Prediction of Stiffness of Asphalt Treated with Surfactant-Based Warm-Mix Additive

Although the tonnage of asphalt pavements constructed with warm-mix technologies has increased rapidly in the United States in recent years, some practical aspects of warm-mix asphalt pavement construction remain incompletely defined. For example, compaction temperatures for many warm-mix technologies cannot be estimated with the standard equiviscous methods common to hot-mix asphalt. This paper reports the preliminary results of research to develop a method for predicting the stiffness (G^*/sin δ) of binder treated with a surfactant-based warm-mix additive as a function of mix production temperature, mix storage and haul time, and warm-mix additive dosage. Asphalt binders were treated in the laboratory with 0.0%, 0.5%, and 1.0% of surfactant-based warm-mix additive and were heated in a rolling thin-film oven at 130°C, 145°C, and 163°C for 0, 25, 55, 85, and 115 min. Regression analyses of the laboratory data yielded equations that with good fit correlated binder stiffness with the formulation (dosage) and process variables (aging temperature and time). The predictive value of these laboratory-developed equations was found to be good when the measured stiffness of binder extracted from field mix obtained at the paver was compared with binder stiffness calculated with the laboratory-developed equations by using the plant mix temperature, total storage and haul time, and surfactant dosage.