In placing mass concrete in large work, the labor costs may be materially reduced where machinery is used for mixing and handling the concrete. Costs from 60 to 75 cents per cubic yard are not uncommon.
In reinforced concrete structural work, the placing of concrete is more expensive than ordinary work mentioned above, and the labor cost of mixing and placing concrete may be from $1.50 to $2 per cubic yard—figures which will vary with the difficulty of spading and compacting in the forms, and with the means of distribution over the work.
In work for which considerable machinery is required, a charge for use of plant and supplies must be included, which will vary with the size of the job and the extent of the plant required. For build ing operations where a hoisting plant is necessary, it will be from 60 cents to Si per cubic yard.
99. Total Costs.—The costs for concrete in place include the costs for materials, labor, and plant. Li the construction of a 1 : :3 : 6 concrete foundation for street pavement, an average cost is approximately as follows: Cement, 1.02 barrel_ at $ 1.75 81.79 Sand, 0.46 cubic yard at $1.00 0.46 Stone, 0.92 cubic yard at $1.40 1.29 Labor, per cubic yard 1.10 Total cost per cubic yard $4.64 For the construction of a concrete building, an average cost for 1 : 2 : 4 concrete of crusher run stone (45 per cent voids) may be as follows: Cement, 1.47 barrel at $1a0.. $2.65 Sand, 0.43 cubic yard at $1 0.43 Stone, 0.87 cubic yard at $1.60 1.39 Labor per cubic yard 1 .50 Plant per cubic yard 0. SO Total cost per cubic yard $6. 77 Allowance should be nracle for waste of materials, which always occurs to some extent—in some cases 5 per cent of the amount of materials necessary to form the required concrete is needed to cover this loss. Care in handling the materials and close supervision of
the mixing may reduce the loss to a negligible quantity, where the work is concentrated in large units.
The above figures do not include the cost of forms or of steel for reinforcement. Forms must be specially designed for each structure and the cost varies widely. In massive construction or in foundation work, the forms may be a comparatively small item, while for heavy walls requiring support on the sides, they may cost $.50 per cubic yard or less. On structural work, including beams and columns, the cost of forms is frequently greater than that of the concrete. In such cases, only a careful design for the forms, and estimate of the materials and labor required for their erection, can give accurate data as to cost. In building work, the cost of forms is sometimes roughly estimated as about S to 10 cents per square foot of surface of concrete, where the use of the materials may be repeated, and when the forms can be used but once the cost is much greater.
Valuable information concerning the cost of concrete construction may be found in " Concrete Costs " by Taylor and Thompson, and in " Concrete Construction " by Gillette and Ilill.
"Concrete, Plain and Reinforced," by Taylor and Thompson, gives a very complete discussion of the materials, proportions, methods of mixing and placing, and properties of plain concrete.