Stiffness assessment of cold recycled asphalt mixtures – Aspects related to filler type, stress state, viscoelasticity, and suction.

• CRAM's compacted specimens total suction (non-contact) test method was proposed. • CRAM produced with low active filler content presents granular mechanical behavior. • A correlation between Tx RM test results and suction pressure values was observed. • CRAM laboratory stiffness evaluation does not accurately represent field behavior. • Hydrated lime at 1% was the most interesting (higher stiffness) filler addition. Cold recycling is an advantageous technique, from economic and environmental perspectives, for asphalt pavement rehabilitation, interventions, and maintenance. Additional investigation is still needed for the widespread of the technique. Some of the issues evolve predicting the recycled material mechanical behavior and performance along its service life. Therefore, stiffness assessment (through triaxial resilient modulus and dynamic modulus tests) and suction tests were performed to better understand the cold recycled asphalt mixture (CRAM) behavior. This paper covered an investigation of the suction pressure phenomenon and its effects regarding the stiffness of emulsion-stabilized cold recycled asphalt mixtures, considering different fillers. A non-contact suction test method was proposed for CRAM compacted specimens in a way to enable total suction readings. Further theoretical analysis, key literature review, and discussions were presented. Some of the findings of the work are: (i) CRAM's stiffness may present similar behavior of a granular material, with confining pressure dependence, and at the same time, presents a temperature/frequency dependence (as asphaltic materials); (ii) suction phenomenon may be responsible for part of the stiffness of CRAM; (iii) the filler type (even in small percentage) affects the mechanical behavior of CRAM. [ABSTRACT FROM AUTHOR]