Impact of Lime on the Mechanical Properties of HMA Mixtures in Nevada

Abstract

The purpose of this research was to evaluate the impact of hydrated lime on the mechanical properties of typical HMA mixtures in Nevada. This research differed from previous studies in several respects. First, because lime is used in HMA primarily for anti-stripping benefits, previous studies rarely quantified lime's other performance benefits. Second, because testing is typically performed on only the HMA mix being considered for a project, and only as necessary to satisfy specifications, typical studies do not capture the full range of failure modes and environmental stresses. Furthermore, once specifications are met, test results are rarely translated into pavement performance characteristics. This research, by contrast, evaluated two typical HMA mixtures from the northern part of Nevada and two HMA mixtures from the southern part of Nevada used by NDOT with the most widely accepted laboratory tests.The Hveem mix design method was used in all mixtures. The tests were conducted at 0 and 6 freeze thaw cycles. The moisture damage was evaluated through the dynamic modulus test at various temperatures and frequencies. The asphalt pavement analyzer test and the repeated load triaxial test were used to evaluate the permanent deformation of the mixtures. The flexural beam test was used to assess the fatigue resistance and the thermal stress restrained specimen test was conducted to evaluate thermal cracking resistance. Additionally, mechanistic analysis was performed as an attempt to determine the pavement responses for each mix.In overall, the laboratory results and the mechanistic analysis showed that lime improved the mechanistic properties of Nevada's mixtures and its relative performance when is compared with the un-treated mixtures.