Computer method for aggregate blending

Abstract : Present computer techniques for determining aggregate blends to meet a specified gradation for bituminous pavement mix design are not entirely satisfactory. Often aggregate blends must still be optimized by trial-and-error hand calculations to approximate the desired gradation. In addition to gradation limits and tolerances, there are limitations for the amounts of particular aggregates to be used in a mix design or for the total amount of fines that can be present in the mix. This study was undertaken to develop the logic for a computer optimization techniques that would blend the given aggregates to conform as closely as possible to the desired gradation and to fall within the specified limits. As a result, two computer programs have been written using two different optimization techniques and are presently being used for bituminous pavement mix design at the U.S. Army Engineer Waterways Experiment Station (WES). Both programs satisfy the requirements of this investigation. (Author)