Tunnel engineering wet-sprayed concrete and preparation and application method thereof

Abstract

The application discloses a kind of wet concrete for tunnel engineering and its preparation, application method, belong to wet concrete technical field.The wet concrete for tunnel engineering, it is characterized in that, according to weight fraction, it is as follows, including: cement 410-440 parts, medium sand 850-980 parts, coarse aggregate 780-860 parts, water 195-215 parts, coated modified porous aggregate 35-45 parts, water reducing agent 9-13 parts, quick-setting agent 12-25 parts.The porous aggregate is modified by coating in the application, so that the wet concrete for tunnel engineering does not affect the state of concrete during preparation and production, but during the concrete spraying process, the coating film of the coated modified porous aggregate may be damaged under the action of pumping and pump pressure, exposing the porous aggregate, and due to the porous and highly water-absorbing nature of the porous aggregate material, it can absorb free water in the concrete, causing the concrete to become viscous during spraying, thereby reducing the rebound rate of the concrete.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of wet shotcrete, in particular, relates to a wet shotcrete for tunnel engineering and a preparation and application method thereof. BACKGROUND

[0002] The most important form of tunnel and roadway support in China at present is anchor shotcrete support, and anchor shotcrete support technology is also widely used in water conservancy projects. The key link of anchor shotcrete support operation is shotcrete technology, which has the advantages of simple process, fast construction, wide application, low cost, etc., and has the effects of sealing the surface, maintaining the strength of surrounding rock, etc. The quality of the shotcrete layer directly affects the quality of the support, so the equipment and process quality used during shotcrete have a significant impact on tunneling and support.

[0003] Wet shotcrete is a method of transporting pre-mixed concrete to the tunnel operation area, using high-pressure air to send it to the nozzle through the shotcrete machine, and mixing with the accelerator to form a high-speed spray on the surface of the rock or concrete.

[0004] If the viscosity of the concrete is not enough during spraying, the rebound rate of the concrete will be large, resulting in waste of concrete, and increasing the viscosity of the concrete, such as reducing the water content during mixing, increasing the amount of water reducing agent, and adding mineral admixtures, etc., will cause the shotcrete pipeline to be blocked, which is not conducive to the shotcrete operation.

[0005] Among them, the pumping process is a very important stage before the shotcrete, when the concrete wet shotcrete machine pipe transportation is abnormal, it will seriously affect the working efficiency of the wet shotcrete support, and even cause the phenomenon of pipe blockage, which has a negative impact on the safety and economy of the wet shotcrete production operation.

[0006] A low-rebound high-strength shotcrete material and its preparation method are disclosed in Chinese patent application No. CN202410299139.4, which comprises, by mass percentage: cement 12-20%, machine-made sand 25-45%, stone material 15-25%, water reducing agent 0.1-1%, accelerator 0.5-1.5%, modified additive 1-3%, functional additive 0.5-3%, and water makes up the balance.

[0007] The above prior art can effectively improve the mechanical properties and cohesiveness of the shotcrete by using multiple types of molecular chain starch and modified additives, thereby enhancing its durability, corrosion resistance and stability, and effectively preventing water seepage; but the defect is that the concrete before entering the pump is already quite viscous, and a greater air pressure of the shotcrete machine is needed to spray the concrete during spraying. The actual construction process requires high professional requirements for equipment and operators, and the rebound rate of the above prior art still has room for improvement.

[0008] Therefore, in order to solve the above problems, the application provides a wet sprayed concrete for tunnel engineering and a preparation and application method thereof. SUMMARY

[0009] In order to solve the defects in the above technical solutions, the application provides a wet sprayed concrete for tunnel engineering and a preparation and application method thereof. The purpose of the application can be achieved by the following technical solutions: a wet sprayed concrete for tunnel engineering, which comprises the following components in parts by weight: cement 410-440 parts, medium sand 850-980 parts, coarse aggregate 780-860 parts, water 195-215 parts, coated modified porous aggregate 35-45 parts, water reducing agent 9-13 parts, and accelerator 12-25 parts.

[0010] The cement is P.O42.5 cement;

[0011] The medium sand has a fineness modulus of 2.3-3.0;

[0012] The coarse aggregate is crushed stone with continuous gradation and a particle size range of 5-10 mm;

[0013] The porous aggregate is a porous aggregate with a water absorption rate greater than 5%, which comprises one or more of a mixture of ceramsite, red brick, recycled aggregate, air-cooled ilmenite slag aggregate, and zeolite;

[0014] The water reducing agent is a polycarboxylic acid water reducing agent;

[0015] The accelerator is a silicate liquid accelerator.

[0016] The preparation method of the coated modified porous aggregate is as follows: the porous aggregate is wrapped with a fine fishing net and placed in a self-made potassium silicate solution. The porous aggregate needs to be completely immersed in the self-made potassium silicate solution, and the porous aggregate is fully stirred every 5 minutes. After soaking for 15 minutes, the soaked porous aggregate is taken out and the excess self-made potassium silicate solution is filtered out. Finally, the treated porous aggregate is placed in an oven for drying. After drying, the coated modified porous aggregate is obtained.

[0017] In the preparation process of the coated modified porous aggregate, the drying temperature is set to 60 degrees Celsius, and the drying time is set to 8 hours.

[0018] The preparation method of the self-made potassium silicate solution is as follows: the silica sol is poured into a three-necked flask, then the three-necked flask is placed in a constant-temperature water bath pot provided with a high-speed stirrer and a temperature control device, the temperature is raised to 50 DEG C, potassium hydroxide and deionized water are slowly added into the three-necked flask while stirring, the mixed solution is continuously stirred for 15 min, then it is poured into a flask under the condition of constant-temperature water bath, the temperature is set to 30 DEG C, the self-made silicon modified acrylic emulsion is slowly added under the condition of stirring, and stirring is conducted for 1 h; finally, hydroxyethyl cellulose is added as a thickening agent, and sodium polyacrylate is added as a dispersing agent, and stirring is continuously conducted for 15 min, so that the self-made potassium silicate solution modified by the silicon acrylic emulsion is prepared.

[0019] The preparation method of the self-made silicon modified acrylic emulsion is as follows: 15 g of styrene, 7 g of butyl acrylate, 11 g of butyl acrylate, 7 g of methyl methacrylate, 6 g of butyl methacrylate, 5 g of sulfonic acid-based acrylate, 80 g of deionized water, 0.6 g of polyethylene glycol p-isooctyl phenyl ether and 0.2 g of sodium dodecyl sulfate are weighed, are placed in a beaker, are stirred at a speed of 650 r / min at room temperature for 30 min, and a milky white mixture is obtained, which is named as component A; 0.8 g of ammonium persulfate is dissolved in 40 g of deionized water, which is named as component B; a mixture of 0.4 g of sodium bicarbonate, 10 g of deionized water and 60 g of component A is placed in a four-necked round-bottom flask, then 20 g of component B is added dropwise into the flask to obtain a uniform mixture; then, the mixed solution of the remaining component A and component B is added dropwise into the flask respectively within 2 hours, and the reaction temperature is kept at 85 DEG C; then, 1.3 g of 3-(trimethoxysilyl) propyl methacrylate is slowly added into the four-necked round-bottom flask, and the reaction is kept at 85 DEG C for 1 hour; finally, the temperature is adjusted to 90 DEG C for 1 hour, and ammonia water is added to adjust the pH to 7-8, so that the self-made silicon modified acrylic emulsion is prepared.

[0020] The preparation method of the wet sprayed concrete for tunnel engineering is as follows: cement and coarse aggregate are added into a forced stirrer, and stirring is conducted for 30 s; then, water reducing agent is uniformly mixed with water, and the mixture is added into a stirring pot and stirred for 45 s; finally, coated modified porous aggregate and medium sand are added into the stirring pot, and stirring is continuously conducted for 2 min; finally, when the spraying operation is conducted, a quick-setting agent is automatically added through a nozzle, so that the wet sprayed concrete for tunnel engineering is prepared.

[0021] The application of the wet sprayed concrete for tunnel engineering in tunnel engineering construction.

[0022] In the application process of the wet sprayed concrete for tunnel engineering, the air pressure of the spraying machine is controlled to be 0.5-0.8 MPa, and the spraying angle is between 60-100 DEG.

[0023] The spraying distance of the nozzle of the wet spraying machine from the rock surface is 0.8-1.2 m.

[0024] The present application has the beneficial effects of:

[0025] 1、The application carries out film modification treatment to the porous aggregate, so that the wet sprayed concrete for tunnel engineering does not affect the state of the concrete during production, but in the concrete spraying process, the film coated on the porous aggregate may be damaged under the action of pumping and pump pressure, exposing the porous aggregate, and due to the porous and water-absorbing characteristics of the porous aggregate material itself, it can absorb the free water in the concrete, causing the concrete to become viscous during spraying, thereby reducing the rebound rate of the concrete and improving the compressive strength of the concrete.

[0026] 2、The application introduces self-made potassium silicate solution to film modify the porous aggregate, wherein the silicon-modified acrylic emulsion introduced in the self-made potassium silicate solution has a special structure of silicon groups, which can improve the adhesion of the self-made potassium silicate solution to the porous aggregate; a film with strong adhesion but poor stability is formed, and after drying and curing, it has excellent water resistance but poor toughness; during pumping, the network film of Si-O-Si may partially depolymerize in the later stage of the pumping process, causing defects in the film, which will lose its binding to the porous aggregate, allowing the porous aggregate to partially absorb free water during pumping. DETAILED DESCRIPTION

[0027] To make the purpose, technical scheme and advantages of the present application clearer, the present application is further described in detail below with examples, the illustrative embodiments of the present application and their descriptions are only used to explain the present application, and not as a limitation of the present application. In addition, for the numerical range in the present application, it is understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Each smaller range between any stated value or intermediate value within the range and any other stated value or intermediate value within the range is also included in the present application. The upper limit and the lower limit of these smaller ranges can be independently included or excluded from the range.

[0028] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which this application belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, preferred methods and materials are described. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials in connection with which the documents are cited. In the case of conflict between any document incorporated by reference and the present specification, the present specification controls.

[0029] Many modifications and variations of the specific embodiments of the application can be practiced in accordance with the teachings of the description of the application, which are within the scope of the present application. Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples of the application are exemplary only.

[0030] As used herein, the terms "comprise", "comprising", "include", "including", "have" and "having" and the like are open-ended terms that are intended to mean including, but not limited to.

[0031] The "parts" indicated in the following examples are all weight parts.

[0032] Example 1

[0033] A wet sprayed concrete for tunnel engineering comprises the following components in parts by weight: cement 410 parts, medium sand 850 parts, coarse aggregate 780 parts, water 195 parts, coated modified porous aggregate 35 parts, water reducing agent 9 parts, and accelerating agent 12 parts.

[0034] The cement is P.O 42.5 cement, which is purchased from Sichuan Esheng Cement Group Co., Ltd.

[0035] The medium sand has a fineness modulus of 2.3-3.0.

[0036] The coarse aggregate is gravel, which is continuously graded and has a particle size range of 5-10 mm.

[0037] The porous aggregate has a water absorption rate of greater than 5%.

[0038] The porous aggregate is a mixture of red bricks and recycled aggregates, which is purchased from a commercially available brand.

[0039] The water reducing agent is a polycarboxylic acid water reducing agent.

[0040] The accelerating agent is a silicate liquid accelerating agent, which is purchased from Shandong Zhengyu Chemical Technology Co., Ltd.

[0041] The preparation method of the coated modified porous aggregate is as follows: the porous aggregate is wrapped with a fine fishing net and is placed in a self-made potassium silicate solution, the porous aggregate needs to be completely immersed in the self-made potassium silicate solution, the porous aggregate is fully stirred every 5 minutes, after soaking for 15 minutes, the soaked porous aggregate is taken out and the excess self-made potassium silicate solution is filtered off; finally, the treated porous aggregate is placed in an oven for drying, and the coated modified porous aggregate is prepared after the drying is completed.

[0042] In the preparation process of the coated modified porous aggregate, the drying temperature is set to 60 degrees Celsius and the drying time is set to 8 hours.

[0043] The preparation method of the self-made potassium silicate solution is as follows: 10 g of silica sol is poured into a three-necked flask, then the three-necked flask is placed in a constant-temperature water bath pot provided with a high-speed stirrer and a temperature control device, the temperature is raised to 50 DEG C, 8 g of potassium hydroxide and 25 g of deionized water are slowly added into the three-necked flask while stirring, the mixed solution is continuously stirred for 15 min, then it is poured into a flask under the condition of constant-temperature water bath, the temperature is set to 30 DEG C, 15 g of self-made silicon modified acrylic emulsion is slowly added under the condition of stirring, and stirring is carried out for 1 h; finally, hydroxyethyl cellulose is added as a thickening agent, and sodium polyacrylate is added as a dispersing agent, and stirring is continuously carried out for 15 min, so that the self-made potassium silicate solution modified by the silicon acrylic emulsion is prepared.

[0044] The preparation method of the self-made silicon modified acrylic emulsion is as follows: 15 g of styrene, 7 g of butyl acrylate, 11 g of butyl acrylate, 7 g of methyl methacrylate, 6 g of butyl methacrylate, 5 g of sulfonic acid-based acrylate, 80 g of deionized water, 0.6 g of polyethylene glycol p-isooctyl phenyl ether and 0.2 g of sodium dodecyl sulfate are weighed and placed in a beaker, stirred at a speed of 650 r / min for 30 min at room temperature, a milky white mixture is obtained, and is named as component A; 0.8 g of ammonium persulfate is dissolved in 40 g of deionized water, and is named as component B; a mixture of 0.4 g of sodium bicarbonate, 10 g of deionized water and 60 g of component A is placed in a four-necked round-bottom flask, then 20 g of component B is added dropwise into the flask to obtain a uniform mixture; then, the mixed solution of the remaining component A and component B is added dropwise into the flask respectively within 2 hours, and the reaction temperature is kept at 85 DEG C; then, 2.6 g of 3-(trimethoxysilyl) propyl methacrylate is slowly added into the four-necked round-bottom flask, and the reaction is kept at 85 DEG C for 1 hour; finally, the temperature is adjusted to 90 DEG C for 1 hour, and ammonia water is added to adjust the pH to 7-8, so that the self-made silicon modified acrylic emulsion is prepared.

[0045] A preparation method of a wet sprayed concrete for tunnel engineering is as follows: cement and coarse aggregate are added into a forced mixer, and stirred for 30 s; then, water reducing agent is uniformly mixed with water, and added into the mixing pot for stirring for 45 s; finally, coated modified porous aggregate and medium sand are added into the mixing pot, and continue to stir for 2 min; finally, when the spraying operation is carried out, the accelerating agent is automatically added through the nozzle, so that the wet sprayed concrete for tunnel engineering is prepared.

[0046] Example 2

[0047] A wet sprayed concrete for tunnel engineering, which comprises the following components in parts by weight: cement 420 parts, medium sand 880 parts, coarse aggregate 800 parts, water 200 parts, coated modified porous aggregate 37 parts, water reducing agent 10 parts and accelerating agent 15 parts.

[0048] The cement is P.O42.5 cement, purchased from Sichuan Esheng Cement Group Co., Ltd.;

[0049] The medium sand fineness modulus is 2.3-3.0;

[0050] The coarse aggregate is gravel, continuous grading, and the particle size range is 5-10mm;

[0051] The water absorption rate of the porous aggregate is greater than 5%;

[0052] The porous aggregate is a mixture of ceramsite and zeolite, purchased from a commercial brand;

[0053] The water reducing agent is a polycarboxylic acid water reducing agent;

[0054] The accelerator is a silicate liquid accelerator, purchased from Shandong Zhengyu Chemical Co., Ltd.

[0055] In example 2, the preparation method of the coated modified porous aggregate and the preparation method of the wet spray concrete for tunnel engineering are the same as those in example 1.

[0056] Example 3

[0057] A wet spray concrete for tunnel engineering, by weight fraction, includes the following components: cement 425 parts, medium sand 920 parts, coarse aggregate 820 parts, water 205 parts, coated modified porous aggregate 40 parts, water reducing agent 11 parts, and accelerator 18 parts;

[0058] The cement is P.O42.5 cement, purchased from Sichuan Esheng Cement Group Co., Ltd.;

[0059] The medium sand fineness modulus is 2.3-3.0;

[0060] The coarse aggregate is gravel, continuous grading, and the particle size range is 5-10mm;

[0061] The water absorption rate of the porous aggregate is greater than 5%;

[0062] The porous aggregate is a mixture of ceramsite and zeolite, purchased from a commercial brand;

[0063] The water reducing agent is a polycarboxylic acid water reducing agent;

[0064] The accelerator is a silicate liquid accelerator, purchased from Shandong Zhengyu Chemical Co., Ltd.

[0065] In example 3, the preparation method of the coated modified porous aggregate and the preparation method of the wet spray concrete for tunnel engineering are the same as those in example 1.

[0066] Example 4

[0067] A wet sprayed concrete for tunnel engineering, comprising the following components in parts by weight: cement 430 parts, medium sand 950 parts, coarse aggregate 840 parts, water 210 parts, coated modified porous aggregate 42 parts, water reducing agent 12 parts, and accelerator 22 parts.

[0068] The cement is P.O42.5 cement, which is purchased from Sichuan Esheng Cement Group Co., Ltd.

[0069] The medium sand has a fineness modulus of 2.3-3.0.

[0070] The coarse aggregate is gravel, which is continuously graded and has a particle size range of 5-10 mm.

[0071] The porous aggregate has a water absorption rate of greater than 5%.

[0072] The porous aggregate is air-cooled ilmenite slag aggregate, which is purchased from a commercially available brand.

[0073] The water reducing agent is a polycarboxylic acid water reducing agent.

[0074] The accelerator is a silicate liquid accelerator, which is purchased from Shandong Zhengyu Chemical Technology Co., Ltd.

[0075] In Example 4, the preparation method of the coated modified porous aggregate and the preparation method of the wet sprayed concrete for tunnel engineering are the same as those in Example 1.

[0076] Example 5

[0077] A wet sprayed concrete for tunnel engineering, comprising the following components in parts by weight: cement 440 parts, medium sand 980 parts, coarse aggregate 860 parts, water 215 parts, coated modified porous aggregate 45 parts, water reducing agent 13 parts, and accelerator 25 parts.

[0078] The cement is P.O42.5 cement, which is purchased from Sichuan Esheng Cement Group Co., Ltd.

[0079] The medium sand has a fineness modulus of 2.3-3.0.

[0080] The coarse aggregate is gravel, which is continuously graded and has a particle size range of 5-10 mm.

[0081] The porous aggregate has a water absorption rate of greater than 5%.

[0082] The porous aggregate is a mixture of ceramsite and red brick, which is purchased from a commercially available brand.

[0083] The water reducing agent is a polycarboxylic acid water reducing agent.

[0084] The accelerator is a silicate liquid accelerator, which is purchased from Shandong Zhengyu Chemical Technology Co., Ltd.

[0085] In the embodiment 5, the preparation method of the coated modified porous aggregate and the preparation method of the wet sprayed concrete for tunnel engineering are the same as those in the embodiment 1.

[0086] Comparative example 1

[0087] A wet sprayed concrete for tunnel engineering comprises, by weight fraction, cement 430 parts, medium sand 950 parts, coarse aggregate 840 parts, water 210 parts, coated modified porous aggregate 42 parts, water reducing agent 12 parts, and accelerating agent 22 parts.

[0088] In the comparative example 1, the preparation method of the coated modified porous aggregate and the preparation method of the wet sprayed concrete for tunnel engineering are the same as those in the embodiment 1.

[0089] The comparative example 1 is based on the embodiment 4, and the difference is that the comparative example 1 does not use the pumping method, and the rebound rate and the pumping condition are not measured, but the prepared concrete is directly prepared into a standard 10*10*10 cm cubic test block, and is cured under standard conditions for 28 days, and only the compressive strength test is performed.

[0090] Comparative example 2

[0091] A wet sprayed concrete for tunnel engineering comprises, by weight fraction, cement 430 parts, medium sand 950 parts, coarse aggregate 840 parts, water 210 parts, porous aggregate 42 parts, water reducing agent 12 parts, and accelerating agent 22 parts.

[0092] In the comparative example 2, the preparation method of the wet sprayed concrete for tunnel engineering is the same as that in the embodiment 1.

[0093] The comparative example 2 is based on the embodiment 4, and the difference is that the comparative example 2 uses a porous aggregate air-cooled ilmenite slag aggregate without any modification.

[0094] Comparative example 3

[0095] A wet sprayed concrete for tunnel engineering comprises, by weight fraction, cement 430 parts, medium sand 950 parts, coarse aggregate 840 parts, water 210 parts, porous aggregate 42 parts, water reducing agent 12 parts, and accelerating agent 22 parts.

[0096] In the comparative example 3, the preparation method of the wet sprayed concrete for tunnel engineering is the same as that in the embodiment 1.

[0097] The comparative example 3 is based on the embodiment 4, and the difference is that the comparative example 3 does not use the pumping method, and the rebound rate and the pumping condition are not measured, but the prepared concrete is directly prepared into a standard 10*10*10 cm cubic test block, and is cured under standard conditions for 28 days, and only the compressive strength test is performed.

[0098] Comparative Example 4

[0099] A wet-mix shotcrete for tunnel engineering comprises, by weight fraction, cement 430 parts, medium sand 950 parts, coarse aggregate 840 parts, water 210 parts, water reducing agent 12 parts, and accelerating agent 22 parts.

[0100] Comparative Example 4 is based on Example 4, except that the addition of porous aggregate is omitted in the wet-mix shotcrete for tunnel engineering.

[0101] Test Example

[0102] Compressive strength test: The concrete is sprayed in an iron mold of 45*35*12 cm, and after the concrete in the mold reaches a certain strength, it is processed into a 10*10*10 cm cube test block, and cured under standard conditions for 28 days, and then subjected to a compressive strength test;

[0103] Rebound rate test: The sprayed concrete is sprayed on a spraying plate fixed on an iron stand; the spraying plate has an area of 2000 mm*800 mm, a thickness of 30 mm, and a 45° angle with the vertical direction to the ground; the spraying plate has sufficient hardness and does not deform under the impact of the sprayed concrete; the iron stand has sufficient stability and does not shake during spraying; the iron stand is placed on two small weigh bridges on both sides for measuring the concrete adhered to the spraying plate; a 3m*3m plastic cloth is placed directly below the iron stand to receive the rebounded concrete; a fixed amount of concrete is sprayed each time, and after spraying is completed, the mass of the concrete adhered to the spraying plate and the plastic cloth is weighed, and the rebound rate of the sprayed concrete is calculated according to the formula: W r = (W2*100) / (W s +W2); the average of two rebound rates is taken as the final result;

[0104] wherein W r is the rebound rate (%), W s is the mass of the sprayed concrete adhered to the spraying plate (kg), and W2 is the mass of the sprayed concrete rebounded on the plastic cloth (kg).

[0105] During the performance test, the air pressure of the spraying machine is controlled between 0.5-0.8 MPa, and the spraying angle is between 60-100°.

[0106] The spraying distance of the nozzle of the wet spraying machine from the spraying plate is 0.8-1.2 m.

[0107] The performance test results are shown in Table 1.

[0108] Table 1

[0109]

[0110] Comprehensive performance analysis: the embodiments 1-5 of the present application all have excellent 28-day compressive strength and excellent rebound rate; and the pumping is good, which can be smoothly pumped.

[0111] The formula components of Comparative Example 1 are completely consistent with those of Example 4, except that pumping is not used, and the 28-day compressive strength is greatly different from that of Examples 1-5. The possible reason is that in the pumping process, the film coated on the porous aggregate may be damaged under the action of pumping and pumping pressure, thereby exposing the porous aggregate, and because the porous aggregate material itself is porous and has the characteristics of easily absorbing water, it can adsorb free water in the concrete, causing the concrete to become viscous when sprayed, thereby reducing the rebound rate of the concrete and increasing the compressive strength of the concrete. The wet shotcrete for tunnel engineering of the present application can achieve the optimal use effect after pumping.

[0112] Comparative Example 2 uses a porous aggregate that has not been modified in any way and has the characteristics of easily absorbing water, which can adsorb free water in the concrete. Because it becomes too viscous, it is difficult to pump under the pumping conditions of the present test, so its rebound rate is not measured.

[0113] Comparative Example 3 uses a porous aggregate that has not been modified in any way to directly prepare a cubic test block, and is cured under standard conditions for 28 days for compressive strength testing. The compressive strength of Comparative Example 3 is close to that of Comparative Example 2.

[0114] Comparative Example 4 omits the addition of porous aggregate, and the pumping is smooth, but the rebound rate is high, which cannot be well applied to tunnel engineering.

[0115] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A wet sprayed concrete for tunnel engineering, characterized in that According to the weight parts, the composition comprises: Cement 410-440 parts, medium sand 850-980 parts, coarse aggregate 780-860 parts, water 195-215 parts, coated modified porous aggregate 35-45 parts, water reducing agent 9-13 parts, and quick setting agent 12-25 parts; The preparation method of the coated modified porous aggregate is as follows: the porous aggregate is wrapped with a fine fishing net and placed in a self-made potassium silicate solution, the porous aggregate needs to be completely immersed in the self-made potassium silicate solution, the porous aggregate is fully stirred every 5 minutes, after soaking for 15 minutes, the soaked porous aggregate is taken out and the excess self-made potassium silicate solution is filtered out; finally, the treated porous aggregate is placed in an oven for drying, and the coated modified porous aggregate is prepared after drying. The preparation and synthesis method of the self-made potassium silicate solution is as follows: the silica sol is poured into a three-necked flask, then the three-necked flask is placed in a constant temperature water bath pot equipped with a high-speed stirrer and a temperature control device, the temperature is raised to 50 degrees Celsius, the potassium hydroxide and deionized water are slowly added into the three-necked flask while stirring, the mixed solution is continuously stirred for 15 minutes, then it is poured into a flask under constant temperature water bath condition, the temperature is set to 30 degrees Celsius, the self-made silicon modified acrylic emulsion is slowly added under stirring, and stirring is carried out for 1 hour; finally, hydroxyethyl cellulose is added as a thickening agent, and sodium polyacrylate is added as a dispersant, and stirring is continued for 15 minutes, to obtain the self-made silicon modified acrylic emulsion. The preparation and synthesis method of the self-made silicon modified acrylic emulsion is as follows: 15g of styrene, 7g of butyl acrylate, 11g of butyl acrylate, 7g of methyl methacrylate, 6g of butyl methacrylate, 5g of sulfonic acid-based acrylate, 80g of deionized water, 0.6g of polyethylene glycol p-isooctyl phenyl ether, and 0.2g of sodium dodecyl sulfate are weighed; they are placed in a beaker and stirred at a speed of 650r / min for 30 minutes at room temperature to obtain a milky white mixture, which is named as component A; 0.8g of ammonium persulfate is dissolved in 40g of deionized water, which is named as component B; a mixture of 0.4g of sodium bicarbonate, 10g of deionized water, and 60g of component A is placed in a four-necked round-bottom flask, then 20g of component B is added dropwise into the flask to obtain a uniform mixture; then, the remaining mixture of component A and component B is added dropwise into the flask within 2 hours, and the reaction temperature is maintained at 85 degrees Celsius; then, 1.3g of 3-(trimethoxysilyl) propyl methacrylate is slowly added into the four-necked round-bottom flask, and the reaction is maintained at 85 degrees Celsius for 1 hour; finally, the temperature is adjusted to 90 degrees Celsius for 1 hour, and ammonia water is added to adjust the pH to 7-8, to obtain the self-made silicon modified acrylic emulsion.

2. A wet-mix shotcrete for tunnel engineering according to claim 1, characterized in that, According to the weight parts, the composition comprises: cement 430 parts, medium sand 950 parts, coarse aggregate 840 parts, water 210 parts, coated modified porous aggregate 42 parts, water reducing agent 12 parts, and quick setting agent 22 parts.

3. A wet-mix shotcrete for tunnel engineering according to claim 1, characterized in that, The fineness modulus of the medium sand is 2.3-3.

0.

4. A wet-mix shotcrete for tunnel engineering according to claim 1, characterized in that, The coarse aggregate is crushed stone with continuous gradation and a particle size range of 5-10mm.

5. A wet-mix shotcrete for tunnel engineering according to claim 1, characterized in that, The porous aggregate is a porous aggregate with a water absorption rate greater than 5%, and comprises one or more of a mixture of ceramic granules, red bricks, recycled aggregates, air-cooled ilmenite slag aggregates, and zeolites.

6. A method of preparing a wet-mix shotcrete for tunnel engineering according to any one of claims 1 to 4, characterized in that The preparation method of the wet shotcrete for tunnel engineering is as follows: first, the cement and the coarse aggregate are added into a forced mixer and stirred for 30 s; then, the water reducing agent is uniformly mixed with water and added into the mixing pot and stirred for 45 s; finally, the coated modified porous aggregate and the medium sand are added into the mixing pot and continuously stirred for 2 min; and finally, the accelerating agent is automatically added through the nozzle during the spraying operation, so that the wet shotcrete for tunnel engineering is prepared.

7. The application of the wet shotcrete for tunnel engineering according to claim 6 in tunnel engineering construction.

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