Asphaltic concrete overlays of rigid and flexible pavements

This study represents the development of a mechanistic approach to asphaltic concrete overlay thickness selection for overlays of flexible, rigid, and composite pavements. The procedure utilizes a deflection analysis to determine pavement rehabilitation needs. Design quides for selecting the overlay thicknesses are presented. Tolerable deflection-traffic load relationships and the deflection attenuation properties of asphaltic concrete have been developed, representing the subgrade support conditions and properties of materials used in Louisiana. The tolerable deflection relationships may require minor adjustments as additional test sections reach the end of life condition. All deflection measurements on asphaltic concrete have been corrected for the effect of temperature. Deflection measurements taken before and after overlay were also adjusted to minimize the effects of seasonal subgrade moisture variation. Several advantages of this approach over existing methods include (1) the elimination of reliance on human judgement in an estimation of pavement strength, (2) elimination of the expenses and inaccuracies associated with destructive sampling and testing of pavement components, and (3) the ability to significantly increase sample sizes or points of evaluation within a pavement system. Overlay thickness requirements computed using the guides developed in this study appear to be in close agreement with overlay requirements determined from the Louisiana-AASHO Flexible Pavement Design Guide. /Author/