Concrete placement

[57] ABSTRACT

A system is provided for delivering a settable concrete mixture to a placement point which includes a gassolids delivery system for transporting dry cementitious material and suitable aggregate to a water addition zone, and thereafter it carries the cementitious material and water to a deceleration and mixing zone having its outlet positioned over the placement point. The deceleration and mixing zone causes the gassolids stream to agitate as it decelerates and thereby thoroughly blends the concrete constituents to form a settable mixture, which drops from the opening on the predetermined concrete placement point.

Claims, 10 Drawing Figures

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PATENTED DEC 18 1973

SHEET 1 OF 4

3,779,519

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21 V 20 21 10

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FIG. 2

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FIG. 5

INVENTORS:

REG A. ANDERSON RONALD W. CHANDLER FREDERICK N. MUELLER NORBERT L. OSBORN

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ATTORNEYS

PATENTED DEC ι 8 1973

3,779,519

SHEET 2 OF 4

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PATENTED DEC 18 1973

3,779,519

SHEET 3 OF 4

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INVENTORS:

REG A. ANDERSON RONALD W. CHANDLER FREDERICK N. MUELLER NORBERT L. OSBORN

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ATTORNEYS

PATENTED DEC 18 1973

SHEET U DE 4

3,779,519

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FIG. 10

INVENTORS'.

REG A. ANDERSON RONALD W. CHANDLER FREDERICK N. MUELLER NORBERT L. OSBORN

<img file="US3779519A_D0013.tif" />

ATTORNEYS

3,779,519

CONCRETE PLACEMENT

This invention relates to concrete placement. In another aspect, this invention relates to a novel method for admixing and delivering a settable, cementitious mixture to a placement point.

Various methods have been devised for delivering a settable cementitious mixture to a desired placement point. It is customary practice to initially admix the proper proportions of Portland cement, aggregate and water in a conventional mixing device such as a mixing truck which provides a constant agitating motion to the mixture until it is ultimately delivered to the placement point.

If the placement point is readily accessible, the truck can merely be positioned adjacent the point and the cement delivered directly thereto in mixed form from a trough attached to the mixer. However, when the placement point is inaccessible to the truck, either manual labor or specialized equipment is necessary to transport the settable mixture from the truck to the placement point. Examples of such specialized cement transporting and placing machines which utilize hoppers in conjunction with endless belts for transporting the settable mixture are disclosed in U.S. Pat. No. 3,185,450 and U.S. Pat. No. 3,367,636. Most such conventional equipment which is utilized for admixing and delivering a mixed cement material to a placement point has the general disadvantages of being (1) very expensive, cumbersome and difficult to maintain, and (2) unsuitable for delivering small quantities of mixed cement because large quantities of the settable cement material must be premixed in the vehicle.

Some advances have been made in transporting water-cement mixtures in airstreams such as disclosed in U.S. Pat. No. 1,534,008. However, this technique requires complicated equipment which initially admixes or suspends a water-cement mixture in an airstream, which is transported to a mixing zone wherein further amounts of water are added thereto. Some other techniques which utilize an air delivery stream include the cement “gunning” systems which deliver a mixture of cementitious material under pressure from a nozzle. Such systems are normally utilized to form vertical walls and the like from a cementitious mixture containing a very fine aggregate and are not adaptable to operations for delivering cement mixtures containing the larger aggregates. An example of such a system is disclosed in U.S. Pat. No. 1,953,091.

Therefore, a system is needed which is capable of delivering either a large or a very small quantity of a cementitious mixture to placement points without the necessity of premixing the mixture. In addition, a system is needed which can deliver settable cement mixtures to placement points which are inaccessible to conventional mixing trucks and other cement mixing equipment.

Thus, one object of this invention is to provide a novel method for mixing and delivering a cementitious mixture to a predetermined point.

According to the invention, a method is provided for suspending a settable cement mixture in an airstream and thereafter transmitting the suspended mixture to a deceleration and mixing zone wherein the constituents of the cement mixture are thoroughly blended as they are decelerated and then allowed to drop therefrom upon the desired placement point.

According to one embodiment of this invention, a method is provided for delivering a settable cement mixture to a placement point by initially suspending dry cement materials including cement and aggregate in an airstream which transports such materials to a water mixing zone wherein the proper amount of water is added to the cement to cause hydration thereof, and thereafter passes the resulting mixture into a deceleration and mixing zone wherein the constituents are thoroughly bended, such as by rotating motion wherein the kinetic energy in the constituents is utilized to cause mixing and result in the deceleration thereof, after which the blended constituents are allowed to drop into place at the cement placement point.

According to a preferred embodiment of this invention, a method is provided for delivering predetermined quantities of cement and aggregate to an airstream in a conduit which contains an annular water delivery nozzle, which in turn provides a constant spray of water to the airstream, to thereby impart the desired quantity of water into the airstream, the conduit communicating from the nozzle to the interior of an enclosed deceleration and mixing chamber, having an outlet at the lower end thereof and adapted to impart rotating motion to the fluid-solids stream delivered by the conduit to thereby provide initimate blending of the constituents of the stream as they decelerate and then drop from said outlet.

This invention can be more easily understood from a study of the drawings in which:

FIG. 1 is a schematic illustration of the concrete placement system of this invention;

FIG. 2 is a sectional view of the water injector illustrated in FIG. 1;

FIG. 3 is an elevational view, partly in section of a preferred concrete mixing and delivery unit of this invention;

FIG. 4 is a sectional view along lines 4—4 of FIG. 3;

FIG. 5 is a sectional view illustrating a modification of the apparatus of FIG. 3;

FIG. 6 is a sectional view of another concrete mixing and delivery unit which can be used within the scope of this invention;

FIG. 7 is a perspective view of the preferred cement delivery apparatus of this invention;

FIG. 8 is a side elevational view partly in section of the apparatus of FIG. 7;

FIG. 9 is an end elevational view, partly in section of the apparatus of FIG. 8; and

FIG. 10 is a schematic view of the delivery system of the apparatus of FIG. 7.

Now referring to the drawings, and particularly to FIG. 1, a schematic view is depicted, illustrating the concrete placement system of the subject invention. As illustrated, conduit 10 communicates between the outlet of air supply unit 11 and the inlet of concrete mixing and delivery unit 12. Solids feeder unit 13 operatively communicates with conduit 10, and can be any suitable mechanism for injecting solids into an airstream. Solids feeder unit 13 generally comprises feeder bin 14 which operatively communicates with an injector mechanism 15 which can be any suitable mechanism known in the art, such as a rotary air lock feeder, screw conveyor, or the like, which is adapted to inject solids material into a flowing airstream. As is set forth below in relation to FIGS. 7-10, solids feeder unit 13 can comprise one or more injector mechanism 15, each equipped with a

3,779,519 feeder bin 14 for delivering cement material, such as Portland cement together with aggregate into an airstream flowing through a conduit.

Water injector 16 operatively communicates with conduit 10, preferably at a point adjacent the inlet of concrete mixing and delivery unit 12, and functions to uniformly inject water into the gas-solids stream flowing through conduit 10. Water delivery conduit 17 operatively communicates with water injector 16.

Concrete mixing and delivery unit 12 carries an outlet 18 at its lower end opposite the upper enclosed end 19 and comprises an enclosed chamber having generally continuous sidewalls and is adapted to receive the fluid-solids stream emitted from conduit 10 and thoroughly blend the constituents therewithin while decelerating them so that they drop downwardly from outlet 18. For example, in the operation of the device as illustrated in FIG. 1, the fluid-solids stream which is emitted from conduit 10 enters concrete mixing and delivery unit 12 tangentially blow the upper enclosed end 19 and thereby rotates within unit 12 and follows a generally spiral path downwardly therein until the material drops from outlet 18. The rotating motion within concrete mixing and delivery unit 12 not only functions to thoroughly blend the cementitious constituents but also functions to decelerate them in a manner so that they will drop from outlet 18 preferably at their “gravitational velocity.” By “gravitational velocity” it is herein meant a velocity which is substantially the same as that solely attributed to the acceleration of gravity acting upon the mixture which is blended within unit 12.

In operation of the system as illustrated in FIG. 1, a gaseous stream, preferably an airstream is induced by air supply unit 11 within conduit 10 at a sufficient solids entraining velocity (a velocity sufficient to entrain solids emitted from solids feeder unit 13) and carries them to concrete mixing and delivery unit 12. Thereafter, a dry cementitious material, for example, Portland cement and a suitable aggregate material is delivered to the interior of conduit 10 at a desired rate by the action of solids feeder unit 13. Water injector 16 functions to impart a uniform spray of water to the interior of conduit 10, preferably an annular spray of water at a desired uniform rate in relation to the amount of hydratable cement material flowing therethrough to yield a fluid-solids stream which tangentially enters the concrete mixing and delivery unit 12 and rotates therewithin along a spiral path toward outlet 18. This shearing action not only decelerates the constituents but causes a thorough blending thereof such that when they fall from outlet 18, they are adequately mixed into a cementitious blend which will uniformly set to yield a hardened concrete material.

Typical operating parameters which can be utilized in the scope of this invention include utilization of an air velocity water injector conduit 10 of from about 75 to about 150 feet per second which will carry the cementitious solids in a weight ratio of solids to air of about from 5:1 to about 20:1. The cementitious materials can comprise from 3 to 100 weight percent Portland cement and from 97 to 0 weight percent of any suitable size of aggregate (for example sand and/or gravel). In addition, water can be uniformly injected into the fluidsolids stream passing through water injector 16 at a rate to produce about 3 to about 9 gallons per 94 lbs. cement. With such an airstream, a concrete mixing and delivery unit of generally a frusto-conical shape, having a tangential inlet and having an average internal diameter of 1 to 3 feet and being 2 to 4 feet in length, depending on the delivery rate, can be utilized to thoroughly admix such streams, decelerate them to substantially their “gravitational velocity” and deposit them as they fall from outlet 18.

In order to assure that a constant velocity of water will be uniformly injected into fluid-solids stream passing through waterinjector 16, it is preferred that water injector 16 have a configuration as illustrated in FIG. 2, which is a cross sectional view of the preferred water injector 16. As illustrated, water injector 16 comprises a tubular housing 20 which is operatively connected within conduit 10 via suitable couplings 21. A water manifold 22 extends around the internal periphery of the middle of housing 20 and communicates with water inlet 23, which in turn operatively communicates with water supply conduit 17. Recesses 24 extend around the sides of water manifold 22 and align with recesses 25 of locking rings 26 which fit within the interior of tubular housing 20. Matching recesses 24 and 25 retain a pair of opposed annular sealing elements 27. Each sealing element 27 comprises an annular body having a cylindrical seating section 27α, which carries a continuous inturned resilient sealing lip 27b. The sealing lips 27b of the opposed sealing elements 27 preferably decrease in thickness toward inturned tip thereof as illustrated in the drawing. Thus, as each sealing element 27 is fitted within the matching opposed recesses 24 and 25, the tips of the sealing lips 27b of each sealing element 27 engage in sealing relationship so that the interior of water manifold 22 is fully enclosed. Sealing elements 27 are made of a resilient material so that the sealing lips 27b thereof will yield inwardly (of sealing element 27) to a predetermined pressure within water manifold 22. Thus, at any predetermined pressure one can be assured that a constant velocity of water will flow through the opposed sealing lips 27b uniformly into the interior of housing 20. Sealing elements 27 can be made of any suitable resilient material, such as natural or synthetic rubber, nylon, spring steel, and the like.

As explained above, concrete mixing and delivery unit 12 is provided with means for imparting a decelerating and turbulent mixing action to the fluid-solids stream delivered into the inlet thereof, to thereby impart blending action to the constituents of said stream while decelerating the constituents to approximately their “gravitational velocity.” Concrete mixing and delivery unit 12 is shown as an enclosed chamber comprising an upper cylindrical section joined to a lower frusto-conical section having outlet 18 at its apex. In addition the chamber has a tangential inlet in the upper portion thereof with no baffles in either the upper cylindrical section or the lower frusto-conical section. FIGS. 3-6 set forth other embodiments of the concrete mixing and delivery unit which can be used in the scope of this invention.

FIG. 3 is an elevational view partly in section of a preferred concrete mixing and delivery unit of this invention designated as unit 12α. As shown, concrete mixing and delivery unit 12α comprises a top cylindrical section 30, which is enclosed at its upper end and carries tangential inlet 31 in operative communication therewith and a lower frusto-conical section 40 which communicates with the bottom of cylindrical section 30. A series of flow control baffles is positioned in the flow path of the fluid-solids stream emitted by tangen

3,779,519 tial inlet 31. The stream normally will travel in a spiral path downwardly in concrete mixing and delivery unit 12α. The position of the flow control baffles is illustrated in FIG. 3 and FIG. 4, which is a sectional view taken along lines 4—4 of FIG. 3. As illustrated, baffle 32 is generally a curved blade positioned at the outlet of tangential inlet 31 within cylindrical section 30. Baffle 32 is suspended therewithin the support members 33, which extend from the walls of cylindrical unit 30. Baffle 34 is positioned in the spiral flow path at a point further around the circumference of cylindrical unit 30 (approximately 90° from baffle 32). Baffle 34 is generally arcuately shaped and positioned to deflect the fluid-solids stream outwardly toward the periphery of cylindrical unit 30. Baffle 34 is suspended within the interior of cylindrical unit 30 by support members 35. As shown, frusto-conical section 40 which operatively communicates at its wider end with the lower portion of cylindrical section 30 converges to a narrower outlet 18α. Baffle 36 is generally arcuately shaped and is positioned approximately 180° from baffle 32. Baffle 36 is suspended from the sides of cylindrical section 30 and frusto-conical section 40 by support members 37, and functions to divide the fluid-solids stream to enhance the mixing action. The actions of baffle 32, 34, and 36 within the concrete mixing and delivery unit 12α will thereby function to direct the fluid-solids stream in a generally spiral downward path toward outlet 18α as shown by flow arrows 38 and cause deceleration and blending of the components thereof.

Another embodiment of the concrete mixing and delivery unit of this invention is set forth in the sectional view of unit 126 as illustrated in FIG. 5. This unit 126 is basically the same unit as the concrete mixing and delivery unit 12α except it does not contain baffles 32, 34 and 36 but contains a single spiral baffle 39. Baffle 39 is a twisted unitary metal piece placed within tangential inlet 31 and imparts a twisting motion of the fluid-solids stream introduced into the interior of the concrete mixing and delivery unit 126, as illustrated by flow arrows 41. Once inside the unit, the fluid-solids stream will pass generally toward the outlet thereof in a spiral path.

A further but lesser preferred embodiment of the concrete mixing and delivery unit of this invention is illustrated in FIG. 6 as unit 12c. FIG. 6 generally comprises an elongated enclosed body comprising an upper cylindrical section 42 operatively communicating with lower frusto-conical section 43. Fluid-solids inlet 45 communicates with the upper portion thereof and delivers the fluid-solids stream to the interior thereof. Rotor 46 is rotatably mounted through the upper portion of unit 12c and carries a pair of paddles 47 extending therefrom by support members 48. Paddles 47 are positioned adjacent the sidewalls of the upper cylindrical section 42. Motor 49 functions to continuously rotate rotor spindle 46 and paddles 47 around the interior of cylindrical section 42 and agitate the fluid-solids material as it becomes deposited therein from fluid-solids inlet 45. The resulting agitated and decelerated material drops from outlet 18c onto a placement point.

Referring again to FIG. 1, air supply unit 12 together with solids feeder unit 13 and water supply for water delivery conduit 17 are preferably contained in a single unit. The unit can be a stationary unit, a towed vehicle, or preferably a truck such as illustrated in FIGS. 7-10.

Now referring to FIG. 7, a preferred embodiment of this invention is illustrated in perspective. As shown, truck 70 contains an air supply unit, and concrete mixing and delivery unit 12 communicating with conduit 10, and a water supply unit communicating with water delivery conduit 17, which are both carried by extendable boom 71. Concrete mixing and delivery unit 12 can be the units 12, 12α, 126 or 12c which are illustrated in FIGS. 1,3,5, and 6, respectively, and is operatively attached to delivery conduit 10.

Extendable boom 71 can be any suitable extendable boom known in the art, such as the three section boom comprising sections 72, 73, and 74, which are operated by hydraulic cylinders 75 and 76; 77 and 78, respectively, which are controlled by a conventional hydraulic system operable by the truck driver.

The body of truck 70 is equipped with suitable material loading means including cement loading port 79; aggregate loading openings 80 and 81, and water loading port 82.

Concrete mixing and delivery unit 12 includes handles 84 adapted for manual manipulation by a workman to thereby hold unit 12 above the concrete placement point. In addition, eye 85 is carried on a top portion of unit 12 to cooperate with hook 86 on the end of section 74 of extendable boom 71 to thereby allow concrete mixing and delivery unit 12 to be remotely positioned over the desired placement point by the action of boom 71.

Referring to FIGS. 8-10, the concrete delivery system carried by truck 70 is shown in detail. As illustrated in FIG. 9, cement loading port 79 operatively communicates with cement hopper 90; aggregate loading opening 80 comprises the upper portion of sand hopper 91; aggregate loading opening 81 comprises the upper portion of rock hopper bin 92; and water loading port 82 operatively communicates with water tank 93.

Cement hopper 90 comprises a conventionally shaped cement hopper wherein the sidewalls converge to the bottom section 94 which is narrower and smaller in cross-sectional area than the upper inlet portion of hopper 90. The bottom section 94 of cement hopper 90 opens directly into feeder unit 95. Feeder unit 95 comprises an enclosed vane-type feeder which includes several vanes 96 mounted upon a spindle 97 which rotates within an enclosed housing which in turn communicates between cement hopper 90 and cement receiving manifold 98. A suitable such feeder unit includes the rotary air lock feeder unit sold under the trademark of ROTO-FLO by Wm. W. Meyer &amp; Sons, Inc., of Skokie, Ill. Thus, the speed at which spindle 97 rotates will control the amount of cement which is delivered to cement receiving manifold 98. The speed control for spindle 97 will be discussed in detail below.

Sand hopper 91 and rock hopper 92 are illustrated as comprising four sidewalls which converge to elongated rectangular shaped bottom sections 99 and 100, respectively. Solids feeder systems 101 and 102 are operatively positioned within each bottom section 99 and 100 of sand hopper 91 and rock hopper 92, respectively. Air blower 103 is positioned under rock hopper 92 and carries an air inlet 104 and air delivery conduit 105 which operatively communicates from the outlet of air blower 103 through solids feeder unit 102, conduit 114, solids feeder unit 101, conduit 115, and cement receiving manifold 98 to air-solids manifold 106.

3,779,519

Solids feeder units 101 and 102 have the same basic components and function basically in an identical manner and will be described specifically in relation to solids feeder unit 102, as illustrated in FIG. 8. The identical components of solids feeder units 101 and 102 are identified by the same arabic character expect those of solids feeder unit 101 are followed by the letter a. As illustrated, solids feeder unit 102 comprises shroud 107, which is a housing positioned around endless belt 108 which in turn is movably mounted over roller 109 and 110. Endless belt 108 carries a series of upright cleats 111, each carrying a resilient lockingportion 112 on the tip thereof, which makes sealing contact between endless belt 108 and shroud 107. As shown, shroud 107 extends completely around endless belt 108, making sealing contact with resilient locking portions 112 of each upright cleat 111. In addition, extensions 113 of shroud 107 extend inwardly into hopper 92, a short distance at the points wherein endless belt 108 enters and exits from bottom section 100 thereof.

Air delivery conduit 105 operatively communicates through the lower middle sidewall of shroud 107 at a point between the lower returning portion 108L of endless belt 108 and bottom section of shroud 107. As shown in FIGS. 9 and 10, conduit 114 communicates between shroud 107 of solids feeder unit 102 and shroud 107α of solids feeder unit 101 opposite the point that air delivery conduit 105 communicates with shroud 107. Thus, conduit 114 communicates with shroud 107a in exactly the same manner that air delivery conduit 105 communicates with shroud 107. In this manner an air flow path is provided from air delivery conduit 105 through the lower middle sidewalls of shroud 107 to the lower middle sidewall portion of shroud 107α via conduit 114. Again referring to FIGS. 9 and 10, conduit 115 communicates from the lower middle sidewall of shroud 107α at a point opposite the place of connection of conduit 114 to cement receiving manifold 98. Therefore, a flow path is provided from air delivery conduit 105 through the lower middle sidewall portion of shroud 107 below the lower portion 108L of endless belt 108 and into conduit 114, from conduit 114 through the lower portion of shroud 107a and under the lower portion 108L of endless belt 108α contained therein, from shroud 107α to conduit 115, and from conduit 115 through cement receiving manifold 98 to air solids manifold 106.

Now referring to FIGS. 8-10, the power connections to the solids feeder units 101 and 102, air blower 103 and the water supply unit in truck 70 will be explained in detail. As shown, transfer case 116 from drive shaft 117 of engine 130 operatively communicates to differential joint 118 for providing power to the rear wheels of vehicle 70, and also to air blower 103 via drive shaft 120. Air blower 103 can be any conventional blower mechanism which is powered by drive shaft 120 and is illustrated (in broken line) as a “Rootes” type blower 121 rotatably mounted within the housing forming the exterior of air blower 103. Transfer case 116 is attached to a conventional control mechanism for controlling the engagement and disengagement of driveshaft 120 to the power train.

In addition, conventional power take-off unit 122, fo example a hydraulic power take-off unit, is attached to driveshaft 117 from the engine 130. Power take-off unit 122 can be any conventional power take-off unit such as for example the one manufactured by Spicer

Corp. Power take-off unit 122 provides rotating power to a spindle 123 which in turn drives pulleys (timing pulleys) 124 and 125. Timing pulley 124 carries a series of four timing belts 150 which in turn drive pulley 126, which is operatively attached through clutch 127 to the power system for solids feeder units 101, 102 and cement feeder unit 95. Clutch 127 is any conventional clutch unit which is adapted to be operated by the driver of vehicle 70. Spindle 128 from clutch 127 communicates to right angle gear box 129. Right angle gear box 129 carries a suitable right angle gear mechanism such as a pair of miter gears which transfer rotating power to feeder drive shaft 131. Feeder drive shaft 131 directly drives roller 109 which functions to drive endless belt 108 and in turn communicates through variable speed drive mechanism 132 which operates to drive roller 109α, which in turn drives endless belt 108α. Variable speed drive mechanism 132 can comprise any conventional drive mechanism such as manufactured by Link Belt Corp, under the tradename “PIV” and functions to rotate shaft 133 for drive roller 109α of endless belt 108α. Feeder drive shaft 131 which passes through variable speed drive mechanism 132 functions to operate variable speed drive mechanism 134 for cement feeder 95. Variable speed drive mechanism 134 can be any conventional variable speed mechanism such as variable speed drive mechanism 132 and functions to drive sprocket 135 at a suitable speed. Sprockets 135 drives chain 136, which in turn communicates over sprocket 137 of cement feeder 95 and functions to rotate the feeder vanes 96 therewithin.

In addition to driving timing pulley 124, spindle 123 of power take-off unit 122 also drives timing pulley 125 which drives timing belts 151 that pass over pulley 138 of water pump 139. Water pump 139 communicates with water tank 93 via conduit 140 and with water delivery conduit 17 via conduit 141.

In operation of truck 70, with the engine 130 running, extendable boom 71 is adjusted in a conventional manner so that concrete mixing and delivery unit 12 can be positioned with its outlet 18 directly over a desired concrete placement point. Next, transfer case 116 is engaged so that driveshaft 120 to air blower 103 is energized, thereby causing a continuous stream of air to pass from air conduit 105 through the lower portion of shroud 107, conduit 114, the lower portion of shroud 107α, conduit 115, cement receiving manifold 98, and air solids manifold conduit 106 to delivery conduit 10 operatively communicated thereto. Next, power take-off unit 122 is engaged to thereby impart rotating motion to pulleys 124 and 125 which in turn impart rotating motion to pulley 126 and pulley 138 which drives water pump 139. The actuation of clutch 127 rotates solids feeder drive shaft 131, and causes the rotation of roller 109 and the subsequent movement of endless belt 108 carrying celats 111 across the bottom of rock hopper 92. Similarly, driveshaft 133 is energized causing the rotation of roller 109α and the subsequent movement of endless belt 108α, causing cleats 111α to move across the bottom of sand hopper 91. In similar manner, sprocket 135 is actuated causing the movement of sprocket 137 and the subsequent rotation of vanes 96 in cement feeder unit 95. This action causes rocks to be entrapped between cleats 111 and carried under shroud 107 adjacent the outlet of conduit 105. Air passing from conduit 105 is maintained at a solids entraining velocity sufficient to entrain the rocks

3,779,519 between adjacent cleats 111 and pass them through shroud 107 into conduit 114. In similar manner, sand is entrapped between cleats Illa as they pass across the bottom of hopper 91 and under shroud 107α. The air containing the entrained rocks passes from conduit 114 through adjacent celats 111α within shroud 107α and entrains the sand therewithin to yield an air-sandrock stream which is delivered to conduit 115. The vanes 96 of cement feeder 95 deposit the requisite amount of the dry Portland cement into the cement receiving manifold 98. This cement is entrained in the air-sand-rock stream to form a combined air-solids stream which is delivered into air-solids manifold conduit 106 which in turn delivers the mixture to fluidsolids conduit 10 which operatively communicates with concrete mixing and delivery unit 12 as explained in detail in FIGS. 1-6. The rotation of endless belts 108 and 108α and the rotation of vanes 96 within cement feeder 95 are synchronized such that a suitable ratio of rock-to-sand-to-cement is delivered through the airstream passing to conduit 10. A suitable such ratio with an air velocity of from 75 to 200 feet per second includes a weight ratio of cement-to-sand-to-rock for example of about 1:3:3.7. The composition of the concrete mixture being delivered is adjusted by varying the speed of the sand and cement and water feeder systems with respect to the rock system. It is well understood that one skilled in the art can alter the ratio between air, cement and aggregate in any suitable manner to provide the desired cementitious mix.

Simultaneously, actuation of water pump 139 by timing belts 151 results in water flow passing from conduit 140 to conduit 141, which is in communication with water delivery conduit 17. Water delivery conduit 17 in turn delivers suitable amounts of water to water injector 16 which uniformly injects water into the fluidsolids stream flowing through conduit 10. With the weight ratios as set forth above, water can be injected into such stream in amounts as required to produce the desired concrete consistency. The fluid-solids stream passing from water injector 16 is passed into the inlet of concrete mixing and delivery unit 12 in a manner as described above in relation to FIGS. 1-6. The stream is decelerated and thoroughly mixed, within unit 12 and is allowed to drop from the outlet 18 thereof upon the predetermined concrete placement point.

While this invention has been described in relation to its preferred embodiments, it is to be understood that various modifications thereof will now be apparent to one skilled in the art upon reading this specification, and it is intended to cover such modifications as fall within the scope of the appended claims.