Cementitious composite structures such as concrete pavements are susceptible to different types of damage, which are primarily caused by fatigue due to repeated loading and long-term deterioration. There is even greater concern that damage can occur more frequently with the use of heavier vehicles or new aircrafts carrying greater payloads. To ensure the safety, reliability, and future usefulness of the airport runway pavements, their condition assessment should be performed in a regular and timely fashion. The goal of this project is to develop nanoengineered concrete pavements that can nondestructively characterize the severity and location of pavement damage. It is envisioned that critical portions of airport pavement or runway can be replaced with these smart concrete materials for load estimation, monitoring, and damage detection. Specifically, these smart concrete pavements will measure deformation and damage directly and will identify (in near real time and wirelessly) the location and size of surface and subsurface damage. This project began with the design and embedment of carbon nanomaterials in concrete pavements to enhance their electromechanical properties. Their mechanical behavior was designed to match (or exceed) that of airport pavements but with enhancements to their piezoresistivity (or strain sensitivity). Distributed and 3D damage detection was achieved by implementing an electrical resistance or impedance tomography algorithm that could reconstruct the electrical conductivity distribution of the smart pavements. Since their electrical conductivity was calibrated to strain, the output was equivalent to a 3D damage map, where localized changes in material conductivity could be correlated to localized damage. Then, a wireless data acquisition system was developed for achieving near-real-time, untethered pavement monitoring. System validation tests for this last phase of study were conducted using a heavy vehicle simulator accelerated pavement test at the University of California Davis. The results validated that self-sensing cementitious composites when coupled with electrical impedance tomography could detect damage in laboratoryscale samples. The large-scale tests also showed that distributed subsurface cracks could be identified before they propagated to the surface. In addition, the conductivity maps also showed how subsurface defects propagated. Overall, this technology will allow airport operators, owners, as well as other Department of Transportation agencies to visualize pavement health (and damage). The long-term vision is to show that smart concrete pavements can potentially reduce the need or frequency for tedious, expensive, and inaccurate nondestructive pavement damage assessment methods currently being used.
DOT/FAA/TC-21/46 Authors: Kenneth J. Loh, Rongzong Wu, and Jerome P. Lynch