Principal Investigator: Mustaque Hossain
Sponsors & Partners
Midwest States APT Pooled Fund Program
Mid-America Transportation Center
About this Project
Brief Project Description & Background
The thin white topping (TWT) can be a cost-effective measure that extends the life of existing asphalt pavements. This project is aimed at calibrating the TWT design method developed by the Colorado Department of Transportation using data from an experiment conducted under the accelerated pavement testing (APT) program at Kansas State University.
The research approach to be used in this study would be to obtain and analyze response of the AC pavements overlaid with TWT. The objective would be to calibrate a design method for TWT that would be effective in lengthening asphalt pavement life.
The project is expected to produce recommendations regarding design of TWT for high truck traffic routes. The most optimum design for a given existing AC pavement condition and truck traffic volume will also be identified.
Due to budget constraints, many highway agencies are becoming interested in pavement preservation or rehabilitation rather than reconstruction to ensure pavement is in serviceable condition. Thin whitetopping (TWT) is the process of rehabilitating distressed asphalt concrete (AC) pavements by using a concrete overlay. This study was done to develop a design catalog for existing AC pavements to be overlaid with TWT. The finite element (FE) analysis was performed with SolidWorks, which is the 3-D FE software program used to develop this design catalog. The design considered varying TWT thicknesses, existing AC layer thickness and modulus, the bonding condition between TWT and the existing AC layer, shoulder conditions and temperature differentials. Each model was built as a three-layer pavement systemâ€”composed of concrete TWT, an asphalt layer, and subgrade soil. The traffic load was modeled as a constant pressure with a rectangular area applied at the surface, and the intensity equal to the tire inflation pressure of 100 psi. The expected lives of TWT overlays were estimated using fatigue equations developed by the Portland Cement Association (PCA).
Results obtained from this study show that interface bonding condition is the most important factor affecting the behavior of TWT. With either the increase of TWT thickness or existing AC thickness, or AC modulus and the addition of a paved shoulder, concrete tensile stress decreases. Curling stress increases with the increase of TWT thickness and is not a function of AC properties. A design catalog was developed in terms of service life of the pavement. Unlike the unbonded TWT with an unpaved shoulder that results in catastrophic loss of rehabilitated pavement life, bonded TWT is expected to last 10 years, assumed in design. Thus, proper bonding must be ensured in order to have extended pavement life.