Sustainable design of a fine RAP fraction high modulus asphalt mixture: screening and validation of EME AC-5

Enrobés à module élevé (EME), a French high modulus asphalt concrete (HMAC) technology mainly adopted for heavily trafficked pavements, typically requires hard-grade binders to achieve high stiffness, increasing material cost and reducing sustainability. This study investigates a fine-graded reclaimed asphalt pavement (RAP)-based high modulus asphalt mixture (EME AC-5). Three RAP-based AC-5 gradations were first screened based on volumetric properties, moisture sensitivity, abrasion resistance, shear strength, and degree of blending (DoB). The selected mixture was then compared with standard EME AC-10 and AC-14 mixtures using dynamic modulus, indirect tensile fatigue, low-temperature cracking resistance, and wheel tracking tests. The selected EME AC-5 exhibited 1.89% air voids, a TSR of 90.7%, 2.65 MPa uniaxial shear strength, and a balanced binder interaction (DoB ≈ 47%). Its dynamic modulus was 24,366 MPa at 20 °C and 10 Hz, while its fatigue life reached 63,933 cycles at 722 kPa, exceeding those of the reference mixtures. It achieved the highest fracture strength (4.82 MPa), with comparable fracture energy (4662.8 J/m³). However, its high-temperature rutting resistance was lower than that of AC-10 and AC-14, highlighting the need to consider permanent deformation before field application. Overall, fine RAP fractions are viable for sustainable high-modulus asphalt mixtures.