The Benefits of Hydrated Lime in Hot Mix Asphalt
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Hydrated lime in hot mix asphalt (HMA) creates multiple benefits. A considerable amount of information exists in the current literature on hydrated lime’s ability to control water sensitivity and its well-accepted ability as an antistrip to inhibit moisture damage. However, recent studies demonstrate that lime also generates other effects in HMA. Specifically, lime acts as an active filler, anti-oxidant, and as an additive that reacts with clay fines in HMA. These mechanisms create multiple benefits for pavements: 1. Hydrated lime reduces stripping. 2. It acts as a mineral filler, stiffening the asphalt binder and HMA. 3. It improves resistance to fracture growth (i.e., it improves fracture toughness) at low temperatures. 4. It favorably alters oxidation kinetics and interacts with products of oxidation to reduce their deleterious effects. 5. It alters the plastic properties of clay fines to improve moisture stability and durability. The ability of lime to improve the resistance of HMA mixtures to moisture damage, reduce oxidative aging, improve the mechanical properties, and improve resistance to fatigue and rutting, has led to observed improvements in the field performance of lime-treated HMA pavements. Life cycle cost analyses have shown that using lime results in approximate savings of $20/ton of HMA mix while field performance data showed an increase of 38% in the expected pavement life.