Notes On Metallurgical Mill Construction

to be screened except for the highest class brick or cut-stone (coursed) masonry. Well made 1:5 portland cement concrete, of good standard gravel or limestone screening, will have a compressive strength at four weeks of over 2000 Ib. per sq. in.; and at one year, over 3000 Ib. Tests made at the Case School of Science showed that 3-in. cubes of $: 6 portland cement and gravel concrete had a compressive strength of 3200 Ib. per sq. in. at six weeks, a sp. gr. of 2.17, and an absorption of water of 4.16 per cent. Similar cubes of 1J parts cement, J hydrated lime, and 6 of sand and gravel had a strength of 3880 Ib., a sp. gr. of 2.18, and an absorption of 4.10. Cubes of 1$ parts of cement and 6 of limestone screening, poured in a porous mold, had a strength of 2000 Ib., a sp. gr. of 2.5, and an absorption of 5.04. The coefficient of expansion of concrete, of the proportions 1:2:4, by heat, has been determined as 0.0000055 for 1 deg. F., which is almost the same as that of untempered steel, which is 0.0000060. In proportioning the material, when the mixture is by volume and the mixing is done by hand, a bottomless box will serve as a simple and effective measure. If the box is made of 2xl2-in. plank, 3 ft. square inside, the dimensions are most satisfactory. Such a box, once even-full of sand, and evenly filled three times with the aggregate, with four bags of cement, will make just 1 cu. yd. of concrete (of the proportion 1?2?6), in place. The cement, of course,... --This text refers to an alternate Paperback edition.