Objective

Most reflective cracking is caused by the combination of two mechanisms, as illustrated in the figure below (a) Horizontal Movement of Slab – usually temperature associated and causes tensile and bending stresses to develop in the overlay, and (b) Vertical Movement at the Joint/Crack Area – primarily load induced and creates shear and tensile stresses within the overlay. In addition, crack initiation and propagation are influenced by the existing pavement structure and conditions, reflective cracking countermeasures (e.g. reinforcing, interlayers), HMA mixture properties, the degree of load transfer at joints and cracks, and other effects.

Mechanisms of Reflective Cracking (Click Image to Zoom)

The crack propagation rate derived from the previous six full-scale indoor tests at the Federal Aviation Administration (FAA) National Airport Pavement Test Facility (NAPTF) using the Temperature Effect Simulation System (TESS), needed to be validated and calibrated to the field conditions that involves both aircraft and temperature loads. At the FAA National Airport Pavement and Material Research Center (NAPMRC), two test pavements were built and instrumented to isolate and compare aircraft gear load and temperature effects on the initiation and propagation of reflection cracks.