JPH0428872B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a spraying method for concrete, etc. BACKGROUND ART A commonly used method for constructing concrete or mortar in tunnels, shafts, chimneys, slopes, etc. is to force-feed dry or wet mixed materials to a spray nozzle using compressed air and spray them onto the construction surface. In this type of spraying method, for urgent construction work, construction work in winter, or work at spring water areas, the material is suddenly added to the normally mixed material in order to speed up curing, improve initial strength, or improve performance such as watertightness. It is becoming more common to spray with admixtures such as binders and water-reducing materials added, and in the past, in the past, it was common to charge the spraying material into the hopper of the spraying machine at the same time. The method used was to charge the admixture into the same spraying machine, and use compressed air to convey the material and the admixture together through a nozzle on the machine side and a hose to a spray nozzle at the tip and spray it. However, in this type of spraying method, the main material to be sprayed and the admixture are mixed in the spraying machine, so it is difficult to disperse and mix the material and the admixture uniformly, and the admixture is excessively mixed per unit amount. In many cases, it is included in the amount, or conversely, it is excessively reduced.
Therefore, there was a drawback that there were many variations in strength at various parts of the formed sprayed surface, and the initial strength was likely to be insufficient overall. In addition, because the materials and admixtures are mixed in the spray machine, the coagulation reaction progresses or completes before they are sprayed from the spray nozzle at the end of the hose, and they adhere to the inside of the spray machine or the conveyance hose. This can easily cause problems such as blockages and blockages. For this reason, the properties of the material are limited to dry mixes, making it impossible to use wet mix materials, which are preferable for improving strength, and requiring the use of aggregates with low water content, which is inconvenient. Furthermore, in this method, since the amount of admixture added to the material is fixed, there is a problem that the amount of admixture added cannot be adjusted at will to immediately respond to the situation at the site during the spraying operation. The present invention solves the problems of the conventional spraying method as described above, and forms a sprayed surface with little variation in strength and high initial strength by uniformly mixing admixtures regardless of the properties of the material. You can also
No equipment troubles occur due to the use of admixtures,
The purpose of this invention is to provide a method for spraying concrete, etc., which allows the admixture to be freely controlled in response to on-site conditions. In order to achieve the above object, the present invention, when spraying concrete, etc. containing an admixture, discharges a fixed amount of material from a spraying machine and conveys it through a conveyance hose toward a spray nozzle, while at the same time In the system, a fixed amount of slurry-like or more liquid-like admixture is cut out, compressed air is added to it to disperse it, and a fixed amount of airflow is conveyed through the hose at a pressure slightly lower than the material conveying pressure, and the dispersed mixture is mixed. The material is mixed with the material being air-flow conveyed at the addition section installed in the conveyance hose at least 20m upstream of the spray nozzle, and the material and admixture are stirred and mixed in the conveyance hose leading to the spray nozzle. It is designed to be sprayed from a spray nozzle. Hereinafter, the present invention will be explained based on the accompanying drawings. Fig. 1 shows an embodiment of the spraying method for concrete, etc. according to the present invention, in which 1 is a spraying machine, 2 is a machine side nozzle (discharge mechanism) provided in the spraying machine 1, and 3 is a conveying hose. , 4 is a spray nozzle connected to the tip of the conveying hose, and 5 is an addition section located behind the spray nozzle 4. The spraying machine 1 includes a storage section 6 for material A, and an air blowing section for discharging a fixed amount of the material A stored therein through a machine-side nozzle 2 to a conveying hose 3 and transporting the material A with airflow toward a spraying nozzle 4. 7 and 7', but there are no other special restrictions. In this embodiment, a rotor 8 having a large number of pockets 9, 9 is rotated under the storage part, and when the pockets reach the machine side nozzle 2, they are discharged by compressed air from the air blowing parts 7, 7'. , which is used as a carrier to be pumped. Instead of this mechanism, a two-tank airtight container type or squeeze type spraying machine may be used. If material A is a wet mixer, a type with a kneading function is recommended. The material A, that is, the mixture of aggregate and cement, is charged into the spraying machine 1, and is discharged to the machine side nozzle 2 by compressed air introduced through the air pipe 10, from where it is transferred to the spraying nozzle 4 by the conveying hose 3. However, in the present invention, the spray nozzle 4 and the water addition section 5 are
An admixture adding section 11 equipped with a main passage 13 communicating with the hose and a communication port 14 for the main passage 13 is connected to the conveyance hose 3 at least 20 m upstream from the spray nozzle 4, and A wet admixture B in the form of a liquid or slurry is added in fixed amounts via an admixture addition section 11 to the material A being conveyed through the hose. Specifically, as shown in FIG. 1, apart from the material spraying machine 1, there is provided a metering pump that is equipped with a storage section 15 for wet admixture B, a metering cutting mechanism 16, a discharge section 17, and a pressurizing air blowing section 18. 12, the discharge part 17 of this metering pump 12 is connected to the communication port 14 of the admixture addition part 11 with a hose 19, and the air piping 10 of the spraying machine 1 is connected to the pressure-feeding air blowing part 18. An air pipe 20 that is independent of or branched from the air pipe 20 is connected via a regulating valve 21. In this embodiment, a screw is used as the quantitative cutting mechanism 16, but it may be of any configuration such as a gear, a rotor, or a squeeze roller. Therefore, when spraying, wet admixture B
is put into the storage section 15, and in synchronization with the start of conveyance of the material A by the spraying machine 1, the quantitative cut-out mechanism 16 is operated to discharge the wet admixture B in fixed amounts into the discharge section 17, and using the air piping 20. The admixture B is conveyed by airflow from the hose 19 to the communication port 14. At this time, it is desirable that the admixture addition pressure, that is, the hose internal pressure, be slightly lower than the material conveyance pressure. The reason for this is that if the internal pressure of the hose is too high, an air curtain will be formed in the main path by the jetting force from the communication port, causing pulsations in the material feeding through the conveying hose. The pressure adjustment is carried out through air piping 10,
This can be easily done by detecting the pressure of 20 with a pressure gauge or the like and adjusting the opening degree of the regulating valve 21 manually or with a controller connected to the pressure gauge. Also, admixture B
The addition amount can also be easily determined by changing the rotational speed of the quantitative cutting mechanism 16. As described above, if material A is quantitatively discharged and conveyed by air in the conveying hose, and in synchronization with this, wet admixture B is fed quantitatively into hose 19 by compressed air, the said admixture becomes granular. Distributed to b and conduction port 1
4 into the main path 13. At this time, the material particles a, which have become dispersed and suspended due to the compressed air flow, are passing through the main path, so a turbulent flow is generated in the main path due to the compressed air introduced from the communication port 14 as described above. As a result, the admixture particles b entrained in the compressed air as shown in Fig. 2 cause vigorous agitation with the material particles a passing through the conveyance hose, and this agitation reaches the spray nozzle 4. 20m until
While passing through the long conveyance hose 3, the admixture particles B adhere around the material particles A due to their retained moisture. In this way, the present invention feeds the wet admixture B, which is also dispensed in a fixed quantity and is in a dispersed state, to the material A, which is dispensed in a fixed quantity and is sent in a dispersed state, and furthermore, these materials and the admixture are used as a conveyance medium. Since the dynamic energy of compressed air is used to stir and advance the mixture, a uniform mixing state is achieved in which the admixture is not locally distributed too much or too little. If an admixture is added at or near the spray nozzle,
Uniform dispersion of the admixture is difficult to achieve because the stirring and mixing effect due to the dynamic energy of compressed air cannot be fully utilized. Then, such a mixture advances through a conveying hose 3, and when the material is a dry mixture type, water is added by a water addition unit 5 in an amount to achieve a predetermined water/cement ratio, and is delivered from a spray nozzle 4 to a construction surface c. Sprayed. Further, when the material A is a wet mix type, water is not added and the material is sprayed as is from the spray nozzle 4. In the case of this wet mix, the amount of water added to the material A can be reduced by the water content of the admixture B, which facilitates pressure feeding in the spray machine 1 and has the advantage of extending the conveyance distance. The present invention is suitable for spraying concrete and mortar, but can also be applied to spraying furnace materials. Next, specific examples of the present invention will be shown. Example () Using the spraying machine and metering pump shown in FIG. 1, concrete was sprayed onto the vertical surface of a tunnel according to the present invention. The material composition is Cement 360.
Kg/m ³ , fine aggregate 997Kg/m ³ , coarse aggregate 662Kg/m ³ ,
S/A was set at 60%, W/C was set at 50-55%, and a slurry-like inorganic salt was used as a wet admixture, which was added in an amount of 6% based on the amount of blended cement. () As the wet admixture addition part, a Y-shaped branch metal fitting with a main pipe with an inner diameter of 65φ connected to a narrow tube with an inner diameter of 25φ is used, and this is connected 20m forward from the nozzle on the side of the spray machine.
Transport hose located 24m behind the spray nozzle
A 25φ, 20m hose was used to connect the inlet of the addition section and the metering pump. () Five types of samples were taken from the sprayed surface as shown in Figure 3, and their initial strength (compressive strength) was tested. The results are shown in Table 1 in comparison with the conventional method of charging the material and admixture into a spraying machine and spraying them all at once.

[Table] From Table 1, it can be seen that according to the present invention, much better strength was obtained using the same amount of admixture. () In order to examine the mixability of the wet admixture in the present invention, the wet admixture was added to a formulation without cement and sprayed, and a PH test was conducted. The spraying conditions, addition conditions, etc. were all the same as the specifications above. The results are shown in comparison with the conventional method.
As shown in the table. The spraying machine hopper sample had a pH of 7, and the sampling location was as shown in Figure 3.

[Table] From Table 2, it can be seen that in the present invention, the admixture is uniformly dispersed and mixed. According to the present invention as described above, while the material is discharged in a fixed amount from the spraying machine and transported by airflow through the conveying hose toward the spray nozzle, a liquid or an admixture similar to this is preliminarily dispensed in a fixed amount in a separate system. The material is cut out, compressed air is added to it, it becomes a mist, it is suspended at high speed, and it is conveyed by a hose, so it can be made into fine droplets of admixture, and it can be sent not to the spray nozzle but to the upstream side. Since the addition section of the conveyor hose is sucked into the material stream being floated and conveyed, the admixture can be quantitatively and smoothly added by avoiding air curtain formation in the addition zone and the resulting pulsation, and the conveyor hose and Since both compressed air causes turbulence in the conveying hose, this can be used as dynamic energy to vigorously stir and mix the material particles and the mist-like admixture, and this stirring mixture reaches the spray nozzle. As the process is repeated many times in the conveying hose, a fixed amount of admixture can be sprayed from the spray nozzle into the material as a uniformly finely dispersed mixture. Therefore, it is possible to make uniform, high-strength concrete that takes advantage of the benefits of adding admixtures, without having to spray expensive admixtures unreacted or causing uneven concrete strength. Excellent results can be obtained.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing an example of the spraying method for concrete, etc. according to the present invention, Fig. 2 is a cross-sectional view showing the state of admixture addition in the present invention, and Fig. 3 is a sample collection in an example of the present invention. It is an explanatory view showing a position. DESCRIPTION OF SYMBOLS 1... Spray machine, 3... Transfer hose, 4... Spray nozzle, 7, 7'... Air blowing part, 11...
...Admixture addition section, 12... Metering pump, 19...
Hose, A...Material, B...Wet admixture.

Claims (1)

[Claims] 1 When spraying concrete, etc. containing admixtures, the material is discharged in a fixed amount from the spraying machine and transported by airflow through the conveyance hose toward the spraying nozzle.
In a separate system, a fixed amount of slurry-like or more liquid-like admixture is cut out, compressed air is added to it to disperse it, and a fixed amount of airflow is transported through the hose at a pressure slightly lower than the material transport pressure. A conveyance hose that brings the material and the admixture to the spray nozzle by making the dispersed admixture join the material that is being conveyed by airflow at the addition section provided in the conveyance hose at least 20 m upstream of the spray nozzle. A method of spraying concrete, etc., which is characterized by stirring and mixing the mixture inside and spraying it from a spray nozzle.