CHAPTER XIV.

METHODS AND COST OF CONSTRUCTING CONCRETE FOUNDATIONS FOR PAVEMENTS. Contractor's skill or want of skill in systematizing and managing labor counts as high in street work as in any class of concrete construction. As previously demonstrated, the cost of mixing is a very small portion of the labor cost of concrete in place; the costs of getting the materials to the mixer and the mixed concrete to the work are the big items, and in street work the opportunity for increasing the cost of these items through mismanagement is magnified by the large area of operations involved per cubic yard of concrete placed. One cubic yard of concrete makes 6 sq. yds. of 6-in. pavement foundations and 100 cu. yds. of concrete make a 6-in. foundation for 300 ft. of 30-ft. street, while 4 to 5 cu. yds. will build 100 ft. of ordinary curb and gutter. Thus the haulage per cubic yard is considerable at best, and lack of plan in distributing stock piles and handling the concrete can easily result in such increased haulage expenses as to change a possible profit into a certain loss. A little thought and skill in planning street work pays a good profit. ~MIXTURES EMPLOYED.~--A comparatively lean concrete will serve for pavement foundations; mixtures of 1-4-8 Portland cement or 1-2-5 natural cement are amply good and it is folly, ordinarily, to employ richer mixtures. Until recently, natural cement has been used almost exclusively; a 1-2-5 natural cement mixture requires about 1.15 bbls. of cement per cubic yard of concrete. A 1-4-8 Portland cement mixture requires about 0.7 bbl. of cement per cubic yard. In the opinion of the authors a considerably leaner mixture of Portland concrete is sufficiently good when it is well mixed in machine mixers--for a 6-in., foundation 0.5 bbl. per cu. yd. The mixtures actually employed are proportioned about as stated and their cost, or that of any other common mixture, may easily be computed from Tables XII and XIII, giving for different mixtures the quantities of cement, sand and stone per cubic yard of concrete; the product of these quantities and the local prices of materials in the stock piles gives the cost. When the concrete is mixed by hand the ordinary labor cost of foundations is 0.4 to 0.5 of a 10-hour day's wages per cubic yard of concrete; occasionally it may be as low as 0.3 of a day's wages where two mixing gangs are worked side by side under different foremen and with an exacting contractor. Data for machine mixing are too few to permit a similar general statement for machine work, but in one case coming under the authors' observation, the cost figured out to a little less than 0.2 of a day's wages per cubic yard. ~DISTRIBUTION OF STOCK PILES.~--Assuming a 30-ft. street and a 1-3-5 concrete laid 6 ins. thick, the quantities of concrete materials required per lineal foot of street are: Cement 0.60 bbl., sand 0.27 cu. yd., stone 0.44 cu. yd. The stock piles should be so distributed that each supplies enough materials for a section of foundation reaching half way to the next adjacent stock pile on each side, and they should not contain more or less material, otherwise a surplus remains to be cleaned up or a deficiency to be supplied by borrowing from another pile. A little care will ensure the proper distribution and it is well paid for in money saved by not rehandling surplus or borrowed materials. For a given mixture and a given width and thickness of foundation, the sizes of the stock piles are determined by their distance apart and this will depend upon whether hand or machine mixing is employed and upon the means adopted for hauling the raw materials and the mixed concrete. It is worth while always in stock piles of any size, to lay a flooring of plank particularly under the stone pile; if dumped directly on the ground it costs half as much again to handle stone. Current practice warrants everything from a continuous bank, to piles from 1,000 to 1,500 ft. apart, in the spacing of stock piles. ~HINTS ON HAND MIXING.~--All but a small percentage of the concrete annually laid in street work is hand mixed. The authors are confident that this condition will disappear as contractors learn more of the advantages of machine mixing, but it prevails at present. The general economics of hand mixing are discussed in Chapter II; in street work as before stated, the big items of labor cost are the costs of handling materials and the data in Chapter II on these processes deserve special attention. It is particularly worth noting that it is seldom economical to handle materials in shovels where carrying is necessary; it is a common thing in street work to see an attempt to get the stock piles so close to the mixing board that the material can be handled with shovels, and this is nearly always an economic error. Street work is readily measured; in fact, its progress can be seen at a glance, and advantage can often be taken of this fact to profit by the rivalry of separate gangs. The authors have known of the labor costs being reduced as much as 25 per cent., due to pitting one gang against another where each could see the progress made by the other. ~METHODS OF MACHINE MIXING.~--Concrete mixers have been slow to replace handwork in laying pavement foundations. In explanation of this fact it is asserted: (1) That frequent shifting of the mixer causes too much lost time, and (2) that the principal item of labor cost in street work is the conveying of materials to and from the mixer, and this item is the same whether hand or machine mixing be employed. The records of machine mixer work given elsewhere in this chapter go far, in the opinion of the authors, toward disproving the accuracy of both assertions. If the machine used and the methods of work employed are adapted to the conditions of street work, machine mixing can be employed to decided advantage. A continuous and large output is demanded in a mixer for street work; the perfection of the mixing is within limits a minor consideration. This at once admits for consideration types of mixers whose product is classed as unsuitable for reinforced concrete work, and also admits of speeding up the output of the better types to a point beyond that at which they turn out their most perfect product. Keeping these facts in mind either of the following two systems of work may be employed: (1) Traction plants which travel with the work and deposit concrete in place, or so nearly in place that little shoveling is necessary; (2) portable plants which are set up at wide intervals along the work and which discharge the concrete into carts or dump wagons which distribute it to the work. The secret of economic work with plants of the class cited first is the distribution of the stock piles so as practically to eliminate haulage from stock pile to mixer. The mixer backs away from the work, its discharge end being toward the work and its charging end away from it. Then deposit the materials so as to form a continuous stock pile along the center of the street; the mixer moving backward from the completed foundation keeps close to the materials and if the latter are uniformly distributed in the pile the great bulk of the charging is done by shoveling direct into the charging bucket. The point to be watched here is that the shovelers do not have to carry the materials; separate stock piles within moderate hauling distance by wheelbarrows are a far more economic arrangement than a continuous pile so irregularly distributed that much of the material has to be carried even a few paces in shovels. Economic work with plants of the second class depends upon efficient and adequate means of hauling the mixed concrete to the work. The plant should not be shifted oftener than once in 1,000 to 2,000 ft., or, say, four city blocks. This does away with the possibility of wheelbarrow haulage; large capacity hand or horse carts must be employed. With 6 cu. ft. hand carts, such as the Ransome cart, a haul of 500 ft. each way from the mixer is possible and with horse carts, such as the Briggs, this economic distance is increased to 1,000 ft. each way from the mixer. The mixer must be close to the stock pile and it will pay to make use of improved charging devices. A 6-in. foundation for 2,000 ft. of 30-ft. street calls for 667 cu. yds. of concrete, and if both sides are curbed at the same time, 100 cu. yds. more are added, or 767 cu. yds. in all; where intersecting streets are to be paved in both directions from the mixer plant these amounts are doubled. A very small saving per cubic yard due to mechanical handling of the materials to the mixer amounts to the interest on a considerable investment in such plant. A point that should not be forgotten is that carts such as those named above spread the concrete in dumping so that little or no shoveling is required. ~FOUNDATION FOR STONE BLOCK PAVEMENT, NEW YORK, N. Y.~--Mr. G. W. Tillson, in "Street Pavements and Paving Materials," p. 204, gives the following data on the cost of granite block pavement in New York City in 1899. The day was 10 hours long: Per Per Per Concrete gang-- day. sq. yd. cu. yd. 1 foreman $ 3.00 $0.0125 $0.075 8 mixers on two boards, at $1.25 10.00 0.0416 0.250 4 wheeling stone and sand, at $1.25. 5.00 0.0208 0.125 1 carrying cement and supplying water, at $1.25 1.25 0.0051 0.031 1 ramming, at $1.25 1.25 0.0051 0.031 ------ ------- ------ Total, 240 sq. yds. (40 cu. yds.). $20.50 $0.0851 $0.512 The concrete was shoveled direct from the mixing boards to place. Cost 1-2-4 concrete-- Per cu. yd. 1-1/3 bbls. natural cement, at $0.90 $1.20 0.95 cu. yd. stone, at $1.25 1.19 0.37 cu. yd. sand, at $1.00 0.37 Labor 0.51 ----- $3.27 In laying 5,167 sq. yds. of granite block pavement on one job in New York City in 1905, the authors' records show that one laborer mixed and laid 1.3 cu. yds. of concrete per day in a 6-in. foundation; this is a very small output. The work was done by contract and the labor cost was as follows: Per Per Item. Total. sq. yd. cu. yd. 28½ days foreman at $3.50 $ 99.75 $0.0193 $0.118 399 days laborers at $1.75 698.25 0.1351 0.826 ------- ------- ------ $798.00 $0.1544 $0.944 The average day's wages was $1.86, so that the labor cost was about 0.5 of a day's wages per cubic yard of concrete. ~FOUNDATION FOR PAVEMENT, NEW ORLEANS. LA.~--Mr. Alfred E. Harley states that in laying concrete foundations for street pavement in New Orleans, a day's work, in running three mixing boards, covering the full width of the street, averaged 900 sq. yds., 6 ins. thick, or 150 cu. yds., with a gang of 40 men. With wages assumed to be 15 cts. per hour the labor cost was: Cts. per cu. yd. 6 men wheeling broken stone 6 3 men wheeling sand 3 1 man wheeling cement 1 2 men opening cement 2 7 men dry mixing 7 8 men taking concrete off 8 3 men tamping 3 3 men grading concrete 3 1 man attending run planks 1 3 water boys 1 2 extra men and 1 foreman 4 -- Total labor cost 39 cts. ~FOUNDATIONS FOR STREET PAVEMENT, TORONTO, CANADA.~--The following cost of a concrete base for pavements at Toronto has been abstracted from a report (1892) of the City Engineer, Mr. Granville C. Cunningham. The concrete was 1-2½-7½ Portland; 2,430 cu. yds. were laid, the thickness being 6 ins., at the following cost per cubic yard: 0.77 bbl. cement, at $2.78 $2.14 0.76 cu. yd. stone, at $1.91 1.45 0.27 cu. yd. sand and gravel, at $0.80 0.22 Labor (15 cts. per hr) 1.03 ----- Total $4.84 Judging by the low percentage of stone in so lean a mixture as the above, the concrete was not fully 6 ins. thick as assumed by Mr. Cunningham. Note that the labor cost was 1½ to 2 times what it would have been under a good contractor. ~MISCELLANEOUS EXAMPLES OF PAVEMENT FOUNDATION WORK.~--The following records of pavement foundation work are taken from the note and time books of one of the authors: _Case 1._--Laying 6-in. pavement foundation; stone delivered and dumped upon 2-in. plank laid to receive it. Sand and stone were dumped along the street, so that the haul in wheelbarrows to mixing board Was about 40 ft. Two gangs of men worked under separate foremen, and each gang averaged 4.5 cu. yds. concrete per hour. The labor cost was as follows for 45 cu. yds. per gang: Per day. Per cu. yd. 4 men filling barrows with stone and sand ready for the mixers, wages 15 cts. per hour $6.00 $0.13 10 men, wheeling, mixing and shoveling to place (3 or 4 steps), wages 15 cts. per hour 15.00 0.33 2 men ramming, wages 15 cts. per hour 3.00 0.07 1 foreman at 30 cts. per hour and 1 water boy, 5 cts 3.50 0.08 ----- ----- Total $27.50 $0.61 _Case II._--Sometimes it is desirable to know every minute detail cost, for which purpose the following is given: ----Per cu. yd.---- Day's labor. Cost. 3 men loading stones into barrows $0.06 $0.09 1 man loading sand into barrows 0.02 0.03 2 men ramming 0.04 0.06 1 foreman and 1 water boy equivalent to 0.035 0.05 Wheeling sand and cement to mixing board 0.02 0.03 Wheeling stone to mixing board 0.026 0.04 9 men mixing mortar 0.013 0.02 Mixing stone and mortar 0.049 0.07 Placing concrete (walking 15 ft.) 0.072 0.11 ------ ----- Total $0.335 $0.50 In one respect this is not a perfectly fair example (although it represents ordinary practice), for the mortar was only turned over once in mixing instead of three times, and the stone was turned only twice instead of three or four times. Water was used in great abundance, and by its puddling action probably secured a very fair mixture of cement and sand, and in that way secured a better mixture than would be expected from the small amount of labor expended in actual mixing. About 9 cts. more per cu. yd. spent in mixing would have secured a perfect concrete without trusting to the water. _Case III._--Two gangs (34 men) working under separate foremen averaged 600 sq. yds., or 100 cu. yds. of concrete per 10-hour day for a season. This is equivalent to 3 cu. yds. per man per day. The stone and sand were wheeled to the mixing board in barrows, mixed and shoveled to place. Each gang was organized as follows: Per day. Per cu. yd. 4 men loading barrows $ 6.00 $0.12 9 men mixing and placing 13.50 0.27 2 men tamping 3.00 0.06 1 foreman 2.50 0.05 ------ ----- Total $25.00 $0.50 These men worked with great rapidity. The above cost of 50 cts. per cu. yd. is about as low as any contractor can reasonably expect to mix and place concrete by hand in pavement work. _Case IV._--Two gangs of men, 34 in all, working side by side on separate mixing boards, averaged 720 sq. yds., or 120 cu. yds., per 10-hour day. Each gang was organized as follows: Per day. Per cu. yd. 6 men loading and wheeling $ 9.00 $0.15 8 men mixing and placing 12.00 0.20 2 men tamping 3.00 0.05 1 foreman 3.00 0.05 ------ ----- Total $27.00 $0.45 Instead of shoveling the concrete from the mixing board into place, the mixers loaded it into barrows and wheeled it to place. The men worked with great rapidity. Mr. Irving E. Howe gives the cost of a 6-in. foundation of 1-3-5 natural cement at Minneapolis, Minn., in 1897, as $2.80 per cu. yd., or $0.467 per sq. yd. Cement cost 76 cts. per barrel and stone and sand cost delivered $1.15 and 30 cts. respectively. Mixers received $1.75 per day. Mr. Niles Meriwether gives the cost of materials and labor for an 8-in. foundation constructed by day labor (probably colored) at Memphis, Tenn., in 1893, as follows: Per sq. yd. Natural cement at $0.74 per bbl $0.195 Sand at $1.25 per cu. yd 0.075 Stone at $1.87 per cu. yd 0.355 Labor mixing and placing 0.155 ----- Total $0.780 Labor was paid $1.25 to $1.50 per 8-hour day and 1.16 bbls. of cement were used per cubic yard of concrete. The cost of materials, as will be noted, was high and the labor seems to have been inefficient. ~FOUNDATIONS FOR BRICK PAVEMENT, CHAMPAIGN, ILL.~--The concrete foundation for a brick pavement constructed in 1903 was 6 ins. thick; the concrete used was composed of 1 part natural cement, 3 parts of sand and gravel, and 3 parts of broken stone. All the materials were mixed with shovels, and were thrown into place from the board upon which the mixing was done. The material was brought to the steel mixing board in wheelbarrows from piles where it had been placed in the middle of the street, the length of haul being usually from 30 to 60 ft. The foundation was 6 ins. thick and it cost as follows for materials and labor: Cost per cu. yd. 1.2 bbls. cement, at $0.50 $0.600 0.6 cu. yd. sand and gravel, at $1 0.600 0.6 cu. yd. broken stone, at $1.40 0.840 6 men turning with shovels, at $2 0.080 4 men throwing into place, at $2 0.053 2 men handling cement, at $1.75 0.023 1 man wetting with hose, at $1.75 0.012 2 men tamping, at $1.75 0.023 1 man leveling, at $1.75 0.012 6 men wheeling stone, at $1.75 0.070 4 men wheeling gravel, at $1.75 0.047 1 foreman, at $4 0.027 ------ $2.387 This is practically 40 cts. per sq. yd., or $2.40 per cu. yd. of concrete for materials and labor. It is evident from the above quantities that a cement barrel was assumed to hold about 4.5 cu. ft., hence the cement was measured loose in making the 1-3-3 concrete. The accuracy of the quantities given is open to serious doubt. It will also be noted that the labor cost of making and placing the concrete was only 35 cts. per cu. yd., wages being nearly $1.85 per day. This is so remarkably low that some mistake would seem to have been made in the measurement of the work. The authors do not hesitate to say that no gang of men ever made any considerable amount of concrete by hand at the rate of 5.75 cu. yds. per man per day. [Illustration: Fig. 112.--Foote Continuous Mixer Arranged for Pavement Foundation Work.] ~FOUNDATION CONSTRUCTION USING CONTINUOUS MIXERS.~--The following are records of two jobs of pavement foundation work using continuous mixers with one-horse concrete carts in one instance and wheelbarrows in the other instance. The mixer used was the Foote mixer, as arranged for the work being described it is shown by Fig. 112. One particular advantage of this and similar mixers for street work is that no proportioning or measuring of the materials is required of the men. The mixers are provided with an automatic measuring device, by means of which any desired proportion of cement, sand and stone is delivered to the mixing trough. The mixer is mounted on trucks, and the hoppers that receive the sand and stone are comparatively low down. The sand can be wheeled in barrows up a run plank and dumped into a hopper on one side of the mixer, and in like manner the gravel or broken stone can be delivered into a hopper on the other side. The cement is delivered in bags or buckets to a man who dumps it into a cement hopper directly over the mixer. All that the operator needs to attend to is to see that the men keep the hoppers comparatively full. The records of work on the two jobs mentioned are as follows: [Illustration: Fig: 113.--Briggs Cart Distributing Concrete for Pavement Foundation.] _Job I._--The sand was delivered from the stock pile by a team hitched to a drag scraper, and was dumped alongside the mixer where two men shoveled it into the hopper. On the same job the concrete was hauled away from the mixer in Briggs' concrete carts. With a gang of 30 men and 2 to 4 horses hauling concrete in Briggs' carts, the contractor averaged 1,200 sq. yds., or 200 cu. yds., per day of 10 hours. With wages of laborers at 15 cts. per hour, and a single horse at the same rate, the cost of labor was 26 cts. per cu. yd., or less than 4½ cts. per sq. yd. of concrete base 6 ins. thick. The coal was a nominal item, and did not add 1 ct. per cu. yd. to the cost. In this case the mixer was set up on a side street and the concrete was hauled in the carts for a distance of a block each way from the mixer. At first four carts were used, but as the concreting approached the mixer, less hauling was required, and finally only two carts were used. An illustration of a Briggs cart is given by Fig. 113; it is hauled by one horse, which the driver leads, and is dumped by an ingenious device operated from the horse's head. The cart dumps from the bottom and spreads the load in a layer about 8 or 9 ins. thick, so that no greater amount of shoveling is necessary than when barrows are used. It took about 20 seconds for the cart to back up and get its load and about 5 seconds to dump and spread the load. _Job II._--In this job the mixer was charged with wheelbarrows and wheelbarrows were also employed to take the mixed concrete to the work, the mixer being moved forward at frequent intervals. The stock piles were continuous, sand on one side of the street and stone on the other side. A 1-3-6 Portland cement concrete was used, a very rich mixture for a 6-in. foundation. The organization of the working gang was as follows: Men loading and wheeling gravel 8 Men assisting in loading gravel 2 Man dumping barrows into hopper 1 Men loading and wheeling sand 3 Man dumping barrows into hopper 1 Men wheeling concrete in barrows 7 Men spreading concrete 3 Men tamping concrete 2 Man pouring cement into hopper 1 Man operating mixer 1 Man shoveling spilled concrete 1 Man opening cement bags 1 Engineer 1 -- Total men in gang 32 The average day's output of this gang was 150 cu. yds., or 900 sq. yds. in 8 hours; but on the best day's work the output was 200 cu. yds., or 1,200 sq. yds. in 8 hours, which is a remarkable record for 32 men and a mixer working only 8 hours. The following is the labor cost of 8,896 sq. yds. of 4½-in. concrete foundation for an asphalt pavement constructed in New York City in 1904: Item. Per sq yd. Foreman at $3.75 $0.030 Laborers at $1.50 0.242 Teams at $5 0.040 Steam engine at $3.50 0.028 ------ Total $0.340 The concrete was a 1-3-6 mixture and was mixed in a Foote mixer. These costs are compiled from data collected by the authors. ~FOUNDATION CONSTRUCTION FOR STREET RAILWAY TRACK USING CONTINUOUS MIXERS.~--The following account of the methods and cost of constructing a concrete foundation for street railway track at St. Louis, Mo., is compiled from information published by Mr. Richard McCulloch. The work was done by day labor by the United Railways Co., in 1906. Figure 114 shows the concrete construction. A 1-2½-6½ Portland cement, broken stone concrete mixed by machine was used. [Illustration: Fig. 114.--Concrete Foundation for Street Railway Track.] The material for the concrete was distributed on the street beside the tracks in advance of the machine, the sand being first deposited, then the crushed rock piled on that, and finally the cement sacks emptied on top of this pile. The materials were shoveled from this pile into the concrete mixing machine without any attempt at hand mixing on the street. Great care was taken in the delivery of materials on the street to have exactly the proper quantity of sand, rock and cement, so that there would be enough for the ballasting of the track to the proper height and that none would be left over. Each car was marked with its capacity in cubic feet, and each receiver was furnished with a table by which he could easily estimate the number of lineal feet of track over which the load should be distributed. The concrete mixing machines were designed and built in the shops of the United Railways Co. Three machines were used in this work, one for each gang. The machine is composed of a Drake continuous worm mixer, fed by a chain dragging in a cast-iron trough. The trough is 36 ft. long, so that there is room for 14 men to shovel into it. Water is sprayed into the worm after the materials are mixed dry. This water was obtained from the fire plugs along the route. In the first machine built, the Drake mixer was 8 ft. long. In the two newer machines the mixer was 10 ft. long. Both the conveyor and the mixer were motor driven, current being obtained for this purpose from the trolley wire overhead. Two types of machines were used, one in which the conveyor trough was straight and 45 in. above the rail, and the other in which the conveyor trough was lowered back of the mixer, being 25 in. above the rail. The latter type had the advantage of not requiring such a lift in shoveling, but the trough is so low that a motor truck cannot be placed underneath it. In the high machine the mixer is moved forward by a standard motor truck under the conveyor. In the low machine the mixer is moved by a ratchet and gear on the truck underneath the mixer. A crew of 27 men is required to work each machine, and under average conditions concrete for 80 lin. ft. of single track, amounting to 22 cu. yds., can be discharged per hour. The costs of the concrete materials delivered per cubic yard of concrete were: Cement, per barrel, $1.70; sand, per cu. yd., $0.675, and stone, per cu. yd., $0.425. The cost of the concrete work per cubic yard and per lineal foot of track was as follows: Item. Per lin. ft. Per cu. yd. Concrete materials $0.791 $2.92 Labor mixing and placing 0.071 0.26 ------ ----- Total labor and materials $0.862 $3.18 ~FOUNDATION CONSTRUCTION USING BATCH MIXERS AND WAGON HAULAGE, ST. LOUIS, MO.~--The following record of the method and cost of laying a concrete foundation for street pavement using machine mixing and wagon haulage is given by Mr. D. A. Fisher. The foundation was 6 ins. thick. The gravel was dumped from wagons into a large hopper, raised by a bucket elevator into bins, and drawn off through gates into receiving hoppers on the charging platform where the cement was added. The receiving hoppers discharged into the mixers, which discharged the mixed concrete into a loading car that dumped into wagons, which delivered it on the street where wanted. The longest haul in wagons was 30 mins., but careful tests showed that the concrete had hardened well. The wagons were patent dump wagons of the drop-bottom type. Mr. Fisher says: "You may consider the following figures a fair average of the plant referred to, working to its capacity. To these amounts, however, must be added the interest on the investment, the cost of wrecking the plant and the depreciation of the same, superintendence, and the pay roll that must be maintained in wet weather. I am assuming the street as already brought to grade and rolled. "With labor at $1.75 per day of 10 hours, teams at $4, engineer and foremen at $3, and engine at $5 per day, concrete mixed and put in place by the above method costs: Per cu. yd. To mix $0.12 to $0.15 To deliver to street 0.10 to 0.14 To spread and tamp in place 0.08 to 0.11 -------------- Total $0.30 to $0.40 "The mixers are No. 2½ Smith, sold by the Contractors' Supply Co., Chicago, Ill., and a ½ yd. cube, sold by Municipal Engineering & Contracting Co., Chicago. "The above figures are on the basis of a batch every 2 minutes, which is easily maintained by using the loading car, as by this means there will be no delay in the operation of the plant owing to the irregularity of the arrival of the teams. "My experience leads me to believe that a better efficiency can be obtained by using mixers of 1 cu. yd. capacity, and that the batch mixer is the only type of machine where any certainty of the proportion of the mixture is realized." [Illustration: Fig. 115.--Chicago Improved Cube Traction Mixer for Pavement Foundation.] ~FOUNDATION CONSTRUCTION USING A TRACTION MIXER.~--In laying a 6-in. foundation for an asphalt pavement in Buffalo, N. Y., an average of 100 sq. yds., or 16.6 cu. yds., of concrete in place was made per hour using the traction mixer shown by Fig. 115. This mixer was made by the Municipal Engineering & Contracting Co., of Chicago, Ill., and consisted of one of that company's improved cube mixers operated by a gasoline engine and equipped with the regulation mechanical charging device and also with a swinging conveyor to deliver the mixed concrete to the work. The feature of the apparatus in its application to paving work is the conveyor. This was 25 ft. long and pivoted at the mixer end so as to swing through an arc of 170°. The mixer discharged into a skip or bucket traveling on the conveyor frame and discharging over the end spreading its load anywhere within a radius of 25 ft. In operation the mixer traveled along the center of the street, backing away from the finished foundation and toward the stock pile, which was continuous and was deposited along the center of the street. The bulk of the sand and stone was thus shoveled direct into the charging bucket and the remainder was wheeled to the bucket in barrows. As the charging bucket is only 14 ins. high the barrows could be dumped directly into it from the ground. The gang worked was 17 including a foreman and one boy, and with this gang 100 sq. yds. of 6-in. foundation was laid per hour. Assuming an average wage of 20 cts. an hour the cost of mixing and placing the foundation concrete was 3.4 cts. per sq. yd. or 20.4 cts. per cu. yd. for labor alone. ~FOUNDATION CONSTRUCTION USING CONTINUOUS MIXER.~--The foundation was 6 ins. thick for an asphalt pavement and was laid in Chicago, Ill. The concrete used was exceptionally rich for pavement foundation work, it being a 1-3-6 Lehigh Portland cement, broken stone mixture. The mixing was done by machine, a mixer made by the Buffalo Concrete Mixer Co., Buffalo, N. Y., being used. This mixer was equipped with an elevating charging hopper and was operated as a continuous mixer. The mixer was mounted on wheels and was pulled along the center of the street ahead of the work with its discharge end toward the work. Moves of about 25 to 30 ft. were made, the mixer being pulled ahead for this distance each time that the concrete came up to its discharge end. The stock piles were continuous, sand on one side and stone on the other side of the street. Cement was stored in a pile at each end of the block. All materials were wheeled from stock piles to mixer in wheelbarrows. The men wheeling sand and stone loaded their own barrows, wheeled them to the mixer and discharged them directly into the elevating hopper. No runways were used, the barrows being wheeled directly on the ground. The cement was brought in barrows, two or three bags being a load, and dumped alongside a cement box which was located close to and at one side of the elevating hopper. A man untied the bags and emptied them into the cement box and another man scooped the cement out of the box in bucketfuls and emptied it over the sand and stone in the elevating hopper. The mixer discharged onto a sheet iron shoveling board, and the concrete was carried in shovels from shoveling board to place, the length of carry being a maximum of 25 to 30 ft. Two men were required to pull down the cone of concrete at the discharge end of the mixer and to keep the stone from separating and rolling down the sides. The gang was organized as follows: No. Men. Loading and wheeling stone 10 Loading and wheeling sand 3 to 4 Loading and wheeling cement 2 Untieing and emptying cement bags 1 Charging cement to hopper 1 Operating mixer and hopper 1 Pulling down and tending discharge 2 Carrying concrete in shovels 8 Spreading concrete 2 Tamping concrete 2 Sweeping concrete 1 General laborers 3 Foreman 1 Watchman 1 Timekeeper 1 -- Total gang 40 This gang averaged 1,000 sq. yds. of 6-in. foundation per 10-hour day; a maximum of 1,400 sq. yds. was laid in a day. We have thus an average of 167 cu. yds. and a maximum of 234 cu. yds. of concrete foundation mixed and placed per 10-hour day. At an average wage of $2 per day the average labor cost of mixing and placing concrete was 48 cts. per cu. yd. or 8 cts. per sq. yd. of 6-in. foundation. It was stated that the gang was larger by three men than was ordinarily used owing to certain extra work being done at the time that the above figures were collected. Taking out three extra men and the timekeeper and watchman we get 34 men actually working in mixing and placing concrete. This reduced gang gives us a labor cost for mixing and placing of about 41 cts. per cu. yd. or 6.8 cts. per sq. yd. of 6-in. foundation. ~FOUNDATION CONSTRUCTION USING A BATCH MIXER.~--The following figures are an average of several jobs using a Ransome ½-cu. yd. mixer for constructing 6-in. foundations. The mixer was moved 1,000 ft. at a time and the work conducted 500 ft. in each direction from each station. The concrete materials were delivered from stock pile to mixer in wheelbarrows and the mixed concrete was hauled to the work in two-wheeled Ransome carts. Run planks were laid for the carts and one man readily pushed a cart holding 6 cu. ft. The men had to work fast on the long haul but had an easy time when the haul was short. The organization of the gang was as follows, wages being $1.50 per day: 10 men loading and wheeling stone $15.00 4 men loading and wheeling sand 6.00 2 men handling cement 3.00 1 fireman 2.00 1 man dumping mixer 1.50 5 men wheeling carts 7.50 3 men spreading and ramming 4.50 1 foreman 3.50 ------ Total wages per day $43.00 This gang averaged 1,080 sq. yds. of 6-in. foundation or 180 cu. yds. of concrete in place per day which gives a labor cost of 24 cts per cu. yd. or 4 cts. per sq. yd. for mixing and placing.