FHWA: Thin HMA Overlays Preserve Pavements
This document defines thin asphalt overlays as dense graded mixtures placed less than 1 1/2 in. in thickness. Gap-graded and open-graded mixtures may be specifically designed for thin placement but they are considered specialty mixtures and aren't discussed in this document. Thin asphalt overlays placed for pavement preservation are functional overlays to extend the service life of the pavement and are not intended to add structural capacity. The key benefits of a thin asphalt overlay are improved ride, corrected rutting, impermeability and reduced noise.
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