JPH10287461A - Concrete and its placing method, and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively prevent peeling off of concrete or generation of dust, by blending a cement, one or both of fine aggregate and coarse aggregate, limestone filler and silica fume fine powder, subjecting the fresh concrete to a hydration reaction in a state that the silica fume fine powder is preferentially distributed around the cement and limestone filler, and solidifying by setting. SOLUTION: This concrete contains cement, one or both of fine aggregate and coarse aggregate, limestone filler in an amount of 10-15% based on the amount of the fine aggregate and silica fume fine powder in an amount of 3-8% based on the amount of the cement. The fresh concrete is sprayed in a state that the silica fume fine powder forms a state of preferentially distributing around the cement and limestone filler and is distributed around the fine aggregate and coarse aggregate, and subjected to a hydration reaction, then solidified by setting. Thus, strength of the concrete and executive property of the sprayed concrete are made to be improvable by increase of viscosity and shell formation of the powder by blending of suitable fine powder (limestone fine powder and silica fume).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concrete containing shotcrete, a method and an apparatus for applying the same, and effectively improves the quality of shotcrete and other concrete used for inner surfaces of tunnels at a relatively low cost. Also, it is an object of the present invention to provide a concrete mechanic capable of effectively reducing the dust and rebound during construction and effectively achieving the above-mentioned object in a state with less variation by improving its strength characteristics, and providing a concrete construction method and a construction method thereof. Is what you do.

[0002]

2. Description of the Related Art Various types of construction are performed using concrete.
Obtaining the required products has generally been performed for a long time.On the other hand, forming a lining by spraying concrete on the inner surface of an excavated tunnel or the ground wall has been widely adopted. Where I came,
Either a wet method in which a quick-setting agent is added to concrete immediately before spraying and spraying, or a dry method in which water is added to a dry-mix material to which a quick-setting agent is previously added and water is sprayed immediately before spraying. Adhesion and curing are performed within a short time of about several seconds.

In September 1991, it was found that the strength of shotcrete obtained by mixing silica fume having an average particle size of 1 μm or less with concrete during the above-mentioned spraying work can be improved. It has been announced at the annual conference of the Japan Society of Civil Engineers (the 46th annual conference).

[0004]

However, in the above-mentioned conventional shotcrete, the concrete rebounds or peels off (ie, rebounds) at the time of spraying, and the generation of dust is remarkable. The workability and working environment deteriorate,
It also has the disadvantage that the efficiency is considerably poor.

[0005] The addition of the above silica fume can be said to be very effective because it increases the strength of shotcrete, but it cannot suppress the above-mentioned rebound and dust generation. In particular, this silica fume is extremely fine powder. In the case of the dry type, the amount of generated dust must be increased accordingly. Moreover, since this silica fume is obtained as a fine powder as described above by a special technique, it requires a considerably high cost, and even if an improvement in the strength of the bending angle is obtained, it is not necessarily economically preferable. Is disadvantageous in that the yield and quality vary widely depending on the construction conditions.

[0006]

SUMMARY OF THE INVENTION The present invention has been studied to solve the problems in the prior art as described above, and uses the silica fume together with cement and limestone powder (calcium carbonate, CaCo ₃ powder), and furthermore, the bone fume is used. Effective shelling even for powders such as cement, by using a specific condition by adopting the split kneading method in relation to cement or limestone powder for materials (especially fine aggregates). And at a relatively low cost,
Moreover, it has succeeded in obtaining shotcrete having favorable quality under conditions in which rebound and generation of dust are suppressed, and is as follows.

(1) Cement, one or both of fine aggregate and coarse aggregate, limestone powder of 10 to 15% of the fine aggregate amount, and silica fume fine of 3 to 8% based on the cement amount. Containing fine powder, the silica fume fine powder forming a state of being preferentially distributed on the peripheral surface of cement and limestone powder, and being distributed on the peripheral surface of one or both of the fine aggregate and the coarse aggregate. A concrete characterized by being hydrated and solidified.

(2) Cement, fine aggregate and / or coarse aggregate, limestone powder in an amount of 10 to 15% of the fine aggregate and silica fume fine in an amount of 3 to 8% based on the cement amount. Containing fine powder, the silica fume fine powder forming a state of being preferentially distributed on the peripheral surface of cement and limestone powder, and being distributed on the peripheral surface of one or both of the fine aggregate and the coarse aggregate. A shotcrete characterized by being sprayed and subjected to a hydration reaction and set and solidified.

(3) The above item (1) or (2), characterized in that an aggregate having a low quality in shape, particle size distribution or material is used as one or both of the fine aggregate and the coarse aggregate. A concrete according to any one of the preceding clauses.

(4) Cement, one or both of fine aggregate and coarse aggregate, and a silica fume fine powder and a limestone powder, and an adsorbed water film of these contents is formed over substantially the entire circumference of the contents. The secondary water and water reduction for obtaining the fluidity required for spraying work after primary kneading under the condition of water limited to such an extent that the cement, the silica fume fine powder and the limestone powder can be maintained in a capillary state. A method of applying shotcrete, comprising adding an agent to perform secondary kneading and spraying the secondary kneaded material.

(5) Fine aggregate, primary water and fine powder of silica fume are charged into a mixer, adjusted for a short time, and then cement and limestone powder are charged to perform primary kneading. The above-mentioned item (4) is characterized in that the secondary kneading is performed by adding the aggregate and performing a short-time adjustment kneading and then adding the secondary water and / or one or both of the quick setting agent and the water reducing agent. Construction method of shotcrete described.

(6) The above item (4) or (5), wherein a limestone powder having an average particle size of 7 to 15 μm and a silica fume fine powder having an average particle size of 0.05 to 1 μm are used.
The method for constructing shotcrete according to any one of the preceding items.

(7) The amount of cement and silica fume fine powder to be added is about 360 to 420 kg / m ³ , and the silica fume fine powder is 4
The method for applying shotcrete according to any one of the above items (4) to (6), characterized in that the content is set to ７7% (14 to ³⁰ kg / m ³ ).

(8) The above (4) to (7), characterized in that fine aggregate of 0.15 mm or less is added to the amount of limestone powder and the amount is added to 10 to 15% of the amount of fine aggregate. Any one of the terms
The construction method of shotcrete described in (1).

(9) The method for constructing shotcrete according to claim 8, wherein fine aggregate of 0.075 mm or less is used.

(10) Coarse aggregate, fine aggregate, cement, silica fume, limestone powder, a water reducing agent and kneading water are respectively added to the mixer, and each of these adding means is provided with a measuring means. The kneading water adding means is provided with a control panel that can be divided into primary water and secondary water, and that can input a program for a control unit provided in each of the adding means described above, A construction apparatus for shotcrete, wherein the kneaded material from the mixer is transported by a concrete transport mixer truck to a spraying mechanism at a construction site to be executed.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention as described above will be described with reference to the accompanying drawings as appropriate. Quality improvement, workability,
The following new findings were obtained as a result of repeated on-site construction tests in various places with the aim of developing high-quality shotcrete for economical purposes. (1) The strength of concrete and the workability of shotcrete (rebound, dust, actual spraying amount) are appropriate fine powders (for example, stone powder, limestone fine powder, silica fume).
It can be improved by increasing the viscosity by mixing and forming a shell of the powder. (2) The shape, particle size distribution, texture or structural low quality of fine aggregate and coarse aggregate can be improved by mixing and covering the fine powder. (3) The cured product sprayed by the above (1) and (2) is further densified to improve strength, durability, and water tightness. (4) Due to these effects, the strength and durability of general concrete can be appropriately improved, and in particular, sufficient economy can be achieved as compared with the conventional spraying method, and cost reduction and high quality of tunnel construction and the like can be achieved. Can be achieved.

The material specifically adopted by the present inventors based on such a technical concept will be described. First, the cement is ordinary Portland cement manufactured by Mitsubishi Materials Corporation, which has a true specific gravity of 3.16. the specific surface area 3270cm ² / g by air permeation method, 11700cm ² with the BET method
/ G, average particle size is 16.49 µm, bulk density is 0.91
3 g / cm ³ , the result of a torque test of the mixture obtained by adding water to the cement alone was as shown in FIG.
At 4%, the maximum point of the torque (load current value) is obtained. The maximum point of the torque during the water-mixing is such that the water attached to the surface of the cement particles is in an adsorbed state and is hard to be separated, so that the water is not mixed during the kneading. Is in a state where the resistance is high, so that the absorbed water ratio can be obtained.

The specific gravity of silica fume is 2.2.
0, the specific surface area could not be measured by the Blaine method, it was 243475 cm ² / g by the BET method, and the average particle size was 0.76 μm.
The results of a torque test of a mixture of silica fume and water added with water as shown in FIG. 2 are shown in FIG. 2, and the maximum torque point is obtained when the water powder ratio is 39%. The point is that the adsorption water rate of the silica fume is the same as that of the cement.

The limestone powder has a true specific gravity of 2.70.
4270cm specific surface area by air permeation method ² / g, ^{10790cm 2} / g by the BET method, average particle size 10.80μm (200
Mesh), a bulk density of 0.82 g / cm ³ , and the results of a torque test of a mixture to which water was added in the same manner as in FIGS. 1 and 2 are shown in FIG. It is determined as 19%, which is understood as the percentage of water absorbed by the limestone powder.

However, a torque test was conducted on a mixed powder in which 5% of the silica fume fine powder shown in FIG. 2 and 15% of limestone powder shown in FIG. 3 were mixed with the cement shown in FIG. 1 described above. The results are as shown in FIG. 4, and the average maximum water powder ratio was determined as 22%, and this value is the percentage of water adsorbed on the mixed powder blended in the above ratio.

Considering the results of FIGS. 1 to 4 described above, the surface area of a single-grain spherical powder generally having the average particle diameter as a representative diameter is measured by the BET method. Then, it can be understood as follows. (a) The thickness of the average adsorbed water film obtained by dividing the amount of adsorbed water by the surface area of the mixed powder as described above depends on the particle diameter. (b) In the case of FIG. 4 in which 5 wt% of silica fume is blended with 15 wt% of cement and limestone powder having a particle size equivalent to that of cement, the ratio of silica fume fine powder covering the surface of cement and limestone powder is about 30%. (c) Adsorption water film thickness of cement and limestone powder is 0.2μm
It is estimated that the particles of the silica fume fine powder are stably attached to such an adsorbed water film. However, the primary kneading is performed under limited water conditions (that is, the state of the maximum torque) to form the above-mentioned adsorbed water film, and then the water necessary for spraying is added and the secondary kneading is performed. Things.

It is necessary to accurately determine the amount of primary water to be charged in the primary kneading as described above.
Such a primary water amount is determined by the following equation from the water powder ratio required for the capillary state of the powder of cement or the like to be used and the restricted water content of the fine aggregate.

[0024]

(Equation 1)

[0025]

(Equation 2)

By the way, as described above, the adsorbed water does not reach the sum of the adsorbed water in each of the cement and limestone powders and the silica fume fine powder added thereto and mixed. It was experimentally confirmed that when the amount was small, the value was smaller than the water absorption rate of the cement.

That is, regarding the result that the adsorbed water rate in the mixed powder as described above is lower than the adsorbed water rate of plain cement, a state in which the silica fume fine powder is mixed in the adsorbed water film of the cement is formed. In this case, it can be understood approximately appropriately by setting the absorbed water rate to a state that is not 39% of the absorbed water rate of the silica fume fine powder alone. That is, when the volume of the silica fume fine powder distributed as described above in the volume corresponding to the adsorbed water rate of 24% in the case of the plain cement is cut off, it is recognized that it is substantially close to the above-mentioned 22% in FIG. Thus, it can be considered that the water adsorbed by silica fume alone is not substantially required.

In addition, with respect to the result of FIG.
FIG. 5 shows a water reducing agent which is indispensably employed in the shotcrete construction according to the present invention (when an AE agent is added, the overall torque change state is the same as that of FIG. 4). However, it was confirmed that, under the condition of adding 0.5% of this water reducing agent, the above-mentioned average maximum water powder ratio was determined as 19%, and the peak state thereof was determined to be steeper. Was.

However, the present inventors have proposed a method for forming a stable adsorbed water film in order to accurately realize the technical concept of the present invention as described above. The primary kneading is performed under the conditions (that is, the amount of water in the state of the maximum torque in the case of FIGS. 4 and 5 described above), and then, the amount of water necessary for spraying, pumping, and forming is given to the secondary kneading, It is proposed as a construction method that kneading is performed and the desired kneaded material is obtained by the split kneading method.

That is, it is confirmed that the state of formation of the adsorbed water film on the particles such as fine aggregate and the fine particles composed of cement, limestone powder and silica fume powder is appropriately stabilized by performing such a split kneading. The results are summarized in FIG. That is, the results of measuring the water retention after applying a centrifugal force of up to 500 G with respect to such a kneaded material show that the water retention decreases as the centrifugal force increases, and in the case of batch kneading, The water retention of plain mortar is close to 30% at about 450G, and about 43% in the case of containing water reducing agent, but it is confirmed that split kneading has higher water retention than batch kneading under any conditions. It is understood that the powder and granules were sufficiently mixed and adsorbed with water.

According to the primary kneading with the limited amount of water as described above, the added water effectively forms the adsorbed water film 15 as shown in FIG. 11 on the surface of each particle other than silica fume which is extremely fine powder. It is presumed that the silica fume fine powder 1 is covered as having a limited degree of formation.
4 is preferentially adsorbed and collected in the adsorbed water film 15. This adsorbed water film 15 has a thickness in the case of cement powder.
In a state of about 0.2 to 0.3 μm, a stable state is formed on the surface of each particle, and the state is as shown in FIG. 11 and FIG. Cement 12 and limestone powder 13 are adsorbed and positioned on the peripheral surface of clear fine aggregate (and coarse aggregate) 11,
The adsorbed water film 15 is formed on the peripheral surface of each of the materials 11 to 13, and the silica fume fine powder 14 is preferentially collected and adhered to the adsorbed water film 15 to form a shell of the powder. .

A small free water area 16 is held in a gap formed in the adsorbed water film 15 between the particles or the powder particles 11 to 13. A capillary state is formed, which is preferentially and stably collected, and a shelling state is formed by adsorption of silica fume fine powder having a relatively high concentration distribution in the adsorbed water film 15 even with relatively small amount of silica fume fine powder 14. Is done.

The kneaded material constituted as shown in FIGS. 11 to 13 undergoes a hydration reaction with time, and the adsorbed water film 15 is formed.
Disappears and becomes a reaction product changed into a crystal or the like generated by a hydration reaction, and a product (hardened body) firmly bound by such a reaction product is obtained. Is naturally maintained the same as before the hydration reaction.

The cement powder 12 or bone adjusted by the above-described method of the present invention and having silica fume fine particles 14 adsorbed in a preferentially high concentration distribution state in the adsorbed water film 15 as shown in FIGS. The kneaded material having the material 11 is cast into a mold or on-site construction area by a conventional method, and is injected by a commonly known method. And in this case cement powder 12
As described above, the hydration reaction proceeds on the adsorbed water film 15 on the peripheral surface of the aggregate 11 and the silica fume fine powder 14 in the state shown in FIGS. 11 to 13.

An outline of equipment for construction according to the method of performing spraying construction of the present invention for such a general casting and pouring method is as shown in FIGS. . That is, FIG. 7 shows a kneading adjustment process in the present invention, in which a twin-screw stirring mechanism is employed as the mixer 1, and a coarse aggregate charging system is provided above the mixer 1. 3, a fine aggregate charging system 2, a cement and limestone powder charging system 4, and a kneading water addition system 5 are provided. A supply tower 6 is provided on the side of the mixer 1, and a cement silo 61 and a limestone silo 62 set in the supply tower 6 are appropriately pumped such as cement or limestone from the road traveling vehicle 17. Duct 6
0, and screw feeders 63, 64 provided at the bottom of the silos 61, 62 as described above are configured to charge the cement and limestone powder charging system 4 with the materials. .

The above-mentioned fine aggregate charging system 2 and coarse aggregate charging system 3
In the material stockyard 7 formed on the ground, the coarse aggregate 3 transported by a vehicle 17 such as a truck
a or fine aggregate 2a is scooped by a bucket 8a suspended from an overhead traveling crane 8, and
b, are dropped into the silos 22 and 23 of the charging systems 2 and 3 by the conveyor provided at the bottom of the hopper, and are charged into the mixer 1.

The kneading water addition system 5 provided in the mixer 1 has a primary water tank 51 and a secondary water tank 52,
Predetermined water is added to the mixer 1 by opening and closing control means 53, 53 such as valves provided in the tanks 51, 52, and the secondary water tank 52 is mixed with the admixture from the admixture tanks 9, 9a. The agent is appropriately added, and the silo 61 and the limestone silo 6 described above are used.
2. The material silos 2b, 3b and the water tanks 51, 52 are provided with measuring means 54, respectively.
The control means 53 is connected to the control mechanism 10 to perform a control operation according to the kneading program according to the present invention. That is, the primary and secondary kneading program, cement amount and 1
The automatic setting of the next water, the correction of the surface water, and the like are automatically controlled by the control mechanism 10.

In the equipment shown in FIG.
FIG. 8 is a flowchart of a concrete kneading operation in which the mixing time is set to one minute, and sand, gravel and primary water are mixed with a mixer 1.
And kneaded for 15 seconds, then put cement, silica fume and limestone powder into it for 30 seconds.
Next, a mixing operation is performed, then silica fume and secondary water are charged, secondary kneading is performed for 45 seconds, and loading is performed in the subsequent 30 seconds, and the flow chart is as shown in FIG. A coarse aggregate G, sand S, silica fume, and primary water are put into a mixer 1 and kneaded, whereby the coarse aggregate acts as a ball mill to enhance the kneading effect. After kneading for 2 seconds, the admixture and secondary water are further added and kneaded to obtain a desired kneaded product.

FIG. 9 shows a kneading adjustment process similar to that of FIG. 7 for the spraying work according to the present invention, and shows a case where a stirring mechanism 21 which revolves while rotating as the mixer 1 is employed. , A coarse aggregate 3a or a fine aggregate 2a carried in by a vehicle 17 such as a truck.
Is scooped by a bucket 8a suspended from an overhead traveling crane 8, and is weighed from hoppers 2b, 3b via weighing hoppers 22, 23 by weighing conveyors 2c, 3c, and put into a mixer 21. .

On the other hand, the cement or limestone powder carried by the tank truck 19 is supplied to the silos 31 and 3 respectively.
2, the silos 31, 32 are loaded into the weighing hoppers 36, 36 via the quantitative cutout mechanisms 33, 33, and the screw feeders 34, 35, and the weighed quantitative destinations are loaded into the mixer 21. . Further, the mixer 21 is provided with a silica fume powder or slurry addition system 37, a primary water and secondary water addition system 38, and an addition system 39 for supplying a high-performance water reducing agent. Another water tank 4 having water tank 40 and stirring means 41
Water fed from 2 through a metering pump 43 is introduced into the mixer 21 via an additive tank 44 by a high-performance water reducing agent addition system 39 different from the addition system 38.

FIG. 1 is a flowchart of the kneading operation with the kneading time of 2 minutes for the one shown in FIG. 9 described above.
As shown in FIG. 0, sand, primary water and silica fume were charged into the mixer 21 to perform primary kneading for 15 seconds, and then kneading was performed after charging and adding cement and limestone powder. The kneading is performed for 45 seconds with the secondary water added, and the loading is performed in the subsequent 30 seconds as in the case of FIG. 9, except that the coarse aggregate G is added together with the secondary kneading water and the kneading is performed for 45 seconds. It is discharged after kneading.

The mortar or concrete kneaded according to the equipment and the flow chart described above is cast from the mixer 1 or 21 immediately or after an appropriate time, or cast into a mold. In the case of spraying, the mixer 1 or 21 is used. Alternatively, it is received by the concrete transport mixer truck 25 from 21 and transported to the target construction site to be sprayed. That is, as shown in FIG. 7 and FIG.
As shown in FIG. 14, the mixture is received by the rotary mixer 41 of No. 0 and charged into the receiving section 46 of the spraying mechanism 45 located at the construction site as shown in FIG.

The spraying mechanism 45 appropriately travels by the driver's operation in the cab 43 to reach the construction position. At the end of the operation arm 47, a spraying nozzle 48 is provided. The pressure-feeding pipe 42 and the blowing-gas pressure-feeding means 44 are connected to each other, so that a desired construction site can be properly blown under lighting conditions such as the lighting means 49.

With respect to the above kneaded product of the present invention, the state of formation of the adsorbed water film on the sand, cement, and limestone powders and the distribution of the silica fume fine powder are as shown in FIGS. 0.2 to 1 in diameter
Silica fume, which is apparently a fine powder of μm, is distributed in kneading water or used as a powder together with other powders such as cement or limestone powder.
In accordance with the method of employing the next kneading, the water addition conditions in the first kneading are limited to such an extent that an adsorbed water film can be formed and maintained over substantially the entire circumference of the kneaded material-containing material, whereby these FIGS. The distribution state of the adsorbed water film and the silica fume as shown in FIG. 13 can be obtained.
That is, the silica fume fine powder 14 mixed in the primary kneading water limited as described above is adsorbed on the peripheral surfaces of the sand 11, the cement 12, and the limestone powder 13 in a dispersed state, so that the silica fume fine powder 14 is concentrated. Those powder 11
13 is adsorbed on the peripheral surface of the substrate 13 to form a shell for the powder.

The thickness of the adsorbed water film 15 as described above with respect to the cement powder 12 is about 0.2 μm.
3, the thickness of the adsorbed water film in the sand 11 is larger, and the silica fume fine powder 14 has an average particle size of about 0.2 to 0.8 μm. The silica fume fine powder protrudes from the above-mentioned adsorbed water film as shown in FIGS. 11 and 12, and almost submerges in the adsorbed water film thickness as shown in FIG. As shown in the figure, since the film is formed, it is substantially immersed in the adsorbed water film 15. Relatively fine silica fume fine powder 14
As shown in FIGS. 11 to 13, the water is covered with the adsorbed water film 15 such as cement, and the cement powder and the like are precisely and uniformly made uniform by the silica fume fine powder through the adsorbed water film as described above. A coating (ie, a shell of the powder) is applied.

[0046]

Reference Example A concrete example of the adjustment work of the present invention as described above will be described. As a reference example, a coarse aggregate and a bone having a maximum dimension of 12 mm as shown in Table 1 below are used. Fine aggregate made of river sand with a fine aggregate ratio of about 64%, and a specific surface area of 327 with an average particle size of 16.5 μm.
0cm ² / g, Portland cement with a specific gravity of 3.16,
The average particle size is 10.8 μm and the specific surface area is 4270 by BET method.
cm ² / g of silica fume fines and water reducing agent is a 243475cm ² / g limestone powder and the average particle size of 0.76μm specific surface area by the BET method, using a quick-setting admixture, below Table 2
As shown in the figure, the unit cement amount (including silica fume fine powder: limestone powder) was 360 kg / m ³ , and fine aggregate 1137 kg /
m ^3, coarse aggregate 644kg / m ^3, relative to the water 208 kg / m ^3,
After mixing the water reducing agent, the quick setting agent was mixed to prepare the concrete.

[0047]

[Table 1]

The aggregate particle size distribution of the aggregates (fine aggregate and coarse aggregate) in Table 1 is as shown in FIG. 16, and those of a... A range from 2.5 to 10 mm. It is a preferred aggregate that has a particle size distribution adjusted in general and has a substantially average particle size distribution throughout, and forms a stable composition when concrete is adjusted. There are, but those of b ... b and c ... c
Disturbed in the range of 2.5 to 5 mm, inferior to that of a ... a. In addition, those of d... D are disturbed in the range of 2.5 to 5 mm and rise rapidly in the range of 5 to 10 mm. As the aggregate in Table 1 described above, the aggregate shown in the curve a ... a in FIG. 16 was employed. .. B, c... C and d... D
In the aggregate of, for example, 0.15 mm or less of fine aggregate is added to the amount of limestone powder and the amount is blended to 10 to 15% of the fine aggregate amount, or the fine aggregate amount of 0.075 mm or less As a result, a stable result close to that of a preferable substantially averaged particle size distribution was able to be obtained by appropriately using together.

[0049]

[Table 2]

That is, in Table 2, the comparative example is the present invention example. Preferred details of the kneading operation in the present invention example are typically shown in FIG. Water and silica fume fine powder are charged and adjusted for about 5 to 10 seconds, and then cement and limestone powder are charged for 25 to 30 seconds or 30 minutes.
First kneading for more than 2 seconds, and then adding coarse aggregate
After the adjustment kneading for about 10 seconds, the secondary water, the quick-setting agent, and the water reducing agent are added, and 30 seconds or more.
It is discharged after the next kneading.

The rebound rate (%) in the case where the above-prepared kneaded material for spraying is sprayed on the inner surface of an excavation tunnel having a radius of about 4.5 to 5 m,
The amount of dust generated (mg / m ³ ), the actual spray amount (m ³ / h), and the strength of the sprayer obtained by such spraying are shown in Table 3 below.
As shown in FIG.

[0052]

[Table 3]

That is, according to the present invention, the rebound rate was reduced by both the conventional method and the comparative example to a half of the conventional method, and the amount of dust generated was determined by the ventilation conditions shown in parentheses. Below one quarter of the conventional method,
It is less than half that of the comparative example, and the actual spray amount is considerably increased. Further, the strength of the obtained spraying work was sufficiently enhanced in both the initial strength by the pull-out method and the long-term strength by coring, and it was confirmed that the initial strength was at least twice that of the conventional method.

In addition, besides such spraying work, the diameter 5c
m, 6 cylindrical molds having a height of 10 cm were prepared, and the above kneaded materials were simply folded and molded into the two molds, respectively, to obtain molded articles in the same manner as in Table 3 described above. The results of measuring the unconfined compressive strength of the molded body of 28 days old are shown in Table 4 below, and it is known that the strength is superior to that of the spraying method in any case. The material was found to have a considerably high strength of 45 to 47 N / mm ² .

[0055]

[Table 4]

[0056]

[Modification] As a modification of the above-described reference embodiment, the same materials as those shown in Table 1 were employed. However, the mixing relation of these materials is shown in Table 5 below. Modified Examples of the present invention and Comparative Examples.
That is, the cement is 305-360 kg / m ³ , the fine aggregate is 1039-1137 kg / m ³ , and the coarse aggregate is 644 kg / m ^3.
Limestone powder is 98 kg / m ³ or 41 kg / m ³ ,
Silica fume powder is considerably high as 36~54kg / m ³ in Comparative Examples 3 and 4 while a 11~29kg / m ³ in the present invention example, water reducing agent in the present invention Examples 1.8 kg / m ³ In contrast, the comparative example was 3.6 kg / m ³ and the quick-setting agent was 25.2 kg / m ^3.
m ³ is constant.

[0057]

[Table 5]

By the way, each of the spray kneaded materials prepared as described above shows the spraying operation situation and the strength of the spraying work as shown in Table 3 above, as in the case of the above-mentioned reference example. The results obtained in the same manner as in the above case are as shown in Table 5 below.

[0059]

[Table 6]

That is, in the rebound rate of the present invention,
Is 14 to 21%, whereas the comparative example (ratio 1 to 1)
The ratio 4) is 20 to 30%, which is reduced by about one-third as in the case of Table 3 relating to the above-mentioned reference example, and the amount of dust generated and the amount of spraying are also preferable. Obviously, the results have been obtained. Furthermore, the strength of the obtained spraying works was confirmed to be the same as those in Table 3 described above, and it was confirmed that the examples of the present invention to the preferred examples obtained favorable results.

[0061]

According to the present invention as described above, the quality of shotcrete used for the inner surface of a tunnel or the like can be effectively improved at a relatively low cost, and dust and rebound during construction can be appropriately reduced. Therefore, the above-mentioned advantages can be advantageously achieved with little variation, so that the invention is industrially highly effective.

[Brief description of the drawings]

FIG. 1 is a table showing a summary of mixer load current (torque) measurement results when water is added to and kneaded with cement, which is a basic material in the present invention, to obtain an average maximum water powder ratio. .

FIG. 2 is a table showing the results of obtaining the average maximum water powder ratio for silica fume, which is another material in the present invention, as in FIG.

FIG. 3 is a table showing the result of obtaining the same average maximum water powder ratio as in FIGS. 1 and 2 for limestone powder, which is still another material in the present invention.

FIG. 4 is a table showing the results of calculating the average maximum powder ratio in the same manner as described above for the mixtures of three types of materials as shown in FIGS.

FIG. 5 is a table showing the results of similarly determining the maximum powder ratio for a mixture obtained by further adding a water reducing agent to the three materials shown in FIG.

6 is a table showing the results of examining the water retention under centrifugal action conditions for each of the kneaded materials obtained by subjecting the mixture as shown in FIG. 5 to batch kneading and divided kneading.

FIG. 7 is an explanatory view showing one example of equipment for adjusting a kneaded material according to the present invention.

FIG. 8 is a flowchart showing a concrete adjusting shelling process by the facility shown in FIG. 7;

FIG. 9 is an explanatory view similar to FIG. 7, showing another example of equipment for adjusting a kneaded material according to the present invention.

FIG. 10 is a flowchart illustrating a concrete adjusting shelling process by the equipment shown in FIG. 9;

FIG. 11 is a cross-sectional explanatory view showing a state of formation of an adsorbed water film on sand, cement, and limestone powder and a distribution state of silica fume fine powder in the kneaded preparation according to the present invention.

FIG. 12 is a cross-sectional explanatory view of a part of FIG. 11, which is partially enlarged.

FIG. 13 is an explanatory cross-sectional view of a case where relatively fine silica fume fine powder is used, which is similar to FIG. 11 and is partially enlarged.

FIG. 14 shows a spraying mechanism 1 for performing construction according to the present invention.
It is the side view which showed the example.

FIG. 15 is a process explanatory view showing details of a preferable kneading operation according to the present invention.

FIG. 16 is a table showing a composite particle size distribution of the aggregate used in the example of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 mixer 2 fine aggregate charging system 2a fine aggregate 2b hopper 2c weighing conveyor 3 coarse aggregate charging system 3a coarse aggregate 3b hopper 3c measuring conveyor 4 limestone powder charging system 5 kneading water addition system 6 supply tower 7 material Yard 8 overhead crane 8a bucket 9 admixture tank 9a admixture tank 10 control mechanism 11 aggregate (fine aggregate) 12 cement 13 limestone powder 14 silica fume fine powder 15 adsorbed water film 16 free water area 17 vehicle 18 mixer truck 21 mixer 22 silo ( Charging system (2)) 23 Silo (Charging system (3)) 24 Chute 31 Cement silo 32 Limestone silo 33 Quantitative cutting mechanism 34 Screw feeder 35 Screw feeder 36 Measuring hopper 37 Silica fume powder or slurry addition system 38 Primary and secondary water Addition system 39 High-performance water-reducing agent addition system 40 Concrete mixer truck 41 Rotary mixer 42 Concrete pumping pipe 43 Operator's cab 44 Blowing gas pumping means 45 Blowing mechanism 46 Receiving part 47 Operating arm 48 Blowing nozzle 49 Lighting means 50 Water tank 51 Primary water Tank 52 Secondary water tank 53 Control means 54 Measuring means 55 Stirring means 56 Separate water tank 57 Metering pump 58 Additive tank 60 Duct 61 Cement silo 62 Limestone silo 63 Screw feeder 64 Screw feeder

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C04B 14:28 22:06) (72) Inventor Mitsuhiro Suenaga 2-14-2 Nagatacho, Chiyoda-ku, Tokyo Japan Railway Construction Corporation (72) Inventor Tadaaki Tamura 2-1-1 Kyobashi, Chuo-ku, Tokyo Livecon Engineering Co., Ltd. (72) Inventor Satoshi 2-2-1 Kyobashi, Chuo-ku, Tokyo Livecon Engineering Co., Ltd.

Claims (10)

[Claims] 1. A cement, one or both of fine aggregate and coarse aggregate, 10-15% of limestone powder based on the fine aggregate amount, and 3-8% silica fume fine powder based on the cement amount. In the state where the silica fume fine powder forms a state of being preferentially distributed on the peripheral surface of cement and limestone powder and is distributed on the peripheral surface of one or both of the fine aggregate and the coarse aggregate. A concrete characterized by being hydrated and set and solidified. 2. A cement, one or both of fine aggregate and coarse aggregate, 10-15% of limestone powder based on the fine aggregate amount, and 3-8% silica fume fine powder based on the cement amount. In the state where the silica fume fine powder forms a state of being preferentially distributed on the peripheral surface of cement and limestone powder and is distributed on the peripheral surface of one or both of the fine aggregate and the coarse aggregate. Shotcrete characterized by being sprayed and hydrated and set and solidified. 3. An aggregate according to claim 1, wherein one or both of the fine aggregate and the coarse aggregate are formed of a low-grade aggregate having a low shape, particle size distribution or material. Concrete according to. 4. A cement, one or both of fine aggregate and coarse aggregate, and a silica fume fine powder and a limestone powder, and an adsorbed water film of these contents is formed on substantially the entire circumference of the contents. Secondary water and a water reducing agent for forming and kneading the cement, silica fume fine powder and limestone powder under primary water-mixing conditions limited to such an extent that they can maintain a capillary state, and then obtaining the fluidity required for spraying construction. And a secondary kneading method, and spray-casting the secondary kneaded material. 5. A fine aggregate, primary water, and fine powder of silica fume are charged into a mixer, adjusted for a short time, and then cement and limestone powder are charged to perform primary kneading. The secondary kneading is carried out by adding a secondary water and one or both of a quick-setting agent and a water-reducing agent after the material has been charged and adjusted for a short time.
Construction method of shotcrete described in 4. 6. A blowing agent according to claim 4, wherein limestone powder having an average particle diameter of 7 to 15 μm and silica fume fine powder having an average particle diameter of 0.05 to 1 μm are used. Construction method of attached concrete. 7. The addition amount of cement and silica fume fine powder as binder is about 360 to 420 kg / m ³ , and said silica fume fine powder is 4 to 7% of the amount of said binder.
(14-30 kg / m ³ ).
6. The method for constructing shotcrete according to any one of items 6 to 6. 8. The method according to claim 4, wherein the fine aggregate having a diameter of 0.15 mm or less is added to the amount of limestone powder and the amount is 10 to 15% of the fine aggregate. Construction method of shotcrete described in. 9. The method for constructing shotcrete according to claim 8, wherein a fine aggregate of 0.075 mm or less is used. 10. A mixer is provided with respective means for adding coarse aggregate, fine aggregate, cement, silica fume, limestone powder, a water reducing agent and kneading water, and a metering means is provided for each of these addition means. The kneading water adding means is divided into primary water and secondary water, and a control panel for inputting a program for a control unit provided in each of the adding means is provided. A shotcrete construction apparatus characterized in that a kneaded material by a mixer is transported by a concrete transport mixer truck to a spraying mechanism at a construction site for construction.