JPH0316469B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to the invention of a concrete spraying method,
Create appropriate conveyance conditions for concrete or refractory material materials, and smooth transfer of concrete with a small water-to-cement ratio or concrete with less water content (in short, a state in which air is interposed between the solid particles in the mixed material). This makes spraying possible, and significantly reduces the amount of rebound to achieve efficient spraying construction, as well as reduce the amount of dust generated.
Furthermore, we would like to obtain a method that can quickly and precisely develop shear stress, sufficiently increase the thickness of the sprayed layer in one step, reduce the amount of quick-setting agent added, and form shotcrete with excellent strength. That is.

The spraying method is already known as one of the concrete construction methods. In other words, while concrete construction like this generally requires forming a formwork and then filling and forming, this spraying method does not require such a formwork and can be applied to walls, slopes, etc. It has the great advantage of completely eliminating the need for the process of installing formwork and removing the formwork after it has hardened, and therefore can complete concrete construction within a short time, and is being put into practical use for tunnel walls and the like. There are three types of concrete spraying methods conventionally employed: dry, wet, and semi-wet, and although each of these methods has its merits, it also has disadvantages and drawbacks. In other words, the wet method is a method in which a mixture of all constituent materials of the concrete to be sprayed is conveyed through a conduit such as a pipe or hose, and is sprayed by ejecting it from a nozzle.
Since it has a high water content in a slurry state that ensures fluidity in the pipe, cement etc. are well moistened and has good adhesion, and the strength of the shotcrete obtained is higher than that of the dry method. The sagging on the sprayed surface is noticeable, and in order to prevent this sagging, it is necessary to add a certain amount of quick-setting agent (including what is called an instant setting agent) to increase the strength on the sprayed surface. In addition, even if the process is in the form of a slurry, the frictional resistance within the pressure-feeding pipeline is large because the excess moisture is minimized, and therefore the pipeline and mechanism for pressure-feeding must each have sufficient pressure resistance. is necessary, and it must necessarily be large and strong. Of course, even if we place restrictions on the size and shape of the coarse aggregate, and pay special consideration to its pipelines and pumping mechanism, the distance it can be conveyed will be limited, at most 50 to 60 meters. It has the disadvantage that it is difficult to respond sufficiently quickly to the actual situation at various construction sites such as tunnels, and in any case, it is sprayed in a state of good fluidity, with the spaces between solid particles completely filled with liquid. Since dripping from the sprayed surface is unavoidable, the sprayed layer thickness is extremely small, and even if the amount of water is limited, the layer thickness obtained with one spraying is at most around several tens of mm. Generally speaking, to obtain the required layer thickness, the spraying process is repeated several times, that is, after the first spraying, a certain amount of time is left to increase the shear strength of the sprayed layer, and then the spraying process is repeated several times. Since the work of spraying twice is required to be repeated many times, there are disadvantages such as the advantage of speed in the spraying work being significantly reduced. Furthermore, it is generally known that the bounce rate is quite high when spraying against vertical or ceiling surfaces;
%, which is a huge loss.
This greatly reduces the construction yield of concrete and the like, and the advantages of spraying construction as described above are significantly impaired. On the other hand, the dry method uses air pressure and has less frictional resistance in pipes, etc.
The relatively simple and compact mechanism and pipelines allow for a desirable long conveyance distance to be freely achieved, so for example, in a mine dug deep underground, it can be pumped from a position sufficiently far away from the target construction location. Although it can be used freely depending on the site, it generates a large amount of dust, and in places such as underground mines, it is difficult to check the desired construction status without interrupting the work every short time. In particular, the blended quick-setting agent is highly irritating, and as it permeates the air under dry spraying conditions, it harms the eyes and throat, significantly harms the working environment, and is harmful to cement, etc. There is a decisive disadvantage in that the strength of the shotguns obtained varies greatly because there is not enough contact with water and the quick-setting agent is not evenly and appropriately mixed, and in particular, the strength is only about half that of the wet method. In addition, even if there is no deformation, the amount of rebound will be as large as in the wet method, and shear stress and adhesion cannot be effectively obtained, resulting in peeling and
As with the wet method, flaking becomes more apparent and the sprayed layer thickness naturally becomes smaller. However, in the semi-wet construction method, which is considered to be an intermediate construction method, the water injection position in the dry construction method is shifted from the nozzle part and water is added in the middle of a conduit such as a pipe or hose. This is the end of the system, and since a part with high frictional resistance is rapidly formed at this end by adding water, and a certain amount of quick setting agent is added, the limit is about 5 to 6 m from the nozzle part. If the distance between the water application position and the nozzle section is made larger, paste, etc. will adhere to the inner surface of the pipe or hose, clogging the pipeline. However, since a large resistance area is formed at the end of the pipe where the pressure has decreased, it requires a high-performance pumping or pipe mechanism that is unexpected in the dry method, and it also requires cement, etc. It is not possible to obtain sufficient mixing with water, and flaking, dripping, and splashing occur, and even if the specific amounts of each change slightly, the total amount of these as a whole is the same as that of the wet and dry methods. or more, and the limits of the sprayed layer thickness at one time are also the same. As mentioned above, in any case, if the spray amount is increased, the pumping pressure increases, making it difficult for the nozzle man to perform the work, and in general, the work efficiency is only about 3 to 6 m ³ /hr, and the worker There is a disadvantage that the technique of spraying greatly affects the properties of the sprayer. In addition, in any of the above cases, a considerable amount of an accelerating agent (5 to 6% or more based on cement) may be added to increase the initial shear stress on the wall surface and obtain stable layer adhesion. It is well known that such quick-setting agents not only make the application more expensive, but also reduce the long-term strength of the spraying process.

However, regardless of which method is used, conventional spraying methods involve adjusting the materials at the construction site and immediately spraying them, so there remains a tendency that the weighing operations and addition and kneading operations of each material are not always carried out accurately. This also has the disadvantage that construction cannot be achieved rationally.

The present invention has been researched to eliminate the disadvantages and disadvantages of the conventional methods as described above, and has been made by adding a retarder to a slurry-like raw kneaded material such as paste, mortar, or concrete, and kneading it for a required period of time. However, the sag during spraying of this product is due to the addition of a separately prepared air-fed powder and granule mixture, resulting in a capillary shape or smaller (i.e., the mixed state of such a liquid and powder and granule mixture is between powder and granule mixtures). From a slurry state in which the gap is completely filled with liquid, the moisture in this gap gradually decreases and air is interposed, and it is classified as capillary, funnel 1, and 2 depending on the amount of air that increases. However, the shear stress can be further improved by adding an accelerating agent using this powder-like mixture, and the shear stress can be further improved by adding an accelerating agent using this powder-like mixture. It is possible to effectively form concrete shotcrete in the inner part of a deeply excavated tunnel in order to increase the desired strength, and also to freely form the layer thickness over a wide range of several hundred mm or more. It was designed to be obtained. In addition, since the method according to the present invention prepares and pumps slurry with appropriate fluidity (pump feeding) and powder granules by air pumping, the conveying distance is sufficiently large and the work efficiency is 10 m ³ /hr. The amount of rebound can be greatly reduced, and construction work can be carried out with significantly less dust generation and dust generation. That is, the present invention uses a paste made by adding water and a retarder to a powder of a hydraulic substance such as cement or gypsum, or a mortar made by blending fine aggregate such as sand or fiber material with the paste for carrying out the above-mentioned spraying construction. Alternatively, a raw mixture of hydraulic substances such as concrete with coarse aggregate added thereto is adjusted in a factory and sent to the construction site by transport vehicle, but the amount of water in this case is pumped through conduits such as pipes and hoses. prepare to obtain the level of liquidity that will be obtained,
For one of these systems, fine aggregate such as hydrated sand or coarse aggregate such as gravel is blended with it, or powdered aggregates such as fibrous materials are added to fine aggregate such as hydrated sand, and sodium aluminate and silica are used. By adhering (adsorbing) a powder or liquid quick-setting agent that exhibits quick-setting (including instant setting) action on the above-mentioned hydraulic substances such as acid soda, calcium chloride, aluminum chloride, and soda carbonate in the presence of an appropriate amount of water. In this method, the other system is prepared, which is transported separately by wind pressure, and then combined in the pipeline and sprayed. To explain the present invention in more detail, the present inventors have investigated the rheological properties of a raw mixture of hydraulic materials such as cement that does not set even after adding water, and the actual state of the flow characteristics of such a raw mixture. , interfacial adhesion between inert aggregates such as coarse aggregates and paste or mortar;
He discovered many previously unknown facts regarding the relationship between adsorption forces on solid surfaces, and proposed new technical methods based on these discoveries. Lid Patent Application No. 157452 (1973)
No. 82389: Method for measuring fluidity of plastic fluid, method for adjusting plastic fluid, method for injecting said plastic fluid, and apparatus therefor), Japanese Patent Application No. 147180 (1983)
No. 71859: Aggregate measurement method, mixing water amount determination method, and apparatus therefor) and Japanese Patent Application No. 126323/1983 (Japanese Patent Application Laid-Open No. 54-60321: Concrete manufacturing method and device). Although we have elucidated the details of the relationship and have made some proposals for applying this to the spraying method, the present invention further develops these relationships and allows for rational adjustment in factories etc. By using the raw kneaded material, spraying can be carried out in remote areas, and by developing the shear strength in the spraying process more quickly and accurately, the layer thickness obtained with one spraying can be several hundred mm as mentioned above. It also allows for smooth and efficient operation in a favorable working environment, and also allows for a reduction in the amount of quick-setting agent added, in any case effectively increasing the long-term strength of the spraying process. It was designed so that it could be improved.

When plastic fluids (Bingham-based or non-Bingham-based fluids) containing solid components, such as paste with capped cement, mortar, and concrete, are deformed and flowed, there is a yield value of shear stress, and its magnitude is determined by mixing. This will vary depending on factors such as the amount of water present, water-cement ratio, cement-sand ratio, coarse aggregate-sand ratio, and initial moisture content of the dispersant and sand. However, the slump test conventionally used to measure the fluidity of concrete generally measures this qualitative quantity; The actual state of plastic fluid cannot necessarily be elucidated, and relative quantitative measurements should be used. Furthermore, in such a plastic fluid, the action of water between particles is not completely eliminated, but there is an adsorption force on the surface of solid particles including cement particles, that is, the amount of adsorbed water on the surface of solid particles increases. If the particles become very small and adjacent particles share adsorbed water with each other, the force becomes quite large. Furthermore, in the case of adding water to cement and kneading it, in the conventional technology, hydration and setting proceed immediately after adding water; Therefore, effectively adjusting this period by using a retarder and performing secondary mixing after such a mixing time will improve adhesion strength with coarse aggregate (i.e. concrete strength) and fluidity. can be advantageously improved.

However, regarding the above-mentioned shear stress yield value, when the above-mentioned raw kneaded material (plastic fluid) is dehydrated (for example, by pressurized dehydration using filter paper), the shear stress yield value increases in proportion to the amount of water removed. Although it increases,
As for such a dehydration method, it is possible to obtain the same dehydration result even if a dry material or a material with a low water content is added to the green kneaded material without using filter paper; As a result, it is possible to obtain a binding relationship based on a large adsorption force due to sharing of adsorbed water as described above. Therefore, firstly, the amount of rebound from the wall surface during spraying can be significantly reduced, resulting in efficient and economical construction. Secondly, the layer thickness obtained by one spraying can be made sufficiently large, which also makes the spraying work more efficient. In addition, as mentioned above, the addition of an accelerating agent has been conventionally carried out, but in this conventional method, the accelerating agent is generally added at the time of spraying, and in the case of a wet method, it is added at the time of kneading or at the time of kneading. If an accelerating agent is added immediately after that, the hydration reaction of cement etc. will proceed rapidly, making it impossible to pump or spray, or at least causing significant trouble.
Furthermore, in the case of a dry method, even if it is added at any stage, the quick-setting agent will simply be mixed in in a free state, and it will be scattered as dust during spraying, and it will not adhere to fine wood or cement powder, so it is not enough. The additive effect cannot be obtained, and since the quick-setting agent is simply added, the mixing is uneven and the quick-setting effect varies widely, and no desirable effect can be obtained from any of them. , it will simply harm the working environment. In contrast, in the present invention, the above-mentioned quick-setting agent is preliminarily attached (adsorbed) to the surface of a powdery compound such as fine aggregate under appropriate water-containing conditions.
By pumping it as a sprayed material, the quick-setting agent is evenly dispersed using the fine aggregate, which is the main component of this type of sprayed material, as a medium. By being incorporated into the kneaded material, construction can be carried out smoothly without these disadvantages. Further, as described above, in combination with the large adsorption force due to adsorption water sharing, favorable construction can be obtained by using a relatively small amount of quick-setting agent, and the long-term strength of the formed sprayed work can be appropriately improved.

In the product according to the present invention, a fibrous material can be blended into either the slurry-like raw kneaded material or the powdery mixture, and such fibrous materials include metallic fiber materials, synthetic fiber materials, and vitreous fiber materials. , asbestos, rock wool, and high slag cotton, one or more of them can be used.

The quick-setting agent to be attached to the granular composition is selected from one or more of sodium silicate, calcium chloride, aluminum chloride, ferric chloride, sodium aluminate, and soda carbonate. In addition, one or more additives such as fly ash, water slag powder, porazone, colloidal silica, polymeric plastic materials, alum, and sodium hydroxide may be blended into the slurry-like kneaded product as required. .

In the present invention, which is based on the background of the prior art as described above, water is added to a hydraulic powder such as cement or gypsum and sufficiently kneaded to sufficiently increase the specific surface area of the powder, and the water-cement ratio is An appropriately selected paste or mortar in the form of a slurry is pumped through a pipe, and after this water-mixing, an appropriate amount of retarder is added to allow the required mixing time. However, this pressure feeding can be carried out at a pressure ΔP determined by the general formula ().

However, Lmax is the maximum distance that can be injected, and Lmax=UfT/ε=X/Ufε, and L=UfT/ε.

Also, if the distance L (cm) for constant rate injection is set to a certain pressure P
The velocity Uf for injection in (g/cm ² ) is given by:

Uf=ΔP√4× ₀ + ^{2 2} +4 ^{2 2}
−(2XLF ₀ λ+ΔP ² ε)/2XLλ ² ...() However, ΔP=P−ρh Furthermore, with constant flow, the maximum velocity Ufmax that can flow L (cm) is determined by the following formula.

Ufmax=X/L・ε...() Then, the final pressure Pn when L (cm) is injected at a constant rate Uf (cm/sec) is determined by the following formula.

In the above equations () to (), F ₀ (g/cm ³ ): Relative shear stress yield value λ (g・sec/cm ³・cm): Relative flow viscosity coefficient Uf (cm/sec): superficial velocity ρ (g/cm ³ ): unit volume weight of plastic fluid L (cm): aggregate layer length ε: aggregate porosity X (cm ² /sec): packing degree per unit time T ( sec): Maximum injection time, which is disclosed in Japanese Patent Application No. 51-157452 (1983)
This is based on the technical method of Publication No.-82389).
Furthermore, in the present invention, in addition to the above-mentioned pumping using a pump that utilizes the fluidity of the powdered hydraulic substance due to moisture, gravel or sand (for paste) is used.
A powder or liquid quick-setting agent as described above is attached to aggregate powder such as gravel, and the mixture is prepared and fed under pressure with air. Even if such aggregate powder granules contain a certain amount of water, smooth air pressure can be obtained under the granular conditions in which the water does not contribute to the fluidity, and such aggregates with an accelerating agent can be easily transported under wind pressure. The pumping distance and pumping amount are determined by the air volume and pipe diameter, and since it is essentially dry, it is sufficient even in cases where the length is several hundred meters or exceeds 1000 meters. It is.

Furthermore, the materials that have been pumped separately in this way are combined to form a sprayed work, but as mentioned above, during the pressure feeding process or conveyance process after adding water to the hydraulic powder, Slurry-like green kneading of the hydraulic powder material, which is pumped by taking an appropriate kneading time and by adding the powder and granular material pumped under dry conditions to obtain appropriate fluidity. It is possible to form a spray gun that increases the shear stress yield value by achieving a dehydration effect on the material, and improves the physical properties, workability, management,
Various performances such as economical efficiency and range of use can be greatly improved, and advantageous construction can be carried out by solving the conflicting physical phenomena of fluidity and adhesion at once.

Specific embodiments of the present invention will be described below.

A slurry mortar made by mixing 1 part of Portland cement, 1 part of river sand with a diameter of 2.5 mm or less, 0.37 parts of water, 0.008 parts of an admixture, and 0.003 parts of an inorganic commercially available retardant was transported 6 km from the plant base and excavated into the excavation tunnel. It was loaded into the spray machine at the back of the building.
That is, the time required for this transportation was approximately 2 hours, and after 2 hours had passed after this mixing, that is, after 2 hours of kneading time, the relative initial shear stress yield value F ₀ for glass beads with a diameter of 20 mm was 0.21 g/ cm ³ , ΔF ₀ is 0.0004g/cm
^4. It was confirmed that λ was 2.1 g・sec/cm ⁴ and the fluidity was approximately the same as that immediately after mixing, and this mortar was passed through a pipe with an inner diameter of 2 inches at a speed of 30/min. It was sent using a pressure pump. On the other hand, 4.2% of water adhering to the surface and river sand of less than 5mm 1214Kg/m ³ and 5-15
849 kg/m ³ of gravel (river sand/gravel 1:0.7) was sprinkled with 24.81 kg/m ³ of sodium aluminate quick setting agent.
Moreover, this was further sprinkled with 357 kg/m ³ of Portland cement, and the W/C (water-cement ratio) of the shell layer made of this sprinkled cement was about 24%.

That is, the aggregate powder particles thus prepared were added under pressure using compressed air at a ratio of 1.3 parts to 1 part of the slurry mortar, and the mixture was sprayed onto the inner surface of the tunnel through a nozzle. The W/C in this shotcrete is 31% and the amount of cement is
560Kg/m ³ , sand 1124Kg/m ³ , gravel 575Kg/m ³ ,
The retardant was 905g/m ³ and the quick-setting agent was 16.8Kg/m ³ .The amount of rebound during spraying was 5.3%, and the amount of dust generated was 1.01mg/m ³ . The coating was sprayed to an average thickness of 350 mm, and was able to be applied smoothly without any flaking in general.
Construction was possible quickly with a construction efficiency of about 8 to 12 m ³ /hr. The compressive strength after 28 days of spraying is 485Kg/cm ² and the coefficient of variation is 3.5%, which is a preferable spraying construction with a strength that is higher than the conventional general method and a coefficient of variation that is reduced to nearly one-fifth. I was able to do that.

In addition, in this spraying construction, if the amount of dust generated is at the level mentioned above, there will be less dust trapped inside the tunnel, and therefore the nozzleman will not feel any irritation to his throat or eyes, making it a preferable method of spraying. This could be carried out continuously over a long period of time, and the reaction of the nozzle during spraying was relatively small. That is, when these relationships are compared between the conventional wet method and dry method, the amount of dust generated in the dry method is generally about 6 to 10 mg/ ^m3 , and the amount of dust generated in the wet method is 2 to 5 mg/ ^m3 . There are far fewer inventions than either of them. Moreover, the reaction of the nozzle during spraying is extremely high in the case of the conventional wet method, whereas the method of the present invention can achieve efficient construction of around 10 m ³ /hr as described above, while the conventional wet method has a spraying speed of 3 to 4 m 3 /hr. Only the same level of recoil force was felt as in the case of dry spraying at a speed of ³ /hr.

On the other hand, when the same composition as above was used using the dry method, the rebound rate was 23.5%.
The dust generation rate was 9.3 mg/ ^m3 , and the maximum spray thickness was 140 mm. Compressive strength after 28 days is
It is 259Kg/cm ² , which is about half of that according to the present invention.

Furthermore, when the same formulation was carried out using the wet method, the rebound rate was 24% and the dust generation rate was 4.5mg/ ^m3 .
The maximum spraying thickness was 7.5 cm, and the compressive strength after 28 days was 298 Kg/cm ² . That is, all of them are considerably inferior to those of the present invention.

According to the present invention as explained above, the effects as summarized below can be obtained.

Appropriate spraying work can be carried out by transporting the kneaded material, which has been rationally prepared in a factory or the like remote from the construction site, to the construction site or the like.

Since the method according to the present invention adds a retardant to the kneaded material prepared in the form of a slurry and allows the required mixing time, it can be rationally adjusted at a factory or the like far away from the tunnel excavation site. The material can be delivered to the excavation site and loaded into a spraying machine for construction, eliminating the need for adjustments at the construction site, where conventional equipment is incomplete and susceptible to fluctuations, allowing for rational and accurate spraying construction. can be carried out smoothly.

It is possible to uniformly mix and deposit the quick-setting agent, thereby reducing the amount of addition thereof, and also greatly reducing the generation of dust.

As mentioned above, in the case of the conventional method, the hydration reaction proceeds rapidly in the wet method, so the quick-setting agent is only added to the material ejected from the nozzle as a mere accompaniment, and therefore favorable mixing cannot be obtained. In the case of the dry method, the quick-setting agent is simply mixed in in a free state, resulting in severe scattering, causing damage to the eyes and throats of workers, as well as incomplete bonding with the aggregate, which interferes with its desired function. In contrast to those that cannot be obtained, according to the present invention, it can be used in a state where it is adsorbed or attached to the aggregate. Since it is added to the surface, the mixing and dispersion of the accelerating agent is done uniformly, so even if the amount of the accelerating agent added is small, sufficient rapid setting results can be obtained, and its scattering is greatly reduced. This allows for smooth spraying work at a preferred work site.

A sufficient spray layer thickness can be obtained.

Conventional methods suffer from severe splashing, rebounding, or peeling, and are generally only able to form a sprayed layer with a thickness of about several tens of mm even under conditions where a quick-setting agent is used. Even with special technology such as Patent Application No. 50060 of 1973 (Japanese Unexamined Patent Publication No. 54-142823), spraying of slightly over 100 mm on a vertical wall can only be achieved.
In order to form a sprayed layer that exceeds this, it is necessary to spray once and leave it for up to several hours to allow the hydration reaction to proceed to a certain extent, and then perform repeated spraying. However, according to the present invention, one sprayed material in the form of powder is mixed with the other sprayed material in the form of a slurry, thereby forming a capillary-shaped sprayed layer or a sprayed layer with relatively less moisture than that, which only increases the shear stress. However, as mentioned above, as a result of adding an accelerating agent while adhering to the aggregate and improving the shear stress by using the effective accelerating agent uniformly and without scattering, it is possible to As shown in the examples, it is possible to smoothly form sprayed walls up to several hundred mm even on vertical walls (the possible layer thickness increases even more on vertical surfaces). (Naturally) This allows the merits of this type of spraying method, which is essentially quick workability, to be fully demonstrated, and it is clear that it has great industrial merits.

The amount of bounce is small.

The rebound rate of the conventional method is quite high, reaching 20 to 40%, while that of the present invention is several percent. This rebound rate is a complete loss even if you take the time to adjust the mixture and operate the spray equipment, and you have no choice but to discard it. The effect of the present invention, which can reduce the ratio to less than one-tenth in some cases, is tremendous.

Spraying efficiency can be doubled.

In the present invention, a slurry-like hydraulic material kneaded material is pumped, and a powder-like aggregate material to which an accelerating agent has been added and attached are separately pumped, and both of these pumpings are carried out under favorable flow conditions. Moreover, since the spraying friction resistance range after mixing and coalescing on the nozzle part or rotating disk is extremely small, efficient construction can be carried out under stable operating conditions. That is, as mentioned above, the work efficiency of the conventional method is about 5 m ³ /hr at most, but according to the present invention, even spraying work exceeding 10 m ³ /hr can be carried out smoothly. As shown in the example, the work efficiency is doubled, and since the amount of dust generated is small, continuous spraying construction can be carried out over a long period of time inside tunnels and indoors. The construction efficiency is increased due to the reduced amount of rebound described above, and in any case, efficient construction can be carried out smoothly, and this has a great merit.

Improves the strength and quality of spraying work.

As mentioned above, the method according to the present invention can form a uniform and loss-free mixing state of the quick-setting agent, and as a result, the amount of quick-setting agent used can be reduced and the long-term strength of the spraying work can be increased. obtain. In other words, if the conventional quick-setting agent cannot be properly dispersed and homogeneous mixing cannot be achieved, the long-term strength of the part where the quick-setting agent is concentrated will decrease even if the amount of the quick-setting agent is the same. This is obvious, and the strength of the spraying process as a whole must be the same as the strength of this reduced part.However, according to the present invention, the fine aggregate is prepared with an accelerating agent attached to it. It is possible to avoid a decrease in strength due to such non-uniform contamination. Moreover, since uniformly dispersed addition is obtained in this way, the amount of quick-setting agent added can be reduced in any case, and from this point of view as well, a desirable improvement in long-term strength can be obtained.

Good workability.

It has already been mentioned that the device according to the present invention generates less dust. In addition, a sufficient spray layer thickness can be freely obtained even on the top surface, and smooth construction can be achieved without particularly requiring technical training for the nozzle man. The amount of rebound is minimal, and even if the work is stopped midway through, the rapid setting agent encounters and coalesces with hydraulic substances such as cement and sufficient moisture for the reaction to proceed. Since there are only a few passages and other parts of the spraying mechanism, there is almost no possibility of clogging and caking during subsequent restarts, and cleaning is also easy. That is, considering all of these circumstances, it can be said that the workability is extremely excellent, and the effect of this is also tremendous.

Claims (1)

[Claims] 1 Adding a retardant to a slurry-like hydraulic material freshly kneaded material such as paste, mortar, or concrete, adjusting it once, and then kneading it for the required time, then pumping the mixture and adding an accelerating agent for the hydraulic material. A powder mixture mainly consisting of fine aggregate such as sand, or a mixture of coarse aggregate such as gravel, is conveyed by air, and each of these separately conveyed materials is transferred to a blowing mechanism. A method for concrete spraying construction, characterized in that the slurry-like hydraulic material raw kneaded material is combined in a concrete container to lower the relative water content of the raw mixed slurry-like hydraulic material, and at the same time, reacts with an accelerating agent to increase the shear stress of the raw sprayed material before spraying.