Hot Mix Asphalt Stiffness Moduli: Laboratory versus Field
In many instances pavement engineers find discrepancies between the laboratory measured and the backcalculated moduli based on the deflection measurements in the field. In addition, during the mix design in the laboratory, for the same mix, the moulded specimens yield different resilient moduli from the cored specimens. This research investigated the effect of confinement on the resilient modulus. Cored specimens yielded significantly lower resilient moduli compared to moulded specimens signifying the effect of the confining stresses that get locked in the moulded specimens. In addition, the effect of specimen geometry (height and diameter), load wave form (sinusoidal versus triangular), compaction method (Marshal versus Gyropac), aggregate gradation (AC10 versus AC14), load duration, and the recoverable preset strain level were thoroughly examined in this study. The maximum nominal aggregate size was the most important factor affecting the resilient modulus followed by the load duration and specimen geometry. The interactions between some factors were also significant.