Crack-resistant concrete and its preparation method

Abstract

The present application discloses a crack-resistant concrete and a preparation method thereof, relating to the field of concrete, which is prepared from the following components in parts by weight: 120-180 parts of modified fine aggregate; 200-300 parts of coarse aggregate; 120-160 parts of cement; 30-50 parts of water; 4-8 parts of water reducing agent; 1-2 parts of modified fiber mesh; 2.5-3.5 parts of retarder; the preparation method of the modified fiber mesh is as follows: soaking polypropylene mesh fiber in polyacrylamide solution and drying to obtain the modified fiber mesh. The present application has the effect of improving the compressive strength and crack resistance of concrete.

Description

Technical Field

[0001] The present application relates to the field of concrete, and particularly to a crack-resistant concrete and a preparation method thereof. Background Art

[0002] Concrete is generally a composite material prepared by mixing coarse aggregate, fine aggregate and water with cement as a gelling material, and is widely used in engineering construction.

[0003] Currently, due to factors such as the concentration of cement hydration heat and concrete shrinkage in concrete, cracks are generated. Therefore, water reducing agents, expansive agents, water reducing agents, short fibers and other admixtures are often added to concrete to improve the crack resistance performance in the initial stage of concrete setting.

[0004] However, the cracks formed during the molding process of concrete will be affected by weather, temperature, etc. during use and expand along the interfaces at the junctions of different materials such as fine aggregate and short fibers, resulting in poor crack resistance of the concrete. Summary of the Invention

[0005] In order to improve the problem of poor crack resistance of concrete caused by crack expansion in concrete, the present application provides a crack-resistant concrete and a preparation method thereof.

[0006] On the one hand, a crack-resistant concrete provided by the present application adopts the following technical solution:

[0007] A crack-resistant concrete is prepared from the following components by weight:

[0008] 120-180 parts of modified fine aggregate;

[0009] 200-300 parts of coarse aggregate;

[0010] 120-160 parts of cement;

[0011] 30-50 parts of water;

[0012] 4-8 parts of water reducing agent;

[0013] 1-2 parts of modified fiber mesh;

[0014] 2.5-3.5 parts of retarder;

[0015] The preparation method of the modified fiber mesh is as follows:

[0016] Soak polypropylene mesh fiber in polyacrylamide solution and dry it to obtain the modified fiber mesh.

[0017] By adopting the above technical solution, cement, as a gelling material, bonds the modified fine aggregate and the coarse aggregate, and a water reducing agent is used to reduce the amount of mixing water, and a retarder is used to delay the hydration of cement, so as to minimize the concentration of hydration heat and reduce the crack incidence rate of concrete during the setting stage. Moreover, the modified fiber mesh limits the shrinkage degree of concrete and further reduces the crack incidence rate of concrete. During the mixing process, the modified fine aggregate rubs against the modified fiber mesh, causing the modified fiber mesh to unfold from a bundle shape into a mesh shape. Among them, polyacrylamide improves the dispersion effect of the modified fiber mesh in concrete during the mixing process. Under the combined action, the modified fiber mesh unfolds and is evenly dispersed in the concrete, inhibiting the expansion of cracks during the setting and subsequent use of the concrete, and improving the compressive strength and crack resistance of the concrete.

[0018] Preferably, the weight ratio of the modified fine aggregate to the modified fiber mesh is (75 - 150):1.

[0019] Preferably, the weight ratio of the modified fine aggregate to the modified fiber mesh is (80 - 120):1.

[0020] Preferably, the weight ratio of the retarder to the modified fiber mesh is (1.5 - 3):1.

[0021] Preferably, the weight ratio of the retarder to the modified fiber mesh is (1.6 - 2.4):1.

[0022] Preferably, the number average molecular weight of the polyacrylamide is 3 million - 8 million.

[0023] Preferably, the length of the polypropylene mesh fiber is 6 - 10 mm.

[0024] Preferably, the mass fraction of polyacrylamide in the polyacrylamide aqueous solution is 4 - 6%.

[0025] Preferably, the drying includes: airing the soaked polypropylene mesh fiber for 1.5 - 2.5 h under the temperature condition of 37 - 452 °C.

[0026] Optionally, the preparation method of the modified fine aggregate is as follows:

[0027] A1. Mix the adhesive and the silane coupling agent to obtain an adhesive;

[0028] A2. Soak the coarse aggregate in the adhesive and then fish it out to obtain the modified fine aggregate.

[0029] Preferably, the preparation method of the modified fine aggregate is as follows:

[0030] Soak the fine aggregate in the polyvinyl alcohol aqueous solution and then dry it to obtain the modified fine aggregate.

[0031] Preferably, the mass fraction of polyvinyl alcohol in the aqueous polyvinyl alcohol solution is 4-8%.

[0032] Preferably, the retarder is selected from one or both of borax and boric acid.

[0033] Preferably, the retarder is selected from borax or boric acid.

[0034] By adopting the above technical solution, by controlling the ratio of the modified fine aggregate to the modified fiber mesh, the length of the polypropylene mesh fiber, the ratio of the retarder to the modified fiber mesh, the type of the retarder, and the number-average molecular weight of the polyacrylamide, the dispersion effect of the modified fine aggregate and the modified fiber mesh during the concrete mixing process is improved. Moreover, during the solidification process of the concrete, the heat released by the hydration of cement causes the polyvinyl alcohol and polyacrylamide on the surface of the modified fine aggregate to dissolve in water. On the one hand, it delays the loss of water, and on the other hand, under the action of the retarder, the polyvinyl alcohol and polyacrylamide dissolved in water crosslink to form a network crosslinked structure, improving the connection strength at the junction of the fine aggregate, the polypropylene mesh fiber, and the coarse aggregate, and forming a support skeleton in the concrete. Under the combined action, while reducing the crack incidence rate during the concrete solidification process, it also inhibits the expansion of cracks, further improving the crack resistance and compressive strength of the concrete.

[0035] On the other hand, a preparation method of the crack-resistant concrete provided by the present application adopts the following technical solution:

[0036] A preparation method of crack-resistant concrete includes the following steps:

[0037] S1. Mix the modified fiber mesh, cement, modified fine aggregate, and coarse aggregate to obtain a reinforcing material;

[0038] S2. Stir the reinforcing material, retarder, water reducer, and water evenly to obtain crack-resistant concrete.

[0039] Preferably, the step S1 includes the following steps:

[0040] S11. Mix and stir the modified fiber mesh and the modified fine aggregate to obtain a pre-dispersed material;

[0041] S12. Stir the cement, coarse aggregate, and the pre-mixed material evenly to obtain a reinforcing material.

[0042] By adopting the above technical solution, pre-mixing the modified fiber mesh with the modified fine aggregate improves the unfolding effect of the modified fine aggregate on the modified fiber mesh, and while improving the dispersion effect of the two in the concrete, it is convenient for the polyacrylamide in the modified fiber mesh to contact the polyvinyl alcohol coated on the surface of the modified fine aggregate when dissolving, facilitating the crosslinking of polyacrylamide and polyvinyl alcohol under the action of borax or boric acid. Under the combined action, the crack resistance and compressive strength of the concrete are improved.

[0043] In summary, the present application includes at least one of the following beneficial technical effects:

[0044] 1. Cement, as a gelling material, bonds the modified fine aggregate and the coarse aggregate, and a water reducer is used to reduce the amount of mixing water. A retarder delays the hydration of cement, minimizing the concentration of hydration heat as much as possible, reducing the crack incidence rate of concrete during the setting stage. Moreover, the modified fiber mesh restricts the shrinkage degree of the concrete, further reducing the crack incidence rate of the concrete. During the mixing process, the modified fine aggregate and the modified fiber mesh rub against each other, causing the modified fiber mesh to unfold from a bundle shape into a network shape. Among them, polyacrylamide improves the dispersion effect of the modified fiber mesh in the concrete during the mixing process. Under the combined action, the modified fiber mesh unfolds and is evenly dispersed in the concrete, inhibiting the expansion of cracks during the setting and subsequent use of the concrete, and improving the compressive strength and crack resistance of the concrete;

[0045] 2. By controlling the ratio of the modified fine aggregate to the modified fiber mesh, the length of the polypropylene mesh fiber, the ratio of the retarder to the modified fiber mesh, the type of the retarder, and the number-average molecular weight of polyacrylamide, the dispersion effect of the modified fine aggregate and the modified fiber mesh during the concrete mixing process is improved. And during the setting process of the concrete, the hydration of cement releases heat, causing the polyvinyl alcohol and polyacrylamide on the surface of the modified fine aggregate to dissolve in water. On the one hand, it delays the loss of water. On the other hand, under the action of the retarder, the polyvinyl alcohol and polyacrylamide dissolved in water crosslink to form a network crosslinked structure, improving the connection strength at the junction of the fine aggregate, the polypropylene mesh fiber, and the coarse aggregate, and forming a support framework in the concrete. Under the combined action, while reducing the crack incidence rate during the concrete setting process, it also inhibits the expansion of cracks, further improving the crack resistance and compressive strength of the concrete;

[0046] 3. Premixing the modified fiber mesh with the modified fine aggregate improves the unfolding effect of the modified fine aggregate on the modified fiber mesh, and while improving the dispersion effect of the two in the concrete, it facilitates the contact between the polyacrylamide in the modified fiber mesh and the polyvinyl alcohol coated on the surface of the modified fine aggregate when the polyacrylamide dissolves, facilitating the crosslinking of polyacrylamide and polyvinyl alcohol under the action of borax or boric acid. Under the combined action, the crack resistance and compressive strength of the concrete are improved. Description of the Drawings

[0047] Figure 1 is a flowchart of the preparation method of the crack-resistant concrete in the present application;

[0048] Figure 2 is Figure 1 a flowchart of step S1 in Detailed Embodiments

[0049] The following further elaborates on this application in conjunction with embodiments. The following embodiments are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For those conditions not specified in the following embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. The methods used, unless otherwise specified, are all conventional methods well-known in the art, and the consumables and reagents used, unless otherwise specified, are all commercially available. Unless otherwise stated, the professional and scientific terms used herein have the same meaning as those familiar to skilled personnel in the art. In addition, any method or material similar or equivalent to the described content can also be applied to the present invention.

[0050] The raw materials used in the examples are all commercially available. Basalt aggregate is used as the coarse aggregate, river sand is used as the fine aggregate, and polycarboxylate water reducer is used as the water reducer.

[0051] Examples 1 - 9

[0052] Examples 1 - 9 provide a crack-resistant concrete and its preparation method, and its composition and ratio are shown in Table 1.

[0053] The preparation method of the modified fine aggregate in Examples 1 - 9 is as follows:

[0054] A1. Sand immersion: Add the fine aggregate into an aqueous solution of polyvinyl alcohol with a mass fraction of 6% and soak for 2 h, then fish it out to obtain wet material;

[0055] A2. Drying: Spread out the wet material and dry it with hot air at 50 °C to obtain the modified fine aggregate.

[0056] The preparation method of the modified fiber mesh in Examples 1 - 9 is as follows:

[0057] B1. Mesh immersion: Pour 6 - mm - long polypropylene mesh fibers into a polyacrylamide solution with a mass fraction of 5%, stir and disperse, soak for 1 h, then fish it out to obtain wet mesh;

[0058] B2. Drying: Air - dry the wet mesh at a temperature of 40 °C for 2 h to obtain the modified fiber mesh.

[0059] The preparation method of the crack - resistant concrete in Examples 1 - 9 is as follows:

[0060] S1. Mixing: Add the modified fiber mesh, cement, modified fine aggregate, and coarse aggregate into a concrete mixer and stir to obtain the enhanced material;

[0061] S2. Pulp making: Weigh the retarder, water reducer, and water, stir the retarder, water reducer, and water evenly, then add them into the concrete mixer and continue to stir to obtain the crack - resistant concrete.

[0062] In Examples 1-9, the degree of polymerization of polyvinyl alcohol used for preparing modified fine aggregate is 1700, and the degree of alcoholysis is 88%; the polyacrylamide used for preparing modified fiber mesh is cationic polyacrylamide, and its number average molecular weight is 5 million; the retarder is borax.

[0063] Table 1: Composition and Mix Ratio of Crack-Resistant Concrete

[0064]

[0065]

[0066] Example 10

[0067] Example 10 provides a crack-resistant concrete and its preparation method. The difference between Example 10 and Example 2 is that: in Example 10, boric acid is used to replace borax.

[0068] Example 11

[0069] Example 11 provides a crack-resistant concrete and its preparation method. The difference between Example 11 and Example 2 is that: in Example 11, the length of the polypropylene mesh fiber used for preparing the modified fiber mesh is 8 mm.

[0070] Example 12

[0071] Example 12 provides a crack-resistant concrete and its preparation method. The difference between Example 12 and Example 2 is that: in Example 12, the length of the polypropylene mesh fiber used for preparing the modified fiber mesh is 10 mm.

[0072] Example 13

[0073] Example 13 provides a crack-resistant concrete and its preparation method. The difference between Example 13 and Example 11 is that: in Example 13, the number average molecular weight of the polyacrylamide used for preparing the modified fiber mesh is 3 million.

[0074] Example 14

[0075] Example 14 provides a crack-resistant concrete and its preparation method. The difference between Example 14 and Example 11 is that: in Example 14, the number average molecular weight of the polyacrylamide used for preparing the modified fiber mesh is 8 million.

[0076] Example 15

[0077] Example 15 provides a crack-resistant concrete and its preparation method. The difference between Example 15 and Example 11 is that: Step S1 includes the following steps:

[0078] S11. Predispersion: Add the modified fiber mesh and the modified fine aggregate into a concrete mixer and stir to obtain a predispersed material;

[0079] S12. Premixing: Add cement and coarse aggregate into the pre-dispersed material in the concrete mixer, and stir evenly to obtain the reinforcing material.

[0080] Comparative Example 1

[0081] Comparative Example 1 provides a crack-resistant concrete and its preparation method. The difference between Comparative Example 1 and Example 2 is that in Comparative Example 1, river sand is used to replace the modified fine aggregate.

[0082] Comparative Example 2

[0083] Comparative Example 2 provides a crack-resistant concrete and its preparation method. The difference between Comparative Example 2 and Example 2 is that in Comparative Example 2, polypropylene mesh fiber is used to replace the modified fiber mesh.

[0084] Comparative Example 3

[0085] Comparative Example 3 provides a crack-resistant concrete and its preparation method. The difference between Comparative Example 3 and Example 2 is that in Comparative Example 3, river sand is used to replace the modified fine aggregate, and polypropylene mesh fiber is used to replace the modified fiber mesh.

[0086] Test and Detection

[0087] The crack-resistant concrete prepared according to Examples 1 - 15 and Comparative Examples 1 - 3 was subjected to the following tests:

[0088] (1) Detect the 28-day compressive strength (MPa) and 28-day splitting tensile strength of the crack-resistant concrete according to GBT 50081-2019.

[0089] (2) Detect the total cracking area per unit area (mm 2 / m 2 ) of the crack-resistant concrete according to GB / T 50082-2009.

[0090] The test data are shown in Table 2.

[0091] Table 2: Compressive strength, splitting tensile strength and total cracking area per unit area of crack-resistant concrete

[0092]

[0093]

[0094] The present application will be described in detail below in combination with the experimental data provided in Tables 1 - 2.

[0095] Examples 1-3 investigated the effects of coarse aggregate, cement, water, and water reducer on the compressive strength and crack resistance of the prepared crack-resistant concrete. Among them, the 28-day compressive strength and 28-day splitting tensile strength of the crack-resistant concrete prepared in Example 2 were greater than those of the crack-resistant concrete prepared in Examples 1 and 3, and the total cracking area per unit area of the crack-resistant concrete prepared in Example 2 was smaller than that of the crack-resistant concrete prepared in Examples 1 and 3, indicating that the crack-resistant concrete prepared in Example 2 had higher compressive strength and stronger crack resistance. Considering comprehensively, Example 2 was the preferred example.

[0096] Taking Example 2 as the control, Examples 4 and 5 investigated the effects of modified fine aggregate on the compressive strength and crack resistance of the prepared crack-resistant concrete. Among them, the 28-day compressive strength and 28-day splitting tensile strength of the crack-resistant concrete prepared in Example 2 were greater than those of the crack-resistant concrete prepared in Examples 4 and 5, and the total cracking area per unit area of the crack-resistant concrete prepared in Example 2 was smaller than that of the crack-resistant concrete prepared in Examples 4 and 5, indicating that the crack-resistant concrete prepared in Example 2 had higher compressive strength and stronger crack resistance. Considering comprehensively, Example 2 was the preferred example.

[0097] Taking Example 2 as the control, Examples 6 and 7 investigated the effects of modified fiber mesh on the compressive strength and crack resistance of the prepared crack-resistant concrete. Among them, the 28-day compressive strength and 28-day splitting tensile strength of the crack-resistant concrete prepared in Example 2 were greater than those of the crack-resistant concrete prepared in Examples 6 and 7, and the total cracking area per unit area of the crack-resistant concrete prepared in Example 2 was smaller than that of the crack-resistant concrete prepared in Examples 6 and 7, indicating that the crack-resistant concrete prepared in Example 2 had higher compressive strength and stronger crack resistance. Considering comprehensively, Example 2 was the preferred example.

[0098] Taking Example 2 as the control, Examples 8 and 9 investigated the effects of the addition amount of retarder on the compressive strength and crack resistance of the prepared crack-resistant concrete. Among them, the 28-day compressive strength and 28-day splitting tensile strength of the crack-resistant concrete prepared in Example 2 were greater than those of the crack-resistant concrete prepared in Examples 8 and 9, and the total cracking area per unit area of the crack-resistant concrete prepared in Example 2 was smaller than that of the crack-resistant concrete prepared in Examples 8 and 9, indicating that the crack-resistant concrete prepared in Example 2 had higher compressive strength and stronger crack resistance. Considering comprehensively, Example 2 was the preferred example.

[0099] Taking Example 2 as a control, Example 10 investigated the effects of the types of retarders on the compressive strength and crack resistance of the crack-resistant concrete prepared. Among them, the 28-day compressive strength and 28-day splitting tensile strength of the crack-resistant concrete prepared in Example 2 were greater than those of the crack-resistant concrete prepared in Example 10, and the total cracking area per unit area of the concrete of the crack-resistant concrete prepared in Example 2 was smaller than that of the crack-resistant concrete prepared in Example 10, indicating that the crack-resistant concrete prepared in Example 2 had a higher compressive strength and stronger crack resistance. Considering comprehensively, Example 2 was a better example.

[0100] Taking Example 2 as a control, Examples 11 and 12 investigated the effects of the length of polypropylene mesh fibers for preparing the modified fiber mesh on the compressive strength and crack resistance of the crack-resistant concrete prepared. Among them, the 28-day compressive strength and 28-day splitting tensile strength of the crack-resistant concrete prepared in Example 11 were greater than those of the crack-resistant concrete prepared in Examples 2 and 12, and the total cracking area per unit area of the concrete of the crack-resistant concrete prepared in Example 11 was smaller than that of the crack-resistant concrete prepared in Examples 2 and 12, indicating that the crack-resistant concrete prepared in Example 11 had a higher compressive strength and stronger crack resistance. Considering comprehensively, Example 11 was a better example.

[0101] Taking Example 11 as a control, Examples 13 and 14 investigated the effects of the number-average molecular weight of polyacrylamide for preparing the modified fiber mesh on the compressive strength and crack resistance of the crack-resistant concrete prepared. Among them, the 28-day compressive strength and 28-day splitting tensile strength of the crack-resistant concrete prepared in Example 11 were greater than those of the crack-resistant concrete prepared in Examples 13 and 14, and the total cracking area per unit area of the concrete of the crack-resistant concrete prepared in Example 11 was smaller than that of the crack-resistant concrete prepared in Examples 13 and 14, indicating that the crack-resistant concrete prepared in Example 11 had a higher compressive strength and stronger crack resistance. Considering comprehensively, Example 11 was a better example.

[0102] Taking Example 11 as a control, Example 15 investigated the influence of the preparation steps of crack-resistant concrete on the compressive strength and crack-resistant ability of the prepared crack-resistant concrete. Among them, the 28-day compressive strength and 28-day splitting tensile strength of the crack-resistant concrete prepared by Example 15 were greater than those of the crack-resistant concrete prepared by Example 11, and the total cracking area per unit area of the concrete of the crack-resistant concrete prepared by Example 15 was smaller than that of the concrete of the crack-resistant concrete prepared by Example 11, indicating that the crack-resistant concrete prepared by Example 15 had a higher compressive strength and strong crack-resistant ability. Considering comprehensively, Example 15 was a better example.

[0103] Taking Example 2 as a control, Comparative Examples 1-3 investigated the influence of modified fine aggregate and modified fiber mesh in crack-resistant concrete on the compressive strength and crack-resistant ability of the prepared crack-resistant concrete. Among them, the 28-day compressive strength and 28-day splitting tensile strength of the specimens prepared by Example 2 were much greater than those of the specimens prepared by Comparative Examples 1-3, and the total cracking area per unit area of the specimens prepared by Example 2 was much smaller than that of the specimens prepared by Comparative Examples 1-3, indicating that the modified fine aggregate and the modified fiber mesh produced a synergistic effect, greatly improving the compressive strength and crack-resistant ability of mass concrete.

[0104] This specific embodiment is only an interpretation of the present application and is not a limitation to the present application. After reading this specification, those skilled in the art can make modifications without creative contributions to this embodiment as needed, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A crack-resistant concrete, characterized in that: It is prepared from components including the following parts by weight: 120 - 180 parts of modified fine aggregate; 200 - 300 parts of coarse aggregate; 120 - 160 parts of cement; 30 - 50 parts of water; 4 - 8 parts of water reducing agent; 1 - 2 parts of modified fiber mesh; 2.5 - 3.5 parts of retarder; The preparation method of the said modified fiber mesh is as follows: Soak polypropylene mesh fiber in polyacrylamide solution and dry it to obtain the modified fiber mesh; The preparation method of the said modified fine aggregate is as follows: Soak fine aggregate in polyvinyl alcohol aqueous solution and dry it to obtain the modified fine aggregate; The said retarder is selected from one or both of borax and boric acid.

2. The crack-resistant concrete according to claim 1, characterized in that: The weight ratio of the said modified fine aggregate to the said modified fiber mesh is (75 - 150):

1.

3. The crack-resistant concrete according to claim 1, wherein: The weight ratio of the said retarder to the said modified fiber mesh is (1.5 - 3):

1.

4. The crack-resistant concrete according to claim 1, wherein: The number average molecular weight of the said polyacrylamide is 3 million - 8 million.

5. The crack-resistant concrete according to claim 1, wherein: The length of the said polypropylene mesh fiber is 6 - 10 mm.

6. The crack-resistant concrete according to claim 1, wherein: The said drying includes: airing the soaked polypropylene mesh fiber for 1.5 - 2.5 h under the temperature condition of 37 - 42 °C.

7. A method for preparing crack-resistant concrete according to any one of claims 1-6, characterized in that: It includes the following steps: S1. Mix the modified fiber mesh, cement, modified fine aggregate and coarse aggregate to obtain the reinforcing material; S2. Stir the reinforcing material, retarder, water reducing agent and water evenly to obtain crack-resistant concrete.

8. The preparation method of the crack-resistant concrete according to claim 7, characterized in that: The said step S1 includes the following steps: S11. Mix and stir the modified fiber mesh and modified fine aggregate to obtain the pre-dispersed material; S12. Stir the cement, coarse aggregate and pre-dispersed material evenly to obtain the reinforcing material.

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