Lbs. per square inch
Tons ,, foot .
Builders, recessed
top and bottom
3-20 X 9-30 X 4-5° : 41-85
Mean . .
Lbs. per square inch
Tons ,, foot .
Compressive stress in pounds when
Cracked
slightly.
Cracked
generally.
Crush'd, steel
yarddropped.
45,680
86,220
91,180
45,590
79,775
90,320
38,760
77,830
89,640
36,180
70,960
85,820
41,552
78,696
89,240
1,010
1,913
2,170
65
123
139-5
40,960
97,240
113,220
39,280
95,270
106,530
36,490
87,382
101,202
33,540
81,180
95,840
36,490
87,382
101,202
872
2,038
2,418
56-1
134-2
155-5
Bedded between pieces of pine 5" thick and recesses filled with cement.
Tests and Strengths of Materials.
17
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Tall Chimney Construction.
•^
Tests of Brick used in the construction of the South
Gate House New Reservoir, New York, U.S.A.
Tested in Hatfield's Hydraulic Press for testing building
materials, built by Messrs. Hoe & Co. The bricks were those
known SiS hard bricks, and made at the yard of ]\Ir. William Call,
Haverstran, on the Hudson River: —
■ —
Square In.
No.
Thick.
Wide.
Broad.
exposed to
pressure.
How bedded.
Remarks.
I
2-30
3-52
4-40
15-488
Between
two pieces of
board ^-in.
thick.
At 30,000-lbs. {■=. 1,937-lbs. per sq.
in.) cracked in centre, kept at
50,000-lbs. (r=3228-3-lbs. per sq. in.)
without crushing.
2
2-24
3-50
4-46
15-610
Layer of
Sand.
Sign of a crack at 50,000-lbs. (rr 3203
per sq. in.), kept at 52,000 (r= 3362
per sq. in.) for 3 minutes and did
not crush, and crack did not extend
through brick.
3
2-34
3'5o
4-52
15-820
Packed with
Sand.
Crushed to pieces at 43,500-lbs.
(2748-7 per sq. in).
4
2-34
3-4(^
4-46
i5-43i(>
Packed with
two pieces of
cigar-box
wood.
Edges crushed off at 30,000-lbs.
(1990-1 per sq. in.)
5
2-30
3-46
4-50
15-570
Packed with
Sand.
Cracked at 27,000-lbs. (i 734-1 per
sq. in.) Crushed at 32,000-lbs.
(2055-3 per sq. in.), crushed and
cracked in all directions, did not
fall to pieces as did No. 3.
6
2-28
3-46
4-66
15-916
Packed with
Sand.
Commenced to crack at 30,000-lbs.
(1884-9 PS"' sq. in.) Crushed to
pieces at 46,500-lbs. (2921-6 per
sq. in.)
Fire-Bricks.
Firc-Bricks should, on fracture, present a compact, uniform
structure — not necessarily close, for indeed some maintain that
a coarse grit of texture is the chief requisite, and that a close,
uniform structure, though pleasing to the eye, is not favorable
to the refractory powers of a fire brick, since the particles
should have a facility for contraction or expansion under heat,
and the air cavities act as valuable non-conductors of heat
The bricks should be free from stones, cracks, and irregular air-
hollows ; and on being struck should emit a clear ringing
sound. The existence of this property usually involves a facility
for cuttinsT-
Tests and Strengths of Materials.
19
Experiments made in the Royal Arsenal upon cubes of
i\" sides, cut from fire-brick "soaps" and placed between
small squares of sheet lead, gave the following results : —
Description.
Stourbridge
Ditto .
Newcastle .
Plympton .
Dinas . .
Kilmarnock
Glenboi" .
Craclccd at.
1,478-lbs. per sq. in.
1,156
8S9
1,689
1,123
2,134
1,067
Crushed at.
2,400-lbs. per sq. in.
1,156
1,512
2,666
1,288
3,378
1,556
Stourbridge Fire Clay. — Authority, S. Clegg, Jun.
The celebrated Stourbridge clay lies about 15' beneath
the lowest of three workable seams of coal (each averaging
6 feet thick) worked at Stourbridge in the lower coal measures
in the south-western extremity of the Dudley coal field. The
bed of clay is 4' thick and the following is the composition: —
Silica 637
Alumina 22-7
Oxide of Iron .... 2-o
AVater ii-6
loo-o
(See also tests of bricks, Edinburgh Gas Works chimney, page 47.)
MORTAR.
Experiments made by Graham Smith, 1874.
^'' JMason's mortar" consisted of, —
I slacked lime. 2 sand. J smithy ashes.
Being the ordinary mortar used in the construction of rubble
masonry for dock walls.
'''■ Bricldaycr's mortar" consisted of, —
I slacked lime. i sand. i smithy ashes.
20
Tall Chivincy Construction.
The mode of testing pursued was as follows : — Bricks, the
quality of which is described in each individual case, were
accurately cut to 4^" in width, these were in all cases
thoroughly wetted, and bedded crossways, with a mortar joint
fV thick and 4^" x 4j", giving a testing area of 18 sq. inches.
On the time arriving for testing, which, unless otherwise men-
tioned, was 168 days, stirrups w^ere passed round the ends of
the bricks, two of these were attached to a beam and on the
remaining two ends was hung a bucket into which perfectly dry
sand was allowed to run from a hopper, the door of which was
immediately closed when the joint parted. The bucket and sand
were then weighed and this was taken to be the breaking weight
of the specimen. In order to ascertain the difference which
would exist in practice from the employment of bricks of various
texture, two qualities were experimented on, viz., •' common
bricks," similar to, although slightly harder, than those known
about London as " ordinary stocks," and " fire-bricks," very
hard and much the same as Staffordshire blue bricks.
Description of
Breaking tensile strain
Bricks.
Mortar.
per 4i-in. x 4i-in.
section.
Common
Fire-bricks
Common
Fire-bricks
Mason's
Do
Bricklayer's
Do
496-lbs.
433-lbs.
610-lbs.
516-lbs.
The above are the average results of three experiments in
each instance, from which it would appear that soft porous
bricks are preferable for work subjected to a tensile strain.
A second series of tests were made by first subjecting the
samples, twenty-four hours after being bedded, to a pressure of
56-lbs., and following this up with an additional 56-lbs. every
day until 4-cwt. had been placed upon each. These broke as
follows : —
Description of
Breaking tensile strain
Bricks.
Mortar.
per 4J-in. x 4j-in.
section.
Common
Fire-bricks
Common
Fire-bricks'
Mason's
Do
Bricklayer's
Do
683-lbs.
403-lbs.
372-lbs.
423-lbs.
Tests and Strengths of Materials.
21
It was thought that the mortar would bear a greater strain
after being compressed as in practice, but this was only borne
out in the first case, the remaining three cases being considerably
below the respective averages given before. It is feared that in
placing on the weights the mortar was disturbed after having
partially set, in which case it will never bind together a second
time.
Samples were tested joined together with mortar re-mixed
with water six days after the first mixing, it was found that, —
"Common" bricks with "Mason's" mortar rc-mixcd . . . broke at 432-lbs.
Do. ,, do. when first mixed . ,, 496-lbs.
Do. ,, " Bricklayer's" mortar re-mixed ... ,, 440-lbs.
Do. ,, do. when first mixed . ,, 610-lbs.
The advantage is thus shewn of using mortar when first
mixed.
The importance of the admixture of ashes with mortar, to
be atmospherically dried, is shewn in the following tests : —
Description of
Breaking tensile strain
Bricks.
Mortar.
per 4|-in. x 4{-in.
section.
Common
Do
Bricklayer's with ashes .
Do. no ashes
S70-lbs.
257-lbs.
These two last tests were tried after a lapse of 84 days.
STONE.
The five following tables show the results of experiments
to ascertain the resistance to thrusting stress of stones made for
Mr. Samuel Trickett, of Millwall.
Laminated stones, as will be seen from the tests, are of far
greater crushing pressure than homogeneous or rock stone; this
was the result that Mr. James Gowan arrived at in his experi-
ments given under head of Edinburgh Gas Works chimney,
page 46, and in which Mr. S. Trickett agrees.
22
Tall Chimney Cojistrudion.
Description.
D
imensions.
Base
area.
Cracked slightly.
Crushed, steel-yard
dropped.
Stress.
Per sq.
inch.
Per sq.
loot.
Stress.
Per sq.
inch.
Per sq.
loot.
Leigh Carr,Lanca- /
shire. Alaminated 1
stone, the crushing I
test being equal to j
many Granites. (
6-o8
6-o8
6-o6
6-10
6 00
6-05
6-00
5-98
5-95
5-90
5-98
6-00
5-88
6-16
5-90
Inches.
6-10 X 6-16
6-06 X 6- 10
6-10 X 6-10
6-00 X 6-00
5-95 X 6-00
6-03 X 6-03
5-95 X 5-98
5-98 X 5-98
5-94 X 5-95
5-90 X 5-92
5-99 X s-98
5-98 X 5-98
5-90 X 5-98
5-98 X 6-02
5-92 X 5-98
Sq in.
37-57
36-96
37-21
36-00
35-70
36-36
35-58
35-76
35-34
34-92
35-82
35-76
35-28
36-00
34-81
lbs.
589,000
572,000
564,000
lbs.
15,677
'5,476
15,157
Tons.
IOO8-I
995-2
974-7
lbs.
617,000
594,360
593,870
lbs.
16,422
16,081
15,959
Tons.
1056-0
1034-1
[O26-3
575,000
15,437
992-7
601,743
16,154
1038-8
Wild Carr.
A laminated I
stone.
376,300
342,400
354,500
10,452
9,591
9,749
672-1
6i6-7
626-9
415,360
404,580
409,750
11,537
",332
11,269
741-9
728-7
724-6
357,733
9,930
638-5
409,896
11,379
731-7
Appleton Quarries
Sheple)'.
A laminated j
stone. /
341,600
369,000
324,500
9,600
10,318
9,182
617-3
663-5
590-4
372,890
411,470
350,850
10,480
11,506
9,927
673-9
739-9
638-3
345,033
9,700
623-7
378,403
10,637
684-0
Corsehill Quarry, 1
Annan, Dumfries- )
shire. A red
laminated stone.
298,620
263,180
200,800
8,551
7,347
5,615
549-9
472-4
361-0
349,180
285,840
207,310
9,999
7,979
5,797
643-0
513-I
372-7
254,200
7,171
46i'i
280,776
7,925
509-6
Bramley Fall, /
Weetwootl |
Quarries, Leeds. %,
A coarse grit 1
stone. (
131,800
126,930
118,950
3,735
3,525
3,417
240-1
226-6
219-7
154,290
148,370
135,920
4,373
4,121
3,904
281-2
265-0
251-0
125,893
3,559
228-8
146,193
4,132
265-7
All bedded between pieces of pine |" thick.
Tests and Strengths of Materials.
23
Description.
Dimensions.
Base
area.
Cracked slightly.
Crushed, steel-yard
dropped.
Stress.
Per s
inch.
Per s,i.
loot.
Stress.
Per s.,
inch.
Per sq.
loot.
Ancaster. )
Tested on the bed ■^
Inches.
I2-00 12-03 X I2-OC
12-00 12-00 X ii'96
12-00 12-00 X ii'93
S(| in.
[44-3^J
143-52
143-16
lbs.
235-300
226,400
174,800
lbs.
1,629
1-577
1,221
Tons.
104-7
101-4
78-5
lbs.
310,788
307,110
208,570
lbs.
2,152
2,139
1,457
Tons.
138-7
'37-5
93-^
Mean.
212,166
1,476
94-8
275,486
1,916
123-2
All bedded between pieces of pine ^" thick.
(See also tests of stone, Edinburgh Gas Works chimney, page 46.)
PORTLAND CEMENT
WcigJif and Sieve Test. — This cement should weigh at least
iio-lbs. per imperial striked bushel, or 85-lbs. per cubic foot,
filled from an inclined plane at an angle of say 45°. The weight
test is also applied by filling the cement in through a hopper
having a rectangular distributing shoot, the height or drop from
the bottom of the hopper to the top of the bushel measure being
18". Fine grinding, however, makes a most important altera-
tion in the weight test, as the following table indicates.
An imperial bu.shel of best cement, freshly ground, passing
through a, —
80 mesh sieve and leaving 10°/^ residue, weighs i lo-lbs.
Do. do. 20 ,, ,, Ii6-lbs.
Do. do. 25 ,, ,, I2i-lbs.
Do. do. 35 ,, ,, 123-lbs.
Cement and Sand Test. — Some engineers have lately dis-
carded the weight test and rely upon test bricks made up as
concrete, in the proportion of three of standard sand and one
of cement, to be broken at 28 days after gauging, during one of
which it has been in the air and 27 days in water. Samples
thus mixed should have a minimum strength of 112-lbs. per
square inch.
24 Tall CJmnney Cofistruction.
Samples made one of cement, weighing 123-lbs. per bushel,
and one of Thames sand, —
I week old, broke at 160-lbs. per sq. inch.
I month ,, ,, 201 -lbs.
3 » » .. 244-lbs.
6 ,, ,, ,, 284-lbs.
9 .. M " 307-lbs.
12 „ „ „ 318-lbs,
24 M „ '. 351-lbS.
Tensile Test. — When mixed up neat and immersed in water
Portland cement should, after seven days, be capable of resisting
a tensile strain of at least 6oo-lbs. per 2} square inches section.
In making the test briquettes the proportion of water should be
9-02. to 40-oz. of cement, both being accurately weighed, as an
excess of water will adversely affect the result.
Chemical A nalysis^ —
Lime 59-13
Silica 23-67
Almnina 8-14
Per oxide of iron 3-26
Sulphuric acid 1-44
Alkali 2-46
Moisture, &c 1-90
loo-oo
A higher proportion of lime gives greater tensile strength
at short dates, but is found not to be depended upon, although
sometimes a long period may elapse before any deterioration
becomes ajDparent.
Compression Test, —
3 months old . .
. I -7 1 tons per sq. inch
6 „
. 2-43
9 .. >, •
• 3-16
Mr. Faija, who is a well-known authority on Portland
cement, has made a great number of crushing tests, and con-
siders they are practically failures. There is a difficulty in the
manufacture of the cube. If it is not perfectly true the weight
first comes on one corner and then on another, and in fact the
cube is attacked in detail, and the result of the test is therefore
not of much value. Tensile strain bears a fixed proportion to
other strains, and as the tensile strain is the easiest to apply, it
is the most useful. Portland cement a week old will carry about
6,ooo-lbs. crushing strain, but in half-a-dozen tests one will get
a variation often of loo per cent.
Tests and StrcngtJis of Maicria/s.
25
Samples of best heavy Portland cement tested by Adie's
machine, 1880; mould ih" X i^" =■ 2\ sq. inches.
Number.
Days after moulding.
Days in water.
Average tensile strain.
2 2 samples . . .
3
2
850-lbs.
22 „ ...
4
3
890-lbs.
42 „ ...
7
6
910-lbs.
42 „ ...
15
14
1,040-lbs.
36 ., ...
31
30
1,190-lbs.
22* ,, ...
91
90
1,360-lbs.
* N.B. — Of these seven bricks unbroken at 1,440-lbs.
Samples of Portland cement tested by Henry Faija ; June,
1884, mould i" X 1" = I sq. inch: —
Average of 25 tests.
3 day test. 7 day test.
Tensile strain per sq. inch 362-Ibs. . . . 404-lbs.
Equal to a strain on i.y X li'o^ .... 814-lbs. . . . 909-lbs.
vSamples of Portland cement tested by D. Kirkaldy & Son,
June, 1884; mould zh" x 2" = 5 sq. inches: —
Average of 10 tests.
Tensile strain per 5 sq. inches 2118 to 2144-lbs.
Equal to a strain per i|-" X is" of 953' i to 964-8-lbs.
,, ,, ,, ,, square inch 423*6 to 428'8-lbs.
Weight per imperial bushel Ii6*8-lbs.
Portland cement may be had guaranteed by the manufac-
turers to weigh and break as follows : —
Description.
Best heavy Portland cement (slow setting) .
Best quick setting cement
Weight per bushel.
116 to 120-lbs.
Ii2-lbs.
Minimum breaking
strain, tj in. x ij-in,
section.
800 to 1,000-lbs.
600 to 800-lbs.
CONCRETE.
Tests of 6 inch cubes of Lias lime concrete, 53 weeks after
being moulded, —
Lime ::= 71 -lbs. and gravel I37j-lbs. per bushel.
c
26 Tall Chimney Constnidion.
The following are the average results of lo tests in each
case: —
„ ^. Wcitrlit per cubic
P'°P°'"°"' toot in lbs.
6 to I 131
8 to I 129-6
10 to I 128
Crashed
at
Tons per
Ions.
super It.
577
=
23-08
2-69
rr
10-76
2-14
=
8-56
DRAUGHT.
In Fig. I let L B = C R = the height of the atmosphere,
F B = the height of a chimney, and A R = a similar column of
external air equal in height to the shaft. The columns C A and L F
of the atmosphere above the chimney are equal, and the pressures
caused at A and F thereby may be disregarded. When the
temperature and density of the air inside the chimney are equal
to those of the similar column A R there will be no tendency to
produce motion, should however the air inside the chimney be
heated, and consequently become of less density than the column
A R, there will be a greater pressure at G M by A R than by F B,
and the excess of pressure will force the heated air in the shaft
upwards. If the outside air as it enters the chimney at G M be
heated and the diminished density of the air within the shaft
maintained, the column of air F B will continue to ascend in
consequence of the preponderating pressure of the outside
column A R. This is what takes place when a fire is lighted
at the base of a chimney and the unbalanced pressure of the
external air causes what is known as the " draught."
The co-effi.cient of expansion of gases on the Fahrenheit
scale is found to be 4-Ly, or in other words by raising the
temperature from freezing point to 491° above freezing point,
the volume will be doubled and its density reduced by one-half.
The volumes of the cold air and heated gases may be found
from the following formula, and also the respective densities,
since the densities vary inversely as the volumes : —
Let / rr: temperature of external air, say 60° F.
T-^ temperature of heated air in shaft.
d ^ density of do. do.
D-=. •0765-lb., the density or weight of a cube foot
of air at 60° F., with the barometer at 30",
Vol. at r= vol. at/ 491 + ?'- 32 ^ ,.ol. at t ^±1 . . (i)
491 J^ t —12 519
459 + ^ ' ^ 459 + 2-
Tests and Strcngtlis of Materials. 2 7
If we take j B as representing the volume of external air
that would, if raised to the temperature of the air in the shaft, fill
the chimney, we then have A D as the head or motive column
of external air producing the draught.
If h r= the height of the chimney in feet,
H = the head of external air in feet graphically shewn by A D,
Then
„ h D — h d . D — d
II =z = /i (x)
D D ^^'
And by (2) we have
T /
H z=^n — — 1- (4)
459 + T '^'
It has been found in practice that the best results in the
draught are obtained when the density of the external atmosphere
is to the density of the gases in the shaft as 2 to i , or when the
temperature of the escaping gas is about 580° F. ; above this
there is no practical gain in the draught and a great waste of
fuel takes place, as well as injury to the brickwork. It is also
found that with a lower exhaustion than V' water pressure it is
diffcult to keep a good fire without constant stirring, which is
wasteful and productive of smoke.
Taking therefore the temperature of the heated air at 580°
we have, —
^=1 (5)
To this head of external air is due the velocity of the air
entering at G M, and by the law of falling bodies this will be
equal to that due to the height A D = h.
Let V =z theoretical velocity of entering cold air per sec.
_§■= acceleration generated by gravity per sec. rr 32-ft.
Then
z'= v/-2^«-^=8//7 (6)
As the velocity of the gases is proportional to their volumes,
and the volume of air we have taken to be doubled upon entering
the shaft, we have the theoretical velocity of the hot air in feet
per second, — ■
v= 2v=iiG y/~ir (7)
Syphon water gauges are commonly used to take the draught
of chimneys, the exhaustion being given in inches of water.
A cube foot of water at 60^ F. weighs 62*5-lbs., therefore
the density of air is -^\t^^ ^^''-^ of water.
If ?r= the theoretical draught of shaft in inches of water pressure,
Then
IV = '1^ (8)
817
And
v — GGyJl-F (9)
r
28
Tall Chimney Construction.
From this data we have the following table of the theoretical
draught powers of chimneys with the external air at 60 and
the internal heated air at 580°: —
Table A.
Height of
Chimney in feet.
Draught in
inches ot water.
Theoretical velocitj
in feet per second.
Cold air entering.
Hot air at outlet.
SO
•367
40-0
8o-8
60
•440
43-8
87-6
70
•514
47-3
94-6
80
•587
50-6
IOI-2
90
•6G0
537
107-4
100
•734
56-6
II3-I
120
•880
62-0
123-9
150
I-IOI
69-3
138-6
175
1-285
74-8
149-6
200
1-468
80-0
i6o-o
225
1-652
84-8
169-7
250
1-836
89-4
178-9
275
2-020
93-8
187-6
300
2-203
98-0
196-0
This theoretical draught is in practice diminished by the
contraction at the entrance of the ash pit and at the bed of fuel
and over the bridge, by the bends in the flues and the friction of
the air or gases passing over the sooty surfaces in the flues and
chimney. From observations and experience it may be taken
that where there are not many restricted passages the velocity
as a rule is that given by using a co-eflicient of "3, then we have
from (7),—
f; = 4-8 ^~H
Table B has been calculated upon this basis, taking lo-lbs.