Underwater concrete preparation method based on high-mud-powder-content machine-made sand and underwater concrete

Abstract

The invention discloses a preparation method of underwater concrete based on high-mud-powder-content machine-made sand and the underwater concrete. The preparation method comprises the steps that the machine-made sand is washed with water; weighing each raw material in the concrete, wherein sand in the concrete is water-washed machine-made sand; respectively mixing solid and liquid in the raw materials to obtain a mixture A and a mixed solution B; and adding the mixed solution B into the mixture A, and uniformly stirring to obtain the underwater concrete. The underwater concrete comprises cement, fly ash, mineral powder, machine-made sand, stones, water and an additive, the machine-made sand is water-washed machine-made sand, the mass content of sandstone powder in the water-washed machine-made sand is smaller than or equal to 5%, and the mass content of a flocculating agent is larger than or equal to 0.02%. According to the method, the residual flocculant in the washed machine-made sand is used for replacing an anti-dispersing agent to prepare the underwater concrete, so that the problem that the high-mud-content machine-made sand cannot be applied is solved, the problem that the working performance of the concrete is influenced due to the fact that the flocculant adsorbs an additive is also solved, the workability of the concrete is improved, and the hydration heat of the concrete is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of concrete materials, and in particular to a method for preparing underwater concrete based on machine-made sand with high mud powder content and underwater concrete. Background Art

[0002] As a substitute for natural sand, machine-made sand has been widely used in concrete production. However, a large amount of mud powder will be produced during the production process of machine-made sand, which not only increases the mud block content and mud content of machine-made sand, but also has an adverse effect on the performance of concrete. The presence of mud powder will adsorb admixtures in concrete (such as water reducers, air entraining agents, etc.), resulting in a significant decrease in the working performance (such as fluidity, slump, etc.) and mechanical properties (such as strength, durability, etc.) of concrete. In order to solve this problem, the traditional method usually uses a water washing process to remove the mud powder in sand and gravel aggregates, and adds flocculants during the water washing process to adsorb the mud powder. However, some flocculants will remain on the surface of sand and gravel aggregates, resulting in increased viscosity of concrete, poor construction performance, and even affecting the final strength of concrete. Therefore, in the context of the shortage of sand and gravel aggregate resources, how to efficiently utilize high-mud content machine-made sand has become a key issue that needs to be urgently solved in the concrete industry.

[0003] At the same time, with the acceleration of urbanization, the development and utilization of urban underground space has become increasingly extensive, and underground construction projects such as bored piles and underground continuous walls have become an important part of infrastructure construction. These projects usually require concrete pouring in an underwater environment, and the performance of underwater concrete is directly related to the quality and safety of the project. In order to ensure the anti-dispersion, fluidity and compactness of underwater concrete in water, it is usually necessary to add anti-dispersants. Anti-dispersants can effectively prevent segregation and dispersion of concrete during underwater pouring, thereby improving the molding quality and durability of concrete. However, traditional underwater concrete has high requirements for raw materials, especially strict restrictions on the mud content of sand and gravel aggregates, which further aggravates the application difficulties of high-mud content machine-made sand. Summary of the invention

[0004] In view of the defects existing in the prior art, the present application provides a method for preparing underwater concrete based on machine-made sand with high mud powder content and underwater concrete.

[0005] In order to achieve the purpose of the above invention, the technical solution provided by the present invention is as follows:

[0006] A method for preparing underwater concrete based on high mud powder content machine-made sand, comprising the following steps:

[0007] S1. Wash the machine-made sand until the mass content of sand and stone powder in the washed machine-made sand is ≤5% and the mass content of flocculant is ≥0.2‰;

[0008] S2. Weigh 160 - 180 parts of cement, 120 - 130 parts of fly ash, 120 - 130 parts of slag powder, 700 - 800 parts of washed machine-made sand obtained from S1, 950 - 1050 parts of gravel, 155 - 165 parts of water, and 4 - 6 parts of admixture by weight;

[0009] S3. Mix the cement, fly ash, slag powder, washed machine-made sand, and gravel evenly to obtain mixture A, and stir the water and admixture evenly to obtain mixed solution B;

[0010] S4. Add mixed solution B to mixture A and stir evenly to prepare underwater concrete.

[0011] In one embodiment, a wheel-type sand washer is selected as the equipment for washing machine-made sand in S1, water is selected as the washing medium, and polyacrylamide flocculant is selected as the washing solvent to wash the machine-made sand.

[0012] In one embodiment, in S3, mixture A is obtained after mixing the cement, fly ash, slag powder, washed machine-made sand, and gravel for one minute, and in S4, underwater concrete is prepared after adding mixed solution B to mixture A and stirring for three minutes.

[0013] In one embodiment, the cement is P.O 42.5 cement; the fly ash is grade II ash with a 28-day activity index ≥ 70%; the slag powder is S95 slag powder with a 28-day activity index ≥ 95%; the gravel is 5 - 25 mm natural crushed stone with an apparent density ≥ 2600 kg / m 3 , and the crushing value index ≤ 20%.

[0014] In one embodiment, the admixture is a high-performance polycarboxylate admixture with a water reduction rate > 25%.

[0015] This application also provides an underwater concrete, which includes 160 - 180 parts of cement, 120 - 130 parts of fly ash, 120 - 130 parts of slag powder, 700 - 800 parts of machine-made sand, 950 - 1050 parts of gravel, 155 - 165 parts of water, and 4 - 6 parts of admixture. The machine-made sand is washed machine-made sand, and the mass content of sand powder in the washed machine-made sand ≤ 5%, and the mass content of flocculant ≥ 0.2‰.

[0016] In one embodiment, the cement is P.O 42.5 cement; the fly ash is grade II ash with a 28-day activity index ≥ 70%; the slag powder is S95 slag powder with a 28-day activity index ≥ 95%; the gravel is 5 - 25 mm natural crushed stone with an apparent density ≥ 2600 kg / m3 and a crushing value index ≤ 20%.

[0017] In one embodiment, the admixture is a high-performance polycarboxylate admixture with a water reduction rate > 25%.

[0018] Compared with the prior art, the present application has at least the following beneficial effects:

[0019] 1. The invention effectively utilizes the residual flocculant in manufactured sand to replace the anti-dispersant for preparing underwater concrete, which not only solves the problem that manufactured sand with high mud content cannot be applied, but also solves the problem that the flocculant adsorbs admixtures and affects the workability of concrete. It not only turns waste into treasure for manufactured sand with high mud content and finds a reasonable application scenario, but also resolves the negative effects brought by the flocculant. At present, with the increasingly shortage of sand and gravel resources, the efficient utilization of this kind of washed manufactured sand with high flocculant content greatly expands the available sand sources, contributing a feasible solution to alleviating the tension of sand and gravel resources and ensuring the stable supply of building materials;

[0020] 2. The present application enables the residual flocculant in washed manufactured sand to cooperate with a large amount of mineral admixtures to optimize the performance of concrete from multiple dimensions. On the one hand, it significantly improves the workability of concrete, enabling the concrete mixture to flow more smoothly and be evenly distributed during mixing, transportation and pouring, reducing the construction difficulty and improving the construction efficiency; on the other hand, the large amount of mineral admixtures itself has the characteristic of low heat of hydration, and the combination of the two effectively reduces the peak value of the heat of hydration of concrete. This characteristic is of great significance for the pouring of large-volume underwater concrete, which can greatly reduce the risk of concrete cracking caused by the accumulation of heat of hydration and ensure the internal quality stability of large-volume structures. In the process of urban underground space development, large-volume underwater concrete is widely used, from the foundation of large underground parking lots to the underwater sections of cross-river tunnels. The present invention helps to pour large-volume underwater concrete with high quality, laying a solid foundation for the safe and efficient expansion of urban underground space and having a profound and positive impact on the booming development of urban underground space. Detailed implementation manners

[0021] To make the purpose, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be described below through specific embodiments. However, it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present invention.

[0022] The terms used in the present disclosure are only for the purpose of describing specific embodiments and are not intended to limit the present disclosure. The singular forms "a", "the" and "that" used in the present disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0023] It should be understood that although the terms first, second, third, etc. may be used in this disclosure to describe various information, such information should not be limited to these terms and should not be construed as indicating or implying relative importance. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of this disclosure, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "when" or "while" or "in response to a determination".

[0024] In the description of the present invention, unless otherwise specified and defined, it should be noted that the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it may be a mechanical connection, or it may be the communication inside two components. It may be directly connected, or it may be indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0025] To better understand the technical solution of the present invention, the present invention will be described in detail below in conjunction with specific embodiments.

[0026] This application provides a method for treating machine-made sand with high mud content, and the method includes:

[0027] Step 1: Water washing: Select a wheel-type sand washer as the cleaning equipment, water as the cleaning medium, and polyacrylamide flocculant as the cleaning solvent. The concentration of the flocculant is determined according to the mud content of the machine-made sand.

[0028] Step 2: Detection: Measure the stone powder content of the machine-made sand after water washing. The stone powder content of the machine-made sand after water washing should be ≤ 5%, and measure that the flocculant content of the water-washed machine-made sand is ≥ 0.2‰. If the above requirements are not met, repeat Step 1 until the stone powder content of the water-washed machine-made sand is ≤ 5%, and the flocculant content of the water-washed machine-made sand is ≥ 0.2‰.

[0029] Select the machine-made sand with high mud content made by the above method as the raw material for underwater concrete in Example 1 and Example 3. The models of other raw materials in the concrete are as follows: The cement is P.O 42.5 cement; the fly ash is Grade II ash, and the 28-day activity index is ≥ 70%; the mineral powder is S95 mineral powder, and the 28-day activity index is ≥ 95%; the stone is 5-25mm natural crushed stone, and the apparent density is ≥ 2600 kg / m 3 , the crushing value index is ≤ 20%; the sand is the above-mentioned water-washed machine-made sand, the stone powder content is ≤ 5%, and the flocculant content is ≥ 0.2‰; the admixture is a high-efficiency polycarboxylate admixture, and the water reduction rate is > 25%.

[0030] Example 1

[0031] Weigh 160 kg of water, 180 kg of cement, 120 kg of fly ash, 130 kg of slag powder, 778 kg of washed machine-made sand, 1008 kg of stones, and 5.16 kg of admixture by weight. The stone powder content in the washed machine-made sand is 3%, and the flocculant content is 0.4‰. After mixing the cement, fly ash, slag powder, washed machine-made sand, and stones for one minute, we get mixture A. After stirring the water and admixture evenly, we get mixed solution B. Add mixed solution B to mixture A and continue stirring for three minutes to obtain underwater concrete with a large amount of mineral admixture.

[0032] Example 2

[0033] Weigh 160 kg of water, 170 kg of cement, 120 kg of fly ash, 130 kg of slag powder, 754 kg of washed machine-made sand, 1041 kg of stones, and 5.25 kg of admixture by weight. The stone powder content in the washed machine-made sand is 4%, and the flocculant content is 0.5‰. After mixing the cement, fly ash, slag powder, washed machine-made sand, and stones for one minute, we get mixture A. After stirring the water and admixture evenly, we get mixed solution B. Add mixed solution B to mixture A and continue stirring for three minutes to obtain underwater concrete with a large amount of mineral admixture.

[0034] Comparative Example 1

[0035] Weigh 160 kg of water, 180 kg of cement, 120 kg of fly ash, 130 kg of slag powder, 778 kg of machine-made sand, 1008 kg of stones, and 5.16 kg of admixture by weight. The machine-made sand is unwashed machine-made sand with a stone powder content of 7% and no flocculant. After mixing the cement, fly ash, slag powder, machine-made sand, and stones for one minute, we get mixture A. After stirring the water and admixture evenly, we get mixed solution B. Add mixed solution B to mixture A and continue stirring for four minutes to obtain underwater concrete with a large amount of mineral admixture.

[0036] Test the underwater concrete prepared in Example 2, Example 3, and Comparative Example 1. The test results are shown in the following table.

[0037]

[0038] It can be seen from the table that the fluidity of the underwater concrete prepared in Example 1 and Example 2 is stronger than that of the underwater concrete prepared in Comparative Example 1, and the compressive strength of the underwater concrete prepared in Example 1 and Example 2 is better than that of the underwater concrete prepared in Comparative Example 1; compared with the underwater concrete prepared in Example 1 and Example 2, the fluidity loss of the underwater concrete prepared in Comparative Example 1 is larger after two hours.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that it is still possible to modify the specific implementation manners of the invention or perform equivalent replacements on some technical features; without departing from the spirit of the technical solutions of the present invention, they should all be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A method for preparing underwater concrete based on high mud powder content machine-made sand, characterized in that: The method comprises the following steps: S1. Wash the machine-made sand with water until the mass content of sand and stone powder in the washed machine-made sand is ≤5% and the mass content of flocculant is ≥0.2‰; S2, weigh 160-180 parts of cement, 120-130 parts of fly ash, 120-130 parts of mineral powder, 700-800 parts of washed sand obtained in S1, 950-1050 parts of gravel, 155-165 parts of water, and 4-6 parts of admixture by a weighing machine; S3, mixing cement, fly ash, mineral powder, washed sand and gravel evenly to obtain a mixture A, and stirring water and admixture evenly to obtain a mixed solution B; S4. Add the mixed solution B into the mixture A and stir evenly to obtain underwater concrete.

2. The method for preparing underwater concrete based on high mud powder content machine-made sand according to claim 1, characterized in that: In S1, a wheel sand washer is used as the equipment for cleaning the machine-made sand, water is used as the cleaning medium, and polyacrylamide flocculant is used as the cleaning solvent to wash the machine-made sand.

3. The method for preparing underwater concrete based on high mud powder content machine-made sand according to claim 1, characterized in that: In S3, cement, fly ash, mineral powder, washed machine-made sand and gravel are mixed for one minute to obtain a mixture A. In S4, a mixed solution B is added to the mixture A and stirred for three minutes to obtain underwater concrete.

4. The method for preparing underwater concrete based on high mud powder content machine-made sand according to claim 1, characterized in that: The cement is PO 42.5 cement; the fly ash is Class II ash, with a 28d activity index of ≥70%; the mineral powder is S95 mineral powder, with a 28d activity index of ≥95%; the stone is 5-25mm natural crushed stone, with an apparent density of ≥2600kg / m 3 , crushing value index ≤20%.

5. The method for preparing underwater concrete based on high mud powder content machine-made sand according to claim 4, characterized in that: The admixture is a high-efficiency polycarboxylic acid admixture with a water reduction rate of more than 25%.

6. An underwater concrete, characterized in that: It includes 160-180 parts of cement, 120-130 parts of fly ash, 120-130 parts of mineral powder, 700-800 parts of machine-made sand, 950-1050 parts of gravel, 155-165 parts of water, and 4-6 parts of admixture. The machine-made sand is washed machine-made sand, the mass content of sand and gravel powder in the washed machine-made sand is ≤5%, and the mass content of flocculant is ≥0.2‰.

7. The underwater concrete according to claim 6, characterized in that: The cement is PO 42.5 cement; the fly ash is Class II ash, with a 28d activity index of ≥70%; the mineral powder is S95 mineral powder, with a 28d activity index of ≥95%; the stone is 5-25mm natural crushed stone, with an apparent density of ≥2600kg / m3 and a crushing value index of ≤20%.

8. The underwater concrete according to claim 6, characterized in that: The admixture is a high-efficiency polycarboxylic acid admixture with a water reduction rate of more than 25%.

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