Asphalt is prone to deterioration when exposed to traffic and weather. The usual types of damage caused by water are cracking and rutting. Water changes the properties of the asphalt, modifying the stress-strain relationship and the mechanical behavior, affecting the service life of the asphalt coating. The flexibility, tensile strength, and stiffness affect the adhesion between aggregate and bitumen. Researchers Chaveli Brondani, Cléber Faccin, Luciano Pivoto Specht, Andrea Valli Nummer, Deividi da Silva Pereira, Pablo Menezes Vestena, and Magnos Baroni, sought to understand the influence aggregates have when affected by moisture.
Their paper, “Evaluation of Moisture Susceptibility of Asphalt Mixtures: Influence of Aggregates, Visual Analysis, and Mechanical Tests” in the Journal of Materials in Civil Engineering, evaluates 20 asphalt mixtures from Brazil’s southern highways. The authors characterized and evaluated asphalt mixes containing different geological formation aggregates, grain-size distributions, asphalt binders, and asphalt plants to assess their susceptibility to moisture. Learn more about their findings at https://doi.org/10.1061/(ASCE)MT.1943-5533.0004603. The abstract is below.
Asphalt pavement failure is directly related to the traffic and climate effects. Temperature and moisture severely impact pavement service life. It is known that moisture changes the stiffness and stress–strain distribution and all the mechanical behaviors of the mixture/structure. There is a huge interest in studying the impact of water on the behavior of flexible pavements, mainly on freeze–thaw regions under tropical climates with high rainfall levels. The scope of the present paper was to check the susceptibility to moisture-induced damage of dense asphalt mixes produced and applied on highways in Brazil’s southernmost region using different laboratory tests: visual adhesion of coarse aggregate; tensile strength ratio (TSR), and dynamic modulus ratio (DMR). Thus, this study evaluated the morphological, chemical, and mineralogical properties of aggregates from 11 quarries, as well as the interaction between aggregates and the respective bituminous binders. Rocks with high Si contents performed worse in visual adhesiveness tests; chemical ratios such as Fe/Si above 1 and Ca/K above 5, as well as the rougher texture of aggregates, considerably improved the coating, reducing the failures in adhesion. Results of TSR and DMR, after applying the induced moisture damage cycle, indicated greater susceptibility to conventional binders than mixtures containing modified binders in their composition. The action of moisture damage for most mixtures caused a reduction in strength and stiffness, warning of a decrease in the binder’s ability within the mixture, completely changing the distribution of efforts within the structure. Therefore, from this study, it is possible to suggest using DMR instead of TSR to assess susceptibility to moisture damage.
Explore the asphalt testing results in the ASCE Library: https://doi.org/10.1061/(ASCE)MT.1943-5533.0004603.