| Proportion of Cement to Sand | 1 to 1 | 1 to 1½ | 1 to 2 | 1 to 2½ | 1 to 3 | 1 to 4 |
| Bbls. | Bbls. | Bbls. | Bbls. | Bbls. | Bbls. | |
| Barrel specified to be 3.5 cu. ft. | 4.62 | 3.80 | 3.25 | 2.84 | 2.35 | 1.76 |
| " " " 3.8 " | 4.32 | 3.61 | 3.10 | 2.72 | 2.16 | 1.62 |
| " " " 4.0 " | 4.19 | 3.46 | 3.00 | 2.64 | 2.05 | 1.54 |
| " " " 4.4 " | 3.94 | 3.34 | 2.90 | 2.57 | 1.86 | 1.40 |
| Cu. yds. sand per cu. yd. mortar | 0.6 | 0.8 | 0.9 | 1.0 | 1.0 | 1.0 |
If the specifications call for proportions by weight, assume a Portland barrel to contain 380 lbs. of cement, and test the actual weight of a cubic foot of the sand to be used. Sand varies extremely in weight, due both to the variation in the per cent. of voids, and to the variation in the kind of minerals of which the sand is composed. A quartz sand having 35 per cent. voids weighs 107 lbs. per cu. ft.; but a quartz sand having 45 per cent. voids weighs only 91 lbs. per cu. ft. If the weight of the sand must be guessed at, assume 100 lbs. per cu. ft. If the specifications require a mixture of 1 cement to 2 of sand by weight, we will have 380 lbs. (or 1 bbl.) of cement mixed with 2 × 380, or 760 lbs. of sand; and if the sand weighs 90 lbs. per cu. ft., we shall have 760 ÷ 90, or 8.44 cu. ft. of sand to every barrel of cement. In order to use the tables above given, we may specify our own size of barrel; let us say 4 cu. ft.; then 8.44 ÷ 4 gives 2.11 parts of sand by volume to 1 part of cement. Without material error we may call this a 1 to 2 mortar, and use the tables, remembering that our barrel is now "specified to be" 4 cu. ft. If we have a brand of cement that yields 3.4 cu. ft. of paste per bbl., and sand having 45 per cent. voids, we find that approximately 3 bbls. of cement per cu. yd. of mortar will be required.
Table XII.—Ingredients in 1 Cubic Yard of Concrete.
(Sand voids, 40%; stone voids, 45%; Portland cement barrel yielding 3.65 cu. ft. paste. Barrel specified to be 3.8 cu. ft.)
| 1:2:4 | 1:2:5 | 1:2:6 | 1:2½:5 | 1:2½:6 | 1:3:4 | |
| Bbls. cement per cu. yd. concr't | 1.46 | 1.30 | 1.18 | 1.13 | 1.00 | 1.25 |
| Cu. yds. sand " " | 0.41 | 0.36 | 0.33 | 0.40 | 0.35 | 0.53 |
| Cu. yds. stone " " | 0.82 | 0.90 | 1.00 | 0.80 | 0.84 | 0.71 |
| Proportions by Volume. | 1:3:5 | 1:3:6 | 1:3:7 | 1:4:7 | 1:4:8 | 1:4:9 |
| Bbls. cement per cu. yd. concr't | 1.13 | 1.05 | 0.96 | 0.82 | 0.77 | 0.73 |
| Cu. yds. sand " " | 0.48 | 0.44 | 0.40 | 0.46 | 0.43 | 0.41 |
| Cu. yds. stone " " | 0.80 | 0.88 | 0.93 | 0.80 | 0.86 | 0.92 |
Note.—This table is to be used where cement is measured packed in the barrel, for the ordinary barrel holds 3.8 cu. ft.
It should be evident from the foregoing discussions that no table can be made, and no rule can be formulated that will yield accurate results unless the brand of cement is tested and the percentage of voids in the sand determined. This being so the sensible plan is to use the tables merely as a rough guide, and, where the quantity of cement to be used is very large, to make a few batches of mortar using the available brands of cement and sand in the proportions specified. Ten dollars spent in this way may save a thousand, even on a comparatively small job, by showing what cement and sand to select.
It will be seen that Tables XII and XIII can be condensed into the following rule:
Add together the number of parts and divide this sum into ten, the quotient will be approximately the number of barrels of cement per cubic yard.