ABSTRACT
ABSTRACT: Intelligent Compaction (IC) is defined as vibratory rollers with accelerometers mounted on the axle of drums, Real-Time Kinematic (RTK) or Virtual Reference System (VRS) Global Positioning System (GPS), and on-board computers that can display various roller operating settings on color-coded maps in real time. IC measurements include roller positions, number of passes, surface temperatures, and stiffness of the compacted materials. Asphalt in-place density, a common measurement for mix durability and performance, is influenced by many factors including material properties, environment, paving, and compaction. Based on the compaction history captured by IC, a stochastic method was developed to correlate the IC measurements to asphalt in-place density, either measured with nuclear density gauges or from cores. Between 2011 and 2014, the US Federal Highway Administration (FHWA) IC Phase II research team has planned nine (9) field projects around the US to validate and enhance the statistical correlation between IC measurements and asphalt in-place density. The validation data from the first three (3) sites show that the critical period of initial breakdown compaction is the most dominating factor to achieve desired density for a given support condition. A nonlinear stochastic model was developed to correlate the in-place density with IC measurements, including the stiffness of asphalt material and underneath layers, asphalt mat temperature, and roller vibration frequency/amplitude. Once the model is fully validated with data from all remaining sites, any IC system may utilize this stochastic method developed under this research to estimate asphalt in-place density in real time and use IC as a quality control tool to optimize asphalt density. Leveraging the IC geospatial data that cover one hundred percent of compacted area, IC can also be a truth metric for compaction uniformity. The ultimate goal of this research is to achieve compaction uniformity for long lasting pavement.
