg / m 3 , high strength coarse aggregate 1025kg / m 3 , multi-scale hybrid fiber 57kg / m 3 , nano-silica modified waterborne polyurethane emulsion 12kg / m 3 , high efficiency water reducing, slump retaining, foam stabilizing and viscosity regulating admixture 9.9kg / m 3 , water 144kg / m 3 ;

[0129] The low shrinkage and crack-resistant composite cement is prepared by compounding P·II 52.5 silicate cement and P·II 42.5 high-iron sulfoaluminate cement containing Q phase; the mass ratio of P·II 52.5 silicate cement to P·II 42.5 high-iron sulfoaluminate cement containing Q phase is 60:40;

[0130] P·II 42.5 high iron phase sulphoaluminate cement containing Q phase was prepared by the following method:

[0131] S1, mixing 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;

[0132] S2. The first mixture is heated to 1330° C. at a rate of 5° C. / min and calcined, and kept at this temperature for 40 min to obtain Q phase-calcium sulfoaluminate clinker;

[0133] S2, mixing 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;

[0134] S3, the second mixed material was heated to 1300℃ at 5℃ / min and kept at this temperature for 45min to obtain sulphoaluminate cement clinker;

[0135] S4, Q phase - calcium sulphoaluminate clinker, The sulphoaluminate cement clinker was mixed in a mass ratio of 50:50 to obtain the Q-rich P·II 42.5 high iron phase sulphoaluminate cement clinker;

[0136] S5, after mixing the Q-rich P·II 42.5 high iron phase sulphoaluminate cement clinker with dihydrate gypsum, grind it to a specific surface area of 340m 2 / kg, that is, P·II 42.5 high iron phase sulphoaluminate cement containing Q phase is obtained; the mass of dihydrate gypsum is 10% of the mass of Q phase-rich P·II 42.5 high iron phase sulphoaluminate cement clinker;

[0137] Viscosity-adjusting and reinforcing mineral admixtures including fly ash microspheres 75kg / m 3 , silica fume 75kg / m 3 The fly ash microspheres have a 28-day activity index of 107% and a water requirement of 101%. The SiO2 content in the silica fume is ≥91% and the specific surface area is ≥20100m 2 / kg, activity index ≥101% at 28 days;

[0138] The fine aggregate is river sand, and the apparent density of fine aggregate is 2600kg / m 3 , fineness modulus is 2.8;

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

[0140] The preparation method of nano-silica modified water-based polyurethane emulsion is as follows:

[0141] Nano-silica was added to the aqueous polyurethane emulsion and uniformly dispersed in the aqueous polyurethane emulsion by ultrasonic dispersion to obtain the nano-silica modified aqueous polyurethane emulsion. The particle size of the nano-silica was 15 nm and the specific surface area was 300 m 2 / g, apparent density is 2.3g / cm 3 ;

[0142] The multi-scale hybrid fibers are composed of high-strength fine straight steel fibers, multi-anchor steel fibers, temperature-shrinkage-induced organic fibers, CaCO3 whiskers and CaSO4 whiskers;

[0143] The high-strength fine straight steel fiber is produced by Wuhan Xintu Engineering New Materials Technology Co., Ltd., with a nominal length of 13mm, an equivalent diameter of 0.20±0.02mm, a breaking strength ≥2200MPa, an elastic modulus of 210GPa, and a tensile strength of 1300Mpa;

[0144] The multi-anchor steel fiber is 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 breaking strength ≥ 1200 MPa, an elastic modulus of 220 GPa, and a tensile strength of 1400 MPa.

[0145] The CaSO4 whiskers were produced by Chuangbo Products Co., Ltd. in Lingshou County, Hebei Province, with a nominal length of 200 μm, an equivalent diameter of 2 μm, and an apparent density of 2.4 g / cm 3 ;

[0146] The CaCO3 whiskers were produced by Chuangbo Products Co., Ltd. in Lingshou County, Hebei Province, with a nominal length of 15 μm and an elastic modulus of 610 GPa;

[0147] The water-based polyurethane emulsion is produced by Anhui Dawei Huatai New Material Technology Co., Ltd., model AH-1704, with a solid content of 30%;

[0148] The addition amount of high-strength fine straight steel fiber is 20kg / m 3 ;

[0149] The addition amount of multi-anchor steel fiber is 25kg / m 3 ;

[0150] The addition amount of temperature shrinkage induced organic fiber is 2kg / m 3 ;

[0151] The addition amount of CaCO3 whiskers is 5kg / m 3 ;

[0152] The addition amount of CaSO4 whiskers is 5kg / m 3 ;

[0153] The high-efficiency water-reducing, slump-retaining, foam-stabilizing and viscosity-adjusting admixture includes polycarboxylate water-reducing agent mother liquor, air-entraining agent, boric acid, tetramethyldecynediol foam control agent, polyhydroxycarboxylate retarder and water; the addition amount of polycarboxylate water-reducing agent mother liquor is 6.138kg / m 3 ; The amount of air entraining agent added is 0.004kg / m 3 ; Boric acid addition amount is 0.12kg / m 3 ; Tetramethyldecynediol foam control agent added in an amount of 0.01kg / m 3 The amount of polyhydroxycarboxylate retarder added is 0.12kg / m 3 ; The amount of water added is 3.508kg / m 3 ;

[0154] Among them, the mother liquor of polycarboxylate water reducer (water reduction rate is 30%-35%, slump retention time is 2h-4h) is -HS polycarboxylic acid slow-release water-reducing agent mother liquor, produced by Jiangsu Subote New Materials Co., Ltd.; air-entraining agent is -III type high efficiency air entraining agent, produced by Jiangsu Subote New Materials Co., Ltd.; boric acid is a white crystalline powder, produced by Tianjin Beichen District Fangzheng Reagent Factory; tetramethyldecynediol foam control agent, produced by Jiangsu Subote New Materials Co., Ltd.; polyhydroxycarboxylate retarders are -SR(II) powder retarder, produced by Jiangsu Subote New Materials Co., Ltd.;

[0155] The method for preparing the multi-scale toughening and shrinkage-compensating C80 high-crack-resistance self-compacting concrete comprises the following steps:

[0156] Low shrinkage and crack-resistant composite cement, viscosity-adjusting and reinforcing mineral admixtures, fine aggregate, high-strength coarse aggregate and multi-scale mixed fibers are mixed and stirred for 100 seconds, and then water, high-efficiency water-reducing and collapse-preserving, foam-stabilizing and viscosity-adjusting admixtures, and nano-silica-modified waterborne polyurethane emulsion are added and stirred for 120 seconds to obtain multi-scale toughening and shrinkage-compensating C80 high-cracking-resistant self-compacting concrete.

[0157] Comparative Example 1

[0158] The C80 concrete provided in this comparative example is the same as that in Example 1, except that water-based polyurethane emulsion is used instead of nano-silica-modified water-based polyurethane emulsion. The rest is the same as that in Example 1.

[0159] Comparative Example 2

[0160] The C80 concrete provided in this comparative example is the same as that in Example 1, except that it does not contain the nano-silica modified waterborne polyurethane emulsion. The rest is the same as that in Example 1.

[0161] Comparative Example 3

[0162] The C80 concrete provided in this comparative example is the same as that in Example 1, except that a common polycarboxylate water-reducing agent is used instead of a high-efficiency water-reducing, slump-preserving, foam-stabilizing, and viscosity-regulating admixture. All other aspects are the same as those in Example 1.

[0163] Comparative Example 4

[0164] The C80 concrete provided in this comparative example is the same as that in Example 1, except that it does not contain CaCO3 whiskers and CaSO4 whiskers. All other aspects are the same as those in Example 1.

[0165] Comparative Example 5

[0166] The C80 concrete provided in this comparative example is the same as that in Example 1, except that P·II 52.5 Portland cement is used instead of low shrinkage and crack-resistant composite cement. The rest is the same as that in Example 1.

[0167] Performance Testing

[0168] The properties of the C80 concrete in Example 1 and Comparative Examples 1 to 5 were tested, and the results are shown in Table 1 below.

[0169] Table 1 - Properties of C80 concrete in different examples and comparative examples

[0170]

[0171] The above results show that the organic and inorganic composite multi-scale toughening and shrinkage-reducing C80 high crack resistance self-compacting concrete obtained by the present invention has good workability, mechanical properties and volume stability, and the compressive strength of the concrete is ≥90MPa. In addition, by comparing Example 1 and Comparative Examples 1 to 2, it can be seen that the water-based polyurethane emulsion has a significant effect on improving the flexural strength and bending toughness of concrete, and the effect is even better after adding nano-silica modified water-based polyurethane. By comparing Example 1 and Comparative Example 3, it is found that high-efficiency water-reducing, slump-preserving, foam-stabilizing and viscosity-regulating admixtures can improve the workability of C80 concrete. When using ordinary polycarboxylic acid water-reducing agent, the expansion of C80 concrete is only 590mm. By comparing Example 1 and Comparative Example 4, it is found that CaCO3 and CaSO4 composite whiskers can improve the bending toughness of C80 concrete, but reduce the fluidity of concrete. By comparing Example 1 and Comparative Example 5, it is found that the low shrinkage and crack-resistant composite cement can compensate for the shrinkage of C80 concrete and reduce the 56d volume shrinkage rate; and the low shrinkage and crack-resistant composite cement can increase the flexural toughness index of C80 concrete to 10.7.

[0172] It can be understood that the various technical features of the above-described embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the various 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.

[0173] The above are merely preferred embodiments of the present application and only specifically describe the technical principles of the present application. These descriptions are intended only to explain the principles of the present application and should not be construed in any way as limiting the scope of protection of the present application. Based on the explanations herein, any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present application, as well as other specific implementations of the present application that can be conceived by those skilled in the art without inventive effort, shall be included within the scope of protection of the present application.

Claims

1. A multi-scale toughening and shrinkage-compensating C80 high crack resistance self-compacting concrete, characterized in that: Includes the following raw materials: low shrinkage and crack-resistant composite cement 400~500 kg / m 3 , viscosity-adjusting and reinforcing mineral admixture 150~200 kg / m 3 , fine aggregate 680~800kg / m 3 , high-strength coarse aggregate 950~1100 kg / m 3 , multi-scale hybrid fiber 50~80 kg / m 3 , nano-silica modified waterborne polyurethane emulsion 9~20 kg / m 3 , high-efficiency water-reducing, slump-preserving, foam-stabilizing and viscosity-adjusting admixture 9~11 kg / m 3 , water 140~160 kg / m 3 ; The low shrinkage and crack-resistant composite cement is compounded by P•II 52.5 silicate cement and P•II 42.5 high iron phase sulphoaluminate cement containing Q phase; The P•II 42.5 high iron phase sulphoaluminate cement containing Q phase is prepared by the following method: Mixing fly ash, limestone, magnesite, and calcium sulfate to obtain a first mixture; The first mixture is heated to 1290-1350°C at a rate of 5-10°C / min and calcined, and kept at this temperature for 40-45 minutes to obtain Q phase-calcium sulfoaluminate clinker; Mixing red mud, limestone, bauxite, and calcium sulfate to obtain a second mixture; The second mixed material is heated to 1290-1350℃ at a rate of 5-10℃ / min and calcined, and kept at this temperature for 40-45min to obtain sulphoaluminate cement clinker; Q phase - calcium sulphoaluminate clinker, The sulphoaluminate cement clinker was mixed to obtain the Q-rich P•II 42.5 high iron phase sulphoaluminate cement clinker; The Q-rich P•II 42.5 high iron phase sulphoaluminate cement clinker is mixed with dihydrate gypsum and ground to a specific surface area of 330-350m 2 / kg, that is, P•II 42.5 high iron phase sulphoaluminate cement containing Q phase is obtained; The high-efficiency water-reducing, slump-preserving, foam-stabilizing and viscosity-adjusting admixture comprises a polycarboxylate water-reducing agent mother liquor, an alkyl ether anion air-entraining stabilized water-reducing agent, boric acid, a tetramethyldecynediol foam control agent, a polyhydroxycarboxylate retarder and water; The multi-scale hybrid fibers are composed of high-strength fine straight steel fibers, multi-anchor steel fibers, temperature shrinkage-induced organic fibers, CaCO3 whiskers and CaSO4 whiskers; The viscosity-adjusting and reinforcing mineral admixture comprises a mixture of fly ash microbeads and silica fume; the preparation method of the nano-silicon dioxide-modified waterborne polyurethane emulsion is as follows: Adding nano-silicon dioxide into aqueous polyurethane emulsion, and uniformly dispersing the nano-silicon dioxide in the aqueous polyurethane emulsion by ultrasonic dispersion or high shear stirring, thereby obtaining nano-silicon dioxide modified aqueous polyurethane emulsion; The fine aggregate is river sand, and the apparent density of the fine aggregate is 2560-2650 kg / m 3 , fineness modulus is 2.8; The high-strength coarse aggregate is basalt coarse aggregate with a continuous gradation of 5 to 16 mm; The high-strength fine straight steel fiber has a nominal length of 6-13 mm, an equivalent diameter of 0.20±0.02 mm, a breaking strength ≥2200 MPa, an elastic modulus of 190-230 GPa, and a tensile strength of 400-2100 MPa; The multi-anchor steel fiber has a nominal length of 6-13 mm, an equivalent diameter of 0.2±0.02 mm, a breaking strength ≥1200 MPa, an elastic modulus of 210-230 GPa, and a tensile strength of 550-2150 MPa; The temperature-shrinkage-induced organic fiber has a tensile strength of 500-1200 MPa, an elastic modulus of 7-35 GPa, a shrinkage rate of 0.5%-12%, and a response temperature of 30°C-100°C; The CaSO4 whiskers have a nominal length of 100-300 μm, an equivalent diameter of 1-3 μm, and an apparent density of 2.3-2.6 g / cm 3 ; The CaCO3 whiskers have a nominal length of 10-20 μm and an elastic modulus of 410-710 GPa; The mass ratio of the P•II 52.5 silicate cement to the P•II 42.5 high iron phase sulphoaluminate cement containing Q phase is (60-70):(30-40); 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 sulphoaluminate clinker, The mass ratio of sulphoaluminate cement clinker is (50~60):(40~50); The mass of the dihydrate gypsum is 10-15% of the mass of the Q-phase-rich P•II 42.5 high-iron phase sulphoaluminate cement clinker.

2. The multi-scale toughening and shrinkage compensating C80 high crack resistance self-compacting concrete according to claim 1, characterized in that: The addition amount of the high-strength fine straight steel fiber is 20-30 kg / m 3 ; The addition amount of the multi-anchor steel fiber is 20-30 kg / m 3 ; The addition amount of the temperature shrinkage inducible organic fiber is 1-2 kg / m 3 ; The amount of CaCO3 whiskers added is 5-8 kg / m 3 The amount of CaSO4 whiskers added is 5-8 kg / m 3 .

3. The multi-scale toughening and shrinkage compensating C80 high crack resistance self-compacting concrete according to claim 1, characterized in that: The amount of fly ash microbeads added is 75-100 kg / m 3 ; The amount of silica fume added is 75-100 kg / m 3 ; The fly ash microbeads have a 28-day activity index of 107% and a water requirement ratio of 101%; The SiO2 mass content in the silica fume is ≥91%, and the specific surface area is ≥20100m 2 / kg, 28-day activity index ≥101%.

4. The multi-scale toughening and shrinkage compensating C80 high crack resistance self-compacting concrete according to claim 1, characterized in that: The particle size of the nano-silicon dioxide is 10-20 nm, and the specific surface area is 200-400 m 2 / g, apparent density is 2.2~2.5g / cm 3 .

5. The multi-scale toughening and shrinkage compensating C80 high crack resistance self-compacting concrete according to claim 1, characterized in that: The amount of polycarboxylate superplasticizer mother liquor added is 6.1~6.2 kg / m 3 ; The addition amount of alkyl ether anionic air-entraining stabilized water reducer is 0.003~0.005 kg / m 3 ; The amount of boric acid added is 0.11~0.13 kg / m 3 ; The addition amount of tetramethyldecynediol foam control agent is 0.01~0.02 kg / m 3 ; The addition amount of polyhydroxycarboxylate retarder is 0.11~0.13 kg / m 3 ; The amount of water added is 3.5~3.7 kg / m 3 .

6. The multi-scale toughening and shrinkage compensating C80 high crack resistance self-compacting concrete according to claim 1, characterized in that: The basalt coarse aggregate has a strength of 169 MPa, a crushing value of 10%, a needle-like content of ≤5%, and an apparent density of 2900-3000 kg / m 3 .

7. A method for preparing the multi-scale toughening and shrinkage-compensating C80 high-crack-resistance self-compacting concrete according to any one of claims 1 to 6, characterized in that: The following steps are involved: Low shrinkage and crack-resistant composite cement, viscosity-adjusting and reinforcing mineral admixtures, fine aggregate, high-strength coarse aggregate and multi-scale mixed fibers are mixed and stirred, and then water, high-efficiency water-reducing and collapse-preserving, foam-stabilizing and viscosity-adjusting admixtures, and nano-silica modified waterborne polyurethane emulsion are added and stirred to obtain multi-scale toughening and shrinkage-compensating C80 high crack-resistant self-compacting concrete.

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