Of Pavement Deflection and Performance

There are three flexible pavement failure modes, namely, fatigue crack, thermal crack and deformation (rutting). When pavement layer materials are properly designed and constructed, the source of rutting is from permanent deformation of the subgrade. Of these failure modes, fatigue crack and rutting are related to number of load repetition and thermal crack is related to time (age) and environmental condition. Lab test proved that fatigue life is a function of maximum tensile strain of the AC layer while rutting life is a function of vertical strain on subgrade. Both strains are directly related to pavement deflection. Therefore, deflection can be a direct measurement, or indicator, of pavement performance. This report summarized data collected from DEL23 project and suggested how deflection can be applied to pavement design and pavement management.