Use of field and laboratory measurements for estimating pavement layer coefficients

There is no question that every country around the world is currently confronted with the enormous task of identifying priorities for the allocation of funds and resources as required to rehabilitate and upgrade existing highways. In giving consideration to future needs for improvements, these rehabilitations are justified to the extent that they contribute to an increased effectiveness of the highway system. To perform this task effectively, data must be available on the relative condition of pavements within the system so that priorities may be established on the basis of their ability and serviceability of carrying traffic loading. This research focused on developing guidelines for implementing structural condition index (SCI), and determining the layer coefficients for asphalt pavements including open-graded friction course (OGFC), dense-graded asphalt concrete (DGAC), stone mastic asphalt (SMA), and bitumen-treated base (BTB). The falling weight deflectometer (FWD) and laboratory tests were conducted to evaluate the load carrying capacity of existing pavements. The SCI score was established to distinguish pavements that required maintenance and rehabilitation (M&R), and was shown to be useful to apply M&R treatments to pavements that were structurally inadequate. Deflection data from FWD testing were used to find the layer coefficients for OGFC, SMA, DGAC, and BTB equal to be 0.150, 0.429, 0.371, and 0.270, respectively.