EFFECT OF COMPACTION AND MOISTURE ON THE PROPERTIES OF ASPHALT CONCRETE MIXTURES

Abstract

Asphalt concrete mix design can not be considered complete until it has been investigated for its resistance to the effect of water, (stripping). This effect should be studied at the expected field air voids. Little effort was undertaken to investigate this effect on the properties of an asphalt concrete mix. The main objective of this research is to investigate the effect of moisture on the strength of asphalt concrete mixtures having different contents of air voids. Mix

- strength was measured in terms of Marshall stability, stiffness and indirect tensile strength. Mix strength was measured for conditioned (soaked) and unconditioned (unsoaked) specimens at different contents of air voids. The percent retained strength was taken to be an indicator for mix sensitivity to moisture action.

Three elements were taken as variables in the study. These variables were aggregate type, percent of air voids and soaking period. Five locally-produced aggregates having different physical and engineering properties were selected to represent a wide range of properties of available aggregates in Egypt. Four levels of air voids ranged from 3 to 10 % were selected to cover a wide range of expected field air voids. This range was selected based on a theoretical relation derived in the study. Four soaking periods ranged from 1 to 4 days were selected in this study.