ABSTRACT
ABSTRACT: The purpose of this study was to investigate moisture absorption characteristics and their impact on tensile properties of asphalt mastics subjected to long-term soaking under ambient conditions (20°C and 50% relative humidity). The objective was to better understand the moisture damage phenomenon by providing suitable material inputs that can be used for numerical simulation. Understanding the effect of moisture on the mechanical properties of the asphalt mastics investigated is of utmost importance because they are commonly used in the construction of open-graded asphalt mixtures. The experimental approach adopted for studying the effect of moisture on mechanical properties of asphalt mastics consisted of exposing initially dry samples to moisture under controlled temperature and relative humidity, recording the moisture uptake until equilibrium using an ultra-sensitive balance, and then drying back and performing mechanical testing at multiple levels of saturation (moisture contents). The mechanical tests were all conducted at 20°C using a loading rate of 20 mm/min on dog-bone shaped samples. Using this approach, it was possible to identify the reversible and irreversible moisture absorption and its effects on mechanical properties. Moisture absorption of up to 0.4 wt% was observed and was largely recoverable upon drying for most of the mastics tested. The results suggest that the degradation of mastic tensile properties associated with moisture absorption is partially recovered upon drying. The effect of moisture conditioning on mastics appears to be aggregate type dependent as higher degradation in stiffness response was observed in the granite mastics than in the limestone mastics. Tensile strength in moisture saturated mastics was generally lower than in drier samples and was largely recoverable upon specimen drying. The failure mode in all the mastics considered were ductile which suggests that at the temperature and loading rate employed, the effect of moisture on failure mode is minimal. Aggregate type can accentuate the influence of moisture on tensile properties of asphalt mastics.
