Full-scale test of thermally induced reflective cracking in airport pavements

Abstract

While a reflective cracking propagation rate of 25 mm per year is well accepted by airport pavement engineers, the mechanism of reflective cracking under field conditions has not been fully investigated. A recently completed project sponsored by the Federal Aviation Administration (FAA) led to the development of the Temperature Effect Simulation System (TESS). After an in-depth evaluation of the TESS, full-scale tests to mechanically simulate thermally induced reflective cracking were conducted. A large simulation matrix was first developed to select promising joint opening and displacement rates using three-dimensional viscoelastic-based finite element analyses. A test pavement was then built, instrumented, and tested at the FAA National Airport Pavement Test Facility (NAPTF). This paper describes the successful full-scale test, crack monitoring under accelerated loading, and the data analysis used to evaluate the crack development. Main research conclusions included: (1) “25 mm per year” was quite conservative for thermally induced reflective cracking; (2) Once bottom-up reflection cracks reached a critical length, the crack evolution became very aggressive. For that reason, it is hypothetical to sandwich a strain-relieving hot mix asphalt interlayer between the Portland cement concrete slabs and the new overlay to minimise overlay stresses and to tolerate horizontal movements at the joint. Furthermore, significant insights into the mechanisms and mitigation of thermally induced reflective cracking were obtained and presented. Findings from this study are of immediate assistance to airports supporting light to medium weight aircraft and experiencing significant temperature cycling.