Effects of Mineral Additives on Cold Recycled Foamed Asphalt Mixtures Cured in Laboratory and Field Conditions

Cold recycling with foamed asphalt has been considered a sustainable pavement rehabilitation technology. During the mix design process, the dry and wet indirect tensile strengths (ITS) and tensile strength ratio (TSR) are important parameters for evaluating performance of a cold mix. These performance parameters can be significantly influenced by the type of mineral additive used in the mixture and conditions in which test specimens are cured before testing. In this study, the objective was to determine the effects of mineral additives on the dry and wet ITS and TSR results of the cold recycled foamed asphalt mixtures in laboratory- and field-curing conditions. Mixtures with four different additives (cement, hydrated lime, baghouse fines, and Class C fly ash) at varied contents were compared to a control mixture without a mineral additive. Specimens were cured in the laboratory and in a field-simulated condition. The results from laboratory curing show that cement and hydrated lime improved both the dry and wet ITS results. Baghouse fines increased the dry ITS but not the wet ITS, while the fly ash only enhanced the wet ITS. Higher additive contents did not improve dry or wet ITS results, except for cement. The field-simulated curing results show all the additives improved the dry ITS over long periods of time but were not effective in the short term. The ITS results from long-term field-simulated curing and laboratory curing ranked these mixtures similarly. Confinement during curing did not have a significant effect on the dry ITS.