Flow in Aggregate-Binder Mixes : Technical Paper

Prediction of field service behavior of a bituminous mix on the basis of its composition or material ingredients, presents a difficult problem. In spite of this, research and experience have provided methods for practical mix designs which are adequate in most cases. The designs used at present are essentially trial and error in nature. The type and gradation of aggregate and the asphalt grade are chosen, then a number of asphalt contents are estimated which hopefully bracket the desired optimum conditions. Next follows the making of specimens and their testing to determine the optimum mix. If the combination of ingredients does not give the specified or desired properties (stability, voids, etc.), the components in the mix are changed and the tests are repeated. The assumption at the start of this investigation was that a knowledge of physical factors of the aggregate and the binder could lead to a more systematic and unified mix design procedure. The specific objectives of this research were: a. To define and measure quantitatively useful mix-design parameters for aggregates. b. To define and analyze the function of asphalt in a mix. c. To try to predict "strength" values for aggregate-asphalt mixtures from composition parameters. d. To initiate an approach to a unified mix design.