A kind of tunnel shotcrete special cement

Abstract

The application relates to the technical field of shotcrete cement, and discloses a special cement for tunnel shotcrete, which comprises, in percentage by mass, cement clinker 80-85%, slag 6-11%, limestone 2-4%, hard gypsum 5-8% and quick-setting agent 6-9%. The quick-setting agent comprises aluminum sulfate, organic alcohol amine, micro-silica powder and silicic acid, and the mass ratio of the components is 6-7:0.5-0.8:1-2:0.6-1.2:0.1-0.4. The application also discloses the application of the cement to a concrete composite layer and a construction method of the concrete composite layer. The application can adjust the pH value of the system by adding silicic acid, thereby promoting the dissolution and hydration of silicates in the cement clinker, separating out Ca 2+ , thereby increasing the concentration of Ca 2+ in the system, and further promoting the generation of calcium aluminate to strengthen the early strength. Further, the cement component is applied to the concrete composite layer, and the construction can achieve the effects of good impermeability and high strength.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of shotcrete cement, and particularly relates to a special cement for tunnel shotcrete. BACKGROUND

[0002] Tunnel shotcrete is an essential engineering technology in the process of building a tunnel, and usually uses a concrete pump, a compressor, a shotcrete machine and the like to spray the mixed slurry on the inner wall of the tunnel. Then, due to different construction processes, the cement used for tunnel shotcrete needs to have higher impermeability, compactness, compressive strength and corrosion resistance compared with the traditional cement used for ordinary buildings. In addition, the cement used for tunnel shotcrete also needs to consider the hardening speed of the concrete after being applied to the concrete so as to improve the construction efficiency. These properties usually need to be realized by using an additive.

[0003] In the prior art, in order to improve the performance of tunnel shotcrete and improve the construction efficiency, an alkali-free accelerator mainly composed of aluminum sulfate is usually added to the cement or concrete as an additive. For example, the patent with the publication number CN116498329A uses aluminum sulfate, polyethyleneimine and silicon powder to form an accelerator, which can not only improve the strength of the concrete, but also shorten the surface drying time, thereby facilitating the rapid formation of support capacity after shotcrete and improving the construction efficiency.

[0004] However, while the accelerator accelerates the hydration of the cement, it also significantly shortens the operable time of the compaction process, which easily leads to uneven compaction and further causes poor compactness of the cement after being applied to the concrete. In addition, the addition of aluminum sulfate as the main material of the alkali-free accelerator also leads to a low pH value of the cement, which further causes water seepage in the tunnel in the later period if the compactness is low, thereby causing serious corrosion of the cement to steel anchors, steel mesh and the like.

[0005] In view of the above, how to ensure the improvement of the impermeability and corrosion resistance of the cement is a problem to be solved at present. SUMMARY

[0006] The present application is used to solve the technical problem that the addition of an alkali-free accelerator to the cement easily causes a too low internal pH value, which further leads to corrosion of metals and poor impermeability in the later period.

[0007] Therefore, the first purpose of the present application is to provide a special cement for tunnel shotcrete, which has a faster setting speed and hydration speed.

[0008] Specifically, a special cement for tunnel shotcrete includes, by mass percentage:

[0009] Cement clinker 80%~85%, slag 6%~11%, limestone 2%~4%, hard gypsum 5%~8%, accelerator 6%~9%;

[0010] The accelerator comprises aluminum sulfate, organic alcohol amine, microsilica powder, and silicic acid, and the mass ratio is 6~7:0.5~0.8:1~2:0.6~1.2:0.1~0.4 in turn.

[0011] The technical mechanism is:

[0012] (1) By adding silicic acid, the pH value of the system can be adjusted, thereby promoting the dissolution and hydration of silicates in the cement clinker, separating out Ca 2+ , thereby increasing the concentration of Ca 2+ in the system, thereby promoting the formation of ettringite and strengthening the early strength.

[0013] (2) By adding microsilica powder, the electric flux of the system can be reduced, thereby improving the later impermeability effect; specifically, the use of aluminum sulfate facilitates the generation of ettringite containing high crystalline water in the early hydration of cement, thereby reducing the content of free water and simultaneously consuming calcium hydroxide, avoiding the adverse effects of excess calcium hydroxide on microstructure density, thereby improving the cohesion of concrete and rapidly forming a skeleton structure while ensuring macroscopic density; after consuming calcium hydroxide, the alkalinity is reduced, thereby reducing the content of calcium silicate compounds (C-S-H) in the early hydration process, thereby facilitating the filling of microsilica powder, reducing the electric flux, and improving the later impermeability effect.

[0014] The second object of the application is to provide a concrete composite layer comprising the above-mentioned cement, comprising:

[0015] A first concrete layer is arranged on the inner wall of the tunnel, which comprises cement clinker 60%~75%, limestone 1%~5%, calcium sulfoaluminate 4%~10%, and silicate-based binder 25%~30% by mass percentage;

[0016] A second concrete layer is arranged on the surface of the first concrete layer and is prepared by injecting and stirring the tunnel shotcrete special cement.

[0017] The technical mechanism is:

[0018] (1) The first concrete layer is used to lay the bottom of the tunnel and cover the metal structures such as steel anchor rods and steel mesh installed on the inner wall of the tunnel, thereby preventing the second concrete layer from being affected, avoiding the further reduction of pH value by silicic acid to promote the separation of Ca 2+ , and improving the early strength of concrete, thereby avoiding the problem of poor impermeability caused by corrosion of metal structures in the later period.

[0019] (2) The silicate-based binder in the first concrete layer plays a role of quickly bonding each component and the subsequently sprayed second concrete layer; further, through the reaction of limestone and calcium sulphoaluminate, microsilica powder is filled in the pores appearing in the slurry after spraying, thereby playing a role of shrinkage compensation for the slurry, so as to improve the density of the slurry while reducing the electric flux of the sprayed slurry and improving the impermeability of the tunnel in the later period.

[0020] (3) The first concrete layer has high viscosity and density, and can also play a role of preliminary processing for the inner wall of the tunnel, so as to reduce the amount of the accelerator used in the second concrete layer, and further provide sufficient operable time for the compaction process after spraying, thereby improving the construction efficiency.

[0021] A third object of the present application is to provide a construction method using the above-mentioned composite concrete layer, which comprises the following construction steps:

[0022] S1: grinding and uniformly mixing cement clinker, limestone and microsilica powder in proportion, and then adding calcium sulphoaluminate and a silicate-based binder to obtain a blend;

[0023] S2: uniformly spraying the blend through a guniting machine to the inner wall of the tunnel to form a first concrete layer;

[0024] S3: grinding cement clinker, slag, limestone and anhydrite in proportion in a cement mill, and then adding microsilica powder and an accelerator to obtain a cement product;

[0025] S4: uniformly spraying the concrete guniting colloid through a guniting machine to the first concrete layer to form a second concrete layer.

[0026] The beneficial effects of the present application are as follows:

[0027] The special cement for tunnel guniting provided by the present application can reduce the setting time by using an accelerator, and also can improve the Ca 2+ rapidly separates from tricalcium silicate, thereby promoting the generation of ettringite and ensuring the density of the cement prepared as a concrete layer in the later period, thereby improving the impermeability;

[0028] Further, the addition of microsilica powder can reduce the electric flux of the system, thereby improving the later impermeability effect;

[0029] In addition, the adhesive first concrete layer is first laid on the inner wall of the tunnel to cover the metal structures such as steel anchor rods and steel mesh installed on the inner wall of the tunnel, thereby playing a role of insulation for the second concrete layer, so as to avoid the problem of poor impermeability due to the corrosion of the metal structure in the later period of the concrete caused by the low pH value of the system. DETAILED DESCRIPTION

[0030] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. If specific conditions are not specified in the embodiments, the conventional conditions or the conditions suggested by the manufacturers are adopted. If the manufacturers of the reagents or instruments are not specified, the conventional products that can be purchased in the market are adopted.

[0031] Firstly, the present application provides a cement special for tunnel shotcrete, comprising, by mass percentage:

[0032] 80-85% of cement clinker, 6-11% of slag, 2-4% of limestone, 5-8% of hard gypsum and 6-9% of quick-setting agent;

[0033] The quick-setting agent comprises aluminum sulfate, organic alcohol amine, microsilica and silicic acid, and the mass ratio is 6-7:0.5-0.8:1-2:0.6-1.2:0.1-0.4 in turn.

[0034] In the present application, the preparation process of the cement clinker is as follows: limestone, sandstone and iron correction raw materials are put into a raw mill in proportion for grinding, and then transferred to a rotary kiln for calcination at 1350 DEG C to obtain the cement clinker; wherein, by mass percentage, the content of limestone is 85-88%, the content of sandstone is 5-10% and the content of iron correction raw materials is 2-5%.

[0035] In the present application, by mass percentage, the content of tricalcium silicate in the cement clinker is 62-68%.

[0036] The cement clinker with tricalcium silicate as the main component is beneficial to produce more ettringite after hydration to ensure the early strength.

[0037] In the present application, by mass percentage, the content of dicalcium silicate in the cement clinker is 10-15%.

[0038] In the present application, by mass percentage, the content of tricalcium aluminate in the cement clinker is 6-7%.

[0039] In the present application, by mass percentage, the content of tetracalcium aluminoferrite in the cement clinker is 7.5-8.5%.

[0040] In the present application, the organic alcohol amine comprises at least one of diethanolamine, triethanolamine and N,N-dimethylethanolamine.

[0041] The second object of the present application is to provide a concrete comprising the above cement, comprising:

[0042] The first concrete layer is arranged on the inner wall of the tunnel and comprises, by mass percentage, cement clinker 60-75%, limestone 1-5%, calcium sulphoaluminate 4-10%, and silicate-based binder 25-30%.

[0043] The second concrete layer is arranged on the surface of the first concrete layer and is prepared by mixing the cement.

[0044] In the present application, the first concrete layer further comprises microsilica 1-3%.

[0045] By further adding microsilica, the microsilica can react with silicates in the binder to form a binding group, so that the first concrete layer has adhesion and compactness, the time for manual compaction is reduced, the second concrete layer can be sprayed quickly, and the later-stage impermeability is further improved.

[0046] In the present application, the ratio of microsilica to silicate-based binder is 1-2.5:0.3-0.7 by mass ratio.

[0047] The third object of the present application is to provide a construction method using the above concrete layer, which comprises the following construction steps:

[0048] S1, cement clinker, limestone, and microsilica are ground and mixed uniformly in a proportion, and then calcium sulphoaluminate and silicate-based binder are added to obtain a blend;

[0049] S2, the blend is uniformly sprayed onto the inner wall of the tunnel by a guniting machine to form the first concrete layer;

[0050] S3, cement clinker, slag, limestone, and anhydrite are ground in a cement mill in a proportion to obtain a cement product;

[0051] S4, microsilica and a quick-setting agent are added to the cement product, and the first concrete layer is uniformly sprayed by a guniting machine to form the second concrete layer.

[0052] <EMBODIMENT>

[0053] Example 1

[0054] (1) Preparation of cement clinker: limestone, sandstone, and iron correction raw materials are put into a raw mill in a mass ratio of 85:5:2 for grinding, and then transferred to a rotary kiln for calcination at 1350 DEG C to obtain cement clinker;

[0055] (2) cement clinker (in which the mass ratio of tricalcium silicate: dicalcium silicate: tricalcium aluminate: tetracalcium aluminoferrite is 65: 12: 6: 7.5), limestone, and microsilica are ground and mixed uniformly at a mass ratio of 50: 2: 1, and then calcium sulphoaluminate, silicate-based binder, and microsilica (in which the mass ratio of calcium sulphoaluminate: silicate-based binder: microsilica is 6: 30: 1.2) are added to obtain a blend;

[0056] (3) cement clinker (in which the mass ratio of tricalcium silicate: dicalcium silicate: tricalcium aluminate: tetracalcium aluminoferrite is 65: 12: 6: 7.5), slag, limestone, and anhydrite are ground in a cement mill, and then microsilica is mixed uniformly (in which the mass ratio of cement clinker: slag: limestone: anhydrite: microsilica is 80: 8: 2: 6: 6), and further a quick-setting agent (in which the mass ratio of aluminum sulfate: N, N-dimethylethanolamine: microsilica: silicic acid is 7: 0.5: 1: 0.3) is added to obtain a cement product;

[0057] (4) using the wet spraying method, first, the blend is sprayed to the inner wall of the tunnel to coat the metal structure erected on the inner wall of the tunnel to form a first concrete layer; then, the cement product, microsilica, and the quick-setting agent are mixed and uniformly sprayed to the first concrete layer by a spraying machine to form a second concrete layer, and further a manual compaction process is performed.

[0058] Example 2

[0059] The difference between this embodiment and embodiment 1 is that the mass ratio of tricalcium silicate: dicalcium silicate: tricalcium aluminate: tetracalcium aluminoferrite in the cement clinker is 70: 15: 6.5: 8.

[0060] Example 3

[0061] The difference between this embodiment and embodiment 1 is that the mass ratio of aluminum sulfate: N, N-dimethylethanolamine: microsilica: silicic acid in the quick-setting agent is 6: 0.5: 1: 0.3.

[0062] Example 4

[0063] The difference between this embodiment and embodiment 3 is that N, N-dimethylethanolamine in the quick-setting agent is replaced by triethanolamine.

[0064] Example 5

[0065] The difference between this embodiment and embodiment 1 is that the mass ratio of calcium sulphoaluminate: silicate-based binder: microsilica is 6: 25: 1.2

[0066] <Comparative example>

[0067] Comparative Example 1

[0068] The difference between the present comparative example and Example 1 is that the silicic acid is not contained.

[0069] Comparative Example 2

[0070] The difference between the present comparative example and Example 1 is that the mass ratio of aluminum sulfate, diethanolamine, microsilica powder and silicic acid in the accelerator is 1:0.5:1:0.3.

[0071] Comparative Example 3

[0072] The difference between the present comparative example and Example 5 is that the mass ratio of calcium sulfoaluminate: silicate-based binder: microsilica powder is 6:10:1.2

[0073] <TEST EXAMPLE>

[0074] Test Example 1

[0075] The initial setting time (minute) and final setting time (minute) tests were carried out on the samples of Examples 1-5 and Comparative Examples 1-3, and the experimental results are shown in Table 1.

[0076] Table 1

[0077] Name Initial setting time / min Final setting time / min Example 1 1.25 2.37 Example 2 1.20 2.45 Example 3 1.18 2.10 Example 4 1.14 2.22 Example 5 1.20 2.39 Comparative Example 1 2.20 4.12 Comparative Example 2 2.90 4.82 Comparative Example 3 2.02 4.07

[0078] Test Example 2

[0079] The post-construction concrete composite layer was tested, the permeable pressure ratio was detected according to JG / T 349-2011, and the experimental results are shown in Table 2.

[0080] Table 2

[0081]

[0082] From the comprehensive analysis of the experimental results in Table 1 and Table 2, it can be seen that by adding the sulfoaluminate accelerator, the setting time of the concrete layer can be effectively shortened, among which, by adding silicic acid, the pH value of the system can be adjusted, thereby promoting the dissolution and hydration of calcium silicate in cement clinker, improving the compressive strength and impermeability; by using the first concrete layer to perform the undercoating treatment on the inner wall of the tunnel in advance, not only the situation that the metal structure is corroded and the impermeability is reduced due to the too low pH value can be avoided, but also the negative effects caused by silicic acid can be further avoided.

[0083] From the embodiment 1, the embodiment 5, the comparative example 3, it can be seen that the silicate binder in the first concrete layer can effectively cement the second concrete layer, and further improve the impermeability and the compressive strength.

[0084] From the embodiment 1 and the embodiment 2, it can be seen that the certain proportion of tricalcium silicate and dicalcium silicate in the cement clinker can improve the compactness of the concrete, and further improve the impermeability and the strength of the concrete; in addition, the certain proportion of tricalcium aluminate and tetracalcium aluminoferrite is beneficial to improve the fluidity of the concrete, so that the concrete has good workability and overall compressive strength.

[0085] The above only describes the preferred embodiments of the present application and is not used to limit the present application, and for those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A tunnel shotcrete composite layer, characterized in that, include: The first concrete layer, set on the inner wall of the tunnel, comprises, by mass percentage, 60%~75% cement clinker, 1%~5% limestone, 4%~10% calcium sulfoaluminate, and 25%~30% silicate binder, with the sum of the percentages of the above components being 100%. The second concrete layer is placed on the surface of the first concrete layer and is made by mixing water with special cement for tunnel shotcreting. By mass percentage, the special cement for tunnel shotcreting comprises: 80%~85% cement clinker, 6%~11% slag, 2%~4% limestone, 5%~8% anhydrite, and 6%~9% quick-setting agent, with the sum of the percentages of the above components being 100%. The quick-setting agent is composed of aluminum sulfate, organic alcohol amine, microsilica powder, and silicic acid, with a mass ratio of 6~7:0.5~0.8:1~2:0.1~0.

4. The organic alcohol amines include at least one of diethanolamine, triethanolamine, and N,N-dimethylethanolamine.

2. The tunnel shotcrete composite layer according to claim 1, characterized in that, The content of tricalcium silicate in the cement clinker is 62% to 68% by mass percentage.

3. The tunnel shotcrete composite layer according to claim 2, characterized in that, The content of dicalcium silicate in the cement clinker is 10% to 15% by mass percentage.

4. The tunnel shotcrete composite layer according to claim 3, characterized in that, The content of tricalcium aluminate in the cement clinker is 6% to 7% by mass percentage.

5. The tunnel shotcrete composite layer according to claim 1, characterized in that, The content of tetracalcium aluminoferrite in the cement clinker is 7.5% to 8.5% by mass percentage.

6. The tunnel shotcrete composite layer according to claim 1, characterized in that, The first concrete layer also contains 1% to 3% microsilica, and the sum of the percentages of all components in the first concrete layer is 100%.

7. The tunnel shotcrete composite layer according to claim 6, characterized in that, The ratio of the microsilica powder to the silicate binder by mass is 1~2.5:0.3~0.

7.

8. A construction method for a tunnel shotcrete composite layer as described in claim 7, comprising the following construction steps: S1 Cement clinker, limestone, and silica fume are ground and mixed in proportion, and then calcium sulfoaluminate and silicate binder are added to obtain a blend. S2 The blend is evenly sprayed onto the inner wall of the tunnel using a shotcrete machine to form the first concrete layer; S3 involves grinding cement clinker, slag, limestone, and anhydrite into a cement mill in a specific ratio, then adding silica fume and an accelerator to obtain the finished cement product. S4 The concrete spraying colloid is evenly sprayed onto the first concrete layer through the spraying machine to form the second concrete layer.

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