Super-early-strength high-fluidity slip-form concrete and application thereof in high-rise structure construction

Abstract

The invention discloses super-early-strength high-fluidity slip-form concrete and application thereof in high-rise structure construction, belongs to the technical field of building materials, and aims to solve the problems that high-temperature slump retaining and early strength of existing slip-form concrete are contradictory, nano materials are agglomerated, and crack resistance and seepage resistance are insufficient. The concrete is prepared from the following raw materials in parts by weight: 200 to 300 parts of Portland cement, 50 to 150 parts of sulphoaluminate cement, 50 to 100 parts of mineral admixture, 700 to 800 parts of fine aggregate, 900 to 1100 parts of coarse aggregate, 130 to 160 parts of water, 5 to 15 parts of polycarboxylate superplasticizer, 0.5 to 3 parts of viscosity modifier, 0.5 to 2 parts of surface modified fiber, 0.5 to 2 parts of modified nano nucleating agent, 2 to 5 parts of composite retarding anti-cracking component and 3 to 8 parts of composite anti-seepage component, during preparation, the modified nano nucleating agent needs to be pre-dispersed. The 120-minute slump expansion loss rate of the concrete at 35 DEG C is less than or equal to 10%, the 16-hour compressive strength is greater than or equal to 22 MPa, the anti-permeability grade is greater than or equal to P12, the concrete is suitable for sliding formwork construction of a high-rise structure, the daily lifting of a formwork is 4-6 m, and the requirements of continuous construction and structural durability are met.

Description

Technical Field

[0001] This invention relates to a high-performance concrete material and its application technology in the field of rapid construction of tall structures. Specifically, it relates to a method for preparing slipform concrete with ultra-early strength, high fluidity, high impermeability and excellent workability retention by optimizing the concrete raw material ratio and adding special functional components, and applying it to the slipform construction of tall structures. Background Technology

[0002] Slipform construction technology, with its advantages of fast construction speed, excellent structural integrity, and high degree of mechanization, is widely used in tall structural projects such as chimneys, water towers, and television towers. Slipform construction of tall structures places extremely stringent requirements on concrete performance: on the one hand, the concrete must have high fluidity to meet the needs of pumping and placement, and maintain workability for a long time in high-temperature environments (especially during summer construction, when ambient temperatures can reach above 35℃) to avoid construction interruptions due to excessively rapid slump loss; on the other hand, the concrete must have ultra-early strength properties to ensure that it can quickly reach the support strength (0.3-0.5MPa) after demolding, matching the formwork lifting speed, while the later strength must meet the structural load-bearing requirements. Furthermore, since tall structures are exposed to the natural environment for extended periods, the concrete must also possess good crack resistance and impermeability to resist the penetration of rainwater and corrosive media, extending the service life of the structure.

[0003] In existing ultra-early strength slipform concrete technology, silicate cement and sulfoaluminate cement are usually used to achieve early strength, but the following technical challenges exist: The contradiction between high-temperature slump retention and crack resistance is very prominent: to improve high-temperature slump retention, the amount of retarder needs to be increased. However, excessive retarder will slow down the development of concrete strength after demolding, and dry shrinkage cracks are easily generated due to excessive moisture evaporation after demolding.

[0004] The effectiveness of nanomaterials is limited: In existing technologies, nano-nucleating agents (such as nano-calcium carbonate and nano-silica) are directly added to improve strength, but nanoparticles are prone to agglomeration and cannot be evenly dispersed in the concrete matrix, which causes their role in promoting hydration and refining pores to fail, and the strength improvement effect does not meet expectations.

[0005] Insufficient impermeability: The impermeability grade of existing concrete is mostly P8-P10, which is difficult to meet the long-term impermeability requirements of tall structures, making them prone to seepage and erosion, leading to corrosion of the internal steel bars.

[0006] Poor matching between strength and workability: In conventional mix design, the synergy between early strength components and fluidity adjustment components is insufficient, often resulting in the problem of "slow strength growth when maintaining slump and rapid fluidity loss when maintaining early strength", which cannot adapt to the rhythm of 24-hour continuous slipform construction.

[0007] To solve the above-mentioned technical problems, there is an urgent need to develop a slipform concrete that combines ultra-early strength, high fluidity, high-temperature slump retention, crack resistance, and impermeability, so as to meet the stringent requirements of slipform construction of tall structures and improve project quality and construction efficiency. Summary of the Invention

[0008] To address the aforementioned technical challenges, this invention develops a slipform concrete with ultra-early high strength and high fluidity, and its application in the construction of tall structures. This concrete achieves ultra-early high strength, high fluidity, and high impermeability by optimizing the raw material ratio and adding functional components, while maintaining excellent workability.

[0009] To achieve the objective of this invention, the technical solution is as follows: This invention first discloses an ultra-early, high-flowability slipform concrete, the key of which lies in that it is made from the following raw materials in parts by weight through the synergistic effect of various functional components: Silicate cement: 200-300 parts; Sulfoaluminate cement: 50-150 parts; Mineral admixtures: 50-100 parts; Fine aggregate: 700-800 parts; Coarse aggregate: 900-1100 parts; Water: 130-160 parts; Polycarboxylate superplasticizer: 5-15 parts; Viscosity modifier: 0.5-3 parts; Surface-modified fiber: 0.5-2 parts; Modified nanonucleating agent: 0.5-2 parts, which synergistically enhances the interfacial transition zone structure with the surface-modified fibers; Composite retarding and crack-resistant component: 2-5 parts; Composite anti-permeability component: 3-8 parts; The modified nano-nucleating agent is a compound composed of nano-calcium carbonate modified with a silane coupling agent and nano-silica in a mass ratio of 1:1-3:1; the composite retarding and crack-resistant component is a compound composed of sodium gluconate derivative and metakaolin in a mass ratio of 1:2-1:4; and the composite impermeable component is a compound composed of sodium-based bentonite and zeolite powder in a mass ratio of 1:3-1:5.

[0010] Furthermore, in the composite cementitious system, the mass ratio of sulfoaluminate cement to silicate cement is 1:2 to 1:4; the mineral admixture is a blend of at least two of fly ash microspheres, silica fume and mineral powder, wherein silica fume accounts for 2%-5% of the total mass of the cementitious material.

[0011] Furthermore, the coarse aggregate is a mixture of 5-10mm and 10-20mm graded crushed stone in a mass ratio of 4:6 to 6:4; the fine aggregate is medium sand of zone II with a fineness modulus of 2.4-2.8, and the stone powder content in particles with a particle size greater than 150μm is ≤10%.

[0012] Furthermore, the polycarboxylate-based high-performance water-reducing agent is an ester or ether polycarboxylate water-reducing agent with high water reduction rate (≥35%) and slow-release function. Its molecular structure has a side chain density of 3-5 strands / nm², and it works synergistically with the composite slow-setting and crack-resistant component to maintain slump for 120 minutes in a high-temperature environment above 35°C.

[0013] Furthermore, the viscosity modifier is at least one of warm roller adhesive, Dettol adhesive, and modified cellulose ether; the viscosity modifier works synergistically with polycarboxylate superplasticizer and composite retarding and crack-resistant component to achieve a slump spread of 650mm±50mm for the concrete mixture, a V-shaped funnel outflow time of 8-15 seconds, and a slump spread loss rate of ≤10% within 120 minutes under 35℃ environmental conditions.

[0014] Furthermore, the surface-modified fiber is a polyacrylonitrile fiber or polypropylene fiber modified with silane coupling agent KH-570, and the fiber length is 6-12mm; the mass ratio of the surface-modified fiber to the modified nano-nucleating agent is 1:1-2:1, and the two work synergistically through interface modification to jointly improve the interfacial bond strength and early crack resistance of concrete.

[0015] Furthermore, the modified nanonucleating agent has an average particle size of 20-50 nm and a specific surface area of ​​≥180 m² / g; in the composite anti-permeability component, the expansion ratio of sodium-based bentonite is ≥20 times, and the specific surface area of ​​zeolite powder is ≥300 m² / g.

[0016] Furthermore, its preparation method includes the following steps: S1: Put the coarse and fine aggregates into the mixer and dry mix for 30-60 seconds; S2: Add the modified nano-nucleating agent and some mineral admixtures into a high-speed disperser and pre-disperse them at a speed of 2000-3000 r / min for 10-15 minutes to obtain a uniform premix, so as to ensure the uniform distribution of nanomaterials in the gelation system. S3: Add silicate cement, sulfoaluminate cement, the premix obtained in step S2, the remaining mineral admixtures, composite impermeable components and surface modified fibers to the mixer in step S1, and continue to dry mix for 30-60 seconds until uniform. S4: Dissolve the polycarboxylate superplasticizer, viscosity modifier, and composite retarding and crack-resistant component in the mixing water to form a mixed solution; S5: Slowly add the mixed solution obtained in step S4 into the running mixer and wet mix for 2-3 minutes until a uniform and workable concrete mixture is obtained.

[0017] Secondly, this invention also discloses the application of ultra-early strong flowability slipform concrete as described above in the slipform construction of tall structures. The key is that the slipform construction system includes a template system, an operating platform, a hydraulic lifting system, and a precision control system. The construction process is a continuous operation. By utilizing the high workability of this concrete to maintain ultra-early strength and high impermeability, the cyclical continuous operation of pouring, vibration, lifting, and finishing is realized. The impermeability grade of the resulting concrete structure is ≥P12, and the surface cracking area rate is ≤0.5% within 24 hours after demolding.

[0018] Furthermore, the formwork lifting speed of the slipform construction is 15-30cm / hour, enabling 24-hour uninterrupted construction with a daily lifting height of 4-6 meters; the concrete demolding strength is controlled at 0.3-0.5MPa, with a 16-hour compressive strength ≥22MPa, a 3-day compressive strength ≥45MPa, a 28-day compressive strength ≥65MPa, and a 28-day flexural strength ≥8MPa.

[0019] Compared with the prior art, the significant advantages of the present invention are: 1. Resolves the contradiction between high-temperature slump retention and crack resistance: This invention, through the synergistic effect of a composite retarding and crack-resistant component with a polycarboxylate-based high-performance water-reducing agent and viscosity modifier, ensures the long-term maintenance of concrete workability under high-temperature conditions while avoiding the problems of slow strength development and drying shrinkage cracks caused by excessive retarder. The sodium gluconate derivative in the composite retarding and crack-resistant component is compounded with metakaolin in a specific ratio, which effectively slows down the cement hydration rate and enhances the later-stage strength and crack resistance of concrete through the pozzolanic effect of metakaolin.

[0020] 2. Fully leveraging the effects of nanomaterials: The modified nanonucleating agent is a compound of nano-calcium carbonate modified with a silane coupling agent and nano-silica, pre-dispersed using a high-speed disperser to ensure uniform distribution of nanomaterials in the cementitious system. This uniform dispersion allows the nanomaterials to fully exert their effects in promoting hydration and refining pores, significantly improving the early strength and microstructural density of concrete.

[0021] 3. Improved concrete impermeability: The composite impermeable component combines sodium-based bentonite and zeolite powder in a specific mass ratio. Sodium-based bentonite has good expansion and adsorption properties, which can fill the pores and capillary channels in the concrete; zeolite powder has a large specific surface area and adsorption properties, which can further improve the pore structure of the concrete. The synergistic effect of the two makes the impermeability grade of the concrete reach ≥P12, effectively meeting the long-term impermeability requirements of tall structures and preventing corrosion of the internal steel reinforcement.

[0022] 4. Achieving a good balance between strength and workability: This invention solves the problem of "slow strength growth due to slump retention and rapid loss of fluidity due to early strength" by optimizing the proportions and synergistic effects of various functional components. The polycarboxylate-based high-performance water-reducing agent, viscosity modifier, composite retarding and crack-resistant component, and modified nano-nucleating agent work together to enable concrete to maintain high fluidity and long-term workability while possessing ultra-early strength properties, adapting to the rhythm of 24-hour continuous slipform construction.

[0023] 5. Improved construction efficiency and project quality: Utilizing this ultra-early, high-flowability slipform concrete for slipform construction of tall structures allows for continuous operation. The formwork lifting speed is 15-30 cm / hour, with a daily lifting height of 4-6 meters. The surface cracking area rate of the concrete within 24 hours of demolding is ≤0.5%, and the strength at all ages meets the load-bearing requirements of tall structures, significantly improving construction efficiency and project quality, and providing reliable technical support for the construction of tall structure projects. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. It should be understood that the following description is merely illustrative and not intended to limit the invention.

[0025] The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used herein, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0026] The present invention provides an ultra-early high-flowability slipform concrete, which is made from the following raw materials in parts by weight through the synergistic effect of various functional components: Silicate cement: 200-300 parts; Sulfoaluminate cement: 50-150 parts; Mineral admixtures: 50-100 parts; Fine aggregate: 700-800 parts; Coarse aggregate: 900-1100 parts; Water: 130-160 parts; Polycarboxylate superplasticizer: 5-15 parts; Viscosity modifier: 0.5-3 parts; Surface-modified fiber: 0.5-2 parts; Modified nanonucleating agent: 0.5-2 parts, which synergistically enhances the interfacial transition zone structure with the surface-modified fibers; Composite retarding and crack-resistant component: 2-5 parts; Composite anti-permeability component: 3-8 parts; The modified nano-nucleating agent is a compound composed of nano-calcium carbonate modified with a silane coupling agent and nano-silica in a mass ratio of 1:1-3:1; the composite retarding and crack-resistant component is a compound composed of sodium gluconate derivative and metakaolin in a mass ratio of 1:2-1:4; and the composite impermeable component is a compound composed of sodium-based bentonite and zeolite powder in a mass ratio of 1:3-1:5.

[0027] This ultra-early, high-flowability slipform concrete possesses numerous superior properties. Due to the rational proportions and synergistic effects of its raw materials, this concrete rapidly achieves high strength in its early stages. The combined use of silicate and sulfoaluminate cement provides fundamental strength support, and the properties of sulfoaluminate cement contribute to rapid early strength formation. The addition of mineral admixtures not only improves the workability of the concrete but also further enhances its later-stage strength and durability.

[0028] The precise proportions of fine and coarse aggregates ensure a stable concrete skeleton structure, giving it excellent resistance to deformation. The appropriate water dosage satisfies both the cement hydration requirements and the concrete's suitable fluidity. The addition of a polycarboxylate-based high-performance water-reducing agent significantly reduces the water-cement ratio of the concrete, improving its strength and durability, while also enhancing its fluidity, allowing for smooth flow and filling during slipform construction.

[0029] The role of viscosity modifiers is to control the viscosity of concrete, ensuring it is neither too thin (leading to segregation) nor too viscous (affecting construction efficiency) during construction. Surface-modified fibers and modified nano-nucleating agents work synergistically to enhance the interfacial transition zone structure, improving the crack resistance and overall strength of the concrete. Composite retarding and crack-resistant components slow down the hydration rate of cement, preventing early cracking due to excessive heat of hydration, while simultaneously improving its crack resistance. Composite impermeable components effectively enhance the impermeability of concrete, enabling it to resist the intrusion of external moisture and harmful substances, extending the service life of the concrete structure.

[0030] In the construction of tall structures, this ultra-early high-flowability slipform concrete has demonstrated significant advantages. Its ultra-early strength characteristic enables rapid slipform construction, shortening the construction cycle and improving efficiency. High flowability ensures that the concrete evenly fills the formwork during the slipform's ascent, avoiding quality issues such as honeycombing and pitting, thus guaranteeing the appearance quality and internal strength of the tall structure. Simultaneously, its excellent crack resistance and impermeability make the tall structure more stable and reliable during long-term use, reducing maintenance costs and safety hazards.

[0031] In specific implementation, the mass ratio of sulfoaluminate cement to silicate cement in the composite cementitious system is 1:2 to 1:4; the mineral admixture is a mixture of at least two of fly ash microspheres, silica fume and mineral powder, wherein silica fume accounts for 2%-5% of the total mass of the cementitious material.

[0032] When the silica fume content is within this range, it can effectively improve the microstructure of concrete, increasing its density and strength. The mixing ratio of fly ash microspheres and mineral powder can be adjusted according to actual engineering needs; generally, a mass ratio of fly ash microspheres to mineral powder between 1:1 and 1:3 is suitable. This mixing method can fully utilize the advantages of different mineral admixtures. Fly ash microspheres have a good ball-bead effect, which can improve the fluidity and workability of concrete; while mineral powder can participate in the hydration reaction of cement, enhancing the later-stage strength of concrete.

[0033] Regarding the composite retarding and crack-resistant components, retarders such as sodium gluconate and citric acid can be used, with a dosage generally ranging from 0.1% to 0.3% of the total cementitious material mass. Crack-resistant fibers such as polypropylene fibers and polyester fibers, with fiber lengths between 6 and 19 mm, can be used, with a dosage of 0.6-1.2 kg per cubic meter of concrete. Appropriate dosages of retarders and crack-resistant fibers can effectively inhibit the generation and development of micro-cracks within the concrete while slowing down the cement hydration rate.

[0034] For composite impermeable components, silicone waterproofing agents and expanding agents can be used. Silicone waterproofing agents form a hydrophobic film on the concrete surface, preventing moisture intrusion; expanding agents cause the concrete to expand during hardening, compensating for shrinkage and thus improving the concrete's impermeability. The dosage of silicone waterproofing agent is 0.5%-1.5% of the total mass of the cementitious materials, and the dosage of expanding agent is 3%-8% of the total mass of the cementitious materials.

[0035] In actual construction, it is also necessary to strictly control the mixing time and process of concrete. The mixing time should generally be no less than 180 seconds to ensure that all components are fully and evenly mixed. At the same time, the concrete mix proportion and construction parameters should be adjusted in a timely manner according to the environmental conditions such as temperature and humidity on site to ensure that the ultra-early high flowability slipform concrete can perform at its best in the construction of tall structures, achieving the goal of fast, efficient and high-quality construction.

[0036] In this embodiment, the coarse aggregate is a mixture of 5-10mm and 10-20mm graded crushed stone in a mass ratio of 4:6 to 6:4; the fine aggregate is medium sand of zone II with a fineness modulus of 2.4-2.8, and the stone powder content in particles with a particle size greater than 150μm is ≤10%.

[0037] This coarse aggregate blending method enables the concrete to form a more reasonable particle size distribution, reducing porosity and improving the density and strength of the concrete. The intermingling of the two-graded crushed stone enhances the stability of the internal structure of the concrete, allowing for more even stress transfer under load. Medium sand with a fineness modulus of 2.4-2.8 (Zone II) is selected as the fine aggregate because this fineness modulus provides good particle shape and gradation, ensuring sufficient bonding strength while maintaining workability. Simultaneously, strictly controlling the stone powder content in particles larger than 150μm to ≤10% avoids excessive stone powder affecting the workability, strength, and durability of the concrete. Excessive stone powder content may absorb too much water, increasing the water demand of the concrete and thus affecting its strength and impermeability. During actual construction, the quality of both coarse and fine aggregates must be strictly controlled, with regular testing to ensure that all indicators meet requirements. The mass ratio of the two-graded crushed stone in the coarse aggregate must be accurately weighed to ensure the accuracy of the blending proportion. The fineness modulus and stone powder content of fine aggregates must be monitored in real time. If any non-compliance is found, the aggregates should be adjusted or replaced promptly to ensure the stable performance of ultra-early high-flowability slipform concrete and meet the requirements of tall structure construction. Furthermore, effective protective measures must be taken during the storage and transportation of aggregates to prevent contamination or segregation, which could affect the quality of the concrete.

[0038] Specifically, the polycarboxylate-based high-performance water-reducing agent is an ester or ether polycarboxylate water-reducing agent with high water reduction rate (≥35%) and slow-release function. Its molecular structure has a side chain density of 3-5 strands / nm², and it works synergistically with the composite slow-setting and crack-resistant component to maintain slump within 120 minutes at a high temperature of above 35°C.

[0039] The unique properties of this polycarboxylate-based high-performance water-reducing agent enable ultra-early, high-flowability slipform concrete to maintain excellent workability even in high-temperature environments. In actual high-rise structure construction, high temperatures often adversely affect concrete performance, leading to excessively rapid slump loss and impacting the pouring and molding quality. This water-reducing agent's high water-reduction rate reduces water consumption while maintaining concrete strength, thus improving density and durability. Its slow-release function continues to work over a longer period, ensuring stable slump for up to 120 minutes, providing ample time for construction operations.

[0040] Meanwhile, the specific side chain density (3-5 strands / nm²) in the molecular structure also plays a crucial role. A suitable side chain density allows the water-reducing agent to better adsorb onto the surface of cement particles, forming a stable dispersion system that effectively prevents particle agglomeration, thereby improving the fluidity of concrete. The synergistic effect with the composite retarding and crack-resistant component further enhances the concrete's performance. The composite retarding and crack-resistant component can slow down the hydration reaction rate of cement, reduce internal temperature and shrinkage stresses in concrete, and prevent crack formation. The synergistic effect of these two components allows ultra-early, high-flowability slipform concrete to maintain good fluidity even at high temperatures, while also exhibiting excellent crack resistance, meeting the stringent performance requirements for concrete in the construction of tall structures.

[0041] Furthermore, when using this polycarboxylate-based high-performance water-reducing agent, its compatibility with other raw materials must be considered. During concrete mix design, thorough testing and adjustments are necessary to ensure the water-reducing agent is compatible with cement, aggregates, admixtures, and other raw materials to achieve optimal performance. Simultaneously, during construction, the dosage of the water-reducing agent must be strictly controlled, added accurately according to design requirements, to avoid affecting concrete performance due to improper dosage. Appropriate measures must also be taken for the storage and transportation of the water-reducing agent to ensure its quality stability and prevent performance degradation due to improper storage conditions. Through the comprehensive implementation of these measures, the advantages of polycarboxylate-based high-performance water-reducing agents can be fully utilized, ensuring the successful application of ultra-early, high-flowability slipform concrete in the construction of tall structures.

[0042] Preferably, the viscosity modifier is at least one of warm roller adhesive, Dettol adhesive, and modified cellulose ether; the viscosity modifier works synergistically with polycarboxylate superplasticizer and composite retarding and crack-resistant component to achieve a slump spread of 650mm±50mm for the concrete mixture, a V-shaped funnel outflow time of 8-15 seconds, and a slump spread loss rate of ≤10% within 120 minutes under 35℃ environmental conditions.

[0043] This performance characteristic allows concrete to maintain good workability for extended periods under high-temperature conditions, providing strong support for the continuous construction of tall structures. In actual construction, when the slump flow and V-funnel outflow time of the concrete are within the aforementioned range, the concrete can smoothly pass through the pumping pipes and evenly fill the formwork, reducing problems such as pipe blockage and inadequate compaction. Simultaneously, the low slump flow loss rate ensures the stable performance of the concrete over a longer period, preventing construction quality from being affected by rapid changes in concrete properties.

[0044] Furthermore, the synergistic effect of viscosity modifiers with polycarboxylate superplasticizers and composite retarder-resistant crack-resistant components also positively impacts the internal structure and mechanical properties of concrete. During the concrete hardening process, this synergistic effect helps form a denser, more uniform microstructure, improving the strength and durability of the concrete. For tall structures, good strength and durability are key factors in ensuring their long-term safe and stable operation. By rationally selecting and using viscosity modifiers, the performance of ultra-early high-flowability slipform concrete can be further optimized, making it better suited to the special requirements of tall structure construction.

[0045] During construction, the type and dosage of viscosity modifiers need to be adjusted appropriately based on specific engineering conditions and environmental factors. For example, the workability and setting time of concrete will vary under different temperature, humidity, and construction speed conditions. In such cases, the viscosity modifier formulation needs to be adjusted accordingly to ensure the concrete maintains optimal performance. Simultaneously, real-time monitoring of concrete performance is crucial to promptly identify and resolve potential problems, ensuring construction quality and progress. Through scientific and rational construction management and quality control, ultra-early high-flowability slipform concrete can maximize its advantages in the construction of tall structures, making a greater contribution to the development of the construction industry.

[0046] In this embodiment, the surface-modified fiber is a polyacrylonitrile fiber or polypropylene fiber modified with silane coupling agent KH-570, and the fiber length is 6-12mm; the mass ratio of the surface-modified fiber to the modified nano-nucleating agent is 1:1-2:1, and the two work synergistically through interface modification to jointly improve the interfacial bond strength and early crack resistance of concrete.

[0047] Polyacrylonitrile fibers or polypropylene fibers modified with silane coupling agent KH-570 exhibit significantly improved surface properties, enabling better bonding with the concrete matrix. KH-570 forms a special film on the fiber surface, enhancing the chemical bond between the fiber and concrete, allowing the fiber to more effectively transfer stress within the concrete. When concrete is subjected to external forces, these surface-modified fibers can disperse stress, inhibit crack propagation, and thus improve the crack resistance of the concrete.

[0048] Modified nanonucleating agents play a crucial role in the hydration process of concrete. They provide numerous nucleation sites, accelerating the formation and growth of cement hydration products and promoting the early strength development of concrete. Simultaneously, the modified nanonucleating agents and surface-modified fibers synergistically enhance each other through interfacial modification, further optimizing the microstructure of concrete. Surface-modified fibers provide a carrier for the attachment and growth of modified nanonucleating agents, enabling them to be more uniformly distributed in the concrete and fully exert their nucleation effect.

[0049] In practical applications, strictly controlling the mass ratio of surface-modified fibers to modified nanonucleating agents within 1:1-2:1 is crucial. If the proportion of surface-modified fibers is too high, it may lead to uneven fiber dispersion in the concrete, causing agglomeration and negatively impacting concrete performance. Conversely, if the proportion of modified nanonucleating agents is too high, it may cause excessively rapid hydration of the concrete, resulting in significant internal temperature and shrinkage stresses and increasing the risk of cracking. Therefore, only within a suitable mass ratio range can the two components fully exert their synergistic effect, jointly enhancing the interfacial bond strength and early crack resistance of the concrete, ensuring that ultra-early high-flowability slipform concrete meets all performance requirements in the construction of tall structures.

[0050] In practical applications, its preparation method includes the following steps: S1: Put the coarse and fine aggregates into the mixer and dry mix for 30-60 seconds; S2: Add the modified nano-nucleating agent and some mineral admixtures into a high-speed disperser and pre-disperse them at a speed of 2000-3000 r / min for 10-15 minutes to obtain a uniform premix, so as to ensure the uniform distribution of nanomaterials in the gelation system. S3: Add silicate cement, sulfoaluminate cement, the premix obtained in step S2, the remaining mineral admixtures, composite impermeable components and surface modified fibers to the mixer in step S1, and continue to dry mix for 30-60 seconds until uniform. S4: Dissolve the polycarboxylate superplasticizer, viscosity modifier, and composite retarding and crack-resistant component in the mixing water to form a mixed solution; S5: Slowly add the mixed solution obtained in step S4 into the running mixer and wet mix for 2-3 minutes until a uniform and workable concrete mixture is obtained.

[0051] After completing the above preparation steps, the prepared ultra-early high-flowability slipform concrete still needs to undergo rigorous quality testing. First, its flowability must be tested using a slump test to ensure that the slump meets the requirements for high-rise structure construction. Generally, the slump should be controlled within a specific, relatively large range to ensure that the concrete can flow smoothly in the slipform and fill the required positions.

[0052] At the same time, the early strength of concrete should be tested. This can be done by using test blocks cured under similar construction conditions. The test blocks are then cured under similar conditions and their compressive strength is tested at specific time points, such as 1 day and 3 days after pouring, to check whether they can achieve the performance index of ultra-early strength and meet the requirements of rapid demolding and continuous construction in the construction of tall structures.

[0053] During transportation, specialized concrete transport equipment must be used, and the transportation time must be strictly controlled. Excessive transportation time may cause changes in the properties of the concrete, such as reduced fluidity and altered setting time. Therefore, transportation time should be minimized to ensure that the concrete maintains good workability upon arrival at the construction site.

[0054] When using this concrete in the construction of tall structures, precise control of the slipform lifting speed is required. The lifting speed should be adjusted appropriately based on the concrete's setting time and early strength gain to avoid instability in the concrete structure due to excessively rapid lifting, or adhesion between the concrete and the formwork due to excessively slow lifting.

[0055] Environmental factors must also be considered during construction. If construction is carried out in a high-temperature environment, appropriate cooling measures must be taken, such as cooling raw materials and adding retarders to the concrete to prevent it from setting too quickly. If construction is carried out in a low-temperature environment, insulation measures must be implemented to ensure the concrete hardens at a suitable temperature, guaranteeing its performance stability and structural safety.

[0056] In addition, proper curing of the concrete structure is essential after construction. Methods such as covering with moisture-retaining materials and spraying curing agents can be used to keep the concrete moist for a certain period, promoting continuous strength gain and performance stability. This allows the ultra-early, high-flowability slipform concrete to achieve its best performance in the construction of tall structures.

[0057] This invention also provides an application of ultra-early strong flowability slipform concrete in the slipform construction of tall structures. The slipform construction system includes a template system, an operating platform, a hydraulic lifting system, and a precision control system. The construction process is a continuous operation. By utilizing the high workability of this concrete to maintain ultra-early strength and high impermeability, the cyclical continuous operation of pouring, vibration, lifting, and finishing is realized. The impermeability grade of the resulting concrete structure is ≥P12, and the surface cracking area rate is ≤0.5% within 24 hours after demolding.

[0058] This continuous operation method significantly improves the efficiency of slipform construction for tall structures. The formwork system is designed to match the characteristics of ultra-early, high-flowability slipform concrete, enabling precise shaping of the desired structural form. The operating platform provides a stable and safe working space for construction personnel, allowing for the orderly execution of various construction operations. The hydraulic lifting system, with its powerful motor, ensures the smooth lifting of the formwork and allows for precise speed adjustments based on the real-time condition of the concrete.

[0059] The precision control system is a crucial guarantee for the entire construction process. It can monitor and adjust various construction parameters in real time to ensure that the verticality, flatness, and other indicators of the tall structure meet design requirements. In the cyclical continuous operation, each pouring, vibration, lifting, and finishing step is closely linked and mutually influential. The high workability of concrete allows it to evenly fill the space within the formwork during pouring, reducing defects such as honeycomb and pitting.

[0060] The vibration compaction process further enhances the density of concrete, fully leveraging its high impermeability. The ultra-early strength characteristic allows the concrete to reach a certain strength in a short time, meeting the requirements for upgrading and finishing. Throughout the construction process, strict control of various parameters ensures that the resulting concrete structure has an impermeability grade ≥ P12, and a surface cracking area rate ≤ 0.5% within 24 hours after demolding, thus guaranteeing the quality and durability of the tall structure. The application of this ultra-early strength, high-flowability slipform concrete in the slipform construction of tall structures provides the construction industry with an efficient and reliable construction solution.

[0061] In practice, the formwork lifting speed of the slipform construction is 15-30cm / hour, enabling 24-hour uninterrupted construction and a daily lifting height of 4-6 meters; the concrete demolding strength is controlled at 0.3-0.5MPa, with a 16-hour compressive strength ≥22MPa, a 3-day compressive strength ≥45MPa, a 28-day compressive strength ≥65MPa, and a 28-day flexural strength ≥8MPa.

[0062] Furthermore, strict control over raw materials is essential during implementation. Cement should be of high strength grade and good stability to ensure the basic strength and stability of the concrete. Coarse aggregate should have a moderate particle size and good gradation, with its mud content strictly controlled to avoid affecting the workability and strength of the concrete. Fine aggregate should be hard, clean, and have a fineness modulus that meets construction requirements. Simultaneously, to further improve concrete performance, appropriate amounts of high-quality admixtures, such as high-efficiency water-reducing agents and accelerators, can be added. High-efficiency water-reducing agents can reduce water consumption while ensuring concrete workability, thereby improving strength and durability; accelerators can accelerate the early strength development of concrete, better meeting the rapid lifting requirements of slipform construction. During concrete mixing, sufficient mixing time must be ensured to allow all raw materials to mix thoroughly and evenly, guaranteeing consistent concrete quality. During transportation, effective measures must be taken to prevent concrete segregation and slump loss, ensuring that it still possesses good workability upon arrival at the construction site. During the slipform construction process, professional technicians are required to conduct real-time monitoring and quality control, and to adjust and optimize the various performance indicators and construction parameters of the concrete in a timely manner to ensure the smooth progress of the slipform construction of the tall structure and the final project quality.

[0063] The technical effects of this invention will be verified below using specific experimental data: I. Raw Material Specifications Silicate cement: P·O42.5 grade, initial setting time 180 min; Sulfoaluminate cement: R·SAC42.5 grade, initial setting time 30 min; Mineral admixtures: fly ash microspheres (fineness ≤5% on 45μm sieve), silica fume (SiO2 content ≥92%), mineral powder (S95 grade); Fine aggregate: Zone II medium sand, fineness modulus 2.6, stone powder content of particles with a particle size >150μm 8%; Coarse aggregate: 5-10mm crushed stone (crushing value ≤10%), 10-20mm crushed stone (crushing value ≤12%); Polycarboxylate superplasticizer: ether type, water reduction rate 38%, side chain density 4 strands / nm²; Viscosity modifier: Wenlun glue (purity ≥ 98%); Surface-modified fiber: KH-570 modified polyacrylonitrile fiber, 8mm in length and 20μm in diameter; Modified nanonucleating agent: KH-550 modified nano calcium carbonate (particle size 30nm) and nano silica (particle size 25nm) are combined; Composite retarding and crack-resistant component: a compound of sodium gluconate derivative (purity 95%) and metakaolin (active SiO2 ≥ 70%); Composite impermeable component: Sodium-based bentonite (expansion ratio 25 times) and zeolite powder (specific surface area 320m² / g).

[0064] II. Implementation Examples and Comparative Examples Prepare concrete according to the proportions shown in Table 1, wherein: Examples 1-3: The raw material ratios and preparation processes all conform to the claims of this invention; Comparative Example 1: No modified nano-nucleating agent, composite retarding and crack-resistant component, or composite impermeable component were added. The fiber was unmodified polypropylene fiber, and no pre-dispersion step was performed during preparation. (Refer to conventional formulations in existing technologies)

[0065] III. Performance Testing Methods The concrete performance was tested according to the following national standards: Slump spread and loss rate: GB / T50080-2016, initial test values ​​and values ​​after 60 min and 120 min at 35℃; V-shaped funnel outflow time: GB / T50080-2016; Compressive strength / flexural strength: GB / T50081-2019, tested at demolding (4h), 16h, 3d, and 28d strength; Permeability grade: GB / T50082-2009, using the step-by-step pressurization method; Crack area ratio 24 hours after demolding: JGJ / T322-2013, calculate the ratio of crack area to specimen surface area.

[0066] IV. Experimental Data and Comparative Analysis 1. Results of the workability test (Table 2)

[0067] analyze: The slump spread loss rate at 120 min in Examples 1-3 was ≤10.6%, which was much lower than the 33.3% in Comparative Example 1. The reason is that in this invention, the polycarboxylate superplasticizer (side chain density 4 / nm²) and the composite retarding and crack-resistant component (sodium gluconate derivative + metakaolin) work synergistically. The retarding component can slow down the rate of heat release during cement hydration and avoid rapid evaporation of water at high temperature. At the same time, the side chains of the superplasticizer can be continuously adsorbed on the surface of cement particles to maintain the dispersion effect. Comparative Example 1, lacking a composite retarding and crack-resistant component, experienced accelerated cement hydration at 35°C, leading to rapid failure of the water-reducing agent and a sharp loss of fluidity, thus failing to meet the requirement of 120 minutes of continuous construction.

[0068] 2. Strength performance test results (Table 3)

[0069] analyze: The 16-hour compressive strength of Examples 1-3 was ≥22MPa, which was 32%-44% higher than that of Example 1 (16.8MPa). The reasons are: ① After modification with KH-550, the compatibility of the modified nano-nucleating agent with the gel matrix interface was improved, and the pre-dispersion process (2500r / min, 12min) avoided particle agglomeration. The nanoparticles can serve as nucleation sites for hydration products, accelerating the formation of CSH gel; ② The surface-modified fiber (KH-570 modified) and the modified nano-nucleating agent (mass ratio 1.2:1) worked synergistically. The hydroxyl groups on the fiber surface formed hydrogen bonds with the hydroxyl groups of the nanoparticles, which improved the interfacial bonding strength and inhibited the propagation of microcracks. Comparative Example 1, due to the lack of modified nanonucleating agents and the absence of fiber modification, exhibited weak interfacial bonding, resulting in slow growth of early hydration products and insufficient strength improvement.

[0070] 3. Test results of impermeability and crack resistance (Table 4)

[0071] analyze: The impermeability grades of Examples 1-3 are ≥P12, and the crack area ratio is ≤0.4%, which is significantly better than that of Comparative Example 1 (P8, 2.5%). The reasons are: ① Sodium-based bentonite in the composite impermeable component expands when it comes into contact with water, filling the pores inside the concrete, and the porous structure of zeolite powder can adsorb free water, reducing the porosity; ② Modified nano-nucleating agent refines the pores of hydration products (pore size is reduced from 50-100nm in Comparative Example 1 to 20-30nm), forming a dense structure; ③ Surface-modified fibers can bridge early drying shrinkage cracks and inhibit crack propagation. Comparative Example 1 lacks composite anti-permeability components and has large pores, making it prone to water penetration. At the same time, the unmodified fibers cannot effectively suppress cracks, resulting in an excessively high cracking rate.

[0072] Technical effect To resolve the contradiction between high-temperature slump retention and early strength: By combining "polycarboxylate superplasticizer (side chain density 3-5 strands / nm²) + composite retarding and crack-resistant components", the slump expansion loss rate at 35℃ for 120 minutes is ≤10%, and the compressive strength at 16 hours is ≥22MPa, making it suitable for continuous construction in high-temperature environments. Improving the utilization rate of nanomaterials: The modified nanonucleating agent, after modification with silane coupling agent and pre-dispersion process, improves the dispersion uniformity by 80% and the early strength by more than 30%. Enhanced crack and impermeability: The composite impermeable component works synergistically with the modified fiber to improve the impermeability grade to P12-P14, and the cracking rate is reduced to below 0.5% within 24 hours of demolding, thus extending the service life of tall structures. Adaptable to slipform construction efficiency: The daily lifting height of the formwork reaches 4-6 meters, which is 20%-30% higher than the existing technology, and the 28-day compressive strength of the concrete is ≥65MPa, meeting the structural load-bearing requirements.

[0073] Supplementary explanation of specific implementation methods The scope of protection of this invention is not limited to the above embodiments. Any adjustments to the raw material composition, preparation process, and performance indicators as defined in the claims of this invention are within the scope of protection of this invention. For example, the mass ratio of the composite retarding and crack-resistant components can be adjusted within the range of 1:2 to 1:4, and the compounding ratio of the modified nanonucleating agent can be varied within the range of 1:1 to 3:1, all of which can achieve similar technical effects.

Claims

1. A type of ultra-early high-flowability slipform concrete, characterized in that, It is made from the following raw materials in parts by weight through the synergistic effect of various functional components: Silicate cement: 200-300 parts; Sulfoaluminate cement: 50-150 parts; Mineral admixtures: 50-100 parts; Fine aggregate: 700-800 parts; Coarse aggregate: 900-1100 parts; Water: 130-160 parts; Polycarboxylate superplasticizer: 5-15 parts; Viscosity modifier: 0.5-3 parts; Surface-modified fiber: 0.5-2 parts; Modified nanonucleating agent: 0.5-2 parts, which synergistically enhances the interfacial transition zone structure with the surface-modified fibers; Composite retarding and crack-resistant component: 2-5 parts; Composite anti-permeability component: 3-8 parts; The modified nano-nucleating agent is a compound composed of nano-calcium carbonate modified with a silane coupling agent and nano-silica in a mass ratio of 1:1-3:1; the composite retarding and crack-resistant component is a compound composed of sodium gluconate derivative and metakaolin in a mass ratio of 1:2-1:4; and the composite impermeable component is a compound composed of sodium-based bentonite and zeolite powder in a mass ratio of 1:3-1:

5.

2. The ultra-early high-flowability slipform concrete according to claim 1, characterized in that, In the composite cementitious system, the mass ratio of sulfoaluminate cement to silicate cement is 1:2 to 1:4; the mineral admixture is a mixture of at least two of fly ash microspheres, silica fume and mineral powder, wherein silica fume accounts for 2%-5% of the total mass of the cementitious material.

3. The ultra-early high-flowability slipform concrete according to claim 1, characterized in that, The coarse aggregate is a mixture of 5-10mm and 10-20mm graded crushed stone in a mass ratio of 4:6 to 6:4; the fine aggregate is medium sand of zone II with a fineness modulus of 2.4-2.8, and the stone powder content in particles with a particle size greater than 150μm is ≤10%.

4. The ultra-early high-flowability slipform concrete according to claim 1, characterized in that, The polycarboxylate-based high-performance water-reducing agent is an ester or ether polycarboxylate water-reducing agent with high water reduction rate (≥35%) and slow-release function. Its molecular structure has a side chain density of 3-5 strands / nm², and it works synergistically with the composite slow-setting and crack-resistant component to maintain slump for 120 minutes in a high-temperature environment above 35°C.

5. The ultra-early high-flowability slipform concrete according to claim 1, characterized in that, The viscosity modifier is at least one of warm roller adhesive, Dettol adhesive and modified cellulose ether; the viscosity modifier works synergistically with polycarboxylate superplasticizer and composite retarding and crack-resistant component to make the slump spread of concrete mixture reach 650mm±50mm, the V-shaped funnel outflow time is 8-15 seconds, and the slump spread loss rate within 120 minutes under 35℃ environmental conditions is ≤10%.

6. The ultra-early high-flowability slipform concrete according to claim 1, characterized in that, The surface-modified fiber is a polyacrylonitrile fiber or polypropylene fiber modified with silane coupling agent KH-570, and the fiber length is 6-12mm; the mass ratio of the surface-modified fiber to the modified nano-nucleating agent is 1:1-2:

1. The two work synergistically through interface modification to improve the interfacial bond strength and early crack resistance of concrete.

7. The ultra-early high-flowability slipform concrete according to claim 1, characterized in that, The modified nanonucleating agent has an average particle size of 20-50 nm and a specific surface area of ​​≥180 m² / g; in the composite anti-permeability component, the expansion ratio of sodium-based bentonite is ≥20 times, and the specific surface area of ​​zeolite powder is ≥300 m² / g.

8. The ultra-early high-flowability slipform concrete according to any one of claims 1-7, characterized in that, Its preparation method includes the following steps: S1: Put the coarse and fine aggregates into the mixer and dry mix for 30-60 seconds; S2: Add the modified nano-nucleating agent and some mineral admixtures into a high-speed disperser and pre-disperse them at a speed of 2000-3000 r / min for 10-15 minutes to obtain a uniform premix, so as to ensure the uniform distribution of nanomaterials in the gelation system. S3: Add silicate cement, sulfoaluminate cement, the premix obtained in step S2, the remaining mineral admixtures, composite impermeable components and surface modified fibers to the mixer in step S1, and continue to dry mix for 30-60 seconds until uniform. S4: Dissolve the polycarboxylate superplasticizer, viscosity modifier, and composite retarding and crack-resistant component in the mixing water to form a mixed solution; S5: Slowly add the mixed solution obtained in step S4 into the running mixer and wet mix for 2-3 minutes until a uniform and workable concrete mixture is obtained.

9. The application of ultra-early high-flowability slipform concrete as described in any one of claims 1-8 in slipform construction of tall structures, characterized in that, The slipform construction system includes a template system, an operating platform, a hydraulic lifting system, and a precision control system. The construction process is a continuous operation. Utilizing the high workability of the concrete to maintain ultra-early strength and high impermeability, the system enables cyclical and continuous operation of pouring, vibration, lifting, and finishing. The resulting concrete structure has an impermeability grade ≥ P12, and the surface cracking area rate is ≤0.5% within 24 hours after demolding.

10. The application according to claim 9, characterized in that, The formwork lifting speed of the slipform construction is 15-30cm / hour, enabling 24-hour uninterrupted construction, with a daily lifting height of 4-6 meters; the concrete demolding strength is controlled at 0.3-0.5MPa, with a 16-hour compressive strength ≥22MPa, a 3-day compressive strength ≥45MPa, a 28-day compressive strength ≥65MPa, and a 28-day flexural strength ≥8MPa.

Images