Moisture susceptibility of warm-mix asphalt mixtures containing nanosized hydrated lime

This research investigated the size effect of hydrated lime on the moisture susceptibility of warm-mix-asphalt (WMA) mixtures with selected additives. A superfine hydrated lime used in the study was produced from regular hydrated lime (RHL) by a Los Angeles abrasion machine. The superfine lime was measured to be 660 nm, approximately half of the RHL size of 1.3 μm, a sub-nano-sized hydrated lime (SNHL). Scanning electron microscope (SEM) pictures were taken to observe the difference of the crushed lime in size, shape, and texture. Experiments for antistripping properties, such as indirect tensile strength (ITS), tensile strength ratio (TSR), flow, and toughness were conducted on WMA mixtures containing SNHL and RHL as control samples. A total of 18 mixtures and 108 specimens were prepared from three types of aggregate, three WMA additives, and two types of lime. The results indicated that the microstructures of the SNHL and RHL are irregular: the lime particles have fractured and rough surfaces with sharp angles; some small spherical particles in the nano size were found in SNHL but not in RHL. Also, WMA mixtures using SNHL have greater ITS and TSR than those using RHL; an increases of 8% in ITS and 10% in TSR by using SNHL over RHL were observed for the WMA mixtures investigated. Finally, the antistripping properties of WMA mixtures containing SNHL were affected predominately by aggregate type and the WMA additive.