Abstract
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.
Highlights
The cold-emulsion asphalt mix used in this study was composed of a blend of reclaimed asphalt pavement (RAP) and virgin aggregates bound with a slow-setting cationic bitumen emulsion
In terms of number of load cycles to failure, Nf, was determined for each of the cold-emulsion reclaimed asphalt pavement specimens as described in Section 2.3 and the results plotted in Figures 4–6 for specimens cured at 5 ◦ C, 25 ◦ C, and 40 ◦ C, respectively
The combined effects of cure temperature and cure duration on fatigue strength, Nf, of a cold-emulsion reclaimed asphalt pavement mixture was studied through the maturity method
Summary
Production of hot-mix asphalts involves batching of virgin stone aggregates with penetration grade bitumen at elevated temperatures. Sustainable construction practices demand that materials for road construction purposes be obtained from environmentally friendly and sustainable sources [1]. This calls for exploration of construction materials and technologies that exert less pressure on sources of virgin aggregates and fossil fuel. Compared to hot-mix asphalts, cold-mix asphalts are more energy efficient, cheaper, and environmentally friendly [2,3,4]. Since they are laid at ambient temperatures, they are well suited
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