Effect of As-Compacted Moisture Content and Density on Pavement Performance in Different Climatic Regimes

While asphalt-concrete layer properties are more sensitive towards temperature variations, the subgrade stiffness have proven to be quite sensitive to moisture content fluctuations. When embankments are needed during the pavement construction, the soil must be compacted at a particular moisture-density condition to reach homogeneous properties. Due to construction variability, the as-compacted conditions might vary from the required specifications. This is of particular interest when dealing with compacted fine grained subgrade materials due to the influence of soil permeability in the seasonal moisture content fluctuation. The main objective of this study is the evaluation of the structural capacity and pavement performance due to the variability associated with the as-compacted moisture and density conditions, for different climatic regions. Three types of materials ranging from silt to clay were used in the analysis. Weather information from three locations was collected to represent different climate regimes. The pavement performance was analyzed using the Mechanistic-Empirical Pavement Design Guide (MEPDG) procedure by using the response of the pavement to three major distresses: fatigue cracking, rutting and thermal cracking. Two different levels of input accuracy were compared: Level 2, which uses simple index material and compaction properties and Level 3, which uses just the simple index material properties to estimate the resilient modulus. Results indicated that the soil compacted to optimum moisture content predicted less amount of distress when compared to the wet or dry optimum conditions for the low plasticity soils; whereas the predicted distresses increase with the increase in the as-compacted moisture content for the high plasticity soils. When compared with ratio of optimum condition, IRI had a maximum increase of 5% in Chicago and Atlanta region exhibited a fatigue cracking increase of 40% while Phoenix area showed a lot of rutting increase of 30%. The difference in the distress results obtained for Level 2 and Level 3 analyses were not significant for the soil compacted at optimum condition, but the dry and wet of optimum conditions resulted in significant larger differences that depended on the location or climate where the pavement is constructed.