The Restricted Zone in the Superpave Aggregate Gradation Specification

TRB's National Cooperative Highway Research Program (NCHRP) Report 464: The Restricted Zone in the Superpave Aggregate Gradation Specification presents the findings of a research project to determine whether the restricted zone requirement is necessary for aggregate gradations designed in accordance with American Association of State Highway and Transportation Officials (AASHTO) MP2 and PP28 if mix volumetric and fine aggregate angularity criteria are met. Its main finding is that, based on an evaluation of the performance properties of hot mix asphalt, the restricted zone requirement is redundant in these circumstances. The report will be of particular interest to materials engineers in state highway agencies, as well as to materials suppliers and paving contractor personnel responsible for the specification and production of hot mix asphalt.

Part A, Part B