A substrate-free cement-based coating for tunnel water leakage control and its preparation method

Abstract

This invention discloses a substrate-free cement-based coating for tunnel water leakage treatment and its preparation method. Using cement as a base material, combined with fly ash, slag, calcium hydroxide, and quartz sand, and with the action of an interface agent and a crystallizing agent, it can treat water leakage. While ensuring the bonding strength with the substrate, it eliminates the need for complex pretreatment of the substrate, solving the problem of cumbersome substrate pretreatment procedures for waterproof coatings used in tunnel construction. It not only achieves tunnel water leakage treatment but also shortens the construction period by more than 90%, significantly improving treatment efficiency.

Description

Technical Field

[0001] This invention relates to the field of waterproof coating technology, specifically to a substrate-free cement-based coating for tunnel leakage control and its preparation method. Background Technology

[0002] Water leakage is the most common problem in tunnel engineering, seriously jeopardizing structural and operational safety. On one hand, long-term water leakage erodes the tunnel lining structure, causing alkaline substances in the concrete to dissolve, reducing its strength and durability. Furthermore, in cold regions, repeated freeze-thaw cycles from leaking water can lead to cracking and spalling of the lining, threatening the overall stability of the tunnel structure. On the other hand, water leakage makes road surfaces slippery, increasing the risk of traffic accidents. In addition, if leakage occurs near electrical equipment, it may cause short circuits, paralyzing lighting, ventilation, and other systems, affecting normal tunnel operation. Therefore, efficient management of tunnel water leakage is crucial for ensuring the structural and operational safety of tunnels and improving the quality of tunnel engineering services.

[0003] With the continuous increase in traffic flow, the operational pressure on tunnels is increasing. To ensure the normal operation of traffic, the time available for interrupting tunnel traffic to carry out comprehensive and thorough leakage control work (i.e., the maintenance window) is very limited. Typically, the maintenance window lasts only a few hours in the early morning, and adjacent maintenance windows may be several days apart. Therefore, the ease of use of leakage control materials is particularly important at this time.

[0004] Existing waterproof coatings often have strict pretreatment requirements for the substrate. Before application, the substrate needs to be repaired, sanded, rinsed, and moistened to ensure it is flat, dust-free, and at a certain degree of wetness or dryness. In tunnel leakage scenarios, due to the long-term effects of water erosion and operational dust on the substrate, the pretreatment time for existing coatings can be several hours or even days. This often prevents the completion of the entire leakage control process within a single window, severely limiting the efficiency of leakage control. If the pretreatment requirements are not met, the adhesion strength between the coating and the substrate will be low, leading to coating peeling during tunnel operation and seriously impacting tunnel safety. Summary of the Invention

[0005] For the reasons mentioned above, the first objective of this invention is to provide a substrate-free cement-based coating for tunnel water leakage treatment, which eliminates the need for pretreatment of the water-permeable substrate during the treatment process and improves the efficiency of tunnel water leakage treatment.

[0006] The second objective of this invention is to provide a method for preparing a substrate-free cement-based coating for treating tunnel water leakage.

[0007] The first objective of this invention can be achieved by adopting the following technical solution:

[0008] A substrate-free cement-based coating for treating tunnel water leakage comprises the following components in parts by weight:

[0009]

[0010] The interface agent is a mixture of oxalic acid, tartaric acid and citric acid; the crystallizing agent is a mixture of sodium sulfate, sodium silicate and potassium aluminum sulfate.

[0011] Furthermore, it also includes 0.1-0.2 parts by weight of water-retaining agent and 0.1-0.2 parts by weight of water-reducing agent.

[0012] Furthermore, the silicate cement is PO42.5 grade silicate cement; the sulfoaluminate cement is rapid-hardening sulfoaluminate cement.

[0013] Furthermore, the fly ash is Grade I fly ash; the slag is S95 grade granulated blast furnace slag powder with a specific surface area of ​​350-450 m². 2 / kg; the fineness of the quartz sand is 40-70 mesh.

[0014] Furthermore, the mass ratio of oxalic acid, tartaric acid and citric acid is (0.1-1):(3-5):(0.2-0.5).

[0015] Furthermore, the mass ratio of sodium sulfate, sodium silicate, and potassium aluminum sulfate is 1:(3-4):(2.5-3.5).

[0016] Furthermore, the water-retaining agent is a mixture of polyethylene-vinyl acetate copolymer emulsion and hydroxypropyl methylcellulose; the mass ratio of the polyethylene-vinyl acetate copolymer emulsion to hydroxypropyl methylcellulose is (0.5-2.5):(8-10).

[0017] Furthermore, the water-reducing agent is a polycarboxylate water-reducing agent; the water reduction rate of the water-reducing agent is 25% to 30%.

[0018] The second objective of this invention can be achieved by adopting the following technical solution:

[0019] The preparation method of the above-mentioned substrate-free cement-based coating for tunnel water leakage control includes the following steps:

[0020] Step S1: Silicate cement, sulfoaluminate cement, fly ash, slag and calcium hydroxide are mixed to obtain a mixed powder.

[0021] Step S2: Quartz sand is added to the mixed powder and the mixture is stirred and mixed to obtain material A.

[0022] Step S3: Mix the interface agent, water-retaining agent, crystallizing agent, and water-reducing agent to obtain material B;

[0023] In step S4, material A and material B are mixed to obtain a substrate-free cement-based coating for tunnel water leakage treatment.

[0024] Furthermore, the stirring conditions in step S1 are: stirring at 50-100 r / min for 15-30 min at 15-30℃;

[0025] The stirring conditions in step S2 are: at 15-30℃, stirring at 50-100 r / min for 30-45 min;

[0026] The stirring conditions in step S3 are: at 15-30℃, stirring at 100-200 r / min for 5-10 min;

[0027] The stirring conditions in step S4 are: at 15-30℃, stirring at 100-150 r / min for 15-30 min.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1. The present invention provides a substrate-free cement-based coating for tunnel water leakage treatment. Using cement as a base material, it combines fly ash, slag, calcium hydroxide, and quartz sand. With the action of interface agents and crystallizing agents, it can treat water leakage. While ensuring the bonding strength with the substrate, it eliminates the need for complex pretreatment of the substrate. It not only achieves tunnel water leakage treatment but also shortens the construction period and significantly improves treatment efficiency.

[0030] 2. The preparation method of the substrate-free cement-based coating for tunnel seepage control of the present invention involves processing the raw materials separately according to different combinations, which is beneficial to the overall performance of the coating; and it can be prepared by physical mixing, which can be used immediately after preparation and is convenient for treating seepage points at any time. Detailed Implementation

[0031] The technical solution of the present invention will now be clearly and completely described with reference to specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0032] Tunnels are becoming increasingly common in road infrastructure construction, and tunnel water leakage is an unavoidable problem. Tunnel water leakage is highly hazardous, significantly impacting construction work during treatment and seriously affecting tunnel operational safety. While some existing waterproofing materials can repair leaks, finding superior coatings remains a key direction for tunnel water leakage control. Therefore, this application provides a substrate-free cement-based coating for tunnel water leakage control and its preparation method, achieving good adhesion strength to the substrate while improving the efficiency of tunnel water leakage control.

[0033] A substrate-free cement-based coating for treating tunnel water leakage comprises the following components in parts by weight:

[0034]

[0035]

[0036] The interface agent is a mixture of oxalic acid, tartaric acid and citric acid; the crystallizing agent is a mixture of sodium sulfate, sodium silicate and potassium aluminum sulfate.

[0037] Using cement as a base material, combined with fly ash, slag, calcium hydroxide, and quartz sand, and with the help of interface agents and crystallizing agents, it can treat water leakage. Oxalic acid, tartaric acid, and citric acid, when mixed with water, ionize, and the resulting anions can complex calcium ions, further causing a slight dissolution of the substrate, effectively roughening the surface chemically. Sodium sulfate, sodium silicate, and potassium aluminum sulfate provide silicate, sulfate, and aluminum ions for the hydration reaction at the interface, promoting the formation of reaction products and increasing interfacial bonding strength. Thus, while ensuring bonding strength with the substrate, no complex pretreatment of the substrate is required; it achieves a bonding strength similar to that of a fully pretreated substrate after applying a waterproof coating, improving the efficiency of tunnel water leakage treatment.

[0038] As one embodiment, it also includes 0.1-0.2 parts by weight of water-retaining agent and 0.1-0.2 parts by weight of water-reducing agent.

[0039] The water-retaining agent increases the consistency of the coating after mixing, improves the water stability of the coating, prevents the coating from losing water too quickly due to the drying of the substrate, and ensures that the coating has sufficient reaction time with the substrate under water-rich conditions. The water-reducing agent reduces the amount of water used in mixing the coating, further reducing the water content and accelerating the drying speed of the substrate.

[0040] In one embodiment, the silicate cement is PO42.5 grade silicate cement; the sulfoaluminate cement is rapid-hardening sulfoaluminate cement.

[0041] In one embodiment, the fly ash is Grade I fly ash; the slag is S95 grade granulated blast furnace slag powder with a specific surface area of ​​350-450 m². 2 / kg; the fineness of the quartz sand is 40-70 mesh.

[0042] As one embodiment, the mass ratio of oxalic acid, tartaric acid and citric acid is (0.1-1):(3-5):(0.2-0.5).

[0043] In one embodiment, the mass ratio of sodium sulfate, sodium silicate, and potassium aluminum sulfate is 1:(3-4):(2.5-3.5).

[0044] In one embodiment, the water-retaining agent is a mixture of polyethylene-vinyl acetate copolymer emulsion and hydroxypropyl methylcellulose; the mass ratio of the polyethylene-vinyl acetate copolymer emulsion to hydroxypropyl methylcellulose is (0.5-2.5):(8-10). Hydroxypropyl methylcellulose is an excellent water-retaining agent, while polyethylene-vinyl acetate copolymer emulsion has excellent water resistance, acid and alkali resistance, and weather resistance, which can enhance the coating's durability. As a high molecular weight polymer, it can also increase the consistency of the coating after mixing with hydroxypropyl methylcellulose in a small amount; this improves the moisture stability of the coating, avoids excessive water loss due to the dryness of the substrate, and ensures sufficient reaction time between the coating and the substrate under water-rich conditions.

[0045] In one embodiment, the water-reducing agent is a polycarboxylate water-reducing agent; the water reduction rate of the water-reducing agent is 25% to 30%.

[0046] This application also provides a method for preparing the above-mentioned substrate-free cement-based coating for tunnel water leakage control, comprising the following steps:

[0047] Step S1: Silicate cement, sulfoaluminate cement, fly ash, slag and calcium hydroxide are mixed to obtain a mixed powder.

[0048] Step S2: Quartz sand is added to the mixed powder and the mixture is stirred and mixed to obtain material A.

[0049] Step S3: Mix the interface agent, water-retaining agent, crystallizing agent, and water-reducing agent to obtain material B;

[0050] In step S4, material A and material B are mixed to obtain a substrate-free cement-based coating for tunnel water leakage treatment.

[0051] As one embodiment, the stirring conditions in step S1 are: stirring at 50-100 r / min for 15-30 min at 15-30℃.

[0052] As one embodiment, the stirring conditions in step S2 are: stirring at 50-100 r / min for 30-45 min at 15-30°C;

[0053] As one implementation method, the stirring conditions in step S3 are: stirring at 100-200 r / min for 5-10 min at 15-30℃.

[0054] As one implementation method, the stirring conditions in step S4 are: stirring at 100-150 r / min for 15-30 min at 15-30℃.

[0055] The following is a further explanation using specific embodiments.

[0056] Example 1

[0057] A substrate-free cement-based coating for treating tunnel water leakage comprises the following components in parts by weight:

[0058] 40 parts silicate cement; 15 parts sulfoaluminate cement; 4 parts fly ash; 4 parts slag; 2 parts calcium hydroxide; 33 parts quartz sand; 0.3 parts interface agent; 0.1 parts water-retaining agent; 1.5 parts crystallizing agent; 0.1 parts water-reducing agent;

[0059] The interface agent used is a mixture of oxalic acid, tartaric acid, and citric acid in a mass ratio of 0.2:4:0.4; the water-retaining agent used is a mixture of polyethylene-vinyl acetate copolymer emulsion and hydroxypropyl methylcellulose in a mass ratio of 1:8; the crystallizing agent used is a mixture of sodium sulfate, sodium silicate, and potassium sulfoaluminate in a mass ratio of 1:3:3; the silicate cement is PO42.5 grade silicate cement; the sulfoaluminate cement is rapid-hardening sulfoaluminate cement; the fly ash is Grade I fly ash; the slag is S95 grade granulated blast furnace slag powder with a specific surface area of ​​400 m². 2 / kg; the fineness of the quartz sand is 40-70 mesh;

[0060] The preparation method is as follows:

[0061] Silicate cement, sulfoaluminate cement, fly ash, slag and calcium hydroxide were stirred at 100 r / min for 30 min at room temperature to obtain a mixed powder.

[0062] Quartz sand was added to the mixed powder, and the mixture was stirred at 100 r / min for 30 min at room temperature to obtain material A.

[0063] The interface agent, water-retaining agent, crystallizing agent, and water-reducing agent were stirred and mixed at 100 r / min for 10 min at room temperature to obtain material B;

[0064] Mix component A and component B at 100 rpm for 30 minutes at room temperature to obtain a substrate-free cement-based coating for tunnel water leakage control.

[0065] Example 2

[0066] The difference between Example 2 and Example 1 is that the interface agent is 0.4 parts by weight; the other components and preparation methods are the same as in Example 1.

[0067] Example 3

[0068] The difference between Example 3 and Example 1 is that the interface agent is 0.5 parts by weight; the other components and preparation methods are the same as in Example 1.

[0069] Example 4

[0070] The difference between Example 4 and Example 1 is that the water-retaining agent is 0.15 parts by weight; the other components and preparation methods are the same as in Example 1.

[0071] Example 5

[0072] The difference between Example 5 and Example 1 is that the water-retaining agent is 0.2 parts by weight; the other components and preparation methods are the same as in Example 1.

[0073] Example 6

[0074] The difference between Example 6 and Example 1 is that the crystallizing agent is 2 parts by weight; the other components and preparation methods are the same as in Example 1.

[0075] Example 7

[0076] The difference between Example 7 and Example 1 is that the crystallizing agent is 2.5 parts by weight; the other components and preparation methods are the same as in Example 1.

[0077] Example 8

[0078] The difference between Example 8 and Example 1 is that the silicate cement is 35 parts by weight and the sulfoaluminate cement is 20 parts by weight; the other components and preparation methods are the same as in Example 1.

[0079] Example 9

[0080] The difference between Example 9 and Example 1 is that the silicate cement is 50 parts by weight; the sulfoaluminate cement is 5 parts by weight; the other components and preparation methods are the same as in Example 1.

[0081] Example 10

[0082] The difference between Example 10 and Example 1 is that fly ash is 3 parts by weight; slag is 5 parts by weight; calcium hydroxide is 3 parts by weight; water-reducing agent is 0.2 parts by weight; other components and preparation methods are the same as in Example 1.

[0083] Example 11

[0084] The difference between Example 11 and Example 1 is that fly ash is 5 parts by weight; slag is 3 parts by weight; calcium hydroxide is 4 parts by weight; other components and preparation methods are the same as in Example 1.

[0085] Example 12

[0086] The difference between Example 12 and Example 1 is that the interface agent used is a mixture of oxalic acid, tartaric acid and citric acid in a mass ratio of 0.1:5:0.4; the water-retaining agent used is a mixture of polyethylene-vinyl acetate copolymer emulsion and hydroxypropyl methylcellulose in a mass ratio of 0.5:10; the crystallizing agent used is a mixture of sodium sulfate, sodium silicate and potassium sulfoaluminate in a mass ratio of 1:4:3; and the other components and preparation methods are the same as in Example 1.

[0087] Example 13

[0088] The difference between Example 13 and Example 1 is that the interface agent used is a mixture of oxalic acid, tartaric acid and citric acid in a mass ratio of 1:5:0.2; the water-retaining agent used is a mixture of polyethylene-vinyl acetate copolymer emulsion and hydroxypropyl methylcellulose in a mass ratio of 1:9; the crystallizing agent used is a mixture of sodium sulfate, sodium silicate and potassium sulfoaluminate in a mass ratio of 1:3:3.5; and the other components and preparation methods are the same as in Example 1.

[0089] Example 14

[0090] The difference between Example 14 and Example 1 is that the interface agent used is a mixture of oxalic acid, tartaric acid and citric acid in a mass ratio of 0.5:4:0.5; the water-retaining agent used is a mixture of polyethylene-vinyl acetate copolymer emulsion and hydroxypropyl methylcellulose in a mass ratio of 2.5:8; the crystallizing agent used is a mixture of sodium sulfate, sodium silicate and potassium sulfoaluminate in a mass ratio of 1:3:2.5; and the other components and preparation methods are the same as in Example 1.

[0091] Comparative Example 1

[0092] The difference between Comparative Example 1 and Example 1 is that the interface agent is 0 parts by weight; the other components and preparation methods are the same as in Example 1.

[0093] Comparative Example 2

[0094] The difference between Comparative Example 2 and Example 1 is that the water-retaining agent is 0 parts by weight; the other components and preparation methods are the same as in Example 1.

[0095] Comparative Example 3

[0096] The difference between Comparative Example 3 and Example 1 is that the crystallizing agent is 0 parts by weight; the other components and preparation methods are the same as in Example 1.

[0097] Comparative Example 4

[0098] The difference between Comparative Example 4 and Example 1 is that the crystallizing agent, water-retaining agent, and interface agent are all 0 parts by weight; the other components and preparation methods are the same as in Example 1.

[0099] Comparative Example 5

[0100] The difference between Comparative Example 5 and Example 1 is that the interface agent used is a mixture of tartaric acid and citric acid in a mass ratio of 10:1; the other components and preparation methods are the same as in Example 1.

[0101] Comparative Example 6

[0102] The difference between Comparative Example 6 and Example 1 is that the interface agent used is oxalic acid; the other components and preparation methods are the same as in Example 1.

[0103] Comparative Example 7

[0104] The difference between Comparative Example 7 and Example 1 is that the water-retaining agent used is a polyethylene-vinyl acetate copolymer emulsion; the other components and preparation methods are the same as in Example 1.

[0105] Comparative Example 8

[0106] The difference between Comparative Example 8 and Example 1 is that the water-retaining agent used is hydroxypropyl methylcellulose; the other components and preparation methods are the same as in Example 1.

[0107] Comparative Example 9

[0108] The difference between Comparative Example 9 and Example 1 is that the crystallizing agent used is a mixture of sodium sulfate and sodium silicate in a mass ratio of 1:3; the other components and preparation methods are the same as in Example 1.

[0109] Comparative Example 10

[0110] The difference between Comparative Example 10 and Example 1 is that the crystallizing agent used is a mixture of sodium sulfate and potassium aluminum sulfate in a mass ratio of 1:3; the other components and preparation methods are the same as in Example 1.

[0111] Comparative Example 11

[0112] The difference between Comparative Example 10 and Example 1 is that the crystallizing agent used is a mixture of sodium silicate and potassium aluminum sulfate in a mass ratio of 1:1; the other components and preparation methods are the same as in Example 1.

[0113] The performance testing process for the substrate-free cement-based coatings for tunnel seepage control prepared in Examples 1-14 and Comparative Examples 1-11 is as follows:

[0114] According to GB18445-2012, the flexural strength, compressive strength, wet substrate bond strength, untreated substrate bond strength, and impermeability of the substrate-free cement-based coating used for tunnel seepage control were tested; the results are shown in Table 1.

[0115] Table 1. Performance of Cement-Based Coatings for Tunnel Leakage Control (No Substrate Treatment Required)

[0116]

[0117]

[0118] As can be seen from Example 1 and Comparative Examples 1-4, the combined application of the three functional additives, interface agent, water-retaining agent and crystallizing agent, at appropriate dosages, improves the wet substrate bonding strength of cement-based coatings and significantly improves the bonding strength of untreated substrates, bringing it close to or enabling it to reach the wet substrate bonding strength.

[0119] As can be seen from Examples 1-3 and Comparative Example 1, the incorporation of the interface agent can effectively improve the bonding strength of cement-based coatings on wet substrates and untreated substrates. However, as the dosage increases further, the effect of the interface agent in delaying hydration gradually becomes apparent, and the bonding strength decreases.

[0120] As can be seen from Examples 1, 4-5 and Comparative Example 2, the incorporation of water-retaining agent can effectively improve the bonding strength of cement-based coatings on wet substrates and untreated substrates. Within the range of water-retaining agent dosage in this application, the higher the dosage, the higher the bonding strength.

[0121] As can be seen from Examples 1, 6-7 and Comparative Example 3, the incorporation of crystallizer can effectively improve the bonding strength of cement-based coatings on wet substrates and untreated substrates. Within the range of crystallizer dosage in this application, changes in crystallizer dosage have no significant effect on bonding strength.

[0122] As can be seen from Examples 1 and 8-14, within the range of cement, fly ash, slag, calcium hydroxide, water-reducing agent, interface agent, water-retaining agent and crystallizing agent dosages protected in this application, the cement content range shows that the untreated substrate bonding strength of the cement-based coating is greater than or equal to 1.0 MPa, the coating impermeability pressure ratio is greater than 250%, and the uncoated impermeability pressure ratio is greater than 175%, which meets the impermeability performance requirements of waterproof coatings in GB18445-2012.

[0123] Comparative Examples 7 and 8 demonstrate that the use of a single water-retaining agent cannot achieve the effect of using both in the examples.

[0124] Comparative Examples 9-11 show that any combination of any two of the crystallizing agents sodium sulfate, sodium silicate, and potassium sulfoaluminate significantly reduces the adhesive strength of the coating and the impermeability of the mortar, indicating that the combination of the three has a synergistic effect that improves the adhesive strength and impermeability of the coating.

[0125] Therefore, within the dosage range of the three functional additives protected in this application, the bonding strength of the cement-based coating on the untreated substrate is greater than or equal to 1.0 MPa, the anti-seepage pressure ratio with coating is greater than 250%, and the anti-seepage pressure ratio without coating is greater than 175%, meeting the anti-seepage performance requirements of waterproof coatings in GB18445-2012. Based on the data from Comparative Examples 1-4, it is evident that the material cannot meet the standard requirements if any one of the components is missing. Based on Comparative Examples 5-11, it is evident that the absence of any specific component among the three types of additives—interface agent, water-retaining agent, and crystallizing agent—will affect the bonding strength of the material on the untreated substrate, causing it to fail to meet the conditions for substrate-free treatment.

[0126] In summary, the cement-based coating for tunnel water leakage treatment that requires no substrate treatment, using cement as a base material and combining fly ash, slag, calcium hydroxide, and quartz sand, can treat water leakage under the action of interface agents and crystallizing agents. While ensuring the bonding strength with the substrate, it eliminates the need for complex pretreatment of the substrate; it not only achieves tunnel water leakage treatment but also shortens the construction period by more than 90%, significantly improving treatment efficiency.

[0127] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A substrate-free cement-based coating for treating tunnel water leakage, characterized in that, Includes the following components by weight: 35-50 parts of silicate cement; 5-20 parts of sulfoaluminate cement; 3-5 parts fly ash; 3-5 parts of slag; 2-4 parts calcium hydroxide; 25-35 parts of quartz sand; Interface agent 0.3-0.5 parts; 1.5-2.5 parts crystallizing agent; Water-retaining agent 0.1-0.2 parts; The interface agent is a mixture of oxalic acid, tartaric acid and citric acid; the crystallizing agent is a mixture of sodium sulfate, sodium silicate and potassium aluminum sulfate.

2. The substrate-free cement-based coating for tunnel seepage control according to claim 1, characterized in that, It also includes 0.1-0.2 parts by weight of water-reducing agent.

3. The substrate-free cement-based coating for tunnel seepage control according to claim 1, characterized in that, The silicate cement is PO 42.5 grade silicate cement; the sulfoaluminate cement is rapid-hardening sulfoaluminate cement.

4. The substrate-free cement-based coating for tunnel seepage control according to claim 1, characterized in that, The fly ash is Grade I fly ash; the slag is S95 grade granulated blast furnace slag powder with a specific surface area of ​​350-450 m². 2 / kg; the fineness of the quartz sand is 40-70 mesh.

5. A substrate-free cement-based coating for tunnel seepage control according to claim 1, characterized in that, The mass ratio of oxalic acid, tartaric acid and citric acid is (0.1-1):(3-5):(0.2-0.5).

6. A substrate-free cement-based coating for tunnel seepage control according to claim 1, characterized in that, The mass ratio of sodium sulfate, sodium silicate and potassium aluminum sulfate is 1:(3-4):(2.5-3.5).

7. A substrate-free cement-based coating for tunnel seepage control according to claim 2, characterized in that, The water-retaining agent is a mixture of polyethylene-vinyl acetate copolymer emulsion and hydroxypropyl methylcellulose; the mass ratio of the polyethylene-vinyl acetate copolymer emulsion to hydroxypropyl methylcellulose is (0.5-2.5):(8-10).

8. A substrate-free cement-based coating for tunnel seepage control according to claim 2, characterized in that, The water-reducing agent is a polycarboxylate water-reducing agent; the water reduction rate of the water-reducing agent is 25%~30%.

9. The method for preparing the substrate-free cement-based coating for tunnel seepage control according to any one of claims 1-8, characterized in that, Includes the following steps: Step S1: Silicate cement, sulfoaluminate cement, fly ash, slag and calcium hydroxide are mixed to obtain a mixed powder. Step S2: Quartz sand is added to the mixed powder and the mixture is stirred and mixed to obtain material A; Step S3: Mix the interface agent, water-retaining agent, crystallizing agent, and water-reducing agent to obtain material B; In step S4, material A and material B are mixed to obtain a substrate-free cement-based coating for tunnel water leakage treatment.

10. The method for preparing a substrate-free cement-based coating for tunnel seepage control according to claim 9, characterized in that, The stirring conditions in step S1 are: at 15-30℃, stirring at 50-100 r / min for 15-30 min; The stirring conditions in step S2 are: at 15-30℃, stirring at 50-100 r / min for 30-45 min; The stirring conditions in step S3 are: at 15-30℃, stirring at 100-200 r / min for 5-10 min; The stirring conditions in step S4 are: at 15-30℃, stirring at 100-150 r / min for 15-30 min.

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