The purpose of this report is to discuss the factors that contributeto the differences that occur in the properties of a Hot Mix Asphalt(HMA) mix designed in the laboratory and the properties of the"same" mix produced in an asphalt batch or drum mixfacility. Emphasis is placed on the causes for the differencesin the mix volumetric characteristics between the lab and thefield with the understanding that laboratory mix design is onlya starting point which must be verified through the HMA plantproduction. Major areas considered are: aggregate, asphalt binder,plant production process, hot mix storage, and hauling of themix.

This publication provides a ranking system to prioritize theimportance of each factor in contributing to the differences whichmay exist. Therefore, this document is intended to serve as areference to assist HMA producers in understanding variables affectingvolumetric properties.