Back-calculation of concrete pavement modulus using road-rater data

This paper deals with the back-calculation of elastic modulus of jointed concrete pavement. A series of road-rater tests are carried out on a jointed, Portland cement concrete (PCC) pavement of a partially completed freeway in Taiwan. The deflection data obtained with a road rater are used to back-calculate the modulus of elasticity of the PCC pavement and the coefficient of subgrade reaction. The back-calculation is done using BACK, a computer program developed based on the plate theory. The validity of the BACK program is verified with measured deflections, as well as predictions by ILLISLAB, an existing finite element code that has been proven reliable in predicting pavement responses. The results of this study show that the BACK program is quite reliable in predicting the elastic modulus of PCC pavement and the coefficient of subgrade reaction. However, the results are based on the analysis of PCC pavement over a granular subgrade and may not be directly applicable to those over asphalt-stabilized subbases.