Low-temperature-resistant high-strength concrete and preparation method thereof

Abstract

The invention relates to the field of low-temperature-resistant concrete, in particular to low-temperature-resistant high-strength concrete and a preparation method thereof. The low-temperature-resistant high-strength concrete comprises the following substances in parts by weight: 35-45 parts of cement; 75 to 100 parts of coarse aggregate; 60 to 80 parts of fine aggregate; 10 to 25 parts of water; 3-5 parts of an additive; 5-10 parts of a low-temperature-resistant modified material; the low-temperature-resistant modified material comprises composite low-temperature-resistant modified fibers prepared by compounding rigid long fibers and elastomer fibers. Through the composite design of the rigid long fibers and the elastomer fibers, a multi-scale reinforcement system of the concrete is constructed. The rigid long fibers form a three-dimensional space network in a concrete matrix by virtue of high elastic modulus and tensile strength, and crack propagation is inhibited by virtue of a bridging effect. Through the synergistic effect of the rigid fibers and the elastic fibers, the rigid fibers bear initial loads, the elastic fibers dissipate stress waves in the later deformation stage, and a gradient anti-cracking path of first rigidity and then flexibility is formed.

Description

Technical Field

[0001] This application relates to the field of low-temperature resistant concrete, and particularly to a high-strength low-temperature resistant concrete and its preparation method. Background Art

[0002] High-strength low-temperature resistant concrete is an essential key building material in extremely cold environments. Traditional concrete is prone to internal structural damage due to the freezing and expansion of water in low-temperature environments. At the same time, the cement hydration reaction is hindered, and the strength development is slow, making it difficult to meet the mechanical properties and durability requirements in environments below -40°C. With the frequent occurrence of extreme climates globally and the increasing demand for infrastructure construction in cold regions, the development of low-temperature resistant concrete with high strength, frost resistance, and construction adaptability has become a research hotspot in the fields of materials science and civil engineering. Such concrete needs to maintain high density, low porosity, and excellent interfacial bonding performance at extremely low temperatures to resist frost heaving stress, salt freeze-thaw erosion, and fatigue damage caused by temperature alternation.

[0003] Currently, the modification technology of low-temperature resistant concrete mainly reduces the freezing point by adding antifreeze agents, but long-term use is likely to cause steel bar corrosion or environmental risks; there is also a solution of introducing microbubbles by adding air-entraining agents to buffer frost heaving, but it will significantly reduce the strength of the concrete.

[0004] In view of the above-mentioned prior art, the inventor found that existing means such as antifreeze agents, air-entraining agents, and fiber reinforcement for high-strength low-temperature resistant concrete often have trade-offs and cannot simultaneously meet the requirements of high strength, high frost resistance, and low thermal conductivity. Summary of the Invention

[0005] To improve the above technical problems, this application provides a high-strength low-temperature resistant concrete and its preparation method.

[0006] In a first aspect, this application provides a high-strength low-temperature resistant concrete, adopting the following technical solution:

[0007] A high-strength low-temperature resistant concrete, comprising the following components by weight: 35 - 45 parts of cement;

[0008] 75 - 100 parts of coarse aggregate; 60 - 80 parts of fine aggregate; 10 - 25 parts of water; 3 - 5 parts of admixture; 5 - 10 parts of low-temperature resistant modifier; the low-temperature resistant modifier includes a composite low-temperature resistant modifier fiber prepared by compounding rigid long fibers and elastomeric fibers.

[0009] Through the above technical scheme, the present application constructs a multi-scale reinforcement system for concrete through a composite design of rigid long fibers and elastomeric fibers. Rigid long fibers form a three-dimensional spatial network in the concrete matrix with high elastic modulus and tensile strength, and inhibit crack propagation through the bridging effect. When the matrix is ​​loaded and microcracks are generated, the rigid fibers span both sides of the cracks, transfer the load to the fibers through the interface shear stress, and delay the crack penetration. The elastic modulus of the elastomeric fibers is significantly lower than that of the matrix, and they deform greatly under the action of frost heave stress, absorbing energy through the viscoelastic energy dissipation mechanism. With the synergistic effect of the two, the rigid fibers bear the initial load, and the elastic fibers dissipate stress waves in the later deformation stage, forming a gradient anti-cracking path of "first rigid and then soft".

[0010] Furthermore, the rigid long fibers include basalt fibers with a length of 6-15 mm and a diameter of 0.1-0.3 mm.

[0011] Through the above technical solution, this application further optimizes the size and material of rigid long fibers. The length (6-15mm) and diameter (0.1-0.3mm) of the adopted basalt fibers are set based on the critical fiber length theory. Ensure that the fibers are fully stressed before the matrix breaks to avoid "pull-out failure". A diameter of 0.1-0.3mm corresponds to an aspect ratio of 20-150. The high aspect ratio increases the contact area between the fiber and the matrix and improves the efficiency of interfacial load transfer. The chemical inertness of basalt fiber makes it more stable than glass fiber in an alkaline environment, ensuring good structural properties of the prepared concrete.

[0012] Furthermore, the surface of the low-temperature resistant modified material is also coated with a silicon dioxide particle interface modification layer, and the silicon dioxide particle interface modification layer is made by the following technical solution:

[0013] Taking the elastomer fiber and immersing it in a silane coupling agent, surface treating it and washing and drying it;

[0014] After washing and drying, the elastomer fiber is immersed in the sol solution, centrifuged, washed and dried, and then cured at low temperature to prepare the silica particle interface modification layer.

[0015] Through the above technical scheme, the present application constructs a nano-SiO2 particle interface layer on the surface of the low-temperature resistant modified material by a sol-gel method. First, the silane coupling agent is hydrolyzed under acidic conditions to generate silanol (Si-OH), which forms a Si-OC covalent bond with the polar groups on the surface of the elastomer (such as -NHCOO- of polyurethane) through a condensation reaction, thereby enhancing the chemical bonding at the interface. Subsequently, the SiO2 nanoparticles generated by the hydrolysis and condensation of tetraethyl orthosilicate in an alkaline sol solution are adsorbed on the fiber surface through van der Waals forces and hydrogen bonds, and low-temperature curing promotes the cross-linking of Si-O-Si bonds between particles to form a continuous dense layer. This layer acts as a physical barrier to prevent moisture from invading the fiber-matrix interface, while its rough surface increases mechanical bite, improves the interfacial shear strength, and ensures good structural performance of the prepared concrete.

[0016] Furthermore, the sol liquid is prepared by mixing ethyl orthosilicate, ethanol, water and ammonia water in a molar ratio of 1:(20-25):(3-5):(0.05-0.08).

[0017] Through the above technical scheme, the present application is regulated by hydrolysis-condensation kinetic balance. Ethanol is used as a solvent to reduce the concentration of tetraethyl orthosilicate to avoid particle agglomeration caused by too fast hydrolysis; water is used as a reactant to participate in the hydrolysis of tetraethyl orthosilicate to promote the formation of a dense film; the concentration of ammonia water is 0.05-0.08 mol / L to control the condensation rate so that SiO2 particles are uniformly nucleated. At the same time, the amount of ammonia water added is adjusted to prevent insufficient condensation when the amount added is too low, and the problem of too fast condensation to form a porous structure when the amount added is too high occurs.

[0018] Furthermore, the elastomeric fiber includes at least one of polyurethane elastomer fiber, rubber fiber or thermoplastic elastomer fiber.

[0019] Through the above technical solution, this application further optimizes the material of the elastomer fiber. The soft segment and hard segment microphase separation structure of the polyurethane elastomer fiber makes it still elastic at -50°C; the vulcanized cross-linked network of the rubber fiber absorbs deformation energy through disulfide bond reconstruction; the physical cross-linking points of the thermoplastic elastomer remain stable at low temperatures. When the three are compounded, the polyurethane elastomer fiber provides low-temperature elasticity, the rubber fiber dissipates impact energy, and the SEBS fiber generates pre-compression stress in the matrix through thermal shrinkage.

[0020] Furthermore, the surface of the silicon dioxide particle interface modification layer is also coated with an aerogel coating modification layer.

[0021] Furthermore, the aerogel coating modified layer is made by the following scheme:

[0022] The composite low-temperature-resistant modified fiber is washed, dried and activated, and then immersed in a precursor sol solution. After the immersion is completed, the temperature is increased and condensed, and vacuum drying is performed to prepare an aerogel-coated modified layer.

[0023] Through the above technical solution, the micropores in the aerogel coating layer provided by the present application adsorb water molecules through capillary action to form amorphous ice, with the freezing point reduced to below -45°C. The mesopores accommodate unfrozen water and continuously participate in the hydration reaction, blocking the penetration of external moisture, reducing the total amount of freezable water. At the same time, the coated aerogel coating modification layer has a low thermal conductivity, blocking the intrusion of external cold;

[0024] Secondly, the aerogel coating modification layer constructed by the present application compresses and absorbs energy, and cooperates with the elastic fiber to release the pre-compression stress, offsetting the frost heave tensile stress. In practical applications, through the synergistic effect of multiple mechanisms of "ice inhibition - heat insulation - energy consumption", the defects of concrete frost heave cracking and sudden strength drop at extremely low temperatures are improved.

[0025] Further, the precursor sol solution includes the following substances in parts by weight:

[0026]

[0027]

[0028] Through the above technical solution, the present application provides a hydrophobic group and a silicon source through methyltrimethoxysilane. Ethanol is used as a solvent to adjust the reaction rate. Acetic acid controls the pH at 4-5, enabling methyltrimethoxysilane to slowly hydrolyze to form a linear prepolymer. Nanocellulose condenses with silanol through hydroxyl groups to form an organic-inorganic hybrid network. The rigid chain segments of cellulose nanofibers enhance the compressive strength of the aerogel, and its entangled structure inhibits crack propagation. When the concentration of methyltrimethoxysilane in the sol is 6-8 parts, the crosslinking density is moderate, avoiding the brittleness problem caused by excessive crosslinking.

[0029] In a second aspect, the present application provides a preparation method for low-temperature resistant high-strength concrete, adopting the following technical solution:

[0030] A preparation method for low-temperature resistant high-strength concrete includes the following preparation steps:

[0031] Dry mix cement, coarse aggregate, and fine aggregate for 3-5 minutes;

[0032] Add water, admixture, and low-temperature resistant modifier, and stir until the slump reaches 180-220 mm;

[0033] Cure at a low-temperature gradient for 28 days to complete the preparation of the low-temperature resistant high-strength concrete.

[0034] Through the above technical solution, the present application realizes the uniform coating of cement and aggregates through a forced mixer, and the aggregates pre-adsorb cement particles on the surface, reducing the demand for slurry during wet mixing. During the wet mixing stage, the feeding sequence is controlled: first, water and additives are added and stirred to form a highly fluid slurry, and then the low-temperature resistant modified material is put in to avoid premature agglomeration of fibers due to the high viscosity of the slurry.

[0035] Further, the low-temperature gradient curing includes:

[0036] First, pre-cure at 5 - 10°C for 24 h, then transfer to -20 to -15°C for 7 days, and then cure at -45 to -40°C until 28 days to complete the low-temperature gradient curing.

[0037] Through the above technical solution, in the present application, first, during the pre-curing stage, the initial hydration heat release of cement is utilized, and the aerogel layer blocks the heat dissipation, raising the internal temperature to 15 - 20°C to promote the hydration of C3S to generate C-S-H gel. In the middle curing stage, the external low temperature causes the surface layer of the concrete to be slightly frozen, and the aerogel layer maintains the temperature in the core area > 0°C, and the unfrozen water continues to hydrate. In the final curing stage, an extreme environment is simulated. The elastic fiber shrinks to generate compressive stress, offsetting the tensile stress caused by frost heave. The heat conductivity of the basalt fiber balances the temperature gradient and avoids thermal stress cracking.

[0038] In summary, the present application has the following beneficial effects:

[0039] First, through the composite design of rigid long fibers and elastic fibers, the present application constructs a multi-scale reinforcement system for concrete. Rigid long fibers, with high elastic modulus and tensile strength, form a three-dimensional spatial network in the concrete matrix and inhibit crack propagation through the bridging effect. When microcracks are generated in the matrix under load, the rigid fibers span both sides of the crack and transfer the load to the fibers through the interfacial shear stress, delaying the crack penetration. The elastic modulus of the elastic fibers is significantly lower than that of the matrix, and large deformations occur under the action of frost heave stress, absorbing energy through the viscoelastic energy dissipation mechanism. Through their synergistic effect, the rigid fibers bear the initial load, and the elastic fibers dissipate the stress wave in the later deformation stage, forming a "rigid first and then flexible" gradient crack resistance path.

[0040] Second, through the supercritical drying process, the present application constructs a nanoporous structure on the fiber surface. The activation treatment etches the fiber surface to generate -COOH and -OH groups, improving the wettability of the aerogel precursor sol. During the impregnation stage, the sol is infiltrated into the micropores on the fiber surface layer through vacuum assistance, and the condensation reaction promotes the cross-linking of the Si-O-Si network. Vacuum drying further removes the residual solvent, forming a continuous coating layer with a thickness of 100 - 200 μm. Ensure that the aerogel layer and the fiber matrix form an interpenetrating network structure.

[0041] Thirdly, in the pre-curing stage of the present application, the initial hydration heat of cement is utilized, and the aerogel layer blocks the heat dissipation, so that the internal temperature rises to 15 - 20 °C, promoting the hydration of C3S to generate C-S-H gel. In the medium-term curing stage, the low external temperature causes the surface layer of the concrete to be slightly frozen, and the aerogel layer maintains the temperature in the core area > 0 °C, and the unfrozen water continues to hydrate. In the final curing stage, the extreme environment is simulated. The elastic fiber shrinks to generate compressive stress, offsetting the frost heaving tensile stress. The heat conductivity of the basalt fiber balances the temperature gradient and avoids thermal stress cracking. Detailed implementation mode

[0042] The present application will be further described in detail below in conjunction with embodiments.

[0043] Preparation Example 1

[0044] Low-temperature resistant modifier 1

[0045] Take 1200 g of basalt fibers with a length of 6 - 15 mm and a diameter of 0.1 - 0.3 mm, 600 g of polyether-based TPU (WHT-EL1150), and 300 g of natural rubber particles, stir and mix them, then add 40 g of compatibilizer POE-g-MAH and 15 g of plasticizer DOP, stir and mix, place them in a twin-screw extruder, melt and then extrude by spinning. The draw ratio is 1:3, water-cooled drawing, and wind up into a bundle to obtain Low-temperature resistant modifier 1.

[0046] Preparation Example 2

[0047] Take 1200 g of basalt fibers with a length of 6 - 15 mm and a diameter of 0.1 - 0.3 mm, 600 g of polyether-based TPU (WHT-EL1150), 200 g of natural rubber particles, stir and mix them, then add 50 g of compatibilizer POE-g-MAH, 20 g of epoxy resin E-51, and 20 g of plasticizer DOP, stir and mix, place them in a twin-screw extruder, melt and then extrude by spinning. The draw ratio is 1:3, water-cooled drawing, and wind up into a bundle to obtain Low-temperature resistant modifier 2.

[0048] Preparation Example 3

[0049] Take 1200 g of basalt fibers with a length of 6 - 15 mm and a diameter of 0.1 - 0.3 mm, 600 g of polyether-based TPU (WHT-EL1150), 5 g of plasticizer DOP, stir and mix them, place them in a twin-screw extruder, melt and then extrude by spinning. The draw ratio is 1:3, water-cooled drawing, and wind up into a bundle to obtain Low-temperature resistant modifier 3.

[0050] Preparation Example 4

[0051] Take tetraethyl orthosilicate, ethanol, water and ammonia water according to a molar ratio of 1:20:3:0.05. Dropwise add tetraethyl orthosilicate into the mixed solution of ethanol, water and ammonia water, stir and mix to prepare a transparent sol solution. Immerse the low-temperature resistant modifier 1 in the sol, react at a constant temperature of 50 °C for 6 h, centrifuge and wash with ethanol at 8000 rpm for 3 times, and then perform heat treatment at 80 °C for 2 h to complete the low-temperature resistant modifier 4 coated with a silica particle interface modification layer.

[0052] Preparation Example 5

[0053] Take tetraethyl orthosilicate, ethanol, water and ammonia water according to a molar ratio of 1:22:4:0.06. Dropwise add tetraethyl orthosilicate into the mixed solution of ethanol, water and ammonia water, stir and mix to prepare a transparent sol solution. Immerse the low-temperature resistant modifier 2 in the sol, react at a constant temperature of 50 °C for 6 h, centrifuge and wash with ethanol at 8000 rpm for 3 times, and then perform heat treatment at 80 °C for 2 h to complete the low-temperature resistant modifier 5 coated with a silica particle interface modification layer.

[0054] Preparation Example 6

[0055] Take tetraethyl orthosilicate, ethanol, water and ammonia water according to a molar ratio of 1:25:5:0.08. Dropwise add tetraethyl orthosilicate into the mixed solution of ethanol, water and ammonia water, stir and mix to prepare a transparent sol solution. Immerse the low-temperature resistant modifier 3 in the sol, react at a constant temperature of 50 °C for 6 h, centrifuge and wash with ethanol at 8000 rpm for 3 times, and then perform heat treatment at 80 °C for 2 h to complete the low-temperature resistant modifier 6 coated with a silica particle interface modification layer.

[0056] Preparation Example 7

[0057] Take 60 g of methyltrimethoxysilane, 300 g of absolute ethanol, 1 g of acetic acid and 2 g of nanocellulose, stir and mix to prepare a precursor sol solution.

[0058] After taking the low-temperature resistant modifier 4, washing and drying it, immerse it in a 5% by mass silane coupling agent KH550 ethanol solution for impregnation activation treatment for 5 min, take it out and then immerse it in the precursor sol solution, perform vacuum-assisted penetration at -0.1 MPa for 10 min, then heat up to 80 °C for condensation treatment for 4 h, and perform vacuum drying at 50 °C for 24 h to prepare the low-temperature resistant modifier 7 coated with an aerogel coating modification layer.

[0059] Preparation Example 8

[0060] Take 70 g of methyltrimethoxysilane, 400 g of absolute ethanol, 3 g of acetic acid and 35 g of nanocellulose, stir and mix to prepare a precursor sol solution.

[0061] After washing and drying the low-temperature resistant modified material 4, it was immersed in a 5% mass fraction ethanol solution of silane coupling agent KH550 for 5 min for impregnation activation treatment. Then it was taken out and immersed in the precursor sol solution again. After vacuum-assisted infiltration at -0.1 MPa for 10 min, the temperature was raised to 80 °C for condensation treatment for 4 h, and then vacuum dried at 50 °C for 24 h, thus obtaining the low-temperature resistant modified material 8 coated with an aerogel coating modification layer.

[0062] Preparation Example 9

[0063] 80 g of methyltrimethoxysilane, 500 g of absolute ethanol, 5 g of acetic acid and 5 g of nanocellulose were taken and stirred and mixed to prepare a precursor sol solution.

[0064] After washing and drying the low-temperature resistant modified material 4, it was immersed in a 5% mass fraction ethanol solution of silane coupling agent KH550 for 5 min for impregnation activation treatment. Then it was taken out and immersed in the precursor sol solution again. After vacuum-assisted infiltration at -0.1 MPa for 10 min, the temperature was raised to 80 °C for condensation treatment for 4 h, and then vacuum dried at 50 °C for 24 h, thus obtaining the low-temperature resistant modified material 9 coated with an aerogel coating modification layer.

[0065] Example

[0066] Example 1

[0067] A low-temperature resistant high-strength concrete comprises the following substances by weight: 35 kg of cement, 75 kg of porous basalt coarse aggregate, 60 kg of sand, 10 kg of water, 3 kg of water reducer and 5 kg of low-temperature resistant modified material 1.

[0068] A preparation method of a low-temperature resistant high-strength concrete comprises the following steps:

[0069] Dry-mix the cement, coarse aggregate and fine aggregate for 3 min;

[0070] Add water, admixture and low-temperature resistant modified material and stir until the slump reaches 180 mm;

[0071] First, pre-cure at 5 °C for 24 h, then transfer to -20 °C for curing for 7 days, and then cure at -45 °C until 28 days, thus obtaining the low-temperature resistant high-strength concrete.

[0072] Example 2

[0073] A low-temperature resistant high-strength concrete comprises the following substances by weight: 40 kg of cement, 82 kg of porous basalt coarse aggregate, 70 kg of sand, 18 kg of water, 4 kg of water reducer and 7 kg of low-temperature resistant modified material 1.

[0074] A preparation method of a low-temperature resistant high-strength concrete comprises the following steps:

[0075] Dry-mix the cement, coarse aggregate, and fine aggregate for 3 - 5 minutes;

[0076] Add water, admixture, and low-temperature resistant modifier, and stir until the slump reaches 180 - 220 mm;

[0077] First, pre-cure at 8°C for 24 hours, then transfer to -18°C for 7 days, and then cure at -42°C until 28 days to prepare the low-temperature resistant high-strength concrete.

[0078] Example 3

[0079] A low-temperature resistant high-strength concrete includes the following substances by weight: 45 kg of cement, 100 kg of porous basalt coarse aggregate, 80 kg of sand, 25 kg of water, 5 kg of water reducer, and 10 kg of low-temperature resistant modifier 1.

[0080] A preparation method of a low-temperature resistant high-strength concrete includes the following steps:

[0081] Dry-mix the cement, coarse aggregate, and fine aggregate for 5 minutes;

[0082] Add water, admixture, and low-temperature resistant modifier, and stir until the slump reaches 220 mm;

[0083] First, pre-cure at 10°C for 24 hours, then transfer to -15°C for 7 days, and then cure at -40°C until 28 days to prepare the low-temperature resistant high-strength concrete.

[0084] Example 4

[0085] A low-temperature resistant high-strength concrete includes the following substances by weight: 40 kg of cement, 82 kg of porous basalt coarse aggregate, 70 kg of sand, 18 kg of water, 4 kg of water reducer, and 7 kg of low-temperature resistant modifier 2.

[0086] A preparation method of a low-temperature resistant high-strength concrete includes the following steps:

[0087] Dry-mix the cement, coarse aggregate, and fine aggregate for 3 - 5 minutes;

[0088] Add water, admixture, and low-temperature resistant modifier, and stir until the slump reaches 180 - 220 mm;

[0089] First, pre-cure at 8°C for 24 hours, then transfer to -18°C for 7 days, and then cure at -42°C until 28 days to prepare the low-temperature resistant high-strength concrete.

[0090] Example 5

[0091] A low-temperature resistant high-strength concrete includes the following substances by weight: 40 kg of cement, 82 kg of porous basalt coarse aggregate, 70 kg of sand, 18 kg of water, 4 kg of water reducer, and 7 kg of low-temperature resistant modifier 3.

[0092] A preparation method of low-temperature resistant high-strength concrete, comprising the following steps:

[0093] Dry-mix the cement, coarse aggregate, and fine aggregate for 3 - 5 min;

[0094] Add water, admixture, and low-temperature resistant modifier, and stir until the slump reaches 180 - 220 mm;

[0095] First, pre-cure at 8°C for 24 h, then transfer to -18°C for 7 days, and then cure at -42°C until 28 days to prepare the low-temperature resistant high-strength concrete.

[0096] Example 6

[0097] A low-temperature resistant high-strength concrete comprises the following substances by weight: 40 kg of cement, 82 kg of porous basalt coarse aggregate, 70 kg of sand, 18 kg of water, 4 kg of water reducer, and 7 kg of low-temperature resistant modifier 4.

[0098] A preparation method of low-temperature resistant high-strength concrete, comprising the following steps:

[0099] Dry-mix the cement, coarse aggregate, and fine aggregate for 3 - 5 min;

[0100] Add water, admixture, and low-temperature resistant modifier, and stir until the slump reaches 180 - 220 mm;

[0101] First, pre-cure at 8°C for 24 h, then transfer to -18°C for 7 days, and then cure at -42°C until 28 days to prepare the low-temperature resistant high-strength concrete.

[0102] Example 7

[0103] A low-temperature resistant high-strength concrete comprises the following substances by weight: 40 kg of cement, 82 kg of porous basalt coarse aggregate, 70 kg of sand, 18 kg of water, 4 kg of water reducer, and 7 kg of low-temperature resistant modifier 5.

[0104] A preparation method of low-temperature resistant high-strength concrete, comprising the following steps:

[0105] Dry-mix the cement, coarse aggregate, and fine aggregate for 3 - 5 min;

[0106] Add water, admixture, and low-temperature resistant modifier, and stir until the slump reaches 180 - 220 mm;

[0107] First, pre-cure at 8°C for 24 h, then transfer to -18°C for 7 days, and then cure at -42°C until 28 days to prepare the low-temperature resistant high-strength concrete.

[0108] Example 8

[0109] A low-temperature-resistant high-strength concrete comprises the following substances by weight: 40 kg of cement, 82 kg of porous basalt coarse aggregate, 70 kg of sand, 18 kg of water, 4 kg of water reducer, and 7 kg of low-temperature-resistant modifier 6.

[0110] A preparation method of a low-temperature-resistant high-strength concrete comprises the following steps:

[0111] Dry-mix the cement, coarse aggregate, and fine aggregate for 3 - 5 min;

[0112] Add water, admixture, and low-temperature-resistant modifier, and stir until the slump reaches 180 - 220 mm;

[0113] First, pre-cure at 8°C for 24 h, then transfer to -18°C for curing for 7 days, and then cure at -42°C until 28 days, then the low-temperature-resistant high-strength concrete can be prepared.

[0114] Example 9

[0115] A low-temperature-resistant high-strength concrete comprises the following substances by weight: 40 kg of cement, 82 kg of porous basalt coarse aggregate, 70 kg of sand, 18 kg of water, 4 kg of water reducer, and 7 kg of low-temperature-resistant modifier 7.

[0116] A preparation method of a low-temperature-resistant high-strength concrete comprises the following steps:

[0117] Dry-mix the cement, coarse aggregate, and fine aggregate for 3 - 5 min;

[0118] Add water, admixture, and low-temperature-resistant modifier, and stir until the slump reaches 180 - 220 mm;

[0119] First, pre-cure at 8°C for 24 h, then transfer to -18°C for curing for 7 days, and then cure at -42°C until 28 days, then the low-temperature-resistant high-strength concrete can be prepared.

[0120] Example 10

[0121] A low-temperature-resistant high-strength concrete comprises the following substances by weight: 40 kg of cement, 82 kg of porous basalt coarse aggregate, 70 kg of sand, 18 kg of water, 4 kg of water reducer, and 7 kg of low-temperature-resistant modifier 8.

[0122] A preparation method of a low-temperature-resistant high-strength concrete comprises the following steps:

[0123] Dry-mix the cement, coarse aggregate, and fine aggregate for 3 - 5 min;

[0124] Add water, admixture, and low-temperature-resistant modifier, and stir until the slump reaches 180 - 220 mm;

[0125] First, cure at 8°C for 24 hours, then transfer to -18°C for 7 days, and then cure at -42°C until 28 days to prepare low-temperature-resistant high-strength concrete.

[0126] Example 11

[0127] A low-temperature-resistant high-strength concrete includes the following substances by weight: 40 kg of cement, 82 kg of porous basalt coarse aggregate, 70 kg of sand, 18 kg of water, 4 kg of water reducer, and 7 kg of low-temperature-resistant modifier 9.

[0128] A preparation method of a low-temperature-resistant high-strength concrete includes the following steps:

[0129] Dry mix the cement, coarse aggregate, and fine aggregate for 3 - 5 minutes;

[0130] Add water, admixture, and low-temperature-resistant modifier, and stir until the slump reaches 180 - 220 mm;

[0131] First, cure at 8°C for 24 hours, then transfer to -18°C for 7 days, and then cure at -42°C until 28 days to prepare low-temperature-resistant high-strength concrete.

[0132] Comparative Example 1

[0133] A low-temperature-resistant high-strength concrete, compared with Example 1, uses basalt fibers with a diameter of 0.1 - 0.3 mm and a length of 6 - 15 mm of equal mass to replace the low-temperature-resistant modifier 1, and the other components and steps are the same as those in Example 1.

[0134] Comparative Example 2

[0135] A low-temperature-resistant high-strength concrete, compared with Example 1, uses TPU fiber (WHT-EL1150) to replace the low-temperature-resistant modifier 1, and the other components and steps are the same as those in Example 1.

[0136] Comparative Example 3

[0137] A low-temperature-resistant high-strength concrete, compared with Example 1, is cured using a conventional curing method until 28 days, and the other components and steps are the same as those in Example 1.

[0138] Performance Testing

[0139] Compressive strength: Compressive strength: GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete".

[0140] Freeze-thaw cycle: GB / T 50082-2009 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete" (-50°C to 20°C cycle).

[0141] The test results are shown in Table 1 below:

[0142] Table 1 Performance test table

[0143]

[0144]

[0145] By comparing Examples 1-5 with Comparative Examples 1 and 2, it can be found that the technical solution of the present application constructs a multi-scale reinforcement system for concrete through a composite design of rigid long fibers and elastomeric fibers. Rigid long fibers form a three-dimensional spatial network in the concrete matrix by virtue of their high elastic modulus and tensile strength, and inhibit crack propagation through a bridging effect. When the matrix is ​​loaded and microcracks are generated, the rigid fibers span both sides of the cracks, transfer the load to the fibers through the interface shear stress, and delay crack penetration. The elastic modulus of the elastomeric fibers is significantly lower than that of the matrix, and they deform greatly under the action of frost heave stress, absorbing energy through a viscoelastic energy dissipation mechanism. With the synergistic effect of the two, the rigid fibers bear the initial load, and the elastic fibers dissipate stress waves in the later deformation stage, forming a gradient anti-cracking path of "rigid first and soft later".

[0146] Comparison between Examples 6-8 and 1-5 illustrates that the technical solution of the present application constructs a nano-SiO2 particle interface layer on the surface of a low-temperature-resistant modified material by a sol-gel method. First, the silane coupling agent is hydrolyzed under acidic conditions to generate silanols, which react with the polar groups on the surface of the elastomer to form Si-OC covalent bonds, thereby enhancing the chemical bonding at the interface. Subsequently, SiO2 nanoparticles generated by hydrolysis and condensation of ethyl orthosilicate in an alkaline sol are adsorbed on the fiber surface through van der Waals forces and hydrogen bonds, and low-temperature curing promotes cross-linking of Si-O-Si bonds between particles to form a continuous dense layer. This layer acts as a physical barrier to prevent moisture from invading the fiber-matrix interface, while its rough surface increases mechanical bite and improves the interface shear strength, thereby ensuring good structural properties of the prepared concrete.

[0147] Finally, by comparing Examples 9-11 with Examples 6-8, it is further explained that the present application firstly uses the micropores in the aerogel coating layer to adsorb water molecules through the capillary effect to form amorphous ice, and the freezing point drops to below -45°C. The mesopores accommodate unfrozen water to continuously participate in the hydration reaction, blocking the penetration of external water, and reducing the total amount of freezable water. At the same time, the thermal conductivity of the coated aerogel coating modified layer is low, which blocks the invasion of external cold.

[0148] Secondly, the aerogel coating modified layer constructed in this application absorbs energy through compression, and cooperates with the elastomer fiber to release the pre-compression stress and offset the tensile stress of frost heave. In practical applications, the defects of concrete frost heave cracking and sudden strength drop under extreme low temperatures are improved through the synergy of multiple mechanisms of "ice suppression-heat insulation-energy consumption".

[0149] Finally, by comparing Examples 1-5 with Comparative Example 3, it can be found that in the pre-curing stage, the technical solution of the present application utilizes the initial hydration heat release of cement, and the aerogel layer blocks the heat dissipation, raising the internal temperature to 15-20 °C, promoting the hydration of C3S to generate C-S-H gel. In the medium-term curing stage, the external low temperature causes the surface layer of the concrete to be slightly frozen, and the aerogel layer maintains the temperature of the core area > 0 °C, and the unfrozen water continues to hydrate. In the final curing stage, the extreme environment is simulated. The elastomeric fibers contract to generate compressive stress, offsetting the frost heave tensile stress. The heat conductivity of the basalt fibers equalizes the temperature gradient and avoids thermal stress cracking.

[0150] This specific embodiment is only an interpretation of the present application, and it does not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A low-temperature resistant high-strength concrete, characterized in that, Comprising the following substances in parts by weight: Cement 35 - 45 parts; Coarse aggregate 75 - 100 parts; Fine aggregate 60 - 80 parts; Water 10 - 25 parts; Admixture 3 - 5 parts; Low - temperature resistant modifier 5 - 10 parts; The low - temperature resistant modifier includes a composite low - temperature resistant modified fiber prepared by compounding rigid long fibers and elastomeric fibers.

2. A low-temperature resistant high-strength concrete according to claim 1, characterized in that The rigid long fibers include basalt fibers with a length of 6 - 15 mm and a diameter of 0.1 - 0.3 mm.

3. A low-temperature resistant high-strength concrete according to claim 1, characterized in that, The low - temperature resistant modifier is further coated with a silica particle interfacial modification layer, and the silica particle interfacial modification layer is made by the following technical scheme: Take elastomeric fibers and immerse them in a silane coupling agent, perform surface treatment and wash and dry. After washing and drying, immerse the elastomeric fibers in a sol solution, perform centrifugal separation, wash and dry, and then cure at low temperature to prepare the silica particle interfacial modification layer.

4. A low-temperature resistant high-strength concrete according to claim 3, characterized in that, The sol solution is prepared by mixing tetraethyl orthosilicate, ethanol, water and ammonia water in a molar ratio of 1:(20 - 25):(3 - 5):(0.05 - 0.08).

5. A low-temperature resistant high-strength concrete according to claim 1, characterized in that, The elastomeric fibers include at least one of polyurethane elastomeric fibers, rubber fibers or thermoplastic elastomeric fibers.

6. A low-temperature resistant high-strength concrete according to claim 3, characterized in that, The silica particle interfacial modification layer is further coated with an aerogel coating modification layer.

7. A low-temperature resistant high-strength concrete according to claim 6, characterized in that, The aerogel coating modification layer is made by the following scheme: Take the low - temperature resistant modifier coated with the silica particle interfacial modification, wash and dry and perform activation treatment, then immerse it in a precursor sol solution. After immersion is completed, heat up and perform condensation treatment, and dry in vacuum to prepare the aerogel coating modification layer.

8. A low-temperature resistant high-strength concrete according to claim 7, characterized in that, The precursor sol solution comprises the following substances in parts by weight: Methyltrimethoxysilane 6 - 8 parts; Ethanol 30 - 50 parts; Acetic acid 0.1 - 0.5 part; Nanocellulose 0.2 - 0.5 part.

9. The preparation method of a low-temperature resistant high-strength concrete according to any one of claims 1-8, characterized in that, Including the following preparation steps: Dry - mix the cement, coarse aggregate and fine aggregate for 3 - 5 min; Add water, admixture and low - temperature resistant modifier, and stir until the slump reaches 180 - 220 mm; Cure at a low - temperature gradient for 28 days to complete the preparation of the low - temperature resistant high - strength concrete.

10. The preparation method of a low-temperature resistant high-strength concrete according to claim 9, characterized in that, The low - temperature gradient curing includes: First, pre - cure at 5 - 10 °C for 24 h, then transfer to - 20 ~ - 15 °C for 7 days, and then cure at - 45 ~ - 40 °C until 28 days to complete the low - temperature gradient curing.

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