Synthesis of design and construction practices

Transportation agencies and the road building industry have traditionally designed and 

based on a pavement type selection (PTS) process to decide the best pavement alternative for a 

particular project.  This process helps pavement engineers determine the most cost-effective 

pavement type capable of supporting anticipated traffic under existing environmental conditions 

and providing safety and driving comfort to the traveling public (VDOT, 2001).   

Composite pavement systems have shown good potential for becoming a cost-effective 

several types of composite pavement structures; however, in this study, a composite structure is 

defined as a multi-layer structure where there is a flexible layer (top-most layer) over a rigid 

layer.  The flexible (asphalt concrete) layer (e.g., dense-graded hot-mix asphalt [HMA], stone 

matrix asphalt [SMA], open-graded friction course [OGFC], etc.) provides a smooth, safe, and 

quiet driving surface, whereas the rigid layer (e.g., cement-treated base [CTB], roller-compacted 

concrete [RCC], continuously reinforced concrete pavement [CRCP], etc.) provides a stiff and 

strong base.  This high modulus rigid base tends to change the traditional pavement concept in 

which the layers’ moduli decrease as depth increases.  In composite structures, the stiffness of 

the base (rigid layer) is greater than that of the surface layer (flexible layer). 

Composite structures are also known as semi-rigid or flexible composite structures in 

volume (50+ million equivalent single axle loads [ESALs]), heavily loaded trucks (which 

translates to high ESALs), and the designer seeks long-life pavements with minimum 

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rehabilitation (such as replacement of the wearing surface) (Nunn, 2004; Jofre and Fernandez, 

2004). 

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