Dr. Reynaldo Roque, a professor from the University of Florida Department of Civil & Coastal Engineering, along with his research team, conducted a study to understand interface debonding and near-surface longitudinal cracking in the wheel path of asphalt pavements. Asphalt pavement is composed of layers that are held together by a tack coat, which in Florida is typically an asphalt emulsion. These layers, when bonded, are more resistant to heavy vehicle loading or extreme thermal weather cycling. However, if the layers are not properly bonded, the top layer can separate (known as debonding), resulting in cracked layers or patches of lost material. To better understand this issue, the researchers (1) modeled asphalt pavements to pinpoint where stresses caused by vehicle loads could make debonding possible, and (2) when the debonding occurred, they wanted to know how the stresses distributed in the separated layers and how it contributed to near-surface longitudinal cracking.

Dr. Roque and his team evaluated various parameters and modeling scales and once a modeling method was determined, a fully-bonded four-layer pavement model was used for the study. The research suggests that the choice of application methods and products is very important to ensure good bonding. Also, the evaluation methods used in this study could be used for testing other materials for debonding, and they serve to advance the current method, which uses simple shear testing to measure the bond strength between layers. By understanding the exact way in which pavements fail, improvements are made to materials and methods, leading to reduced maintenance and more durable Florida roadways. To read the full report, visit: http://www.fdot.gov/research/Completed_Proj/Summary_SMO/FDOT-BDV31-977-37-rpt.pdf.