Effect of Moisture on Modulus Values of Base and Subgrade Materials

Abstract

Moisture in the base and subgrade layers of pavement can significantly decrease the modulus values of these layers. Recently, a study was performed on several Florida state roads for the purpose of evaluating the decrease in moduli of bases and subgrades due to the proximity of the water table. Dynaflect and falling weight deflectometer (FWD) tests were performed on pavement test sections throughout Florida for the purpose of backcalculation of the modulus values of the different layers. Testing was performed at different times of the year, and the water table fluctuations were recorded throughout the study. The Dynaflect and FWD deflections, water contents, depths to water table, layer thicknesses, pavement temperatures, and air temperatures were recorded on all test sections over a 5-year period. EVERCALC was used for back-calculation of modulus values on the basis of FWD tests. The Dynaflect data were also used for calculation of layer properties on the basis of a procedure developed by the Florida Department of Transportation. Both Dynaflect and FWD showed that the water table had a significant negative impact on the modulus values of the base and subgrade materials. Such results are extremely beneficial aids for establishing acceptable embankment depths so that the effects of moisture on the modulus values of pavements may be reduced.