Show PHYSICAL TEST ON CONCRETE WRITTEN BY E H beckstrand M M E an fn in the new experimental laboratory for the testing of materials of engineering in the university of utah last spring and winter there were a great many tests per in the state school of mines many of these tests were repetitions of similar ones that have already been made in the laboratories of other institutions and so their y teays o boy C os tf ay 00 cz boj i 70 oJ a elo yow lam c Z f P y 30 60 00 0 joao facco fuu cloea 40 2 4 AY 0 14 13 T w arr X oaf ap feam cac r alea al ea 13 ayo differ 00 oo e zo e JJ 0 0 0 decof ee cof echea rca cement these tests were made by milan crandall and louis seek les who presented the results and conclusions as a thesis for the engineers degree values is a corroboration of the r suits of others other s but their engi engineering value lies in the fact that they a an r the results of tests made maddon on utah portland cortlan ment ement the material that is principally ased for concrete construction in this state it is necessary that cement should be tested ested as it is manufactured or before it s used because a comparatively small va the kind of stress that it is to withstand in the structure rather than to depend depend on the tensile strength alone as a gauge for the quality and strength of the ce cement ment the machines for testing beams and for Z h y 7 00 N J nation in the composition or the burning may cause a wide variation in the strength ordinarily the tests made on cement consist of determining the time of set the tensile strength the permanency of volume testing concrete in compression are very expensive such as are usually installed in engineering schools and therefore therefore it is from these institutions as a rule that such data come a 7 da t 1 dw avlo reinforced concrete beam broken in olsen pound testing machine and sometimes the chemical composition for engineering purposes however the physical tests are the ones relied upon concrete is used mainly in compression and as beams I 1 rather than in simple tension it would seem better to test the material with in investigating the tensile and crushing strength of cement briquettes and cubes were made of neat cement and one part of cement to one two three and four parts of standard sand and allowed to set for one and two weeks the effect of tempera ture on the strength of neat cement is also shown in table 1 all of the specimens in table 1 were allowed to set one day in air at a temperature slightly above the freezing point and were then immersed in water 0 4 concrete beam broken jn in testing machine and kept at the temperature there shown they were then taken from the water and tested in no 10 there was alternate freezing and thawing tests I 1 and 7 no doubt TABLE 1 I tensile strength of briquettes crushing strength of cubes no tem per break Z sz crush load no of pera cent of i 1 CZ cra in per days ture sand I 1 load oab ad 6 B loada load of ayin sain set deg F Z as 0 cube ibs S ul 1 7 33 3 3 0 2 6 1555 3 2 7 39 0 1 3 3 7 50 0 2 4 21 33 0 2 1150 2712 5 21 45 0 2 6 21 51 0 2 0 7 28 32 0 2 8 28 46 0 2 9 aa 50 0 3 10 42 31 32 to as 48 0 3 16 2 11 42 40 46 0 3 I 1 12 42 51 0 3 13 7 70 50 3 2717 14 7 70 66 3 1 lilt 1111 15 7 70 75 3 16 7 70 so 80 63 1 2300 17 14 70 50 2 0 Is 18 14 70 6 6 2 3 3 19 1 11 70 75 77 as 3 3 0 20 14 SO 80 98 3 34 8 0 received most of 0 f their r strength during the th e first day set in air very little strength was added during the time the cement was im beaded in the ice but no 10 shows that after TABLE III ADHESION N TEST CONCRETE reinforce reinforcing Rein forc bars 0 ca el E l A to H 1 I 8 lf 1 P p ii i i 33 3 40 wi a 3 no j type a g sm CS cd en E S a tt 02 au a c A w a 10 CZ C r S S i so S 1 o 1 45 6 Jo linson 0 25 6 1630 0 01 2 45 6 y 6 1770 3 45 6 vt 6 2040 4 42 6 plain PI aln 0 IN 6 1420 5 42 6 1 n 0 jpy 6 1710 1710 6 42 6 i 5 1320 7 3 35 6 It ran ansome some Vs 6 8 35 3 6 6 9 35 G i vt 6 thawing 1 ng again 6 the cement can go on hardening the effect A of sand is shown in expert ments 13 to 20 these results are the averages of from three to five samples concrete cubes were also tested for crushing these cubes were made of 1 3 5 per square inch these are average values the temperature e during set sel and hardening was between 60 and 70 degrees one of the primary objects for carrying f 4 v A k briquettes and cubes broken to determine tensile and compressive strength of cement mixtures of cement sand and gravel and of sizes three inches and six inches they were allowed to set in air as ordinary cement sets and hardens they were tested after on these tests was to investigate beams made of concrete both reinforced and not reinforced the beams were twelve inches and eight inches wide four inches six TABLE II 11 reinforced CONCRETE BEAMS CONCRETE 1 35 reinforcing bars beams deflection age load max no length cracks breaks break 9 bendi at days ins load no per lbs type size effect moment breake bars cent depth depth width load 1 66 johnson yin y in 6 8 7 12 42 2 66 M in 12 6 5 12 36 3 66 min M 34 in 6 6 5 8 4 86 plain Vs in 6 4 3 12 2750 5 86 yin y in 4 6 5 12 6 69 vain va in 2 6 5 8 69 00 0 7 81 ransome yin y in 6 4 3 12 69 8 81 in 4 6 5 12 0 n 9 62 ln in 2 6 5 8 69 10 72 4 3 12 67 non 11 72 6 5 12 I 1 reinforced 1250 12 58 in 6 5 8 69 13 1 58 11 11 6 1 5 1 8 11 34 1 1 1675 1 1 TABLE IV comparison OF FORMULAE 45 1 2 3 4 5 6 no 11 el considene Con formula general sewall wentworth goldmark taylor 0 thompson 4 S S X Y M X Y 11 X Y M X Y na M X Y M X y Y M 1 2 05 1150 0 70 3 0 40 4 2 38 2 23 22 5 6 7 8 SOO 2 70 9 0 2 10 2 35 55 11 06 12 1 Y alst D from top of beam to NA in inform form 26 2 6 computed using effective depth 8 stress in steel crandall thirty eight days set the six inch cubes broke at a total load of pounds being 1409 pounds per square inch the three inch cubes broke at pounds or 1840 pounds inches and eight inches deep and seventy two inches long some were reinforced by plain steel rods some by johnson bars others by ransome bars table 2 gives the age kind of reinforcing size per cent of steel dimensions loads greatest bending moment and deflection the beams were not all of the same size and so direct comparisons of the maximum bending moments cannot be made the cement on the underside of the beams developed transverse cracks reaching up to the steel and past it up towards the center of the beam much before the breaking load was reached to show the adhesion between the concrete and the steel bars were pulled out from the middle of six inch cubes c u bes of concrete the results and data are shown in table III these tests for adhesion do not show anything very important because in nearly every structure the cement would give way due to the tension or shear in the concrete before the cement would loose its grip on the rods plate III shows the characteristics of the steel used the curves are plotted between load in tension and stretch A is for mild steel B is for johnson bars and G C is for ransome bars the elastic limit of the ransome bars is higher and the ductility less because the mild steel square bars are taken and twisted cold and not subsequently annealed this raises the elastic limit and makes it more brittle the lower curves marked A B C are for the same steel as above these curves are for loads below the elastic limit and the upper scale of extension is used in plotting the lower curves plates V and VI show the relation between the load on the center of beams and the amount of deflection of the beams the numbers above the curves refer to the beams shown in table II 11 in table II 11 beams numbered 10 11 12 and 13 were not reinforced and their breaking loads should be compared with the breaking loads of beams I 1 to 9 inclusive clu sive many writers have developed formulas for the safe carrying load of beams reinforced with steel the theory underlying the formulas will not be given here these formulas show a considerable variation in results when applied to the same beam the bending moments as given by five different formulae are given in table IV under M Y is the distance to the neutral axis from the top of beam as shown by computation these bending moments can be compared with the actual abdual breaking bending moments the tension in the steel S was computed by a formula given by con the values are seen to be below the elastic limit for steel |