Buffalo Breakwater.]
Figure 80 shows the arrangement of the mixing plant. The mixer was a
5-ft. cube mixer holding 125 cu. ft., mounted on a trestle and operated
by a 9×12-in. horizontal engine taking steam from a 4×10-ft. locomotive
boiler, also supplying steam to two derrick engines. The material scow
contained two pockets for sand, one for gravel and one housed over for
cement. Two inside cement men passed out the bags in lots of six to one
outside cement man who cut and emptied them into the charging bucket.
Three sand shovelers each loaded a 3.6 cu. ft. barrow and wheeled them
tandem to the bucket, and two gravel men each loaded a 2.7 cu. ft.
barrow and wheeled them tandem to the bucket. The broken stone was
loaded by eight shovelers into another bucket, also containing 21.6 cu.
ft. The two buckets were alternately hoisted and emptied into the mixer
hopper, there being a dump man on the mixer who dumped the buckets and
attended to the water supply. A charger put the mixer in operation and
when the charge was mixed the car men dumped it into a skip resting on
a small car which was then run out on the track under the mixer to the
derrick which handled the skip to the work. Derrick A handled the
materials from the scows and derrick B handled the mixed concrete. The
force on the derricks consisted of two enginemen, four tagmen and the
fireman.
The ten parapet wall sections containing 841 cu. yds. were built in 46
hours, making 17 batches of 1.07 cu. yds., or 18.2 cu. yds. placed per
hour. The 17 parapet deck sections containing 1,720 cu. yds. were built
in 88 hours, making 18.8 batches of 1.08 cu. yds., or 19.5 cu. yds.
placed per hour. For the parapet deck work the force was increased by 2
men handling materials and 1 man on the mixer. The labor cost of mixing
and placing the concrete was as follows:
Per Per
Loading Gang-- day. cu. yd.
1 assistant foreman 2.00 $0.011
3 cement handlers 5.25 0.029
3 sand shovelers 5.25 0.029
2 gravel shovelers 3.50 0.020
8 stone shovelers 14.00 0.076
1 hooker on 1.75 0.010
------ ------
Totals $31.75 $0.175
Mixer Gang--
1 dumpman $ 1.75 $0.010
1 charging man 1.75 0.010
2 car men 3.50 0.020
2 enginemen at $3.25 6.50 0.035
4 tagmen at $2 8.00 0.044
1 fireman 2.00 0.011
------ ------
Totals $23.50 $0.130
Wall Gang--
1 Signalman $ 1.75 $0.010
1 dumper 1.75 0.010
6 shovelers at $2 12.00 0.065
4 rammers 7.00 0.038
1 foreman 4.00 0.022
------ -----
Totals $26.50 $0.145
Grand totals $81.75 $0.450
[Illustration: Fig. 81.--Concrete Blocks for Pier at Port Colborne
Harbor.]
[Illustration: Fig. 82.--Forms for Molding Blocks, Port Colborne Harbor
Pier.]
[Illustration: Fig. 83.--Device for Handling Blocks, Port Colborne
Harbor Pier.]
~PIER CONSTRUCTION, PORT COLBORNE, ONT.~--In constructing the new harbor
at Port Colborne, Ont., on Lake Erie, the piers consisted of parallel
rows of timber cribs set the width of the pier apart and filled in and
between with stone blasted and dredged from the lake bottom in deepening
the harbor. The tops of the cribs terminated below water level and were
surmounted by concrete walls set on the outer edges. These walls were
filled between with stone and the top of the filling was floored part
way or entirely across, as the case might be, with a thick concrete
slab. The footings of the walls to just above the water level were made
of concrete blocks 4½×4×7 ft., constructed as shown by Fig. 81. The wall
above the footing course and the floor slab were of concrete molded in
place. The concrete work consisted of molding and setting concrete
blocks and of molding concrete wall and slab in place.
The blocks were molded on shore, shipped to the work on scows and set in
place by a derrick. Figure 82 shows the construction of the forms for
molding the blocks; the bottom tie rods passed through the partitions
forming the ends of the molds. The sides were removed in 48 hours and
used over again. Figure 83 shows the hooks used for handling the molded
blocks. Considerable trouble was had in setting these blocks level and
close jointed, owing to the difficulty of leveling up the stone filling
under water.
[Illustration: Fig. 84.--Scow Plant for Mixing and Placing Concrete,
Port Colborne Harbor Pier.]
The mass concrete was mixed and placed by the scow plant, shown by Fig.
84. The scow was loaded with sufficient sand and cement for a day's work
and towed to and moored alongside the pier. Forms were set for the wall
on top of the block footing. These forms were placed in lengths of 60 to
75 ft. of wall and resembled the block forms with partitions omitted.
The bottoms of the rear uprights were held by being wedged into the
grooves in the blocks, and the bottoms of the front uprights were held
by bolts resting on top of the blocks. The tops of the uprights were
held together across the wall by tie bolts. The forms being placed, the
mode of procedure was as follows:
The crusher fed directly into a measuring box. After some 6 ins. of
stone had run into the box the door of the crusher spout was closed. A
wheelbarrow load of sand was spread over the stone in the box and over
this were emptied and spread two or three bags of cement. Another layer
of stone and then of sand and of cement were put in and these operations
repeated until the box was full. The box was then hoisted and dumped
into the hopper of a gravity mixer of the trough type which ran along a
track on the scow and fed directly into the forms. The gang worked
consisted of 1 foreman, 1 derrickman and 18 common laborers. This gang
placed from 65 to 75 cu. yds. of concrete per day at a labor cost of 50
cts. per cu. yd.
[Illustration: Fig. 85.--Cross-Section of Concrete Pier, Superior, Wis.]
~CONCRETE BLOCK PIER, SUPERIOR ENTRY, WIS.~--The methods and cost of
constructing a concrete pier 3,023 ft. long and of the cross-section
shown by Fig. 85 at Superior entry, Wisconsin, are given in the
following paragraphs.
_Molds and Molding._--About 80 per cent. of the concrete was deposited
in molds under water, according to a plan devised by Major D. D.
Galliard, corps of engineers. In brief the concrete was built in place
in two tiers of blocks, the lower tier resting directly on piles and
being entirely under water and the upper tier being almost entirely
above water. As shown by Fig. 85, a pile trestle was built on each side
of the proposed pier and a traveler for raising and lowering the molds
spanned the space between trestles.
The molds were bottomless boxes built in four pieces, two sides and two
ends, held together by tie rods. Fig. 86 shows an end and a side of one
of the shallow water molds and Fig. 87 shows in detail the method of
fastening the end to the side. It will be seen that the 1¼-in.
turnbuckle rods pass through the ends of beams that bear against the
outside of the mold. These tie rods have eyes at each end in which rods
with wedge-shaped ends are inserted. The molds were erected on the
trestle by a locomotive crane and were then lifted by the mold traveler,
carried and lowered into place. The largest one of these molds with its
iron ballast, weighed 40 tons. To remove a mold, after the block had
hardened, the nuts on the wedge-ended rods were turned, thus pulling the
wedge end from the eye of the tie rod and releasing the sides of the
mold from the ends. The locomotive crane then raised the ends and sides,
one at a time, and assembled them ready to be lowered again for the next
block. The time required to remove one of these 40-ton molds, reassemble
and set it again rarely exceeded 60 minutes and was sometimes reduced to
45 minutes.
[Illustration: Fig. 86.--Mold for Concrete Block for Pier at Superior,
Wis.]
The concrete was deposited in alternate blocks and the molds described
were for the first blocks; for the intermediate blocks molds of two side
pieces alone were used, the blocks already in place serving in lieu of
end pieces. The two side pieces were bolted together with three tie rods
at each end; the tie rods were encased in a box of 1-in. boards 4×4 ins.
inside which served as a strut to prevent the sides from closing
together and as a means of permitting the tie rods to be removed after
the concrete had set. The mold was knocked down just as was the full
mold described above and the boxes encasing the tie rods were left in
the concrete.
[Illustration: Fig. 87.--Device for Locking End and Side of Mold for
Concrete Blocks for Pier at Superior, Wis.]
An important feature was the device for handling the molds; this, as
before stated, was a traveler, which straddled the pier site, it having
a gage of 31 ft. It carried a four-drum engine, the drums of which were
actuated, either separately or together, by a worm gear so as to operate
positively in lowering as well as in raising. The load was hung from
four hooks, depending by double blocks and 5/8-in. wire rope from four
trolleys suspended from the trusses of the traveler; this arrangement
allowed a lateral adjustment of the mold. The hoisting speed was 6 ft.
per minute and the traveling speed 100 ft. per minute. The locomotive
crane also deserves mention because it was mounted on a gantry high
enough to permit material cars to pass under it on the same trestle,
thus making it practicable to work two cranes.
[Illustration: Fig. 88.--Bucket for Depositing Concrete Under Water for
Pier at Superior, Wis.]
The concrete was received from the mixer into drop bottom buckets of the
form shown by Fig. 88. The buckets were taken to the work four at once
on cars, and there lifted by the locomotive crane and lowered into the
mold where they were dumped by tripping a latch connected by rope to the
crane. To prevent the concrete from washing, the open tops of the
buckets were covered with 3×4 ft. pieces of 12-oz. canvas in which were
quilted 110 pieces of 1/16×1×3-in sheets of lead. Two covers were used
on each bucket and were attached one to each side of the bucket top so
as to fold over the top with a lap. This arrangement was entirely
successful for its purpose.
_Concrete Mixing._--The proportions of the subaqueous concrete were
1-2½-5 by volume, or 1-2.73-5.78 by weight, cement being assumed to
weigh 100 lbs. per cu. ft.; the proportions of the superaqueous concrete
were 1-3.12-6.25 by volume, or 1-3.41-7.22 by weight. The dry sand
weighed 109.2 lbs. per cu. ft., the voids being 35.1 per cent.; the
pebbles weighed 115.5 lbs. per cu. ft., the voids being 31 per cent.
The pebbles for the concrete were delivered by contract and were
unloaded from scows by clam-shell bucket into a hopper. This hopper fed
onto an endless belt conveyor which delivered the pebbles to a rotary
screen. Inside this screen water was discharged under a pressure of 60
lbs. per sq. in. from a 4-in. pipe to wash the pebbles. From the screen
the pebbles passed through a chute into 4-cu. yd cars which were hauled
up an incline to a height of 65 ft. by means of a hoisting engine. The
cars were dumped automatically, forming a stock pile. Under the stock
pile was a double gallery or tunnel provided with eight chutes through
the roof and from these chutes the cars were loaded and hauled by a
hoisting engine up an inclined trestle to the bins above the concrete
mixer. The sand was handled from the stock pile in the same manner. The
cement was loaded in bags on a car in the warehouse, hauled to the mixer
and elevated by a sprocket chain elevator.
Chutes from the bins delivered the materials into the concrete mixer,
which was of the Chicago Improved Cube type, revolving on trunnions
about an axial line through diagonal corners of the cube. The mixer
possessed the advantage of charging and discharging without stopping. It
was driven by a 7×10-in. vertical engine with boiler. The mixer
demonstrated its ability to turn out a batch of perfectly mixed concrete
every 1-1/3 minutes. It discharged into a hopper provided with a cut-off
chute which discharged into the concrete buckets on the cars.
_Labor Force and Costs._--In the operation of the plant 55 men were
employed, 43 being engaged on actual concrete work and 12 building molds
and appliances for future work. The work was done by day labor for the
government and the cost of operation was as follows for one typical
week, when in six days of eight hours each, the output was 1,383 cu.
yds., or an average of 230 cu. yds. per day. The output on one day was
considerably below the average on account of an accident to the plant,
but this may be considered as typical.
Pebbles from Stock Pile to Mixer-- Per cu. yd.
4 laborers at $2 $0.0348
1 engineman at $3 0.0131
Coal, oil and waste at $1.03 0.0043
Sand from Stock Pile to Mixer--
5 laborers at $2 $0.0434
1 engineman at $2.50 0.0109
Coal, oil and waste at $0.82 0.0035
Cement from Warehouse to Mixer--
5 laborers at $2 $0.0434
Mixing Concrete--
1 engineman at $2.50 $0.0109
1 mechanic at $2.50 0.0108
Coal, oil and waste at $1.29 0.0056
Transporting Concrete--
4 laborers at $2 $0.0348
1 engineman at $3 0.0130
Coal, oil and waste at $0.66 0.0028
Depositing Concrete in Molds--
4 laborers at $2 $0.0348
1 engineman at $3 0.0130
1 rigger at $3 0.0130
Coal, oil and waste at $1.18 0.0051
Assembling, Transporting, Setting and Removing Molds--
4 laborers at $2 $0.0347
1 engineman at $3.25 0.0141
1 carpenter at $3 0.0130
1 mechanic at $2.50 0.0109
Coal, oil and waste at $1.39 0.0060
Care of Tracks--
1 laborer at $2 $0.0086
1 mechanic at $2.50 0.0109
Supplying Coal--
3 laborers at $2 $0.0260
Blacksmith Work--
1 laborer at $2 $0.0086
1 blacksmith at $3.25 0.0141
1 waterboy at $0.75 0.0032
-------
Total per cubic yard $0.4473
Add 75% of cost of administration 0.1388
-------
Total labor per cu. yd. $0.5861
The total cost of each cubic yard of concrete in place was estimated to
be as follows:
Per cu. yd.
Ten-elevenths cu. yd. pebbles at $1.085 $0.9864
Ten-twenty seconds cu. yd. sand at $0.00 0.0000
1 26 bbls. cement at $1.77 2.2302
Labor as above given 0.5861
Cost of plant distributed over total yardage 0.8400
-------
Total $4.6427
It will be noted that the sand cost nothing as it was dredged from the
trench in which the pier was built, and paid for as dredging. The cost
of the plant is distributed over this south pier and over the proposed
north pier work on the basis of only 20 per cent. salvage value after
the completion of both piers. It is said, however, that 80 per cent. is
too high an allowance for the probable depreciation.
~DAM, RICHMOND, INDIANA.~--The dam shown in cross-section in Fig. 89 was
built at Richmond, Ind. It was 120 ft. long and was built between the
abutments of a dismantled bridge. The concrete was made in the
proportion of 1 bbl. Portland cement to 1 cu. yd. of gravel; old iron
was used for reinforcement. The foundations were put down by means of a
cofferdam which was kept dry by pumping. On completion it was found that
there was a tendency to scour in front of the apron and accordingly
piling was driven and the intervening space rip-rapped with large
stone. Labor was paid as follows per day: Foreman, $3; carpenter, $2.50;
cement finisher, $2; laborers, $1.50. The concrete was mixed by hand and
wheeled to place in wheelbarrows. The cost of the work was as follows:
Materials-- Per cu. yd.
204 bbls. cement at $1.60 $1.485
Sand and gravel 0.800
Lumber 0.610
Tools, hardware, etc. 0.445
------
Total materials $3.34
Labor--
Clearing and excavating $0.96
Setting forms and mixing concrete 1.01
Pumping 0.27
-----
Total labor $2.24
Total materials and labor $5.58
[Illustration: Fig. 89.--Concrete Dam at Richmond, Ind.]
~DAM AT ROCK ISLAND ARSENAL, ILLINOIS.~--The dam was in the shape of an L
with one side 192 ft. and the other side 208 ft. long; it consists of a
wall 30½ ft. high, 3½ ft. wide at the top and 6½ ft. wide at the bottom
with a counterfort every 16 ft., 26 in all. Each counterfort extended
back 16 ft. and was 4 ft. thick for a height of 6 ft. and then 3 ft.
thick. There were 3,500 cu. yds. of concrete in the work, which was done
by day labor under the direction of the U. S. Engineer in charge.
The forms consisted of front and back uprights of 8×10-in. stuff 24 ft.
high, connected through the wall by ¾-in. rods which were left in the
concrete. The lagging was 2×12-in. plank dressed down 1¾ ins. placed
inside the uprights. These forms were built full height in 16-ft.
sections with a counterfort coming at the center of each section. Each
section contained 95 cu. yds. of concrete and was filled in a day's
work. The concrete was a 1-4-7 mixture wet enough to quake when rammed.
Run of crusher limestone was used of which 50 per cent. passed a 1-in.
sieve, 17 per cent. a No. 3 sieve and 9 per cent. a No. 8 sieve. The
concrete was mixed in Cockburn Barrow & Machine Co.'s screw-feed mixer
which discharged into 2-in. plank skips 2 ft. wide 5-1/3 ft. long and 14
ins. deep, holding ¼ cu. yd. These skips were taken on cars to a derrick
crane overhanging the forms and by it hoisted and dumped into the forms.
The derrick was moved along a track at the foot of the wall as the work
progressed. The concrete was spread and rammed in 6-in. layers. The men
were paid $1.50 per 8-hour's work and the work cost including footing,
as follows:
Item-- Total. Per cu. yd.
Cement $1,500.00 $0.429
Sand 400.00 0.114
Storing and hauling cement 460.00 0.131
Taking sand from barge to mixer 96.00 0.027
Crushing stone 1,450.00 0.414
Mixing concrete 4,825.00 1.378
Placing concrete 1,670.00 0.477
Lumber for forms, etc. 600.00 0.171
Erecting and taking down forms 2,450.00 0.700
---------- ------
Totals $13,451.00 $3.841
~DAM AT McCALL FERRY, PA.~--The dam was 2,700 ft. long and 48 ft. high of
the cross-section shown by Fig. 90 and with its subsidiary works
required some 350,000 cu. yds. of concrete. The plant for mixing and
placing the concrete was notable chiefly for its size and cost. Parallel
to the dam, which extended straight across the river, and just below its
toe a service bridge consisting of a series of 40-ft. concrete arch
spans was built across the river. This service bridge was 50 ft. wide
and carried four standard gage railway tracks besides a traveling crane
track of 44 ft. gage. This very heavy construction of a temporary
structure was necessitated by the frequency of floods against which only
a solid bridge could stand; it was considered cheaper in the long run to
provide a bridge which would certainly last through the work than to
chance a structure of less cost which would certainly go out with the
floods. The concrete service bridge was designed to be destroyed by
blasting when the dam had been completed. The method of construction was
to build the dam in alternate 40 ft. sections, mixing the concrete on
shore, taking it out along the service bridge in buckets on cars and
handling the buckets from cars to forms by traveling cranes.
[Illustration: Fig. 90.--Steel Forms for McCall Ferry Dam.]
The concrete mixing plant is shown by Fig. 91. Cars loaded with cement,
sand and stone were brought in over the tracks carried on the wall tops
of the bins and were unloaded respectively into bins A, B and C,
of which there were eight sets. Each set supplied material by means of
measuring cars to a 1 cu. yd. Smith mixer. Two sets of cars were used
for each mixer so that one could be loading while the other was
charging. The mixers discharged into 1 cu. yd. buckets set two on a car
and eight cars were hauled to the work in train by an 18-ton "dinky." At
the work the buckets were picked up by the traveling cranes and the
concrete dumped into the forms. Figure 90 shows the construction of the
steel forms. Six sets of forms were used. Each set consisted of five
frames spaced 10 ft. apart and braced together in the planes parallel to
the dam, and each set molded 40 ft. of dam. The lagging consisted of
wooden boxes 8½ ft. wide and 10 ft. long. For the vertical face of the
dam these boxes were attached by bolts to the vertical post, for the
curved face they were bolted to a channel bent to the curve and held by
struts from the inclined post of the steel frame.
[Illustration: Fig. 91.--Concrete Mixing Plant for McCall Ferry Dam.]
In construction the footing and the body of the dam to an elevation of 5
ft. above the beginning of the curve were built continuously across the
river; above this elevation the dam was built in alternate 40-ft.
sections. The strut back to the service bridge shown in the lower right
hand corner of Fig. 90, shows the manner of bracing the first 30-ft.
section of the inclined post to hold the lagging for the continuous
portion. The lagging was added a piece at a time as concreting
progressed. The ends of each set of frames for a 40-ft. section were for
the isolated sections closed by timber bulkheads carrying box forms to
mold grooves into which the concrete of the intermediate sections would
bond.
[Illustration: Fig. 92.--Traveler for Concreting Dam, Chaudiere Falls,
Quebec.]
The concrete used was a 1-3-5 mixture, the stone ranging in size from 2
to 5 ins. Rubble stone from one man size to ½ ton were bedded in the
concrete. The capacity of the concrete plant was 2,000 cu. yds. per day
or about 250 cu. yds. per mixer per 10-hour day.
~DAM, CHAUDIERE FALLS, QUEBEC.~--The dam was 800 ft. long and from 16 to
20 ft. high, constructed of 1-2-4 concrete with rubble stone embedded.
The rubble stones were separated at least 9 ins. horizontally and 12
ins. vertically and were kept 20 ins. from faces. At one point the
rubble amounted to 40 per cent. of the volume, but the average for the
dam was 25 to 30 per cent. The stone was broken at the work, some by
hand, but most by machine, all to pass a 2-in. ring. Hand-broken stone
ran very uniform in size and high in voids, often up to 50 per cent.
Stone broken by crusher with jaws 2 ins. apart would run 20 to 30 per
cent. over 2 ins. in size and give about 45 per cent. voids; with
crusher jaws 1½ ins. apart from 98 to 100 per cent. was under 2 ins. in
size and contained about 42 per cent. of voids. It was found that if the
crushers were kept full all the time the product was much smaller,
particularly with Gates gyratory crusher, though a little more than
rated power was required when the crusher was thus kept full. This
practice secured increased economy in both quantity and quality of
product. The concrete was made and placed by means of a movable traveler
shown by Fig. 92. Concrete materials were supplied to the charging
platform of the traveler by means of a traveling derrick moving on a
parallel track. In placing the concrete on the rock bottom it was found
necessary in order to secure good bond to scrub the rock with water and
brooms and cover it with a bed of 2 ins. of 1-2 mortar. The method of
concreting in freezing weather is described in Chapter VII.
CHAPTER XII.
METHODS AND COST OF CONSTRUCTING BRIDGE PIERS AND ABUTMENTS.
The construction of piers and abutments for bridges is best explained by
describing individual examples of such work. So far, in America, bridge
piers have been nearly always of plain concrete and of form and section
differing little from masonry piers; where reinforcement has been used
at all it has consisted of a surface network of bars introduced chiefly
to ensure monolithic action of the pier under lateral stresses. In
Europe cellular piers of reinforced concrete have been much used. Plain
concrete abutments differ little in form and volume from masonry
abutments. Reinforced concrete abutments are usually of L-section with
counterforts bracing the upright slab and bridge seat to the base slab.
Form work for reinforced abutments is somewhat complex; that for plain
abutments and piers is of simple character, the only variations from
plain stud and sheathing construction being in the forms for moldings
and coping and for cut-waters. For piers of moderate height the form is
commonly framed complete for the whole pier, but for high piers it is
built up as the work progresses by removing the bottom boards and
placing them at the top. Opposite forms are held together by wire ties
through the concrete. Movable panel forms have been successfully
employed, but they rarely cheapen the cost much. Sectional forms, which
can be shifted from pier to pier where a number of piers of identical
size are to be built, may frequently be used to advantage. An example of
such use is given in this chapter.
Derricks are the recognized appliances for hoisting and placing the
concrete in pier work; they are the only practicable appliance where the
pier is high and particularly where it stands in water and mixing barges
are employed. For abutment work and land piers of moderate height
derricks and wheelbarrow or cart inclines are both available and where
much shifting of the derricks is involved the apparently more crude
method compares favorably in cost.
The methods of placing concrete under water for pier foundations are
described in Chapter V, and the use of rubble concrete for pier
construction is illustrated by several examples in Chapter VI. The
following examples of pier and abutment construction cover both large
and small work and give a clear idea of current practice.
[Illustration: Fig. 93.--Pier and Cofferdam for a Railway Bridge.]
~COST OF CONSTRUCTING RECTANGULAR PIER FOR A RAILWAY BRIDGE.~--This pier,
Fig. 93, was built in water averaging 5 ft. deep. The cofferdam
consisted of triple-lap sheet piling, of the Wakefield pattern, the
planks being 2 ins. thick, and spiked together so as to give a cofferdam
wall 6 ins thick. The cofferdam enclosed an area 14×20 ft., giving a
clearance of 1 ft. all around the base of the concrete pier, and a
clearance of 2 ft. between the cofferdam and the outer edge of the
nearest pile. The cofferdam sheet piles were 18 ft. long, driven 11 ft.
deep into sand, and projecting 2 ft. above the surface of the water.
The concrete base resting on the foundation piles was 12×18 ft. The
concrete pier resting on this base was 7×13 ft. at the bottom, and 5×11
ft. at the top. The pier supported deck plate girders. There were 100
cu. yds. of concrete in the pier and base.
The cost of this pier, which is typical of a large class of concrete
pier work, has been obtained in such detail that we analyze it in
detail, giving the costs of cofferdam construction and excavation as
well as of mixing and placing the concrete.
Setting up and taking down derrick and platform:
4 days foreman at $5.00 $ 20.00
¾ days engineman at $3.00 2.25
¾ days blacksmith at $3.00 2.25
¾ days blacksmith helper at $2.00 1.50
22 days laborers at $2.00 44.00
-------
Total $ 70.00
Cofferdam--
7 days foreman at $5.00 $ 35.00
4 days engineman at $3.00 12.00
38 days laborers at $2.00 76.00
1 ton coal at $3.00 3.00
-------
Total labor on 7,900 ft. B. M. at $16.00 $126.00
7,900 ft. B. M. at $20.00 158.00
-------
Total for 58 cu. yds. excavation $284.00
Wet Excavation--
1.8 days foreman at $5.00 $ 9.00
1.5 days engineman at $3.00 4.50
9 days laborers at $2.00 18.00
½ ton coal at $3.00 1.50
-------
Total labor on 58 cu. yds. at 57c. $ 33.00
Foundation Piles--
960 lin. ft. at 10c $ 96.00
4 days setting up driver and driving 24 piles at $20 per
day for labor and fuel 80.00
-------
Total $176.00
Concrete--
100 cu yds. stone at $1.00 $100.00
40 cu. yds. sand at $0.50 20.00
100 bbls. cement at $2.00 200.00
5 days foreman at $5.00 25.00
50 days laborers at $2.00 100.00
5 days engineman at $3.00 15.00
2 tons coal at $3.00 6.00
-------
Total, 100 cu. yds. at $4.66 $466.00
8 days carpenters at $3.00 24.00
2,400 ft. B. M. 2-in. plank at $25.00 60.00
1,000 ft. B. M. 4×6-in. studs at $20.00 20.00
Nails, wire, etc 2.00
-------
Total forms for 100 cu. yds. at $1.06 $106.00
Summary--
Setting up derrick, etc. $ 70.00
Cofferdam (7,900 ft. B. M.) 284.00
Wet excavation (58 cu. yds.) 33.00
Foundation piles (24) 176.00
Concrete (100 cu. yds.) 466.00
Forms (3,400 ft. B. M.) 106.00
---------
Total $1,135.00
Transporting plant 20.00
20 days rental of plant at $5.00 100.00
---------
Total cost of pier $1,252.00
Regarding the item of plant rental, it should be said that the plant
consisted of a pile driver, a derrick, a hoisting engine, and sundry
timbers for platforms. There was no concrete mixer. Hence an allowance
$5 per day for use of plant is sufficient.
It will be noted that no salvage has been allowed on the lumber for
forms. As a matter of fact, all this lumber was recovered, and was used
again in similar work.
Referring to the cost of cofferdam work, we see that, in order to
excavate the 58 cu. yds. inside the cofferdam, it was necessary to spend
$284, or nearly $5 per cu. yd. before the actual excavation was begun.
The work of excavating cost only 57 cts. per cu. yd., but this does not
include the cost of erecting the derrick which was used in raising the
loaded buckets of earth, as well as in subsequently placing the
concrete. The sheet piles were not pulled, in this instance, but a
contractor who understands the art of pile pulling would certainly not
leave the piles in the ground. A hand pump served to keep the cofferdam
dry enough for excavating; but in more open material a power pump is
usually required.
The above costs are the actual costs, and do not include the
contractor's profits. His bid on the work was as follows:
Piles delivered 12 cts. per ft.
Piles driven $5 each
Cofferdam $37 per M.
Wet excavation $1.00 per cu. yd.
Concrete $8.00 per cu. yd.
In order to ascertain whether or not these prices yielded a fair profit,
it is necessary to distribute the cost of the plant transportation and
rental over the various items. We have allowed $120 for plant
transportation and rental, and $70 for setting up and taking down the
plant, or $190 in all. The working time of the plant was as follows:
Per cent. Prorated
Days. of time. plant cost.
Cofferdam 7 39 $74
Excavation 2 11 21
Foundation piles 4 22 42
Concrete 5 28 53
-- --- ----
Totals 18 100 $190
As above given, the labor on the 7,900 ft. B. M. in the cofferdam cost
$126, or $16 per M.; but this additional $74 of prorated plant costs,
adds another $9 per M., bringing the total labor and plant to $25 per
M., to which must be added the $20 per M. paid for the timber in the
cofferdam, making a grand total of $45 per M. This shows that the
contractor's bid of $37 per M. was much too low.
The labor on the excavation cost 57 cts. per cu. yd., to which must be
added the prorated plant cost of $21 distributed over the 58 cu. yds.,
or 36 cts. per cu. yd., making a total of 93 cts. per cu. yd. This shows
that the bid of $1 per cu. yd. was hardly high enough.
The labor on the 24 foundation piles cost $80, or $3.33 each. The
prorated plant cost is $42, or $1.75 per pile, which, added to $3.33,
makes a total of $5.08. This shows that the bid of $5 Per pile for
driving was too low. However there was a profit of 2 cts. per ft., or 80
cts. per pile, on the cost of piles delivered.
The concrete amounted to 100 cu. yds. Hence the prorated plant cost of
$53 is equivalent to 53 cts. per cu. yd. Hence the total cost of the
concrete was:
Per cu. yd.
Cement, sand and stone $3.20
Foreman (at $5) 0.25
Labor (at $2) 1.00
Engineman (at $3) 0.15
Coal (at $3) 0.06
Carpenters (at $3) 0.24
Forms (at $23.50, used once) 0.80
Wire, nails, etc 0.02
Prorated plant cost 0.53
-----
Total $6.25
Since the contract price for concrete was $8 per cu. yd., there was a
good profit in this item.
~BACKING FOR BRIDGE PIERS AND ABUTMENTS.~--Six piers and two abutments of
the City Island bridge were constructed in 1906 at New York city, of
masonry backed with 1-2-4 concrete below and 1-3-5 concrete above high
water. The piers and abutments were all sunk to rock or hard material by
means of timber cofferdams. Table XVI gives the labor cost of mixing and
placing the concrete backing for one abutment and three piers, after the
materials were delivered on the scows. The concrete was mixed by a
rectangular horizontal machine mixer and deposited by 2-cu. yd. bottom
dump buckets handled by derrick scows and stiff leg derricks. The high
cost of concreting on Pier 2 was due to the fact that the concrete was
improperly deposited and had to be removed and the higher cost in
Abutment 1 was probably due to the fact that the abutment was so long
and narrow that it was difficult to handle the bucket.
TABLE XVI.--COST OF CONCRETE BACKING FOR MASONRY PIERS.
[Transcriber's note: Table split to be less than 80 column width]
Abutment No. 1. Pier No. 2.
Wages Cost Cost
per No. Total per No. Total per
Hour. hrs. Cost. cu. yd. hrs. Cost. cu. yd.
Superintendent 70 24 $16.80 $0.03 47 $32.90 $0.09
Foreman 35 160 56.00 0.09 128 44.80 0.13
Laborers 15-20 2555 383.25 0.65 2038 313.60 0.92
Engineman 30 365 109.50 0.19 196 58.50 0.19
Timekeeper 40 86 34.40 0.06 46 18.40 0.06
Pier No. 3. Pier No. 4.
Wages Cost Cost
per No. Total per No. Total per
Hour. hrs. Cost. cu. yd. hrs Cost. cu. yd.
Superintendent 70 72 $50.40 $0.05 16 $11.20 $0.03
Foreman 35 324 113.40 0.12 54 18.90 0.06
Laborers 15-20 3513 526.95 0.56 940 141.00 0.44
Engineman 30 244 73.20 0.08 60 18.00 0.06
Timekeeper 40 81 32.40 0.04 10 4.00 0.01
Summary.
Wages Total Total Av.
Hrs. cost. per cu. yd.
Superintendent 70 159 $111.30 $0.05
Foreman 35 666 233.10 0.11
Laborers 15-20 9046 1364.90 0.62
Engineman 30 865 259.50 0.12
Timekeeper 40 223 89.20 0.04
~PNEUMATIC CAISSONS, WILLIAMSBURG BRIDGE.~--Mr. Francis L. Pruyn, Assoc.
M. Am. Soc. C. E., gives the following costs of concreting the pneumatic
caissons for the Brooklyn tower of the Williamsburg bridge at New York
city. The work comprised the mixing and placing of some 13,637 cu. yds.
of concrete in two caissons. Table XVII shows the itemized costs for one
caisson and Table XVIII shows them for the other caisson. The methods of
work were as follows:
After each caisson was built it was towed to its proper site, where it
was held in place by temporary pile dock built completely around it. On
these docks the concrete was placed; a 2 cu. yd. cubical mixer of the
usual pattern being used for mixing. The concrete materials, consisting
of sand, stone and cement was handled direct from barges alongside, into
the mixer. The concrete was placed by a derrick located in the center of
the caisson, which was a bad feature as the caisson was usually out of
level and considerable difficulty was experienced in swinging the
derrick. On the South caisson ¾ cu. yd. bottom dump buckets were used in
placing the concrete, on the North caisson the size of these was
increased to 1½ cu. yd. which reduced the cost of placing 15 cts. per
cu. yd. There were placed in the South caisson 3,827 cu. yds. in 32 days
of actual working time--120 cu. yds. per day of 10 hrs. The gross time
was 2 months. On the North caisson 5,693 cu. yds. were placed in 46 days
worked--124 cu. yds. per day. The gross time was 4 months.
The rates of labor were as follows per 10-hour day:
Foreman $5.00
Assistant foreman 2.50
Hoisters 2.50
Fireman 1.60
Laborer 1.50
Proportions concrete were 1: 2.5: 6.
The low price of sand in the North caisson was brought about by the
finding of good building sand in the excavation for the anchorage, which
work was done by the same contractor.
When the caissons had been sealed the iron material shafts were removed.
This left holes 5 ft.×6 ft. extending from the roof of the caisson up
to Mean H.W. which were filled with concrete. These shaft holes were 80
ft. deep on the South caisson and 100 ft. deep on the North caisson.
They were partially filled with water and the concrete had to be placed
with considerable care. Wooden chutes were used on the South caisson;
they rested on the caisson roof, were filled with concrete and then
raised allowing concrete to flow out at the bottom. The shaft holes were
too deep on the North caisson for chutes and 20 cu. ft. bottom dump
buckets were used. They had to be lowered to bottom of shaft each trip
before dumping, a slow operation, which greatly added to the cost.
Proportion for concrete 1-2.5-6.
The proportion for concrete in working chamber was the same as for all
other concrete. The specifications called for 6 in. of mortar, of 1 part
of cement to 2½ parts of sand, between the concrete and all bearing
areas; that is, under the cutting edge and directly under the roof of
the working chamber. The concrete was mixed in the cubical mixer and
dumped on the bottom door of the material lock, the top door of the lock
was then closed, the bottom door opened and the concrete fell through
the shaft to the working chamber. It was then shoveled by the sand hogs
into place. A 6-in. space was left below all bearing surfaces into which
damp mortar was tightly rammed. Concreting the South caisson took 10¼
working days of 24 hours, the gangs working night and day in twelve
2-hour shifts; 1,566 cu. yds. of concrete and mortar were placed, or at
the rate of 140 cu. yds. per 24 hours. The gross time including Sundays
was 14½ days. The sand hogs worked in shifts of 2 hours each and
received $3.50 for the two hours work. The twelve foremen received 1
dollar more: the average gang consisted of 12 sand hogs.
On the North caisson the organization was much better, owing to the
experience gained on the first caisson; and in spite of the fact that
the sand hogs, on account of the increased depth, received $4.00 for 1½
hours' work, or an increase of $22.00 per man per 24 hrs. over that on
the South caisson, the work was done for less money. There were placed
1,566 cu. yds. of concrete in 7 working days of 24 hrs., or at the rate
of 224 cu. yds. per day. The gross time was 11½ days including Sundays.
The average number of men in the sand hog gangs was 18, with one
foreman, who received $5 for 1½ hours work.
TABLE XVII.--ITEMIZED COST OF CONCRETING SOUTH CAISSON FOR BROOKLYN
TOWER OF THE WILLIAMSBURG BRIDGE: COST OF CONCRETING CAISSONS ABOVE
ROOF.
South Caisson (3,827 cu. yds.).
Materials. Quantity. Rate. Amount.
Cement 4,480 bbls. $1.57 $7,034.00
Sand 1,288 cu. yds. .60 773.00
Broken stone 3,421 cu. yds. 1.50 5,132.00
Water 36.00
------- ------ ---------
Total 3,827 cu. yds. $3.39 $12,975.00
Labor.
Mixing and placing 3,827 cu. yds. $0.90 $3,432.00
Plant charges 2,280.00
Plant labor 742.00
------- ------ ---------
Total plant 3,827 cu. yds. $0.79 $3,022.00
------- ------ ---------
Total cost 3,827 cu. yds. $5.08 $19,429.00
General expenses, 10% 3,827 cu. yds. .51 1,943.00
------- ------ ---------
Grand total 3,827 cu. yds. $5.59 $21,372.00
COST OF CONCRETING SHAFTS.
South Caisson.
Materials. Quantity. Rate. Amount.
Concrete 612½ bbls. $1.57 $962.00
Sand 193 cu. yds. .40 77.00
Stone 493 cu. yds. 1.10 542.00
------- ------ ---------
Total 541 cu. yds. $2.92 $1,581.00
Labor.
Handling, mixing and placing 541 cu. yds. $0.96 $519.00
Plant charges, etc. 541 cu. yds. 1.06 576.00
------- ------ ---------
Total 541 cu. yds. $4.94 $2,676.00
General expenses, 10% 541 cu. yds. .49 267.00
------- ------ ---------
Grand total 541 cu. yds. $5.43 $2,943.00
COST OF CONCRETE IN WORKING CHAMBERS.
South Caisson. (1,435 cu. yds.)
Materials. Quantity. Rate. Amount.
Cement for concrete 1,666 bbls. $1.57 $2,615.00
Cement for mortar 459 bbls. 1.57 720.00
Sand for both 670 cu. yds. .40 268.00
Broken stone 1,181 cu. yds. 1.10 1,299.00
------- ------ ---------
Total materials 1,435 cu. yds. $3.42 $4,902.00
Labor.
Top labor, mixing and placing 1,435 cu. yds. $1.09 $1,575.00
Pneumatic labor 1,435 cu. yds. 4.93 7,117.00
Compressor house labor 1,435 cu. yds. .19 275.00
------- ------ ---------
Total labor 1,435 cu. yds. $6.21 $8,967.00
Plant.
Coal at $2.40 per ton 1,435 cu. yds. .10 140.00
Concrete plant 1,435 cu. yds. .79 1,145.00
Pneumatic plant 1.435 cu. yds. 1.05 1,522.00
-------- ------ ---------
Total plant 1,435 cu. yds. $1.94 $2,807.00
Totals 1,435 cu. yds. $11.57 $16,676.00
General expenses, 10% 1,435 cu. yds. 1.16 1,667.00
-------- ------- ----------
Grand total 1,435 cu. yds. $12.73 $18,343.00
TABLE XVIII.--ITEMIZED COST OF CONCRETING NORTH CAISSON FOR BROOKLYN
TOWER OF THE WILLIAMSBURG BRIDGE:
COST OF CONCRETING CAISSON ABOVE ROOF (5,692 cu. yds.)
Materials. Quantity. Rate. Amount.
Cement 6,707½ bbls. $1.57 $10,531.00
Sand 2,133 cu. yds. .40 845.00
Broken stone 4,938 cu. yds. 1.10 5,432.00
Water 51.00
------- ------ ---------
Total 5,692 cu. yds. $2.96 $16,859.00
Labor.
Mixing and placing 5,692 cu. yds. $0.73 $4,159.00
Plant charges 2,952.00
Plant labor 517.00
------- ------ ---------
Total 5,692 cu. yds. $0.61 $3,469.00
Total cost 5,692 cu. yds. $4.30 $24,487.00
General expenses, 10% 5,692 cu. yds. .43 2,448.00
Grand total 5,692 cu. yds. $4.73 $26,935.00
COST OF CONCRETING SHAFTS.
Materials. Quantity. Rate. Amount.
Cement 614½ bbls. $1.57 $965.00
Sand 204 cu. yds. .40 82.00
Stone 521 cu. yds. 1.10 574.00
------- ------ ---------
Total 576 cu. yds. $2.82 $1,621.00
Labor.
Mixing and placing 576 cu. yds. 1.70 982.00
Plant charges, etc. 576 cu. yds. 1.36 795.00
------- ------ ---------
Total 576 cu. yds. $5.88 $3,398.00
General expenses, 10% 576 cu. yds. .59 339.00
------- ------ ---------
Grand total 576 cu. yds. $6.47 $3,737.00
COST OF CONCRETING WORKING CHAMBERS (1,566 cu. yds.).
Materials. Quantity. Rate. Amount.
Cement for concrete 1,559 bbls. $1.51 $2,446.00
Cement for mortar 442 bbls. 1.51 $694.00
Sand for both 630 cu. yds. .40 252.00
Broken stone 1,380 cu. yds. 1.10 1,518.00
------- ------ ---------
Total 1.566 cu. yds. $3.14 $4,910.00
Labor.
Top labor, mixing and placing 1,566 cu. yds. $0.78 $1,198.00
Pneumatic labor 1,566 cu. yds. 4.91 7,694.00
Compressor house labor 1,566 cu. yds. .11 180.00
------- ------ ---------
Total labor 1,566 cu. yds. $5.80 $9,072.00
Plant.
Coal at $2.40 per ton 1,566 cu. yds. .06 87.00
Concrete plant 1,566 cu. yds. .86 1,352.00
Pneumatic plant 1,566 cu. yds. .81 1,272.00
------- ------ ---------
Total plant 1,566 cu. yds. $1.73 $2,711.00
------- ------ ---------
Totals 1,566 cu. yds. $10.67 $16,693.00
------- ------ ---------
General expenses, 10% 1,566 cu. yds. 1.06 1,669.00
------- ------ ---------
Grand total 1,566 cu. yds. $11.73 $18,362.00
~COST OF FILLING PIER CYLINDERS.~--The following costs were obtained in
mixing and placing concrete in steel cylinder piers. The sand and gravel
were wheeled 100 ft. to the mixing board at the foot of the cylinder,
mixed and shoveled into wooden skips, hoisted 20 ft. by horsepower and
dumped into the cylinder. The foreman worked on the mixing board and the
men worked with great energy. The costs were as follows:
Item-- Per day. Per cu. yd.
6 men wheeling materials and mixing at 15
cts. per hour 9.00 $0.45
2 men dumping skips and ramming at 15 cts.
per hour 3.00 0.15
1 team and driver at 40 cts. per hour 4.00 0.20
1 foreman at 30 cts. per hour 3.00 0.15
----- ----
Totals $19.00 $0.95
~PIERS, CALF KILLER RIVER BRIDGE.~--The following methods and costs of
building two new piers and extending three old piers with concrete are
given by Mr. J. Guy Huff. The work was done by the railway company's
masonry gangs. Figure 94 shows the arrangement of the several piers and
the character of the work on each and Fig. 95 gives the detail
dimensions of the three main piers.
The sand and aggregate, consisting of blast furnace slag, were unloaded
from cars to platforms on a level with the top of rail, placed about 100
ft. south from the south end of the bridge. A cubical 1/6 cu. yd. mixer
was used. This was operated by a gasoline engine, and was located on a
platform about 50 ft. south of the south end pier. A tank near the mixer
to supply water was elevated enough to get the desired head, and was
kept filled by a pump run by another gasoline engine located down by the
river bank. The cement house was located between the mixer platform and
slag pile.
[Illustration: Fig. 94.--Diagram Arrangement of Piers, Calf Killer River
Bridge.]
[Illustration: Fig. 95.--Details of Pier for Calf Killer Elver Bridge.]
Slag and sand were delivered to the mixer by means of wheelbarrows. The
mixer was so placed that it would dump onto a platform, and the concrete
could then be shoveled into a specially designed narrow-gage car. This
car ran on one rail of the main track and an extra rail outside. A
turnout for clearing passing trains was provided at both ends of the
bridge. The track over the bridge from the mixer had a descending grade
of about 1 per cent., so that with a little start the concrete car would
roll alone down to the required points on the bridge. Only in returning
the empty cars to the mixer was it necessary to push them by hand, and
then only for a distance of never more than 400 ft.
Over the piers on the bridge in the center of the concrete car track
openings were sawed to let the concrete pass to the forms below. To get
the concrete into the forms, there were used zig-zag chutes with arms
about 10 ft. long, which sections were removed as the concrete in the
forms was increased. These chutes were a convenience by their ends
alternating from one side to the other as the arms were removed in
coming up.
The cost of the concrete work was as follows:
Unloading Material.
Rate Total days Per cu. yd.
per day. worked. Total. concrete.
Foreman $3.40 5 $17.00 $0.04
11 laborers 1.36-8/10 52 71.14 .15
-----
Total for unloading material $0.19
Building Forms, Bins, Etc.
Foreman $3.40 18 $61.20 $0.14
9 carpenters 2.25 166 373.50 .81
New lumber, 23.7 M. ft.
at $17.80 421.86 .92
Old lumber, 6 M. ft. at
$8.33 49.98 .11
-----
Total for building forms, bins, etc. $1.98
Cofferdam Excavation (45 cu. yds.)
Foreman $3.40 8 $27.20 $0.06
9 laborers 1.15 6/10 74½ 86.12 .19
-----
Total for cofferdam excavation $0.25
Cofferdam Concrete (37 cu. yds.)
Foreman $3.40 8 $27.20 $0.06
11 laborers 1.36 3/10 79 107.68 .23
Cofferdam lumber, 2.25
M. ft. at $20.00 45.00 .09
----
Total for cofferdam concrete $0.38
Concrete Mixing and Placing.
Foreman $3.40 30 $102.00 $0.22
9 laborers 1.15 6/10 282 325.99 .71
Cement, 452 bbls. at
$1.55 701.00 1.52
Slag, 437 cu. yds. at $0.20 87.40 .19
Sand, 220 cu. yds. at
$0.30 66.00 .14
-----
Total for mixing and placing $2.78
Taking Down Forms and Clearing Up.
Foreman $3.40 13 $44.20 $0.09
11 laborers 1.17 1.43 107.31 .36
-----
Total for taking down forms, etc. $200.00 $0.45
Engineering and supervision .43
-----
Grand total, 460 cu. yds. concrete $6.46
The wages given are the average wages. The men worked a 10-hour day. The
concrete was a 1-3-6 mixture. The cofferdam work was done in connection
with the construction of the fourth pier, this pier being the only one
coming in the bed of the river to be built entirely new. The work on
this was started in water about 6 ft. deep. The 37 cu. yds. of concrete
is included in the total of 460 cu. yds. in the above tabulation. By
itself the cost of the cofferdam work, not including cost of cement,
sand and slag was as follows:
Per cu. yd.
Total. Concrete.
Lumber $ 45.00 $1.21
Labor, excavating 113.32 3.06
Labor, concrete 134.88 3.64
-----
Total 37 cu. yds. concrete $7.91
[Illustration: Fig. 96.--Details of Piers for K. C., M. & O. Ry.
Bridge.]
~METHOD AND COST OF CONSTRUCTING 21 BRIDGE PIERS.~--The following account
of the methods and cost of constructing 21 concrete piers for a railway
bridge consisting of 20 50-ft. plate girder spans has been compiled from
records kept by Mr. W. W. Colpitts, Assistant Chief Engineer, Kansas
City, Mexico & Orient Ry. The shape and dimensions of the piers are
shown by Fig. 96 and Fig. 97 shows the construction of the forms. Sheet
pile cofferdams to solid rock were used for constructing the
foundations.
[Illustration: Fig. 97.--Forms for Piers for K. C., M. & O. Ry. Bridge.]
The 1-3-5 concrete was mixed in a Smith mixer having a batch capacity of
9 cu. ft. The mixer was located on the slope of the embankment
approach, with the main track at its rear and facing a temporary
material track. This temporary track turned out from the main track
about 500 ft. beyond the mixer and extended diagonally down the
embankment approach on a 3 per cent. grade and across the river bottom
alongside the pier sites. The portion of the track in the river bottom
was supported on bents of spliced ties, jetted to the rock, and wired to
the cofferdam to avoid the danger of loss in case of high water. The
sand and crushed rock were delivered by cars from the main line track,
immediately above the mixer, and the cement was stored in a shanty at
one side of the mixer. The concrete materials and machinery were, in
this manner, very conveniently located for rapid work and well above the
high water line. The concrete was transported to the pier sites in
improvised dump boxes, set on push cars. These dump boxes were hinged
longitudinally and discharged directly into the cofferdams. The grade of
the temporary track carried the push cars by gravity to the cofferdams
and they were returned by teams, for which purpose a straw and brush
road had been built paralleling the track. As the work progressed
farther into the stream, more cars were added properly to balance the
work. While the concrete in the base was still fresh, a number of steel
reinforcing bars, 8 ft. in length, were set in place along each end to
insure a good bond between the base and shaft.
In general, the work of putting in the bases was organized so that about
the same time was required in filling a cofferdam with concrete, in
excavating the sand from the next, and in driving the sheet piling for
the third. These three operations were thus carried on simultaneously
and, although interruptions in one part of the work or the other
occurred frequently, the gangs were interchangeable and no appreciable
loss was suffered, except in time, because of such delays.
In piers 19 and 20, where the rock was from 17 to 19 ft. below the
surface, some difficulty was encountered due to the presence of fissures
in the rock, from which it was necessary to remove the sand to fill with
concrete. In such cases, the larger leaks were stopped as much as
possible by driving sheet piles against the outside face of the
cofferdam and into the fissures, and the smaller leaks by manure in
canvas bags rammed into the openings.
Upon the completion of all the bases, the forms for several shafts were
set in position and the work of filling with concrete proceeded as in
the case of the bases, except that a derrick erected on a flat car and
stationed at the pier was utilized to raise the dump boxes in depositing
the concrete in the forms. As soon as the concrete in one shaft had set
sufficiently to permit of it, the forms were removed and placed on the
pier ahead. Four sets of forms were used for the shafts.
The following are the average prices paid for materials and labor:
Materials.--Lumber for forms, etc., $16.50 per M. ft., B. M.; cement,
Kansas Portland, $1.50 per bbl.; broken limestone, 45c per cu. yd.;
sand, Arkansas River, 15c per ton.
Labor.--General foreman, $110 per month; assistant foreman, $75 per
month; timekeeper, $60 per month; riveters, 35c per hour; blacksmith,
30c per hour; blacksmith assistant, 20c per hour; carpenters, 22½c and
25c per hour; enginemen, 25c per hour; firemen, 20c per hour; night
watchman, 20c per hour; laborers, 17½c and 20c per hour; team (including
driver), 40c per hour. The prices quoted for lumber, cement, limestone
and sand are prices f. o. b., Louisiana, Iola, Kan., El Dorado, Kan.,
and Wichita, Kan.
The total and unit cost of constructing the concrete piers and abutments
and of erecting the steel superstructure are given in the following
tabulation. Altogether there was about 2,300 cu. yds. of concrete in the
substructure, most of which, as stated above, was a 1-3-5 mixture.
Machinery and Supplies.
Concrete mixer, 20% of cost $ 152.10
Supplies, freight, hauling, setting up 505.04
--------
Total $ 657.14
Centrifugal sand pump, 20% of cost $ 27.00
Supplies, freight, hauling, setting up 277.50
Rent of traction engine to operate 83.25
--------
Total $ 387.75
Water pump and pipe, 20% of cost $ 29.00
Supplies, freight, hauling, setting up 177.32
--------
Total $ 206.32
Pile driver engine, 20% of cost $ 100.00
Supplies, freight, hauling, setting up 243.65
--------
Total $ 343.65
--------
Grand total $1,594.86
Cofferdams.
Materials, lumber and nails $1,285.26
Freight and train haul 306.33
Labor making piles 696.82
Labor driving piles 1,384.05
---------
Total $3,672.46
The sheet piling took 63,500 ft. B. M. of lumber; the cost per 1,000 ft.
B. M. for the sheet piling was then:
Materials, lumber and nails $ 20.08
Freight and haulage 4.82
Labor making piles 10.97
Labor driving piles 21.80
--------
Total $ 57.67
Forms, Platforms and Runways.
Lumber, hardware, etc. $ 224.59
Freight and train haul. 40.20
Labor making, removing and placing. 556.51
---------
Total $ 821.30
Concrete Materials.
Cement, freight, unloading and storing. $4,617.48
Sand, freight, unloading, etc. 1,336.05
Broken stone, freight, unloading, etc. 2,026.92
---------
Total $7,980.45
This gives us for 2,300 cu. yds. of concrete a cost of $3.47 per cu. yd.
for materials, including freight, storage, and unloading charges of all
kinds. A line on the proportion of the cost contributed by these latter
items may be got by taking the prices of the materials f. o. b. at the
places of production and assuming the proportions for a 1-3-5 concrete.
According to tables in Chapter II, a 1-3-5 broken stone concrete
requires per cubic yard 1.13 bbls. cement, 0.48 cu. yd. sand and 0.80
cu. yd. broken stone. We have then:
1.13 bbls. cement, at $1.50 $1.69
0.48 cu. yd. sand, at 20c .10
0.80 cu. yd. stone, at 45c .36
-----
Total $2.15
This leaves a charge of $1.32 per cubic yard of concrete for freight and
handling materials. The cost of mixing concrete and placing it in the
forms was $3,490.87, or $1.52 per cu. yd. We have then:
Cost of concrete materials per cu. yd. $3.47
Cost of mixing and placing concrete. 1.52
-----
Total. $4.99
The miscellaneous expenses of the work comprised:
Watchman, tools, telephone, etc. $ 722.48
Shanties, furnishings, supplies, etc. 829.04
---------
Total. $1,551.52
To this has to be added $1,134.28, the cost of excavating the
cofferdams. The total and unit costs of the different items of the
concrete substructure work can now be summarized as follows:
Item. Total. Per cu. yd.
Machinery and supplies 1,594.86 $ .69
Cofferdams 3,672.49 1.60
Forms, etc 821.30 .36
Concrete materials 7,980.45 3.47
Mixing and placing concrete 3,490.87 1.53
Excavating cofferdams 1,134.28 .49
Miscellaneous 1,551.52 .67
---------- -----
Total $20,245.74 $8.81
~COST OF PERMANENT WAY STRUCTURES KANSAS CITY OUTER BELT & ELECTRIC
RY.~--The following cost of concrete work including retaining walls,
abutments and box culverts, for the permanent way of the Kansas City
Outer Belt & Electric Ry., is given by Mr. W. W. Colpitts. These figures
are of particular interest, for the variation in prices of materials
during the two-year period while work was in progress and as giving the
average cost of the work on the whole line as well as for individual
structures. The culverts were all box culverts with wing walls and the
abutments were for girder bridges. Walls and abutments were of L section
with triangular or trapezoidal counterforts at the back between base
slab and coping. The form work was thus rather complex.
All work was reinforced concrete, and was done by contract under the
following conditions: The work of preparing foundations, including
excavation, pile driving, diversions of streams, etc., was done by the
railroad company, which also bore one-half the cost of keeping
foundations dry while forms were being built and concrete placed. The
railroad company also furnished the reinforcing bars at the site of each
opening. The concrete work was let at $9 per cu. yd., which figure
covered all the labor and materials necessary to complete the work,
other than the exceptions mentioned. The concrete proportions were
1-3-5. The cement used was Iola Portland and Atlas Portland. The sand
was obtained from the bed of the Kansas River in Kansas City. The rock
used was crushed limestone, passing a 2-in. ring and freed from dust by
screening. Corrugated reinforcing bars, having an elastic limit of from
50,000 to 60,000 lbs. per sq. in., manufactured by the Expanded Metal &
Corrugated Bar Co. of St. Louis, Mo., were used exclusively. The
concrete in the smaller structures was mixed by hand, in the larger by a
No. 1 Smith mixer. In the first structures built 2-in. form lumber was
used, with 2 by 6-in. studs placed 3 ft. on centers. This was abandoned
later for 1-in. lumber with 2 by 6-in. studs, 12 ins. on centers, and
was found to be more satisfactory in producing a better face. The
structures were built in the period from April, 1905, to May, 1907.
The cost of materials and the wages paid labor were as follows:
Cement--
Per barrel at structure, April, 1905 $1.25
Per barrel at structure, April, 1907 1.92
Average cost per barrel at mill 1.42
Freight per barrel 0.21
Hauling 1½ miles and storage 0.12
Average cost at structure 1.75
Average cost per cu. yd. concrete (1.1 bbls.) 1.93
Sand--
Per cu. yd. at structure, April, 1905 $0.625
Per cu. yd. at structure, April, 1907 0.75
Average cost per cu. yd., river bank 0.30
Freight per cu. yd 0.22
Hauling 1½ miles 0.20
Average cost at structure 0.72
Average cost per cu. yd. concrete (½ cu. yd.) 0.36
Stone--
Per cu. yd. at structure, April, 1905 $1.10
Per cu. yd. at structure, April, 1907 1.75
Average cost per cu. yd. at crusher 0.65
Hauling 4 miles 0.84
Average cost at structure 1.49
Average cost per cu. yd. concrete (0.9 cu. yd.) 1.34
Lumber--
Per M. ft. at structure, April, 1905 $15.00
Per M. ft. at structure, April, 1907 22.50
Average cost per M. at structure 19.00
Average cost per cu. yd. concrete 0.49
Labor-- Max. Min.
Common labor, cts. per hour 20 17
Carpenters, cts. per hour 40 30
With these prices and wages the average cost of concrete work for the
whole line was:
Item. Per cu. yd.
Form building and removing $1.98
Mixing and placing concrete 0.74
Placing reinforcement 0.10
Wire, nails, water, etc. 0.20
1.1 bbls. cement at $1.75 1.93
½ cu. yd. sand at $0.72 0.36
0.9 cu. yd. stone at $1.49 1.34
Lumber for forms 0.49
------
Total $7.14
The following are the costs of specific structures built at different
times:
Example I.--Indian Creek Culvert. 14×15 ft., 250 long, completed
November, 1905:
Per cu. yd.
Cement $1.37
Sand .34
Stone 1.10
Labor 2.48
Lumber .76
Miscellaneous .18
Total $6.23
Example II.--Third Street Abutments and Retaining Wall. Completed
November, 1906:
Per cu. yd.
Cement $1.78
Sand .35
Stone 1.35
Lumber .74
Labor 2.75
Miscellaneous .16
-----
Total $7.13
Example III.--Abutments, Overhead Crossing with Union Pacific and Rock
Island. Completed May, 1907:
Per cu. yd.
Cement $1.92
Sand .32
Stone 1.74
Lumber .98
Labor 2.96
Miscellaneous .16
-----
Total $8.08
~COST OF PLATE GIRDER BRIDGE ABUTMENTS.~--The following record of the
construction of 20 abutments for 10 four-track plate girder bridges over
streets in Chicago, Ill., are given by Mr. W. A. Rogers. The work was
done between May 1 and Oct. 1, 1898, in which time 8,400 cu. yds. of
concrete were placed, all the work being done by company labor. The
forms were made of 2-in. plank and 6×6-in. posts bolted together at the
top and bottom with ¾-in. rods. The lumber was used over and over again.
When the dressed plank became too poor for the face it was used for the
back. The concrete was 1 Portland cement, 3 gravel and 4 to 4½ limestone
(crusher run up to 3-in. size). A mortar face 1½ ins. thick was built up
with the rest of the concrete. The concrete was made quite wet, and each
man ramming averaged 18 cu. yds. a day rammed. The concrete was mixed by
a machine of the Ransome type, operated by a 12-HP. portable gasoline
engine. The load was very light for the engine, and 8 HP. would have
been sufficient. The engine made 235 revolutions per minute, and the
pulley wheels were proportioned so that the mixer made 12 revs, per
minute. One gallon of gasoline was used per hour, and the mixing was
carried on day and night so as not to give the concrete time to set. The
time required for each batch was 2 to 3 mins., and about ½ cu. yd. of
concrete was delivered per batch. The average output was 70 cu. yds. per
10-hr, shift, with a crew of 28 men; but as high as 96 cu. yds. were
mixed in 10 hrs. The concrete was far superior to hand mixed concrete.
The water for the concrete was measured in an upright tank and
discharged by a pipe into the mixer. The sand and stone were delivered
to the mixer in wheelbarrows, and the concrete was taken away in
wheelbarrows. No derricks were used at all. Each wheelbarrow of concrete
was raised by a rope passing over a pulley at the top of a gallows
frame, one horse and a driver serving for this raising. A small gasoline
hoisting engine would have been more satisfactory than the horse which
was worked to its full capacity. After the barrows were raised (12 ft.),
they were wheeled to the abutment forms and dumped. The empty
wheelbarrows were lowered by hand, by means of a rope passing over a
sheave and provided with a counterweight to check the descent of the
barrow. The cost of the concrete (built by company labor) was as
follows:
Per cu. yd.
Cement, gravel and stone delivered $3.28
Material in forms (used many time) .11
Carpenters building and taking down forms .34
Labor 1.18
-----
Total per cu. yd $4.91
The labor cost includes moving plant from one bridge to the next,
building runways, gasoline for engine, oil for lights at night and
unloading materials, as well as mixing, transporting and placing
concrete. Wages were $1.75 per 10-hour day for laborers and $2.50 for
carpenters.
~COST OF ABUTMENTS AND PIERS, LONESOME VALLEY VIADUCT.~--Mr. Gustave R.
Tuska gives the following on the concrete substructure of the Lonesome
Valley Viaduct, near Knoxville, Tenn. There were two U-shaped abutments
and 36 concrete piers made of a light limestone that deteriorates
rapidly when used for masonry. Derricks were not needed as would have
been the case with masonry piers, and colored labor at $1 for 11 hrs.
could be used. The piers were made 4 ft. square on top, from 5 to 16 ft.
high, and with a batter of 1 in. to the foot. The abutments average 26
ft. high, 26 ft. long on the face, with wing walls 27 ft. long; the wall
at the bridge seat is 5 ft. thick, and the wing walls are 3½ ft. wide on
top. Batters are 1 in. to the foot.
The forms were made of 2-in. tongued and grooved plank, braced by posts
of 2×10-in. plank placed 3 ft. c. to c. for the abutments, and at each
corner for the piers. At the corners one side was dapped into the other,
so as to prevent leakage of cement. The posts were braced by batter
posts from the earth. For the piers a square frame was dropped over the
forms and spiked to the posts. The abutment forms were built up as the
concreting progressed. The north abutment forms were made in sections 6
ft. high, held by ¾-in. bolts buried in the concrete. The lower sections
were removed and used again on the upper part of the work, thus saving
plank. The inside of forms was painted with a thin coat of crude black
oil. The same form was used for several piers.
The concrete was 1-2-5, the barrel being the unit of measure, making
about ¾ cu. yd. of concrete per batch. The mortar was mixed with hoes,
but shovels were used to mix in the stone. By passing the blade of a
shovel between the form and the concrete, the stone was forced back and
a smooth mortar face was secured. Rammers weighing 30 to 40 lbs. were
used for tamping. Two days after the completion of a pier the forms were
removed. The concrete was protected from the sun by twigs, and was
watered twice a day for a week. It was found by actual measurement that
1 cu. yd. Of concrete (1-2-5), the ingredients being measured in
barrels, consisted of 1¼ bbls. of Atlas cement, 10 cu. ft. of sand, and
26½ cu. ft. of stone. The total amount of concrete was 926 cu. yds. of
which two-thirds was in the two abutments. The work was done (in 1894)
by contract, for $7 per cu. yd., cement costing $2.80 per bbl., sand 30
cts. per cu. yd., and wages $1 a day. A slight profit was made at this
price. A gang of 15 men and a foreman would mix and lay about 40 cu.
yds. in 11 hrs. when not delayed by lack of materials. The cost of
making the concrete, with wages at $1 a day, was:
Cts. per cu. yd.
1 man filling sand barrels and handling water 2.7
2 men filling rock barrels 5.4
4 men mixing sand and cement 10.6
4 men mixing stone and mortar 10.6
2 men wheeling concrete 5.3
1 man spreading concrete 2.7
1 man tamping 2.7
1 foreman 5.0
----
Total labor 45.0
~COST OF HAND MIXING AND WHEELBARROW WORK FOR FOUR BRIDGE PIERS.~--The
following figures of the cost of hand-mixed concrete for bridge piers
and abutments are given by Mr. Fred R. Charles of Richmond, Ind. The
figures cover three jobs. All concrete was mixed by hand and with one
exception noted below was moved to place in wheelbarrows. The concrete
was a 1-2½-5½ mixture. In this connection it is well to note that in one
or two of the jobs where the proportion of the aggregate seems too small
for the yardage of concrete the difference is accounted for by the fact
that large stones were placed in the foundations, these stone being on
the ground and costing nothing but the labor to throw them in.
_Job I._--The first job consisted of the construction of one abutment
and six piers for a bridge over the Miami River at Fernald, O. The stone
was procured on the site and crushed by a portable crusher run by a
traction engine. The rough stone cost 10 cts. a cubic yard, and this,
with the cost of handling, fuel and hire of engine and crusher, made the
cost of crushed stone about $1 per cu. yd. Sand was obtained close to
the work, but the cement had to be teamed 10 miles. Labor was paid $1.75
per day. The cost of materials and labor per cubic yard of concrete in
place was as follows:
Item. Per cu. yd.
1.16 bbls. cement at $2.10 $1.58
Sand 0.35
Stone 0.75
Lumber 0.64
Tools, hardware, etc. 0.20
Labor (including 15 cts. per cu. yd. for pumping) 2.78
-----
Total materials and labor $6.30
_Job II._--The second job was the construction of two abutments
containing 434 cu. yds. of concrete for a viaduct at Ernst Street,
Cincinnati, O. The abutments were constructed at the street and the
excavation was clay and shale. Labor received $1.75 per day. The cost of
materials and labor per cubic yard of concrete in place was as follows:
Materials-- Per cu. yd.
376 bbls. cement at $1.70 $1.48
224 cu. yds. sand at $1.20 0.64
255 cu. yds. stone at $1.55 1.00
Lumber 0.40
Tools, hardware, etc. 0.06
Total materials $3.58
Labor--
Clearing and excavating $1.12
Mixing and placing concrete 1.13
Building forms, etc. 0.25
-----
Total labor $2.50
Total labor and materials $6.08
_Job III._--This job consisted in placing 570 cu. yds. of concrete in
the pedestals for a viaduct at Quebec Avenue, Cincinnati, O. The
pedestals were 5 ft. square on top and from 8 to 20 ft. high. The
location of the work was very inconvenient for the delivery of
materials, all materials having to be teamed or wheeled. Labor was paid
$1.75 per day. The cost of labor and materials per cubic yard of
concrete in place was as follows:
Item. Per cu. yd.
500 bbls. cement at $1.60 $1.40
239 cu. yds. sand at $1.25 0.53
560 cu. yds. stone at $1.88 1.84
Lumber 0.38
Tools, hardware, etc. 0.05
Labor 2.96
-----
Total labor and materials $7.16
_Job IV._--This job consisted in placing 2,111 cu. yds. of concrete in a
railway viaduct at Cincinnati, O. For one pier 56 ft. high the concrete
was raised to place by a derrick; for the remainder of the work it was
wheeled or teamed to place. Labor was paid $1.75 per day. The cost of
labor and materials per cubic yard of concrete in place was as follows:
Item. Per cu. yd.
1,908 bbls. cement at $1.60 $1.44
1,105 cu. yds. sand at $1.95 0.50
1,468 cu. yds. stone at $1.48 1.03
Lumber 0.54
Tools, hardware, etc. 0.25
Water 0.03
Labor 3.44
-----
Total labor and materials $7.23
CHAPTER XIII.
METHODS AND COST OF CONSTRUCTING RETAINING WALLS.
Concrete retaining walls may for construction purposes be divided into
two classes: Plain concrete walls of gravity section and reinforced
concrete walls consisting of a thin slab taking the thrust of the earth
as a cantilever anchored to a base slab or as a flat beam between
counterforts. The reinforced wall requires much less concrete for a
given height than does the plain, gravity wall, but the concrete is more
expensive owing to the reinforcement and to the more complex form of
construction, and, in some measure, to the greater cost of placing the
mixture in narrow forms and around reinforcement. It is common, too, to
require a richer concrete for the reinforced than for the plain wall.
[Illustration: Fig. 98.--Comparison of Plain and Reinforced Sections for
Retaining Walls (C. E. Graff).]
~COMPARATIVE ECONOMY OF PLAIN AND REINFORCED CONCRETE WALLS.~--Prior to
the construction of some 2,000 ft. of retaining wall ranging in height
from 2 ft. to 38 ft., at Seattle, Wash., calculation was made by the
engineers of the Great Northern Ry. to determine the comparative economy
of plain concrete and reinforced concrete sections. The sections assumed
were those shown by Fig. 98, and comparisons were made at heights of 10,
20, 30 and 40 ft., with the following results:
Height in Plain. Reinforced. Per cent.
feet. Cu. yds. per ft. Cu. yds. per ft. Saving.
10 1.63 1.29 20.4
20 4.08 2.59 36.4
30 8.40 4.73 43.3
40 14.70 8.07 45.0
The saving in concrete increased as the height of the wall increased;
for a 40-ft. wall reinforced concrete at nearly double the cost per
cubic yard in place would be as cheap as plain concrete.
[Illustration: Fig. 99.--Comparison of Plain and Reinforced Sections for
Retaining Wall (F. F. Sinks).]
Taking substantially the section of reinforced wall being used on the
Chicago track elevation work of the Chicago, Burlington & Quincy R. R.,
and comparing it with a plain wall as shown by Fig. 99, Mr. F. F. Sinks
obtained the following results:
Plain Wall, Cost per Lineal Foot--
4.8 cu. yds. concrete at $4 $19.20
115 ft. B. M. of forms at $31 3.56
------
Total 4.8 cu. yds. at $4.74 $22.76
Reinforced Wall, Cost per Lineal Foot--
3.46 cu. yds. concrete at $4.10 $14.18
115 ft. B. M. of forms at $31 3.56
109 lbs. reinforcing steel at 3¼ cts. 3.54
1.34 cu. yds. extra fill at 20 cts. 0.27
0.32 cu. yd. extra excavation at 20 cts. 0.06
-----
Total, 3.46 cu. yds. concrete at $6.25 $21.61
The saving in this case was $1.15 per lineal foot of wall with the unit
cost of reinforced concrete in place 24 per cent. greater than the unit
cost of plain concrete. It will be noted that there is some 28 per cent.
less concrete per lineal foot of wall in the reinforced section and also
that this section is so designed that the form work is about as simple
for one section as for the other. Another point to be noticed is that
there is no saving in excavation by using a reinforced section instead
of a gravity section, in fact the excavation runs slightly more for the
reinforced section.
[Illustration: Fig. 100.--Forms for Retaining Wall Work, N. Y. C. & H.
R. R. R.]
~FORM CONSTRUCTION.~--Retaining wall work often affords an opportunity for
constructing the forms in panels and this opportunity should be taken
advantage of when possible. Several of the walls described later give
examples of form work that may be studied with profit in this respect.
Figure 100 shows a panel form construction employed on the New York
Central & Hudson River R. R. The 3×8-in. studs are erected, care being
taken to get them in proper line and to true batter and also to brace
them rigidly by diagonal props. Generally the studding is erected for a
section of wall 50 ft. long at one time. The lagging, made in panels 2½
ft. wide and 10 ft. long, by nailing 2-in. plank to 2×4-in. cleats, is
attached to the studding a panel at a time and beginning at the bottom,
by means of the straps, wedges and blocks shown. Five bottom panels
making a form 2½ ft. high and 50 ft. long are placed first. When the
concrete has been brought up nearly to the top of these panels, a second
row of panels is placed on top of the first. When it is judged that the
concrete is hard enough the lowermost panels are loosened and made free
by removing the wedges, blocks and straps and the panels are drawn out
endwise from behind the studding and used over again for one of the
upper courses. The small size of the panels makes it practicable to lay
bare the concrete while it is yet soft enough to work with a float or to
finish by scrubbing as described in Chapter VIII. In cases where this
object is not sought, panels of much larger size may be used. Working
with panels 2¼×12½ ft. of 2-in. plank it was found that each panel could
be used 16 times before becoming unfit for further use, but as, owing to
the nicety of molded surface demanded, panels were discarded when
showing comparatively small blemishes, this record cannot be taken as a
true indication of the life of such forms. These panel forms are used by
the railway named for long abutments and piers as well as for retaining
walls.
A different type of sectional form construction is illustrated by Figs.
101 and 102. It has been extensively used for retaining wall work by the
Chicago, Burlington & Quincy R. R. The studding and waling are framed in
units as shown. The lagging is framed in panels for the rear of the
wall, for the face of the coping, and for the inclined toe of the wall,
and is ordinary sheathing boards for the main face of the wall. The
make-up of the several panels is shown by the drawings. The reason for
using ordinary sheathing instead of panels for the face of the wall is
stated by Mr. L. J. Hotchkiss, Assistant Bridge Engineer, to be that
"the sections become battered and warped with use, do not fit closely
together, and leave the wall rough when they are removed." The manner of
bracing the form and of anchoring it down against the up-thrust of the
wet concrete is shown by Fig. 102.
Two other examples of sectional form construction are given in the
succeeding descriptions of work for the Grand Central Station terminal
in New York City and for the Chicago Drainage Canal. In the former work
it is notable that panels 51×20 ft. were used, being handled by
locomotive crane. The panels used on the drainage canal work and in the
forms previously described are of sizes that can be taken down and
erected by hand, and the means of handling them should always be given
consideration in deciding on the sizes to be adopted for form panels not
only in wall construction but in any other class of work where sectional
forms may be used. Wet spruce or yellow pine will weigh 4½ lbs. per ft.
B. M., so that a panel 10×2½ ft. made of 2-in. plank and three 2×4-in.
battens will weigh some 225 lbs. In form work where the panels are
removed and re-erected in succession facility in handling is an
important matter. When one figures that he may handle both the concrete
and the form panels with it a cableway or a locomotive crane becomes a
tool well worth considering in heavy wall work.
[Illustration: Fig. 101.--Forms for Retaining Wall Work, C., B. & Q. R.
R.]
Three details in retaining wall form work that are often sources of
annoyance out of proportion to their magnitude are alignment, coping
construction and wall ties. Small variations from line in the face of
the wall are seldom noticeable, but a wavy coping shows at a glance.
For this reason it is often wise to build the coping after the main body
of the wall has been stripped, or if both are built together to provide
in the forms some independent means of lining up the coping molds. In
the form shown by Fig. 101 the latter is done by bracing the coping
panel so as to permit it to be set and lined up independently of the
main form. A separate form for molding the coping after the main body of
the wall is completed may be constructed as shown by Fig. 103. Bolts at
B and C permit the yokes to be collapsed and the form to be shifted
ahead as the work advances. This mold provides for beveling the top
edges of the coping and also the edge of the overhang, and the beveling
or rounding of these edges should never be omitted where a neat
appearance is desired. It is not essential, however, that this finishing
be done in the molds. By stripping the concrete while it is still
pliable the edges can be worked down by the ordinary cement sidewalk
edger.
[Illustration: Fig. 102.--Sketch Showing Method of Bracing Form Shown by
Fig. 101.]
[Illustration: Fig. 103.--Sectional Form for Constructing Coping.]
Wall ties are commonly used to hold the face and back forms to proper
spacing, but occasionally they are not permitted. In the latter case the
bracing must be arranged to hold the forms from tipping inward as well
as from being thrust outward. A good arrangement is that shown by Fig.
102. In fastening the forms with ties the choice is usually between long
bolts which are removed when the molds are taken down and wire ties
which are left embedded in the concrete. The selection to be made
depends upon the character of the work. When sectional forms are used
like the one shown by Fig. 101, for long stretches of wall of nearly
uniform cross-section bolts are generally more economical and always
more secure. If the bolts are sleeved with scrap gas pipe having the
ends corked with waste the bolts can be removed ordinarily without
difficulty. To make the pipe sleeve serve also as a spacer the end next
the face may be capped with a wooden washer which is removed and the
hole plastered when the forms are taken down. With bolt ties the forms
can be filled to a depth of 15 to 20 ft with sloppy concrete. This is
hardly safe with wire ties unless more wire and better tieing are
employed than is usual. It takes four strands of No. 10 to give the same
working stress as a ½-in. threaded rod and the tieing in of four strands
of wire so that they will be without slack and give is a task requiring
some skill. Bolts are much more easily placed and made tight. In the
matter of cost of metal left in the wall, the question is between the
cost of scrap gas pipe and of wire; the pound price of the wire is
greater but fewer pounds are used and the metal is in more convenient
shape to cut to length and to handle. This convenience in shaping the
tie to the work gives the advantage to wire ties for isolated jobs or
jobs which involve a continual change in the length and spacing of the
ties. In general the contractor will find bolts preferable where
sectional forms are used and wire ties preferable when using continuous
forms.
One objection urged against the use of wire ties is that the metal is
exposed at the face of the work when they are clipped off unless the
concrete is chipped and the cavity plastered. To obviate this objection
various forms of removable "heads" have been devised. Two such devices
are shown by Figs. 104 and 105. In both the bolt is unscrewed, leaving
the "heads" embedded. The head shown by Fig. 104 has the advantage that
it can be made by any blacksmith, while the head shown by Fig. 105 is a
special casting.
[Illustration: Fig. 104.--Tie for Wall Forms.]
[Illustration: Fig. 105.--Tie for Wall Forms.]
~MIXING AND PLACING CONCRETE.~--Where a long stretch of wall is to be
built the system of mixing and handling the concrete must be capable of
being shifted along the work. For isolated walls of short length this
problem is a simpler one. Where the mixer can be installed on the bank
above, wheeling to chutes reaching down to the work is the best
solution. As shown in Chapter IV concrete can be successfully and
economically chuted to place to a greater extent than most contractors
realize. Where the mixer has to be installed at the foot of the wall
wheelbarrow inclines, derricks, gallows frames, etc., suggest themselves
as means of handling the concrete. It is not this class of work,
however, but the long stretches of heavy section walls such as occur in
depressed or elevated railway work in cities that call for thought in
the arrangement and selection of mixing and handling plant.
In building the many miles of retaining wall in the work of doing away
with grade crossings in Chicago, Ill., trains made up of a mixer car and
several material cars have been used. The mixer is mounted on a flat car
set at the head of the train and is covered by a decking carrying two
charging hoppers set above the mixer. The material cars are arranged
behind, the sand and stone or gravel being in gondola cars. Portable
brackets hooked to the sides of the gondola cars carry runways for
wheelbarrows. Sand and stone or gravel are wheeled to the charging
hoppers, the work being continuous since one hopper is being filled
while the other is being discharged into the mixer. The mixer discharges
either into a chute, wheelbarrows or buckets. The foregoing is the
general arrangement; it is modified in special instances, as is
mentioned further on. The chief objection to the method is the
difficulty of loading the wheelbarrows standing on runways level with
the tops of the gondola sides. The lift from the bottom of the car is
excessive, and as pointed out previously, shoveling stone or gravel by
digging into it from the top is a difficult task.
The delivery of the concrete into the forms was accomplished by chute
where possible, otherwise by wheelbarrows or cranes, and in one case by
belt conveyor. In the last instance the mixer car was equipped with a
Drake continuous mixer and was set in front. Behind it came three or
four gondola cars of sand and stone, and at the rear end a box car of
cement. All material was wheeled on side runways to two charging hoppers
over the mixer. The mixer discharged onto a belt conveyor carried by a
25-ft. boom guyed to an A-frame on the car and pivoted at the car end to
swing 180° by means of a tag line. The outer end of the conveyor was
swung over the forms. A ¾-in. wire rope wrapped eight times around two
drums on the mixer car and passing through slots in the floor to anchors
placed one 500 ft. in front and one 500 ft. to the rear enabled the
train to be moved back and forth along the work. This scheme of
self-propulsion saved the hire of a locomotive. In another case the
mixer was discharged into buckets which were handled by a crane
traveling back and forth along a track laid on two flat cars.
[Illustration: Fig. 106.--Side Elevation of Traveling Mixer Plant,
Galveston Sea Wall.]
Another type of movable mixer plant used in constructing a sea-wall some
3½ miles long at Galveston, Tex., is shown by Figs. 106 and 107. Two of
these machines mixed and placed some 127,000 cu. yds. of concrete, in 1
cu. yd. batches. Two 12-HP. engines operated the derricks and one 16-HP.
engine operated the Smith mixer; all engines took steam from a 50-HP.
boiler. The rated capacity of each machine was 300 to 350 cu. yds. per
day. The method of operation is clearly indicated by the drawings.
[Illustration: Fig. 107.--End Elevation of Traveling-Mixer, Galveston
Sea Wall.]
Placing the concrete in the forms is generally required to be done in
layers; with wet mixtures this means little more than distributing the
concrete somewhat evenly along the wall and slicing and puddling it to
get rid of air and prevent segregation. Where mortar facing is required
the face form described in Chapter VIII may be used. A reasonably good
surface can be secured without mortar facing by spading the face. With
dry concrete, placing and ramming in layers, calls for such care as is
necessary in dry concrete work everywhere. Where new concrete has to be
placed on concrete placed the day before, good bond may be secured and
the chance of efflorescence be reduced by the methods described in
Chapter VIII.
~WALLS IN TRENCH.~--In canal excavation, in subway work in cities, and the
like, it is often necessary to dig trenches and build retaining walls in
them before excavating the core of earth between the walls. The
following examples of such work are taken from personal records:
_Example I._--A Smith mixer was used, the concrete being delivered where
wanted by a Lambert cableway of 400 ft. span. The broken stone and sand
were delivered near the work in hopper-bottom cars which were dumped
through a trestle onto a plank floor. Men loaded the material into
one-horse dump carts which hauled it 900 ft. to the mixer platform. This
platform was 24×24 ft. square, and 5 ft. high, with a planked approach
40 ft. long and contained 7,300 ft. B. M. The stone and sand were dumped
at the mouth of the mixer and shoveled in by 4 men. Eight men, working
in pairs, loaded the broken stone into the carts, and 2 men loaded the
sand. Each cart was loaded with about 70 shovelfuls of stone on top of
which 35 shovelfuls of sand were thrown. It took 3 to 5 minutes to load
on the stone and 1 minute to load the sand. The carts traveled very
slowly, about 150 ft. a minute--in fact, all the men on the job,
including the cart drivers, were slow. After mixing, the concrete was
dumped into iron buckets holding 14 cu. ft. water measure, making about
½ cu. yd. in a batch. The buckets were hooked on to the cableway and
conveyed where wanted in the wall. Steam for running the mixer was taken
from the same boiler that supplied the cableway engine. The average
output of this plant was 100 cu. yds. of concrete per 10-hour day,
although on many days the output was 125 cu. yds., or 250 batches. The
cost of mixing and placing was as follows, on a basis of 100 cu. yds.
per day:
Per day. Per cu. yd.
8 men loading stone into carts $12.00 $ .12
2 men loading sand into carts 3.00 .03
1 cart hauling cement 3.00 .03
8 carts hauling stone and sand 24.00 .24
4 men loading mixer 6.00 .06
1 man dumping mixer 1.50 .01
2 men handling buckets at mixer 3.00 .03
6 men dumping buckets and ramming 9.00 .09
12 men making forms at $2.50 30.00 .30
1 cable engineman 3.00 .03
1 fireman 2.00 .02
1 foreman 6.00 .06
1 waterboy 1.00 .01
1 ton coal for cableway and mixer 4.00 .04
------- -----
Total $107.50 $1.07
In addition to this cost of $1.07 per cu. yd. there was the cost of
moving the whole plant for every 350 ft. of wall. This required 2 days,
at a cost of $100, and as there were about 1,000 cu. yds. of concrete in
350 ft. of wall 16 ft. high, the cost of moving the plant was 10 cts.
per cu. yd. of concrete, bringing the total cost of mixing and placing
up to $1.17 per cu. yd. As above stated, the whole gang was slow.
The labor cost of making the forms was high, for such simple and heavy
work, costing $10 per M. of lumber placed each day. The forms were 2-in.
sheeting plank held by 4×6-in. upright studs 2½ ft. apart, which were
braced against the sides of the trench. The face of the forms was
dressed lumber and all cracks were carefully puttied and sandpapered.
The above costs relate only to the massive part of the wall and not the
cost of putting in the facing mortar, which was excessively high. The
face mortar was 2 ins. thick, and about 3½ cu. yds. of it were placed
each day with a force of 8 men! Two of these men mixed the mortar, 2 men
wheeled it in barrows to the wall, 2 men lowered it in buckets, and 2
men put it in place on the face of the wall. If we distribute this labor
cost on the face mortar over the 100 cu. yds. of concrete laid each day,
we have another 12 cts. per cu. yd.; but a better way is to regard this
work as a separate item, and estimate it as square feet of facing work.
In that case these 8 men did 500 sq. ft. of facing work per day at a
cost of nearly 2½ cts. per sq. ft. for labor.
_Example II._--The building of a wall similar to the one just described
was done by another gang as follows: The stone and sand were delivered
in flat cars provided with side boards. In a stone car 5 men were kept
busy shoveling stone into iron dump buckets having a capacity of 20 cu.
ft. water measure. Each bucket was filled about two-thirds full of
stone, then it was picked up by a derrick and swung over to the next car
which contained sand, where two men filled the remaining third of the
bucket with sand. The bucket was then lifted and swung by the derrick
over to the platform of the mixer where it was dumped and its contents
shoveled by four men into the mixer, cement being added by these men.
The mixer was dumped by two men, loading iron buckets holding about ½
cu. yd. of concrete each, which was the size of each batch. A second
derrick picked up the concrete bucket and swung it over to a platform
where it was dumped by one man; then ten men loaded the concrete into
wheelbarrows and wheeled it along a runway to the wall. One man assisted
each barrow in dumping into a hopper on the top of a sheet-iron pipe
which delivered the concrete. The two derricks were stiff-leg derricks
with 40-ft. booms, provided with bull-wheels, and operated by double
cylinder (7×10-in.) engines of 18-HP. each. About 1 ton of coal was
burned daily under the boiler supplying steam to these two hoisting
engines. The output of this plant was 200 batches or 100 cu. yds. of
concrete per 10-hr. day, when materials were promptly supplied by the
railroad; but delays in delivering cars ran the average output down to
80 cu. yds. per day.
On the basis of 100 cu. yds. daily output, the cost of mixing and
placing the concrete was as follows:
Per day. Per cu. yd.
5 men loading stone $ 7.50 $.07½
2 men loading sand 3.00 .03
4 men charging mixer 6.00 .06
2 men loading concrete into buckets 3.00 .03
1 man dumping concrete from buckets .50 .01½
10 men loading and wheeling concrete .00 .15
1 man dumping wheelbarrows 1.50 .01½
3 men spreading and ramming 4.50 .04½
2 enginemen 5.00 .05
1 fireman 2.00 .02
1 waterboy 1.00 .01
1 foreman 6.00 .06
10 men making forms 25.00 .25
1 ton coal 4.00 .04
Total 85.00 $.85
In addition there were 8 men engaged in mixing and placing the 2-in.
facing of mortar as stated above.
~CHICAGO DRAINAGE CANAL.~--The method and cost of constructing some 20,000
ft. of concrete wall by contract in building the Chicago Drainage Canal
is compiled from records kept by Mr. James W. Beardsley. The work was
done on two separate sections, Section 14 and Section 15. In both cases
a 1-1½-4 natural cement concrete was used with a 3-in. facing and a
3-in. coping of 1-3 Portland cement mortar.
_Section 14._--The average height of the wall was 10 ft., and the
thickness at base was one-half the height. The stone for the concrete
was obtained from the spoil bank of the canal, loaded into wheelbarrows
and wheeled about 100 ft. to the crusher; some was hauled in wagons. An
Austin jaw crusher was used, and it discharged the stone into bins from
which it was fed into a Sooysmith mixer. The crusher and the mixer were
mounted on a flat car. Bucket elevators were used to raise the stone,
sand and cement from their bins to the mixer; the buckets were made of
such size as to give the proper proportions of ingredients, as they all
traveled at the same speed. Only two laborers were required to look
after the elevators. The sand and cement were hauled by teams and dumped
into the receiving bins. There were 23,568 cu. yds. on Section 14 and
the cost was as follows:
Typical Wages per Cost per
General force: force. 10 hrs. cu. yd.
Superintendent 1.0 $5.00 $0.026
Blacksmith 1.1 2.75 0.016
Timekeeper 0.5 2.50 0.007
Watchman 0.6 2.00 0.007
Waterboys 3.9 1.00 0.022
Wall force:
Foreman 0.9 2.50 0.013
Laborers 8.6 1.50 0.073
Tampers 2.3 1.75 0.022
Mixer force:
Foreman 1.2 2.50 0.017
Enginemen 1.8 2.50 0.025
Laborers 6.7 1.50 0.057
Pump runner 1.0 2.00 0.010
Mixing machines 1.7 1.25 0.012
Timber force:
Foreman 0.6 2.50 0.008
Carpenters 4.7 2.50 0.057
Laborers 1.2 1.50 0.010
Helpers 5.3 2.50 0.075
Hauling force:
Laborers 2.6 1.75 0.026
Teams 6.3 3.25 0.116
Crushing force:
Foreman 0.5 2.50 0.007
Engineman 1.7 2.50 0.023
Laborers 3.5 1.50 0.032
Austin crushers 1.7 1.20 0.011
Loading stone:
Foreman 1.7 2.50 0.023
Laborers 32.9 1.50 0.280
------
Total for crushing, mixing and placing $0.975
The daily costs charged to the mixers and crushers include the cost of
coal, at $2 a ton, and the cost of oil.
The gang "loading stone" apparently did a good deal of sledging of large
stones, and they also wheeled a large part of it in barrows to the
crusher.
The plant cost $9,600, distributed as follows:
2 jaw crushers $3,000
2 mixers 3,000
Track 1,260
Lumber 500
Pipe 840
Sheds 400
Pumps 600
-----
Total $9,600
If this first cost of the plant were distributed over the 23,568 cu.
yds. of concrete it would amount to 41 cts. per cu. yd.
The cost of the concrete was as follows:
Per cu. yd.
Utica cement, at $0.65 per bbl. $0.863
Portland cement, at $2.25 per bbl. 0.305
Sand, at $1.35 per cu. yd. 0.465
Stone and labor, as above given 0.975
------
Total $2.608
First cost of plant $0.407
_Section 15._--The conditions on this section were much the same as on
Section 14, just described, except that the limestone was quarried from
the bed of the canal, and was crushed in a stationary crusher, No. 7
Gates. The stone was hauled 1,000 ft. to the crusher on cars drawn by a
cable from a hoisting engine. The output of this crusher averaged 210
cu. yds. per day of 10 hrs. The crushed stone was hauled in dump cars,
drawn by a locomotive, to the mixers. Spiral screw mixers mounted on
flat cars were used, and they delivered the concrete to belt conveyors
which delivered the concrete into the forms.
The forms on Section 15 (and on Section 14 as well) consisted of upright
posts set 8 ft. apart and 9 ins. in front of the wall, held at the toe
by iron dowels driven into holes in the rock, and held to the rear posts
by tie rods. The plank sheeting was made up in panels 2 ft. wide and 16
ft. long, and was held up temporarily by loose rings which passed around
the posts which were gripped by the friction of the rings. These panels
were brought to proper line and held in place by wooden wedges. After
the concrete had set 24 hrs. the wedges were struck, the panels removed
and scraped clean ready to be used again.
The cost of quarrying and crushing the stone, and mixing the concrete on
Section 15 was as follows:
Typical Wages per Cost per
General force-- force. 10 hrs. cu. yd.
Superintendent 1.0 $5.00 $0.024
Blacksmith 0.9 2.75 0.011
Teams 1.7 3.00 0.025
Waterboy 4.5 1.00 0.022
Wall force--
Foreman 1.1 2.50 0.010
Laborers 14.4 1.50 0.105
Tampers 0.1 1.75 0.001
Mixer force--
Foreman 2.1 2.50 0.026
Enginemen 2.1 2.50 0.022
Laborers 23.1 1.50 0.180
Mixing machines 2.1 1.25 0.022
Timber force--
Carpenters 0.8 3.00 0.013
Laborers 0.7 1.50 0.005
Helpers 10.2 2.50 0.125
Hauling force--
Foreman 0.7 2.50 0.009
Enginemen 1.4 2.50 0.019
Fireman 0.4 1.75 0.003
Brakeman 2.2 2.00 0.018
Teams 0.4 3.25 0.007
Laborers 1.5 1.50 0.010
Locomotives 1.4 2.25 0.015
Crushing force--
Foreman 1.0 2.50 0.014
Enginemen 1.0 2.50 0.014
Laborers 11.1 1.50 0.081
Firemen 1.0 1.75 0.008
Gyratory crusher 1.0 2.25 0.011
Quarry force--
Foreman 1.2 2.50 0.012
Laborers 19.0 1.50 0.140
Drillers 1.8 2.00 0.017
Drill helpers 1.8 1.50 0.013
Machine drills 1.8 1.25 0.011
------
$0.993
The first cost of the plant for this work on Section 15 was $25,420,
distributed as follows:
1 crusher, No. 7 Gates $12,000
Use of locomotive 2,200
Car and track 5,300
3 mixers 3,000
Lumber 1,200
Pipe 720
Small tools 1,000
-------
Total $25,420
This $25,420 distributed over the 44,811 cu. yds. of concrete amounts to
57 cts. per cu. yd.
It will be noted that 2 mixers were kept busy. Their average output was
100 cu. yds. each per day, which is the same as for the mixers on
Section 14.
The total cost of concrete on Section 15 was as follows:
Per cu. yd.
Labor quarrying, crushing and mixing $0.991
Explosives 0.083
Utica cement, at $0.60 per bbl. 0.930
Portland cement, at $2.25 per bbl. 0.180
Sand, at $1.35 per cu. yd. 0.476
------
Total $2,660
First cost of plant $0.567
It is not strictly correct to charge the full first cost of the plant to
the work as it possessed considerable salvage value at the end.
_Comparison._--For the purpose of comparing Sections 14 and 15 the
following summary is given of the cost per cubic yard of concrete:
Sec. 14. Sec. 15.
General force $0.078 $0.082
Wall force 0.108 0.116
Mixing force 0.121 0.250
Timbering force 0.150 0.140
Hauling force 0.142 0.081
Crushing force 0.073 0.128
Quarry force 0.303 0.275
Cement, natural 0.863 0.930
Cement, Portland 0.305 0.180
Sand 0.465 0.476
Plant (full cost) 0.407 0.567
------ -------
Total $3.015 $3.225
It should be remembered that on Section 14 there was no drilling and
blasting of the rock, but that the "quarry force" not only loaded but
hauled the stone to the crusher. The cost of mixing on Section 15 is
higher than on Section 14 because the materials were dumped on platforms
and shoveled into the mixer, instead of being discharged from bins into
the mixer as on Section 14.
[Illustration: Fig. 108.--Cross Section of Retaining Wall. New York
Central Terminal Work.]
[Illustration: Fig. 109.--Portable Concrete Mixing Tower, N. Y. Central
Terminal Work.]
~GRAND CENTRAL TERMINAL, NEW YORK, N. Y.~--In building a retaining wall of
the cross-section, shown in Fig. 108, a traveling tower moving on tracks
parallel to the wall contained the concrete mixing plant. The
construction of the tower is shown in Fig. 109. The tower had two
platforms, one at the top carrying two 10-cu. yd. bins for sand and
stone and the other directly below carrying 40 cu. ft. (4 cu. ft.
cement, 12 cu. ft. sand and 24 cu. ft. stone) Ransome mixer driven by a
30 H.P. motor and a Lidgerwood motor hoist. The elevator tower carried
two 40-cu. ft. Ransome dumping buckets traveling in guides and dumping
automatically into the bins. These buckets were operated by the
Lidgerwood motor hoist on the mixer platform. Sand and broken stone on
flat cars were brought alongside the tower. The sand was shoveled direct
from the car into the sand bucket, but the broken stone was shoveled
into wheelbarrows which were wheeled over a light bridging from car to
bucket and dumped. Wheelbarrows were used for handling the stone chiefly
because the capacity of the plant was so great that enough men could not
be worked in the limited space around the bucket to keep up the supply
by shoveling. The wheelbarrow work added materially to the cost. Cement
was carried from the cars to the sand bucket, hoisted and stored on the
mixer platform which provided storage room for 100 bags. A 1-3-6 mixture
was used; the sand and stone were chuted directly from the bins to the
charging hopper and the cement was charged by hand. The mixed concrete
was delivered to two 1 cu. yd. dump cars running on a 2-ft. gage track
laid in sections on the cross pieces connecting the uprights of the
forms. The track had no switches, so that one car had to wait for the
other. Four men were required to push each car and two more men assisted
in dumping the car and kept the track clear. The wall was built in
sections 51 ft. long, each containing 250 cu. yds. One of these sections
was filled in 8 hours with ease and by a little hustling a section was
filled in 6¾ hours, which is at the rate of 37 cu. yds. of concrete per
hour. Working 8 hours per day the cost of mixing, transporting and
placing concrete with this mixing plant, with wages for common labor of
$1.50 per day, was as follows:
Total. Per cu. yd.
2 men carrying cement $ 3.00 $0.012
6 men shoveling sand 9.00 0.036
17 men shoveling stone 25.00 0.100
11 men wheeling stone 16.00 0.064
2 men at stone and sand bins 3.00 0.012
2 men opening cement bags 3.00 0.012
1 man dumping hopper 1.50 0.006
1 man dumping mixer 1.50 0.006
1 man cleaning chute, mixer, etc. 1.50 0.006
1 motorman or engineer 3.00 0.012
------- -------
Total labor mixing $66.50 $0.266
8 men pushing 2 cars 12.00 0.048
2 men cleaning track, etc. 3.00 0.012
7 men spading concrete 10.50 0.042
------- -------
Total labor transporting, placing $ 25.50 $0.102
1 foreman 5.00 0.020
Electricity estimated 7.00 0.028
------- -------
Total general $ 12.00 $0.048
Grand total $104.00 $0.416
It will be noted that the cost of shoveling and wheeling the broken
stone amounts to 16.4 cts. per cu. yd., or nearly 40 per cent. of the
total cost of mixing and placing. The cost of spading the concrete is
also high for a sloppy mixture, but is probably accounted for by the
fact that the concrete had to be spaded so as to have 2 or 3 ins. of
clear mortar next the forms. The forms used in constructing the wall
are shown by Figs. 110 and 111. They were made in panels 51 ft. long and
a locomotive crane was used to shift the panels. This crane worked
handling forms only a small part of the time, but a form gang of 10
carpenters was kept busy all of the time moving and reassembling.
Assuming the work of the crane to amount to $5 per day and the wages of
the carpenter gang to amount to $25, we get a cost of 12 cts. per cubic
yard of concrete for shifting forms. It should be noted carefully that
the costs given for this work do not include cost of materials, interest
on plant, superintendence and other items.
[Illustration: Fig. 110.--End View of Forms for Retaining Wall, New York
Central Terminal Work.]
~WALL FOR RAILWAY YARD.~--For building a retaining wall 7 ft. high, forms
were made and placed by a carpenter and helper at $8 per M., wages being
35 cts. and 20 cts. an hour, respectively. Concrete materials were
dumped from wagons alongside the mixing board. Ramming was unusually
thorough. Foreman expense was high, due to small number in gang; 2 cu.
yds. were laid per hour by the gang.
[Illustration: Fig. 111.--Corner Detail of Retaining Wall Forms, New
York Central Terminal Work.]
Per day. Per cu. yd.
7 mixers, 15 cts. per hour $10.50 $0.53
2 rammers, 15 cts. per hour 3.00 0.15
1 foreman 30 cts. per hr., 1 waterboy 5 cts. 3.50 0.17
------- ------
Total labor $17.00 $0.85
The total cost was as follows per cubic yard:
Per cu. yd.
0.8 bbls. Portland cement, at $2 $1.60
Sand 0.30
Gravel 0.70
Labor mixing and placing 0.85
Lumber for forms, at $16 per M. 0.56
Labor on forms, at $8 per M. 0.28
------
Total, per cubic yard $4.29
The sheathing plank for the forms was 2-in. hemlock.
~CONCRETE FOOTING FOR RUBBLE MASONRY RETAINING WALL.~--In constructing a
footing for a retaining wall at Grand Rapids, Mich., a 1-2½-5 natural
cement concrete was used. It was found that 1 cu. yd. of concrete was
equivalent to 29.8 cu. ft. of material composed of 3.6 cu. ft. or 1.1
bbls. of cement, 8.4 cu. ft. or 2.7 bbls. of sand and 17.8 cu. ft. or
5.5 bbl. of broken stone. The labor cost of 15.5 cu. yds. of concrete
was as follows:
Item. Total. Per cu. yd.
Foreman, 14 hours at 40 cts. $ 5.60 $0.3613
Foreman, 20 hours at 22.5 cts. 4.50 0.2903
Laborers, 49 hours at 12.5 cts. 6.11 0.3942
Mason, 2 hours at 35 cts. 0.70 0.0451
------ --------
Total labor $16.91 $1.0909
All material was furnished by the railway company, the contractor
furnishing labor only; his contract price for this was $1 per cu. yd.
~TRACK ELEVATION, ALLEGHENY, PA.~--The wall was 6,100 ft. long and 75 per
cent. was on curves. The first wall built had a top width of 2½ ft. and
a bottom width of 0.4 the height with the back on a smooth batter. Later
the back was stepped and last the wall was proportioned as follows:
Calling the height from top of foundation to under coping, then width of
base was 0.45 (h + 3), the top measuring 2½ ft. The back was arranged
in steps 24 ins., 30 ins. and 36 ins. high, and the thickness of wall at
each step was, calling h equal to height of step from base, 0.45 (h + 3).
Several forms of expansion joints were tried. The first was tarred
paper extending through the wall every 50 ft.; the second was ½-in.
boards running through the wall every 50 ft.; the third was ½-in. board
extending 2 ft. into the wall, with a ¼-in. cove at the angles, every 25
ft. The third construction gave perfect satisfaction.