The United States Government, various scientific and engineering societies, and other interested organizations have collaborated in the preparation of specifications for cement and cement tests. These specifications can be found in Trans. Am. Soc. Civil Engineers, Vol. 82, 1918, p. 166, and in other publications. The following abstracts have been taken from the proposed tentative specifications for Concrete Aggregates, of the Am. Society for Testing Materials, issued June 21, 1921: 1. Fine aggregate shall consist of sand, stone screenings, or other inert materials with similar characteristics, or a combination thereof, having clean, hard, strong, durable uncoated grains, free from injurious amounts of dust, lumps, soft or flaky particles, shale, alkali, organic matter, loam or other deleterious substances. 2. Fine aggregates shall preferably be graded from fine to coarse, with the coarser particles predominating, within the following limits: Passing No. 4 sieve 100 per cent Passing No. 50 sieve, not more than 50 per cent Weight removed by elutriation test, not more than 3 per cent Sieves shall conform to the U. S. Bureau of Standards specifications for sieves. 3. The fine aggregate shall be tested in combination with the coarse aggregate and the cement with which it is to be used and in the proportions, including water, in which they are to be used on the work, in accordance with the requirements specified in Section 6.... 7. Coarse aggregate shall consist of crushed stone, gravel or other approved inert materials with similar characteristics, or a combination thereof, having clean, hard, strong, durable, uncoated pieces free from injurious amounts of soft, friable, thin, elongated or laminated pieces, alkali, organic or other deleterious matter. * * * * * The following Table indicates desirable gradings, in percentages, for coarse aggregate for certain maximum sizes. GRADINGS OF COARSE AGGREGATES