Early Life Study of the FA409 Full-Depth Asphalt Concrete Pavement Sections

Abstract

The Illinois Department of Transportation (IDOT) is currently implementing a mechanistic thickness design procedure for full-depth asphalt concrete pavements. This procedure is based on the relationship between pavement performance (fatigue cracking of the asphalt concrete and rutting of the subgrade) and pavement structural parameters (asphalt concrete thickness (Tac), asphalt concrete resilient modulus (Eac), and subgrade resilient modulus (Eri)). The relationship between performance and structure is based on the ILLI-PAVE nonlinear, stress dependent, finite element pavement structural model.

This thesis is an early design-life investigation of full-depth asphalt concrete pavements, constructed on FA409 near Carlyle, Illinois in 1986. Included in the study are: sampling and testing of paving and subgrade materials; extensive non-destructive testing (NDT) using the Falling Weight Deflectometer (FWD); development of techniques for interpreting NDT data; determination of as-built structural characteristics of the various pavement sections; evaluation of subsurface drainage and lime-treated soil behavior; and examination of the validity of the ILLI-PAVE computer model.

The simplicity of a full-depth asphalt concrete pavement allows useful information regarding pavement structure to be determined from FWD surface deflection data. The ILLI-PAVE model was used in conjunction with statistical methods to quantify, in the form of regression equations or algorithms, the relationship between pavement structure (Tac, Eac, and Eri) and pavement response to FWD loading. Testing of pavement and subgrade material samples was used to validate these algorithms. In addition to structural features, an algorithm for the determination of critical asphalt concrete tensile strain ($\vartheta$ac) directly from FWD surface deflection data was developed. These algorithms, in conjunction with extensive FWD testing and the testing of material samples taken from the completed pavement, were used to establish the as-built structural and fatigue life characteristics of the pavement sections. Useful data and information were developed concerning NDT, fatigue life variability, and the effect of lime-treated soil and subsurface drainage on structural response. In addition, the basic concepts utilized in developing the IDOT proposed full-depth asphalt concrete thickness design procedure were validated.