High-flow-state high-stone low-sand pumping machine-made sand concrete and special admixture thereof

Abstract

The invention discloses high-flow-state high-stone low-sand pumping machine-made sand concrete and a special admixture thereof. The concrete is prepared from the following components in parts by weight: 260 to 280 parts of cement, 60 to 70 parts of mineral powder, 50 to 60 parts of fly ash, 650 to 750 parts of yellow sand, 1000 to 1100 parts of broken stone, 6 to 8 parts of the special admixture and 160 to 170 parts of water, wherein the special admixture is a polycarboxylic admixture and comprises the following components in percentage by weight: 3%-5% of a polycarboxylic water reducer, 12%-15% of a polycarboxylic slump retaining agent, 8%-10% of a polycarboxylic viscosity reducer, 1%-3% of a viscosity modifier, 2%-4% of a retarder and the balance of water. By adopting a high-stone and low-sand pumping machine-made sand concrete technology, the sand rate is reduced, the high strength of the structure is ensured, the cracking risk is greatly reduced, the problems of insufficient concrete slurry, stone exposure and the like caused by the use of high-stone and low-sand are solved by adopting the special admixture, and the workability of the concrete is improved; in addition, the concrete provided by the invention can reduce the use amount of cement and sand, reduce carbon emission and resource consumption and reduce cost, and has the advantages of greenness and low carbon.

Description

Technical Field

[0001] The invention belongs to the technical field of concrete material preparation, and in particular relates to a high-fluidity high-stone and low-sand pumpable machine-made sand concrete and a specially formulated admixture thereof. Background Art

[0002] After searching, the Chinese invention application document with the existing publication number CN117361993A discloses a high-stone, low-sand concrete and its preparation method, "the raw materials include the following components in parts by weight: 40-60 parts of limestone, 40-60 parts of granite, 30-50 parts of gabbro, 20-30 parts of fly ash, 40-60 parts of cement, 10-20 parts of gelling agent, 5-10 parts of nano boron nitride, 2-4 parts of water reducer, 2-4 parts of antifreeze agent; the gelling agent is a mixture of silica sol, tungsten disulfide and calcium sulfate in a mass ratio of 5-10:3:2". Although the application mentioned in the background technology that "high-stone, low-sand concrete is a new type of building material", the high-stone, low-sand concrete mentioned in the application is a relatively general concept and scope, and the high-stone, low-sand technology of high-stone, low-sand concrete in the limited scope of using machine-made sand and pumping as the construction method is rarely mentioned either in the literature or in actual projects. Moreover, the high-stone, low-sand concrete in this application solves the strength problem of high-stone, low-sand concrete, and does not involve relevant solutions to problems such as the workability of the mixture and the high risk of structural cracking of high-stone, low-sand pumpable machine-made sand concrete, and has certain limitations.

[0003] High-stone and low-sand pumped artificial sand concrete refers to a type of concrete that uses artificial sand as fine aggregate and adopts pumping as the construction method, and achieves a low sand ratio by increasing the amount of coarse aggregate and reducing the amount of fine aggregate. At present, artificial sand is widely used in the production of concrete in mixing stations. However, due to its own production process, artificial sand has sharp particles, many edges and corners, rough surface, and fineness modulus of more than 3.0. Compared with natural river sand, the particle grading of artificial sand is poor, and there are more particles larger than 2.5mm and smaller than 0.08mm, which will lead to poor workability of concrete; at the same time, the change of artificial sand parent material will cause fluctuations in the quality of artificial sand, which brings certain difficulties to the control of the quality of pumped concrete.

[0004] In order to solve this problem, mixing stations often increase the sand ratio to increase the wrapping and fluidity of the concrete mixture, so as to meet the purpose of engineering pumping construction. However, excessive sand dosage will reduce the density and strength of the concrete, causing expansion and contraction deformation of the concrete, resulting in cracks on the surface of the concrete. On the other hand, it will increase the total specific surface area of ​​the fine aggregate, requiring more cement slurry to wrap it, which will increase the amount of cement. Therefore, it is urgent to develop a high-stone and low-sand pumpable machine-made sand concrete to solve the current problems. On the basis of increasing the amount of stone and reducing the amount of sand, the density of the concrete mixture can be enhanced, the risk of cracking can be greatly reduced, and the amount of cement can be reduced at the same time.

[0005] At the same time, the use of high-stone and low-sand pumped machine-made sand concrete technology will increase the amount of coarse aggregate and reduce the amount of fine aggregate, and the excessive amount of stone will cause poor concrete workability, often resulting in insufficient concrete slurry and difficulty in wrapping coarse aggregate. Therefore, it is also necessary to develop a special admixture to solve the problems of insufficient slurry and exposed stone, improve the workability of high-stone and low-sand pumped machine-made sand concrete, and increase the performance and application range of high-stone and low-sand pumped machine-made sand concrete. Summary of the invention

[0006] In order to solve the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a high-flowability high-stone, low-sand pumpable machine-made sand concrete and its specially formulated admixture, which can not only reduce the sand rate by adopting high-stone, low-sand to ensure the high strength of the structural entity and greatly reduce the risk of cracking, but also improve the problems of insufficient concrete slurry and exposed stone caused by the use of high-stone, low-sand by adopting specially formulated admixtures, and improve the workability of high-stone, low-sand pumpable machine-made sand concrete; further, the high-stone, low-sand pumpable machine-made sand concrete provided by the present invention can reduce the amount of cement and sand, reduce carbon emissions and the consumption of natural resources, reduce costs, and has the advantages of being green and low-carbon.

[0007] In order to achieve the above-mentioned purpose and other related purposes, the present invention adopts the following technical solutions:

[0008] The first aspect of the present invention provides a highly fluid high-stone and low-sand pumpable machine-made sand concrete, which comprises the following components, measured by weight: 260-280 parts of cement, 60-70 parts of mineral powder, 50-60 parts of fly ash, 650-750 parts of yellow sand, 1000-1100 parts of crushed stone, 6-8 parts of specially formulated admixtures, and 160-170 parts of water.

[0009] As a preferred technical solution, the specially formulated admixture is a polycarboxylic acid admixture with a solid content of 14% and a density of 1.032 kg / m 3 .

[0010] As a preferred technical solution, the cement is PO 42.5 silicate cement with a specific surface area of ​​350-400m 2 / kg, the initial setting time and final setting time are 120-150min and 300-360min respectively, and the 3d and 28d compressive strengths are 27-32MPa and 48-53MPa respectively.

[0011] As a preferred technical solution, the mineral powder is S95 grade mineral powder with a specific surface area of ​​420kg / m 3 , 7d activity index is greater than 75%, and 28d activity index is greater than 95%.

[0012] As a preferred technical solution, the fly ash is Class C II fly ash, with an activity index greater than 80% and a carbon content less than 1%.

[0013] As a preferred technical solution, the yellow sand is a type of machine-made sand with a fineness modulus of 3.0-3.1, an MB value of 0.75, and a stone powder content of less than 8%.

[0014] As a preferred technical solution, the crushed stone is 5-25 mm in size, continuously graded, and has a mud content of less than 1%.

[0015] The second aspect of the present invention provides a specially formulated admixture for use in any one of the above-mentioned high-fluidity high-stone and low-sand pumpable machine-made sand concrete, which comprises the following components by weight percentage: 3%-5% polycarboxylic acid water reducer, 12%-15% polycarboxylic acid slump retaining agent, 8%-10% polycarboxylic acid viscosity reducer, 1%-3% viscosity regulator, 2%-4% retarder, and the remainder water.

[0016] As described above, the present invention has the following beneficial effects:

[0017] (1) The high-flowability high-stone and low-sand pumpable machine-made sand concrete and its specially formulated admixture of the present invention adopt a high-stone and low-sand mix design, with a high amount of coarse aggregate and a low water consumption, thereby reducing the sand ratio, thereby increasing the strength and elastic modulus of the structural entity, and significantly reducing the risk of cracking caused by the high sand ratio in the current production process of pumpable machine-made sand concrete; in addition, the use of specially formulated admixtures can improve the problems of insufficient concrete slurry and exposed stone caused by the use of high-stone and low-sand, thereby enhancing the workability of the high-stone and low-sand pumpable machine-made sand concrete.

[0018] (2) The high-flowability, high-stone, low-sand pumpable machine-made sand concrete and its specially formulated admixture of the present invention use less cement and less sand. By reducing the amount of cement and sand, it not only reduces carbon emissions and natural resource consumption, achieves low energy consumption and low carbon emissions, but also reduces the overall production cost, showing the advantages of green and low carbon, while maintaining the high performance of concrete, and is an economical and environmentally friendly green building material.

[0019] (3) The present invention provides a highly fluid high-stone, low-sand pumpable machine-made sand concrete and its specially formulated admixture. The specially formulated admixture is obtained by adopting a compounding technology of admixtures and is specially developed and optimized to solve the problems of poor workability and high cracking risk of high-stone, low-sand pumpable machine-made sand concrete. The specially formulated admixture comprises a variety of admixtures such as a water reducer, a slump retainer, a viscosity reducer, and a viscosity regulator. The viscosity regulator is a modified polyamide mixture that can effectively adjust the viscosity and enhance the wrapping of the slurry to the aggregate. The viscosity reducer is a maleic acid dicarboxylic acid synthetic polyether mixture that can increase the total amount of concrete mixture slurry, solve the problems of insufficient concrete mixture slurry and exposed stone in the high-stone, low-sand pumpable machine-made sand concrete, and significantly enhance the workability of the high-stone, low-sand pumpable machine-made sand concrete.

[0020] (4) The high-flowability high-stone, low-sand pumpable machine-made sand concrete and its specially formulated admixture of the present invention have a simple preparation method and a small number of raw material types. By simplifying the types of raw materials and optimizing the preparation process, the material cost is reduced and the construction efficiency is improved, and the high-stone, low-sand pumpable machine-made sand concrete with high strength and elastic modulus is obtained, which solves the problem of high cracking risk caused by excessive sand ratio when machine-made sand is used in large-scale production of mixing stations and the construction method is pumping. At the same time, through the application of specially formulated admixtures, the problems of insufficient slurry and exposed stones in the use of high-stone, low-sand pumpable machine-made sand concrete are further solved, the workability of high-stone, low-sand pumpable machine-made sand concrete is increased, and the high strength and durability of the structural entity are guaranteed. DETAILED DESCRIPTION

[0021] In order to better understand the purpose, structure and function of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Unless otherwise specified, the raw materials used in the examples are all well-known, commercially available chemical raw materials.

[0023] Example 1

[0024] This embodiment provides a high-flowability, high-stone, low-sand pumpable machine-made sand concrete, which is obtained by the following preparation steps:

[0025] Step 1: Pour 280 parts of P.O42.5 silicate cement, 60 parts of mineral powder, 60 parts of fly ash, 720 parts of yellow sand and 1020 parts of crushed stone into a drum mixer in sequence and stir for 1 minute to obtain dry mix A1.

[0026] in,

[0027] The cement is silicate cement with a strength grade of P.O42.5 and a specific surface area of ​​350-400m 2 / kg, initial setting time and final setting time are 120-150min and 300-360min respectively, and 3d and 28d compressive strength are 27-32MPa and 48-53MPa respectively;

[0028] The mineral powder is S95 grade, with a specific surface area of ​​420kg / m 3 , 7d activity index is greater than 75%, 28d activity index is greater than 95%;

[0029] The fly ash is Class C II powder, with an activity index greater than 80% and a carbon content less than 1%.

[0030] The yellow sand is a type of machine-made sand with a fineness modulus of 3.0-3.1, an MB value of 0.75, and a stone powder content of less than 8%;

[0031] The crushed stone is 5-25 mm in size, continuously graded, and has a mud content of less than 1%.

[0032] Step 2: Add 7 parts of specially formulated admixture to 170 parts of water and stir evenly, add to dry mix A1, mix and stir for 3 minutes to obtain a high-stone and low-sand pumpable machine-made sand concrete mixture B1 with good uniformity and fluidity.

[0033] The specially formulated admixture is prepared in advance before the preparation of high-stone and low-sand pumped machine-made sand concrete. Specifically, the specially formulated admixture is a polycarboxylic acid-based admixture with a solid content of 14% and a density of 1.032 kg / m 3 ; And, the specially formulated admixture is composed of the following components in percentage by weight: 3%-5% of polycarboxylic acid water reducer, 12%-15% of polycarboxylic acid slump retainer, 8%-10% of polycarboxylic acid viscosity reducer, 1%-3% of viscosity regulator, 2%-4% of retarder, and the rest is water; wherein, the viscosity regulator is a modified polyamide mixture; and the polycarboxylic acid viscosity reducer is a maleic acid dicarboxylic acid synthetic polyether mixture.

[0034] Example 2

[0035] This embodiment provides a high-flowability, high-stone, low-sand pumpable machine-made sand concrete, which is obtained by the following preparation steps:

[0036] Step 1: Pour 270 parts of P.O42.5 silicate cement, 60 parts of mineral powder, 60 parts of fly ash, 700 parts of yellow sand and 1050 parts of crushed stone into a drum mixer in sequence and stir for 1 minute to obtain dry mix A2.

[0037] Step 2: Add 6 parts of specially formulated admixture to 165 parts of water and stir evenly, add to dry mix A2, mix and stir for 3 minutes to obtain a high-stone and low-sand pumpable machine-made sand concrete mixture B2 with good uniformity and fluidity.

[0038] Example 3

[0039] This embodiment provides a high-flowability, high-stone, low-sand pumpable machine-made sand concrete, which is obtained by the following preparation steps:

[0040] Step 1: Pour 260 parts of P.O42.5 silicate cement, 60 parts of mineral powder, 60 parts of fly ash, 680 parts of yellow sand and 1080 parts of crushed stone into a drum mixer in sequence and stir for 1 minute to obtain dry mix A3.

[0041] Step 2: Add 6 parts of specially formulated admixture to 160 parts of water and stir evenly, add to dry mix A3, mix and stir for 3 minutes to obtain a high-stone and low-sand pumpable machine-made sand concrete mixture B3 with good uniformity and fluidity.

[0042] Comparative Example 1

[0043] This embodiment provides a conventional machine-made sand concrete, which is obtained by the following preparation steps:

[0044] Step 1: Pour 260 parts of PO 42.5 silicate cement, 60 parts of mineral powder, 60 parts of fly ash, 680 parts of yellow sand and 1080 parts of crushed stone into a drum mixer in sequence and stir for 1 minute to obtain a dry mix A3.

[0045] Step 2: Add 6 parts of polycarboxylic acid water reducer into 170 parts of water and stir evenly, then add into dry mix A3, mix and stir for 3 minutes to obtain concrete mixture B4.

[0046] Among them, the polycarboxylic acid-based water reducer is a medium-efficiency water reducer that is common and widely used on the market. Medium-efficiency is classified according to different water reduction rates. Even if it is replaced with a high-efficiency or high-performance water reducer, it can only increase the water reduction rate, but cannot solve the problems of insufficient slurry and exposed stone in high-stone and low-sand pumped machine-made sand concrete.

[0047] The differences between the above embodiments and Comparative Example 1 are as follows:

[0048] Embodiment 1:

[0049] Through the above steps, a high-stone and low-sand pumpable machine-made sand concrete mixture B1 is finally obtained.

[0050] Embodiment 2:

[0051] Change the weight of cement from 280 to 270 parts;

[0052] The weight parts of yellow sand were changed from 720 parts to 700 parts;

[0053] The weight proportion of crushed stone was changed from 1020 to 1050.

[0054] The weight proportion of the specially formulated admixture was changed from 7 to 6;

[0055] The weight parts of water were changed from 170 to 165 parts;

[0056] Others are the same as in Example 1;

[0057] That is, on the basis of Example 1, Example 2 reduces the weight percentages of cement, yellow sand, specially formulated admixtures and water, and increases the weight percentage of crushed stone, thereby finally obtaining a high-stone and low-sand pumpable machine-made sand concrete mixture B2.

[0058] Embodiment 3:

[0059] Change the weight of cement from 270 to 260 parts;

[0060] The weight parts of yellow sand were changed from 700 to 680 parts;

[0061] The weight proportion of crushed stone was changed from 1050 to 1080;

[0062] The weight parts of water were changed from 165 to 160 parts;

[0063] Others are the same as in Example 2;

[0064] That is, Example 3, while keeping the weight proportion of the specially formulated admixture in Example 2 unchanged, further reduced the weight proportions of cement, yellow sand and water, and further increased the weight proportion of crushed stone, ultimately obtaining a high-stone and low-sand pumpable machine-made sand concrete mixture B3.

[0065] Comparative Example 1:

[0066] The specially formulated admixture was changed to a common medium-effective polycarboxylic acid-based water reducer on the market; the weight of water was changed from 160 parts to 170 parts;

[0067] Others are the same as in Example 3;

[0068] That is, in Comparative Example 1, on the basis of Example 3, the specially formulated admixture was replaced with a conventional admixture, and the weight percentage of water was adaptively adjusted, and finally a concrete mixture B4 was obtained.

[0069] The test data results of each concrete mixture prepared in each embodiment and comparative example are shown in Table 1.

[0070] Table 1 Test data results table

[0071]

[0072] Implementation effect:

[0073] From the detailed data analysis of Example 1 to Experimental Example 3, it can be concluded that as the sand ratio gradually decreases, the 7d and 28d compressive strengths of concrete both show an upward trend, while the working performance of concrete does not significantly decrease due to the reduction of the sand ratio, and the inverted emptying time and expansion are basically maintained at the same level. In particular, in Example 3, the sand ratio has been reduced to 38.6%, but the 28d compressive strength is still as high as 48.6MPa, the inverted emptying time is 4.0s, and the expansion is nearly 600mm, showing that the concrete mixture has excellent mechanical properties and working performance, and basically reaches the performance level when natural sand is used. This is due to the addition of a specially formulated admixture, which can effectively solve the problem of insufficient slurry and poor aggregate encapsulation of pumped concrete mixtures caused by high stone and low sand, and significantly improve the stability, cohesion and fluidity of the mixture.

[0074] In addition, further analysis of Experimental Example 2 and Experimental Example 3 shows that compared with Example 1, Example 2 reduces the amount of cement by 10kg and the amount of machine-made sand by 20kg. Compared with Example 1, Example 3 reduces the amount of cement by 20kg and the amount of machine-made sand by 40kg. This not only helps to significantly reduce the release of CO2 in the production process, but also significantly reduces the consumption of machine-made sand resources, thereby making the preparation process of concrete more green and environmentally friendly.

[0075] In contrast, by observing the data of Comparative Example 1, it can be seen that: in Comparative Example 1, when no special admixture is added and only conventional admixture is used, the inverted emptying time exceeds 10s and the expansion is only 390mm. Compared with Example 1, Experimental Example 2, and Experimental Example 3, the concrete mixture of Comparative Example 1 has poor workability. At the same time, due to the poor density and uniformity of the concrete, its strength is also lower than that of Examples 1-3. Therefore, the concrete mixture obtained in Comparative Example 1 is difficult to meet the engineering pumping requirements. This further proves the significant role of special admixtures in improving the performance of concrete.

[0076] In order to gain a deeper understanding of this phenomenon, the relationship between the microstructure and macroscopic properties of concrete can be further explored. As a multiphase composite material, the performance of concrete depends not only on the properties of each component, but also on the interaction between the components. In a high-stone and low-sand concrete system, the addition of specially formulated admixtures significantly improves the interface transition zone between cement paste and aggregate, thereby enhancing the internal structure of concrete. This improvement in the interface transition zone enables concrete to transfer stress more effectively when subjected to external loads, thereby improving its compressive strength.

[0077] In addition, the use of specially formulated admixtures also improves the fluidity of concrete, which is crucial to the construction performance of concrete. Good fluidity can ensure that concrete will not be blocked during pumping, and can also ensure the uniform distribution of concrete in the formwork, thereby avoiding uneven strength and durability problems caused by improper construction. Therefore, specially formulated admixtures not only improve the mechanical properties of concrete, but also optimize its construction performance, making it more suitable for the needs of modern construction projects.

[0078] In summary, through the research of Experimental Examples 1 to 3 and the comparative analysis of Comparative Example 1, it can be seen that the specially formulated admixture has a significant effect in improving the performance of concrete, which not only provides a new technical path for the preparation of concrete, but also provides new ideas for the sustainable development of concrete engineering.

[0079] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application belong to the scope protected by the present invention.

Claims

1. A high-flowability, high-stone, low-sand pumpable machine-made sand concrete, characterized in that: Calculated by weight, the components include: 260-280 parts of cement, 60-70 parts of mineral powder, 50-60 parts of fly ash, 650-750 parts of yellow sand, 1000-1100 parts of crushed stone, 6-8 parts of specially formulated admixture, and 160-170 parts of water.

2. The high-flowability high-stone and low-sand pumpable machine-made sand concrete according to claim 1, characterized in that: The specially formulated admixture is a polycarboxylic acid admixture with a solid content of 14% and a density of 1.032 kg / m 3 .

3. The high-flowability high-stone and low-sand pumpable machine-made sand concrete according to claim 1, characterized in that: The cement is PO 42.5 silicate cement with a specific surface area of ​​350-400m 2 / kg, the initial setting time and final setting time are 120-150min and 300-360min respectively, and the 3d and 28d compressive strengths are 27-32MPa and 48-53MPa respectively.

4. The high-flowability high-stone and low-sand pumpable machine-made sand concrete according to claim 1, characterized in that: The mineral powder is S95 grade mineral powder with a specific surface area of ​​420kg / m 3 , 7d activity index is greater than 75%, and 28d activity index is greater than 95%.

5. The high-flowability high-stone and low-sand pumpable machine-made sand concrete according to claim 1, characterized in that: The fly ash is Class C II fly ash, with an activity index greater than 80% and a carbon content less than 1%.

6. The high-flowability high-stone and low-sand pumpable machine-made sand concrete according to claim 1, characterized in that: The yellow sand is a kind of machine-made sand, with a fineness modulus of 3.0-3.1, an MB value of 0.75, and a stone powder content of less than 8%.

7. The high-flowability, high-stone, low-sand pumpable machine-made sand concrete according to claim 1, characterized in that: The crushed stone is 5-25 mm in size, continuously graded, and has a mud content of less than 1%.

8. A specially formulated admixture for use in a highly fluid high-stone and low-sand pumpable machine-made sand concrete as claimed in any one of claims 1 to 7, characterized in that: The composition includes the following components by weight percentage: 3%-5% of polycarboxylic acid water reducing agent, 12%-15% of polycarboxylic acid slump retaining agent, 8%-10% of polycarboxylic acid viscosity reducing agent, 1%-3% of viscosity regulator, 2%-4% of retarder and the rest of water.

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