Mechanistic Properties of Hot-Mix Asphalt Mixtures Containing Hydrated Lime

Permanent deformation and moisture damage are common distresses found in pavements today. The use of hydrated lime is known to decrease moisture susceptibility, and as a mineral filler it increases the stiffness of the mixture. The objectives of this study were (a) to evaluate the fundamental engineering properties of hot-mix asphalt (HMA) mixtures containing hydrated lime compared with conventional mixture's designed to meet the current Louisiana Superpave (R) specifications and (b) to evaluate the influence of hydrated lime on the mechanical properties of the resulting HMA mixtures. Nine 19.0-mm Level 2 HMA mixtures were designed and examined. Siliceous limestone aggregates that are commonly used in Louisiana were included in this study. The nine mixtures were divided into three sets; each set contained three mixtures. The first set included three mixtures that are conventional, as control mixtures, containing no hydrated lime and an SB polymer-modified asphalt cement meeting Louisiana specifications for PG 76-22M, PG 70-22M, and a neat PG 64-22. The second set included three mixtures that contained hydrated lime that was incorporated into the aggregate and asphalt cement mixture as slurry. The asphalt cements used were identical to the ones used in the first set, namely PG 76-22-M, PG 70-22M, and conventional PG 64-22. The third set included three mixtures that contained hydrated lime that was blended dry with the asphalt cements used in the first and second sets, that is, PG 76-22M, PG 70-22M, and PG 64-22. Mechanistic tests were conducted to define the permanent deformation and endurance life of HMA mixtures with and without hydrated lime. The results indicated that the addition of hydrated lime as a mineral filler improved the permanent deformation characteristics of the asphaltic concrete mixtures. This improvement was particularly apparent at higher testing temperatures with mixes containing polymer-modified asphalt and limestone aggregate.