Influence of Environmental Conditions on the Performance of Bituminous Mixtures

Abstract

Aging and moisture damage are considered as major environmental factors which affect the performance of bituminous mixtures. This study investigated the effect of aging and moisture invasion on the performance of bituminous mixtures in terms of tensile strength and rutting resistance. Two different types of aggregates sources and one unmodified bituminous binder with and without warm additive were used. Bituminous mixtures were subjected to two levels of aging conditions (short-term and long-term aged) and two levels of moisture conditions (1 and 3 freeze-thaw cycles). A total of 24 different combinations were investigated for tensile strength and permanent deformation characteristics. Mineralogical investigations characterized the crushed stone as calcareous and bank run as siliceous aggregates. Results from this study demonstrate that levels of aging had a significant impact on the tensile strength of bituminous mixtures with warm mix additive as compared to conventional bituminous mixtures. Fracture work density, a surrogate cracking parameter was able to adequately capture the influence of aggregate mineralogy on the moisture susceptibility of long term aged mixtures. In addition, moisture conditioning was found to influence fracture work density of mixtures more than aging. Further, the rutting resistance of mixtures was determined in terms of flow numbers obtained using Francken model. In general, the rutting resistance of conventional mixtures was relatively higher than a mixture with warm mix additive. As expected, the flow number of conventional mixtures increased with aging and further reduced with moisture conditioning. Interestingly, the flow numbers of bituminous mixtures with warm mix additive was not negatively impacted by moisture at short term aged conditions. However, flow number of both mixtures after long term aging exhibited a similar trend. Additionally, statistical analysis showed that an increase in freeze-thaw cycles from one to three did not significantly impact the tensile characteristics of the mixtures.