Anti-freezing concrete and preparation method thereof

Abstract

The invention relates to anti-freezing concrete and a preparation method thereof, and relates to the field of building materials, and the anti-freezing concrete comprises Portland cement, slag powder, fly ash, silica fume, water, coarse aggregate, fine aggregate, functional super absorbent resin, an air entraining agent and a polycarboxylic acid water reducer. The functional super absorbent resin subjected to pre-saturated water treatment actively sucks and seals free water in pores in the freezing and thawing process based on a capillary potential difference principle, so that the content of freeze water is reduced; meanwhile, microbubbles generated by the air entraining agent are enriched around the super absorbent resin under the assistance of the viscosity adjusting type polycarboxylic acid water reducing agent to form a composite structure, expansion stress generated when water stored in the super absorbent resin is frozen is locally buffered, and cooperation of directional water transportation and stress localization buffering is achieved; the concrete has freezing resistance; and the polyvinyl alcohol grafted nanocellulose dispersed in the water reducing agent enhances the freezing resistance of the concrete by virtue of the synergistic effect of the polyvinyl alcohol grafted nanocellulose and functional components.

Description

Technical Field

[0001] This application relates to the field of building materials, specifically to an antifreeze concrete and its preparation method. Background Technology

[0002] As a key material in modern construction engineering, the durability of concrete directly determines the service life and safety of a structure. In frigid regions, freeze-thaw cycles, and projects using de-icing salt, concrete structures are subjected to long-term freeze-thaw damage. The repeated freezing, expansion, and thawing of pore water within the concrete leads to stress accumulation, causing surface spalling, internal cracking, and deterioration of mechanical properties, ultimately resulting in premature structural failure and posing significant economic and safety risks.

[0003] Currently, in addition to conventional technologies, the industry has explored other technical approaches to improve the freeze-thaw resistance of concrete. One approach is to incorporate various organic fibers or polymer emulsions (such as acrylic emulsions) into the concrete. The bridging effect of the fibers or the film-forming properties of the polymers enhance the tensile strength and toughness of the matrix, thus resisting frost heave stress. Another approach is to treat the concrete as a whole or on its surface using crystalline waterproofing agents or hydrophobic agents. This reduces the material's water absorption or permeability, delaying moisture intrusion and saturation. However, these methods have significant limitations: the introduction of fibers and polymers often negatively impacts the workability and volume stability of the concrete, and their main function is to passively resist existing stresses rather than reducing the source of damage at its root. Furthermore, waterproofing and hydrophobic treatments cannot guarantee their long-term effectiveness under freeze-thaw fatigue, and their protective effect diminishes drastically once the external protective layer is damaged.

[0004] Therefore, developing concrete with better frost resistance is crucial for extending the service life of critical infrastructure. Summary of the Invention

[0005] This application provides an antifreeze concrete and its preparation method, which has excellent antifreeze properties.

[0006] Firstly, the antifreeze concrete provided in this application adopts the following technical solution: A type of frost-resistant concrete is composed of the following components in parts by weight: 450-520 parts of cementitious material, 140-160 parts of water, 1000-1100 parts of coarse aggregate, 650-750 parts of fine aggregate, 0.3-0.8 parts of functional superabsorbent resin, 0.01-0.5 parts of air-entraining agent, and 4.8-9.4 parts of polycarboxylate superplasticizer; The cementitious material comprises the following components by weight percentage: 50-60% silicate cement, 20-30% slag powder, 10-20% fly ash, and 3-8% silica fume; The functional superabsorbent resin is cross-linked sodium polyacrylate with a particle size distribution of 30-100 μm; The air-entraining agent is a saponin-based air-entraining agent or an ether-based block copolymer-type air-entraining agent; The polycarboxylate superplasticizer is a viscosity-modifying polycarboxylate superplasticizer. The polycarboxylate superplasticizer contains 0.05-0.15 parts of polyvinyl alcohol-grafted nanocellulose pre-dispersed within it.

[0007] By adopting the above technical solution, ordinary silicate cement, slag powder, fly ash and silica fume form a quaternary cementitious system. The secondary hydration reaction of slag powder and fly ash can continuously consume calcium hydroxide and generate more stable low calcium-to-silica CSH gel, thereby optimizing the long-term pore structure. Silica fume, with its extremely fine particle size, exerts a physical filling effect, refines the capillary pore size, and transforms most of the interconnected pores into closed micropores to form a dense microstructure. This not only improves mechanical strength but also reduces water permeability and freeze saturation, providing a stable platform for the subsequent functional components.

[0008] The introduction of functional superabsorbent polymer (SAP) allows for the slow release of water stored within the SAP as internal humidity decreases during cement hydration. This promotes deep hydration of cementitious materials (especially slag and fly ash), reduces the risk of autogenous shrinkage and early plastic cracking in concrete, and further enhances the homogeneity and integrity of the matrix. Simultaneously, the interior of the SAP can be considered a reservoir, with a capillary potential significantly higher than that of the surrounding cement matrix's micropores. When the ambient temperature drops to freezing point, the free water in the capillaries begins a phase change, disrupting the system's chemical potential equilibrium. Based on thermodynamic principles, unfrozen free water spontaneously migrates directionally from the high chemical potential region (the micropores about to freeze) to the low chemical potential region (the interior of the SAP). This process actively draws in and seals a large amount of free water that would otherwise freeze within the SAP particles. Furthermore, the strong binding effect of the SAP polymer network on water molecules lowers the freezing point of the sealed water, delaying the freezing process. Through this directional water transport mechanism, the actual freezeable water content in the concrete capillaries is reduced, weakening the driving force of frost heave damage.

[0009] However, the moisture trapped inside the SAP will eventually freeze and expand at extremely low temperatures. To address this, a high-performance air-entraining agent was introduced. In the moderately viscous slurry environment created by the viscosity-modifying polycarboxylate superplasticizer, the introduced micron-sized bubbles, influenced by rheological processes, tend to accumulate and stabilize around flexible SAP particles during stirring, spontaneously forming composite functional units of "SAP core-bubble shell" in space. When the water inside the SAP freezes and generates expansion pressure, the stress is immediately absorbed by the tightly encapsulated bubble shell. This means that the destructive expansion force is confined within the composite unit, achieving localized stress buffering and preventing stress propagation, convergence, and macroscopic cracking of the cementitious matrix.

[0010] In the synergistic effect of SAP and air-entraining agent described above, viscosity-modifying polycarboxylate superplasticizer not only provides a high water reduction rate to ensure high fluidity at low water-cement ratios, but its moderate thickening effect also stabilizes the SAP hydrogel particles, preventing them from floating or segregating during transportation and casting; it also maintains the stability of the bubble system, effectively inhibiting the merging of small bubbles and the escape of large bubbles; at the same time, by increasing the viscosity of the pore solution, it provides a longer action time window and a more stable migration path for the aforementioned water-oriented transport process.

[0011] In polycarboxylate superplasticizers, the pre-dispersed polyvinyl alcohol-grafted nanocellulose has a high degree of compatibility with the ice crystal lattice through the arrangement of hydroxyl groups on the molecular chain. According to the Kelvin effect, it can recognize and adsorb on the edge face of ice nucleus growth. This molecular pinning effect is like imposing a constraint on ice crystal growth, which can change the ice crystal growth mode and force it to transform from destructive needle-shaped or dendritic ice crystals into spherical or disk-shaped morphologies with small surface area and weak piercing force on the pore wall, thereby eliminating the tip concentration effect of frost heave stress.

[0012] Based on this, under rapid cooling conditions, the recrystallization inhibition effect of polyvinyl alcohol grafted nanocellulose can reduce the nucleation temperature of ice and slow down the growth rate of ice crystals. This kinetic delay creates a time window for SAP, ensuring that unfrozen water has enough time to migrate smoothly from the capillaries into the SAP under the drive of chemical potential difference. This avoids the risk of SAP failure due to water freezing in situ before it can migrate due to excessively rapid cooling, and realizes the suction and sealing of free water in the capillaries.

[0013] Meanwhile, regarding bubble stability, the amphiphilic polyvinyl alcohol-grafted nanocellulose exhibits a Pickering emulsion effect during stirring, spontaneously aligning at the gas-liquid interface. This not only prevents bubble coalescence and breakage during construction vibration but also strengthens the structural strength of the "SAP core-bubble shell" composite unit, giving it higher toughness and resilience when subjected to ice crystal expansion and compression. Furthermore, as a high-strength nanofiber, it bridges the CSH gel network and micropores within the cement matrix, effectively sealing microcracks caused by temperature stress and preventing them from expanding into macroscopic cracks.

[0014] Optionally, the preparation method of the polyvinyl alcohol-grafted nanocellulose includes the following steps: S1. Mix nanocellulose with water, ultrasonically disperse for 30-40 min, adjust the pH value to 4.0-4.5, add KH-560, and stir at 45-50℃ for 1-2 h to obtain a modified nanocellulose suspension. S2. Dissolve PVA powder in hot water at 90℃ to make a solution, cool it to 60℃, and then add it dropwise to the modified nanocellulose suspension obtained in step S1. Stir at 75-80℃ for 5-6 hours. S3. After the reaction is complete, the precipitate is washed, centrifuged to remove unreacted free PVA and KH-560, and dispersed in water to produce polyvinyl alcohol grafted nanocellulose with a solid content of 2-5%.

[0015] By employing the above technical solution, in step S1, the methoxy group of KH-560 hydrolyzes to generate a silanol group under reaction conditions, which then undergoes a condensation reaction with the hydroxyl groups on the surface of the nanocellulose, introducing epoxy groups onto its surface. Subsequently, in step S2, under reaction conditions, the epoxy group at the other end of KH-560 undergoes ring-opening under heating conditions, reacting with the hydroxyl groups on the PVA molecular chain to undergo an etherification reaction, thereby firmly attaching the long PVA chain to the nanocellulose backbone, thus obtaining polyvinyl alcohol-grafted nanocellulose.

[0016] Optionally, the functional superabsorbent resin is pre-saturated with water before use, and the pre-saturation rate is 40-70% of its own dry powder weight.

[0017] By adopting the above technical solution, the initial workability loss caused by excessive competition for mixing water when dry SAP is directly added is effectively avoided, ensuring that the concrete has good workability. Furthermore, this specific range of pre-saturated water allows the SAP particles to exist in the form of a hydrogel during the mixing stage, laying the material foundation for its continuous internal curing function in the later stages of cement hydration, promoting the secondary hydration reaction of the cementitious materials, increasing matrix density, and reducing autogenous shrinkage.

[0018] Optionally, the air-entraining agent is a high-performance air-entraining agent capable of generating microbubbles with an average pore size of less than 200 μm.

[0019] By employing the above technical solution, micron-sized bubbles exhibit a more numerous and uniformly distributed discrete state within the cement matrix. Their large specific surface area enables them to more efficiently absorb and buffer the osmotic pressure and crystallization pressure generated during freeze-thaw cycles. Compared to large bubble systems, this highly refined bubble structure not only provides ample expansion space for water freezing but, more importantly, disperses macroscopic freeze-thaw stress into countless micro-intervals of localized stress, greatly avoiding stress concentration and effectively suppressing the initiation and propagation of microcracks.

[0020] Optionally, the slag powder is S95 grade or higher slag powder.

[0021] By adopting the above technical solution, S95 grade and above slag powder effectively refines the capillary network of concrete through physical filling effect. At the same time, its high activity drives a deep secondary hydration reaction, continuously consuming calcium hydroxide in the system and generating more stable CSH gel with low calcium-to-silicon ratio, thereby improving the density and homogeneity of the matrix.

[0022] Optionally, the fly ash is Class I fly ash.

[0023] By adopting the above technical solutions, Class I fly ash particles are finer, have higher sphericity, and lower unburned carbon content. These characteristics enable them to exert a better physical filling effect in concrete systems, effectively refine capillary pore size, and at the same time, their high pozzolanic activity allows them to participate more fully in the secondary hydration reaction, continuously consuming calcium hydroxide in the system and generating more stable low-alkalinity CSH gel, thereby improving the density and homogeneity of the matrix.

[0024] Optionally, the silica content of the silica ash is not less than 90%.

[0025] By adopting the above technical solution, high-purity silica fume is rich in highly active amorphous silica. Its extremely fine particle size can efficiently fill the nanoscale voids between cement particles. This physical filling effect refines the capillary pore size of concrete, reduces the connectivity of pores, and thus improves the density and strength of the matrix.

[0026] Secondly, this application provides a method for preparing frost-resistant concrete, comprising the following steps: S1: Premix the functional superabsorbent resin with a portion of the mixing water to allow it to fully absorb water and form hydrogel particles; S2: Mixing: First, put the coarse and fine aggregates and the remaining mixing water into the mixer for preliminary mixing, then add all the cementitious materials and mix, and finally add the hydrogel particles obtained in step S1, polycarboxylate superplasticizer and air-entraining agent, and mix thoroughly until a uniform concrete mixture is obtained.

[0027] By adopting the above technical solution, prehydrated SAP ensures the formation of complete hydrogel particles, laying the foundation for subsequent internal curing and moisture control functions. A three-step feeding sequence of aggregate-cementing material-functional components is used to first form a uniform cement paste matrix, and finally add prehydrated SAP, water-reducing agent, and air-entraining agent. This avoids the adsorption of admixtures by the aggregate and ensures that each functional component is fully dispersed in the system.

[0028] Optionally, the air content of the concrete in step S2 is controlled at 4.0-5.5%.

[0029] By adopting the above technical solution, the air content is precisely controlled within the range of 4.0-5.5%, which aims to introduce a sufficient amount of stable micro-closed air bubbles. These air bubbles, as an efficient pressure buffer, can effectively absorb the expansion stress generated by the freezing of pore water during freeze-thaw cycles, thereby preventing micro-cracks from forming in the internal structure of concrete.

[0030] In summary, this application includes at least one of the following beneficial technical effects: 1. In a moderately viscous slurry environment constructed with viscosity-modifying polycarboxylate superplasticizers (SAP), SAP, based on the principles of capillary action and chemical potential, draws in and seals free water in capillary pores during the initial freeze-thaw cycle, reducing the content of freezeable water in the matrix and weakening the driving force of frost heave. Simultaneously, microbubbles introduced by the air-entraining agent, under rheological control, preferentially accumulate around SAP particles, forming unique SAP-bubble composite functional units. When the water sealed inside the SAP eventually freezes and expands, the resulting expansion stress is efficiently absorbed by the outer bubble layer, achieving localized stress buffering. In this process, the superplasticizer not only ensures high workability at low water-cement ratios, but its viscosity-modifying function also ensures unobstructed water migration pathways and the stability of the composite unit structure. Therefore, this synergistic system, by actively managing moisture and precisely dissipating stress, endows concrete with excellent freeze-thaw resistance. 2. The introduced polyvinyl alcohol-grafted nanocellulose exhibits a high degree of compatibility with the ice crystal lattice through the hydroxyl arrangement of its molecular chains. It recognizes and adsorbs onto the edges of ice nuclei, and this molecular pinning effect acts as a constraint on ice crystal growth, altering its growth pattern and forcing it to transform from destructive needle-like or dendritic ice crystals into spherical or disk-shaped forms with small surface areas and weak piercing force against pore walls. This eliminates the tip concentration effect of frost heave stress. Furthermore, under rapid cooling conditions, the recrystallization inhibition effect of polyvinyl alcohol-grafted nanocellulose lowers the ice nucleation temperature and slows down the ice crystal growth rate. This ensures that unfrozen water has sufficient time to migrate smoothly from the capillaries into the SAP (Symptom Aqueous Plasma) driven by the chemical potential difference, avoiding the risk of SAP failure due to in-situ freezing before water can migrate, caused by excessively rapid cooling. Meanwhile, the amphiphilic polyvinyl alcohol-grafted nanocellulose spontaneously aligns at the gas-liquid interface during stirring, preventing bubble coalescence and rupture during construction vibration. This not only strengthens the structural strength of the "SAP core-bubble shell" composite unit, giving it higher toughness and resilience when subjected to ice crystal expansion and compression. Furthermore, as a high-strength nanofiber, it bridges the CSH gel network and micropores within the cement matrix, effectively sealing microcracks caused by temperature stress and preventing their propagation into macroscopic cracks. Detailed Implementation

[0031] Preparation Example 1 The preparation method of polyvinyl alcohol grafted cellulose nanoparticles includes the following steps: S1. Mix nanocellulose with water, ultrasonically disperse for 30 min, adjust the pH value to 4.5, add KH-560, and stir at 50℃ for 1.5 h to obtain a modified nanocellulose suspension. S2. Dissolve PVA powder in hot water at 90°C to make a solution, cool it to 60°C, and then add it dropwise to the modified nanocellulose suspension obtained in step S1. Stir at 80°C for 6 hours. S3. After the reaction is complete, the precipitate is washed, centrifuged to remove unreacted free PVA and KH-560, and dispersed in water to prepare polyvinyl alcohol grafted nanocellulose with a solid content of 4%.

[0032] Example 1 A type of frost-resistant concrete is composed of the following components in parts by weight: 450 parts of cementitious material, 140 parts of water, 1000 parts of coarse aggregate, 650 parts of fine aggregate, 0.3 parts of functional superabsorbent resin, 0.2 parts of air-entraining agent, and 4.8 parts of polycarboxylate superplasticizer; wherein the cementitious material includes the following components in weight percentage: 55% silicate cement, 25% slag powder, 15% fly ash, and 5% silica fume.

[0033] Among them, the functional superabsorbent resin is cross-linked sodium polyacrylate with a particle size distribution of 30-100μm; the air-entraining agent is a saponin-based air-entraining agent that can generate microbubbles with an average pore size of less than 200μm; the polycarboxylate superplasticizer is a viscosity-modifying polycarboxylate superplasticizer, and 0.1 parts of a pre-dispersed preparation example of polyvinyl alcohol grafted nanocellulose are obtained in the polycarboxylate superplasticizer; the slag powder is S95 grade slag powder; the fly ash is Grade I fly ash; and the silica content of silica fume is not less than 90%.

[0034] A method for preparing frost-resistant concrete includes the following steps: S1: Premix the functional superabsorbent resin with a portion of the mixing water to allow it to fully absorb water and form hydrogel particles; S2: Mixing: First, put the coarse and fine aggregates and the remaining mixing water into the mixer for preliminary mixing, then add all the cementitious materials and mix, and finally add the hydrogel particles obtained in step S1, polycarboxylate superplasticizer and air-entraining agent, and mix thoroughly until a uniform concrete mixture is obtained.

[0035] In step S1, the pre-saturation rate of the functional superabsorbent resin is 40-70% of its own dry powder weight; in step S2, the air content of the concrete is controlled at 4.0-5.5%.

[0036] Example 2 A type of frost-resistant concrete, which differs from Example 1 in that it is composed of the following components in parts by weight: 485 parts of cementitious material, 150 parts of water, 1050 parts of coarse aggregate, 700 parts of fine aggregate, 0.6 parts of functional superabsorbent resin, 0.35 parts of air-entraining agent, and 7.5 parts of polycarboxylate superplasticizer.

[0037] Example 3 A type of frost-resistant concrete, which differs from Example 1 in that it is composed of the following components in parts by weight: 520 parts of cementitious material, 160 parts of water, 1100 parts of coarse aggregate, 750 parts of fine aggregate, 0.8 parts of functional superabsorbent resin, 0.5 parts of air-entraining agent, and 9.4 parts of polycarboxylate superplasticizer.

[0038] Example 4 A type of frost-resistant concrete, which differs from Example 1 in that the cementitious material comprises the following components by weight percentage: 60% silicate cement, 27% slag powder, 10% fly ash, and 3% silica fume.

[0039] Example 5 A type of frost-resistant concrete, which differs from Example 1 in that the cementitious material comprises the following components by weight percentage: 50% silicate cement, 22% slag powder, 20% fly ash, and 8% silica fume.

[0040] Comparative Example 1 A type of frost-resistant concrete differs from Example 1 in that the raw material components do not contain functional superabsorbent resin and air-entraining agent, and the water-reducing agent is a common polycarboxylate water-reducing agent.

[0041] Comparative Example 2 A type of frost-resistant concrete differs from Example 1 in that the raw material components do not contain functional superabsorbent resin, and the water-reducing agent is a common polycarboxylate water-reducing agent.

[0042] Comparative Example 3 An antifreeze concrete differs from Example 1 in that the raw material components do not contain a high-performance air-entraining agent, and the water-reducing agent is a common polycarboxylate water-reducing agent.

[0043] Comparative Example 4 A type of frost-resistant concrete, which differs from Example 1 in that the water-reducing agent does not contain pre-dispersed polyvinyl alcohol-grafted nanocellulose.

[0044] Comparative Example 5 A type of frost-resistant concrete, which differs from Example 1 in that the water-reducing agent is a common polycarboxylate water-reducing agent.

[0045] Detection example According to GB / T 50082-2009, the relative dynamic modulus of elasticity (Er) retention rate and mass loss rate of concrete after 300 freeze-thaw cycles were tested to detect the freeze-thaw resistance of concrete; according to GB / T 50081-2019, the compressive strength of concrete was tested; and according to GB / T 50080-2016, the air content of concrete was tested. The specific test results are shown in Table 1.

[0046] Table 1 As shown in Table 1 of the performance test data for Examples 1-5 and Comparative Examples 1 and 4, Comparative Example 1 lacks any anti-freeze design, and the huge frost heave stress generated during the freeze-thaw process has nowhere to be absorbed, leading to rapid failure. The relative dynamic elastic modulus retention rates of Examples 1-5 fully demonstrate that the system constructed in this scheme can effectively resist freeze-thaw damage.

[0047] As shown in Table 1 of the performance test data for Examples 1-5 and Comparative Examples 1-3, in a moderately viscous slurry environment constructed with a viscosity-modifying polycarboxylate superplasticizer, the functional superabsorbent polymer (SAP) absorbs and seals free water in the capillary pores during the initial freeze-thaw cycle, reducing the content of freezeable water in the matrix and weakening the driving force of frost heave, based on the principles of capillary action and chemical potential. Simultaneously, the microbubbles introduced by the air-entraining agent preferentially accumulate around the SAP particles under rheological regulation, forming unique SAP-bubble composite functional units. When the water sealed inside the SAP eventually freezes and expands, the resulting expansion stress is efficiently absorbed by the outer bubble layer, achieving localized stress buffering. In this process, the superplasticizer not only ensures high workability at low water-cement ratios, but its viscosity-modifying function also ensures unobstructed water migration paths and stable composite unit structures. Therefore, this synergistic system, by actively managing moisture and precisely dissipating stress, endows concrete with excellent freeze-thaw resistance.

[0048] As can be seen from the performance test data in Table 1 of Examples 1-5 and Comparative Examples 4-5, the pre-dispersion of polyvinyl alcohol grafted with nanocellulose in polycarboxylate superplasticizer further enhances the frost resistance of concrete, demonstrating its auxiliary effect on functional components.

[0049] Please note that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. An anti-freeze concrete, characterized in that, Consists of the following components by weight: cementitious material 450-520 parts, water 140-160 parts, coarse aggregate 1000-1100 parts, fine aggregate 650-750, functional superabsorbent resin 0.3-0.8 parts, air entraining agent 0.01-0.5 parts, polycarboxylic acid type water reducing agent 4.8-9.4 parts; The cementitious material comprises the following components by mass percentage: Portland cement 50-60%, slag powder 20-30%, fly ash 10-20%, silica fume 3-8%; The functional superabsorbent resin is crosslinked sodium polyacrylate with particle size distribution of 30-100 μm; The air entraining agent is a saponin type air entraining agent or an ether type block copolymer type air entraining agent; The polycarboxylic acid type water reducing agent is a viscosity adjusting type polycarboxylic acid water reducing agent; The polycarboxylic acid type water reducing agent has 0.05-0.15 parts of polyvinyl alcohol grafted nanocellulose pre-dispersed therein.

2. The freeze-resistant concrete according to claim 1, characterized in that, The preparation method of the polyvinyl alcohol grafted nanocellulose comprises the following steps: S1, mixing nanocellulose with water, ultrasonic dispersion for 30-40 min, adjusting the pH value to 4.0-4.5, then adding KH-560, stirring at 45-50℃ for 1-2h, obtaining modified nanocellulose suspension; S2, dissolving PVA powder in hot water at 90℃ to form a solution, cooling to 60℃, then adding dropwise into the modified nanocellulose suspension obtained in step S1, stirring at 75-80℃ for 5-6h; S3, after the reaction is completed, precipitating and washing, centrifugal separation to remove unreacted free PVA and KH-560, dispersing in water to form polyvinyl alcohol grafted nanocellulose with solid content of 2-5%.

3. The freeze resistant concrete of claim 1, wherein, The functional superabsorbent resin is pre-saturated before use, and the pre-saturation rate is 40-70% of the weight of the dry powder itself.

4. The freeze resistant concrete of claim 1, wherein, The air entraining agent is a high-performance air entraining agent capable of generating micro-bubbles with an average pore size of less than 200 μm.

5. The freeze resistant concrete of claim 1, wherein, The slag powder is S95 grade or above.

6. The freeze resistant concrete of claim 1, wherein, The fly ash is I grade fly ash.

7. The freeze resistant concrete of claim 1, wherein, The silica content of the silica fume is not less than 90%.

8. A method of producing a frost-resistant concrete according to any of claims 1-7, characterized in that, Comprises the following steps: S1: pre-mixing the functional superabsorbent resin with part of the mixing water to allow it to fully absorb water and form hydrogel particles; S2: mixing, first mixing the coarse and fine aggregates with the remaining mixing water in a mixer, then adding all the cementitious materials for stirring, and finally adding the hydrogel particles obtained in step S1, the polycarboxylic acid type water reducing agent and the air entraining agent, and fully stirring until a uniform concrete mixture is obtained.

9. A method of producing a frost-resistant concrete according to claim 8, characterized in that, The air content of the concrete in step S2 is controlled at 4.0-5.5%.

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