Assessments of Potential Service Characteristics of Ethanol and Ethanol-NaHCO3 Foamed WMA Mixtures

Abstract

In the field, the workability and compactability of asphalt mixtures are essential to obtain the desired smoothness and sufficient density of a compacted pavement, especially for the asphalt mixtures prepared at low temperatures. This is mainly because the handling of the asphalt mixture, at a given temperature, is greatly influenced by the viscosity of the asphalt binder. This study evaluated the workability, coatability, and compactability of warm-mix asphalt (WMA) mixtures prepared using foamed asphalt binders incorporating ethanol and sodium bicarbonate (NaHCO3) as foaming agents. The service characteristics of foamed asphalt mixtures that were prepared at 80°C and 100°C were compared with those of the control hot-mix asphalt (HMA). PG 58-28 asphalt binder and aggregates from local sources were selected. The control HMA samples were prepared at 155°C and 100°C for the workability and coatability tests and compacted at 145°C and 100°C for the evaluation of the compactability characteristics. It was found that the application of ethanol as a foaming agent has a high potential for improving the mixture coatability, workability, and compactability at low production temperatures. However, the combination of NaHCO3 with 1% ethanol was optimum for these foamed WMA mixtures to maintain the coatability and workability of foamed WMA mixtures. Future work using an antistripping additive (nanohydrated lime) is highly recommended to improve the adhesive and cohesive characteristics and to enhance the moisture-damage resistance of foamed WMA mixtures.