Concrete Construction Part 33

The gravel used for the concrete was obtained from a pit situated on top of a hill not far from the main shaft leading down to the tunnel. This gravel bed contains very closely the proper proportions of sand and gravel for the concrete aggregates. The gravel was excavated and loaded by hand into side dump cars of 35 cu. ft. capacity. These cars were run to the edge of the hill where the gravel was dumped upon a screen from which it ran by gravity, pa.s.sing thence into storage bins. From the storage bins the sand and gravel were drawn off into dump wagons having a capacity of 2 cu. yds. and hauled a distance of one-half mile to a second set of storage bins located at the top of the shaft leading into the tunnel. The road from the storage bins at the gravel pit to the storage bins at the head of the shaft was down grade. A two-horse team could readily haul 2 cu. yds. of gravel over this road. The storage bins at the top of the shaft leading into the tunnel communicated with the measuring boxes at the bottom of the shaft by means of chutes. The measuring boxes discharged directly into tram cars. The average length of haul from the mixer to the place of deposition of concrete was about 4,500 ft.

The concrete was placed in the side walls by means of a traveler, which was so operated in the tunnel as to allow the pa.s.sage of the concrete trains beneath it. The traveler was 64 ft. long and was provided with a slow motion electric hoist, by which the cars containing the concrete were elevated to the top of the traveler and thence transferred to any desired position. The concrete was dumped from these cars into boxes where any remixing or tempering that was required was done, after which the concrete was shoveled directly into the forms. The entire operation of handling the materials of the concrete, it will be seen, utilized gravity to the greatest possible degree.

In order to get a good average cost per cubic yard for handling gravel and sand, this a.n.a.lysis has been based on five months' operation, from November, 1906, to March, 1907. In these five months there were 4,123 cu. yds. of sand and gravel handled. The concrete considered was placed during the month of March. Below is given the distribution of the cost of the concrete as to the specified divisions of the work and as to the cla.s.s of work involved in each division. Measurements taken at the mixer show that each cubic yard of concrete contained 0.74 cu. yds. of gravel, 0.445 cu yds. of sand and 5.6 sacks of Portland cement. The total of the aggregates is, therefore, 1.185 cu. yds. per cubic yard of concrete. The cement costs $0.62 per sack on the work, making a cost of $3.472 per cubic yard of concrete.

Excavating and screening 4,123 cu. yds. gravel-- Total Per cu. yd.

cost. gravel.

Foreman, 66-7/8 days at $3.04 $ 203.30 $0.049 Labor, 397 days at $2.56 1,017.60 0.247 Labor, 116 days at $2.08 241.80 0.059 -------- ------ Total $1,462.70 $0.355

Hauling 4,123 cu. yds. gravel and sand--

2-horse team and driver, 210 days at $3.60 $756.00 $0.183 2-horse team and driver, 4 days at $4 18.00 0.005 ------- ------ Total $774.00 $0.188

As there were 1.185 cu. yds. of gravel per cubic yard of concrete the cost of gravel per cubic yard of concrete was for--

Excavating and screening (1.185 $0.355) $0.421 Hauling (1.185 $0.188) 0.223 ------ Total $0.644

Adding to this the cost of cement $0.62 5.6 = $3.472, we have $0.644 + $3.472 = $4.116, as the cost of concrete materials per cubic yard of concrete. The cost of labor, mixing and placing was as follows for 616 cu. yds.:

Total Per cu. yd.

Mixing 616 cu. yds. concrete-- cost. concrete.

Superintendent, 2 days at $5.83-1/3 $ 11.67 $0.020 Foreman, 1 day at $4.50 4.50 0.007 Labor, 45 days at $3.04 130.72 0.215 Labor, 93 days at $2.56 238.08 0.381 Hoist engineer, 34 days at $3.52 119.68 0.196 ------- ------ Total $504.65 $0.819

Transporting 616 cu. yds. concrete--

Superintendent, 1 day at $5.83-1/3 $ 5.83 $0.009 Foreman, 1 day at $4.50 4.50 0.007 Motorman, 34 days at $3.04 103.36 0.175 Brakeman, 34 days at $2.56 87.04 0.135 ------- ------ Total $200.73 $0.326

Depositing 616 cu. yds. concrete--

Superintendent, 4 days at $5.83-1/3 $ 23.33 $0.038 Foreman, 4 days at $4.50 18.00 0.029 Foreman, 68 days at $3.04 200.72 0.326 Labor, 238 days at $2.56 610.56 0.991 ------- ------ Total $852.61 $1.384

Setting and moving forms--

Superintendent, 2 days at $5.83-1/3 $ 11.67 $0.018 Foreman, 2 days at $4.50 9.00 0.014 Carpenter foreman, 10 days at $5 50.00 0.080 Carpenter, 13 days at $3.20 41.60 0.067 Labor, 49 days at $3.04 148.96 0.241 Labor, 19 days at $2.56 48.64 0.078 ------- ------ Total $309.87 $0.498

Summarizing we have the following cost:

Materials-- Cement, 5.6 bags at $0.62 $3.472 Gravel (excavating and screening) 0.421 Hauling gravel and sand 0.223 ------ Total, materials $4.116

Labor--

Mixing concrete $0.819 Transporting concrete 0.326 Depositing concrete 1.394 Setting and moving forms 0.498 ------ Total, labor $3.037 Grand total $7.153

~COST OF CONCRETE WORK IN LINING NEW YORK RAPID TRANSIT SUBWAY.~--The costs given here refer alone to the concrete work in constructing the jack arch and steel beam lining of the original standard subway. Figure 143 shows the character of this construction. Arch panel forms were set up between the wall beams and hung from the floor beams and filled behind and above with 1-2-4 trap rock concrete. The form panels were used over and over and the concrete was machine mixed. Common labor was paid $1.50 per 8-hour day; foremen, $3; carpenters, $3; enginemen, $3.50; and masons, $4. The costs cover three sections and are in each case the averages for the whole section. They are, we believe, the only itemized costs that have been published for concrete work on this road.

[Ill.u.s.tration: Fig. 143.--Cross-Section of New York Rapid Transit Subway.]

_Two-Track Subway._--In this section of two-track subway there were 8,827 cu. yds. of foundation concrete and 6,664 cu. yds. of concrete in wall and roof arches. The two cla.s.ses of work cost as follows:

Foundations-- Total. Per cu. yd.

Labor mixing $ 4,669 $0.53 Labor placing 5,142 0.58 Materials and plant 211 0.02 Cement, sand, stone, etc. 30,719 3.48 -------- ------- Total $40,741 $4.61 Roof and side walls-- Labor mixing $ 5,444 $0.82 Labor placing 5,623 0.84 Labor setting forms 14,746 2.21 Labor plastering arches 431 0.06 Materials and plant 1,176 0.18 Cement, sand, stone, etc. 23,888 3.58 -------- ------ Total $51,308 $7.69

Averaging the work we have 15,491 cu. yds. of concrete placed at a cost of $5.94 per cu. yd.

_Four-Track Subway._--On two sections of four-track subway the labor cost of mixing and placing concrete similarly divided was as follows:

Section A. Section B.

Foundations-- Per cu. yd. Per cu. yd.

Labor mixing $0.97 $0.94 Labor placing 0.96 0.95 Power 0.14 0.16 -------- -------- Total $2.07 $2.05 Roof and side walls-- Labor mixing $0.79 $0.91 Labor placing 0.85 0.94 Labor setting forms 2.01 1.20 Labor plastering arches 0.16 0.23 Power 0.28 0.15 ------- ------- Total $4.09 $3.43

[Ill.u.s.tration: Fig. 144.--Traveling Form for Side Walls, New York Subway Tunnels.]

~TRAVELING FORMS FOR LINING NEW YORK RAPID TRANSIT RY. TUNNELS.~--In constructing the tunnels under Park Ave. and under the north end of Central Park for the New York Rapid Transit Ry., traveling centers and side wall forms were used for the concrete lining. The mixing plants were installed in the shafts and consisted generally of gravity mixers charged at the surface and discharging into skip cars running on the tunnel floor.

[Ill.u.s.tration: Fig. 145.--Traveling Form for Roof Arch. New York Subway Tunnels.]

The forms used in the Park Ave. tunnel are shown by Figs. 144 and 145; those used in the Central Park tunnel differed only in details. The method of work was slightly different in the two tunnels, but was substantially as follows: Three platforms mounted on wheels were used in each set and two sets were employed. Ahead came a traveler carrying the side wall forms, next came a shorter traveler carrying a derrick, and last came the traveler carrying the roof centers. The arrangement as operated in the Central Park tunnel is shown by Fig. 146. In the Park Ave. tunnel the "bridges" were dispensed with, the skips being hoisted through the open end bays of the derrick car and set directly on the cars on the center traveler.

[Ill.u.s.tration: Fig. 146.--Sketch Plan of Traveling Forms, New York Subway Tunnels.]

The traveler carrying the side wall forms was set in position and blocked, the grade and line being given by the track rails, which had been set exactly for that purpose. The side wall forms differed slightly in the two tunnels; those for the Park Ave. tunnel shown by Fig. 144 formed the vertical portion of the wall only so that when the arch forms, Fig. 145, followed a s.p.a.ce A B was left which had to be molded by separate sector-like forms. The side wall forms for the Central Park work were constructed as shown by Fig. 147, being curved at the top to merge into the arch centers. In the Park Ave. work the wall studs were adjusted in or out by means of wedges and slotted bolt holes. In the Central Park work the studs A Fig. 145 were hung by -in. bolts from the pieces B spiked to line onto the cross-braces. The bottom was then lined up by means of wedges at D. The side wall studs being lined up, the bottom lagging boards were placed and filled behind by shoveling the concrete into them direct from skip cars on the adjacent tracks on the tunnel floor. In this way the side walls were built up to the tops of the forms.

[Ill.u.s.tration: Fig. 147.--Sketch Showing Detail of Side Wall Forms. New York Subway Tunnels.]

As soon as the side wall concrete had set the forms were struck and the traveler was moved ahead and set for another section of wall. The derrick and roof arch travelers were then moved into position between the finished walls, and the arch traveler was jacked up and aligned.

Skip cars coming from the mixer were run under the derrick traveler, where the skips were lifted by the derrick and set on the platform cars to be run alongside the work. The arch lagging was placed a piece at a time and filled behind by shoveling direct from the skips. As the crown was approached the lagging was placed in short lengths and filled in over the ends, the concrete being shoveled in two lifts; in Fig. 145 the line C D indicates the position of the shoveling board. The centers were struck by lowering the jack supported traveler down onto the track rails.

~COST OF MIXING AND PLACING SUBWAY LINING, LONG ISLAND R. R., BROOKLYN, N. Y.~--The subway carrying the two tracks of the Long Island R. R. under Atlantic Ave., in Brooklyn, New York city, has a lining consisting of an invert arch 12 ins. thick at the center, side walls 4 ft. thick at the base and 3 ft. thick at the top, and a roof of jack arches between steel I-beams 5 ft. apart. The dimensions inside the concrete are 1620 ft. A 1-8 mixture of cement, sand, gravel and stone was used in the floor and walls and a 1-6 mixture of the same materials in the jack arches. A bag of cement was called 1 cu. ft., so that a barrel was 4 cu.

ft. A Hains gravity mixer and a batch mixer were used and careful records were kept of all quant.i.ties.

_General Data._--During 1903, about 13,880 cu. yds. of the 1-8 concrete were placed, 90 per cent. of which was mixed in the gravity mixer and 10 per cent. in the batch mixer. Of the 1-6 concrete 5,320 cu. yds. were placed, 85 per cent, of which was mixed in the gravity mixer and 15 per cent, in the batch mixer.

_Gravity Mixer Work._--During 1903, there were 16,940 cu. yds. of concrete mixed in gravity mixers, requiring 2,860 days' labor mixing and 4,000 days' labor placing. Wages were $1.50 a day and the cost was 26 cts. per cu. yd. for mixing and 33 cts. for placing, making a total of 59 cts. per cu. yd. During the month of August when 2,800 cu. yds. were mixed the cost was as low as 24 cts. for mixing, plus 22 cts. for placing, or a total of 46 cts. per cu. yd. for mixing and placing. The mixer averaged about 113 cu. yds. per day with a gang of 19 men mixing and 26 men placing. The average size of batch was 0.46 cu. yd. In 1904, 20,000 cu. yds. were mixed in 190 days, worked with a gang of 19 men mixing; the gang placing consisted of 25 men. The cost was as follows:

Item. Total. Per cu. yd.

2,950 days labor mixing $ 4,870 24 cts.

4,760 days labor placing 7,300 36 cts.

--------- -------- Total $12,170 60 cts.

During the best month of 1904, the labor cost was 16 cts. for mixing and 29 cts. for placing, or a total of 45 cts. per cu. yd.

_Batch Mixer Work._--During 1903 the batch mixer mixed 2,390 cu. yds. in 970 labor days mixing and 740 labor days placing at a cost of 59 cts.

per cu. yd. for mixing and 55 cts. per cu. yd. for placing, or a total of $1.04 per cu. yd. During the month of June the cost was as low as 40 cts. for mixing and 30 cts. for placing, or 70 cts. per cu. yd. for mixing and placing. The wages paid were $1.50 per day and the average gangs were 11 men mixing and 14 men placing; the average batch mixed was 0.57 cu. yd. and the average output was 35 cu. yds. per day. During 1904, the mixer worked 153 days and averaged 46 cu. yds. per day; the average size of batch was 0.44 cu. yd. The average gangs were 13 men mixing and 11 men placing. The labor cost of 7,000 cu. yds. was as follows:

Item. Total. Per cu. yd.

1,910 days labor mixing $3,175 45 cts.

1,740 days labor placing 2,660 38 cts.

------- -------- Total $5,835 83 cts.