Evaluation of performance of whitetopping pavement as a rehabilitation strategy

Xiaojun Li

Whitetopping overlay is a relatively new rehabilitation technology for deteriorated asphalt pavement. It is defined as a Portland cement concrete (PCC) overlay on the deteriorated existing hot mixed asphalt (HMA) pavement to improve both the structural and functional capability. When the PCC overlay thickness is less than or equal to 4in., it is referred to as ultra-thin whitetopping (UTW). The primary objectives of this thesis are to evaluate the performance of whitetopping pavement as a rehabilitation strategy and study the falling weight deflectometer (FWD) backcalculation method for whitetopping. Forensic investigation was conducted including FWD test, field distress survey, and shear strength test. Traditional FWD backcalculation methods for whitetopping pavement layer properties, like Modcomp6 and equations based on “AREA” theory, were found not applicable to UTW. A new Critical Distance Method is proposed and its potential advantages are highlighted. The parameter of “relative slab stiffness” could be used to estimate the backcalculation error and as a criterion to select suitable FWD backcalculation method for UTW. Thermal stress has little effect on typical UTW overlay. However, for WT overlay with the joint spacing and slab thickness increased, thermal stress could become a major cause of fatigue. 3-D finite element modeling and fatigue life analysis indicated that whitetopping pavement is very sensitive to a load level higher than the 18-kip standard axle loads. Slightly increase in the axle load could significantly decrease the fatigue live of whitetopping pavements. Design of whitetopping should be based on a traffic spectrum or heavier loads than the 18-kip standard axle load. Slab thickness, slab size, and overlay age were found to be statistically significant variables that affect the performance of whitetopping pavements. Slab thickness should be thicker than 4 in. and slab size should be smaller than 36 sq. ft. to get better whitetopping pavement performance.Coring and shear strength testing indicated that the bond was lost quickly in the field. The design method of whitetopping should fully consider the real bond condition, or based on unbond condition, to be conservative.

Evaluation of performance of whitetopping pavement as a rehabilitation strategy

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