ins. ins. per foot.
6 1¼ $0.0571
8 1¼ 0.0730
10 1-3/8 0.0998
12 1½ 0.1278
The sand cost was based on 15 cts. per cubic yard for loading, and a
haul of two miles of 1 cu. yd. to the load, making five trips per day,
at $4 for man and team. It bears a constant ratio to cement cost, being
11.2 per cent. of the cement cost. The labor cost of making was based on
the foreman's estimate that a foreman, tamper, mortar mixer, and water
man should finish 250 joints a day of 6 or 8-in. pipe. For the 10 and
12-in. pipe, the labor was assumed to be greater in proportion to the
material. The foreman was taken at $3, one man at $2.50 and two at $2.
The cement for painting the inside was neglected. Hauling the pipe to
place was taken at twice the cost of hauling the sand per mile, and a
haul of 4 miles was assumed. The cost of laying was based on a foreman's
estimate of 2 cts. per foot for trench, and that one man to lay, one man
to plaster the joints, one helper and one man to back-fill would lay 600
ft. per day of 6 or 8-in. pipe. The larger sizes were assumed to cost
more in proportion to their material.
These various costs gave the following results for small size pipe:
--Cost per foot for--
6-in. 8-in. 10-in. 12-in.
pipe. pipe. pipe. pipe.
Cement $0.057 $0.073 $0.099 $0.128
Sand 0.006 0.008 0.011 0.014
Labor 0.019 0.019 0.026 0.034
Hauling 0.024 0.032 0.044 0.056
Laying 0.024 0.024 0.032 0.042
Trench 0.020 0.020 0.020 0.020
------ ------ ------ ------
Totals. $0.15 $0.176 $0.232 $0.294
The above costs show that the pipe in place costs about twice as much as
pipe in the yard, even with cement at $4.45.
[Illustration: Fig. 270.--Bordenave Pipe for Swansea, England, Water
Works.]
~MOLDED PIPE WATER MAIN, SWANSEA, ENGLAND.~--As a good example of foreign
practice in molded pipe conduit work a water main constructed at
Swansea, England, has been selected. This pipe line had to operate under
a head of 185 ft.; it was constructed under the patents of the French
engineer, Mr. R. Bordenave, who has built many miles of the same type of
conduit on the Continent.
Fig. 270 shows the construction of the pipe, the drawing being a part
longitudinal section through the shell at the joint. The pipe consists
of an inner and an outer reinforcement separated by a sheet steel tube
and all embedded in a 1-2 mortar. Both inner and outer reinforcements
consists of longitudinal bins of cruciform (+) section wound by a spiral
bar of the same section wired to them at every intersection. Only the
outer reinforcement and the steel tube are considered in calculating the
strength of the pipe, the inner reinforcement being considered as simply
supporting the mortar.
_Fabrication of Reinforcement_.--The steel tube is made of 1 mm. (0.04
in.) thick sheets of steel bent to a cylinder and jointed longitudinally
by welded butt joints, welded by a blow pipe using acetylene and oxygen.
Tests of this welded joint by R. H. Wyrill, Waterworks Engineer,
Swansea, showed it to be quite as strong as the unwelded steel cut from
the shell. The circumferential joints of the tube were made by turning
up the edges of the sheets and welding them; this gives a flexible
watertight joint. The tube was made in lengths of 9 ft. 9½ ins. and its
ends were turned up all around; just back from the turned-up ends a
vertical sheet steel collar was welded to the tube to form a strip end
for the external coating. These details are shown in Fig. 270. When the
tube for a length of pipe is completed the inside shell reinforcement
previously made is slipped into it and the outside shell reinforcement
is formed on it as a mandril, as shown by Fig. 271.
[Illustration: Fig. 271.--Applying External Reinforcement to Bordenave
Pipe.]
[Illustration: Fig. 272.--Casting Bordenave Pipe at Swansea, England.]
_Molding._--When the three positions of the steel skeleton were
completed, as shown by Fig. 271, they were set on curved wooden curbs
made to the exact shape necessary to center them and preserve the
correct thickness of cement coating. A collapsible core was lowered into
position in the inside, and a two-part sheet steel mold was erected
outside; the space between core and mold was then poured with a thin
mortar of one part Portland cement to two parts clean river sand. During
the process of pouring, the outer steel mold is sharply struck with
wooden mallets to facilitate the escape of air bubbles. The mortar was
mixed on an elevated traveling platform which is shown in Fig. 272,
which also shows a completed pipe, a core being withdrawn, a filled mold
and a section of reinforcement set up. The difficult feature of the
molding process was found to be the determination of the time for
withdrawing the core and removing the exterior mold; the time of setting
of the mortar was different in warm and in cool weather and varied with
the wetness of the mixture, the brand of cement, etc. By using a single
brand of cement that ran very uniform in quality and time of setting it
was possible, however, for the workmen, after a little practice, to gage
very accurately the correct time for removing the molds. With four sets
of molds a gang of eight men would curb 16 pipes per day under favorable
conditions, but when the temperature was low it was not possible to make
more than six or eight pipes. The pipes were allowed to stand four or
five days after the removal of the mold; they could then be removed by a
crane and laid in stock until used. It was found advisable to let the
pipes age about four weeks before laying; by this time, it is stated,
they would stand as much rough usage as cast iron pipe.
_Laying_.--The pipes were laid much in the same way as cast-iron pipes
are laid; they were each 9 ft. 9½ ins. long and weighed each about 12
cwt., and were handled by ordinary tackle. In laying, the pipes were
adjusted end to end and the joint enclosed by a temporary steel ring
inside which the bitumen seal, Fig. 270, was run and allowed to set when
the steel ring was removed. The joint was then encircled by a collar of
similar construction to the pipe itself and the space between collar and
pipe was poured with cement mortar. About ten lengths of pipe were laid
per day by one gang of men, one jointer and his assistant making all the
cement and bitumen joints as fast as the gang could lay the pipes.
CHAPTER XXII.
METHODS AND COST OF CONSTRUCTING RESERVOIRS AND TANKS.
Floor, wall and roof work of structurally very simple character sum up
the task of the constructor in reservoir and tank construction. The only
intricacy involved lies in form design and construction for cylindrical
tank work. Several examples of such work are given in this chapter, and
in each the construction and handling of the forms are described. To
repeat details here would serve no purpose, but one general instruction
may be enunciated. No care is too great which ensures rigidity and
invariable form, both in the construction of the individual form units
and in the assembling of these units into the complete form. This is
particularly true of cylindrical tank work and especially high
cylindrical tank work where the forms are moved upward as the work
progresses. To the designer it may be suggested that any beauty he may
gain by giving the walls of his standpipe a batter is paid in the extra
cost of form work.
Concreting in tank work is expensive. The reasons are two. The work has
to be done in a narrow space, commonly pretty well filled with a network
of steel rods or bars. Again the work has to be done uniformly well, not
only for appearance sake but because of the necessity of watertightness.
Making a reservoir watertight is, when all things are said, the one
difficult constructional task in tank work and the contractor who
accepts the task lightly courts trouble. Exceptionally good concreting
is essential in tank work if watertightness is to be secured.
The illustration of these general admonitions will be found in the
specific examples of tank and reservoir work which follow.
~SMALL COVERED RESERVOIR.~--The reservoir was designed to hold 75,000
gallons of water for fire purposes. As it is of a type which is certain
to be frequently constructed and as we have personal knowledge of the
costs recorded we describe the work in some detail. The specifications
stipulated that the reservoir must be absolutely watertight and that the
roof should be capable of sustaining a load of 300 tons evenly
distributed and a live load of 5,000 lbs. on two wheels. Figure 273
shows a plan, Fig. 274 a longitudinal section, Fig. 275 a transverse
section and Fig. 276 the column construction.
[Illustration: Fig. 273.--Sectional Plan of 75,000-Gallon Reservoir.]
_Quantities of Work._--The excavation called for the removal of 579 cu.
yds. of earth. There were 83 cu. yds. of concrete in the structure,
although the plans called for less, the additional amount being used in
increasing the two 4-in. walls to 6-in. and increasing the bottom and
top, on one end, so as to give perfect drainage. The yardage was
divided as follows:
Cu. yds.
Footings 3.5
Columns 6.8
Sides 22.6
Girders 11.0
Top 20.0
Floor 19.1
----
Total 83.0
[Illustration: Fig. 274.--Longitudinal Section of 75,000-Gallon
Reservoir.]
A manhole had to be put in the top and a sump in the bottom. Several
pipes also had to be placed in the concrete. None of these details is
shown on the plan. The structure had to be waterproofed.
_Excavation._--The excavation was made with pick and shovel and the
material hauled away in carts, the distance to the dump being 700 ft.
The top was shoveled directly into the carts, while the rest was handled
two and three times. When the reservoir was finished dirt had to be
filled in around the sides and puddled.
_Wages._--The following rates of wages were paid on the job:
Foreman $3.00
Carpenter 3.50
Carts and driver 3.50
Laborers 1.50
The carpenters worked 8 hours a day and were paid time and a half for
overtime. The rest worked ten hours per day and were paid regular rates
for overtime.
[Illustration: Fig. 275.--Transverse Section of 75,000-Gallon
Reservoir.]
_Forms._--Carpenters framed and erected the forms, but laborers did all
the carrying for them. Laborers also tore down the forms. For the
girders and columns 2-in. boards were used, but for the sides 1-in.
boards with 3×4-in. scantlings were used. The props for supporting the
girder and top forms were 3×4. Except for columns and girders and some
props, all the forming was used three times. The lumber cost:
400 ft. B. M. at $24 $ 9.60
8,000 ft. B. M. at $18 144.00
-------
Total $153.60
[Illustration: Fig. 276.--Column Construction for 75,000-Gallon
Reservoir.]
This makes an average price per 1,000 ft. of about $18.30, which price
we shall use in giving costs.
The cost of framing and erecting the forms was $167.27 for the sides,
columns, girders and top. In the forms for the sides, forming was only
used on one side of the concrete for two sides, the earth bank being
used for the other side of the forms, but on the other two sides the
banks had caved in, and forming was used on both sides of the wall. The
cost per cubic yard for forms was:
Lumber $2.54
Framing and erecting 2.77
Tearing down .54
-----
Total $5.85
This cost is for the yardage of 60.4 on which forms were actually used.
For the total yardage in the tank the cost was:
Lumber $1.85
Framing and erecting 2.01
Tearing down .40
-----
Total $4.26
The common labor cost of assisting to erect the forms was 15 per cent of
the total. Nothing is allowed for foreman, for the contractor acted as
his own foreman.
The cost of forms per 1,000 ft. for the amount of lumber purchased was:
Lumber $18.30
Framing and erecting 19.90
Tearing down 4.00
------
Total $42.20
As the lumber was used three times, the cost per thousand for all work
and materials on the forms would be just one-third of this--namely:
$14.06.
Since the framing, erecting and tearing down cost $19.90 plus $4, or
$23.90 per M. ft. B. M. purchased, and since the lumber was used three
times, the labor cost nearly $8 per M. each time that the lumber was
used. It will be noted that 8,400 ft. B. M. were required for the 83 cu.
yds. of concrete, or a trifle more than 100 ft. B. M. per cubic yard.
It will be of interest to see the labor costs of forms for the various
parts of the structure.
For the sides the cost of framing and erecting the forms was $4.19 per
cubic yard. Of this cost 4 per cent. was for common labor and the rest
for carpenters. The tearing down cost 47 cts. per cubic yard. For the
columns the erecting was $2.35, of which 1 per cent. was for common
labor. The tearing down cost 47 cts. For the girders and top the
erecting cost $1.83, of which 35 per cent. was common labor. The tearing
down cost 61 cts. per cubic yard. A summary would show:
Girders
Sides Columns and
per per top per
cu. yd. cu. yd. cu. yd.
Framing and erecting $4.19 $2.35 $1.83
Tearing down .47 .47 .61
----- ----- -----
Total $4.66 $2.82 $2.44
The greater cost of the columns forms over the girders and top was due
to the fact that the columns forms were handled almost exclusively by
the carpenters, and also in setting them great care and much time had to
be used to get them plumb and in line. The cost of the forms for the
sides was about twice as great as that for the top and girders. The
reasons for this are evident. The walls had forms on both sides, while
the top needed forming only underneath it, the area covered on the forms
being about 2,200 sq. ft. as compared to 1,000 sq. ft. The side forms
had to be set plumb and kept so. The framing was done ahead, but nearly
half of the lumber in the sides was erected as the concrete was being
put in place. The forms for the top were all put in place before any
concreting was done on the top, and the carpenters discharged. A much
larger per cent. of common labor could be used in placing forms for top
and girders than on the sides. The props were nearly all put in place
by laborers. The extra cost of tearing down the forms for the top was
due to the fact that the lumber all had to be handled one piece at a
time through a small manhole in the top, and carried about 150 ft. to be
piled.
To all the costs for forming should be added 6 cts. per cubic yard for
nails, wire and lines used on the forms.
_Concrete._--The mixtures varied for the different members. The cost of
materials was as follows:
Cement, 110 bbls. @ $1.12 $123.20
¾-in. stone, 80 cu. yds., @ $1.86 148.80
Gravel, 3 cu. yds., @ $1.33 4.00
Sand, 42 cu. yds., @ $1.20 50.40
The sides were first put in place, then the center columns were built,
following which the bottom was placed. Then the forms were erected for
the top and the girders, and these cast. In building the sides, one side
and half of the two ends were built at one time, and then forms erected
for the other half of the sides. For the sides the mixing was done in
the bottom of the reservoir. For the rest of the structure it was done
on the ground, the mixing board being along side of the reservoir. The
labor cost of the concrete work for the various members and the average
per cubic yard was as follows:
Columns
and
Sides. Footings. Bottom. Girders. Top. Average.
Cubic yards 22.6 10.3 19.1 11 20.0 83.
Preparing and cleaning up $0.166 $0.060 $0.095 $0.065
Handling materials 1.022 .306 $0.070 .198 $0.187 .404
Cleaning out forms .040 .070 .053 .032
Mixing and placing 1.542 .728 .353 .792 1.080 .952
Ramming 1.090 .540 .455 .450 .597 .673
Handling steel .890 .020 .395 .083 .324
------ ------ ------ ------ ------ ------
Total $4.750 $1.654 $0.878 $2.000 $2.000 $2.450
The total cost of labor was $203.35. The mixing was done entirely by
hand. Some plastering was done to the walls after the forms were taken
off, and the sides and bottom were washed with a brush with cement and
water. The plastering cost $6.60, including a barrel of cement and the
washing or grouting, two coats, cost $9.10, including a barrel of
cement. This added a cost of 19 cts. per cubic yard to the concrete
work, making the total cost per cubic yard $2.65.
It was a mistake to have mixed the concrete for the sides in the bottom
of the reservoir, as it made two handlings of the materials and
compelled all the concrete to be raised by hand to place it in the
forms. This accounts for the high cost of these two items.
The handling of the steel was high for the side walls, as it was all
separated and put into piles for the different panels and members in
getting it out of the pile for the sides. The rammers not only rammed
the concrete but they also bent down the prongs of the steel to get them
in place in the narrow forms, and afterwards had to pull out these
prongs. This had to be done for every piece of steel used, and readily
doubled the cost of ramming. The high cost of ramming the top was caused
by the fact that the 6 ins. of concrete had to be placed in three layers
and each rammed. The steel handling was high on account of the prongs
entangling the pieces with others, making them hard to handle. The cost
of handling steel per ton was about $4, or 0.2 ct. per pound. The steel
was all handled by common laborers.
The stock piles of material had to be made along a street and alley and
thus caused the material to be handled in wheelbarrow several hundred
feet.
The preparing to mix concrete, the cleaning up afterwards and the
cleaning out of forms are items that are seldom kept separate from the
others.
The cost of mixing and placing is high, owing to the fact that working
space was small and the mixers had to wait until the concrete was taken
off the board and placed in the forms before starting another batch.
This also meant an increased cost in the ramming, as the rammers were
idle some time waiting for a new batch to be mixed.
The total cost of concrete, including labor and materials, per cubic
yard on a basis of the 83 cu. yds. was:
Per cu. yd.
Cement, 1-1/3 bbls., @ $1.12 $ 1.49
Stone, 1 cu. yd. 1.86
Sand ½ cu. yd. .60
Steel 4.76
Forms, 100 ft. B. M., @ $18.30 1.85
Labor on forms 2.41
Labor on concrete and steel 2.65
------
Total $15.62
The cost of a foreman is not included in this, as the contractor looked
after the men himself.
_Waterproofing._--The waterproofing of the structure proved a serious
problem. It was thought at first that the concrete itself would be
nearly water tight, but the tank leaked like a sieve. After considering
several methods, an agent of a European waterproofing mixture prevailed
upon those interested to try his compound. To apply it, the walls had to
be dry, so a large coal burning stove was put in the reservoir and a
fire kept up day and night. While this drying process was going on
several light falls of snow occurred, and this had to be cleared away to
make the walls and roof dry. Two coats of the mixture were applied
according to the agent's instructions, and the reservoir was tested. The
water fell nearly half a foot in an hour's time.
Then a waterproofing contractor agreed to make the reservoir water tight
with paper and tar, by applying it on the inside. Three thicknesses of
paper were laid on the bottom and run well up on the sides, each layer
of paper being well covered with a preparation of tar. Upon testing it,
it was found that the leaking had been reduced about 50 per cent. A
preparation of asphalt was then placed over this, but upon a third test
the tank still leaked. As the sub-contractor had verbally agreed to make
it water tight for $125, only this amount was paid him. After this last
test he refused to do any more work.
After these attempts the sides of the reservoir were exposed on the
outside by excavating around it, and a one-brick-wall built up a few
inches from the concrete. This space was filled in with rich cement
mortar and the ground once more filled in around the structure. This
work and the materials used in it cost $1,240. Upon a fourth test the
reservoir was found to be water tight. Thus more than a third of the
cost of the entire work was in waterproofing the structure, and this
made the contract a money losing one, as this heavy cost was not
anticipated.
Several items of miscellaneous work are listed in the total cost of the
reservoir, such as filling in and puddling around reservoir and
replacing cobble paving. The top of the structure was used as a bin for
the storage of coal. For this purpose eight I-beams were embedded in
concrete around the top to be used as posts for the sides of the bin.
The cost of placing these is given.
_Total Cost._--The cost of the structure without any profits was:
579 cu. yds. excavation @ $.896 $ 529.65
Steel 395.00
Crushed stone 148.80
Gravel 4.00
Sand 50.40
Cement 123.20
Lumber 153.60
Labor on forms 200.09
Labor on concrete 203.35
Plastering 6.60
Sides and bottom 9.10
Nails, wire, etc. 4.98
Bailing water 21.19
Building temporary fence 1.65
Extra excavation for forms, footings, etc. 13.90
Setting I-beams in concrete 17.65
Filling in and pudding around reservoir 34.47
Replacing cobble paving 4.30
Hauling tools 3.60
Heating reservoir and handling snow 14.50
Waterproof mixture 29.00
Labor applying it 9.74
Applying paper and tar, labor and materials 125.00
Labor and materials of final waterproofing 1,240.00
Tools 48.75
General expense 210.00
---------
Total $3,602.52
~COVERED RESERVOIR, AT FORT MEADE, SOUTH DAKOTA.~--The following account
of the method and cost of constructing a 500,000-gallon reservoir is
compiled from information furnished by Mr. Samuel H. Lea, M. Am. Soc. C.
E. As shown by Fig. 277, the reservoir consists of two equal
compartments, each 50×60 ft. inside dimensions, with rounded corners.
Both compartments are covered with a 3-in. slab roof carried on the
walls and interior columns.
The concrete was a 1-2-4 Portland cement, sand and broken stone mixture,
mixed by hand on a movable platform. A concrete gang consisted of four
men who were each paid $2.75 per day. They wheeled the materials from
the supply piles to the mixing platform, mixed the concrete and
deposited it in place. During the construction of the footings and floor
two concrete gangs were employed, but after the walls were started, one
gang only was required for concrete work; the other gang was then put to
work assisting the carpenters.
[Illustration: Fig. 277.--Reservoir at Ft. Meade, S. D.]
The sand and stone were wheeled to the platform in iron wheelbarrows of
2½ cu. ft. capacity. The cement was in ¼-bbl. sacks and each sack was
taken as 1 cu. ft. Each batch of concrete contained the following
quantity of material:
2½ sacks of cement 2½ cu. ft.
2 wheelbarrows of sand 5 cu. ft.
4 wheelbarrows of stone 10 cu. ft.
The quantities of sand and stone were adjusted so as to form the proper
proportion for making a dense concrete. From time to time, as the work
progressed, experiments were made to determine the percentage of voids
both in the sand and the crushed stone; and, in this way, uniformity in
composition was secured. The mixture was made quite wet in order to
insure a free flow around the reinforcing bars. On account of the narrow
space inside the forms and the number of reinforcing bars therein care
was taken to cause the mixture to be well distributed throughout. The
wet concrete was well spaded in an effort to secure a smooth surface
next to the forms. This was generally accomplished, but some rough
places which showed after the removal of the forms required patching up.
In constructing the footings some concrete was first deposited in place
and the metal reinforcement was embedded therein. For the floor
reinforcement the lower bars were carefully embedded in the concrete
after it had been brought to a suitable height; the upper bars were then
placed crosswise upon the lower ones and kept in position until the
remainder of the concrete had been deposited around and over them. In
the wall footings a depression or groove, several inches deep, was left
under the wall space for its entire length. This ensured a good bond
between the wall proper and the footing.
The concrete floor in each compartment was built in one continuous
operation, the object being to secure a practically monolithic
construction. The lower reinforcing bars in the floor were embedded at
the proper depth in the fresh concrete and the upper bars were then
placed crosswise upon the lower ones; the two sets were then wired
together at a sufficient number of places to prevent displacement while
the remaining concrete was being deposited around and over them.
The reinforcement for the walls and columns was erected in place upon
the footings and formed a steel skeleton around which the forms were
erected. The upright bars in the walls were held together and at the
proper distance apart by means of templates consisting of wooden strips
in which holes were bored at suitable intervals to receive the bars. The
templates were maintained in a horizontal position and were moved upward
as the concrete advanced in height. The horizontal reinforcing bars
were wired in place to the upright bars; they were placed in position
ahead of the concreting as the wall was built up.
The corrugated bars in beam and girders were placed in position in the
forms and held up by blocks which were removed as the forms were filled
with concrete. The expanded metal reinforcement for the roof slab was
placed so as to be close to the lower face of the slab, but far enough
up to be entirely enveloped in the concrete.
The wall forms were made of 2-in. planks, surfaced on the inner side and
placed horizontally on edge. They were held in place by 4×4-in. posts
spaced at intervals of about 4 ft., in pairs on opposite sides of the
wall. The posts were firmly braced on the outside; they were prevented
from spreading by connecting wires passing through the wall space
between the edges of adjacent planks. At the rounded corners of the
reservoir the pairs of posts were spaced about two feet apart and the
curve was made by springing thin boards into place to fit the curve and
nailing them to the posts. The posts were high enough to reach to the
top of the wall; the siding was built up one plank at a time as the
concrete work progressed. Column forms were made of 2-in. planks on end,
extending from floor to girder. Three sides were enclosed and one side
was left open to receive the concrete; this side was closed up as the
concreting advanced in height.
The beam and girder forms were open troughs of the required dimensions,
made of 2-in. plank, surfaced on inner faces. The form of centering for
the roof slab consisted of a smooth, tight floor of 2-in. planks,
extending between the open tops of column, beam and girder forms over
the entire area between enclosing walls of the reservoir. The centering
and the beam and girder forms were supported by 6×6-in. posts resting
upon the floor below.
The regular carpenter gang consisted of a foreman carpenter at $5 per
day, a carpenter at $3.50 per day, and two helpers at $2.75 per day.
During the early concrete work of making footings and floor, where forms
were not required, the carpenter force was employed in erecting the
steel skeleton for the walls. The upright bars were placed in position
and secured by temporary wooden stays extending from the upper portion
of bars to the surface of ground outside of excavation. These stays were
removed after concreting had advanced to a sufficient height to hold the
steel securely in place.
The wages paid the concrete gang which mixed and placed all the concrete
and the carpenter gang which constructed and erected the forms and
placed the reinforcement have been given above. The costs of
construction materials on the site were:
Cement, per barrel $2.57
Sand, per cu. yd. 1.80
Stone, per cu. yd. 3.15
Lumber, per M. ft. B. M. 27.50
The quantities in the completed concrete structure were as follows:
Total volume of concrete in reservoir 704.71 cu. yds.
Total volume of steel reinforcement in reservoir. 5.57 cu. yds.
------
Total volume of material in completed structure. 710.28 cu. yds.
The steel was, therefore, about 0.8%.
Volume of material in structure exclusive of roof slab 648.35 cu. yds.
Volume of material in roof slab 61.93 cu. yds.
------
Total 710.28 cu. yds.
The cost of the structure per cubic yard of concrete, exclusive of the
roof slab, was as follows:
Item. Per cu. yd.
Crushed stone $ 3.168
Sand .842
Cement 3.859
Reinforcement 4.959
Labor, mixing and placing concrete 1.721
Forms, labor and material 2.960
-------
Total $17.509
In constructing the roof slab the expanded metal reinforcement raised
the unit cost. For this portion of the work the costs were:
Item. Per cu. yd.
Expanded metal reinforcement $ 5.241
Other items, same as above 12.550
-------
Total $17.791
The floor and the inside surface of reservoir walls were covered with a
coating of cement mortar composed of one part Portland cement and one
part sand. The wall plastering was from ½ in. to ¾ in. thick; it was
applied in two coats. The floor finish was laid in alternate strips
about 1 in. thick and 3 ft. wide. After the strips first laid had
hardened the remaining strips were laid, the edges being grouted to
ensure tight joints.
The outside of walls and roof was covered with a coating of tar which
was heated in an open kettle to a temperature of about 360º F. and then
applied with a brush or mop.
The cost of wall and floor plastering was 44.4 cts. per square yard,
itemized as follows:
Cement 26.4 cts.
Sand 2.6 cts.
Labor 15.4 cts.
-----
Total 44.4 cts.
The cost of outside waterproofing was 4 cts. per square yard,
distributed as follows:
Material 2.5 cts.
Labor 1.5 cts
---
Total 4.0 cts.
While some of the cost items are apparently high when compared with the
cost of similar work in other places, it should be remembered that the
isolated locality and the local conditions were unfavorable for low
cost. Owing to the isolated location of the reservoir with respect to
large markets and also to local sources of supply the cost of material
and labor was quite high. All construction material, except some of the
stone for crushing, had to be hauled over a mountain road from 3 to 4
miles to the top of the hill selected for the reservoir site. Labor was
scarce and commanded a wage of $2.50 per day for ordinary work; the
laborers mixing concrete were paid $2.75 per day. Another source of much
relative expense was the high cost of lumber and carpenter work on the
forms. On account of the thinness of the walls and roof, the cost of
lumber and labor required per cubic yard of concrete was considerable. A
part of the lumber was used the second time in forms, but it was found
impracticable to delay the work by waiting for the concrete to harden
before beginning the new portions of the walls. This lumber was sold
after the completion of the work, but the salvage was inconsiderable,
amounting to less than 10 per cent. of the original cost.
[Illustration: Fig. 278.--Reservoir Forms. Bloomington, Ill.]
~CIRCULAR RESERVOIR, BLOOMINGTON, ILL.~--An open circular reinforced
concrete reservoir was constructed in 1905-6 for the water-works of
Bloomington, Ill. This reservoir is 300 ft. in diameter, 15 ft. deep at
the circular wall and 25 ft. deep at the center of the spherical bottom.
The wall construction is shown clearly by Fig. 278, and the floor is a
6-in. spherical slab reinforced by a mat of ¼-in. round rods placed 6
ins. on centers in both directions. The wall reinforcement is corrugated
bars. Neither the wall nor the bottom has expansion joints.
_Concrete._--The specifications required not less than 1 part Portland
cement to 2 parts sand and 5 parts clean gravel, and stipulated that
there should always be more than enough cement to fill the voids in the
sand more than enough mortar to fill the voids in the gravel. The
proportions were varied, depending on the character of the available
material and on the location the concrete was to occupy. The
stipulations regarding the minimum quantities of cement and mortar were,
however, always at least fulfilled. A 1-3-4 mixture of cement, broken
stone and gravel was largely used in the footing and wall. The gravel
was fine and contained 40 to 50% of sand; the broken stone was the
crusher-run, with the dust screened out, and the maximum-sized pieces
not larger than those which would pass a 2-in. screen. The mortar facing
on the front face of the wall was made of 1 part cement to 4 parts fine
gravel, containing sand. Some gravel from the excavation was used in the
concrete for the floor. This gravel was so fine that about one-quarter
of it was replaced with broken stone and the mixture made 1-6. Both
faces of the wall were painted with a 1-1 mixture of cement and sand;
the inner face was also painted with a 1-1 mixture of waterproof Star
Stettin Portland cement and sand. The sidewalk finish on the surface of
the floor consisted of 1-1½ mortar.
_Mixing and Handling._--The concrete mixing plant was set up outside of
the site of the reservoir along a side track from the railroad. The
concrete materials were delivered on the side track, except some gravel
from the excavation that was used. A Foote portable continuous mixer was
used in making the concrete for the wall footings and the wall. It was
mounted so it could discharge into dump cars on a service track laid on
the ground. A double hopper was built up over the mixer, one compartment
for sand and one for broken stone. The end of a service track leading
from the side track was laid on an inclined trestle up to a floor level
with the top of this double hopper, the materials being hauled in dump
cars from the side track to the hopper. The service track from the mixer
extended entirely around the wall, and 10 ft. from it, on the
embankment made there with earth from the trench for the wall-footing.
The concrete was dumped from the cars on the service track to portable
shoveling platforms near the point where work on the wall was in
progress. It was shoveled by hand from these platforms to place in the
forms as the presence of the reinforcement bars in the narrow forms
precluded dumping in large quantities. The footing was built without
forms up to the right-angle joint between it and the base of the wall at
the front, and to the top of the 45° slope on its rear face. A layer of
concrete 2.5 in. thick was first placed in the completed trench. The
reinforcement bars near the bottom were then laid on this green
concrete, the vertical bars near the front face of the wall usually
being erected at the same time. The concrete in the toe of the footing
and in the footing proper up to the top layer of reinforcement was then
laid. After the top layer of reinforcing bars had been laid, the footing
was completed, except for a top layer about 2 ins. thick at the base of
the front face of the wall and 15 ins. thick at the toe of the footing.
This left a strip of surface about 6 ft. wide, sloping at about 1 in 6
from the wall toward the center of the reservoir, and furnished the
widest and best possible bond for the joint which had to be made when
floor was laid.
_Location and Construction of Forms and Wall._--The design of the wall
of the reservoir, although simple in itself, required unusually accurate
work in the location and construction of the forms for it. The location
was made with very little difficulty, however, by an arrangement devised
by the contractor which enabled the foreman, without the aid of an
engineer, to set the necessary grade and reference stakes. A post, 10
ins. in diameter, was set very accurately and firmly in the ground at
the center of the reservoir. This post was sawed off squarely on top so
that the line of collimation of an engineer's transit set on it without
a tripod would be exactly at the grade of the top of the completed wall
of the reservoir. A 200-ft. steel tape was used to measure the radial
distance from a nail in the center post to the posts of the back, or
outside forms for the wall. In the form for the back face of the wall
2×6-in. posts, spaced one one-hundredth of the circumference apart, were
set considerably in advance of any concrete work, and were made the
basis of all measurement in building the forms. The forms as originally
planned are shown in Fig. 278.
The wall, when started, was built continuously in both directions from
the starting point. The back forms consisted of planks for lagging
nailed to vertical posts, which were accurately set and firmly braced.
The front forms were made in lengths equal to one one-hundredth of the
circumference of the reservoir, and when set up were fastened to the
back forms. Twenty-one of these front form sections were built and all
set up at once. Concrete was filled in between the front and back forms,
starting at the central form, and was rammed in inclined layers,
sloping, at about 1 on 6, both ways towards the end forms. This method
was adopted in order that the concrete might be laid continuously and
without joints. The lagging of 1-in. boards on the vertical portion of
the sections was nailed to the vertical posts, and was carried up just
ahead of the concrete filling.
When the concrete had reached the top of the central one of the 21
sections of the forms, and the concrete in that section had set
sufficiently, the section was broken up and removed, leaving two sets of
10 sections of the forms. Subsequently the other forms could be removed
in turn as desired without being broken up. As the filling-in proceeded
between the two sets of 10 forms each, the form in each set nearest the
starting point was removed, carried forward, and put in place at the
other end of its set of forms. Twelve men were required to take down and
transport one of the front form sections.
In setting up a front form, its inner toe was firmly supported by a
stake driven into the ground and by the horizontal board, nailed
transversely under the bottom 4×4-in. horizontal stringers, which rested
on the ground. The upper part of the form was then securely fastened to
the 2×6-in. posts of the back forms by temporary wooden connecting
strips, which were removed as the concrete filling was carried up. The
sections of the front forms were also securely tied to each other.
A facing of gravel concrete, rich in cement and with no pebbles larger
than ½-in. was placed on the front face of the wall, extending from the
back edges of the vertical reinforcing bars to the surface. A sheet-iron
plate, about 8 ins. wide by 5 ft. long, was placed vertically just back
of those bars. The concrete was shoveled in loose to the top of these
iron plates, and then the mortar was poured in between the latter and
the front face forms from buckets. The iron plates were next drawn by
handles attached to them, and the mortar and concrete tamped together
before either had set. In making joints, the old concrete surfaces were
always brushed and wet down, and, if necessary slushed with a grout of
neat cement before new concrete was laid on them.
_Construction of Floor._--The excavation over the site of the reservoir
floor was brought accurately to grade 6 ins. below the surface of the
finished concrete by hand after the scoop-bucket excavator had passed
over. In making the excavation the levels were given on radial lines
drawn from the ends of the 10-ft. sections of the wall to the center. A
rod, on which the elevations of the sub-grade at every 10 ft. from the
wall to the center of the reservoir were clearly marked, was used in
connection with a transit on the center post in locating the elevations
of different points in the reservoir floor. By using this method the
elevations required were easily found by the foreman in charge without
the assistance of an engineer. When the work approached the center, the
post was removed and the transit was placed on a portable pedestal which
was set on points of known elevation on the finished concrete.
The slanting surface left on the top of the footing inside the wall
formed, together with the projecting reinforcement rods, an excellent
bond between the concrete of the wall and that of the floor, when the
latter was laid. A circular strip of the floor, 16 ft. wide, was put
down next to the wall first, and the remainder of the floor was laid
according to the progress of the excavation. The lower 3½ ins, of the
concrete was usually first spread out over an area 12 or 16 ft. square,
then the reinforcement was placed, and after that the top 2 ins. of
concrete and a ½-in. sidewalk finish surface were laid.
[Illustration: Fig. 279.--Standpipe at Haverhill, Mass.]
The ¼-in. rods in the bottom are 6-ins. on centers in both directions.
They were in 12 and 16-ft. lengths and were partly woven together in
mats before being placed. The rods in one direction were all laid out
and woven with four or five of those in the other direction, the joints
being tied with small wire. The remaining cross rods were laid after the
mat had been placed. The mats were overlapped 1 ft. This method of
placing proved economical and efficient, giving at the same time
something permanent on which to lay the remaining concrete.
~STANDPIPE AT ATTLEBOROUGH, MASS.~--The stand pipe was 50 ft. in diameter
and 106 ft. high inside, with walls 18 ins. thick at the bottom and 8
ins. thick at the top. Figure 279 shows the general arrangement of the
reinforcement. Round bars of 0.4 carbon steel were used; the bars came
in 56½-ft. lengths, so that three lengths with laps of 30 ins., made a
complete ring around the tank. The concrete was a 1-2-4 mixture of ¼ to
1½-in. broken stone with screenings used as portion of sand.
The floor was built first, and on it was erected a tower to a height of
60 ft. and a derrick with a 40-ft. boom was set on its top. The derrick
was operated by an engine on the ground which also had a revolving gear
attached. When the work had reached the top of this tower, the tower was
raised to 110 ft. in height and the derrick shifted to the new
elevation. The forms were convex and concave sections 7½ ft. high and
about 11 ft. long. The concave or outside forms were made in 16 panels,
with horizontal ribs and vertical lagging; two complete rings of panels
were used. The panels were joined into a ring by clamps across the
joints, this clamping action and the friction of the concrete holding
them in place. The inside forms consisted of vertical ribs carrying
horizontal lagging put in place a piece at a time as the filling
proceeded. They were supported by staging from the derrick tower. The
remaining plant comprised a Sturtevant roll jaw crusher feeding to
screens which discharged fines below ¼-in. into one bin, medium stone
into another bin and coarse stone into a third bin. These bins fed to
the measuring hopper of a Smith mixer, which discharged into the derrick
bucket.
The mode of procedure was as follows: The reinforcing rings were erected
to a height of 7½ ft. The bars were bent by being pulled through a tire
binder and around a curved templet by a steam engine. The bending gave
some trouble, due, it was thought, to the stiffness of the high carbon
steel. Vertical channels 4 ins. deep were set with webs in radial planes
or across wall at four points in the circumference. The flanges of these
channels were punched exactly to the vertical spacing of the reinforcing
rings. Through the punched holes were passed short bars on the opposite
ends of which the reinforcing rings were supported and wired. The three
sections of rod of which each ring was composed, were lapped 30 ins. and
connected by Crosby clips. Considerable difficulty was had in holding
the reinforcing rings in line by the method employed; it is stated by
the engineer that a greater number than four channels would have been
much better.
The reinforcement being in place, an inside and an outside ring of forms
was erected. Concreting was then carried on simultaneously from four
points on the circumference and a ring 7½ ft. high was concreted in one
operation. Several facts were brought out in the concreting; careful and
conscientious spading was necessary to get a smooth dense surface; a too
wet mixture allowed the stone to settle and segregate; care was
necessary in this thin wall containing two rings of bars to keep the
stone from wedging among and around the bars and thus causing voids. The
engineer states that for this reason the substitution of mortar for
concrete in tank walls is worth considering. He estimates that in this
work, costing $35,000, that the use of a 1-2 mortar in place of the
1-2-4 concrete would have increased the cost by $2,300, a 1-2½ mortar by
$1,500, and a 1-3 mortar by $750. It was also found that there was
danger from a movement of the reinforcement in the concrete and of the
forms in placing the concrete.
When a ring of wall 7½ ft. high had been concreted, the reinforcement
was placed as before described for another ring. The two rings of forms
below those just filled were removed from the wall, hoisted up and set
in place on top. These two operations of placing reinforcement and
setting forms for another ring of wall took three days, so that the top
surface of the wall to which new concrete was to be added, had become
hard. This hard surface was very thoroughly washed and then coated with
neat cement immediately before depositing the fresh concrete. Water was
admitted to the tank as the work progressed, being kept about 20 ft.
below the work in progress. Numerous small leaks developed, but only two
were large enough for the water to squirt beyond the face of the wall.
These leaks appeared to grow smaller as time went on. To do away with
them entirely, the inside wall was plastered. The first coat of plaster
was not successful in stopping the leaks, so the standpipe was emptied
and replastered, five coats being used in the lower 20 ft. This did not
serve so resort was had to a Sylvester wash. A boiling hot solution of
12 ozs. to the gallon of water of pure olive oil castile soap was
applied to the dry wall. In 24 hours this was followed with a 2 ozs. to
the gallon solution of alum applied at normal temperature. Four coats of
each solution were applied, which reduced the leakage to a small amount.
To do away with all leakage another four-coat application of Sylvester
wash was used.
Details of the cost of the work are not available. There were 770 cu.
yds. of concrete in the walls and 185 tons of steel bars. Altogether
3,000 Crosby clips, costing $1,100 were used. The cost of the concrete
in place was about as follows:
Cement, per cu. yd. of concrete $ 4.80
Sand and stone, per cu. yd. of concrete 3.90
Mixing, per cu. yd. of concrete 0.40
Placing, per cu. yd. of concrete 2.20
Forms, per cu. yd. of concrete 2.65
------
Total per cu. yd. of concrete $13.95
~GAS HOLDER TANK, DES MOINES, IOWA.~--The tank was 84 ft. in diameter and
21 ft. 5 ins. deep. It had a horizontal floor 16 ins. thick 5 ft. below
ground level and a wall 21 ft. high, 18 ins. thick at base and 12 ins.
thick at top under coping and with alternate pilasters and piers around
the outside. The concrete for the floor was a 1-2½-5 2-in. stone mixture
and the concrete for the walls was a 1-2-4 1-in. stone mixture. The
floor was constructed first, with a circular channel for the wall
footing, and then the wall was constructed.
Piles were driven in the bottom and their heads cut to level and filled
around with tamped cinders. Two circumferential rows of posts were
driven around the edge so that a pair of posts, one inner and one outer,
came on each radius through a wall pilaster or pier. These posts served
primarily to carry the frames for the wall forms and secondarily for
holding the forms for the circular wall footing channel as shown by the
sketch Fig. 280. The floor concrete was put in in diamond-shaped panels
between forms, whose top edges were set to floor level. Each form was
designed to make a groove in the edge of the slab so that adjacent slabs
would bond with it. The concrete was wheeled to place in barrows,
thoroughly tamped, roughly floated to surface and finally given a trowel
finish.
[Illustration: Fig. 280.--Forms for Constructing Channel for Wall in
Reservoir Floor.]
To construct the walls, the posts before mentioned, were cut off to
exact level 6 ins. above the finished floor. A bent for the wall forms
was then erected on each radial pair as shown by Fig. 281. The bents
were erected by hand and carefully plumbed and lined up, both radially
and circumferentially. The pier and pilaster forms were then erected
across wall opposite each bent as shown by Fig. 281. The forms for the
wall between pilasters and piers consisted of panels 4 ft. high.
[Illustration: Fig. 281.--Frame for Forms for Circular Reservoir Wall.]
[Illustration: Fig. 282.--Form Panels for Circular Reservoir Wall.]
A panel for the inner face of the wall is shown by Fig. 282, the panel
for the outer face was similar in construction but was, of course,
concave instead of convex. Enough panels of each kind were made to reach
entirely around the tank. The inside panels were bolted at the ends to
the uprights of the bents; the outside panels were similarly lag screwed
to the uprights of the pier and pilaster forms; Fig. 281 shows the holes
for bolts and lag screws. The spaces between ends of inside panels in
front of the bents was closed by a ½×6-in. steel plate the full height
of the wall; this plate was bolted to the bents and had anchor bolts
every 3 ft., reaching into the wall. This anchoring of the plate to the
wall permitted the diagonal bracing of the bents to be removed to allow
runways to be laid on the cross-pieces, since the plate held firmly the
bent post to which it was bolted as indicated by Fig. 283. A complete
circle of inside and outside forms was erected and filled, then the
forms were raised 3 ft. by block and tackle from cross timbers across
wall between bent and pilaster form, and this depth concreted and the
forms raised again. The forms were oiled on the faces coming against the
concrete. It took about half a day to raise and set a complete circle of
forms. The concrete was mixed outside the tank and was wheeled up
inclines and dumped onto runways laid on the cross pieces of the bents
and then loaded and wheeled to place. The runway was raised to
successive horizontals as the work progressed.
[Illustration: Fig. 283.--Sketch Showing Filler for Joint Between Form
Panels.]
Only a few general cost figures are available. The labor for mixing and
placing concrete was as follows:
For floor, per cu. yd. 3.4 hrs.
For walls, per cu. yd. 5.2 hrs.
For cornice, per cu. yd. 5.4 hrs.
The cost of unloading the reinforcing steel from cars and placing it in
the structure was $7 per ton, or 0.35 ct. per lb. The cost of form
lumber, framing, erecting and taking down forms was 9 cts. per square
foot of wall covered.
~GAS HOLDER TANK, NEW YORK CITY.~--The tank for the Central Union Gas
Co.'s gas holder at 136th St. and Locust Ave. has an interior diameter
of 189 ft. and a depth of 41 ft. 6 ins. The exterior wall is 42 ft. 6
ins. deep, 5 ft. 6 ins. thick at the base and 4 ft. 6 ins. thick at the
top; concentric with it and 11 ft. 6 in. away is the interior wall 166
ft. in external diameter and 16 ft. 6 ins. high with a uniform
thickness of 2 ft. 6 ins. The bottom of the tank enclosed by the
interior wall is a truncated cone whose base is at the level of the wall
top. Fig. 284 shows the arrangement.
It was specified that the diameter of this tank should not vary more
than 2 ins. and that the exterior wall should not vary more than 1 in.
from the vertical. The main form was a circular drum whose exterior face
formed the inner face of the main wall. Its framework consisted of 40
vertical trusses or radial frames 6 ft. deep and 42 ft. high set
equidistant around the tank, these trusses being braced together on both
edges by circumferential timbers. Radial horizontal pieces nailed across
the radial frames and projecting beyond their faces carried vertical
iron guide strips against which the movable panels of lagging were
seated. These panels were cylindrical segments 5 ft. high and long
enough to span between two radial frames or 14 ft. 11-5/8 ins. The
panels were adjusted radially by wedges to give 1/8 in. clearance in
respect to inner face of wall; enough of them were made to form a
complete circle and they were set with 1-in. clearance between vertical
edges of adjacent panels to allow for swelling when wetted.
[Illustration: Fig. 284.--Section of Gas Holder Tank, New York City.]
The concrete bottom of the annular space between walls was first
constructed. On this floor were set 6×6-in.×8-ft. sills for the radial
frames; these were located accurately by transit. The radial frames were
then set on the sills by a derrick, adjusted to exact radial position by
a measuring wire swiveled to the center point of the tank and plumbed
by transit. A complete circle of lagging panels was then adjusted to the
frames at the bottom of the trench. For concreting, the wall was divided
circumferentially into three sections. These sections were separately
concreted to the top of the lagging panels, that is to a height of 5 ft.
After the concrete had set 48 hours the panels were hoisted 4 ft., so
that their lower edges still overlapped the concrete 12 ins., and
another ring of wall was concreted. This procedure was repeated until
the wall was completed. The back of the wall was formed against the side
of the trench where possible and in other places against rough board
lagging held in position in any convenient way.
For handling the concrete, four equidistant panels of the form framework
were converted into double compartment elevator shafts providing for two
balanced cars controlled by a sheave provided with a friction brake.
Three mixers supplied concrete to these elevators. Considering a single
elevator, two barrows of concrete were wheeled from the mixer onto the
car at the top of the elevator frame, the friction brake was released
and the loaded car descended to the work hoisting at the same time its
twin car loaded with two empty barrows. The elevators distributed to
wheeling platforms cantilevered out from the outer face of the framework
and located successively 5 ft., 15 ft., 20 ft., etc., above the bottom
of the trench. On these platforms the concrete was distributed as
required, the maximum wheeling distance being never over one-eighth the
circumference of the tank. The concrete was mixed very wet and deposited
in 6-in. layers.
The inner and outer surfaces of the wall were both painted with two
coats of stiff cement grout neat, and in addition the inner surface was
rubbed smooth by carborundum brick. Regarding this finishing work Mr.
Howard Bruce, Engineer of Construction, writes:
"The scouring was done on each section of the wall immediately after the
forms supporting these sections had been removed. The object was to rub
this interior surface with carborundum before the surface of the
concrete had taken its final set. By rubbing the concrete at this stage
and at the same time applying with a brush a coating of neat cement
grout, we believe the face of the concrete was made more or less
impermeable, as examination shows the pores of the concrete are very
largely filled up. We have no accurate figures as to the cost per square
yard of this treatment, but one can readily see that this cost would be
insignificant as compared with the possible improvement of the work. The
carborundum brick was selected on account of its hardness. I believe
practically any stone would answer the same purpose. In addition to
filling the pores of the concrete, this treatment gives the surface a
good smooth finish."
~LINING A RESERVOIR, QUINCY, MASS.~--The following methods and costs are
given by Mr. C. M. Saville, M. Am. Soc. C. E., for lining the Forbes
Hill Reservoir at Quincy, Mass. This reservoir is 100×280 ft. on the
floor, with side slopes of 1 on 1.75, and was built by contract in
1900-1901.
[Illustration: Fig. 285.--Section of Reservoir Lining, Quincy, Mass.]
Figure 285 is a section of the concrete lining; the bottom layer for the
floor was a 1-2-5 natural cement concrete, and for the sides a 1-2½-6½
Portland cement concrete; the top layer on both floor and sides was a
1-2½-4 Portland cement concrete; 2½-in. stone was the maximum size
allowed in any concrete and 1½-in. the maximum allowed in the top layer.
Smaller stone was used for special surface work, as noted further on.
The stone was cobbles turned up in the excavation work and had to be
gathered from scattered piles and washed before crushing. A 9×15 Farrel
crusher, operated by a 12 HP. engine did the crushing; it was rated at
125 tons a day, but averaged only about 40 tons. The fine dust was
screened out and the remainder discharged into a 30-cu. yd.,
three-compartment bin, one compartment for stone less than 1½ ins.,
another for 1½ to 2½-in. stone and a third for returns. The stone had 46
per cent. voids and weighed 95 lbs. per cu. ft. The sand was of
excellent quality. Atlas and Beach's Portland and Hoffman natural cement
were used.
All concrete was mixed and placed by hand, the concrete gang consisting
generally of 1 sub-foreman, 2 men measuring materials, 2 men mixing
mortar, 3 men turning concrete three times, 3 men wheeling concrete, 1
man placing concrete and 2 men ramming concrete. Two gangs were
ordinarily employed, each mixing and placing about 20 cu. yds. per day,
or 1.43 cu. yds. per man per day. The materials (sand and stone) were
measured in bottomless boxes, the following sizes being used:
--Sand Box-- --Stone Box--
Prop. of Mix. Size. Vol. cu. ft. Size. Vol. cu. ft.
1-2½-4[H] 2'9"×2'×1'8" 9.25 5'×4'5½" 14.8
1-3-6[H] 2'9"×2'×2' 11.1 5'×6'8" 22.2
1-2-5 2'9"×2'×1'4" 7.4 5'×6'6-5/8" 18.5
1-2½-6½ 2'9"×2'×1'8" 9.25 5'×7'2½" 24.05
[Footnote H: These mixtures were used for gate house and standpipe
foundation work.]
The bottom layer was placed in a continuous sheet; the top layer was
laid in 10-ft. squares on the floor and in 8×10-ft. squares on the
sides; these squares alternated in both directions, one-half being first
laid and allowed to set. In laying the sides the surface was left 1 in.
low and then before the concrete had set was brought to plane by a 1-in.
layer of 1-2½-4 mixture using stone and stone dust less than 3/8 in. The
concrete for the floor was mixed rather wet and rammed until it quaked;
on the sides a drier mixture was necessary to prevent flow. The cost of
the lining concrete was as follows:
Bottom Layer on Floor: 1-2-5 Mixture:
1.25 bbls. natural cement at $1.08 $1.350
0.34 cu. yd. sand at $1.02 0.347
0.86 cu. yd. stone at $1.57 1.350
4½ ft. B. M. lumber at $20 per M. 0.090
Labor, on forms 0.100
Labor mixing and placing 1.170
Labor general expenses 0.080
------
Total $4.487
Bottom Layer on Sides: 1-2½-6½ Mixture:
1.08 bbl. Portland cement at $1.53 $1.652
0.37 cu. yd. sand at $1.02 0.377
0.96 cu. yd. stone at $1.57 1.507
Lumber for forms (about 1 ft. B. M.) at $20 0.016
Labor, on forms. 0.121
Labor, mixing and placing 1.213
Labor, general expenses 0.177
------
Total $5.063
Top Layer on Floor and Sides: 1-2½-4 Mixture:
1.37 bbls. Portland cement at $1.53 $2.09
0.47 cu. yd. sand at $1.02 0.48
0.75 cu. yd. stone at $1.57 1.17
12½ ft. B. M. form lumber at $20 per M. 0.25
Labor, on forms 0.26
Labor, mixing and placing 1.530
Labor, general expenses 0.150
------
Total $5.93
The side finish with 1-2½-4 concrete of 3/8-in. stone cost $0.154 per
sq. yd. 1 in. thick. This work was done by a gang of 3 plasterers and 3
helpers.
The layer of plaster between the concrete layers was put down on 4-ft.
strips and finished similarly to the surface of a granolithic walk. This
layer consisted of 1-2 mortar finished with a 4-1 mortar. To keep the
plaster from cracking it was covered with strips of coarse burlap soaked
in water; this precaution was not entirely successful, some cracks
appeared and had to be grouted. Three gangs, each consisting of 1
plasterer and 1 helper, did the plastering, each gang laying about 700
sq. yds. per day. The cost of the plaster layer was as follows:
Item. Per 100 sq. ft. Per sq. yd. Per cu. yd.
Cement at $1.53 $1.15 $0.103 $7.42
Sand at $1.02 0.13 0.012 0.86
Burlap 0.02 0.002 0.14
Labor 0.92 0.083 6.00
----- ------ ------
Totals $2.22 $0.200 $14.42
It will be noted that it took over 5 bbls. of cement per cubic yard, and
that the labor cost was $6 per cubic yard.
~RELINING A RESERVOIR, CHELSEA, MASS.~--The following account of relining
the Powder Horn Hill Reservoir at Chelsea, Mass., is taken from a paper
by Mr. C. M. Saville. This reservoir which holds about 1,000,000 gallons
is oval in shape, 98×175 ft. at the top, 68×148 ft. at the bottom and 15
ft. deep, with side slopes about 1 on 1. The work was done by day labor.
For sake of completeness the costs of excavation and back-filling are
given here as well as the concrete costs.
The top of the bank was too narrow to allow the use of carts and an
18-in. gage railroad was decided upon as most convenient for handling
materials. A 65-ft. boom derrick with a 70-ft. mast was used for
removing the excavated material and for depositing concrete. The derrick
was operated by a 15-h.p. double drum hoisting engine, was held in place
by six wire guy ropes, and had a reach such that only one moving was
necessary after it was placed. The engine and derrick were set up on the
floor of the reservoir, and the work of excavation was begun at about
the middle of the south side. In order to facilitate the work, a
platform supported on A frames was set up. These frames were spaced
about 15 ft. apart and rested on the bottom and slope of the reservoir,
being held in place by bolts driven into the floor.
The paving blocks on the top of the slope were removed and piled up to
be taken away. The old lining and the material excavated from the bank
were shoveled into the scale pan of the derrick, hoisted to the cars on
the top of the bank, and then run by gravity to a dump a short distance
down the hillside. Here the cars were run out on a rough trestle, the
load dumped, and the empties hauled back to the work by a rope carried
through pulleys to the winch head on the hoisting drum of the engine.
For the storage of some of the materials, two small portable storehouses
were set up--one 8×10×7 ft., the other 11×16 x 7 ft. The bulky portions,
such as cement, sand, and stone, were delivered as necessary, a few
days' supply only being kept on hand. A branch from the railroad was so
arranged that it passed the storehouses and stone piles, while the sand
was piled close to the concrete mixing board. The intention on the work
was to do nothing by hand that could possibly be done by steam, except
that all of the concrete was mixed by hand. As great a proportion of
water was used as could be done without causing the material to slide
when rammed in place.
The lower layer of concrete was of the proportion by volume of 1 cement,
2½ sand, and 6½ crushed stone (sizes from ¾ to 1½ ins.). This was rather
a lean mixture, and as it could not be rammed enough to flush all over,
the surface was finished where necessary by a thick mortar made in the
proportion of 1 cement to 6 sand, and applied with heavy brushes. Before
placing any of the concrete, the bank back of the old concrete left in
place was thoroughly rammed with iron railroad tampers, and the edge of
the old concrete was scrubbed with water and a stiff brush and then
coated with 1 to 4 grout, which was allowed to fill in the angle between
the concrete and the slope. Just before placing the concrete the earth
bank was well wet in order that moisture might not be drawn from the
concrete while it was soft.
In order to make the new lining as waterproof as possible, a layer of
asphalt was placed on top of the lower layer of concrete and brought up
on the exposed edge of the old layer at the bottom of the new work.
This, it was expected would make an elastic and watertight joint between
the new and the old work.
Venezuela asphalt, "Crystal Brand," was used, being poured upon the top
of the concrete layer and allowed to run down the slope, care being
taken that the concrete was entirely and perfectly covered. After the
first layer of asphalt was cool, a second layer was similarly applied,
and the resulting sheet was about ¼ in. thick. Any inclination to crawl
down the slope when exposed to the sun was readily stopped by throwing
on a pailful of cold water. A most particular part of this work was to
get the asphalt as hot and liquid as possible and yet not burn it. All
of the concrete was protected from the sun and kept damp by being
covered with strips of burlap, which were moistened by sprinkling.
The upper layer of concrete was composed of a much richer mixture of
concrete than that used in the bottom layer, the proportions by volume
being 1 cement, 1¼ sand, 1¼ stone dust, and 4 broken stone of the sizes
mentioned above. On account of the steep slope it was possible to do
only a little ramming, and the material was laid as wet as possible. To
make this layer more impervious and also to obtain a smooth surface, the
concrete was left about an inch below and a finish coat applied by
expert granolithic finishers. This coating was applied as soon as it was
possible to do so after the main layer was in place, but on account of
the steepness and the liability of the wet concrete to flow, care had to
be taken not to begin work too soon.
The top finishing coat was made in the proportion of 1 part cement,
1-2/3 part sand, and 3-1/3 parts stone dust. In order to help in
bonding, the last ramming on the concrete was done with rammers studded
with pieces of iron about 1 in. long and ½ in. deep.
The finishing was done in three operations: The material was spread on
the concrete and thoroughly worked into it by the finishers, using rough
wooden floats; after this it was gone over and partially smoothed down
with a thin steel float; and finally it was worked to give the finished
appearance and an impervious surface.
The under layer of concrete was placed in a continuous sheet. The upper
layer was put down in alternate strips, 10 ft, long (the whole length of
the layer) and 5 ft. wide. These blocks were built up in forms, which
were not removed until the concrete had set. Finally, the back or edge
of the block toward the bank was well wet and thoroughly plastered, to
prevent, as far as possible, the infiltration of any water. The plaster
was mixed in the proportion of 1 part cement to 4 parts sand. When the
forms were wholly removed, the space between the concrete and the bank
was refilled, to within about 6 ins. of the top, with a clayey material
previously excavated, and the space was filled and graded to the top of
the bank with loam. During the work two holidays intervened; the men
were also transported to and from the work. Charges were made for these
items, amounting to $209.77, and this sum, together with the cost of
installing the plant ($716.03) are proportionally charged against the
work as follows:
Per cent. Total. Per cu. yd.
Excavation 70.3 $651 $2.17
Lower concrete 12 111 1.16
Upper concrete 15.4 143 1.11
Back fill 2.3 21 .28
The detailed cost of repairing the reservoir lining is given in the
following tabulations:
Excavation.
Rate. Per cu. yd.
Foreman 9 5/9 days $4.00 $0.13
Engineman 12 3/9 days 3.00 .12
Carpenter 2 days 2.67 .02
Laborers 9 6/9 days 2.25 .07
Laborers 110 2/9 days 2.00 .73
Laborers 46 5/9 days 1.75 .27
Derrick 12 3/9 days 3.75 .15
Rails and cars 11 2/9 days 0.40 .02
Stove coal 3.05 tons 6.50 .07
Egg coal .95 tons 6.25 .02
----
Total, 300 cu. yds. 1.60
Estimated proportionate charge for plant
installation and holidays 2.17
----
Grand total 3.77
Lower Layer Concrete.
Rate. Per cu. yd.
Foreman 3-7/9 days $4.00 $0.16
Engineer 2-3/9 days 3.00 0.07
Carpenters 7 days 2.67 0.20
Laborers 1-7/9 days 2.25 0.06
Laborers 89 days 2.00 1.87
Laborers 4 days 1.75 0.07
Derrick and engine 2-3/9 days 3.75 0.08
Rails and cars 2-2/9 days 0.40 0.01
Cement 106-3/8 bbls. 1.35 1.50
Sand 37.4 cu. yds. 1.10 0.43
Broken stone 117.9 tons 1.35 1.67
Egg coal .41 tons 6.25 0.03
Lumber 1.3 M. ft. 21.00 0.28
----
Total, 95.5 cu. yds. $6.43
Estimated proportionate charge for
plant installation and holidays 1.16
----
Grand total $7.59
Upper Layer Concrete.
Rate. Per cu. yd.
Foreman 6-7/9 days $4.00 $0.21
Engineer 1-8/9 days 3.00 0.04
Carpenter 18-5/9 days 2.67 0.38
Laborers 1-7/9 days 2.25 0.03
Laborers 119-5/9 days 2.00 1.85
Derrick and engine 1-8/9 days 3.75 0.05
Rails and cars 8-3/9 days 0.40 0.03
Cement 176½ bbls. 1.35 1.86
Sand 30.2 cu. yds. 1.10 0.26
Stone dust 41.6 tons 1.50 0.48
Broken stone 122.8 tons 1.35 1.28
Egg coal .2 tons 6.25 0.00
Lumber 4 M. ft. 21.00 0.65
Burlap 300 yds. 0.04½ 0.10
Nails 170 lbs. 0.05 0.03
----
Total, 129.2 cu. yds. $7.25
Estimated proportionate charge for
plant installation and holidays 1.11
----
Grand total $8.36
Back Plaster.
Rate. Per cu. yd.
Plasterer 3-8/9 days $5.40 $0.08½
Plasterer 8/9 days 6.00 0.02
Plasterer 5-5/9 days 4.50 0.09
Laborers 9-3/9 days 2.25 0.08½
Laborers 3/9 days 2.00 0.00
Cement 6 bbls. 1.35 0.03
Sand 3.3 cu. yds. 1.10 0.01
----
Total, 262 sq. yds. 0.32
Surfacing.
Rate. Per cu. yd.
Plasterer 7-6/9 days $5.40 $0.09
Plasterer 2-1/9 days 6.00 0.03
Plasterer 9-4/9 days 4.50 0.09
Laborers 12-8/9 days 2.25 0.06
Laborers 2-4/9 days 2.00 0.01
Cement 22¼ bbls. 1.35 0.06
Sand 5.07 cu. yds. 1.10 0.02
Stone dust 14 tons 1.50 0.04
----
Total, 460 sq. yds. $0.40
Asphalt.
Rate. Per cu. yd.
Foreman 1/9 day $4.00 $0.00
Asphalt man 11 days 2.00 0.05
Laborers 6 days 2.00 0.02½
Asphalt kettle 11 days 1.50 0.03½
Asphalt 3.9 tons 30.00 0.25
Asphalt mops 3.00 0.01
----
Total, 464 sq. yds. $0.37
Back Filling.
Rate. Per cu. yd.
Foreman 1-3/9 days $4.00 $0.07
Laborers 23-3/9 days 2.00 0.62
Laborers 9 days 1.75 0.21
Rails and cars. 2-2/9 days 0.40 0.02
Loam 27-5/9 cu. yds. 1.25 0.46
-----
Total, 75 cu. yds. $1.38
Estimated proportionate
charge for installing plant and holidays $0.28
-----
Grand total $1.66
Installing Plant.
Total.
Foreman 15-4/9 days $4.00 $61.78
Sub-foreman 1 day 3.00 3.00
Engineer 8-4/9 days 3.00 25.33
Carpenter 3 days 2.67 8.00
Watchman 42 days 2.00 84.00
Laborers 17-4/9 days 2.25 38.36
Laborers 149-8/9 days 2.00 299.78
Double team 10½ days 5.00 52.50
Single team 6 days 2.00 12.00
Single team 1 day 3.50 3.50
Teaming (total) 53.00
Derrick and engine. 11-4/9 days 3.75 49.92
Rails and cars 8-2/9 days 0.40 3.29
Broken stone 7.05 tons 1.35 9.52
Egg coal .6 ton 6.25 3.75
Kerosene 30 gal. 0.11 3.30
Oil 4 gal. 0.25 1.00
Spikes 220 lbs. 0.05 11.00
-------
Total $723.03
The cost of the concrete work in the lower and upper layers can be still
further detailed as shown below:
Lower Layer Concrete.
95.5 cu. yds., 1-2½-6½ concrete.
Materials: Rate. Per cu. yd.
Atlas cement 1.11 bbl. $1.35 $1.50
Sand .39 cu. yd. 1.10 0.43
Broken stone (.97 cu. yd.) 1.23 tons 1.35 1.66
Miscellaneous, plant, coal, etc. 1.28
Labor:
Mixing and placing $2.09
Carpenter work on forms at $24.00 per M. .34
-----
Total per cu. yd. in place $7.30
Upper Layer Concrete.
129.2 cu. yds., 1-1¼-1¼-4 concrete.
Materials: Rate. Per cu. yd.
Atlas cement 1.37 bbl. $1.35 $1.85
Sand .24 cu. yd. 1.10 0.26
Stone dust (.25 cu. yd.) .32 ton 1.50 0.48
Broken stone (.75 cu. yd.) .96 ton 1.35 1.30
Lumber 0.31 M. ft. 21.00 0.65
Miscellaneous, plant, etc. 1.32
Labor:
Mixing and placing 1.85
Carpenter work on forms at $21.00 per M. 0.66
-----
Total per cu. yd. in place $8.37
The following approximate labor costs are also given: Transporting,
erecting and removing derrick, $260.85. Equivalent time: Foreman, 6
days; engineer, 4 days; laborer, 85 days.
Transporting, laying and removing track, $125.03. Equivalent time:
Foreman, 4 days; laborer, 40 days.
Caring for dump and disposing of surplus by rough grading, $70.28.
Equivalent time: Foreman, 1 day; laborer, 33 days.
The total cost of the work was $3,503.66, divided up as follows:
Excavation $ 480.79
Lower layer concrete 614.15
Upper layer concrete 937.94
Back plaster 84.73
Surfacing 186.04
Asphalting 170.94
Back filling 103.27
Installing plant 716.03
Transportation and holidays 209.77
---------
Grand total $3,503.66
~LINING JEROME PARK RESERVOIR.~--The bottom of the reservoir that was
lined covered 250 acres, and the concrete lining was 6 ins. thick. The
lining was laid in alternate strips 16 ft. wide between forms set to
grade. The concrete was mixed in 18 Ransome mixers provided with
charging hoppers and mounted on trucks without boilers. Steam was
supplied to the mixer engines from the boilers of the contractor's
locomotives. One locomotive supplied steam for three or four mixers.
Tracks were laid in parallel lines across the reservoir bottom from 150
to 200 ft. apart. Sand and stone were hauled in on these tracks. The
sand was dumped in stock piles at intervals; the stone was shoveled from
the cars directly into the charging hopper and the sand was delivered by
wheelbarrows to the same hopper. Four men shoveled the stone for each
mixer. To deliver the concrete from the mixer to the work required six
men with wheelbarrows. Two men leveled off the concrete discharged by
the barrows and two other men floated the surface by means of a
straight-edge spanning the 16-ft. strips and riding on the forms. By
using a wet but not sloppy concrete and moving the straight-edge back
and forth a good surface was secured. The gang mixing and placing
consisted of 20 men for each mixer and 18 gangs laid approximately 1½
acres per 10-hour day. The gang organization and wages were as follows:
Item. Per 10 hours.
4 men shoveling stone at $1.50 $ 6.00
2 men wheeling sand at $1.50 3.00
2 men delivering cement at $1.50 3.00
1 man dumping mixer at $1.50 1.50
1 man tending engine and water at $1.50 1.50
6 men wheeling concrete at $1.50 9.00
2 men spreading concrete at $1.50 3.00
2 men leveling concrete at $1.50 3.00
1 foreman 3.00
------
Total per day $33.00
These costs do not include the fraction of a day's labor for fireman or
the cost of fuel.
~RESERVOIR FLOOR, CANTON, ILL.~--The following costs are given by Mr. G.
W. Chandler for lining the bottom of a 160×80-ft. reservoir with corners
of 20-ft. radius and vertical brick sidewalls. A 1-3½-7½ crushed stone
concrete was used; it was mixed by hand in batches of 2.7 cu. ft.
cement, 9 cu. ft. sand and 20¼ cu. ft. stone. The sand and stone were
measured separately, the sand and cement mixed dry, then shoveled into a
pile with the rock, well wetted, shoveled over again and then shoveled
into wheelbarrows. The stone had 40 per cent. voids and the sand 30 per
cent. voids. The lining was 10 ins. thick including a ¾-in. coat of 1-2¼
mortar spread and worked smooth with a trowel. The cost per cubic yard
of the lining in place was as follows:
0.856 bbl. cement at $2.50 $2.14
10.1 bu. sand (100 lbs. per bu.) at 5¾ cts 0.58
0.857 cu-yd-stone at $2.17 1.86
Labor, mixing and placing at 19 cts. per hr. 0.80
-----
Total $5.38
~RESERVOIR FLOOR, PITTSBURG, PA.~--The following methods and costs of
laying a reservoir floor are given by Mr. Emile Low, M. Am. Soc. C. E.,
for the Hiland Reservoir constructed at Pittsburg, Pa., in 1884, by
contract. There were 7,681 cu. yds. of concrete in the floor which was 5
ins. thick and laid on a clay puddle foundation.
Natural cement costing $1.35 per barrel was used. The broken stone
varied in weight from 147 to 152 lbs. per cu. ft.; it was quarried and
hauled 20 miles by rail and then unloaded into small cars and hauled ½
mile to the reservoir. The cost of the stone per cubic yard delivered
was:
Quarrying, per cu. yd. $0.45
Breaking, per cu. yd. 0.35
Transporting, per cu. yd. 0.50
Total $1.30
The sand was obtained on the site at the cost of excavation, or 1¼ cts.
per bushel.
The method of proportioning and mixing the concrete was as follows:
Platforms 10×16 ft. of 2-in. plank were laid on the puddle foundation
and by these were set 5×4×1½-ft. boxes on legs. Into these boxes 1 bbl.
of cement and 2 bbls. of sand were emptied and thoroughly mixed dry,
then mixed with water to a thin grout. Five barrels of stone were placed
on the platform and thoroughly wetted; the grout was then emptied over
the stone and the two turned over three times with shovels. The concrete
was rammed until the mortar flushed to the surface. The following costs
cover various periods as follows:
Two Days Work (101 cu. yds.): Total. Per cu. yd.
27 laborers, 2 days, at $1.25 $72.90 $0.7217
1 foreman, 2 days, at $2.50 5.00 0.0495
------ -------
Total $77.90 $0.7712
One Month's Work (1,302 cu. yds.):
642 days, laborers, at $1.35 $ 866.70 $0.6649
17 days, water boy, at $0.60 10.20 0.0078
22 days, foreman, at $2.50 55.00 0.0421
------ -------
Total $931.90 $0.7148
Two Days Work (101 cu. yds.): Total. Per cu. yd.
27 laborers, 2 days, at $1.25 $72.90 $0.7217
1 foreman, 2 days, at $2.50 5.00 0.0495
------ -------
Total $77.90 $0.7712
One Month's Work (1,302 cu. yds.):
642 days, laborers, at $1.35 $ 866.70 $0.6649
17 days, water boy, at $0.60 10.20 0.0078
22 days, foreman, at $2.50 55.00 0.0421
------ -------
Total $931.90 $0.7148
Total Work (7,861 cu. yds.):
Quarrying stone $0.45
Transporting stone 0.50
Breaking stone 0.35
1-1/3 bbl. natural cement 1.80
8 bu. sand 0.10
Water 0.05
Labor mixing and laying at $1.25 0.75
Incidentals 0.05
-----
Total $4.05
The contract price was $6 per cu. yd.
[Illustration: Fig. 286.--Form for Constructing Silo.]
~CONSTRUCTING A SILO.~--The form construction shown in Fig. 286 was
employed in building a silo 28 ft. high, 22 ft. 3 ins. interior
diameter, and having 6-in. walls. The bottom of the silo was made 9 ins.
thick and set 2 ft. below the surface. The reinforcement consisted of
ten 2½×3/16-in. rings spaced equally in the lower half and of woven wire
fencing in the upper half. The iron rings were hoops removed from an old
wooden silo. The concrete was a 1-6 mixture of Portland cement and sandy
gravel. Figure 286 is a section through the forms. There were twenty
T-shaped posts, which extended perpendicularly from the ground to a
height of 28 ft., being secured at top and bottom by a system of guy
ropes and posts. The rings, of which there are four, two inside and two
outside, were built of weather boards with their edges reversed. Four
thicknesses of board were used in each ring. The curbing consisted of
2×8-in. sticks 4 ft. long. Wedges driven between the vertical posts and
the rings held the latter in place. When the forms were to be removed
the wedges were knocked out and the rings sprung enough to permit the
removal of the curbing. The rings were then pushed up and fastened in
place for another section. The average rate of progress was one 4-ft.
section per day. The forms were filled in the afternoon and moved up the
following forenoon. Five-foot sections could have been built just as
readily.
The work was all done by farm laborers hired by the month and 100
man-days of such labor were required, excluding seven days work of a
mason brushing and troweling the surface. The cost of the work, not
including the old hoop iron or the old lumber used in forms, was as
follows:
Item. Total. Per cu. yd.
Cement $100.00 $2.62
Gravel and sand 35.00 0.92
1 20-rod roll of fencing 5.20 0.01
New lumber 18.00 0.47
100 days labor at $1.75 175.00 4.60
7 days mason troweling at $3.50 24.50 0.64
------- -----
Total, 38.2 cu. yds. $357.70 $9.26
The external area of the silo is 1,950 sq. ft., which makes the cost of
brushing and troweling 1¼ cts. per sq. ft. There were about 2,300 ft. B.
M. of lumber used in the forms, or about 61 ft. B. M. per cu. yd. of
concrete.
~GROINED ARCH RESERVOIR ROOF.~--The following data are given by Mr. Allen
Hazen and Mr. William B. Fuller, in Trans. Am. Soc. C. E. 1904. The
concrete was mixed in 5-ft. cubical mixers in batches of 1.6 cu. yds. at
the rate of 200 cu. yds. per mixer day. One barrel of cement, 380 lbs.
net, assumed to be 3.8 cu. ft., was mixed with three volumes of sand
weighing 90 lbs. per cu. ft., and five volumes of gravel weighing 100
lbs. per cu. ft. and having 40 per cent voids. On the average 1.26 bbls.
of cement were required per cu. yd. The conveying plant consisted of two
trestles (each 900 ft. long) 730 ft. apart, supporting four cableways.
The cables were attached to carriages, which ran on I-beams on the top
of the trestles. Rope drives were used to shift the cableways along the
trestle. Three-ton loads were handled in each skip. The installation of
this plant was slow, and its carrying capacity was less than expected.
It was found best to deliver the skips of concrete to the cableway on
small railway track, although the original plan had been to move the
cableways horizontally along the trestle at the same time that the skip
was traveling.
The cost of mixing and placing the concrete was as follows:
Per cu. yd.
Measuring, mixing and loading $0.20
Transporting by rail and cables 0.12
Laying and tamping floors and walls including setting forms 0.22
-----
Total $0.54
The cost of laying and tamping the concrete on the vaulting was 14 cts.
per cu. yd. The vaulting is a groined arch 6 ins. thick at the crown and
2½ ft. thick at the piers.
The lumber of the centering for the vaulting was spruce for the ribs and
posts, and 1-in. hemlock for the lagging. The centering was all cut by
machinery, the ribs put together to a template, and the lagging sawed to
proper bevels and lengths. The centers were made so that they could be
taken down in sections and used again. The cost of centering was as
follows:
Labor on centers covering 62,560 sq. ft.
Foreman, 435 hrs. at 35 cts. $ 152.25
Carpenters, 4,873 hrs. at 22½ cts. 1,096.42
Laborers, 3,447 hrs. at 15 cts. 517.05
Painters, 577 hrs. at 15 cts. 86.55
Teaming, 324 hrs. at 40 cts. 121.60
---------
Total labor building centers, 313 M. at $6.37 $1,973.87
Materials for centers covering 62,560 sq. ft.
313,000 ft. B. M. lumber, at $18.20 $5,700.00
3,700 lbs. nails, at 3 cts. 111.00
8 bbls. tar, at $3 24.00
---------
Total $5,835.00
These centers covered two filters, each having an area of 121-1/3×258
ft. There were six more filters of the same size, for which the same
centers were used. The cost of taking down, moving and putting up these
centers (313 M.) three times was as follows:
Foreman, 2,359 hrs. at 35 cts. $ 825.65
Carpenters, 12,766 hrs. at 22½ cts. 2,872.35
Laborers, 24,062 hrs. at 15 cts. 3,609.30
Team, 430 hrs. at 40 cts. 172.00
3,000 ft. B. M. lumber, at $20 60.00
3,000 lbs. nails, at 3 cts. 90.00
---------
Total cost of moving centers to cover 196,660 sq. ft. $7,629.30
[Illustration: Fig. 287.--Forms for Constructing Grain Elevator Bins.]
The cost of moving the centers each time was $8.10 per M., showing that
they were practically rebuilt; for the first building of the centers, as
above shown, cost only $6.37 per M. In other words, the centers were not
designed so as to be moved in sections as they should have been.
Although the centers were used four times in all, the lumber was in fit
condition for further use. The cost of the labor and lumber for the
building and moving of these centers for the 8 filter beds, having a
total area of 259,220 sq. ft., was $15,438, or 6 cts. per sq. ft.
~GRAIN ELEVATOR BINS.~--In constructing cylindrical bins 30 ft. in
diameter and 90 ft. high for a grain elevator the forms shown by Fig.
287 were used. For the inside wall a complete ring of lagging 4 ft. high
nailed to circular horizontal ribs of 2×8-in. planks was used. For the
outside wall two, three or four segments fitting the clear spaces
between adjoining tanks were used, these panel segments being also 4 ft.
high. The inside and outside rings were held together by yokes
constructed as shown, and bolted to the inner and outer ribs. A staging
built up inside the tank carried jack screws, on which were seated the
inner legs of the yokes.
CHAPTER XXIII.
METHODS AND COST OF CONSTRUCTING ORNAMENTAL WORK.
The safest rule for ornamental work is to leave its construction to
those who make a specialty of such work. This is perfectly practicable
in most concrete structures having ornament. Bridge railings can be and
usually are made up of separately molded posts, balusters, bases and
rail. Ornamental columns in building work, keystones, medallions,
brackets, dentils, rosettes, and cornice courses can be similarly molded
and placed in the structure as the monolithic work reaches the proper
points. The general constructor, therefore, can readily delegate these
special parts of his concrete bridge or building to specialists at
frequently less cost to himself and nearly always with greater certainty
of good results than if he installed molds and organized a trained gang
for doing the work.
Good concrete ornament is not alone a matter of good design. It is also
a matter of skilled construction. Nearly anyone can mold an ornament,
but few can mold an ornament which is durable. To produce clean, sharp
lines and arises which will endure, the molder must have special
knowledge and familiarity with the action of cement and of concrete
mixtures, both in molding and on exposure to the elements. This is
knowledge that the general concrete worker rarely possesses but which
the ornament molder does possess if he knows his business. Special work
is always best left to the specialist.
While the more intricate ornamental work is best done by sub-contract,
so far at least as the actual molding of the ornaments is concerned,
there is a large amount of simple paneling and molding which the general
practitioner not only can do but must do. Knowledge of the best methods
of doing such work is essential and it is also essential that the
constructor should know in a general way of the special methods of
molding intricate ornaments.
~SEPARATELY MOLDED ORNAMENTS.~--The cement for ornamental work must be
strong and absolutely sound. Where an especially light color is wished a
light colored cement is desirable. So called white cements are now being
manufactured. Lafarge cement, a light colored, non-staining cement made
in France, gives excellent results. Of American cements, Vulcanite
cement has a light color, and next to it in this respect comes Whitehall
cement. A light colored ornament can, however, be secured with any
cement by using white sand or marble or other white stone screenings.
Some authorities advocate this method of securing light colored blocks
as always cheaper and usually superior to the use of special cements.
The choice between the two methods will be governed by the results
sought; where as nearly as possible a pure white is desired it stands to
reason that a white or nearly white cement will give the better results.
In the matter of sand and aggregate for ornamental work, the kinds used
will ordinarily be the kinds that are available. They must conform in
quality to the standard requirements of such materials for concrete
work. Where special colors or tints are wanted they can be secured by
using for sand and aggregate screenings from stones of the required
color. This is in all respects the best method of securing colored
blocks, as the color will not fade and the concrete is not weakened. A
great variety of pigments are made for coloring concrete; these colors
all fade in time, and with few exceptions they all weaken the concrete.
The mixtures used in ornamental work will depend upon the detail of the
ornament and upon whether color is or is not required. Generally a rich
mixture of cement and sand or fine stone screenings will be used for the
surface and will be backed with the ordinary concrete mixture. A surface
mixture of fine material is necessary where clear, sharp lines and edges
or corners are demanded.
The molds used for ornament are wooden molds, iron molds, sand molds and
plaster of Paris and special molds. Each kind has its field of
usefulness, and its advantages over the others. They will be considered
briefly in the order named.
~Wooden Molds.~--Wooden molds are perhaps the best for general work where
plain shapes and not too delicate ornamentation are wanted. They give
the best results only with a quite dry and rather coarse grained surface
mixture. If a wet mixture is used such water as flushes to the surface
cannot escape and small pits and holes are formed, which necessitates
grout or other finishing. The following are examples of wooden mold
work:
In constructing a five-span reinforced concrete arch bridge at Grand
Rapids, Mich., in 1904, the railings and ornamental parts of the bridge,
such as keystones, brackets, consols, dentiles and panels, were cast in
molds and set in place much as cut stone would be. Special molds were
employed for each of these different shapes. These molds were plastered
with an earth damp mortar composed of 1 part cement and 2½ parts fine
sand, which was followed up with a backing of wet concrete composed of 1
part cement, 2 parts sand and 3 parts broken stone passing a ¾-in. ring.
The facing mortar was made 1½ ins. thick. The castings cannot be told
from dressed stone at a few feet distance.
The part elevation and sections in the drawings of Fig. 288 show the
arrangement of the various castings to form the completed railing,
coping, etc. To specify, A is the arch ring, B the brackets, C the
coping, and D, E, F, respectively, the base, balusters and rail of
the bridge railing. The blocks G and H show the keystone and railing
post. The forms or molds for each of these parts are shown by the other
drawings of Fig. 288. A description of each of these forms follows:
The keystones were molded in wooden forms, consisting of one piece, a,
forming the top and front; of two side pieces, f, of a bottom
consisting of two parts, b and c; and of a back piece, g. The back
and side pieces are stiffened with 2×3½-in. pieces, and the front, sides
and back are held together by yokes or clamps. The front of the mold was
the only portion calling for particular work, and this was made of
boards laminated together.
The bracket molds consisted of two side pieces provided with grooves for
receiving the front and back pieces, and with slots for tie rods
clamping the whole mold together. It will be noted also that the side
pieces had nailed to them inside a beveled strip to form a groove in
each side of the cast block. The purpose of this groove was to provide a
bond to hold the bracket more firmly in the adjoining concrete of the
wall. The bottom of the mold was formed by a 2-in. plank, and when the
concrete had been tamped in place the forms were removed, and the
bracket was left on the bottom to set. It may be noted here that a
goodly number of the brackets showed a crack at the joint marked x
caused by tamping at the point y. In construction the bracket castings
were set at proper intervals on the spandrel walls, which had been
completed up to the level of the line X Y. The coping course was then
built up around the bracket blocks to the level of the bottom of the
railing base.
[Illustration: Fig. 288.--Molds for Railings and Ornaments for Concrete
Arch Bridge.]
The mold or form for the coping course was designed to build the coping
in successive sections, and was built up around the bracket blocks, and
supported from the centers as shown by the drawings. To form the
expansion joints in the coping course there were inserted across the
mold at proper intervals a short iron plate ¼ in. thick, cut to fit. The
cutting of this plate was found to be a slow operation.
The forms for the base of the railing (Section D) consisted of 1¾-in.
stock for the sides, and ¾-in. stock for the slopes. They extended
across the arch, and were held together by a very simple though very
efficient clamp. This consisted of two 2×3×33-in. pieces nailed to a
2×3×17-in. piece by means of galvanized iron strips. About half-way down
the long pieces, a ½-in. rod was run through, and secured up against
blocks, h, placed about 56 ins. apart. These blocks were removed as
the concrete was put in place. It will be noticed from the cross-section
of the railing that the balusters are set into sockets formed in the top
of the base course. These sockets were formed by means of the mold shown
at W and Z.
In casting the balusters, Section (E), a 3/8-in. cast iron mold,
consisting of four iron sides and an iron top, was used. Originally
there were two end plates of iron, but it was found more convenient to
have the bottom one of wood and allow the cast spindle to stand and set.
The mold was held together by ½-in. bolts. It would have been more
practical to have had the side casting composed of two parts.
The form for the railing is built up around the tops of the spindles.
The bottom piece is 1×9 ins., to which 4¼-in. ogee molding is nailed.
The sides are of 1-in. stock, and are clamped together. The top is
finished off with a trowel.
The mold for the posts is made in four parts, which fit together at the
top and bottom by a bevel joint, as shown in the one-fourth section. The
broad sides rest against the narrow ones, and are held against the same
by means of ½-in. rods running through 2×3-in. stock: 2-in. projections
of the broad sides facilitate the removal of the form from the completed
post.
[Illustration: Fig. 289.--Molds for Ornamental Railing Posts for
Concrete Facade for Bridge.]
In constructing a concrete facade for a plate girder bridge at St.
Louis. Mo., the railing above the base was constructed of separately
molded blocks as follows: The balusters were cast in plaster molds. To
make these molds a box square in plan and the height of the baluster
was constructed of wood and cut vertically into three sections. The
inside lateral dimensions of this box were made 6 ins. greater than the
largest dimension of the baluster. A full size wooden pattern of the
baluster was set up and the three sections of the box were set around
it. Sheets of thin galvanized metal, with their inner edges cut to
conform to the curves of the baluster, were inserted in the joints of
the assembled box so as to divide the vacant space between the pattern
and the box into vertical sections.
[Illustration: Fig. 290.--Railing for Arch Bridge.]
[Illustration: Fig. 291.--Form for Lattice Panels Shown by Fig. 290.]
A mixture of 1 part Portland cement and 1 part plaster of Paris, made
wet, was then poured around the pattern until the box was filled. When
this mixture had become hard, the box was taken down, leaving a plaster
and cement casing separated into three parts by the sheets of galvanized
metal. This casing was separated from the pattern and given a coat of
shellac on the inside. Four or five molds of this description were cast.
To cast a baluster, the sections were assembled and a ½-in. corrugated
bar was set vertically in the center. A mixture of 1 part Portland
cement and 3 parts sand was then poured into the mold and allowed to
harden. The molds for the urns on the railing post and the balls on the
end posts were made in exactly the same manner as the baluster molds.
The construction of the railing posts is shown by the drawings of Fig.
289. Referring first to the end posts, it will be seen that they were
molded in place in seven sections marked A, B, C, E, F, and G. The
construction of the mold for each section is shown by the
correspondingly lettered detail. The intermediate posts were built up of
the separately molded pieces I, K and H. The costs of molding the
several parts were: Balusters, 60 cts. each; hand rail, 40 cts. per lin.
ft. The six intermediate posts cost $12 each, and the four end or newel
posts cost $75 each.
[Illustration: Fig. 292.--Form for Hand Rail Shown by Fig. 290.]
In constructing the 72-ft. span-ribbed arch bridge over Deer Park Gorge,
near La Salle, Ill., a hand railing of the design shown by Fig. 290, was
used. In constructing this railing, the posts were molded in place, but
the open work panels between posts and the hand rail proper were molded
separately and set in place between the posts as indicated. For molding
the panels a number of boxes constructed as shown by Fig. 291, were
used. These were simple rectangular boxes on the bottom boards of which
were nailed blocks of the proper shape and in the proper position to
form the openings in the railing. The bottom of the form was first
plastered with mortar, then the concrete was filled in and plastered on
top. As soon as the concrete had begun to set the blocks were removed so
that final setting could take place without danger of cracking. When the
concrete had set so that the panel could be safely handled, it was
removed from the form and stored until wanted. The hand rail for each
side was molded in two pieces in forms constructed as shown by Fig. 292.
The total cost of the railing in place was about $2 per lineal foot.
The concrete was a 1-2-4 mixture of screenings and 7/8-in. broken stone.
~Iron Molds.~--Iron molds have the same disadvantages as wooden molds in
the use of wet mixtures. They can be made to mold more intricate
ornaments, and in the matter of durability, are, of course, far superior
to wood. Iron molds can be ordered cast to pattern in any well equipped
foundry. Many firms making block machines also make standard column,
baluster, ball and base, cornice, and base molds of various sizes and
patterns. These molds are made in two, three or more sections which can
be quickly locked together and taken apart. A column mold, for example,
will consist of a mold for the base, another for the shaft, and a third
for the capitol, each in collapsible sections. Where the pattern of the
shaft changes in its height, two shaft molds are commonly used, one for
each pattern. Prices of iron molds are subject to variation, but the
following are representative figures: Plain baluster molds 14 to 18 ins.
high, $7.50 to $10 each; fluted square balusters, 14 to 18 ins. high,
$10, each; ball and base, 10 to 18-in. balls, $15 to $25 each; fluted
Grecian column, base, capitol and one shaft molds, $30; Renaissance
column, base, capitol and two shaft molds, $45.
~Sand Molding.~--Molding concrete ornaments in sand is in all respects
like molding iron castings in a foundry. Sand molding gives perhaps the
handsomest ornament of any kind of molding process, the surface texture
and detail of the block being especially fine. It is, however, a more
expensive process than molding in wooden or iron molds, since a separate
mold must be made for each piece molded. The process was first employed
and patented in 1899, by Mr. C. W. Stevens, of Harvey, Ill., and for
this reason it is often called the Stevens process. Sand molded
ornaments and blocks are made by a number of firms to order to any
pattern. The process as employed at the works of the Roman Stone Co., of
Toronto, Ont., is as follows: The stone employed for aggregate, is a
hard, coarse, crystalline limestone of a light grey color, being
practically 97 per cent. calcium carbonate, with a small percentage of
iron, aluminia and magnesia. Nothing but carefully selected quarry
clippings are used and these are crushed and ground at the factory and
carefully screened into three sizes, the largest about the size of a
kernel of corn. Daily granulometric tests are made of the crusher output
to regulate the amount of each size got from the machines. It has been
found that next in importance to properly graded aggregates is the
gaging of the amount of water used in the mixture. This is done by an
automatically filled tank into which lead both hot and cold water and in
which is fixed a thermometer to properly regulate the temperature. In
gaging the mix about 20% of water is used, but of course when the cast
is made the surplus is immediately drawn off into the sand, where it is
retained and serves as a wet blanket to protect the cast and supply it
with the proper amount of water during crystallization. Experiments seem
to indicate that about 15% by weight gives the greatest amount of
strength of mortar at the age of six months, while, giving less strength
at shorter time tests than mortar gaged with a smaller percentage of
water.
The method of handling the mix and casting is quite simple and almost
identical with the practice in iron foundries. The mixture is made in a
batch mixer to about the same consistency as molasses, from which it is
poured into a mechanical agitator and carried about the foundry by a
traveling crane. This agitator is so constructed that it keeps the
materials in motion constantly and prevents their segregation. In each
cast is inserted the proper reinforcing rods, lifting hooks and tie
rods, and the casts are allowed to remain for a proper period in the wet
sand after they are poured; they are then taken to the seasoning room
which is kept at as constant a temperature as it is practical to
maintain. Each cast is marked with the number which determines its
location in the building and the date it was cast, and it is then kept
in the storage shed a fixed time before shipping.
Records are kept of each cast made and the company is able to get, as in
mills rolling structural steel, the exact number and location of all
casts made from the same mix. Careful records are always kept of the
tests of cement and material, and test cubes are made from each
consignment of cement so tested; in this way all danger of defective
stone through inferior cement is eliminated. The patterns used in
making the molds and the method of molding are quite similar to ordinary
iron foundry practice except that the sand used is of special nature.
The finish of the stone is generally tooled finish molded in the sand,
the different textures of natural stone being produced by the veneering
of the pattern with thin strips of wood which are run through a machine
producing the different finishes. Each stone is provided with setting
hooks cast in the blocks which take the place of the ordinary lewis
holes used in cut stone.
~Plaster Molds.~--Plaster of Paris molds are made from clay, gelatin or
other patterns in the usual manner adopted by sculptors. They are
particularly adapted to fine line and under cut ornaments. The concrete
is poured into the plaster mold and after the cement has become hard,
the plaster is broken or chiseled away, leaving the concrete exposed.
Two examples of excellent work in intricate concrete ornaments are
furnished by the power house for the Sanitary District of Chicago, and
by the State Normal School building, at Kearney, Neb. In the power
house, the ornamental work consisted of molded courses, cornice work;
and particularly of heavy capitals for pilasters. These capitals were
very heavy, being 7½ ft. long and of the Ionic design. These were made
from plaster molds; made so as to be taken apart or knocked down and to
release in this way, perfectly. There were also scrolls, keystones and
arches in curved design over all of the 40 windows. None of this
ornament was true under cut work. In building the Normal School
building, Corinthian capitals, in quarters, halves, corners and full
rounds were made in plaster molds. There were some 30 of these capitols.
They were made in solid plaster molds; the molds having been cast in
gelatine molds, one for each capitol. Into these, the concrete was
tamped, made very wet, and after the concrete had hardened, the plaster
cast was chiseled away. This was very easily accomplished. These
capitols were true Corinthians, having all the floriation and under-cut
usually seen in such capitols.
~ORNAMENTS MOLDED IN PLACE.~--Molding ornaments in place is usually, and
generally should be, confined to belt courses, cornices, copings and
plain panels. Relief work, like keystones, scrolls or rosettes, can be
molded in place if desired, by setting plaster molds in the wooden forms
at the proper points. This method is often advantageous in bridge work,
where comparatively few ornaments are required, such as keystones.
[Illustration: Fig. 293.--Spandrel Wall Mold for Arch Bridge.]
The construction of forms for ornamental work in place is best described
by taking specific examples. Figure 293, shows the face form for the
arch ring, spandrel wall and cornice or coping course of the Big Muddy
River Bridge on the Illinois Central R. R. The section is taken near the
crown of the arch. The lagging only is shown; this was, of course,
backed with studding. The point to be noted in this form is the
avoidance of any approach to under cut work; there are, in fact, very
few straight cut details. This brings up a point that must be carefully
watched if trouble is to be avoided, namely, the construction of the
form work in sections which can be removed without fracturing the
ornament. To illustrate by an assumed example, supposing it is required
to mold the wall and cornice shown by Fig. 294. It is clear that if the
backing studs are in single pieces, notched as shown, the forms cannot
be removed without fracturing at least the corner A. If the studs and
lagging be constructed in two parts, separated along the line a b, the
form is possible of removal if great care is used without damage to the
concrete. The construction shown by this sketch does not greatly
exaggerate matters. Figure 295 shows a wall form that has been given
several times as a presumably good example in which, as will be seen it
is impossible to remove the board a, without breaking the concrete
even if the narrow face were not broken by the swelling of the lumber
before ever it became time to take down the forms.
[Illustration: Fig. 294.--Diagram Illustrating Details of Mold
Construction.]
[Illustration: Fig. 295.--Example of Poor Wall Form Construction.]
This matter of making provision for the swelling of the forms is another
point to be watched. Referring again to Fig. 294 it will be seen that
the swelling of the lagging, even if the cornice instead of being under
cut at A were straight cut on the line c d, is liable so to crowd
the lagging into the corner A and B that the concrete is cracked
along the lines e f or g h. A suggested remedy for this danger is
shown by Fig. 296. At a distance of every 3 or 4 ft. insert a narrow
piece of lagging a and behind these lagging strips cut notches b in
the studs. When the concrete has got its initial set pull back the
lagging strip a into the notches b, leaving an open joint to provide
for expansion due to swelling.
[Illustration: Fig. 296.--Notched Studding for Removal of Lagging Board
to Permit Swelling.]
[Illustration: Fig. 297.--Form for Concrete Facade Shown by Fig. 298.]
[Illustration: Fig. 298.--Concrete Facade for Plate Girder Bridge.]
[Illustration: Fig. 299.--Forms for Curved Concrete Abutments.]
[Illustration: Fig. 300.--Cornice Form.]
[Illustration: Fig. 301.--Method of Supporting Cornice Form Shown by
Fig. 300.]
In constructing a concrete facade for a plate girder bridge at St.
Louis, Mo., the form shown by Fig. 297 was used. The completed facade is
shown by Fig. 298. The ceiling slab was first built and allowed to set
and then the forms were erected for the frieze and coping. After these
were molded the forms were continued upward as shown for the base of the
railing. Above this point the several parts were separately molded as
shown by Fig. 285 previously described. Molded in this manner the
ceiling cost 25 cts. per sq. ft.; the frieze and coping cost $2 per lin.
ft., and the railing base cost 45 cts. per lin. ft. In constructing the
concrete abutments of this same structure use was made of the forms
shown by Fig. 299. These abutments had curved wing walls and for molding
these girts cut to the radii of the curves were fastened to the studs
and vertical lagging was nailed to the girts. All the lagging was tongue
and groove stuff.
[Illustration: Fig. 302.--Cornice and Balustrade for Arch Bridge.]
In constructing an open spandrel arch bridge at St. Paul, Minn., the
cornice form shown by Fig. 300, supported as shown by Fig. 301, was
used. The particular feature of this form was the use of a lath and
plaster lining to the lagging. This lining was used for all exposed
surfaces of the bridge. So called patent lath consisting of boards with
parallel dovetail grooves and ridges was used. This was plastered with
cement mortar and the concrete was deposited directly against the
plaster after smearing the plaster surface with boiled linseed oil. This
lining is stated to have given an excellent surface finish to the
concrete. It cost 55 cts. per sq. ft. for materials and labor. A section
of the balustrade and cornice is shown by Fig. 302. The posts, balusters
and railing were molded separately. The balusters were molded in zinc
molds. At first some trouble was had in getting good casts on account
of air pockets. This was largely done away with by filling the mold as
compactly as possible and then driving a ¾-in. iron rod through the
center vertically; this rod crowded the concrete into all parts of the
mold and also served to strengthen the baluster. The baluster molds were
made in two parts; this proved a mistake--three parts would have been
better.
CHAPTER XXIV.
MISCELLANEOUS DATA ON MATERIALS, MACHINES AND COSTS.
The following cost data comprise such miscellaneous items as do not
properly come in the preceding chapters. They are given not as including
all the miscellaneous purposes for which concrete is used but as being
such items of costs as were secured in collecting the more important
data given in preceding sections.
[Illustration: Fig. 303.--Device for Drilling Green Concrete.]
~DRILLING AND BLASTING CONCRETE.~--Concrete is exceedingly troublesome
material in which to drill deep holes, and this statement is
particularly true if the concrete is green. The following mode of
procedure proved successful in drilling 1½-in. anchor bolt holes 6 ft.
and over in depth in green concrete. The apparatus used is shown by Fig.
303, re-drawn from a rough sketch made on the work by one of the
authors, and only approximately to scale. The drill is hung on a small
pile driver frame, occupying exactly the position the hammer would
occupy in a pile driver, and is raised and lowered by a hand windlass.
By this arrangement a longer drill could be used than with the ordinary
tripod mounting and less changing of drills was necessary. A wide flare
bit was used, permitting a small copper pipe to be carried into the hole
with the drill; through this pipe water was forced under pressure,
carrying off the chips so rapidly that no wedging was possible. By this
device drilling which had previously cost over 25 cts. a hole was done
at a cost of less than 5 cts. a hole.
In removing an old cable railway track in St. Louis, Mo., holes 8 ins.
deep were drilled in the concrete with a No. 2 Little Jap drill, using a
1¼-in. bit and air at 90 lbs. pressure. A dry hole was drilled, the
exhaust air from the hollow drill blowing the dust from the hole keeping
it clean. The concrete was about 18 years old and very hard. Two holes
across track were drilled, one 10 ins. inside each rail; lengthwise of
the track the holes were spaced 24 ins. apart, or four pairs of holes
between each pair of yokes.
Common labor was used to run the drills and very little mechanical
trouble was experienced. Three cars were fitted up, one for each gang,
each car being equipped with a motor-driven air compressor, water for
cooling the compressors being obtained from the fire plugs along the
route. The air compressors were taken temporarily from those in use in
the repair shops, no special machines being bought for the purpose.
Electricity for operating the air compressor motors was taken from the
trolley wire over the tracks. The car was moved along as the holes were
drilled, air being conveyed from the car to the drills through a
flexible hose. Two drills were operated normally from each car. One of
the air compressors was exceptionally large and at times operated four
drills. The total number of holes drilled in the reconstruction of the
track was 31,000. The total feet of hole drilled was 20,700 ft.
With the best one of the plants operating two to three drills 30 8-in.
holes, or 20.3 ft. of hole, were drilled per hour per drill at a labor
cost of 2.7 cts. per foot.
For blasting, a 0.1-lb. charge of 40 per cent. dynamite was used in each
hole. A fulminating cap was used to explode the charge, and 12 holes
were shot at one time by an electric firing machine. The dynamite was
furnished from the factory in 0.1-lb. packages, and all the preparation
necessary on the work was to insert the fulminating cap in the dynamite,
tamp the charge into the hole and connect the wires to the firing
machine. In order to prevent any damage being done by flying rocks at
the time of the explosion, each blasting gang was supplied with a cover
car, which was merely a flat car with a heavy bottom and side boards.
When a charge was to be fired, this car was run over the 12 holes and
the side boards let down, so that the charge was entirely covered. This
work was remarkably free from accidents. There were no personal accident
claims whatever, and the total amount paid out for property damages for
the whole six miles of construction was $685. Most of this was for glass
broken by the shock of explosion. There was no glass broken by flying
particles. The men doing this work, few of whom had ever done blasting
before, soon became very skillful in handling the dynamite, and the work
advanced rapidly. The report made by the firing of the 12 holes was no
greater than that made by giant fire-crackers.
For the drilling and blasting the old rail had been left in place to
carry the air compressor car and the cover car. After the blasting, this
rail was removed and the concrete, excavated to the required depth. In
most cases the cable yokes had been broken by the force of the blast.
Where these yokes had not been broken, they were knocked out by blows
from pieces of rail. The efficacy of the blasting depended largely upon
the proper location of the hole. Where the holes had been drilled close
to the middle of the concrete block, so that the dynamite charge was
exploded a little below the center of gravity of the section, the
concrete was well shattered and could be picked out in large pieces.
Where the hole had been located too close to either side of the concrete
block, however, the charge would blow out at one side and a large mass
of solid concrete would be left intact on the other side. The total
estimated quantity of concrete blasted was 6,558 cu. yds., or 0.2 cu.
yd. of concrete per lineal foot of track. The cost of the dynamite
delivered in 0.1 lb. packages was 13 cts. per pound. The exploders cost
$0.0255 each.
The cost of drilling and blasting was as follows:
Item. Per mile. Per lin. ft. Per cu. yd.
Labor, drilling $ 89.76 $0.017 $0.085
Blasting labor and materials. 285.12 0.054 0.268
------- ------ ------
Total drilling and blasting. $374.88 $0.071 $0.353
[Illustration: Fig. 304.--Bench Monument, Chicago, Ill.]
The cost of blasting with labor and materials, separately itemized, was
as follows, per cubic yard:
Dynamite and exploders $0.192
Labor 0.076
------
Total $0.268
Two cubic yards of concrete were blasted per pound of dynamite.
~BENCH MONUMENTS, CHICAGO, ILL.~--The standard bench monuments, Fig. 304,
used in Chicago, Ill., are mostly placed in the grass plot between the
curb and the lot line, so that the top of the iron cover comes just
level with the street grade or flush with the surface of the cement
walk. The monument consists of a pyramidal base 6 ft. high and 42 ins.
square at the bottom, with a ¼-in.×2-ft. copper rod embedded, and of a
cast iron top and cover constructed as shown by the drawing. Mr. W. H.
Hedges, Bench and Street Grade Engineer, Department of Public Works,
Chicago, Ill., gives the following data regarding quantities and cost.
The materials required for each monument are: 1.78 cu. yd. crushed
stone, 0.6 cu. yd. torpedo sand, 1½ bbls. cement, 60 ft. B. M. lumber,
one ¼×24-in. copper rod, one top and cover. A gang consisting of 1
foreman, 4 laborers and 2 teams construct from one to three monuments
per day, the average number being two per 8-hour day. In 1906 the
average cost of the monuments was $24.12 each, based on above material
and labor charges.
[Illustration: Fig. 305.--Base for Wooden Pole.]
[Illustration: Fig. 306.--Mile Post, Chicago & Eastern Illinois Ry.]
~POLE BASE.~--Figure 305 shows a concrete base for transmission line poles
invented by Mr. M. H. Murray, of Bakersfield, Cal., and used by the
Power Transit & Light Co. of that city. These bases are molded and
shipped to the work ready for placing. They weigh about 420 lbs. each.
One base requires 37½ lbs. of 2×¼-in. steel bar, 40 lbs. of Portland
cement, 3 cu. ft. of broken stone or gravel and enough sand to fill the
form or mold, which is 10×10 ins. by 4½ ft. Unskilled labor is employed
in the molding and two men can mold ten bases per 8-hour day. The cost
of molding is as follows per base:
2 men at $2 per day $0.40
Brace irons per set 2.50
1-9 cu. yd. stone at $4.05 0.45
40 lbs. cement at 1½ cts. 0.60
Sand 0.15
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Total cost $4.10