Drying path of a Water Retention Curve (WRC) on asphalt mixtures Trayectoria de secado de una Curva de Retención de Agua (WRC) en mezclas asfálticas

Abstract

The unsaturated behavior of bituminous materials has yet to be studied at present. However, the atmosphere-asphalt layer interaction in terms of humidity changes has forced different specifications or world standards to consider it appropriate to link in the designs the variable that controls this response, known as suction. This phenomenon is because it is the layer most exposed to atmospheric changes, therefore with a particular susceptibility to significant hygrometric changes. The construction of a water retention curve (WRC) is required to observe the changes in specific suction moisture ranges, which indicates the unique tandem suction-moisture value for a given material. The suction in the specimens of this research has been measured using a traditional filter-paper method, widely used in other types of soil engineering materials. Until now, suction on asphalt mixtures has only been measured using psychrometers, inducing invasive processes within the sample that can alter the results. The filter paper method only allows obtaining the drying path of the material; therefore, the probable hysteresis of the WRC cannot be obtained. Extensive experimentation time and experience in interpreting the tests was required because it is a technique that has not been used before for asphalt mixtures. The results show a restricted curve in moisture values and the suction spectrum. However, they reveal suction values that should be considered in stages of understanding the mechanical behavior of the material, especially for design purposes.