Spherical end steel fiber reinforced zirconia nanoparticle ultra-high performance concrete and preparation method thereof

Abstract

The invention discloses spherical end steel fiber reinforced zirconia nanoparticle ultra-high performance concrete and a preparation method thereof, the concrete comprises cement, silica fume, quartz powder, quartz sand, water, a superplasticizer, zirconia nanoparticles and spherical end steel fiber, the contact area between the steel fiber and a matrix is increased and a mechanical interlocking structure is formed through the spherical structure at the end of the steel fiber, the mechanical anchoring effect is remarkably enhanced, an efficient bridging system is formed in the matrix, and the fiber absorbs a large amount of energy through end anchoring and self deformation during crack expansion. Zirconium oxide nanoparticles are combined to strengthen a matrix and optimize fiber-matrix interface stress transfer, and the zirconium oxide nanoparticles and the matrix cooperate to promote the material to present a remarkable strain hardening behavior before damage, so that the toughness and the energy-dissipating capacity are greatly improved, and the tensile strength, the compressive strength, the bending property and the toughness are remarkably improved; the problems that interface bonding is weak, and microcracks are often induced by stress concentration at the ends of the fibers are solved.

Description

Technical Field

[0001] This invention relates to the field of ultra-high performance concrete technology, and in particular to an ultra-high performance concrete with spherical-end steel fiber reinforced zirconia nanoparticles and its preparation method. Background Technology

[0002] Ultra-high performance concrete (UHPC) is a new type of engineering material with extremely high strength, high toughness, and excellent durability. Due to its outstanding compressive strength, durability, and potential high toughness, it has become an ideal material for high-rise buildings, long-span bridges, and special protective structures. However, the UHPC matrix is ​​still inherently brittle, with limited tensile strength and deformation capacity. It is prone to sudden fracture under tensile and bending loads, a characteristic that severely restricts its widespread application in critical load-bearing structures.

[0003] To overcome the brittleness bottleneck of UHPC, fiber incorporation has become the most effective reinforcement method. For example, CN107285700B discloses an ultra-high toughness concrete and its preparation method, which discloses the following raw material composition: 380-580 parts cement, 150-170 parts slag powder, 250-380 parts fly ash, 200-400 parts quartz sand, 13-15 parts bamboo phenolic liquefaction resin, 13-18 parts polypropylene resin, 0.5-1.5 parts carboxymethyl cellulose, 23-47 parts core-shell acrylic elastic emulsion, 5-10 parts chemical-resistant modifier, 14-18 parts bamboo fiber, 2.5-8.5 parts nano-silicon particles, 7-13 parts nano-calcium carbonate, 3-5 parts anionic polyacrylamide, 3.7-8.3 parts polydimethyldiallylammonium chloride, 0.4-1 parts polyethylene glycol acrylate, 20-30 parts acrylic emulsion, 3-6 parts high-strength imitation steel wire fiber, 4-8 parts CFRP reinforcement, and 190-270 parts water. This patent incorporates bamboo fiber and high-strength steel-like fiber into concrete. Their randomized distribution and overlapping nature act as reinforcement, supporting aggregates and preventing segregation. Simultaneously, it reduces interconnected pores caused by water seepage, lowering porosity. Furthermore, during concrete hardening, the randomized fiber distribution cuts off capillary channels, reducing the water loss area of ​​the matrix and the capillary shrinkage tension, hindering water migration, and improving the pore structure, thereby enhancing the concrete's strength and impermeability. Steel fibers, with their high tensile strength and elastic modulus, effectively bridge cracks, delay the failure process, and significantly improve the material's toughness and post-cracking performance. However, the interfacial bond between traditional straight steel fibers and the cement matrix is ​​weak, relying mainly on limited chemical bonding and friction. Under stress, fiber slippage or even pull-out easily occurs, leading to low reinforcement efficiency, and stress concentration at the fiber ends often induces microcracks. Furthermore, steel fibers still face challenges such as processing difficulties, easy clumping during mixing, poor dispersion uniformity, and potential damage to the matrix during drawing, resulting in unsatisfactory actual reinforcement effects and construction applicability. Additionally, this patent utilizes a combination of nano-silicon particles and nano-calcium carbonate to create a new network structure on top of the existing network structure of the concrete paste, effectively preventing the propagation of microcracks within the concrete and improving its flexural tensile strength. However, achieving uniform dispersion of nanoparticles in UHPC and ensuring effective synergy with the fiber reinforcement mechanism remains a key technological challenge. Summary of the Invention

[0004] To overcome the problems of weak interfacial bonding with the cement matrix, frequent microcracks induced by stress concentration at the fiber ends, and uneven dispersion caused by traditional straight steel fiber reinforcement in existing technologies, the present invention aims to provide ultra-high performance concrete with spherical-end steel fiber reinforcement of zirconia nanoparticles and its preparation method.

[0005] To achieve the above objectives, the technical solution provided by the present invention is as follows: A type of ultra-high performance concrete with spherical-end steel fiber reinforced zirconia nanoparticles, comprising the following components by unit volume mass: Cement 650~700 kg / m 3 ; Silica fume 180~210 kg / m³ 3 ; Quartz sand 1000~1100 kg / m³ 3 ; Quartz powder 270~300 kg / m 3 ; Water 170~190 kg / m 3 ; High-efficiency water-reducing agent 20~25 kg / m 3 ; Zirconia (ZrO2) nanoparticles 5~10 kg / m 3 ; The water-cement ratio is 0.18~0.22, and spherical steel fibers are added, with a volume content of 1%~4%.

[0006] This invention employs a spherical end design for the steel fibers to reduce mechanical entanglement between fibers, effectively lowering the risk of fiber clumping and defect formation. This not only improves the material's pull-out properties but also significantly enhances its workability. Simultaneously, the filling effect of the nano-zirconia particles reduces the water requirement for the hydration reaction, and the "ball effect" of the nano-zirconia particles further improves the slurry rheology, enhances matrix uniformity and encapsulation, making the fibers easier to disperse and less prone to clumping, thus further improving workability.

[0007] Furthermore, the spherical end steel fiber has a fiber diameter of 0.3~0.5 mm, a spherical end diameter of 0.5~0.8 mm, a fiber length of 20~35 mm, and an aspect ratio of 50~75.

[0008] Furthermore, the spherical end steel fiber is a copper-plated steel fiber with a tensile strength of not less than 1180 MPa. The spherical end of the steel fiber significantly enhances the anchoring effect by increasing the contact area with the matrix and forming a mechanical interlocking structure. At the same time, the spherical shape minimizes the stress concentration at the fiber end, reducing the possibility of slippage or local failure.

[0009] Furthermore, the zirconium oxide nanoparticles have an average particle size of 100~150 nm and a purity of ≥99.9%. The zirconium oxide nanoparticles exert a "filling effect," effectively blocking micropores and greatly improving the density of the matrix. At the same time, they serve as hydration nucleation sites, promoting CSH gel formation, accelerating the hydration process, and refining the microstructure.

[0010] Furthermore, the cement is silicate cement with a strength grade of not less than 42.5.

[0011] Furthermore, the average particle size of the silica fume is 100~300 nm.

[0012] Furthermore, the average particle size of the quartz sand is 0.1~0.3 mm.

[0013] Furthermore, the average particle size of the quartz powder is 6~14μm.

[0014] Furthermore, the high-efficiency water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent with a water-reducing efficiency of up to 30%. It has a high water-reducing efficiency, which can improve the working performance of UHPC and the flowability of the mixture, as well as reduce the water-cement ratio, reduce the internal porosity and increase the density of the microstructure, effectively ensuring the excellent mechanical properties and durability of UHPC.

[0015] A high-performance concrete made of zirconia nanoparticles reinforced with spherical-ended steel fibers, comprising the following steps: S1. Pretreatment: Zirconia nanoparticles are premixed with a portion of silica fume and uniformly dispersed to obtain a zirconia-silica fume mixture; S2. Dry mixing: Add cement, remaining silica fume, quartz powder, and quartz sand to the mixer and dry mix until uniform; S3. Wet mixing: Add water and high-efficiency water-reducing agent, and stir until the slurry flows evenly; S4. Incorporation of nano-mixtures: Add the pretreated zirconium oxide-silica fume mixture from S1 to the slurry in S2, and continue stirring; S5. Add fiber: Add spherical steel fiber and stir until the fiber is evenly dispersed.

[0016] Compared with the prior art, the beneficial effects of the present invention are: This invention incorporates spherical-end steel fibers into ultra-high performance concrete. The spherical ends significantly enhance the anchoring effect by increasing the contact area with the matrix and forming a mechanical interlocking structure. During the drawing process, the steel fibers undergo a multi-stage energy-consuming process of "bonding-debonding-mechanical interlocking-final failure," effectively delaying interfacial failure and fully utilizing the fiber strength. Furthermore, the ZrO2 nanoparticles added in this invention exert a "filling effect" during hydration, effectively blocking micropores and increasing matrix density. Simultaneously, the ZrO2 nanoparticles act as hydration nucleation sites, promoting CSH gel formation, accelerating the hydration process, and refining the microstructure. Moreover, the phase transformation (tetragonal phase → monoclinic phase) of the ZrO2 nanoparticles under stress, accompanied by volume expansion, can inhibit microcrack propagation, producing a "phase transformation toughening" effect.

[0017] This invention effectively combines the performance advantages of steel fibers and ZrO2 nanoparticles in concrete. It fully utilizes the inherent toughness and ductility of the spherical-end steel fibers, which form a highly efficient bridging system within the matrix. During crack propagation, the fibers absorb a significant amount of energy through end anchoring and deformation, resulting in excellent bending performance and toughness in the concrete, enabling high energy absorption. Furthermore, this invention incorporates nanoparticles to further strengthen the matrix and optimize stress transfer at the fiber-matrix interface. Specifically, the synergistic effect of the spherical-end steel fibers and zirconium oxide nanoparticles manifests as follows: the zirconium oxide nanoparticles strengthen the matrix through filling and nucleation effects, reducing stress concentration at the fiber ends, while the spherical-end fibers enhance anchoring through mechanical interlocking, jointly improving interfacial bonding strength and stress transfer efficiency. This synergy leads to significant strain hardening behavior in the material before failure, greatly enhancing toughness and energy dissipation capacity, thereby improving the structure's impact and seismic resistance.

[0018] The main innovation of this application lies in the steel fiber end structure and the use of zirconium oxide. It is possible to further explain whether the synergistic effect of the two can be combined to highlight the unexpected effect produced by the combination of the two materials. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a spherical end steel fiber structure; Figure 2 This is a partial schematic diagram of the spherical end steel fiber; Figure 3 (a) Bending strength test; (b) Compressive strength test. Detailed Implementation

[0020] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] Example 1 This embodiment provides an ultra-high performance concrete with spherical-end steel fiber-reinforced zirconia nanoparticles, comprising: The cement used is CEM Type I 52.5R ordinary Portland cement, with a dosage of 670 kg / m³. 3 ; Silica fume, with an average particle size of 200 nm, is used at a rate of 200 kg / m³. 3 ; Quartz powder, with an average particle size of 10 μm, was used at a dosage of 285 kg / m³. 3 ; Quartz sand, with an average particle size of 0.2 mm, is used at a rate of 1020 kg / m³. 3 ; Water, usage: 178 kg / m³ 3 The water-to-binder ratio is 0.20; High-efficiency water-reducing agent, using polycarboxylate-based high-efficiency water-reducing agent, with a water reduction rate of not less than 30%, and a dosage of 20.1 kg / m³. 3 ; Zirconia (ZrO2) nanoparticles, with a purity of 99.9% and an average particle size of 120 nm, were used at a dosage of 6.7 kg / m³. 3 ; Spherical end steel fibers, made of copper-plated steel fibers, fiber diameter D f The diameter of the spherical end is 0.4 mm. D e The fiber thickness is 0.6 mm, the fiber length is 30 mm, the volume fraction is 2%, and the dosage is 157 kg / m². 3 .

[0022] The preparation steps include: S1. Pretreatment: Zirconia nanoparticles are premixed with some silica fume and dispersed for 15 minutes using an ultrasonic disperser at a power of 600 W to ensure uniform dispersion of nanoparticles; S2. Dry mixing: Add cement, remaining silica fume, quartz powder, and quartz sand to a forced mixer and dry mix at low speed (120 r / min) for 3 minutes until uniform; S3. Wet mixing: Add all water and high-efficiency water-reducing agent, increase the speed to 200 r / min, and stir for 5 minutes until the slurry flows evenly; S4. Incorporation of nano-mixtures: Add the pretreated zirconium oxide-silica fume mixture and continue stirring at 200 r / min for 5 minutes; S5. Adding Fiber: Slowly and evenly add the spherical steel fiber, control the rotation speed at 180 r / min, and stir for 10 minutes until the fiber is evenly dispersed and there is no clumping.

[0023] Comparative Example 1 The process in this comparative example is the same as that in Example 1, except that the steel fibers used in this comparative example are conventional steel fibers with a diameter of 0.4 mm and a length of 30 mm, as shown in Table 1 below: Table 1

[0024] Example 2 This embodiment provides an ultra-high performance concrete with spherical-end steel fiber-reinforced zirconia nanoparticles, comprising: The cement used is CEMⅠ type 52.5R grade ordinary Portland cement, with a dosage of 670 kg / m³. 3 ; Silica fume, with an average particle size of 200 nm, is used at a rate of 200 kg / m³. 3 ; Quartz powder, with an average particle size of 10 μm, was used at a dosage of 285 kg / m³. 3 ; Quartz sand, with an average particle size of 0.2 mm, is used at a rate of 1020 kg / m³. 3 ; Water, usage: 178 kg / m³ 3 The water-to-binder ratio is 0.20; High-efficiency water-reducing agent, using polycarboxylate-based high-efficiency water-reducing agent, with a water reduction rate of not less than 30%, and a dosage of 20.1 kg / m³. 3 ; Zirconia (ZrO2) nanoparticles, with a purity of 99.9% and an average particle size of 120 nm, were used at a dosage of 6.7 kg / m³. 3 ; Spherical end steel fibers, made of copper-plated steel fibers, fiber diameter D f The diameter of the spherical end is 0.4 mm. D e The fiber thickness is 0.6 mm, the fiber length is 30 mm, the volume fraction is 1.5%, and the dosage is 118 kg / m². 3 .

[0025] The preparation steps are the same as in Example 1.

[0026] Comparative Example 2 The raw materials used in this comparative example are the same as those in Example 2, except that the steel fibers used are conventional steel fibers with a diameter of 0.4 mm and a length of 30 mm, as shown in Table 2 below: Table 2

[0027] Example 3 This embodiment provides an ultra-high performance concrete reinforced with zirconia nanoparticles, comprising: The cement used is CEM Type I 52.5R ordinary Portland cement, with a dosage of 670 kg / m³. 3 ; Silica fume, with an average particle size of 200 nm, is used at a rate of 200 kg / m³. 3 ; Quartz powder, with an average particle size of 10 μm, was used at a dosage of 285 kg / m³. 3 ; Quartz sand, with an average particle size of 0.2 mm, is used at a rate of 1020 kg / m³. 3 ; Water, usage: 178 kg / m³ 3 The water-to-binder ratio is 0.20; High-efficiency water-reducing agent, using polycarboxylate-based high-efficiency water-reducing agent, with a water reduction rate of not less than 30%, and a dosage of 20.1 kg / m³. 3 ; Zirconia (ZrO2) nanoparticles, with a purity of 99.9% and an average particle size of 120 nm, were used at a dosage of 6.7 kg / m³. 3 .

[0028] Comparative Example 3 The process of this comparative example is the same as that of Example 3, except that zirconium oxide nanoparticles and steel fibers were not added. The specific composition is shown in Table 3 below: Table 3

[0029] The mixtures from the examples and comparative examples were poured into standard molds and vibrated on a vibrating table for 2 minutes to remove air bubbles and compact the material. The surface was then smoothed. The surface was covered with plastic film and cured for 24 hours at 20±2℃ and ≥95% relative humidity before demolding. The concrete was then transferred to a standard curing room (under the same temperature and humidity conditions) for continued curing until 28 days of age. The concrete performance was tested, and the results are shown in Table 4 below. Table 4

[0030] As can be seen from the flexural and compressive strengths of Examples 1 and 2 and Comparative Examples 1 and 2 in Table 4, the ultra-high performance fiber-reinforced concrete made by the formulation of the present invention using spherical end steel fibers and zirconia nanoparticles for synergistic reinforcement is significantly better than the UHPC using straight steel fibers in the comparative examples in terms of flexural and compressive strength.

[0031] As shown in Example 3 and the comparative example, compared with the conventional UHPC without zirconia nanoparticles and steel fibers, the UHPC with zirconia nanoparticles exhibits significant advantages in flexural and compressive strength, indicating that zirconia nanoparticles can enhance the strength of concrete. Compared to Example 3, the UHPC in Comparative Example 1 with both zirconia nanoparticles and steel fibers shows a compressive strength as high as 189 MPa and a flexural strength as high as 20.61 MPa, demonstrating the synergistic strengthening effect of adding spherical-end steel fibers and zirconia nanoparticles on UHPC.

[0032] The mixture of this invention exhibits a slump expansion of over 20%, a plastic viscosity reduction of 30%, and uniform fiber dispersion, effectively preventing clumping and porosity defects, thus improving construction efficiency and molding quality. Compared to traditional steel fiber UHPC materials, this material achieves significant improvements in mechanical properties and energy efficiency at the same fiber content, demonstrating higher performance-to-price ratio and greater potential for engineering applications.

[0033] The ultra-high performance concrete prepared by this invention has ultra-high compressive strength, high tensile strength and excellent toughness. Under the condition of adding 1wt% zirconium oxide nanoparticles and 2% spherical end steel fibers with a volume parameter, the flexural strength is higher than 22MPa, the pull-out energy absorption is higher than 28 N·m, and the excellent deformation performance is far superior to the traditional straight fiber reinforced system.

[0034] Meanwhile, the present invention also has excellent crack resistance and impermeability. The excellent crack resistance is manifested by a significant improvement in the fiber-matrix interface bonding strength. The maximum pull-out force of the spherical end steel fiber is 124% higher than that of the straight fiber, which effectively inhibits crack propagation. Due to the filling and nucleation effect of zirconia nanoparticles, the UHPC material has high matrix density and low porosity, and its impermeability level is much higher than that of P12. It has excellent durability and is suitable for waterproof and protective structures in harsh environments.

[0035] Example 4 This embodiment provides an ultra-high performance concrete with spherical-end steel fiber-reinforced zirconia nanoparticles, comprising: The cement used is CEM Type I 52.5R ordinary Portland cement, with a dosage of 650 kg / m³. 3 ; Silica fume, with an average particle size of 200 nm, was used at a rate of 180 kg / m³. 3 ; Quartz powder, with an average particle size of 10 μm, was used at a rate of 270 kg / m³. 3 ; Quartz sand, with an average particle size of 0.2 mm, is used at a rate of 1000 kg / m³. 3 ; Water, usage: 190 kg / m³ 3 The water-to-binder ratio is 0.22; High-efficiency water-reducing agent, using polycarboxylate-based high-efficiency water-reducing agent, dosage is 20.0 kg / m³. 3 ; Zirconia (ZrO2) nanoparticles, with a purity of 99.9% and an average particle size of 120 nm, were used at a dosage of 5 kg / m³. 3 ; The spherical end steel fiber is made of copper-plated steel fiber with a volume fraction of 1%.

[0036] Example 5 This embodiment provides an ultra-high performance concrete with spherical-end steel fiber-reinforced zirconia nanoparticles, comprising: The cement used is CEM Type I 52.5R grade ordinary Portland cement, with a dosage of 700 kg / m³. 3 ; Silica fume, with an average particle size of 200 nm, was used at a rate of 210 kg / m³. 3 ; Quartz powder, with an average particle size of 10 μm, was used at a dosage of 300 kg / m³. 3 ; Quartz sand, with an average particle size of 0.2 mm, is used at a rate of 1100 kg / m³. 3 ; Water, usage: 170 kg / m³ 3 The water-to-binder ratio is 0.18; High-efficiency water-reducing agent, using polycarboxylate-based high-efficiency water-reducing agent, with a dosage of 25.0 kg / m³. 3 ; Zirconia (ZrO2) nanoparticles with an average particle size of 120 nm were used at a dosage of 10 kg / m³. 3 ; The spherical end steel fiber is made of copper-plated steel fiber with a volume fraction of 4%.

[0037] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A high-performance concrete with spherical-end steel fiber-reinforced zirconia nanoparticles, characterized in that, The component unit volume mass includes cement 650~700 kg / m³ 3 Silica fume 180~210 kg / m³ 3 Quartz sand 1000~1100 kg / m³ 3 Quartz powder 270~300 kg / m 3 Water 170~190 kg / m 3 High-efficiency water-reducing agent 20~25 kg / m 3 Zirconia nanoparticles 5~10 kg / m 3 The water-cement ratio is 0.18~0.22, and spherical end steel fibers are added, with a volume content of 1%~4%.

2. The ultra-high performance concrete with spherical-end steel fiber reinforced zirconia nanoparticles according to claim 1, characterized in that, The spherical end steel fiber has a fiber diameter of 0.3~0.5 mm, a spherical end diameter of 0.5~0.8 mm, a fiber length of 20~35 mm, and an aspect ratio of 50~75.

3. The ultra-high performance concrete with spherical-end steel fiber reinforced zirconia nanoparticles according to claim 1, characterized in that, The spherical end steel fiber is a copper-plated steel fiber.

4. The ultra-high performance concrete with spherical-end steel fiber reinforced zirconia nanoparticles according to claim 1, characterized in that, The average particle size of the zirconium oxide nanoparticles is 100~150 nm.

5. The ultra-high performance concrete with spherical-end steel fiber reinforced zirconia nanoparticles according to claim 1, characterized in that, The cement is silicate cement with a strength grade of not less than 42.

5.

6. The ultra-high performance concrete with spherical-end steel fiber reinforced zirconia nanoparticles according to claim 1, characterized in that, The average particle size of the silica fume is 100~300 nm.

7. The ultra-high performance concrete with spherical-end steel fiber reinforced zirconia nanoparticles according to claim 1, characterized in that, The average particle size of the quartz sand is 0.1~0.3 mm.

8. The ultra-high performance concrete with spherical-end steel fiber reinforced zirconia nanoparticles according to claim 1, characterized in that, The average particle size of the quartz powder is 6~14μm.

9. The ultra-high performance concrete with spherical-end steel fiber reinforced zirconia nanoparticles according to claim 1, characterized in that, The high-efficiency water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent.

10. The ultra-high performance concrete with spherical-end steel fiber reinforced zirconia nanoparticles according to claim 1, characterized in that, The preparation steps include: S1. Pretreatment: Zirconia nanoparticles are premixed with a portion of silica fume and uniformly dispersed to obtain a zirconia-silica fume mixture; S2. Dry mixing: Add cement, remaining silica fume, quartz powder, and quartz sand to the mixer and dry mix until uniform; S3. Wet mixing: Add water and high-efficiency water-reducing agent, and stir until the slurry flows evenly; S4. Incorporation of nano-mixtures: Add the pretreated zirconium oxide-silica fume mixture from S1 to the slurry in S2, and continue stirring; S5. Add fiber: Add spherical steel fiber and stir until the fiber is evenly dispersed.

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