JPS6131265B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the creation of a concrete spraying method, which aims to appropriately transport concrete materials using coarse aggregate with a diameter of 5 to 15 mm, and to achieve preferable spraying of concrete with a small water-to-cement ratio. enable,
In addition, the patent No. 1 was created for forming shotcrete with excellent strength by reducing the amount of rebound and the amount of dust generated.
Regarding the improvement of No. 1299968 (Japanese Patent Publication No. 60-22153), it has the characteristics of this original invention and relatively reduces the amount of cement by increasing the amount of coarse aggregate mixed in this type of shotcrete,
Furthermore, it is intended to facilitate the adjustment of the sprayed material and to make the mixing state of the slurry-like wet mixture and the dry mixture uniform, thereby achieving appropriate and economical construction of shotcrete concrete.

The spraying method is already known as one of the concrete construction methods, and this spraying method allows concrete to be applied to walls and slopes without formwork, so it has the great advantage of being able to perform construction in a short time and economically. , is gradually becoming popular in various civil engineering works. However, there are three types of concrete spraying methods commonly used: dry, wet, and semi-wet, and although each of these methods has its merits, it also has disadvantages and drawbacks. There is. In other words, in the wet method, a mixture of all the constituent materials of the concrete to be sprayed is conveyed by a pump through a conduit such as a pipe or hose, and is sprayed by spraying from a nozzle, so that the cement etc. is well moistened. The strength of the shotcrete obtained by this method is also higher than that of the dry method, but the frictional resistance in the pressure-fed pipeline is large,
Therefore, the pipes and mechanisms for pressure feeding must have sufficient pressure resistance, and must necessarily be large and strong, and there are no restrictions on the size and shape of the coarse aggregate. In addition, even if special consideration is given to the pipe line and pressure feeding mechanism, the conveyance distance is limited to about 50 to 60 m at most, which has the disadvantage that it is difficult to respond quickly enough to the actual situation at various construction sites. In terms of strength, which is the above-mentioned advantage, following the water-cement ratio to obtain optimal strength results in the highest viscosity, so it is practical to increase the water-cement ratio to ensure pressure-feeding sprayability. In addition, when spraying on vertical surfaces or ceiling surfaces, it is essential to mix a considerable amount of an accelerating agent, and for both of these reasons, the strength, especially the long-term strength It is practically difficult to obtain an ideal coating, making it difficult to achieve the desired advantages, and the amount of flaking from the sprayed surface is considerable, and there is also a limit to the thickness of the sprayed layer due to other factors. There is. On the other hand, the dry method uses high-pressure air to transport the air, so there is little frictional resistance in the pipes, etc., and the relatively simple and compact mechanism and pipes allow you to freely obtain the desired transport distance. It can be pumped from a position sufficiently far away from the target construction location in a deeply excavated mine, and in this sense it can be used freely depending on the site, but the amount of dust generated is large and In some cases, it may even become impossible to check the desired construction status without interrupting the work every short period of time, which seriously harms the working environment and prevents cement etc. from coming into sufficient contact with water. There is a definite disadvantage that the strength of the sprayed layer is only about half that of the wet method, and it is more important than the wet method that it is unavoidable to use a quick setting agent when spraying on vertical surfaces or ceiling surfaces.
Moreover, there is a drawback that the amount of rebound is even larger. However, in the semi-wet construction method, which is considered to be an intermediate construction method between these methods, 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.
The water application position is limited to about 5 to 6 meters from the nozzle, as a portion with high frictional resistance is formed at the end of the pumping system. etc. will stick to it and block the pipe, and even if you try to take full advantage of the advantage of increasing the pumping distance in the dry method, a large resistance will be formed at the end of the pipe where the pressure has decreased. Therefore, it requires a high-performance pumping or piping mechanism that is unexpected in the dry method, and it is not possible to obtain sufficient encounter kneading of cement, etc. and water as in the wet method. In this case as well, in order to improve the adhesion of the raw kneaded material and reduce the amount of rebound and flaking, rapid setting of sodium silicate, calcium chloride, sodium aluminate, sodium carbonate, etc. is used.
It is the same that a large amount of supersetting agent is required,
It is well known that such rapid setting and instant setting agents significantly reduce the long-term strength of shotcrete.

However, the present inventors conducted research to eliminate the disadvantages and shortcomings of the conventional single conveyance method as described above, and also attempted to increase the preferable strength by using a sprayed layer of ready-mixed concrete with a small water-cement ratio. The patent No.
No. 1299968 (Special Publication No. 60-22153) was proposed. That is, this method is based on the present inventors' research on the actual rheological properties and flow properties of this type of raw kneaded material that has not yet solidified after being added with water, the interfacial adhesion effect between inert aggregates such as coarse aggregates, and paste or mortar,
He discovered many new facts that were previously unknown regarding the adsorption effect on solid surfaces, and based on these discoveries, proposed new technical methods (Japanese Patent Application Nos. 157452 and 147180). , special application 1972-
No. 126323), by utilizing these techniques and immediately responding to the above-mentioned spraying construction, the slurry-like raw kneaded material and the substantially dry granular compound such as coarse aggregate are separately pumped. The materials are combined and sprayed, and by using this method, the above-mentioned characteristics can be appropriately obtained and advantageous spraying can be performed.

However, as a result of practical implementation and repeated studies of this prior application method, even if it has the above-mentioned advantages, it is still difficult to use coarse aggregate such as gravel (as coarse aggregate for spraying with a diameter of 5 to 15 mm). As is well known, it is difficult to obtain a sufficient amount of the material for spraying, as described above, the materials for spraying must be mixed separately, requiring a considerable amount of man-hours to adjust the mixture. Since coarse aggregate is mixed into only one of the two materials that are pumped separately, there are disadvantages such as a tendency that the mixing condition when they are combined and sprayed remains unfavorable. The present invention also improves these points and allows truly desirable and advantageous spraying construction to be achieved.

That is, in the present invention, as in the original invention, the flow characteristics of a plastic fluid such as a cement kneaded product are grasped by relative quantitative measurement values,
In addition, taking into consideration the changes in physical properties of cement particles etc. after adding water, we developed a raw kneaded material in order to satisfy both the favorable conditions for fluidized pumping in such a kneaded material and the binding relationship that takes advantage of the large adsorption force due to the sharing of adsorbed water. and a dry powder/granular mixture are separately pumped, and methods such as kneading time, secondary kneading, and sprinkling with hydraulic material powder such as cement are used in combination as appropriate. An appropriate amount of gravel or other coarse aggregate with a diameter of 5 to 15 mm is mixed into the slurry-like mixed material, and this is combined with coarse aggregate, fine aggregate, etc. sent separately under dry conditions. It is suggested that the product be sprayed in a dry manner. This is because coarse aggregate with a diameter of 5 to 15 mm, such as gravel, is mixed into both the green mix and the dry powder, and such coarse aggregate generally tends to make the kneading operation difficult. Although this may seem complicated at first glance, it is preferable to mix solid components such as sand, gravel, or cement in advance when preparing the green kneaded material, as mentioned in the above-mentioned prior invention. In this technical system, it is possible to mix both pressurized materials together and add water to only one of them to form a green kneaded material, which substantially simplifies the preparation of the pressurized material. In addition, by blending coarse aggregate into the green mix as described above, the amount of the green mix increases and the amount of cement that should be contained in a certain amount of the green mix can be reduced. It is possible to achieve economical construction by reducing the amount of cement required for the entire sprayed layer, and on the other hand, compared to the method of the previous application, which actually mixes sand in both the green mix and the dry pumped mixture. This enables spraying construction with an appropriately increased amount of coarse aggregate with a diameter of 5 to 15 mm.
It is therefore possible to provide a sprayed layer that is naturally stable and has high strength. Furthermore, since the masses of the two pumped materials having coarse aggregate banded on both sides are similar, it is relatively easy to combine and mix under fluid pumping conditions, and from this point of view, a homogeneous and advantageous sprayed layer can be obtained. When spraying on a vertical wall surface, etc., there is no need for quick setting or instant setting agents, and at least the amount added can be significantly reduced to obtain sufficient long-term strength of the sprayed layer.

In carrying out the method of the present invention, the slurry-like fresh concrete is generally pumped at a pressure △P whose relative fluid fluidity is determined by the following equation () using a hose or pipe as a resistor. is the same as the original invention.

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

Further, the rate Uf for injecting L (cm) at P (g/cm ² ) by constant rate injection is given by the following equation.

However, ΔP=P−ρh Furthermore, with constant flow, the maximum speed Ufmax at which L (cm) can be caused to flow is determined by the following equation.

Ufmax=X/L・ε......() Then, the final pressure when L (cm) is injected at a constant speed Uf (cm/sec), that is, the pressure Pn at the injection port when it overflows, is calculated by the following formula. is required.

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): Length of aggregate layer ε: Aggregate cavity cable X: Volume injected per unit time T (sec): Maximum injection This is possible time and is based on the technical method disclosed in Japanese Patent Application No. 157452/1983.

Specific examples of the method of the present invention will be described below.

The coarse aggregate used in these examples and comparative examples was gravel produced in Sakaide City with a diameter of 5 to 15 mm (5 to 10 mm: 42.4%, 10 to 13 mm: 47.9
%, 13-15 mm: 9.7%), and the spraying surface was symmetrical with respect to a vertical surface. Furthermore, the amount of dust generated was measured between 10 and 11 minutes after the start of spraying.

Example 1 1 part cement, 1 part sand, 0.38 part water, admixture
The slump value of the slurry-like mixture prepared by mixing 0.007 parts of mortar with 1 part of gravel with a diameter of 5 to 15 mm was approximately 24 cm, and the slump value was 24 cm. However, it still behaved as a slurry-like kneaded product. On the other hand, 1 part of cement was added to 3.8 parts of 2.5 mm sand with surface water adjusted to 8% as aggregate, and the mixture was sprinkled on the surface of river sand particles to make the surface appear dry. 3.9 parts of gravel of 5 to 15 mm was added to the aggregate, which was then pumped a distance of 60 m using high-pressure air, and the aggregate was mixed with the slurry-like mixture described above near the nozzle. It was sprayed onto a vertical wall. The water amount for spraying construction is 157.5Kg/ ^m3 .

In other words, the mixing ratio of the slurry-like mixed material and the air-forced aggregate was approximately 1:1.2, the rebound rate during spraying was 15.6%, and the amount of dust generated was 7.
mg/ ^m3 , all of which are good.The results of analyzing the composition of the shotcrete formed were approximately 1:1 of cement, 1.81 of sand, 1.93 of gravel, and 0.33 of water (157.5
The cement content is 443 kg/m ³ ), the finished surface of the shotcrete thus formed is good, and its maximum shear force is 273 g/m ³ ). cm ² and the compressive strength after 3 days of spraying is 343Kg/cm ² , after 7 days it is 536Kg/cm ² , and after 28 days
It was 642Kg/ ^cm2 .

On the other hand, according to the original invention, the cement, sand and water are the same as above, no gravel is mixed, and the admixture is added at 0.005%.
The mortar mixed as part has an F ₀ of 3.5 g/cm ³ and △
F ₀ is 0.04 g/cm ⁴ and λ is 4 g·sec/cm ⁴ . For this mortar, air-forced aggregate with the exact same composition as above was added, and the ratio of mortar to air-forced aggregate was 1:1. The composition of shotcrete is 1.63 parts of sand, 1.0 part of gravel, 0.35 part of water, and admixtures.
0.004, the amount of gravel is about half that of the above case, and the amount of sand is also relatively small (therefore, the amount of cement is relatively large at 577 Kg/m ³ ). However, the bounce rate when spraying is 12%.
The amount of dust generated is 9 mg/ ^m3 , which is preferable, and the maximum shear stress of this concrete is 205
g/cm ² , compressive strength after 3 days is 332Kg/cm ² , after 7 days
515Kg/cm ² , and 615Kg/cm ² after 28 days.

For these products according to the present invention and the original invention, according to the conventional wet method, except for water, the mixture was made according to the embodiment of the present invention: With the increase in water to enable pressure-feeding, other than cement was relatively mixed. reduced (cement 443Kg/m ³ , sand 735Kg/m ³ , gravel 788Kg/m 3 )
m ³ , admixture 2.11Kg/m ³ ), the water content is 208Kg/m ³ , and 5% quick-setting agent is added to stabilize the spraying process, which can barely be pumped. The maximum pressure-feeding distance is 40m, and even if this product generates 10mg/ ^m3 of dust when it is sprayed for 40m, which is approximately preferable, the rebound rate is
The compressive strength 28 days after spraying was extremely low at around 315 kg/cm ² . Furthermore, when the formulation according to the above-mentioned example of the present invention was added with 5% of an accelerating agent and applied using a conventional dry method, the amount of dust generated was 21 mg/cm. ^m3 , and the rebound rate is 42%, which is higher than that of the wet method.It is impossible to carry out appropriate spraying work due to high dust generation, and the 4-week strength is 220%.
It was extremely inferior, at around Kg/ ^cm2 .

Example 2 A material prepared by mixing 1 kg of cement with 2 kg of sand and 2 kg of gravel with 10% surface water was prepared, and the cement was thoroughly sprinkled on the sand and gravel. The mixture was divided into 1 part and 1.25 parts, and 0.2 part of cement, 0.1 part of water, and 0.003 part of admixture were added to 1 part to make a slurry-like mixture, which had a slump value of 23.
cm was obtained, and this was pumped 80 m, and 1.25 parts of the above-mentioned 1.25 parts was pumped into this using high-pressure air, mixed near the spray nozzle, and sprayed.

The amount of water in this spraying construction was 169.6/ ^m3 , and the rebound rate during spraying was 19%.
Furthermore, the dust generation was 7 mg/m ³ , which enabled favorable construction.

The composition of the formed shotcrete is 1 part cement, 1.4 parts sand and gravel, and 1 part water.
0.31 (admixture 0.006), its maximum shear stress is 213g/cm ² , and its strength after 3 days is 285Kg/cm 2 .
cm ² , 421 Kg/cm ² after 7 days, and 623 Kg/cm ² after 28 days, indicating that a preferable sprayed layer could be obtained.

That is, according to this example, the entire material was mixed under dry conditions, then divided into two parts, and only one part was further mixed with water and cement to form a slurry-like mixture. The equipment is simplified, and in particular, only one weighing input system for weighing and inputting each material prior to kneading is sufficient for at least sand and gravel, which improves both equipment and mixing operation. It has been confirmed that this method is extremely advantageous and can form a preferable sprayed layer.

On the other hand, if the wet method is used, the amount of water mixed is
The composition was the same as in the previous example, except that it was set at 257/m ³ (however, as the amount of water increased, everything except the amount of cement decreased relatively in terms of m ³ , and both sand and gravel became 656/m 3 ).
Kg/m ³ ) with 5% quick setting agent added is 40
In other words, the result of spraying by pumping 40 m is that the dust generation is 11 mg/ ^m3 , the rebound rate is about 25%, and the average compressive strength after 4 weeks is 365 kg/m3. cm ² , but specifically there was a significant strength variation of 100 Kg/cm ² or more in each part.

Also, the same composition as in the above example, but with 5% quick setting agent.
As a result of spraying the added material using the dry method, the dust generation was considerably high at 16mg/m ³ , the amount of rebound was around 45%, and the 4-week strength was on average 303Kg/cm ² . The variation was greater than in the case of the wet method, and it was inferior to the wet method in all respects (however, in terms of pumpability, it was possible to pump over 100 m).

According to the present invention as explained above, it is possible to transport one material under pressure in a slurry state under substantially favorable flow conditions, and the other material can be transported under dry conditions over considerable distances. By using relatively simple equipment and pressure conditions, this method can be used to carry out pressure-feeding over a wide range of areas, and by combining these methods, effective spraying can be achieved in areas such as capillary areas where the amount of mixed water is small, thereby achieving efficient spraying. Furthermore, it is possible not only to avoid using quick-setting agents on vertical surfaces, but also to greatly reduce the amount of additive used in spraying construction, and to reduce the amount of cement used in the spraying construction, and to improve the quality of spraying materials. It facilitates adjustment, makes the mixing state of the slurry-like green kneaded material and the dry blend uniform and stable, and allows spraying construction to be carried out which is advantageous in these respects, and as mentioned above, an quick-setting agent is essentially not required. This invention is industrially very effective because it effectively increases the long-term strength of the sprayed layer.

Additional Relationships The present invention relates to an improvement of Patent No. 1299968 (Japanese Patent Publication No. 60-22153) (hereinafter referred to as the original invention), and relates to a paste made by adding water to a hydraulic substance such as cement or gypsum, or the like. A slurry-like kneaded material mixed with sand or similar fine-grained materials, and coarse aggregate with a diameter of 5 to 15 mm such as gravel, or one type of coarse aggregate with sand or other fine aggregate or powder. Alternatively, it is different from the above-mentioned original invention to force-feed a powdery compound made by mixing two or more types in a substantially dry state through separate pipe lines, and to combine these separate pumped products and perform spraying. Similarly, in the present invention, gravel and other coarse aggregates with a diameter of 5 to 15 mm are added to the slurry-like kneaded material described above to form a slurry-like ready-mixed concrete. While aiming to reduce the amount of dust generated and the amount of splashing, the amount of coarse aggregate mixed in the spraying process can be increased to freely select it, and the amount of hydraulic substances such as cement can be reduced to achieve economical construction. In addition, it is possible to perform spraying work that is preferable in terms of strength, and also to make the mixing state of the slurry-like green kneaded material and the dry powder/granular mixture uniform and stable, and to obtain excellent quality spraying work in this respect as well. Therefore, the present invention relates to an improvement of the original invention.

Claims (1)

[Scope of Claims] 1. A paste made by adding water to a powder of a hydraulic substance such as cement or gypsum, or a paste containing sand or similar fine-grained material and gravel or other coarse aggregate with a diameter of 5 to 15 mm. A dry method in which slurry-like ready-mixed concrete and coarse aggregate with a diameter of 5 to 15 mm, such as gravel, or one or more types of sand, other fine aggregate, or powder, are mixed with the coarse aggregate in a substantially dry state. A concrete spraying construction method characterized by pumping powder and granular mixtures through separate pipes, and combining these separately pumped materials for spraying. 2. A claim in which a mixture of hydraulic substance powder, fine granules, and coarse aggregate is prepared, and one is used as a slurry ready-mixed concrete and the other is used as a dry powder/granular mixture. 1st
Concrete spraying construction method described in section.