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:
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 |