Part 33 (1/2)
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.