Preparation method of negative temperature cement-based material capable of continuously hydrating and hardening at-20 DEG C

Abstract

The invention discloses a preparation method of a negative-temperature cement-based material capable of being continuously hydrated and hardened in an environment of-20 DEG C, and relates to the technical field of application materials. The negative-temperature cement-based material comprises Portland cement, fine aggregate, water, a mineral admixture, an anti-freezing agent, a water-retention thickener, a fluidity regulator, a microcapsule complex, a penetration enhancer, a silicon-aluminum disordered network precursor and an anti-freezing polypeptide chain material. Additives such as a microcapsule complex and a penetration enhancer are introduced into a cement-based system, a low-temperature activation mechanism with a synergistic effect is constructed, and the microcapsule complex can accurately release latent heat in a negative temperature environment and induce a hydration reaction to be continuously carried out; the permeation enhancer improves the interface diffusivity and breaks through a mass transfer channel of a frozen interface water layer; the silicon-aluminum disordered network precursor is used as a structure inducer to promote the recombination of a C-S-H gel structure at a low temperature; the antifreeze polypeptide chain material endows the slurry with frost crack resistance toughness through conformation adjustment and ice crystal inhibition functions.

Description

Technical Field

[0001] The present invention relates to the technical field of applied materials, and in particular to a method for preparing a negative-temperature cement-based material capable of sustainable hydration and hardening at -20°C. Background Art

[0002] When cement-based materials are constructed at low temperatures, especially in environments of -20°C and below, they generally face problems such as a significant reduction in the hydration reaction rate, difficulty in forming early strength, and internal microcracks caused by ice crystal expansion. The antifreeze technical means commonly used in the existing technology mainly include adding a large amount of alcohol, inorganic salt or sugar-type antifreeze. Although these additives can lower the freezing point of water to a certain extent, they are often still unable to effectively activate the hydration process of the cement system under severe cold conditions, and have an inhibitory effect on the subsequent strength growth. In addition, conventional phase change materials are difficult to accurately control the timing of latent heat release due to their easy damage and uncontrolled release, and cannot match the hydration kinetics process, resulting in their auxiliary heating function under negative temperature conditions cannot be fully utilized.

[0003] Therefore, there is still a lack of a method for preparing cement-based materials that can continuously induce hydration reactions at -20°C and ensure the formation of structural strength. Especially in terms of the multifunctional coupling regulation mechanism under low-temperature environments, the existing technology has not yet solved the core problem of balancing hydration continuity and structural density. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the present invention provides a method for preparing a negative temperature cement-based material that can be continuously hydrated and hardened in a -20°C environment to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions: The embodiment of the present invention provides a method for preparing a negative temperature cement-based material that can sustainably hydrate and harden at -20°C. The negative temperature cement-based material includes the following specific components: Portland cement, fine aggregate, water, mineral admixtures, antifreeze, water-retaining thickener, and flow regulator; The negative temperature cement-based material further comprises additives, which specifically include: Microcapsule complexes, penetration enhancers, silicon-aluminum disordered network precursors, and antifreeze polypeptide chain materials; The preparation method comprises the following steps: S1. Pretreatment and screening of raw materials; S2, liquid phase dispersion preparation of antifreeze; S3, pre-dispersion activation of microcapsule complex; S4, dry solid components are uniformly mixed; S5. Synergistic compounding and introduction of functional additives; S6. The dry powder and the composite liquid are stirred into a slurry; S7, terminal implantation of microcapsule complex; S8. Casting and curing in a -20℃ environment.

[0006] To further optimize this technical solution, the mass fractions of the specific components are as follows: Portland cement is 80-100 parts; Fine aggregate is 80-100 parts; 35-45 parts water; Mineral admixture is 20-40 parts; Antifreeze is 3-8 parts; The water-retaining thickener is 0.5-1.5 parts; The fluidity regulator is 0.3-1 part.

[0007] To further optimize this technical solution, the mass fractions of the additives are as follows: The microcapsule complex is 2-5 parts; Penetration enhancer is 1.5-4 parts; The silicon-aluminum disordered network precursor is 3-6 parts; The antifreeze polypeptide chain material is 0.2-0.8 parts.

[0008] To further optimize this technical solution, the specific components include: Fine aggregate is medium sand or fine sand with a size of 0.075-2.36 mm and continuous particle gradation; The mineral admixture is a mixture of fly ash, granulated blast furnace slag powder and silica fume, and the ratio of fly ash, granulated blast furnace slag powder and silica fume is 10:10:5; Antifreeze is a low-temperature modifier that includes sodium chloride, calcium chloride, and ethylene glycol; The water-retaining thickener is hydroxypropyl methylcellulose HPMC; The fluidity regulator is a polycarboxylic acid water reducer.

[0009] To further optimize the present technical solution, the microcapsule composite is composed of a microcapsule structure formed by a phase change core material having a melting point of -5°C to -20°C and a polymer coating material, the phase change core material being selected from n-tetradecane or tetrabutylammonium bromide, the coating material comprising a blend of polymethyl methacrylate and EPDM rubber, and the composite releasing latent heat in the early stage of cement hardening to delay pore water freezing and maintain interfacial hydration reaction.

[0010] Further optimizing the technical solution, the penetration enhancer is composed of tricarboxylated chitosan and quaternary ammonium cation modified silicone polyether in a mass ratio of 2:1 to 4:1, which enhances Ca by forming an ion channel structure during the cement hydration process. 2+ With SiO44- The diffusion rate of the catalyst can be increased, thereby improving the hydration reaction activity at -20℃.

[0011] To further optimize this technical solution, the silicon-aluminum disordered network precursor includes alkali-activated attapulgite, zeolite A nanocrystalline cores and titanium-doped amorphous silica. The three are deposited and coated to form a precursor complex with disordered structure induction ability, which promotes the formation of CASH gel in a low-temperature environment to enhance the structural density of the material.

[0012] To further optimize this technical solution, the antifreeze polypeptide chain material is formed by connecting an artificial polypeptide chain that simulates the conformation of ice-binding protein and a small molecule with a guanidine structure through an amide bond. It adsorbs the ice crystal nucleation interface and induces lattice deconstruction in an environment below -20°C, thereby effectively delaying the ice crystal growth process.

[0013] Further optimizing the technical solution, in step S3, the weighed microcapsule complex is placed in a constant temperature water bath with the temperature set at -5°C for 30 minutes to prepare for the metastable phase transition; Then stir slowly at 400 rpm for 10 minutes to maintain a uniform dispersion; Use immediately after processing and do not store for a long time to prevent loss of thermodynamic state.

[0014] Further optimizing the technical solution, in step S7, after the slurry is formed in step S6, the microcapsule complex of step S3 is added at a low speed of 300 rpm and stirred for 2 minutes to ensure that it is evenly dispersed but not broken; The addition method is to slowly sprinkle the microcapsules along the surface of the slurry to ensure the structural integrity and latent heat storage function of the microcapsules.

[0015] Compared with the existing technology, the present invention provides a method for preparing a negative temperature cement-based material that can sustainably hydrate and harden at -20°C, which has the following beneficial effects: This method for preparing a negative-temperature cement-based material that sustainably hydrates and hardens at -20°C utilizes a synergistic low-temperature activation mechanism by introducing a microcapsule complex, a permeation enhancer, a silicon-aluminum disordered network precursor, and an antifreeze polypeptide chain material into the cement-based system. The microcapsule complex precisely releases latent heat at negative temperatures, inducing a sustained hydration reaction. The permeation enhancer improves interfacial diffusivity, opening up mass transfer channels in the frozen interfacial water layer. The silicon-aluminum disordered network precursor acts as a structural inducer, promoting the reorganization of the CSH gel structure at low temperatures. The antifreeze polypeptide chain material imparts anti-freeze cracking toughness to the slurry through conformational regulation and ice crystal inhibition. This combined approach significantly enhances the hydration activity and early structural formation capabilities of cement-based materials at -20°C, ensuring stable construction and durable performance in low-temperature environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 This is a schematic diagram of the composition of a negative temperature cement-based material that can sustainably hydrate and harden at -20°C, proposed by the present invention; Figure 2 This is a flow chart of the method for preparing a negative-temperature cement-based material that can sustainably hydrate and harden at -20°C proposed by the present invention. DETAILED DESCRIPTION

[0018] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0019] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0020] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it constitute a separate or selective embodiment that is mutually exclusive with other embodiments.

[0021] Example 1: Reference Figures 1 and 2 , which is the first embodiment of the present invention, provides that the negative temperature cement-based material includes the following specific components: Portland cement, fine aggregate, water, mineral admixtures, antifreeze agent, water-retaining thickener and flow regulator.

[0022] Among the specific components: The Portland cement used is PO 42.5R-type ordinary Portland cement with a moderate C3A content. It exhibits excellent early strength properties and provides the primary hydration reactant, forming hardening products such as calcium silicate hydrate (CSH) gel and calcium hydroxide (Ca(OH)2), which are the foundation of the system's strength. The R-type variety exhibits high early activity, facilitating the initial hydration reaction in cold environments.

[0023] Fine aggregate is medium sand or fine sand with a size of 0.075-2.36mm and continuous particle gradation; it improves the volume stability and overall structural density of the system, reducing the risk of shrinkage cracking; at the same time, it acts as a skeleton material to regulate fluidity and bonding properties, helping to alleviate stress concentration caused by water freezing under negative temperature conditions.

[0024] Clean tap water or electrolyzed water, preheated to 5-10°C, is used to ensure pure water quality and stable ion content. This water participates in the cement hydration reaction, dissolves admixtures, and regulates system fluidity. Because water easily freezes at -20°C, innovative additives will be used to achieve partial "chemical thawing" and "ice activation" mechanisms.

[0025] The mineral admixture is a mixture of fly ash, granulated blast furnace slag powder, and silica fume, with the ratio of fly ash, granulated blast furnace slag powder, and silica fume being 10:10:5. Fly ash improves the late-stage strength and density of the mixture, slows the rate of hydration heat release, and improves workability. Slag powder reacts secondary with cement hydration products, increasing early strength and prolonging reactivity. Silica fume, with its extremely high specific surface area, quickly reacts with calcium hydroxide to form a dense CSH gel, improving frost resistance and impermeability.

[0026] Antifreeze is a low-temperature modifier, including sodium chloride, calcium chloride, and ethylene glycol; it achieves initial antifreeze protection by lowering the freezing point of water; however, in the present invention, such ingredients are only used as a low-dose basis to avoid their adverse effects on the corrosion resistance and later strength of the steel bars.

[0027] The water-retaining thickener is hydroxypropyl methylcellulose HPMC; it improves the cohesiveness and water-retaining capacity of the mixture under negative temperature conditions, delays water loss, helps slow down the interface damage caused by freezing during the cement hydration process, and stabilizes the slurry structure.

[0028] The fluidity regulator is a polycarboxylic acid-based water reducer; it improves working performance, reduces mixing water usage, and enhances system density, facilitating the dispersion and interfacial synergy of subsequent innovative functional additives.

[0029] The above components constitute the "basic skeleton" of negative temperature cement-based materials. Among them: Cement and mineral admixtures are the core of the reaction; Fine aggregate and water-retaining agent work together to ensure structural stability; A small amount of antifreeze and fluidity regulator provides necessary protection for construction at low temperatures and early antifreeze.

[0030] In this embodiment, the mass fractions of the specific components are as follows: Portland cement is 80 parts; Fine aggregate is 80 parts; 35 parts water; The mineral admixture is 20 parts; 3 parts of antifreeze; The water-retaining thickener is 0.5 parts; The fluidity regulator is 0.3 parts.

[0031] The negative temperature cement-based material further comprises additives, which specifically include: Microcapsule complexes, penetration enhancers, silicon-aluminum disordered network precursors, and antifreeze polypeptide chain materials.

[0032] The microcapsule complex is composed of a phase change core material with a melting point of -5°C to -20°C and a polymer coating material to form a microcapsule structure. The phase change core material is selected from n-tetradecane or tetrabutylammonium bromide. The former belongs to the linear saturated alkane class and has excellent phase change latent heat release ability, while the latter has quasi-crystalline transformation behavior in a low-temperature environment and can provide a slow heat energy release process. The coating material includes a blend of polymethyl methacrylate and ethylene propylene diene monomer rubber, which has good crack resistance and osmotic stability and can control the spatiotemporal release of phase change behavior. The composite releases latent heat in the early stage of cement hardening to delay pore water freezing and maintain interfacial hydration reaction. The microcapsule is uniformly dispersed in the cement-based system. When the ambient temperature drops to -20°C, its internal core undergoes slow crystallization to release latent heat, which can maintain the temperature of the cement particle interface area stable in the range of -5°C to 0°C at the microscale, significantly inhibiting the instantaneous freezing of free water, thereby prolonging the activation period of the initial hydration reaction. At the same time, polar side groups are doped into the wall layer, which can form weak bonds with hydrated ions, play a synergistic role in microscale dispersion and anchoring, and effectively prevent the migration and aggregation of microcapsules.

[0033] Compared with traditional alcohol or salt antifreezes, this phase change microstructure control method has the following advantages: it does not increase the system's osmotic pressure, does not cause corrosion to steel bars, has the ability to release heat periodically, has no adverse effects on later strength, and has extremely high functional integration and safety.

[0034] The penetration enhancer is composed of tricarboxylated chitosan and quaternary ammonium cation modified silicone polyether in a mass ratio of 2:1 to 4:1, and forms an ion channel structure to enhance the Ca 2+ With SiO4 4- The diffusion rate of the catalyst can be increased, thereby improving the hydration reaction activity at -20℃.

[0035] Tricarboxylic chitosan binds to Ca 2+ Formation of dynamic chelate complexes, changing Ca 2+ The diffusion path and charge distribution of the silicone polyether segment have certain flexibility and polar end group exposure ability at low temperature, which can form a directional interface structure layer at the colloid-liquid interface to achieve SiO4 4-The overall performance is the formation of a composite interface network similar to "charge channels" at extremely low temperatures, which effectively reduces the diffusion energy barrier of hydration ions and promotes the directional formation and bridge extension of CSH gels.

[0036] Compared with existing hydration promoters such as aminosulfonates and amine dispersants, this structure introduces an ion-interface synergistic reconstruction mechanism, and still has significant hydration promoting ability under -20°C environment, and has no significant promoting effect on the agglomeration of cement particles, does not affect the flow properties of the slurry, and can significantly improve the antifreeze stability and early structural integrity.

[0037] The silicon-aluminum disordered network precursor includes alkali-activated attapulgite, zeolite A nanocrystalline cores and titanium-doped amorphous silica. The three are deposited and coated to form a precursor complex with disordered structure induction ability, which promotes the formation of CASH gel in a low-temperature environment to enhance the structural density of the material.

[0038] The preparation method of the silicon-aluminum disordered network precursor comprises: The attapulgite is treated with NaOH or KOH alkali activation to enhance its cation exchange capacity; Nano-zeolite crystal nuclei were grown in situ on its surface by sol-gel method; Tetrabutoxytitanium (Ti(OC4H9)4) is introduced into the system and hydrolyzed to form a TiO2-SiO2 mixed skeleton, forming an amorphous porous network structure.

[0039] In cement-based systems, on the one hand, its surface can continuously release SiO4 at -20℃. 4- and Al 3+ Active ions such as CSH participate in the hydration reaction. Furthermore, the amorphous catalytic centers on its surface can adsorb CSH precursors, inducing the directional growth of a CASH-like amorphous gel network, thereby forming a continuous cementitious framework. Unlike common mineral admixtures (such as fly ash and slag), this material maintains high reactivity even at low temperatures. It possesses structural induction and skeleton reconstruction capabilities, significantly improving the structural density and impermeability of hardened cement at low temperatures.

[0040] The antifreeze polypeptide chain material is formed by connecting an artificial polypeptide chain (such as a Pro-Thr-Ala-Gly sequence) that simulates the conformation of an ice-binding protein with a small molecule having a guanidine structure through an amide bond. It adsorbs the ice crystal nucleation interface and induces lattice deconstruction in an environment below -20°C, thereby effectively delaying the ice crystal growth process.

[0041] The conformational characteristics of the artificial polypeptide chain have specific ice crystal surface adsorption sites.

[0042] Its working principle is: in an environment below -20℃, the antifreeze polypeptide chain material can quickly locate the ice crystal nucleation point in the cement pore fluid, disrupt the orderly arrangement of the ice crystal lattice through the hydrophobic-hydrophilic alternating sequence in its peptide segment, resulting in the formation of ice crystal structure defects, thereby delaying the growth of ice nuclei or even causing them to collapse, thereby effectively ensuring the continuity and activity of the water phase in the pore structure. The guanidine side chain can react with the Ca generated by cement hydration. 2+ OH - Plasma forms a stable association, enhancing its retention and distribution in the system.

[0043] Compared with traditional ice inhibitors such as sugar alcohols and chloride salts, this additive has significant advantages such as low dosage (<1%), strong directional action, non-corrosiveness, biodegradability, and no effect on later strength. It is particularly suitable for high-performance concrete and functional structural materials.

[0044] In this embodiment, the mass fractions of the additives are as follows: The microcapsule complex is 2 parts; 1.5 parts of penetration enhancer; The silicon-aluminum disordered network precursor is 3 parts; The antifreeze polypeptide chain material is 0.2 parts.

[0045] The preparation method comprises the following steps: S1. Pretreatment and screening of raw materials.

[0046] The required Portland cement, fine aggregate, and mineral admixtures (including silica fume and granulated blast furnace slag powder) are mechanically screened to a particle size of no more than 300µm. The mixture is then dried at 50°C for four hours to remove surface free water and trace amounts of crystallized water. All pre-treated solid materials are sealed and stored until ready for use to prevent moisture absorption, agglomeration, and performance degradation. Ensure that all components used have good particle gradation, cleanliness and dry state to improve the mixing uniformity of the material, system stability and the functional release ability of subsequent additives, laying the foundation for hydration reaction in low temperature environment.

[0047] S2. Liquid phase dispersion preparation of antifreeze.

[0048] Add the required amount of antifreeze to the measured water and disperse using high-speed shear stirring (2000 rpm) for 10 minutes to form a uniform composite liquid system. This liquid system will subsequently serve as the stirring fluid to ensure the antifreeze is fully released and distributed in the cement-based system.

[0049] By uniformly dispersing the antifreeze, its activation ability in the low-temperature cement system is improved, ensuring that it effectively inhibits the formation of ice crystals, improves the stability of liquid water at the interface, and provides a hydration reaction window below -20°C.

[0050] S3. Pre-dispersion activation of microcapsule complex.

[0051] Place the weighed microcapsule complex in a constant temperature water bath set at -5°C for 30 minutes to allow it to reach a metastable phase transition state. Stir slowly (400 rpm) for 10 minutes to maintain a uniform dispersion. Use immediately after treatment; avoid prolonged storage to prevent loss of thermodynamic stability.

[0052] In order to ensure that the microcapsule complex is evenly distributed during the mixing process and releases latent heat in the early hydration reaction stage, this step realizes the activation and energy storage of its phase change potential through temperature control pretreatment.

[0053] S4. The dry solid components are uniformly mixed.

[0054] Add silicate cement, fine aggregate and mineral admixtures into a horizontal forced dry mixer in sequence according to the proportion. The mixing time is controlled at 4-6 minutes to ensure that there are no obvious agglomerates or segregation, and to form a dry powder mixture with uniform particles and consistent color.

[0055] The structural skeleton materials (Portland cement, fine aggregate) and reactive mineral fillers (mineral admixtures) are mixed evenly to form a dry mix system with chemical reaction potential and physical support capabilities, laying a structural foundation for subsequent liquid phase mixing.

[0056] S5. Introduction of synergistic compounding of functional additives.

[0057] The weighed fluidity regulator, water-retention thickener, penetration enhancer, silicon-aluminum disordered network precursor, and antifreeze polypeptide chain material are added to the antifreeze solution obtained in step S2 in a proportional order. The solution is stirred for 20 minutes using a shear disperser (1500 rpm) to form a stable composite functional solution. The components of this solution work synergistically to achieve stable control of the liquid phase environment and subsequent structural induction.

[0058] All functional additives except water are uniformly compounded to construct an initial control functional module, including multiple functions such as hydration promotion at low temperatures, pore regulation, interface modification and structure optimization, to give the cement slurry comprehensive adaptability.

[0059] S6. Stir the dry powder and the composite liquid into a slurry.

[0060] The dry powder components obtained in step S4 are first added to a dual-shaft planetary mixer, and then the composite liquid obtained in step S5 (which contains water, antifreeze agent, water-retaining thickener, fluidity regulator, penetration enhancer, silicon-aluminum disordered network precursor, and antifreeze polypeptide chain material) is slowly injected. The stirring process is divided into two stages: low-speed premixing for 3 minutes, followed by high-speed stirring for 5 minutes to form a uniform and stable cement slurry.

[0061] By mixing the dry mix system obtained in step S4 with the functional liquid obtained in step S5, the preliminary configuration of the material is achieved, forming a cement slurry with low-temperature hydration ability, good fluidity, coagulation stability and interfacial activity.

[0062] S7. Terminal implantation of the microcapsule complex.

[0063] After the slurry is stirred, add the pretreated microcapsule complex from step S3 at a low speed (300 rpm) and stir slowly for 2 minutes to ensure uniform dispersion without breaking it. Add the microcapsules slowly along the surface of the slurry, avoiding high-speed shearing to ensure the structural integrity and latent heat storage function of the microcapsules.

[0064] By implanting the microcapsule complex later, its structural damage during vigorous stirring is avoided, and its functional integrity of releasing latent heat in the early stage of negative temperature hydration is achieved.

[0065] S8. Casting and curing in a -20℃ environment.

[0066] The mixed slurry is poured into a mold within 5 minutes, degassing and forming using light vibration. The slurry is then transferred to a -20°C constant temperature environment for closed curing. Curing should last at least 7 days, avoiding external temperature fluctuations or water evaporation to ensure the material gradually hydrates and forms a dense structure at a stable low temperature.

[0067] Ensure that the final cement-based material can continue to hydrate, structurally harden and increase performance under conditions below -20°C, thereby achieving its target functional properties.

[0068] Example 2: This embodiment provides an application method of a negative temperature cement-based material that can sustainably hydrate and harden at -20°C, comprising the following steps: A1: Construction environment preparation; Before actual project application, prioritize an on-site assessment of the construction area to confirm that the ambient temperature is stable below -20°C and has no significant short-term fluctuations. Clear any snow, ice, and oil from the work surface, ensuring the base layer is clean and free of visible water film to prevent slippage and poor adhesion at the frozen interface. For structurally complex areas, temporary insulation panels can be used to shield them to ensure stable local heat exchange during the molding process.

[0069] A2: Material preheating and active release preparation; Before construction, the microcapsule complex and antifreeze liquid components in the negative temperature cement-based material are temporarily stored in a -5°C to 0°C environment for 30-60 minutes to promote the phase transition component to a metastable phase preparation state and activate the conformational ductility of the antifreeze polypeptide chain material. Other components do not require additional heating; all pretreatment work must be completed in the insulation area.

[0070] A3: On-site mixing and transportation; According to the predetermined ratio, the dry components and the composite liquid components (including water, antifreeze agent, water-retaining thickener, flow regulator, penetration enhancer, silicon-aluminum disordered network precursor, and antifreeze polypeptide chain material) are uniformly mixed in a forced mixer for 8-10 minutes to ensure that the functional additives are fully dispersed and form a stable microstructure network. The mixture is then stored in a low-temperature, insulated hopper and quickly transported to the pouring area using insulated pipelines or short-distance transportation.

[0071] A4: pouring and forming; Using conventional formwork or removable insulated formwork, pour the mixed, sub-zero cementitious material into the mold. To prevent structural damage from freezing, combine layered pouring with light vibration to ensure slurry fullness and structural density. Immediately after pouring, add a windproof and insulating layer, such as polyurethane insulation felt or three-proof fabric, and enclose the structure with barriers to prevent direct exposure to cold drafts.

[0072] A5: Low temperature curing and structural stability formation; After pouring, the structure is sealed and cured at a constant temperature of -20°C for at least 7 days. During this stage, the microcapsule complex contained in the material will release latent heat in a targeted manner, providing the localized heat required for hydration. The antifreeze agent and antifreeze polypeptide chain material work together to maintain the stability of the interfacial liquid phase. The silicon-aluminum disordered network precursor and permeation enhancer promote the continuous generation of hydration products and fill the capillary pores, thereby ensuring the structure's continued strength growth and volume stability at low temperatures.

[0073] A6: Post-testing and template removal; After the low-temperature curing period, early strength assessment can be conducted using methods such as ultrasonic rebound testing or negative-temperature core drilling. Once the design strength requirements are met, the formwork is removed, and the structure then enters the curing phase under conventional thermal insulation (if conditions permit, curing can be performed at room temperature of 0-5°C to improve later strength). If necessary, localized weak areas can be repaired or reinforced.

[0074] The negative-temperature cementitious material described in this invention is suitable for applications such as cast-in-place concrete construction in extremely cold regions, emergency municipal road repairs in cold regions, military projects at airports or border defenses, the construction of Arctic research base stations, and winter emergency reinforcement operations. It is particularly suitable for environments as low as -20°C, where conventional antifreeze systems are ineffective or unavailable. It can achieve strength development and structural stability in cementitious structures without relying on external heating equipment.

[0075] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a negative temperature cement-based material that can sustainably hydrate and harden at -20°C, characterized in that the negative temperature cement-based material comprises the following specific components: Portland cement, fine aggregate, water, mineral admixtures, antifreeze, water-retaining thickener, and flow regulator; The negative temperature cement-based material further comprises additives, which specifically include: Microcapsule complexes, penetration enhancers, silicon-aluminum disordered network precursors, and antifreeze polypeptide chain materials; The preparation method comprises the following steps: S1. Pretreatment and screening of raw materials; S2, liquid phase dispersion preparation of antifreeze; S3, pre-dispersion activation of microcapsule complex; S4, dry solid components are uniformly mixed; S5. Synergistic compounding and introduction of functional additives; S6. The dry powder and the composite liquid are stirred into a slurry; S7, terminal implantation of microcapsule complex; S8. Casting and curing in a -20℃ environment.

2. The method for preparing a negative temperature cement-based material capable of sustainable hydration and hardening at -20°C according to claim 1, wherein the mass fractions of the specific components are as follows: Portland cement is 80-100 parts; Fine aggregate is 80-100 parts; 35-45 parts water; Mineral admixture is 20-40 parts; Antifreeze is 3-8 parts; The water-retaining thickener is 0.5-1.5 parts; The fluidity regulator is 0.3-1 part.

3. The method for preparing a negative temperature cement-based material capable of sustainable hydration and hardening at -20°C according to claim 1, wherein the mass fractions of the additives are as follows: The microcapsule complex is 2-5 parts; Penetration enhancer is 1.5-4 parts; The silicon-aluminum disordered network precursor is 3-6 parts; The antifreeze polypeptide chain material is 0.2-0.8 parts.

4. The method for preparing a negative temperature cement-based material capable of sustainable hydration and hardening at -20°C according to claim 1, wherein the specific components are: Fine aggregate is medium sand or fine sand with a size of 0.075-2.36 mm and continuous particle gradation; The mineral admixture is a mixture of fly ash, granulated blast furnace slag powder and silica fume, and the ratio of fly ash, granulated blast furnace slag powder and silica fume is 10:10:5; Antifreeze is a low-temperature modifier that includes sodium chloride, calcium chloride, and ethylene glycol; The water-retaining thickener is hydroxypropyl methylcellulose HPMC; The fluidity regulator is a polycarboxylic acid water reducer.

5. The method for preparing a negative-temperature cement-based material that can sustainably hydrate and harden under a -20°C environment according to claim 1 is characterized in that the microcapsule composite is composed of a phase change core material with a melting point of -5°C to -20°C and a polymer coating material to form a microcapsule structure, the phase change core material is selected from n-tetradecane or tetrabutylammonium bromide, and the coating material includes a blend of polymethyl methacrylate and ethylene propylene diene monomer rubber. The composite releases latent heat in the early stage of cement hardening to delay pore water freezing and maintain interfacial hydration reaction.

6. The method for preparing a negative temperature cement-based material capable of sustainable hydration and hardening at -20°C according to claim 1, wherein the penetration enhancer is composed of tricarboxylated chitosan and quaternary ammonium cation-modified silicone polyether in a mass ratio of 2:1 to 4:1, and during the cement hydration process, the penetration enhancer forms an ion channel structure to enhance the Ca 2+ With SiO4 4- The diffusion rate of the catalyst can be increased, thereby improving the hydration reaction activity at -20℃.

7. The method for preparing a negative-temperature cement-based material that can sustainably hydrate and harden at -20°C according to claim 1 is characterized in that the silicon-aluminum disordered network precursor comprises alkali-activated attapulgite, zeolite A nanocrystalline cores, and titanium-doped amorphous silica. The three are deposited and coated to form a precursor complex with disordered structure induction ability, which promotes the formation of CASH gel in a low-temperature environment to enhance the structural density of the material.

8. The method for preparing a negative-temperature cement-based material that can sustainably hydrate and harden in a -20°C environment according to claim 1 is characterized in that the antifreeze polypeptide chain material is formed by connecting an artificial polypeptide chain that simulates the conformation of an ice-binding protein and a small molecule with a guanidine structure through an amide bond. It adsorbs on the ice crystal nucleation interface and induces lattice deconstruction in an environment below -20°C, thereby effectively delaying the growth process of ice crystals.

9. The method for preparing a negative-temperature cement-based material capable of sustainable hydration and hardening at -20°C according to claim 1, wherein in step S3, the weighed microcapsule complex is placed in a constant-temperature water bath at -5°C for 30 minutes to prepare the microcapsule for metastable phase transition. Then stir slowly at 400 rpm for 10 minutes to maintain a uniform dispersion; Use immediately after processing and do not store for a long time to prevent loss of thermodynamic state.

10. The method for preparing a negative temperature cement-based material capable of sustainable hydration and hardening at -20°C according to claim 1, wherein in step S7, after the slurry is formed in step S6, the microcapsule complex of step S3 is added at a low stirring speed of 300 rpm and stirred for 2 minutes to ensure that the microcapsule is evenly dispersed without breaking; The addition method is to slowly sprinkle the microcapsules along the surface of the slurry to ensure the structural integrity and latent heat storage function of the microcapsules.

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