JPS61176764A - Spraying of concrete - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (3-1) Industrial Application Field The present invention is a concrete method that enables spraying of high-quality concrete in working environments such as inside tunnels where it is necessary to extremely limit the generation of dust. Spraying is related to construction methods.

(3-2) Conventional technology Recently, the NATM method has been widely used as a tunnel construction method. In this method, concrete is sprayed on the excavated surface immediately after excavation to prevent cracks from forming in the ground. , is characterized by the stability of the excavation surface.

There are two types of concrete spraying methods: wet and dry. The wet method is a method in which concrete mixed in a mixer is sent to a nozzle using compressed air, while the dry method is a method in which cement and aggregate are mixed in a mixer and sent to a nozzle using compressed air, and then pressurized water is blown out at the tip of the nozzle to join the concrete. This is the way to do it.

When spraying concrete, it is necessary to promote setting to prevent the attached concrete from flaking off, and it is also necessary to accelerate hardening in order to quickly obtain the strength required for shoring and to withstand the vibrations of blasting. For this reason, it is necessary to conduct on-site tests, etc. and add a quick-setting agent and other additives that are most suitable for the construction site.Furthermore, in order to reduce splashing during construction, fine aggregate should be added to the aggregate. Although it is desirable to use only coarse aggregate, it is uneconomical and has a negative effect on the quality of concrete, so 30 to 40% of coarse aggregate with a diameter of 10 to 15 mm is mixed in.

Therefore, during construction, ready-mixed concrete may be purchased from a ready-mixed concrete factory. In most cases, the constructor installs mixing equipment and storage equipment to control quality.

In addition to controlling the additives and particle size of the aggregate mentioned above, a major issue in quality control is controlling the surface water of the aggregate.

In other words, in the dry method described above, if the aggregate is too dry, the friction during spraying will generate static electricity and increase the generation of dust, so it is easier to work if the aggregate is slightly damp. If the limit value of 5% is exceeded, the following problems will occur.

In other words, when cement and aggregate are mixed, a hydration reaction occurs, and if the spraying takes a long time to reach the surface after mixing,
As the reaction progresses, the adhesion of the sprayed concrete decreases and it becomes easier to fall off1.If the reaction progresses partially, the aggregate, unhydrated cement, and bone attached to the hydrated cement may be removed in the hose. Separate streams of materials, etc. emerge from the nozzle at different flow velocities. As a result, light and fine dust and unhydrated cement may not reach the surface or rebound and become floating dust.

It is possible to prevent the above-mentioned problems by making the mixing equipment portable, placing the spraying near the location, and shortening the time it takes for spraying to reach the surface after mixing, but there is a limit to how compact the mixing equipment can be. This method cannot be used for tunnels with small cross sections.

In the wet method, there is no direct effect as mentioned above, but fluctuations in surface water lead to fluctuations in the water-cement ratio, making it difficult to maintain a constant slump and causing pulsations, which can cause rebound and dust generation. becomes. In addition, the distance that can be pumped using the wet method is short (l/3 that of the dry method), and if you try to pump it beyond that limit, you will end up using concrete with weak adhesion, which will effectively reduce the rebound rate. This results in higher prices.

Fluctuations in surface water lead to fluctuations in the water-cement ratio, leading to various problems in the case of the dry method as well as in the case of the wet method described above.

As mentioned above, the management of aggregate surface water has a decisive influence on the success or failure of the concrete spraying method, so the storage facility is equipped with drainage equipment and drying equipment to manage surface water. This is necessary, and the equipment capacity is required to be doubled to the value determined from the usage amount due to rough drainage curing.

It also requires heating and curing during the cold winter months. Moreover, even with such facilities, it is still difficult to control surface water within limits.

In addition, conventional SEC spraying based on sand shell-forming theory is based on the system (S
and Enveloped with Ce+wen
t), but this method has serious flaws. In other words, the shell-building effect of sand cannot be achieved unless the surface water content is approximately 15 to 20% or more of the aggregate (sand). Therefore, spraying is S/A (
Since the sand-to-aggregate ratio) is extremely large, in order to achieve SEC°EC, the water-cement ratio must be extremely large, which is practically impossible. If .9t, S/A=0.6, S=0.6X1.9=1.140 (t)=
'1140 (Kg) If the surface water is 20%.

1140X0.2=228 (Kg) If the cement used is 350Kg/rn".

Surface water alone results in a high water-cement ratio of W/C, 0.65 (65%).Accordingly, in actual SEC spraying, the system uses sand from a low surface water wheel, where the SEC effect can hardly be achieved. Since it is used, there is almost no difference from conventional dry or wet spraying methods. In other words, when using fine aggregate (sand) that is currently available in Japan, rebound and dust generation cannot be significantly reduced no matter what conventional spraying method is used.

(3-3) Problems to be Solved by the Invention The present invention solves the above-mentioned drawbacks of the conventional concrete spraying method for tunnels, etc., suppresses the generation of dust, etc., and produces high quality and uniform concrete spraying. We are trying to provide a concrete spraying method that can be easily attached and has low equipment costs.

(3-4) Means for Solving the Problems The present invention was made with an eye to the fact that premixed concrete-related products such as dry mortar and rock capsules are produced in factories. Fine aggregate in a dry state, coarse aggregate in an absolutely dry state, and cement.

Concrete material mixed with additives such as aggregate separation preventive agents in appropriate proportions is produced in advance at a factory under strict quality control, and is packed in bags to prevent deterioration and separation. use

The concrete spraying equipment consists of a material hopper, a mixer connected to this, a pre-wet watering pipe that sprinkles water to this mixer, a dry spraying machine installed at the outlet of the mixer, and a spraying machine attached to the outlet of the concrete spraying machine. It consists of a flexible tube, a nozzle attached to the tip of the tube, and a water addition ring that opens at the inlet of the nozzle.The above-mentioned problems can be solved by putting the above-mentioned materials into this device and spraying them. It's resolved.

(3-5) Example Embodiments of the present invention will be described below based on the drawings.

Fig. 1 is a schematic diagram illustrating the concrete spraying apparatus according to the present invention, and Fig. 2 is a diagram showing details of the dry spraying machine.
Mixer 3, pre-wet watering pipe 4, dry spray Ia5
, a flexible tube 6, a spray nozzle 7, and a water addition ring 8.

The mixer 3 is connected to the hopper 2, and in this example consists of a case and a screw, and also serves as a conveyor.

The pre-wet water pipe 4 is installed above the mixer 3 so that water is evenly distributed throughout the mixer.

The spray 115 is composed of a hopper 5A, a closed fi room 5B, a feed wheel 5C, an outlet 5D, a valve 5E, etc., and is portable with wheels 5F. The airtight chamber 5B is maintained at high pressure by compressed air connected to the nozzle 5G. For spraying, the hopper 5A of the machine 5 is the mixer 3.
It is installed so that it is below.

For spraying, a flexible tube 6 such as a pressure hose is attached to the outlet 5D of the machine, and a nozzle 7 is attached to the tip of the flexible tube 6. Further, a water addition ring 8 is attached to the part where the flexible tube 6 of the nozzle 7 is attached.

The above-mentioned spraying is carried out by unpacking and putting the bags of concrete produced in the factory mentioned above into the hopper 2 of the device 1. If you aim, you can get the required quality spraying of concrete walls.

In the above embodiment, the mixer 3 has a structure that also serves as a conveyor, but this mixer is not necessarily limited to the one shown in the example, and one bag of concrete 9 and pre-wet water are mixed appropriately, and the spraying is carried out mechanically. For example, it may be a combination of a so-called bread mixer and a belt conveyor.

In addition, in the spraying of the embodiment, the concrete material to be fed into the equipment is not necessarily limited to bagged and packed concrete material, but the concrete material produced at the factory is filled into a container with a special structure that prevents deterioration and separation during transportation. It is also possible to carry it to the construction site by loading it on a vehicle, etc., and directly spraying from the container into the material hopper of the device. It is clear that the present invention can be effectively implemented even in that case.

As explained above, in the present invention, spraying is performed using absolutely dry fine aggregate and coarse aggregate, which are produced under strict quality control in factories as concrete materials and have almost no surface water, and cement. .

Since additives such as aggregate separation prevention agents and quick setting agents are mixed in appropriate proportions and packaged in bags, and humidification is performed using a mixer and pre-wet watering pipes, moisture management is extremely strict. Therefore, the generation of dust due to static electricity and the generation of dust due to the hydration reaction of cement can be prevented, and high-quality concrete can be sprayed during construction.

(3-8) Effects of the invention The present invention combines absolutely dry fine aggregate and absolutely dry coarse aggregate produced in a factory, cement, and additives such as an aggregate separation prevention agent in appropriate proportions. Using mixed concrete materials, concrete spraying is carried out by means of concrete spraying equipment, which has a material hopper, mixer, pre-wet watering pipe, dry spraying machine, flexible pipe, and nozzle. It has excellent effects as shown.

■ Large storage facilities at the construction site can be omitted, resulting in significant savings in equipment costs.

■ Extremely high quality sprayed concrete can be obtained.

■ Spraying can significantly reduce dust generation in the workplace.

■ It can make a major contribution to improving the quality of tunnel construction, reducing construction costs, and improving the working environment.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram illustrating a concrete spraying apparatus according to the present invention, and FIG. 2 is a diagram showing details of the dry spraying machine. l... Spraying device 2... Hopper 3... Mixer 4, fist, Briwet watering pipe 511... Dry spraying machine 5A... Hopper 53... Airtight chamber 5C... Feed wheel 5D... Outlet 5E...Valve 5F...Wheel
5G・Fist nozzle 6...Flexible tube 7...
・Nozzle 8...Water addition ring 9...Bagged concrete material

Claims (1)

[Claims] a material hopper; a mixer connected to the hopper;
A pre-wet watering pipe that sprinkles water on the mixer, a dry spraying machine provided at the outlet of the mixer, a spraying nozzle attached to the outlet of the spraying machine via a flexible pipe, and a spraying nozzle attached to the outlet of the spraying machine, Using a concrete spraying device having a water addition ring opening at the inlet, the material hopper is filled with absolutely dry fine aggregate, absolutely dry coarse aggregate, cement, an aggregate separation prevention agent, A concrete spraying method in which the concrete is mixed with other additives in appropriate proportions and packed in bags before being unpacked and placed in the bag.