Quantification of environmental impacts on the performance of asphalt pavements

Environmental changes have a direct impact on the structural capacity of the pavement, and consequently its performance. While the subgrade soil and the unbound materials are sensitive to moisture variation, the Asphalt Concrete (AC) layers are more sensitive to temperature variations. Quantifying the effect of these two environmental factors, moisture and temperature, is necessary for incorporation in the pavement design process. The main goal of this research is to quantify these effects on the structural capacity of the pavement layers, and determine their influence on the pavement performance.; The approach adopted was to monitor the variation of the moisture and temperature at various instrumented pavement sites in Idaho. The moisture and temperature data were collected on a monthly basis for almost three years. However, due to budget constraints, structural capacity evaluation using Falling Weight Deflectometer (FWD) testing was conducted only once a year. Therefore, the research relied on the FHWA LTPP seasonal monitoring program (SMP) database to acquire seasonal FWD data for many sites across the country.; Data acquired from the LTPP-SMP database were used to develop a series of correlation models that quantify the variation of the resilient modulus of unbound materials and relate it to moisture variation. Similarly, models to relate the modulus of asphalt concrete layer to the temperature variation were also developed. The developed models showed dependency of the modulus on many other factors such as material type, mix design, climatic region, and other design related parameters.; The developed models were then checked using the collected data at the specific sites instrumented in Idaho. Then, the models were incorporated in a mechanistic-empirical pavement design process to quantify the effect of the seasonal variation on pavement performance.; Results of the mechanistic analysis, which incorporated the developed models, indicated that the incorporation of the seasonal variation in pavement design process leads to the prediction of significantly shorter pavement service life. This finding is critical to pavement designers, since the lack of consideration of such seasonal variations could result in a premature failure.