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Concrete Construction - Methods and Costs
by Halbert P. Gillette
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Duty. No. Men. P. C. Cost.

Handling cement 3 5.26 Filling and pushing sand car 5 8.77 Filling and pushing stone car 9 15.79 Measuring water 1 1.75 Dumping bucket on top platform 3 5.26 Opening and closing door of mixer 1 1.75 Operating friction clutch 1 1.76 Attending concrete cars under mixer 1 1.76 Dumping cars at forms 2 3.51 Spreading concrete in forms 3 5.26 Tamping concrete in forms 10 17.54 Mixing mortar for facing 6 10.53 Finishing top of wall 2 3.51 Hauling concrete cars with 1 horse 1 3.51 Engineman operating hoist 1 3.51 Engineman operating engine 1 3.51 Foreman in charge of forms 1 3.51 General foreman 1 3.51 — ——— Total 52 100.00

The percentages of cost in this statement have been calculated by the authors upon the assumption that each laborer received one-half as much wages as each engineman, foreman and horse and driver per 8 hours, which would make the total daily wages equivalent to the wages of 57 men. Wages of common labor were $1.50 per day. Considering the size of the gang the output of 40 batches of mortar and 60 batches of concrete per day was very small. The total yardage of concrete in the guard lock was 3,762 cu. yds., 2,212 cu. yds. in the walls and 1,550 cu. yds. in foundations, culverts, etc. Its cost per cubic yard was made up as follows:

Item. Total. Per Cu. Yd.

5,246 bbls. Portland cement $15,604} } $4.170 152 bbls. natural cement 84} 2,910 cu. yds. stone 2,901 0.771 126 cu. yds. pebbles 113} } 0.401 1,970 cu. yds. sand 1,398} 145,000 ft. B. M. lumber (th cost) 659 0.175 Iron for forms, trestles, etc. 90 0.024 Coal, oil, miscellaneous 327 0.087 Carpenter work 2,726 0.724 Mixing and placing concrete 6,693 1.780 Pumping, engineering, misc. 742 0.197 20 per cent of plant 550 0.146 ———- ——— Total $31,887 $8.475



Lock No. 37.—The character of the forms used in constructing the lock walls is shown by Fig. 75. The walls were built in sections and work was continuous with three 8-hour shifts composed about as specified for the guard lock work except that one or two men were added in several places making the total number 58 men. The average output per shift was 65 batches of concrete and 31 batches of facing mortar. The cost of the work, comprising 3,767 cu. yds., was as follows:

Item. Total. Per Cu. Yd.

4,564 bbls. Portland cement $14,181 $3.764 2,460 cu. yds. crushed stone 4,521 1.200 250 cu. yds. pebbles 325 0.086 1,750 cu. yds. gravel 2,335 0.619 450 cu. yds. sand 450 0.119 180,000 ft. B. M. lumber (th cost) 990 0.236 Fuel, light, repairs, etc. 1,171 0.311 Carpenter work 2,526 0.671 Pumping 270 0.071 Mixing and placing concrete 6,170 1.632 20% cost of plant 730 0.193 ———- ——— Total $33,669 $8.902

Lock No. 36.—The forms used were of the construction shown by Fig. 75. Three shifts were worked, each composed as specified for the guard lock, except that the number of tampers and spreaders was doubled, bringing the gang up to 65 men. The average output per gang per shift was 76 batches of concrete and 35 batches of facing mortar. The cost of 2,141 cu. yds. of concrete in this lock was as follows:

Item. Total. Per Cu. Yd.

3,010 bbls. Portland cement $9,057 $4.23 1,377 cu. yds. broken stone 1,922 0.90 393 cu. yds. pebbles 354 0.17 459 cu. yds. gravel 310 0.15 500 cu. yds. sand 889 0.42 150,000 ft. B. M. lumber (th cost) 600 0.28 Fuel, light, repairs, etc. 253 0.68 Carpenter work 1,472 0.11 Mixing and placing concrete 3,897 1.82 20% cost of plant 650 0.30 ———- ——- Total $19,404 $9.06

The preceding data, made public by Mr. Woermann in 1894, are supplemented by the following information prepared for the authors:

"If any criticism was to be made of the concrete masonry erected in 1893 and 1894, it would probably be to the effect that it was too expensive. The cost of the masonry erected during those two seasons was $8 to $9 per cu. yd. Our records showed that about 45 per cent. of this cost was for Portland cement alone, and moreover, that 40 per cent. of the total cement used at a lock was placed in the 8-in. facing and 5-in. coping. So in the seven locks erected in 1895 on the eastern section, the facing was reduced to 3 ins. and the proportions changed from 1-2 to 1-2.

"In 1898 this cost received another severe cut, and Major Marshall's instructions stated that the facing should not exceed 1 ins. in thickness nor be less than -in., while the layer of fine material on top of the coping was to be only sufficient to cover the stone and gravel. The amount of sand was again increased so that the proportions were 1-3.

"The cost of the Portland cement concrete was likewise cheapened by increasing the amount of aggregates. On the earlier work the proportions were 1-2-2-3, while on the work in 1898 the proportions were 1-4-4. The cost of the walls was further cheapened by using Utica cement in the lower steps of the wall, with 2 ft. of Portland cement concrete on the face. The proportions used in the Utica cement concrete were 1-2-2. This lower step is one-third of the height, or about 7 ft.



"The forms were of the same character as those used on the first locks, except that for lining the inner face, 310-in. hard pine planks were substituted for the 48-in. white pine. The hard pine was damaged less by the continuous handling, and the cost was practically the same. There was also an important change made in the manner of fastening the plank to the 810-in. posts. A strip 1 ins. square was thoroughly nailed to each post, once for all, with 20d. spikes, and the planking was then nailed from the outside, as shown in Fig. 76. This kept the face of the plank in a perfectly smooth condition, and prevented the formation of the little knobs on the face of the concrete which represented all the old nail holes. This style of forming was also easier to take apart after the setting of the concrete. Rough pine planks, 212-in., were used for the back of the form, the same as before.

"In order to keep ahead of the concrete force it was necessary to use two gangs of carpenters, erecting the forms for the next two locks. Each gang consisted of about 20 carpenters (at $2.25) and 10 helpers (at $1.50); but men were transferred from one to the other, according to the stage of completion of the two locks. In addition to these two gangs, two carpenters were on duty with each concrete shift to put in the steps in the back of the forms. Sufficient lumber was required for the forms for three complete locks, and 14 locks (Nos. 8 to 21) were built.

"The same type of mixer has been used as on the earlier work at Milan, namely, a 4-ft. cubical steel box mounted on corners diagonally opposite. On account of the greater number of locks to be built on the eastern section, however, two mixers were found necessary, so that while the concrete force was at work at one lock, the carpenters and helpers were erecting the mixer at the next lock. The facing was mixed by hand. After turning over the dry cement and sand at least twice with shovels, the mixture was then cast through a No. 5 sieve, after which the water was incorporated slowly by the use of a sprinkling can so as to avoid washing. The secret of good concrete, after the selection of good materials, is thorough mixing and hard tamping. Each batch of concrete, consisting of about 1.2 cu. yds. in place, was turned in the mixer for not less than 2 mins. at the rate of 9 revolutions per minute. The amount of tamping is indicated by the fact that about 16 men out of 72 on each shift did nothing but tamp. The rammers used were 6 ins. square and weighed 33 lbs. The bottom of the rammer consisted of three ridges, each 1-in. in height, so as to make more bond between the successive layers.

"On the eastern section the top of the lock walls was higher above the ground, as a rule, than at the Milan locks, and the cars were run up an incline with a small hoisting engine. A 15-HP. portable engine and boiler operated the bucket hoist from one pulley, the mixer from the other pulley, and also furnished steam for the hoist which pulled the cars up the incline. The incline made an angle of about 30 with the ground. The practice of carrying on two sections at once was continued the same as on the western section. Each main wall was systematically divided into 11 sections, making each section about 20 ft. long. The corners of the coping were dressed to a quadrant of about 3 ins. radius with a round trowel like those used on cement walks. In fact, the whole method of finishing the coping was the same as is used on concrete walks. The mortar was put on rather wet and then allowed to stand for about 20 mins. before finishing. This allowed the water to come to the surface and prevented the formation of the fine water cracks which are sometimes seen on concrete work. After its final set the coping was covered with several inches of fine gravel which was kept wet for at least a week.

"The last concrete laid during the season was in November, on Lock No. 21, and Aqueducts Nos. 2 and 3. Portions of these structures were built when the temperature was below freezing. The water was warmed to about 60 or 70 F., by discharging exhaust steam into the tank. Salt was used only in the facing, simply sufficient to make the water taste saline. The maximum amount used on the coldest night when the temperature was about 20 F. was 1 per cent.

The concrete force on each shift was as follows:

Men.

Filling and pushing stone car 10 Filling and pushing gravel car 8 Measuring cement 3 Measuring water and cleaning bucket 2 Dumping bucket on top platform 2 Operating mixer 2 Loading concrete cars 1 Pushing and dumping cars on forms 3 Switchmen on forms 2 Spreading concrete in forms 12 Tamping concrete in forms 16 Mixing facing 3 Water boys 2 — Total laborers 66 Operating hoists 2 Finishing coping 2 Fireman 1 Sub-overseers 2 Overseer 1 — Total force 74

The cost of material and labor at Lock No. 15 (10-ft. lift), which contains 2,559 cu. yds. of concrete, was as follows:

Materials. Per cu. yd.

0.56 bbl. Portland cement (0.96 per cu. yd.) $1.42 0.64 bbl. Utica cement (1.58 per cu. yd.) .30 0.58 cu. yd. stone 1.15 0.60 cu. yd. gravel .52 14 ft. B. M. lumber[F] at $15 per M. .21 0.6 lb. spikes .01 Coal (10 tons in all, at $1.70) .01 0.35 gal. kerosene .03 ——- Total materials $3.65

Labor.

Erecting forms ($7 per M.) .45 Removing forms ($2 per M.) .13 Erecting and removing mixer ($161) .06 Loading and unloading materials at yards and lock sites .23 Track laying ($86) .03 Train service (narrow gage road) .09 Delivering materials to mixer .28 Mixing concrete .11 Depositing concrete .21 Tamping concrete .21 Mixing, depositing and tamping, 69 cu. yds. face mortar ($160) .23 General construction ($553) .22 ——- Total labor $2.25

[Footnote F: The lumber was used nearly five times, which accounts for its low cost per cu. yd.]

There were 1,430 cu. yds. of Portland cement concrete. 69 cu. yds. of Portland cement mortar facing, and 1,059 cu. yds. of Utica cement concrete. The Portland concrete cost $6.43 per cu. yd.; the Utica concrete, $4.77 per cu. yd. The following is the cost of labor on Lock No. 20 (11-ft. lift.; 2,750 cu. yds.):

Per cu. yd.

Erecting forms ($7 per M.) $.434 Removing forms ($1.70 per M.) .113 Erecting and removing mixer ($151) .058 Loading and unloading at yards, lock sites, etc. .614 Tracks .024 Train service (narrow gage) .016 Pumping .114 Delivering material to mixer .288 Mixing concrete .134 Depositing concrete .205 Tamping concrete .192 Mixing, depositing and tamping, 85 cu. yds. face mortar .071 General construction .246 ——— Total $2.509

COST OF HAND MIXING AND PLACING, CANAL LOCK FOUNDATION.—Mr. Geo. P. Hawley gives the following record of mixing and placing 4,000 cu. yds. of 1-4 gravel concrete for the foundation of a lock constructed for the Illinois and Mississippi Canal in 1897. The concrete was mixed on 1416-ft. board platforms, from which it was shoveled directly into place. The materials were brought to the board in wheelbarrows. Two boards were used, the usual gang for each being 4 men wheeling gravel, 4 men mixing, 1 man sprinkling, 2 men depositing and leveling and 2 men tamping. The two gangs were worked against each other. Ten hours constituted a day's work, and the average time and cost per cubic yard for mixing and placing were:

Cts.

Foreman, 0.21 hr., at 30 cts 6.30 Laborers, 3.339 hrs., at 15 cts 50.09 Pump runner, 0.129 hr., at 20 cts 3.58 Water boy, 0.087 hr., at 7 cts 0.65 ——- Total labor per cu. yd., cents. 60.62

BREAKWATER AT MARQUETTE, MICH.—The breakwater extends out from the shore and consists of a prism of concrete resting on timber cribs filled with stone. Originally the cribs carried a timber superstructure; this was removed to give place to the concrete work. A typical cross-section of the concrete prism is shown by Fig. 77; the prism is 23 ft. wide on the base. Farther in shore the base width was reduced to 20 ft., and in the shore section the prism was changed to a triangular trapezoid by continuing the first slope to the bottom cutting off the berm and second slope. The wooden structure was removed to a level 1 ft. below mean low water and on it a concrete footing approximately 2 ft. thick was constructed for the prism proper. This footing reached the full width of the crib and was constructed in various ways during the 5 years through which the work continued. At first the footing concrete was deposited loose under water by means of bottom dumping buckets; later the stone filling of the cribs was simply leveled up by depositing concrete in bags, and last toe and heel blocks were molded and set flush with the sides of the crib and filled between. Methods of construction and records of cost are reported for portions only of the work and these are given here.



Footing Placed under Water with Buckets.—Besides the material track which was constructed along the old wooden structure the plant consisted of a mixing scow and a derrick scow, which were moored alongside the work. The sand, stone and cement were brought out in cars between working hours and stored on the mixing scow, enough for one day's work at a time. The derrick handled a 40-cu. ft. bottom dump bucket, which sat in a well on the mixing scow with its top flush with the deck. The concrete was mixed by hand on the deck and shoveled into the bucket; the bucket was then handled by the derrick to the crib and lowered and dumped under water. The gang consisted of 24 men, 1 foreman, 1 master laborer, 14 men shoveling and mixing, 3 men wheeling materials, 1 derrick man and 3 men placing and depositing concrete. No record of output of this gang is available. The cost of the concrete in place with wages $1.25 to $1.40 per day for common labor is given as follows:

Materials. Per cu. yd.

1.21 bbls. (459 lbs.) cement at $2.20 $2.657 1 cu. yd. stone at $1.58 1.580 0.5 cu. yd. sand at $0.50 0.250 2.02 lbs. burlap at $0.037 0.075 Twine and needles 0.005 ——— Total materials $4.567

Labor.

Loading scow with materials $0.4114 Mixing concrete 0.8459 Depositing concrete 0.5242 ———- Total labor $1.7815 Grand total $6.348

These figures are based on some 757 cu. yds. of concrete footing. In explanation of the items of burlap, etc., it should be said that the cribs were carpeted with burlap to prevent waste of concrete into the stone fill.



Leveling Off Cribs with Concrete in Bags.—The sketch, Fig. 78, shows the method of leveling off the cribs with concrete in bags. The concrete was mixed by hand on shore and filled into 8-oz. burlap bags, 6 ft. long and 80 ins. around, holding 2,000 lbs. The bags were filled while lying in position in a skip holding one bag. A skip was lifted by gallows frame and tackle onto a car and run out to the work where the derrick scow handled the skip to the crib, lowered it into the water and dumped the bag. The cost of making and placing some 375 cu. yds. of concrete in bags is given as follows:

Materials. Total. Per cu. yd.

453 bbls. cement at $2.627 $1,190.03 $3.173 375 cu. yds. stone at $1.619 607.13 1.619 180 cu. yds. sand at $0.392 70.56 0.188 3,220 yds. burlap at $0.03304 106.39 0.283 Twine and needles 6.36 0.017 ————- ——— Total materials $1,980.47 $5.280

Labor Mixing.

108 hrs. master laborer at $0.21-7/8 $ 23.42 $0.062 1,750 hrs. labor at $0.175 306.25 0.816 Superintendence 12.55 0.033 ———— ——— Total labor mixing $ 342.22 $0.911

Labor transporting.

306 hrs. labor at $0.175 $ 53.55 $0.142 Superintendence 5.25 0.014 ———— ——— Total labor transporting. $ 58.80 $0.156

Labor Depositing.

108 hrs. engineman at $0.25 $ 27.00 $0.072 108 hrs. master laborer at $0.21-7/8 23.42 0.062 510 hrs. labor at $0.175 89.25 0.238 Superintendence 13.25 0.035 ———— ——— Total labor depositing $ 152.92 $0.407 Grand total labor $ 553.94 $1.477 Grand total materials and labor $2,534.41 $6.757

Molding Footing Blocks.—The blocks used at the toe of the prism were of the form and dimensions shown by Fig. 79. They were molded in a temporary shed heated to 50 to 65 F., and provided with a 28-in. dressed plank floor on 1212-in. sills. The floor formed the bottoms of the block molds. Four molds were used, each consisting of four sides. Three laborers molded one block, 2.22 cu. yds. per day, wheeling, mixing, erecting and removing forms, placing concrete and doing all other work. The cost of making 40 blocks was recorded as follows:

Materials. Total. Per cu. yd.

126 bbls. cement at $2.75 $346.50 $3.893 88.9 cu. yds. screenings at $1.10 97.79 1.098 40.1 cu. yds. sand at $0.45 18.04 0.203 5 gals. oil at $0.65 3.25 0.036 ———- ——— Total materials $465.58 $5.230

Labor.

1,000 hrs. labor at $0.125 $125.00 $1.404 Watchman 29.15 0.327 Labor cutting wood for fuel 23.80 0.267 Superintendence 42.66 0.480 ———- ——— Total labor $220.61 $2.478 Total labor and materials $686.19 $7.708



Molding Concrete Prism in Place.—The concrete prism was molded in alternate sections 10 ft. long; the form for the isolated sections consisted of eight pieces so constructed that when assembled in place and secured with bolts and turnbuckles the form was self-contained as to strength and required no outside support or bracing. The form once in place, all that remained to be done was to fill it, the block with the gallery through it being molded in one operation. The forms for the connecting blocks consisted of two slope panels, a panel for the harbor face and the gallery form, the blocks previously molded making the other sides of the form. The concrete was mixed by hand on shore, conveyed to the work in 1 cu. yd. cars and shoveled into the forms, where it was rammed with 35-lb. rammers. The following record covers 1,231 cu. yds. of concrete prism. In this concrete some 214 cu. yds. of rubble stone were embedded. The costs given are as follows:

Per Materials— Total. cu. yd.

1,780 bbls. natural cement at $1.068 $1,901.04 $1.545 963 cu. yds. stone at $1.619 1,559.91 1.267 53 cu. yds. screenings at $0.392 20.97 0.017 485.6 cu. yds. sand at $0.392 190.36 0.154 Miscellaneous materials 78.15 0.063 ————- ——— Totals $3,750.43 $3.046

Labor Mixing— 254 hrs. master laborer at $0.21-7/8 $ 55.56 $0.045 4,470 hrs. labor at $0.175 782.42 0.635 Superintendence 18.20 0.015 ———— ——— Total labor mixing $ 856.18 $0.695

Labor Transporting and Placing— 35 days overseer at $2.33-1/3 $ 81.67 $0.066 1,949 hrs. labor at $0.175 342.07 0.277 Superintendence 34.98 0.028 ———- ——— Total labor transporting and placing $ 458.72 $0.371 Grand total, labor $1,314.90 1.066 Total labor and materials $5,065.33 4.112

No charge is made under materials for rubble stone as the only cost for this was cost of handling and this is included in transporting and placing.

BREAKWATER, BUFFALO, N. Y.—The following methods and costs of mixing and placing some 2,561 cu. yds. of concrete are given by Mr. Emile Low, for 10 parapet wall sections and 17 parapet deck sections for a breakwater at Buffalo, N. Y.

The concrete used was a 1 cement, 1 gravel, 1 sand grit and 4 unscreened broken stone. One bag of cement was assumed to measure 0.9 cu. ft. The voids in the sand grit and gravel were 27 per cent. and in the unscreened stone 39 per cent. The hardened concrete weighed 152 lbs. per cu. ft.



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 912-in. horizontal engine taking steam from a 410-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



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 447 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.



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.



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 1-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.



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 44 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.



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.



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 34 ft. pieces of 12-oz. canvas in which were quilted 110 pieces of 1/1613-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 1-2-5 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 710-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



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 30 ft. high, 3 ft. wide at the top and 6 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 810-in. stuff 24 ft. high, connected through the wall by -in. rods which were left in the concrete. The lagging was 212-in. plank dressed down 1 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 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.



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 8 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.



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.



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 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 1 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.



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 1420 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 1218 ft. The concrete pier resting on this base was 713 ft. at the bottom, and 511 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 days engineman at $3.00 2.25 days blacksmith at $3.00 2.25 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 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. 46-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 cu. yd. bottom dump buckets were used in placing the concrete, on the North caisson the size of these was increased to 1 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 2 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 10 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 14 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 1 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 11 days including Sundays. The average number of men in the sand hog gangs was 18, with one foreman, who received $5 for 1 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 612 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 6,707 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 614 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.



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 74 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



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.



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, 22c and 25c per hour; enginemen, 25c per hour; firemen, 20c per hour; night watchman, 20c per hour; laborers, 17c 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 1 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 1 miles 0.20 Average cost at structure 0.72 Average cost per cu. yd. concrete ( 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 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. 1415 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 66-in. posts bolted together at the top and bottom with -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 4 limestone (crusher run up to 3-in. size). A mortar face 1 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 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 3 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 210-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 -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 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 1 bbls. of Atlas cement, 10 cu. ft. of sand, and 26 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 1-2-5 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.

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