Experimental Study on the Grading Distribution of Cold Recycled Asphalt Mixtures Produced with Bitumen Emulsion and High Strength Cement

Cold recycled asphalt mixtures (CRAM) can lead to real economic advantages only if their performance is comparable to that of traditional hot mix asphalt. This experimental study aims to investigate the effect of the grading distribution on the volumetric and mechanical properties of CRAM produced with high reclaimed asphalt dosage (>70%), bitumen emulsion and high strength cement. Four grading distributions were analysed: two continuously graded curve (derived from the Fuller-Thompson maximum density curve) with nominal maximum aggregate size (NMAS) 16 and 10 mm. The third was obtained increasing the filler dosage, and the fourth grading distribution was a gap-graded type, with NMAS 16 mm. Workability and compactability of the fresh CRAM were evaluated using the gyratory compactor. CRAM long-term complex modulus was measured using cyclic compression tests. Results showed that the gap-graded and the high-filler grading distributions allowed obtaining the lower voids in the mixture. Having fixed the number of voids in the mixture, the gap-graded CRAM showed a higher stiffness modulus and lower phase angle if compared to CRAM produced with the continuously graded curve.