GB2048446A

GB2048446A - Drying fine granular material, particularly in the preparation of mortar or concrete

Info

Publication number: GB2048446A
Application number: GB8008468A
Authority: GB
Original assignee: Taisei Corp
Current assignee: Taisei Corp
Priority date: 1979-03-13
Filing date: 1980-03-13
Publication date: 1980-12-10
Also published as: CH649225A5; FR2457166A1; FR2457166B1; GB2111659A; FR2457165A1; DE3009332A1; FR2457165B1; GB2048446B; GB2111659B

Abstract

The quantity of water on the surface of sand particles is reduced by applying an impulsive force, e.g. centrifugal force created by a rotating disc 2. The sand thus produced is especially suitable for preparing a green concrete compound or a cement mortar by mixing with water, gravel, and cement. The disc 2, which may have radial vanes 7, is rotated about a vertical axis by an electric motor 4, the wet sand being flung against an annular ring 6, water being removed by impact. A water spray pipe 16 may be provided in the hopper 1. In other embodiments (Figs. 17 to 20, not shown) the wet sand is propelled by rotors or by endless belts onto fixed impact plates, or by an air blast (Fig. 19). <IMAGE>

Description

SPECIFICATION Adjusting the quantity of liquid deposited on fine granular material, particularly in the preparation of mortar or concrete This invention relates to a method and aparatus for adjusting the quantity of liquid, typically water, deposited on the surface of the particles fine granular material, and a method of preparing mortar or concrete by utilizing the treated granular material.

Fine aggregates comprising river or mountain sand or artificial fine particles are widely used to prepare cement mortar or limestone type hydraulic mortar which is used to construct buildings and many other civil engineering structures. When digging or crushing various ores utilized in metallurgy or ceramic industry and coal, fine particles or dust are formed. Further, depending upon the field of use, it is necessary to crush the ores or coal into granules having a predetermined size.

When pulverizing or refining these substances or when using them for chemical reactions, fine granulates in the form of sludge or the like are often forded. As is well known, these fine granulates contain substantial quantity of water adhering to the surface of the grains.

This is true not only for river or mountain sand but also coal. Especially, in recent years these substances are excavated by using jet water so that the quantity of the deposited water is large. Even a converter slag, which is free from water when it is formed becomes wet when water is used to collect it. Moreover, as these materials are stored in the outdoor they are wetted by rain, dew, or snow.

Such wet particles can not be used directly.

For example, when sintering these material or converting them to coke, and even when they are directly charged in a furnace, it is necessary to preliminarily dry them before actual use. This requires extra heat energy, i.e. fuel.

As will be described later in more detail, when a fine aggregate composed of river or mountain sand is used for the preparation of mortar or cement, the quantity of the deposited or surface water is an important factor which influences the quality of the product.

Although the composition and particle size of sand also influence the quality of the product, so long as sand collected from the same source is used it is easy to utilize sand having the same composition and particle size, and it is rare to admix sands from different sorces.

When the sand contains particles of different size it is easy to classify them into fine, medium, and coarse particles with aisieve, and a small difference in the particle size does not result in a great difference in the quality of the product. However, the quantity of the surface water varies greatly depending upon the source and the methods of collecting, conveying, and storing the sand. Moreover, the specific surface area of the fine particles of sand is large, so that the relative quantity of the deposited water is large. Moreover, sand contains water in the interstices of the sand particles, which varies from time to time depending upon weather conditions. More particularly, when sand from the same source is piled up on the ground, its water content varies at the top and the bottom, and in the morning and at noon.

When preparing cement mortar or concrete by using a fine aggregate, the ratio of water to cement (W/C), the ratio of cement to sand (C/S), and the ratio of sand or cement to gravel or other coarse aggregate (S/G or C/G) have a great influence upon the strength of the resulting product and on its fluidity, moldability, and workability. Thus, when an excessive quantity of water is incorporated, segregation and breezing are inevitable, thus decreasing the mechanical strength of the product. On the other hand deficient water impairs moldability and pouring property, so that even when vibration or pressure is applied at the time of molding or pouring it is difficult to obtain a dense structure, and this also decreases the mechanical strength.As above described, nothwithstanding the fact that it is essential to select adequate W/C etc., as the quantity of the deposited water varies greatly and as it is difficult to simply and accurately measure the quantity of the surface water, it is difficult to realize ideal ratios W/C, S/C, etc. Although it has been proposed to completely dry the fine aggregate or to measure the qeight thereof in water, such methods are not suitable in the field where a large quantity of sand is used. More particularly, the former method requires a large quantity of heat energy and time and the latter method requires a step of perfectly permeating the sand with water so as to drive off air (according to JIS (Japanese Industrial Standard) it is prescribed to immerse the sand in water for 24 hours) and a step of draining the water contained in the sand.

What is desired is a method and apparatus for quickly and accurately adjusting the quantity of water deposited on fine granular aggregate, whereby, for example, cement mortar or concrete of improved quality can be prepared by utilizing the fine aggregate with its quantity of surface water adjusted to a desired value.

According to one aspect of this invention there is provided a method of adjusting a quantity of liquid of deposited on fine particles, i.e. sand, comprising the steps successively s supplying a predetermined quantity of the fine particle deposited with liquid, and then applying an impact force larger than the adhesive force of the liquid to the fine parti cles thereby removing the deposited liquid.

According to another aspect of this invention there is provided apparatus for separating liquid from fine particles comprising liquid separating means for applying a impulse force to the fine particles so as to remove excess liquid deposited on the particles and means for successively supplying the fine particles to the liquid separating means.

The impact force can be due to kinetic energy imparted by centrifugal force created by a rotating disc, a conveyor running at a high speed, or pressurized gas.

The invention is especially suitable to adjust the quantity of water on sand particles which are used to prepare cement mortar or a green concrete compound. The quantity of water remaining on the surface of the sand particles is used to determine the quantity of water to be subsequently added to a mixture of sand, gravel, and cement.

In the accompanying drawings: Figure 1 is a general side view showing one example of the apparatus utilized to carry out the method of the invention; Figure 2 is a longitudinal sectional view of the water separator A shown in Fig. 1; Figure 3 is a longitudinal sectional view showing a modified water separator; Figure 4 is a partial longitudinal sectional view showing a modification of the water separator shown in Fig. 3; Figure 5 is a side view of the water separator with auxiliary equipments; Figure 6 is a longitudinal sectional view showing the upper portion of a modified water separator; Figure 7 is a perspective view showing an impact frame shown in Fig. 6 Figure 8 is a plan view of the rotating disc shown in Fig. 6 taken along a line VIll-VIll; Figure 9 is a sectional plan view taken along a line IX-IX in Fig. 6;; Figure 10 is a side view, partly in longitudina#l section, of another embodiment of the water separator; Figure 11 is a perspective view showing a manner of attaching a section of an impact surface Figure 12 is an enlarged sectional view showing the relationship between the impact surface, a cleaning water tank, a water receiving tank, and a receptacle; Figure 13 is a partial sectional view showing means for removing deposited sand particles; Figures 14 and 15 show modified means for removing the deposited sand particles, which are simpler than that shown in Fig. 13 Figure 16 is a sectional view showing another embodiment of the water separator not utilizing a rotating disc Figures 17, 18A, 18B, 19, and 20 show still other modifications of the water separator; Figure 21 is a graph showing the result of water removal;; Figure 22 is a longitudinal sectional view showing one example of a mixer; Figure 23 is a cross-sectional view of the mixing chamber shown in Fig. 22 taken along a line XXIII-XXIII Figure 24 is a cross-sectional view showing a modified pressure applying chamber; Figures 25 and 26 are longitudinal sectional views showing modified mixers; Figure 27 is a longitudinal sectional view showing still another mixer; Figure 28 is a cross-sectional view of the mixer shown in Fig. 27 taken along a line XXVIII-XXVIII; Figures 29 and 30 are perspective views showing the relative arrangement of the main and auxiliary mixing members; Figure 31 is longitudinal view showing a modified mixing chamber Figure 32 is a perspective view showing the modified mixing chamber shown in Fig. 31; and Figures 33 and 34 are sectional views showing modified mixing members.

Before describing preferred embodiments of the invention in detail with reference to the accompanying drawings, the principle and advantages of the invention will firstly be described.

Where excessive surface water is removed by heat or wind power it is not only difficult to accurately adjust the quantity of water deposited on the fine aggregate but also requires a large quantity of heat energy and time. As above described according to this invention, the quantity of water is adjusted by applying an impact force or velocity energy to the fine aggregate but with this improved method the quantity of water that can be efficiently removed varies depending upon the quantity of water originally contained. For this reason the impulse force applied to the sand must be determined depending upon the quantity of water originally contained. The impact force or shock can be applied by beating but it is more advantageous to apply it as velocity energy.Where the quantity of the deposited water is relatively large, use of the velocity energy caused by gravity is effective to remove a certain amount of water.

More advantageous velocity energy is that utilizing wind power, rotating force, or centrifugal force. One or combinations of two or more of these velocity energies can be used.

It is also possible to sprinkle the particles of the coarse aggregate by applying thereto the velocity energy of rotating force or centrifugal force to cause the sprinkled particles to collide against a surface to remove the surface water.

Alternatively, while the particles are standstill or slowly dropping under gravity an impact force may be applied to cause the particles to collide against a rotating body. In each case, the surface water is transferred to the surface or body collided by the particles to adjust the quantity of water remaining on the surface thereof. Thus, the quantity of remaining water is inversely proportional to the strength of the impact force whereby the quantity of the remaining water can be adjusted to a desired value by suitably selecting the strength of the impact force. In other words, irrespective of the particle size (fine, medium, or coarse) of a fine aggregate which usually contain a relatively small amount of water, for example 2 to 4%, the water can be removed adequately by using a suitable impact force.However the quantity of the deposited water is large for example 7-8% or more, water beyond a certain limit can be removed by the impact energy, the degree of removal being proportional to the impact energy. A fine aggregate whose quantity of deposited water varies in a relatively small range, for example from 2.5-6% is advantageous to determine the quantities of water and cement to be incorporated subsequently. When the quantity of the water deposited on the particles of the fine aggregate is reduced or adjusted to a predetermined value, it is possible to readily obtain desired ratios of W/C, C/S, and G/S, thus ensuring uniform quality of the resulting product.

From the standpoint of cost of installation and operating power, it is advantageous to cause the particles of the fine aggregate to collide against a stationary surface by using a rotating disc in which case the particles are supplied to the central portion of the disc to cause them to fly by centrifugal force. The sand often contains mud or clay which deposit on the surface of the sand particles, and in an extreme case the layer of the deposited mud or clay bonds together the particles of the fine aggregate colliding thereupon to increase the thickness of the layer. Further, the deposited layer acts as a cushion layer to decrease the impact force applied to the particles thereby varying the quantity of the deposited water even with the same impact force.

In such a case it is necessary to clean the stationary surface with water or with a rotating wiper or by rotating the surface.

In cold season, water containing sand freezes, in which case the sand is defrozen with steam to separate its particles. When sea and sand is used salt contained therein can ge removed when the quantity of the deposited water is reduced by the method of this invention.

Fig. 1 is a side view of one example utilized to carry out the method of this invention which comprises an impact water separator A into which a fine aggregate is continuously supplied by a conveyor or the like and a mixer B. It is advantageous that the mixer B is of a continuous type and provided with mechanisms C, D, and E respectively for incorporating a powder of hydraulic substance, water, and such additives as a dispersing agent.

Although any type of impact water separator A can be usd in this invention, a preferred separator shown in Fig. 2 comprises a hopper 1, a rotating disc 2 disposed beneath the hopper 1. The rotary disc 2 is provided with a central opening 12 to receive the fine aggregate from the hopper and a plurality of radial vanes 7. The rotary disc 2 is supported by a rotatable sleeve 13 supported by a stationary sleeve 14 through bearings 3. The sleeve 13 is rotated by an electric motor 4 through pulleys 5 and 15 and a belt passing about these pulleys. An annular ring 6 is disposed to surround the rotary disc 2 with a suitable distance therebetween, the annular ring being detachably mounted on the inner side of a lower frust conical hollow casing 10. Funnel shaped receiver 8 is contained in the lower portion of the lower casing 10 with a suitable gap therebetween.Adjacent the discharge opening 18 at the lower end of the receiver 8 is disposed a conveyor 11 for receiving the fine aggregate which falls down after collision against the annular ring 6. The annular ring 6 is slightly inclined, and if desired its upper edge may be bent inwardly for preventing upward sprinkling of the sand particle. With this construction vanes 7 may be omitted. By increasing the inclination angle of the annular ring the collection of the sand particles by the receiver 8 can be improved. A water spray pipe 16 is provided at the lower end of the hopper 1 and if desired a screw type or ribbon type agitator may be provided at the lower end of the hopper to uniformly apply a suitable quantity of water to the sand particles. The water separated by the collision against the annular ring falls down as shown by dotted line arrows to the bottom of the lower casing 10.

Fig. 3 shows a modified water separator. A utilized in this invention in which the relative arrangement of the hopper 1, rotating disc 2, the motor 4, th sleeve 13, and the motor 4 is generally similar.to that of the first embodiment. However, the annular ring or impact plate 6 against which the sand particle are ejected by the centrifugal force created by the rotating disc 2 is interposed between separated upper portions of a bell shaped receiver 10 and reinforced by an outer ring 1 8a secured to the annular ring by screws 19. This construction allows ready exchange of the annular ring 6. The lower end 20 is bulged outwardly to receive the upper end of a receptacle 9 supported by a frame 22.A small gap is defined between the upper end of the receptacle 9 and the bulged out end 20 to permit passage of the separated water, whereas dehydrated sand particles fall down into the receptacle.

Although not shown in Fig. 3, it should be understood that a conveyor is installed beneath the receptacle in the same manner as in Fig. 2 to convey the sand particles to the mixer B shown in Fig. 1 The casing 10 of the water separator shown in Fig. 3 may be modified as shown in Fig. 4 and various auxiliary equipments may be provided as shown in Fig. 5. Thus, as shown in Fig. 4, a plurality of telescoped annular members 9a and 9b connected by connecting members 31 to the upper edge member 9e of the receptacle 9 are disposed within the annular ring 6. The upper ends of respective annular members 9a, 9b, and 9care sharped to define a passage for passing air and water together with the inner surface of the casing 10.These knife edge shaped upper ends further function to deflect the sand particles moving along the inner surface of the casing 10 away therefrom toward the inside of the receptacle 9.

An annular rotating disc 2a slightly inclined toward lower as shown by dotted lines may be attached to the rotating disc 2 for directing the sand particles to the lower side. With this construction the projected sand particles are blasted against the lower portion of the annular ring 6 but a centrifugal force sufficient to separate the sand particles can be applied by the inclined auxiliary rotating disc 2a so that the vanes 7 may be omitted. In this case, the spacings between the annular members 9a, 9b, and 9cand the casing 10 may be made smaller than those shown in Fig. 4.

When the water separator shown in Fig. 4 is operated under optimum operating conditions to be described later, the substance that flows downwardly along the inner surface of the casing consists essentially of water and mud which can be discarded.

However, optimum operating conditions are not always obtained depending upon the characteristic of the sand particles. In such a case, the substance falling to the outside of the receptacle 9 through a gap between the lower inner surface of the casing 10 and the knife edge shaped portion 9c is separated into water, mud and sand particles which can be recharged into the hopper 1 by a conveyor or the like. The water component separated by the water separator may be used to prepare concrete mortar in the subsequent step.

Fig. 5 shows one example of a practical installation designed by taking into consideration above described factors. More particularly, an elongated inclined trough 34 is installed beneath the lower end of the casing 10 and the receptacle 9 is formed like a funnel with its lower end 18b faced to a conveyor 11 so that certain amount of the sand particles adjusted their water quantity accumulates in the lower portion of the receptacle 9 so as to substantially seal the same. A discharge pipe 34a is provided between the lower end of the trough 34 and a funnel shaped water receiver 36 contained in a drain water tank 35 for accumulating the separated water in the water receiver 36. An inclined endless conveyor 33 with pick up pieces 33a is provided to discharge solid components accumulated in the bottom portion of the receiver 36 out of the water tank 18.Also a discharge pipe 32 having a suction port 23 is provided to discharge the water in the water tank 35 by a suitable pump, not shown, for using the water to prepare cement mortar or concrete. A water feed pipe 25 having a level detector 24 is provided for the water tank 35 so as to maintain the level of the water contained therein always at a constant level. If desired, the water feed pipe 25 may be opened in the trough 34 to clean the same or opened near the discharge end of a conveyor 30 utilized to load sand particles into the hopper 1 for adding water to the sand particles.

Although the purpose of the water separator of this invention is to adjust the quantity of the water deposited on the sand particles, that is the surface water, when the sand is substantially dry, i.e. contains only a small quantity of water, it is necessary to add water to the sand contained in the hopper 1. As above described, in some cases, the sand contains mud or clay which tends to adhere to the surface of the annular ring 6 especially when the water content of the sand is low, so that addition of water is effective. Thus, the added water removes the mud or clay deposited on the annular ring.

Where the tendency of depositing mud or clay on the inner surface of the annular ring 6 is large a scraper 28 is mounted on the lower end of a shaft 27 rotated by a motor 4a at a relatively low speed, for example less than 10 rev/min. A layer of mud deposited on the annular ring 6 acts as a cushion layer so that the effect of adjusting the quantity of water by using an impact force would be impaired.

Moreover, the adhesive layer of the deposited mud arrests the sand particles. Where such adhesive mud layer is removed by the scraper 28, the efficiency of adjusting the water quantity can be improved.

A screw 29 may be mounted on the vertical shaft 27 to constantly feed the sand onto the rotating disc 2 from the hopper 1. Variation in the quantity of the sand supplied to the rotating disc 2 prevents uniform adjustment of the water content.

Details of modified water separator are shown in Figs. 6 to 9. As shown in Fig. 6, a vertical supply pipe 51 a connected to the bottom of a hopper 51 is directed to the central portion of a rotating disc 52 and at the lower end of the supply pipe 51 a are formed discharge openings 51 b on the opposite sides. As shown in Fig. 8, the rotating disc 52 is provided with a plurality of radial vanes 57 for distributing and projecting sand particles supplied through the discharge openings 51 b. As shown in Figs. 7 and 9, the rotating disc 52 is contained in an inverted dish shaped rectangular impact frame 60 so that the projected sand particles collide against the inner surface 60a of the impact frame 60.

The lower end thereof surrounds the upper end of a receptacle 59 with gaps 59a therebetween, and water receiving troughs 58 are mounted near the upper ends of the shorter sides of the receptacle to receive separated water through gaps 59a. A bushing 54 adapted to support the rotating disc 52 is rotatably supported by a supporting cylinder 56 at the upper center of the impact frame 60 through bearings 53 and pulley 55 is secured to the upper end of the bushing 54 for rotating the rotating disc at a predetermined speed by an electric motor, not shown.

The modified embodiment shown in Figs. 6 to 9 operates as follows: Thus, the sand particles supplied from the hopper 51 is discharged on the rotating disc 52 in the specified direction, i.e. about the middle of the longer sides of the impact frame 60 in case of example shown in Fig. 9 and the sand particles projected by the rotating disc 52 are directed mainly to the shorter sides of the impact frame 60. The sand particles projected upon the longer sides will be guided to the shorter sides by an angle between the projection and the longer sides. In other words, substantially all portions of the projected sand particles would collide upon the shorter sides where excessive water is removed by the impact force, whereby sand particles with adjusted quantity of water would be collected in the receptacle.The separated water flows down along the inner surface 60a of the impact frame 60 and then received by troughs 58. Mud or clay contained in the original sand is also collected in the troughs 58. With this modification, as substantially all projected sand particles are caused to collide upon the shorter sides, the efficiency of water quantity adjustment can be improved.

Still another modification of the water separator and various modifications of its parts are shown in Figs. 10 to 15. In the modification shown in Figs. 10 to 12 an impact frame 60b takes the form of an inverted frustum of a cone and is constructed such that its impact surfaces can be exchanged. The sand particles from a hopper 51 are caused to collide upon the inner surface of the impact frame to be removed excess water. Since the sand pa#rticles are abrasive, the inner surface of the impact frame 60b wears rapidly. Accordingly, an impact plate 68 is divided into a plurality of section and each section is secured to the impact frame through a packing 68b by a fastener 68 c as shown in Figs. 10 and 11. To exchange a section it is inclined by a handle 68a and then pulled out of the impact frame 60b through an opening 60c.About the lower skirt 60d a portion of the impact frame 60b is provided with an annular water tank 62. Cleaning water is supplied into the water tank 62 through an inlet port 62a to a level higher than the upper edge of the skirt 60d by h. The purpose of the cleaning water is to prevent stagnation of mud contained in the water. The water overflows through a discharge port 62b into a water receiving trough 58. Also the water flows along the inner surface of the skirt 62dtoward the water receiving trough 58.

When the water separator is used in the field, the sand particles tend to adhere to the inner surface of the receptacle 59. To prevent this tendency, a vibrator 61 is installed in the receptacle 59. The sand particles adhere especially to the upper portion of the receptacle, so means for removing the deposited sand particles are provided for the upper portion as shown in Figs. 13, 14, and 15.

In an example shown in Fig. 13, an air bag 67 is interposed between the side wall 59a of the receptacle 59 and a hard rubber ring 66.

By periodically varying the air pressure in the air bag 67 the sand particles deposited on the inner surface of the hard rubber ring 66 can be readily removed. In the example shown in Fig. 14, only the hard rubber ring 66 is secured to the upper edge receptacle 59.

Even with this simple construction, the hard rubber ring 66 is caused to vibrate by the sand particles blasted thereon, thus peeling off the deposited sand particles. In the example shown in Fig. 15 a hard rubber ring 66a is secured to the upper portion 59a of the receptacle 59 with a suitable air gap 65 therebetween. With the construction shown in Fig. 15, the hard rubber ring 66a can vibrate more freely to more efficiently remove the deposited sand particles.

In the water separator described above, since the mud deposited on the skirt 60 and the sand particles deposited on the upper portion of the receptacle increase their volume with time, these deposited substances prevent smooth flow of water or sand particles; it will be clearly noted that use of the means for removing deposited substances is advantageous. When a rotating disc provided with vanes is used, air flow is created along the wall surfaces which is more or less effective to prevent deposition, but where the sand particles deposit, it will prevent smooth flow of air and grows rapidly.

Fig. 16 shows another example of the water separator with removes excessive water by an impact force without utilizing the centrifugal force created by the rotating disc. In this modification, a fine aggregate, i.e. sand, is loaded into a hopper 1 by a conveyor 71 and then supplied to a horizontal rotor 77 provided with a plurality of radial vanes 79 by a metering device 76 which sequentially supplies the sand of a definite quantity. The rotor 77 is rotated by an electric motor 74 to apply a definite impact force to the sand particle received by the rotor. In front of the rotor 77 are disposed first to third hoppers 84, 85, and 86 to receive sand particles projected in the foreward direction by the rotor 77. Each hopper is provided with a discharge damper 83 for discharging sand particles collected in the hopper.

More particularly, the first hopper 84 is used to receive water and mud deposited on the sand particles, whereas the second and third hoppers 85 and 86 are used to receive sand particles with their surface water has been adjusted. The hopper 86 collects coarse sand particles. Generally speaking, the sand particles impacted by the rotor are projected over different distances depending upon the mass of the sand particles. Water content adheres to the vanes and gathered at the tip of the vanes 79 by centrifugal force and then discharged into the hopper 84 in the form of drops. A cover 200 is provided to cover hoppers 84, 85, and 86 which are partitioned by adjustable partition plates 81.

As above described, with the water separator shown in Fig. 16, excess water is removed by an impact force while the sand particles are classified according to their particle size.

Since the quantity of water remaining on the treated sand particles differs depending upon the particle size, this modified water separator is especially suitable fo a fine aggregate containing particles of different size because the sand particles are classified according to their size. Accordingly, the sand particles collected in each of the hoppers 85 and 86 have substantially the same particle size and the quantity of water remaining on the sand particles is also substantially constant.

Still another embodiments of the water separator are illustrated in Figs. 17 and 18. In Fig. 17, the fine aggregate, i.e. sand, is caused to drop between a pair of parallel spaced-apart hard rubber rotors 75 which are rotated at a speed higher than the falling speed of the sand, and is then discharged downwardly to impinge upon an inclined impact plate 78 secured by a fastener 78c.

Then, the water deposited on the surface of the sand particles is separated and the sand particles are deflected toward the left as shown by solid arrows to be taken out through a discharge port 73. The separated water and mud are'collected in a trough 74.

Cleaning water is supplied and discharged from a storage tank 62 through inlet and outlet ports 62a and 62b in the same manner as in the embodiment shown in Fig. 12 to wash away mud accumulated on the rear side of the skirt 62d. The sand particles may be projected in the horizontal direction or slightly downwardly in the same manner as in Figs. 6 to 15. Furthermore, two or more pairs of the rotors 75 may be juxtaposed to increase the quantity of the sand to be treated.

In still another modification shown in Fig.

18A, the sand particles dropping from the hopper are projected at a high speed against an inclined impact plate 78 secured by a fastener 78e by means of a pair of conveyors 72 running at a high speed, and cleaning water is supplied to a skirt 62d at a lower position than the impact plate 78 to prevent mud from adhering to the inner surface of the skirt. By the high speed belt conveyors 72 a large velocity energy is applied to the projected sand particles regardless of the quantity thereof. Where it is not desired to run the belt conveyors 72 at a high speed, the upper belt conveyor 72 is replaced by a rotating member 80 situated at the discharge end of the lower belt conveyor so as to impart the required velocity energy.Where the belt conveyors are run at a high speed, the sand particles tend to jump and splash, thereby decreasing the efficiency of imparting the velocity energy.With the construction shown in Fig. 18B it is possible to efficiently remove water without dropping the sand particles away from the conveyor. Where it is not desirable to project the sand particles in the horizontal direction against gravity, the sand particles may be projected downwardly in the same manner as in Fig. 17.

In a modification shown in Fig. 19, the sand particles from the hopper 1 are supplied to a high pressure air nozzle 98 via a metering device 97 to eject the particles against the impact plate 78 by the velocity energy of the high pressure air, thereby removing excess surface water. As before, the inner surface of the skirt is cleaned by the cleaning water.

According to the embodiments described above, since substantially all sand particles imparted a high velocity energy are caused to collide upon the impact plate, the impact plate wears quickly so that it is necessary to frequently exchange the same. The modification shown in Fig. 20 is constructed to obviate this problem and comprises a pair of spaced belt conveyors 95 adapted to impart high velocity energy to the sand particles so that sand particles projected by the belt conveyors collide with each other in a space between the conveyors, thus sprinkling the water removed from the sand particles in the space. A motor driven blower 241 is used to exhaust air entraining the sprinkled water to the outside through a duct 212 which may contain a mist separator (not shown). With this construction, although all projected sand particle do not collide with each other, only a small amount of the projected sand particles collide upon an inverted funnel shaped impact plate 212, so that the wear thereof is small.

With the embodiment shown in Fig. 20, however, the impact force is different for respective sand particles so that the quantity of the water remaining on the sand particles is not always constant. To eliminate this problem, an impact plate 234 shown by dot and dash lines may be positioned between the belt conveyors 235. Where sand particles contain ing mud are projected, the impact plate 94 is taken out through a window, not shown, and cleaned. The impact plate 234 may be a thick casting.

In any of the embodiments described above, substantially uniform impact force is imparted to the fine aggregate so as to remove excess water. So long as the impact force is larger than the adhering force of the water to the particles of the fine aggregate it is possible to remove surplus water. The removed water flows down along the impact plate while the particles of the fine aggregate are permitted to fall down or move outwardly.

The result of water separation effected by the water separator according to this invention is shown in Fig. 21. As can be noted from the curves shown in Fig. 21, irrespective of the difference in the quantity of the surface water which differs dependent upon the particle size, so long as the quantity of the surface water exceeds a predetermined limit before treatment, substantially constant quantity of water remains on the sand particles after the treatment. Even when the quantity of the initial water is less than the predetermined limit, a quantity of water proportional to the initial water quantity can be removed. When the impulse force is increased by increasing the speed of the rotating disc the quantity of the water remaining after the treatment decreases and vice versa, but the shape of the resulting curves resembles to that shown in Fig. 21.For this reason, in order to make uniform the quantity of water remaining after the treatment, a quantity of water is added to the fine aggregate to adjust its initial water quantity to be higher than 15%, for example.

In the embodiment shown in Fig. 1, water is added to the mixer B in two stages to be admixed with the fine aggregate treated by the water remover A.

More particularly, at the first stage water is added to the treated fine aggregate with a water sprinkler D, and the aggregate is thoroughly mixed together to apply uniform quantity of water on respective particles. Then, a powder of hydraulic substance, e.g. cement, is added by an adder C and admixed with the fine aggregate to form shells of cement about the particles of the fine aggregate. An additional quantity of water is added by a water adder D2 and the mixture is then kneaded.

The shells thus formed are stable enough to withstand to the subsequent addition of water and kneading. Accordingly, the structure molded with this mixture has a large mechanical strength. After incorporation of the hydraulic substance the mixture can be conveyed to a remote station.

It should be understood that according to this invention it is not always necessary to add water in two stages and to add the hydraulic substances between the additions of water. Thus, water may be added at one time.

The fine aggregate, with its quantity of surface water adjusted to a predetermined value by impact force, determines the quantity of water to be subsequently added to prepare a kneaded compound, thereby reasonably determining the water to cement ratio W/C, the ratio of sand to cement S/C, and other factors of compounding to cause uniformity and to increase the mechanical strength of the products. Although coarse aggregate may be added at any stage, it is advantageous to add it immediately prior to the addition of the primary water.

A preferred example of the mixer is illustrated in Fig. 22, which comprises a mixing chamber 110 containing a screw mechanism 104. As shown in Fig. 23, the mixing chamber 110 has a U-shaped cross-sectional configuration and is lined with a resilient film 105.

Pressure applying chambers 106 are provided on the outside of the resilient film 105 to urge inwardly the resilient film 105. Fine aggregate, which has been adjusted in its surface water, and coarse aggregate are fed into the mixing chamber 110 at its lefthand end from hoppers 101 and 103 respectively by a belt conveyor 111. A predetermined quantity of water is then added from a water tank 114 through a pipe 115 including a valve 115a. Secondary water is admitted into an intermediate section of the mixing chamber 110 from water tank 1 14 via a branch pipe 116 including a valve 1 1 6 a. One or more of such additives as a dispersing agent, a delay agent, a quick setting agent, etc., are supplied to the branch pipe 11 6a from a tank 117 through a pipe 118 including a valve 118a.

Where it is not desirable to simultaneously incorporate a plurality of types of the additives, a plurality of independent tanks each containing an additive of one type may be installed. At the rear or righthand end is formed an exhaust port 109 to discharge kneaded compound into a receiver 120. The compound in the receiver is conveyed to a working station by a tank car, a pipe, a conveyor, or the like.

The pressure applying chamber 106 is sealed and is supplied with pressurized air or water. When pulsating pressurized fluid is applied it is easy to remove the compound adhered to the resilient film 105. The pressure applying chambers 106 contain elastic tubes 8. But the tubes 8 can be substituted by sponge rubber or a hair rock (a mixture of human or animal hairs bonded by latex or an artificial resin binder and having a substantial elasticity). Although the pressure applying chamber 106 can be provided along the entire bottom length of the mixing chamber 110 it is advantageous to install a plurality of spaced apart pressure applying chambers 106 as shown in Fig. 22. This construction prevents the resilient film from excessively bulging into the mixing chamber to interfere with the operation of the screw mechanism 104.

Where the mixer shown in Fig. 22 is used to prepare such compounds as mortar or concrete, a powder of cement is supplied to the mixing chamber 110 from a concrete tank 102 through a metering device 112. An operation between sand hopper 101 and the cement tank 102 comprises a first step l; an operation between the cement tank 102 and the secondary water supply pipe 116 comprises a second step ll; and an operation between the pipe 116 and the discharge port 109 comprises a third step Ill. More particularly, to prepare mortar or cement, in the first step I a portion of water necessary to prepare the final compound is added to a mixture of sand and gravel through pipe 115 and the water content of the mixture is made to be uniform by the screw mechanism 104.Then, a measured quantity of cement is incorporated into the mixture to form stable shells of cement about respective sand particles in the second step II.

When preparing cement mortar, in the third step the secondary water is added through pipe 11 6 together with one or more desired additives. With the connection shown in Fig.

22, the additive is firstly admixed with a large quantity of the secondary water in pipe 11 6 so that even an additive having a high viscosity can be uniformly admixed.

Instead of using a single resilient tubes 108 maybe used as shown in Fig. 24. With this construction it is not necessary to construct the pressure applying chamber 106 to be sufficiently air tight. Furthermore, the tubes 108 which should be air-tight would not be damaged by the friction caused by the screw mechanism 104. Where water is filled into the pipes 108, their internal pressure can readily be adjusted by merely changing the level of a water tank. For example, the water tank may be positioned at a position higher than that of the pipes 108 by 1.5 to 2 meters. It was found that this level of the water tank is sufficient to prepare satisfactory cement mortar or concrete.

As shown in Fig. 23 additional pressure applying chambers 126 each containing a resilient tube may be provided above the screw mechanism 104. The resilient tubes 128 not only assist the action of the resilient tube 108 at the bottom of the mixing chamber but also reinforce the U-shaped resilient film 105, especially when it is more or less aged or elongated, thus maintaining a desirable sealing relationship to the screw mechanism 104.

The discharge port 109 can be formed at one side of the mixing chamber 110 as shown in Fig. 22 because this construction can contain the compound throughout the entire length of the mixing chamber so that even when the compound has a considerably high fluidity the entire length of the mixing chamber can be efficiently utilized.

Figs. 25 and 26 show modified mixers.

Thus, while in Fig. 22, the mixing chamber 110 is made of a single integral member, in Figs. 25 and 26 the mixing chamber 110 is made up of a plurality of sections. More particularly, in the example shown in Fig. 25, the mixing chamber 110 comprises a plurality of cascade connected sections 11 ova, 11 orb, and 110which are disposed at different levels. A sand tank 101, a water tank 121, and a first section 104a driven by a motor M are provided for the first section 11 Oa. A water content measuring device 122 is provided for the sand tank 101 to measure the water content of the sand treated by the water remover A described above so as to control the quantity of water supplied from the water tank 121.The second section 1 106 com- prises a second section 104b of the screw mechanism and a hopper 11 Oe adapted to receive the mixture of sand and water from the first section 1 10a and a measured quantity of cement from the cement tank 102. The third section 1 10c is provided with a hopper 11 Od adapted to receive kneaded mixture from the second section 11 Ob and secondary water from a water tank 123, and a discharge port 109 at the end of the third section and connected to a discharge pipe 124 for conveying the resulting compound to a receiver 120.

The section 104b of the screw mechanism is secured to a hollow tube comprising the second section, the hollow tube being rotated by a motor M2 through a pinion and a ring gear 134 secured to the tube. A horizontal shaft 135 extends through the third section 11 or and driven by a motor M3. The horizontal shaft 135 is provided with a plurality of paddles 136 which are set at a predetermined angle to assure uniform mixing.

In the modification shown in Fig. 26, the sections 11 Oa, 11 Ob, and 11 0c are arranged coaxially to form a continuous mixing chamber. Sections 104a, 104b, and 104e are mounted on a common shaft 140 driven by a motor M4 located at the lefthand end of the mixing chamber. The second and third sections 11 Ob and 11 or are rotated by motors M2 and Ms respectively in a direction opposite to that of the screw sections 104b and 1 04c for the purpose of improving the mixing efficiency. For the purpose of adding the secondary water at the same position as that shown in Fig. 25 the shaft 140 at least in the third section is made hollow to feed water from a water tank 133 through perforations 133a at -one end of the third section 11 0c.

Although the multiple section construction of the mixing chamber shown in Figs. 25 and 26 is more or less complicated, since the volume of the contents of respective sections vary by the ingredients added in respective sections it is possible to construct respective sections to contain contents of varying volume. Mixers of different types may be used as shown in respective sections.

Another example of the mixer utilized in this invention is illustrated in Figs. 27 and 28. As shown, a mixing chamber has a U-shaped sectional configuration and a length sufficient to complete the entire mixing and kneading operations. A horizontal rotatable shaft 159 extends through the mixing chamber 160 and provided with a plurality of mixing members 158 which are arranged generally along a helix. The angles of inclination and the pitches of respective mixing members are varied in accordance with the mixing steps. Sand with its water content has been adjusted by the water recover A described above is supplied to the lefthand end of the first section I by a belt conveyor 151. The primary water is added at substantially the same position through a water pipe 155.Coarse aggregate, i.e. gravel, is added from a gravel tank 155a at a joint between the first and second sections I and II while cement is added from a cement tank 1 55c adjacent the gravel tank 155a. The secondary water and the additive are incorporated at a joint between the second and third sections II and Ill through pipes 155b and 155 d respectively. In addition to the mixing members 158 relatively small auxiliary mixing members 157 are also mounted on the portions of the shaft 159 in the first and second sections I and II. These auxiliary mixing members 157 incline in a direction opposite to that of the main mixing members 158.If the direction of the auxiliary mixing members is the same as that of the main mixing members the angle of inclination of the auxiliary mixing members is made to be larger than that of the main mixing members.

The main and auxiliary mixing members are inclined and are arranged along continuous helical lines respectively. As shown in Figs.

29, 30, 33, and 34, the main mixing members are separated more than 30 about the periphery of the rotating shaft 159 and constructed such that each main mixing member does not extend over an angle of at least 360 . As shown in Figs. 29 and 30 the auxiliary mixing members 157 has a smaller height than the main mixing members 158 and in the case shown in Fig. 30 the auxiliary mixing members 157 are utilized to support the main mixing members 158.

As shown in Figs. 33 and 34, both main and auxiliary mixing members 158 and 157 are secured to the rotating shaft 159 by means of suitable fasteners 156.

In the construction shown in Figs. 27 through 37 the speed of moving the mixture toward the discharge opening 166 varies depending upon the angle of inclination of the mixing members 157 and 158 with respect to the rotating shaft 159 corresponding to the variation in the bulk of the mixed composition charged. Considering only the weight, the speed of movement is the minimum at the charging end, while it is the maximum at the discharge end, but in the method of this invention where the water content of the mixture varies the problem is not so simple.

Thus, the volume varies between a case wherein sand contains a relatively small quantity of water, e.g. 2-3%, and a case wherein sand contains much more water. In a relatively dry mixture incorporated with cement which forms shells, its volume shows a maximum, whereas when water is added to increase the fluidity of the mixture the weight thereof increases but its volume decreases greatly. In the step shown in Fig. 27 in which the primary water is added to make uniform the surface water, the angle of inclination of the main mixing members 157 is made to be a standard whereas the auxiliary mixing members 157 are inclined in the opposite direction to realize a relatively slow feed speed.In the second step II, the angle of inclination of the main mixing members 158 is made relatively large as shown in Fig. 29 whereas the angle of inclination of the auxiliary mixing members 157 is made larger so as to obtain higher feed speed thus allowing an increase in the bulk in step II. In the step Ill, after incorporation of the secondary water the fluidity increases thus further decreasing the volume.

For this reason, in step Ill, the angle of inclination of the main mixing members 158 is made to be standard to decrease the feed speed than that of section II. For the reason described above, with a mixing chamber 160 having a uniform cross-sectional area the mixture can be mixed together with a constant surface level irrespective in the variation of the bulk. At the discharge port 166, the surface level of the mixture decreases rapidly as the mixture is discharged so that it is advantageous to provide an auxiliary mixing member 157a at this portion to made long as far as possible the stay time of the mixture at this portion. The compound discharged through the port 166 is received by the receiver 170 but the discharged mixture can be conveyed by a conduit or a pump.

While in the embodiment shown in Figs.

27-30, the variation in the bulk is coped with by varying the angle of inclination of the mixing members 158, in the embodiment shown in Figs. 31 and 32, the variation in the bulk is coped with by varying the volume of the mixing chamber 160. More particularly, the height of the side walls 1 60d of the mixing chamber 160 at section 11 is increased to increase the volume thereof. Because in the step in which shells of cement are formed about sand particles the quantity of water between the sand particles is very small, even when the volume of the mixture increases, its fluidity is small so that the variation of the bulk can be coped with by merely increasing the height of the side walls 160d.Even when the high side walls 160d are provided, the cross-sectional configuration of the mixing chamber 160 is generally U-shaped so that transfer of the mixture can be performed efficiently by the inclined mixing members 158, and the portion of the mixture bulged upwardly in section II is subjected to efficient mixing operation. When the pitch of the mixing member in section II is suitable selected, efficient mixing and kneading of the mixture can be assured with a relatively short length of the section II.

The embodiments shown in Figs. 27-30 are suitable for preparing a large quantity of cement mortar or cement compound of excellent characteristic.

To have better understanding of the invention the following Examples are given.

Example 1 In this example the apparatus shown in Fig.

2 was used which is provided with a rotating disc 2 having a diameter of 400 mm and driven by motor 4 at a speed of 1100 rpm (rev/min). Fine river sand containing 3.98% of water and having a finess modulus (F.M.) of 1.28 mm, said F.M. being determined ccording to the equation

where P, is weight percent of aggregate remaining in a mesh of 0.15,0.3,0.6, 1.2, 2.5 or 5.0 mm after meshing, the quantity of surface water varying from 4% to 25%, was supplied to the rotating disc 2 to cause the sand particles to collide upon the impact plate 6. The rate of supply of the water containing sand to the hopper 1 was varied in a range of 50 to 160 kg/min and the water content of the sand conveyed by the coveyor 11 was measured to be 9.4-10.1%, showing that the quantity of the surface water is substantially constant.

Where the speed of the rotating disc 2 was increased to 5000 rpm the quantity of the surface water was measured to be 6.06-6.38%, which shows that the quantity of the surface water was substantially reduced from that when the rotating disc was rotated at a lower speed and the variation in the quantity of the surface water is much smaller.

Example 2 With the same apparatus utilized in Example 1, sand particles of medium size and containing 2.25% of water and having F.M.

of 2.28 mm was treated in the same manner.

In this example, however, water was added to the sand at the exit of the hopper 1 at a rate of 4 I/min. When the rotating disc 2 was rotated at a speed of 1100 rpm the water content of the treated sand was 4.7-5.3% showing that the quantity of the surface water has been decreased because the treated sand had a larger particle size. However, it was found that the range in which the quantity of the surface water varies has been narrowed.

In contrast, when the speed of the rotating disc 2 was increased to 5,000 rpm the quantity of the surface water varied in a narrower range of 4.33 to 4.85%.

Example 3 Coarse sand produced from a different origin from that utilized in Example 1 and having a water content of 3.31% and F.M. of 2.96 mm was treated in the same manner as in Example 2. More particularly, when the rotating disc 2 was rotated at a relatively low speed of 1100 rpm, the quantity of the surface water was 3.3-4.2% whereas at a higher rotating speed of 5000 rpm, the quantity of the surface water was 3.2 to 3.52%, showing a narrower range.

Example 4 In this example, the apparatus shown in Figs. 4 and 5 was used in which the rotating disc 2 having a diameter of 450 mm was rotated by motor 4 at a speed of 1250 rpm.

Medium size river sand having a water content of 2.25% and F.M. of 3.27% was caused to collide against the impact plate 6.

Water-containing sand was fed into the hopper 1 at a rate of 25 m3/hour. 5-40 I/min of water was sprinkled onto the sand while it was being conveyed by conveyor 30. The treated sand collected in the bottom portion of the receptacle 9 was conveyed by the conveyor 11. The conveyed sand was sampled at each minute to measure the water content of the treated sand. The water content measured was in a range of 8.79-8.93% and it was found that the quantity of the surface water was substantially constant, i.e. from 6.54 to 6.58%. The quantity of the recovered sand after the treatment was 24.1 m3/hour, showing a high yield of 96.2%. Not recovered quantity consisted essentially of mud.

When the speed of the rotating disc 2 was increased to 1500 rpm the water content of the treated sand was 6.92-7.04% (the quantity of the surface water is 4.66-4.77%). At a higher speed of 1750 rpm, the water content of the treated sand was 5.79-5.88% (the quantity of the surface water was 3.53-3.62%). Thus, in each case the quantity of the surface water was reduced and is substantially constant. The quantity of the treated and recovered sand was 24.28 m3/hour for 1500 rpm, and 24.52 m3/hour for 1750 rpm.

Example 5 The same apparatus utilized in Example 4 was used to treat medium size sea sand having a water content of 2.46%, a salt content of 0.33% and F.M. of 2.62%. In this example, 30 I/min of water was added to the sand while it was being conveyed by the conveyor.

In this Example, when the rotating disc was rotated at a lower speed, the water content of the treated sand was 8.56-8.71% (the quantity of the surface water was 6.40-6.55%).

Even with the same rotation speed of the disc, since the sand is coarse, its quantity of surface water has been decreased. Although the treated sand still contains 0.03% of salt, it can be used for preparing green mortar or green concrete because of the formation of the cement shells, and the quantity of the recovered sand was 23.8 m3/hour.

When the rotating disc 2 was rotated at a speed of 1500 rpm the water content of the treated sand was 6.76-6.83% (the quantity of the surface water was 4.30-4.37%) whereas when the speed of the rotating disc was increased to 1750 rpm, the water content of the treated sand was 5.51-5.58% (the quantity of the surface water was 3.05-3.12, which shows that the variation in the water quantity is also small. The salt contents were 0.028% and 0.027% for 1500 rpm and 1750 rpm respectively and such salt-containing sand could be used to prepare a concrete compound.

To remove salt conventionally it is necessary to use clean water in a quantity at least equal to that of sea sand, so that to remove salt from 25 m3 of sea sand it is necessary to use 25-80 m3 clean water. In contrast, according to this example the quantity of water added to the sea sand is only 30 I/min, or 1.8 m3/hour.

When salt is removed by sprinkling water onto sea sand, the salt is not removed uniformly. For example, even though the average quantity of the remaining water is 0.03%, it varies between 0.002 and 0.150%, meaning that a considerable quantity of washed water contained more than 0.04% of the remaining salt, which is the permissible upper limit.

According to this example, when water is added to the sea sand being conveyed by the conveyor at a rate of only 30 I/min, since the separation of water is efficiently performed by the impact force, the quantity of the remaining salt is only 0.007-0.038%.

Example 6 Fine particles of a slag pulverized by water and having F.M. of 2.53 mm and containing 2.90% of water was treated in the same manner as in Example 4.

More particularly, when water is removed at the rotating speed of 1250 rpm of the disc 2, the water content of the slag particles was 8.99-9.27% (the quantity of the surface water was 6.09-6.37%) whereas at the speed of 1750 rpm, the water content was decreased to 6.19-6.28% (the quantity of the surface water was 4.29-4.38%) and the quantity recovered sand was 24.0 m3, 24.3 m3, and 24.51 m3 at the speeds of 1250, 1500, and 1750 rpm respectively.

Example 7 In this example, the apparatus shown in Figs. 6-9 was used. Coal dust having a particle size of 0.1 5-5 mm and containing 3-15% of surface water was treated by the apparatus. The feed speed was selected in a range of from 80 to 200 kg/min.

The rotating member 52 was provided with vanes having a length of 250 mm between the axis and the outer end and the rotating member was rotated at a speed of 1500 rpm to remove water from the coal dust. After treatment, the coal dust contained 4.2-4.3% of the surface water showing uniform water removal. Mud on the particles of the coal dust was also efficiently separated.

Example 8 In this example, the apparatus shown in Figs. 10, 11, and 12 was used to remove water from blast furnace slag containing 20.5-57.5% of surface water.

The rotating member 52 had a radius of 300 mm and rotated at a speed of 2000 rpm.

The treated slag contained 12-15% of the surface water. The particle size of the slag was larger than 0.1 m which can be classified.

Example 9 The apparatus shown in Figs. 6-9 was used, and in this example mineral particles having a water content of 28-46% and a grain size of less than 3 mm was preheated to about 80'C and then supplied to the hopper 1.

The rotating member 52 was provided with blades having a length of 250 mm between the axis and the ends of the blades. The rotating body was rotated at a speed of 1850 rpm, and the impadt plate 60a was heated to about 60 C. After the treatment, the quantity of oil remaining on the mineral particles was 4.8-5.3%, showing substantially uniform removal of oil According to a prior art method of removing oil contained in mineral particles, the oil was removed by evaporation. To this end it has been necessary to heat the particles at a high temperature of 500 C for a considerable period while agitating. Furthermore it is necessary to recover evaporated oil by condensation, which requires an expensive equipment.

In contrast, the apparatus of this invention is simple in construction and consumes less operating energy.

The following examples show use of the fine particles removed with water by the method and apparatus described above.

Example 10 To prepare cement mortar according to a conventional method, nearly perfectly dried medium size river sand, water, and 956 kg of cement were used at a C/S ratio of 1:1 and at a W/C ratio of 35%. 765 kg of a lignin sulphonic acid type dispersing agent was added and the mixture was kneaded. The resulting mixture evolved a considerable number of air bubbles and had a fluidity of 42 sec when measured with a J funnel 6.5 cm in diameter of feed side, 45 cm in height, and 1.0 cm in diameter of discharge side. The percentage of breezing after 3 hours was 6%. The product molded with this mortar had a compression strength of 375 kg/cm2, 489 kg/cm2, and 563 kg/cm2 respectively after 3, 7, and 28 days.

The coefficient of variation after 28 days was 15.3%.

The same sand was dehydrated according to the process of Example 4c by using the apparatus shown in Fig. 4. When the rotating disc was rotated at a speed of 1750 rpm, the quantity of the surface water after the treatment was 3.53%. Cement, water (total water minus the remaining water), and a dispersion agent were added to the treated sand in quantities to obtain the same W/S and W/C ratios described above. After kneading for two minutes, a cement mortar was obtained having a fluidity of 13 seconds when measured with a J funnel and the percentage of breezing was 0.5% after 3 hours. Products molded with this mortar had a compression strength of 532 kg/cm2, 698 kg/cm2, and 790 kg/cm2 respectively after 3, 7, and 28 days, the variation coefficient being 4.8%.

The water content of the same medium size sand was reduced at a rotating speed of 1750 rpm of the rotating disc to adust the quantity of the surface water to 3.53%. After uniformly incorporating 16.47% of primary water to the sand thus treated, a quantity of cement sufficient to obtain a ratio C/S = 1:1 and the mixture was admixed to form cement shells having a W/C ratio of 20% about the sand particles. After adding 15% of the secondary water and 0.8% of a dispersing agent the mixture was kneaded to obtain cement mortar having a fluidity of 19 sec, and zero breezing percentage after 3 hours. The compression strength of the products molded with this mortar was 619kg/cm2, 739kg/cm2, and 855 kg/cm2 respectively after 3, 7, and 28 days, the variation coefficient being 2.2%.

When compared with products prepared by the prior method, the products according to this invention have higher compression strength and are more stable.

Example 11 The same quantity of the same sand as that of Example 10 but not dehydrated according to the method of this invention, 347 kg of cement, 3.5 kg of a dispersing agent, and water were mixed together to obtain mortar having ratios C/S = 1 :2, C/G = 1:3.6 and W/C = 42% to prepare mortar having a slump value of 2.1 cm and appreciable breezing and air bubbles. The compressive strength of the products molded with this mortar was 208 kg/cm2, 284 kg/cm2, and 334 kg/cm2 respectively after 3, 7, and 28 days, the variation coefficient being 17.4%.

Similar mortar was prepared except that the surface water had been reduced to 3.53%.

The mortar, less than 2.5 minutes after kneading, had a slump value of 8.2 cm and showed certain segregation and breezing. The products molded with this mortar had a compression strength of 274 kg/cm2, 348 kg/cm2, and 482 kg/cm2 after 3, 7, and 28 days respectively and a variation coefficient of 8.2%, showing increase in the strength by 50% and uniform quality.

6.47% of primary water was added to the same river sand adjusted in its quantity of surface water to 3.53% and the same quantity as above described of sand was added to form cement shells whose W/C ratio was 20%. Therefore gravel, 22% of secondary water, and 1 % of a dispersing agent based on the quantity of cement were incorporated and kneaded together to obtain a concrete compound having a slump value of 11.6 cm. The product molded with this concrete compund had a compression strength of 308 kg/cm2, 382 kg/cm2, and 513 kg/cm2 respectively after 3, 7, and 28 days and a variation coefficient of 5.1%, showing an increase of 50% of the compression strength and uniformity of the products.

Example 12 To a concrete compound having the same formulation as that of Example 11 was added 1.5% by volume of steel fibers. The sand was not dehydrated according to the method of this invention. The resulting concrete compound had a slump value of 1.5 cm and showed large segregation and breezing. The bending strength of the concrete product molded with this concrete compound was 58 kg/cm2 after 28 days.

In contrast, similar concrete compound utilizing the same sand dehydrated by the method of this invention had a slump value of 7.4 cm immediately after the kneading and showed slight segregation and breezing. But a concrete product molded with this concrete composition showed a bending strength of 75 kg/cm2 after 28 days.

A concrete compound utilizing dehydrated sand particles formed with cement shells having a ratio of W/C of about 20% and incorporated with the steel fibers had a slump value of 1 2.8 cm, and showed no breezing. The concrete product molded with this concrete compound had a bending strength of 92 kg/cm2 after 28 days.

Example 13 The same river sand as that used in Examples 10-12 was used. 350 kg of cement, 1120 kg of sand, 700 kg of a coarse aggregate, and 10.5 kg of a quick setting agent were admixed under dry state. The resulting mixture was conveyed by high pressure air to a working station where water was added in an amount to obtain a W/C ratio of 50%.

The resulting concrete compound was blasted against a vertical wall through a blasting nozzle. The quantity of rebound was above 35%.

When blasted against the wall of a tunnel, the quantity of dust generated was about 750 CPM. 28 days after blasting the concrete had a compression strength of 232 kg/cm2 and a variation coefficient of 14.5%.

A concrete compound, having the same composition as in Examples 10-12 except that the quantity of the surface water was adjusted to be 3.53%, was prepared and the concrete compound was blasted under the same conditions, and it was found that the quantity of rebound was 18% and the quantity of dust generated was 340 CPM. The blasted concrete had a compression strength of 363 kg/cm2 after 28 days and a variation coefficient of 5.3%.

The same sand adjusted in its surface water to 3.53% and a quantity of cement were mixed together to form cement shells having a W/C ratio of 20%. Then a quantity of water to ensure ratio W/C = 34.2% and 0.6%, based on the weight of cement, of a dispersing agent were added to prepare a mortar having a high fluidity. The mortar was conveyed under pressure through a pipe. Another dry compound was prepared having ratios C/S = 1:3.01 and S/A (A represents a coarse aggregate) of 56% and conveyed under pressure through another pipe. The two compounds were admixed at the working station at a ratio of 1:1.75 by volume together with a suitable quantity of a quick setting agent. The concrete composition suitable for blasting had a ratio W/C of 42% and contained 352 kg of cement, and was blasted against a wall.The amount of rebound at the time of blasting was 8.9% and the quantity of dust generated was 72 CPM. The compression strength of the blasted concrete after 28 days was 542 kg/cm2 and the variation coefficient was 3.2%. The compression strength was increased by 100% and the variation coefficient was reduced to 1/5 when compared with the conventional concrete compound.

Example 14 In this example the water remover A shown in Fig. 16 was combined with the mixer B shown in Fig. 27. A medium size river sand (containing 23% of water and a quantity of surface water of 3-27%) and having F.M. of 2.1 was treated by the water remover A.

The rotating member 77 was provided with vanes 79 having a length of 225 mm and rotated at a speed of 1250 rpm. The water containing sand was supplied to the hopper 1 at a rate of 50-120 kg/min. The sand in the hopper 85 contained 6.7-6.9% of the surface water, and that in the hopper 86 contained 6.4-6.8% of the surface water. The quantity of the surface water of the sand contained in the hopper 86 corresponds to that of the medium size sand.

Where the speed of the rotating member was increased to 1500 rpm, the water content of the sand in the hopper 85 was 5.6-5.9%, that of the sand in the hopper 86 was 5.2-5.4%. When the speed is increased further to 1750 rpm the water content of the sand in the hopper 85 was 3.9-4.2% and that of the said in the hopper 86 was 4.1-4.3%, showing substantially equal water content.

Cement, water, and 1 % of a dispersing agent based on the volume of cement were added to the sand thus treated to obtain ratios of C/S = 1 :2 and W/C = 43%. The quantity of water added corresponds to the difference between the added water and the surface water. The kneaded mixture had such fluidity that it had an initial shear strength Fo of 1.54 g/cm2, a relative viscosity coefficient A of 0.86 g/sec#cm4, a relative closure coefficient AFo of 0.0034 g/cm4, and a segregation and breezing of 0.05%. The compression strength of a molded product utilizing the mortar thus prepare had a compression strength of 438-452 kg/cm2 (average 447 kg/cm2) and 521-545 kg/cm2 (average 534 kg/cm2) after 7 and 28 days respectively.Although a little segregation and breezing were noted, the product had uniform strength.

In addition to the kneading operation in which all quantity of water is added at a time, another process was also performed which includes the shell forming step and water was added in two stages. More particularly, secondary water was added through pipe 155 to ensure surface water of 10%, then a quantity of Portland cement was added to obtain a ratio W/C of 20%. Finally, 153 kg of the secondary water and 1 % based on the volume of the cement of a dispersing agent were incorporated to prepare cement mortar having ratios S/C = 2 and W/C = 43%. The fluidity of the mortar was such that it has an initial shear strength Fo of 2.63 g/cm3, a relative viscosity coefficient A of 1.08 g#sec/cm4, and a relative closure coefficient AFo of 0.0072 g/cm4.No segregation and breezing was noted. The molded product had a compression strength of 521-545 kg/cm2 (average 535 kg/cm2) and 628-656 kg/cm2 (average 642 kg/cm2) after 7 and 28 days respec tively.

A portion of piled-up sand, 285 kg of water, and 664 kg of cement were admixed and kneaded to obtain a mortar having Fo of 0.74 g/cm3, A of 1.37 g#sec/cm4, AFo of 0.014 g/cm4, and a segregation and breezing of 1.4%. The product molded with this mortar had a compression strength of 268-367 kg/cm2 (average 332 kg/cm2) and 353-501 kg/cm2 (average 397 kg/cm2) respectively after 7 and 28 days. Thus the mechanical strength is substantially lower and varies widely.

Example 15 A mixer A shown in Figs. 6 to 9 was used for dehydration. Fine water-containing sand (the quantity of the surface water of 3 to 27%, percentage of water absorption of 2.8%, and F.M. of 1.93) was supplied to the upper portion of the hopper 51 and water was sprinkled onto the sand at a rate of 30 I/min while the sand was being conveyed. The rotating member 52 was rotated at a speed of 1500 rpm to project the sand at a rate of 360-450 kg/min. The quantity of water remaining on the sand particles after the dehydration treatment was 8.3-8.5%, showing a small variation. This means that, even when the rotating speed is varied more or less, it is possible to adjust the quantity of the surface water as desired.

Cement, gravel, and water were added to the dehydrated sand in such amounts as to obtain ratios S/C = 1:2, S/G = 38.5%, and W/C = 43%. 1.2% (based on the volume of the cement) of a dispersing agent was added and then kneaded. The resulting concrete had an excellent fluidity and a slump value of 15.6 cm and only a slight segregation and breezing were noted. The product molded with this concrete compound had an average compression strength of 285 kg/cm2 and 412 kg/cm2 after 7 and 28 days respectively, the variation coefficient thereof being 8.8%.

Where the mixer shown in Fig. 27 was used, the primary water was added to the treated sand to adjust its surface water to be 10%; 1150 kg of gravel and a powder of Portland cement were then added to adjust the ratio W/C to be 20%. Then 83 kg of the secondary water and 1.2% (based on the volume of the cement) of a dispersing agent were added to obtain a concrete compound having ratios S/C = 2, S/A = 38.5, and W/C = 43% and a high fluidity of 17.2 cm in terms of the slump value. The product molded with this concrete compound had an average compression strength of 351 kg/cm2 after 7 days and 468 kg/cm2 after 28 days, showing only 5% variation coefficient.

As a control, the water content of the same sand was measured and corrected. Then, 360 kg of cement, 155 kg of water, 720 kg of sand, and 1150 kg of gravel were admixed with a mixer to produce a concrete compound having the same formulation as above described, and a slump value of 12 cm. The average compression strength of a molded product was 197 kg/cm2 and 343 kg/cm2 after 7 and 28 days respectively. Thus, not only the variation coefficient is 15.6%, but also the strength is lower and varies.

Example 16 The water separator shown in Figs. 10 to 12 was used to treat a coarse river sand containing 3.8-26% of water (percentage of absorption of 1.7%) and coarseness of 3.35.

The rotating member 52 was rotated at a speed of 1750 rpm to adjust the surface water to 3.2-3.3% of the sand supplied from the hopper 51 at a rate of 360 to 450 kg/min. After incorporating the primary water into the treated sand to adjust its surface water to 14%, a powder of Portland cement was added to produce a W/C ratio of 20%.

Thereafter, 290 kg of the secondary water and 1.2% based on the volume of the cement of a dispersing agent were added and kneaded to obtain a mortar having ratios S/C = 1.5, W/C = 38% and such fluidity that it had an initial shear strength Fo of 0.69 g/cm2, a relative viscosity coefficient A of 0.35 g#sec/gm4, and a relative closing coefficient AF0 of 0.0032 g/cm4. The mortar was transported by a pump to a station 120 m away through a pipe having an inner diameter of 5 cm at a speed of 67 m/min. At the station 1 part of sand, the surface water of which had been adjusted to 3.2-3.3%, 0.95 parts of gravel having a size of 1-15 mm, and a powder of cement were incorporated to form cement shells in which W/C is about 18%, at a point 5 m before a blasting nozzle.

The concrete compound was then blasted against the inner wall of a tunnel.

The quantity of the blasted concrete composition was about 8 m3 per hour, the ratio W/C thereof was 33.4%, and the quantity of cement was 509 kg/m3. The amount of rebound at the time of blasting was 6.5% and the quantity of dust generated was 1.21 mg/m3. The round upper wall of the tunnel was satisfactory blasted to a thickness of 120 mm without any peeling. The average compression strength of the blasted concrete was 329 kg/cm2 and 603 kg/cm2 after 3 and 8 days respectively. The variation coefficient was 3.2% and the average strength was higher by 1.4 times that of the prior art concrete having the same formulation, while the variation coefficient was reduced to 1/5.

Where the quantity of the surface water of all portions of the sand was not adjusted but only a sampled portion was adjusted and when concrete was prepared by admixing the sand and then blasted according to the prior art wet or dry process, the amount of dust generated at the time of wet blasting was 6-10 mg/m3 whereas that of the dry blasting was 6-10 mg/m3. The quantity of dust, i.e.

1.21 mg/m3, of this invention is much lower than these values. While with conventional concrete the amount of rebound is 20-30%, in both wet and dry blasting according to this invention the amount of rebound was reduced to a fraction of these amounts. Moreover, the reaction applied to the nozzle is much smaller than blasting prior art concrete compound.The conveyed quantity of 3-4 m3/hour of the prior art concrete could be doubled when a pipe line having an inner diameter of 5 cm was used.

Example 17 In this example the water separator shown in Fig. 10 was used to treat a river sand containing 3-15% of the surface water (percentage of water absorption 2.3% and coarseness of 2.1). In this example, water was added to the sand at a rate of 32 I/min while the sand was being conveyed by the conveyor. The rotating member 52 was rotated at a speed of 1780 rpm and the sand was supplied thereto at a rate of 360-450 kg/min. The quantity of the surface water remaining on the sand particles was 4.6-4.7%, showing uniform water removal.

After adding the primary water to the treated sand such that its surface water would be 7.6%, 1196 kg of gravel and a quantity of Portland cement were added such that the ratio W/C would be 18%. The resulting mixture was transported by trucks to a working station 2 hours' journey away. 92.4 kg of the secondary water and 1.2% (based on the volume of the cement) of a dispersing agent were incorporated into the mixture at the working station to prepare a concrete compound having ratios of W/C = 2.34, S/A = 38.5%, and W/C = 46.8%. The concrete had a high fluidity as evidenced by its slump value of 12.5 cm and no segregation and breezing was noted. The product molded with the concrete compound had an average compression strength of 303 kg/cm2 and 420 kg/cm2 after 7 and 28 days respectively and a variation coefficient of 4.3%.

On the other hand, a green concrete having the same formulation but prepared according to the prior art method decreases its slump value in proportion to the time required for transportation, thus degrading workability. For this reason, it is necessary to agitate the green concrete during transportation. In addition, after transporting over a long distance it has been necessary to further add water at the working station, which decreases the mechanical strength of the product. For example, the compression strength, after 28 days, of the product prepared with such green concrete was only 300 kg/cm2 and its variation coefficient was about 15%, which should be compared with 4.3% of this invention. In addition, according to this invention it is not necessary to transport the total quantity of the water.

Example 18 In this example, the mixer shown in Fig. 22 was used having an inner diameter of 350 mm of the mixing chamber 110 and a total length of 40 m. The shaft or screw 190 was rotated at a speed of 70 rpm. River sand with its surface water adjusted to 3.8-4.2% by the water remover shown in Fig. 4 and 5 was supplied to the mixing chamber from the hopper 101 at a rate of 232 kg/min, and gravel was supplied from the hopper 103 at a rate of 412 kg/min. Then water was supplied through pipe 115 at a rate of 11.25 I/min, to adjust the surface water of the aggregates to 11.6-12.6%. Then cement was added to the aggregate from tank 102 at a rate of 115 kg/min, to form cement shells whose W/C ratio was adjusted to be about 24%.To the mixture were added the secondary water and a mixture of lignin and sulphonic acid through pipe 116 at respective rates of 18.6 I/min and 1.13 I/min, followed by continuous kneading to form a green concrete, at a rate of 20 m3/hour, in which W/C = 42%, C/S = 1 :2, and S/G = 1:1.78.

This green concrete had a slump value of 12 cm and showed no segregation and breezing. The product molded with this green concrete had a compression strength of 254 kg/cm2, 345 kg/cm2, and 442 kg/cm2 respectively after 3, 7, and 8 days.

Example 19 The mixer shown in Fig. 25 was used.

Thus, an artificial light-weight fine aggregate (specific gravity 1.4) containing 8% of surface water, and an artificial light-weight coarse aggregate (specific gravity 1.6) having a particle size of about 15 mm and containing about 1 % of surface water was prepared. The fine aggregate was charged into the hopper 101 at a rate of 159 kg/min, while the coarse aggregate was charged into the hopper 101 at the same rate. Water was sprinkled upon the aggregates from tank 121 at a rate of 11 I/min to adjust the surface water of the aggregates to 15%.

A powder of cement was added to the mixture of the fine and coarse aggregates from hopper 102 at a rate of 117 kg/min to form cement shells about the aggregates.

Then water and naphthalene sulphonate type water-decreasing agent were incorporated from tank 123 at rates of 31 I/min and 6 I/min respectively.

The resultant concrete had an excellent fluidity as evidenced by it slump value of 15 cm, and no segregation and breezing was noted. The composition of the green concrete comprised 350 kg of cement, 480 kg of sand, 1621 of water, and 18 1 of water decreasing agent, each per cubic meter. Its W/C ratio was 46%, and the percentge of the coarse aggregate was 50%. The producted molded with this green concrete had a compression strength of 216 kg/cm2 and 386 kg/cm2 respectively after 7 and 28 days. The product prepared by the prior art method had a compression strength of 173 kg/cm2 and 331 kg/cm2 after 7 and 28 days respectively.

Example 20 In this example, the mixer shown in Fig. 26 was used. More particularly, sand having a particle size of less than 5 mm and containing 6% of surface water and gravel having a grain size of 25 mm and containing 1% of surface water were prepared and charged into hopper 101 at rates of 260 kg/min and 348 kg/min respectively. Water was supplied to the tank 101 from tank 121 at a rate of 8 I/min to adjust the surface water of the aggregates.

Then cement was added to the mixture of the sand and gravel from hopper 102 at a rate of 117 kg/min to form cement shells about the aggregates.

A mixture of water (at a rate of 31 I/min) and lignin sulphonate type water-decreasing agent (at a rate of 6 I/min) was supplied to the mixing chamber from hopper 133. The green concrete discharged into the receiver 120 had a slump value of 17 cm and no segregation and breezing was noted, showing high fluidity. The composition of the green concrete was: 350 kg of cement, 780 kg of sand, 1043 kg of gravel, 162 l of water, and 18 1 of the water-decreasing agent, each per cubic meter, and its W/C ratio was 46%.

The product molded with this green concrete had a compression strength of 224 kg/cm2 and 403 kg/cm2 after 7 and 28 days respectively. The concrete products prepared by the prior art method had a compression strength of 183 kg/cm2 and 348 kg/cm2 after 7 and 28 days respectively, which proves excellent property of the product of this invention.

Claims

1. A method of adjusting the quantity of a liquid adhering to the surfaces of fine particles, comprising applying to the particles an impulsive force larger than the adhesive force of the liquid, thereby removing at least part of the liquid.

2. A method as claimed in claim 1, wherein the said force is due to kinetic energy.

3. A method as claimed in claim 2, wherein the kinetic energy is imparted by centrifugal force or a gas flow or both.

4. A method as claimed in claim 1, wherein the said force is applied to the particles by a rotating member.

5. A method as claimed in claim 1, including the further steps of applying liquid to the particles in an amount larger than the quantity of water remaining on the particles after the application of the said force, and then applying to the particles a substantially uniform impulsive force.

6. A method as claimed in claim 1, wherein the particles have different quantities of the liquid thereon.

7. A method as claimed in claim 1, wherein the particles are of equal grain size.

8. A method as claimed in claim 1, wherein the said force is applied by centrifugal force in a closed chamber.

9. A method as claimed in claim 1, wherein the particles are contaminated with an impurity, the method comprising the steps of adding liquid to the fine particles and then applying the said force to simultaneously remove impurity and adjust the quantity of liquid.

10. A method of preparing a cement compound comprising the sequential steps of adjusting the quantity of water adhering to the surfaces of particles of sand to a predetermined value by applying an impulsive force to the sand particles, adding a quantity of water to the sand to increase its water content, applying to the sand particles an impulsive force stronger than the adhesive force of the water to remove excess water, and mixing cement with the sand particles.

11. A method of preparing a hydraulic compound, comprising the sequential steps of applying an impulsive force to a fine aggregate to remove excess water on the particles of the aggregate, adding a first portion of the amount of water necessary to prepare the hydraulic cmpound, adding a hydraulic substance to the resulting mixture of fine aggregate and water to form shells of the hydraulic substance about the particles of the aggregate, adding the remaining portion of the said amount of water necessary to prepare the hydraulic compound, and kneading a resulting mixture.

12. A method as claimed in claim 11, wherein an additive is incorporated together with the said remaining portion of water.

13. A method as claimed in claim 11, wherein the quantity of the said first portion of water is determined according to a quantity of water remaining on the particles of the aggregate.

14. A method as claimed in claim 11, including adding a coarse aggregate and/or a fibrous subtance to the fine aggregate.

15. A method as claimed in claim 11, wherein the fine aggregate from which excess water has been removed and other ingredients of the hydraulic compound are conveyed to a working station by independent conveying means and then mixed together and blasted at the working station.

1 e. Apparatus for separating liquid from fine particles comprising liquid separating means for applying an impulsive force to the particles so as to remove liquid from the particles and means for successively supplying the particles to the liquid separating means.

17. Apparatus as claimed in claim 16, which further comprises means for supplying liquid to the particles before they are supplied to the liquid separating means.

18. Apparatus as claimed in claim 16, wherein the liquid separating means comprises a rotatable disc and an impact plate against which the particles are projected by centrifugal force created by the rotating disc.

19. Apparatus as claimed in claim 18, wherein the disc is provided with a plurality of radial vanes and the particles are supplied to a central portion of the disc.

20. Apparatus as claimed in claim 16, wherein the impulsive force is applied by pressurized gas.

21. Apparatus as claimed in claim 16, wherein the impulsive force is applied by a conveyor belt running at a high speed.

22. Apparatus as claimed in claim 18, which further comprises means for dividing the particles from the liquid separated from the particles as a result of collision against the impact plate.

23. Apparatus as claimed in claim 22, wherein the said dividing means is provided on an upper edge of a container of particles from which liquid has been removed.

24. Apparatus as claimed in claim 18, wherein the impact plate is removably mounted on an inverted dish shaped member whereby water removed from the particle as a result of collision against the impact plate flows down along an inner surface of the member.

25. Apparatus as claimed in claim 18, including a pipe for continuously supplying the particles to a central portion of the disc and means for adding liquid to the particles at the exit end of the pipe.

26. Apparatus as claimed in claim 24, which further comprises a receiver of treated particles, an upper edge of the receiver being spaced from a lower edge of the inverted dish shaped member.

27. Apparatus as claimed in claim 18, wherein the disc is contained in a casing having a rectangular cross-sectional configuration and inner surfaces of the casing are inclined downwardly in the path of particles projected by the rotating disc.

28. Apparatus as claimed in claim 18, which further comprises means for supplying cleaning liquid to the impact plate.

29. Apparatus as claimed in claim 18, which further comprises a receptacle for receiving particles projected upon the impact plate, and means for removing particles adhering to an upper portion of the receptacle.

30. Apparatus as claimed in claim 29, wherein the removing means comprises an elastic tube.

31. Apparatus as claimed in claim 30, which further comprises means for inflating the elastic tube.

32. Apparatus as claimed in claim 16, wherein the liquid separating means comprises a wheel rotatable about a horizontal axis and having a plurality of radial vanes, means for supplying the fine particles to a space between adjacent vanes, means for rotating the wheel at a speed sufficient to remove liquid from the particles, means for discharging the particles from the wheel substantially in a horizontal direction and a plurality of particle receivers juxtaposed in the horizontal direction to classify the particles according to their size.

33. Apparatus as claimed in claim 16, for preparing cement mortar or concrete compound, including a kneading mechanism for successively incorporating water and cement into a fine aggregate from which excess water has been removed by the liquid removing means.

34. Apparatus as claimed in claim 33, wherein the kneading means comprises primary and secondary water supply means, and cement supply means disposed between the primary and secondary water supply means.

35. Apparatus as claimed in claim 33, wherein the kneading mechanism comprises means for adding at least one of the following: a dispersing agent, a rapid setting agent, and a delay agent.

36. Apparatus as claimed in claim 33, wherein the kneading mechanism comprises a shaft provided with a plurality of mixing members which are disposed substantially along a helix.

37. Apparatus as claimed in claim 36, wherein the mixing members are divided into a plurality of sections along the shaft, and the helical pitches of the mixing members are different in different sections.

38. Apparatus as claimed in claim 36, wherein the inclination angles of the mixing members are different in different sections.

39. Apparatus as claimed in claim 36, wherein the shaft is contained in a mixing chamber divided into a plurality of sections along the shaft and the volumes of the sections are different according to the bulk of the mixture being kneaded in each section.

40. Apparatus as claimed in claim 36, wherein the mixing members comprise interleaved larger and smaller mixing members.

41. Apparatus as claimed in claim 40, wherein the larger and smaller mixing members are inclined in opposite directions.

42. Apparatus as claimed in claim 36, wherein the shaft is contained in a mixing chamber, and the shaft and the mixing chamber are relatively rotated.

43. Apparatus as claimed in claim 42, wherein the mixing chamber comprises a U shaped member lined with a flexible member and an elastic tube is disposed between a bottom portion of the flexible member and the U-shaped member, the elastic tube being inflatable by a pressurized fluid.

44. A method as claimed in claim 1 substantially as described in any of Examples 1 to 20.

45. A method as claimed in claim 10 or 11, substantially as described in any of Examples 10 to 20.

46. Apparatus as claimed in claim 16, substantially as described with reference to, and as shown in, Fig. 2, Fig. 3, Fig. 4, Fig.

5, Figs. 6 to 9, Figs. 10 to 12, Fig. 16, Fig.

17, Fig. 18A or B, Fig. 19, or Fig. 20 of the accompanying drawings.