Thesis (B.S.)--University of Illinois, 1902.Typescript

Lundgren, Carl Leonard

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LUNDGRENComparative Strength ' *'..^of Gravel and t..^^fBroken-Stone Concretes ''^'^1902Civil EngineeringB. S. /*orII.I . 1 niHAHV* )f ^* ^4 ^, ,# >f 'f f f f ^, . ,^ ^"^'u-t- ^- * ^ 5^ ^ + * *^,# # # # #^ ^^^^^^^ ^^^^- ^^,^- ^ ^ * * f ^4- f ^ 4- 4^ if. ^ 4 ^^- ^ + ^" # # # ^ ^ ^# f ^ * #^- ^ f * f^< Tit- ^ ^-f ^ # ^ ^ I University of Illinois.0' ' ^ ^ ll* S CLASS. BOOK. VOLUME. ^ ^%^:| .# # * # U Accession No.' v/f,f I'm ^Ctatniiig anJ) jfaborLIBRARYo1^ ^:h *4 fif"t>*f44- -^^It f f ^ # # + f ^ ^^ ^ ^ ^ ^ ^ ^ ^ ii^ ^1^ ^41^^ ^ liN# ## ^ ^ ^1^-^^^ ft + ^ ^ 4#;+ ^^ 4^ # ^# #4 ## il^ #1^ ^ ^* # ^ #f- 1* # * #•4 # f # # ^=-^r!?* ^ 4 <^ if>. 4- 1* f- 4^ +# f + ^ ^I- *4 *iCOMPARATIVE STRENGTH QGRAVEL AND BROKEN-STONECONCRETESBYCARL LEONARD LUNDGRENTHESIS FOR DEGREE OF BACHELOR OF SCIENCEIN CIVIL ENGINEERINGCOLLEGE OF ENGINEERINGUNIVERSITY OF ILLINOISPRESENTED JUNE 1902UNIVERSITY OF ILLINOIS190THIS IS TO c;eiitify that the thesis prepared under my supervision by:...'(L.M.:r:X..:L.. Q^:<;...:I«H!^^ Q[^.*.4U.4M^J^.^,ENTITLED ^..^yLjl/y^ '^^ThrA^..^^:>-e-J^ AA.— .<^..^^i?s-<^ 1Iq..,4M>-ic 'lucIS APPROVED BY ME AS FULFII.LING THIS PART OP THE REQUIREMENTS FOR THE DEGREEOF«as^:*L»-jd(S^i^!ijS!i»cHEAD OF DEPARTMENT OF..GRAVEL VS. BROKEN STONE CONCRETE.The object of this thesis is to deterraine the relativemerits of gravel and brolcen stone as an aggregate for concrete.The question has been before the engineering public for some time,and has been discussed vigorously by some of the most capableengineers; but a conclusion satisfactory to all has not yet beenreached. The question arose v/ith the adoption of coTicrete as asubstitute for masonry, and interest in experiments made alongthis line has been increasing in proportion to the demand forconcrete in engineering structures. Every engineer may be surethat he will be called upon at one time or another, to put inmasonry of some sort; and if it should be concrete, as it is quitelively to be, he should knov; whether gravel or broken stone — thetwo materials most comj;,only used for concrete — makes the betteraggregate for concrete. The chief bone of contention lies in therelative strength of the concrete v/hen these t;7o materials areused as the aggregate.The writer, therefore, undertook a series of experimentsto determine the relative crushing strength of concrete made withgravel and that made with broken stone. The experiments consistedIn making a series of six- inch cubes using crushed limestone inone case, and gravel in the other, as the aggregate.Time was not available for testing cubes made of more thanone kind of cement; and, therefore, it v/as considered whether53464Digitized by the Internet Archivein 2013http://archive.org/details/comparativestrenOOIund~ 2 -natural or Portland cement should be employed, but it was decidedto use the latter, since it Is usually more uniform in quality andsince the recent decrease in price has made it much more comFionthan previouslj''. However, the kind of cement would make no practi-cal difference, as the conclusion reached would rem.ain relativelythe same whichever cement v;as used.The cement employed was Milton's English Portland, havinga tensile strength of 450 pounds per square inch, and a finenessas shown in the table follov^ing. The top row of figures denotethe number of meshes per square inch; the middle row the weight ingrams v/hlch was caught upon the sieve, except the last quantity,which denoteo the quantity that passed the No. 200 sieve; and thebottom row shov/a the preceding quantities in percent s.^50 it74: *100 =*200 *2005.5 120.^3 56.4 165 638.50.5 12.0 5.6 16.5 - 65.3The sand was taken from a bank north of Urbana, Illinois,and had been in a perfectly dry place for six months previous tothe time of its use in this experiment. It was sharp and clean,a small quantity rubbed between the hands leaving them unsoiled.It was screened through a sieve having forty-two meshes to thesquare inch, before being used.The gravel was also taken fiorii a pit in Urbana, Illinois,and was stored in a perfectly dry place until it was used. Seventy-five percent, by weight, of the gravel passed through a sieve havingholes one inch in diameter and was caught upon a sieve having holes- 3 -one-half inch in diameter, and the remaining twenty-five percentpassed a sieve with holes 2 inches in diameter and was caught upona sieve v;ith holes 1-inch in diaineter. It vras v/ashed free from alldirt and sand and was allov/ed to dry before being used.The crushed stone wac limestone from Kan>:a?.ee, Illinois,It was screened the same as the gravel and the same quantity ofeach size was used. It was perfectly dry and free from all foreignmaterial.The proportions of the concrete v:ere adjusted so that thevoids of the sand were filled with cement and the voids of theaggregate v;ith cement mortar.The voids in the gravel and the broken stone were determined asfollov.'s:- After a quantity of gravel had been v;eighed, a large pailwas partially filled v/ith water and the gravel poured into it.Finally a Known weight of water was added until it just coveredthe gravel. It is not sufficient to pour the water on the gravel,since the air contained in the latter can not escape freely, andhence will vitiate the result. The weight of the gravel and pailis Known, so the weight of the water required to fill the voids isdetermined. The weight of one cubic centimeter of water equalsone gram, so the number of grams of water used equals the nuraberof cubic centimeters of sand required to fill the voids. Therefore,the volume of sand required to fill the voids is equal to thevolume of the water so required, or the weight of sand is equal tothe weight of water in grams multiplied by the weight in grams ofa cubic centimeter.- 4 -The amount of sand by weight required to fill the voids inthe broken stone was determined in the saine manner as above, asalso the amount of cement to fill the voids of the sand, Thejfigures below show the quantity of sand to fill tlie voids in a;| certain number of grams of the aggregate, also the number of gramsof cement to fill the voids in the sand used to fill the voids ofthe agi^regate. The ratio of these weights gives the ratio of theIingredients of the concrete.Determination of ratio of ingredients in broken stoneconcrete.Weight of broken stone = 21,000 grams; V/eight of v;ater to fillvoids in stone - 5,123 gj'ams; and 1 cubic centimeter of sand weighs1.495 grams. 5123 x 1.493 = 7647 grpjns which - the weight of thesand required to fill the voids in 21,000 grams of broken stone.Weight of water required to fill the voids in 7647 grams of sand =2522 grama; 1 c.c. of cement weighs 1.19 grans; and 2522 x 1.19 =Ij3001 grams, the v/eight of the cement required to fill the voids inj7647 grams of sand. Ratio of ingredients = 3001, cement: 7647,j^sand: 21,000, gravel: or 1, cement : 2 l/2 sand: 7, gravel.IDetermination of ratio of ingredients in gravel concrete,jWeight of gravel = 19,500 graias; V/eight of v/ater required to fillthe voids in 19,500 grams of gravel ~ 5073 grams; and 5073 x 1.493||grams = 7574 grams, v/hi:?h = the total weight of sand required to'Ii; fllT the voids in 19,500 grams of gravel. Ratio of ingredients ='w5000, cement: 7574, sand: 19500, gravel = 1, cement: 2 l/2, sand:6 1/2 gravel.- 5 -The amount of water to be used in mixing the cenient andsand was determined by making a fevj mixtures and deciding accordingto the writer's own judgment.The cubes were made as follows:- After the gravel, stone-,cement and sand had been measured out in their proper proportions,the sand and cement were carefully mixed upon a slate table untila uniform color was obtained. The water v/as then added and thewhole mixed thoroughly. The aggregate — gravel or broken stone —was sprinkled with water, so it v/ould absorb no water from thematrix, and was then mixed with the mortar. All lumps of mortarwere crushed as the mixing proceeded. The concrete was then readyfor the moulds.The moulds were made of 1 1/2 inch material planed smooth,and consisted of two side boards and four cross pieces, which fitinto grooves in the side pieces. The sides of the mould weredrawn tightly against the intermediate pieces by means of four1/2 inch bolts just outside of the ends. The moulds are easilyremoved from around the cubes with no danger of crushing thecorners.The concrete was placed in the moulds in 1 1/2 inch layersand tamped with a 10 pound tamper until water flushed to the sur-face. The three cubes in the mould v/ere carried up together andtheir tops smoothed off with a straight-edge to obtain perfectsurfaces. They were left in the moulds for twenty-four hours, andthen were removed and placed in water until tested.6 -The testing was done on the macliine in the UniversitylaboratoiT, Too much care can not bo taken in preparing the cubesfor the laachine. Their surfaces should be perfectly flat andparallel to each other. Every cube v/as examined with a try-squareand all surfaces smoothed v/ith a file until they v/ere as nearlyperfect as could be obtained. Experiments show that cubes may bebroken at any angle desired by leaving a corner or a small portionof the area higher than the remainder, sjnce the pressui'e isapplied upon only a portion of the area. This gives very undesir-able as well as unfair results, because of the lacK: of similarityin the distribution of the pressure on different cubes. So it isvery important that the surfaces should be as nearly flat as pos-sible. The cubes were placed upon the table of the machine and aself-adjusting cap placed upon them. The pressure was applied asslowly as the machine would run until the ultimate crushingstrength was reached, when the reading v/as recorded and notes v/eremade of the manner of rupture and other conditions of interest.The table on the following page shov/s the results of thetests made on the cubes. The same data is shown graphically inPLATE 1 on page - 8- I-1These experiments show conclusively that broken stonejconcrete is stronger than that made V7ith gravel — see the lastcolumn of TABLE 1, on page - 7 -. It will be noticed, that thebroken stone is at the early ages twice as strong as gTavel concreteand that this ratio decreases as the concrete grows older until atninety-eight days it is one and one-tliird times as strong. IThe greater strength of the broken stone concrete is due tothe fact that the cement adheres more closely to the rough surfacesiof the fragments of broken stone than to the smooth surface of thegravel. Also, part of the resist ence to crushing is due to thejfriction of one piece upon another; and consequently broken stonehas an advantage in tliis particular. It is owing to this elementtiiat the ratio of the strength of the broken stone concrete to the;gravel concrete is greater at the earlier ages of the concrete.The above conclusions ax-e in hannony with the well knovmfact that broken stone macadam is better than a gravel surface fora road, as was to be expected, since concrete is simply macadamiiwith a better binder. "On making the cubes there developed an objection to gravelconcrete which seems not heretofore mentioned. The gravel concreteseemed to be somewhat plastic, so that when it was tamped dov/ii inone place it sprang up in another, particularly v/hen completingthe cubes. This is what might have been expected since there isbut little internal friction between the rounded surfaces of thegravel.j- 10 ~In viev/ of the above factr? it nust be concluded that unlessthero I3 a marked difference in the cost of gravel and broKenstone that the latter should be preferred in malting concrete.END.# ' # ^ 4 ^,' # ^ ^# , #: # ;[;,#- ^ ^ * ^•^,;,#-:,..4-^:i,#-_. ^ V ^^ , 4. # " r ^ ^ ^ ^ f ^# # ^ * ^ f4- ''^ f ^ ^ >f ^# f f ^ ^ 4 f +# ' # 1^ , f f f ^ --^^f- # . f ff f ^' f 1?- ^ f ^ 1^i(^^-,:T^ f ih f,^4'';_ 1^ ^ ^ ^1^ t4 * ^#1^41^1^-1^4jik ^ ^ "^siL I -dlL, ^-If" li^ il^v ^Ip.sptfT^ 'f ^^ i ^f f i-4 4-^f*ffIf-^ 1^ 4 f'If #^f"T Tit 1^ it^-,^ 4 f.4 f f f # #4^ * ^„, ,#,f t # ^ *^ 4 ^ #* t4 f'* f # +^Ji^ ijfc -Jt jit*-t f1^ ^ ins*,„'. ^ ^# f # * ^ 4 t . #4 # ^4. ^ f ^ f ^,^ ^# # 4 f .f1^^ 4 ' 4 + ii^ f1*^^* f^ f # .# ^ i-4# # f ^f ^ # 1^ 4 iL^' + 4 I f 1^ ' # f + ^.'^-ff -f * + ' 4' ^ 4= I,+' ^ # T '* # # # f-^ 4 ih* f \S 4 i' , # , 4 * #* ^'^fc ' 4 ' * A-K* * * * 4. * * *f 4 4 f * t * * * *1...I. •I^ ^' 4 ^ 4 , 4 4 # ^ 4 .Jf , # # ' 4 <f # ^ + ^4 * *,* # + 4 f*' f r v#-;;r , * + i^

Comparative strength of gravel and broken-stone concretes

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Typescript.Thesis (B.S.)--University of Illinois, 1902.Mode of access: Internet

Lundgren, Carl Leonard.

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