Development of a structural design program for HMA overlaid fractured PCC pavements with emphasis on HMA tensile strain criteria

Abstract

<p>Although HMA overlays have been commonly used as rehabilitation method for deteriorated PCC pavements, the appearance of reflection cracking significantly reduces pavement life. Fractured slab techniques have been successfully used to reduce the appearance of reflection cracking. Among the different techniques available, the rubblization technique has been widely used. The newer technique of rubblization leads to true "flexible" pavement, but the same empirical techniques used for HMA overlays over cracked-and-seated pavements have been applied, with mixed success. Since a rubblized PCC slab, overlain with HMA meets the classical definition of a flexible pavement, it seems reasonable to apply the more appropriate flexible pavement design techniques. Most state, county and city agencies use empirical design methods, which are based on experiments or experience, and mechanistic design methods, which explain phenomena only by reference to physical causes. A more reasoned approach would be to apply a "mechanist-empirical" approach. The Mechanistic-empirical (M-E) approach is based on the mechanics of materials that relates an input to an output or pavement response. M-E design models incorporate a combination of mechanistic models and field data. This project seeks to provide a realistic M-E design method for use with fractured slab technology. A limited calibration has been performed using an instrumented section of IA-141 in Polk County. The results have been analyzed, a database as been created, and a Visual Basic (VB) program has been developed to predict the HMA overlay design thickness. Longer term validation will require performance monitoring of such projects.</p>