US2043457A

US2043457A - Concrete aggregate testing device

Info

Publication number: US2043457A
Application number: US603579A
Authority: US
Inventors: Mark A Weckerly
Original assignee: Toledo Scale Manufacturing Co
Current assignee: Toledo Scale Manufacturing Co
Priority date: 1932-04-06
Filing date: 1932-04-06
Publication date: 1936-06-09
Anticipated expiration: 1953-06-09

Description

M. A. WECKERLY 2,043,457

CONCRETE AGGREGATE TESTING DEVICE Filed April 6, .1932

June 9; 1936.

2 Sheets-Sheet l 5 5' I Mark A. Weck /g INVENTOR.

A TTORNEY.

June 9,- 1936. M. A. WECKERLY 2,043,457

CONCRETE AGGREGATE TESTING DEVLCE Filed April 6, 1952 2 Sheets-Sheet 2 I'N.VENTOR. Mark A. Weaker/y.

A TTORNE Y.

Patented June 9, 1936 I UNITED STATES CQNCRETE AGGREGATE TESTING DEVICE Mark A; Weckerly,.Toledo, Ohio, assignor to Toledo Scale Manufacturing Company, Toledo, Ohio, a corporation of New Jersey Application April 6, 1932, Serial-No.- 603,579.

3 Claims;

. Concrete is made of cement, water and: sand;

gravel or crushed. stone; a mixture of sandand gravel or crushedstone often being used. Other inert materials, such as cinders and slag, are sometimes substituted in wholeor in partfor the sand and gravel. The sand, gravel and other inert materials are known as aggregates.

The economical production of'concrete having maximum strengthhis. dependent upon proper proportioning of the materials entering into each batch, particularly the water and cement, since thestrength of the concrete depends largely upon the. water-cement ratio. There. is practically always some Water adhering to the particles. of sand and other fine aggregates which constitutes an. unknown variable. Such water is. known as surface moisture, and-ait may vary in. quantity from: less than 1. per cent of the weight of sand which has been piled in covered sheds for a long while to nearly 15 per cent of the weight of freshly washedsanid or of unprotected sand after a rain. Each 1 per cent of vari-- ation of surface moisture in the aggregate may change the water-cement ratio 4 per cent or more. Because of such variation it has. been customary'to build concrete structures with factors of safety ranging up to 9, and large factors of safety employed to insure proper strength.re.- quire more material to be used than wouldibe necessary if smaller factors could be employed. The determination of the amountof water ad-.- hering to the sand is, therefore, an important prerequisite to the eflicient production of concrete. It has been attemptedito compensatefor surface moisture in the sandlby. so-oalledrvolumetric displacement or inundation methods, but many authorities on concrete construction have become dissatisfied with such methods and now recommend proportioning the concrete ingredi ents more accurately on the basis of weight.

The principal object of my invention is the provision of improved means for determining with accuracy the amount of surface moisture and/or totalmoisture in sand and other concrete aggregates;

Another object of this invention is the pro-.- vision of improved means for determining with accuracy characteristics of concrete. aggregates, knowledge of which is necessary for. economical production of concrete having high strength and durability.

A further object is the provision of improved means for determining the specific gravity'of concrete aggregate and other water insoluble material.

A furtherobject isthe provision of improved means. for determining the amount of moisture adhering tothe surfaces of concrete aggregates and similar materials.

A further object is the provision of improved means of determining the amount of the' socalled water of crystallization in sand and other concrete aggregates.

A still further object of the invention is the provisionrof-improved means for determining the totalimoisture content of sand and. other concrete aggregates.

These and other objects and advantages will be apparent from the following description and the accompanying drawings wherein similar reference numerals designate similar parts throughout the several views.

In the-drawingsaa Figure I is a front elevational view of a scale embodying one of the several possible different formsof my invention.

Figure II isanenlarged front elevational view of. the load-counterbalancing and" indicating mechanism thereof.

Figure III is an enlarged cross sectional view of the receptacle for the'material to be tested for moisture.

Figure IV is a fragmentary sectional back View through-a portion of the. housing and showing, the mechanism of a manually operated pointer.

Figure V is a sectional view along the line V.V of Figure IV.

Referring to the drawings in detail, the scale with which I have shownthe embodiment of my invention' incorporated is of the well known Toledo-type and fully illustrated and explained in UnitediStatesPatent No. 1,543,768 to Halvor O. Hem,.and:Iwi1l, therefore, describe it only insofar as islnecessary to properly disclose my invention. The scale as showncomprisesa base I, prefer+ ably'a:solidzironcasting, which is mounted on Wheels 2 for ease in transportation. Suitable leverxmechanism: (not shown) supported by the base: I in turn' supports aload+receiving platform 3.; Thelevermechanismpivotally engages the bottomiofra connecting rodd and serves to transmitthef'orcexof a-loadstanding on the platform to aratiolever 5.fulcrumed at 6 in a column 1 which. is rigidly. bolted to: an extending end of the basevl. Iii-spaced relation with the fulcrum pivot:irr'ztheleverrfv are a load pivot 8 and a force transmission" pivot 9: The upper end of the connecting rod: engages" a stirrup l0 suspended from the load.pivots-8.- The force transmission pivot 9 is equipped with a stirrup II and is engaged by a short connecting rod l2 whose upper end is connected to a stirrup i3 engaging a load pivot 14 fixed in a ratio lever l5 fulcrumed at I6 upon the bracket I'I stationed and secured within a substantially watch-case-shaped housing is which surmounts the column I.

The lever l 5 is also provided with a nose pivot l9 which engages a stirrup 2U fastened to the lower end of a rod 2| which is adjustably held .in a yoke-like member 22. Connected to this member are ribbons 23, the upper ends of which are secured to and overlie arcuate surfaces of power sectors 24 which are a part of the load-counterbalancing pendulums 25. These pendulums also are provided with fulcrum sectors 26 having arcuate surfaces to the lower ends of which are fastened flexible metallic ribbons 2? whose upper ends are secured to a frame 28 and thusform a suspension for the pendulums 25. Secured to the fulcrum sectors 26 are pendulum bodies 29 into which stems 38 are threaded and adjustably secured on the stems 30 are pendulum weights (H. A so-called compensating frame 32 is pivoted to the pendulums 25 at 33 and partakes of the vertical movement of the pendulum bodies. Midway between the suspension points 33 of the frame 32 a rack 34 is pivotally suspended. The

teeth of this rack engage the teeth of a pinion (not shown) fixed on an axle 35 mounted in suitable ball bearings in the frame 28. An indicator hand 36 is fastened to a projecting end of the axle 35 and is thus actuated by the movements of the pendulum.

When a load is placed on the scale platform 3, the force resulting from its weight is transmitted through the rods 4 and I2, levers 5 and l 5 and the ribbons 23 to the pendulums 25 to move them outwardly and upwardly until their increased load moment balances the force. The movement of the pendulums is proportional to the weight of a load on the platform and the indicator being directly driven by the pendulums assumes an angle from its initial zero position which is in proportion to the weight of the load and indicates the weight on weight indicia 31 on a chart 38 which is mounted in the housing H8.

The scale thus far described is adapted to accurately indicate the weights of loads on the platform 3. For the purpose of supporting samples of aggregates and/ or other materials to be tested, the lever 5 has secured to one of its projecting ends a bracket 40 provided with a pivot 4| which is in spaced relation to the fulcrum 5. This pivot 4| is engaged by a stirrup 42 and suspended therefrom is a' material receptacle 43 provided with a snugly fitting cover 44 having a centrally located vent hole 45 and a hook-like projection 46 which is driven into its body. For the purpose of adjusting the weight of the receptacle 43, a cavity 41 is provided adapted to be filled with lead shot or other adjusting material and closed by a screw plug 48.

The upper edge of the receptacle body is machined to form a seat for a flange on the cover 44 and the bulk of the portion of the cover which projects into the receptacle body is adjusted by machining so that when the cover is in place the capacity of the receptacle is 2 pounds of water. Temperature changes and matter in solution cause slight variations in the weight of the receptacle full of water, but such variations as resultfrom changes in atmospheric temperature and from impurities ordinarily occurring in water have been demonstrated to be inconsiderable. When the receptacle is filled with water to near its upper edge and the cover is placed thereon, some of the water is forced through the vent, leaving a definite volume, and if the receptacle contain water only, a definite weight.

When anything is placed in the receptacle 43, the force resulting from its weight is transmitted through the levers 40 and i5 and the connections to the pendulum load-counterbalancing mechanism. The pendulums, under the influence of the load, move outwardly and upwardly until their increased weight moment balances the load in the receptacle, and the indicator hand 36 is moved to a position on the chart corresponding to the weight of the load. The weights and proportions of the parts are such that a load of 2 pounds in the receptacle will cause the indicator hand to move through an angle of 90 degrees. The position assumed by the indicator hand under the influence of the weight of a 2 pound load in the receptacle may be called the 2 pound position of the indicator hand. If 2 pounds of material, such as sand, having a greater density than water be placed in the receptacle and water be added to fill the receptacle to capacity, as shown in Figure III, the weight of the contents of the receptacle will be suflicient to move the indicator hand beyond the 2 pound position to a point depending upon the additional amount of water in the receptacle. The greater the density of the sand, and hence the higher its specific gravity, the less the bulk of a 2 pound sample and the greater the weight of the Water necessary to complete the filling of the receptacle; hence the greater the total weight of the sand and water. The total weight of contents of the receptacle may be found by solving for any value of specific gravity the following equation:

where S is the weight of a specimen of sand, W is the weight of a volume of water equal to the total capacity of the receptacle, sp. gr. is the specific gravity of the sand, and T is the total weight of the sand and water filling the receptacle. Since the weight of the specimen of sand has been taken for convenience as 2 pounds and the weight of a volume of water equal to the total capacityof the receptacle is 2 pounds, the weight of the water which remains in the receptacle with the sand is 2 pounds less the Weight of the water which is displaced, that is 2 pounds minus the quantity (1 divided by the specific gravity of the sand multiplied by the weight of the sand.

For sand having a specific gravity of 2.50 the equation becomes:

2 2+2- )3.2 pounds The indicium indicating specific gravity of 2.50, therefore, is placed at the point on the chart to which the indicator hand is moved by a total weight in the receptacle of 3.2 pounds. By similar calculations the proper location for an indicium indicating a specific gravity of 2.60 is determined to be the point to which the indicator hand would be moved bya total weight in the receptacle of 3.23077, the indicium for specific gravity 2.67 is located at a point corresponding to a total weight of 3.250936 pounds, etc.

The chart beingv thus calibrated and marked with the group 53 of specific gravity indicia, when it is desired to determine the specific gravity of a sample of sand the sandis first surfacedried by subjecting it to moderate heat. Exposure to the sun fora short time is often sumcient. In surface dryingthe sand care must be taken not-to drive out the water of crystallization. Enough of the surface dry sand ispoured into the dry receptacle 43 tocause'the indicator to move through an angle of degrees to its 2 pound position. The receptacle is then filled with water and the cover put on, after which all water adhering to the outside of the receptacle and cover is wiped off. The force exerted by the weight of the contents of the receptacle acts through the lever and pendulum mechanism to cause the indicator hand to move to a position in which it indicates on the group of indicia 53 the specific gravity of the sand in the sample being tested.

In testing sand for surface moisture thesize of the sample taken depends upon the specific gravity of the particular sand being tested for moisture. Specific gravities of most sands used as concrete aggregates are near 2.67. For this reason, a mark on the chart at the 2 pound position of the indicator hand is arbitrarily designated 2.67 and when sandhaving a specific gravity of 2.67 is to be tested for moisture a 2 pound sample is used.

Supposing a 2 pound sample of sand having a specific gravity of 2.67 to be placed in the receptacle and the receptacle filled with water as in making a test for specific gravity. If the sand were surface dry, the indicator would move to a position indicating 2.67 on the specific gravity group of indicia, since the amounts of sand and water in the receptacle would be the same as before, and the total weight of the contents would be 3.250936 pounds. Being the position taken by the indicator hand when there is no surface moisture in the sand, this position is marked 0 on the percentage of moisture group of indicia 52. If a given weight of sand which is not surface dry is placed in the receptacle, the sand and moisture will occupy more space than would be occupied by the same weight of surface dry sand. Therefore, less water will be required to fill the receptacle and the totalweight of thecontents of the receptacle will beless than it would be if the sand were surface dryythe more surface moisture the sand contains the less the weight of added water necessary to fill the receptacle, and hence the less the total weight.

The total weight for sand having a specific gravity of 2.67 depends upon the weight of moisture in the sand and is determined according to the equation where S is the weight of surface dry sand in the sample, X is the weight of moisture in the sample, W is the weight of a volume of water equal to the total capacity of the receptacle, and T is the total weight of the sand and water filling the receptacle.

Since the weight ofthe sample taken is 2 pounds, the quantity (S'+X) becomes 2 and the quantity S becomes 2-X. The weight of a volume of water equal to the total capacity of the receptacle is 2 pounds. Therefore. 2 maybe substituted in the equation forthe quantity W. Substituting these values. in the equation, we have but weight of sample multiplied by 200 The indicia 52 on the chart representing percentages of moisture are located by assigning val.- ues to Y ranging from 0 to 25. For example, the

location of the indicium for 10 per cent of moisn ture is determined thus:

Hence the indicium for 10 per cent of moisture is located at the point to which the indicator hand is moved by a total load of 3.1372 pounds in the receptacle.

If the specific gravity of the sand being tested for surface moisture is below 2.67, it is necessary to use a heavier sample in order that the percentage of moisture may be indicated on the same group 52 of indicia. If the specific gravity of the sand in the sample is higher, a lighter sample is used.

The indicia of the weight of sand group 5| are so located that a weight of surface dry sandin the receptacle sufficient to move the indicator to the indicium corresponding to the specific gravity of the sand plus water sufilcient to fill the receptacle when the cover is in place will move the in dicator hand to the zero mark on the percentage of moisture group, that is, to the 3.250936 position.

The indicia in the weight of sand group 5| are located by substituting figures representing specific gravities, ranging from 2.50 to 2.80, for sp. gr. in the equation.

sp. gr.

where S" is the weight of the sample of surface dry sand, W" is the weight of a volume of water equal to the total capacity of the receptacle, and sp. gr. is the specific gravity of the sand. Substituting, for example, a value of 2.60 for sp. gr. and solving forS", We obtain 2.03277. Using the value 2.60 for sp. gr. and the value 2.03277 for the quantity S+X in the equation sp.gr.

we obtain 2.03277X 4.03277 +X)T But of the moisture and is equal to 2.03277 pounds minus S, that is, the weight of the sample minus the surface dry weight of the sand. Therefore By substituting this value of X and simplifying, the value of T becomes for a sample of sand having a specific gravity of 2.60. This is the same value for T as was found for a 2 pound sample of sand having a specific gravity of 2.67, thus indicating that the total weight of a 2.03277 pound sample of sand having a specific gravity of 2.60 and containing a certain percentage of surface moisture, with enough water added to fill the receptacle, is the same as the total weight of a 2 pound sample of sand having a specific gravity of 2.67 and containing the same percentage of surface moisture with enough water added to fill the receptacle. Similarly, it can be shown that the value of T is the same for sand of any specific gravity if the weight of the sample employed is such as to move the indicator hand to the indicium in the weight of sand group 5| corresponding to the specific gravity of the sand. Hence the same percentage of moisture indicia may be used to indicate the percentage of moisture of sand of any specific gravity.

It is sometimes desired to determine the deficiency of absorbed moisture or water of crystallization in aggregates or the amount of moisture which will be reabsorbed by aggregate which has been made bone dry by driving out the absorbed moisture. Therefore, the percentage of moisture group of indicia 52 has been calibrated for a short distance on the minus side of zero. In making a test to determine the amount of moisture which will be absorbed by bone dry aggregate, the procedure is the same as in determining the percentage of surface moisture except that the sample in the receptacle should be covered with water and allowed to stand until maximum absorption has taken place before water is added to fill the receptacle. The weight of the absorbed moisture will cause the indicator hand to move to correct indicating position beyond the zero mark on the percentage of moisture group of indicia.

In addition to the weight graduations and the groups of indicia marked Specific gravity, Percentage of moisture and Weight of sand, the chart 38 is provided with an arcuate row of graduations for use in making sieve analyses of aggregates. The capacity and arrangement of the sieve analysis row of graduations is such that 2 pounds of sand or other aggregate in the receptacle will bring the indicator hand to the 100 per cent mark. The sample then may be separated by screening into as many parts as desired and when each of the parts so separated is placed in the receptacle the indicator hand will overlie the mark on the arcuate row of graduations 50 indicating the percentage of the whole that is constituted by the part in the receptacle.

Adjacent to the weight of sand series of indicia 5| is a narrow slot 54 through which a pointer 55 projects. The pointer is actuated from the exterior of the housing l8 by a thumb nut 56 and is adapted to be set in registry with any of the graduations and numerals of the weight of sand series of indicia. Secured to the rear of the chart 38, near the slot 54, is a formed sheet metal stamping 51, and near one end of the stamping a twoarmed bracket 58 is riveted, the arms of the bracket being provided with apertures through which a pintle 59 extends. A U-shaped member 60 is fulcrumed upon this pintle and is provided at the other end of the arms forming the U with apertures through which a stem 6| projects. One end of the stem is driven into the thumb nut 56 and on that portion lying between the arms of the member 69 a roller 62 is fastened. This roller is covered by a section of a rubber tube 63 which frictionally engages a plate-like member 64 provided with two short pins 55 which project into an arcuate slot 66 punched in the stamping 51. The center of curvature of the arcuate slot 66 is coincident with the radial point of the several series of indicia on the chart. The pointer 55, previously referred to, is fastened to the plate 64. To insure driving friction of the roller 62 against the plate 64, a spring 67 continuously urges the roller 63 against the plate 64.

To prevent mistakes from occurring should the operator forget the specific gravity determined, which determination will remain good so long as sand from the same source of supply is being used, the pointer 55 is moved into registration with the proper indicium by turning the thumb nut 56, which in turn moves the plate 84 and the thereto attached indicator 55 in a manner which can be readily understood by referring to Figures IV and V.

The embodiment of my invention herein shown and described is to be regarded as illustrative only, and it is to be understood that the invention is susceptible to variation, modification and change within the spirit and scope of the subj oined claims.

Having described my invention, I claim:

1. In apparatus for determining characteristics of concrete aggregates, the combination of a sample receptacle of definite volume, automatic load-counterbalancing means, means for connecting said receptacle to said automatic loadcounterbalancing means so that the load in said receptacle Will be counterbalanced by said automatic load-counterbalancing means, and indicating means operatively connected to said automatic load-counterbalancing means, said indicating means including a relatively movable chart and indicator, said chart being marked with a series of indicia for indicating percentages of moisture, the indicia of said series being located in positions to which said indicator will be brought by total loads in said receptacle according to the equation where S is the weight of surface dry aggregate in the specimen, X is the weight of moisture in the specimen, W is the weight of a volume of water equal to the total capacity of the receptacle, sp. gr. is the specific gravity of the aggregate, and T is the total weight of aggregate and water filling the receptacle, and the equation weight of sample multiplied by 100 200 where Y is moisture in terms of percentage of weight of surface dry aggregate.

2. In apparatus for determining characteristics of concrete aggregates, the combination of a sample receptacle of definite volume, automatic load-counterbalancing means, means for connecting said receptacle to saidautomatic loadcounterbalancing means so that the load in said receptacle will be counterbalanced by said automatic load-counterbalancing means, and indicating means operatively connected to said automatic load-counterbalancing means, said indicating means including a relatively movable chart and indicator, said chart being marked with a series of indicia for indicating weights of samples to be used in testing for percentage of moisture, the indicia of said series being located according to the equation I! WII S s sp. gr.

Where S" is the Weight of surface dry sand in the sample, W is the weight of a volume of water equal to the total capacity of the receptacle, and sp. gr. is the specific gravity of the aggregate.

3. In a device of the class described, in combination, means for weighing out a definite quantity of moist aggregate, said quantity being dependent upon its specific gravity, measuring means incorporated with said weighing means for measuring a definite volume comprised of said quantity of moist aggregate and water, and means connected to said Weighing means for automatically indicating the percentage of moisture in said moist aggregate.

MARK A. WECKERLY.