Negative temperature type quick-hardening early-strength repair mortar and preparation method thereof

Abstract

The invention provides negative temperature type quick-hardening early-strength repair mortar and a preparation method thereof. The negative-temperature quick-hardening early-strength repair mortar is suitable for concrete in alpine regions, and is prepared from the following raw materials: quick-hardening sulphoaluminate cement, a thermal activator, standard cement, a mineral admixture, polyacrylate redispersible latex powder, fibers, a negative-temperature admixture, a nano material, a defoaming agent, fine aggregate, a water reducing agent and water. The repair mortar has good early compressive strength and bonding strength, ensures sustainable development of middle and later performances, does not shrink, and can meet the repair requirements of infrastructures in a negative temperature environment. The invention also provides a preparation method of the negative temperature type rapid hardening early strength repair mortar.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a negative temperature type fast-hardening and early-strength repair mortar and its preparation method. Background Technology

[0002] In high-latitude, high-altitude, and frigid regions, the climate is extremely harsh, with low average annual temperatures and long, frigid winters where temperatures often remain below freezing. In these challenging environments, concrete infrastructure structures such as highway pavements, bridges, and airport runways, which bear critical socio-economic functions, face numerous severe tests over time. The continuous application of mechanical loads, intense ultraviolet radiation, complex chemical weathering, and repeated freeze-thaw cycles interact to continuously erode concrete structures, leading to various damage problems such as cracking, spalling, and decreased strength. These issues severely affect the integrity and service performance of the structures, posing a significant threat to the safe and stable operation of infrastructure, necessitating timely repair work to restore their functionality.

[0003] However, the repair of concrete structures in high-altitude and cold regions faces unique construction challenges. Since these infrastructures are often core facilities in critical sectors such as transportation, their operational disruptions can trigger a chain reaction, causing significant socio-economic losses. Therefore, repair work often requires rapid and efficient completion, meaning projects must be carried out immediately in low-temperature or even sub-zero environments. However, sub-zero temperatures present technical bottlenecks for traditional repair materials: on the one hand, low temperatures significantly inhibit the hydration rate of cement, drastically extending the setting time of the repair mortar and causing extremely slow or even complete stagnation of early strength development, making it impossible to reach the design strength requirements within the specified time, thus affecting the progress and quality of the repair project; on the other hand, free water within the repair mortar that does not participate in the hydration reaction in time will freeze into ice, causing volume expansion and leading to internal stress concentration, resulting in micro-cracks in the mortar structure, causing low-temperature freezing damage, and severely reducing the durability and service life of the repaired structure.

[0004] To address the challenges of construction in low-temperature winters, several technologies have emerged, such as using early-strength cement or constructing insulated sheds. However, these methods have significant limitations. Early-strength cement exhibits a significantly reduced early-strength effect in deep sub-zero temperatures, failing to meet the strength requirements for rapid repairs. External insulation measures, such as constructing insulated sheds, not only involve complex construction processes and substantial investment of manpower and resources, leading to substantial increases in construction costs, but also have poor adaptability to irregularly shaped structures or large-area repair projects, hindering efficient and rapid repairs. Furthermore, while related technologies mention some strength indicators for sub-zero temperature repair mortars, they do not disclose key performance parameters such as early compressive strength and interfacial bond strength, making it difficult to comprehensively assess their early performance and bonding reliability in sub-zero temperatures. This fails to fully meet the practical engineering needs of concrete structure repairs in cold regions. Therefore, developing a repair mortar that can adapt to sub-zero environments, achieve rapid setting and hardening, possesses good early compressive strength and interfacial bond strength, and exhibits stable performance development in the mid-to-late stages has become an urgent technical requirement for ensuring the safe and stable operation of infrastructure in cold regions and extending its entire lifespan, possessing significant engineering application value. Summary of the Invention

[0005] This invention aims to address the core technical challenges of repairing concrete structures in sub-zero temperatures in high-altitude and frigid regions: First, low temperatures significantly inhibit cement hydration, leading to a substantial increase in the setting time of traditional repair mortars and slow or even stagnant early strength development, failing to meet the construction requirements for rapid infrastructure repair. Second, unhydrated free water within the repair mortar easily freezes, causing volume expansion and resulting in low-temperature freezing damage, reducing the durability of the repaired structure. Third, existing winter construction techniques (such as early-strength cement and insulation shed construction) suffer from limitations in deep sub-zero temperatures, high costs, complex construction, and poor adaptability. Therefore, this invention provides a sub-zero temperature-sensitive, fast-hardening, early-strength repair mortar suitable for concrete in high-altitude and frigid regions. It simultaneously solves the technical difficulties of achieving rapid setting and hardening, excellent early mechanical properties, reliable interfacial bonding performance, and stable mid-to-late-stage performance development in repair mortars under sub-zero conditions. Ultimately, this enables efficient and high-quality repair of concrete infrastructure in high-altitude and frigid regions, avoiding significant socio-economic losses caused by operational interruptions.

[0006] This invention provides a negative temperature type fast-hardening and early-strength repair mortar.

[0007] The present invention also provides a method for preparing a negative temperature type fast-hardening and early-strength repair mortar.

[0008] The first aspect of this invention provides a negative-temperature rapid-hardening and early-strength repair mortar, the raw materials for which are prepared by weight are:

[0009] Rapid-hardening sulfoaluminate cement: 70-90 parts Thermal activator: 1-2 parts Standard cement: 10-30 parts Mineral admixtures: 10-20 parts Polyacrylate redispersible latex powder: 1-3 parts, Fiber: 2-6 parts Negative-temperature admixture: 0.1~1 part, Nanomaterials: 1-3 parts Defoamer: 0.02~0.05 parts, Fine aggregate: 90-130 parts Water-reducing agent: 0.5~1.5 parts, Water: 20-30 parts.

[0010] The negative-temperature rapid-hardening and early-strength repair mortar of the present invention has at least the following beneficial effects: This invention utilizes the rapid hydration characteristic of fast-hardening sulfoaluminate cement to generate a large amount of ettringite and provide heat of hydration, thus providing significant early strength and initial structural framework for the system. The synergistic thermal activator rapidly releases heat upon contact with water, directly raising the initial temperature of the system and resisting the inhibition of hydration by negative temperature environments. The reference cement accelerates hydration under high heat of hydration, synergistically with the secondary hydration reaction of the mineral admixtures, ensuring stable strength growth in the repair mortar during both the mid- and late-stage processes.

[0011] This invention introduces redispersible polyacrylate latex powder as a bonding agent, which, after curing, forms a continuous and flexible polymer film within the cement paste. This polymer film not only significantly enhances the chemical and mechanical bonding strength between the repair mortar and the old concrete substrate through the polar functional groups on its macromolecular chains, but also effectively bridges microcracks, improving the interfacial adhesion and freeze-thaw resistance of the repair. The fibers uniformly dispersed in the matrix effectively dissipate energy, inhibit the generation and propagation of plastic shrinkage and drying shrinkage cracks, significantly improve flexural strength and toughness, and effectively resist impact loads.

[0012] Furthermore, based on the closest packing theory, this invention achieves comprehensive filling from coarse to fine scales through a rational particle size distribution design using a compound of cement, silica fume, and nanomaterials. The nucleation effect of nanomaterials provides nucleation sites for hydration products, significantly accelerating the hydration of the cementitious system at sub-zero temperatures. Simultaneously, the combination of nanomaterials with the hydration promoters of early-strength agents or the freezing point lowering effects of antifreeze agents creates a highly efficient and stable sub-zero temperature protection and early-strength system, ensuring that the repair mortar can still rapidly set, harden, and develop strength under extremely cold conditions.

[0013] According to some embodiments of the present invention, the rapid-hardening sulfoaluminate cement comprises R·SAC42.5 grade cement; and / or, the reference cement comprises P·I42.5 grade cement.

[0014] According to some embodiments of the present invention, the thermal activator includes calcium oxide.

[0015] According to some embodiments of the present invention, the mineral admixture includes at least one of fly ash, mineral powder and microsilica.

[0016] According to some embodiments of the present invention, the mineral admixture is a mixture of fly ash, mineral powder and microsilica.

[0017] According to some embodiments of the present invention, the fly ash is Class II fly ash, obtained by cooling coal from a thermal power plant, and the amount used is 50-75 wt% of the total amount of the mineral admixture.

[0018] According to some embodiments of the present invention, the fly ash is Class II fly ash, obtained by cooling coal in a thermal power plant, and the amount used is any one of 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, and 75wt% of the total amount of the mineral admixture, such as 60wt%, or any range formed by both, such as 55wt% to 65wt%.

[0019] According to some embodiments of the present invention, the fly ash is Class II fly ash with a particle size of 5~35μm.

[0020] According to some embodiments of the present invention, the fly ash is Class II fly ash with a particle size of any value among 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, and 35μm, such as 15μm, or any range formed by both, such as 20μm to 30μm.

[0021] According to some embodiments of the present invention, the specific surface area of ​​fly ash is 250~450m². 2 / kg.

[0022] According to some embodiments of the present invention, the fly ash has a specific surface area of ​​250 m². 2 / kg, 275m 2 / kg, 300m 2 / kg, 325m 2 / kg, 350m 2 / kg, 375m 2 / kg, 400m 2 / kg, 425m 2 / kg, 450m 2 Any value in / kg, such as 300m 2 / kg, or any range of the two, such as 350m 2 / kg~400m 2 / kg.

[0023] According to some embodiments of the present invention, the mineral powder is S95 grade mineral powder, which is obtained by drying and grinding blast furnace slag, and the amount used is 15~30wt% of the total amount of the mineral admixture.

[0024] According to some embodiments of the present invention, the mineral powder is S95 grade mineral powder, obtained by drying and grinding blast furnace slag, and the amount used is any value among 15wt%, 16wt%, 17wt%, 18wt%, 19wt%, 20wt%, 21wt%, 22wt%, 23wt%, 24wt%, 25wt%, 26wt%, 27wt%, 28wt%, 29wt%, and 30wt% of the total amount of the mineral admixture, such as 20wt%, or any range formed by both, such as 22wt% to 28wt%.

[0025] According to some embodiments of the present invention, the particle size of the mineral powder is 10~50μm.

[0026] According to some embodiments of the present invention, the particle size of the mineral powder is any value among 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, and 50μm, such as 25μm, or any range formed by both, such as 30μm to 40μm.

[0027] According to some embodiments of the present invention, the specific surface area of ​​the mineral powder is 350~500 m². 2 / kg.

[0028] According to some embodiments of the present invention, the specific surface area of ​​the mineral powder is 350 m². 2 / kg, 360m 2 / kg, 370m 2 / kg, 380m 2 / kg, 390m 2 / kg, 400m 2 / kg, 410m 2 / kg, 420m 2 / kg, 430m 2 / kg, 440m 2 / kg, 450m 2 / kg, 460m 2 / kg, 470m 2 / kg, 480m 2 / kg, 490m 2 / kg, 500m 2 Any value in / kg, such as 400m 2 / kg, or any range of the two, such as 420m 2 / kg~480m 2 / kg.

[0029] According to some embodiments of the present invention, the SiO2 content in the microsilica powder is greater than 95%, and it is a by-product generated during the smelting of ferrosilicon or industrial silicon (metallic silicon) of ferroalloys, and the amount used is 10 to 20 wt% of the total amount of the mineral admixture.

[0030] According to some embodiments of the present invention, the particle size of the microsilica powder is 0.1~0.15μm.

[0031] According to some embodiments of the present invention, the particle size of the microsilica powder is any value among 0.10μm, 0.11μm, 0.12μm, 0.13μm, 0.14μm, and 0.15μm, such as 0.12μm, or any range formed by both, such as 0.11μm to 0.13μm.

[0032] According to some embodiments of the present invention, the specific surface area of ​​the microsilica powder is 15,000~25,000 m². 2 / kg.

[0033] According to some embodiments of the present invention, the specific surface area of ​​the microsilica powder is 15000 m². 2 / kg, 16000m 2 / kg, 17000m 2 / kg, 18000m 2 / kg, 19000m 2 / kg, 20000m 2 / kg, 21000m 2 / kg, 22000m 2 / kg, 23000m 2 / kg, 24000m 2 / kg, 25000m 2 Any value in / kg, such as 18000m 2 / kg, or any range of the two, such as 20000m 2 / kg~23000m 2 / kg.

[0034] According to some embodiments of the present invention, the fiber includes at least one of copper-plated steel fiber and polypropylene fiber.

[0035] Polyacrylate redispersible latex powder can form a polymer film in water, which causes cement hydration products to aggregate and fuse, significantly increasing the bond strength.

[0036] Fibers can significantly enhance the flexural strength and toughness of mortar, absorb impact energy, and improve impact resistance and vibration damping performance.

[0037] According to some embodiments of the present invention, the negative temperature admixture includes at least one of an early strength agent and an antifreeze agent.

[0038] According to some embodiments of the present invention, the early strength agent includes at least one of lithium carbonate and triethanolamine.

[0039] According to some embodiments of the present invention, the antifreeze includes at least one of calcium nitrite, urea, and ethylene glycol.

[0040] According to some embodiments of the present invention, the nanomaterial includes at least one of nano-silica, nano-CSH seeds, and carbon nanotubes.

[0041] Nanomaterials have significant nucleation and nanoscale filling effects, which can serve as nuclei for the growth of hydration products, greatly accelerating the hydration process and filling micropores at the nanoscale, thereby improving the density of the slurry.

[0042] According to some embodiments of the present invention, the defoamer includes at least one of silicone defoamers, polyether defoamers, and higher alcohol defoamers.

[0043] According to some embodiments of the present invention, the fine aggregate is quartz sand with a fineness modulus of 2.2 to 3.0.

[0044] According to some embodiments of the present invention, the fine aggregate is quartz sand with a fineness modulus of any value among 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, and 3.0, such as 2.6, or any range of two such values, such as 2.4 to 2.8.

[0045] According to some embodiments of the present invention, the water-reducing agent includes at least one of polycarboxylate-based high-efficiency water-reducing agents, naphthalene-based high-efficiency water-reducing agents, and amino acid salt high-efficiency water-reducing agents.

[0046] A second aspect of the present invention provides a method for preparing a negative-temperature rapid-hardening and early-strength repair mortar, comprising the following steps: S1: According to the proportion, the rapid-hardening sulfoaluminate cement, reference cement, mineral admixtures, fibers, polyacrylate redispersible latex powder, thermal activator, defoamer and fine aggregate are mixed and placed in a mixer to obtain a repair mortar premix; the negative temperature admixture, nanomaterials, water-reducing agent and water are mixed and ultrasonically dispersed in a water bath to obtain an ultrasonic dispersion. S2: Add the ultrasonic dispersion to the repair mortar premix to obtain the negative temperature type fast hardening early strength repair mortar.

[0047] The method for preparing negative-temperature rapid-hardening and early-strength repair mortar of the present invention has at least the following beneficial effects: In step S1, the solid components such as rapid-hardening sulfoaluminate cement, reference cement, and mineral admixtures are first mixed to prepare a premix, which ensures that each solid component is uniformly dispersed and avoids local component concentration imbalances that affect the overall performance of the mortar. At the same time, the negative-temperature admixture, nanomaterials, water-reducing agent are mixed with water and then ultrasonically dispersed in a water bath, which can effectively break the agglomeration of nanomaterials and other components, so that they form a uniform and stable dispersion system in the liquid phase. This lays the foundation for the efficient reaction after subsequent mixing with the premix, solves the problem of uneven dispersion and insufficient effect of nanomaterials in traditional mixing methods, and significantly improves the synergistic effect between components.

[0048] This preparation method, through a combination of stepwise mixing and ultrasonic dispersion, fully leverages the rapid hydration characteristics of fast-hardening sulfoaluminate cement and the exothermic effect of the thermal activator. Combined with uniformly distributed negative-temperature admixtures and nanomaterials after ultrasonic dispersion, it effectively resists the inhibition of hydration reactions by negative-temperature environments, accelerates the hydration process of the cementitious system, and allows the repair mortar to quickly set and harden under negative-temperature conditions, ensuring rapid early strength development. Simultaneously, the uniformly dispersed redispersible polyacrylate latex powder forms a continuous polymer film after curing, and the fibers are also uniformly distributed in the matrix, significantly improving the interfacial flexural strength and tensile bond strength between the repair mortar and the old concrete matrix, enhancing flexural performance and toughness, and inhibiting crack initiation and propagation.

[0049] The entire preparation process is simple and efficient, with clear and easy-to-operate steps. It requires no complex equipment or harsh construction conditions, making it suitable for the rapid repair needs of cold regions. It can effectively shorten the construction cycle and reduce construction costs. The repair mortar prepared by this method not only has excellent early mechanical and bonding properties in sub-zero temperatures, but also ensures continuous and stable development of mid-to-late-stage performance without shrinkage through the secondary hydration reaction of the reference cement and mineral admixtures. This significantly improves the quality and durability of repair projects and extends the life cycle of concrete infrastructure in cold regions.

[0050] According to some embodiments of the present invention, the negative temperature admixture, nanomaterials, water-reducing agent and water are mixed and ultrasonically dispersed in a water bath in an ultrasonic cell disruptor.

[0051] According to some embodiments of the present invention, the time for ultrasonic dispersion in a water bath can be 10 to 20 minutes.

[0052] According to some embodiments of the present invention, the time for ultrasonic dispersion in a water bath can be any value among 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min, and 20 min, such as 15 min, or any range formed by both, such as 12 min to 18 min.

[0053] According to some embodiments of the present invention, the ultrasonic dispersion is added to the repair mortar premix, and the mixture is first stirred slowly and then stirred rapidly.

[0054] The slow stirring time can be 1 to 2 minutes.

[0055] The slow stirring speed is 135~145 rpm for rotation and 57~67 rpm for revolution.

[0056] The stirring time can be 1 to 2 minutes.

[0057] The speed of rapid stirring is 275~295 rpm for rotation and 115~135 rpm for revolution. Detailed Implementation

[0058] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0059] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0060] Unless otherwise specified, "room temperature" in this invention means 25℃±5℃.

[0061] Unless otherwise specified, "about" in this invention means that the allowable error is within ±2%.

[0062] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0063] Rapid-hardening sulfoaluminate cement is R·SAC42.5 grade cement with an average particle size of 15μm and a specific surface area of ​​400~550m². 2 / kg, purchased from Tangshan Polar Bear Building Materials Co., Ltd.

[0064] The reference cement is P·I42.5 grade cement with an average particle size of 20μm and a specific surface area of ​​300~400m². 2 / kg. Purchased from China Building Materials Academy Co., Ltd.

[0065] The fly ash is Class II fly ash obtained from the cooling of coal in thermal power plants, with an average particle size of 20 μm and a specific surface area of ​​250~450 m². 2 / kg; purchased from Henan Hengyuan New Materials Co., Ltd.

[0066] The mineral powder is S95 grade mineral powder obtained by drying and grinding blast furnace slag, with an average particle size of 18μm and a specific surface area of ​​350~500m². 2 / kg; purchased from Henan Hengyuan New Materials Co., Ltd.

[0067] Microsilica powder is a byproduct of ferroalloy smelting (ferrosilicon) or industrial silicon (metallic silicon). It has an average particle size of 0.15 μm and a specific surface area of ​​15,000–25,000 m². 2 / kg. Purchased from Shanghai Elken International Trading Co., Ltd.

[0068] The copper-plated steel fibers are straight, copper-plated microfibers with a diameter of 0.19~0.23mm and a length of 8~12mm. They were purchased from Shandong Chuhe New Materials Co., Ltd.

[0069] The polypropylene fiber is an ultra-high molecular weight polypropylene fiber with a weight-average molecular weight of 1.5 million to 3 million, a diameter of 18 to 40 μm, and a length of 10 to 17 mm. It was purchased from Shijiazhuang Chuangsheng Building Materials Technology Co., Ltd.

[0070] The polyacrylate redispersible latex powder has an average particle size of 30 μm. It was purchased from Shanghai Zengye Industrial Co., Ltd.

[0071] The nano-silica particles have a spherical morphology and an average particle size of 20 nm. They were purchased from Suzhou Sailon Nano New Materials Co., Ltd.

[0072] The nano-CSH seed crystals have a porous gel-like morphology with an average particle size of 50 nm. They were purchased from Shanghai Xuri Polymer Materials Co., Ltd.

[0073] The carbon nanotubes exhibit a one-dimensional hollow tubular structure with an average diameter of 30 nm and a length of 2-10 μm. They were purchased from Shanghai Zhenmo New Materials Co., Ltd.

[0074] The silicone defoamer is specifically a polydimethylsiloxane composite emulsion defoamer, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0075] The polycarboxylate superplasticizer is specifically a methyl allyl polyoxyethylene ether type polycarboxylate superplasticizer, purchased from Hunan Zhongyan Building Materials Technology Co., Ltd.

[0076] The polypropylene fiber was purchased from Shijiazhuang Chuangsheng Building Materials Technology Co., Ltd.

[0077] The fine aggregate is quartz sand with a fineness modulus of 2.2~3.0. It was purchased from Henan Minghai Environmental Protection Technology Co., Ltd.

[0078] In this embodiment, the preparation method of the negative temperature rapid hardening and early strength repair mortar is as follows: According to the proportion, the two types of cement, mineral admixtures, fibers, binders, heat activators, defoamers and fine aggregates are mixed and placed in a mixer and thoroughly mixed to obtain the repair mortar premix. The negative temperature additive, nanomaterials, water-reducing agent and water were thoroughly mixed and stirred, and then placed in an ultrasonic cell disruptor. After ultrasonic dispersion in a water bath for 15 minutes, an ultrasonic dispersion was obtained. Add ultrasonic dispersion to the repair mortar premix, stir slowly for 1 minute, then stir rapidly for 1 minute.

[0079] Example 1 A negative-temperature rapid-hardening and early-strength repair mortar for concrete in high-altitude and cold regions was prepared. The raw materials, by weight, are: Rapid-hardening sulfoaluminate cement: 80 parts Calcium oxide as a thermal activator: 1 part Standard cement: 20 parts Mineral admixtures: 18 parts, specifically 10 parts fly ash, 5 parts mineral powder, and 3 parts silica fume. Polyacrylate redispersible latex powder: 2 parts Copper-plated steel fiber: 3 parts 0.15 parts of lithium carbonate as a negative temperature additive. Nano-silica: 1.5 parts Organosilicon defoamer: 0.02 parts, Fine aggregate quartz sand: 120 parts Polycarboxylate superplasticizer: 1.5 parts Water: 25 parts.

[0080] Example 2 A negative-temperature rapid-hardening and early-strength repair mortar for concrete in high-altitude and cold regions was prepared. The raw materials, by weight, are: Rapid-hardening sulfoaluminate cement: 75 parts Calcium oxide as a thermal activator: 1 part Standard cement: 30 parts Mineral admixtures: 17 parts, specifically 12 parts fly ash, 4 parts mineral powder, and 1 part silica fume. Polyacrylate redispersible latex powder: 1, Copper-plated steel fiber: 5 parts 0.3 parts of triethanolamine, an additive for negative temperature applications. Nano CSH seed crystals: 2 parts Organosilicon defoamer: 0.04 parts, Fine aggregate quartz sand: 110 parts Polycarboxylate superplasticizer: 0.7 parts Water: 22 portions.

[0081] Example 3 A negative-temperature rapid-hardening and early-strength repair mortar for concrete in high-altitude and cold regions was prepared. The raw materials, by weight, are: Rapid-hardening sulfoaluminate cement: 85 parts Calcium oxide as a thermal activator: 2 parts Standard cement: 10 parts Mineral admixtures: 14 parts, specifically 8 parts fly ash, 4 parts mineral powder, and 2 parts silica fume. Polyacrylate redispersible latex powder: 2 parts Polypropylene fiber: 4 parts Calcium nitrite admixture for negative temperature applications: 1 part Nano silica: 3 parts Organosilicon defoamer: 0.05 parts, Fine aggregate quartz sand: 90 parts Polycarboxylate superplasticizer: 1.4 parts, Water: 26 portions.

[0082] Example 4 A negative-temperature rapid-hardening and early-strength repair mortar for concrete in high-altitude and cold regions was prepared. The raw materials, by weight, are: Rapid-hardening sulfoaluminate cement: 90 parts Calcium oxide as a thermal activator: 2 parts Reference cement: 15 parts Mineral admixtures: 13 parts, specifically 7 parts fly ash, 3 parts mineral powder, and 3 parts silica fume. Polyacrylate redispersible latex powder: 3 parts Polypropylene fiber: 6 parts Ethylene glycol as a negative temperature admixture: 0.8 parts Carbon nanotubes: 3 parts Organosilicon defoamer: 0.03 parts, Fine aggregate quartz sand: 100 parts Polycarboxylate superplasticizer: 1 part Water: 23 portions.

[0083] Comparative Example 1 The difference from Example 1 is that no fibers were added.

[0084] Comparative Example 2 The difference from Example 1 is that no adhesive additive was added.

[0085] Comparative Example 3 The difference from Example 1 is that no nanomaterials were added.

[0086] Comparative Example 4 The difference from Example 1 is that no early strength agent was added.

[0087] Comparative Example 5 The difference from Example 1 is that no thermal activator was added.

[0088] Performance testing All examples and comparative examples were immediately placed in a -10℃ negative temperature curing chamber after preparation and cured until the required testing age. The physical and mechanical properties of the repair mortar were tested according to the relevant provisions of "Repair Mortar" (JC / T2381-2016). For the interfacial flexural strength test, a 40mm×40mm×80mm base cement mortar block was poured; for the tensile bond strength test, a 70mm×70mm×20mm base cement mortar block was poured. The mix ratio of the base cement mortar block used for the bond strength test was reference cement: standard sand: water = 1:3:0.5, and it was cured under standard curing conditions for 28 days before use. The test results are shown in Table 1.

[0089] Table 1

[0090] As can be seen from the test results of Examples 1-4, the present invention is a negative temperature type fast hardening early strength repair mortar for concrete in cold regions. It has high flexural and compressive strength, low compression-flexural ratio, good impact resistance and vibration reduction performance at -10℃, high interfacial flexural strength and tensile bond strength, and good bonding performance after repair. It is suitable for repair construction of concrete structure infrastructure in cold regions during winter.

[0091] As can be seen from Example 1 and Comparative Example 1, the addition of fibers can significantly improve the flexural strength of the repair mortar and also has a certain effect on improving the compressive strength of the repair mortar.

[0092] As can be seen from Example 1 and Comparative Example 2, the addition of redispersible latex powder adhesive can increase the interfacial flexural strength and tensile bond strength of the repair mortar, and enhance the bonding performance between the repair mortar and the old concrete interface.

[0093] As can be seen from Examples 1, 3, 4 and 5, the addition of early strength agent, nanomaterials and thermal activator all shortened the setting time of repair mortar and significantly improved the early strength of repair mortar. They also resisted the negative impact of negative temperature environment on early hydration of repair mortar by increasing the heat of hydration release.

[0094] In summary, this invention aims to solve the core technical problems faced in repairing concrete structures in sub-zero temperatures in high-altitude and cold regions: First, low temperatures significantly inhibit cement hydration, leading to a substantial increase in the setting time of traditional repair mortar, slow or even stagnant early strength development, which fails to meet the construction requirements for rapid infrastructure repair. Second, the free water inside the repair mortar that does not participate in hydration easily freezes into ice, causing volume expansion and triggering low-temperature freezing damage, reducing the durability of the repaired structure. Third, existing winter construction technologies (such as early-strength cement and the construction of insulation sheds) have shortcomings such as limited effectiveness in deep sub-zero temperatures, high cost, complex construction, and poor adaptability. Furthermore, related patented technologies do not disclose key parameters such as early compressive strength and interfacial bond strength, making it difficult to guarantee repair quality. Simultaneously, this invention solves the technical challenge of repair mortar achieving rapid setting and hardening, excellent early mechanical properties, reliable interfacial bond performance, and stable mid-to-late-stage performance development under sub-zero conditions. Ultimately, it enables efficient and high-quality repair of concrete infrastructure in high-altitude and cold regions, avoiding the huge socio-economic losses caused by operational interruptions.

[0095] The present invention has been described in detail above with reference to the embodiments. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A negative-temperature type rapid-hardening and early-strength repair mortar, characterized in that, The raw materials for preparation, by weight, include: Rapid-hardening sulfoaluminate cement: 70-90 parts Thermal activator: 1-2 parts Standard cement: 10-30 parts Mineral admixtures: 10-20 parts Polyacrylate redispersible latex powder: 1-3 parts, Fiber: 2-6 parts Negative-temperature admixture: 0.1~1 part, Nanomaterials: 1-3 parts Defoamer: 0.02~0.05 parts, Fine aggregate: 90-130 parts Water-reducing agent: 0.5~1.5 parts, Water: 20-30 parts.

2. The negative-temperature rapid-hardening and early-strength repair mortar according to claim 1, characterized in that, The rapid-hardening sulfoaluminate cement includes R·SAC 42.5 grade cement; and / or, the reference cement includes P·I 42.5 grade cement.

3. The negative-temperature rapid-hardening and early-strength repair mortar according to claim 1, characterized in that, The thermal activator includes calcium oxide.

4. The negative-temperature rapid-hardening and early-strength repair mortar according to claim 1, characterized in that, The mineral admixture includes at least one of fly ash, mineral powder, and microsilica; and / or, the mineral admixture is a mixture of fly ash, mineral powder, and microsilica, wherein the fly ash is Grade II fly ash, and the amount used is 50-75 wt% of the total amount of the mineral admixture; the mineral powder is Grade S95 mineral powder, and the amount used is 15-30 wt% of the total amount of the mineral admixture; and the microsilica has a SiO2 content greater than 95%, and the amount used is 10-20 wt% of the total amount of the mineral admixture.

5. The negative-temperature rapid-hardening and early-strength repair mortar according to claim 1, characterized in that, The fiber includes at least one of copper-plated steel fiber and polypropylene fiber.

6. The negative-temperature rapid-hardening and early-strength repair mortar according to claim 1, characterized in that, The negative temperature admixture includes at least one of an early-strength agent and an antifreeze agent.

7. The negative-temperature rapid-hardening and early-strength repair mortar according to claim 1, characterized in that, The nanomaterials include at least one of nano-silica, nano-CSH seeds, and carbon nanotubes.

8. The negative-temperature rapid-hardening and early-strength repair mortar according to claim 1, characterized in that, The defoamer includes at least one of silicone defoamers, polyether defoamers, and higher alcohol defoamers.

9. The negative-temperature rapid-hardening and early-strength repair mortar according to claim 1, characterized in that, The fine aggregate includes quartz sand.

10. A method for preparing a negative-temperature rapid-hardening and early-strength repair mortar as described in any one of claims 1 to 9, characterized in that, Includes the following steps: S1: According to the proportion, the rapid-hardening sulfoaluminate cement, reference cement, mineral admixtures, fibers, polyacrylate redispersible latex powder, thermal activator, defoamer and fine aggregate are mixed and placed in a mixer to obtain a repair mortar premix; the negative temperature admixture, nanomaterials, water-reducing agent and water are mixed and ultrasonically dispersed in a water bath to obtain an ultrasonic dispersion. S2: Add the ultrasonic dispersion to the repair mortar premix to obtain the negative temperature type fast hardening early strength repair mortar.

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