ABSTRACT
Falling weight deflectometer (FWD) test is used to evaluate structural capacity of an existing pavement. However, FWD measurements are influenced by the temporal variations and therefore, consideration of such effect is essential for accurate assessment of pavement structural condition. Long-term Pavement Program (LTPP) Seasonal Monitoring Program (SMP) was designed to evaluate the influence of such temporal variations on pavement structural characteristics. This paper presents typical effects of seasonal and daily variations on pavement deflections and back-calculated moduli. Available FWD deflection measurements and back-calculated moduli, in the LTPP database for different pavement layers for all SMP pavement sections were evaluated. Results showed that HMA moduli decrease from morning to afternoon (i.e., increasing FWD pass number), and for different seasons in a year (i.e., different months). PCC moduli and k-values also exhibited significant variations with increasing FWD pass number. Sub-surface layer material properties for both flexible and rigid pavement sections also showed noticeable variations when measured in different seasons of the year.
