Characterizing as-built hot mix asphalt using small-scale specimens
Loading...
Date
2019
Authors
Hajibandeh, Erfan
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Measuring the quality of as-built Asphalt Concrete (AC) mixtures provide useful information about the current and long-term performance of pavements. By the advent of the mechanistic-empirical pavement design method, the dynamic modulus has become one of the primary performance indicators required for characterizing the performance of AC mixtures. The dynamic modulus is commonly measured using cylindrical specimens having a 100 mm diameter and a 150 mm height (full-size specimens). Testing as-built AC mixtures using this geometry is rarely possible because the required specimen height is greater than the typical AC lift thickness. In this study, the feasibility of using small-scale cylindrical specimens to measure the dynamic modulus of AC mixtures was investigated. Initially, the specimens were prepared in the laboratory using loose mixtures obtained from the field. Dynamic modulus test was conducted on full-size and two small-scale (common height of 110 mm and two diameters of 38 and 50 mm) geometries extracted from gyratory compacted samples. A uniaxial hydraulic loading frame was used to test specimens at the standard temperatures and frequencies. Both small geometries showed similar performances to full-size specimens except at high temperature of 37.8°C, where they resulted in greater dynamic modulus values compared to full-size geometry. The coefficient of variation for 38mm-diameter specimens was found to be higher than two other geometries. Secondly, field cores were collected from highways to characterize as-built AC mixtures using three tests, including dynamic modulus, Hamburg Wheel-Tracking (HWT), and ignition oven. Ignition oven test was performed on field cores to mainly control the aggregate gradation of mixtures. For the dynamic modulus test, small-scale specimens were extracted from field cores, and stiffness values at 37.8°C were corrected using calibration factors obtained from the initial phase. For the HWT test, the heights of field cores were adjusted, and the test output parameters were correlated with the calibrated dynamic modulus values at 37.8°C. The results showed that small-scale specimens are capable of measuring the as-built dynamic modulus of AC mixtures and predicting their rutting performance in the laboratory.
Description
Keywords
Small-scale specimens, As-built AC mixtures, Dynamic modulus