Manual for Thin Asphalt Overlays

Abstract

This manual presents best practices on project selection, mix design, and construction to ensure a superior product when constructing thin asphalt overlays. Experience shows these treatments provide excellent performance when placed on pavements in fair to good condition using proper construction techniques. Though sometime referred to by other names, thin asphalt overlays have been widely used for pavement preservation throughout the world for over 50 years. Limited infrastructure funding at the local, state, and federal levels has resulted in greater emphasis on the use of pavement preservation techniques to extend pavement life and reduce maintenance costs. Thin asphalt overlays are one of many preventative maintenance treatments. Thin asphalt overlays are placed directly on existing pavement and can range from 1/2 inch to 1 1/2 inches in thickness. Thin asphalt overlays have proven to be an economical means for maintaining and improving the functional condition of an existing pavement since the 1960s. Specifically, this manual provides guidance for engineers regarding where and when to use thin asphalt overlays including: (1) Types and variations of thin overlays; (2) Materials and the design process; (3) Construction; (4) Quality Assurance; and (5) Troubleshooting. This chapter by chapter guidance enables an Agency’s engineers to design and construct a successful thin asphalt overlay project to completion. This manual is one of four new manuals prepared by the California Pavement Preservation Center (CP2Center) using funding from California Senate Bill 1 (SB-1), passed in April 2017. The other three manuals provide detailed design and construction information for (1) chip seals, (2) slurry surfacing, and (3) Cape seals. The creation of these manuals was a task funded entirely from SB-1 monies for the purpose of disseminating training and technical information on highway pavement preservation to local agencies throughout California.