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 $.07 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 .01 10 men loading and wheeling concrete .00 .15 1 man dumping wheelbarrows 1.50 .01 3 men spreading and ramming 4.50 .04 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 Ca.n.a.l.~--The method and cost of constructing some 20,000 ft. of concrete wall by contract in building the Chicago Drainage Ca.n.a.l 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 1-1-4 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 ca.n.a.l, 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 ca.n.a.l, 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 pa.s.sed 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 sc.r.a.ped 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.
[Ill.u.s.tration: Fig. 108.--Cross Section of Retaining Wall. New York Central Terminal Work.]
[Ill.u.s.tration: 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 s.p.a.ce 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 a.s.sisted 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 6 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 rea.s.sembling.
a.s.suming 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.