US1733410A - Method of proportioning aggregates and water for concrete - Google Patents

Description

Oct. 29, 1929. c, s, JOHNSON 1,733,410

METHOD OF PROPORTIONING AGGREGATES AND WATER FOR CONCRETE Filed Feb. 26, 1927 nmammml 2%,

Pasta oa.29,1929 i 1,133,410,

UNITED STATES PATENT; OFFICE CHARLES S. JOHNSON, OF GHAMPAIGN, ILLINOIS METHOD or raoron'rxomne aeenmaras AND WATER ron concurs Application filed February 26, 1927. Serial m3. 171,310.

The invention relates generally to the art well as to sand.) Moist sand is also subject of making concrete and more particularly to to such changes of density or compaction. a method of accurately proportioning the If the sand be submerged it is still subject amount of total water in the mix indeto density changes or changes in compaction pendently of the amount of moisture conwhen jarred or tam ed or allowed to stand 55 tained in the aggregates. undisturbed, these 0 langes again depending It is well recognized that the strength of in part upon the gradation. Thus these prior concrete depends largely upon the total processes wherein the quantity of sand has amount of water in the mix. If the amount been measured by volume have been unsatisofwater is just suificient fully to react with factory in, that they do not rovide an ac- 60 the cement, the resulting mix gives the maxicurate means to determine t 1e total quanmum strength, but the mix is too stilt for tity of water in the mix. This error has most practical purposes. \Vith a lesser been due largely to the fact that the gradaamount of water the strength of the concrete tion and voids of commercial sand vary, and

decreases rapidly in proportion to the amount that the density changes. 5

of water while with an excess of water the The specific gravity of commercial sand, strength of the concrete also decreases rapidhowever, is a quality that cannot be altered 1y with increasing quantities of water so that by handling, jarring, tamping, gradation or with 100% excess water the strength of the standing undisturbed, and tests have shown concrete is about 20% of the maximum obthat commercial building sand coming from 70 tainable with no excess water/ It follows many separated sources is remarkably unithat the accurate determination of the quanform in its specific gravity. If therefore tity of water included in each mix is highly water is combined with sand until the total essential to obtain concrete of uniform and weight of the. water and sand equals a prepredetermined strength. determined amount at a predetermined vol- It is the object of the invention to provide ume, the total amount of water in the mix an improved method of accurately propormay be accurately determined. Furthermore, tioning the total water in a concrete mix. changes in the moisture content in commer In the processes used heretofore wherein cial sand alter the apparent volume of the tlle normally moist aggregates are measured sand due to the resulting changes in bulkby volume and then introduced into a coning,'but do not alter the total absolute volcrete mix with separately proportioned units ume of the sand particles. The changes in of water, variations in the moisture content apparent volume are not directly propor of the aggregates have caused variations in tional to the changes in moisture content 5 the total water in the mix. These ariations throughout the full range ofpossible moisin total water content in concrete mixtures ture content in the sand. However, an analychange the consistency of the mixed concrete, sis of the bulking characteristics of comincrease the placing expense dueto changes mercial sand has disclosed that the absolute in workability, cause changes in the strength volume of sand in equal apparent volumes of 40 of the concrete, all other factors being held moist sand is quite constant within a certain constant, and may cause honey combed con range of moisture variation, and records discrete. close that in commercial sand the moisture Loose dry sand is subject to density content holds quite closely within the limits changes or changes in compaction by jarring of'this range. 45 or tamping, these changes depending in part Thus the variation in absolute volume of upon the gradation. (The term sandwill sand measured by apparent volume is practihereinafter be used instead of aggregate, it cally negligible in commercial work, and sand being understood that the invention is apmeasured by apparent volume will give pracplicable to aggregates generally, i. e., those tically uniform absolute volumes independent 50 coarser than sand such as gravel or stone, as of the moisture cc ntent within this range.

I utilize these facts in providing a process for proportioning the total amount of water for a concrete mix, the process consisting generally of measuring a predetermined volume of moist commercial sand and then combining with that sand a quantity of water such that the combined sand and water equals a predetermined volume. The weight of the combined sand and water is then checked against the weight of a like volume of sand and water having a predetermined weight.

For the purpose of more clearly illustrating and disclosing the invention, I have shown in the drawing the preferred form of an apparatus which is adapted to utilize the process, together with diagrammatic sectional views of the apparatus at various stages of the process. However, it is to be clearly understood that the form of the apparatus may be varied and altered at will without departing from the spirit and scope of the invention as defined in the appended claims.

As shown in the drawings:

Figure 1 is an elevational view of the preferred form of the apparatus.

Figs. 2 and 3 are sectional views thereof at difierent stages of progress of the process.

Referring to the drawings, the apparatus as illustrated comprises a bin 1, an adjustable measuring hopper 2 and a weighing mechanism designated generally as 3. The bin may be supported by any suitable means (not shown) and the hopper and weighing device are herein shown as suspended from the bin.

The weighing device in the preferred form of the invention comprises an adapter frame or bracket 4 having an annular ring portion 5 and an arm-like extension 6. The ring portion may be secured to the bin 1 as by means of bolts 7 and has an aperture 8 therein which coincides with a discharge opening 9 in the bin. An annular valve frame 10 is clamped against the annular portion 5 of the bracket 6 by means of bolts 11 which are entered through apertures in lugs 12 on said parts.

This valve frame has an opening 10 there-' through coinciding with the apertures 9 and 8 in the bin 1 and bracket 4 thereby to form a discharge pipe for the bin which may be opened and closed by means of a gate 13. This gate is pivotally mounted on the valve frame 10 and is operable by means of a handle 14.

A load supporting member or scale ring 15 is positioned surrounding the annular valve frame 10 and serves as the scales for the weighing device. A beam 16 is fulcrumed intermediate its ends at 17 bv means of a link 18 which is suspended from the arm 6. This beam is connected to the scale ring 15 by means including a lever 19 pivoted intermediate its endsto a depending portion 20 of the arm 6, a linkage 21 connecting the outer end of this lever with apivot 22 on the beam, and linkage 23 between the inner end of the lever 19 and a suitable leverage system of a well known construction designated generally as 24 which latter provides a suspension means for the scale ring (not shown in detail). The outer end of the beam 16 passes through an end opening in the arm 6 and may be locked against a stop pin 25 by means of the usual beam lock 26.

A sprin scale having an indicating dial 27 is suspended from the arm 6 by means of a link 28 and has its scale hook 29 connected to one end of a lever 30, the other end of which is connected to the free end 31 of the beam 16 by means of a link 32. The lever 30 is fulcrumed intermediate its end on a pivot 33 which is suspended from the arm 6 by means of a linkage 34 and has a weight 35 suspended therefrom.

The beam 16 is provided with two sliding poises 36 and 37, one positioned upon each side of the fulcrum 17 and has graduations 36 and 37 thereon reading both ways from the said fulcrum, as hereinafter more fully set forth. The pointer 38 of the dial 27 will register the amount off-balance between the setting of the poises on the beam and the weight of the measuring hopper and its contents which is suspended from the scale ring 15. With the poises set at zero the pointer also indicates zero, the spring scale then balancing the weight of the hopper empty.

The measuring hopper 2 as illustrated herein, comprises an upper conical portion or member 39 and a lower container 40. The container is generally cylindrical in form but has inwardly sloping sides 41 at the bottom thereof converging to define a circular discharge port 42, thereby to insure complete discharge of material from the hopper. The upper member 39 is preferably perforated to permit water to flow freely therethrough and is herein shown supported from the scale ring 15 of the wei hing device by means of a plurality of brac (ets 43 secured to the member 39 and chains 44 which are attached at their opposite ends to the said brackets and to the ring 15. The container 40 is adjustable relative to the conical member 39 of the hopper to permit of adjustment of the volumertic content of the hopper. For this purpose the container maybe suspended from the brackets 43 by means of chains and adjustable screw devices 46 having hooked portions 47 areprovided one on each bracket to receive the free end of a chain. Should it be desired to adjust the volume of the hop: per to a greater extent than that provided for by the screw devices, a lower link on each chain may be caught over the hooks 47. The volume of the hopper may be indicated by means of a scale 43 secured to a bracket 43.

A gate 48 having a water tight gasket 49 is provided to control the discharge port 42 of the hopper. This gate is carried on a 1,7as,41o

lever pivotally supported intermediate its ends at 51 on a bracket 52 which is secured rigidly to the container 40. The end 50 of this arm is loosely pivoted to an outstanding lug 53 positioned centrally on the gate. As herein illustrated the lever 50 is operable by means of a hand lever 54 pivoted at 55 on the bracket 52, and a toggle link 56 connecting the adjacent ends of the lever 54 and lever 50. Thus the gate may be opened and closed by means of the hand lever 54 and in its closed position the gate is held locked by the-toggle device, a stop lug 57 being provided on the hand lever and arranged to engage the bracket 52. lVith the force exerted by the lever 50 applied centrally of the gate the pressure of the gasket 49 on the container is equalized and uniform so as to insure an effective seating action throughout its periphery.

Inthe apparatus illustrated in the drawings means is provided to combine water with the sand in the hopper. For this pu1--- pose a pipe 58 leading'to a suitable supply of I water (not shown) is connected to the lower portion of the container 40. A valve 59 in this pipe line is adapted to controlthe flow therethrough. I

An adjustable overflow 60 is provided on the container 40 and is secured thereto by means including the bolts 61 anchored on the container. By loosening the nuts 62 of these bolts the overflow may be raised or lowered, graduations 63 being preferably provided upon the container adJaCent the overflow to indicate the volume of the container to which the overflow is set.

The process when utilized in connection with the apparatus disclosed consists generally in first measuring a predetermined volume of bulk or normally moist aggregate; second, combining water with said aggregate until the, combined aggregate and water equals a second predetermined volume, and

third, weighing the combined mass to determine the accuracy of the proportioning of the ag regate and water. For purposes of simpliclty, I shall continue to refer to aggregates as sand although as mentioned hereinbefore, the invention contemplates coarser aggregates as well.

For purposes of illustration it is desired to proportion 10 cubic feet of sand with 4 cubic feet of water. Assuming that bulk or normally moist sand contains 100 pounds of dry sand per cubic foot, specific gravity of sand is 2.70, and water weighs 62.5 pounds per cubic foot, then the absolute volume of 10 cubic feet of sand equals10X100/2.7 X625 or 1000/168.7 5 or 5.93 cubic feet.

Adding 5.93 to 4 (cubic feet of water) the total absolute volume of the combined mass equals 9.93 cubic feet, to which point on the scale 63 the overflow 60 is then'set.

The poises 36 and 37, the moment arms of these ises about the fulcrum 17 and the leverage etween the beam 16 and scale ring 15 are so designed that with the poises adjacent the fulcrum the beam balances the empty hopper and the pointer 38 indicates zero, i. e., a balanced condition. The graduations to the left of the fulcrum indicate combined volumes and the graduations to the right of the fulcrum and on the dial 27 indiacte cubic feet of water. Thus by setting the poise 36 at the combined volume- (in this instance 9.93), setting the poise 37 at the volume of water (in this instance 4) and adjusting the hopper to measure 10 cubic feet of bulk sand (as shown by the scale 43), the. apparatus is ready for operation.

The two poises and the graduations on the scale beam are provided in this manner so as to facilitate settin -up the a paratus for various combined vo umes an volumes of water to becontained therein. To obtain these results the oise 36 is such that its weight multiplied y its moment arm equals the combined volume (in this instance 9.93

cubic feet) of solid sand, i. e., sand without voids.

Thus with the overflow 60 and the poise 36 both set at 9.93 cubic feet (the poise 37 being set at zero) the beam 16 would balance with the hopper filled with solid sand. Inasmuch as part of this volume, however, is to be filled with water (in this instance 4 cubic feet), the poise 37 must counterbalance the poise 36 to the extent of .the difference in weight of that volume of water and a like volume of sand. This difference is equal to the volume of water multiplied by the difference between the specific gravities of the sand and water. Thus the combined or resultant weight indicated by the two poises on the beam equals the weight of the combined volume of solid sand minus the volume of water multiplied by the difference between the specific gravities of sand and water.

B =the combined weight of sand and water,

A=the combined absolute volume of sand.

and water, S ific gravity of sand=2.7, A the volume of the water, and 62.5=weight of a cubic foot of water,

then

, With the poises 36 and 37 set at 9.93 and 4 respectively, the overflow 60 set at 9.93 cubic feet and the volume of the hopper adjusted to 10 cubic feet on the scale 43", the preferred operation of the apparatus to utilize the process is as follows:

The gate 48 is closed, and the gate 13 is then opened to permit normally moist sand to discharge from the bin into the hopper. As shown in Fig. 2, when the sand stops flowing the gate 13 may be closed, thereby striking oif the column of sand and leaving the desired quantity of sand (10 cubic feet) in the hopper.

Water is then admitted from the supply line 58 by opening the valve 59, until the water in the hopper reaches the height of the overflow 60 as shown in Fig. 3. This point is generally determined by permitting some water to discharge over the overflow. Inasmuch as the conical member of the hopper is perforated the water rising within the cone and that between the cone and the container quickly assume a common level.

If now the pointer 38 indicates zero with the beam 16 unlocked, the water and sand have been combined in the proportion of 5.93 cubic feet absolute volume of sand and 4 cubic feet of water. This indicates that the assumption that one cubic foot of bulk sand contained 100 pounds of dry sand content was correct.

If, however, the pointer does not indicate zero, it is apparent that the bulk sand contained either more or less than 100 pounds of dry sand per cubic foot. Thus, if the pointer indicates to the right of zero (assuming that additional weight in the hopper turns the pointer clockwise) then it is obvious that the bulk sand contained more than 100 pounds of dry sand per cubic foot and that there is too much sand and therefore too little water in the hopper. If the pointer indicates to the left, the opposite is true.

The dial is preferably calibrated to indicate directly in cubic feet the excess or deficienc of water in the combined mass. lnasmuci as one cubic foot of dry sand weighs 168.75 pounds and a cubic foot of water weighs 62.5 pounds, one cubic foot of excess sand adds 168.75 minus 62.5 or

106.25 pounds excess weight to the combined mass. If therefore the poises 36, 37 are at the zero points of the scales 36, 37, and 106.25 pounds weight placed in the empty hopper, the pointer 38 will indicate one cubic foot on the scale of the dial 27. By adding increments of 106.25 pounds to the weight in the hopper, this sug ested method can be extended to calibrate t e entire scale.

With the dial calibrated in this manner the pointer 38 will indicate in cubic feet the excess or deficienc of water in the combined mass. Should t is excess or deficiency be within allowable limits, the contents of the container may discharged therefrom and used in a concrete mix. Should the pointer indicate a deficiency of water beyond the allowable limit, this means an excess of sand in the combined mass and to obtain the desired proportioning of sand and water, a second batch is prepared wherein the volume of bulk sand as premeasured is decreased by adjusting the hopper to decrease the volumetric content thereof, as indicated on the scale 43. Additional experimental batches may then be combined until the ointer indicates within the allowable limits. If, however, the pointer indicates an excess of water within the allowable limit, the opposite adjustment of the measuring hopper is effected in the succeeding experimental batches.

It is apparent that by this process the moisture introduced into the container as measured in the sand becomes a part of the total water and that the total water in the container is complementary in volume to the absolute volume of the sand. Inasmuch as the variation in absolute volume of sand measured by apparent or bulk volumes is less than the moisture variation within the range hereinbefore mentioned, it will be apparent that the variation in total water measured by this process will be less than that encountered when water and moist sand are measured by weight or by volume and later combined in a mix.

The process is particularly well adapted for use with ap aratus of simple construction and ready adjustment and because of its ease of operation lends itself particularly to field work. When used with the apparatus disclosed herein, and this apparatus has been calibrated as hereinbefore described, it is merely necessary for an operator to open the gate on the sand bin and thereby discharge sand into the hop er until the sand stops flowing. Then by c osing the gate he strikes off the sand to the predetermined volume. The valve 59 in the water line 56 is then opened and water permitted to flow into the hopper until some of it runs out through the overflow 60. The valve is then closed and if the ointer 38 indicates within the allowable limlts of water variation, the

combined mass is ready to be mixed with the.

measuring a predetermined volume of normally moist aggregate, combining water with said measured -aggregate so that the moisture in the aggregate combines with the added water until the combined aggregate and water equals a second predetermined volume, and weighing said combined mass.

2. A process for proportioning the water in a concrete mix which comprises placing a pre-measured quantity of moist aggregate in a container, flowing water upwardly through the a gregate to a predetermined level, and weig ling the combined. aggregate and water.

3. A process of proportionin water and a normally moist aggregate 0? concrete which consists in measuring by apparent volume a quantity of such aggregate, combining said aggregate with water so that the normal moisture in the aggregate combines with the water to produce a predetermined combined volume, and weighing the combined mass.

4. The process for proportioning water and-an aggregate for a concrete mix which consists in placing a measured quantity of bulk aggregate in a he per having a water outlet located at a pre etermined level, admitting water to the hopper from a point below said outlet until a quantity is free to run off through the outlet, and weighing the combined mass of aggregate and water.

In testimony whereof, I have hereunto affixed my signature.

CHARLES S. JOHNSON.

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