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125 84 (


3 C 1" round




136 67 (


3


V>' round


" "


157 50 (


3 T '%" round 1


36


147



1164 CONCRETE.

For Directory to Experiments, see pp 1135-9.

Nat cem; (d) 1 cem : 2 sand, 15 % water; (e) 1 cem : 1 sand : 1 screen-
ings, 15 % water; (/) 1 cem : 2 screenings, 17 % water.

Hollow Cylinders; 6* diam, 8" long, 2" hole; Port cem and sand,
1 : 1, 10 % water.

Treatment. Water (clear) brought to centers of specimens. Cubes,
1 day in air, 6 in water. Cyls, 1 d in air, 27 in water, 4 in air.

Results. Leakage past thru mortar 1 y? to 2" thick. Cubes: under
50 Ibs/Q" (115 ft head) maintained from 3 to 16 hrs, little or no water
(max = 0.16 gal/hour per D ft) past thru the Port cem cubes; from 0.29
to 2.40 gals/hour/G ft thru the nat cem cubes. Portland, leakage became
appreciable at 60 to 75 Ibs/Q" (138 to 173 ft); nat, at 15 Ibs (35 ft). The
1 : 2 sand cubes were the most permeable. Cylinders, 15 to 30 Ibs/Q"
(35 to 70 ft); leakage 0.00023 to 1.228 gals/hour/Q ft.

Leakage diminished very noticeably with time.

66

66. W. J. Douglas, Engr in Charge of Bridges for Wash, D. C., E N, '06,
Dec 20, p 649.

66 a. A bridge, painted with a cement rich in free lime,

showed afterward a mass of blotches of different colors.

67

67. Prof C. von Bach, Zeitschrift des Vereins Deutscher Ingenieure,
'95, '97.

67 a. Relation between unit stretch and unit stress.
" Potenzgesetz (Law of powers).

Specimens. Cone cylinders, 25 cm diam, 1 m long. Deformations
measd on a length of 75 cm.

Treatment. Load of 8 kg/sq cm alternately applied and released until
the deformation no longer increased. Then similarly with 16 kg/Q cm,
and so on to 40 kg/Q cm.

Results. From the beginning, the deformations increased faster than
the loads. Let

s = unit stress = stress per unit of cross-section area;

L = original measd length of 75 cm;

I = reduction of L under compression;

e = l/L = unit deformation;

c = a coefficient, depending upon character of material;

m = an exponent,

Then, e = l/L = c . 8 m

Approximate Values

Mixture 1/c



Cem
1
1

1
1


Sand
2.5
2.5
3.0
1.5


Gravel
5





Stone

5




For sin kg/Q cm.
298,000
457,000
315,000
356,000


For sin Ibs/Q".
6,147,000
9,940,000
6,672,000
6,781,000


TO

1.14
1.16
1.15
1.11



(1/c for 8 in Ibs/Q") -f- (1/c for s in kg/Q cm) = 14.2234 m .

68

68. R. C. Carpenter. A S T M, Procs, '07, Vol 7, p 398. Linseed
and engine oil; soundness and tensile strength. Neat cem
briquets, some with 2 % of linseed or of engine oil added to the mixing
water; the others without oil. No. of briquets not stated.

68 a. Soundness. 24 hours in moist air. Briquets, mixt without
oil, S9und after 8 days in either oil. Briquets mixt with and without oil,
remained sound after boiling for 3 hours.



EXPERIMENT AND PRACTICE.



1165



For abbreviations, symbols and references, see p 947 1.



68 b. Tensile strength.

Oil in mix

1 day 7 days

None 430 696

2 % linseed 180 493

2 % engine 332 689



Tensile strength, Ibs/D"

28 days
743
572
696



69. M. R. Barnett, Inst C E, Procs, '07, Vol 167, p 153.

69 a. Action of soft water upon limestone cone. Thirlmere
aqueduct, water supply of Manchester, Eng. Section of aqueduct, made
with limestone cone. Floor, 9" thick, reduced about W in thickness,
honeycombed, eaten thru in many places, and leaking badly.

69 b. Samples of the limestones, from which the cone was made, were
kept, for 6 mos, in running soft water, in the aqueduct, and were found to
lose wt at rates ranging from 6.8 to 18.1 % per year, while sample blocks
of neat and 1 : 1 Port cem mortar, gained 5.5 and 3.6 % respectively.
Deg of hardness of water, 2.18.

- 70 -

70. Prof Ira H. Woolson, AS T M, Procs, '05, p 335; '07, p 404.
High temperatures and thermal conductivity.

70 a. Mixture, 1 : 2 : 4; with cinder, 1:2:5. Cem, an equal mix of
3 Portlands. Sand, sharp, fair qual, "not especially clean"; 90 % past a
12-mesh sieve. Agg, fair quality boiler cinder, with most of the fine ashes
removed; %" clean quartz gravel; crusht trap. Mixt moderately wet;

flusht t




I 1 '

H



800
600
400



tampt in molds until water

2,000

1,800
| 1,600
I; 1,400
& 1,200



to surf.












500 1,000 1,500 c

Temperature, in degrees F.
Fig 6. Heat Resistance.



2,000 C



7Ob. High temperatures. '05, p 335. Fig 6.

Specimens. For comp strgth, 4" cubes; for elasticity, prisms 6* X 6*
X 14". 3 cubes and 3 prisms tested without heating; 3 cubes and 2 prisms
of each agg (trap and limestone) at each temp.

Results.



7O c. Elastic modulus, E.

nearly coincided.



For E, the trap and limestone curves



7O d. After heating to 2000 and 2250 F, the limestone cubes appeared
sound while hot, but disintegrated when cooled.



1166



CONCRETE.



For Directory to Experiments, see pp 1135-9.

7O e. Alter cooling from 750 F, both trap and limestone prisms
were covered with minute cracks. Under higher temps, these cracks in-
creased in number and in size, and the prisms warped and disintegrated
after cooling from 1500 F.

7O f. The trap and cinder cone specimens remained sound, while
the gravel cone specimens cracked and crumbled in pieces, probably
owing to high expansion coeff of quartz, and to the fact that this coeff
in one direction, is double that in the perp direction.

Heated Face A5





t 5 fi


?3 '




il

|| i






!! !


11 II














5 S


)


ooo


3 H




!* 3



Fig 7. Thermal Conductivity.



MOO
1,200



1,000



400
200




10 20 30 -to 50 60 70 80 90 100 110 120
Time, in Minutes.

Trap.
Fig 8. Thermal Conductivity.

7O g. Thermal conductivity, '07, p 404. Figs 7 and 8.

Specimens. Cone blocks, with holes as in Fig 7. Dimensions in inches.
Thermo couple in each hole. Mixture as in 7O a.

Treatment. Specimens in molds 24 hrs, in water 48 hrs, kept moist
2 or 3 wks, allowed to dry well. Age, at test, about 2 mos. Blocks placed
in furnace doorway.

Results. Fig 8 shows, for one of the trap cone specimens, the times,
in mins, reqd to transmit the furnace temps thru diff thicknesses
of cone. Each curve is marked with this thickness in ins. Drop of curves,
at and near 200 F, attributed to steam generation.



EXPERIMENT AND PRACTICE. 1167

For abbreviations, symbols and references, see p 947 1.

7O h. 2 to 2 W of cone (if it remains in place) will protect

reinfg metal during any ordinary conflagration.

7O i. Exposed reinforcing metal will not conduct heat injuri-
ously to imbedded portion.

7O.5. Wm. B. Fuller and Sanford E. Thompson, " The Laws
of Proportioning Concrete," A S C E, Trans, '07/Dec, Vol 59, pp 139-143.

Elastic modulus, E, under compression.

Specimens. 6" sq cone prisms, 18" long ; age, abt 140 ds. Giant Port
cem. Agg: Cowe Bay sand (CS), Jerome Park screenings (JSc). Agg :
Cowe Bay gravel (CG), Jerome Park stone (JSt).

Results.

Effect of maximum size of stone.

Mix 1:9* 1:3:6 1 : 2.81 : 5.62 1 : 2.92 : 5.88

Stone Elastic modulus, E, in millions of pounds per square inch.

2.25 ins 2.1 2.4 3.3 3.0

1.00 " 1.7 1.8 3.1 2.6

0.50 " 1.4 0.9 ... 2.2

Effect of quantity of cement, in % of total dry material.*
Elastic modulus, E, in millions of pounds per square inch.



Cem..
E..



With JSc and JSt.
8 10 12.5 15
1.8 2.1 2.3 4.7



With CS and CG
8.5 10.6 13.25 15.9
2.3 3.9 3.7 4.3



With JSc and CG

10.2 12.75 15.3

3.5 3.8 3.5



71

71. Richard L. Humphrey, U. S. G S Bull, No. 324, '07. Report
on San Francisco fire of Apr 18, '06.

Results.

71 a. Cone probably the best material for fireproofing cols. Its
stiffness supports the steel within, softened by the heat.

71 b. " Cone proved superior to brick as a fireproofing medium. "
71 c. At high temps, cone loses its water of crystallization.

71 d. Cone, especially when reinfd, resisted both earthquake and
fire. The cone dam, at San Mateo, altho within a few hundred yds of
the fault, was uninjured. Solid cone floors, altho of very poor quality,
proved satisfactory The cinder cone used, in floors and elsewhere,
was high in sulfides, and injurious to reinfmt.

72

72. Wm. B. Fuller, Natl Assn of Cem Users, Procs, '07, pp 95-7.
Grading and proportions.

72 a. Tests of 6 beams, 6" square, 6 ft long; 1 cem to 8 of sand and stone;
rupture moduli in Ibs/Q": 1:2:6, 319; 1:3:5, 285; 1:4:4, 209;
1:5:3, 151; 1:6:2, 102; 1 : 8 : 0, 41.

72 b. With a given percentage of cem, the densest mixture of sand
and agg gives the strongest, the least permeable and therefore the most
durable cone, and that which works most easily and therefore best fills up
voids and corners.

73

73. Commission du ciment arm, Paris, '07.

73 a. Shrinkage and expansion. Cone shrinks while hardening
in air, and expands under water.

* Material, larger than 0.2" diam (abt 62 to 68 % of total) graded in
accordance with the recommendations of the authors. See Plain Concrete,
Uil 23 to 25, p 1089.



1168



CONCRETE.



For Directory to Experiments, see pp 1135-9.

- 74 -



74. T.



Condron, of Condron and Sinks Co., representing Expanded
Metal & Corr Bar Co. Jour, Western Socof Engrs, '07, Feb. Vol 12, No. 1.
Experiments by Prof C. E. De Puy, Lewis Inst., Chicago.

74 a. Adhesion ; plain and deformed bars.

Specimens.

Cone cylinders, 6" diam, 8", 12", 16", 20", 24" long. Hand mixt, accu-
rately proportioned; 1:2:4, Port cem, coarse sand, broken limestone,
W and under, without dust. Fairly wet, so as to enter molds easily and be
churned with a small rod. All the cone mixt in one batch. The 8" and 16"
blocks were 25 days old when tested, the others 31 ds. The rods past en-
tirely thru the blocks. .

Results. .' Stress, Ibs/D* of imbedded surf



Round

Square

Twisted, Buffalo...
Twisted, Ransome*.
Johnson, f New.
Johnson, Old*



Diam
in

inches

*

10 A



75



Slip > 0.01'
Imbedded



1/32"



12"

269
316
334
324
474
651



24"



178
229
291
332
471
535




Adhesion, Ibs/Q*



289
341
357
366
612
786



190
242
306
350
506
535



75. A. A. Knndson, Am Inst Elec Engrs, Procs, '07, Feb, Vol. 26,
Part I, p 231; E N, '07, Mar 21, p 328.

75 a. Electrolysis.
Specimens.

1 : 1 cem and sand, Port and Rosendale. Blocks molded in metal water
pail; positive electrode, a short 2" wrought iron pipe in axis of block, im-
mersed about 8".

Treatment. Blocks placed in water (one in fresh, one in salt) in tank;
negative electrode, a piece of sheet iron, immersed in tank. Current 0.1
ampere.

Results. After 30 days, Portland blocks (which had cracked
under current) were easily broken, and showed yellowish deposits (ap-
parently iron rust) and softened cone, in the seams. Pipes lost more
than 2 % by corrosion. .Final electrical resistance = 10 X initial
resistance, and about = resistance of dry cone. Rosendale, cracks ap-
peared in 6 days. One of the pipes eaten thru.

76

76. J. 1,. Van Ornum, A S C E Trans, Vol. 51, p 443, '03 /Dec, and
Vol 58, p. 294, '07/Jun.

76 a. Fatigue. Neat cem blocks in comp. Repeated loadings cause
failure if the load is > abt half that reqd to crush with one application.

Vol 58, p 294.

76 b. Fatigue. About 600 tests.

Specimens.

Blocks 5" X 5", 12" long, in cqmp, and beams, 4" wide, 6" deep, 6 ft span,
reinfd by 2 plain steel bars, W* in square. Each batch made 8 blocks or 4
beams. Mix, 1 : 3 : 5 by vol. Standd Am Tort cem, tested by A S C E
specifications (p 942). Sand from Mississippi R, water-worn, rather fine,
99 to 110 Ibs/cu ft; voids 30 to 38 %. Broken limestone from near St.

* Covered with thin coat of rust, but without scales. The others fresh
from the rolls and free from rust.

t A. L. Johnson's corrugated bar, Fig. 2d, p 1130; Expanded Metal and
Corrugated Bar Co.



EXPERIMENT AND PRACTICE.



1169



For abbreviations, symbols and references, see p 947 1.

Louis, 80 to 95 Ibs/cu ft, passing 1%" screen; abt half the stones larger than
1", about one-tenth of the stones less than^"; voids 42 to 48 %. Voids,
in 3 sand + 5 agg, 16 to 19 %.

Treatment. Comp specimens left in molds in air 1 day, beams 2 ds;
then all in water 2 wks; then in air, protected from drafts, until tested.

Comp specimens, 1 mo and 1 yr old, loaded 4 to 8 times per min; beams,
1 mo, 6 mos and 1 yr, loaded 2 to 4 times per min.

Results. Effect of rate of repetition insignificant; but be-
lieved to increase rapidly with rates above 10 per min.



peatecl load-r-max. strength

o lo ^ bj bo c




















V










































































4 8 12 16 20 24 >28 32

^No. of Thousands of Repetitions necessary to produce failure.

Fig 9. Fatigue.

Fatigue. The curve, Fig 9, fairly represents the results obtained under
these varying conditions.

76 c. Cone, repeatedly stressed, below the fatigue limit (i. e., below about
half max strgth, see Fig) "has imparted to it a definite elastic limit,
within which stresses are proportional to strains" (i. e., within which the
elastic modulus, E, is constant).

76 d. Fatigue and Adhesion.

Specimens. Plain %" square steel bars imbedded in cone as above.
Specimens made with great care and very thoroly tamped.

Treatment. In molds 2 days, in water 7 ds, in air 3 wks. 30 fatigue
specimens subjected to "a combined blow, pressure and the accompanying
vibration"; 150 blows per min, each blow = 740 inch-lbs. Av, 50,000
blows to each specimen.

Results. Av initial adhesion, 125 Ibs/Q* of imbedded surf; friction
(after slip) 90 Ibs/Q". Unfatigued. specimens, 150 and 100 Ibs/D"
respectively.

76 e. Fatigue under continued load, p 318. 2 cone prisms
remained unaffected for a month under 90 % of their crushing strgth. "A
few cone blocks failed in comp in a few hours under constant pres of higher
%." A reinfd cone beam failed in 10 mos under 90 % of its breakg load.

77

77. Henry S. Spackman. Assn Am Port Cem Mfrs, New York,
07, Dec.

77 a. Mortar reground after hardening.

Briquets of Port cem, broken in testing. Reground and made into
new briquets. These showed, in general, about half the tensile
strengths of the original briquets. Of the original cem, 91.5
No. 100 sieve, 76.2 % past No. 200. The reground material hi
same fineness.

78

78. R. Feret, A S C E, Trans, '07, Dec, Vol 59, p 152.

78 a. Permeability. "Experiments give inr general uncer-
tain results. It is not unusual to see many blocks of the same cone

no

(UNIVERSITY)



7 o past a
abt the



1170



CONCRETE.



For Directory to Experiments, see pp 1135-9.

which, altho treated in an identical manner, permit very diff quantities of
water to filter thru them."



78 b. Age of block, days



365



5 29 30

Flow, in grams/min per
Presfrom71 to2841bs/n"; Avge 0.554 0.044 0.159 0.294

.After remaining under 284 Ib /Q" 2 hrs 0.349 0.034 0.133 0.278
78 c. Percolation "very nearly proportional to pressure."

78 d. 3 blocks, 1 year old. Block ABC

Flow, in grams/min per Ib/D*
At2841b/sqin .......................... 0.067 0.111 0.108

Raised to 412 Ib/CT ...................... 0.077 0.114 0.126

Reduced to 284 lb/D* .................... 0.068 0.114 0.111

"as if the effect of the momentary increase of pres had been to open new
passages for the water, or partly to clear out the passages already existing."

- 79 -

79. Win. B. Fuller and S. E. Thompson, A S C E, Trans, '07,
Dec, Vol. 59, p 67.

Strength, density and permeability, as affected by propor-
tions and character of sand and agg. Expts at Jerome Park
Reservoir, New York.

79 a. {Specimens. Port cem, as received for use on the reservoir;
agg (1) stone and screenings from crushers at reservoir, mica schist, 35 %
mica, which, in mortar or cone, "does not form planes which affect the strgth
seriously." (2) Cowe Bay gravel and sand, dredged from river ("water-
worn round^A bank gravel and sand, thoroly clean, and consisting almost
entirely of quartz particles." Sp gr abt 2.65). Max size of stone, 2M",
I",




20 40 60 808.5 1010.6 ^12 13 14 15.

.Pressure, l$s. %er sq. in. Cement, per cent of total dry material.

Fig 1O. . Permeability.

Tests were made with " graded mix " (proportions giving max density
of agg) and "natural mix" (1 : 2.5 : 6.5, 1:3:6, 1 : 3.5 : 5.5).
Results.
79 b. Size of aggregate ; strength and density.

Max stone size, inches 2 M 1 H

Relative strength.

Compression 1.00 0.83 0.72

Transverse 1.00 0.91 0.75

Cem read for equal strgth, relative 1.00 1.17 1.33

Relative density 1.00 0.96 0.93



EXPERIMENT AND PRACTICE. 1171

For abbreviations, symbols and references, see p 947 1.

79 c. Kind of aggregate. Sand vs screenings. Relative
strengths and densities.

Comp strgth Transv strgth Density

Sand and stone 100 100 100

" gravel 94 89 102

Screenings and stone 67 85 98

79 d. Graded mix gave density = 1.14 X density with natural mix;
for equal strgth, graded mix reqd 0.88 X the cem reqd with nat mix.

(This means an av saving of about 25 cts per cu yd of cone. Allen
Hazen, Trans, A S C E, Vol 59, p. 150, Dec, '07.)

79 e. An excess of fine or of medium sand, or a deficiency of fine sand
in a lean cone, diminishes strgth and density.

79 f. Strength: and density max when mortar just fills voids.

79g. Permeability. See Fig 10. " Little is known of the action of
cone in resisting the flow of water." As betwn "diff proportions and diff
siy.es of the same class of materials, the laws of watertightness are somewhat
similar to those of strgth." With given percentage of cem, the densest
specimens are usually most watertight. With equal densities, the
richest specimens are most watertight (See Fig). The ratios, how-
ever, are very diff from those of either density or strgth, a slight diff in the
composition producing a great effect upon the watertightness. *' IMflf
kinds of agg produce very diff results in watertightness." Fig shows
effect of pressure upon permeability.

79 h. Cone with Jerome Park stone and screenings gave very much
higher rates of percolation thruout (max, 369 grams per min) than that
with Cowe Bay sand and gravel. Cone with stone and sand gave about
half the rates shown in Fig 10.

79 i. Permeability is sometimes greater with large and sometimes
with small stones. Results especially erratic with the Jerome Park
reservoir broken stone and screenings.

79 j. " Permeability decreases materially with age ; " increases much
more rapidly than the thickness of the cone decreases;

less with sand and gravel than with stone and screenings;

" sand ;
" stone " screenings ;

80

SO. Richd H. Gaines, New York Board of Water Supply, A S C E,
Trans, Vol 59, '07, Dec, p 159.

so a. Permeability and strength; Clay and alnm.

Specimens. Mortar, 1:3, Portland, Cowe Bay sand. Tensile tests
on standard briquets; comp and tensile tests on 2" cubes. Age of specimens,
28 to 30 days. Pressures, 40 and 80 Ibs/D".

Results. (1) Replacing the mixing water with a 2.5 to 5 % (1 to 2%
sufficient) alum solution gave nearly complete impermeability.

(2) Replacing 5 to 10 % of the sand with dried and finely ground clay, and
(3) combining (1) and (2), gave still better results.

The clay specimens (with and without alum) showed from 12 to 18 % gain
in strength over those without clay.

The process is based upon a theory of physico-chemical action
between ions of the electrolyte (alum) and the colloid (glue-like) molecules
of the clay.

None of the processes hitherto in use, and examined, were found
suitable for extensive use.

Slaked lime slightly decreases permeability, but this advantage
is more than offset by loss of strength. There is no chemical reason why
this should be otherwise.



1172



CONCRETE.



For Directory to Experiments, see pp 1135-9.

81

81. Prof E. Morsch, Zurich; for Wayss and Freytag A.-G., Neustadt.
"Der Eisenbetonbau, " Stuttgart, Konrad Wittwer, '08, to which the pages
given refer.

81 a. Elastic relations, pp 27-32. Specimens; Square prisms;
measured length, 35 cm (13 i^")- 1 part Mannheim Port cem, with 3 parts
of a mixture of Rhine sand and gravel consisting of 3 parts sand, 05 mm;
2 parts gravel, 5-20 mm. (0.197'M).78"). Water, 14 %. Each stress main-
tained 3 mins. Some of the specimens tested in tension; the others in comp.

Compression) in millionfhs of 'or iginaf length.
50 100 150 200 250 800 350 ^



S2

1!
8$



















1400
1200 |
1000 |
800 f

600
g

400 1
200 |

og












^>


,^*^^










8 <^


^^








JVft


l'$>
J^^_


^' ota










J0A


jg[?










s^'


~-'&p










x"















-60

Elongation



Fig 11. Stress and Stretch.



*



Deformation, in millionfhs of original length.
50 100 150 200 250 300




.2.5

-50 50 100 1$0 200 250 300 350

Deformation, in.millionths of original length^

Fig 12. Elastic Modulus.

Results. Unit stresses and stretches as in Fig 11. Ult ten-
sions, lbs/n" : 3 mos, 149; 2 yrs, 224.
Elastic Modulus, E, See Fig 12.
With mix 1:4, for a given stress in comp, E was in general from 15



EXPERIMENT AND PRACTICE.



1173



For abbreviations, symbols and references, see p 947 1.

to 20 % less than with 1:3. In tension, E was more nearly the same for
both mixes.

"With water 8 %, for a given stress, E was in general from 10 to 20 %
higher than with water 14 %.

81 b. Shear. Fig 13. Dimensions in centimeters. Prisms, 18 cm
square, 40 cm long, p 40. Mixture of sand and gravel as in Expt 81 o.



1




Figf 13. Shear.

Plain. Specimen first cracked, as beam, at a. Pres then increased until
shearing crack, b, appeared.

Ult av shear, lbs/D"*

No. of , ,

Mix Water % Age Specimens Observed Calculatedf

1:3 14 2 ' yr 3 936



1 :4



14



yr

1.5 m



8



530



550



Reinforced. The bars (1 cm diam) served merely to hold the speci-
mens together, so that the pres could be increased as desired. The cone
sheared first.



Mix
1 :4
1 :4



Water %
14
14



Age
1.5 m
1.5m



No of

specimens

2

3



Ult Av shear, lbs/D"



Concrete
522

484



Steel
46400
50800



81 c. Torsion, p 45. Mix, 1 : 4. 4 solid cylinders. 79 to 98

days old; 26 cm diam; length under exp, 34 cm. Hexagonal heads. M =
torsional moment; R = radius of cyl;

t = torsional stress in extreme fibers (see p 500, this book) = 2 M fir R 3

t, in lbs/D"; max, 275; mean, 243; min, 189.

3 hollow cyls, as above, 52 to 55 days old; inner diam abt 15 cm;
r = inner radius.

t = 2M R/n (ft* r 4 ),

t, in lbs/D"; max, 134; mean, 126; min, 112.

The much higher unit strength of the solid cylinders as
given by the formulas, is attributed partly to their somewhat greater age,
but chiefly to the increase in unit stress from the circumf inward, owing
to which the material near the center transmits more than its share of the
torsional stress, and thus relieves the outer portions.

* = y^ total force applied -4- area of one shearing surf,
t From ult tensile strgth, t, and ult comp strgth, c, of test pieces of same
mix and age, and formula, shear = \/ t c.



1174 CONCRETE.

For Directory to Experiments, see pp 1135-9.

81 d. Adhesion, p 49. Figs 14 and 15.

Specimens. Cubes, 20 cm. Mix, 1:4; 10 to 15 % water; age 4
Round bars 2 cm diam, Fig 15, spiral 10 cm diam ; wire 0.45 cm diam.



Fig 14.

Adhesion.




15.



Treatment. Bars pushed out. Pres rapidly increased to max.
Results. Adhesion, means of 12 testa each, Ibs/D"; Fig 14, adhe-
sion = 518 ; Fig 15, adhesion = 713.

After overcoming the adhesion, considerable frictional resistance

remained.

81 e. Ductility and shear in reinforced concrete, p 60.

Specimens. 4 reinforced hollow cylinders in torsion, as in
Experiment 81 c, reinforced with spirals in the mifldle of their wall thick-
ness.' Spirals at 45, so placed as to be in tension under the twisting
moment. 2 cyls each with 5 spirals of 7 mm round iron, two cyls each
with 10 spirals of 10 mm round iron. Diam of spiral, 21 cm.

Stresses in iron, at instant of first cracking in cone, Ibs/Q";
max, 8960 ; mean, 8300 ; min, 7700.

Stretch of iron and of cone at instant of first cracking in cone, av:
0.00027 X original length.

Foregoing deduced from comparison with results obtained with plain
cyls in torsion, Expt 81 c.

Shear, Ibs/Q" Max Mean Min

At first cracking ................ 620 480 347

At rupture .................... 767 624 430

81 f. Specimens. 6 reinforced beams, 15 X 30 cm, 2 m span,

E62. Fig 16, p 1175. Dimensions in centimeters. Thickness of reinfg
ars as below. 2 concentd loads, P P, equidistant from cen and 1 m apart.
Mix 1:4; age 3 mos. Measurements on central length of 80 cm. Bendg
mom constant thruout this length. Stretch of steel observed by means of


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