<![CDATA[The establishment of strong interlayer bonding between the base course and asphalt surface is critical for the durability of flexible pavements. Inadequate adhesion at this junction commonly causes slippage, fissures, and early deterioration, consequently diminishing pavement longevity and escalating maintenance expenses. Conventional prime coats, such as cutback and emulsified asphalts, possess drawbacks, including ecological issues and variable efficacy in adverse site conditions. This study investigates the Prime Coal Fly Ash Coat (PCFAC), which is developed utilizing Coal Fly Ash (CFA), an abundant industrial by-product, as an eco-friendly substitute for prime coats. Experimental work involved preparing granular base layers in accordance with laboratory specifications, followed by the application of PCFAC mixtures at different CFA-to-water ratios and distribution rates. Specimens were cured under laboratory conditions for 24 hours following base preparation and an additional 24 hours subsequent to PCFAC application before testing. Findings indicated that higher CFA content enhanced mixture stability and adhesion, with PCFAC-2.5 demonstrating optimal performance. The optimum distribution rate of 1.75 kg/m² was determined by comparing penetration depth, pull-off strength, and direct shear strength, balancing sufficient infiltration with strong adhesion and effective workability. At this rate, the PCFAC attained a pull-off tensile strength of 322 kPa and a direct shear strength of 3.5 MPa, signifying the highest values among the investigated PCFAC formulations. The findings highlight PCFAC’s capability to enhance interlayer bonding while valorizing industrial waste, thereby contributing to sustainable pavement practices. The manuscript further examines the limitations of the study, such as the adaptation of current testing standards, and proposes recommendations for further research and field validation.]]>
