Deleterious Constituents of Indiana Gravels

This paper reports the results of tests on Indiana gravels ranging from good to poor in field performance in Portland cement concrete. The gravels were separated by heavy liquid flotation into various specific gravity ranges. The gravel fractions thus obtained were tested to deter­ mine absorption, specific gravity, degree of saturation, lithologic compo­ sition and durability in air entrained concrete subjected to freezing and thawing. The results show that the principal deleterious constituents of Indiana gravels are sandstones and cherts. They are characterized by low specific gravity, high absorption and degree of saturation and pro­ duce nondurable concrete when used as the coarse aggregate. The con­ crete durability can be improved by heavy media separation of the aggre­ gate. Greater durability is obtained as the specific gravity at which the separation is made is increased.