Aggregate toughened modified ultra-high performance concrete and method of making

Abstract

This invention discloses an aggregate-strengthened and toughened ultra-high performance concrete and its preparation method. The concrete comprises the following components by weight: 600-800 parts silicate cement, 150-250 parts silica fume, 50-200 parts molybdenum slag powder, 1050-1150 parts aggregate, 20-35 parts aggregate surface modifier, 0.1-0.6 parts nano-modifier, 117-234 parts steel fiber, 8-15 parts water-reducing agent, 1-2 parts defoamer, and 150-180 parts water. The preparation process is as follows: the aggregate surface modifier and carbon nanotubes are polymerized and modified on the aggregate surface, then mixed evenly with other dry materials, and then mixed with the remaining raw materials to form a slurry. The slurry is then molded, vibrated, smoothed, and cured to obtain the final product. This concrete, based on the synergistic modification of aggregate surfaces by aggregate surface modifiers and carbon nanotubes, significantly improves the energy absorption and toughness of concrete while ensuring its mechanical strength. It effectively solves the problem of insufficient matrix deformation capacity of ultra-high performance concrete and broadens the application range of ultra-high performance concrete.

Description

Technical Field

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

[0002] Ultra-high performance concrete (UHPC) is the most innovative cement-based material developed in the 1990s. It has extremely high mechanical strength and a dense microstructure, and it has shown great potential in engineering applications with special requirements, such as protective engineering, long-span bridges, and port terminals.

[0003] With the continuous improvement of the mechanical strength of concrete, the probability of brittle failure of high / ultra-high performance concrete matrix is ​​increasing. More significantly, ultra-high strength concrete is basically in the brittle failure mode of bursting, which brings great safety hazards to the service life of concrete structures.

[0004] To address the aforementioned issues, the toughening and brittle reduction of modern ultra-high performance concrete (UHVPC) has become particularly important and has attracted widespread attention from researchers. Current research suggests incorporating flexible particles such as rubber to improve the deformation capacity of cement-based materials; however, it has been found that the incorporation of rubber particles significantly reduces the strength of concrete. Therefore, to balance the contradiction between strength and toughness (or deformation capacity), there is an urgent need to effectively improve the deformation capacity and toughness of UHVPC without significantly reducing its strength, thereby more effectively developing its application potential in specialized engineering projects. Summary of the Invention

[0005] To address the problems of existing technologies, the first objective of this invention is to provide an aggregate-strengthened and toughened ultra-high performance concrete. This concrete is based on the synergistic modification of the aggregate surface by aggregate surface modifiers and carbon nanotubes. While ensuring the mechanical strength of the concrete, it significantly improves the energy absorption effect and flexural toughness of the concrete, effectively solving the problem of insufficient matrix deformation capacity of ultra-high performance concrete and broadening the application range of ultra-high performance concrete.

[0006] The second objective of this invention is to provide a method for preparing aggregate-strengthened and toughened ultra-high performance concrete. This method involves polymerizing and modifying the aggregate surface with a surface modifier and carbon nanotubes, then mixing them evenly with other dry materials to obtain a dry mixture, which is then mixed with the remaining raw materials to form a slurry. The slurry is then molded, vibrated, smoothed, and cured to obtain the final product. This method is simple, easy to implement, requires no additional equipment investment, and is suitable for large-scale industrial production.

[0007] To achieve the above-mentioned technical objectives, the present invention provides an aggregate-strengthened and toughened ultra-high performance concrete, comprising the following components by weight: 600-800 parts of silicate cement, 150-250 parts of silica fume, 50-200 parts of molybdenum slag powder, 1050-1150 parts of aggregate, 20-35 parts of aggregate surface modifier, 0.1-0.6 parts of nano-modifier, 117-234 parts of steel fiber, 8-15 parts of water-reducing agent, 1-2 parts of defoamer, and 150-180 parts of water.

[0008] As a preferred embodiment, the silicate cement is at least one of P·II 42.5, P·II 52.5, P·II 42.5R, and P·II 52.5R.

[0009] As a preferred embodiment, the silica fume has a SiO2 content ≥93wt% and a specific surface area ≥16000m². 2 / kg.

[0010] As a preferred embodiment, the molybdenum slag powder has a D50 particle size ≤ 20 μm and a specific surface area ≥ 500 m². 2 / kg.

[0011] As a preferred embodiment, the aggregate is quartz sand and / or river sand.

[0012] As a preferred embodiment, the aggregate consists of 0.60–1.18 mm quartz sand, 1.18–2.36 mm river sand I, and 2.36–4.75 mm river sand II, with a mass ratio of 0.25–0.30:0.30–0.35:0.35–0.40. The proportions of each component in the aggregate are calculated using a close-packed model. The purpose is to adjust the initial bulk density of the aggregate particles by adjusting the proportions of each component. Combined with a defoamer, this effectively solves the problem of excessive viscosity and difficulty in compaction in ultra-high performance concrete, thereby significantly improving the compactness of the material's microstructure and enhancing the later-stage mechanical strength and toughness of the concrete.

[0013] As a preferred embodiment, the aggregate surface modifier is at least one of epoxy resin emulsion, styrene-butadiene rubber emulsion, and polyacrylate emulsion.

[0014] As a preferred embodiment, the solid content of each emulsion in the aggregate surface modifier is 40-60%.

[0015] The aggregate surface modifier used in this invention is a polymer emulsion. On the one hand, the polymer emulsion has a certain fluidity, which can fully coat the surface of the aggregate particles to form a thin, flexible layer with uniform texture. On the other hand, the polymer emulsion contains a large number of grafting sites, which facilitates subsequent modification of the aggregate.

[0016] As a preferred embodiment, the nanomodifier is a high-purity carboxylated multi-walled carbon nanotube with a purity >98%, an inner diameter of 5–10 nm, an outer diameter of 10–20 nm, a length of 10–30 μm, a carboxyl content of 1.5–3 wt%, and a specific surface area >200,000 m². 2 / kg. This invention uses carboxylated multi-walled carbon nanotubes as a nanomodifier. It can undergo a grafting reaction with the thin flexible layer formed by the carboxyl groups and the aggregate surface modifier, further modifying the aggregate surface at the nanoscale. While enhancing the toughness of concrete, it effectively inhibits the propagation of microcracks generated under stress by changing the interfacial effect of aggregates in concrete, thus solving the technical problem of explosive brittle failure caused by excessive brittleness in ultra-high performance concrete.

[0017] As a preferred embodiment, the steel fiber is a straight, copper-plated microfiber with a diameter of 0.18–0.20 mm and a length of 8–13 mm.

[0018] As a preferred embodiment, the water-reducing agent is a powdered polycarboxylate superplasticizer.

[0019] As a preferred option, the defoamer is a polyether-based high-performance powder defoamer.

[0020] This invention also provides a method for preparing aggregate-strengthened and toughened ultra-high performance concrete. The method involves polymerizing an aggregate surface modifier and a nano-modifier onto the aggregate surface through high-speed stirring to form a film, thus obtaining modified aggregate. The modified aggregate, silicate cement, silica fume, and molybdenum slag powder are thoroughly mixed, and then steel fibers are added to obtain a dry mixture. This dry mixture is then mixed with the water-reducing agent, defoamer, and water to form a slurry. The slurry is then sequentially processed through molding, vibration, finishing, and curing to obtain the final product.

[0021] As a preferred embodiment, the conditions for high-speed stirring are: stirring blade rotation speed of 120-300 r / min and time of 3-10 min.

[0022] Compared with the prior art, the beneficial technical effects of the technical solution of the present invention are as follows:

[0023] 1) The ultra-high performance concrete provided by this invention utilizes the synergistic modification effect of aggregate surface modifiers and carbon nanotubes on the aggregate surface, which significantly improves the energy absorption effect and toughness of concrete while ensuring the mechanical strength of concrete, effectively solving the problem of insufficient matrix deformation capacity of ultra-high performance concrete and broadening the application scope of ultra-high performance concrete.

[0024] 2) In the preparation method provided by the present invention, the aggregate surface modifier and carbon nanotubes are polymerized and modified on the aggregate surface, and then mixed evenly with other dry materials to obtain a dry material mixture. The mixture is then mixed with the remaining raw materials to form a slurry, which is then molded, vibrated, smoothed and cured to obtain the final product. This method is simple, easy to implement, requires no additional equipment investment, and is suitable for large-scale industrial production.

[0025] 3) The technical solution provided by this invention, by adding solid waste materials such as silica fume and molybdenum slag, not only improves the capacity for disposing of solid waste materials and realizes the resource-based treatment of solid waste materials, but also significantly reduces the amount of silicate cement used, thereby achieving the goal of carbon emission reduction. Furthermore, the concrete material prepared by the technical solution of this invention, compared with traditional ultra-high performance concrete, has a 30-50% increase in deformation capacity, and its flexural energy absorption capacity and flexural toughness index are both increased by 15-25%. Attached Figure Description

[0026] Figure 1 The diagrams show the flexural strength test results of the ultra-high performance concrete provided in Embodiment 1 and Comparative Examples 1-4 of this invention.

[0027] Figure 2 The peak deflection test diagrams of the ultra-high performance concrete provided in Embodiment 1 and Comparative Examples 1 to 4 of the present invention are shown.

[0028] Figure 3 These are test diagrams of the bending energy absorption capacity of the ultra-high performance concrete provided in Embodiment 1 and Comparative Examples 1 to 4 of the present invention.

[0029] Figure 4 The diagram shows the flexural toughness index test results of the ultra-high performance concrete provided in Embodiment 1 and Comparative Examples 1 to 4 of this invention. Detailed Implementation

[0030] Numerous specific details are set forth in the following description to provide a full understanding of the invention. However, the invention can be practiced in many other ways different from those described herein, and similar modifications can be made by those skilled in the art without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0032] In the following examples and comparative examples, the silicate cement used was P·II 42.5 cement; the silica fume was Elken 940 grade microsilica powder; the molybdenum slag powder was obtained by grinding molybdenum tailings with a grinding aid; the aggregate surface modifier was a mixture of epoxy resin emulsion, styrene-butadiene latex and polyacrylate emulsion (all with a solid content of 50%) in a mass ratio of 5:5:90; the nanomodifier was commercial high-purity carboxylated multi-walled carbon nanotubes with a purity of 99%, an inner diameter of 5-10 nm, an outer diameter of 10-20 nm, a length of 10-30 μm, and a -COOH content of 2.00 wt%, as well as non-functionalized multi-walled carbon nanotubes of the same size; the steel fiber was copper-plated straight fiber with a diameter of 0.2 mm and a length of 13 mm; the water-reducing agent was SD-600P-S type polycarboxylate superdispersant; and the defoamer was CQ-406 high-performance defoamer.

[0033] Example 1

[0034] The raw material composition per cubic meter of the ultra-high performance concrete provided in this embodiment is shown in Table 1 below, and its specific preparation method includes the following steps:

[0035] S1. Weighing of raw materials: Weigh the corresponding raw materials according to the raw material ratio in Table 1;

[0036] S2. Dry material mixing: Place the aggregate into a mixing pot and dry mix evenly. Then add the aggregate surface modifier and carboxylated carbon nanotubes (Example 1), and stir at high speed for 5 minutes until uniform. Then add P·II 42.5 cement, silica fume and molybdenum slag powder. Next, slowly add steel fibers and dry mix evenly to obtain a dry material mixture with toughened aggregate surface.

[0037] S3. Preparation of fresh concrete: Add a mixed solution of water, water-reducing agent and defoamer to the mixing pot and stir evenly with the dry material mixture to form a slurry;

[0038] S4. Concrete molding: The slurry obtained in step S3 is poured into a 40mm×40mm×160mm mold, then vibrated and smoothed. After the molded surface is covered with a film, it is placed at room temperature (20±1℃) for curing to obtain high-strength ultra-high-performance concrete with strong aggregate interface.

[0039] Comparative Example 1

[0040] The raw material composition per cubic meter of the ultra-high performance concrete provided in this comparative example is shown in Table 2 below. The specific preparation method includes the following steps:

[0041] S1. Weighing of raw materials: Weigh the corresponding raw materials according to the raw material ratios described in Table 2;

[0042] S2. Mixing of dry materials: Put the aggregate into the mixing pot and mix at high speed for 5 minutes until uniform. Then add P·II42.5 cement, silica fume and molybdenum slag powder. Next, slowly add steel fiber and dry mix evenly to obtain a dry material mixture.

[0043] S3. Preparation of fresh concrete: Add a mixed solution of water, water-reducing agent and defoamer to the mixing pot and stir evenly with the dry material mixture to form a slurry;

[0044] S4. Concrete molding: The slurry obtained in step S3 is poured into a 40mm×40mm×160mm mold, then vibrated and smoothed. After the molded surface is covered with plastic film, it is placed at room temperature (20±1℃) for curing to obtain the ultra-high performance concrete of Comparative Example 1.

[0045] Comparative Example 2

[0046] The raw material composition per cubic meter of the ultra-high performance concrete provided in this comparative example is shown in Table 2 below. The specific preparation method includes the following steps:

[0047] S1. Weighing of raw materials: Weigh the corresponding raw materials according to the raw material ratios described in Table 2;

[0048] S2. Dry material mixing: Put the aggregate into the mixing pot and dry mix evenly. Then add the aggregate surface modifier and mix at high speed for 5 minutes until uniform. Then add P·II 42.5 cement, silica fume and molybdenum slag powder. Next, slowly add steel fiber and dry mix evenly to obtain a dry material mixture.

[0049] S3. Preparation of fresh concrete: Add a mixed solution of water, water-reducing agent and defoamer to the mixing pot and stir evenly with the dry material mixture to form a slurry;

[0050] S4. Concrete molding: The slurry obtained in step S3 is poured into a 40mm×40mm×160mm mold, then vibrated and smoothed. After the molded surface is covered with plastic film, it is placed at room temperature (20±1℃) for curing to obtain the ultra-high performance concrete of Comparative Example 2.

[0051] Comparative Example 3

[0052] The raw material composition per cubic meter of the ultra-high performance concrete provided in this comparative example is shown in Table 2 below. The specific preparation method includes the following steps:

[0053] S1. Weighing of raw materials: Weigh the corresponding raw materials according to the raw material ratios described in Table 2;

[0054] S2. Dry material mixing: Put the aggregate into the mixing pot and dry mix evenly. Then add the non-functionalized carbon nanotubes and stir at high speed for 5 minutes until uniform. Then add P·II 42.5 cement, silica fume and molybdenum slag powder. Then slowly add steel fiber and dry mix evenly to obtain a dry material mixture.

[0055] S3. Preparation of fresh concrete: Add a mixed solution of water, water-reducing agent and defoamer to the mixing pot and stir evenly with the dry material mixture to form a slurry;

[0056] S4. Concrete molding: The slurry obtained in step S3 is poured into a 40mm×40mm×160mm mold, then vibrated and smoothed. After the molded surface is covered with plastic film, it is placed at room temperature (20±1℃) for curing to obtain the ultra-high performance concrete of Comparative Example 3.

[0057] Comparative Example 4

[0058] The raw material composition per cubic meter of the ultra-high performance concrete provided in this comparative example is shown in Table 2 below. The specific preparation method includes the following steps:

[0059] S1. Weighing of raw materials: Weigh the corresponding raw materials according to the raw material ratios described in Table 2;

[0060] S2. Dry material mixing: Put the aggregate into the mixing pot and dry mix evenly. Then add carboxylated carbon nanotubes and stir at high speed for 5 minutes until uniform. Then add P·II 42.5 cement, silica fume and molybdenum slag powder. Then slowly add steel fiber and dry mix evenly to obtain a dry material mixture.

[0061] S3. Preparation of fresh concrete: Add a mixed solution of water, water-reducing agent and defoamer to the mixing pot and stir evenly with the dry material mixture to form a slurry;

[0062] S4. Concrete molding: The slurry obtained in step S3 is poured into a 40mm×40mm×160mm mold, then vibrated and smoothed. After the molded surface is covered with plastic film, it is placed at room temperature (20±1℃) for curing to obtain the ultra-high performance concrete of Comparative Example 4.

[0063] Depend on Figures 1-4As can be seen, compared with the ultra-high performance concrete of Comparative Examples 1-4, the ultra-high performance concrete provided in Example 1 of this invention, under the synergistic effect of the aggregate surface modifier and carboxylated carbon nanotubes, effectively forms a polymer flexible film on the aggregate surface. Furthermore, the carboxylated carbon nanotubes not only play a role in bridging microcracks in nanofibers, but also form an interfacial network structure through chemical bonding between the carboxyl groups and the polymer film and hydration products, thereby significantly improving the energy absorption capacity and toughness of the ultra-high performance concrete. Specifically, after treating the aggregate surface, compared with Comparative Example 1, Example 1 can achieve a significant improvement in the deformation capacity, energy absorption capacity, and flexural toughness of ultra-high performance concrete without substantially sacrificing mechanical strength. The deformation capacity is increased by approximately 40%, and the flexural energy absorption and flexural toughness index are both increased by 15-25%. This indicates that the ultra-high performance concrete developed and prepared by this invention has the advantages of high energy absorption and high toughness, overcoming to a certain extent the disadvantage of insufficient matrix deformation capacity in ultra-high performance concrete. Therefore, the ultra-high performance concrete described in this invention shows good engineering application prospects in special engineering projects with large deformation and high crack resistance requirements.

[0064] Table 1 shows the raw material mix proportions per cubic meter of ultra-high performance concrete provided in Example 1 (kg / m³). 3 )

[0065]

[0066] Table 2 shows the raw material mix proportions (kg / m³) of the ultra-high performance concrete provided in Comparative Examples 1-4. 3 )

[0067]

[0068] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0069] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. Those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this invention should be determined by the appended claims.

Claims

1. An aggregate-strengthened and toughened ultra-high performance concrete, characterized in that: The composition includes the following components by weight: 600-800 parts silicate cement, 150-250 parts silica fume, 50-200 parts molybdenum slag powder, 1050-1150 parts aggregate, 20-35 parts aggregate surface modifier, 0.1-0.6 parts nano modifier, 117-234 parts steel fiber, 8-15 parts water-reducing agent, 1-2 parts defoamer, and 150-180 parts water. The aggregate surface modifier is at least one selected from epoxy resin emulsion, styrene-butadiene rubber emulsion, and polyacrylate emulsion; the solid content of each emulsion in the aggregate surface modifier is 40-60%. The nanomodifier is a high-purity carboxylated multi-walled carbon nanotube with a purity >98%, an inner diameter of 5-10 nm, an outer diameter of 10-20 nm, a length of 10-30 μm, a carboxyl content of 1.5-3 wt%, and a specific surface area >200,000 m². 2 / kg.

2. An aggregate-strengthened and toughened ultra-high performance concrete according to claim 1, characterized in that: The silicate cement is at least one of P•II 42.5, P•II 52.5, P•II 42.5R and P•II 52.5R.

3. The aggregate-strengthened and toughened ultra-high performance concrete according to claim 1, characterized in that: The silica fume has an SiO2 content of ≥93wt% and a specific surface area of ​​≥16000 m². 2 / kg.

4. The aggregate-strengthened and toughened ultra-high performance concrete according to claim 1, characterized in that: The molybdenum slag powder D 50 Particle size ≤20μm, specific surface area ≥500m² 2 / kg; the aggregate is quartz sand and / or river sand.

5. An aggregate-strengthened and toughened ultra-high performance concrete according to claim 1 or 4, characterized in that: The aggregate consists of 0.60~1.18mm quartz sand, 1.18~2.36mm river sand I and 2.36~4.75mm river sand II, with a mass ratio of 0.25~0.30:0.30~0.35:0.35~0.

40.

6. The aggregate-strengthened and toughened ultra-high performance concrete according to claim 1, characterized in that: The steel fiber is a straight, copper-plated fine steel fiber with a diameter of 0.18~0.20mm and a length of 8~13mm; the water-reducing agent is a powdered polycarboxylate superplasticizer; and the defoamer is a polyether-based high-performance powdered defoamer.

7. A method for preparing aggregate-strengthened and toughened ultra-high performance concrete according to any one of claims 1 to 6, characterized in that: The aggregate surface modifier and nano-modifier are polymerized on the aggregate surface to form a film by high-speed stirring, thus obtaining modified aggregate; Modified aggregate, silicate cement, silica fume, and molybdenum slag powder are thoroughly mixed and then steel fibers are added to obtain a dry material mixture. The dry material mixture is then mixed with the water-reducing agent, defoamer, and water to form a slurry. The slurry is then subjected to molding, vibration, finishing, and curing in sequence to obtain the final product.

8. The method for preparing aggregate-strengthened and toughened ultra-high performance concrete according to claim 7, characterized in that: The conditions for high-speed stirring are: stirring blade rotation speed of 120~300 r / min, and time of 3~10 min.

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