Concrete Construction: Methods and Costs

by Halbert Powers Gillette; Charles Shattuck Hill

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.

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:

	Days.	Per cent. of time.	Prorated 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.

		Abutment No. 1.			Pier No. 2.			Pier No. 3.			Pier No. 4.			Summary.
	Wages per Hour.	No. hrs.	Total Cost	Cost per cu. yd.	No. hrs.	Total Cost	Cost per cu. yd.	No. hrs.	Total Cost	Cost per cu. yd.	No. hrs.	Total Cost	Cost per cu. yd.	Total Hrs.	Total cost.	Av. per cu. yd.
Superintendent	70	24	$16.80	$0.03	47	$32.90	$0.09	72	$50.40	$0.05	16	$11.20	$0.03	159	$111.30	$0.05
Foreman	35	160	56.00	0.09	128	44.80	0.13	324	113.40	0.12	54	18.90	0.06	666	233.10	0.11
Laborers	15-20	2555	383.25	0.65	2038	313.60	0.92	3513	526.95	0.56	940	141.00	0.44	9046	1364.90	0.62
Engineman	30	365	109.50	0.19	196	58.50	0.19	244	73.20	0.08	60	18.00	0.06	865	259.50	0.12
Timekeeper	40	86	34.40	0.06	46	18.40	0.06	81	32.40	0.04	10	4.00	0.01	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.

Fig. 94.—Diagram Arrangement of Piers, Calf Killer River Bridge.

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 per day.	Total days worked.	Total.	Per cu. yd. concrete.
Foreman	$3.40	5	$17.00	$0.04
11 laborers	1.368/10	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	1.156/10	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	1.363/10	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	1.156/10	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:

	Total.	Per cu. yd. 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

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.

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

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