Optimizing prime coat application rates: integrating penetration, permeability, and shear strength

Abstract This study investigates the optimal application rate of medium curing (MC) prime coats in flexible pavement construction through a combined experimental and numerical approach. Prime coat rates ranging from 0.0 to 2.0 kg/m 2 were applied to asphalt-base specimens and assessed using penetration depth, permeability, and shear strength tests. An application rate of 1.5 kg/m 2 yielded the most favorable results, with a penetration depth of 3.64 cm, permeability reduced to 0.648 cm 3 /s, and cohesion increased to 43 kPa. Finite element simulations conducted in PLAXIS 2D supported these findings, indicating reduced vertical settlement (2.797 mm) and lateral displacement (0.1619 mm) at this rate. The study demonstrates that applying the prime coat at 1.5 kg/m 2 optimizes the bonding between the base and asphalt layers, significantly enhancing mechanical stability and reducing deformation under traffic loads. Additionally, excessive application rates (> 1.5 kg/m 2 ) resulted in marginal improvements or adverse effects, such as increased permeability and decreased shear strength, highlighting the importance of precise dosage control. This integrated approach, combining practical testing with numerical modeling, offers a comprehensive evaluation of prime coat performance and provides practical guidelines for material-specific application rates to improve pavement durability and cost-effectiveness.