Water reducing agent for reducing resilience, preparation method of water reducing agent and concrete

Abstract

The invention relates to the technical field of concrete, and particularly discloses a water reducing agent for reducing resilience, a preparation method of the water reducing agent and concrete, and the water reducing agent comprises the following components in parts by weight: 200-230 parts of a cohesive energy enhancing water reducing agent, 2-5 parts of a self-made air entraining agent, 10-20 parts of a self-made thickening agent, 15-30 parts of lithium carbonate and 745-788 parts of deionized water. The water reducing agent for reducing resilience is added in concrete mixing to improve the cohesiveness of concrete, and is matched with a high-performance alkali-free accelerator to obviously improve the spraying construction effect, so that the problem of high resilience rate of sprayed concrete in the construction process can be solved, the waste of engineering materials is reduced, the environment of a working surface is improved, and the service life of the concrete is prolonged. And the spraying construction cost is obviously reduced.

Description

Technical Field

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

[0002] With the large-scale development of engineering construction in my country, tunnel construction in railways and highways has also developed rapidly. As an important component of the lining support system in tunnel construction, shotcrete, with its rapid setting and hardening, high early strength, is widely used in initial support, playing an important role in controlling the stability of the surrounding rock and ensuring construction safety. Shotcrete is produced using two processes: dry shotcrete and wet shotcrete.

[0003] Among them, the dry spraying process has gradually been replaced by the wet spraying process due to problems such as large dust, harsh construction environment, difficulty in controlling the water-cement ratio, large fluctuations in concrete quality, and large loss of strength in the later stage.

[0004] Wet shotcrete is currently the most prevalent method in tunnel construction. This process improves the working environment, increases efficiency, and shortens construction periods. However, the high rebound rate of concrete during shotcrete construction remains a major challenge, with many tunnel projects experiencing rebound rates as high as 30%-40%, resulting in significant material waste. This high rebound rate is a major challenge that the industry urgently needs to address.

[0005] There are two main aspects that affect the rebound rate of wet sprayed concrete: one is the concrete materials and mix ratio, such as cementitious materials, mineral admixtures, accelerator dosage, sand ratio, etc.; the other is the spraying construction technology, such as spraying wind pressure, spraying angle, single spraying thickness, etc.

[0006] Based on this, in order to solve the problems such as large rebound in shotcrete construction, it is urgent to prepare a high-performance shotcrete that can effectively reduce the rebound rate of shotcrete, improve construction safety, and be economical and environmentally friendly. Summary of the Invention

[0007] The purpose of the present invention is to provide a water-reducing agent for reducing rebound, which is added to concrete mixing to improve the cohesiveness of concrete and solve the problem of high rebound rate of shotcrete during construction.

[0008] At this time, the present invention also provides a method for preparing the above-mentioned water-reducing agent for reducing rebound and concrete added with the water-reducing agent for reducing rebound.

[0009] The present invention is achieved through the following technical solutions:

[0010] A water-reducing agent for reducing rebound, comprising the following components in parts by weight:

[0011] 200-230 parts of cohesive energy enhancing water reducer, 2-5 parts of homemade air entraining agent, 10-20 parts of homemade thickener, 15-30 parts of lithium carbonate, 745-788 parts of deionized water;

[0012] Among them, the preparation process of cohesive energy enhanced water reducer is as follows:

[0013] Under stirring, sodium p-aminobenzenesulfonate and hydroquinone are added to deionized water, the temperature is raised to 50-55°C, and then a 30% sodium hydroxide solution is added. The temperature is raised to 60-70°C and stirred for 30-40 minutes. A formaldehyde aqueous solution (35% mass concentration) is added dropwise and reacted for 60-80 minutes. The temperature is further raised to 90-95°C, polyethylene glycol is added, and the reaction is carried out for 220-230 minutes. Deionized water and 30% sodium hydroxide are then added, the temperature is kept at this temperature for 90-100 minutes, and the temperature is then lowered.

[0014] Among them, the preparation process of the homemade air-entraining agent is as follows:

[0015] Heat the sodium hydroxide solution to 80-85°C, add oleic acid, react for 120-150 minutes, then add hydroxypropyl cellulose, keep warm for 60-90 minutes, and cool down;

[0016] Among them, the preparation process of the homemade thickener is as follows:

[0017] Heat the ethyl acrylate aqueous solution to 60-65°C, then add methacrylic acid aqueous solution and ammonium persulfate aqueous solution dropwise, react for 60-70 minutes, add 1,4-butadiene, react for 45-60 minutes, and cool down.

[0018] The molecular structure of the cohesive energy enhancing water reducer of the present invention contains hydrophilic groups such as sulfonate and polyethylene glycol, which form hydrogen bonds with water molecules and form a solvation layer on the surface of cement particles (formed after the cement particles are dispersed, the particle surface is a water molecule layer, and the water molecule layer is the solvation effect), preventing the cement particles from agglomerating, thereby playing a water-reducing role. The phenyl and methylene groups (introduced by formaldehyde) in the molecules are strong hydrophobic groups, and intermolecular association effects are formed between the molecules, thereby increasing the cohesive energy of the system, effectively increasing the cohesion of the concrete, significantly reducing the falling of concrete during the spraying process of the shotcrete, and increasing the bonding performance between the concrete and the rock wall, effectively reducing the rebound rate of the shotcrete.

[0019] The homemade air-entraining agent of the present invention contains fatty acid salt molecules, whose linear structure can accelerate their movement speed in the cement slurry and quickly arrange them in a directional manner in the bubbles, thereby enhancing the efficiency of air entrainment. The hydroxypropyl cellulose therein can increase the thickness of the bubble wall, thereby improving the air stabilization performance of the air-entraining agent, increasing the concrete encapsulation, playing a vibration-reducing role when concrete is sprayed onto the tunnel wall, and reducing concrete rebound.

[0020] The molecular structure of the homemade thickener of the present invention is a cross-linked acrylate. In a neutral or slightly acidic solution, the viscosity is low. However, in cement paste, the esters are hydrolyzed, the charges between the anionic groups are repelled, the molecular chains are unfolded, the viscosity of the system increases, the fluidity of the concrete is reduced, the cohesive energy is increased, and the rebound rate of the shotcrete is reduced.

[0021] The lithium carbonate of the present invention can be combined with an alkali-free quick-setting agent to improve the early strength of shotcrete, thereby reducing the rebound rate of the shotcrete.

[0022] In summary, the rebound-reducing water-reducing agent of the present invention is added to concrete mixing to improve the cohesiveness of concrete, thereby solving the problem of high rebound rate of shotcrete during construction.

[0023] In a preferred embodiment, when preparing the cohesive energy enhancing water reducing agent, the weight ratio of sodium p-aminobenzenesulfonate, hydroquinone, formaldehyde aqueous solution and polyethylene glycol is: (30-38): (40-48): (40-45): (5-10).

[0024] In a preferred embodiment, when preparing the cohesive energy enhancing water reducer, the weight ratio of the first added deionized water, the first added sodium hydroxide solution, sodium aminobenzenesulfonate and hydroquinone is (100-110): (5-10): (30-38): (40-48);

[0025] The weight ratio of the deionized water added for the second time, the sodium hydroxide solution added for the second time, and the formaldehyde aqueous solution is (100-110):(10-15):(40-45).

[0026] In a preferred embodiment, when preparing the cohesive energy enhancing water reducing agent, the formaldehyde aqueous solution is added dropwise for 85-105 minutes.

[0027] In a preferred embodiment, when preparing the homemade air-entraining agent, when preparing the sodium hydroxide solution, the weight ratio of solid sodium hydroxide to deionized water is (4-8): (70-80); the weight ratio of solid sodium hydroxide, oleic acid and hydroxypropyl cellulose is (4-8): (12-18): (0.1-0.5).

[0028] In a preferred embodiment, when preparing the homemade thickener, an ethyl acrylate aqueous solution is obtained by uniformly mixing 10-15 parts of methacrylic acid and 10-12 parts of deionized water; an ammonium persulfate aqueous solution is obtained by uniformly mixing 0.8-1.0 parts of ammonium persulfate and 10-15 parts of deionized water; and an ethyl acrylate aqueous solution is obtained by uniformly mixing 25-30 parts of ethyl acrylate and 110-120 parts of deionized water.

[0029] In a preferred embodiment, the weight ratio of ethyl acrylate, methacrylic acid, ammonium persulfate and 1,4-butadiene is (25-30): (10-15): (0.8-1.0): (0.1-0.5).

[0030] In a preferred embodiment, when preparing the homemade thickener, the dripping time of the ethyl acrylate aqueous solution is 60-75 minutes, and the dripping time of the ammonium persulfate aqueous solution is 90-105 minutes.

[0031] A method for preparing a water reducer for reducing rebound comprises the following steps: adding deionized water into a container, adding a cohesive energy enhancing water reducer while stirring, stirring for 5-10 minutes, adding a homemade air entraining agent, stirring for 10-20 minutes, then adding a homemade thickener and lithium carbonate, stirring for 20-30 minutes, stopping stirring, and obtaining the water reducer for reducing rebound.

[0032] A concrete, wherein the above-mentioned water reducing agent for reducing rebound is added during the mixing process.

[0033] The concrete of the present invention may specifically be shotcrete, which can be used in infrastructure projects such as transportation, mining, structural reinforcement, and underground construction.

[0034] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0035] The rebound-reducing water-reducing agent of the present invention is added to concrete mixing to improve the cohesiveness of the concrete, and is combined with a high-performance alkali-free quick-setting agent to significantly improve the spraying construction effect, and can solve the problem of high rebound rate of sprayed concrete during the construction process. It not only reduces the waste of engineering materials and improves the working surface environment, but also significantly reduces the cost of spraying construction, promotes cost reduction and efficiency improvement of concrete projects, and reduces the safety risks of engineering construction, and has important practical significance for improving the research on industrial technology of sprayed concrete. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the examples. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention. The embodiments described below are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0037] In the following description, numerous specific details are set forth to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that these specific details are not necessarily required to practice the present invention. In other examples, well-known structures, materials, or methods are not specifically described to avoid obscuring the present invention. The materials, instruments, and reagents used in the following examples, unless otherwise specified, are commercially available. The techniques used in the examples, unless otherwise specified, are conventional techniques well known to those skilled in the art.

[0038] A water-reducing agent for reducing rebound, comprising the following components in parts by weight:

[0039] Cohesive energy enhancing water reducer 200-230 parts, homemade air entraining agent 2-5 parts, homemade thickener 10-20 parts, lithium carbonate 15-30 parts, deionized water 745-788 parts.

[0040] Among them, the preparation process of cohesive energy enhanced water reducer is as follows:

[0041] In a 1L three-necked flask, add 100-110 parts deionized water and 30-38 parts sodium p-aminobenzenesulfonate. Start stirring, add 40-48 parts hydroquinone, raise the temperature to 50-55°C, and add 5-10 parts 30% sodium hydroxide solution. Raise the temperature to 60-70°C, stir for 30-40 minutes, and dropwise add 40-45 parts formaldehyde aqueous solution (35% mass concentration) for 85-105 minutes. Once the addition is complete, react for 60-80 minutes. Continue heating to 90-95°C, add 5-10 parts polyethylene glycol, react for 220-230 minutes, add 100-115 parts deionized water and 10-15 parts 30% sodium hydroxide. After incubating for 90-100 minutes, cool to room temperature, and discharge to obtain a cohesive energy-enhancing water-reducing agent.

[0042] In the above preparation process, sodium hydroxide mainly acts as a catalyst, and the specific reaction process is as follows:

[0043]

[0044]

[0045]

[0046] Among them, the preparation process of the homemade air-entraining agent is as follows:

[0047] In a 250 mL three-necked flask, add 70-80 parts of deionized water and 4-8 parts of solid sodium hydroxide, start mechanical stirring, heat to 80-85°C, add 12-18 parts of oleic acid, react for 120-150 minutes, add 0.1-0.5 parts of hydroxypropyl cellulose, keep warm for 60-90 minutes; cool to room temperature, and discharge to obtain a homemade air-entraining agent.

[0048] Among them, the preparation process of the homemade thickener is as follows:

[0049] In a 250mL three-necked flask, add 110-120 parts deionized water, 0.2 parts emulsifier OP-10, and 25-30 parts ethyl acrylate. Start stirring and heat to 60-65°C. Prepare dropwise addition solutions A and B: Material A is prepared by mixing 10-15 parts methacrylic acid and 10-12 parts deionized water. Material B is prepared by mixing 0.8-1.0 parts ammonium persulfate and 10-15 parts deionized water. Add materials A and B simultaneously dropwise. Add material A for 60-75 minutes and material B for 90-105 minutes. Continue the reaction for 60-70 minutes. Add 0.1-0.5 parts 1,4-butadiene and let it react for 45-60 minutes. Cool to room temperature to obtain the thickener.

[0050] The preparation method of the above-mentioned water reducer for reducing rebound is as follows: deionized water is added to a container, and while stirring, a cohesive energy enhancing water reducer is added, stirred for 5-10 minutes, a homemade air entraining agent is added, stirred for 10-20 minutes, and then a homemade thickener and lithium carbonate are added, stirred for 20-30 minutes, and stirring is stopped to obtain a water reducer for reducing rebound.

[0051] A shotcrete, wherein the above-mentioned water-reducing agent for reducing rebound is added during the mixing process. The shotcrete can be used in infrastructure projects such as transportation, mining, structural reinforcement and underground construction.

[0052] In order to better illustrate the technology of this embodiment, the following specific case is used for illustration:

[0053] Example 1:

[0054] A water-reducing agent for reducing rebound, comprising the following components in parts by weight:

[0055] 200 parts of cohesive energy enhancing water reducer, 2 parts of homemade air entraining agent, 10 parts of homemade thickener, 15 parts of lithium carbonate, and 745 parts of deionized water.

[0056] Preparation process of the above-mentioned water-reducing agent for reducing rebound:

[0057] First, the cohesive energy enhancing water reducer, the homemade air entraining agent and the homemade thickener were prepared respectively. Deionized water was added to a 2L three-necked flask, and the electric mechanical stirring was turned on. The homemade cohesive energy enhancing water reducer was added and stirred for 5 minutes. The homemade high-efficiency air entraining agent was added and stirred for 10 minutes. Then the homemade thickener and lithium carbonate were added and stirred for 20 minutes. The stirring was stopped to obtain the water reducer for reducing rebound.

[0058] Among them, the preparation process of cohesive energy enhanced water reducer is as follows:

[0059] In a 1L three-necked flask, add 100 parts deionized water and 30 parts sodium p-aminobenzenesulfonate. Start stirring, add 40 parts hydroquinone, raise the temperature to 50°C, and add 5 parts 30% sodium hydroxide solution. Raise the temperature to 60°C, stir for 30-40 minutes, and dropwise add 40 parts formaldehyde aqueous solution (35% mass concentration) for 85 minutes. Once the addition is complete, react for 60 minutes. Continue heating to 90°C, add 5 parts polyethylene glycol, react for 220 minutes, add 100 parts water, and 10 parts 30% sodium hydroxide. After holding for 90 minutes, cool to room temperature, and discharge to obtain a cohesive energy-enhancing water-reducing agent.

[0060] Among them, the preparation process of the homemade air-entraining agent is as follows:

[0061] In a 250 mL three-necked flask, add 70 parts of deionized water and 4 parts of solid sodium hydroxide. Start mechanical stirring, raise the temperature to 80°C, add 12 parts of oleic acid, react for 120 minutes, add 0.1 parts of hydroxypropyl cellulose, and keep warm for 60 minutes. Cool to room temperature and discharge to obtain the homemade air-entraining agent.

[0062] Among them, the preparation process of the homemade thickener is as follows:

[0063] In a 250mL three-necked flask, add 110 parts deionized water, 0.2 parts emulsifier OP-10, and 25 parts ethyl acrylate. Stir and heat to 60°C. Prepare dropwise solution A: Material A is a mixture of 10 parts methacrylic acid and 10 parts deionized water. Material B is a mixture of 0.8 parts ammonium persulfate and 10 parts deionized water. Add materials A and B dropwise simultaneously, adding material A for 60 minutes and material B for 90 minutes. Continue the reaction for 60 minutes, then add 0.1 parts 1,4-butadiene and let it react for 45 minutes. Cool to room temperature to prepare a homemade thickener.

[0064] Example 2:

[0065] A water-reducing agent for reducing rebound, comprising the following components in parts by weight:

[0066] 230 parts of cohesive energy enhancing water reducer, 5 parts of homemade air entraining agent, 20 parts of homemade thickener, 30 parts of lithium carbonate, and 788 parts of deionized water.

[0067] Preparation process of the above-mentioned water-reducing agent for reducing rebound:

[0068] First, the cohesive energy enhancing water reducer, the homemade air entraining agent and the homemade thickener were prepared respectively. Deionized water was added to a 2L three-necked flask, and the electric mechanical stirring was turned on. The homemade cohesive energy enhancing water reducer was added and stirred for 10 minutes. The homemade high-efficiency air entraining agent was added and stirred for 20 minutes. Then the homemade thickener and lithium carbonate were added and stirred for 30 minutes. The stirring was stopped to obtain the water reducer for reducing rebound.

[0069] Among them, the preparation process of cohesive energy enhanced water reducer is as follows:

[0070] In a 1L three-necked flask, add 110 parts deionized water and 38 parts sodium p-aminobenzenesulfonate. Start stirring, add 48 parts hydroquinone, raise the temperature to 55°C, and add 10 parts 30% sodium hydroxide solution. Raise the temperature to 70°C and stir for 40 minutes. Add 45 parts formaldehyde aqueous solution (35% mass concentration) dropwise for 105 minutes. Once the addition is complete, react for 80 minutes. Continue heating to 95°C, add 7 parts polyethylene glycol, react for 230 minutes, add 115 parts water, and 15 parts 30% sodium hydroxide. Keep warm for 100 minutes, then cool to room temperature. Discharge the product to obtain a cohesive energy-enhancing water reducer.

[0071] Among them, the preparation process of the homemade air-entraining agent is as follows:

[0072] In a 250 mL three-necked flask, add 80 parts of deionized water and 8 parts of solid sodium hydroxide. Start mechanical stirring, raise the temperature to 85°C, add 18 parts of oleic acid, react for 150 minutes, add 0.5 parts of hydroxypropyl cellulose, and keep warm for 90 minutes. Cool to room temperature and discharge to obtain the homemade air-entraining agent.

[0073] Among them, the preparation process of the homemade thickener is as follows:

[0074] In a 250mL three-necked flask, add 120 parts deionized water, 0.2 parts emulsifier OP-10, and 30 parts ethyl acrylate. Stir and heat to 65°C. Prepare dropwise solutions A and B: Material A is a mixture of 15 parts methacrylic acid and 12 parts deionized water, while Material B is a mixture of 1.0 parts ammonium persulfate and 15 parts deionized water. Add materials A and B simultaneously, dripping over the mixture for 75 minutes and 105 minutes, respectively. Continue the reaction for 70 minutes, then add 0.5 parts 1,4-butadiene and let it react for 60 minutes. Cool to room temperature to prepare a homemade thickener.

[0075] Example 3:

[0076] A water-reducing agent for reducing rebound, comprising the following components in parts by weight:

[0077] 220 parts of cohesive energy enhancing water reducer, 3 parts of homemade air entraining agent, 15 parts of homemade thickener, 22 parts of lithium carbonate, and 761 parts of deionized water.

[0078] Preparation process of the above-mentioned water-reducing agent for reducing rebound:

[0079] First, the cohesive energy enhancing water reducer, the homemade air entraining agent and the homemade thickener were prepared respectively. Deionized water was added to a 2L three-necked flask, and the electric mechanical stirring was turned on. The homemade cohesive energy enhancing water reducer was added and stirred for 7 minutes. The homemade high-efficiency air entraining agent was added and stirred for 15 minutes. Then the homemade thickener and lithium carbonate were added and stirred for 25 minutes. The stirring was stopped to obtain the water reducer for reducing rebound.

[0080] Among them, the preparation process of cohesive energy enhanced water reducer is as follows:

[0081] In a 1L three-necked flask, add 105 parts deionized water and 35 parts sodium p-aminobenzenesulfonate. Start stirring, add 44 parts hydroquinone, raise the temperature to 53°C, and add 7 parts 30% sodium hydroxide solution. Raise the temperature to 65°C and stir for 35 minutes. Add 43 parts formaldehyde aqueous solution (35% mass concentration) dropwise over 92 minutes. Once the addition is complete, react for 70 minutes. Continue heating to 92°C, add 8 parts polyethylene glycol, react for 225 minutes, add 112 parts water, and 13 parts 30% sodium hydroxide. After holding for 95 minutes, cool to room temperature. Discharge to obtain a cohesive energy-enhancing water reducer.

[0082] Among them, the preparation process of the homemade air-entraining agent is as follows:

[0083] In a 250 mL three-necked flask, add 75 parts of deionized water and 6 parts of solid sodium hydroxide. Start mechanical stirring, raise the temperature to 83°C, add 15 parts of oleic acid, react for 135 minutes, add 0.3 parts of hydroxypropyl cellulose, and keep warm for 75 minutes. Cool to room temperature and discharge to obtain the homemade air-entraining agent.

[0084] Among them, the preparation process of the homemade thickener is as follows:

[0085] In a 250mL three-necked flask, add 115 parts deionized water, 0.2 parts emulsifier OP-10, and 28 parts ethyl acrylate. Stir and heat to 63°C. Prepare dropwise solutions A and B: Material A is a mixture of 13 parts methacrylic acid and 11 parts deionized water, while Material B is a mixture of 0.9 parts ammonium persulfate and 13 parts deionized water. Add Material A and B dropwise simultaneously, adding Material A for 70 minutes and Material B for 98 minutes. Continue the reaction for 65 minutes, then add 0.3 parts 1,4-butadiene and let it react for 52 minutes. Cool to room temperature and prepare a homemade thickener.

[0086] Example 4:

[0087] A water-reducing agent for reducing rebound, comprising the following components in parts by weight:

[0088] 200 parts of cohesive energy enhancing water reducer, 5 parts of homemade air entraining agent, 10 parts of homemade thickener, 30 parts of lithium carbonate, and 745 parts of deionized water.

[0089] Preparation process of the above-mentioned water-reducing agent for reducing rebound:

[0090] First, the cohesive energy enhancing water reducer, the homemade air entraining agent and the homemade thickener were prepared respectively. Deionized water was added to a 2L three-necked flask, and the electric mechanical stirring was turned on. The homemade cohesive energy enhancing water reducer was added and stirred for 10 minutes. The homemade high-efficiency air entraining agent was added and stirred for 10 minutes. Then the homemade thickener and lithium carbonate were added and stirred for 30 minutes. The stirring was stopped to obtain the water reducer for reducing rebound.

[0091] Among them, the preparation process of cohesive energy enhanced water reducer is as follows:

[0092] In a 1L three-necked flask, add 100 parts deionized water and 38 parts sodium p-aminobenzenesulfonate. Start stirring, add 40 parts hydroquinone, raise the temperature to 55°C, and add 5 parts 30% sodium hydroxide solution. Raise the temperature to 70°C and stir for 30 minutes. Add 45 parts formaldehyde aqueous solution (35% mass concentration) dropwise for 85 minutes. Once the addition is complete, react for 80 minutes. Continue heating to 90°C, add 10 parts polyethylene glycol, react for 230 minutes, add 100 parts water, and 15 parts 30% sodium hydroxide. After holding for 90 minutes, cool to room temperature. Discharge the product to obtain a cohesive energy-enhancing water reducer.

[0093] Among them, the preparation process of the homemade air-entraining agent is as follows:

[0094] In a 250 mL three-necked flask, add 70 parts of deionized water and 8 parts of solid sodium hydroxide. Start mechanical stirring, heat to 80°C, add 18 parts of oleic acid, react for 120 minutes, add 0.5 parts of hydroxypropyl cellulose, and keep warm for 60 minutes. Cool to room temperature and discharge to obtain the homemade air-entraining agent.

[0095] Among them, the preparation process of the homemade thickener is as follows:

[0096] In a 250mL three-necked flask, add 110 parts deionized water, 0.2 parts emulsifier OP-10, and 30 parts ethyl acrylate. Stir and heat to 60°C. Prepare dropwise solutions A and B: Material A is a mixture of 15 parts methacrylic acid and 10 parts deionized water, while Material B is a mixture of 1.0 part ammonium persulfate and 10 parts deionized water. Add materials A and B dropwise simultaneously, adding material A for 60 minutes and material B for 105 minutes. Continue the reaction for 60 minutes, then add 0.5 parts 1,4-butadiene and let it react for 45 minutes. Cool to room temperature to prepare a homemade thickener.

[0097] Comparative Example 1:

[0098] The rebound reducing water reducer used in this comparative example is commercially available PCE, and the commercially available PCE model is Point-THS polycarboxylate high-performance water reducer.

[0099] Comparative Example 2:

[0100] The rebound reducing water-reducing agent in this comparative example is a combination of commercially available PCE and SD-JK-SNJ alkali-free quick-setting agent; the commercially available PCE model is Point-THS polycarboxylate high-performance water-reducing agent.

[0101] The above four embodiments and commercially available PCE were used for C30 concrete testing. Esheng PO 42.5 ordinary silica cement was selected as the cementitious material, and fly ash was Fangyuan II grade ash; artificial machine-made sand was used as fine aggregate, and coarse sand with a fineness modulus of 2.6; crushed stone was continuously graded with a particle size of 5-31.5 mm. A water-reducing agent concrete test was carried out in accordance with GB8076-2016. The initial slump and expansion were measured, and after adding 8% SD-JK-SNJ alkali-free accelerator (SD-JK-SNJ alkali-free accelerator was added after mixing, and the amount of SD-JK-SNJ alkali-free accelerator was calculated based on the cementitious material of the concrete. SD-JK-SNJ alkali-free accelerator is a commercially available product), the rebound rate of the concrete was tested. The concrete mix ratio is shown in Table 1, and the concrete test results are shown in Table 2:

[0102] Table 1 Concrete mix ratio

[0103] cement coal ash sand stone water 430 40 913 843 174

[0104] Table 2 Concrete test results

[0105]

[0106]

[0107] Note: The dosage of water reducer for reducing rebound is 1.0% of cementitious material.

[0108] Note: The data of Examples 1 to 4 and commercially available PCE in Table 2 are test data of concrete prepared by adding the admixture formulas of Examples 1 to 4 and commercially available PCE to the concrete and adding SD-JK-SNJ alkali-free accelerating agent at the same time.

[0109] From the data in Table 2, we can see that:

[0110] 1) Adding a rebound-reducing water-reducing agent to concrete mixing can improve concrete cohesion. Combined with a high-performance alkali-free accelerator (SD-JK-SNJ alkali-free accelerator), it significantly enhances the effectiveness of spraying, resolving the high rebound rate of shotcrete during construction. Concrete prepared using commercially available PCE combined with the SD-JK-SNJ alkali-free accelerator can achieve a rebound rate of 32%. The rebound reduction rate of the present invention can reach up to 90.6%, a significant reduction in the rate of rebound in shotcrete.

[0111] 2) The amount of the water-reducing agent for reducing rebound of the present invention is only 1% of the cementitious material, which is a relatively low addition amount. Compared with the 7-8% amount of the water-reducing agent for reducing rebound in the prior art, the amount of the water-reducing agent for reducing rebound is greatly reduced, and the rebound rate of the shotcrete can be greatly reduced.

[0112] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A water reducing agent for reducing rebound, characterized in that: It comprises the following components in parts by weight: 200-230 parts of cohesive energy enhancing water reducer, 2-5 parts of homemade air entraining agent, 10-20 parts of homemade thickener, 15-30 parts of lithium carbonate, 745-788 parts of deionized water; The preparation process of the cohesive energy enhanced water reducer is as follows: Under stirring, sodium p-aminobenzenesulfonate and hydroquinone are added to deionized water, heated to 50-55°C, then 30% sodium hydroxide solution is added, heated to 60-70°C, stirred for 30-40 minutes, and formaldehyde aqueous solution is added dropwise to react for 60-80 minutes; the temperature is further raised to 90-95°C, polyethylene glycol is added, and the reaction is carried out for 220-230 minutes; deionized water and 30% sodium hydroxide are then added, the temperature is kept at 90-100 minutes, and the temperature is then lowered; The preparation process of the self-made air-entraining agent is as follows: Heat the sodium hydroxide solution to 80-85°C, add oleic acid, react for 120-150 minutes, then add hydroxypropyl cellulose, keep warm for 60-90 minutes, and cool down; Wherein, the preparation process of the homemade thickener is as follows: Heat the ethyl acrylate aqueous solution to 60-65°C, then add methacrylic acid aqueous solution and ammonium persulfate aqueous solution dropwise, react for 60-70 minutes, add 1,4-butadiene, react for 45-60 minutes, and cool down.

2. A water reducing agent for reducing rebound according to claim 1, characterized in that: When preparing the cohesive energy enhancing water reducer, the weight ratio of the sodium p-aminobenzenesulfonate, the hydroquinone, the formaldehyde aqueous solution and the polyethylene glycol is: (30-38): (40-48): (40-45): (5-10).

3. The water reducing agent for reducing rebound according to claim 1, characterized in that: When preparing the cohesive energy enhancing water reducer, the weight ratio of the deionized water added for the first time, the sodium hydroxide solution added for the first time, the sodium aminobenzenesulfonate and the hydroquinone is (100-110): (5-10): (30-38): (40-48); The weight ratio of the deionized water added for the second time, the sodium hydroxide solution added for the second time and the formaldehyde aqueous solution is (100-110): (10-15): (40-45).

4. The water reducing agent for reducing rebound according to claim 1, characterized in that: When preparing the cohesive energy enhancing water reducing agent, the formaldehyde aqueous solution is added dropwise for 85-105 minutes.

5. The water reducing agent for reducing rebound according to claim 1, characterized in that: When preparing the homemade air-entraining agent, when preparing the sodium hydroxide solution, the weight ratio of solid sodium hydroxide to deionized water is (4-8): (70-80); the weight ratio of the solid sodium hydroxide, the oleic acid and the hydroxypropyl cellulose is (4-8): (12-18): (0.1-0.5).

6. The water reducing agent for reducing rebound according to claim 1, characterized in that: When preparing the homemade thickener, the ethyl acrylate aqueous solution is obtained by uniformly mixing 10-15 parts of methacrylic acid and 10-12 parts of deionized water; the ammonium persulfate aqueous solution is obtained by uniformly mixing 0.8-1.0 parts of ammonium persulfate and 10-15 parts of deionized water; and the ethyl acrylate aqueous solution is obtained by uniformly mixing 25-30 parts of ethyl acrylate and 110-120 parts of deionized water.

7. The water reducing agent for reducing rebound according to claim 6, characterized in that: The weight ratio of the ethyl acrylate, the methacrylic acid, the ammonium persulfate and the 1,4-butadiene is (25-30):(10-15):(0.8-1.0):(0.1-0.5).

8. The water reducing agent for reducing rebound according to claim 1, characterized in that: When preparing the homemade thickener, the dripping time of the ethyl acrylate aqueous solution is 60-75 minutes, and the dripping time of the ammonium persulfate aqueous solution is 90-105 minutes.

9. The method for preparing a water-reducing agent for reducing rebound according to any one of claims 1 to 8, characterized in that: Deionized water was added to a container, and the cohesive energy enhancing water reducer was added under stirring, and stirred for 5-10 minutes. The homemade air entraining agent was added and stirred for 10-20 minutes. The homemade thickener and lithium carbonate were then added and stirred for 20-30 minutes. The stirring was stopped to obtain the water reducer for reducing rebound.

10. A concrete, characterized in that: The concrete is mixed with the water-reducing agent for reducing rebound according to any one of claims 1 to 8.

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