The Project Gutenberg eBook of Concrete Construction, by
Mr. J. J. R. Croes, M. Am. Soc. C. E., states that 1 bbl. of Rosendale cement and 2 bbl. of sand (8 cu. ft.) make 9.7 cu. ft. of mortar, the extreme variations from this average being 7 per cent. Frequently concrete is made by mixing one volume of cement with a given nuer of volumes of pit gravel; no sand being used other than the sand that is found naturally mixed with the gravel.