Springback-reducing admixture for sprayed concrete and preparation method thereof

Abstract

The invention provides a springback-reducing admixture for sprayed concrete and a preparation method of the springback-reducing admixture, and relates to the technical field of concrete admixtures. The springback-reducing admixture for the sprayed concrete comprises the following raw materials in percentage by mass: 40-70% of a component A and 30-60% of a component B, the component A comprises the following raw materials in percentage by mass: 30%-50% of calcined kaolin, 10%-20% of light calcined magnesia and 40%-60% of semi-hydrated gypsum. And the component B comprises the following raw materials in percentage by mass: 60-90% of cement, 5-10% of modified rubber powder and 5-10% of cellulose. The springback-reducing admixture for sprayed concrete provided by the invention is applied to sprayed concrete and has relatively low springback rate and relatively high strength.

Description

Technical Field

[0001] The invention relates to the technical field of concrete admixtures, and in particular to a rebound-reducing admixture for shotcrete and a preparation method thereof. Background Art

[0002] As an important transportation project and underground project, the construction quality and construction period of the tunnel are directly related to the safety and economic benefits of the entire project. Among them, shotcrete is a construction method that forms a concrete surface layer of uniform thickness and strength by spraying concrete on the construction surface at high speed. It is the most commonly used material in tunnel support. During the construction process of shotcrete, its rebound is a key parameter. Excessive rebound will inevitably lead to waste of concrete and increase project costs. Therefore, how to reduce the rebound of shotcrete has become an important issue that needs to be solved during tunnel construction. Summary of the invention

[0003] Based on the technical problems existing in the background technology, the present invention proposes a rebound-reducing admixture for shotcrete and a preparation method thereof.

[0004] The invention discloses a rebound reducing admixture for shotcrete, which comprises the following raw materials in percentage by mass: 40% to 70% of component A and 30% to 60% of component B.

[0005] Preferably, the component A comprises the following raw materials in percentage by mass: 30% to 50% calcined kaolin, 10% to 20% light-burned magnesia, and 40% to 60% hemihydrate gypsum.

[0006] More preferably, the calcination temperature of the calcined kaolin is 800-1000° C., and the fineness is 1500-2500 mesh.

[0007] More preferably, the calcination temperature of the light-burned magnesium oxide is 600-800° C., and the fineness is 700-900 mesh.

[0008] More preferably, the hemihydrate gypsum is α-hemihydrate gypsum.

[0009] Preferably, the B component comprises the following raw materials in percentage by mass: 60% to 90% cement, 5% to 10% modified rubber powder, and 5% to 10% cellulose.

[0010] More preferably, the viscosity of the cellulose is 100,000 to 150,000.

[0011] More preferably, the cellulose is hydroxypropyl methylcellulose.

[0012] More preferably, the cement is selected from one or more of PO 52.5 cement, rapid hardening sulphoaluminate cement and magnesia cement.

[0013] More preferably, the method for preparing the modified rubber powder comprises the following steps: uniformly mixing the rubber powder and the silane aqueous solution, ultrasonicating, and drying to obtain the modified rubber powder.

[0014] More preferably, the rubber powder includes vinyl acetate and ethylene copolymer rubber powder (VAC / E), ethylene, vinyl chloride and vinyl laurate terpolymer rubber powder (E / VC / VL), and vinyl acetate, ethylene and higher fatty acid vinyl ester terpolymer rubber powder (VAC / E / VeoVa).

[0015] More preferably, the mass ratio of the vinyl acetate and ethylene copolymer rubber powder (VAC / E), the ethylene, vinyl chloride and vinyl laurate terpolymer rubber powder (E / VC / VL), and the vinyl acetate, ethylene and higher fatty acid vinyl ester terpolymer rubber powder (VAC / E / VeoVa) is (1-3):(0.5-1):1.

[0016] More preferably, the silane comprises one or more of vinyl tris-(2-methoxyethoxy)-silane and 3-acryloxypropyl trimethoxysilane.

[0017] More preferably, the mass fraction of the silane aqueous solution is 1 wt% to 5 wt%.

[0018] More preferably, the mass ratio of the rubber powder to the silane aqueous solution is (1-3):(10-20).

[0019] The present invention also provides a method for preparing a rebound-reducing admixture for shotcrete, comprising the following steps:

[0020] Calcined kaolin, light-burned magnesia and hemihydrate gypsum are uniformly mixed to obtain component A, cement, modified rubber powder and cellulose are uniformly mixed to obtain component B, and component A and component B are uniformly mixed to obtain a rebound-reducing admixture for shotcrete.

[0021] The beneficial effects of the present invention are:

[0022] The present invention proposes a rebound-reducing admixture for shotcrete, which includes calcined kaolin, light-burned magnesium oxide, hemihydrate gypsum, cement, modified rubber powder, and cellulose. The raw materials work synergistically, and the prepared rebound-reducing admixture for shotcrete is applied to shotcrete, which is beneficial to reducing the rebound rate and saving engineering costs. The modified rubber powder in the present invention can not only enhance the intermolecular force of shotcrete and reduce the rebound elasticity of shotcrete, but also the surface energy of the modified rubber powder after modification is reduced, which improves the dispersibility of the admixture in the shotcrete, so that the admixture is evenly dispersed in the shotcrete system. Compared with uncalcined kaolin, calcined kaolin has more active points and higher tensile strength. Light-burned magnesium oxide has a loose texture, good activity, and stable quality, and is applied to shotcrete to facilitate uniform dispersion. Hemihydrate gypsum has a short setting time, and after mixing with water, it can be modulated into a plastic slurry. After a period of reaction, it will lose its plasticity and solidify and harden into a solid with a certain strength. Rapid-hardening sulphoaluminate cement still has a fast setting and hardening speed without adding accelerating setting and hardening components, and has good low-temperature performance, which is beneficial to process operation. The addition of cellulose not only makes the slurry have a better water retention effect, but also helps to reduce the generation of cracks. The present invention can effectively reduce the rebound of shotcrete in water-rich areas by adding a rebound-reducing admixture (replacing cement in equal amounts) to shotcrete. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is described in detail through specific embodiments.

[0024] Unless otherwise specified, the materials, reagents, etc. used in the following examples and comparative examples can be obtained from commercial sources.

[0025] Example 1

[0026] A rebound-reducing admixture for shotcrete comprises the following raw materials in mass percentage: 40% component A and 60% component B. Component A comprises the following raw materials in mass percentage: 30% calcined kaolin, 10% lightly calcined magnesia, and 60% α-type semi-hydrated gypsum. Component B comprises the following raw materials in mass percentage: 40% PO 52.5 cement, 40% fast-hardening sulphoaluminate cement, 10% modified rubber powder, and 10% hydroxypropyl methylcellulose with a viscosity of 100,000. The calcination temperature of the calcined kaolin is 900°C and the fineness is 2000 mesh; the calcination temperature of the lightly calcined magnesia is 700°C and the fineness is 800 mesh.

[0027] The preparation method of modified rubber powder comprises the following steps: VAC / E, E / VC / VL, VAC / E / VeoVa and 3wt% vinyl tri-(2-methoxyethoxy)-silane aqueous solution are mixed uniformly in a mass ratio of 2:0.5:1:15, ultrasonically treated, and dried to obtain modified rubber powder.

[0028] A method for preparing a rebound-reducing admixture for shotcrete comprises the following steps:

[0029] Calcined kaolin, light-burned magnesium oxide and α-type hemihydrate gypsum are uniformly mixed to obtain component A, PO 52.5 cement, fast-hardening sulphoaluminate cement, modified rubber powder and 100,000 viscosity hydroxypropyl methylcellulose are uniformly mixed to obtain component B, and component A and component B are uniformly mixed to obtain a rebound-reducing admixture for shotcrete.

[0030] Example 2

[0031] A rebound-reducing admixture for shotcrete comprises the following raw materials in mass percentage: 30% component A and 70% component B. Component A comprises the following raw materials in mass percentage: 30% calcined kaolin, 10% lightly calcined magnesia, and 60% α-type semi-hydrated gypsum. Component B comprises the following raw materials in mass percentage: 40% PO 52.5 cement, 40% fast-hardening sulphoaluminate cement, 10% modified rubber powder, and 10% hydroxypropyl methylcellulose with a viscosity of 100,000. The calcination temperature of the calcined kaolin is 900°C and the fineness is 2000 mesh; the calcination temperature of the lightly calcined magnesia is 700°C and the fineness is 800 mesh.

[0032] The preparation method of modified rubber powder comprises the following steps: mixing VAC / E, E / VC / VL, VAC / E / VeoVa and 3wt% vinyl tri-(2-methoxyethoxy)-silane aqueous solution at a mass ratio of 3:1:1:20, ultrasonicating and drying to obtain modified rubber powder.

[0033] A method for preparing a rebound-reducing admixture for shotcrete comprises the following steps:

[0034] Calcined kaolin, light-burned magnesium oxide and α-type hemihydrate gypsum are uniformly mixed to obtain component A, PO 52.5 cement, fast-hardening sulphoaluminate cement, modified rubber powder and 100,000 viscosity hydroxypropyl methylcellulose are uniformly mixed to obtain component B, and component A and component B are uniformly mixed to obtain a rebound-reducing admixture for shotcrete.

[0035] Example 3

[0036] A rebound-reducing admixture for shotcrete comprises the following raw materials in mass percentage: 40% component A and 60% component B. Component A comprises the following raw materials in mass percentage: 50% calcined kaolin, 10% lightly calcined magnesia, and 40% α-type semi-hydrated gypsum. Component B comprises the following raw materials in mass percentage: 40% PO 52.5 cement, 40% fast-hardening sulphoaluminate cement, 10% modified rubber powder, and 10% hydroxypropyl methylcellulose with a viscosity of 100,000. The calcination temperature of the calcined kaolin is 900°C and the fineness is 2000 mesh; the calcination temperature of the lightly calcined magnesia is 700°C and the fineness is 800 mesh.

[0037] The preparation method of modified rubber powder comprises the following steps: VAC / E, E / VC / VL, VAC / E / VeoVa and 3wt% vinyl tri-(2-methoxyethoxy)-silane aqueous solution are mixed uniformly in a mass ratio of 2:0.5:1:15, ultrasonically treated, and dried to obtain modified rubber powder.

[0038] A method for preparing a rebound-reducing admixture for shotcrete comprises the following steps:

[0039] Calcined kaolin, light-burned magnesium oxide and α-type hemihydrate gypsum are uniformly mixed to obtain component A, PO 52.5 cement, fast-hardening sulphoaluminate cement, modified rubber powder and 100,000 viscosity hydroxypropyl methylcellulose are uniformly mixed to obtain component B, and component A and component B are uniformly mixed to obtain a rebound-reducing admixture for shotcrete.

[0040] Comparative Example 1

[0041] No rebound reducing admixture was added to the shotcrete as comparative example 1.

[0042] Comparative Example 2

[0043] A rebound-reducing admixture for shotcrete comprises the following raw materials in percentage by mass: 30% calcined kaolin, 10% light-burned magnesia and 60% alpha-type hemihydrate gypsum.

[0044] A method for preparing a rebound-reducing admixture for shotcrete comprises the following steps:

[0045] Calcined kaolin, light-burned magnesia and alpha-type hemihydrate gypsum are uniformly mixed to obtain a rebound-reducing admixture for shotcrete.

[0046] Comparative Example 3

[0047] A rebound-reducing admixture for shotcrete comprises the following raw materials in percentage by mass: 40% PO 52.5 cement, 40% fast-hardening sulphoaluminate cement, 10% modified rubber powder and 10% 100,000 viscosity hydroxypropyl methylcellulose.

[0048] The preparation method of modified rubber powder comprises the following steps: VAC / E, E / VC / VL, VAC / E / VeoVa and 3wt% vinyl tri-(2-methoxyethoxy)-silane aqueous solution are mixed uniformly in a mass ratio of 2:0.5:1:15, ultrasonically treated, and dried to obtain modified rubber powder.

[0049] A method for preparing a rebound-reducing admixture for shotcrete comprises the following steps:

[0050] The rebound-reducing admixture for shotcrete is obtained by uniformly mixing PO 52.5 cement, fast-hardening sulphoaluminate cement, modified rubber powder and hydroxypropyl methylcellulose with a viscosity of 100,000.

[0051] Comparative Example 4

[0052] A rebound-reducing admixture for shotcrete comprises the following raw materials in mass percentage: 40% component A and 60% component B. Component A comprises the following raw materials in mass percentage: 30% calcined kaolin, 10% lightly calcined magnesium oxide, and 60% α-type hemihydrate gypsum. Component B comprises the following raw materials in mass percentage: 40% PO 52.5 cement, 40% fast-hardening sulphoaluminate cement, 10% rubber powder, and 10% hydroxypropyl methylcellulose with a viscosity of 100,000.

[0053] A method for preparing a rebound-reducing admixture for shotcrete comprises the following steps:

[0054] Calcined kaolin, light-burned magnesia and α-type hemihydrate gypsum are uniformly mixed to obtain component A, PO 52.5 cement, fast-hardening sulphoaluminate cement, rubber powder and 100,000 viscosity hydroxypropyl methylcellulose are uniformly mixed to obtain component B, and component A and component B are uniformly mixed to obtain a rebound-reducing admixture for shotcrete.

[0055] The rebound-reducing admixtures for shotcrete prepared in the above-mentioned Examples 1 to 3 and Comparative Examples 1 to 4 were applied to shotcrete according to the following concrete mix ratios. The specific concrete mix ratios are shown in Table 1:

[0056] Table 1

[0057]

[0058]

[0059] The concrete mixes of Examples 1 to 3 and Comparative Examples 1 to 4 were uniformly mixed to obtain shotcrete, and the shotcrete was tested for its rebound rate, 7d strength, and 28d strength according to the Technical Specification for Application of Shotcrete JGJ / T 372-2016 and the Test Method for Rebound Rate of Shotcrete JSCE-F563-2005. The test results are shown in Table 2.

[0060] Table 2

[0061]

[0062]

[0063] It can be seen from the data in Table 2 that the rebound-reducing admixture for shotcrete prepared by the present invention is applied to shotcrete, so that the shotcrete has a lower rebound rate and higher 7d strength and 28d strength, indicating that the rebound-reducing admixture prepared by the present invention can be effectively applied to shotcrete, reduce the rebound rate, save engineering costs, and improve its strength. It can be seen from the data of Comparative Example 1 and the embodiment that the rebound rate of shotcrete without adding the rebound-reducing admixture is as high as 15%, and the 7d strength and 28d strength are slightly reduced. It can be seen from the data of Comparative Examples 2 to 3 and the embodiment that only adding component A or component B as a rebound-reducing admixture to shotcrete increases the rebound rate and reduces the strength. It can be seen from the data of Comparative Example 4 and the embodiment that the addition of modified rubber powder is beneficial to reducing the rebound rate of shotcrete.

[0064] In summary, the rebound-reducing admixture for shotcrete provided by the present invention is applied to shotcrete and has a lower rebound rate and higher strength.

[0065] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A rebound reducing admixture for shotcrete, characterized in that: The invention comprises the following raw materials in mass percentage: 40% to 70% of component A and 30% to 60% of component B, wherein the component B comprises the following raw materials in mass percentage: 60% to 90% of cement, 5% to 10% of modified rubber powder and 5% to 10% of cellulose.

2. The rebound reducing admixture for shotcrete according to claim 1, characterized in that: The preparation method of the modified rubber powder comprises the following steps: uniformly mixing the rubber powder and the silane aqueous solution, ultrasonicating, and drying to obtain the modified rubber powder.

3. The rebound reducing admixture for shotcrete according to claim 2, characterized in that: The rubber powder includes vinyl acetate and ethylene copolymer rubber powder, ethylene and vinyl chloride and vinyl laurate ternary copolymer rubber powder, and vinyl acetate and ethylene and higher fatty acid vinyl ester ternary copolymer rubber powder; the mass ratio of the vinyl acetate and ethylene copolymer rubber powder, the ethylene and vinyl chloride and vinyl laurate ternary copolymer rubber powder, and the vinyl acetate and ethylene and higher fatty acid vinyl ester ternary copolymer rubber powder is (1-3): (0.5-1):

1.

4. The rebound reducing admixture for shotcrete according to claim 2, characterized in that: The silane includes one or more of vinyl tri-(2-methoxyethoxy)-silane and 3-acryloxypropyl trimethoxysilane; the mass fraction of the silane aqueous solution is 1wt% to 5wt%; the mass ratio of the rubber powder to the silane aqueous solution is (1 to 3): (10 to 20).

5. The rebound reducing admixture for shotcrete according to claim 1, characterized in that: The viscosity of the cellulose is 100,000 to 150,000; the cement is selected from one or more of PO 52.5 cement, fast-hardening sulphoaluminate cement and magnesia cement.

6. The rebound reducing admixture for shotcrete according to claim 1, characterized in that: The component A comprises the following raw materials in percentage by mass: 30% to 50% calcined kaolin, 10% to 20% light-burned magnesia, and 40% to 60% hemihydrate gypsum.

7. The rebound reducing admixture for shotcrete according to claim 6, characterized in that: The calcination temperature of the calcined kaolin is 800-1000°C, and the fineness is 1500-2500 meshes; the calcination temperature of the light-burned magnesium oxide is 600-800°C, and the fineness is 700-900 meshes; and the semi-hydrated gypsum is α-type semi-hydrated gypsum.

8. The method for preparing the rebound-reducing admixture for shotcrete according to any one of claims 1 to 7, characterized in that: The following steps are involved: Calcined kaolin, light-burned magnesia and hemihydrate gypsum are uniformly mixed to obtain component A, cement, modified rubber powder and cellulose are uniformly mixed to obtain component B, and component A and component B are uniformly mixed to obtain a rebound-reducing admixture for shotcrete.

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