COST OF CONCRETE WORK Cost of Materials.—The cost of cement varies with the demand, and for different localities, with the cost of transportation. Prices for cement delivered should always he obtained in making estimates for work. The cost of wagon transportation in delivery of cement to the work varies with the condition of the roads and the means of transport available. A team may haul 10 or 12 barrels of cement on a fair country road, and travel about 20 miles per day; on hard-surface roads the loads may be increased, and auto trans portation over good roads is less expensive.
The approximate quantities of materials required may be taken from the tables in Section 77. The following figures represent costs of work previous to the World War. The unsettled prices since existing make it impracticable to give later data of any value. These costs should probably be doubled at present (spring, 1920).
Sand.—For ordinary work in urban communities, sand may usually he purchased delivered, and estimates should be based upon the local prices, which vary in different localities (about t.70 to $1.60 is common) according to the nearness of the source of supply and the way in which the sand is delivered.
When sand is purchased by the ton, the weight per cubic yard must he ascertained to figure the cost accurately. Ordinary screened sand, with about 45 per cent voids, weighs from 2400 to 2500 pounds per cubic yard.
For sand taken from a pit, the costs include digging the sand, loading into wagons, and hauling to the work. In digging and load ing, 1 to 12 hours labor is ordinarily required per cubic yard and at 20 cents per hour the cost may be from 25 to 35 cents per cubic yard. On well-organized work, where hauling is continuous, hauling may cost 7 to 10 cents per 1000 feet of distance, while on smaller and less well-arranged work, the cost may reach 12 to 15 cents, with team and driver at S5 per day, but decreases as the length of haul increases. Hand screening usually costs somewhat less than loading, perhaps from 15 to 25 cents per cubic yard.
Stone and Gravel.—Broken stone or gravel, like sand, may usually be purchased for ordinary work by the cubic yard or by the ton. The weight per cubic yard depends upon the specific gravity of the stone and the percentage of voids. For ordinary crusher-run stone
with the chips removed and about 45 per cent voids, granite or hard limestone weighs about 2500 pounds per cubic yard, trap about 2700 pounds; stone containing more fine material, in which the voids are 40 per cent, weighs about 10 per cent more than these figures.
When gravel is to be obtained front a pit, the cost of digging and loading, with labor at 20 cents an hour, commonly varies from about 35 to 50 cents per cubic yard, according to the quantity required and the arrangements for loading, while hauling is about the same as for sand. The cost of screening gravel by hand may vary from 30 to 55 cents per cubic yard, 45 cents being an ordinary average.
Average Costs.—Under average conditions, with a moderate haul the price of sand delivered on work varies from about 90 cents to $1.20 per cubic yard; similarly screened gravel, $1.20 to $1.50, and broken stone, $1.40 to $1.75. When gravel or broken stone is delivered on cars, about 15 cents per cubic yard must be allowed for unloading.
98. Cost of Labor.—The labor required in concrete work includes handling the materials to the mixing platform, mixing the concrete and handling the concrete to place. The cost varies with the organiz ation of the work and the experience of the men. The ability of the foreman to systematize and control the work is one of the most important items. The author on one occasion had two almost identical pieces of work in progress at the same time, and found after the first few days that one job was costing about 90 per cent more than the other, due almost entirely to differences in the manage ment of the foremen.
When materials are conveniently arranged and the concrete, after mixing, may be shoveled into place from the mixing platform, the cost. of mixing and placing concrete is commonly from $0.90 to $1.25 per cubic yard, with labor at 20 cents per hour. Wheeling the concrete to place costs about 15 cents per cubic yard for the first 50'feet and 5 cents for each additional 50 feet. For work of moder ate size the cost of machine mixing does not differ very materially from hand mixing, when the overhead charges are included.