Early-strength agent for shotcrete and its preparation method

Abstract

This invention relates to the field of cement-based building material admixtures, and in particular to an early-strength agent for shotcrete and its preparation method. Specifically, by preparing an early-strength component, a reinforcing component, a viscosity-increasing and elasticity-reducing component, and a slump-retaining component, it promotes cement setting, accelerates the formation of the early-stage ettringite framework in cement, improves the 8-hour strength of shotcrete, promotes the early-stage strength growth of cement, significantly improves the 1-day strength of shotcrete, and can also improve the cohesion of shotcrete and reduce the rebound rate.

Description

Technical Field

[0001] This invention relates to the field of cement-based building material admixtures, and in particular to an early-strength agent for shotcrete and its preparation method. Background Technology

[0002] Tunnel engineering is often involved in the construction of infrastructure such as highways and high-speed railways. A crucial part of tunnel construction is the construction of support engineering, and shotcrete is a commonly used building material in tunnel construction.

[0003] One of the biggest challenges in shotcrete construction is the slow early strength development. Although there are various quick-setting agent products on the market that can meet the needs of rapid setting and hardening to a certain extent, the early strength of these products is still low within 8 hours and 24 hours, which is far from meeting the needs of rapid support for some emergency projects, thus affecting the progress of tunnel construction.

[0004] Currently, improving early strength involves increasing the amount of cement and other binders and adding some traditional early strength agents. However, the strength improvement is limited, and the addition of traditional early strength agents results in severe concrete slump and poor durability, causing problems for construction. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides an early-strength agent for shotcrete. Specifically, by preparing an early-strength component, a reinforcing component, a viscosity-increasing and elasticity-reducing component, and a slump-retaining component, it promotes cement setting, accelerates the formation of the early-stage ettringite framework in cement, improves the 8-hour strength of shotcrete, promotes the early-stage strength growth of cement, significantly improves the 1-day strength of shotcrete, and can also improve the cohesion of shotcrete and reduce the rebound rate.

[0006] Specifically, the early-strength agent for shotcrete of the present invention is composed of the following raw materials in parts by weight: 50-75 parts of early-strength component, 30-50 parts of reinforcing component, 0.5-4 parts of thickening and elasticity-reducing component, and 2-5 parts of slump-retaining component.

[0007] Preferably, the preparation process of the early-strength component is as follows: limestone, montmorillonite, granite, bauxite, magnesium sulfate, and lithium carbonate are mixed evenly in a mass ratio of (20-25):(32-36):(19-21):(7-9):(7-9):(5-7), sintered at high temperature, cooled, and ground to obtain a fine powder. The fine powder and calcium silicate crystal nuclei are then mixed evenly in a mass ratio of (7-8):(2-3) to obtain the final product. The early-strength component prepared by this invention can promote cement setting and accelerate the formation of the early-stage ettringite framework in cement, thereby improving the 8-hour compressive strength of shotcrete.

[0008] Preferably, the preparation process of the reinforcing component is as follows: sodium carbonate, diethanolamine, and triethanolamine are mixed evenly in a mass ratio of (4-6):(55-65):(15-25), heated to 120-130℃ to obtain a mixture, 15-20% (by mass) of calcium oxide is added to the mixture, stirred evenly, and cooled to obtain reinforcing powder. The reinforcing powder, magnesium sulfate, and calcium formate are mixed evenly in a mass ratio of (13-16):(28-32):(50-60) to obtain the final product. The reinforcing component prepared by this invention is a powder, which overcomes the problems caused by adding triethanolamine in liquid form. Furthermore, the reinforcing component can accelerate the early hydration process of cement, promote the early strength growth of shotcrete, and significantly improve the 1-day strength of shotcrete.

[0009] Preferably, the thickening and elasticity-reducing component is at least one of fast-soluble polyvinyl alcohol and nano-silica. The thickening and elasticity-reducing component can increase the cohesion of shotcrete, and combined with the use of early-strength components and existing quick-setting agents, it can significantly reduce the rebound rate of shotcrete.

[0010] Preferably, the slump-retaining component is polymerized from acrylic acid, diallyl tartaric acid diamide, hydroxyethyl acrylate, and macromonomers in a mass ratio of (18-22):(7-10):(28-32):360, and after vacuum drying, it is mixed with a retarder in a mass ratio of 1:(2-4). After wet mixing with water, the cement in shotcrete begins to hydrate. To ensure the smoothness of shotcrete construction, adding the slump-retaining component of this invention can reduce the loss of fluidity caused by the rapid hydration of cement in the early stages.

[0011] This invention addresses the shortcomings of shotcrete, such as low early strength, high rebound rate, and unstable setting time, by combining the aforementioned early strength components, reinforcing components, viscosity-increasing and elasticity-reducing components.

[0012] More preferably, in the early strength component preparation process, magnesium sulfate and lithium carbonate are mixed evenly in a mass ratio of 23:35:20:8:8:6.

[0013] More preferably, in the early strength component preparation process, sintering is carried out at 900-950℃ for 3-4 hours.

[0014] More preferably, the fine powder has a particle size ≤45μm.

[0015] More preferably, in the preparation process of the reinforcing component, sodium carbonate, diethanolamine, and triethanolamine are in a mass ratio of 5:60:20.

[0016] More preferably, in the preparation process of the reinforcing component, the reinforcing powder, magnesium sulfate, and calcium formate are in a mass ratio of 15:30:55.

[0017] More preferably, the slump-preserving component is polymerized from acrylic acid, diallyl tartaric acid diamide, hydroxyethyl acrylate, and macromonomers in a mass ratio of 20:8:30:360, and after vacuum drying, it is mixed with a retarder in a mass ratio of 1:3.

[0018] More preferably, the macromonomer is at least one of TPEG, MPEG, and GPEG.

[0019] More preferably, the preparation process of the slump-preserving component is as follows:

[0020] ① Weigh out 20 parts acrylic acid, 30 parts water, 8 parts diallyl tartaric acid diamide, and 30 parts hydroxyethyl acrylate, mix them, and add oil to obtain material A.

[0021] ② Weigh out 0.5 parts of vitamin C, 60 parts of water, 2.1 parts of mercaptopropionic acid, and 2 parts of sodium bisulfite, mix them thoroughly to obtain material B.

[0022] ③ Weigh out 360 parts of the macromonomer and 300 parts of water, mix them evenly, add 2 parts of caustic soda flakes, 0.05 parts of ferrous sulfate, and 3 parts of hydrogen peroxide, mix evenly, and obtain the base material.

[0023] ④ Add material A and material B simultaneously to the base material over a period of 1.5 hours, maintain the temperature for 0.5 hours, and then vacuum dry to obtain powder.

[0024] ⑤ Mix the powder and retarder in a 1:3 ratio to obtain the final product.

[0025] More preferably, the retarder is at least one of sodium gluconate, borax, sucrose, and sodium citrate.

[0026] This invention also relates to a method for preparing the aforementioned early-strength agent for shotcrete, specifically comprising the following steps:

[0027] 1) Weigh each raw material according to its weight.

[0028] 2) Mix the early strength component, reinforcing component, thickening and elasticity reducing component, and slump retention component evenly to obtain the final product.

[0029] This invention also relates to the application of the aforementioned early-strength agent in the production and construction of shotcrete. Preferably, the amount of early-strength agent added is 4-8% of the mass of the shotcrete cementitious material.

[0030] This invention has the following technical advantages:

[0031] 1. The early-strength agent for shotcrete of this invention can improve the early strength of shotcrete, especially the 8-hour and 1-day strength.

[0032] 2. The preparation process of the early-strength agent for shotcrete of this invention is simple, it can be used in conjunction with commercially available alkali-free quick-setting agents, and it is convenient to use.

[0033] 3. The early-strength agent for shotcrete of this invention can further reduce the rebound rate of shotcrete, and is suitable for rock burst prevention and spraying in seepage tunnels in mines, water conservancy, tunnels and subways. It can meet the needs of rapid support in emergency projects and the spraying process that conventional shotcrete cannot complete in seepage tunnels. Detailed Implementation

[0034] To characterize the technical effect of the present invention, an early strength agent was prepared and its performance was tested. During the testing process, the amount of early strength agent added in the examples and comparative examples was 6% of the mass of the cementitious material, and 6% of the mass of the cementitious material was added with commercially available alkali-free accelerator based on aluminum sulfate. The setting time of cement paste and the compressive strength of cement mortar were tested according to JC477-2005, and the rebound rate of mortar spraying was tested.

[0035] Example 1

[0036] The early-strength agent is characterized by comprising the following raw materials in parts by weight: 65 parts early-strength component, 40 parts reinforcing component, 2.4 parts thickening and elasticity-reducing component, and 3 parts slump-retaining component.

[0037] The preparation process of the early strength component is as follows: limestone, montmorillonite, granite, bauxite, magnesium sulfate, and lithium carbonate are mixed evenly in a mass ratio of 25:33:19:9:8:5, sintered at 950℃ for 3 hours, cooled, and ground to obtain fine powder. The fine powder and calcium silicate crystal nuclei are then mixed evenly in a mass ratio of 8:2 to obtain the final product.

[0038] The preparation process of the reinforcing component is as follows: sodium carbonate, diethanolamine, and triethanolamine are mixed evenly in a mass ratio of 6:55:25, heated to 120°C to obtain a mixed solution, 18% (by mass) of calcium oxide is added to the mixed solution, stirred evenly, and cooled to obtain reinforcing powder. The reinforcing powder, magnesium sulfate, and calcium formate are then mixed evenly in a mass ratio of 1:31:57 to obtain the final product.

[0039] The thickening and elasticity-reducing component is fast-soluble polyvinyl alcohol.

[0040] The slump-preserving component is polymerized from acrylic acid, diallyl tartrate diamide, hydroxyethyl acrylate, and TPEG in a mass ratio of 21:8:28:360, and after vacuum drying, it is mixed with a retarder in a mass ratio of 1:2.5.

[0041] The test results showed that the initial setting time of the cement paste was 3.6 min, the final setting time was 10.4 min, the 8-hour compressive strength was 4.0 MPa, the 1-day compressive strength was 15.3 MPa, and the crown resilience was 6.2%.

[0042] Example 2

[0043] Early strength agent, characterized in that it is composed of the following raw materials in parts by weight: 75 parts early strength component, 45 parts reinforcing component, 3 parts thickening and elasticity reducing component, and 2 parts slump retention component.

[0044] The preparation process of the early-strength component is as follows: limestone, montmorillonite, granite, bauxite, magnesium sulfate, and lithium carbonate are mixed evenly in a mass ratio of 23:35:20:8:8:6, sintered at 900℃ for 4 hours, cooled, and ground to obtain fine powder. The fine powder and calcium silicate crystal nuclei are then mixed evenly in a mass ratio of 7:3 to obtain the final product.

[0045] The preparation process of the reinforcing component is as follows: sodium carbonate, diethanolamine, and triethanolamine are mixed evenly in a mass ratio of 5:60:20, heated to 125°C to obtain a mixed solution, 20% (by mass) of calcium oxide is added to the mixed solution, stirred evenly, and cooled to obtain reinforcing powder. The reinforcing powder, magnesium sulfate, and calcium formate are then mixed evenly in a mass ratio of 15:30:55 to obtain the final product.

[0046] The thickening and elasticity-reducing component is nano-silica.

[0047] The slump-preserving component is polymerized from acrylic acid, diallyl tartaric acid diamide, hydroxyethyl acrylate, and MPEG in a mass ratio of 20:8:30:360. After vacuum drying, it is mixed with a retarder in a mass ratio of 1:3.

[0048] The test results showed that the initial setting time of the cement paste was 3.5 min, the final setting time was 9.3 min, the 8-hour compressive strength was 4.3 MPa, the 1-day compressive strength was 15.8 MPa, and the crown resilience was 5.8%.

[0049] Comparative Example 1

[0050] Early strength agent, characterized in that it is composed of the following raw materials in parts by weight: 75 parts calcium chloride, 45 parts reinforcing component, 3 parts thickening and elasticity-reducing component, and 2 parts slump-retaining component.

[0051] The preparation process of the reinforcing component is as follows: sodium carbonate, diethanolamine, and triethanolamine are mixed evenly in a mass ratio of 5:60:20, heated to 125°C to obtain a mixed solution, 20% (by mass) of calcium oxide is added to the mixed solution, stirred evenly, and cooled to obtain reinforcing powder. The reinforcing powder, magnesium sulfate, and calcium formate are then mixed evenly in a mass ratio of 15:30:55 to obtain the final product.

[0052] The thickening and elasticity-reducing component is nano-silica.

[0053] The slump-preserving component is polymerized from acrylic acid, diallyl tartaric acid diamide, hydroxyethyl acrylate, and MPEG in a mass ratio of 20:8:30:360. After vacuum drying, it is mixed with a retarder in a mass ratio of 1:3.

[0054] The test results showed that the initial setting time of the cement paste was 4.5 min, the final setting time was 11.0 min, the compressive strength at 8 h was 2.7 MPa, the compressive strength at 1 day was 12.7 MPa, and the resilience of the arch crown was 12.4%.

[0055] Comparative Example 2

[0056] Early strength agent, characterized in that it is composed of the following raw materials in parts by weight: 75 parts early strength component, 45 parts reinforcing component, 3 parts thickening and elasticity reducing component, and 2 parts slump retention component.

[0057] The preparation process of the early-strength component is as follows: limestone, granite, bauxite, and lithium carbonate are mixed evenly in a mass ratio of 23:20:8:6, sintered at 900℃ for 4 hours, cooled, and ground to obtain the final product.

[0058] The preparation process of the reinforcing component is as follows: sodium carbonate, diethanolamine, and triethanolamine are mixed evenly in a mass ratio of 5:60:20, heated to 125°C to obtain a mixed solution, 20% (by mass) of calcium oxide is added to the mixed solution, stirred evenly, and cooled to obtain reinforcing powder. The reinforcing powder, magnesium sulfate, and calcium formate are then mixed evenly in a mass ratio of 15:30:55 to obtain the final product.

[0059] The thickening and elasticity-reducing component is nano-silica.

[0060] The slump-preserving component is polymerized from acrylic acid, diallyl tartaric acid diamide, hydroxyethyl acrylate, and MPEG in a mass ratio of 20:8:30:360. After vacuum drying, it is mixed with a retarder in a mass ratio of 1:3.

[0061] The test results showed that the initial setting time of the cement paste was 4.0 min, the final setting time was 10.5 min, the 8-hour compressive strength was 2.9 MPa, the 1-day compressive strength was 12.6 MPa, and the crown resilience was 11.9%.

[0062] Comparative Example 3

[0063] Early strength agent, characterized in that it is composed of the following raw materials in parts by weight: 75 parts early strength component, 45 parts reinforcing component, 3 parts thickening and elasticity reducing component, and 2 parts slump retention component.

[0064] The preparation process of the early-strength component is as follows: limestone, montmorillonite, granite, bauxite, magnesium sulfate, and lithium carbonate are mixed evenly in a mass ratio of 23:35:20:8:8:6, sintered at 900℃ for 4 hours, cooled, and ground to obtain fine powder. The fine powder and calcium silicate crystal nuclei are then mixed evenly in a mass ratio of 7:3 to obtain the final product.

[0065] The preparation process of the reinforcing component is as follows: sodium carbonate, diethanolamine, triethanolamine, magnesium sulfate, and calcium formate are mixed evenly in a mass ratio of 5:60:20:6:11 to obtain the desired product.

[0066] The thickening and elasticity-reducing component is nano-silica.

[0067] The slump-preserving component is polymerized from acrylic acid, diallyl tartaric acid diamide, hydroxyethyl acrylate, and MPEG in a mass ratio of 20:8:30:360. After vacuum drying, it is mixed with a retarder in a mass ratio of 1:3.

[0068] The test results showed that the initial setting time of the cement paste was 4.1 min, the final setting time was 9.8 min, the compressive strength at 8 h was 3.5 MPa, the compressive strength at 1 day was 10.4 MPa, and the resilience rate of the arch crown was 9.1%.

[0069] Comparative Example 4

[0070] Early strength agent, characterized in that it is composed of the following raw materials in parts by weight: 75 parts early strength component, 45 parts reinforcing component, 3 parts thickening and elasticity reducing component, and 2 parts slump retention component.

[0071] The preparation process of the early-strength component is as follows: limestone, montmorillonite, granite, bauxite, magnesium sulfate, and lithium carbonate are mixed evenly in a mass ratio of 23:35:20:8:8:6, sintered at 900℃ for 4 hours, cooled, and ground to obtain fine powder. The fine powder and calcium silicate crystal nuclei are then mixed evenly in a mass ratio of 7:3 to obtain the final product.

[0072] The preparation process of the reinforcing component is as follows: sodium carbonate, diethanolamine, and triethanolamine are mixed evenly in a mass ratio of 5:60:20, heated to 125°C to obtain a mixed solution, then calcium oxide (20% by mass of the mixed solution) is added, stirred evenly, and cooled to obtain the final product.

[0073] The thickening and elasticity-reducing component is nano-silica.

[0074] The slump-preserving component is polymerized from acrylic acid, diallyl tartaric acid diamide, hydroxyethyl acrylate, and MPEG in a mass ratio of 20:8:30:360. After vacuum drying, it is mixed with a retarder in a mass ratio of 1:3.

[0075] The test results showed that the initial setting time of the cement paste was 3.8 min, the final setting time was 10.6 min, the 8-hour compressive strength was 3.7 MPa, the 1-day compressive strength was 11.1 MPa, and the crown resilience was 9.5%.

[0076] Comparative Example 5

[0077] Early strength agent, characterized in that it is composed of the following raw materials in parts by weight: 75 parts early strength component, 45 parts reinforcing component, 3 parts thickening and elasticity reducing component, and 2 parts slump retention component.

[0078] The preparation process of the early-strength component is as follows: limestone, montmorillonite, granite, bauxite, magnesium sulfate, and lithium carbonate are mixed evenly in a mass ratio of 23:35:20:8:8:6, sintered at 900℃ for 4 hours, cooled, and ground to obtain fine powder. The fine powder and calcium silicate crystal nuclei are then mixed evenly in a mass ratio of 7:3 to obtain the final product.

[0079] The preparation process of the reinforcing component is as follows: sodium carbonate, diethanolamine, and triethanolamine are mixed evenly in a mass ratio of 5:60:20, heated to 125°C to obtain a mixed solution, 20% (by mass) of calcium oxide is added to the mixed solution, stirred evenly, and cooled to obtain reinforcing powder. The reinforcing powder, magnesium sulfate, and calcium formate are then mixed evenly in a mass ratio of 15:30:55 to obtain the final product.

[0080] The thickening and elasticity-reducing component is nano-silica.

[0081] The slump-preserving component is polymerized from acrylic acid, acrylamide, hydroxyethyl acrylate, and macromonomers in a mass ratio of 20:8:30:360. After vacuum drying, it is mixed with a retarder in a mass ratio of 1:3.

[0082] The test results showed that the initial setting time of the cement paste was 3.4 min, the final setting time was 9.8 min, the 8-hour compressive strength was 4.1 MPa, the 1-day compressive strength was 15.2 MPa, and the crown resilience was 8.2%.

[0083] Blank example

[0084] The difference between the blank example and Example 2 is that the blank example does not add an early strength agent, but only adds 6% by weight of commercially available alkali-free accelerator based on aluminum sulfate.

[0085] The test results showed that the initial setting time of the cement paste was 4.9 min, the final setting time was 11.4 min, the 8-hour compressive strength was 2.4 MPa, the 1-day compressive strength was 10.6 MPa, and the crown resilience was 14.7%.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An early-strength agent for shotcrete, characterized in that, It is composed of the following raw materials in parts by weight: 50-75 parts early strength component, 30-50 parts reinforcing component, 0.5-4 parts thickening and elasticity reducing component, and 2-5 parts slump retention component. The preparation process of the early strength component is as follows: limestone, montmorillonite, granite, bauxite, magnesium sulfate, and lithium carbonate are mixed evenly in a mass ratio of (20-25):(32-36):(19-21):(7-9):(7-9):(5-7), sintered at high temperature, cooled, and ground to obtain fine powder. The fine powder and calcium silicate crystal nuclei are then mixed evenly in a mass ratio of (7-8):(2-3) to obtain the final product. The preparation process of the reinforcing component is as follows: Sodium carbonate, diethanolamine, and triethanolamine are mixed evenly in a mass ratio of (4-6):(55-65):(15-25), heated to 120-130℃ to obtain a mixed solution, 15-20% (by mass) of calcium oxide is added to the mixed solution, stirred evenly, and cooled to obtain reinforcing powder. The reinforcing powder, magnesium sulfate, and calcium formate are mixed evenly in a mass ratio of (13-16):(28-32):(50-60) to obtain the final product. The thickening and elasticity-reducing components are at least one of fast-dissolving polyvinyl alcohol and nano-silica. The slump-preserving component is polymerized from acrylic acid, diallyl tartaric acid diamide, hydroxyethyl acrylate, and macromonomers in a mass ratio of (18-22):(7-10):(28-32):

360. After vacuum drying, it is mixed with a retarder in a mass ratio of 1:(2-4).

2. The early-strength agent for shotcrete according to claim 1, characterized in that, In the preparation process of the early strength component, limestone, montmorillonite, granite, bauxite, magnesium sulfate, and lithium carbonate are mixed evenly in a mass ratio of 23:35:20:8:8:

6.

3. The early-strength agent for shotcrete according to claim 1, characterized in that, In the preparation process of the early strength component, sintering is carried out at 900-950℃ for 3-4 hours.

4. The early-strength agent for shotcrete according to claim 1, characterized in that, The fine powder has a particle size ≤45μm.

5. The early-strength agent for shotcrete according to claim 1, characterized in that, In the preparation process of the reinforcing component, sodium carbonate, diethanolamine, and triethanolamine are in a mass ratio of 5:60:

20.

6. The early-strength agent for shotcrete according to claim 1, characterized in that, In the preparation process of the reinforcing component, the reinforcing powder, magnesium sulfate, and calcium formate are in a mass ratio of 15:30:

55.

7. The early-strength agent for shotcrete according to claim 1, characterized in that, The slump-preserving component is polymerized from acrylic acid, diallyl tartaric acid diamide, hydroxyethyl acrylate, and macromonomers in a mass ratio of 20:8:30:

360. After vacuum drying, it is mixed with a retarder in a mass ratio of 1:

3.

8. The early-strength agent for shotcrete according to claim 7, characterized in that, The preparation process of the collapse-preserving component is as follows: ① Weigh out 20 parts acrylic acid, 30 parts water, 8 parts diallyl tartaric acid diamide, and 30 parts hydroxyethyl acrylate, mix them, and add oil to obtain material A. ② Weigh out 0.5 parts of vitamin C, 60 parts of water, 2.1 parts of mercaptopropionic acid, and 2 parts of sodium bisulfite, mix them thoroughly to obtain material B. ③ Weigh out 360 parts of the macromonomer and 300 parts of water, mix them evenly, add 2 parts of caustic soda flakes, 0.05 parts of ferrous sulfate, and 3 parts of hydrogen peroxide, mix evenly, and obtain the base material. ④ Add material A and material B simultaneously to the base material over a period of 1.5 hours, maintain the temperature for 0.5 hours, and then vacuum dry to obtain powder. ⑤ Mix the powder and retarder in a 1:3 ratio to obtain the final product.

9. The early-strength agent for shotcrete according to claim 1, characterized in that, The retarder is at least one of sodium gluconate, borax, sucrose, and sodium citrate.

10. The method for preparing the early-strength agent for shotcrete according to any one of claims 1-9, characterized in that, Includes the following steps: 1) Weigh each raw material according to its weight. 2) Mix the early strength component, reinforcing component, thickening and elasticity reducing component, and slump retention component evenly to obtain the final product.