Moisture sensitivity of unbound granular materials

Shafiqur Rahman

One of the main structural units in thin flexible pavement is the unbound aggregate base course. It contributes to the overall load spreading mechanism of the structure due to traffic loading and provides an underneath support to the asphalt concrete layer. The material characteristic of unbound layers are therefore of great importance for the performance of the structure. Unbound base courses show stress as well as moisture dependent behaviour during external loading. This is true for both their stiffness and resistance against permanent deformation properties. A series of Repeated Load Triaxial (RLT) tests has been carried out on a typical unbound aggregate base layer to investigate its behaviour in order to improve the modelling of the moisture sensitivity. Both the resilient test and multi-stage loading approach have been used providing information on the resilient as well as the permanent deformation characteristics. Results showed that the stiffness decreases and permanent deformation increases with increasing moisture content.

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