A catalyst for shotcrete and its preparation method

Abstract

This invention provides a catalyst for shotcrete and its preparation method, belonging to the field of concrete admixtures. The shotcrete catalyst, by weight percentage, comprises the following components: 10-12% water-reducing agent, 0.3-0.5% modified viscosity modifier, 1-5% ion chelating agent, 6-8% modified setting aid, 0.1-0.2% air-entraining agent, and the balance being water. The preparation method of the catalyst includes the following steps: adding the modified viscosity modifier to water, stirring evenly, and then sequentially adding the water-reducing agent, ion chelating agent, modified setting aid, and air-entraining agent, stirring to obtain the product. This invention, through the synergistic effect of the modified viscosity modifier and modified setting aid, obtains a catalyst specifically for C25 shotcrete. In application, it not only reduces the cement content of concrete, meeting the standard strength of C25 shotcrete at 28 days, but also reduces the dosage of accelerators, lowers the rebound rate, and is less prone to pipe clogging.

Description

Technical Field

[0001] This invention relates to the field of shotcrete admixtures, and more specifically to a catalyst for shotcrete and its preparation method. Background Technology

[0002] Shotcrete is a construction method that uses a pressure spray gun to apply and pour fine aggregate concrete. It is commonly used for pouring linings for thin-walled structures such as tunnel linings, walls, and ceilings, as well as for the protective layer of steel structures. Wet shotcrete uses compressed air as power, employing concrete spraying machinery to mix cement, sand, aggregate, accelerators, admixtures, and water in a specific ratio, transport the mixture through pipelines, and spray it at high speed onto the surface of rock or concrete. Due to its unique application method, wet shotcrete requires a larger quantity and incurs higher costs in actual construction.

[0003] It is well known that approximately 300 kg of cement per cubic meter is sufficient to meet the design strength of C25 shotcrete, but currently we use 440-500 kg / m³; this is a huge waste in terms of strength and extremely environmentally unfriendly. The main purpose of increasing cement usage in existing technologies is to enable the concrete to reach initial strength faster, reduce spalling, and control the rebound rate. Therefore, increasing cement usage is not to meet the design strength, but to control the rebound rate. While existing C25 shotcrete technologies use increased cement usage to control the rebound rate, this wastes a large amount of cement and is also environmentally unfriendly. Based on this, this invention proposes a catalyst for shotcrete and its preparation method, which, while reducing cement usage, meets the initial strength requirements of concrete and effectively controls the rebound rate. Summary of the Invention

[0004] The main objective of this invention is to provide a catalyst for shotcrete and its preparation method, so as to solve the problems in the background art.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A catalyst for shotcrete, comprising the following components by weight percentage:

[0007] Water-reducing agent 10-12%, modified viscosity modifier 0.3-0.5%, ion chelating agent 1-5%, modified coagulant 6-8%, air-entraining agent 0.1-0.2%, balance is water.

[0008] Preferably, the preparation method of the modified viscosity modifier includes the following steps:

[0009] Nano-silica was added to a dispersion solvent and ultrasonically dispersed. After uniform dispersion, it was fed into a grinder and ground for 10-15 minutes at a speed of 1000-1500 r / min to obtain a ground mixture.

[0010] Add the coupling agent to deionized water to prepare an aqueous solution with a mass concentration of 3-6%. Stir at 800-1000 r / min for 5-8 min, then add hydroxymethyl cellulose ether and ultrasonically mix for 10-15 min to obtain a hydroxymethyl cellulose ether mixture.

[0011] Mix the ground mixture and the hydroxymethyl cellulose ether mixture evenly, react at 80-90℃ for 6-8 hours, and then dry in an oven at 80-100℃ to obtain the modified viscosity modifier.

[0012] More preferably, the dispersing solvent is anhydrous ethanol;

[0013] The nano-silica and the dispersing solvent are prepared into an ethanol mixture with a mass concentration of 5-8%;

[0014] The coupling agent is a silane coupling agent.

[0015] The silane coupling agent is methacryloxysilane.

[0016] More preferably, the mass ratio of the nano-silica, coupling agent and hydroxymethyl cellulose ether is 1:0.1-0.3:1.2-2.

[0017] In this invention, nano-silica is uniformly dispersed in anhydrous ethanol, and then mixed with a mixture of silane coupling agent and hydroxymethyl cellulose ether. The hydroxymethyl cellulose ether reacts with the hydroxyl groups on the surface of the modified nano-silica to form hydrogen bonds and crosslink into a network structure, thereby improving the cohesion of the subsequent concrete and improving the viscosity and stability of the concrete.

[0018] Preferably, the preparation method of the modified coagulant includes the following steps:

[0019] Add a 20-25% aluminum sulfate solution to a 10-15% aluminum hydroxide aqueous solution, stir and mix, react at 115-130℃ for 3-3.5 hours, then react at 85-100℃ for 4-5 hours, and finally add the modifier and stir evenly to obtain the modified coagulant.

[0020] More preferably, the molar ratio of aluminum sulfate to aluminum hydroxide is 0.8-1.2:1.

[0021] More preferably, the modifier is a mixture of acetic acid and polyacrylamide in a mass ratio of 2-3:1.

[0022] This invention modifies the setting aid by using a two-component system of aluminum sulfate and aluminum hydroxide in a molar ratio of (0.8-1.2):1. Compared with a single aluminum sulfate component (a molar ratio of aluminum to sulfate of 0.66), the two-component setting aid increases the aluminum content and decreases the sulfate content. The molar ratio of aluminum to sulfate in the setting aid is increased to 0.9-1.1. This can reduce the impact on concrete durability while ensuring the setting effect, thus overcoming the limitations of the traditional single aluminum sulfate component to a certain extent.

[0023] Preferably, the water-reducing agent is one of a polycarboxylate water-reducing agent or a naphthalene sulfonate water-reducing agent.

[0024] More preferably, the water-reducing agent is a polycarboxylate water-reducing agent.

[0025] Preferably, the ion chelating agent is one of EDTA, sodium tripolyphosphate, or sodium gluconate.

[0026] Preferably, the air-entraining agent is one of rosin-based air-entraining agents, alkylbenzene sulfonates, or fatty alcohol sulfonates.

[0027] Preferably, the air-entraining agent is a rosin-based air-entraining agent.

[0028] More preferably, the air-entraining agent is sodium rosinate.

[0029] Another object of the present invention is to provide a method for preparing a catalyst for shotcrete, comprising the following steps:

[0030] Weigh each component according to the above weight percentages, including water-reducing agent, modified viscosity modifier, ion chelating agent, modified coagulant, air-entraining agent and water;

[0031] Add a modified viscosity modifier to water, stir evenly, and then add water-reducing agent, ion chelating agent, modified coagulant and air-entraining agent in sequence. Stir at 600-800 r / min for 40-60 minutes to obtain the catalyst for shotcrete.

[0032] The present invention also provides the application of the aforementioned catalyst for shotcrete in C25 shotcrete.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. This invention uses water-reducing agent, modified viscosity modifier, ion chelating agent, modified setting aid and air-entraining agent as raw materials, and coordinates the percentage of each component to prepare a catalyst for C25 shotcrete. When applied, it can not only reduce the amount of cement used in concrete to meet the standard strength of C25 shotcrete at 28 days, but also reduce the dosage of quick-setting agent, reduce the rebound rate, and prevent pipe blockage.

[0035] 2. This invention, through the synergistic effect between modified viscosity modifiers and modified setting aids, can meet the initial strength requirements of concrete while reducing cement usage, and significantly and effectively control the rebound rate.

[0036] 3. The catalyst of the present invention can significantly improve the construction quality of shotcrete while ensuring the long-term mechanical properties and durability of shotcrete. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and data. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the scope of the invention in any way. Furthermore, the technical features involved in the various embodiments of the invention described below can be combined with each other as long as they do not conflict with each other.

[0038] All substances involved in the embodiments of this invention are commercially available.

[0039] Example 1

[0040] This embodiment provides a catalyst for shotcrete, comprising the following components by weight percentage: 10% water-reducing agent, 0.3% modified viscosity modifier, 1% ion chelating agent, 6% modified setting aid, 0.1% air-entraining agent, and the remainder being water.

[0041] The water-reducing agent mentioned above is a polycarboxylate water-reducing agent, the ion chelating agent is EDTA, and the air-entraining agent is sodium rosinate.

[0042] The preparation method of the sprayed concrete catalyst provided in this embodiment is as follows:

[0043] S1. Preparation of modified viscosity modifier:

[0044] S101. Nano-silica is added to anhydrous ethanol and ultrasonically dispersed at an ultrasonic power of 250W. After uniform dispersion, it is fed into a grinder and ground for 10 minutes at a grinding speed of 1000r / min to obtain a ground mixture.

[0045] The nano-silica and the dispersing solvent are prepared into an ethanol mixture with a mass concentration of 5%.

[0046] S102. Add the silane coupling agent to deionized water to prepare an aqueous solution with a mass concentration of 3%, stir at 800 r / min for 5 min, then add hydroxymethyl cellulose ether, and ultrasonically mix for 10 min with an ultrasonic power of 250 W to obtain a hydroxymethyl cellulose ether mixture.

[0047] The mass ratio of the nano-silica, silane coupling agent, and hydroxymethyl cellulose ether is 1:0.1:1.2.

[0048] S103. Mix the grinding mixture and the hydroxymethyl cellulose ether mixture evenly, react at 80°C for 6 hours, and then dry in an oven at 80°C to obtain the modified viscosity modifier.

[0049] S2. Preparation of modified coagulating aid:

[0050] A 20% aluminum sulfate solution was added to a 10% aluminum hydroxide solution and stirred until homogeneous. The mixture was first reacted at 115°C for 3 hours, then at 85°C for 4 hours. Finally, a modifier was added and stirred until homogeneous to obtain the modified coagulant.

[0051] The aluminum hydroxide to aluminum sulfate equivalent ratio is 1:1; the modifier is a mixture of acetic acid and polyacrylamide in a mass ratio of 2:1.

[0052] S3. Preparation of catalysts for shotcrete:

[0053] Weigh each component according to the above proportions, add the modified viscosity modifier to the water, stir evenly, and then add the water-reducing agent, ion chelating agent, modified coagulant and air-entraining agent in sequence. Stir for 40 minutes at a speed of 600 r / min to obtain the catalyst for shotcrete.

[0054] Example 2

[0055] This embodiment provides a catalyst for shotcrete, comprising the following components by weight percentage: 12% water-reducing agent, 0.5% modified viscosity modifier, 5% ion chelating agent, 8% modified setting aid, 0.2% air-entraining agent, and the remainder being water.

[0056] The aforementioned water-reducing agent is a polycarboxylate water-reducing agent, the ion chelating agent is sodium gluconate, and the air-entraining agent is sodium rosinate.

[0057] The preparation method of the sprayed concrete catalyst provided in this embodiment is as follows:

[0058] S1. Preparation of modified viscosity modifier:

[0059] S101. Nano-silica is added to anhydrous ethanol and ultrasonically dispersed at an ultrasonic power of 250W. After uniform dispersion, it is fed into a grinder and ground for 15 minutes at a grinding speed of 1500r / min to obtain a ground mixture.

[0060] The nano-silica and the dispersing solvent are prepared into an ethanol mixture with a mass concentration of 8%.

[0061] S102. Add the silane coupling agent to deionized water to prepare an aqueous solution with a mass concentration of 6%, and stir at 1000 r / min for 8 min. Then add hydroxymethyl cellulose ether and ultrasonically mix for 15 min with an ultrasonic power of 250 W to obtain a hydroxymethyl cellulose ether mixture.

[0062] The mass ratio of the nano-silica, silane coupling agent, and hydroxymethyl cellulose ether is 1:0.3:2.

[0063] S103. Mix the grinding mixture and the hydroxymethyl cellulose ether mixture evenly, react at 90°C for 8 hours, and then dry in an oven at 100°C to obtain the modified viscosity modifier.

[0064] S2. Preparation of modified coagulating aid:

[0065] A 25% aluminum sulfate solution was added to a 15% aluminum hydroxide solution and stirred until homogeneous. The mixture was first reacted at 130°C for 3.5 hours, then at 100°C for 5 hours. Finally, a modifier was added and stirred until homogeneous to obtain the modified coagulant.

[0066] The aluminum hydroxide to aluminum sulfate equivalent ratio is 1:1; the modifier is a mixture of acetic acid and polyacrylamide in a mass ratio of 2:1.

[0067] S3. Preparation of catalysts for shotcrete:

[0068] Weigh each component according to the above weight percentages, add the modified viscosity modifier to the water, stir evenly, and then add the water-reducing agent, ion chelating agent, modified coagulant and air-entraining agent in sequence. Stir for 60 minutes at a speed of 800 r / min to obtain the catalyst for shotcrete.

[0069] Example 3

[0070] This embodiment provides a catalyst for shotcrete, comprising the following components by weight percentage: 11% water-reducing agent, 0.4% modified viscosity modifier, 3% ion chelating agent, 7% modified setting aid, 0.15% air-entraining agent, and the remainder being water.

[0071] The water-reducing agent mentioned above is a polycarboxylate water-reducing agent, the ion chelating agent is EDTA, and the air-entraining agent is sodium rosinate.

[0072] The preparation method of the sprayed concrete catalyst provided in this embodiment is as follows:

[0073] S1. Preparation of modified viscosity modifier:

[0074] S101. Nano-silica is added to anhydrous ethanol and ultrasonically dispersed at an ultrasonic power of 250W. After uniform dispersion, it is fed into a grinder and ground for 15 minutes at a grinding speed of 1500r / min to obtain a ground mixture.

[0075] The nano-silica and the dispersing solvent are prepared into an ethanol mixture with a mass concentration of 6%.

[0076] S102. Add the silane coupling agent to deionized water to prepare an aqueous solution with a mass concentration of 5%, stir at 900 r / min for 6 min, then add hydroxymethyl cellulose ether and ultrasonically mix for 12 min with an ultrasonic power of 250 W to obtain a hydroxymethyl cellulose ether mixture.

[0077] The mass ratio of the nano-silica, silane coupling agent, and hydroxymethyl cellulose ether is 1:0.2:1.6.

[0078] S103. Mix the grinding mixture and the hydroxymethyl cellulose ether mixture evenly, react at 85°C for 7 hours, and then dry in an oven at 90°C to obtain the modified viscosity modifier.

[0079] S2. Preparation of modified coagulating aid:

[0080] A 20% aluminum sulfate solution was added to a 10% aluminum hydroxide solution and stirred until homogeneous. The mixture was first reacted at 120°C for 3.5 hours, then at 90°C for 4.5 hours. Finally, a modifier was added and stirred until homogeneous to obtain the modified coagulation aid.

[0081] The aluminum hydroxide to aluminum sulfate equivalent ratio is 1:1; the modifier is a mixture of acetic acid and polyacrylamide in a mass ratio of 2.5:1.

[0082] S3. Preparation of catalysts for shotcrete:

[0083] Weigh each component according to the above proportions, add the modified viscosity modifier to the water, stir evenly, and then add the water-reducing agent, ion chelating agent, modified coagulant and air-entraining agent in sequence. Stir for 50 minutes at a speed of 700 r / min to obtain the catalyst for shotcrete.

[0084] Comparative Example 1

[0085] The comparative example is basically the same as Example 3, except that nano-silica was not added when preparing the modified viscosity modifier. Otherwise, it is the same as Example 3.

[0086] Comparative Example 2

[0087] The comparative example is basically the same as Example 3, except that the dispersing solvent anhydrous ethanol was not added when preparing the modified viscosity modifier. Otherwise, it is the same as Example 3.

[0088] Comparative Example 3

[0089] This comparative example is basically the same as Example 3, except that no grinding mixture was added when preparing the modified viscosity modifier. Otherwise, it is the same as Example 3.

[0090] Comparative Example 4

[0091] The comparative example is basically the same as Example 3, except that hydroxymethyl cellulose ether is used directly instead of the modified viscosity modifier. Otherwise, it is the same as Example 3.

[0092] Comparative Example 5

[0093] This comparative example is basically the same as Example 3, except that acetic acid is used alone as the modifier, otherwise it is the same as Example 3.

[0094] Comparative Example 6

[0095] The comparative example is basically the same as Example 3, except that polyacrylamide is used alone as the modifier, and everything else is the same as in Example 3.

[0096] Comparative Example 7

[0097] The comparative example is basically the same as Example 3, except that no modifier was added, otherwise it is the same as Example 3.

[0098] Comparative Example 8

[0099] The comparative example is basically the same as Example 3, except that the modified coagulant uses a single-component system of aluminum sulfate, and everything else is the same as in Example 3.

[0100] Concrete performance testing:

[0101] The rebound rate and compressive strength of shotcrete were tested according to the test methods for rebound rate, specimen preparation and compressive strength of shotcrete in the "Technical Specification for Application of Shotcrete" (JGJ / T372).

[0102] 1.1 C25 shotcrete was prepared using the catalysts of Examples 1-3 and Comparative Examples 1-8 of the present invention. The mix proportions of the C25 shotcrete are shown in Table 1.

[0103] Table 1 Concrete Mix Proportions

[0104]

[0105] In Table 1, the admixtures include catalysts and accelerators. The accelerators are alkali-free, the catalyst dosage is 1%, and the average accelerator dosage is 3.96%.

[0106] 1.2 C25 shotcrete was prepared using existing polycarboxylate superplasticizers. The mix proportions of the concrete are shown in Table 2.

[0107] Table 2 Concrete Mix Proportions

[0108]

[0109] In Table 2, the admixtures include water-reducing agents and accelerators, with an average accelerator dosage of 6.36%.

[0110] 1.3 C25 sprayed concrete was prepared using the catalysts of Examples 1-3 and Comparative Examples 1-8 of the present invention, and its performance was tested. The results are shown in Table 3.

[0111] Table 3 Performance Test Results

[0112]

[0113] As shown in Table 3, the shotcrete prepared by the catalyst in Examples 1-3 of this invention meets the standard strength of C25 shotcrete after 28 days of curing, and the average rebound rate of the prepared C25 shotcrete is between 5.2% and 5.5%. In Comparative Examples 1-3, one component of the modified viscosity modifier in the catalyst of this invention was changed, and the performance of the shotcrete prepared was significantly lower than that of Example 3. In Comparative Examples 5-7, one component of the modified setting aid in the catalyst of this invention was changed, and the performance of the shotcrete prepared was significantly lower than that of Example 3. In Comparative Example 4, the modified viscosity modifier of the catalyst of this invention was hydroxymethyl cellulose ether, and the performance of the shotcrete prepared was far lower than that of Example 3. In Comparative Example 8, the modified setting aid of the catalyst of this invention was a single-component system of aluminum sulfate, and the performance of the shotcrete prepared was far lower than that of Example 3. Therefore, it can be seen that the catalyst of this invention can significantly reduce the rebound rate of shotcrete and enhance the compressive strength of concrete.

[0114] Analysis of the data in Tables 1-3 shows that the rebound rate of C25 shotcrete prepared with existing polycarboxylate superplasticizers is 9.72%, and the dosage of accelerator is 6.36%. In contrast, the rebound rate of concrete prepared with the catalyst in Example 3 of this invention is 5.2%, and the dosage of accelerator is 3.96%. Therefore, it can be seen that the concrete prepared using the catalyst of this invention significantly reduces the amount of cement used, while meeting the C25 design strength, and also reduces the dosage of accelerator, thereby reducing the rebound rate, concrete loss, and construction costs.

[0115] In summary, this invention, through the synergistic effect between modified viscosity modifiers and modified setting aids, enables the prepared catalyst to meet the initial strength requirements of C25 shotcrete while reducing cement usage, and to significantly and effectively control the rebound rate.

[0116] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A catalyst for shotcrete, characterized in that: By weight percentage, it includes the following components: 10-12% water-reducing agent, 0.3-0.5% modified viscosity modifier, 1-5% ion chelating agent, 6-8% modified coagulant, 0.1-0.2% air-entraining agent, and the balance being water; The preparation method of the modified viscosity modifier includes the following steps: Nano-silica was added to a dispersion solvent and ultrasonically dispersed. After uniform dispersion, it was fed into a grinder and ground for 10-15 minutes at a speed of 1000-1500 r / min to obtain a ground mixture. Add the coupling agent to deionized water to prepare an aqueous solution with a mass concentration of 3-6%. Stir at 800-1000 r / min for 5-8 min, then add hydroxymethyl cellulose ether and ultrasonically mix for 10-15 min to obtain a hydroxymethyl cellulose ether mixture. Mix the grinding mixture and the hydroxymethyl cellulose ether mixture evenly, react at 80-90℃ for 6-8 hours, and then dry in an oven at 80-100℃ to obtain the modified viscosity modifier. The preparation method of the modified coagulant includes the following steps: Add a 20-25% aluminum sulfate solution to a 10-15% aluminum hydroxide aqueous solution, stir and mix, react at 115-130℃ for 3-3.5 hours, then react at 85-100℃ for 4-5 hours, and finally add the modifier and stir evenly to obtain the modified coagulant.

2. The catalyst for shotcrete according to claim 1, characterized in that: The dispersing solvent is anhydrous ethanol; the coupling agent is a silane coupling agent, specifically methacryloxysilane.

3. The catalyst for shotcrete according to claim 2, characterized in that: The nano-silica is prepared with a dispersing solvent to form an ethanol mixture with a mass concentration of 5-8%.

4. The catalyst for shotcrete according to claim 1, characterized in that: The mass ratio of the nano-silica, coupling agent and hydroxymethyl cellulose ether is 1:0.1-0.3:1.2-2.

5. The catalyst for shotcrete according to claim 1, characterized in that: The molar ratio of aluminum sulfate to aluminum hydroxide is 0.8-1.2:

1.

6. The catalyst for shotcrete according to claim 1, characterized in that: The modifier is a mixture of acetic acid and polyacrylamide in a mass ratio of 2-3:

1.

7. The catalyst for shotcrete according to claim 1, characterized in that: The water-reducing agent is one of polycarboxylate water-reducing agent or naphthalene sulfonate water-reducing agent; The ion chelating agent is one of EDTA, sodium tripolyphosphate, or sodium gluconate. The air-entraining agent is one of rosin-based air-entraining agents, alkylbenzene sulfonates, or fatty alcohol sulfonates.

8. A method for preparing a catalyst for shotcrete according to any one of claims 1-7, characterized in that: Includes the following steps: Weigh each component according to the above weight percentages, including water-reducing agent, modified viscosity modifier, ion chelating agent, modified coagulant, air-entraining agent and water; Add a modified viscosity modifier to water, stir evenly, and then add water-reducing agent, ion chelating agent, modified coagulant and air-entraining agent in sequence. Stir at 600-800 r / min for 40-60 minutes to obtain the catalyst for shotcrete.

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