Quality Control for Natural Sand Content of Asphalt Concrete

Excessive natural sand contents can increase the susceptibility of asphalt concrete to permanent deformation-type distresses. For this reason, pavement construction specifications usually include a limit for the proportion of natural sand that can be included in an aggregate blend. Although proportions of natural sand are controlled during the development of asphalt mixture designs, direct methods for monitoring natural sand contents are typically not included as part of construction quality control plans. The packing density of free-fallen aggregates, which can provide an indirect measure of particle angularity and surface texture, shows promise as a tool for monitoring natural sand content in aggregate blends. In the laboratory study presented in this paper, the free-fallen packing densities of aggregates extracted from asphalt concrete permitted predictions of natural sand contents to within approximately 5%. When used as a quality control tool in this study, these packing density measurements effectively identified changes in the natural sand content of asphalt concrete.