Ultra-high performance concrete and method for producing the same

Abstract

This invention relates to the field of concrete technology and proposes an ultra-high performance concrete and its preparation method. An ultra-high performance concrete comprises the following raw materials in parts by weight: 70-80 parts silicate cement, 15-25 parts silica fume, 5-10 parts limestone, 2-5 parts metakaolin, 100-120 parts quartz sand, 24-42 parts hydroxylated steel fiber, 6-24 parts carboxylated nitrile latex, 2.0-3.5 parts water-reducing agent, and 15-22 parts water. This technical solution solves the problem of poor chloride ion penetration resistance in existing ultra-high performance concrete.

Description

Technical Field

[0001] This invention relates to the field of concrete technology, specifically to an ultra-high performance concrete and its preparation method. Background Technology

[0002] Ultra-high performance concrete (UHPC), with its extremely low water-cement ratio and excellent mechanical properties, has broad application prospects in harsh and corrosive environments such as marine engineering and construction in saline-alkali soil areas. However, chloride ion penetration-induced steel fiber corrosion and matrix deterioration are core technical issues restricting its long-term service stability. Chloride ions, as a highly corrosive medium, can penetrate to the surface of steel fibers through pores and cracks within the concrete, damaging the passivation film and initiating electrochemical corrosion. This leads to a decline in the mechanical properties of the steel fibers, matrix cracking, and ultimately, a shortened structural service life.

[0003] To address these issues, existing technologies often add modifiers such as organic latex. However, due to the lack of active groups on the surface of steel fibers, the interfacial adhesion between commonly used organic latex and the steel fiber surface is weak, preventing them from adhering tightly to the steel fiber surface. They can only physically fill some pores in the concrete matrix and cannot form a chemical bond with the steel fiber. During service, this easily leads to the delamination of the commonly used organic latex from the steel fiber and cement matrix. After delamination, not only is the original anti-permeability function lost, but new pores and cracks are also formed at the delamination site, further aggravating chloride ion penetration. Therefore, there is an urgent need for an ultra-high performance concrete with chloride ion penetration resistance. Summary of the Invention

[0004] This invention proposes an ultra-high performance concrete and its preparation method, which solves the problem of poor chloride ion permeability resistance of ultra-high performance concrete in related technologies.

[0005] The technical solution of the present invention is as follows:

[0006] This invention proposes an ultra-high performance concrete comprising the following raw materials in parts by weight: 70-80 parts silicate cement, 15-25 parts silica fume, 5-10 parts limestone, 2-5 parts metakaolin, 100-120 parts quartz sand, 24-42 parts hydroxylated steel fiber, 6-24 parts carboxylated nitrile latex, 2.0-3.5 parts water-reducing agent, and 15-22 parts water.

[0007] As a further technical solution, the hydroxylated steel fiber is obtained by treating steel fiber with an alkaline solution.

[0008] As a further technical solution, the concentration of the alkaline solution is 15wt%~20wt%;

[0009] As a further technical solution, the processing time is 0.5~1h.

[0010] As a further technical solution, the alkaline solution includes sodium hydroxide solution and / or sodium carbonate solution.

[0011] As a further technical solution, the mass ratio of the hydroxylated steel fiber to the carboxylated nitrile latex is 7:3~5.

[0012] As a further technical solution, the hydroxylated steel fibers are modified; the modification process includes the following steps:

[0013] A1. Disperse the silane coupling agent in a solvent, add nano-silica, stir, and obtain the modified solution;

[0014] A2. Disperse the hydroxylated steel fibers in the modified liquid, stir twice, and dry to obtain modified steel fibers.

[0015] As a further technical solution, the mass-to-volume ratio of the silane coupling agent to the solvent is 8:100;

[0016] The solvent consists of anhydrous ethanol and water in a mass ratio of 3:1.

[0017] As a further technical solution, the mass ratio of the silane coupling agent to nano-silica is 8~12:1.

[0018] As a further technical solution, in step A1, the stirring temperature is 70~85℃.

[0019] In this invention, the chloride ion penetration resistance of ultra-high performance concrete is further improved by modifying hydroxylated steel fibers with nano-silica and silane coupling agents. Specifically, the reaction between the silane coupling agent and nano-silica enhances the dispersibility of the nano-silica. The silane coupling agent also forms a silane coating on the steel fiber surface. The uniformly dispersed nano-silica fills the pores of the coating, improving its density and roughness. The roughened coating film strengthens the bond with the substrate through physical interlocking, reducing penetration channels caused by interfacial gaps. Simultaneously, the nano-silica in the coating film can participate in the cement hydration reaction, converting loose Ca(OH)2 near the fibers into dense CSH gel, reducing the porosity of the interfacial transition zone and decreasing chloride ion diffusion channels.

[0020] As a further technical solution, the ultra-high performance concrete also includes the following raw materials in parts by weight: 1.5 to 3.0 parts of redispersible latex powder, 0.1 to 0.3 parts of defoamer, and 1 to 3 parts of expansion agent.

[0021] As a further technical solution, the steel fiber includes any one of the following: end-hooked steel fiber, milled steel fiber, and sheared corrugated steel fiber;

[0022] Preferably, the steel fiber is a hook-shaped steel fiber.

[0023] As a further technical solution, the water-reducing agent includes any one of naphthalene sulfonate water-reducing agent, aminosulfonate water-reducing agent and polycarboxylate water-reducing agent;

[0024] Preferably, the water-reducing agent is a polycarboxylate-based water-reducing agent.

[0025] As a further technical solution, the defoamer includes any one of polyether defoamer and silicone defoamer;

[0026] Preferably, the defoamer includes a polyether defoamer.

[0027] As a further technical solution, the polyether defoamer includes one or more of polyether L-61, polyether L-64, and polyether F-68;

[0028] Preferably, the polyether defoamer is a mixture of polyether L-64 and polyether F-68 in a mass ratio of 1:1.

[0029] In this invention, polyether L-64 and polyether F-68 are used together as defoamers. Both belong to the polyether class of defoamers. Polyether L-64 contains ethylene oxide and propylene oxide segments in its molecular structure, which have low surface tension. After rapidly migrating to the surface of bubbles, it can destroy the surface film of the bubbles due to its low surface tension, causing the bubbles to rupture. Polyether F-68 has high hydrophilicity and wettability, which can reduce the interfacial tension between bubbles and concrete paste, making bubbles easier to disperse and merge with other bubbles, thereby accelerating the escape of bubbles. The combination of the two can effectively eliminate bubbles in concrete, improve the density of concrete, and hinder chloride ion penetration.

[0030] As a further technical solution, the expanding agent includes any one of calcium oxide expanding agents, calcium sulfoaluminate expanding agents, and magnesium oxide expanding agents;

[0031] Preferably, the expanding agent is a calcium sulfoaluminate expanding agent.

[0032] In this invention, when the expansive agent is a calcium sulfoaluminate-based expansive agent, one of the main components of the calcium sulfoaluminate-based expansive agent is anhydrous calcium sulfoaluminate. During the hydration process of ultra-high performance concrete, anhydrous calcium sulfoaluminate reacts with calcium hydroxide produced by cement hydration and water to form ettringite. Tettringite is a needle-shaped or rod-shaped crystal, and its formation process is accompanied by significant volume expansion. It can fill the pores and capillaries inside the concrete caused by cement hydration, making the concrete structure more compact. At the same time, it can compensate for the volume shrinkage of the concrete during the hardening process and prevent the concrete from cracking.

[0033] This invention also proposes a method for preparing ultra-high performance concrete, comprising the following steps:

[0034] S1. A dry mixture is obtained by mixing silicate cement, silica fume, limestone, metakaolin, quartz sand, and hydroxylated steel fibers.

[0035] S2. Mix the dry material mixture with the remaining raw materials to obtain a slurry, and spray the slurry onto the sprayed surface to obtain the ultra-high performance concrete.

[0036] The working principle and beneficial effects of this invention are as follows:

[0037] In this invention, the resistance of ultra-high performance concrete to chloride ion penetration is improved by combining hydroxylated steel fibers with carboxylated nitrile butadiene latex. Specifically, the hydroxyl groups on the surface of the steel fibers interact with the carboxyl and cyano groups in the carboxylated nitrile butadiene latex, enhancing its adhesion to the latex. This allows the latex to adhere tightly to the steel fiber surface, filling the pores between interfaces, increasing the microstructure density of the concrete, reducing porosity and cracks, thereby reducing chloride ion penetration channels and improving the resistance of ultra-high performance concrete to chloride ion penetration. Detailed Implementation

[0038] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0039] In the following examples and comparative examples, the silicate cement was grade 52.5R; the D50 of silica fume was 0.2 μm; the D50 of limestone was 5 μm; the D50 of metakaolin was 3 μm; the D50 of quartz sand was 0.2 mm; the steel fiber was an end-hooked steel fiber with an average length of 30 mm and a diameter of 0.2 mm; the redispersible latex powder was grade 5010N; the polycarboxylate superplasticizer was grade PCE-750; the carboxylated nitrile butadiene latex was grade SH-820; the carboxylated styrene-butadiene latex was grade SD623; the average solid content of the nitrile butadiene latex was 44 wt%, and the test conditions were 130℃ / 30 min.

[0040] Example 1

[0041] An ultra-high performance concrete comprises the following raw materials in parts by weight: 70 parts silicate cement, 15 parts silica fume, 5 parts limestone, 2 parts metakaolin, 100 parts quartz sand, 33.6 parts hydroxylated steel fiber, 14.4 parts carboxylated nitrile latex, 2 parts polycarboxylate superplasticizer, 15 parts water, 1.5 parts redispersible latex powder, 0.05 parts polyether L-64, 0.05 parts polyether F-68, and 1 part calcium sulfoaluminate expansive agent;

[0042] The preparation method of hydroxylated steel fibers includes the following steps:

[0043] The steel fibers were soaked in a 15 wt% sodium hydroxide solution for 1 hour, washed, and dried to obtain hydroxylated steel fibers.

[0044] A method for preparing ultra-high performance concrete includes the following steps:

[0045] S1. After mixing silicate cement, silica fume, limestone, metakaolin, quartz sand, and hydroxylated steel fibers, a dry mixture is obtained.

[0046] S2. Mix the dry material mixture with the remaining raw materials to obtain a slurry. Spray the slurry onto the surface to be sprayed to obtain ultra-high performance concrete.

[0047] Example 2

[0048] An ultra-high performance concrete comprises the following raw materials in parts by weight: 80 parts silicate cement, 25 parts silica fume, 10 parts limestone, 5 parts metakaolin, 120 parts quartz sand, 33.6 parts hydroxylated steel fiber, 14.4 parts carboxylated nitrile latex, 3.5 parts polycarboxylate superplasticizer, 22 parts water, 3.0 parts redispersible latex powder, 0.15 parts polyether L-64, 0.15 parts polyether F-68, and 3 parts calcium sulfoaluminate expansive agent;

[0049] The preparation method of hydroxylated steel fibers includes the following steps:

[0050] The steel fibers were soaked in a 20 wt% sodium hydroxide solution for 0.5 h, washed, and dried to obtain hydroxylated steel fibers.

[0051] A method for preparing ultra-high performance concrete includes the following steps:

[0052] S1. A dry mixture is obtained by mixing silicate cement, silica fume, limestone, metakaolin, quartz sand, and hydroxylated steel fibers.

[0053] S2. Mix the dry material mixture with the remaining raw materials to obtain a slurry. Spray the slurry onto the surface to be sprayed to obtain ultra-high performance concrete.

[0054] Example 3

[0055] An ultra-high performance concrete comprises the following raw materials in parts by weight: 75 parts silicate cement, 20 parts silica fume, 8 parts limestone, 4 parts metakaolin, 110 parts quartz sand, 33.6 parts hydroxylated steel fiber, 14.4 parts carboxylated nitrile latex, 3 parts polycarboxylate superplasticizer, 20 parts water, 2 parts redispersible latex powder, 0.1 parts polyether L-64, 0.1 parts polyether F-68, and 2 parts calcium sulfoaluminate expansive agent;

[0056] The preparation method of hydroxylated steel fibers includes the following steps:

[0057] The steel fibers were soaked in a 18 wt% sodium hydroxide solution for 0.8 h, washed, and dried to obtain hydroxylated steel fibers.

[0058] A method for preparing ultra-high performance concrete includes the following steps:

[0059] S1. A dry mixture is obtained by mixing silicate cement, silica fume, limestone, metakaolin, quartz sand, and hydroxylated steel fibers.

[0060] S2. Mix the dry material mixture with the remaining raw materials to obtain a slurry. Spray the slurry onto the surface to be sprayed to obtain ultra-high performance concrete.

[0061] Example 4

[0062] The difference between this embodiment and Embodiment 1 lies only in the ultra-high performance concrete, which includes the following raw materials in parts by weight: 70 parts silicate cement, 15 parts silica fume, 5 parts limestone, 2 parts metakaolin, 100 parts quartz sand, 28 parts hydroxylated steel fiber, 20 parts carboxylated nitrile latex, 2 parts polycarboxylate superplasticizer, 15 parts water, 1.5 parts redispersible latex powder, 0.05 parts polyether L-64, 0.05 parts polyether F-68, and 1 part calcium sulfoaluminate expansive agent.

[0063] Example 5

[0064] The difference between this embodiment and Embodiment 1 lies only in the ultra-high performance concrete, which includes the following raw materials in parts by weight: 70 parts silicate cement, 15 parts silica fume, 5 parts limestone, 2 parts metakaolin, 100 parts quartz sand, 42 parts hydroxylated steel fiber, 6 parts carboxylated nitrile latex, 2 parts polycarboxylate superplasticizer, 15 parts water, 1.5 parts redispersible latex powder, 0.05 parts polyether L-64, 0.05 parts polyether F-68, and 1 part calcium sulfoaluminate expansive agent.

[0065] Example 6

[0066] The difference between this embodiment and Embodiment 1 lies only in the ultra-high performance concrete, which includes the following raw materials in parts by weight: 70 parts silicate cement, 15 parts silica fume, 5 parts limestone, 2 parts metakaolin, 100 parts quartz sand, 24 parts hydroxylated steel fiber, 24 parts carboxylated nitrile latex, 2 parts polycarboxylate superplasticizer, 15 parts water, 1.5 parts redispersible latex powder, 0.05 parts polyether L-64, 0.05 parts polyether F-68, and 1 part calcium sulfoaluminate expansive agent.

[0067] Example 7

[0068] The only difference between this embodiment and Embodiment 1 is that the hydroxylated steel fibers are replaced with an equal amount of modified hydroxylated steel fibers; the preparation method of the modified hydroxylated steel fibers includes the following steps:

[0069] A0. Soak steel fibers in a 15wt% sodium hydroxide solution for 1 hour, wash, and dry to obtain hydroxylated steel fibers.

[0070] A1. Disperse silane coupling agent KH-550 in a mixed solvent, add nano-silica, and stir at 70°C to obtain a modified solution. The mass ratio of silane coupling agent KH-550 to mixed solvent is 8:100. The mixed solvent is composed of anhydrous ethanol and water in a mass ratio of 3:1. The mass ratio of silane coupling agent to nano-silica is 8:1.

[0071] A2. Immerse and disperse the hydroxylated steel fibers in the modification solution, stir twice, and dry at 120°C to obtain the modified hydroxylated steel fibers.

[0072] Example 8

[0073] The only difference between this embodiment and Embodiment 1 is that the hydroxylated steel fibers are replaced with an equal amount of modified hydroxylated steel fibers; the preparation method of the modified hydroxylated steel fibers includes the following steps:

[0074] A0. Soak steel fibers in a 15wt% sodium hydroxide solution for 1 hour, wash, and dry to obtain hydroxylated steel fibers.

[0075] A1. Disperse silane coupling agent KH-550 in a mixed solvent, add nano-silica, and stir at 85°C to obtain a modified solution. The mass ratio of silane coupling agent KH-550 to mixed solvent is 8:100. The mixed solvent is composed of anhydrous ethanol and water in a mass ratio of 3:1. The mass ratio of silane coupling agent to nano-silica is 12:1.

[0076] A2. Immerse and disperse the hydroxylated steel fibers in the modification solution, stir twice, and dry at 120°C to obtain the modified hydroxylated steel fibers.

[0077] Comparative Example 1

[0078] The only difference between this comparative example and Example 1 is that it is an ultra-high performance concrete, comprising the following raw materials in parts by weight: 70 parts silicate cement, 15 parts silica fume, 5 parts limestone, 2 parts metakaolin, 100 parts quartz sand, 33.6 parts steel fiber, 14.4 parts carboxylated nitrile latex, 2 parts polycarboxylate superplasticizer, 15 parts water, 1.5 parts redispersible latex powder, 0.05 parts polyether L-64, 0.05 parts polyether F-68, and 1 part calcium sulfoaluminate expansive agent.

[0079] Comparative Example 2

[0080] The only difference between this comparative example and Example 1 is that it is an ultra-high performance concrete, comprising the following raw materials in parts by weight: 70 parts silicate cement, 15 parts silica fume, 5 parts limestone, 2 parts metakaolin, 100 parts quartz sand, 33.6 parts hydroxylated steel fiber, 14.4 parts carboxylated styrene-butadiene latex, 2 parts polycarboxylate superplasticizer, 15 parts water, 1.5 parts redispersible latex powder, 0.05 parts polyether L-64, 0.05 parts polyether F-68, and 1 part calcium sulfoaluminate expansive agent.

[0081] Comparative Example 3

[0082] The only difference between this comparative example and Example 1 is that it is an ultra-high performance concrete, comprising the following raw materials in parts by weight: 70 parts silicate cement, 15 parts silica fume, 5 parts limestone, 2 parts metakaolin, 100 parts quartz sand, 33.6 parts hydroxylated steel fiber, 14.4 parts nitrile latex, 2 parts polycarboxylate superplasticizer, 15 parts water, 1.5 parts redispersible latex powder, 0.05 parts polyether L-64, 0.05 parts polyether F-68, and 1 part calcium sulfoaluminate expansive agent.

[0083] Comparative Example 4

[0084] The only difference between this comparative example and Example 1 is that it is an ultra-high performance concrete, comprising the following raw materials in parts by weight: 70 parts silicate cement, 15 parts silica fume, 5 parts limestone, 2 parts metakaolin, 100 parts quartz sand, 48 parts hydroxylated steel fiber, 2 parts polycarboxylate superplasticizer, 15 parts water, 1.5 parts redispersible latex powder, 0.05 parts polyether L-64, 0.05 parts polyether F-68, and 1 part calcium sulfoaluminate expansive agent.

[0085] Experimental Example 1

[0086] Chloride ion penetration resistance test: The slurries prepared in Examples 1-8 and Comparative Examples 1-4 were sprayed into 100mm×100mm×100mm molds. The chloride ion penetration resistance of the specimens was tested according to the Rapid Chloride Ion Migration Coefficient Method (RCM Method) in GB / T 50082-2024 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete". The specimen size was 100mm×100mm×50mm. The chloride ion migration coefficient was tested. The test results are shown in Table 1.

[0087] Table 1 Results of chloride ion permeability test

[0088]

[0089] By comparing the data from Examples 1-8 and Comparative Examples 1-4, the chloride ion migration coefficient of the ultra-high performance concrete prepared in Examples 1-8 was lower than that in Comparative Examples 1-4. This indicates that the use of hydroxylated steel fibers and carboxylated nitrile latex in combination improved the chloride ion penetration resistance of the ultra-high performance concrete. By comparing the data from Examples 1 and Examples 4-6, Examples 1 and 4 further improved the chloride ion penetration resistance of the ultra-high performance concrete by optimizing the mass ratio of hydroxylated steel fibers to carboxylated nitrile latex to 7:3-5.

[0090] By comparing the data from Examples 1-3 and Examples 7-8, the chloride ion migration coefficient of the ultra-high performance concrete prepared in Examples 7-8 was smaller than that in Examples 1-3. This indicates that further modification of hydroxylated steel fibers with silica and silane coupling agents improved the chloride ion penetration resistance of the ultra-high performance concrete.

[0091] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A type of ultra-high performance concrete, characterized in that, The raw materials include the following parts by weight: 70-80 parts silicate cement, 15-25 parts silica fume, 5-10 parts limestone, 2-5 parts metakaolin, 100-120 parts quartz sand, 24-42 parts hydroxylated steel fiber, 6-24 parts carboxylated nitrile latex, 2.0-3.5 parts water-reducing agent, 15-22 parts water, 1.5-3.0 parts redispersible latex powder, 0.1-0.3 parts defoamer, and 1-3 parts expanding agent.

2. The ultra-high performance concrete according to claim 1, characterized in that, The hydroxylated steel fiber is obtained by treating steel fiber with an alkaline solution.

3. The ultra-high performance concrete according to claim 2, characterized in that, The concentration of the alkaline solution is 15wt%~20wt%.

4. The ultra-high performance concrete according to claim 1, characterized in that, The mass ratio of the hydroxylated steel fiber to the carboxylated butadiene nitrile latex is 7:3~5.

5. The ultra-high performance concrete according to claim 1, characterized in that, The hydroxylated steel fibers are modified; the modification process includes the following steps: A1. Disperse the silane coupling agent in a solvent, add nano-silica, stir, and obtain the modified solution; A2. Disperse the hydroxylated steel fibers in the modified liquid, stir twice, and dry to obtain modified steel fibers.

6. The ultra-high performance concrete according to claim 5, characterized in that, The mass ratio of the silane coupling agent to nano-silica is 8~12:

1.

7. The ultra-high performance concrete according to claim 5, characterized in that, In step A1, the stirring temperature is 70~85℃.

8. The ultra-high performance concrete according to claim 1, characterized in that, The steel fibers include any one of the following: end-hooked steel fibers, milled steel fibers, and sheared corrugated steel fibers; The water-reducing agent includes any one of naphthalene sulfonate water-reducing agents, aminosulfonate water-reducing agents, and polycarboxylate water-reducing agents; The defoamer includes either polyether defoamer or silicone defoamer; The expanding agent includes any one of calcium oxide expanding agents, calcium sulfoaluminate expanding agents, and magnesium oxide expanding agents.

9. A method for preparing ultra-high performance concrete, used to prepare the ultra-high performance concrete according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1. After mixing silicate cement, silica fume, limestone, metakaolin, quartz sand, and hydroxylated steel fibers, a dry mixture is obtained. S2. Mix the dry material mixture with the remaining raw materials to obtain a slurry, and spray the slurry onto the sprayed surface to obtain the ultra-high performance concrete.

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