JPH01198972A - Wet type spraying method for cement kneaded substance - Google Patents

Abstract

PURPOSE:To facilitate the forced feed of concrete of dry consistency and to prevent sagging of a sprayed surface, by a method wherein air bubbles are mixed in concrete of dry consistency to provide fluidity and the concrete is sprayed against a work executing portion, and by executing deaeration during spraying, fluidity is lowered. CONSTITUTION:Compressed air from an air compressor 21 is fed in concrete of dry consistency forcibly fed with the aid of a concrete pump 11 to produce air bubbles for provision of fluidity. By injection of concrete through a nozzle 16, spraying against a given portion is effected. In this case, through utilization of the loosening action of a cement kneaded substance itself, an impact action on a work executing portion, or a defoaming action and an accelerating action due to a defoaming agent and an accelerating agent mixed in the cement kneaded substance, the cement kneaded substance is deaerated to lower fluidity.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a cement mixture that is sprayed by imparting fluidity to a hard-mixed cement mixture with low fluidity by utilizing the action of mixed air bubbles. Wet spraying is related to construction methods.

[Conventional technology]

When excavating a tunnel or forming a steep slope on the slope of another mountain, spraying cement mixture is a method that prevents the collapse of rock and strata and forms walls, but does not require formwork or the like. This method has been commonly used for a long time as it is easy to carry out and can be constructed in a short period of time.

This kind of spraying is a construction method in which, for example, an organic binder and aggregate are thoroughly mixed in advance, a cement mixture is sent under pressure to the construction site using a pump or high-pressure air, and the spraying is carried out using a nozzle. However, in this case, it is necessary to adjust the cement mixture to a state where it can be fluidized and pumped in a hose or other conduit. For this purpose, a considerable amount of an organic binder such as a resin or asphalt type binder must be mixed into the cement mixture to form a slurry and impart fluidity. However, with materials that have been given fluidity in this way, after spraying, sagging will occur on the sprayed surface, and in order to prevent sagging, reducing the mixing ratio of organic binder to aggregate will improve fluidity. There was a drawback that special high-pressure pumping conditions had to be provided due to the decrease in the pressure.

Therefore, as a way to eliminate the above drawbacks,
No. 3229 discloses the following construction method.

As shown in Figure 2, this consists of a powdery solid content such as aggregate 1 and an organic binder such as resin or asphalt, or liquid or slurry liquid fluid bone 2 mainly composed of an organic binder such as resin or asphalt.
The liquefied fluidized bones 2 are dispersed and added to the pumped solid content 1 near the nozzle 4, and the spraying in the high-pressure air pipe 3 that pumps the powdery solid content is carried out from this addition position to the surface 5. The above-mentioned two materials are mixed in the process leading to the spraying process.

[Problem to be solved by the invention]

However, in this conventional wet spraying construction method, the water-cement ratio W/ C may be increased, or a considerable amount of organic binder and quick-setting agent such as resin or asphalt, or a liquid or slurry containing liquid or slurry liquid bone such as resin or asphalt may be added (for example, granular solid content may be added to liquid bone). (volume ratio of 1:2 or more), which increases material costs and reduces economic efficiency, and is unsuitable in cases where hard mixed concrete is required, such as in dams and paving concrete. There were problems such as.

The present invention has been made in view of such conventional problems, and aims to solve the above problems by adding air bubbles to hard-mixed concrete to impart fluidity.

[Means to solve the problem]

In order to achieve the above object, the wet spraying method of the present invention involves mixing air bubbles of 6 to 20% by volume into a hard cement mixture with extremely low fluidity, and the air bubbles have a lubricating effect. This is a construction method in which the fluidity of the cement mixture is increased using a pump, and the mixture is pumped and sprayed onto the construction site, and this spraying is sometimes done by deaerating the cement mixture to reduce its fluidity and then supplying it to the construction site. It is.

In addition, the deaeration of the cement mixture is caused by (a) the loosening effect of the cement mixture during spraying, (b) the impact effect when the cement mixture reaches the construction site, and (C) the inside of the cement mixture. This is carried out by one or more actions selected from among the defoaming action of the mixed antifoaming agent, the quick setting action of the quick setting agent mixed into the dl cement kneaded material, etc.

[Effect]

The hard cement mixture, which has low fluidity, has increased fluidity due to the lubricating effect of the air bubbles and the reduction in specific gravity, and it is pumped through a pressure pipe and wet sprayed from a nozzle to the construction site in the same way as a normal cement mixture. It will be done. However, when spraying, the composition of this cement mixture itself,
For properties and spraying, one or more of the actions described below are selected depending on the construction target, etc., and deaeration is performed to create a dense and strong cement mixture with reduced fluidity. Forms a wall surface (sprayed surface) and prevents dripping.

Here, the deaeration action selected is a loosening action in which the cement mixture splits from the air bubbles and becomes fine agglomerates when injected from the nozzle, and a loosening action in which the cement mixture separates and becomes fine agglomerates collides with the spraying surface. These include the shock effect of degassing due to the impact of the cement, the defoaming effect of an antifoaming agent mixed in with the cement mixture in advance, and the rapid setting effect of a quick setting agent mixed in the same way.

〔Example〕

Hereinafter, the present invention will be explained with reference to the drawings and experimental results.

FIG. 1 is a diagram showing an embodiment according to the present invention.

In the figure, 1) is a concrete pump, and as shown in the experimental results table below, the concrete pumped by this pump contains 6 to 20% air bubbles (air content) in the hard cement mixture by volume. ) is uniformly mixed with a certain amount of foaming agent, for example, 0.025 to 0.04% based on the weight of cement, so as to improve fluidity.

A is a transport pipe system for hardened cement whose fluidity has been increased by mixing air bubbles, 12 is a concrete pipe, 13 is a concrete hose, 14 is a mixing pipe, 15 is a hose at the tip, and 16 is this tip. It is a nozzle attached to a hose.

21 is a near compressor, B is an air supply pipe system for compressed air from this compressor, 22 is a ball valve for adjusting the flow rate, 23 is a pressure reducing valve, and 24 is a pressure gauge. B
, is a bypass for the air pipe system B, and is used when a problem occurs in the air pipe system B, and is used for spraying immediately before starting or finishing work, and 25 is a ball valve for adjusting the flow rate.

Reference numeral 31 denotes a pressure-feeding device for quick-setting agent, C a hose for pressure-feeding quick-setting agent from this pressure-feeding device, and 32 a ball valve for controlling the flow rate and also for preventing backflow.

Next, when starting the spraying work, first, the ball valve 22 of the air pipe system B and the ball valve 3 of the quick setting agent pressure feeding hose C are
2 is closed, and the ball valve 25 of bypass B+ is fully opened, and the compressed air from the near compressor 21 is supplied to the mixing pipe 14. The above-mentioned path is cleaned by ejecting it from the nozzle 16 through the tip hose 15. When the cleaning is finished, the concrete pump 1) starts pumping the hard mixed concrete whose fluidity has been increased by mixing air bubbles, closes the ball valve 25 of B1, and closes the ball valve 22 of the air supply pipe system B.
is opened to such an opening that the pressure gauge 24 indicates the appropriate air pressure. Thereupon, the hard mixed concrete is jetted toward the wall surface 5 from the nozzle 16 via the tip hose 15 by the compressed air jetted into the mixing pipe 14.

When spraying onto the construction site such as the wall surface 5 mentioned above, the cement mixture such as concrete or mortar has one or two effects as described below depending on the composition and properties of the mixture itself and the spraying target. The above method is selected to perform deaeration, reduce fluidity, form a dense and strong wall surface (sprayed surface) in a sprayed state, and prevent the occurrence of dripping.

Here, the degassing effect is the loosening effect in which the cement mixture splits from the air bubbles contained in it and becomes fine agglomerates when it is injected from the nozzle, and the loosening effect in which the cement mixture separates and becomes fine agglomerates and collides with the spraying surface. These include the impact effect of crushing and degassing due to the impact of the cement, the defoaming effect of an antifoaming agent in advance in the cement mixture, and the quick setting effect of a quick setting agent mixed into the cement mixture in advance.

In addition, depending on the situation, especially when spraying requires rapid setting,
The quick-setting agent is pumped by the quick-setting agent pumping device 31 and the ball valve 32 is opened to cause the compressed air from the air pipe system B to blow into the mixing pipe 14 from the mixing pipe 14 to the nozzle 1.
It is mixed uniformly into the cement mixture up to 6.

For spraying, once the construction is completed, use the concrete pump 1.
), the ball valves 22 and 32 are fully closed, and the ball valve 25 is fully open, and compressed air is injected from the nozzle 16 through the bypass pipe B1, through the mixing pipe 14, and before the residue in the pipe hardens. Discharge.

The table below shows the results of an experimental example in which mortar and concrete were constructed using the above-mentioned spraying method.

In the case of mortar, the mixture used in the experiment was cement: sand = 1
: 3. W/C=55%, unit cement amount 360kg/rrr for concrete, S/A=65%,
W/C = 57%, the amount of foaming agent added is 0.025 to 0.04% to the cement weight (this means that the amount of air (air amount) in the cement mixture before spraying is 6 to 20%). (within the range of N), and when using an accelerating agent, the amount added was 5%. Table 1 shows the results for mortar spraying, and Table 2 shows the results for concrete spraying.

Table-1 Table-2 From the above experimental results table, the amount of air (bubbles) contained in the cement mixture before spraying was approximately 60% of that without the quick-setting agent in Table-1, and with the addition of the quick-setting agent. As shown in Table 2, the decrease was approximately 80%, and the decrease was approximately 53% without the quick-setting agent and approximately 68% with the addition of the quick-setting agent, and it is thought that a cement mixture with extremely low fluidity was sprayed. It will be done.

Note that if the volume ratio of air bubbles to the cement mixture is less than 6%, the fluidity is too low, and the ratio of 7 kgf/c in this example is
At an air pressure of d, there was a problem with spraying, and at an air pressure of 20% or higher, the amount of residual air after spraying was large, and the strength of the wall surface was below a predetermined value.

〔Effect of the invention〕

As explained above, according to the present invention, the following effects can be obtained.

(1) Compared to the conventional wet spraying method currently in use, it can be expected to improve the quality of the cement mixture and reduce costs due to the reduction in the water-cement ratio and the amount of quick-setting agent used.

(2) Concrete with a small amount of cement or hard mixed concrete can be easily pumped and placed, and can be applied to dam construction and road paving.

(3) Concrete can be transported over long distances if there is no need to add an accelerating agent.

(4) Since the fluidity is increased by the inclusion of air bubbles, a small diameter pressure feed pipe can be used.

(5) Wet spraying can greatly reduce avalanches that occur in construction methods.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an embodiment according to the present invention, and FIG. 2 is a schematic diagram of a conventional example. Patent applicant Taisei Corporation Agent Patent attorney Tetsuya Mori Attorney Yoshiaki Naito Attorney Patent attorney Tadashi Shimizu

Claims (2)

[Claims] (1) Air bubbles of 6 to 20% by volume are mixed into a hard cement mixture with extremely low fluidity, and the lubrication effect of the air bubbles is used to increase the fluidity of the cement mixture. A wet spraying method for a cement mixture, characterized in that the cement mixture is pumped and sprayed onto the construction site, and during this spraying, the cement mixture is deaerated to reduce its fluidity before being supplied to the construction site. (2) The deaeration of the cement mixture is caused by (a) the loosening effect of the cement mixture during spraying, (b) the impact effect when the cement mixture reaches the construction site, and (c) the inside of the cement mixture. (d) The quick-setting action of the quick-setting agent mixed into the cement mixture.
Wet spraying method of cement mixture as described in Section 3.