Weak interlayers found in flexible and semi-flexible road pavements

Abstract

Weak interlayers within the upper structural layers of road pavements are specifically prohibited in most road-building specifications. However, such layers are extremely common and often lead to premature pavement distress. Heavy Vehicle Simulator (HVS) evaluation indicates that the presence of such layers within the structural layers of a flexible/semi-flexible pavement is far more deleterious than is commonly appreciated. These effects are modelled using examples based an HVS testing and simplistic mechanistic pavement analyses. In particular, weak upper base courses of lightly cemented pavement under thin bituminous surfacing may lead to severe surfacing and upper base failure within a matter of months after opening to traffic, not excluding failure during construction. The causes of these adverse conditions, together with simple detection methods during construction and analyses of their effects on the structural capacity of flexible and semi-rigid (cemented) road pavements, are briefly discussed. Methodologies are available to detect and investigate the existence of these weak layers in cemented pavement layers. Analysis were done on a typical recycled hot mix asphalt (HMA) pavement, cemented base pavement and a granular base pavement, with and without these weak layers and interface conditions. The analyses focused on the strain energy of distortion (SED) as a pavement response parameter indicating the potential for structural damage. SED shows some potential for quantifying relative distortional effects of these weak layers and/or weak interfaces within flexible and semi-flexible pavements. In this paper a very brief overview of above is given.