Emulsion asphalts are cost-effective, environmentally friendly, and sustainable alternatives to hot-mix asphalts. Laboratory curing protocols currently used to simulate field curing of emulsion asphalts have been observed to offer conflicting predictions. This study employed the maturity method to account for the combined effects of temperature and time on fatigue-strength development in emulsion asphalts. An emulsion asphalt, composed of 55% reclaimed asphalt pavement, 45% virgin aggregates, 6.2% bitumen emulsion, and 4% pre-mix water was designed following the Asphalt Institute procedure. A total of 168 specimens from the mix were variously cured at 5 °C, 25 °C, 40 °C, and 50 °C for time intervals of 1, 3, 5, 7, 14, 21, and 28 days, before being tested for fatigue-strengths on the four-point bending test jig. It was observed that fatigue-strengths increased with an increase in cure temperature but decreased with an increase in cure duration. A parabolic hyperbolic fatigue-maturity model was developed from results of specimens cured at 5 °C, 25 °C, and 40 °C and validated with results from specimens cured at 50 °C. A strong correlation was observed between predicted fatigue-maturity and laboratory-determined fatigue-strengths at test strain levels between 125 µm/m and 200 µm/m. The study concluded that the laboratory characterization of emulsion asphalts should consider the curing history of the mix.

Bitumen emulsion asphalts, especially those incorporating marginal and secondary aggregates, are energy efficient, environment friendly, and sustainable alternatives to hot-mix asphalts. This study set out to compare engineering properties of a bitumen emulsion asphalt composed entirely of virgin aggregates with another composed of 55% reclaimed asphalt and 45% virgin aggregates. The aggregates were bound with a slow setting cationic bitumen emulsion composed of 65% base bitumen and 35% water. Marshall specimens molded at varying pre-mix water and bitumen emulsion contents were cured in molds for 24 h before being de-molded and cured for a further 72 h at 40 • C. Dry densities, porosities, and indirect tensile strengths for the cured specimens were determined in dry and soaked states. Virgin aggregate mix, at an optimum binder content of 6.1%, had a tensile strength ratio of 1.3 with corresponding air voids and moisture absorption values of 10.1% and 0.92%, respectively. Similarly, reclaimed asphalt mix at an optimum binder content of 6.2% had a tensile strength ratio of 1.03, with corresponding air voids and moisture absorption values of 7.9% and 0.38%, respectively. Compared to virgin mix, reclaimed asphalt mix had lower air voids and lower moisture absorption values with the overall benefit of enhanced resistance to moisture damage. ultimate engineering properties upon completion of batching, strength gain in cold asphalts proceed at rates dependent on breaking of the emulsion and evaporation of the resultant water. They behave like improved granular materials in the early stages of their lives but eventually attain properties similar to those of hot-mix asphalts once all the moisture is lost through curing [2][3][4].Compared to hot-mix asphalts, cold asphalts are energy efficient, cheaper, and environmentally friendly, but have the downsides of requiring longer curing times, having high air-void contents, and low early-life strengths [5]. Further, environmental and monetary savings accrue when marginal and secondary aggregates, like recycled asphalts, are used in cold-asphalt mixtures. In their study, Kandhal and Mallick [6] estimated cost savings of between 14% and 34% when recycled asphalt aggregates varying between 20% and 50% by mass of total mix were used in conjunction with virgin aggregates. In another study by Thanaya [7], energy savings of up to 40% were realized when bitumen emulsions were used in place of penetration grade bitumen in asphalt production. A study by Oke et al. [8] estimated savings of between 40% and 60% when cold reclaimed asphalt pavement mixtures were used in place of hot-mix asphalt.Currently, there is no universally accepted laboratory asphalt mix design procedure for cold asphalt mixtures, rather a myriad of procedures have been developed by countries and agencies to suit their local conditions and needs [9][10][11][12][13]. In the United States, Asphalt Institute, Chevron Inc., U.S. Navy, and the states of Oregon, Pennsylvania, Indiana, California, Texas, and New Mexico [14...