Rut resistance and volumetric composition of asphalt concrete mixtures

This paper describes a model for estimating mixture rut resistance using the concept of mixture resistivity, which is the inverse of the permeability of the mixture aggregate to the specific binder used in the mixture at the temperature of interest. Laboratory testing using the repeated shear at constant height test showed very good correlations between resistivity, compaction effort, and maximum permanent shear strain as determined using the repeated shear at constant height test. To verify the usefulness of the proposed model field rutting data from Mn/Road, WesTrack and the National Center for Asphalt Technology (NCAT) Test Track were modeled, using resistivity, N sub design, and relative field density as predictor variables. The resulting model predicted rutting rates for all three projects simultaneously with an r supra 2 value of 89%. This model was used to analyze the effects of changes in mixture composition, binder grade, and compaction on rut resistance, and also in a preliminary analysis of the current Superpave mix design system. The most important factor affecting rut resistance in Hot Hot Mix Asphalt Concrete (HMAC) mixtures is binder grade, followed by aggregate fineness relative to voids in mineral aggregates (VMA). This suggests that both VMA and aggregate fineness should be tightly controlled to ensure that a given mixture exhibits the desired level of rut resistance.