The bulk of concrete obtained from a mixture of proper proportions of lime, sand, and aggregate, varies considerably according to the nature and proportions of the materials and method of treatment; but it should in general be a little more than the cubic content of the aggregate before mixing, as the other substances, if in proper proportion, should nearly fit into and disappear in its voids. The following examples show how the bulk of concrete produced varies according to circumstances - (a) Concrete of 1 Portland cement to 6 shingle (or broken stone) and 2 sand : 27 cub. ft. shingle or broken stone, 9 cub. ft. sand, 4 1/2 cub. ft. Portland cement (3 1/2 bush.), 25 gal. water, make 1 cub. yd. concrete, (b) Concrete of 1 Portland cement to 7 Thames ballast (consisting of 2 stone 1 sand): 33 cub. ft ballast, 4 1/2 cub. ft. Portland cement (3 1/2 bush.), 30 gal. water, make 1 cub. yd. of concrete. (c) Concrete of 1 Portland cement to 12 gravel, used at Chatham dockyard: 32 cub. ft. gravel (before shrinkage), 2 cub. ft. Portland cement, 50 gal. water, made 1 cub. yd. of concrete in situ. (d) Concrete of 1 Portland cement to 8 stone and sand, used at Cork Harbour works : 27 cub. ft. stone broken to 1 1/2-in. gauge, 9 cub. ft. sand, 4 1/2 cub. ft.

Portland cement, made 1 cub. yd. of concrete in situ, (e) In some concrete landings made with breeze from gasworks and Port" and cement: 29 cub. ft. breeze broken to 3/4 in. gauge, 8 cub. ft. Portland cement, made 1 cub. yd. of concrete in situ. (/) Concrete used at Portland Breakwater Fort, stone used in 2 sizes and mortar mixed separately: 14cub. ft. stones broken to 3 1/2-in. gauge, 14 cub. ft. stones broken to l 1/2-in. gauge, 10 cub. ft. sand, 5 cub. ft. Portland cement, 23 1/2 gal. water, made 1 cub. yd. of concrete in situ.

Hulk Produced 1177Hulk Produced 1178

After being rammed, the concrete is compressed into about 9/10 the volume it occupies when first made.