A pneumatic spraying method for wet shotcrete

Abstract

The invention discloses a pneumatic spraying method for wet shotcrete, wherein cement, sand, pebbles, admixtures and water are added to a mixer to form a fluidized concrete mixture, wherein cement accounts for 21% to 29% of the total materials; an atomized quick-setting agent is subjected to a swirl treatment in a spray nozzle, and then mixed with the prepared fluidized concrete mixture by rotation, and then quickly sprayed to a construction site. The method of the invention can greatly improve the utilization rate of the quick-setting agent and the quick-setting effect, while reducing the rebound amount of the shotcrete and effectively improving the strength of the shotcrete; and avoids pipe blockage and pulse dripping of the concrete mixture during the spraying construction.

Description

Technical Field

[0001] The invention belongs to the technical field of concrete spraying construction, and in particular relates to a pneumatic spraying method for wet sprayed concrete. Background Art

[0002] After decades of development, concrete spraying construction has been widely used in rock tunnel support in construction foundation pits, subways, slope protection, highways, high-speed rail tunnels and mining projects. Shotcrete is a concrete construction method that uses a spraying machine, compressed air or other power to add a quick-setting agent to concrete mixed in a certain mix ratio, and then sprays it at high speed through a delivery hose under the action of high-pressure wind onto the sprayed rock surface and structure, and can quickly coagulate and harden.

[0003] The existing concrete spraying construction, whether using a large trolley or a small wet spraying machine, has many problems such as concrete spraying pipe blockage, discharge pulse dripping and large rebound of construction concrete, which seriously affects the spraying concrete construction. The most fundamental problem is that the current wet spraying concrete process greatly affects the utilization rate of the accelerator and the quick-setting effect of the accelerator. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a pneumatic spraying method for wet shotcrete in view of the deficiencies in the above-mentioned prior art, which realizes uniform mixing of the accelerator and the concrete mixture through cyclone assistance, improves the quick-setting effect of the accelerator on cement, avoids pipe blockage and adhesion, and pulse dripping in concrete construction, and greatly reduces the amount of concrete rebound in spraying construction.

[0005] The present invention adopts the following technical solutions:

[0006] A pneumatic spraying method for wet shotcrete comprises the following steps:

[0007] S1. Add cement, sand, pebbles, admixtures and water into a mixer to prepare a fluidized concrete mixture, wherein cement accounts for 21% to 29% of the total material mass, and the mass ratio of cement: sand: pebbles: admixtures: water is 1: (1.1 to 2.0): (1.0 to 1.3): (0.005 to 0.015): (0.35 to 0.50);

[0008] S2, subjecting the atomized accelerating setting agent to a swirl treatment in a spray nozzle, and then subjecting it to swirl mixing with the fluidized concrete mixture prepared in step S1, and then rapidly spraying it to the construction site.

[0009] Specifically, the injection nozzle includes a mixing pipe and a discharge pipe, one end of the mixing pipe is connected to one end of the concrete feeding pipe; the other end is connected to one end of the discharge pipe, and at least one group of wind-atomized accelerating-setting agent interfaces is opened on the side wall of the mixing pipe, each group of wind-atomized accelerating-setting agent interfaces includes two rows of wind-atomized accelerating-setting agent interfaces, and each row of wind-atomized accelerating-setting agent interfaces includes a number of interfaces arranged at intervals.

[0010] Furthermore, the concrete mixture is 5 to 28 m 3 / h and transported into the mixing pipe.

[0011] Furthermore, 0.4-0.8Mpa rotating wind with atomized quick-setting agent is introduced along the tangent or normal direction of the side wall of the mixing pipe; and then 0.4-0.8Mpa rotating wind pressure is introduced along the tangent or normal direction of the side wall of the mixing pipe.

[0012] Furthermore, two rows of wind-assisted atomized quick-setting agent interfaces are symmetrically arranged.

[0013] Furthermore, each interface is arranged along the tangent or normal direction of the side wall of the mixing pipe, and an inclination angle of 30° to 90° is set between the opening direction of the interface and the axial direction of the mixing pipe.

[0014] Furthermore, the diameter of the interface is 10 to 50 mm.

[0015] Furthermore, the length of the mixing pipe is 10 to 90 cm and the diameter is 30 to 80 mm.

[0016] Furthermore, one end of the discharge pipe is a tapered pipe opening with a length of 50 to 100 cm and a diameter of 30 to 80 mm.

[0017] Specifically, according to the percentage of cement dosage, the water reducing agent is 0.5% to 1.5%, and the air entraining agent is 0.005% to 0.02%.

[0018] Compared with the prior art, the present invention has at least the following beneficial effects:

[0019] The present invention discloses a pneumatic spraying method for wet shotcrete. Concrete mixture is produced at a mixing station with cement, sand, gravel, admixture and water in different proportions. When the fluid concrete mixture reaches the mixing pipe through the pumping conveying pipe and is mixed with the atomized accelerating setting agent, the atomized accelerating setting agent is subjected to a swirl treatment, which can greatly exert the quick-setting effect of the accelerating setting agent. Since the pumped concrete mixture is a viscous fluid, according to the existing nozzle design, adding a direct current wind of the accelerating setting agent with a pressure of 0.4 to 0.8 MPa is very likely to cause problems such as pipe blockage, dripping or poor quick-setting effect. Therefore, the above-mentioned problems that are prone to occur in the existing spraying construction can be solved by allowing the power wind containing the accelerating setting agent or the wind added again to rotate and enter in the tangential or normal direction. The specific method is that the wind-blown atomized accelerator passes through the interface along the inner wall of the mixing pipe, cuts obliquely into the inner cavity of the mixing pipe, and mixes along the flow direction of the concrete. In addition, the higher injection pressure of the wind-blown atomized accelerator can make the accelerator and concrete fully mixed, thereby improving the utilization rate of the accelerator, making the reaction efficiency of the concrete and the atomized accelerator high, while reducing the rebound of the shotcrete and effectively improving the strength of the shotcrete; avoiding pipe blockage and pulse dripping during the spraying construction of the concrete mixture with the accelerator; the nozzle with a special structure mixing pipe has more than 50% lower rebound than the traditional jacketed nozzle under the same conditions, and the use of the accelerator is reduced by more than 1 / 3, and the phenomenon of pipe blockage or dripping is completely eliminated, with a frequency of zero occurrence.

[0020] Furthermore, the interface is arranged along the tangent or normal line of the side wall of the mixer, which can provide wind power to rotate and stir the concrete to which the quick-setting agent has been added in the mixer, thereby achieving the purpose of quick setting and reducing rebound as well as preventing pipe blockage and dripping.

[0021] Furthermore, according to the characteristics of the wet spraying machine and concrete mixture, in order to ensure construction safety and project quality, the wind pressure is best set between 0.4 and 0.8 MPa. The dynamic wind rotation can not only fully mix the accelerator, but also prevent the addition of the accelerator from causing a series of problems such as concrete sticking to the wall and blocking the pipes, dripping or poor quick-setting effect.

[0022] Furthermore, the opening angle of the interface is set at 30° to 90°, and the concrete with the accelerated setting agent added is stirred and mixed to the maximum extent through multiple pneumatic cuts at different angles.

[0023] In summary, the method of the present invention can greatly improve the utilization rate of the accelerating agent and the accelerating effect, while reducing the rebound of the shotcrete and effectively improving the strength of the shotcrete; and avoiding pipe blockage and pulse dripping of the concrete mixture during the spraying construction.

[0024] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A structural diagram of a conventional spray nozzle used at a construction site;

[0026] Figure 2 Another conventional spray nozzle structure diagram for use at construction sites;

[0027] Figure 3 A nozzle structure for the spraying method of the present invention;

[0028] Figure 4 Another nozzle structure used in the spraying method of the present invention. DETAILED DESCRIPTION

[0029] At present, in the construction of shotcrete, the concrete mix ratio, shot volume and wind pressure all play a decisive role in the construction quality. Among them, the most critical issue is the treatment method when the pumped shotcrete or wind-delivered shotcrete intersects with the wind force added with the accelerator and the wind vortex is ejected.

[0030] The present invention adopts a pneumatic spraying method for wet shotcrete, comprising the following steps:

[0031] S1. Add cement, sand, pebbles, admixtures and water into a mixer to prepare a fluid concrete mixture, wherein cement accounts for 21% to 29% of the total material mass;

[0032] The mass ratio of cement: sand: gravel: water: admixture is 1:(1.1~2.0):(1.0~1.3):(0.35~0.50):(0.005~0.015); the admixture ratio is based on the proportion of cement: water reducer is 0.5%~1.5%, and air entraining agent is 0.005%~0.02%.

[0033] S2, subjecting the atomized accelerating setting agent to a swirl treatment in a spray nozzle, and then subjecting it to swirl mixing with the fluidized concrete mixture prepared in step S1, and then rapidly spraying it to the construction site.

[0034] The specific usage process is:

[0035] The wet spraying machine delivers the fluid concrete mixture to the nozzle through a feed hose; after the atomized accelerator is cyclone-treated by the spray nozzle, the flow mode of the atomized accelerator is changed to cause air flow agitation with the fluid concrete mixture to achieve sufficient reaction and mixing, thereby improving the utilization rate of the accelerator, enhancing the quick-setting effect of the accelerator, and improving the cohesion between the concrete mixtures; the rotating wind assists the concrete to be sprayed out smoothly, reducing the rebound of the shotcrete and avoiding pipe blockage and pulse dripping during concrete construction.

[0036] See also Figure 3 and Figure 4The invention discloses a nozzle for a pneumatic spraying method of wet shotcrete, comprising a mixing pipe and a discharging pipe, wherein one end of the mixing pipe is connected to one end of a concrete feeding pipe, and the other end is connected to one end of a discharging pipe. At least one group of wind-driven atomized accelerator interfaces is provided on the side wall of the mixing pipe, and each group of wind-driven atomized accelerator interfaces preferably has two symmetrical interfaces. Multiple groups of wind-driven stirring interfaces can also be connected.

[0037] Preferably, each interface is arranged along a tangent or normal direction of the side wall of the mixing pipe.

[0038] Preferably, an angle of 30° to 90° is set between the opening direction of each interface and the axial direction of the mixing pipe.

[0039] Preferably, the interface diameter is 10 to 50 mm.

[0040] Preferably, the mixing pipe has a length of 10 to 90 cm and a diameter of 30 to 80 mm.

[0041] Preferably, one end of the discharge pipe is a tapered pipe opening with a length of 50 to 100 cm and a diameter of 30 to 80 mm.

[0042] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can usually be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in 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.

[0043] See also Figure 1 , which is a conventional spray nozzle used on the construction site. The specific construction process is:

[0044] S1 adds cement, sand, pebbles, admixtures and water into a mixer to prepare a fluid concrete mixture, wherein cement accounts for 29% of the total materials;

[0045] S2 concrete mixture is 28m 3 / h speed into the mixed flow pipeline, mixed with the atomized quick-setting agent, and then sprayed onto the sprayed surface through the discharge pipeline.

[0046] Figure 2The method shown is: use a traditional sprinkler to add atomized accelerating agent, then connect high-pressure air through multiple tangential or normal air inlets to strongly rotate and stir the concrete mixture and spray it out.

[0047] Example 1

[0048] S1: Cement, sand, pebbles, admixtures and water are added into a mixer in the proportions of 1:2.0:1.3:0.005:0.40 and 0.50 to prepare a fluidized concrete mixture, with a water reducer of 0.5%, an air entraining agent of 0.005% and cement accounting for 21% of the total materials;

[0049] S2 concrete mixture is 21m 3 / h speed to the mixed flow pipeline, mixed with the atomized quick-setting agent and then transported to the mixing pipeline.

[0050] S3 introduces 0.4Mpa rotating wind pressure along the tangent or normal direction of the side wall of the mixing pipe, fully disturbs the concrete mixture, and then passes through the discharge pipe and sprays to the sprayed surface.

[0051] Example 2

[0052] S1 Add cement, sand, pebbles, admixtures and water in the proportions of 1:1.4:1.1:0.005:0.40 and 0.50 into a mixer to prepare a fluidized concrete mixture, with a water reducer of 0.5%, an air entraining agent of 0.008% and cement accounting for 25% of the total materials;

[0053] S2 concrete mixture is 18m 3 / h speed to the mixed flow pipeline, mixed with the atomized quick-setting agent and then transported to the mixing pipeline.

[0054] S3 introduces 0.6Mpa rotating wind pressure along the tangent or normal direction of the side wall of the mixing pipe, fully disturbs the concrete mixture, and then passes through the discharge pipe and sprays to the sprayed surface.

[0055] Example 3

[0056] S1: Cement, sand, pebbles, admixtures and water are added into a mixer in the proportions of 1:1.1:1.0:0.005:0.40 and 0.50 to prepare a fluidized concrete mixture, wherein the water reducing agent is 0.5%, the air entraining agent is 0.009%, and cement accounts for 29% of the total materials;

[0057] S2 concrete mixture is 28m 3 / h speed to the mixed flow pipeline, mixed with the atomized quick-setting agent and then transported to the mixing pipeline.

[0058] S3 introduces 0.8Mpa rotating wind pressure along the tangent or normal direction of the side wall of the mixing pipe, fully disturbs the concrete mixture, and then passes through the discharge pipe and sprays to the sprayed surface.

[0059] A plurality of rows of wind-sprayed quick-setting agent interfaces are provided on the mixer side wall at the front end of the spray nozzle, and are arranged along the tangent or normal direction of the mixer side wall. The wind-sprayed quick-setting agent can be rotated in along the tangent or normal direction of the side wall, fully mixed with the concrete mixture and sprayed out. The structure is as follows: Figure 3 shown.

[0060] Example 4

[0061] S1: Cement, sand, pebbles, admixtures and water are added into a mixer in the proportions of 1:2.0:1.3:0.005:0.40 and 0.50 to prepare a fluidized concrete mixture, with a water reducer of 0.5%, an air entraining agent of 0.006% and cement accounting for 21% of the total materials;

[0062] S2 concrete mixture is 15m 3 / h speed is transported to the mixing pipeline.

[0063] S3 introduces 0.4Mpa rotating wind with atomized accelerating setting agent along the tangent or normal direction of the side wall of the mixing pipe. After being fully disturbed with the concrete mixture in the mixing pipe, it passes through the discharge pipe and is sprayed to the sprayed surface.

[0064] Example 5

[0065] S1 Add cement, sand, pebbles, admixtures and water in the proportions of 1:1.4:1.1:0.005:0.40 and 0.50 into a mixer to prepare a fluidized concrete mixture, with a water reducer of 0.5%, an air entraining agent of 0.007% and cement accounting for 25% of the total materials;

[0066] S2 concrete mixture is 5m 3 / h speed is transported to the mixing pipeline.

[0067] S3 introduces 0.6Mpa rotating wind with atomized accelerating setting agent along the tangent or normal direction of the side wall of the mixing pipe. After being fully disturbed with the concrete mixture in the mixing pipe, it passes through the discharge pipe and is sprayed to the sprayed surface.

[0068] Example 6

[0069] S1: Cement, sand, pebbles, admixtures and water are added into a mixer in the proportions of 1:1.1:1.0:0.005:0.40 and 0.50 to prepare a fluidized concrete mixture, with a water reducer of 0.5%, an air entraining agent of 0.010% and cement accounting for 29% of the total materials;

[0070] S2 concrete mixture is 10m3 / h speed is transported to the mixing pipeline.

[0071] S3 introduces 0.8Mpa rotating wind with atomized accelerating setting agent along the tangent or normal direction of the side wall of the mixing pipe. After being fully disturbed with the concrete mixture in the mixing pipe, it passes through the discharge pipe and is sprayed to the sprayed surface.

[0072] Multiple rows of wind-sprayed quick-setting agent interfaces and air inlets are provided on the mixer side wall at the front end of the spray nozzle. The wind-sprayed quick-setting agent interfaces and air inlets are arranged along the tangent or normal direction of the mixer side wall. The wind-sprayed quick-setting agent can first be rotated into the mixer along the tangent or normal direction of the side wall and fully mixed with the concrete mixture. Then, the high-pressure airflow connected to multiple tangent or normal air inlets strongly disturbs the concrete mixture for the second time and then rotates and sprays out, such as Figure 4 shown.

[0073] Example 7

[0074] S1: Cement, sand, pebbles, admixtures and water are added into a mixer in the proportions of 1:2.0:1.3:0.005:0.40 and 0.50 to prepare a fluidized concrete mixture, with a water reducer of 0.5%, an air entraining agent of 0.006% and cement accounting for 21% of the total materials;

[0075] S2 concrete mixture is 21m 3 / h speed is transported to the mixing pipeline.

[0076] S3 introduces 0.4Mpa rotating wind with atomized quick-setting agent along the tangent or normal direction of the side wall of the mixing pipe, and fully mixes it with the concrete mixture in the mixing pipe.

[0077] S4 introduces 0.4Mpa rotating wind pressure along the tangent or normal direction of the side wall of the mixing pipe, and after secondary disturbance of the concrete mixture, it passes through the discharge pipe and is sprayed to the sprayed surface.

[0078] Example 8

[0079] S1 Add cement, sand, pebbles, admixtures and water in the proportions of 1:1.4:1.1:0.005:0.40 and 0.50 into a mixer to prepare a fluidized concrete mixture, with a water reducer of 0.5%, an air entraining agent of 0.008% and cement accounting for 25% of the total materials;

[0080] S2 concrete mixture is 25m 3 / h speed is transported to the mixing pipeline.

[0081] S3 introduces 0.4Mpa rotating wind with atomized quick-setting agent along the tangent or normal direction of the side wall of the mixing pipe, and fully mixes it with the concrete mixture in the mixing pipe.

[0082] S4 introduces 0.6Mpa rotating wind pressure along the tangent or normal direction of the side wall of the mixing pipe, and after secondary disturbance of the concrete mixture, it passes through the discharge pipe and is sprayed to the sprayed surface.

[0083] Example 9

[0084] S1: Cement, sand, pebbles, admixtures and water are added into a mixer in the proportions of 1:1.1:1.0:0.005:0.40 and 0.50 to prepare a fluidized concrete mixture, wherein the water reducing agent is 0.5%, the air entraining agent is 0.009%, and cement accounts for 29% of the total materials;

[0085] S2 concrete mixture is 28m 3 / h speed is transported to the mixing pipeline.

[0086] S3 introduces 0.4Mpa rotating wind with atomized quick-setting agent along the tangent or normal direction of the side wall of the mixing pipe, and fully mixes it with the concrete mixture in the mixing pipe.

[0087] S4 introduces 0.8Mpa rotating wind pressure along the tangent or normal direction of the side wall of the mixing pipe, and after secondary disturbance of the concrete mixture, it passes through the discharge pipe and is sprayed to the sprayed surface.

[0088] Table 1 Comparison of the effects of pneumatic spraying methods for wet shotcrete

[0089]

[0090]

[0091] If the probability of pipe blockage exceeds 20%, it is considered easy to block the pipe. If the probability of pipe blockage is less than 3%, it is considered not easy to block the pipe.

[0092] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A pneumatic spraying method for wet shotcrete, characterized in that: The following steps are involved: S1. Add cement, sand, pebbles, admixtures and water into a mixer to prepare a fluidized concrete mixture. Cement accounts for 21% to 29% of the total material mass. The mass ratio of cement: sand: pebbles: admixtures: water is 1: (1.1 to 2.0): (1.0 to 1.3): (0.005 to 0.015): (0.35 to 0.50). The admixture is based on the percentage of cement dosage. The water reducer is 0.5% to 1.5%, and the air entraining agent is 0.005% to 0.02%; S2, after the atomized accelerating setting agent is subjected to swirl treatment in the spray nozzle, it is mixed with the fluidized concrete mixture prepared in step S1 through rotation, and then quickly sprayed to the construction site, specifically: A rotating wind with atomized quick-setting agent of 0.4~0.8Mpa is introduced along the tangent or normal direction of the side wall of the mixing pipe; then a rotating wind pressure of 0.4~0.8Mpa is introduced along the tangent or normal direction of the side wall of the mixing pipe. The length of the mixing pipe is 10~90cm and the diameter is 30~80mm; The spray nozzle includes a mixing pipe and a discharge pipe. One end of the mixing pipe is connected to one end of the concrete feeding pipe; the other end is connected to one end of the discharge pipe. One end of the discharge pipe is a tapered pipe mouth with a length of 50~100cm and a diameter of 30~80mm. At least one group of wind-atomized accelerator interfaces is opened on the side wall of the mixing pipe. Each group of wind-atomized accelerator interfaces includes two rows of wind-atomized accelerator interfaces. Each row of wind-atomized accelerator interfaces includes a number of interfaces arranged at intervals. The concrete mixture is transported to the mixing pipe at a speed of 5~28m3 / h. Each interface is arranged along the tangent or normal direction of the side wall of the mixing pipe. An inclination angle of 30°~90° is set between the opening direction of the interface and the axial direction of the mixing pipe.

2. The pneumatic spraying method for wet shotcrete according to claim 1, characterized in that: Two rows of wind-assisted atomized quick-setting agent interfaces are arranged symmetrically.

3. The pneumatic spraying method for wet shotcrete according to claim 1, characterized in that: The diameter of the interface is 10~50mm.

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