XXII. W. E. COOK. 
Now completely empty the tank, and fill again with dry 
aggregate from which the sand has been screened, care 
being taken to pack the aggregate exactly as before. 
Again fill up with water, this time with y bucketsful 
(giving time for absorption), then let off the water, and fill 
again with 2 bucketsful. 
From the data thus obtained the following deductions 
can be made:—Voids in nq cubic feet of wet aggregate, 
free from sand = zq cubic feet. Therefore the aggregate 
has 100 “ per cent. of voids. Water absorbed by dry 
aggregate, free from sand, = (y—2) q cubic feet, and 
therefore 100 ae is the percentage of water absorbed. 
Contained sand in nq cubic feet of aggregate is (e—x) q 
cubie feet, and therefore 100 See is the percentage of 
contained sand. The actual quantity of cement, sand and 
water ean be obtained by inspection from diagram, com- 
bined with simple calculations. 
Thus, suppose an aggregate has 15 of sand, and when 
freed from sand has 40% of voids, and that it absorbs 15% of 
water, and that the concrete is to contain 1 of cement to 
3 of sand, from diagram it will be seen that to produce 1 
cubic foot of mortar of this quality, °3 cubic feet of cement, 
‘9 cubic feet of sand, 1°35 gallons of water are needed. 
Further, 1 cubic yard, or 27 cubic feet of aggregate, 
requires 1°2 x 27 xX ‘4 = 12°96 cubic feet of mortar to 
fill voids and give 20% over. 
Required cement = 12°96 xX *3 = 3°89 cubic feet per cubic 
yard of aggregate. 
Required water for mortar 3 pee 
12°96 x 1°35 = 17°50] — ee 
bsorbed OF 80) ores 
” ae 15 lons to allow 
yA ae aa x 64+ = 25°3| for waste. 
