Farhad Salour Doctoral Thesis

4.
 
Moisture Influence on Pavement Performance and Bearing 
Capacity 
In pavement engineering, it is generally recognized that the presence of excess moisture 
content in unbound pavement materials, especially when combined with heavy traffic 
loads, can result in accelerated pavement deterioration and significant reduction in 
service life (ARA, 2004; Berntsen and Saarenketo, 2005; Erlingssson, 2010). The 
moisture related deterioration mechanisms greatly depend on the type of pavement 
structure, the material, the topography of the section, the climate and the condition of 
the pavement surface. In thin flexible pavement structures, unbound granular layers and 
subgrade soils undergo higher traffic load stresses. Since unbound pavement materials 
are generally sensitive to moisture content, thin pavement structures show higher 
sensitivity to moisture variations. Thus, their performance is highly dependent on their 
moisture condition and prolonged exposure to high moisture content can result in 
pavement instability and large resilient and accumulated permanent deformations. This 
highlights the significant role of maintaining an intact surface course with a functional 
drainage system. 
However, thicker flexible pavement structures are usually exhibit less sensitivity to 
moisture content variations due to the fact that lower stress levels are experienced by 
the unbound layers (Huang, 2003) due to surface traffic loads. Nevertheless, high 
moisture content can still indirectly contribute to pavement deterioration. High 
moisture content in unbound layers which results in softer support to the asphalt 
concrete course leads to higher tensile stresses at the bottom of this layer caused by the 
traffic load. This in return will accelerate crack propagation in the asphalt concrete layer 
which will then allow for surface water infiltration to the pavement structure 
(Cedergren, 1988). 
In concrete pavement systems, the water related deteriorations are mainly concentrated 
around the slab joints and edges if water is present at the slab and supporting layer 
interface (Hansen et al., 1991). Along the joints, water pressure can locally increase 
under traffic load passages, resulting in movements of water with high velocity which 
can causes erosion in the slab edges and the supporting unbound layers.