The utilization of reclaimed asphalt pavement (RAP) material in road construction has gained prominence with the backdrop of sustainability. The present study evaluates the usage of a significant amount of RAP material with virgin aggregates (VA) stabilized with low and high calcium, alkali-activated fly ashes as pavement base materials. The role of a liquid alkaline activator (LAA) on the reactivity of various fly ashes are highlighted. Three distinct fly ashes sourced from different locations were adopted to stabilize the RAP:VA bases. To establish an optimum LAA ratio for these fly ashes, alkaline solutions with varied proportions of Na2SiO3∶NaOH (0∶100, 30∶70, 50∶50, 70∶30, and 90∶10) with a constant NaOH molarity were considered. It was noticed that the strength and stiffness of the mixes at a 28-day curing period were increased with an increase in the LAA ratio. However, in contrary to the existing understanding, the LAA is not a constant ratio (50∶50) for all types of fly ashes. The optimum LAA ratio was found to be 50∶50 for low calcium fly ashes and 70∶30 for high calcium fly ash; however, it depends on the reactive potential of the fly ash. The 60% RAP, 40% VA, and 20% fly ash blended specimens prepared mostly with LAA ratios of 50∶50 and 70∶30 were found to be suitable as pavement base course materials as per design standards. A set of regression models were developed and validated to estimate the base layer coefficients from the corresponding layer's resilient modulus for various subgrade conditions. Based on the proposed models, a new set of base layer coefficients (a3) were developed for fly ash-stabilized base layers. © 2020 American Society of Civil Engineers.