CHAPTER XI.

METHODS AND COST OF HEAVY CONCRETE WORK IN FORTIFICATIONS, LOCKS, DAMS, BREAKWATERS AND PIERS. The construction problem in building concrete structures of massive form and volume is chiefly a problem of plant arrangement and organization of plant operations. In most such work form construction is simple and of such character that it offers no delay to placing the concrete as rapidly as it can be produced. The same is true of the character of the structure, it is seldom necessary for one part of the work to wait on the setting and hardening of another part. As a rule, there is no reinforcement to fabricate and place and where there is it is of such simple character as not to influence the main task of mixing, handling, and placing concrete. Stated broadly, the contractor in such work generally has a certain large amount of concrete to manufacture, transport and deposit in a certain space with nothing to limit the rapidity of these operations, except the limitations of plant capacity and management. Installation and operation of mixing and conveying plant, then are matters to be considered carefully in heavy concrete work. In the following sections we have given one or more examples of nearly every kind of heavy concrete work excepting bridge foundations and retaining walls, which are considered in Chapters XII and XIII, and except rubble concrete work, which is considered in Chapter VI. In each case so far as the available records made it possible, we have given an account of the plant used and of its operation. ~FORTIFICATION WORK.~--Concrete for fortification work consists very largely of heavy platforms and walls for gun foundations and enclosures and of heavily roofed galleries and chambers for machinery and ammunition. The work is very massive and in the majority of cases of simple form. A large number of data are to be found in the reports of the Chief of Engineers, U. S. A., on all classes of fortification work, but the manner in which they are recorded makes close analysis of relative efficiencies of methods or of relative costs almost impossible. The following data are given, therefore, as examples that may be considered fairly representative of the costs obtained in fortification work done under the direction of army engineers; these data are not susceptible of close analysis because wages, working force, outputs, etc., are nearly always lacking. ~Gun Emplacements, Staten Island, N. Y.~--The work comprised 5,609 cu. yds. of concrete in two 12-in. gun emplacements, and 3,778 cu. yds. of concrete in two 6-in. gun emplacements. Concrete was mixed in a revolving cube mixer with the exception of 809 cu. yds. in the 6-in. emplacements which were mixed by hand at a cost of 56 cts. more per cubic yard than machine mixing cost. The body of the concrete was a 1-3-5 Portland cement, beach sand and broken trap rock mixture. The floors and upper surface of the concrete had a pavement consisting of 6 ins. of 1-3-5 concrete surfaced with 2 ins. of 1-3 mortar. Wages are not given, but for the time and place should have been about $1.50 per 8-hour day for common labor. The cost of materials was: Alpha Portland cement, per bbl. $1.98 Broken trap rock, per cu. yd. 0.81 12-in. emplacement, hauling sand per cu. yd. 0.175 6-in. emplacement, hauling sand per cu. yd. 0.20 The cost of the concrete in place was as follows: 12-in., per 6-in., per Body Concrete-- cu. yd. cu. yd. Cement, at $1.98 per bbl. $2.546 $2.546 Broken stone, at 81 cts. per cu. yd. 1.041 1.041 Sand, at 17½ and 20 cts. per cu. yd. 0.225 0.257 Receiving and storing materials at 11.6 cts. per cu. yd. and 8.4 cts. per bbl. 0.149 0.180 Mixing, placing and ramming 0.879 1.110 Forms, lumber and labor 0.477 0.950 Superintendence and miscellaneous 0.190 0.150 ------ ------ Total $5.507 $6.234 Concrete Pavement-- Materials $2.97 $3.06 Labor 4.63 4.72 ------ ------ Total $7.60 $7.78 [Illustration: Fig. 68.--Sketch Plans of Concrete Making Plant for Mortar Battery Platform.] ~Mortar Battery Platform, Tampa Bay, Fla.~--The platform contained 8,994 cu. yds. of concrete composed of a mixture of Portland cement, sand, shells and broken stone. The broken stone and cement were brought in by vessel and the sand and shells were obtained from the beach near by. The plant for the work was arranged as shown by the sketch, Fig. 68. Sand, stone and shells were stored in separate compartments in the storage bins. Box cars, divided into compartments of such size that when each was filled with its proper material, the car would contain the proper proportions for one batch of concrete, were pushed by hand under the several compartments of the bin in succession until charged; then they were hooked to a cable and hauled to the platform over the mixer and dumped. The charge was then turned over with shovels and shoveled into the hopper of a continuous mixer, located beneath. Two cars were used for charging the mixer, running on separate tracks as shown. The mixer discharged into buckets set on flat cars, which were hauled by mules under the cableway, which then lifted and dumped the bucket and returned it empty to the car. By using three bucket cars, one was always ready to receive the mixer discharge as soon as the preceding one had been filled, so that the mixer operated continuously. The cableway had a working span of 270 ft., the cable being carried by traveling towers 69 ft. high; the cableway was very easily operated back and forth along the work. The cableway complete, with 497 ft. of six-rail track for each tower, cost $4,700. The cost of materials and labor for the 8,994 cu. yds. of concrete was as follows: Per cu. yd. 1 bbl. cement at $2.46 $2.46 0.89 cu. yd. stone, at $2.95 2.622 0.315 cu. yd. shells, at $0.45 0.142 0.51 cu. yd. sand, at $0.12 0.062 Mixing and placing 0.693 ------- Total $5.979 The above batch tamped in place to 30 cu. ft., or 1-1/9 cu. yds., which gives the cost as follows: Per cu. yd. Cost of concrete tamped in place $5.381 Cost of form work 0.370 ------- Total cost $5.751 In the preceding prices of cement and stone, 59 cts. and 29 cts. per cubic yard, respectively, are included for storage. The costs of sand and shells are costs of screening and storing. Rough lumber for forms cost $10.25, and dressed lumber $12.75 per M. ft. B. M. ~Emplacement for Battery, Tampa Bay, Fla.~--The emplacement contained 6,654 cu. yds. of Portland cement, sand, shells and broken stone concrete. The plant arrangement is shown by Fig. 69. The sand and shells were got near the site, using an inclined cableway running from a 40-ft. mast near the mixer to a deadman at the shell bank. All the sand for the fill around the emplacement was obtained in the same way. The other materials were brought by vessel to a wharf, loaded by derrick onto cars operated by an endless cable, and taken to the work. The storage bins and mixing plant were operated much like those for the mortar battery work, previously described. A cube mixer was used, and the concrete was handled from it to the work by a crane derrick covering a circle of 100 ft. in diameter. The cost of materials and concrete was as follows: Cement, plus 7 cts. for storage per bbl. $ 2.532 Stone, plus 38 cts. for storage per cu. yd. 3.047 Shells, excavating and storage. 0.481 Sand, excavating and storage. 0.250 Lumber, rough per M. ft. B. M. 10.25 Lumber, dressed per M. ft. B. M. 12.75 [Illustration: Fig. 69.--Sketch Plans of Concrete Making Plant for Battery Emplacement.] A batch made up as follows, tamped in place to a volume of 30 cu. ft. or 1-1/9 cu. yds.: 1 bbl. cement, at $2.532. $ 2.532 0.315 cu. yd. shells, at $0.481. 0.151 0.51 cu. yd. sand, at $0.25. 0.130 0.89 cu. yd. stone, at $3.047. 2.710 Mixing and placing. 0.761 -------- Total for 30 cu. ft. $ 6.284 This gives a cost per cubic yard of concrete in place as follows: Concrete in place, per cu. yd. $ 5.655 Forms, per cu. yd. of concrete. 0.220 -------- Total cost of concrete per cu. yd. $ 5.875 ~United States Fortification Work.~--The following methods and cost of mixing and placing concrete by hand and by cubical mixers is given by Mr. L. R. Grabill for U. S. Government fortification work done in 1899. _Hand Mixing and Placing._--The work was done by contract, using a 1 cement, 2 sand, 2 pebbles and 3 stone mixture turned four times. A board large enough for three batches at a time was used; one batch was being placed, one being mixed and one being removed at the same time so that the mixers moved without interval from one to the other. Two gangs were worked, each mixing 64 batches of 0.75 cu. yd., or 48 cu. yds. of concrete per day at the following cost: Per Per Hand Mixing 9,000 Cu. Yds.-- day. cu. yd. 6 men wheeling materials $ 7.50 $0.16 8 men mixing 10.00 0.21 8 men wheeling away 10.00 0.21 6 men placing and ramming 7.50 0.16 1 pump man 1.25 0.02 1 waterboy 1.00 0.02 1 foreman 2.00 0.04 ------- ------- Totals $39.25 $0.82 The entire cost of plant for this work was about $500. _Machine Mixing and Placing._--The concrete was mixed in a 4-ft. cubical mixer operated by a 12 hp. engine which also hauled the material cars up the incline to the mixer. These cars passed by double track under the material bins where the compartments of the car body were filled through trap doors; they then passed the cement house where the cement was placed on the load, then up the incline to the mixer and dumped, and then empty down an opposite incline. Seven turns of the mixer mixed the charge which was discharged into iron tubs on cars hauled by horses to two derricks whose booms covered the work. One gang by day labor mixed and placed 168 batches of 0.7 cu. yd., or 117.6 cu. yds. per day at the following cost: Per Per Machine Mixing 4,000 Cu. Yds.-- day. cu. yd. 32 men at $1.25 $40.00 $0.34 1 pumpman 1.25 0.01 1 teamster and horse 2.00 0.02 2 waterboys at $1 2.00 0.02 1 engineman 1.70 0.02 1 derrickman 1.50 0.01 1 fireman 1.50 0.01 1 foreman 2.88 0.03 Fuel (cement barrels largely) 1.25 0.01 ------- ------- Totals $54.08 $0.47 The cost of the plant was about $5,000. [Illustration: Fig. 70.--Concrete Making Plant for Constructing Lock Walls, Cascades Canal.] ~LOCK WALLS, CASCADES CANAL.~--Four-fifths or 70,000 cu. yds. of lock masonry was concrete, the bulk of which was mixed and deposited by the plant shown by Fig. 70. The concrete was Portland cement, sand, gravel and broken stone. Cement was brought in in barrels by railway, stored and tested; from the store house the barrels were loaded onto cars and taken 250 ft. to a platform onto which the barrels were emptied and from which the cement was shoveled into the cement hopper and chuted to cars which took it to the charging hopper of the mixer. The stone was crushed from spalls and waste ends from the stone cutting yards, where stone for wall lining and coping and other special parts was prepared. These spalls and ends were brought in cars and dumped into the hopper of a No. 5 Gates crusher, with a capacity of 30 tons per hour. From the crusher the stone passed to a 2½-in. screen, the pieces passing going to a bin below and the rejections going to a smaller Blake crusher and thence to the bin. The dust and small particles were not screened out. The sand and gravel were obtained by screening and washing pit gravel. The gravel was excavated and brought in cars to the washer. This consisted of a steel cylinder 2 ft. 6½ ins. in diameter and about 18 ft. long, having an inclination of 1 in. per foot. An axial gudgeon supported the cylinder at the lower end and it rested on rollers at the other end and at an intermediate point. The gravel was fed by hopper and chute into the upper end and into this same end a 3-in. perforated pipe projected and extended to about mid-length of the cylinder. The cylinder shell was solid and provided with internal fins for about half its length from the feed end. For the remainder of its length nearly to the end, the shell was perforated with 2½-in. holes. For a length of 4 ft. beyond mid-point it was encircled by a concentric screen of 1/8-in. holes, and this screen for 3 ft. of its length was encircled by another screen of 30 meshes to the inch. The pit mixture fed into the cylinder was gradually passed along by the combined inclination and rotation, being washed and screened in the process. The sand fell into one bin and the gravel into another, and the waste water was carried away by a flume. The large stones passed out through openings at the lower end of the shell and were chuted into cars. The cars came to the mixer as clearly shown by Fig. 70. The stone and gravel cars were side dump and the cement car was bottom dump. The mixers were of the cube type 4 ft. on each edge and operated by a 7×12-in. double cylinder engine at nine revolutions per minute. The usual charge was 32 cu. ft. of the several ingredients, and it was found that 15 revolutions requiring about 1½ minutes were sufficient for mixing. The average work of one mixer was 17 batches or about 13 cu. yds. per hour, but this could be speeded up to 20 batches per hour when the materials were freely supplied and the output freely removed. Two cars took the concrete from the mixer to the hopper, from which it was fed to the work by chute. The hopper was mounted on a truck and the chute was a wrought iron cylinder trussed on four sides and having a 45° elbow at the lower end to prevent scattering. The chute fed into a car running along the wall and distributing the material. It was found impracticable to move the chute readily enough to permit of feeding the concrete directly into place. As the concreting progressed upward the trestle was extended and the chute shortened. It was found that wear would soon disable a steel chute so that the main trussed cylinder had a smaller, cheaply made cylinder placed inside as a lining to take the wear and be replaced when necessary. The plant described worked very successfully. Records based on 9,614.4 cu. yds. of concrete laid, gave the following: Cu. yds. Concrete mixed by hand 1,777.0 Concrete mixed by machine 7,837.4 Total concrete laid 9,614.4 Concrete placed by derricks 2,372.0 Concrete placed by chute 7,242.4 Concrete 1-2-4 mixture 156.0 Concrete 1-3-6 mixture 1,564.0 Concrete 1-4-8 mixture 6,892.0 The average mixture was 1 cement, 3.7 sand, 4.8 gravel and 2.6 broken stone. The average product was 1.241 cu. yds. concrete per barrel of cement and 1.116 cu. yds. of concrete per cubic yard of stone and gravel. The average materials for 1 cu. yd. of concrete were: Cement 0.805 bbl., sand 0.456 cu. yd., gravel 0.579 cu. yd., and stone 0.317 cu. yd. The cost of these 9,614.4 cu. yds. of concrete in place was: Hand Mixed and Placed by Derrick-- Per cu. yd. Labor mixing 1,777 cu. yds $1,072 Repairs, fuel, etc 0.016 ------- Total cost mixing $1,088 Labor placing 2,372 cu. yds. 0.6025 Fuel, tramways, etc. 0.1958 ------- Total cost placing $0.7983 Machine Mixed and Placed by Chute-- Labor mixing 7,837 cu. yds. $0.388 Repairs, fuel, etc 0.046 ------ Total cost mixing $0.434 Labor placing 7,242 cu. yds 0.414 Fuel, tramways, etc. 0.045 ------ Total cost placing $0.459 Materials and Supplies 9,614 cu. yds.-- Timbering $0.145 Cement 3.289 Sand and gravel 1.073 Broken stone 0.536 Cement testing, repairs, etc. 0.223 ------ Total $5,266 Plant and Superintendence, 9,614 Cu. Yds.-- Engineering, superintendence, repairs, etc. $1,508 20% cost of plant 0.165 ------ Total $1,673 The comparative cost of hand and machine mixing and handling was thus: Item-- Hand. Machine. Mixing per cu. yd. $1.088 $0.434 Placing per cu. yd. 0.798 0.459 Materials, etc., per cu. yd. 5.466 5.466 Plant, etc., per cu. yd. 1.673 1.673 ------ ------ Totals $9.025 $8.032 The average total costs of all the concrete placed were: Mixing per cu. yd. $0.555 Placing per cu. yd. 0.543 Materials per cu. yd. 5.266 Plant, etc., per cu. yd. 1.673 ------ Total $8.037 ~LOCKS, COOSA RIVER, ALABAMA.~--The following methods and costs are given by Mr. Charles Firth for constructing lock No. 31 for the Coosa River canalization, Alabama. This lock is 420 ft. long over all, 322 ft. between quoins, 52 ft. clear width, 14.7 ft. lift and 8 ft. depth of water on sills; it contained 20,000 cu. yds. of concrete requiring 21,500 bbls. cement, half Alsen and half Atlas. Figure 71 shows the concrete mixing plant, consisting of two 4×4 ft. cube mixer, driven by a 10×16-in. engine. The top floor of the mixer house stored the cement, 2,000 bbls. The concrete was a 1-3-5½ stone mixture. Each mixer charge consisted of 3 cu. ft. cement, 9 cu. ft. sand and 16.5 cu. ft. stone; the charge was turned over four times before and six times after watering at a speed not exceeding eight revolutions per minute. The average output of the plant was 200 cu. yds. per 8-hour day, or 100 cu. yds. per mixer, but it was limited by the means for placing. [Illustration: Fig. 71.--Concrete Mixing Plant for Lock Construction, Coosa River, Alabama.] The concrete was mixed dry, deposited in 6 to 8-in. layers, and rammed with 30-lb. iron rammers with 6-in. square faces. For all exposed surfaces a 6-in. facing of 1-3 mortar was placed by setting 2×12-in. planks 4 ins. from the laggings, being kept to distance by 2×4-in. spacers, placing and ramming the concrete behind them, then withdrawing them, filling the 6-in. space with mortar and tamping it to bond with the concrete. The walls were carried up in lifts, each lift being completed entirely around the lock before beginning the next; the first lift was 10.7 ft. high and the others 6 ft., except the last, which was 4.5 ft., exclusive of the 18-in. coping. The coping was constructed of separately molded blocks 3 ft. long, made of 1-2-3 concrete faced with 1-1 mortar and having edges rounded to 3 ins. radius. In constructing the forms a row of 6×8-in. posts 24 ft. long and 5 to 7 ft. apart was set up along the inside of each wall and a similar row of posts 12 ft. long was set up along the outside. From the tops of the short posts 6×8-in. caps reached across the wall and were bolted to the long posts; these caps carried the stringers for the concrete car tracks. The lagging consisted of 3×10-in. planks dressed on all sides. The backs of the walls were stepped and as each step was completed the rear 12-ft. posts were lifted to a footing on its top and carried in the necessary distance. The front posts remained undisturbed until the wall was completed. The lagging was moved up as the filling progressed. As no tie bolts were permitted, these forms required elaborate bracing. From the mixing plant, which was located on the bank above reach of floods, the concrete cars were dropped by elevator to the level of the track over the walls and then run along the wall and dumped onto platforms inside the forms and just below the track. This arrangement was adopted, because it was found that even a small drop separated the stone from the mortar. The concrete was shoveled from the platforms to place and rammed. The cars were bottom dumping with a single door hinged at the side; this door when swinging back struck the track stringers and jarred the form so that constant attention was necessary to keep it in line. It would have been much better to have had double doors swinging endwise of the car. Another point noted was that unless the track was high enough to give good head room at the close of a lift the placing and ramming were not well done. The cost of 8,710 cu. yds. of concrete placed during 1895 by day labor employing negroes at $1 per 8-hour day was as follows per cubic yard: 1 bbl. cement $2.48 0.88 cu. yd. stone at $0.76 0.67 0.36 cu. yd. sand at $0.34 0.12 Mixing, placing and ramming 0.88 Staging and forms 0.42 ---- Total $4.57 ~LOCK WALLS, ILLINOIS & MISSISSIPPI CANAL.~--The locks and practically all other masonry for the Illinois & Mississippi Canal are of concrete. The following account of the methods and cost of doing this concrete work is taken from information published by Mr. J. W. Woermann in 1894 and special information furnished by letter. The decision to use concrete was induced by the fact that no suitable stone for masonry was readily available (the local stone was a flinty limestone, usually without bed, or, at best, in thin irregular strata, and cracked in all directions with the cracks filled with fire clay) while good sand and gravel and good stone for crushing were plentifully at hand. The concrete work done in 1893-4 comprised dam abutments, piers for Taintor gates and locks. _Dam Abutments._--Four dam abutments were constructed, three of which were L-shaped, with sides next to the river 40 ft. long and sides extending into the banks 20 ft. long; the top thickness was 3 ft., the faces were vertical and the backs stepped with treads of 14 to 16 ins., and the width of base was 0.4 of the height. Each of these abutments was built in four 30-cu. yd. sections, each section being a day's work. The forms consisted of 2×8-in. planks, dressed on both sides, 2×8-in. studs spaced 2 ft. on centers and 4×6-in. braces. For the first two of the four abutments, the forms were erected in sections, the alternate sections being first erected and filled. When these sections had hardened the forms were shifted to the vacant sections and lined up to and braced against the completed sections. This method did not give well aligned walls, so in subsequent work the forms were erected all at once. The concrete was mixed by hand. The sand and cement were mixed dry, being turned four times and spread in a layer Pebbles and broken stone previously wetted were spread over the sand and cement and the whole turned four times, the last turn being into wheelbarrows; about five common buckets of water were added during the mixing. The mixture sought was one that would ram without quaking. Two forms of rammers were used; for work next to forms a 4×6-in. rammer and for inside work 6-in diameter circular rammer weighing 20 lbs. The gang mixing and placing concrete consisted usually of: Item. Per Day. Per Cu. Yd. 2 handling cement and sand $ 3.00 $0.10 3 filling barrows with aggregate 4.50 0.15 8 mixing concrete 12.00 0.40 2 shoveling concrete into barrows 3.00 0.10 5 wheeling concrete to forms 7.50 0.25 1 spreading concrete 1.50 0.05 5 tamping concrete 7.50 0.25 ------ ----- Total, 26 men $39.00 $1.30 These cubic yard costs are based on 30 cu. yds. of wall completed per 8-hour day. The cost in detail of two abutments containing 254 cu. yds. was per cubic yard as follows: Item. Per Cu. Yd. 1.65 bbls. Portland (Germania) cement $ 5.60 0.5 cu. yd. crushed stone 2.07 0.24 cu. yd. gravel 0.59 0.53 cu. yd. sand 0.24 Lumber, forms, warehouses, platforms[D] 0.55 Carpenter work[E] ($9 per M.) 1.10 Mixing and placing 1.47 20 per cent. first cost of plant 0.31 Engineering and miscellanies 0.31 ------ Total $12.24 [Footnote D: Charging ¼ of first cost of $18 per M. ft.] [Footnote E: Carpenters $3.50, laborers $1.50 per day; there was one laborer to two carpenters.] The large amount of cement 1.65 bbls. per cubic yard was due to facing the abutments with 8 ins. of 1-2 mortar. The concrete in the body of the wall was 1 cement, 2 sand, 2 gravel and 2 broken stone mixture. A dry mixture was used and this fact is reflected in the cost of ramming, 25 cts. per cu. yd. The cost of mixing was also high. [Illustration: Fig. 72.--Concrete Mixing Plant for Lock Walls, Illinois & Mississippi Canal.] _Piers for Taintor Gates._--The masonry at this point consisted of three piers 6×30 ft., and two abutments 30 ft. long, 6 ft. thick at base and 4 ft. thick at top, with wing walls; it amounted to 460 cu. yds. The feet of the inclined braces were set into gains in the horizontal braces and held by an 8-in. lag screw; after the posts were plumbed a block was lag-screwed at the upper end of each brace. These forms proved entirely satisfactory. The cost of the work per cubic yard was as follows: Item. Per Cu. Yd. 1.45 bbls. Portland cement $4.330 0.55 cu. yd. crushed stone 0.604 0.252 cu. yd. pebbles 0.328 0.465 cu. yd. sand 0.419 40,000 ft. B. M. lumber (¼ cost of $16 per M.) 0.348 Carpenter work on forms 0.780 Mixing and placing concrete 1.909 20 per cent. cost of plant 0.090 Miscellaneous 0.182 ----- Total $8.99 _Mixing Plant._--The concrete for all the lock work of 1893-4 was mixed by the plant shown by Figs. 72 and 73. The mixer plant proper consisted of a king truss carried by two A-frames of unequal height; under the higher end of the truss was a frame carrying a 4-ft. cubical mixer and under the lower end a pit for a charging box holding 40 cu. ft. This charging box was hoisted by ½-in. steel cable running through a pair of double blocks as shown; the slope of the lower chord of the truss was such that the cable hoisted the box and carried it forward without the use of any latching devices. On two sides of the pit were tracks from the sand and stone piles and on the other two sides were the cement platform and water tank. The charging box dumped into the hopper above the mixer and the mixer discharged into cars underneath. A 15-HP. engine operated the hoist by one pulley and the mixer by the other pulley. Nine revolutions of the mixer made a perfect mixture. The plant as illustrated was slightly changed as the result of experience in constructing the guard lock. The charging hopper was lowered 6 ins. and the space between the mixer and lower platform reduced by 9 ins.; diagonal braces were also inserted under the timbers carrying the mixer axles. This plant cost for framing and erection $300 and for machinery delivered $706. The crushing plant shown by Fig. 73 consisted of a No. 2 Gates crusher delivering to a bucket elevator. [Illustration: Fig. 73.--Stone Crushing Plant for Lock Walls, Illinois & Mississippi Canal.] [Illustration: Fig. 74.--Forms for Guard Lock, Illinois & Mississippi Canal.] _Guard Lock._--The forms employed in constructing the guard lock are shown by Fig. 74, and in this drawing the trestle and platform for the concrete cars are to be noted. The walls were concreted in sections. A batch of concrete consisted of 1 bbl. cement, 10 cu. ft. sand and 20 cu. ft. crushed stone. The average run per 8-hour day was 40 batches of facing and 60 batches concrete, representing 100 bbls. cement. The gang worked was as follows: 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 (¼th 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 [Illustration: Fig. 75.--Forms for Regular Lock Walls, Illinois & Mississippi Canal.] _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 (¼th 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.