Resilient modulus of base course containing recycled asphalt pavement

Twenty resilient modulus (MR) tests were conducted for specimens with different ratios of recycled asphalt pavement (RAP) and aggregate to investigate the effect on material stiffness. Specimens were prepared by a gyratory compactor instead of a vibratory hammer, because the density of a gyratory-compacted specimen was closer to the field density. Moisture content and density were estimated before and during the tests according to the NCHRP 1-28A protocol requirements. M_R data were evaluated by quality control-quality assurance (QC/QA) criteria such as the angle of rotation, signal-to-noise ratio, and coefficient of variance, and about 95% of the sequences passed the QC/QA criteria. Specimens with 65% optimum moisture content were stiff er than the specimens with 100% optimum moisture content at all confining pressures. The 50% aggregate-50% RAP specimens developed stiffness equivalent to 100% aggregate specimens at lower confining pressures; at higher confinement, the RAP specimens were stiffer. However, from the tracking of axial displacement during the conditioning sequence, it appeared that the specimens with RAP exhibited greater permanent deformation than the 100% aggregate material.