Effects of surfactants on the formulation, cohesion build-up and moisture resistance of virgin and recycled cold bituminous mixtures and relationship to emulsion breakup

The use of bitumen emulsion in pavement structures, coupled with the introduction of reclaimed asphalt pavement (RAP), is an effective approach to preserve non-renewable resources and save energy. The formulation of virgin and recycled cold mix asphalt (CMA) requires the compatibility of the emulsion with the aggregates and RAP, according to their respective physicochemical characteristics. The objective of this research was to investigate the influence of parameters related to the bitumen emulsion and asphalt mixture composition on the implementation and durability of virgin and recycled CMA. The study focused on granite-based CMA with recycling rates of 0 and 50 %. Six emulsions were produced by varying the nature and content of the surfactant (0.9, 1.2 and 1.5 wt%). The mixtures were fabricated with different total water contents. The cohesion build-up and the compressive strength of the optimized mixtures were assessed. The results showed that the optimal total water content of virgin and recycled CMA differed with the surfactant type and decreased when the surfactant content increased, regardless of the composition. Likewise, the kinetics of cohesion build-up of mixtures is influenced by the amount of added water, surfactant nature and content. The moisture resistance of the mixtures is related to their short-term cohesion and is the highest at an optimum emulsifier content. Finally, the recycled asphalt mixes exhibited better compaction properties, higher mechanical strength (+ 0.5-0.7 MPa) and water resistance than those of virgin asphalt mixes