GB2098264A - Method and apparatus for applying mortar or concrete - Google Patents

Abstract

One of the ingredients of green mortar or concrete are supplied to a rotary disc 18 through a central pipe 13 by a pump or low pressure air and the other ingredient is supplied to the disc 18 from a hopper 11 by screw conveyor 19. These ingredients are mixed together on the disc 18 and then projected by centrifugal force. Since the green mortar or concrete is projected by centrifugal force instead of pressurized air, quantities of dust and rebound formed at a projected surface are small. <IMAGE>

Description

SPECIFICATION Method and apparatus for applying mortar or concrete This invention relates to a method and apparatus for applying mortar or concrete by projection.

Application of a cememt mortar or concrete by blasting can be done without preassembling a frame or mould, and it is not necessary to disassembly a mould after setting of the applied mortar or cement, so that surface finishing can be immediately made. Thus, this method not only greatly simplifies the work but also greatly shortens the working period. For this reason, in present days, the method of blasting is used in many cases.

Among the methods of blasting may be mentioned, wet method, dry method, and semiwet method. However, these prior art methods are advantageous in one case but disadvantageous in other cases. More particularly, according to the blasting method, such hydraulic substance as cement, an aggregate, and water are kneaded to prepare a green concrete having a desired water to cement ratio (W/C), the green concrete is conveyed to the working field with a concrete pump, and then projected upon a wall surface through a nozzle. With this method, since cement is sufficiently wetted, the concrete product has a high mechanical strength. However, where a green concrete of a W/C ration manifesting the highest strength is prepared, such green concrete is difficult to convey through a conduit because of its high frictional resistance and high viscosity.Consequently, a pump pressure of the order of 50 kg/cm2 is necessary, thus requiring a large driving power and strong conduit. Even with such expedient the maximum distance of conveyance is at most 50 to 60 m so that it is impossible to apply this method for constructing a long tunnel. Accordingly, in practice, the ratio W/C is increased more or less to improve fluidity of the green concrete, thus making it impossible to fully use the advantage of the wet method. On the other hand, according to the dry method, concrete ingredients are conveyed to the field in a dry state with high pressure air, and the necessary quantity of water is added to the concrete ingredients in a blasting nozzle at the working field.The pressure of the air necessary to convey the concrete ingredients through a pipe may be about 5-6 kg/cm2 so that the dry method is advantageous to convey the concrete ingredients over a long distance with a simple and inexpensive installation. However, kneading of the dry ingredients and water can not be performed efficiently and cement dust is generated in a great quantity so that it is impossible to apply kneaded concrete over a long time. Moreover, the mechanical strength of the blasted concrete is only one half of that of the concrete formed by the wet method, which is a fatal defect of the dry method. The semiwet method is an intermediate method in which water is incorporated at an intermediate point of the conveyance pipe instead of at the end thereof.Where water is added at a point 5 to 6 m ahead of the nozzle, the fluidity decreases greatly, thus clogging the pipe, so that it is impossible to use a long pipe as in the dry method.

Where water is added at a point close to the nozzle, it is difficult to sufficiently knead the concrete, this difficulty being similar to that encountered in the dry method. With any method, the resulting concrete is blasted to a surface with high pressure air so that concrete once applied onto the surface tends to be blown away by the blast. A quick setting agent normally used at the time of blasting is added at the nozzle, but it is difficult to uniformly admix the quick setting agent with concrete, whereby the applied concrete lacks uniformity. Also, loss of the quick setting agent at the time of blasting is large and the lost agent forms a stimulative atmosphere which makes it difficult to work over a long time.Considering the shear strength of the blasted concrete layer, in both the dry method and the wet method the shear strength is low because in the former the quantity of air in the blasted layer is large, while in the latter, the content of water is high.

What is desired is an improved method and apparatus for applying mortar or concrete without various accompanying defects of the prior art methods described above.

The present invention provides a method of applying mortar or concrete comprising the steps of preparing first and second materials necessary to prepare the mortar or concrete, conveying the first material to a working field with pressure means, conveying the second material to the working field with mechanical means, admixing the first and second materials at the working field and projecting a resulting mixture with a rotary energy.

The invention also provides apparatus for projecting mortar or concrete comprising a first material supply pipe for conveying under pressure the first material, one of ingredients of the mortar or concrete, a hopper charged with second material, the other ingredient of the mortar or concrete, a second material supply pipe connected to the hopper, a rotary screw disposed in the second material supply pipe for mechanically conveying the second material supplied from the hopper, a rotary disc for admixing the first and second materials conveyed through the first and second material supply pipes to project a resulting mixture, the first and second material supply pipes and the rotary disc being arranged coaxially and the first and second material supply pipes being arranged concentrically.

The method and apparatus of the invention enable one to apply mortar or concrete without utilizing pressurized air, thus decreasing generation of dust and rebound at the working field.

Optional and preferred features of the method and apparatus are set forth in the sub-claims and in the following description, by way of example, with reference to the drawings. The method and apparatus as described below, are capable of uniformly incorporating a quick setting agent into green mortar or concrete and preventing splashing of the quick setting agent when the green mortar or concrete is applied, capable of independently adjusting speed of conveyance of concrete ingredients and speed of projecting green concrete, capable of projecting green concrete in any desired direction, and capable of projecting green concrete and smoothing the surface of the applied concrete layer.

In the accompanying drawings: Figure 1 is a diagrammatic representation of an embodiment of apparatus of this invention utilized to project concrete, and various devices for preparing ingredients of concrete; Figure 2 is a longitudinal sectional view showing an example of a rotary projecting apparatus embodying the invention; Figure 3 is a side view, partly in longitudinal section, showing a modified rotary projecting apparatus embodying the invention; Figure 4 is an end view showing a projection direction control cylinder utilized in the apparatus shown in Figures 2 and 3; Figures 5A, 5B and 5C are sectional views of an arch type tunnel in which the inner surface of the tunnel is applied with a concrete coating by using the apparatus shown in Figures 2 and 3;; Figure 6 is a side view of projecting apparatus mounted on a carriage and used for projecting concrete; Figure 7 is a side view, partly in longitudinal section, showing modified embodiment of this invention; Figure 8 is a perspective view showing a base plate of an agitator utilized in the apparatus shown in Figure 7; Figure 9 is a sectional view of a projection direction control device utilized in the apparatus shown in Figure 7; Figure 10 shows sectional views of an arch type tunnel, the inner surface thereof being applied with a concrete coating by using the apparatus shown in Figure 7; Figure 11 is a longitudinal sectional view showing a modified rotary disc and agitator utilized in this invention; Figure 1 2 is a side view showing the base plate of the agitator utilized in the apparatus shown in Figure 11;; Figure 13 is a side view, partly in longitudinal section, showing still another modification of this invention; Figures 14 and 1 5 are diagrammatic representations showing the apparatus shown in Figure 1 3 and various devices for preparing ingredients of concrete; Figure 1 6 is a diagrammatic representation showing the apparatus of this invention applied for wet method; Figure 17 is a longitudinal sectional view showing a modified projector capable of obliquely projecting green concrete; Figure 18 is a sectional view of a modified projector; Figure 19 is a longitudinal sectional view showing still another modification of this invention; and Figure 20 is an end view thereof.

The projecting apparatus 1 is utilized in a system as shown in Figure 1. The projecting apparatus 1 is connected to apparatus 2 for preparing a flowable substance, mortar or paste for example, via pump 5 and conduits. Either one or both of mixers 21 and 22 are connected with the apparatus 2 through conveyors 7 and 7a or the like. A cement hopper 24, a sand hopper 23, an additive hopper 25, and a water addition pipe 26 are provided for the mixer 21, while similar hoppers 23-25, a primary water addition pipe 26, and a secondary water addition pipe 27 are provided for the mixer 22. Dry material preparing devices 3 and 4 are provided for the projecting apparatus 1 and dry materials prepared by the devices 2 and 3 are conveyed by conveyors such as belt conveyors 6 and 6a into a hopper 11 provided on the projecting apparatus 1.

A coarse aggregate hopper 31, a fine aggregate hopper 32, and a quick setting agent hopper 33 are mounted above the dry material preparing device 3, whereas the dry material preparing device 4 is provided with a mixer 40 above which are mounted a coarse aggregate hopper 41, a fine aggregate hopper 42, and a quick setting agent hopper 43. Each of the hoppers 23-25, 31-33 and 41-43 is provided with a constant feeder so that predetermined amounts of the additives are supplied to the preparation devices. Predetermined quantities of the primary and secondary waters are also incorporated.

The concrete projecting apparatus may be constructed as a carriage type as shown in Figure 2 or a robot type as shown in Figure 3. A central pipe 13 (Figure 2) for conveying flowable materials is connected to a pipe from the pump 5 and extends in the horizontal direction along the axis of the projecting apparatus 1. The outer end of the central pipe 13 is opened toward the centre of a rotary disc 1 8 having a plurality of blades 1 6. A dry material supply cylinder 12 concentrically surrounds the central pipe 13, and a screw conveyor 19 extends therebetween from the hopper 11 to the rotary disc 1 8. As shown in Figure 2, the screw conveyor 19 may be secured to the inner surface of the supply cylinder 22 which is rotated by a pulley 11 a secured thereto and a belt, or as shown in Figure 3, the screw conveyor 1 9 may be secured to the periphery of the central pipe 13 which is rotated by an electric motor. In the latter case, the supply cylinder 12 is held stationary.In any case, by the rotation of the screw conveyor 19, the material supplied from hopper 11 is conveyed to the rotary disc 1 8 through the supply cylinder 12. The quantity of the material supplied to the rotary disc 18 is proportional to the number of revolutions of the screw conveyor 1 9.

The rotary disc 18 is secured to one end of a rotary cylinder 14 surrounding the supply cylinder 12.

The rotary cylinder 1 4 is rotated by a pulley 1 4a secured to the other end thereof for radially projecting the material on the rotary disc 1 8. A projection direction control cylinder 1 7 is provided between the rotary cylinder 1 4 and the supply cylinder 1 2 to project toward the rotary blades 1 6 beyond the front end of the supply cylinder 1 2. An operating member 1 7b is formed at the opposite end of the cylinder 1 7 for controlling the direction of projection as shown in Figure 4.Consequently, by adjusting the position of the rotary projecting apparatus 1 and the operating member 1 7a it is possible to project concrete onto the inner surface of an arch type tunnel having a large or small cross-section as shown in Figs. SA-SC.

As shown in Figures 2 and 3, a dish shaped plate 28 is secured to the centre of the rotary disc 1 8 at a position confronting the discharge end of the central pipe 13 to receive the flowable slurry material discharged from the central pipe 1 3. The material is then radially and uniformly discharged from the dish shaped plate 28 to be mixed with dry material supplied by the supply cylinder 1 2. Radial blades 1 6 secured to the periphery of the rotary disc 1 8 impart desirable projection energy to the mixture thus formed. The rotary disc 1 8 and the screw conveyor 1 9 may be rotated at different speeds.The speed of the conveyor determines the quantity of the dry material supplied to the rotary disc 1 8, while that of the rotary disc 1 8 determines the projection energy. Of course, the quantity of the flowable material through the central pipe 13 can be varied properly. By a suitable combination of these parameters, any desired concrete projection can be made.

Where a carriage type is adopted as shown in Figure 2, materials prepared by the preparation devices 2 and 3 can also be conveyed to the working field by the carriage. Such construction is shown in Figure 6. More particularly, a first carriage 101 carries a rotary projector 1; a second carriage 102 carries a hopper 35 for storing materials prepared by the dry material preparation device 3. The dry material in the hopper 35 is taken out from the bottom thereof by a take out mechanism 36 and then conveyed to the projector 1 by conveyors 37 and 37a. A third carriage 103 carries a hopper 55 for storing flowable material prepared by the flowable material preparation device 2.An agitator 56 driven by an electric motor 56a is disposed in the bottom of the hopper 55, and a duct 56b extending from the agitator 56 is connected to a mortar pump 57 driven by an electric motor 57a, and the central pipe 13 of the projector 1 is connected to a discharge port 57b opening at the upper portion of the mortar pump 57.

The projector 1 is mounted on the first carriage 101 via slide blocks 104 which are moved on the first carriage 101 by electric motors 105 to move forwardly or rearwardiy the projector 1 while all carriages 101-103 are stopped depending upon the conditions of the working field for projecting green concrete upon the surface of a tunnel just digged. An electric motor 115 is mounted on the first carriage 101 for rotating the rotary disc 18 of the projector 1, and another motor 11 6 is mounted for rotating the screw conveyor 1 9.

When the apparatus shown in Figure 6 is used for a wet type concrete working, the carriage 103 is replaced by a green concrete wagon, and the carriage 102 is reciprocated between an inlet and the working field in a tunnel so as to load the green concrete kneaded in the green concrete wagon into the hopper carried by the carriage 102 at the inlet of the tunnel. The carriage 102 is moved to the carriage 101 at the working field and the green concrete is transferred to the carriage 101. In this case, since the green concrete is forced to pass through the central pipe 1 3 by a pump, it is advantageous to increase the fluidity of the green concrete. It is advantageous to convey a green mortar consisting of cement, a fine aggregate and water through the central pipe 13, while to supply a dry coarse aggregate and a quick setting agent from hopper 11.Then, it becomes possible to successively convey green concrete carefully prepared to the tunnel inlet by a green concrete wagon for carrying out the wet method without instailing a concrete mixer in the tunnel.

In a modification shown in Figure 3, the projector 1 is mounted on an operating base 50 through a swinging mechanism 51, and the operating base 50 is supported by a supporting arm 52 and an operating cylinder 53, so that the projector 1 can be moved in the vertical direction by the cylinder 53 and swung by the swinging mechanism 51 for projecting green concrete at a desired position and in a desired direction.

Figure 7 shows still another embodiment of this invention, in which the central pipe 13, for supplying flowable material, and the dry material supply cylinder 12 are disposed concentrically, and dry materials in the hopper 11 are conveyed to the rotary disc 1 8 by the screw conveyor 1 9 in the same manner as in Figures 2 and 3. In this modification, however, an agitator 85 is secured to the rotary disc 18 at a position confronting the discharge end of the central pipe 1 3. More particularly, as shown in Figure 8, the agitator 85 is mounted on the inner side of a base plate 86 fitted to the central portion of the rotary disc 1 8 and provided with a plurality of agitating blades 87 and 88 as shown in Figure 7. The base plate86 is secured to the rotary disc 1 8 by a bar 89 held by anchors 1 8a on the periphery of fthe rotary disc 1 8. By depressing a spring member 89a, the bar 89 is disengaged from the anchors 1 8a so that it is possible to dismount the base plate 86 by grasping handles 86a for cleaning or adjusting the agitator blades 87 and 88. The modification shown in Fig. 7 is advantageous in that it does not use the cylinder 1 7 shown in Figs. 2 and 3 so that the direction of projecting is adjustable with a simplified construction. More particularly, the supply cylinder 12 surrounds the agitation blades 87 and 88 and extends close to the rotary disc 1 8.As shown in Fig. 9, a portion of the cylinder 12 is removed at 1 2b so that as the angular position of the supply cylinder 12 is adjusted the direction of projection can be varied, thus enabling projection of green concrete in any desired direction as shown in Fig. 1 0.

With the agitator shown in Figures 7 and 8 the agitation is effected mainly by the blades 87, whereas the blade 88 is slightly inclined with respect to the axis of the rotary screw 19 for conveying the green concrete to the rotary disc 1 8.

Figures 11 and 12 show a modified agitator. In this modification a feeder 85a comprising long and short blades 87a and 87b is provided on the inside of the base plate 86 fitted in the central portion of the rotary disc 1 8, and an agitation blade 88 is provided at the fore end of the screw conveyor 19. Each of the blades 87a and 87b is shaped such that its cross-section gradually decreases in the direction of conveyance of the material. Thus, the dry material is conveyed by the screw conveyor 1 9, agitated by blade 88 and then fed onto the rotary disc 18 by the feeder 85a. The base plate 86 is fastened to the rotary disc 18 by a fastening member 89b and bolts 89c on the opposite ends thereof. However, the base plate 86 may be removably secured to the rotary disc as shown in Figure 8.

Where the green concrete is applied onto the irregular surface of a tunnel it is advantageous to use a reversible motor for rotating the rotary cylinder 1 4 so as to reverse the direction of rotation of the rotary disc 1 8. Then, a portion where it is difficult to cover with concrete when the rotary disc 18 is rotated in one direction can be covered.

As above described according to the apparatus of this invention, it is possible to suitably combine machines installed on the outside and inside of a tunnel depending upon the diameter of the tunnel and the condition of the working field. This combination is illustrated by a hatched portion and cross hatched portion shown in Figure 1. At a minimum, the projector 1 and preparation device 4 are installed at the working field and the other machines are installed on the outside of the tunnel. In a certain case, the pump 5 and flowable material preparation device 2 can be installed in the tunnel and, in a larger tunnel, other machines shown by dot and dash lines can also be installed in the tunnel.

The apparatus of this invention can be advantageously applied for conventional projection method. For example, in the wet method, green mortar or green concrete is conveyed through the central pipe 13 by using a pump as has been described in connection with Figure 6, and gravel is supplied to the supply cylinder 12 together with such quick setting agent as caustic silicate, calcium chloride, sodium aluminate, and sodium carbonate for adding then to the flowable substance on the rotary disc 1 8 and then projecting the mixture. In a conventional wet method, the diameter of the conduit is decreased at the nozzle and high pressure air is utilized for blasting so that it is necessary to use a pump operating at a high pressure. Even with such measure, it has been difficult to convey the materials over a long distance, as has been pointed out hereinbefore.According to the apparatus of this invention it is not necessary to use high pressure air and to reduce the diameter of the conduit near the nozzle, so that it is possible to convey materials over a long distance with a small pump. Moreover, as the green concrete is projected by the centrifugal force of the rotary disc, even when the materials are conveyed to the rotary disc at a relatively low speed, sufficiently large projecting energy can be applied to the materials. When the invention is applied to the dry method, water is added to a dry mixture conveyed by the screw conveyor in the supply cylinder through the central pipe. When an agitator shown in Figure 7 or 11 is used, the mixture is thoroughly admixed to increase the mechanical strength of the projected concrete.Moreover, reflection of the projected concrete is decreased, thus obviating defects of the dry method while enjoying advantageous merits thereof.

The utility of the apparatus of this invention shown in Figure 1 can be enhanced by providing the device 8 for hoppers 23 and 32 supplying sand or fine aggregate in order to make uniform the surface water on the fine aggregate. Sand is collected in the river side or sea side and then transported to a concrete mixer. The quantity and state of water on the particles of sand vary variously. For example, even with the sand produced from the same source, when the sand is piled up in a yard, the quantity of water differs greatly at the top, bottom, and centre of the pile. Even in the sand sampled at the top, the content of water is greatly influenced by weather. More particularly, some of the sand particles are dry while the others are wet.As is well known in the art, when preparing a green concrete the amounts of water and air contained therein have a great influence upon the strength of the resulting concrete as weil as upon the viscosity and workability of the green concrete. According to this invention, the quantity and state of water on the sand particles are preferably made uniform for determining a rational proportion of the ingredients. When the amount of water on the sand particles is made uniform, the water to cement ratio W/C essential to the preparation of green concrete can be accurately determined.

Regarding sand to cement ratio S/C and sand to gravel ratio S/A, where the amount of water on the sand particles is made uniform these ratios can also be made accurate. Advantageously, cement powder is firstly incorporated to sand with adjusted surface water, to form shells about sand particles.

Such shells contain cement at a high proportion so that they are stable and would not be broken during conveyance with a pump and when projected by the rotary disc. Moreover the shells make irregular sand particles to be spherical which makes it easy to convey with a conveyor. To make uniform the quantity of water on the sand particles various methods may be used.

According to this invention, since the green concrete is projected against a surface by centrifugal force without using any high pressure air there is no sputtering of the projected concrete caused by the high pressure air and the applied concrete is compressed by the velocity energy of subsequently projected green concrete. Although the flowable slurry material conveyed by a pump has a sufficiently high fluidity, as it is thoroughly admixed with dry materials on the rotary disc, the concrete product after projection has a sufficiently high shear strength. More particularly, during the admixture, due to the dry materials the ratio W/C is decreased, while the ratio S/C or A/C is increased so that the shear strength of the product can be improved. In other words, a concrete layer having a sufficient thickness can be formed by a single projection.

Furthermore, according to this invention, the quick setting agent can be used more efficiently. For example, when the apparatus of this invention is used for the wet method, the quick setting agent is added in a dry state. In this case, it is possible to uniformly admix the quick setting agent with green concrete or green mortar conveyed through the central pipe 1 3 by using an agitator as shown in Figure 7 or 11, thus improving the action of the quick setting agent.In a dry method, the quick setting agent is supplied together with such dry ingredients as cement powder and aggregate; the quick setting agent will be uniformly admixed with dry ingredients until they arrive at the rotary disc 1 8. According to the prior art blasting method, immediately prior to the blasting (that is at the nozzle) as the quick setting agent is added t6 the viscous material with its W/C and S/C ratios suQ$.ly-adjusted, particles of the quick setting agent would adhere to the surface of lump or particle shaped viscous material, thus failing to uniformly dispersing the quick setting agent. Where high pressure air is used for blasting, fine particles of the quick setting agent would float in the surrounding atmosphere thus forming a stimulative atmosphere.According to this invention as above described, since the quick setting agent can be uniformly distributed and since no high pressure air is used, the defects described above can be obviated.

When an aggregate formed with cement shells is supplied through the supply cylinder 12 in a dry state, a relatively low speed quick setting agent is used to prevent setting in the supply tube.

As above described, according to this invention, since the quick setting agent is uniformly distributed and no high pressure air is used, the quantity of the quick setting agent can be reduced, which is not only economical but also improves the strength of the resulting concrete structure over a long time.

In a modification shown in Figure 13, a plurality of material supply pipes are provided through the central pipe 13. More particularly a main ingredient supply pipe 1 3a and an auxiliary supply pipe 1 3b are inserted through the central pipe 1 3 and these supply pipes are connected with conduits 1 30a and 1 30b respectively.

Materials are supplied to the supply pipes 1 30a and 1 30b and to the hopper 11 in a manner as shown in Figure 14. More particularly, materials taken out from the tank 64 are sent to the hopper 11 of the projector 1 via a conveyor 64a, while main and auxiliary materials are supplied to the supply pipes 1 3a and 1 3b in the central pipe 13 from tanks 65 and 66 via flow meters 67 and pump 68. For example, where a resin concrete is to be projected, a main material of the resin concrete and a quick setting agent are contained in the main and auxiliary tanks 65 and 67 respectively, and such aggregate as silicate sand or stone is discharged from the tank 64.

When the apparatus shown in Figure 14 is used for coating the inner surface of a tunnel, the tanks 64, 65 and 66 and projector 1 are installed in a tunnel A, and a mixture is supplied to the tank 64 from a mixer 70 installed on the outside of the tunnel A. Conventional feeders 71-74 are provided for the mixer 70 to supply such materials as cement, a powder of a quick setting agent, a fine aggregate such as sand, and a coarse aggregate such as gravel or crushed stone. Water is supplied to the main tank 65, while a liquid quick setting agent is supplied to the auxiliary tank 66. Then the apparatus of this invention can be satisfactorily used for the dry process.

In the foregoing description, although flowable material such as cement paste or mortar or liquid was fed through the central pipe 13 and a dry aggregate and or additives were fed through the supply cylinder 12, it will be clear that the invention is not limited to such arrangement. Briefly stated, according to this invention, among first and second materials necessary to prepare green concrete or mortar to be projected are prepared, the first material is conveyed through the central pipe 13 with low pressure air or a pump and the second material is loaded into the supply cylinder 12 through hopper 11 and then mechanically conveyed with screw conveyor 1 9. Finally, these materials are admixed and projected by a rotary projector. Since the central pipe 13 has a smaller diameter than the supply cylinder 12 and since the first material is conveyed through the central pipe under pressure, the first material should have a fluidity of a certain degree. On the other hand, the second material is not required to be flowable, because it is conveyed to the hopper with a conveyor belt or a large diameter pipe and then mechanically conveyed by a screw conveyor 1 9.

Considering these factors, an arrangement shown in Figure 1 6 is suitable for use in the apparatus of this invention for the wet method. The projector 1 and the preparation device 120 for a quick setting agent are installed in a tunnel, and a green concrete conveyed by a concrete mixer car 117 is supplied to the hopper 11 by a pump 118 and a conduit 119 and then mechanically conveyed by a screw conveyor 1 9. Where a liquid agent is used, it is supplied through the central pipe 1 3 under its hydrostatic pressure, whereas when a powdery quick setting agent is used it is conveyed by air pressure. The preparation and conveyance of the materials are the same as the prior art wet method, and the fluidity of the green concrete prepared to have a desired ratio W/C is also small.However, according to this invention, only the conveyance of the green concrete to the hopper 11 is important and no blasting energy is required. Accordingly, it is possible to greatly reduce the pressure necessary for conveyance and to increase the length of conveyance.

In the projector shown in Figures 1-16, the green concrete is projected in a direction perpendicular to the direction of conveyance. Figures 17 and 18 show modified projectors capable of obliquely projecting the green concrete. In working a tunnel, a framework is generally fabricated with H shaped steel bars or the like so that with a projector that projects only in the vertical direction, it is difficult to project concrete into the framework. Consequently the projected concrete does not efficiently bond to the framework. But where a projector as shown in Figure 17 or 1 8 is used the green concrete can be efficiently projected into the framework.In the modified projector an annular auxiliary projection plate 180 having an inclined guide surface 181 is secured to the discharge end of the rotary disc 1 8, the auxiliary projection plate 1 80 being also provided with blades 1 86. In a case shown in Figure 17, the guide plate 1 81 is directed forwardly, whereas in a case shown in Figure 18, the guide plate 181 is directed rearwardly. It is advantageous to prepared both types of the guide plate and selected one of them is secured to the rotary disc with set screws 1 83 and 1 84. The auxiliary projecting plate 180 may be divided into a plurality of sections for facilitating assembly.

When these modified projectors are used, the direction of the projected green concrete is determined by the guide surface 181 ofthe auxiliary projection plate 180 as shown in Figure 17 so that when a framework is fabricated with H type steel stocks 1 50 on the inner surface a tunnel, the concrete is efficiently projected into the framwork 1 50 thus preventing formation of voids in the projected concrete.

When the green concrete is to be projected against the opposite side of the framework the direction of movement of the apparatus is reversed or reciprocated, or the auxiliary projecting plate 1 80 shown in Figure 18 is used. The agitator 85 shown in Figure 17 is constituted by blades 87 and 88 and is slightly different from those shown in Figures 7 and 11 but operates similarly.

Figures 19 and 20 show still another embodiment of this invention especially suitable for use in a circular tunnel to obtain a smooth finished surface. The circular tunnel has a high pressure resistant property characteristic and where water is passed therethrough it can resist against the water pressure.

When a concrete coating is applied with a prior art blasting method the surface of the blasted concrete layer becomes irregular so that it is necessary to blast again concrete mortar to obtain a smooth finish surface.

The modification shown in Figures 19 and 20 is constructed to eliminate these disadvantages. At first a shell 100 made of steel plate is applied to the inner surface of a tunnel, and a carriage 10 supporting blasting apparatus of this invention is run along rails 113. A green concrete is supplied to the rotary disc 18 to project the concrete by centrifugal force. Ironing plates 108 are rotated concentrically with the rotary disc 18 to finish the surface of the projected concrete layer 128. More particularly, the rotary disc 18 is mounted on the front end of the rotary cylinder 14 and is rotated by an electric motor 114 through gears 11 4a and 14a.A cover 1 Oa is provided for the front end of the carriage 10, and a large diameter ring gear 109 is rotatably supported by a support 1 Ob in the cover 1 Oa. A circular disc 107 is secured to the gear 109 through connecting rods 106. A plurality of ironing member supporting members 1 07a are mounted on the periphery of the disc 107 at an equal spacing, and the ironing members 108 are secured to the supporting members 1 07a by rods 111. A gear 11 4h driven by the motor 114 engages the inner gear of the ring gear 109 to drive the same. Rails 113 on which the carriage 1 0 runs are embedded in a concrete layer 128 formed by projection so that these rails act to reinforce the concrete layer.

In addition to various advantages described in connection with Figures 1 through 18, with the embodiment shown in Figures 19 and 20 the ironing members 108 apply pressure to the coated concrete layer to smoothly finish its surface and to make uniform its thickness.

To have better understanding of this invention, the following examples are given in which all % are weight percent.

EXAMPLE 1 A batch mixer 22 and the dry material preparing device 4 were installed on the outside of a tunnel (mixer 21 and preparation device 3 were not used). River sand was conveyed from a yard 9 and loaded in the hoppers 23 and 42, and No. 6 crushed stone was loaded in the hopper 41 of the batch mixer 40 located on the outside of the tunnel. Cement was loaded in hopper 24 and a quick setting agent was loaded in hopper 43 to prepare materials to be projected. These materials were conveyed to the projector 1 installed in the tunnel and projected against the inner surface thereof having a diameter of 2.2 m. In this case no cement shell was formed and the mortar prepared by the mixer 21 had S/C = 1.5, and W/C = 39%. To this mortar were added sand, gravel, and a quick setting agent supplied from the preparation device 4 to obtain a green concrete having S/C = 3.7, W/C =43.5%, S/A = 70%, and containing 1 7.5 Kg/m3 of the quick setting agent. The rate of supply of the mortar through the central pipe 1 3 was 2.7 m3/h, while the rate of supply of dry materials by the screw conveyor was 8,200 kg/h.

The quantity of projected concrete was 6.3 m3/h. The pressure of the mortar pump 9 was relatively small, e.g., of the order of 4 Kg/cm2.

The quantity of dust produced in the tunnel, the quantity of rebound, and the strength of the resulting concrete are shown in the following Table I. After projection for 1.5 hours, no stimulative atmosphere was formed caused by the sputtering of the quick setting agent irrespective of the fact that the diameter of the tunnel was only 2.2 m.

EXAMPLE 2 In the same manner as in Example 1, mixer 22 and the preparation device 4 were used but instead of loading river sand into the mixer 22, sand with its surface water adjusted to 4% by the water content adjusting device was loaded in the hopper 42. Thus, the mixer 22 prepared a cement paste having a ratio W/C = 35% and the cement paste was conveyed through the central pipe 13, while all quantities of the fine and coarse aggregates were supplied to the supply cylinder 12. The supply quantity of the cement paste through the central pipe 13 was greatly reduced than the quantity of mortar in Example 1, that is, was about 1.4 m3/h, and the cement paste was conveyed under pressure of 2.8 Kg/cm2.The concrete projected had W/C = 48%, S/A = 60%, S/C = 3.3 and contained 350 Kg/m3 of cement, 1,142 Kg/m3 of sand, 770 Kg/m3 of No. 6 crushed stone, and 17.5 Kg/m3. of the quick setting agent.

The quantity of the dust produced is also shown in the following Table I. Since paste was fed through the central pipe, the quantity of dust was increased, but the quantity of rebound was decreased and the resulting concrete was found to have a high mechanical strength.

EXAMPLE 3 The continuous mixer 21 and the preparation device 3 shown in Figure 1 was used (mixer 22 and the preparation device 4 were not used) to prepare fine aggregate formed with shells. The fine aggregate used was river sand and its surface water was adjusted to 4% and this sand was loaded in hoppers 23 and 32. The same coarse aggregate and quick setting agent as in Example 1 were used. In mixer 21, cement and the primary water were incorporated into the sand from the hopper 23 to form shells containing water and cement at a ratio of W/C = 1 8%. Then the secondary water was added through pipe 27 to prepare a cement mortar having a ratio W/C = 39%.The resulting mortar was supplied through the central pipe 13 and after being admixed with materials sent from hoppers 31-33 via supply pipe 12, and the resulting green concrete was projected. The green concrete had ratios S/C =3.7, W/C = 43.5% and S/A = 70% and contained 1 7.5 Kg/m3 of the quick setting agent, which is the same as in Example 1. The torque of the pump 5 was 3 Kg/cm2, which was smaller by 25% than that of Example 1.

As shown in the following Table I, the quantity of dustwas reduced greatly, and the percentage of rebound was decreased by more than that of Example 2.

EXAMPLE 4 Cement was added to a mixture of sand having 4% of surface water and No. 6 dry crushed stone to form cement shells.

The projected green concrete had S/C = 2.3, W/C = 35%, S/A = 64% and contained 500 Kg/m3 of cement, 1,1 35 Kg/m3 of sand and 550 Kg/m3 of the crushed stone. In the case, since the coarse aggregate was also formed with cement shells the resulting concrete had larger strength than that Example 3.

The quantity of dust produced was a little larger than that of Example 3 but smaller than those of Examples 1 and 2. The quantity of rebound was extremely small. The green concrete of this Example could be projected just like that of Example 3.

The quantities of the dust generated, the percentage of rebound formed at the time of projecting green concrete of Examples 1-4, and the strengths of the resulting concretes are shown in the following Table I. The quantity of dust was measured after projecting the green concrete for 30 minutes without exchanging ambient air but it was found that even when the projecting time was increased beyond 30 minutes, the quantity did not change. In contrast, in the case of the prior art method, the quantity of dust reached 25-30 mg/m3 after blasting for 1 5 minutes, thus disenabling further operation. This means that the method and apparatus have greatly improved this defect.

TABLE I

Quantity | | Strength (kg/cm) Example dust produced Rebound No. . (mgIm3) (%) 7 days after 28 days after 1 3.5 22.0 209 285 2 3.8 12.0 218 293 3 1.6 10.5 240 320 4 2.4 8.5 430 582 EXAMPLE 5 Batch mixer 22 and dry material preparation device 4 shown in Figure 1 were installed in a tunnel.

Mountain sand S was used as the fine aggregate, No. 7 crushed stone G as the coarse aggregate, and a compound consisting essentially of an aluminate (trade name Natomic No. 5) as the quick setting agents.

These ingredients were mixed together. In the flowable material preparation device 2, the mountain sand S, an ordinary Portland cement C acting as a hydraulic powder, and water W were mixed together at weight ratios as shown in the following Table II.

TABLE II

Fundamental compositionm3 Flowable material conveyed by pump # Dry material dehydra- Quick Sample W/C C S W tion S G setting No. (%) S/C (kg) (kg) (kg) agent (I) (kg) (kg) agent (%) 1 47 1.75 350 612.5 | 161.7 2.8 790.2 357A 1.0 2 50 2.0 350 700 172.2 2.8 682 345 0 3 50 2.0 350 700 172.2 2.8 682 345 5.0 4 50 2.0 350 700 172.2 2.8 682 345 7.1 The rotary projector shown in Figure 7 was used. The rotary disc 18 thereof had a diameter of 50 cm and rotated at a speed of 500 r.p.m. The quantity of the mortar conveyed by the mortar pump 5 was 59 1/min in each Example. Quantities of the dry materials conveyed by the conveyor was 140.6 Kg/min in Example 1, and 109.2 Kg/min in Examples 2,3 and 4. The compositions of the green concrete projected upon the inner surface of a tunnel, percentage of rebound, and the strengths of the resulting concrete are shown in the following Table Ill.

TABLE III

Composition of projected cement/m Compression strength quick (kg/cm) setting Sample W/C S/A C S G W agent Rebound one day 7 days 28 days No. (%) S/C (%) (kg) (kg) (kg) (kg) (kg) (%) after after after 1 45.3 4.1 79.3 360 1495 390 163 3.6 19.6 - 219.6 251.9 2 49.2 4.0 79.7 356 1438 367 175 0 9.8 65.6 175.4 242.5 3 " " " " " " " 17.8 18.9 96.6 214.4 265.7 4 " " " " " " " 24.8 16.9 61.4 175.9 221.9 As can be noted from this table, the percentage of the dust was small in each Example so that the work could be continued after working over several tens of minutes to two or more hours.

EXAMPLE 6 The same conditions as in Example Gwere used but the composition and additives were changed as shown in the following Table IV.

TABLE IV

Fundamental composition/m Flowable material conveyed by pump Dry material quick dehydration setting Sample C S W W/C S/C agent S G agent C No. (kg) (kg) (kg) (%) (%) (I) additive (kg) (kg) (%) (kg) 1 350 1050 207.2 60 3.0 2.8 - 332.6 347 5 2 " 850 200.2 57 2.5 " - 509.2 347.4 " 3 " 612.5 161.7 47 1.75 " - 790.2 357.4 4.8 4 " 700 172.2 50 2.0 " - 682 345 5.1 5 " 850 200.2 57 2.5 " - 509.2 347.4 8.8 6 " " " " " " - " " 5.7 7 " " " " " " - " " 8.1 8 " 700 172.2 50 2.0 " viscosity 682 345 5.0 intensifier 0.05% 9 " " " " " " viscosity " " 4.5 intensifier 0.1% 10 " " " " " " steel fiber " " 7.1 0.5% 11 " - 115.5 33 - " - 1381 603.2 6.7 12 " - 115.5 " - " - 1285 566 2.8 150 13 " 700 234.7 67.1 2.0 " - 682 345 2.4 The quantity of the materials supplied to the rotary disc 18 through central pipe 1 3, and supply pipe 14, the number of revolutions of the rotary disc 18 and the composition of the green concrete prepared were varied variously as shown in the following Table V.

TABLE V

Discharged quantity Composition of projected cement (kg/m ) Number of quick revolutions Central supply hardening of rotary pipe pipe C S G W agent W/C S/C S/A disc 18 (l/min) (kg/min) (kg) (kg) (kg) (kg) (%) (%) (%) (rpm) 1 61.6 70 340 1396 407 201 17 59.1 4.1 77.4 500 2 41.9 87 308 1433 476 172 15.4 55.6 4.7 75.1 " 3 59 140.6 360 1495 390 163 17.3 45.3 4.1 79.3 " 4 " 109.2 356 1438 367 175 10 49.2 4.0 79.7 " 5 59 87 353 1415 387 197 31.1 55.8 " 78.5 " 6 " " " " " " 20.1 " " " 600 7 " " " " " " 28.6 " " " 700 8 " 109.2 356 1438 367 175 - 49.2 " 79.7 500 9 " " " " " " - " " " " 10 " " " " " " - " " " " 11 21.6 133 438 1184 515 200 21 45.7 2.7 70.3 " 12 " 127 569.8 1093 481 202 9.8 35.5 1.92 70 " 13 59 109.2 338 1384 358 226 81 66.9 4.1 79.4 " Remark: In example 13, the projector shown in Figs. 11 and 12 was used and its direction of rotation was reversed.

The compression strength of the resulting concretes, the quantity of the dust and percentage of rebound generated at the time of projecting green concretes of respective Examples are shown in the following Table VII.

TABLE VI

Compression strength (kg/m) Sample Rebound Dust No. 7 days after 28 days after (%) (mg/m) 1 169 245 17.6 2.1 2 183 263 19 1.8 3 175 279 12.5 2.0 4 180 251 14.8 2.5 5 173 232 12.4 1.5 6 215 284 13.3 1.2 7 201 253 10.2 2.3 8 174 226 12.4 1.9 9 193 289 19.9 3.0 10 221 272 11.9 3.1 11 284 352 12.6 2.3 12 389 476 14.8 2.5 13 165 253 9.1 2.3 As can be noted from this table the quantity of dust generated is small in each Example.

Claims (20)

1. A method of applying mortar or concrete, comprising: (a) preparing first and second materials necessary to constitute mortar or concrete; (b) conveying the first material to a working field with pressure means; (c) conveying the second materials to the working field with mechanical means; (d) mixing the first and second materials together at the working field; and (e) projecting the resulting mixture with rotational energy.

2. A method as claimed in claim 1, in which first material is flowable and the second material is in a dry state.

3. A method as claimed in claim 2, in which flowable first material comprises cement paste, green mortar, or green concrete.

4. A method as claimed in claim 2, in which the flowable first material comprises a slurry mortar formed by adding a powder of hydraulic substance to a fine aggregate covered with surface water to form shells of the hydraulic substance about the fine aggregate, adding water to the fine aggregate provided with the shells, and then mixing.

5. A method as claimed in any of claims 2 to 4, in which the dry second material comprises a fine aggregate, a coarse aggregate, or a quick setting agent, or a combination of at least two thereof.

6. A method as claimed in claim 1, in which the first material comprises a quick setting agent and the second material comprises green concrete prepared to have a predetermined water to cement ratio.

7. Apparatus for projecting mortar or concrete, comprising: (a) a first material supply pipe for conveying under pressure a first material, being one of the ingredients of the mortar or concrete; (b) a hopper for receiving a second material, being the other ingredient of the mortar or concrete; (c) a second material supply pipe connected to the hopper; (d) a rotary screw disposed in the second material supply pipe for mechanically conveying the second material supplied from the hopper; and (e) a rotary disc for mixing the first and second materials conveyed to the disc through the first and second material supply pipes and projecting the resulting mixture, the discharge end portions of the first and second material supply pipes extending along the rotational axis of the disc and being arranged one inside the other.

8. Apparatus as claimed in claim 7, including means for controlling the direction of projection of the mixture from the disc.

9. Apparatus as claimed in claim 7, in which the discharge end of the second material supply pipe extends close to the disc and is provided with a notch for controlling the direction of projection of the mixture.

1 0. Apparatus as claimed in claim 9, including means for rotating the second material supply pipe.

11. Apparatus as claimed in any of claims 7 to 10, in which the central region of the disc is provided with means for agitating the mixture.

12. Apparatus as claimed in claim 11, in which the disc comprises an outer ring and a central disc body removably mounted in the outer ring, the said agitating means being supported by the central disc body.

13. Apparatus as claimed in any of claims 7 to 12, in which the rotary screw is secured to the outside of the first material supply pipe.

14. Apparatus as claimed in any of claims 7 to 12, in which the rotary screw is secured to the inside of the second material supply pipe.

15. Apparatus as claimed in any of claims 7 to 14, in which the first material supply pipe accommodates a main ingredient supply pipe and an auxiliary ingredient supply pipe.

1 6. Apparatus as claimed in claim 7, in which the disc is provided with annular projecting means having a projecting surface inclined to the disc.

1 7. Apparatus as claimed in claim 7, in which the disc is provided with a plurality of ironing members arranged on a circle having a larger diameter than the disc, for smoothing the surface of a projected layer.

1 8. A method of applying mortar or concrete, substantially as described with reference to any of the embodiments illustrated in the accompanying drawings.

1 9. A method of applying mortar or concrete, substantially as described in any of the Examples.

20. Apparatus for projecting mortar or concrete, substantially as described with reference to any of the embodiments illustrated in the accompanying drawings.