With the data given in Tables 60 and 61 and a knowledge of unit prices of the materials used in the mortar, one may estimate the Cost of the materials in a given quantity of mortar. The cost of the mixing will, of course, depend upon the Cost of labor, the method employed, etc., and may vary from fifty cents to a dollar and fifty cents per cubic yard. If we assume, for illustration, that natural cement can be delivered on the mixing platform for $1.10 per barrel of 280 pounds net, that sand costs 60 cents per cubic yard, and the mixing costs $1.00 per yard of mortar, then we have for the Cost of a mortar composed of one part cement to two parts sand by weight: —

3.46 bbls. cement at $1.10...........$3.80

0.72 cu. yd. dry sand at .60............43

Cost of mixing per cu. yd............ 1.00

Total Cost of one cu. yd. of mortar........$5.23

289. For approximate results, Tables 62 and 63 give the Cost of the materials used in a cubic yard of mortar for different prices of cement. In Table 62 the proportions by weight only are indicated, since for Portland the proportions by volume of loose sand to packed cement vary so little from proportions by weight.

Table 62. Cost Of Portland Cement Mortar. Cost Of Cement And Sand In One Cubic Yard Of Portland Cement Mortar. Sand, 75 Cents Per Cubic Yard

Table 63. Cost Of Natural Cement Mortar. Cost Of Cement And Sand In One Cubic Yard Of Natural Cement Mortar. Sand, 75 Cents Per Cubic Yard

In Table 63 the Cost of materials in one cubic yard of natural cement mortar is given, 1st, for various parts of sand to one of cement by weight when*the cost of cement refers to a barrel of 265 pounds; 2d, when this Cost is for a barrel of 300 pounds net; 3d, for various parts sand to one cement when the proportions are expressed as parts by volume, dry loose sand to one volume of packed cement weighing 265 pounds per barrel; and 4th, when the proportions are expressed as parts of dry loose sand to one volume of packed cement weighing 300 pounds per barrel. The quantities in the table are based upon the assumption that the sand used is similar to that used in the experiments from which Tables 60 and 61 were derived, and that the cost of sand is seventy-five cents per cubic yard.

290. Example

To indicate the use of these tables, let us determine the Cost per cubic yard of natural cement mortar composed of one volume of packed cement to three volumes of loose dry sand when the cement weighs 300 pounds per barrel, net, and costs $1.25 per barrel, while sand costs $1.00 per cubic yard. In the fourth section of Table 63, opposite three parts sand and under $1.20 and $1.30, we find, respectively, $3.02 and $3.22; then with cement costing $1.25 and sand $0.75, we should have cost of mortar per cubic yard $3.12. But in our example sand is assumed to Cost $1.00 per cubic yard, or twenty-five cents more than the price for which the tables are computed, and from Table 61 we find that for this mortar 0.83 cubic yard of sand is required. We must therefore add to $3.12, .83 X 25 = 21 cents, giving $3.33 as Cost of materials in one cubic yard of the mortar. The Cost of mixing the mortar must be added to obtain the total Cost per cubic yard.