Mixed UHPC (Ultra High Performance Concrete) admixture

Abstract

The invention belongs to the technical field of concrete, and particularly relates to a mixed UHPC admixture. The mixed UHPC admixture is reasonable in design, the modified water reducing agent takes the polycarboxylic acid water reducing agent as a main body substance, and the synergistic effect of hydrophilic groups carboxyl and amino, hydrophobic groups ester groups and polyether side chains contained in the polycarboxylic acid water reducing agent is beneficial to wetting and adsorption of concrete and concrete particle surfaces and relative lubrication of aggregate particles; by quantitatively doping the defoaming agent and the modified lignin, a proper amount of air can be entrained in the concrete, the workability of the concrete is improved, the viscosity of the concrete is reduced, and the slump retaining performance of the concrete is improved by assisting the slump retaining agent. The modified water reducing agent, the slump retaining agent and the defoaming agent have a synergistic effect, the modified water reducing agent reduces the water-binder ratio and improves the flowability, the slump retaining agent keeps the flowability stable, the defoaming agent ensures the microstructure compactness by eliminating bubbles, and finally the comprehensive performance of high strength, high toughness and high durability of UHPC is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of concrete, and particularly relates to a hybrid UHPC admixture. Background Art

[0002] Ultra-High-Performance Concrete (UHPC) is an advanced building material that has shown great application potential and advantages in the field of construction engineering due to its excellent performance characteristics. The following are several main advantages of UHPC: 1) Extremely high strength and durability: The compressive strength of UHPC usually exceeds 150 MPa, and its tensile strength is also much higher than that of ordinary concrete. This enables it to withstand extreme loads and environmental conditions, such as high wind speeds and earthquakes, while showing good durability and extending the service life of the structure. 2) Excellent toughness: Compared with traditional concrete, UHPC has a higher energy absorption capacity, can effectively resist the formation and expansion of cracks, and improves the overall toughness and safety of the structure. 3) High density and low permeability: Due to its dense microstructure, UHPC has an extremely low permeability, can effectively prevent the intrusion of moisture, chemical substances, and gases, thereby protecting the internal steel bars from corrosion and further enhancing the durability of the structure. 4) Potential for lightweight design: Although the raw material density of UHPC may be similar to that of ordinary concrete, due to its high strength, thinner cross-sections or more complex shapes can be used in design, thereby achieving lightweight structures, reducing material usage and transportation costs. 5) Good workability and molding ability: UHPC has a high degree of plasticity and is easy to pour and mold structures with complex shapes, such as the streamlined bridge deck and slender members, which are not only beautiful but also highly functional. 6) Environmentally friendly: During the preparation process of UHPC, by optimizing the mix ratio and using high-performance admixtures, the amount of cement used can be reduced, thereby reducing carbon emissions and meeting the requirements of sustainable development.

[0003] In Ultra-High-Performance Concrete (UHPC), water reducers, slump retainers, and defoamers are key admixtures. Existing admixtures for UHPC are found to have deficiencies when used. The formula designs of their water reducers, slump retainers, and defoamers are not reasonable enough to achieve the comprehensive performance of high strength, high toughness, and high durability of UHPC. Therefore, optimization and improvement are needed. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above problems existing in the traditional technology and provide a hybrid UHPC admixture.

[0005] To achieve the above technical purposes and reach the above technical effects, the present invention is realized through the following technical solutions:

[0006] A hybrid UHPC admixture, which contains the following raw materials in parts by weight:

[0007] 320 - 350 parts of modified water reducer

[0008] 500 - 600 parts of slump retaining agent

[0009] 10 - 20 parts of defoaming agent

[0010] 60 - 100 parts of water.

[0011] Furthermore, the raw materials of the modified water reducer in parts by weight include:

[0012] 6 - 10 parts of amino acid

[0013] 12 - 18 parts of polycarboxylate water reducer

[0014] 6 - 8 parts of melamine

[0015] 8 - 12 parts of lignosulfonate

[0016] 7 - 20 parts of modified lignin.

[0017] Furthermore, the modified lignin is prepared by the following steps: placing corn straw lignin in a vacuum drying oven at 60 °C for sufficient drying; after drying, stirring and dissolving it in a sodium hydroxide solution with a mass fraction of 30 wt%, then adding a 20 wt% pyruvaldehyde solution at room temperature, reacting at 60 °C for 4 h, and cooling the product to room temperature; precipitating the lignin in the product with a 1 mol / L hydrochloric acid solution, then washing it with distilled water until the filtrate is neutral, and drying it in a vacuum drying oven at 60 °C for sufficient drying to obtain the modified lignin.

[0018] Furthermore, the dosage ratio of the pyruvaldehyde solution to the dried lignin is 1 mL:0.4 - 0.6 g.

[0019] Furthermore, after adding the pyruvaldehyde solution, adjust the pH value of the system to 11.4 - 11.6.

[0020] Furthermore, the preparation method of the modified water reducer is as follows:

[0021] S1. Put the modified lignin into a reaction kettle, add amino acid and stir evenly;

[0022] S2. Add lignosulfonate and melamine, and react at a temperature of 65 - 85 °C for 1.5 - 4.5 h;

[0023] S3. Then add polycarboxylate water reducer, raise the temperature to 70 - 90 °C, stir and react for 3 - 6 h. After the reaction is completed, cool to room temperature to obtain the modified water reducer.

[0024] Further, the slump retention agent is the SPT-B2060 slow-release slump retention agent.

[0025] Further, the defoaming agent is a non-ionic polyether defoaming agent.

[0026] The beneficial effects of the present invention are as follows:

[0027] 1. In the present invention, the design of the mixed UHPC admixture is reasonable. The modified water-reducing agent uses polycarboxylate water-reducing agent as the main substance. The synergistic effect of the hydrophilic groups (carboxyl group, amino group), hydrophobic group (ester group) and polyether side chain contained in the polycarboxylate water-reducing agent is conducive to its wetting, adsorption on the surface of concrete and concrete particles, and relative lubrication between aggregate particles. By quantitatively incorporating the defoaming agent and modified lignin, air can be introduced appropriately in the concrete, improving the workability of the concrete and reducing the viscosity of the concrete, and assisting the slump retention agent to improve the slump retention performance of the concrete.

[0028] 2. The slump retention agent of the mixed UHPC admixture in the present invention is reasonably selected, and its main functions are as follows: a) Maintaining slump stability: delaying the hydration rate of cement, preventing the loss of fluidity caused by time lapse or environmental temperature, and ensuring the operability of UHPC in long-distance transportation or complex construction scenarios. b) Adjusting the setting time: through the retarding effect, extending the initial setting and final setting times of UHPC to meet the requirements of mass or continuous pouring.

[0029] 3. The defoaming agent of the mixed UHPC admixture in the present invention is reasonably selected, and its main functions are as follows: a) Eliminating harmful bubbles: destroying the bubble structure generated during the mixing process, reducing the porosity, and avoiding the reduction of the compactness and mechanical properties of UHPC due to bubbles. b) Inhibiting the generation of new bubbles: forming a protective film by reducing the surface tension of the gas-liquid interface to prevent the generation of new bubbles, and further improving the compressive strength and impermeability. c) Optimizing the surface quality: reducing the surface pores of the concrete after forming, and improving the appearance and durability of UHPC components.

[0030] 4. The modified water-reducing agent, slump retention agent and defoaming agent in the present invention have a synergistic effect. The modified water-reducing agent reduces the water-binder ratio and improves the fluidity, the slump retention agent maintains the fluidity stability, and the defoaming agent ensures the denseness of the microstructure by eliminating bubbles, ultimately realizing the comprehensive performance of high strength, high toughness and high durability of UHPC.

[0031] Of course, it is not necessary for any product implementing the present invention to achieve all of the above advantages simultaneously. Detailed implementation mode

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0033] The relevant specific embodiments of the present invention are as follows:

[0034] Example 1

[0035] A hybrid UHPC admixture, which contains the following raw materials in parts by weight:

[0036] 334 parts of modified water reducer

[0037] 571 parts of slump retaining agent

[0038] 15 parts of defoaming agent

[0039] 80 parts of water.

[0040] In this embodiment, the raw materials of the modified water reducer by weight include:

[0041] 8 parts of amino acid

[0042] 14 parts of polycarboxylate water reducer

[0043] 7 parts of melamine

[0044] 10 parts of lignosulfonate

[0045] 14 parts of modified lignin.

[0046] In this embodiment, the modified lignin is prepared by the following steps: placing corn straw lignin in a vacuum drying oven at 60 °C for sufficient drying; after drying, stirring and dissolving it in a sodium hydroxide solution with a mass fraction of 30 wt%, and then adding a 20 wt% pyruvaldehyde solution at room temperature. The dosage ratio of the pyruvaldehyde solution to the dried lignin is 1 mL:0.5 g. After adding the pyruvaldehyde solution, adjust the pH value of the system to 11.5. React at 60 °C for 4 h, and cool the product to room temperature; precipitate the lignin in the product with a 1 mol / L hydrochloric acid solution, and then wash it with distilled water until the filtrate is neutral, and dry it thoroughly in a vacuum drying oven at 60 °C to obtain the modified lignin.

[0047] In this embodiment, the preparation method of the modified water reducer is as follows:

[0048] S1. Put the modified lignin into a reaction kettle, add amino acid and stir evenly;

[0049] S2. Add lignosulfonate and melamine and react at 70 °C for 2 h;

[0050] S3. Then add polycarboxylate superplasticizer and heat up to 80 °C, stir and react for 4 h. After the reaction is completed, cool down to room temperature to obtain the modified superplasticizer.

[0051] In this example, the slump retaining agent is the SPT-B2060 slow-release slump retaining agent.

[0052] In this example, the defoaming agent is a non-ionic polyether defoaming agent.

[0053] Use the hybrid UHPC admixture provided in this example to prepare the UHPC module. The UHPC module consists of the following components: cementitious component, mixing water, recycled fine aggregate, quartz sand, hybrid UHPC admixture, hybrid fiber; among them, the cementitious component accounts for 35 wt%, the recycled fine aggregate accounts for 25 wt%, the quartz sand accounts for 15 wt%, the hybrid UHPC admixture accounts for 1 wt%, and the balance is mixing water.

[0054] The 7-day compressive strength of the UHPC module is shown in Table 1:

[0055] Table 1

[0056]

[0057] The 28-day compressive strength of the UHPC module is shown in Table 2:

[0058] Table 2

[0059]

[0060]

[0061] The 7-day flexural strength of the UHPC module is shown in Table 3:

[0062] Table 3

[0063]

[0064] The 28-day flexural strength of the UHPC module is shown in Table 4:

[0065] Table 4

[0066]

[0067]

[0068] Example 2

[0069] A hybrid UHPC admixture, which contains the following raw materials in parts by weight:

[0070] 300 parts of modified superplasticizer

[0071] 600 parts of slump retaining agent

[0072] 10 parts of defoaming agent

[0073] 100 parts of water.

[0074] In this embodiment, the raw materials of the modified water reducing agent are as follows by weight:

[0075] 6 parts of amino acid

[0076] 18 parts of polycarboxylate water reducing agent

[0077] 6 parts of melamine

[0078] 12 parts of lignosulfonate

[0079] 70 parts of modified lignin.

[0080] In this embodiment, the modified lignin is prepared by the following steps: Place corn straw lignin in a vacuum drying oven at 60 °C for sufficient drying; after drying, stir and dissolve it in a sodium hydroxide solution with a mass fraction of 30 wt%. Then add a 20 wt% methylglyoxal solution at room temperature. The dosage ratio of the methylglyoxal solution to the dried lignin is 1 mL:0.5 g. After adding the methylglyoxal solution, adjust the pH value of the system to 11.5. React at 60 °C for 4 h, and cool the product to room temperature; precipitate the lignin in the product with a 1 mol / L hydrochloric acid solution, and then wash it with distilled water until the filtrate is neutral. Dry it in a vacuum drying oven at 60 °C for sufficient drying to obtain the modified lignin.

[0081] In this embodiment, the preparation method of the modified water reducing agent is as follows:

[0082] S1. Put the modified lignin into a reaction kettle, add amino acid and stir evenly;

[0083] S2. Add lignosulfonate and melamine, and react at 70 °C for 2 h;

[0084] S3. Then add the polycarboxylate water reducing agent, raise the temperature to 80 °C, stir and react for 4 h. After the reaction is completed and cooled to room temperature, the modified water reducing agent is obtained.

[0085] In this embodiment, the slump retaining agent is SPT-B2060 sustained-release slump retaining agent.

[0086] In this embodiment, the defoaming agent is a non-ionic polyether defoaming agent.

[0087] Example 3

[0088] A mixed UHPC admixture, which contains the following raw materials in parts by weight:

[0089] 350 parts of modified water reducer

[0090] 500 parts of slump retaining agent

[0091] 20 parts of defoamer

[0092] 600 parts of water.

[0093] In this embodiment, the raw materials of the modified water reducer by weight include:

[0094] 10 parts of amino acid

[0095] 12 parts of polycarboxylate water reducer

[0096] 8 parts of melamine

[0097] 8 parts of lignosulfonate

[0098] 20 parts of modified lignin.

[0099] In this embodiment, the modified lignin is prepared by the following steps: Place corn straw lignin in a vacuum drying oven at 60 °C for sufficient drying; after drying, stir and dissolve it in a sodium hydroxide solution with a mass fraction of 30 wt%. Then add a 20 wt% pyruvaldehyde solution at room temperature, and the dosage ratio of the pyruvaldehyde solution to the dried lignin is 1 mL: 0.5 g. After adding the pyruvaldehyde solution, adjust the pH value of the system to 11.5. React at 60 °C for 4 h, and cool the product to room temperature; precipitate the lignin in the product with a 1 mol / L hydrochloric acid solution, and then wash it with distilled water until the filtrate is neutral, and dry it thoroughly in a vacuum drying oven at 60 °C to obtain the modified lignin.

[0100] In this embodiment, the preparation method of the modified water reducer is as follows:

[0101] S1. Put the modified lignin into a reaction kettle, add amino acid and stir evenly;

[0102] S2. Add lignosulfonate and melamine and react at 70 °C for 2 h;

[0103] S3. Then add the polycarboxylate water reducer and raise the temperature to 80 °C, stir and react for 4 h. After the reaction is completed, cool it to room temperature to obtain the modified water reducer.

[0104] In this embodiment, the slump retaining agent is the SPT-B2060 slow-release slump retaining agent.

[0105] In this embodiment, the defoamer is a non-ionic polyether defoamer.

[0106] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A hybrid UHPC admixture, characterized in that The hybrid UHPC admixture contains the following raw materials in parts by weight: 320 - 350 parts of modified water reducer 500 - 600 parts of slump retaining agent 10 - 20 parts of defoamer 60 - 100 parts of water.

2. The hybrid UHPC admixture according to claim 1, characterized in that, The raw materials of the modified water reducer in parts by weight include: 6 - 10 parts of amino acid 12 - 18 parts of polycarboxylate water reducer 6 - 8 parts of melamine 8 - 12 parts of lignosulfonate 7 - 20 parts of modified lignin.

3. The hybrid UHPC admixture according to claim 2, wherein The modified lignin is prepared by the following steps: Place corn straw lignin in a vacuum drying oven at 60°C for sufficient drying; after drying, stir and dissolve it in a sodium hydroxide solution with a mass fraction of 30wt%, then add a 20wt% methylglyoxal solution at room temperature, react at 60°C for 4h, and cool the product to room temperature; precipitate the lignin in the product with a 1mol / L hydrochloric acid solution, and then wash it with distilled water until the filtrate is neutral, and place it in a vacuum drying oven at 60°C for sufficient drying to obtain modified lignin.

4. The hybrid UHPC admixture according to claim 3, characterized in that, The dosage ratio of the methylglyoxal solution to the dried lignin is 1mL:0.4 - 0.6g.

5. The hybrid UHPC admixture according to claim 4, characterized in that, After adding the methylglyoxal solution, adjust the pH value of the system to 11.4 - 11.

6.

6. The hybrid UHPC admixture according to claim 4, characterized in that, The preparation method of the modified water reducer is as follows: S1. Put the modified lignin into a reaction kettle, add amino acid and stir evenly; S2. Add lignosulfonate and melamine, and react at a temperature of 65 - 85°C for 1.5 - 4.5h; S3. Then add polycarboxylate water reducer and raise the temperature to 70 - 90°C, stir and react for 3 - 6h. After the reaction is completed, cool to room temperature to obtain the modified water reducer.

7. The hybrid UHPC admixture according to claim 1, characterized in that, The slump retaining agent is SPT - B2060 slow - release slump retaining agent.

8. The hybrid UHPC admixture according to claim 1, characterized in that, The defoamer is a non - ionic polyether defoamer.

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